CN110280589A - Thick steel plate and rolling method thereof - Google Patents

Abstract

The invention discloses a thick steel plate and a rolling method thereof. The rolling method includes a sequence of billet heating, two-stage rolling, and post-rolling cooling, wherein the two-stage rolling process includes a rough rolling stage and a finish rolling stage, and in the rough rolling stage, the The billet is subjected to multiple rough rolling passes, and the rolling method further includes performing an online cooling process on the billet during rough rolling after at least two or all odd passes of rough rolling. The thick steel plate prepared by the rolling method utilizes differential temperature rolling, and a certain temperature difference is formed between the surface layer and the core of the billet. The deformation is larger during rolling, the porosity and shrinkage cavity of the core are effectively rolled together, the quality and mechanical properties of the core are improved, the pass rate of flaw detection is greatly improved, and the rolling efficiency is improved at the same time.

Description

Thick steel plate and its rolling method

technical field

The invention belongs to the technical field of iron and steel smelting, relates to a rolling method of a thick steel plate, and also relates to a thick steel plate prepared by the rolling method.

Background technique

During the solidification process of the thick steel plate, due to the large thickness and the instability of heat transfer, the growth rate of the columnar crystals is different. When the liquid steel in the lower part of the bridge is solidified and shrinks, it cannot be replenished by liquid steel and forms central looseness or shrinkage cavity. If these center porosities or shrinkage cavities are not effectively deformed during rolling, rolling cannot be carried out, resulting in poor quality and mechanical properties of the center of the thick steel plate, and a low pass rate of flaw detection.

Contents of the invention

The purpose of the present invention is to provide a rolling method for thick steel plates, which performs instant on-line cooling during the two-stage rolling, so as to solve the problems caused by the lack of effective deformation of the medium-thick steel plates in the prior art due to the central porosity or shrinkage cavity during rolling. The technical problem of poor core quality and mechanical properties; and the purpose of the present invention is to provide a thick steel plate prepared by the rolling method.

In order to achieve one of the above objects, an embodiment of the present invention provides a rolling method of a thick steel plate. The rolling method includes sequentially performing billet heating, two-stage rolling and cooling after rolling, wherein the The two-stage rolling process includes a rough rolling stage and a finish rolling stage, in which the billet is subjected to a plurality of rough rolling passes, and the rolling method also includes at least two odd passes or all odd passes After the second rough rolling, the billet is subjected to an on-line cooling process during the rough rolling period.

In this way, the billet is cooled on-line immediately during the rough rolling process, so that the low temperature is too late to be transmitted to the core of the billet, and a certain temperature difference is formed between the surface layer of the billet and the core. High, large deformation during rolling, forming fine equiaxed grains, recrystallization is relatively sufficient, the porosity and shrinkage cavity in the core are effectively rolled together, the quality and mechanical properties of the core are improved, and the pass rate of flaw detection is greatly improved , while improving the rolling efficiency.

As a further improvement of an embodiment of the present invention, in the finish rolling stage, the billet is subjected to multiple passes of finish rolling; the rolling method also includes performing an online cooling process on the billet before finish rolling before the finish rolling stage , and/or, after at least one even-numbered pass or all even-numbered passes, the billet is subjected to an online cooling process during the finish rolling period. In this way, it can further ensure that there is still a certain temperature difference between the surface layer and the core of the billet. The temperature of the surface layer of the billet is low, and the temperature of the core is relatively high. During finish rolling, the deformation of the non-recrystallized area can be further promoted, the grains are further refined, and the structure is more refined. Flat, the porosity and shrinkage cavities in the core are effectively rolled together, the quality of the core is improved again, and the pass rate of flaw detection is greatly improved.

As a further improvement of an embodiment of the present invention, in any one or several of the on-line cooling process during the rough rolling period, the on-line cooling process before the finish rolling, and the on-line cooling process during the finish rolling period, the upper surface of the billet and the The lower surface is cooled by water supply, wherein the water pressure is 0.5MPa, the water flow rate on the upper surface is 60-120m ³ /h/share, and the water flow rate on the lower surface is 120-240m ³ /h/share. The water flow ratio on the upper surface is greater than or equal to 2, and the moving speed of the billet is 0.5-5 m/s. By controlling the amount of water flow on the upper and lower surfaces of the blank, water pressure, water flow, the ratio of water flow between the lower surface and the upper surface, and the moving speed of the blank, the cooling speed of the upper and lower surfaces of the blank is controlled. The billet is cooled evenly and effectively, and at the same time, the conduction of low temperature to the core of the billet is avoided, and the temperature difference between the upper and lower surfaces of the billet and the core is ensured.

As a further improvement of an embodiment of the present invention, in any one or several of the on-line cooling process during the rough rolling period, the on-line cooling process before the finish rolling, and the on-line cooling process during the finish rolling period, the upper surface of the billet and the lower surface The cooling speed, cooling temperature and cooling depth of the surface are the same, so that the billet can be cooled uniformly and effectively, so that the deformation of the upper and lower surfaces during rolling is small and consistent, and the temperature difference between the upper and lower surfaces of the billet and the core is guaranteed.

In order to achieve one of the above objects, an embodiment of the present invention also provides a rolling method of a thick steel plate. The rolling method includes sequentially performing billet heating, two-stage rolling and cooling after rolling, wherein the The two-stage rolling process includes a rough rolling stage and a finish rolling stage. In the finish rolling stage, the billet is subjected to multiple passes of finish rolling, and the rolling method also includes performing An online cooling process before finish rolling, and/or, after at least one even-numbered pass or all even-numbered passes, the billet is subjected to an online cooling process during finish rolling.

In this way, the billet is cooled on-line immediately during the finish rolling process, so that the low temperature is too late to be transmitted to the core of the billet, and a certain temperature difference is formed between the surface layer of the billet and the core. High, large deformation during rolling, which promotes the deformation of the non-recrystallized area, forms fine grains, makes the structure flatter, the looseness and shrinkage cavity in the core are effectively rolled, the quality of the core is improved, and the flaw detection is qualified rate has been greatly increased.

In order to achieve one of the above objects, an embodiment of the present invention also provides a rolling method of a thick steel plate, the rolling method comprising steps:

Blank heating;

Two-stage rolling is carried out on the heated billet with double stands; among them, the billet is firstly subjected to multiple passes of rough rolling through the rough rolling mill, and then finished rolled into a thick steel plate through the finishing mill;

cooling the thick steel plate;

During the two-stage rolling, after rough rolling for at least two or all odd passes, the billet leaves the roughing mill and enters the first instant cooling device for on-line cooling during the roughing period, after which the billet returns to the roughing The rolling mill performs even-numbered passes roughing or feeds to the finishing mill.

In this way, the billet enters the first instant cooling device during the rough rolling process for instant on-line cooling during the rough rolling period. On the one hand, the cooling time can be shortened and the rolling efficiency can be improved; There is a certain temperature difference with the core, the temperature of the billet surface is low, and the deformation is small during rolling, while the temperature of the core of the billet is high, and the deformation is large during rolling, forming fine equiaxed grains, and the recrystallization is relatively sufficient. The porosity and shrinkage cavity of the core are effectively rolled together, the quality and mechanical properties of the core are improved, and the pass rate of flaw detection is greatly improved.

