High-temperature-resistant stainless steel forge piece and preparation method thereof

Abstract

The invention relates to a high-temperature-resistant stainless steel forge piece and a preparation method thereof, and belongs to the technical field of stainless steel forge piece preparation. The structure of the stainless steel forge piece is single austenite, and the method comprises the steps that a stainless steel blank is subjected to hot forging, the deformation ratio of hot forging is controlled, and the stainless steel forge piece is obtained; and the stainless steel forge piece is sequentially subjected to heat treatment including a first heating section, a first heat preservation section and a cooling section, the temperature of the first heat preservation section is controlled, and the high-temperature-resistant stainless steel forge piece is obtained. The high-temperature-resistant stainless steel forge piece meets the following indexes that the tensile strength Rm is larger than or equal to 520 MPa, the specified non-proportional extension strength Rp0.2 is larger than or equal to 220 MPa, the percentage elongation after fracture A is larger than or equal to 45%, and the room-temperature impact absorbing energy KV2 is larger than or equal to 60 J; and at the temperature of 300 DEG C, the tensile strength Rm is greater than or equal to 409 MPa, and the specified non-proportional extension strength Rp0.2 is greater than or equal to 132 MPa.

Description

Technical Field

[0001] The present application relates to the technical field of stainless steel forging preparation, and in particular to a high temperature resistant stainless steel forging and a preparation method thereof. Background Art

[0002] At present, new requirements have been put forward for some stainless steel forgings, which require not only some mechanical properties at room temperature, but also high temperature mechanical properties. 026Cr18Ni12Mo2N forgings are one of them. The room temperature tensile strength Rm requirement is Rm≥520MPa, and the 300℃ high temperature tensile strength Rm requirement is Rm≥409MPa. Usually the strength of the material decreases significantly with the increase of temperature. From the required value, the strength of this material only decreases by 111MPa from room temperature to 300℃, which is difficult to guarantee.

[0003] 026Cr18Ni12Mo2N is an austenitic stainless steel, and the measured data of room temperature tensile strength Rm is about 530-590MPa. It is difficult to improve the strength of this material by refining the grains through solid solution treatment. How to ensure the high temperature strength at 300℃ has become a difficulty in manufacturing forgings of this material and is worthy of study. Summary of the invention

[0004] The present application provides a high temperature resistant stainless steel forging and a preparation method thereof to solve the following technical problem: how to improve the high temperature resistance of austenitic stainless steel.

[0005] In a first aspect, the present application provides a method for preparing a high temperature resistant stainless steel forging, wherein the structure of the stainless steel forging is a single austenite, and the method comprises:

[0006] Hot forging a stainless steel blank and controlling the deformation ratio of the hot forging to obtain a stainless steel forging;

[0007] The stainless steel forging is subjected to a heat treatment including a first heating section, a first heat preservation section and a cooling section in sequence, and the temperature of the first heat preservation section is controlled to obtain a high temperature resistant stainless steel forging.

[0008] Optionally, the deformation ratio is ≥5.5.

[0009] Optionally, the hot forging includes a first hot forging and a second hot forging; wherein the deformation ratio of the first hot forging is greater than 3.5.

[0010] Optionally, the second hot forging includes heating and forging, and the total time of the heating satisfies the following relationship: t=K1×k2×t1;

[0011] Among them, t-heating time / h; K1-furnace loading coefficient, the value range is 1.0~2.0; K2-billet size coefficient, the value range is 0.7~1.0; t1-single billet heating time / h, the value range is (D / 100)×(1.20~1.40), D-billet diameter;

[0012] The heating includes a preheating section, a second temperature rising section and a second heat preservation section. The time of the preheating section is 10% to 20% of the total heating time, and the time of the second heat preservation section is 15% to 20% of the total heating time.

[0013] Optionally, the temperature of the first insulation section is 1060°C to 1080°C.

[0014] Optionally, the time of the first insulation section is 1.8 min / mm to 2.4 min / mm.

[0015] Optionally, the heating rate of the first heating section is 100°C / h to 150°C / h.

[0016] Optionally, the cooling section uses a circulating water cooling method, and the temperature of the circulating water is ≤40°C.

