A high-efficiency heat treatment process for medium plate

Abstract

The present invention relates to a high-efficiency heat treatment process for a middle plate, and belongs to the field of heat treatment technology. The present invention first heat treats a 0Cr16Ni5Mo1 martensitic stainless steel middle plate at a temperature higher than 110-150°C Ac3 for a period of time to make it completely austenitized, and then cools it to 10-30°C Ac3 temperature and then performs water cooling and oil cooling quenching, which significantly reduces the quenching temperature and thermal stress, thereby reducing the residual stress of the whole middle plate after quenching. At the same time, since the heating furnace contains silica aerogel, the silica aerogel has excellent thermal insulation performance, which makes the cooling speed slower during the furnace cooling process, thereby reducing the temperature difference between the surface layer and the core of the middle plate during the cooling process, and reducing the residual stress. The residual stress can be significantly reduced and the grain size can be refined without multiple quenching or tempering treatments, and the heat treatment process is simple and efficient.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment, and in particular relates to a high-efficiency heat treatment process for a middle plate. Background Art

[0002] 0Cr16Ni5Mo1 martensitic stainless steel is a new type of super martensitic stainless steel designed on the basis of traditional high chromium stainless steel by reducing the carbon content and increasing elements such as nickel and molybdenum. It has excellent strength, hardness and impact toughness and is widely used in electric power, aviation, shipbuilding, petrochemical and other industries.

[0003] Quenching is an essential step in the heat treatment process of steel materials. The quenching temperature and cooling rate have an important influence on the structure and performance of the workpiece. The current conventional quenching temperature of 0Cr16Ni5Mo1 martensitic stainless steel is 1100℃±10℃, and oil quenching is performed after keeping warm for 50-70 minutes. At such a high quenching temperature, martensitic stainless steel will catch fire and produce thick smoke when directly immersed in quenching oil, which will not only cause certain safety hazards but also affect the cooling effect. At the same time, it will produce large residual stress and large grain size, which will seriously affect the performance of the steel and limit its application. Therefore, it is necessary to provide an efficient heat treatment process for medium plates that can solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide an efficient heat treatment process for a middle plate. First, the 0Cr16Ni5Mo1 martensitic stainless steel middle plate is heat treated at a temperature higher than Ac3 by 110-150°C for a period of time to make it completely austenitized. Then, it is cooled to a temperature higher than Ac3 by 10-30°C in the furnace and then quenched by water or oil cooling, which significantly reduces the quenching temperature and thermal stress, thereby reducing the residual stress of the whole middle plate after quenching. At the same time, since the heating furnace contains silica aerogel, the silica aerogel has excellent thermal insulation performance, which makes the cooling rate slower during the furnace cooling process, thereby reducing the temperature difference between the surface and the core of the middle plate during the cooling process and reducing the residual stress. The residual stress can be significantly reduced and the grain size can be refined without multiple quenching or tempering treatments. The heat treatment process is simple and efficient.

[0005] The technical problem to be solved by the present invention is that the conventional quenching temperature of 0Cr16Ni5Mo1 martensitic stainless steel is 1100°C±10°C at present, and oil quenching is performed after keeping warm for 50-70 minutes. At such a high quenching temperature, when martensitic stainless steel is directly immersed in quenching oil, it will catch fire and produce thick smoke, which will not only cause certain safety hazards but also affect the cooling effect, and at the same time, it will produce large residual stress and large grain size, which will seriously affect the performance of the steel and limit its application.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A high-efficiency heat treatment process for a middle plate comprises the following steps:

[0008] A1. Place the 0Cr16Ni5Mo1 martensitic stainless steel middle plate into a heating furnace, heat it to 960-1000℃, and keep it warm for 40-70min;

[0009] Furthermore, in step A1, silica aerogel is placed in the heating furnace.

[0010] Furthermore, the silica aerogel particles have a particle size of 1-3 μm and a density of 0.05-0.3 g / L.

[0011] Furthermore, in step A1, a protective gas is introduced into the heating furnace.

[0012] Furthermore, the protective gas is nitrogen.