As a further improvement of an embodiment of the present invention, when the billet passes through the first immediate cooling device, the upper header ^of the first immediate cooling device flows toward the The upper surface of the billet is cooled by water supply, and the lower header of the first instant cooling device supplies water to the lower surface of the billet for cooling with a water pressure of 0.5 MPa and a water flow rate of 120-240 m ³ /h. The water flow ratio of the tube and the upper header is ≥2, and the moving speed of the billet on the roller table is 0.5-5m/s. By controlling the number of upper and lower headers, water pressure, water flow, water flow ratio and the moving speed of the billet on the roller table in the first instant cooling device, the cooling speed and cooling rate of the upper and lower surfaces of the billet can be controlled. The temperature and cooling depth are basically kept the same, and the billet is uniformly and effectively cooled, so that the deformation of the upper surface and the lower surface of the billet is small and consistent during rolling, and at the same time, the low temperature is prevented from being transmitted to the center of the billet, ensuring that the upper and lower surfaces of the billet and the core temperature difference between parts.

As a further improvement of an embodiment of the present invention, the roller table of the first instant cooling device is 6400 mm long and 3500 mm wide, and has 8 sets of upper headers and lower headers corresponding to each other. The width of the first instant cooling device is set to match the width of the billet, and the upper and lower headers are reasonably arranged according to the length and width of the first instant cooling device to ensure that the cooling speed and cooling depth of the upper surface and the lower surface of the billet are generally consistent, and avoid billet The upper and lower surfaces are warped due to uneven cooling.

As a further improvement of an embodiment of the present invention, the billet is passed through a finishing mill for multiple passes of finish rolling; during the two-stage rolling, after the billet leaves the first instant cooling device and before entering the finishing mill , using the second instant cooling device to perform an online cooling process before finishing rolling, and/or, during the two-stage rolling, after at least one even-numbered pass or all even-numbered passes, the billet leaves the finishing mill and enters the first The second instant cooling device performs the on-line cooling process during the finish rolling period, and then the billet returns to the finish rolling mill for odd-numbered passes of finish rolling.

The intermediate billet enters the second instant cooling device before entering the finishing rolling mill for on-line cooling before finishing rolling, which can shorten the cooling time and improve the rolling efficiency, while maintaining a certain temperature difference between the surface layer and the core of the billet, and the surface temperature of the billet is low. The deformation is small during finish rolling, while the temperature of the core is high, and the deformation is large during finish rolling, which can form fine flat grains, the porosity and shrinkage cavities in the core are effectively rolled together, and the quality and mechanical properties of the core are improved. The passing rate of flaw detection has been greatly improved; and the online cooling during the finishing rolling period after several even-numbered passes can shorten the cooling time and improve the rolling efficiency, so that the low temperature is too late to be transmitted to the core of the billet, and the billet forms a certain temperature difference between the surface layer and the core In the case of multi-pass finish rolling, the surface layer of the billet has a small deformation due to the low temperature, while the core temperature is high, and the deformation is large during finish rolling, which can further promote the deformation of the non-recrystallized area and further refine the grains. The tissue is flatter, the energy is more, the looseness and shrinkage cavity of the core are further effectively rolled, and the quality, mechanical properties and pass rate of flaw detection of the core are further improved.

As a further improvement of an embodiment of the present invention, when the billet passes through the second immediate cooling device, the upper header ^of the second immediate cooling device flows toward the The upper surface of the billet is cooled by water supply, and the lower header of the second instant cooling device supplies water to the lower surface of the billet for cooling with a water pressure of 0.5 MPa and a water flow rate of 120-240 m ³ /h. The water flow ratio of the tube and the upper header is ≥2, and the moving speed of the billet on the roller table is 0.5-5m/s. . Control the cooling of the upper and lower surfaces of the billet by controlling the number of upper and lower headers, water pressure, water flow, water flow ratio of the lower and upper surfaces in the second immediate cooling device, and the moving speed of the billet on the roller table in the second immediate cooling device The speed, cooling temperature and cooling depth are basically consistent, and the upper and lower surfaces of the billet are further uniformly and effectively cooled to ensure the temperature difference between the upper and lower surfaces of the billet and the core.

As a further improvement of an embodiment of the present invention, the roller table of the second instant cooling device is 4800mm long and 3500mm wide, and has 6 sets of one-to-one corresponding upper headers and lower headers. The width of the second immediate cooling device is set to match the width of the billet. Since the billet has been overcooled during rough rolling, the length of the second immediate cooling device and the number of upper and lower headers are appropriately reduced. The two are matched and arranged reasonably. The cloth can effectively cool the upper and lower surfaces of the billet to ensure that the cooling speed and cooling depth of the upper and lower surfaces of the billet are roughly consistent, and avoid the buckling of the upper and lower surfaces of the billet due to uneven cooling.

In order to achieve one of the above objects, an embodiment of the present invention also provides a rolling method of a thick steel plate, the rolling method comprising steps:

Blank heating;

Two-stage rolling is carried out on the heated billet with double stands; among them, the billet is first rough rolled by the rough rolling mill, and then passed through the finishing mill for multiple passes of finish rolling to produce thick steel plates;

cooling the thick steel plate;

During the two-stage rolling, after the billet leaves the first instant cooling device and before entering the finish rolling mill, the second instant cooling device is used to perform an online cooling process before finish rolling, and/or, in the two-stage During rolling, after at least one even-numbered pass or all even-numbered passes are finished rolling, the billet leaves the finishing mill and enters the second instant cooling device for on-line cooling during the finish rolling period, and then returns the billet to the finishing mill for odd-numbered passes Finish rolling.

In this way, before entering the second instant cooling device to carry out on-line cooling before finishing rolling, the cooling time can be shortened, the rolling efficiency can be improved, and at the same time, there is a certain temperature difference between the surface layer and the core of the billet, and the surface layer temperature of the billet is low. The deformation is small during finish rolling, while the core temperature is high, and the deformation is large during finish rolling. The porosity and shrinkage cavity in the core are effectively rolled together, and small flat grains can be formed at the same time, and the quality and mechanical properties of the core are improved. Improvement, the pass rate of flaw detection has been greatly improved; and the online cooling of the finish rolling period after at least one even-numbered pass finish rolling can shorten the cooling time, improve the rolling efficiency, and prevent the low temperature from being transmitted to the core of the billet. The multi-pass finish rolling is carried out under the condition of a certain temperature difference in the part. The surface layer of the billet has a small deformation due to the low temperature, while the core part has a high temperature and a large deformation during finish rolling, which can promote the deformation of the non-recrystallization area and refine the grain. The particles make the tissue flatter, the looseness and shrinkage cavity of the core are effectively rolled together, and the quality, mechanical properties and pass rate of flaw detection of the core are improved.

Correspondingly, in order to achieve one of the above objects, an embodiment of the present invention further provides a thick steel plate, the thick steel plate is prepared by the rolling method of the thick steel plate. In the rolling process of the thick steel plate, differential temperature rolling is adopted, the surface temperature is low, the rolling deformation is small, and the core temperature is high, the rolling deformation is large, and the porosity and shrinkage cavity in the core are effectively rolled together, which has the advantages of With excellent comprehensive mechanical properties and core quality, the passing rate of flaw detection has been greatly improved, which not only meets the current industry requirements for high strength and good low-temperature toughness of thick steel plates, but also enables large-scale production of thick steel plates.