[0017] Optionally, the high temperature resistant stainless steel forging meets the following indicators:

[0018] Tensile strength Rm ≥ 520MPa, non-proportional elongation strength Rp0.2 ≥ 220MPa, elongation after fracture A ≥ 45%, room temperature impact absorption energy KV2 ≥ 60J;

[0019] At a temperature of 300°C: tensile strength Rm ≥ 409MPa, and non-proportional elongation strength Rp0.2 ≥ 132MPa.

[0020] In a second aspect, the present application provides a high temperature resistant stainless steel forging, which is prepared by the method described in any one of the embodiments of the first aspect.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] The preparation method of the high temperature resistant stainless steel forging provided in the embodiment of the present application, the structure of the stainless steel forging is single austenite, the method comprises: hot forging the stainless steel billet, and controlling the deformation ratio of the hot forging to obtain the stainless steel forging; sequentially performing heat treatment including a heating section, a first insulation section and a cooling section on the stainless steel forging, and controlling the temperature of the first insulation section to obtain the high temperature resistant stainless steel forging. The stainless steel billet is hot forged, and the deformation ratio of the hot forging is controlled, and the deformation ratio makes the deformation degree of the stainless steel billet fine grains, laying the foundation for the subsequent high temperature mechanical properties of the high temperature resistant stainless steel forging; the stainless steel forging is sequentially subjected to heat treatment including a heating section, a first insulation section and a cooling section, and the temperature of the first insulation section is controlled, so that the structure of the stainless steel forging can undergo austenite transformation, uniform chemical composition and avoid grain growth, and obtain a single austenite structure. Therefore, the stainless steel billet can ensure the room temperature mechanical properties of the stainless steel forging and the high temperature mechanical properties of 300°C after hot forging and heat treatment, thereby improving the high temperature resistance of austenitic stainless steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 A schematic flow chart of a method for preparing a high temperature resistant stainless steel forging provided in an embodiment of the present application;

[0026] Figure 2 A heating curve in the second hot forging in a method for preparing a high temperature resistant stainless steel forging provided in an embodiment of the present application;

[0027] Figure 3 A heat treatment process curve in a method for preparing a high-temperature resistant stainless steel forging provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0029] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0030] In this application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the specification of this application, the terms "include", "comprise", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0031] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0032] In a first aspect, the present application provides a method for preparing a high temperature resistant stainless steel forging, wherein the structure of the stainless steel forging is a single austenite. Figure 1 For a schematic diagram of a method for preparing a high temperature resistant stainless steel forging provided in an embodiment of the present application, see Figure 1 , the method comprising:

[0033] S1. hot forging a stainless steel blank and controlling the deformation ratio of the hot forging to obtain a stainless steel forging;

[0034] In some embodiments, the deformation ratio is ≥5.5.

[0035] In the embodiments of the present application, hot forging refers to a process of forging a metal material after it is heated to a certain temperature. The hot forging deformation ratio is an important indicator to measure the degree of deformation of a metal during hot forging, which can usually be expressed by a forging ratio. The hot forging deformation ratio can be ≥5.5, and this deformation ratio allows the stainless steel billet to be deformed to a degree that can refine the grains, laying the foundation for the high-temperature mechanical properties of subsequent high-temperature resistant stainless steel forgings. Exemplarily, the deformation ratio can be 5.5, 5.6, 5.7, 5.8, 6, 7, 8, 9, etc.

[0036] In some embodiments, the hot forging includes a first hot forging and a second hot forging; wherein the deformation ratio of the first hot forging is greater than 3.5.

[0037] In the embodiment of the present application, hot forging includes first hot forging and second hot forging. The deformation ratio of the first hot forging can be greater than 3.5. The first hot forging can make the grains in the stainless steel billet thinner and longer, thereby fully ensuring the mechanical properties of the subsequent high-temperature resistant stainless steel forgings. The second hot forging further elongates the grains and crushes the grains on the basis of the first forging. Exemplarily, the deformation ratio of the first hot forging can be 3.6, 3.7, 3.8, 3.9, 4.0, etc. In addition, at this time, it is divided into two situations according to whether the direction of the second hot forging is consistent with the direction of the first hot forging: for those with consistent directions, only simple superposition is performed to ensure the total forging ratio. For those with inconsistent directions, it is necessary to consider adding intermediate processes (for example: increasing the number of upsetting times) to maximize the metal deformation in the main forging direction, and the forging ratio in this direction is dominant, generally controlled at 3 to 3.5.

