High-strength 1Cr11Ni2W2MoV steel and heat treatment method

Abstract

The invention discloses high-strength 1Cr11Ni2W2MoV steel and a heat treatment method, and relates to the field of 1Cr11Ni2W2MoV steel heat treatment.The heat treatment method comprises the steps that a 1Cr11Ni2W2MoV hot-rolled bar is subjected to pre-heat treatment, and a pre-heat-treated workpiece is obtained; and quenching and secondary tempering are conducted on the workpiece subjected to pre-heat treatment. The mechanical property of the 1Cr11Ni2W2MoV steel is improved, and the strength of the 1Cr11Ni2W2MoV steel can reach 1450 MPa or above.

Description

Technical Field

[0001] The present application relates to a heat treatment method for high-strength 1Cr11Ni2W2MoV steel, and particularly to the comprehensive research and analysis of the strengthening heat treatment system for this material. Background Art

[0002] In the more than 100-year development history of martensitic stainless steel, due to its excellent mechanical properties and corrosion resistance, it has been widely used in various fields such as aviation, aerospace, and shipbuilding. 1Cr11Ni2W2MoV steel is a typical martensitic precipitation-hardening stainless steel. In 12% Cr steel, elements such as W, Mo, and V are added, which are ferrite-forming elements that significantly narrow the austenite phase region, enabling it to have the ability of martensitic phase transformation hardening. Martensitic stainless steel usually contains 12% Cr element. The Cr element obtains a martensite structure through rapid cooling after high-temperature austenitization. Subsequently, after annealing the martensite structure, a steel part with good comprehensive properties is obtained. 1Cr11Ni2W2MoV steel combines high strength and high toughness and is a new steel type derived from 12% Cr steel. 1Cr11Ni2W2MoV steel has a low carbon content and is also known as low-carbon martensitic stainless steel. Compared with 1Cr13 stainless steel, its carbon content is significantly reduced, and various alloying elements are added to obtain better machining performance and corrosion resistance. In addition, the addition of elements such as nickel, tungsten, and vanadium can produce good age-hardening or precipitation-hardening effects. The addition of nickel enables the formation of reverse-transformed austenite in martensite after heat treatment of low-carbon martensitic stainless steel, significantly improving the toughness of the material. The addition of the above alloying elements endows 1Cr11Ni2W2MoV steel with good comprehensive mechanical properties. Such martensitic stainless steel can adjust the heat treatment system according to different usage requirements and scenarios to obtain products with different properties. Therefore, it is particularly important to explore a suitable heat treatment process. In some fields, higher strength requirements are imposed on this material, but the heat treatment parameters given in the current heat treatment standards cannot meet the above requirements. Summary of the Invention

[0003] The technical problem solved by the present application is: overcoming the deficiencies of the prior art, providing a heat treatment method for improving the strength of 1Cr11Ni2W2MoV steel and improving the mechanical properties of 1Cr11Ni2W2MoV steel.

[0004] Combined with the characteristics of 1Cr11Ni2W2MoV steel material, through a large number of experimental studies, the present invention conducts research on the strengthening heat treatment process system and obtains a heat treatment method for high-strength (Rm > 1450 MPa) 1Cr11Ni2W2MoV steel, filling the blank of the heat treatment parameters for high-strength mechanical properties in the existing standard specifications of 1Cr11Ni2W2MoV steel.

[0005] The technical solution provided by this application is as follows:

[0006] A heat treatment method for high-strength 1Cr11Ni2W2MoV steel, comprising: performing preliminary heat treatment on a 1Cr11Ni2W2MoV hot-rolled piece, the preliminary heat treatment including normalizing, and performing the first tempering after normalizing; after the 1Cr11Ni2W2MoV hot-rolled piece undergoes preliminary heat treatment, a preliminary heat-treated workpiece is obtained;

[0007] Quenching the preliminary heat-treated workpiece, the quenching holding temperature being 1080°C ± 10°C, the quenching holding time being 45 - 50 min, and performing the second tempering after quenching.

[0008] Further, the normalizing holding temperature is 1080 ± 10°C, and the normalizing holding time is 45 - 50 min.

