Double-phase stainless steel with superplasticity and preparation method thereof

Abstract

The invention belongs to the field of superplastic steel, and relates to duplex stainless steel with superplasticity and a preparation method thereof. The invention discloses duplex stainless steel which comprises the following components in percentage by mass: 0 to 0.05 weight percent of C (carbon), 0 to 1.5 weight percent of Si (silicon), 0 to 3.0 weight percent of Mn (manganese), 18.0 to 25.0 weight percent of Cr (chromium), 4.0 to 10.0 weight percent of Ni (nickel), 0.5 to 2.0 weight percent of Cu (copper), 0.1 to 2.0 weight percent of Mo (molybdenum), 0.08 to 0.20 weight percent of N (nitrogen), 0 to 0.002 weight percent of S (sulfur) and the balance of iron and inevitable impurities. The invention further discloses a preparation method of the duplex stainless steel. The preparation method comprises the steps of smelting, forging, hot rolling and cold rolling. The metal plasticity and toughness of the duplex stainless steel prepared by adopting the components and the preparation method are obviously improved under the action of a magnetic field.

Description

Technical Field

[0001] The invention belongs to the field of superplastic steels and relates to a duplex stainless steel with superplasticity and a preparation method thereof. Background Art

[0002] Duplex stainless steel has the advantages of both austenitic and ferritic stainless steels and is widely used in industries, construction, marine engineering and other fields. Duplex stainless steel has excellent superplasticity under certain conditions. Superplastic forming technology can be used to produce high-quality, high-precision thin-walled, thin-web and other complex-shaped products. Usually, the realization of superplasticity requires certain organizational conditions, that is, small equiaxed grains, and generally requires a grain size of 0.5 to 5 μm or less.

[0003] At present, more and more studies have begun to pay attention to the superplasticity of duplex stainless steel, but the organizational conditions and organizational formation mechanism of superplastic deformation of duplex stainless steel still need further study, and the relationship between the organization of duplex stainless steel and its properties including superplasticity also needs to be further explored. The two-phase ratio, organizational morphology, content and morphology of σ phase of duplex stainless steel have an important influence on the superplastic forming process and product quality. Duplex stainless steel often precipitates intermetallic phases such as σ phase at high temperature, which causes the toughness and plasticity of duplex stainless steel to drop sharply. Therefore, exploring the appropriate two-phase ratio of duplex stainless steel is crucial to the development of superplastic duplex stainless steel. At the same time, the magnetic field will affect the stability of austenite and ferrite phases in duplex stainless steel, thereby affecting the dynamics of deformation-induced martensitic transformation. The application of a magnetic field will change the movement and accumulation of dislocations, thereby affecting the plastic behavior of duplex stainless steel. Summary of the invention

[0004] Based on the above background, the present invention provides a duplex stainless steel with superplasticity and a preparation method thereof. The duplex stainless steel prepared by the present invention can have better superplasticity under the action of a magnetic field.

[0005] A first aspect of the present invention provides a duplex stainless steel, the components of which are, by mass percentage, C: 0-0.05wt%, Si: 0-1.5wt%, Mn: 0-3.0wt%, Cr: 18.0-25.0wt%, Ni: 4.0-10.0wt%, Cu: 0.5-2.0wt%, Mo: 0.1-2.0wt%, N: 0.08-0.20wt% and S: 0-0.002wt%, with the balance being iron and unavoidable impurities.

[0006] In a preferred embodiment, the components of the duplex stainless steel are: in mass percentage, C: 0-0.05wt%, Si: 0-1.5wt%, Mn: 0-3.0wt%, Cr: 18.0-25.0wt%, Ni: 4.0-8.0wt%, Cu: 0.5-2.0wt%, Mo: 0.1-2.0wt%, N: 0.08-0.20wt% and S: 0-0.002wt%, with the balance being made up by iron and unavoidable impurities.

