Formula of duplex stainless steel and manufacturing method of plate adopting formula

Abstract

The invention discloses a formula of duplex stainless steel and a manufacturing method of a plate adopting the formula, and the formula of the duplex stainless steel comprises the following components in percentage by weight: 0 to 0.03 percent of carbon, 0.4 to 0.9 percent of silicon, 4.50 to 5.5 percent of manganese, 0 to 0.030 percent of phosphorus, 0 to 0.001 percent of sulfur, 21.5 to 21.8 percent of chromium, 1.3 to 1.7 percent of nickel, 0.1 to 0.4 percent of molybdenum, 0.20 to 0.24 percent of nitrogen, 0.1 to 0.4 percent of copper, less than or equal to 0.1 percent of impurities and the balance of iron. The manufacturing method of the plate adopting the formula comprises the following steps: S1) hot coiling solution treatment: carrying out solution treatment on a hot-rolled coiled plate at 1080-1110 DEG C for 3.5-4.5 minutes, then pickling to form a coiled plate with a 2B surface, discharging from a furnace, and carrying out water cooling; and S2, hot rolling and cold rolling are conducted, specifically, cold rolling is conducted on the rolled plate subjected to hot rolling solution treatment for multiple times, and annealing process treatment is conducted after each time of cold rolling. The plate obtained by adopting the manufacturing method can be used for manufacturing equipment with higher requirements on corrosion resistance and strength, such as a box type heating storage tank.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a stainless steel plate, and in particular to a formula of duplex stainless steel and a method for manufacturing a plate using the formula. Background Art

[0002] As a new type of stainless steel material, duplex stainless steel has the advantages of both ferritic stainless steel and austenitic stainless steel by adding elements such as nickel, chromium, and molybdenum, namely, high strength, high corrosion resistance, and good welding performance. It has been widely used in the fields of petrochemicals, storage tanks, pipelines, structures, etc. However, since the current duplex stainless steel is mainly improved by adding relatively expensive elements such as nickel, chromium, and molybdenum to improve its strength, corrosion resistance, etc., the production cost of the duplex stainless steel is high, which limits its further promotion and application. Moreover, under the current traditional production process, when only N elements are added to improve the strength and corrosion resistance of duplex stainless steel, pores are often generated in the product, resulting in poor surface quality and overall performance of the obtained product; in addition, the plastic deformation ability of duplex stainless steel obtained by the traditional production process is poor, and it is difficult to produce high-quality products, which also limits its further promotion and application. Therefore, how to develop a manufacturing method of duplex stainless steel with high corrosion resistance, high strength, and economy is the main problem currently faced. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a formula of duplex stainless steel with high corrosion resistance and high strength and capable of reducing material cost.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a formula of duplex stainless steel, which includes, by weight percentage: 0-0.03% carbon, 0.4-0.9% silicon, 4.50-5.5% manganese, 0-0.030% phosphorus, 0-0.001% sulfur, 21.5-21.8% chromium, 1.3-1.7% nickel, 0.1-0.4% molybdenum, 0.20-0.24% nitrogen, 0.1-0.4% copper, ≤0.1% impurities, and the rest is iron.

[0005] The present invention provides a method for manufacturing a duplex stainless steel plate having high corrosion resistance and high strength and capable of reducing material costs. The duplex stainless steel plate adopts the formula of the duplex stainless steel of the present invention. The specific steps of the manufacturing method of the duplex stainless steel plate include:

[0006] S1): Hot coil solution treatment: The hot rolled coil is subjected to solution treatment at 1080-1100°C for 3.5-4.5 min and then pickled to form a coil with 2B surface, which is then water-cooled after being taken out of the furnace;

[0007] S2): Hot coil cold rolling: The coil after hot coil solid solution treatment is cold rolled several times, and annealing process is performed after each cold rolling.