[0009] Further, the holding temperature of the first tempering is 740 ± 10°C, and the holding time is 70 - 100 min.

[0010] Further, after quenching, it is oil-cooled to room temperature, the oil temperature for oil cooling being 20 - 80°C; during oil cooling, the cooling transfer time ≤ 60 s, and the residence time in the medium ≥ 5 min.

[0011] Further, the second tempering holding is 150 - 180°C, and the tempering holding time is 70 - 100 min.

[0012] Further, the second tempering is performed within 8 h after the completion of quenching.

[0013] A high-strength mechanical property 1Cr11Ni2W2MoV steel, the hot-rolled piece of 1Cr11Ni2W2MoV steel is prepared by the heat treatment method of a high-strength 1Cr11Ni2W2MoV steel according to any one of the above.

[0014] In summary, this application at least includes the following beneficial technical effects:

[0015] 1. In this application, normalizing + the first tempering are carried out on the hot-rolled parts before quenching. This preliminary heat treatment process can, to a certain extent, eliminate the chemical composition segregation generated during the cold working or hot working process of the material, make the internal structure of 1Cr11Ni2W2MoV steel more uniform, eliminate the defects generated during the cold working and hot working processes, and prepare the microstructure for quenching. Since the diffusion rates of elements such as Cr, Ni, W, Mo, and V in this steel type are different, it is necessary to adopt a higher temperature and a longer time to promote their homogenization. At the same time, too high a temperature may lead to grain coarsening (above 1200 °C), and too long a holding time is likely to form harmful carbides for elements such as W, Mo, and V. Therefore, combined with the size and shape of the specimens in this method, the following preliminary heat treatment system and final heat treatment system are adopted.

[0016] 2. Preliminary heat treatment system: Normalizing holding temperature 1080 ± 10 °C, holding time 45 - 50 min, air cooling; the first tempering holding temperature 740 ± 10 °C, holding time 70 - 100 min, air cooling. Through the preliminary heat treatment, the material is austenitized and the grains are refined. By air cooling, the cooling rate due to normalizing is between annealing and quenching, and the obtained pearlite lamellar spacing is smaller, so its microstructure is more refined and uniform, and the hardness is also higher.

[0017] Final heat treatment system: 1080 °C ± 10 °C, quenching holding time 45 - 50 min, oil cooling; the second tempering holding is 150 - 180 °C, tempering holding time is 70 - 100 min, air cooling. After heat treatment according to the above system, its strength can reach more than 1450 MPa. Among them, quenching is a heat treatment process in which the workpiece is heated to austenitize and then martensite or (and) bainite is obtained in an appropriate manner.

[0018] Since Cr, Mo, etc. in 1Cr11Ni2W2MoV steel are all strong carbide-forming elements, it is necessary to appropriately increase the quenching temperature to dissolve them in austenite. In addition, the role of V is to form fine carbides to improve the strength and hardness of the material, and the carbides of V need a higher temperature to dissolve. Therefore, appropriately increasing the quenching temperature is beneficial to increasing the content of alloying elements in martensite, helping more fine carbides to precipitate during tempering, and improving the final properties of 1Cr11Ni2W2MoV steel.

[0019] At the same time, reasonable control of the quenching temperature and quenching time can balance the problems of carbide dissolution and grain coarsening. High temperature and short time are often better than medium and low temperature and long time. Therefore, appropriately increasing the quenching temperature can effectively reduce the risk of grain coarsening. The stability of austenite is enhanced at high quenching temperatures, so oil quenching or high-pressure gas quenching is often required to avoid the influence of non-martensite structure caused by insufficient cooling on the material properties. Description of the Drawings

[0020] Figure 1Schematic diagram of normalizing for 1Cr11Ni2W2MoV;

[0021] Figure 2 Schematic diagram of quenching for 1Cr11Ni2W2MoV;

[0022] Figure 3 Schematic diagram of tempering for 1Cr11Ni2W2MoV;

[0023] Figure 4 Microstructure of normalizing + high-temperature tempering;

[0024] Figure 5 Microstructure of normalizing + high-temperature tempering + quenching (oil cooling) + tempering (air cooling);

[0025] Figure 6 Microstructure of normalizing + high-temperature tempering + quenching (oil cooling) + tempering (water cooling);

[0026] Figure 7 Microstructure of specimens at different tempering holding temperatures: (a) 150°C; (b) 180°C; (c) 210°C; (d) 240°C.