[0038] In some embodiments, the second hot forging includes heating and forging, and the total time of the heating satisfies the following relationship: t=K1×k2×t1;

[0039] Among them, t-heating time / h; K1-furnace loading coefficient, the value range is 1.0~2.0; K2-billet size coefficient, the value range is 0.7~1.0; t1-single billet heating time / h, the value range is (D / 100)×(1.20~1.40), D-billet diameter;

[0040] The heating includes a preheating section, a second temperature rising section and a second temperature keeping section. Figure 2 This is a heating curve in the second hot forging in a method for preparing a high temperature resistant stainless steel forging provided in an embodiment of the present application; see Figure 2 ;

[0041] The preheating time is 10% to 20% of the total heating time;

[0042] The time of the second heat preservation section is 15% to 20% of the total heating time.

[0043] In the embodiment of the present application, the heating time is calculated according to the above t=K1×k2×t1, which can better control the grain size. The time of the preheating section can be 10% to 20% of the total heating time. The purpose of preheating is to make the billet have a certain temperature, improve the thermal conductivity of the billet, improve the plasticity and forgeability, and at the same time reduce the surface and internal temperature difference and uniform the temperature of the billet. The time of the second insulation section can be 15% to 20% of the total heating time, so that the billet can obtain its best plasticity, ensure forgeability, and meet the needs of forging deformation. Exemplarily, the time of the preheating section can be 10%, 12%, 14%, 16%, 18%, 20%, etc. of the total heating time; the time of the second insulation section can be 15%, 16%, 17%, 18%, 19%, 20%, etc. of the total heating time. Exemplary, the heating process of the second hot forging: the charging temperature is controlled at 600-700°C, and the preheating stage is entered after the charging, and the preheating time is estimated at 10%-20% of the heating time. After the preheating is completed, the heating stage begins, and the holding time after reaching the initial forging temperature is estimated at 15%-20% of the heating time. When the forging temperature is lower than the final forging temperature and the forging deformation is not completed, it should be returned to the furnace and reheated to the initial forging temperature. At this time, the heating time should be half of the first heating time.

[0044] The initial forging temperature of the second hot forging can be 1150℃, which can prevent the precipitation of a large amount of delta ferrite. This ferrite will promote the formation of brittle phases and deteriorate the forging performance. The precipitation should be reduced as much as possible. The final forging temperature of the second hot forging can be 870℃~910℃, which can prevent the precipitation of too many carbides and increase the deformation resistance, and avoid low-temperature forging cracks. The cooling method after the second hot forging is air cooling. Air cooling can avoid the precipitation of too many carbides, reduce the risk of intergranular corrosion, and reduce internal stress.

[0045] Second, hot forging process: The stainless steel has a large deformation resistance in the hot state. When selecting equipment, you should choose equipment with a tonnage that is 1 / 3 larger than that of ordinary steel forging, so as to facilitate forging through and grain refinement. At the beginning of forging, you should strike lightly, and then strike hard to forge through after the plasticity is improved.

[0046] S2, subjecting the stainless steel forging to a heat treatment including a first temperature rising section, a first temperature holding section and a cooling section in sequence, and controlling the temperature of the first temperature holding section, Figure 3 This is a heat treatment process curve in a method for preparing a high temperature resistant stainless steel forging provided in an embodiment of the present application; see Figure 3 , and obtain high temperature resistant stainless steel forgings.

[0047] In some embodiments, the temperature of the first insulation section is 1060°C to 1080°C.

[0048] In the embodiment of the present application, the heat treatment process is mainly to avoid grain growth as much as possible to ensure the mechanical properties at room temperature and 300°C high temperature. The stainless steel forging is sequentially subjected to heat treatment including a heating section, a first insulation section and a cooling section, and the temperature of the first insulation section is controlled, so that the stainless steel forging structure can undergo austenite transformation, uniform chemical composition and avoid grain growth, and obtain a single austenite structure. If the temperature of the first insulation section is higher than 1080°C, it will cause the grain growth of the stainless steel forging to a certain extent, resulting in a coarse structure, thereby reducing the high temperature resistance of the stainless steel forging; if the temperature of the first insulation section is lower than 1060°C, it will cause insufficient austenite dissolution of carbides to a certain extent, and there will be impurities in the stainless steel forging structure after the heat treatment. Exemplarily, the temperature of the first insulation section can be 1060°C, 1062°C, 1064°C, 1066°C, 1068°C, 1070°C, 1072°C, 1074°C, 1076°C, 1078°C, 1080°C, etc.

