A method for preparing high-performance duplex stainless steel

Abstract

This invention discloses a method for preparing high-performance duplex stainless steel, belonging to the field of duplex stainless steel technology. This invention achieves optimal performance of duplex stainless steel by adjusting its chemical composition and preparation method. The preparation method includes the following steps: a stainless steel billet is sequentially forged, rolled, and solution-treated, then water-quenched, and finally aged at 680-860℃ for 0.5-60 hours. The chemical composition and mass percentage of the stainless steel billet are: C: 0.01-0.02%, Si: 0.03-0.04%, Mn: 8.25-8.40%, Cr: 21.02-22.03%, Ni: 0.54-0.56%, Mo: 0.91-1.02%, Cu: 0.30-0.32%, N: 0.24-0.25%, P≤0.01%, S≤0.01%, with the balance being Fe and unavoidable impurities. The high-performance duplex stainless steel described in this invention can significantly improve its impact toughness while maintaining high strength and plasticity, and the use of Mn to replace Ni can greatly save costs.

Description

Technical Field

[0001] This invention belongs to the field of duplex stainless steel technology, and specifically relates to a method for preparing high-performance duplex stainless steel. Background Technology

[0002] Duplex stainless steel is composed of two phases, ferrite (δ) and austenite (γ), each accounting for about 50%, and the content of the lesser phase is generally more than 30%. It combines the advantages of ferritic stainless steel and austenitic stainless steel, and has excellent mechanical and corrosion resistance properties. It is currently widely used in petrochemical, marine, papermaking and energy industries.

[0003] Chinese invention application CN85106667A discloses a method for preparing duplex ultra-high strength aging stainless steel, but the high Ni content in this duplex stainless steel increases product cost. Chinese invention application CN114959223A discloses a method for optimizing the properties of duplex stainless steel. By designing the chemical composition of the duplex stainless steel and combining it with solution treatment, a manganese-substituted nickel-saving duplex stainless steel with optimal mechanical properties and corrosion resistance is obtained; however, its mechanical properties are not significantly improved. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing high-performance duplex stainless steel.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing high-performance duplex stainless steel, which achieves optimal performance of duplex stainless steel by adjusting its chemical composition and preparation method; includes the following steps:

[0007] After the stainless steel billet is forged, rolled, and solution treated in sequence, it is then water-quenched and finally aged at 830-860℃ for 0.5-60 hours.

[0008] The chemical composition and mass percentage of the stainless steel billet are as follows: C: 0.01-0.02%, Si: 0.03-0.04%, Mn: 8.25-8.40%, Cr: 21.02-22.03%, Ni: 0.54-0.56%, Mo: 0.91-1.02%, Cu: 0.30-0.32%, N: 0.24-0.25%, P≤0.01%, S≤0.01%, with the balance being Fe and unavoidable impurities.

[0009] When the aging treatment is carried out at a temperature of 830-860℃ for a time of 0.5-60h, duplex stainless steel with better mechanical properties is obtained.

[0010] In a preferred embodiment of the present invention, when the aging treatment is carried out at a temperature of 850°C for 54 hours, duplex stainless steel with the best mechanical properties is obtained.

[0011] As a preferred embodiment of the present invention, the forging conditions are as follows: forging begins at a temperature of 1050-1150℃, the forging ratio is 2-3, the final forging temperature is ≥980℃, and cooling occurs after forging.

[0012] As a preferred embodiment of the present invention, the rolling conditions are: initial rolling temperature of 1120-1180℃ and final rolling temperature of >960℃.

[0013] In a preferred embodiment of the present invention, the rolling process is followed by room temperature water quenching to obtain a sheet metal.

[0014] In a preferred embodiment of the present invention, the solution treatment temperature is 1050°C and the time is 30 min.

[0015] Excessively high or low solution temperatures can cause a significant decrease in the impact absorption energy of the prepared material, down to as low as 178 J.

[0016] In a preferred embodiment of the present invention, the water quenching is performed at room temperature.

[0017] In a preferred embodiment of the present invention, the aging treatment is followed by room temperature water cooling to obtain high-performance duplex stainless steel.

[0018] As a preferred embodiment of the present invention, when the solution treatment temperature is 1050℃ and the time is 0.5h, and the aging temperature is 830~860℃ and the time is 0.5~1.5h, the high-performance duplex stainless steel obtained has an impact energy ≥258.4J, a tensile strength ≥731MPa, and a reduction of area ≥73%.

