WO2022062176A1

WO2022062176A1 - Ew 420 extra thick marine steel sheet and manufacturing method therefor

Info

Publication number: WO2022062176A1
Application number: PCT/CN2020/133458
Authority: WO
Inventors: 车马俊; 赵晋斌; 陈林恒; 张晓雪; 李恒坤; 邱保文; 伯飞虎; 黄建华
Original assignee: 南京钢铁股份有限公司
Priority date: 2020-09-24
Filing date: 2020-12-02
Publication date: 2022-03-31
Also published as: AU2020470046A1; CN112501494A; AU2020470046B2

Abstract

An EW 420 extra thick marine steel sheet, which relates to the technical field of steel production. Internal defects such as blank segregation and loosening are reduced and the inclusion elements As, Sn, Sb, Pb, Bi and B are controlled by smelting clean steel; columnar crystals are crushed and austenite grains are refined by means of rough rolling at high temperature, at a low speed and under high pressure; and the objective of controlling tissue morphology and grain size is obtained by means of finish rolling cumulative deformation and cooperative cooling control.

Description

A kind of EW420 extra-thick marine steel plate and its manufacturing method

technical field

The invention relates to the technical field of iron and steel production, in particular to an EW420 extra-thick marine steel plate and a manufacturing method thereof.

Background technique

The development of offshore oil in my country started relatively late, and it was only in the 1980s that it had its own offshore oil platform. In the past 10 years, domestic offshore platform steel plates have only been widely used in my country's offshore oil projects. At present, my country has basically achieved localization of steel used for offshore platforms below EH36 level, accounting for 90% of the steel used for platforms. With the gradual implementation of the project, the field of marine engineering equipment and high-tech ships will vigorously develop deep-sea exploration, resource development and utilization, marine operation support equipment and its key systems and special equipment; to promote the development and engineering of deep-sea space stations and large floating structures, it is inevitable The demand and requirements for steel for offshore platforms are also expanding, gradually developing towards high strength and thick specifications.

Traditional offshore enterprises have very high requirements on the performance uniformity and performance fluctuation value of 420MPa grade offshore steel, and generally require delivery in quenched and tempered state. Small line energy welding. With the high-quality development of the offshore equipment industry, the requirements for the welding performance of steel plates are getting higher and higher, and with the intelligent and large-scale rolling equipment of iron and steel enterprises, the TMCP-state easy-to-weld offshore steel is gradually favored by downstream customers. accept.

The invention patent No. CN 104674117 A provides a 420MPa grade marine engineering steel plate and its manufacturing method. The inclusion elements As, Sn, Sb, Pb, Bi, and B are not effectively controlled, and the smelting process is passed by, and there is no practical For maneuverability, the actual maximum thickness can only be up to 80mm. Similarly, the invention patent No. CN 104357742 A provides a large-thickness hot-rolled steel sheet for marine engineering with a level of 420MPa and a production method thereof. The inclusion elements As, Sn, Sb, Pb, Bi, and B are not effectively controlled, and the actual thickness is 70mm. , and it is produced by the electric furnace process. The two patents do not specify the content of Cr, Cu, C, Si, Mn and other elements in order to improve the welding performance.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention provides an EW420 extra-thick marine steel plate, whose chemical composition and mass percentage are as follows: C: 0.04%-0.07%, Si: 0.15%-0.25%, Mn: 1.30%-1.60%, P≤0.013%, S≤0.003%, Nb: 0.010%～050%, V: 0.020%～0.040%, Ti: 0.005%～0.020%, Cr: 0.10%～0.20%, Ni: 0.10%～0.70%, Cu: 0.20%～0.30%, Cr+Cu≤0.50%, C+Si/30+Mn/20≤0.15%, Al: 0.0250%～0.050%, Mo free, O≤12ppm, N≤35ppm, H≤ 1.5ppm, impurity elements As≤0.012%, Sn≤0.010%, Sb≤0.010%, Pb≤0.010%, Bi≤0.010%, B≤0.003%, the balance is Fe and inevitable impurities.

Technical effect: The invention develops EW420 extra-thick marine steel with a thickness of 81-100mm which is easy to weld, within the chemical composition range of GB712 and the ten major classification societies standards, with stable production process and excellent mechanical properties. The load requirement of the rolling mill is not too high, and the general wide and heavy plate rolling mill can be produced. Therefore, it has wide applicability and is suitable for the production of most wide and heavy plate factories in China.