[0007] In a preferred embodiment, the components of the duplex stainless steel are: in mass percentage, C: 0-0.05wt%, Si: 0-1.5wt%, Mn: 0-3.0wt%, Cr: 18.0-25.0wt%, Ni: 4.0-10.0wt%, Cu: 1.0-2.0wt%, Mo: 0.1-2.0wt%, N: 0.08-0.20wt% and S: 0-0.002wt%, with the balance being made up by iron and unavoidable impurities.

[0008] In a preferred embodiment, the components of the duplex stainless steel are: in mass percentage, C: 0-0.05wt%, Si: 0-1.5wt%, Mn: 0-3.0wt%, Cr: 18.0-25.0wt%, Ni: 4.0-8.0wt%, Cu: 1.0-2.0wt%, Mo: 0.1-2.0wt%, N: 0.08-0.20wt% and S: 0-0.002wt%, with the balance being made up by iron and unavoidable impurities.

[0009] In a preferred embodiment, the components of the duplex stainless steel are: in mass percentage, C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 18.0-20.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, Mo: 0.1-2.0wt%, N: 0.08-0.10wt% and S: 0.002wt%, and the balance is made up of iron and unavoidable impurities.

[0010] In a preferred embodiment, the components of the duplex stainless steel are the following component 1 or component 2:

[0011] Component 1: in terms of mass percentage, C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 20.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, Mo: 1.5wt%, N: 0.10wt% and S: 0.002wt%, the balance being iron;

[0012] Component 2: in terms of mass percentage, C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 18.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, Mo: 1.5wt%, N: 0.08wt% and S: 0.002wt%, with the balance being made up of iron.

[0013] A second aspect of the present invention provides a method for preparing duplex stainless steel, comprising the following steps:

[0014] (5) Melting: placing the raw materials in a vacuum electric furnace for smelting and casting;

[0015] (6) Forging: Forging the blank at 900-1300°C to obtain a blank;

[0016] (7) Hot rolling: the billet is hot rolled for multiple times at 1150-1250° C., and then hot rolled at 1200-1300° C. and subjected to water quenching and solution treatment;

[0017] (8) Cold rolling: Grind the blank and cold roll it several times.

[0018] In the step (1), the ingot is preferably electroslag remelted again after being cast.

[0019] In the step (2), the start forging temperature is 1100-1300°C, preferably 1150-1250°C, for example 1200°C.

[0020] In the step (2), the final forging temperature is 900-1100°C, preferably 950-1050°C, for example 1000°C.

[0021] In the step (3), the hot rolling temperature is preferably 1200°C.

[0022] In the step (3), the hot rolling may be performed 2-5 times, preferably 2-4 times, for example 3 times.

[0023] In the step (3), the thickness of the hot-rolled billet may be 10-20 mm, preferably 12-18 mm, for example 15 mm.

[0024] In the step (3), the temperature of the heat preservation after hot rolling is preferably 1250°C.

[0025] In the step (3), the insulation time is 20-60 min, preferably 30-40 min.

[0026] In the step (4), the cold rolling may be performed 10-30 times, preferably 15-25 times, for example 20 times.

[0027] In the step (4), the thickness of the cold-rolled blank may be 0.5-1.5 mm, preferably 0.8-1.2 mm, for example 1.0 mm.

[0028] In the step (4), the deformation amount of the cold rolling may be 80-95%, preferably 85-95%, for example 90%.

[0029] In a preferred embodiment, the preparation method comprises the following steps:

[0030] (1) Melting: The above raw materials are smelted in a vacuum electric furnace, cast into billets and forged into Φ40 mm round bars, and then further refined by electroslag remelting;

[0031] (2) Forging: The cast ingot is forged again to form a rectangular billet. The forging temperature is controlled at 1200°C and the final forging temperature is greater than 1000°C.

[0032] (3) Hot rolling: at 1200°C, further hot rolled to 15 mm thickness through 3 passes, then subjected to 1250°C, heat preservation for 30 min, and water quenching and solution treatment;

[0033] (4) Cold rolling: The surface of the slab after solution treatment is ground and then cold rolled to 1.0 mm through 20 passes. The deformation of the cold rolling is 90%.

