Martensite and austenite duplex stainless steel with enhanced Al3Ti precipitated phase and preparation method of martensite and austenite duplex stainless steel

Abstract

The invention relates to the technical field of alloy materials, in particular to martensite and austenite duplex stainless steel with an enhanced Al < 3 > T precipitated phase and a preparation method of the martensite and austenite duplex stainless steel. The stainless steel comprises the following alloy components in percentage by mass: 0 to 0.07 weight percent of C, 10 to 14 weight percent of Cr, 8 to 12 weight percent of Ni, 2 to 4 weight percent of Mo, 0.5 to 1 weight percent of Al, and the balance of Fe and inevitable impurities, wherein T is 1.8 times of that of Al. The method comprises the steps of smelting, solid solution, quenching, rolling and tempering. By adjusting the alloy content ratio and combining a specific high-temperature tempering preparation process, the stainless steel material contains two strong hydrogen trap structures, namely an austenite structure and a precipitated phase, so that the stainless steel material has good hydrogen embrittlement resistance, plasticity and strength and has wide application fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alloy materials, in particular to a martensite-austenite dual-phase stainless steel reinforced by Al3Ti precipitated phase and a preparation method. BACKGROUND

[0002] Super martensitic stainless steel is a series of new type stainless steel developed by reducing C content, controlling Ni content and Mo content and other alloy design on the basis of traditional martensitic stainless steel. Super martensitic stainless steel has high strength, excellent toughness and corrosion resistance. In addition, super martensitic stainless steel also overcomes the poor weldability problem of traditional martensitic stainless steel.

[0003] However, for hydrogen service, super martensitic stainless steel cannot be widely used due to the possible hydrogen embrittlement problem. Through literature research, it is known that for steels with single-phase structure, it is generally believed that steels with martensitic structure have high hydrogen embrittlement sensitivity, and steels with austenitic structure have low hydrogen embrittlement sensitivity. At the same time, it is generally believed that the higher the strength of the steel, the higher the hydrogen embrittlement sensitivity, which is obviously related to the fact that the steels with martensitic structure generally have high strength, while the steels with ferrite and austenite structure generally have low strength.

[0004] At present, there is no stainless steel material with good brittleness resistance, high strength and good plasticity, which seriously limits its application field. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a martensite-austenite dual-phase stainless steel reinforced by Al3Ti precipitated phase and a preparation method, so as to solve the problem that the existing stainless steel material cannot have good brittleness resistance, high strength and good plasticity.

[0006] The technical solution of the present application to solve the above technical problem is as follows:

[0007] The present application provides a martensite-austenite dual-phase stainless steel reinforced by Al3Ti precipitated phase, which contains the following alloy components in terms of mass percentage: C: 0-0.07wt%, Cr: 10-14wt%, Ni: 8-12wt%, Mo: 2-4wt%, Al: 0.5-1wt%, Ti is 1.8 times of Al, and the balance is Fe and inevitable impurities.

[0008] On the basis of the above technical solution, the present application can also be improved as follows.

[0009] Further, the stainless steel contains the following alloy components in percentage by mass: C: 0.05-0.06wt%, Cr: 10-14wt%, Ni: 8-12wt%, Mo: 2-3wt%, Al: 0.6-0.8wt%, Ti: 1.8 times of Al, and the balance of Fe and inevitable impurities.

[0010] Further, the stainless steel contains a martensite-austenite dual phase structure, and the volume percentage of the austenite in the dual phase structure is 15%-35%.

[0011] Further, in the stainless steel, the size of the Al3Ti precipitated phase is less than 50nm.

[0012] Further, the yield strength of the stainless steel is greater than 800MPa, the tensile strength is 920-980MPa, and the elongation is greater than 25%.

[0013] The application also provides a preparation method of the Al3Ti precipitated phase reinforced martensite-austenite dual phase stainless steel as described above, comprising the steps of melting, solid solution, quenching, rolling and tempering.

[0014] Further, the method comprises the following steps:

[0015] S1. Melting under vacuum according to the alloy components to obtain a cast material;

[0016] S2. Solid solution of the cast material at a temperature of 1000-1200℃ for 2-4 hours;

[0017] S3. Quenching at a temperature greater than or equal to 950℃ after the solid solution is completed;

[0018] S4. Rolling the material after quenching is completed;

[0019] S5. Tempering the rolled material at a temperature of 550-680℃ for 1-2 hours.

[0020] Further, in step S4, the deformation amount of the rolling is 40%-70%.

[0021] Further, in step S5, the tempering temperature is 680℃, and the tempering time is 2 hours.

[0022] Further, after step S5 is completed, the material is cooled to obtain the Al3Ti precipitated phase reinforced martensite-austenite dual phase stainless steel.