[0008] As a preferred embodiment, in the method for manufacturing a duplex stainless steel plate, assuming that the thickness of the coil after the hot coil solution treatment in step S1) is T1, the thickness of the coil after the hot coil cold rolling in step S2) is T2, and the cold rolling rate is X1, then: When C is less than 1, the number of cold rolling times N is 1; when C is greater than 1 and the decimal part of C is ≥0.15, the number of cold rolling times N is an integer greater than C; when C is greater than 1 and the decimal part of C is <0.15, the number of cold rolling times N is an integer less than C.

[0009] As a preferred embodiment, in the method for manufacturing a duplex stainless steel plate, the thickness of the coil after the hot coil solution treatment in step S1) is 5.0-6.0 mm, the number of cold rolling is two, the first cold rolling controls the thickness of the coil to between 2.5 and 3.0 mm, and the second cold rolling controls the thickness of the coil to between 1.2 and 1.6 mm.

[0010] As a preferred solution, in the method for manufacturing a duplex stainless steel plate, assuming that the thickness of the rolled plate is x, in millimeters,

[0011] Then: Annealing time y ≥ -k1x 3 +k2x 2 -k3x+3.8965, in minutes;

[0012] Where: k1 = 0.0685 minutes / cubic millimeter, k2 = 0.9785 minutes / square millimeter, k3 = 1.7865 minutes / mm;

[0013] Correspondingly, when annealing is performed after the first cold rolling, the annealing time is greater than 4.95 minutes, and when annealing is performed after the second cold rolling, the annealing time is greater than 3.12 minutes.

[0014] As a preferred embodiment, in the manufacturing method of a duplex stainless steel plate, when annealing is performed after the first cold rolling: the annealing furnace temperature is set between 1070 and 1090°C, and the solution treatment time is between 5 and 6 minutes; when annealing is performed after the second cold rolling: the annealing furnace temperature is set between 1050 and 1070°C, and the solution treatment time is between 3.2 and 4.2 minutes.

[0015] As a preferred embodiment, in the manufacturing method of the duplex stainless steel plate, for the coil with a thickness between 2.5 and 3.0 mm, the traveling speed during coil annealing is For coils between 1.2 and 1.6 mm, the travel speed during coil annealing

[0016] As a preferred embodiment, in the method for manufacturing a duplex stainless steel plate, when annealing is performed after the first cold rolling, the traveling speed of the coil is controlled between 30 and 36 m / min; when annealing is performed after the second cold rolling, the traveling speed of the coil is controlled between 25 and 33 m / min.

[0017] The beneficial effects of the present invention are:

[0018] 1. The duplex stainless steel of the present invention uses manganese and nitrogen elements with lower prices to replace part of the nickel element, thereby greatly reducing the manufacturing cost of the duplex stainless steel; due to the increase in N content, not only the occurrence of pore defects will increase, but also the strength difference between the two phases during hot rolling will increase, reducing the hot workability of the steel, while the increase in Ni and Mo content will lead to an increase in cost; the increase in Mn content causes Mn and S to form manganese sulfide, resulting in decreased corrosion resistance and hot workability; the present invention improves the yield strength and corrosion resistance of the duplex stainless steel plate by reasonably configuring the important percentages of Ni, Mo, Mn and N elements in the duplex stainless steel plate, and by adopting a lower heating furnace temperature and controlling the solution treatment time; the plastic deformation of the duplex stainless steel plate is achieved, and its plastic deformation capacity is improved.

[0019] 2. The present invention reduces the occurrence of surface oxidation of the steel strip and improves the surface quality of the white coil after annealing and pickling by adopting the low-temperature heating method of the hot-rolled coil in the furnace and controlling the solid solution treatment time.

[0020] 3. The present invention can directly calculate the annealing time and the travel speed for the coil thickness after each cold rolling, thereby greatly shortening the design cycle of designers and reducing work pressure and labor intensity; and by controlling the annealing time and the travel speed, the final plate has an Rp0.2 (yield strength) of more than 540MPa, an Rm (tensile strength) of more than 740MPa, and an A50 (elongation) of more than 32.0%, and has high yield strength, tensile strength and corrosion resistance. DETAILED DESCRIPTION

[0021] The following describes in detail a formulation of a duplex stainless steel according to the present invention and a detailed implementation scheme of a method for manufacturing a plate using the formulation.