The technical scheme that the present invention is further limited is:

The chemical composition and mass percentage of the aforementioned EW420 extra-thick marine steel sheet are as follows: C: 0.04%, Si: 0.15%, Mn: 1.60%, P: 0.013%, S: 0.0025%, Nb: 0.010% , V: 0.040%, Ti: 0.020%, Cr: 0.10%, Ni: 0.10%, Cu: 0.20%, Cr+Cu: 0.30%, C+Si/30+Mn/20: 0.125%, Al: 0.050% , without Mo, O: 0.0012%, N: 0.0035%, H: 0.00015%, impurity elements As: 0.003%, Sn: 0.0003%, Sb: 0.0003%, Pb: 0.005%, Bi: 0.002%, B: 0.003 %, and the balance is Fe and inevitable impurities.

The chemical composition and mass percentage of the aforementioned EW420 extra-thick marine steel sheet are as follows: C: 0.06%, Si: 0.20%, Mn: 1.50%, P: 0.012%, S: 0.0030%, Nb: 0.025% , V: 0.030%, Ti: 0.005%, Cr: 0.18%, Ni: 0.45%, Cu: 0.25%, Cr+Cu: 0.43%, C+Si/30+Mn/20: 0.142%, Al: 0.040% , without Mo, O: 0.0011%, N: 0.0033%, H: 0.00014%, impurity elements As: 0.002%, Sn: 0.0003%, Sb: 0.0003%, Pb: 0.003%, Bi: 0.001%, B: 0.002 %, and the balance is Fe and inevitable impurities.

The chemical composition and mass percentage of the aforementioned EW420 extra-thick marine steel sheet are as follows: C: 0.07%, Si: 0.25%, Mn: 1.30%, P: 0.011%, S: 0.0015%, Nb: 0.050% , V: 0.020%, Ti: 0.015%, Cr: 0.20%, Ni: 0.70%, Cu: 0.30%, Cr+Cu: 0.50%, C+Si/30+Mn/20: 0.143%, Al: 0.025% , without Mo, O: 0.0010%, N: 0.0030%, H: 0.00011%, impurity elements As: 0.002%, Sn: 0.0002%, Sb: 0.0002%, Pb: 0.003%, Bi: 0.001%, B: 0.0015 %, and the balance is Fe and inevitable impurities.

The aforementioned EW420 extra-thick marine steel plate has a thickness of 81-100mm.

Another object of the present invention is to provide a manufacturing method of EW420 extra-thick marine steel plate,

Steelmaking and continuous casting process: target S≤0.002% after molten iron desulfurization; high blowing and low pulling method is used for dephosphorization in converter smelting, the drain is clean and free of defects, and the converter taps slag; white slag is used for refining, and the retention time of white slag is ≥ 15 minutes, target alkalinity 5~7; vacuum treatment holding time ≥ 25 minutes; seamless calcium wire treatment after vacuum treatment; continuous casting uses five-hole nozzle, and the target temperature of the middle bag is liquidus temperature + (5~15) ℃, the pulling speed is stable;

Rolling process: The controlled rolling and controlled cooling process is adopted, which is a two-stage rolling process; the controlled rolling and controlled cooling process is adopted. ; Laminar cooling after rolling, the final cooling temperature is 300-450°C, and the cooling rate is 7-12°C/s; then air cooling.

In the aforementioned manufacturing method of EW420 extra-thick marine steel plate, the cumulative reduction ratio of three passes after finishing rolling is greater than 30%.

The beneficial effects of the present invention are:

(1) in the present invention, molten iron pretreatment is carried out to reduce sulfur, and the converter adopts high blowing and low pulling method to reduce phosphorus and tap slag to prevent returning to phosphorus, to ensure the refining time and basicity of white slag, to absorb inclusions as much as possible and reduce the amount of S, O and other element content; use seamless calcium wire treatment to improve the shape of inclusions; long-term high-vacuum vacuum treatment, so that N≤35ppm, H≤1.5ppm, and finally obtain a continuous casting billet with better internal quality;

(2) In the present invention, the heating temperature of the continuous casting billet before rolling is 1130°C to 1200°C, so as to ensure that the microalloying elements are completely dissolved, so that the original austenite grains are as small as possible; grains, internal defects of welded billets, and refined austenite grains; the cumulative reduction ratio of three passes after finishing rolling is greater than 30%, and the ferrite mechanism and high undercooling are induced by the large deformation at low temperature not in the crystallization zone. Under rapid cooling, the purpose of controlling the microstructure and grain size is obtained.