[0049] In some embodiments, the time of the first insulation section is 1.8 min / mm to 2.4 min / mm.

[0050] In the embodiment of the present application, the time of the first insulation section can be 1.8 min / mm to 2.4 min / mm, so as to coordinate with the temperature of the above insulation section to make the stainless steel forging structure undergo austenite transformation, uniform chemical composition and avoid grain growth, and obtain a single austenite structure. Exemplarily, the time of the first insulation section can be 1.8 min / mm, 1.9 min / mm, 2.0 min / mm, 2.1 min / mm, 2.2 min / mm, 2.3 min / mm, 2.4 min / mm, etc.

[0051] In some embodiments, the heating rate of the heating section is 100° C. / h to 150° C. / h.

[0052] In the embodiment of the present application, the heating rate of the first heating section is 100℃ / h~150℃ / h, which can quickly pass the temperature near the phase change transition point so that the organizational transformation is carried out within the holding time range, and will not cause stress due to uneven temperature everywhere due to the excessively fast heating rate. Exemplarily, the heating rate of the first heating section can be 100℃ / h, 105℃ / h, 110℃ / h, 115℃ / h, 120℃ / h, 125℃ / h, 130℃ / h, 135℃ / h, 140℃ / h, 145℃ / h, 150℃ / h, etc. In addition, the charging temperature of the stainless steel forgings for heat treatment can be no higher than 700℃.

[0053] In some embodiments, the cooling section uses a circulating water cooling method, and the temperature of the circulating water is ≤40°C.

[0054] In the embodiment of the present application, the cooling section uses a circulating water cooling method, which takes away the water with increased temperature through circulating cooling, and replaces it with new low-temperature water to continue to absorb heat, thereby achieving continuous cooling of the workpiece. The temperature of the circulating water can be ≤40°C, thereby preventing the change of the structure of the stainless steel forging and regulating the thermal stress inside it, thereby ensuring the mechanical properties of the target forging. Exemplarily, the temperature of the circulating water can be 40°C, 39°C, 38°C, 37°C, 36°C, 35°C, 34°C, etc.

[0055] In summary, the method for preparing high temperature resistant stainless steel forgings provided in the embodiments of the present application has the following advantages:

[0056] 1. The role of deformation ratio:

[0057] During the hot forging process, it is crucial to control the deformation ratio. A suitable deformation ratio can cause sufficient deformation of the stainless steel billet during the forging process, and this deformation will refine the grains. For example, when the deformation ratio increases, the grains inside the metal will be broken and rearranged under stress, and new crystal nuclei will form and grow, thereby reducing the grain size. The refined grain structure lays the foundation for the subsequent improvement of the mechanical properties of stainless steel forgings at high temperatures. This is because fine-grained materials have better creep resistance and strength at high temperatures, and are more resistant to deformation at high temperatures than coarse-grained materials.

[0058] 2. Heat treatment: Holding section: This is the key link of heat treatment. Controlling the temperature of the first holding section is of great significance. The appropriate holding temperature can promote the austenite transformation of the stainless steel forging structure. In this process, the chemical composition is evenly distributed in the austenite phase through the diffusion and rearrangement of atoms. At the same time, precise temperature control can prevent excessive grain growth at high temperatures. Because too high a temperature will accelerate the migration of grain boundaries, resulting in the merging and growth of grains, and too large grains will reduce the mechanical properties of the material, especially the high-temperature mechanical properties. By reasonably controlling the temperature of the holding section, a single austenite structure can be obtained, which has good stability and excellent mechanical properties at high temperatures.

[0059] 3. Performance improvement effect

[0060] Through the combination of hot forging and heat treatment, this preparation method can not only ensure that the stainless steel forgings have good mechanical properties such as strength and toughness at room temperature, but also significantly improve their mechanical properties at high temperatures of 300°C.