[0027] Figure 8 Microstructure of quenching (oil cooling) + tempering (560°C); (without normalizing + high-temperature tempering);

[0028] Figure 9 Microstructure of quenching (oil cooling) + tempering (150°C); (without normalizing + high-temperature tempering); Detailed implementation manner

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the following will further describe in detail the disclosed implementation manners of this application in conjunction with the accompanying drawings.

[0030] The chemical composition of 1Cr11Ni2W2MoV steel described in this invention is shown in Table 1.

[0031] Table 1 Composition requirements of 1Cr11Ni2W2MoV material

[0032] Element C Si Mn Cr Ni W Mo V S P Content 0.13 0.31 0.25 11.23 1.61 1.65 0.45 0.26 0.022 0.018

[0033] The heat treatment process can generally be divided into two categories: preliminary heat treatment and final heat treatment. The purpose of preliminary heat treatment is to eliminate certain defects caused by previous processing, such as coarse grains, banded structure, etc. In addition, it also has the functions of reducing hardness to meet the needs of subsequent machining, adjusting the tissue state to prepare for the final heat treatment, etc. For 1Cr11Ni2W2MoV material, the preliminary heat treatment is quenching and tempering, and the final heat treatment refers to the quenching and tempering processes that can strengthen the steel.

[0034] (1) Preliminary heat treatment

[0035] Normalizing is a heat treatment process in which the workpiece is heated above the austenitizing transformation temperature and cooled in air. The cementite in the steel completely dissolves to form a single austenite, providing a uniform matrix for subsequent heat treatment. The schematic diagram of normalizing is shown in Figure 1 , where A C3 represents the temperature at which ferrite is completely transformed into austenite during the heating process, and A Cm represents the temperature at which cementite is completely transformed into austenite during the heating process.

[0036] The purpose of high-temperature tempering after normalizing is to obtain the required mechanical properties, eliminate the non-uniformity of the original microstructure of the raw material, improve the microstructure, promote the dissolution of fully aggregated carbides, and meet the required mechanical properties.

[0037] (2) Final heat treatment

[0038] Quenching is a heat treatment process in which the workpiece is heated to austenitize and then martensite and bainite are obtained in an appropriate manner (schematic diagram shown in Figure 2 ). The martensite obtained by quenching is a high-strength and high-hardness structure, which can be divided into lath martensite (low- and medium-carbon steels, dislocation strengthening) and plate martensite (high-carbon steels, twin strengthening) according to its carbon content and morphology. Different from the equilibrium or near-equilibrium structures obtained by normalizing and annealing, martensite is a non-equilibrium structure and has a tendency to spontaneously transform into other structures. The lower bainite obtained by isothermal quenching of bainite has better plasticity and toughness matching and lower crack sensitivity compared with martensite of the same hardness, and is more suitable for use environments with high hardness and good comprehensive properties. Since the martensite structure obtained by quenching has high strength and high hardness and is an unstable brittle phase, it has no practical application value and must be tempered to decompose and transform into other structures to obtain the required tissue properties. Quenching and tempering are the most basic means of steel transformation. The quenching temperature of the 1Cr11Ni2W2MoV steel used in this application is 1080 ± 10 °C. This is because the dissolution amount of carbides increases with the increase of the solution temperature, and continued heating will produce excessive δ-ferrite, which is a manganese-poor phase rich in tungsten, molybdenum, vanadium, etc. and is the main reason for the reduction of impact toughness. Therefore, by controlling the reasonable quenching temperature to inhibit the formation of δ-ferrite, a fully martensite structure can be obtained.