Description of drawings

Fig. 1 is a schematic diagram of a rolling system adopted in a rolling method of a thick steel plate according to an embodiment of the present invention;

Fig. 2 is the metallographic structure photograph of test example A in the embodiment of the present invention 1;

Fig. 3 is the metallographic structure photograph of test example B in the embodiment of the present invention 1;

Fig. 4 is the metallographic structure photograph of test example C in the embodiment of the present invention 1;

Fig. 5 is the metallographic structure photograph of test example D in the embodiment of the present invention 1;

Fig. 6 is the metallographic structure photograph of the embodiment of the present invention 2;

Fig. 7 is the metallographic structure photograph of the embodiment of the present invention 3;

Fig. 8 is the metallographic structure photo of embodiment 4 of the present invention;

Fig. 9 is the metallographic structure photograph of the embodiment of the present invention 5;

Fig. 10 is the metallographic structure photograph of embodiment 6 of the present invention;

Fig. 11 is the metallographic structure photograph of the embodiment of the present invention 7;

Fig. 12 is the metallographic structure photograph of embodiment 8 of the present invention;

Fig. 13 is the metallographic structure photograph of embodiment 9 of the present invention;

Fig. 14 is the metallographic structure photo of comparative test example E of the present invention;

Fig. 15 is the metallographic structure photograph of comparative test example F of the present invention;

Fig. 16 is the metallographic structure photo of comparative test example G of the present invention;

Fig. 17 is a photo of the metallographic structure of comparative test example H of the present invention.

Detailed ways

An embodiment of the present invention provides a method for rolling a thick steel plate, and a thick steel plate produced by the rolling method. The rolling method of the thick steel plate is described in detail below, including the steps of billet heating, two-stage rolling, on-line cooling in the rolling stage, and post-rolling cooling in sequence, wherein:

(1) Blank heating process

Preferably, the heating temperature for the billet is 1150-1240°C.

(2) Two-stage rolling and rolling stage online cooling process, including

a. Rough rolling stage: at this stage, the billet is subjected to rough rolling for multiple passes;

b. Finish rolling stage: at this stage, multiple passes of finish rolling are carried out on the billet;

c. On-line cooling in the rolling stage: in the rough rolling stage, and/or, in the finish rolling stage, the billet is cooled on-line immediately;

(3) Cooling process after rolling

The prepared thick steel plate is cooled by ultra-rapid cooling or on-line slow natural cooling.

By cooling the billet on-line in real time during the rolling stage, the temperature of the surface layer of the billet can be quickly reduced, and the low temperature is too late to be transmitted to the core of the billet, and a temperature difference is formed between the surface layer and the core of the billet. During rolling, the surface temperature of the billet is low and the deformation Small, but the core of the billet is greatly deformed due to high temperature. Even if it is a thick steel plate, the looseness and shrinkage cavity of the core can be effectively rolled, the grains are refined, the quality of the core is improved, and the comprehensive mechanical properties are greatly improved.

Specifically, in a preferred embodiment, the two-stage rolling and on-line cooling process in the rolling stage include on-line cooling during rough rolling, on-line cooling before finish rolling, and on-line cooling during finish rolling. Details. Of course, in the variation of this embodiment, any one or any two of the on-line cooling during the rough rolling period, the on-line cooling process before the finish rolling and the on-line cooling process during the finish rolling period can be canceled, that is, two-stage rolling and rolling. The on-line cooling process in the manufacturing stage includes any one or any combination of the on-line cooling in the rough rolling period, the on-line cooling process before the finish rolling and the on-line cooling process in the finish rolling period.

Furthermore, in this embodiment, in the two-stage rolling and rolling stage online cooling process, the billet is subjected to immediate online cooling in the rough rolling stage. Specifically, after at least two odd-numbered passes of rough rolling, the billet is subjected to a rough-rolling on-line cooling process, preferably, after all odd-numbered rough-rolling passes, the billet is subjected to a rough-rolling on-line cooling process.

Preferably, in the on-line cooling process during the rough rolling stage, the upper surface and the lower surface of the billet are cooled by water supply, wherein the water pressure is 0.5 MPa, and the water flow rate of each water supply pipe on the upper surface of the billet is ^60-120m3 /h, the water flow rate of each water supply pipe on the lower surface of the billet is 120-240m ³ /h, the ratio of the water flow rate between the lower surface and the upper surface is ≥2, and the moving speed of the billet is 0.5-5m/s. In this way, the cooling rate, cooling temperature and cooling depth of the upper surface and the lower surface of the blank can be guaranteed to be the same, but not limited to being completely the same, and basically the same can also be used to ensure the temperature difference between the upper and lower surfaces of the blank and the core, and to ensure that the blank is uniformly cooled. , Effective cooling, so that the deformation of the upper and lower surfaces is small and consistent during rolling.

Further, before the finish rolling stage, the billet is subjected to an online cooling process before finish rolling. On the one hand, the cooling time can be shortened, and the rolling efficiency can be improved. At the same time, there is still a certain temperature difference between the surface layer and the core of the billet. Low, the deformation is small during finish rolling, while the temperature of the core is high, the deformation is large during finish rolling, and fine flat grains can be formed, the porosity and shrinkage cavities in the core are effectively rolled, and the quality and mechanical properties of the core are improved. Improvement, the pass rate of flaw detection has been greatly improved.

Further, after at least one even-numbered pass finish rolling, the billet is subjected to an online cooling process during the finish rolling period, preferably, after all the even-numbered pass finish rolling, the billet is subjected to an online cooling process during the finish rolling period. The rapid cooling of the gap can further shorten the cooling time and improve the rolling efficiency, so that the low temperature is too late to be transmitted to the core of the billet. The billet is subjected to multi-pass finish rolling under the condition of a certain temperature difference between the surface layer and the core part. Due to the low temperature of the billet surface layer, The deformation is small, but the temperature of the core is high, and the deformation is large during finish rolling, which can further promote the deformation of the non-recrystallized area, further refine the grains, make the structure flatter, and further effectively reduce the looseness and shrinkage of the core. Rolling, to further improve the core quality, mechanical properties and flaw detection pass rate.

Preferably, in the on-line cooling process before the finish rolling and the on-line cooling process between the finish rolling, the upper surface and the lower surface of the billet are cooled by water supply, wherein the water pressure is 0.5 MPa, and the water flow rate on the upper surface of the billet is 60 ～120m ³ /h/strand, the water flow rate on the lower surface of the billet is 120～240m ³ /h/strand, the water flow ratio between the lower surface and the upper surface is ≥2, and the moving speed of the billet is 0.5～5m/s . In this way, the cooling rate, cooling temperature and cooling depth of the upper surface and the lower surface of the blank can be guaranteed to be the same, but not limited to being completely the same, and basically the same can also be used to ensure the temperature difference between the upper and lower surfaces of the blank and the core, and to ensure that the blank is uniformly cooled. , Effective cooling, so that the deformation of the upper and lower surfaces is small and consistent during rolling.

Referring to the rolling system provided in Fig. 1, it can be used to realize the rolling method in the above-mentioned embodiment, and the rolling system includes heating equipment, a rough rolling mill, a first instant cooling device, and a second instant cooling device arranged in sequence , a finishing mill, and cooling equipment. The rolling system is connected by a roller table to form a continuous billet conveying line extending from the heating equipment to the cooling equipment from front to back. The first instant cooling device is arranged at the exit of the rough rolling mill, so that the billet can be directly connected to the first instant cooling device for cooling after the odd-numbered rough rolling; the second instant cooling device is arranged at the entrance of the finishing mill, so that the intermediate billet Enter the second instant cooling device for cooling before finish rolling and directly enter the second instant cooling device for cooling after even-numbered passes of finish rolling. Such settings can shorten the cooling time and improve rolling efficiency. Certainly, in the variation of this embodiment, any one of the first instant cooling device and the second instant cooling device may also be cancelled.

Wherein, the roller table of the first instant cooling device is 6400mm long and 3500mm wide, and has 8 sets of upper headers and lower headers arranged in one-to-one correspondence, which can supply water to cool the upper and lower surfaces of the billet; the second The roller table of the instant cooling device is 4800mm long and 3500mm wide, with 6 sets of one-to-one corresponding upper and lower headers, which can supply water to cool the upper and lower surfaces of the billet.