[0061] In some embodiments, the high temperature resistant stainless steel forging meets the following indicators:

[0062] Tensile strength Rm ≥ 520MPa, non-proportional elongation strength Rp0.2 ≥ 220MPa, elongation after fracture A ≥ 45%, room temperature impact absorption energy KV2 ≥ 60J;

[0063] At a temperature of 300 °C: the tensile strength Rm ≥ 409 MPa, and the proof strength Rp0.2 ≥ 132 MPa.

[0064] In the embodiments of the present application, hot forging deforms a stainless-steel blank to form a forging, enabling the forging to obtain refined grains and increasing the number of grain boundaries; heat treatment completes the microstructure transformation to obtain a single austenite microstructure; the combination of forging and heat treatment enables the forging to achieve high-temperature mechanical properties.

[0065] In addition, the chemical composition (wt%) of the above high-temperature resistant stainless-steel forging may include: 0 < C ≤ 0.035%, 0 < Si ≤ 1.00%, 0 < Mn ≤ 2.00%, P ≤ 0.030%, S ≤ 0.015%, 11.50% ≤ Ni ≤ 12.50%, 17.00% ≤ Cr ≤ 18.20%, 2.25 ≤ Mo ≤ 2.75, 0 < N ≤ 0.080%, Cu ≤ 1.00%, and the matrix element Fe.

[0066] In a second aspect, the present application provides a high-temperature resistant stainless-steel forging, which is prepared by the method described in any one of the embodiments of the first aspect.

[0067] This high-temperature resistant stainless-steel forging is realized based on the preparation method of the above high-temperature resistant stainless-steel forging. The specific steps of the preparation method of this high-temperature resistant stainless-steel forging can refer to the above embodiments. Since this high-temperature resistant stainless-steel forging adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated one by one here.

[0068] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods without specific conditions noted in the following embodiments are generally determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0069] Example 1

[0070] The chemical composition of the stainless-steel blank in Example 1, by mass fraction: C: 0.021%, Si: 0.41%, Mn: 1.23%, P: 0.023%, S: 0.001%, Ni: 11.54%, Cr: 17.57%, Mo: 2.46%, N: 0.019%, Cu: 0.080%, and the rest is Fe and unavoidable impurities.

[0071] A method for preparing a high-temperature resistant stainless steel forging, comprising: hot forging a stainless steel blank, and controlling the deformation ratio of the hot forging to obtain a stainless steel forging; wherein the deformation ratio of the hot forging is 6.2, the hot forging includes a first hot forging and a second hot forging, and the deformation ratio of the first hot forging is 4.2; the second hot forging includes heating and forging, the heating time t=K1×k2×t1=240 / 100×1.2×1.0×0.7=2h, the heating includes a preheating section, a second temperature rise section and a second heat preservation section, the preheating section time is: 2×0.1=0.2h, the second heat preservation section time is: 2×0.15=0.3h, the furnace charging temperature is: 600°C, the initial forging temperature is: 1150°C, and the final forging temperature is: 875°C; the deformation ratio of the forging is 2.0; the cooling method after forging is air cooling;

[0072] The stainless steel forging is subjected to heat treatment including the first heating stage, the first heat preservation stage and the cooling stage in sequence, and the temperature of the first heat preservation stage is controlled to obtain a high temperature resistant stainless steel forging. Among them, the furnace charging temperature is 600°C, the heating rate of the first heating stage is 100°C / h, the temperature of the first heat preservation stage is 1080°C, the time of the first heat preservation stage is 2.4×93=223min; the water cooling temperature of the cooling stage is 35°C.

[0073] The properties of the high temperature resistant stainless steel forgings prepared in Example 1 are: Rm: 532MPa, Rp0.2: 266MPa, A: 60.0%, Z: 88%, KV2 (room temperature): average 382J, Rm at 300°C: 411MPa, Rp0.2 at 300°C: 161MPa, grain size level 4, and no tendency to intergranular corrosion.

[0074] Example 2

[0075] The chemical composition of the stainless steel billet in Example 2, by mass fraction, is as follows: C: 0.021%, Si: 0.41%, Mn: 1.23%, P: 0.023%, S: 0.001%, Ni: 11.54%, Cr: 17.57%, Mo: 2.46%, N: 0.019%, Cu: 0.080%, and the rest is Fe and unavoidable impurities.