[0039] Tempering is a heat treatment process in which the quenched martensitic steel is heated to a temperature below the critical point A1 (the temperature at which austenite begins to form), held for an appropriate time and then cooled to room temperature (schematic diagram shown in Figure 3) The purpose of tempering is to eliminate the quenching stress, transform the structure of the steel into a relatively stable state, and improve its plasticity and toughness without reducing or appropriately reducing the hardness and strength of the material. After quenching, the steel usually has high hardness and large brittleness and generally needs to be tempered before use. From a thermodynamic perspective, quenched martensite is unstable and has a tendency to transition to a stable structure. There is still a certain amount of retained austenite in many steels after quenching. Therefore, the tempering process is essentially a complex process of heating the quenched steel within a certain temperature range to make the thermodynamically unstable structure in the steel transition to a stable structure.

[0040] Tempering is generally divided into low-temperature tempering (below 250 °C), medium-temperature tempering (250 - 500 °C), and high-temperature tempering (above 500 °C). Different tempering temperatures result in different tempered structures and corresponding different properties. Generally speaking, as the tempering temperature increases, the hardness and strength gradually decrease, the plasticity increases, and the toughness has a special change process. The 1Cr11Ni2W2MoV steel used in this application has two temper embrittlement zones: 350 - 530 °C and 600 - 670 °C. Special attention should be paid when selecting the tempering temperature to avoid the above ranges.

[0041] Example 1 (Preliminary heat treatment):

[0042] Step 1: Select a 1Cr11Ni2W2MoV hot-rolled bar with a specification of Φ30×200, check the shape, size, and surface quality of the specimen to be processed, and no knocks, bruises, or cracks are allowed.

[0043] Step 2: The normalizing holding temperature is 1080 °C, the normalizing holding time is 45 min, and air cooling is used.

[0044] Step 3: The first tempering holding temperature is 740 °C, the holding time is 80 min. After tempering is completed, it is taken out of the furnace and air-cooled. The tempering equipment is an air resistance furnace.

[0045] Step 4: Test the mechanical properties of the specimen and observe the metallographic structure (attached Figure 4 ).

[0046] The mechanical properties after heat treatment are shown in Table 2, and the metallographic photos after heat treatment are shown in Figure 4 . Through metallographic analysis, it can be known that the structure after normalizing + high-temperature tempering is a P + F (pearlite + ferrite) mixed structure. After normalizing, Rm is about 930 MPa, Rp0.2 is about 745 MPa, δ5 is about 17%, ψ is about 60%, and Aku is about 140 J. The strength value of the material after normalizing + high-temperature tempering is relatively low, and the plasticity index is relatively strong, which is convenient for the next operation and prepares for the subsequent processes.

[0047] Table 2 Mechanical property values of normalizing + high-temperature tempering

[0048]

[0049] Example 2 (Final Heat Treatment):

[0050] Step 1: Select the bar stock after the preliminary heat treatment in Example 1, and check the shape, size, and surface quality of the specimen to be processed. Knocks, dents, and cracks are not allowed.

[0051] Step 2: When the temperature reaches the required value, put it into the furnace. The quenching holding temperature is 1080°C, the quenching holding time is 45 min, oil cooling is used, the oil temperature is 35°C, the residence time in the medium is 7 min, and it is cooled to room temperature.

[0052] Step 3: Conduct the second tempering within 8 h after quenching is completed. Tempering equipment: circulating air resistance furnace

[0053] Step 4: The second tempering holding temperature is 560°C and the holding time is 80 min respectively. After the holding is completed, take it out of the furnace and air cool it.

[0054] Step 5: Test the mechanical properties of the specimen and observe the metallographic structure of the specimen under each heat treatment regime (attached Figure 5 ).

[0055] The mechanical properties after heat treatment are shown in Table 3, and the metallographic structure after heat treatment is shown in Figure 5 . Through metallographic analysis, it can be known that the metallographic structure under this regime is tempered sorbite structure. After quenching and tempering, Rm is about 1205 MPa, Rp0.2 is about 1040 MPa, δ5 is about 19.5%, ψ is about 75%, and Aku is about 115 J. The material has good toughness and plasticity under this regime, and at the same time has relatively high strength, with good comprehensive mechanical properties.

