CN114798736A - Method for producing thin-specification patterned steel plate by thin slab continuous casting and rolling process - Google Patents

Abstract

The invention discloses a method for producing thin-gauge patterned steel plates through a thin slab continuous casting and rolling process, belonging to the technical field of low-carbon steel patterned steel plates. , the continuous rolling includes rough rolling, induction heating and finishing rolling; the thickness of the continuous casting process is 90-110 mm, the fan-shaped section is rapidly cooled by high-pressure water in the front section, and the rear section is cooled by aerosol; In the rolling process, the rough rolling outlet temperature is 950-1100°C; the finishing rolling outlet temperature is 740-810°C; the thickness range of the pattern steel plate obtained at the end of the finish rolling stand outlet is 0.8-6.0mm; the coiling temperature is 600-700°C. Compared with the prior art, on the basis of reducing energy consumption, the structure uniformity and bean height and bean shape of the thin-gauge strip steel after deformation are improved, and a patterned steel plate with uniform performance is obtained.

Description

A method for producing thin-gauge patterned steel plate by thin slab continuous casting and rolling process

technical field

The invention relates to the technical field of low-carbon steel patterned steel plate production, in particular to a method for producing thin-sized patterned steel plates by using a ferrite rolling process based on a thin slab continuous casting and rolling process.

Background technique

In recent years, the steel market has continued to decline, competition in the steel industry has been fierce, and domestic attention has also been paid to environmental protection issues. Therefore, it is necessary for the steel industry to explore cost-reducing and environmentally friendly production processes. Therefore, making full use of the thin slab continuous casting and rolling process to develop and apply new products is in line with the overall national plan and industry needs.

At present, there are many researches on the production of thin-sized patterned steel plates based on the continuous casting and rolling process of thin slabs, such as "A Method for Producing Patterned Plates with a Thickness of 1.4mm by CSP Process" (Publication No. CN107716552B), and our company's "ESP-based method" The method of producing thin-sized patterned steel plate by continuous casting and rolling process of thin slab" (publication number CN106077090B), both of which adopt the whole process of austenite zone rolling. When the deformation resistance is large, it is very difficult to roll thin checkered plates. Therefore, after rough rolling, the cast slab in the prior art needs to be heated to 1120-1180°C in an induction heating furnace, and the finish rolling outlet temperature is ≥850°C. Part or most of the steel is deformed in the high-temperature austenite region with low deformation resistance, but this rolling method consumes a lot of energy. When the exit temperature of finishing rolling is 850℃, the steel is low-temperature austenite and part of ferrite, and the strength of the steel is large, which requires a large rolling force and reduction ratio (20% to 25%), which further increases the energy consumption cost and Increase the wear of the work rolls and shorten the online service time.

The ferritic rolling process is a controlled rolling technology for low carbon series steels. Finish rolling. This process has the advantages of low heating temperature, low rolling temperature and small temperature loss, and can produce thin-gauge hot-rolled low carbon steel, which is the best choice for reducing production costs and increasing product profits. However, when the ferritic rolling process is introduced into the company's existing thin slab continuous casting and rolling process to produce the thin-gauge patterned steel plate process (CN106077090B), some or most of the finishing rolling units will be in low-temperature iron with low steel deformation resistance. Rolling in the temperature range of the element body, the temperature of the surface and edge of the strip is low, and the friction force is large, resulting in small deformation of the intermediate billet to the finished strip and uneven structure; the bean height is too small, the bean shape is not full, and the strength is too high , the defect of low elongation; and the temperature of the edge of the strip is low, the wear of the work roll is large, and it cannot be mass-produced for a long time. The above defects limit further energy saving, emission reduction, cost reduction and efficiency increase in the production of thin-gauge patterned steel plates.

SUMMARY OF THE INVENTION

The technical task of the present invention is to aim at the deficiencies of the above prior art, to provide a method for producing thin-gauge patterned steel plates by thin slab continuous casting and rolling process, which can realize the production of thin-gauge patterned steel plates of 0.9-1.5 mm, shorten the production cycle, and adopt The low-temperature ferrite process can effectively reduce production costs, save energy and protect the environment.