[0019] As a preferred embodiment of the present invention, when the solution treatment temperature is 1050℃ and the time is 0.5h, and the aging temperature is 830~860℃ and the time is 53~55h, the high-performance duplex stainless steel obtained has an impact energy ≥283.6J, tensile strength ≥733MPa, and reduction of area ≥78%.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The high Mn ultra-low Ni duplex stainless steel obtained by the present invention through adjusting the chemical composition and content of duplex stainless steel and combining it with the aging treatment preparation process can significantly improve its impact toughness while maintaining high strength and plasticity, and the substitution of Ni with Mn can greatly save costs and effectively improve the mechanical properties of duplex stainless steel. Detailed Implementation

[0021] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0022] Example 1

[0023] The chemical composition and mass percentage of the stainless steel billet are as follows: C: 0.01%, Si: 0.03%, Mn: 8.40%, Cr: 21.44%, Ni: 0.56%, Mo: 0.91%, Cu: 0.31%, N: 0.24%, P: 0.01%, S: 0.01%, with the balance being Fe and unavoidable impurities.

[0024] The method for preparing the high-performance duplex stainless steel includes the following steps:

[0025] (1) The stainless steel billet was prepared by a 50kg vacuum melting furnace. The stainless steel billet was pre-forged at 1160℃, the forging ratio was 4, the final forging temperature was 980℃, and it was rapidly cooled after forging. Then it was pre-rolled at 1150℃ and the final rolling temperature was 960℃. After water quenching, the plate was obtained.

[0026] (2) The board obtained in step (1) is subjected to solution treatment at 1050℃ for 30 minutes, and then cooled at room temperature.

[0027] (3) The board obtained in step (2) is subjected to aging treatment under the following conditions: 850℃ for 1 hour, and then cooled at room temperature.

[0028] (4) The mechanical properties of the sheet were tested by tensile test and impact test. The impact test results are shown in Table 1 and the tensile test results are shown in Table 2.

[0029] Example 2

[0030] The chemical composition and mass percentage of the stainless steel billet described in this embodiment are the same as those in Example 1.

[0031] The only difference between the preparation method of the high-performance duplex stainless steel described in this embodiment and that in embodiment 1 is that the aging treatment time in step (3) is 54 hours.

[0032] The mechanical properties of the sheet were tested using tensile and impact tests. The results of the impact test are shown in Table 1, and the results of the tensile test are shown in Table 2.

[0033] Example 3

[0034] The chemical composition and mass percentage of the stainless steel billet described in this embodiment are the same as those in Example 1.

[0035] The only difference between the preparation method of the high-performance duplex stainless steel described in this embodiment and that in embodiment 1 is that the aging treatment time in step (3) is 30 hours.

[0036] The mechanical properties of the sheet were tested using tensile and impact tests. The results of the impact test are shown in Table 1, and the results of the tensile test are shown in Table 2.

[0037] Comparative Example 1

[0038] The only difference between the preparation method of the high-performance duplex stainless steel described in this comparative example and Example 1 is that the chemical composition and mass percentage of the stainless steel billet are: C: 0.023%, Si: 0.47%, Mn: 1.34%, Cr: 22.41%, Ni: 5.15%, Mo: 3.10%, Cu: 0.16%, N: 0.16%, P: 0.02%, S: 0.01%, with the balance being Fe and unavoidable impurities.

[0039] The mechanical properties of the sheet were tested using tensile and impact tests. The results of the impact test are shown in Table 1, and the results of the tensile test are shown in Table 2.

[0040] Comparative Example 2

[0041] The only difference between the preparation method of the high-performance duplex stainless steel described in this comparative example and Example 2 is that the chemical composition and mass percentage of the stainless steel billet are: C: 0.023%, Si: 0.47%, Mn: 1.34%, Cr: 22.41%, Ni: 5.15%, Mo: 3.10%, Cu: 0.16%, N: 0.16%, P: 0.02%, S: 0.01%, with the balance being Fe and unavoidable impurities.

[0042] The mechanical properties of the sheet were tested using tensile and impact tests. The results of the impact test are shown in Table 1, and the results of the tensile test are shown in Table 2.

[0043] Comparative Example 3

[0044] The only difference between the preparation method of the high-performance duplex stainless steel described in this comparative example and Example 3 is that the chemical composition and mass percentage of the stainless steel billet are: C: 0.023%, Si: 0.47%, Mn: 1.34%, Cr: 22.41%, Ni: 5.15%, Mo: 3.10%, Cu: 0.16%, N: 0.16%, P: 0.02%, S: 0.01%, with the balance being Fe and unavoidable impurities.

[0045] The mechanical properties of the sheet were tested using tensile and impact tests. The results of the impact test are shown in Table 1, and the results of the tensile test are shown in Table 2.

[0046] Comparative Example 4

[0047] The chemical composition and mass percentage of the stainless steel billet are as follows: C: 0.01%, Si: 0.03%, Mn: 8.40%, Cr: 21.44%, Ni: 0.56%, Mo: 0.91%, Cu: 0.31%, N: 0.24%, P: 0.01%, S: 0.01%, with the balance being Fe and unavoidable impurities.