[0056] Table 3 Mechanical property values of quenching (oil cooling) + tempering (air cooling)

[0057]

[0058] Example 3 (Final Heat Treatment):

[0059] Step 1: Select the bar stock after the preliminary heat treatment in Example 1, and check the shape, size, and surface quality of the specimen to be processed. Knocks, dents, and cracks are not allowed.

[0060] Step 2: When the temperature reaches the required value, put it into the furnace. The quenching holding temperature is 1080°C, the quenching holding time is 45 min, oil cooling is used, the oil temperature is 35°C, the residence time in the medium is 7 min, and it is cooled to room temperature.

[0061] Step 3: Conduct the second tempering within 8 h after quenching is completed. The tempering equipment is a circulating air resistance furnace

[0062] Step 4: The second tempering holding temperature is 560°C and the holding time is 80 min respectively. After the holding is completed, take it out of the furnace and water cool it.

[0063] Step 5: Test the mechanical properties of the specimens and observe the metallographic structures of the specimens under each heat treatment regime (Appended Figure 6 ).

[0064] This heat treatment regime is a control test of quenching (oil cooling) + tempering (air cooling). The purpose of the test is to study the influence of the tempering cooling method on the material properties and structures under the same quenching regime. The mechanical properties after heat treatment are shown in Table 4, and the metallographic structures after heat treatment are shown in Figure 6 . It can be known from the metallographic analysis that the microstructure under this regime is also tempered sorbite. After quenching and tempering, Rm is about 1250 MPa, Rp0.2 is about 1090 MPa, δ5 is about 18%, ψ is about 72%, and Aku is about 112 J.

[0065] Table 4 Mechanical property values of quenching (oil cooling) + tempering (water cooling)

[0066]

[0067] Example 4 (final heat treatment):

[0068] Step 1: Select the bar stock after the preliminary heat treatment in Example 1, check the shape, size, and surface quality of the specimens to be treated, and no knocks, dents, or cracks are allowed;

[0069] Step 2: Load the specimens into the furnace at room temperature, evacuate to a vacuum degree in the furnace less than 5 Pa, heat up to the preheating temperature in 90 min, after holding at 830 °C for 30 min, heat up to 1080 °C in 60 min; the quenching holding temperature is 1080 °C, the quenching holding time is 20 min, after the holding is completed, cool with high-purity nitrogen gas, the inflation pressure is 2 bar, and after cooling to below 50 °C, take out of the furnace and air cool;

[0070] Step 3: Conduct the second tempering within 8 h after the quenching is completed;

[0071] Step 4: The holding temperature of the second tempering is 600 °C, and the holding time is 50 min respectively. After the holding is completed, take out of the furnace and air cool;

[0072] Step 5: Test the mechanical properties of the specimens.

[0073] Table 5 Mechanical property values of quenching (vacuum high-pressure gas quenching) + tempering (air cooling)

[0074]

[0075] Example 5 (final heat treatment):

[0076] Step 1: Select the bar stock after the preliminary heat treatment in Example 1, check the shape, size, and surface quality of the specimens to be treated, and no knocks, dents, or cracks are allowed;

[0077] Step 2: quenching and holding temperature is 1080°C, quenching and holding time is 45min, oil cooling, oil temperature is 36°C, cooling transfer time is ≤60s, and residence time in the medium is ≥5min;

[0078] Step 3: Tempering within 8 hours after quenching, tempering equipment: air resistance furnace;

[0079] Step 4: the tempering and holding temperatures are 150°C, 180°C, and 210°C, respectively; the tempering and holding time is 80 minutes, and air cooling is performed;

[0080] Step 5: Test the mechanical properties of the samples and observe the metallographic structures of the samples under each heat treatment system (see Appendix Figure 7 ).