By controlling the number of upper and lower headers, water pressure, water flow, water flow ratio, and the conveying speed of the roller table, the cooling speed, cooling temperature and cooling depth of the upper and lower surfaces of the billet can be controlled to be basically consistent, And the billet is uniformly and effectively cooled, so that the deformation of the upper and lower surfaces of the billet is small and consistent during rolling, and at the same time, the conduction of low temperature to the core of the billet is avoided, and the temperature difference between the upper and lower surfaces of the billet and the core is guaranteed.

It should be understood that although the terms first, second, etc. may be used herein to describe various means, these descriptions should not be limited by these terms. These terms are only used to distinguish these described objects from one another.

In the following, the method for rolling a thick steel plate according to this embodiment will be specifically introduced in combination with the rolling system shown in FIG. 1 .

The billet enters the heating equipment to heat the billet.

The billets after heating are rolled in two stages including a rough rolling stage and a finish rolling stage using two stands. Among them, specifically, after the billet leaves the heating equipment, it is transported backwards into the roughing mill, and reciprocates multiple cycles at the roughing mill to perform rough rolling for multiple passes, and finally the intermediate billet is produced; the intermediate billet continues to be transported backwards into the finishing mill. Rolling mill, and reciprocating multiple cycles at the finishing mill to perform multiple passes of finish rolling, and finally produce thick steel plate; After that, the thick steel plate is transported backward to cooling equipment, using cooling equipment, preferably ultra-rapid cooling system or cooling bed The produced thick steel plate is cooled.

In one embodiment, as mentioned above, after at least two odd-numbered passes of rough rolling, the billet is transported out of the rough rolling mill from front to back and enters the first instant cooling device for on-line cooling during the rough rolling period. After the odd-numbered rough rolling, the billet is transported out of the roughing mill from front to back and enters the first instant cooling device for on-line cooling during rough rolling. After the online cooling is completed, the billet is transported back to the roughing mill for even Pass rough rolling or continue to the downstream of the first instant cooling device from front to back to the finishing mill.

For example, for example, the billet has gone through 7 passes of rough rolling, and enters the first instant cooling device after the 1st, 3rd, and 5th passes of rough rolling respectively. After single cooling or reciprocating cooling in the middle, center on the roller table behind the roughing mill, and then return to the roughing mill for the 2nd, 4th, and 6th rough rolling respectively, and enter the The first instant cooling device, after performing single cooling or reciprocating cooling in the first immediate cooling device, is transported to the finishing mill, or passes through the first immediate cooling device after the 7th pass of rough rolling But without cooling, it is directly sent to the finishing mill.

Preferably, in the on-line cooling process during the rough rolling stage, the eight upper headers of the first immediate cooling device supply water to the upper surface of the billet with a water pressure of 0.5 MPa and a water flow rate of 60-120 m ³ /h Cooling, the 8 lower headers of the first immediate cooling device supply water to the lower surface of the billet for cooling with a water pressure of 0.5MPa and a water flow rate of 120-240m ³ /h, the lower headers, the upper headers The water flow ratio of the tube is ≥2, and the moving speed of the billet on the roller table is 0.5-5 m/s.

Preferably, when the intermediate billet leaves the first immediate cooling device and is conveyed downstream to the finishing mill from front to back, the intermediate billet passes through the second instant cooling device and undergoes an online cooling process before finishing rolling, and then the intermediate billet The billet then enters the finish rolling mill for multiple passes of finish rolling. For example, before the finish rolling stage, the intermediate billet enters the second instant cooling device for on-line cooling process before finish rolling, and is centered on the roller table before the finish rolling mill, and then the intermediate billet enters the finish rolling mill A total of 5 passes of finish rolling were performed.

Preferably, after at least one even-numbered pass of finish rolling, preferably after all even-numbered passes of finish rolling, the intermediate billet is transported out of the finish rolling mill from back to front and enters the second instant cooling device for on-line cooling during the finish rolling period, Afterwards, the intermediate billet is transported from front to back and returned to the finish rolling mill for the next pass of finish rolling. For example, the intermediate slab has undergone 5 passes of finish rolling, firstly through the 1st and 2nd passes of finish rolling, and after the 2nd pass of finish rolling, enters the second instant cooling device, After single cooling or reciprocating cooling in the instant cooling device, it is centered on the roller table in front of the finishing mill, and then returns to the finishing mill for the 3rd, 4th, and 5th pass of finishing rolling respectively, and the 5th pass of finishing rolling After the end, the finish rolling stage ends.

Preferably, in the on-line cooling process before the finish rolling and the on-line cooling process during the finish rolling period, the six upper headers of the second immediate cooling device are equipped with a water pressure of 0.5 MPa and a water flow rate of 60-120 m ³ /h Water is supplied and cooled to the upper surface of the intermediate billet, and the six lower headers of the second instant cooling device are used to supply water to the lower surface of the intermediate billet for cooling with a water pressure of 0.5 MPa and a water flow rate of 120 to 240 m ³ /h , the water flow ratio of the lower and upper headers is greater than or equal to 2, and the intermediate billet passes through the roller table of the second instant cooling device at a speed of 0.5-5 m/s.

An embodiment of the present invention also provides a thick steel plate, the thick steel plate is prepared by the rolling method of the thick steel plate, and the thick steel plate has excellent comprehensive mechanical properties and core quality.

In summary, compared with the prior art, the present invention has the following beneficial effects:

(1) Through the on-line cooling process during the rough rolling period, the billet is cooled on-line after at least two or all odd-numbered passes of rough rolling. There is a certain temperature difference with the core, the temperature of the billet surface is low, and the deformation is small during rolling, while the temperature of the core of the billet is high, and the deformation is large during rolling, forming fine equiaxed grains, and the recrystallization is relatively sufficient. The porosity and shrinkage cavity in the core are effectively rolled together, the quality of the core is improved, the pass rate of flaw detection is greatly improved, and the rolling efficiency is improved at the same time.

(2) Through the on-line cooling process before or during finish rolling, the cooling time can be shortened, the rolling efficiency can be improved, and at the same time, a certain temperature difference between the surface layer and the core of the intermediate billet can be maintained. The surface temperature of the intermediate billet is low, and the deformation during finish rolling is larger Small, but the core temperature is high, and the deformation is large during finish rolling, which can refine the grains, promote the deformation of the non-recrystallized area, make the structure flatter, and effectively roll the loose and shrinkage cavities in the core of the intermediate billet. The internal quality and mechanical properties are improved, and the pass rate of flaw detection is increased.

(3) By controlling the amount of water flow, water pressure, water flow, water flow ratio and the moving speed of the billet on the roller table on the upper surface and the lower surface, the cooling speed, cooling temperature and cooling depth of the upper and lower surfaces of the billet can be basically maintained Consistent, uniform and effective cooling of the billet, so that the deformation of the upper and lower surfaces during rolling is small and consistent, and at the same time avoid low temperature conduction to the core of the billet, ensuring the temperature difference between the upper and lower surfaces of the billet and the core.

(4) The thick steel plate prepared by the rolling method of the thick steel plate provided by the invention, due to the differential temperature rolling in the rolling process, the surface temperature is low, the rolling deformation is small, and the core temperature is high, and the rolling The deformation is large, the porosity and shrinkage cavity in the core are effectively rolled together, with excellent comprehensive mechanical properties and core quality, the pass rate of flaw detection is greatly improved, not only meeting the current industry requirements for high strength and good low temperature toughness of thick steel plates , and can achieve large-scale production of thick steel plates.

Below, the present invention is illustrated in detail in conjunction with examples and comparative examples.