[0023] The Al3Ti precipitated phase reinforced martensite-austenite duplex stainless steel of the present application has the advantages that by adjusting the alloy content ratio and combining with a specific high-temperature tempering preparation process, the stainless steel material contains two strong hydrogen trap structures of austenite structure and precipitated phase, so that the stainless steel material has good hydrogen embrittlement resistance, plasticity and strength, and has a wide application field. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The microstructure diagram of the precipitated phase in the material of Example 1 of the Al3Ti precipitated phase reinforced martensite-austenite duplex stainless steel of the present application. DETAILED DESCRIPTION

[0025] The principles and features of the present application are described below in conjunction with the accompanying drawings, and the examples are only used to explain the present application and not to limit the scope of the present application.

[0026] The Al3Ti precipitated phase reinforced martensite-austenite duplex stainless steel of the present application contains the following alloy components in terms of mass percentage: C: 0-0.07wt%, Cr: 10-14wt%, Ni: 8-12wt%, Mo: 2-4wt%, Al: 0.5-1wt%, Ti is 1.8 times of Al, and the balance is Fe and inevitable impurities.

[0027] The Al3Ti precipitated phase reinforced martensite-austenite duplex stainless steel of the present application introduces two strong hydrogen trap structures of austenite structure and precipitated phase by adjusting the content of each alloy component. Austenite as a strong hydrogen trap can improve the hydrogen embrittlement resistance of the material, but will reduce the strength of the material. The Al3Ti precipitated phase not only increases the strength of the material, but also is a strong hydrogen trap that can improve the hydrogen embrittlement resistance of the material. Therefore, the stainless steel material of the present application has hydrogen embrittlement resistance, good plasticity and strength, and is a new hydrogen embrittlement resistant high-strength stainless steel material.

[0028] The Al3Ti precipitated phase reinforced martensite-austenite duplex stainless steel of the present application has a wide application field.

[0029] Preferably, the stainless steel contains the following alloy components in terms of mass percentage: C: 0.05-0.06wt%, Cr: 10-14wt%, Ni: 8-12wt%, Mo: 2-3wt%, Al: 0.6-0.8wt%, Ti is 1.8 times of Al, and the balance is Fe and inevitable impurities.

[0030] Preferably, the stainless steel of the present application contains a martensite-austenite duplex structure, and the volume percentage of austenite in the duplex structure is 15%-35%.

[0031] Preferably, in the stainless steel of the present invention, the size of the Al3Ti precipitate is less than 50 nm.

[0032] Preferably, the stainless steel of the present invention has a yield strength greater than 800 MPa, a tensile strength of 920 MPa to 980 MPa, and an elongation greater than 25%.

[0033] The method for preparing Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel of the present invention includes the steps of smelting, solution treatment, quenching, rolling and tempering.

[0034] The preparation method of the present invention, based on the above alloy composition, combined with a specific tempering heat treatment process, enables the formation of an austenitic structure containing 15-35% austenite, constituting a martensitic austenitic duplex structure, and increases the strength of the matrix material by introducing Al3Ti precipitates.

[0035] The preferred and specific steps are as follows:

[0036] S1. Based on the alloy composition, the alloy is melted under vacuum conditions to obtain the cast material.

[0037] Specifically, the melting process needs to be carried out using vacuum melting equipment to avoid oxygen being mixed into the material, which would affect the material's properties.

[0038] Preferably, the furnace is cooled after smelting.

[0039] S2. Under the condition of 1000℃~1200℃, the as-cast material is solution treated for 2~4 hours.

[0040] S3. After solution treatment, quench at a temperature greater than or equal to 950℃.

[0041] Preferably, the quenching medium is water or ice water.

[0042] S4. Roll the quenched material.

[0043] Preferably, the deformation during rolling is 40% to 70%.

[0044] S5. Temper the rolled material at a temperature of 550-680℃ for 1-2 hours.

[0045] Preferably, the tempering temperature is 680℃ and the tempering time is 2 hours.

[0046] Preferably, after completing step S5, the material is cooled to obtain Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel.

[0047] The method described above in this invention increases the hydrogen embrittlement resistance of the material by introducing austenite and Al3Ti precipitates; at the same time, the Al3Ti precipitates compensate for the decrease in mechanical properties caused by the introduction of austenite, thus obtaining a new high-strength, hydrogen embrittlement-resistant duplex stainless steel material.

[0048] The present invention will be illustrated by specific embodiments below.

[0049] Example 1

[0050] The stainless steel material of this embodiment was prepared using the method of the present invention.

[0051] The stainless steel alloy composition of this embodiment is as follows: C: 0.02wt%, Cr: 12wt%, Ni: 8wt%, Mo: 2wt%, Al: 1wt%, Ti: 1.8wt%, with the balance being Fe and unavoidable impurities.