[0081] 1Cr11Ni2W2MoV steel is similar to structural steel 30CrMnSiA. After heat treatment, the strength and hardness values ​​are very high. The strength value Rm of 30CrMnSiA can reach 1700MPa after low temperature tempering. Therefore, this test adopts low temperature tempering to try to obtain higher hardness and strength. The mechanical properties after heat treatment are shown in Table 6, and the metallographic structure after heat treatment is shown in Table 6. Figure 7 , Figure 8 . Through metallographic analysis, it can be seen that the metallographic structure under the quenching 1080℃ / 45min+tempering 150℃ / 60min system is tempered martensite structure, and the Rm after quenching and tempering can reach 1510MPa, while Rp0.2 is 1185MPa, and the elongation is about 16.5%. Under this system, the material has very high strength, Rm reaches 1510MPa, which greatly meets our strength requirements for the material, but at the same time, the plasticity index of the material decreases a lot, δ5 is about 16.5%, A is about 57%, and Z is about 65%. Therefore, if you pursue high strength and do not have too high requirements for plasticity, heat treatment with this system is a good choice.

[0082] Table 6 Mechanical properties of samples under different heat treatment systems

[0083]

[0084]

[0085] Comparative Example 1 (final heat treatment):

[0086] Step 1: Select hot-rolled bars (without preliminary heat treatment, only final heat treatment), check the shape, size and surface quality of the samples to be processed, and do not allow bumps and cracks to exist;

[0087] Step 2: put into the furnace at the temperature, quenching and holding temperature is 1080℃, quenching and holding time is 45min, oil cooling, oil temperature is 56℃, and the residence time in the medium is 7min;

[0088] Step 3: Perform the second tempering within 8 hours after quenching is completed. The tempering equipment is a circulating air resistance furnace;

[0089] Step 4: The holding temperature for the second tempering is 560 °C, and the holding time is 80 minutes respectively. After the holding is completed, take the sample out of the furnace and cool it in water;

[0090] Step 5: Test the mechanical properties of the sample and observe the metallographic structure of the sample under each heat treatment regime (append Figure 8 ).

[0091] Step 5: Test the mechanical properties of the sample and observe the metallographic structure of the sample under each heat treatment regime (newly append Figure 8 )

[0092] Compared with Example 3 that "has undergone preliminary heat treatment", the performance is lower, which proves that for the same quenching + tempering regime, the performance is higher if it has undergone preliminary heat treatment. After normalizing + high-temperature tempering of hot-rolled bars, the grain size can be refined, the non-uniformity of the original structure of the raw material can be eliminated, the structure can be improved, and the carbide that has fully aggregated can be dissolved, providing a better microstructure for subsequent quenching. When reheating after quenching, the carbide is easily dissolved into austenite, increasing the alloying degree of austenite and improving the mechanical properties after quenching and tempering.

[0093] Table 7 Mechanical property values of quenching (oil cooling) + tempering without pretreatment

[0094]

[0095] Comparative Example 2 (final heat treatment):

[0096] Step 1: Select hot-rolled bar stock (without preliminary heat treatment, only final heat treatment), check the shape, size and surface quality of the sample to be treated, and no knocking damage and cracks are allowed;

[0097] Step 2: The quenching holding temperature is 1080 ± 10 °C, the quenching holding time is 45 - 50 minutes, oil cooling, the oil temperature is 20 - 80 °C, the cooling transfer time ≤ 60 s, and the residence time in the medium ≥ 5 minutes;

[0098] Step 3: Perform tempering within 8 hours after quenching is completed. Tempering equipment: air resistance furnace;

[0099] Step 4: The tempering holding temperature is 150 ± 10 °C, the tempering holding time: 70 - 100 minutes, air cooling;

[0100] Step 5: Test the mechanical properties of the sample and observe the metallographic structure of the sample under each heat treatment regime (append Figure 9 )

[0101] Compared with the tempering at 150 ± 10°C in Example 5 of "already subjected to preliminary heat treatment", the mechanical properties are lower, which proves that for the same quenching + tempering system, the properties are higher if subjected to preliminary heat treatment. This is because after normalizing + high-temperature tempering of the hot-rolled bar, the grain refinement can be achieved, the non-uniformity of the original structure of the raw material can be eliminated, the structure can be improved, and the fully aggregated carbides can be promoted to dissolve, providing a better microstructure for subsequent quenching. When reheated after quenching, the carbides are easily dissolved into austenite, increasing the alloying degree of austenite and improving the mechanical properties after quenching and tempering.