[0034] The third aspect of the present invention provides a stainless steel prepared by the preparation method of the above duplex stainless steel, wherein the components thereof are, by mass percentage, C: 0-0.05wt%, Si: 0-1.5wt%, Mn: 0-3.0wt%, Cr: 18.0-25.0wt%, Ni: 4.0-10.0wt%, Mo: 0.1-2.0wt%, Cu: 0.5-2.0wt%, N: 0.08-0.20wt% and S: 0-0.002wt%, with the remainder being made up by iron and unavoidable impurities.

[0035] In a preferred embodiment, the stainless steel is prepared by the following preparation method:

[0036] (1) Melting: The raw materials are smelted in a vacuum electric furnace, cast into billets and forged into Φ40 mm round bars, and then further refined by electroslag remelting;

[0037] (2) Forging: The cast ingot is forged again to form a rectangular billet. The forging temperature is controlled at 1200°C and the final forging temperature is greater than 1000°C.

[0038] (3) Hot rolling: at 1200°C, further hot rolled to 15 mm thickness through 3 passes, then subjected to 1250°C, heat preservation for 30 min, and water quenching and solution treatment;

[0039] (4) Cold rolling: The surface of the slab after solution treatment is ground and then cold rolled to 1.0 mm through 20 passes. The deformation of the cold rolling is 90%;

[0040] The raw materials include: C: 0-0.05wt%, Si: 0-1.5wt%, Mn: 0-3.0wt%, Cr: 18.0-25.0wt%, Ni: 4.0-10.0wt%, Cu: 0.5-2.0wt%, Mo: 0.1-2.0wt%, N: 0.08-0.20wt% and S: 0-0.002wt%, and the balance is duplex stainless steel composed of iron and inevitable impurities.

[0041] In a preferred embodiment, the preparation method of the stainless steel is as described above, and the components of the stainless steel are as described above.

[0042] The reagents and raw materials used in the present invention are commercially available.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The present invention provides a duplex stainless steel with superplasticity and a preparation method thereof. The duplex stainless steel of the present invention has significantly improved metal plasticity and toughness under the action of a magnetic field. DETAILED DESCRIPTION

[0045] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0046] wt% means mass percentage.

[0047] Example 1

[0048] (1) Ingredients: The raw materials for preparation include carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum, tungsten, niobium, copper and nitrogen, wherein C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 20.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, Mo: 1.5wt%, N: 0.10wt% and S: 0.002wt%, and the balance is iron and unavoidable impurities to form a duplex stainless steel composed of component 1.

[0049] (2) Melting: The above raw materials are smelted in a vacuum electric furnace, cast into billets and forged into Φ40 mm round bars, and then further refined by electroslag remelting.

[0050] (3) Forging: The cast steel ingot is forged again, the forging temperature is controlled at 1200℃, the final forging temperature is greater than 1000℃, and it is forged into a rectangular billet with a size of 25mm×25mm.

[0051] (4) Hot rolling: At 1200℃, it is further hot rolled to 15 mm thickness through 3 passes, and then subjected to water quenching and solution treatment at 1250℃ for 30 min.

[0052] (5) Cold rolling: The surface of the slab after solution treatment is ground to a thickness of 13 mm, and then cold rolled to 1.0 mm through 20 passes, with a cold rolling deformation of 90%.

[0053] (6) Magnetic superplasticity verification: The duplex stainless steel slab was placed on a constant temperature hot tensile testing machine equipped with a 3T magnetic field unit for a tensile test. It was heated to the deformation temperature at a heating rate of 2°C / s. After being kept at this temperature for 5 minutes, a tensile test was performed at a strain rate of 1×10 -3 / s.

[0054] Example 2

[0055] (1) Ingredients: The raw materials for preparation include carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum, tungsten, niobium, copper and nitrogen, wherein C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 18.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, Mo: 1.5wt%, N: 0.08wt% and S: 0.002wt%, and the balance is iron and unavoidable impurities to form a duplex stainless steel composed of component 2.