Example 1

In this embodiment, four test examples with serial numbers A, B, C, and D are illustrated, and the specific details of this embodiment will be introduced below.

The selected steel type is Q345B steel, and the continuous casting billet is used. The thickness of the billet is shown in Table 1.

(1) Blank heating process:

The billet is heated, and the heating temperature is 1150-1240°C.

(2) Two-stage rolling and online cooling process in the rolling stage, using two-stage rolling of the billet with two stands, including

a. Rough rolling stage: the heated billet enters the rough rolling mill for 7 passes of rough rolling to obtain an intermediate billet;

Among them, the billet enters the first instant cooling device at the exit of the roughing mill after the 1st, 3rd, and 5th rough rolling for on-line cooling during the rough rolling period. After performing single cooling or reciprocating cooling in the first instant cooling device, Centering on the roller table after the roughing mill, and then return to the roughing mill for the 2nd, 4th, and 6th rough rolling respectively, and enter the first instant cooling device for on-line cooling during the roughing period after the 7th rough rolling After that, it is sent to the finishing mill. The pass reduction and pass reduction rate information of rough rolling are shown in Table 1.

The first instant cooling device is 6400mm long and 3500mm wide. It is equipped with 8 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 1.

b. Finish rolling stage: After rough rolling, the intermediate slab enters the finish rolling mill for 5 passes of finish rolling to produce a thick steel plate. The first pass reduction and the first pass reduction rate information of the finish rolling are shown in Table 1 .

Among them, before the finish rolling stage, the intermediate billet enters the second instant cooling device at the entrance of the finish rolling mill to carry out the on-line cooling process before finish rolling. After performing single cooling or reciprocating cooling in the second instant cooling device, Centered on the roller table, and then the intermediate billet enters the finishing mill for 5 passes of finishing rolling.

The second instant cooling device has a length of 4800mm and a width of 3500mm. It is equipped with 6 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the cooling device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 1.

(3) Cooling process after rolling: the thick steel plate is cooled by an ultra-rapid cooling system.

Flaw detection and mechanical performance testing of thick steel plates, yield strength (Rp0.2), tensile strength (Rm), elongation (A), impact absorption at -20°C at 1/4 and 1/2 of thick steel plates Work (-20°C 222), impact absorption energy at -40°C (-40°C 222 ), average core grain size (μm), flaw detection grade and other information are shown in Table 2. Among them, -20°C 222 and -40°C 222 to measure 3 different parts of the thick steel plate, the 3 measurement data are shown in Table 2, and the metallographic structure photos of test examples A, B, C, and D are shown in Figures 2, 3, 4, and 5, respectively.

[Table 1]

[Table 2]

Example 2

The selected steel type is Q345B steel, and the continuous casting billet is used. The thickness of the billet is shown in Table 3.

(1) Blank heating process:

The billet is heated, and the heating temperature is 1150-1240°C.

(2) Two-stage rolling and online cooling process in the rolling stage, using two-stage rolling of the billet with two stands, including

a. Rough rolling stage: the heated billet enters the rough rolling mill for 7 passes of rough rolling to obtain an intermediate billet;

Among them, the billet enters the first instant cooling device at the exit of the roughing mill after the 1st, 3rd, and 5th rough rolling for on-line cooling during the rough rolling period. After performing single cooling or reciprocating cooling in the first instant cooling device, Centering on the roller table after the roughing mill, and then return to the roughing mill for the 2nd, 4th, and 6th rough rolling respectively, and enter the first instant cooling device for on-line cooling during the roughing period after the 7th rough rolling After that, it is sent to the finishing mill. The pass reduction and pass reduction rate information of rough rolling are shown in Table 3.

The first instant cooling device is 6400mm long and 3500mm wide. It is equipped with 8 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 3.

b. Finish rolling stage: After rough rolling, the intermediate slab enters the finish rolling mill for 5 passes of finish rolling to produce a thick steel plate. The first pass reduction and first pass reduction rate information of the finish rolling are shown in Table 3 .

(3) Cooling process after rolling: using a cooling bed to cool the thick steel plate.

Flaw detection and mechanical performance testing of thick steel plates, yield strength (Rp0.2), tensile strength (Rm), elongation (A), impact absorption at -20°C at 1/4 and 1/2 of thick steel plates The energy (-20°C 222), the impact absorption energy at -40°C (-40°C 222 ), the average grain size of the core (μm), and the flaw detection level are shown in Table 4. Among them, -20°C 222 and -40°C 222 were measured on three different parts of the thick steel plate, the three measurement data are shown in Table 4, and the photo of the metallographic structure of Example 2 is shown in Figure 6.

[table 3]

[Table 4]

Example 3

The selected steel type is Q345B steel, and the continuous casting billet is used. The thickness of the billet is shown in Table 5.

(1) Blank heating process:

The billet is heated, and the heating temperature is 1150-1240°C.

(2) Two-stage rolling and online cooling process in the rolling stage, using two-stage rolling of the billet with two stands, including

a. Rough rolling stage: the heated billet enters the rough rolling mill for 7 passes of rough rolling to obtain an intermediate billet;

Among them, the billet enters the first instant cooling device at the exit of the roughing mill after the 1st, 3rd, and 5th rough rolling for on-line cooling during the rough rolling period. After performing single cooling or reciprocating cooling in the first instant cooling device, Centering on the roller table after the roughing mill, then return to the roughing mill for the 2nd, 4th, and 6th rough rolling respectively, after the 7th rough rolling, pass through the first instant cooling device without cooling, and directly transport to the finishing mill. The pass reduction and pass reduction rate information of rough rolling are shown in Table 5.

The first instant cooling device is 6400mm long and 3500mm wide. It is equipped with 8 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 5.

b. Finish rolling stage: After rough rolling, the intermediate slab enters the finish rolling mill for 5 passes of finish rolling to produce a thick steel plate. The first pass reduction and the first pass reduction rate information of the finish rolling are shown in Table 1 .

Among them, before the finish rolling stage, the intermediate billet enters the second instant cooling device at the entrance of the finish rolling mill to carry out the on-line cooling process before finish rolling. After performing single cooling or reciprocating cooling in the second instant cooling device, Centered on the roller table, and then the intermediate billet enters the finishing mill for 5 passes of finishing rolling.

The second instant cooling device has a length of 4800mm and a width of 3500mm. It is equipped with 6 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the cooling device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 5.

(3) Cooling process after rolling: the thick steel plate is cooled by an ultra-rapid cooling system.

Carry out flaw detection and mechanical performance test to described thick steel plate, measure yield strength (Rp0.2), tensile strength (Rm), elongation (A), -20 The impact absorption energy at ℃ (-20℃222), the impact absorption energy at -40℃ (-40℃222), the average grain size of the core (μm), and the flaw detection level are shown in Table 6. Among them, -20℃222 and -40°C 222 to measure 3 different parts of the thick steel plate respectively. The data of the 3 measurements are shown in Table 6, and the photo of the metallographic structure of Example 3 is shown in Figure 7.

[table 5]

[Table 6]

Example 4

The selected steel type is Q345B steel, and the continuous casting billet is used. The thickness of the billet is shown in Table 7.

(1) Blank heating process:

The billet is heated, and the heating temperature is 1150-1240°C.