[0076] A preparation method of a high-temperature resistant stainless steel forging, comprising: hot forging a stainless steel blank, and controlling the deformation ratio of the hot forging to obtain a stainless steel forging; wherein the deformation ratio of the hot forging is 6.5, the hot forging includes a first hot forging and a second hot forging, and the deformation ratio of the first hot forging is 4.3; the second hot forging includes heating and forging, the heating time t=K1×k2×t1=240 / 100×1.4×2.0×1.0=6.7h, the heating includes a preheating section, a temperature rise section and a second heat preservation section, the preheating section time is: 6.7×0.2=1.3h, the second heat preservation section time is: 6.7×0.2=1.3h, the furnace charging temperature is: 700°C, the initial forging temperature is: 1150°C, and the final forging temperature is: 870°C; the deformation ratio of the forging is 2.2; the cooling method after forging is air cooling;

[0077] The stainless steel forging is subjected to heat treatment including a heating stage, a first heat preservation stage and a cooling stage in sequence, and the temperature of the first heat preservation stage is controlled to obtain a high temperature resistant stainless steel forging. Among them, the furnace charging temperature is 700°C, the heating rate of the first heating stage is 150°C / h, the temperature of the first heat preservation stage is 1060°C, the time of the first heat preservation stage is 1.8×135=243=243min; the water cooling temperature of the cooling stage is 33°C.

[0078] The properties of the high temperature resistant stainless steel forgings prepared in Example 2 are: Rm: 555MPa, Rp0.2: 296MPa, A: 57.0%, Z: 85%, KV2 (room temperature): average 361.3J, Rm at 300°C: 427MPa, Rp0.2 at 300°C: 168MPa, grain size level 6, and no tendency to intergranular corrosion.

[0079] Example 3

[0080] The chemical composition of the stainless steel blank in Example 3, by mass fraction: C: 0.027%, Si: 0.48%, Mn: 1.81%, P: 0.016%, S: 0.003%, Ni: 12.50%, Cr: 17.40%, Mo: 2.66%, N: 0.073%, Cu: 0.10%

[0081] A method for preparing a high-temperature resistant stainless steel forging, comprising: hot forging a stainless steel blank, and controlling the deformation ratio of the hot forging to obtain a stainless steel forging; wherein the deformation ratio of the hot forging is 5.7, the hot forging includes a first hot forging and a second hot forging, and the deformation ratio of the first hot forging is 3.7; the second hot forging includes heating and forging, the heating time t=K1×k2×t1=240 / 100×1.3×1.5×0.8=3.7h, the heating includes a preheating section, a temperature rise section and a second heat preservation section, the preheating section time is: 3.7×0.15=0.6h, the second heat preservation section time is: 3.7×0.18=0.7h, the furnace charging temperature is: 650°C, the initial forging temperature is: 1150°C, and the final forging temperature is: 903°C; the deformation ratio of the forging is 2.0; the cooling method after forging is air cooling;

[0082] The stainless steel forging is subjected to heat treatment including the first heating stage, the first heat preservation stage and the cooling stage in sequence, and the temperature of the first heat preservation stage is controlled to obtain a high temperature resistant stainless steel forging. Among them, the furnace charging temperature is 500°C, the heating rate of the first heating stage is 120°C / h, the temperature of the first heat preservation stage is 1070°C, the time of the first heat preservation stage is 1.9×160=304min; the water cooling temperature of the cooling stage is 38°C.

[0083] The properties of the high temperature resistant stainless steel forgings prepared in Example 3 are: Rm: 539 MPa, Rp0.2: 283 MPa, A: 64.5%, Z: 86%, KV2 (room temperature): average 365.5 J, Rm at 300°C: 431 MPa, Rp0.2 at 300°C: 176 MPa, grain size level 5, and no tendency to intergranular corrosion.

[0084] Comparative Example 1

[0085] Based on the disclosure of Example 1, the difference between Comparative Example 1 and Example 1 is that the temperature of the heat treatment insulation section is 1090°C.