[0013] Furthermore, the silica aerogel and the protective gas are mixed to form a protective atmosphere, and the density of the protective atmosphere is 0.03-0.2 g / L.

[0014] Furthermore, in step A1, a circulation fan is provided in the heating furnace.

[0015] Furthermore, in step A1, the heating rate is 2-5°C / s.

[0016] During the above operation, protective gas is introduced into the heating furnace, the protective gas is mixed with silica aerogel to form a protective atmosphere, and the circulating fan is used to make the silica aerogel evenly distributed in the heating furnace under the action of the protective gas. Silica aerogel has a porous structure and a low density, and can be mixed with the protective gas to form a uniform medium. At the same time, its thermal conductivity is low, so it has good thermal insulation properties. Mixing it with the protective gas as a protective atmosphere and circulating it in the furnace can accelerate the uniformity of the temperature in the furnace, thereby ensuring the uniformity of the temperature at each position of the middle plate and reducing the furnace temperature loss.

[0017] A2. Cool the heat-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate to 860-890°C with the furnace and keep it warm for 10-20 minutes;

[0018] During the above operation, the heat-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate is cooled to 860-890°C, which is 10-30°C higher than the Ac3 temperature, so that the quenching temperature is significantly reduced, the thermal stress is reduced, and thus the residual stress of the whole middle plate after quenching is reduced. At the same time, since the heating furnace contains silica aerogel, the silica aerogel has excellent thermal insulation performance, so that the cooling speed during the furnace cooling process is slow, thereby reducing the temperature difference between the surface and the core of the middle plate during the cooling process, thereby reducing the residual stress.

[0019] A3. Remove the 0Cr16Ni5Mo1 martensitic stainless steel middle plate treated in step A2 from the heating furnace and water-cool it to a surface temperature of 200-250°C; oil-cool the water-cooled 0Cr16Ni5Mo1 martensitic stainless steel middle plate to a surface temperature below 50°C, then place it in an ice-water mixture for cold treatment for 80-100 minutes, take it out and place it in the air to room temperature;

[0020] During the above operation, the 0Cr16Ni5Mo1 martensitic stainless steel middle plate is first water-cooled and then oil-cooled to avoid safety hazards caused by direct oil cooling. At the same time, the cooling effect of water cooling is better than that of oil cooling. The present invention first water-cools the middle plate to 200-250°C, then oil-cools it to room temperature, and finally performs cold treatment, which effectively removes residual stress in the middle plate and refines the grain size.

[0021] Furthermore, in step A3, the water temperature during water cooling is lower than 50°C, the oil temperature during oil cooling is lower than 50°C, and the temperature of the ice-water mixture is 0-5°C.

[0022] A4. Temper the cold-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate at 500-540°C for 60-140 min, and then air-cool to room temperature.

[0023] Beneficial effects of the present invention:

[0024] (1) In the technical solution of the present invention, the 0Cr16Ni5Mo1 martensitic stainless steel middle plate is first heat treated at a temperature higher than Ac3 by 110-150°C for a period of time to achieve complete austenitization, and then cooled to a temperature higher than Ac3 by 10-30°C in the furnace and then quenched by water or oil cooling, which significantly reduces the quenching temperature and thermal stress, thereby reducing the residual stress of the whole middle plate after quenching. At the same time, since the heating furnace contains silica aerogel, the silica aerogel has excellent thermal insulation performance, which makes the cooling speed slower during the furnace cooling process, thereby reducing the temperature difference between the surface and the core of the middle plate during the cooling process and reducing the residual stress.

[0025] (2) In the technical solution of the present invention, during the quenching process, the 0Cr16Ni5Mo1 martensitic stainless steel middle plate is first water-cooled and then oil-cooled, thereby avoiding safety hazards caused by direct oil cooling. At the same time, the cooling effect of water cooling is better than that of oil cooling, thereby reducing the cooling time. The present invention first water-cools the middle plate to 200-250°C, then oil-cools it to room temperature, and finally performs a cold treatment, thereby effectively removing the residual stress in the middle plate and refining the grain size.