The technical scheme of the present invention to solve the technical problem is as follows: a method for producing a thin-sized patterned steel plate by a thin slab continuous casting and rolling process, including smelting, continuous casting, continuous rolling, and coiling to make patterned steel plates of different thicknesses. The continuous rolling includes rough rolling, induction heating and finishing rolling; it is characterized in that: in the continuous casting process, the thickness of the cast slab is 90-110 mm, the fan-shaped section is rapidly cooled by high-pressure water in the front section, and the rear section is cooled by aerosol; the In the continuous rolling process, the rough rolling outlet temperature is 950-1100°C; the finishing rolling outlet temperature is 740-810°C; the thickness range of the pattern steel plate obtained at the end of the finish rolling stand outlet is 0.8-6.0mm; the coiling temperature is 600-700°C.

Further, in the above-mentioned smelting process, the C content is controlled at 0.01-0.05%.

Further, in the above continuous casting process, the front section of the fan-shaped section is rapidly cooled by high-pressure water, the water pressure is 10-20 bar, and the water volume accounts for 75-85% of the total cooling water volume.

Further, the above-mentioned finishing rolling inlet temperature is 870-1000°C.

Further, the upper work rolls of the above-mentioned finishing rolling stand are patterned rolls, the patterned rolls are formed by flat roll engraving rolls, and the lower work rolls are ordinary concave rolls, with a convexity of -30 to -70 μm.

Further, dynamic roll shifting is applied to the above-mentioned finishing stand.

Further, the above-mentioned finishing rolling stand should be lubricated rolling.

Further, the oil-water ratio of the organic lubricating liquid used in the above-mentioned lubricating rolling is 1:50.

Further, the reduction ratio of the above-mentioned finishing rolling stand is 14-20%.

Further, the thickness range of the pattern steel plate obtained at the outlet of the above-mentioned finishing rolling stand is 0.9-1.5 mm.

Compared with the prior art, the present invention has the following outstanding beneficial effects:

1. The present invention is based on the thin slab continuous casting and rolling technology, eliminating the need for slab transportation and reheating, multi-pass repeated rolling and other processes. The production process is shorter than the traditional hot continuous rolling, and at the same time, it is shorter than the thin strip continuous casting and rolling single rolling. Large output and high production efficiency;

2. The present invention can realize the production of thinner-thickness patterned steel plate, 0.9-1.5mm thickness patterned steel plate, of which the ratio of ≤1.2mm thickness specification is more than 50%, which can be directly applied to the market and shorten the product cycle;

3. The present invention adopts a lower finishing rolling outlet temperature (740-810°C), so that part or most of the finishing rolling unit can be rolled in the low temperature ferrite temperature range with less steel deformation resistance; The 1100-1200°C required for intensitic rolling production is reduced to 870-1000°C, which greatly reduces the heating cost and saves power consumption. It is an energy-saving and environmentally friendly production process;

4. The present invention adopts a straight arc type high-speed continuous casting machine. The fan-shaped section of the continuous casting machine adopts rapid cooling in the front section and aerosol cooling in the rear section. The deformation resistance of the steel during the rolling process; it lays the foundation for the subsequent rolling in the low temperature ferrite temperature range of the finishing mill;

5. The present invention adopts the rolling lubrication and dynamic shifting of the final stand to improve the microstructure uniformity and bean-to-high bean shape of the thin-gauge strip after deformation, and obtain a patterned steel plate with uniform performance, which overcomes the problem of low-temperature rolling under the final stand. The rapid cooling of the outlet strip deformation leads to too small and uneven grains, as well as poor shape caused by residual stress, so as to obtain better shape and formability.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