[0052] The preparation steps in this embodiment are as follows:

[0053] S1. Based on the alloy composition, the alloy is smelted under vacuum conditions to obtain a cast material. After smelting, the material is cooled in the furnace.

[0054] S2. The as-cast material is solution-treated at a temperature of 1200℃ for 4 hours.

[0055] S3. After solution treatment, quench at a temperature greater than or equal to 950℃, using water as the quenching medium.

[0056] S4. Roll the quenched material to a deformation of 50%.

[0057] S5. Temper the rolled material at a temperature of 580℃ for 1 hour.

[0058] After completing step S5, the material is cooled to obtain Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel.

[0059] The stainless steel of this embodiment was tested and found to have a yield strength of 840 MPa, a tensile strength of 980 MPa, and an elongation of 30%. The microstructure of the precipitated phase is as follows: Figure 1 As shown, through Figure 1 It can be seen that the size of the Al3Ti precipitate is less than 50 nm.

[0060] Example 2

[0061] The stainless steel material of this embodiment was prepared using the method of the present invention.

[0062] The stainless steel alloy composition of this embodiment is as follows: C: 0.05wt%, Cr: 14wt%, Ni: 10wt%, Mo: 2wt%, Al: 0.6wt%, Ti: 1.8wt%, with the balance being Fe and unavoidable impurities.

[0063] The preparation steps in this embodiment are as follows:

[0064] S1. Based on the alloy composition, the alloy is smelted under vacuum conditions to obtain a cast material. After smelting, the material is cooled in the furnace.

[0065] S2. The as-cast material is solution-treated at a temperature of 1100℃ for 3 hours.

[0066] S3. After solution treatment, when the temperature drops to 1000℃, quench in ice water.

[0067] S4. Roll the quenched material to a deformation of 60%.

[0068] S5. Temper the rolled material at a temperature of 600℃ for 2 hours.

[0069] After completing step S5, the material is cooled to obtain Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel.

[0070] The material in this embodiment has a yield strength of 850 MPa, a tensile strength of 920 MPa, and an elongation of 31%, as tested.

[0071] Example 3

[0072] The stainless steel material of this embodiment was prepared using the method of the present invention.

[0073] The stainless steel alloy composition of this embodiment is as follows: C: 0.06wt%, Cr: 12wt%, Ni: 12wt%, Mo: 2.5wt%, Al: 0.7wt%, Ti: 2.1wt%, with the balance being Fe and unavoidable impurities.

[0074] The preparation steps in this embodiment are as follows:

[0075] S1. Based on the alloy composition, the alloy is smelted under vacuum conditions to obtain a cast material. After smelting, the material is cooled in the furnace.

[0076] S2. The as-cast material is solution-treated at a temperature of 1000℃ for 2 hours.

[0077] S3. After solution treatment, when the temperature drops to 980℃, quench in water.

[0078] S4. Roll the quenched material to a deformation of 40%.

[0079] S5. Temper the rolled material at a temperature of 630℃ for 2 hours.

[0080] After completing step S5, the material is cooled to obtain Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel.

[0081] The material in this embodiment has a yield strength of 845 MPa, a tensile strength of 930 MPa, and an elongation of 35%, as tested.

[0082] Example 4

[0083] The stainless steel material of this embodiment was prepared using the method of the present invention.

[0084] The stainless steel alloy composition of this embodiment is as follows: C: 0.06wt%, Cr: 10wt%, Ni: 8wt%, Mo: 3wt%, Al: 0.8wt%, Ti: 2.4wt%, with the balance being Fe and unavoidable impurities.

[0085] The preparation steps in this embodiment are as follows:

[0086] S1. Based on the alloy composition, the alloy is smelted under vacuum conditions to obtain a cast material. After smelting, the material is cooled in the furnace.

[0087] S2. The as-cast material is solution-treated at a temperature of 1200℃ for 2 hours.

[0088] S3. After solution treatment, when the temperature drops to 1000℃, quench in ice water.

[0089] S4. Roll the quenched material to a deformation of 40%.

[0090] S5. Temper the rolled material at a temperature of 680℃ for 2 hours.

[0091] After completing step S5, the material is cooled to obtain Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel.

[0092] The material in this embodiment has a yield strength of 861 MPa, a tensile strength of 925 MPa, and an elongation of 33%, as tested.

[0093] Comparative Example 1

[0094] The stainless steel alloy composition of this comparative example is as follows: C: 0.05 wt%, Cr: 14 wt%, Ni: 10 wt%, Mo: 2 wt%, with the balance being Fe and unavoidable impurities. Al and Ti were not added to this comparative example.

[0095] The preparation steps for this comparative example are as follows:

[0096] S1. Based on the alloy composition, the alloy is smelted under vacuum conditions to obtain a cast material. After smelting, the material is cooled in the furnace.