[0026] (3) In the technical solution of the present invention, the residual stress can be significantly reduced and the grain size can be refined without multiple quenching or tempering treatments, and the heat treatment process is simple and efficient. DETAILED DESCRIPTION

[0027] The following will be combined with 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.

[0028] The mass percentage of each element in the 0Cr16Ni5Mo1 martensitic stainless steel middle plate in the following embodiment is: C: 0.067%, Cr: 15.91%, Ni: 4.69%, Mo: 0.93%, Si: 0.31%, Mn: 0.86%, P: 0.006%, S: 0.003%, Cu: 0.05%, Sn: 0.0024%, and the rest is Fe and unavoidable impurity elements. The thickness of the 0Cr16Ni5Mo1 martensitic stainless steel middle plate is 25 mm.

[0029] Example 1

[0030] A1. Place the silica aerogel in a heating furnace, then place the 0Cr16Ni5Mo1 martensitic stainless steel middle plate in the heating furnace, close the heating furnace door, introduce nitrogen, and start the circulating fan, then heat the heating furnace from room temperature to 960°C at a heating rate of 2°C / s, and keep the temperature for 40 minutes; wherein the particle size range of the silica aerogel particles is 1-3μm, the density is 0.05g / L, and the density of the protective atmosphere formed by the mixture of the silica aerogel and the protective gas is 0.03g / L;

[0031] A2. Cool the heat-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate to 860°C with the furnace and keep it warm for 10 minutes;

[0032] A3. Remove the 0Cr16Ni5Mo1 martensitic stainless steel middle plate treated in step A2 from the heating furnace and water-cool it to a surface temperature of 200°C; oil-cool the water-cooled 0Cr16Ni5Mo1 martensitic stainless steel middle plate to a surface temperature below 50°C, then place it in a 0°C ice-water mixture for cold treatment for 80 minutes, take it out and place it in the air to room temperature;

[0033] A4. The cold-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate is tempered at 500°C for 60 minutes and then air-cooled to room temperature.

[0034] Example 2

[0035] A1. Place the silica aerogel in a heating furnace, then place the 0Cr16Ni5Mo1 martensitic stainless steel middle plate in the heating furnace, close the heating furnace door, introduce nitrogen, and start the circulating fan, then heat the heating furnace from room temperature to 980°C at a heating rate of 3°C / s, and keep the temperature for 50 minutes; wherein the particle size range of the silica aerogel particles is 1-3μm, the density is 0.1g / L, and the density of the protective atmosphere formed by the mixture of the silica aerogel and the protective gas is 0.08g / L;

[0036] A2. Cool the heat-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate to 870°C and keep it at this temperature for 15 minutes;

[0037] A3. Remove the 0Cr16Ni5Mo1 martensitic stainless steel middle plate treated in step A2 from the heating furnace and water-cool it to a surface temperature of 200°C; oil-cool the water-cooled 0Cr16Ni5Mo1 martensitic stainless steel middle plate to a surface temperature below 50°C, then place it in a 5°C ice-water mixture for cold treatment for 90 minutes, take it out and place it in the air to room temperature;

[0038] A4. The cold-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate is tempered at 510°C for 80 minutes and then air-cooled to room temperature.

[0039] Example 3

[0040] A1. Place the silica aerogel in a heating furnace, then place the 0Cr16Ni5Mo1 martensitic stainless steel middle plate in the heating furnace, close the heating furnace door, introduce nitrogen, and start the circulating fan, then heat the heating furnace from room temperature to 980°C at a heating rate of 4°C / s, and keep the temperature for 55 minutes; wherein the particle size range of the silica aerogel particles is 1-3μm, the density is 0.15g / L, and the density of the protective atmosphere formed by the mixture of the silica aerogel and the protective gas is 0.1g / L;

[0041] A2. Cool the heat-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate to 870°C and keep it at this temperature for 20 minutes;

[0042] A3. Remove the 0Cr16Ni5Mo1 martensitic stainless steel middle plate treated in step A2 from the heating furnace and water-cool it to a surface temperature of 230°C; oil-cool the water-cooled 0Cr16Ni5Mo1 martensitic stainless steel middle plate to a surface temperature below 50°C, then place it in a 0°C ice-water mixture for cold treatment for 90 minutes, take it out and place it in the air to room temperature;

[0043] A4. The cold-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate is tempered at 520°C for 110 min and then air-cooled to room temperature.