[0086] The properties of the high temperature resistant stainless steel forgings prepared in Comparative Example 1 are: Rm: 539 MPa, Rp0.2: 256 MPa, A: 58.5%, Z: 88%, KV2 (room temperature): average 355 J, Rm at 300°C: 406 MPa, Rp0.2 at 300°C: 193 MPa, grain size level 5, and no tendency to intergranular corrosion.

[0087] Comparative Example 2

[0088] Based on the disclosure of Example 1, the difference between Comparative Example 2 and Example 2 is that the deformation ratio of hot forging is 5, the deformation of the first hot forging is 3.6, and the deformation ratio of the second hot forging is 1.4.

[0089] The properties of the high temperature resistant stainless steel forgings prepared in Comparative Example 2 are: Rm: 550MPa, Rp0.2: 274MPa, A: 58.0%, Z: 86%, KV2 (room temperature): average 360.8J, Rm at 300°C: 401MPa, Rp0.2 at 300°C: 160MPa, grain size level 6, and no tendency to intergranular corrosion.

[0090] From the analysis of Examples 1 to 3 and Comparative Examples 1 to 2, it can be seen that the embodiments of the present application control the total deformation ratio of the forging to refine the grains, and adopt a reasonable heat treatment system to ensure both the mechanical properties at room temperature and the mechanical properties at 300°C.

[0091] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0092] (1) The embodiment of the present application controls the total deformation ratio of the forging to refine the grains, and adopts a reasonable heat treatment system to ensure both the mechanical properties at room temperature and the mechanical properties at 300°C;

[0093] (2) The forging obtained by the method for preparing a high temperature resistant stainless steel forging provided in the embodiment of the present application can achieve the effect of having no tendency to intergranular corrosion;

[0094] (3) The distribution ratio of the total forging ratio in the first hot forging and the second hot forging in the method for preparing a high-temperature resistant stainless steel forging provided in an embodiment of the present application is simple to operate and has a moderate degree of deformation for forgings using billet reforging (equivalent to the second hot forging).

[0095] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a high temperature resistant stainless steel forging, wherein the structure of the stainless steel forging is a single austenite, the method comprising: Hot forging a stainless steel blank and controlling the deformation ratio of the hot forging to obtain a stainless steel forging; The stainless steel forging is subjected to a heat treatment including a first heating section, a first heat preservation section and a cooling section in sequence, and the temperature of the first heat preservation section is controlled to obtain a high temperature resistant stainless steel forging.

2. The method according to claim 1, characterized in that The deformation ratio is ≥5.

5.

3. The method according to claim 1 or 2, characterized in that: The hot forging includes a first hot forging and a second hot forging; wherein the deformation ratio of the first hot forging is greater than 3.

5.

4. The method according to claim 3, characterized in that The second hot forging includes heating and forging, and the total time of the heating satisfies the following relationship: t=K1×k2×t1; wherein, t-heating time / h; K1-furnace loading mode coefficient, ranging from 1.0 to 2.0; K2-billet size coefficient, ranging from 0.7 to 1.0; t1-heating time / h of a single billet, ranging from (D / 100)×(1.20 to 1.40), D-billet diameter; The heating includes a preheating section, a second temperature rising section and a second heat preservation section. The time of the preheating section is 10% to 20% of the total heating time, and the time of the second heat preservation section is 15% to 20% of the total heating time.

5. The method according to claim 1, characterized in that The temperature of the first insulation section is 1060°C to 1080°C.

6. The method according to claim 1 or 5, characterized in that: The time of the first insulation section is 1.8 min / mm to 2.4 min / mm.

7. The method according to claim 1, characterized in that The heating rate of the first heating stage is 100° C. / h to 150° C. / h.

8. The method according to claim 1, characterized in that The cooling section uses a circulating water cooling method, and the temperature of the circulating water is ≤40°C.

9. The method according to claim 1, characterized in that: The high temperature resistant stainless steel forgings meet the following indicators: Tensile strength Rm ≥ 520MPa, non-proportional elongation strength Rp0.2 ≥ 220MPa, elongation after fracture A ≥ 45%, room temperature impact absorption energy KV2 ≥ 60J; At a temperature of 300°C: tensile strength Rm ≥ 409MPa, and non-proportional elongation strength Rp0.2 ≥ 132MPa.

10. A high temperature resistant stainless steel forging, wherein the high temperature resistant stainless steel forging is prepared by the method according to any one of claims 1 to 9.

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