A Fe-15Mn-22Cr-0.9N austenitic stainless steel and preparation method thereof

Abstract

The present invention relates to the technical field of high nitrogen austenitic stainless steel, specifically a Fe‑15Mn‑22Cr‑0.9N austenitic stainless steel, wherein the chemical components and weight percentages thereof are respectively: C≤0.068%, Si≤0.42%, Mn≤15%, P≤0.003%, Ni: 1.0-1.5%, Cr: 21-23%, N: 0.5-1%, and the rest are Fe and unavoidable impurities. The preparation method comprises: performing multiple passes of rolling a Fe‑15Mn‑22Cr‑0.9N steel plate at 600°C, wherein the pressing amount per pass in the early stage is 1mm, and the pressing amount is changed to 0.5mm after the deformation amount is 50%, and the sample is put back into a heating furnace for insulation for 2 min before each pass of rolling, and the rolling temperature is controlled to change by no more than 5%, and finally obtaining samples with nominal rolling amounts of 20%, 40%, 60% and 75%. The present invention uses a warm rolling + annealing process, and preheating the material can reduce deformation resistance during rolling, thereby reducing the difficulty of preparing high-strength and high-nitrogen austenitic stainless steel plates.

Description

Technical Field

[0001] The invention relates to the technical field of high nitrogen austenitic stainless steel preparation, and in particular to Fe-15Mn-22Cr-0.9N austenitic stainless steel and a preparation method thereof. Background Art

[0002] High nitrogen austenitic stainless steel has the characteristics of high strength, good toughness, creep resistance, corrosion resistance and good formability, and is widely used in various industrial and technical fields, attracting the attention of many material scholars. At present, Russia, Japan and many European countries are accelerating the research and development of new high nitrogen austenitic stainless steel. my country has included high nitrogen austenitic stainless steel in the key funding areas to promote the research and application of high nitrogen austenitic stainless steel.

[0003] However, high nitrogen austenitic stainless steel is generally used in a coarse-grained solid solution state, and its strength still cannot meet the service requirements of key components and special working conditions, so it needs to be treated to improve its strength. The conventional practice to improve the strength of austenitic stainless steel is to introduce dislocations and refine grains by combining plastic deformation and heat treatment. However, this material strengthening method is not applicable to high nitrogen austenitic stainless steel. Because the nitrogen element is in an oversaturated state, high nitrogen steel produces a large number of dislocations after plastic deformation, which promotes the precipitation of nitrides, and the material becomes brittle. Therefore, the industrial technology field urgently needs a method for preparing high-strength, high-toughness, high-nitrogen austenitic stainless steel with a single-phase austenitic structure. In this regard, this patent targets the work hardening behavior and deformation mechanism of Fe-15Mn-22Cr-0.9N austenitic stainless steel rolled at different temperatures, as well as the influence of deformation organization characteristics on nitride precipitation in subsequent annealing, and couples deformation and phase transformation to prepare high-strength and high-toughness high nitrogen austenitic stainless steel. The technical path achieves high strength of the material without compromising toughness. Summary of the invention

[0004] The object of the present invention is to provide a Fe-15Mn-22Cr-0.9N austenitic stainless steel and a preparation method thereof. The present invention uses a warm rolling + annealing process. Preheating the material can reduce the deformation resistance during rolling, thereby reducing the difficulty of preparing high-strength and high-nitrogen austenitic stainless steel sheets. Annealing after warm rolling can significantly reduce the precipitation of harmful nitrides and avoid the brittleness problem, thereby obtaining high-strength and high-plasticity austenitic stainless steel to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above-mentioned object, one aspect of the present invention provides a Fe-15Mn-22Cr-0.9N austenitic stainless steel, wherein the chemical components and weight percentages of the Fe-15Mn-22Cr-0.9N austenitic stainless steel are: C≤0.068%, Si≤0.42%, Mn≤15%, P≤0.003%, Ni: 1.0~1.5%, Cr: 21~23%, N: 0.5~1%, and the rest are Fe and unavoidable impurities.