[0022] Embodiment 1:

[0023] The formula of the duplex stainless steel of the present invention has the following chemical composition by weight percentage:

[0024] C: 0.02%, Si: 0.45%, Mn: 4.60%, P: 0.02%, S: 0.001%, Cr: 21.5%, Ni: 1.43%, Mo: 0.17%, N: 0.22%, Cu: 0.16%, unavoidable impurities ≤ 0.04%; the rest is iron.

[0025] The method for manufacturing the duplex stainless steel plate of the above formula comprises the following steps:

[0026] S1) Hot coil solution treatment: The hot rolled coil with a thickness of 6.0 mm is solution treated at 1100°C for 4.5 min and then taken out of the furnace for water cooling.

[0027] S2) Hot coil cold rolling: two cold rolling processes are adopted. The target thickness of the first cold rolling is 3.0 mm. Annealing is performed after cold rolling. The annealing furnace temperature is set to 1090°C, the coil travel speed is set to 30 m / min, and the solution treatment time is set to 6 min. The target thickness of the second cold rolling is set to 1.6 mm. Annealing is performed after cold rolling. The annealing furnace temperature is set to 1070°C, the coil travel speed is set to 25 m / min, and the solution treatment time is set to 4.2 min.

[0028] The final duplex stainless steel plate has the following material properties: Rp0.2=545MPa, Rm=775MPa, A50=35.0%.

[0029] Embodiment 2:

[0030] The formula of the duplex stainless steel of the present invention has the following chemical composition by weight percentage:

[0031] C: 0.01%, Si: 0.56%, Mn: 4.7%, P: 0.022%, S: 0.0006%, Cr: 21.7%, Ni: 1.41%, Mo: 0.17%, N: 0.21%, Cu: 0.16%, unavoidable impurities ≤ 0.03%; the rest is iron.

[0032] The method for manufacturing the duplex stainless steel plate of the above formula comprises the following steps:

[0033] S1) Hot coil solution treatment: The hot rolled coil with a thickness of 5.5 mm is subjected to solution treatment at 1095°C for 4 minutes and then taken out of the furnace and water cooled.

[0034] S2) Hot coil cold rolling: two cold rolling processes are adopted. The target thickness of the first cold rolling is 3.0mm. Annealing is performed after cold rolling. The annealing furnace temperature is set to 1080℃, the coil travel speed is set to 30m / min, and the solution treatment time is set to 5.5min. The target thickness of the second cold rolling is set to 1.4mm. Annealing is performed after cold rolling. The annealing furnace temperature is set to 1060℃, the coil travel speed is set to 28.6m / min, and the solution treatment time is set to 3.5min.

[0035] Finally, a duplex stainless steel plate is obtained, and its material properties are: Rp0.2=553MPa, Rm=765MPa, A50=34.0%.

[0036] Embodiment 3:

[0037] The formula of the duplex stainless steel of the present invention has the following chemical composition by weight percentage:

[0038] C: 0.015%, Si: 0.48%, Mn: 4.74%, P: 0.027%, S: 0.0008%, Cr: 21.6%, Ni: 1.51%, Mo: 0.16%, N: 0.22%, Cu: 0.16%; unavoidable impurities ≤ 0.02%; the rest is iron.

[0039] The method for manufacturing the duplex stainless steel plate of the above formula comprises the following steps:

[0040] S1) Hot coil solution treatment: The hot rolled coil with a thickness of 5.0 mm is subjected to solution treatment at 1080°C for 3.5 min and then taken out of the furnace for water cooling.

[0041] S2) Hot coil cold rolling: two cold rolling processes are adopted. The target thickness of the first cold rolling is 2.5mm. Annealing is performed after cold rolling. The temperature of the annealing furnace is set to 1070℃, the travel speed of the coil is set to 36m / min, and the solution treatment time is set to 5min. The target thickness of the second cold rolling is set to 1.2mm. Annealing is performed after cold rolling. The temperature of the annealing furnace is set to 1050℃, the travel speed of the coil is set to 33.3m / min, and the solution treatment time is set to 3.2min.