(2) Two-stage rolling and online cooling process in the rolling stage, using two-stage rolling of the billet with two stands, including

a. Rough rolling stage: the heated billet enters the rough rolling mill for 7 passes of rough rolling to obtain an intermediate billet;

Among them, the billet enters the first instant cooling device at the exit of the roughing mill after the 1st, 3rd, and 5th rough rolling for on-line cooling during the rough rolling period. After performing single cooling or reciprocating cooling in the first instant cooling device, Centering on the roller table after the roughing mill, and then return to the roughing mill for the 2nd, 4th, and 6th rough rolling respectively, and enter the first instant cooling device for on-line cooling during the roughing period after the 7th rough rolling After that, it is sent to the finishing mill. The pass reduction and pass reduction rate information of rough rolling are shown in Table 7.

The first instant cooling device is 6400mm long and 3500mm wide. It is equipped with 8 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 7.

b. Finish rolling stage: After rough rolling, the intermediate slab enters the finish rolling mill for 5 passes of finish rolling to produce thick steel plates. The first pass reduction and the first pass reduction rate information of the finish rolling are shown in Table 7 .

Among them, before the finish rolling stage, the intermediate billet enters the second instant cooling device at the entrance of the finish rolling mill to carry out the on-line cooling process before finish rolling. After performing single cooling or reciprocating cooling in the second instant cooling device, centered on the roller table, and then the intermediate billet enters the finish rolling mill for 5 passes of finish rolling, wherein, the intermediate billet enters the second instant cooling device after the first and second passes of finish rolling, and is single-passed in the second instant cooling device. After secondary cooling or reciprocating cooling, it is centered on the roller table in front of the finishing mill, and then returns to the finishing mill for the 3rd, 4th, and 5th passes of finishing rolling without entering the second instant cooling device. The finish rolling stage ends after the first finish rolling.

The second instant cooling device has a length of 4800mm and a width of 3500mm. It is equipped with 6 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the cooling device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 7.

(3) Cooling process after rolling: use a cooling bed to cool the thick steel plate.

Flaw detection and mechanical performance testing of thick steel plates, yield strength (Rp0.2), tensile strength (Rm), elongation (A), impact absorption at -20°C at 1/4 and 1/2 of thick steel plates The energy (-20°C 222), the impact absorption energy at -40°C (-40°C 222 ), the average grain size of the core (μm), and the flaw detection grade are shown in Table 8. Among them, -20°C 222 and -40°C 222 were measured on three different parts of the thick steel plate, the three measurement data are shown in Table 8, and the photo of the metallographic structure of Example 4 is shown in Figure 8.

[Table 7]

[Table 8]

Example 5

The selected steel type is Q345B steel, and the continuous casting billet is used. The thickness of the billet is shown in Table 9.

(1) Blank heating process:

The billet is heated, and the heating temperature is 1150-1240°C.

(2) Two-stage rolling and online cooling process in the rolling stage, using two-stage rolling of the billet with two stands, including

a. Rough rolling stage: the heated billet enters the rough rolling mill for 7 passes of rough rolling to obtain an intermediate billet;

Among them, the billet enters the first instant cooling device at the exit of the roughing mill after the 1st, 3rd, and 5th rough rolling for on-line cooling during the rough rolling period. After performing single cooling or reciprocating cooling in the first instant cooling device, Centering on the roller table after the roughing mill, and then return to the roughing mill for the 2nd, 4th, and 6th rough rolling respectively, and enter the first instant cooling device for on-line cooling during the roughing period after the 7th rough rolling After that, it is sent to the finishing mill. The pass reduction and pass reduction rate information of rough rolling are shown in Table 9.

The first instant cooling device is 6400mm long and 3500mm wide. It is equipped with 8 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 9.

b. Finish rolling stage: After rough rolling, the intermediate slab enters the finish rolling mill for 5 passes of finish rolling to produce thick steel plates. The first pass reduction and first pass reduction rate information of finish rolling are shown in Table 9 .

Among them, before the finish rolling stage, the intermediate billet passes through the second instant cooling device at the entrance of the finish rolling mill without cooling, and is centered on the roller table in front of the finish rolling mill, and then the intermediate billet enters the finish rolling mill for the first pass of finish rolling, Among them, the intermediate billet enters the second instant cooling device after the 2nd and 4th passes of finishing rolling respectively, and after performing single cooling or reciprocating cooling in the second instant cooling device, it is centered on the roller table in front of the finishing mill, and then Return to the finish rolling mill to carry out the 3rd and 5th pass finish rolling respectively.

The second instant cooling device has a length of 4800mm and a width of 3500mm. It is equipped with 6 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the cooling device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 9.

(3) Cooling process after rolling: the thick steel plate is cooled by an ultra-rapid cooling system.

Flaw detection and mechanical performance testing of thick steel plates, yield strength (Rp0.2), tensile strength (Rm), elongation (A), impact absorption at -20°C at 1/4 and 1/2 of thick steel plates Work (-20°C 222), impact absorption energy at -40°C (-40°C 222 ), average core grain size (μm), flaw detection grade and other information are shown in Table 10, where -20°C 222 and -40°C 222 were measured on three different parts of the thick steel plate, the three measurement data are shown in Table 10, and the photo of the metallographic structure of Example 5 is shown in Figure 9.

[Table 9]

[Table 10]

Example 6

The selected steel type is Q345B steel, and the continuous casting slab is used. The thickness of the slab is shown in Table 11.

(1) Blank heating process:

The billet is heated, and the heating temperature is 1150-1240°C.

(2) Two-stage rolling and online cooling process in the rolling stage, using two-stage rolling of the billet with two stands, including

a. Rough rolling stage: the heated billet enters the rough rolling mill for 7 passes of rough rolling to obtain an intermediate billet;

Among them, the billet enters the first instant cooling device at the exit of the roughing mill after the 1st, 3rd, and 5th rough rolling for on-line cooling during the rough rolling period. After performing single cooling or reciprocating cooling in the first instant cooling device, Centering on the roller table after the roughing mill, then return to the roughing mill for the 2nd, 4th, and 6th rough rolling respectively, after the 7th rough rolling, pass through the first instant cooling device without cooling, and directly transport to the finishing mill. See Table 11 for rough rolling pass reduction and pass reduction rate information.

The first instant cooling device is 6400mm long and 3500mm wide. It is equipped with 8 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 11.

b. Finish rolling stage: After rough rolling, the intermediate slab enters the finish rolling mill for 5 passes of finish rolling to produce thick steel plates. The first pass reduction and the first pass reduction ratio of the finish rolling are shown in Table 11 .

Among them, before the finish rolling stage, the intermediate billet passes through the second instant cooling device at the entrance of the finish rolling mill without cooling, and is centered on the roller table in front of the finish rolling mill, and then the intermediate billet enters the finish rolling mill for the first pass of finish rolling, Among them, the intermediate billet enters the second instant cooling device after the 2nd and 4th passes of finishing rolling respectively, and after performing single cooling or reciprocating cooling in the second instant cooling device, it is centered on the roller table in front of the finishing mill, and then Return to the finish rolling mill to carry out the 3rd and 5th pass finish rolling respectively.

The second instant cooling device has a length of 4800mm and a width of 3500mm. It is equipped with 6 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the cooling device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 11.

(3) Cooling process after rolling: the thick steel plate is cooled by an ultra-rapid cooling system.

Flaw detection and mechanical performance tests were carried out on thick steel plates, and the yield strength (Rp0.2), tensile strength (Rm), elongation (A), and The impact absorption energy (-20°C 222), the impact absorption energy at -40°C (-40°C 222 ), the average grain size of the core (μm), and the flaw detection level are shown in Table 12. Among them, -20°C 222 and - 40°C and 222 were used to measure 3 different parts of the thick steel plate. The data of the 3 measurements are shown in Table 12. For the photo of the metallographic structure of Example 6, see Figure 10.

[Table 11]

[Table 12]

Example 7

The selected steel type is Q345B steel, and the continuous casting billet is used. The thickness of the billet is shown in Table 13.