[0006] Preferably, the yield strength of the Fe-15Mn-22Cr-0.9N austenitic stainless steel is ≥1200 MPa, the tensile strength is ≥1500 MPa, and the uniform elongation is ≥12%.

[0007] Another aspect of the present invention provides a method for preparing Fe-15Mn-22Cr-0.9N austenitic stainless steel, comprising:

[0008] The Fe-15Mn-22Cr-0.9N steel plate is warm rolled to obtain Fe-15Mn-22Cr-0.9N stainless steel with a single-phase austenite structure. After the warm rolling is completed, aging annealing is performed to obtain a high-strength and high-toughness Fe-15Mn-22Cr-0.9N austenitic stainless steel plate.

[0009] The warm rolling comprises:

[0010] The Fe-15Mn-22Cr-0.9N steel plate was rolled in multiple passes at 600 ℃. The initial pressing amount for each pass was 1 mm. After the deformation reached 50%, the pressing amount was changed to 0.5 mm. Before each rolling pass, the sample was put back into the heating furnace for 2 min. The rolling temperature change was controlled not to exceed 5%. Finally, samples with nominal rolling amounts of 20%, 40%, 60% and 75% were obtained.

[0011] The preparation method further comprises:

[0012] Before warm rolling, the Fe-15Mn-22Cr-0.9N steel plate was placed in a 600 ℃ heating furnace for 10 min, and then placed in a heating furnace for 2-3 min before each rolling. After rolling, it was placed in a heating furnace at 600 ℃ for 1 h of isothermal treatment and slowly cooled in air to obtain the desired plate.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The preparation method of Fe-15Mn-22Cr-0.9N austenitic stainless steel provided in the embodiment of the present invention adopts a warm rolling process. Preheating the material can reduce the deformation resistance during rolling, thereby reducing the difficulty of preparing high-strength and high-nitrogen austenitic stainless steel sheets; the uniform elongation of the warm-rolled sample is significantly improved after annealing (doubled compared with before annealing), and a better strength-plasticity match is obtained at the same time; the present invention relies on conventional rolling equipment, has a simple operation process, is conducive to large-scale continuous production, has a short production cycle time, high production efficiency, and low production cost; the yield strength ≥1200 MPa, the tensile strength ≥1500 MPa, and the uniform elongation ≥12% are obtained by this method. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of a processing flow of a method for preparing Fe-15Mn-22Cr-0.9N austenitic stainless steel provided in an embodiment of the present invention;

[0016] Figure 2 The optical microstructure diagram of the Fe-15Mn-22Cr-0.9N austenitic stainless steel plate after treatment in Example 1 and Comparative Example 2 in the embodiments of the present invention.

[0017] Figure 3 Engineering stress-strain curves of tensile tests of Fe-15Mn-22Cr-0.9N austenitic stainless steel plates after treatment in Examples 1 and 2 and Comparative Examples 1-3 in the embodiments of the invention.

[0018] Description of reference numerals:

[0019] 1. Fe-15Mn-22Cr-0.9N steel plate, 2. Heating furnace, 3. Upper roller, 4. Lower roller. Implementation

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The invention provides a Fe-15Mn-22Cr-0.9N austenitic stainless steel. The chemical components and weight percentages of the Fe-15Mn-22Cr-0.9N austenitic stainless steel are respectively: C≤0.068%, Si≤0.42%, Mn≤15%, P≤0.003%, Ni: 1.0-1.5%, Cr: 21-23%, N: 0.5-1%, and the rest are Fe and unavoidable impurities.

[0022] Furthermore, the yield strength of the Fe-15Mn-22Cr-0.9N austenitic stainless steel is ≥1200 MPa, the tensile strength is ≥1500 MPa, and the uniform elongation is ≥12%.