Description of drawings

Fig. 1 is the typical microstructure diagram of embodiment 1 steel plate under the metallographic microscope;

Fig. 2 is the typical microstructure diagram of embodiment 2 steel plate under the metallographic microscope;

3 is a typical microstructure diagram of the steel sheet of Example 3 under a metallographic microscope.

detailed description

A kind of EW420 extra-thick marine steel plate and its manufacturing method provided by this embodiment, the chemical composition is shown in Table 1,

Table 1 Chemical composition (wt, %) of EW420 extra-thick marine steel sheets of Examples 1-3

The production method of the 81mm thick EW420 extra-thick marine steel plate of embodiment 1 is as follows:

Steelmaking and continuous casting process: target sulfur is 0.002% after molten iron desulfurization; converter smelting adopts high blowing and low pulling method to dephosphor , the target alkalinity is 5; the vacuum treatment holding time is 25 minutes; the seamless calcium wire treatment is carried out after the vacuum treatment; the five-hole nozzle is used for casting, and the target temperature of the continuous casting medium bag is the liquidus temperature + 15 ℃, and the pulling speed is stable;

Rolling process: The controlled rolling and controlled cooling process is adopted, which is two-stage rolling; the heating temperature of the continuous casting slab before rolling is 1200 °C; ; The starting temperature of finishing rolling is 840°C, the cumulative reduction rate of the last three passes is 30%; the laminar flow cooling after rolling, the final cooling temperature is 450°C, and the cooling rate is 12°C/s; followed by air cooling. The obtained 81mm thick EW420 extra-thick marine steel plate.

The production method of the 90mm thick EW420 extra-thick marine steel plate of embodiment 2 is as follows:

Steelmaking and continuous casting process: the target sulfur is 0.0018% after the molten iron desulfurization; the converter smelting adopts the high blowing and low pulling method to dephosphor , the target alkalinity is 6; the vacuum treatment holding time is 30 minutes; the seamless calcium wire treatment is carried out after the vacuum treatment; the five-hole nozzle is used for casting, and the target temperature of the continuous casting medium bag is the liquidus temperature + 10 ℃, and the pulling speed is stable;

Rolling process: Controlled rolling and controlled cooling process is adopted, which is two-stage rolling; the heating temperature of the continuous casting slab before rolling is 1150 °C; ; The starting temperature of finishing rolling is 800°C, the cumulative reduction rate of the last three passes is 30%; the laminar flow cooling after rolling, the final cooling temperature is 350°C, and the cooling rate is 8°C/s; then air cooling. The obtained 90mm thick EW420 extra-thick marine steel plate.

The production method of the 100mm thick EW420 extra-thick marine steel plate of embodiment 3 is as follows:

Steelmaking and continuous casting process: target sulfur is 0.0015% after molten iron desulfurization; converter smelting adopts high blowing and low pulling method for dephosphorization, the water outlet is clean and free of defects, and the converter taps steel as slag; white slag is used for refining, and the white slag retention time is 20 minutes , the target alkalinity is 7; the vacuum treatment holding time is 34 minutes; the seamless calcium wire treatment is carried out after the vacuum treatment; the five-hole nozzle is used for casting, and the target temperature of the continuous casting medium bag is the liquidus temperature +5 °C, and the pulling speed is stable;

Rolling process: The controlled rolling and controlled cooling process is adopted, which is two-stage rolling; the heating temperature of the continuous casting slab before rolling is 1130 °C; ; The starting temperature of finishing rolling is 780°C, the cumulative reduction rate of the last three passes is 30%; the laminar flow cooling after rolling, the final cooling temperature is 300°C, and the cooling rate is 7°C/s; then air cooling. The obtained 100mm thick EW420 extra-thick marine steel plate.

It can be seen from Figure 1-3 that through reasonable composition design and precise rolling process control, a fine and uniform bainite-based microstructure is obtained, and the comprehensive mechanical properties are excellent.

After smelting + rolling treatment, the transverse tensile properties and transverse cold bending properties at 1/4 of the plate thickness and 1/2 of the plate thickness of Examples 1 to 3 are shown in Table 2, and the transverse impact properties and Z-direction properties are shown in Table 3 ,

Table 2 Transverse tensile properties and transverse cold bending properties at 1/4 of the plate thickness and 1/2 of the plate thickness of Examples 1 to 3

Table 3 Transverse impact properties and Z-direction properties at 1/4 of the plate thickness and 1/2 of the plate thickness of Examples 1 to 3

Among them, the impact performance of the welded joint of the steel plate of Example 3 under the condition of 50kJ/cm line energy is shown in Table 4,

Table 4 The impact properties of welded joints of the steel plate of Example 3 under the condition of 50kJ/cm line energy

It can be seen from Table 2 and Table 3 that the mechanical properties of the steel plates of the examples meet the performance requirements of the 420-grade E-grade ultra-high-strength marine steel in the standards of major classification societies, the yield strength is ≥ 439 MPa, the tensile strength is ≥ 545 MPa, and the elongation is ≥ 545 MPa. ≥23%, Z-direction section shrinkage rate ≥66%. It can be seen from Table 4 that the impact performance of the welded joint is excellent under the condition of 50kJ/cm line energy, which meets the requirements of EW420 extra-thick marine steel plate. It has the characteristics of stable production process and excellent mechanical properties.