[0056] (2) Melting: The above raw materials are smelted in a vacuum electric furnace, cast into billets and forged into Φ40 mm round bars, and then further refined by electroslag remelting.

[0057] (3) Forging: The cast steel ingot is forged again, the forging temperature is controlled at 1200℃, the final forging temperature is greater than 1000℃, and it is forged into a rectangular billet with a size of 25mm×25mm.

[0058] (4) Hot rolling: At 1200℃, it is further hot rolled to 15 mm thickness through 3 passes, and then subjected to water quenching and solution treatment at 1250℃ for 30 min.

[0059] (5) Cold rolling: The surface of the slab after solution treatment is ground to a thickness of 13 mm, and then cold rolled to 1.0 mm through 20 passes, with a cold rolling deformation of 90%.

[0060] (7) Magnetic superplasticity verification: The duplex stainless steel slab was placed on a constant temperature hot tensile testing machine equipped with a 3T magnetic field unit for a tensile test. It was heated to the deformation temperature at a heating rate of 2°C / s. After keeping the temperature for 5 min, a tensile test was performed at a strain rate of 1×10 -3 / s.

[0061] Example 3

[0062] (1) Ingredients: The raw materials for preparation include carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum, tungsten, niobium, copper and nitrogen, wherein C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 20.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, Mo: 1.5wt%, N: 0.10wt% and S: 0.002wt%, and the balance is iron and unavoidable impurities to form a duplex stainless steel composed of component 1.

[0063] (2) Melting: The above raw materials are smelted in a vacuum electric furnace, cast into billets and forged into Φ40 mm round bars, and then further refined by electroslag remelting.

[0064] (3) Forging: The cast steel ingot is forged again, the forging temperature is controlled at 1200℃, the final forging temperature is greater than 1000℃, and it is forged into a rectangular billet with a size of 25mm×50mm.

[0065] (4) Hot rolling: At 1200℃, it is further hot rolled to 15 mm thickness through 3 passes, and then subjected to water quenching and solution treatment at 1250℃ for 30 min.

[0066] (5) Cold rolling: The surface of the slab after solution treatment is ground to a thickness of 13 mm, and finally cold rolled to 1.0 mm through 21 passes, with a cold rolling deformation of 90%.

[0067] (6) Tensile test: The duplex stainless steel slab was placed on a constant temperature hot tensile testing machine for a tensile test. It was heated to the deformation temperature at a heating rate of 2 °C / s. After keeping the temperature for 5 min, a tensile test was performed at a strain rate of 1 × 10 -3 / s. .

[0068] Example 4

[0069] (1) Ingredients: The raw materials for preparation include carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum, tungsten, niobium, copper and nitrogen, wherein C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 18.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, N: 0.08wt% and S: 0.002wt%, and the balance is iron and unavoidable impurities to form a duplex stainless steel composed of component 2.

[0070] (2) Melting: The above raw materials are smelted in a vacuum electric furnace, cast into billets and forged into Φ40 mm round bars, and then further refined by electroslag remelting.

[0071] (3) Forging: The cast steel ingot is forged again to form a blank. The forging temperature is controlled at 1200°C and the final forging temperature is greater than 1000°C. The blank is forged into a rectangular blank with a cross-sectional area of ​​25 mm × 25 mm in thickness and width.

[0072] (4) Hot rolling: At 1200℃, it is further hot rolled to 15 mm thickness through 3 passes, and then subjected to water quenching and solution treatment at 1250℃ for 30 min.

[0073] (5) Cold rolling: The surface of the slab after solution treatment is ground to a thickness of 13 mm, and finally cold rolled to 1.0 mm through 21 passes, with a cold rolling deformation of 90%.