[0023] The present invention provides a method for preparing Fe-15Mn-22Cr-0.9N austenitic stainless steel. The specific processing flow diagram is as follows: Figure 1 As shown, specifically including:

[0024] The Fe-15Mn-22Cr-0.9N steel plate 1 was rolled in multiple passes at 600 °C by using the upper roller 3 and the lower roller 4. The pressing amount of each pass was 1 mm in the early stage, and the pressing amount was changed to 0.5 mm after the deformation reached 50%. Before each rolling, the sample was put back into the heating furnace 2 for 2 min, and the rolling temperature change was controlled not to exceed 5%. Finally, samples with nominal rolling amounts of 20%, 40%, 60% and 75% were obtained.

[0025] Before warm rolling, the Fe-15Mn-22Cr-0.9N steel plate 1 was placed in a 600°C heating furnace 2 for 10 min, and then before each rolling pass, the Fe-15Mn-22Cr-0.9N steel plate 1 was placed in a heating furnace 2 for 2-3 min. Then, the steel plate was placed in a heating furnace at 600°C for isothermal treatment for 1 h.

[0026] Figure 2 The optical microstructure diagram of the Fe-15Mn-22Cr-0.9N austenitic stainless steel plate after treatment in Example 1 and Comparative Example 2 in the embodiment of the present invention is shown in FIG. Figure 3 Engineering stress-engineering strain curves of tensile tests of Fe-15Mn-22Cr-0.9N austenitic stainless steel plates after treatment in Examples 1 and 2 and Comparative Examples 1-3 in the embodiments of the invention. The present invention is further described in detail below in conjunction with the embodiments. Example

[0027] (1) Warm rolling: The Fe-15Mn-22Cr-0.9N austenitic stainless steel in the solid solution state is processed into a plate with a thickness of 10 mm. The surface is degreased and mechanically ground; before each rolling pass, it is placed in a heating furnace at 600°C for 2-3 minutes; the plate is rolled to a thickness of 6.1 mm ± 0.1 mm in 6 passes, with a total rolling reduction of 40%.

[0028] (2) The Fe-15Mn-22Cr-0.9N austenitic stainless steel plate obtained by the above method in this embodiment has a yield strength of 1350 MPa, a tensile strength of 1462 MPa, and a uniform elongation of 3.4%. The OM image of the stainless steel plate after treatment in Example 1 is as follows: Figure 2As shown in Figure a, the engineering stress-strain curve is Figure 3 shown. Example

[0029] (1) Warm rolling-annealing: The Fe-15Mn-22Cr-0.9N austenitic stainless steel in the solid solution state is processed into a plate with a thickness of 10 mm. The surface is degreased and mechanically ground; before each rolling pass, it is placed in a heating furnace at 600°C for 2-3 minutes. The plate is rolled to a thickness of 6.1 mm ± 0.1 mm in 6 passes, with a total rolling reduction of 40%; after rolling, it is placed in a heating furnace at 600°C for isothermal treatment for 1 h.

[0030] (2) The Fe-15Mn-22Cr-0.9N austenitic stainless steel plate obtained by the above method in this embodiment has a yield strength of 1220 MPa, a tensile strength of 1548 MPa, and a uniform elongation of 14%. The engineering stress-strain curve of the stainless steel plate after treatment in Example 2 is shown in FIG. Figure 3 shown.

[0031] Comparative Example 1

[0032] The yield strength of Fe-15Mn-22Cr-0.9N austenitic stainless steel plate in solid solution state is 440 MPa, the tensile strength is 1400 MPa, the uniform elongation is 42%, and the engineering stress-strain curve is as follows: Figure 3 shown.

[0033] Comparative Example 2

[0034] (1) Cold rolling: Fe-15Mn-22Cr-0.9N austenitic stainless steel in solid solution state is processed into a plate with a thickness of 10 mm; its surface is degreased and mechanically ground, and the plate is rolled to a thickness of 6.1 mm ± 0.1 mm in 6 passes at room temperature, with a total rolling reduction of 40%.

[0035] (2) The Fe-15Mn-22Cr-0.9N austenitic stainless steel sheet obtained by the above method in this comparative example has a yield strength of 1400 MPa, a tensile strength of 1579 MPa, and a uniform elongation of 2.9%. The OM image of the stainless steel sheet after the treatment in comparative example 2 is as follows: Figure 2 As shown in the middle b picture, the engineering stress-strain curve is Figure 3 shown.