(1) Blank heating process:

The billet is heated, and the heating temperature is 1150-1240°C.

(2) Two-stage rolling and online cooling process in the rolling stage, using two-stage rolling of the billet with two stands, including

a. Rough rolling stage: the heated billet enters the rough rolling mill for 7 passes of rough rolling, and after the 7th pass of rough rolling, it enters the first instant cooling device for online cooling during the rough rolling period, and then the intermediate billet is produced and transported to the finishing mill. See Table 13 for rough rolling pass reduction and pass reduction rate information.

The first instant cooling device is 6400mm long and 3500mm wide. It is equipped with 8 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 13.

b. Finish rolling stage: After rough rolling, the intermediate slab enters the finish rolling mill for 5 passes of finish rolling to produce a thick steel plate. The first pass reduction and the first pass reduction ratio of the finish rolling are shown in Table 13 .

Among them, before the finish rolling stage, the intermediate billet passes through the second instant cooling device at the entrance of the finish rolling mill without cooling, and is centered on the roller table in front of the finish rolling mill, and then the intermediate billet enters the finish rolling mill for the first pass of finish rolling, Among them, the intermediate billet enters the second instant cooling device after the 2nd and 4th passes of finishing rolling respectively, and after performing single cooling or reciprocating cooling in the second instant cooling device, it is centered on the roller table in front of the finishing mill, and then Return to the finish rolling mill to carry out the 3rd and 5th pass finish rolling respectively.

The second instant cooling device has a length of 4800mm and a width of 3500mm. It is equipped with 6 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the cooling device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 13.

(3) Cooling process after rolling: use a cooling bed to cool the thick steel plate.

Flaw detection and mechanical performance tests were carried out on thick steel plates, and the yield strength (Rp0.2), tensile strength (Rm), elongation (A), and The impact absorption energy (-20°C 222), the impact absorption energy at -40°C (-40°C 222 ), the average grain size of the core (μm), and the flaw detection grade are shown in Table 14. Among them, -20°C 222 and - 40°C and 222 were used to measure 3 different parts of the thick steel plate. The data of the 3 measurements are shown in Table 14. For the photo of the metallographic structure of Example 7, see Figure 11.

[Table 13]

[Table 14]

Example 8

The selected steel type is Q345B steel, and the continuous casting billet is used. The thickness of the billet is shown in Table 15.

(1) Blank heating process:

The billet is heated, and the heating temperature is 1150-1240°C.

(2) Two-stage rolling and online cooling process in the rolling stage, using two-stage rolling of the billet with two stands, including

a. Rough rolling stage: the heated billet enters the rough rolling mill for 7 passes of rough rolling to obtain an intermediate billet;

The intermediate billet passes through the first instant cooling device but is not cooled, and is directly transported to the finishing mill. See Table 15 for rough rolling pass reduction and pass reduction rate information.

b. Finish rolling stage: After rough rolling, the intermediate slab enters the finish rolling mill for 5 passes of finish rolling to produce a thick steel plate. See Table 15 for information on the first pass reduction and the first pass reduction rate of the finish rolling .

Among them, before the finish rolling stage, the intermediate billet enters the second instant cooling device at the entrance of the finish rolling mill to carry out the on-line cooling process before finish rolling. After performing single cooling or reciprocating cooling in the second instant cooling device, centered on the roller table, and then the intermediate billet enters the finishing mill for 5 passes of finishing rolling. Among them, the intermediate billet enters the second instant cooling device after the 2nd and 4th pass of finishing rolling, and is carried out in the second instant cooling device. After single cooling or reciprocating cooling, center on the roller table in front of the finishing mill, and then return to the finishing mill for the 3rd and 5th pass finishing rolling respectively.

The second instant cooling device has a length of 4800mm and a width of 3500mm. It is equipped with 6 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the cooling device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 15.

(3) Cooling process after rolling: the thick steel plate is cooled by an ultra-rapid cooling system.

Flaw detection and mechanical performance testing of thick steel plates, yield strength (Rp0.2), tensile strength (Rm), elongation (A), impact absorption at -20°C at 1/4 and 1/2 of thick steel plates Work (-20°C 222), impact absorption energy at -40°C (-40°C 222 ), average core grain size (μm), flaw detection grade and other information are shown in Table 16. Among them, -20°C 222 and -40°C 222 to measure 3 different parts of the thick steel plate, the 3 measurement data are shown in Table 16, and the photo of the metallographic structure of Example 8 is shown in Figure 12.

[Table 15]

[Table 16]

Example 9

The selected steel type is Q345B steel, and the continuous casting slab is used. The thickness of the slab is shown in Table 17.

(1) Blank heating process:

The billet is heated, and the heating temperature is 1150-1240°C.

(2) Two-stage rolling and online cooling process in the rolling stage, using two-stage rolling of the billet with two stands, including

a. Rough rolling stage: the heated billet enters the rough rolling mill for 7 passes of rough rolling, and after the 7th pass of rough rolling, it enters the first instant cooling device for online cooling during the rough rolling period, and then the intermediate billet is produced and transported to the finishing mill. See Table 17 for rough rolling pass reduction and pass reduction rate information.

The first instant cooling device is 6400mm long and 3500mm wide. It is equipped with 8 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 17.

b. Finish rolling stage: After rough rolling, the intermediate billet enters the finish rolling mill for 5 passes of finish rolling to produce thick steel plates. For information on the first pass reduction and the first pass reduction rate of finish rolling, see Table 17 .

Among them, before the finish rolling stage, the intermediate billet enters the second instant cooling device at the entrance of the finish rolling mill to carry out the on-line cooling process before finish rolling. After performing single cooling or reciprocating cooling in the second instant cooling device, centered on the roller table, and then the intermediate billet enters the finish rolling mill for 5 passes of finish rolling, wherein, the intermediate billet enters the second instant cooling device after the first and second passes of finish rolling, and is single-passed in the second instant cooling device. After secondary cooling or reciprocating cooling, it is centered on the roller table in front of the finishing mill, and then returns to the finishing mill for the 3rd, 4th, and 5th passes of finishing rolling without entering the second instant cooling device. The finish rolling stage ends after the first finish rolling.

The second instant cooling device has a length of 4800mm and a width of 3500mm. It is equipped with 6 sets of upper headers and lower headers corresponding to each other. The hydraulic pressure of the upper headers and lower headers is 0.5MPa. The moving speed on the roller table of the cooling device, the water flow of the upper header, the water flow of the lower header, and the water flow ratio of the lower and upper headers are shown in Table 17.

(3) Cooling process after rolling: the thick steel plate is cooled by an ultra-rapid cooling system.

Flaw detection and mechanical performance testing of thick steel plates, yield strength (Rp0.2), tensile strength (Rm), elongation (A), impact absorption at -20°C at 1/4 and 1/2 of thick steel plates Work (-20°C 222), impact absorption energy at -40°C (-40°C 222 ), average core grain size (μm), flaw detection grade and other information are shown in Table 18. Among them, -20°C 222 and -40°C 222 to measure 3 different parts of the thick steel plate, the 3 measurement data are shown in Table 18, and the photo of the metallographic structure of Example 9 is shown in Figure 13.

[Table 17]

[Table 18]

comparative example

Four comparative test examples whose serial numbers are E, F, G, and H are illustrated in the comparative examples, and the specific details of the comparative examples are introduced below.

The selected steel type is Q345B steel, and the continuous casting billet is used. The thickness of the billet is shown in Table 19.

(1) Blank heating process:

The billet is heated, and the heating temperature is 1150-1240°C.