[0074] (6) Tensile test: The duplex stainless steel slab was placed on a constant temperature hot tensile testing machine for a tensile test. It was heated to the deformation temperature at a heating rate of 2 °C / s. After keeping the temperature for 5 min, a tensile test was performed at a strain rate of 1 × 10 -3 / s.

[0075] Comparative Example 1

[0076] (1) Ingredients: The raw materials for preparation include carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum, tungsten, niobium, copper and nitrogen, wherein C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 20.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, Mo: 1.5wt%, N: 0.10wt% and S: 0.002wt%, and the balance is iron and unavoidable impurities to form a duplex stainless steel composed of component 1.

[0077] (2) Melting: The above raw materials are smelted in a vacuum electric furnace, cast into billets and forged into Φ40 mm round bars, and then further refined by electroslag remelting.

[0078] (3) Forging: The cast steel ingot is forged again, the forging temperature is controlled at 850°C, the final forging temperature is greater than 900°C, and it is forged into a rectangular billet with a size of 25 mm × 25 mm.

[0079] (4) Hot rolling: At 1000℃, it is further hot rolled to 15 mm thickness through 3 passes, then heated to 1100℃ for 30 min and water quenched for solution treatment.

[0080] (5) Cold rolling: The surface of the slab after solution treatment is ground to a thickness of 13 mm, and then cold rolled to 1.0 mm through 20 passes, with a cold rolling deformation of 90%.

[0081] (6) Magnetic superplasticity verification: The duplex stainless steel slab was placed on a constant temperature hot tensile testing machine equipped with a 3T magnetic field unit for a tensile test. It was heated to the deformation temperature at a heating rate of 2°C / s. After being kept at this temperature for 5 minutes, a tensile test was performed at a strain rate of 1×10 -3 / s.

[0082] Comparative Example 2

[0083] (1) Ingredients: The raw materials for preparation include carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum, tungsten, niobium, copper and nitrogen, wherein C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 20.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, Mo: 1.5wt%, N: 0.10wt% and S: 0.002wt%, B: 0.005%, and the balance is iron and inevitable impurities to form a duplex stainless steel composed of component 1.

[0084] (2) Melting: The above raw materials are smelted in a vacuum electric furnace, cast into billets and forged into Φ40 mm round bars, and then further refined by electroslag remelting.

[0085] (3) Forging: The cast steel ingot is forged again, the forging temperature is controlled at 1200℃, the final forging temperature is greater than 1000℃, and it is forged into a rectangular billet with a size of 25mm×25mm.

[0086] (4) Hot rolling: At 1200℃, it is further hot rolled to 15 mm thickness through 3 passes, and then subjected to water quenching and solution treatment at 1250℃ for 30 min.

[0087] (5) Cold rolling: The surface of the slab after solution treatment is ground to a thickness of 13 mm, and then cold rolled to 1.0 mm through 20 passes, with a cold rolling deformation of 90%.

[0088] (6) Magnetic superplasticity verification: The duplex stainless steel slab was placed on a constant temperature hot tensile testing machine equipped with a 3T magnetic field unit for a tensile test. It was heated to the deformation temperature at a heating rate of 2°C / s. After being kept at this temperature for 5 minutes, a tensile test was performed at a strain rate of 1×10 -3 / s.

[0089] The experimental results of Examples 1-4 are compared, as shown in Table 1.

[0090] Table 1: Results of plasticity test in the embodiments of the present invention and comparative examples (please provide experimental equipment, test methods, steps, etc. for plasticity test)

[0091] Optimum deformation temperature m-value Elongation Example 1 950℃ 0.67 320％ Example 2 980℃ 0.62 314％ Example 3 950℃ 0.49 290％ Example 4 980℃ 0.45 281％ Comparative Example 1 1050℃ 0.51 287％ Comparative Example 2 950℃ 0.67 318％

[0092] m value: strain rate sensitivity coefficient.

[0093] From the experimental data in Table 1, it can be clearly seen that the m value of the duplex stainless steel obtained in the present invention is increased by at least 35% under a magnetic field, and the elongation is also increased by more than 30%. The mechanical properties of the two are significantly improved under a magnetic field, and the superplasticity is significantly improved.