[0048] The method for preparing the high-performance duplex stainless steel includes the following steps:

[0049] (1) The stainless steel billet was prepared by a 50kg vacuum melting furnace. The stainless steel billet was pre-forged at 1160℃, the forging ratio was 4, the final forging temperature was 980℃, and it was rapidly cooled after forging. Then it was pre-rolled at 1150℃ and the final rolling temperature was 960℃. After water quenching, the plate was obtained.

[0050] (2) The plate obtained in step (1) is subjected to solution treatment at 1050℃ for 30 min, and then cooled at room temperature to obtain high-performance duplex stainless steel.

[0051] The mechanical properties of the sheet were tested using tensile and impact tests. The results of the impact test are shown in Table 1, and the results of the tensile test are shown in Table 2.

[0052] Comparative Example 5

[0053] The chemical composition and mass percentage of the stainless steel billet described in this comparative example are the same as those in Example 1.

[0054] The only difference between the preparation method of the high-performance duplex stainless steel described in this comparative example and that in Example 1 is that the aging treatment temperature in step (3) is 700°C.

[0055] The mechanical properties of the sheet were tested using tensile and impact tests. The results of the impact test are shown in Table 1, and the results of the tensile test are shown in Table 2.

[0056] Comparative Example 6

[0057] The chemical composition and mass percentage of the stainless steel billet described in this comparative example are the same as those in Example 1.

[0058] The only difference between the preparation method of the high-performance duplex stainless steel described in this comparative example and that in Example 1 is that the aging treatment temperature in step (3) is 800°C.

[0059] The mechanical properties of the sheet were tested using tensile and impact tests. The results of the impact test are shown in Table 1, and the results of the tensile test are shown in Table 2.

[0060] Table 1

[0061]

[0062] Table 2

[0063]

[0064] As shown in Tables 1-2, the impact energy of Examples 1-3 is much higher than that of Comparative Examples 1-6, while the reduction of area of ​​Comparative Examples 1-3 is much lower than that of Examples 1-3. The plasticity of Comparative Examples 4-6 is not much different from that of the Examples. Due to the redistribution of elements and the reduction of as-cast stress during the aging process, the material properties change during aging, that is, while maintaining high tensile strength, yield strength and reduction of area, the impact absorption energy is significantly improved. This further illustrates that the high-Mn ultra-low-Ni duplex stainless steel obtained by adjusting the chemical composition and content of duplex stainless steel and combining forging, rolling, solution treatment and aging treatment processes can significantly improve its impact toughness while maintaining high strength and plasticity. Moreover, replacing Ni with Mn significantly saves costs and effectively improves the mechanical properties of duplex stainless steel.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing high-performance duplex stainless steel, characterized in that, The optimal performance of duplex stainless steel is achieved by adjusting its chemical composition and preparation method. The preparation method includes the following steps: The stainless steel billet is forged, rolled, and solution treated in sequence, then water-quenched, and finally aged at 850℃ for 54 hours. The chemical composition and mass percentage of the stainless steel billet are as follows: C: 0.01~0.02%, Si: 0.03~0.04%, Mn: 8.25~8.40%, Cr: 21.02~22.03%, Ni: 0.54~0.56%, Mo: 0.91~1.02%, Cu: 0.30~0.32%, N: 0.24~0.25%, P≤0.01%, S≤0.01%, with the balance being Fe and unavoidable impurities.

2. The method for preparing high-performance duplex stainless steel as described in claim 1, characterized in that, The forging conditions are as follows: forging begins at a temperature of 1050-1150℃, the forging ratio is 2-3, the final forging temperature is ≥980℃, and cooling is performed after forging.

3. The method for preparing high-performance duplex stainless steel as described in claim 1, characterized in that, The rolling conditions are as follows: initial rolling temperature is 1120-1180℃, and final rolling temperature is >960℃.

4. The method for preparing high-performance duplex stainless steel as described in claim 1, characterized in that, The rolled material is then quenched in water at room temperature to obtain a sheet metal.

5. The method for preparing high-performance duplex stainless steel as described in claim 1, characterized in that, The solution treatment temperature was 1050℃ and the time was 30 minutes.

6. The method for preparing high-performance duplex stainless steel as described in claim 1, characterized in that, The water-cooled quenching is performed at room temperature.

7. The method for preparing high-performance duplex stainless steel as described in claim 1, characterized in that, The aging treatment is followed by room temperature water cooling to obtain high-performance duplex stainless steel.

8. The method for preparing high-performance duplex stainless steel as described in claim 5, characterized in that, When the aging temperature is 850℃ and the time is 54h, the high-performance duplex stainless steel obtained has an impact energy of 283.6J, a tensile strength of 733MPa, and a reduction of area of ​​78%.

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