(2) Two-stage rolling process, using double stands to roll the billet in two stages, including

a. Rough rolling stage: the heated billet enters the rough rolling mill for 7 passes of rough rolling to obtain an intermediate billet, and then enters the finish rolling stage after air cooling on the roller table. Among them, the pass reduction, pass reduction rate and intermediate billet thickness information of rough rolling are shown in Table 19.

b. Finish rolling stage: After rough rolling, the intermediate billet enters the finish rolling mill for 5 passes of finish rolling to produce thick steel plates. The first pass reduction of the finish rolling, the reduction rate of the first pass and the thickness information of the steel plate See Table 19.

(3) Cooling process after rolling: use ultra-rapid cooling system or cooling bed to cool the thick steel plate.

Flaw detection and mechanical performance tests were carried out on thick steel plates, and the yield strength (Rp0.2), tensile strength (Rm), elongation (A), and The impact absorption energy (-20°C 222), the impact absorption energy at -40°C (-40°C 222 ), the average grain size of the core (μm), and the flaw detection grade are shown in Table 20. Among them, -20°C 222 and - 40°C and 222 were used to measure three different parts of the thick steel plate. The three measurement data are shown in Table 20. The metallographic photos of comparative test examples E, F, G, and H are shown in Figures 14, 15, 16, and 17, respectively.

[Table 19]

serial number E. f G h Blank thickness (mm) 320 320 270 220 Rough rolling pass reduction (mm) ≥20 ≥20 ≥20 ≥20 Rough rolling pass reduction rate (%) ≥10 ≥10 ≥10 ≥10 Intermediate billet thickness (mm) 190 160 160 120 Rolling reduction in the first pass of finish rolling (mm) ≥12 ≥12 ≥12 ≥12 Rolling reduction in the first pass of finish rolling (%) ≥12 ≥12 ≥12 ≥12 Thick steel plate thickness (mm) 150 120 110 90

[Table 20]

Claims (13)

1. A rolling method for a thick steel plate, comprising sequentially carried out billet heating, two-stage rolling and cooling after rolling, wherein the two-stage rolling process includes a rough rolling stage and a finish rolling stage, in the In the rough rolling stage, the billet is subjected to a plurality of rough rolling passes, and the rolling method further includes performing an on-line cooling process on the billet during rough rolling after at least two or all odd passes of rough rolling . 2. The rolling method of thick steel plate according to claim 1, characterized in that, in the finish rolling stage, the billet is subjected to a plurality of passes of finish rolling; The rolling method also includes performing an on-line cooling process on the billet before the finish rolling stage before the finish rolling stage, and/or, performing on-line cooling on the billet during the finish rolling period after at least one even-numbered pass or all even-numbered passes. process. 3. The rolling method of thick steel plate according to claim 2, characterized in that, in any one of the online cooling process during the rough rolling period, the online cooling process before the finish rolling, and the online cooling process during the finish rolling period or several of them, supply water to cool the upper and lower surfaces of the billet, wherein the water pressure is 0.5MPa, the water flow rate on the upper surface is 60-120m ³ /h/strand, and the water flow rate on the lower surface is 120-240m ³ / h/strand, the water flow ratio between the lower surface and the upper surface is ≥2, and the moving speed of the billet is 0.5-5m/s. 4. The method for rolling a thick steel plate according to claim 2, wherein any one of the on-line cooling process during the rough rolling period, the on-line cooling process before the finish rolling, and the on-line cooling process during the finish rolling period In one or more of them, the cooling rate, cooling temperature and cooling depth of the upper surface and the lower surface of the billet are the same. 5. A rolling method for a thick steel plate, comprising a sequence of billet heating, two-stage rolling and cooling after rolling, wherein the two-stage rolling process includes a rough rolling stage and a finish rolling stage, in the In the finish rolling stage, the billet is subjected to multiple passes of finish rolling, and the rolling method further includes performing an online cooling process on the billet before the finish rolling stage, and/or, in at least one After even-numbered passes or all even-numbered passes are finished-rolled, the billet is subjected to an online cooling process during the finish-rolling period. 6. A method for rolling a thick steel plate, comprising the steps of: Blank heating; Two-stage rolling is carried out on the heated billet with double stands; among them, the billet is firstly subjected to multiple passes of rough rolling through the rough rolling mill, and then finished rolled into a thick steel plate through the finishing mill; The thick steel plate is cooled; it is characterized in that, During the two-stage rolling, after rough rolling for at least two or all odd passes, the billet leaves the roughing mill and enters the first instant cooling device for on-line cooling during the roughing period, after which the billet returns to the roughing The rolling mill performs even-numbered passes roughing or feeds to the finishing mill. 7. The rolling method of thick steel plate according to claim 6, characterized in that, when the billet passes through the first immediate cooling device, the upper header of the first immediate cooling device is filled with a water pressure of 0.5 MPa. The upper surface of the billet is supplied with water for cooling at a water flow rate of 60-120m ³ /h, and the lower header of the first instant cooling device supplies water to the upper surface of the billet with a water pressure of 0.5MPa and a water flow rate of 120-240m ³ /h. The lower surface is cooled by water supply, the water flow ratio of the lower header and the upper header is ≥2, and the moving speed of the billet on the roller table is 0.5-5m/s. 8. The rolling method of thick steel plate according to claim 7, characterized in that, the roller table of the first instant cooling device is 6400mm long and 3500mm wide, and has 8 sets of one-to-one corresponding upper headers and lower headers . 9. The rolling method of thick steel plate according to claim 6, characterized in that, the billet is subjected to a plurality of passes of finish rolling by a finish rolling mill; During the two-stage rolling, after the billet leaves the first instant cooling device and before entering the finish rolling mill, the second instant cooling device is used to perform an online cooling process before finish rolling, and/or, in the two-stage During rolling, after at least one even-numbered pass or all even-numbered passes are finished rolling, the billet leaves the finishing mill and enters the second instant cooling device for on-line cooling during the finish rolling period, and then returns the billet to the finishing mill for odd-numbered passes Finish rolling. 10. The rolling method of thick steel plate according to claim 9, characterized in that, when the billet passes through the second immediate cooling device, the upper header of the second immediate cooling device is filled with a water pressure of 0.5 MPa. The upper surface of the billet is supplied with water for cooling at a water flow rate of 60-120m ³ /h, and the lower header of the second instant cooling device supplies water to the upper surface of the billet with a water pressure of 0.5MPa and a water flow rate of 120-240m ³ /h. The lower surface is cooled by water supply, the water flow ratio of the lower header and the upper header is ≥2, and the moving speed of the billet on the roller table is 0.5-5m/s. 11. The rolling method of thick steel plate according to claim 10, characterized in that, the roller table of the second instant cooling device is 4800 mm long and 3500 mm wide, and has 6 sets of one-to-one corresponding upper headers and lower headers . 12. A method for rolling a thick steel plate, comprising the steps of: Blank heating; Two-stage rolling is carried out on the heated billet with double stands; among them, the billet is firstly rough-rolled through the rough rolling mill, and then passed through the finishing mill for multiple passes of finish rolling to produce thick steel plates; The thick steel plate is cooled; it is characterized in that, During the two-stage rolling, after the billet leaves the first instant cooling device and before entering the finish rolling mill, the second instant cooling device is used to perform an online cooling process before finish rolling, and/or, during the two-stage rolling During this period, after at least one even-numbered pass or all even-numbered passes, the billet leaves the finishing mill and enters the second instant cooling device for an online cooling process during the finish rolling period, and then the billet returns to the finishing mill for odd-numbered passes. . 13. A thick steel plate, characterized in that the thick steel plate is prepared by the rolling method according to any one of claims 1-12.