[0094] In summary, the duplex stainless steel prepared by the method of the present invention has significantly improved mechanical properties under a magnetic field, providing a new composition and new technology for preparing duplex stainless steel with magnetic superplasticity by using the influence of a magnetic field on plasticity. This technology further improves the superplasticity of duplex stainless steel in the prior art, and the duplex stainless steel of the present invention has significantly improved metal plasticity and toughness.

Claims

1. A duplex stainless steel, characterized in that: Its components are: in mass percentage, C: 0-0.05wt%, Si: 0-1.5wt%, Mn: 0-3.0wt%, Cr: 18.0-25.0wt%, Ni: 4.0-10.0wt%, Cu: 0.5-2.0wt%, Mo: 0.1-2.0wt%, N: 0.08-0.20wt% and S: 0-0.002wt%, and the balance is made up of iron and inevitable impurities.

2. The duplex stainless steel according to claim 1, characterized in that The components of the duplex stainless steel are selected from any one of the following groups: (1) In terms of mass percentage, C: 0-0.05 wt%, Si: 0-1.5 wt%, Mn: 0-3.0 wt%, Cr: 18.0-25.0 wt%, Ni: 4.0-8.0 wt%, Mo: 0.1-2.0 wt%, Cu: 0.5-2.0 wt%, N: 0.08-0.20 wt% and S: 0-0.002 wt%, with the balance being iron and unavoidable impurities; (2) in terms of mass percentage, C: 0-0.05 wt%, Si: 0-1.5 wt%, Mn: 0-3.0 wt%, Cr: 18.0-25.0 wt%, Ni: 4.0-10.0 wt%, Cu: 1.0-2.0 wt%, Mo: 0.1-2.0 wt%, N: 0.08-0.20 wt% and S: 0-0.002 wt%, with the balance being iron and unavoidable impurities; (3) In terms of mass percentage, C: 0-0.05wt%, Si: 0-1.5wt%, Mn: 0-3.0wt%, Cr: 18.0-25.0wt%, Ni: 4.0-8.0wt%, Cu: 1.0-2.0wt%, Mo: 0.1-2.0wt%, N: 0.08-0.20wt% and S: 0-0.002wt%, with the balance being iron and unavoidable impurities.

3. The duplex stainless steel according to claim 2, characterized in that The components of the duplex stainless steel are selected from any one of the following groups: (1) In terms of mass percentage, C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 18.0-20.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, Mo: 1.5wt%, N: 0.08-0.10wt% and S: 0.002wt%, with the balance being iron and unavoidable impurities; (2) In terms of mass percentage, C: 0.05 wt%, Si: 1.5 wt%, Mn: 3.0 wt%, Cr: 20.0 wt%, Ni: 6.0 wt%, Cu: 1.0 wt%, Mo: 1.5 wt%, N: 0.10 wt% and S: 0.002 wt%, with the balance being iron; (3) In terms of mass percentage, C: 0.05wt%, Si: 1.5wt%, Mn: 3.0wt%, Cr: 18.0wt%, Ni: 6.0wt%, Cu: 1.0wt%, Mo: 1.5wt%, N: 0.08wt% and S: 0.002wt%, with the balance being iron.

4. A method for preparing duplex stainless steel, characterized in that: It includes the following steps: (1) Melting: placing the raw materials in a vacuum electric furnace for smelting and casting; (2) Forging: Forging at 900-1300°C to obtain a blank; (3) Hot rolling: The billet is hot rolled for multiple times at 1150-1250°C, and then hot rolled at 1200-1300°C and subjected to water quenching and solution treatment; (4) Cold rolling: Grind the blank and cold roll it several times.