[0044] Example 4

[0045] A1. Place the silica aerogel in a heating furnace, then place the 0Cr16Ni5Mo1 martensitic stainless steel middle plate in the heating furnace, close the heating furnace door, introduce nitrogen, and start the circulating fan, then heat the heating furnace from room temperature to 990°C at a heating rate of 4°C / s, and keep the temperature for 60 minutes; wherein the particle size range of the silica aerogel particles is 1-3μm, the density is 0.2g / L, and the density of the protective atmosphere formed by the mixture of the silica aerogel and the protective gas is 0.15g / L;

[0046] A2. Cool the heat-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate to 880°C with the furnace and keep it at this temperature for 10 minutes;

[0047] A3. Remove the 0Cr16Ni5Mo1 martensitic stainless steel middle plate treated in step A2 from the heating furnace and water-cool it to a surface temperature of 230°C; oil-cool the water-cooled 0Cr16Ni5Mo1 martensitic stainless steel middle plate to a surface temperature below 50°C, then place it in a 5°C ice-water mixture for cold treatment for 90 minutes, take it out and place it in the air to room temperature;

[0048] A4. The cold-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate is tempered at 530°C for 120 min and then air-cooled to room temperature.

[0049] Example 5

[0050] A1. Place the silica aerogel in a heating furnace, then place the 0Cr16Ni5Mo1 martensitic stainless steel middle plate in the heating furnace, close the heating furnace door, introduce nitrogen, and start the circulating fan, then heat the heating furnace from room temperature to 1000°C at a heating rate of 5°C / s, and keep the temperature for 40 minutes; wherein the particle size range of the silica aerogel particles is 1-3μm, the density is 0.3g / L, and the density of the protective atmosphere formed by the mixture of the silica aerogel and the protective gas is 0.2g / L;

[0051] A2. Cool the heat-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate to 890°C with the furnace and keep it at this temperature for 10 minutes;

[0052] A3. Remove the 0Cr16Ni5Mo1 martensitic stainless steel middle plate treated in step A2 from the heating furnace and water-cool it to a surface temperature of 250°C; oil-cool the water-cooled 0Cr16Ni5Mo1 martensitic stainless steel middle plate to a surface temperature below 50°C, then place it in an ice-water mixture at 0°C for cold treatment for 80 minutes, take it out and place it in air to room temperature;

[0053] A4. The cold-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate is tempered at 540°C for 60 minutes and then air-cooled to room temperature.

[0054] Example 6

[0055] A1. Place the silica aerogel in a heating furnace, then place a 0Cr16Ni5Mo1 martensitic stainless steel middle plate in the heating furnace, close the heating furnace door, introduce nitrogen, and start the circulating fan, then heat the heating furnace from room temperature to 1000°C at a heating rate of 5°C / s, and keep the temperature for 70 minutes; wherein the particle size range of the silica aerogel particles is 1-3μm, the density is 0.3g / L, and the density of the protective atmosphere formed by the mixture of the silica aerogel and the protective gas is 0.2g / L;

[0056] A2. Cool the heat-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate to 890°C with the furnace and keep it at this temperature for 20 minutes;

[0057] A3. Remove the 0Cr16Ni5Mo1 martensitic stainless steel middle plate treated in step A2 from the heating furnace and water-cool it to a surface temperature of 250°C; oil-cool the water-cooled 0Cr16Ni5Mo1 martensitic stainless steel middle plate to a surface temperature below 50°C, then place it in an ice-water mixture at 5°C for cold treatment for 100 minutes, take it out and place it in air to room temperature;

[0058] A4. The cold-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate is tempered at 540°C for 140 min and then air-cooled to room temperature.