[0036] Comparative Example 3

[0037] (1) Cold rolling-annealing: The Fe-15Mn-22Cr-0.9N austenitic stainless steel plate in the solid solution state was processed into a plate with a thickness of 10 mm; its surface was degreased and mechanically ground, and the plate was rolled to a thickness of 6.1 mm ± 0.1 mm in 6 passes at room temperature, with a total rolling reduction of 40%; then it was placed in a heating furnace at 600 °C for isothermal treatment for 1 h.

[0038] (2) The Fe-15Mn-22Cr-0.9N austenitic stainless steel plate obtained by the above method in this comparative example has a yield strength of 1325 MPa, a tensile strength of 1682 MPa, and a uniform elongation of 4.8%. The engineering stress-strain curve is shown in Figure 3 shown.

[0039] according to Figure 2 It can be seen that the evolution of metallographic structures of cold rolling and warm rolling can reveal differences in their organizational morphology. There are more deformation twins and slip bands in the cold rolling structure, while it is difficult to see the existence of deformation twins in the warm rolling structure under an optical microscope. This shows that the deformation mechanisms of cold rolling and warm rolling are different. Cold rolling deformation is mainly twinning, while warm rolling deformation is mainly dislocation slip.

[0040] according to Figure 3 It can be seen that the cold-rolled-annealed samples still maintain a long uniform plastic stage after yielding, indicating that annealing can improve the uniform elongation of room temperature rolled samples to a certain extent, and also indicate that the annealed samples have a certain work hardening ability, but annealing will cause the sample toughness to drop sharply and brittle fracture. Although the yield strength of the warm-rolled samples is reduced due to annealing, its uniform elongation is significantly improved (doubled compared to before annealing), and a better strength-plasticity match is obtained. Through the above analysis, it can be found that warm rolling + annealing is an effective technical path to obtain high nitrogen steel with strong plasticity matching, that is, high-strength-high-plasticity austenitic stainless steel sheets can be obtained by warm rolling at 600 ℃ for 40% and annealing at 600 ℃ for 1h.

[0041] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A Fe-15Mn-22Cr-0.9N austenitic stainless steel, characterized in that: The chemical components and weight percentages of the Fe-15Mn-22Cr-0.9N austenitic stainless steel are: C≤0.068%, Si≤0.42%, Mn≤15%, P≤0.003%, Ni: 1.0-1.5%, Cr: 21-23%, N: 0.5-1%, and the rest are Fe and unavoidable impurities; The Fe-15Mn-22Cr-0.9N austenitic stainless steel has a yield strength of ≥1200 MPa, a tensile strength of ≥1500 MPa, and a uniform elongation of ≥12%; The preparation method of the Fe-15Mn-22Cr-0.9N austenitic stainless steel comprises: The Fe-15Mn-22Cr-0.9N steel plate was warm rolled to obtain Fe-15Mn-22Cr-0.9N stainless steel with a single-phase austenite structure. After rolling, it was placed in a heating furnace at 600°C for 1 h and slowly cooled in air to obtain a high-strength and high-toughness Fe-15Mn-22Cr-0.9N austenitic stainless steel plate. The warm rolling comprises: The Fe-15Mn-22Cr-0.9N steel plate was rolled in multiple passes at 600 ℃. The initial pressing amount for each pass was 1 mm. After the deformation reached 50%, the pressing amount was changed to 0.5 mm. Before each rolling pass, the sample was put back into the heating furnace for 2 min. The rolling temperature change was controlled not to exceed 5%. Finally, samples with nominal rolling amounts of 20%, 40%, 60% and 75% were obtained.

2. The Fe-15Mn-22Cr-0.9N austenitic stainless steel according to claim 1, characterized in that: The preparation method further comprises: Before warm rolling, the Fe-15Mn-22Cr-0.9N steel plate was placed in a 600 ℃ heating furnace and kept warm for 10 min. Then, before each rolling pass, the Fe-15Mn-22Cr-0.9N steel plate was placed in a heating furnace and kept warm for 2 to 3 min.

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