In addition to the above-described embodiments, the present invention may also have other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

An EW420 extra-thick marine steel plate, characterized in that its chemical composition and mass percentage are as follows: C: 0.04%-0.07%, Si: 0.15%-0.25%, Mn: 1.30%-1.60%, P≤0.013%, S≤0.003%, Nb: 0.010%～050%, V: 0.020%～0.040%, Ti: 0.005%～0.020%, Cr: 0.10%～0.20%, Ni: 0.10%～0.70%, Cu: 0.20%～ 0.30%, Cr+Cu≤0.50%, C+Si/30+Mn/20≤0.15%, Al: 0.0250%～0.050%, no Mo, O≤12ppm, N≤35ppm, H≤1.5ppm, impurity elements As≤0.012%, Sn≤0.010%, Sb≤0.010%, Pb≤0.010%, Bi≤0.010%, B≤0.003%, the balance is Fe and inevitable impurities.
An EW420 extra-thick marine steel plate according to claim 1, characterized in that its chemical composition and mass percentage are as follows: C: 0.04%, Si: 0.15%, Mn: 1.60%, P: 0.013%, S: 0.0025%, Nb: 0.010%, V: 0.040%, Ti: 0.020%, Cr: 0.10%, Ni: 0.10%, Cu: 0.20%, Cr+Cu: 0.30%, C+Si/30+Mn/20: 0.125%, Al: 0.050%, Mo free, O: 0.0012%, N: 0.0035%, H: 0.00015%, impurity elements As: 0.003%, Sn: 0.0003%, Sb: 0.0003%, Pb: 0.005%, Bi : 0.002%, B: 0.003%, and the balance is Fe and inevitable impurities.
An EW420 extra-thick marine steel plate according to claim 1, characterized in that: its chemical composition and mass percentage are as follows: C: 0.06%, Si: 0.20%, Mn: 1.50%, P: 0.012%, S: 0.0030%, Nb: 0.025%, V: 0.030%, Ti: 0.005%, Cr: 0.18%, Ni: 0.45%, Cu: 0.25%, Cr+Cu: 0.43%, C+Si/30+Mn/20: 0.142%, Al: 0.040%, Mo free, O: 0.0011%, N: 0.0033%, H: 0.00014%, impurity elements As: 0.002%, Sn: 0.0003%, Sb: 0.0003%, Pb: 0.003%, Bi : 0.001%, B: 0.002%, and the balance is Fe and inevitable impurities.
An EW420 extra-thick marine steel plate according to claim 1, characterized in that: its chemical composition and mass percentage are as follows: C: 0.07%, Si: 0.25%, Mn: 1.30%, P: 0.011%, S: 0.0015%, Nb: 0.050%, V: 0.020%, Ti: 0.015%, Cr: 0.20%, Ni: 0.70%, Cu: 0.30%, Cr+Cu: 0.50%, C+Si/30+Mn/20: 0.143%, Al: 0.025%, Mo free, O: 0.0010%, N: 0.0030%, H: 0.00011%, impurity elements As: 0.002%, Sn: 0.0002%, Sb: 0.0002%, Pb: 0.003%, Bi : 0.001%, B: 0.0015%, and the balance is Fe and inevitable impurities.
A kind of EW420 extra thick marine steel plate according to claim 1 is characterized in that: the thickness of the steel plate is 81-100mm.
A manufacturing method of EW420 extra-thick marine steel plate, characterized in that: applied to any one of claims 1-5,

Steelmaking and continuous casting process: target S≤0.002% after molten iron desulfurization; high blowing and low pulling method is used for dephosphorization in converter smelting, the drain is clean and free of defects, and the converter taps slag; white slag is used for refining, and the retention time of white slag is ≥ 15 minutes, target alkalinity 5~7; vacuum treatment holding time ≥ 25 minutes; seamless calcium wire treatment after vacuum treatment; continuous casting uses five-hole nozzle, and the target temperature of the middle bag is liquidus temperature + (5~15) ℃, the pulling speed is stable;

Rolling process: The controlled rolling and controlled cooling process is adopted, which is a two-stage rolling process; the controlled rolling and controlled cooling process is adopted. ; Laminar cooling after rolling, the final cooling temperature is 300-450°C, and the cooling rate is 7-12°C/s; then air cooling.
A method for manufacturing EW420 extra-thick marine steel sheet according to claim 6, characterized in that the three-pass cumulative reduction ratio after finishing rolling is greater than 30%.