[0059] Comparative Example 1

[0060] Compared with Example 3, in Comparative Example 1, no water cooling was performed, and oil cooling was performed directly to room temperature. The other steps and raw materials were the same as those in Example 3.

[0061] Comparative Example 2

[0062] Compared with Example 3, in Comparative Example 2, the 0Cr16Ni5Mo1 martensitic stainless steel middle plate was heated at 980°C and kept warm for 75 minutes, and then directly water-cooled without being cooled to 870°C with the furnace. Other steps and raw materials were the same as in Example 3.

[0063] Comparative Example 3

[0064] Compared with Example 3, no silica aerogel was added to the heating furnace of Comparative Example 3, and other steps and raw materials were the same as those of Example 3.

[0065] Performance Testing

[0066] The mechanical properties of the middle plates prepared in Examples 1-6 and Comparative Examples 1-3 were tested, and the yield strength, tensile strength and elongation were measured with reference to the national standard GB / T 228.1-2021, and the impact toughness was measured with reference to the national standard GB / T 229-2020.

[0067] Table 1

[0068]

[0069] It can be seen from the data in Table 1 that the 0Cr16Ni5Mo1 martensitic stainless steel middle plate obtained by the heat treatment process provided by the present invention has excellent mechanical properties, and the impact toughness can reach 191.9 J / cm 2 , and has a smaller grain size. From the data of Example 3 and Comparative Example 1, it can be seen that when the middle plate is directly oil-cooled, the mechanical properties decrease slightly, and the grain size increases. From the data of Example 3 and Comparative Example 2, it can be seen that due to the high quenching temperature of the 0Cr16Ni5Mo1 martensitic stainless steel middle plate, the residual stress increases, resulting in a significant decrease in mechanical properties and an increase in grain size. From the data of Example 3 and Comparative Example 3, it can be seen that the introduction of silica aerogel during the high-temperature heat treatment of the middle plate can improve the uniformity of the temperature at various positions of the middle plate, and at the same time, the cooling rate is slower during furnace cooling, so that the residual stress disappears, the grain size is refined, and the mechanical properties of the middle plate are improved.

[0070] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0071] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A high-efficiency heat treatment process for a middle plate, characterized by: The following steps are involved: A1. Place the 0Cr16Ni5Mo1 martensitic stainless steel middle plate into a heating furnace, heat it to 960-1000℃, and keep it warm for 40-70min; A2. Cool the heat-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate to 860-890°C with the furnace and keep it warm for 10-20 minutes; A3. Remove the 0Cr16Ni5Mo1 martensitic stainless steel middle plate treated in step A2 from the heating furnace and water-cool it to a surface temperature of 200-250°C; oil-cool the water-cooled 0Cr16Ni5Mo1 martensitic stainless steel middle plate to a surface temperature below 50°C, then place it in an ice-water mixture for cold treatment for 80-100 minutes, take it out and place it in the air to room temperature; A4. Temper the cold-treated 0Cr16Ni5Mo1 martensitic stainless steel middle plate at 500-540°C for 60-140 min, and then air-cool to room temperature; In the step A1, a silica aerogel is placed in the heating furnace, the particle size of the silica aerogel particles is 1-3 μm, and the density of the silica aerogel is 0.05-0.3 g / L; In the step A1, a protective gas is introduced into the heating furnace, and the silica aerogel is mixed with the protective gas to form a protective atmosphere, the density of the protective atmosphere is 0.03-0.2 g / L, and a circulating fan is provided in the heating furnace.

2. The high-efficiency heat treatment process for a middle plate according to claim 1 is characterized in that: The protective gas is nitrogen.

3. The high-efficiency heat treatment process for a middle plate according to claim 1 is characterized in that: In the step A1, the heating rate is 2-5°C / s.

4. The high-efficiency heat treatment process for a middle plate according to claim 1 is characterized in that: In step A3, the water temperature during water cooling is lower than 50° C., the oil temperature during oil cooling is lower than 50° C., and the temperature of the ice-water mixture is 0-5° C.

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