[0042] Finally, a duplex stainless steel plate is obtained, and its material properties are: Rp0.2=560MPa, Rm=768MPa, A50=36.0%.

[0043] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Any equivalent changes and modifications made on the basis of the claims of the present invention are within the protection scope of the present invention.

Claims

1. A formulation of duplex stainless steel comprising, by weight percentage: 0-0.03% carbon, 0.4-0.9% silicon, 4.50-5.5% manganese, 0-0.030% phosphorus, 0-0.001% sulfur, 21.5-21.8% chromium, 1.3-1.7% nickel, 0.1-0.4% molybdenum, 0.20-0.24% nitrogen, 0.1-0.4% copper, ≤0.1% impurities, and the rest is iron.

2. A method for manufacturing a duplex stainless steel plate, wherein the duplex stainless steel plate adopts the formula of the duplex stainless steel according to claim 1, and the specific steps of the method for manufacturing the duplex stainless steel plate include: S1): Hot coil solution treatment: The hot rolled coil is subjected to solution treatment at 1080-1100°C for 3.5-4.5 min and then pickled to form a coil with 2B surface, which is then water-cooled after being taken out of the furnace; S2): Hot coil cold rolling: The coil after hot coil solid solution treatment is cold rolled several times, and annealing process is performed after each cold rolling.

3. The method for manufacturing a duplex stainless steel plate according to claim 2, characterized in that: Assuming that the thickness of the coil after the hot coil solution treatment in step S1) is T1, the thickness of the coil after the hot coil cold rolling in step S2) is T2, and the cold rolling rate is X1, then: When C is less than 1, the number of cold rolling times N is 1; when C is greater than 1 and the decimal part of C is ≥0.15, the number of cold rolling times N is an integer greater than C; when C is greater than 1 and the decimal part of C is <0.15, the number of cold rolling times N is an integer less than C.

4. The method for manufacturing a duplex stainless steel plate according to claim 3, characterized in that: After step S1), the thickness of the coil after the hot coil solution treatment is 5.0-6.0 mm, the number of cold rolling is two, the first cold rolling controls the thickness of the coil to between 2.5-3.0 mm, and the second cold rolling controls the thickness of the coil to between 1.2-1.6 mm.

5. The method for manufacturing a duplex stainless steel plate according to claim 4, characterized in that: Assume that the thickness of the rolled plate is x, in millimeters. Then: Annealing time y ≥ -k1x 3 +k2x 2 -k3x+3.8965, in minutes; Where: k1 = 0.0685 minutes / cubic millimeter, k2 = 0.9785 minutes / square millimeter, k3 = 1.7865 minutes / mm; Correspondingly, when annealing is performed after the first cold rolling, the annealing time is greater than 4.95 minutes, and when annealing is performed after the second cold rolling, the annealing time is greater than 3.12 minutes.

6. The method for manufacturing a duplex stainless steel plate according to claim 5, characterized in that: When annealing is performed after the first cold rolling: the annealing furnace temperature is set between 1070 and 1090°C, and the solution treatment time is between 5 and 6 minutes. When annealing is performed after the second cold rolling: the annealing furnace temperature is set between 1050 and 1070°C, and the solution treatment time is between 3.2 and 4.2 minutes.

7. The method for manufacturing a duplex stainless steel plate according to claim 6, characterized in that: For coils with a thickness between 2.5 and 3.0 mm, the travel speed during coil annealing For coils between 1.2 and 1.6 mm, the travel speed during coil annealing 8. The method for manufacturing a duplex stainless steel plate according to claim 7, characterized in that: When annealing is performed after the first cold rolling, the traveling speed of the coil is controlled between 30 and 36 m / min; when annealing is performed after the second cold rolling, the traveling speed of the coil is controlled between 25 and 33 m / min.

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