5. The preparation method according to claim 4, characterized in that: The preparation method satisfies one or more of the following: (a) In the step (1), the casting is electroslag remelted again; (b) In the step (2), the forging start temperature is 1100-1300°C; (c) In step (2), the final forging temperature is 900-1100° C.; (d) In step (3), the hot rolling temperature is 1200° C. (e) In the step (3), the number of hot rolling is 2-5 times; (f) In the step (3), the thickness of the hot-rolled blank is 10-20 mm; (g) In the step (3), the temperature of the heat preservation after hot rolling is 1250°C; (h) In step (3), the insulation time is 20-60 min; (i) In step (4), the number of cold rolling is 10-30 times; (j) In step (4), the cold rolling deformation is 80-95%; (k) In step (4), the thickness of the blank after cold rolling is 0.5-1.5 mm.

6. The preparation method according to claim 5, characterized in that: The preparation method satisfies one or more of the following: (b1) In step (2), the forging start temperature is 1150-1250°C; (c1) In step (2), the final forging temperature is 950-1050°C; (e1) In step (3), the hot rolling is performed 2 to 4 times; (f1) In step (3), the thickness of the hot-rolled billet is 12-18 mm; (h1) In step (3), the insulation time is 30-40 min; (i1) In step (4), the number of cold rolling is 15-25 times; (j1) In step (4), the cold rolling deformation is 85-95%; (k1) In step (4), the thickness of the blank after cold rolling is 0.8-1.2 mm.

7. The preparation method according to claim 6, characterized in that: The preparation method satisfies one or more of the following: (b2) In the step (2), the forging start temperature is 1200°C; (c2) In step (2), the final forging temperature is 1000°C; (e2) In step (3), the hot rolling is performed three times; (f2) In step (3), the thickness of the blank after hot rolling is 15 mm; (i2) In step (4), the number of cold rolling is 20 times; (j2) In step (4), the cold rolling deformation is 90%; (k2) In step (4), the thickness of the blank after cold rolling is 1.0 mm.

8. The preparation method according to claim 7, characterized in that: The preparation method comprises the following steps: (1) Melting: The above raw materials are smelted in a vacuum electric furnace, cast into billets and forged into Φ40 mm round bars, and then further refined by electroslag remelting; (2) Forging: The cast ingot is forged again to form a rectangular billet. The forging temperature is controlled at 1200°C and the final forging temperature is greater than 1000°C. (3) Hot rolling: at 1200°C, further hot rolled to 15 mm thickness through 3 passes, then subjected to 1250°C, heat preservation for 30 min, and water quenching and solution treatment; (4) Cold rolling: The surface of the slab after solution treatment is ground and then cold rolled to 1.0 mm through 20 passes. The deformation of the cold rolling is 90%.

9. A duplex stainless steel, characterized in that: The components thereof are as described in any one of claims 1 to 3, and the preparation method thereof is as described in any one of claims 4 to 8.

10. The duplex stainless steel according to claim 9, characterized in that: The stainless steel is prepared by the following preparation method (1) Melting: The raw materials are smelted in a vacuum electric furnace, cast into billets and forged into Φ40 mm round bars, and then further refined by electroslag remelting; (2) Forging: The cast ingot is forged again to form a rectangular billet. The forging temperature is controlled at 1200°C and the final forging temperature is greater than 1000°C. (3) Hot rolling: at 1200°C, further hot rolled to 15 mm thickness through 3 passes, then subjected to 1250°C, heat preservation for 30 min, and water quenching and solution treatment; (4) Cold rolling: The surface of the slab after solution treatment is ground and then cold rolled to 1.0 mm through 20 passes. The deformation of the cold rolling is 90%; The raw materials include: C: 0.05wt% or less, Si: 1.5wt% or less, Mn: 3.0wt% or less, Cr: 18.0-25.0wt%, Ni: 4.0-10.0wt%, preferably 4.0-8.0wt%, Cu: 0.5-2.0wt%, preferably 1.0-2.0wt%, Mo: 0.1-2.0wt%, N: 0.08-0.20wt% and S: 0.002wt% or less, and the balance is iron and inevitable impurities. The duplex stainless steel is composed of components.