For the purposes of the following detailed description, it should be understood that the invention is capable of various alternative modifications and order of steps unless explicitly indicated to the contrary. Furthermore, except in any working example or where otherwise indicated, all numbers representing quantities of ingredients such as used in the specification and claims should in all instances be understood to be modified by the term "about". At the very least, and not as an attempt to limit the application of the principle of equivalence to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

It is also to be understood that any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges between (and including) the stated minimum value of 1 and the stated maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

In this application, unless specifically stated otherwise, the use of the singular includes the plural and the plural encompasses the singular. Also, in this application, the use of "or" means "and/or" unless expressly stated otherwise, even though "and/or" may be expressly used in certain circumstances. Further, in this application, the use of "a" or "an" means "at least one" unless specifically stated otherwise. For example, "a" first material, "a" coating composition, etc., refers to one or more of any of these items.

The chemical composition and mass percentage content of the pattern steel plate of the present invention are: C: 0.01-0.05%, Si: 0.01-0.1%, Mn: 0.06-0.3%, P<0.035%, S<0.006%, N<0.006%, and the rest are: Fe and inevitable impurities.

Key ingredient control description of the present invention:

C: C has a significant effect on the transformation point of steel, and is one of the key elements that determine the ferrite rolling process window. Generally, with the increase of C content, the ferrite temperature range decreases, and austenite turns to ferrite phase. The variable temperature decreases. If the C element content is controlled too low, the smelting cost will be greatly increased. The research shows that the average deformation resistance of low carbon steel is almost equal to the rolling deformation resistance in the austenite temperature range (900-1010℃) and the ferrite temperature range (750-840℃), and the C content is greater than 0.05% When the low carbon steel is rolled by ferrite, the deformation resistance is too large, the structure of the finished product is uneven, and the elongation is low. When the C content is in the range of 0.06% to 0.15%, the molten steel solidification process is affected by the peritectic reaction, which makes the surface of the cast slab prone to cracks, which may cause a breakout accident in severe cases, and an excessively high C content is unfavorable to the welding performance. Therefore, the present invention uses C The content is controlled at 0.01-0.05%.

N: N atoms have two forms of existence, one is in a solid solution state, and the other is in a precipitation state. The solid solution N seriously affects the formability of steel, and after the interaction of N atoms and dislocations to form Coriolis gas clusters, it affects the strain aging of steel. Therefore, the present invention controls the N content to be less than 0.006%.

Mn: Mn has a solid solution strengthening effect, which can expand the γ region, reduce the γ→α transformation temperature, and refine the grains. Mn can also delay the transformation of pearlite, which is beneficial to the formation of bainite. Therefore, the present invention controls the Mn content to be 0.06-0.3%.

P and S: P and S are residual harmful elements in molten iron, so the present invention ensures the production stability and formability of steel, P<0.035%, S<0.006%.

The technological process route of the invention is as follows: smelting, continuous casting, continuous rolling, and coiling to make pattern steel plates of different thicknesses. The specific method is as follows:

S1: Smelting

The raw materials are smelted in converter and LF furnace to obtain molten steel; the chemical composition and mass percentage content of molten steel are: C: 0.01-0.05%, Si: 0.01-0.1%, Mn: 0.06-0.3%, P<0.035%, S<0.006 %, N<0.006%, and the rest are Fe and inevitable impurities.

S2: Continuous casting

A straight arc type high-drawing speed continuous casting machine is used, and the molten steel obtained from smelting enters the continuous casting machine to obtain the slab; the slab thickness is 90-110 mm, and the drawing speed is related to the slab thickness. The billet pulling speed should be low. In this embodiment, the casting billet is 110 mm, and the pulling speed is in the range of 3.8 to 5.8 m/min.

The fan-shaped section is rapidly cooled by high-pressure water in the front section, the water pressure is 10-20 bar, and the water volume accounts for 75-85% of the total cooling water volume;

In the latter stage, aerosol cooling is applied to make full use of the reverse temperature field with high temperature in the core of the billet to improve the uniformity of the structure of the billet; and the heat from the core of the billet diffuses to the surface to reduce the temperature loss during the production of the billet.