[0097] S2. The as-cast material is solution-treated at a temperature of 1100℃ for 3 hours.

[0098] S3. After solution treatment, when the temperature drops to 1000℃, quench in ice water.

[0099] S4. Roll the quenched material to a deformation of 60%.

[0100] S5. Temper the rolled material at a temperature of 600℃ for 2 hours.

[0101] After completing step S5, the material is cooled to obtain stainless steel.

[0102] The material in this comparative example was tested and found to have a yield strength of 690 MPa, a tensile strength of 780 MPa, and an elongation of 30%.

[0103] Comparative Example 2

[0104] The stainless steel alloy composition of this comparative example is as follows: C: 0.06 wt%, Cr: 10 wt%, Ni: 8 wt%, Mo: 3 wt%, Al: 0.8 wt%, Ti: 2 wt%, with the balance being Fe and unavoidable impurities. The Al to Ti ratio in this comparative example is not 1:3.

[0105] The preparation steps in this embodiment are as follows:

[0106] S1. Based on the alloy composition, the alloy is smelted under vacuum conditions to obtain a cast material. After smelting, the material is cooled in the furnace.

[0107] S2. The as-cast material is solution-treated at a temperature of 1200℃ for 2 hours.

[0108] S3. After solution treatment, when the temperature drops to 1000℃, quench in ice water.

[0109] S4. Roll the quenched material to a deformation of 40%.

[0110] S5. Temper the rolled material at a temperature of 680℃ for 2 hours.

[0111] After completing step S5, the material is cooled to obtain stainless steel.

[0112] Due to the change in elemental ratio, the ratio of Al to Ti content is no longer 1:3, which causes Al and Ti to not completely form metallic compounds. Some Ti may react with C to form TiC, resulting in changes in the precipitated phase of the material and a deterioration in plasticity.

[0113] Tests showed that the material in this comparative example had a yield strength of 840 MPa, a tensile strength of 920 MPa, and an elongation of 15%. It can be observed that the plasticity was significantly reduced.

[0114] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0115] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0116] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0117] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0118] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A martensitic-austenitic duplex stainless steel reinforced with Al3Ti precipitates, characterized in that, The stainless steel contains the following alloy composition by weight percentage: C: 0-0.07 wt%, Cr: 10-14 wt%, Ni: 8-12 wt%, Mo: 2-4 wt%, Al: 0.5-1 wt%, Ti is 1.8 times that of Al, and the balance is Fe and unavoidable impurities.

2. The Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel according to claim 1, characterized in that, The stainless steel contains the following alloy composition by weight percentage: C: 0.05-0.06 wt%, Cr: 10-14 wt%, Ni: 8-12 wt%, Mo: 2-3 wt%, Al: 0.6-0.8 wt%, Ti is 1.8 times that of Al, and the balance is Fe and unavoidable impurities.

3. The Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel according to claim 1 or 2, characterized in that, The stainless steel contains a martensitic-austenitic duplex structure, wherein the volume percentage of austenite in the duplex structure is 15% to 35%.

4. An Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel according to claim 1 or 2, characterized in that, In the stainless steel, the size of the Al3Ti precipitate is less than 50 nm.

5. An Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel according to claim 1 or 2, characterized in that, The stainless steel has a yield strength greater than 800 MPa, a tensile strength of 920 MPa to 980 MPa, and an elongation greater than 25%.

6. A method for preparing Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel as described in any one of claims 1 to 5, characterized in that, It includes the steps of smelting, solution treatment, quenching, rolling and tempering.

7. The method for preparing Al3Ti precipitated phase reinforced martensitic austenitic duplex stainless steel according to claim 6, characterized in that, Includes the following steps: S1. According to the alloy composition, the melting is carried out under vacuum conditions to obtain the as-cast material; S2. The as-cast material is subjected to solid solution treatment at a temperature of 1000℃~1200℃ for 2~4 hours. S3. After the solution treatment is completed, the quenching is performed at a temperature greater than or equal to 950°C. S4. The quenched material is then rolled. S5. The rolled material is tempered at a temperature of 550-680°C for 1-2 hours.

8. The method for preparing Al3Ti precipitated phase reinforced martensitic austenitic duplex stainless steel according to claim 7, characterized in that, In step S4, the deformation during rolling is 40% to 70%.

9. The method for preparing Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel according to claim 7, characterized in that, In step S5, the tempering temperature is 680°C and the tempering time is 2 hours.

10. The method for preparing Al3Ti precipitated phase reinforced martensitic austenitic duplex stainless steel according to claim 7, characterized in that, After completing step S5, the material is cooled to obtain the Al3Ti precipitate-reinforced martensitic austenitic duplex stainless steel.

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