S3: Continuous rolling

Specifically, it includes: rough rolling→induction heating→high pressure descaling→finishing rolling.

Rough rolling: the outlet temperature of rough rolling is 950～1100℃; the thickness of the intermediate billet is 9～18mm. The higher rough rolling outlet temperature setting makes full use of the heat diffused from the core of the billet to the surface, and the higher heat storage in the core of the billet during the continuous casting process can be utilized, and the temperature distribution of the billet presents a reverse temperature of the high core temperature. It reduces the deformation resistance of the steel during the rolling process of the roughing mill, improves the uniformity of the structure after deformation, and lays a foundation for the subsequent rolling in the finishing mill in the low-temperature ferrite temperature range.

Finishing:

(1) The inlet temperature of finishing rolling is 870~1000℃, and the control range of outlet temperature is 740~810℃. The purpose of controlling the exit temperature of finishing rolling is achieved by adjusting the outlet temperature setting of the induction heating furnace. Part or all of the finishing rolling mill is rolled in the low-temperature ferrite temperature range where the steel deformation resistance is small, which greatly reduces the heating cost and saves power consumption. It is an energy-saving and environmentally friendly production process;

(2) The upper work roll of the finishing stand adopts pattern roll, the pattern roll is formed by flat roll engraved roll, the lower work roll adopts ordinary concave roll, the convexity is -30～-70μm, and the roll shape length is about 1330mm in the embodiment. For the production of patterned steel plates with a width of 1250mm;

(3) Dynamic roll shifting is applied to the finishing stand (F5) to compensate for the adverse effects of uneven local wear of the work rolls during use, which is conducive to maintaining the original roll shape of the work rolls and improving the shape of the strip;

(4) The last stand (F5) should be lubricated and rolled with a rolling lubricant of 100:5000 (ml, oil-water ratio, organic lubricant) to reduce the damage to the bean-shaped roll during the bean-shaped demoulding process on the surface of the checker plate. Reduce the rolling load, reduce the friction between the strip and the work rolls, prolong the service life of the work rolls, and effectively increase the output of thin-gauge pattern plates. And it helps to improve the surface quality of the strip, reduce the power consumption of the rolling machine, and at the same time improve the uniformity of the structure of the thin-gauge strip after deformation, and obtain a patterned steel plate with uniform performance;

(5) The reduction ratio of the finishing stand (F5) is 14-20%, and the thickness of the pattern steel plate available at the F5 outlet is 0.8-6.0mm. The thickness is preferably 0.9 to 1.5 mm.

S4: Coiling

The coiling temperature is 600 to 700°C.

The present invention adopts higher coiling temperature setting and lower finishing rolling outlet temperature setting to achieve the effect of laminar cooling without water cooling, and can also be implemented by turning off laminar cooling and disabling the function of the equipment. Avoid the residual cooling water on the upper surface of the patterned steel plate due to the obstruction of the bean height, resulting in uneven cooling of the strip and excessive residual stress resulting in poor plate shape. After the strip steel at the exit of the last stand is deformed, it is completely cooled by the heat transfer between the strip steel and the air and the contacting equipment, so as to avoid the rapid cooling of the strip steel at the exit of the last stand, which will cause the grains to be too small and uneven, and promote the ferrite grains. of growing up. At the same time, the higher coiling temperature is conducive to the release of the internal stress after the strip is coiled, so as to obtain better plate shape and formability.

Finally, 0.9-1.5mm thin patterned steel plate is obtained.

In order to better compare the present application with the prior art, comparative experiments were carried out.

Embodiments 1 to 4 are the composition design and production process of the application.

The control group adopts the composition design of Example 1, combined with the process plan in the company's patent "Method for producing thin-sized patterned steel plates based on ESP thin slab continuous casting and rolling process" (publication number CN106077090B). On the basis of fog cooling, the cooling water can be strengthened, or the fan-shaped section mode can be extended to obtain a lower rough rolling outlet temperature (800-860 °C). The coiling cooling method is to pass through the bottom cooling of the layer cooling system and the upper part of the layer cooling system in sequence, but the finishing rolling part is rolled in the low temperature ferrite temperature range.

1. Each component design:

2. Refer to the following table for the control of production parameters of each group:

The comparison results are shown in the table below:

It can be seen from the above results that, using each example group of the present invention, the thinnest patterned steel plate with a thickness of 0.9 mm can be produced. 1.2mm thickness patterned steel plate, the measured substrate thickness is 1.199mm, and the bean height is 0.220mm, which meets the market customer needs of thin patterned steel plate. The rolling process with the number of continuous casting furnaces (about 2300t molten steel) produces more than 1300 tons of patterned steel plates with 1.2mm specification, which meets the industrialized continuous production. In the control group, traditional continuous casting and rough rolling were used, and low-temperature ferrite rolling was only improved in the finishing rolling part, and the adjustment of the final stand (F5) was not carried out. As a result, the surface of the steel plate was obviously rough and the bean height It is too small, the bean shape is not full, and the strength is too high, and the elongation is low, which cannot meet the performance requirements.

It should be noted that the specific embodiments of the present invention have been described in detail, and for those skilled in the art, various obvious changes can be made to it without departing from the spirit and scope of the present invention. within the protection scope of the present invention.

Claims (10)

1. A method for producing thin-gauge pattern steel plates by a thin slab continuous casting and rolling process comprises the steps of smelting, continuous casting, continuous rolling and coiling to prepare pattern steel plates with different thicknesses, wherein the continuous rolling comprises rough rolling, induction heating and finish rolling; the method is characterized in that: in the continuous casting process, the thickness of a casting blank is 90-110 mm, the sector section is rapidly cooled by high-pressure water at the front section, and the rear section is cooled by aerial fog; the outlet temperature of the rough rolling in the continuous rolling procedure is 950-1100 ℃; the outlet temperature of the finish rolling is 740-810 ℃; the thickness range of the pattern steel plate obtained at the outlet of the finish rolling final stand is 0.8-6.0 mm; the coiling temperature is 600-700 ℃.

2. The method for producing a thin gauge pattern steel sheet according to the thin slab continuous casting and rolling process of claim 1, wherein: in the smelting process, the content of C is controlled to be 0.01-0.05%.

3. The method for producing a patterned thin steel sheet according to claim 1, wherein the method comprises the steps of: in the continuous casting process, high-pressure water at the front section of the fan-shaped section is rapidly cooled, the water pressure is 10-20 bar, and the water amount accounts for 75-85% of the total cooling water amount.

4. The method for producing a patterned thin steel sheet according to claim 1, wherein the method comprises the steps of: and the finish rolling inlet temperature is 870-1000 ℃.

5. The method for producing a patterned thin steel sheet according to claim 1, wherein the method comprises the steps of: the upper working roll of the last finish rolling machine frame adopts a patterned roll, the patterned roll is formed by a flat roll and a carving roll, the lower working roll adopts a common concave roll, and the convexity is-30 to-70 mu m.

6. The method for producing a patterned thin steel sheet according to claim 1, wherein the method comprises the steps of: the finish rolling end stand employs dynamic roll shifting.

7. The method for producing a patterned thin steel sheet according to claim 1, wherein the method comprises the steps of: the finish rolling end stand is lubricated for rolling.

8. The method for producing a patterned thin steel sheet according to claim 7, wherein the method comprises the steps of: the oil-water ratio of the organic lubricating liquid used for the lubricating rolling is 1: 50.

9. The method for producing a patterned thin steel sheet according to claim 1, wherein the method comprises the steps of: the reduction rate of the finish rolling end frame is 14-20%.

10. The method for producing a patterned thin steel sheet according to claim 1, wherein the method comprises the steps of: the thickness range of the pattern steel plate obtained at the outlet of the finish rolling final stand is 0.9-1.5 mm.