[0102] Table 8 Mechanical property values of quenching (vacuum high-pressure gas quenching) + tempering (air cooling) without preliminary heat treatment

[0103]

[0104] (1) When the tempering holding temperature of the 1Cr11Ni2W2MoV material in the final heat treatment is 150°C, Rm reaches 1515 MPa and 1498 MPa. When the tempering holding temperature of the final heat treatment is 180°C, Rm reaches 1496 MPa and 1505 MPa, and high-strength mechanical properties are obtained. Therefore, the high-strength heat treatment process for the 1Cr11Ni2W2MoV material of the present invention is preliminary heat treatment + final heat treatment. The preliminary heat treatment system is: normalizing holding temperature 1080°C, normalizing holding time 45 min, air cooling; the first tempering holding temperature 740°C, holding time 80 min, air cooling. The final heat treatment system is: quenching holding temperature 1080°C, quenching holding time 45 min, oil cooling; tempering holding temperature 150 - 180°C, tempering holding time 70 - 100 min, air cooling.

[0105] (2) Quenching + tempering of 1Cr11Ni2W2MoV steel is the most basic strengthening heat treatment system for this material and is also the most used system in actual production. In actual production, different tempering temperatures can be selected according to different requirements. When tempering at medium and high temperatures, the material has a good combination of strength and plasticity; if low-temperature tempering is selected, the strength value of the material is higher.

[0106] (3) The strength of 1Cr11Ni2W2MoV steel after normalizing + high-temperature tempering is relatively low, and Rm is only about 900 MPa, which can be used as preliminary heat treatment to provide a pre-preparation for subsequent quenching + tempering. After adding preliminary heat treatment, the mechanical properties of this material, especially the strength index, are significantly better, and it can be popularized for the strengthening heat treatment of this material.

[0107] The content not described in detail in the specification of this application belongs to the well-known technology of those skilled in the art.

[0108] The present application has been described in detail above in conjunction with specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present application. Those skilled in the art understand that without departing from the spirit and scope of the present application, various equivalent substitutions, modifications, or improvements can be made to the technical solutions and their implementation manners of the present application, and all of these fall within the scope of the present application. The protection scope of the present application shall be subject to the appended claims.

Claims

1. A heat treatment method for high-strength 1Cr11Ni2W2MoV steel, characterized in that: include: Performing preliminary heat treatment on the 1Cr11Ni2W2MoV hot-rolled piece, the preliminary heat treatment including normalizing, followed by first tempering; after the 1Cr11Ni2W2MoV hot-rolled piece is subjected to preliminary heat treatment, a preliminary heat-treated workpiece is obtained; The workpiece to be heat treated is quenched at a quenching and holding temperature of 1080°C ± 10°C for a quenching and holding time of 45 to 50 minutes. After quenching, a second tempering is performed.

2. The heat treatment method of a high-strength 1Cr11Ni2W2MoV steel according to claim 1, characterized in that: The normalizing and holding temperature is 1080±10° C., and the normalizing and holding time is 45 to 50 minutes.

3. The heat treatment method of high-strength 1Cr11Ni2W2MoV steel according to claim 1, characterized in that: The first tempering has a holding temperature of 740±10° C. and a holding time of 70 to 100 minutes.

4. The heat treatment method of high-strength 1Cr11Ni2W2MoV steel according to claim 1, characterized in that: After the quenching, the oil is cooled to room temperature, and the oil temperature of the oil cooling is 20-80° C. During the oil cooling process, the cooling transfer time is ≤60s, and the residence time in the medium is ≥5min.

5. The heat treatment method of high-strength 1Cr11Ni2W2MoV steel according to claim 1, characterized in that: The second tempering and heat preservation is 150-180°C, and the tempering and heat preservation time is 70-100 minutes.

6. The heat treatment method of high-strength 1Cr11Ni2W2MoV steel according to claim 1, characterized in that: The second tempering is carried out within 8 hours after the quenching is completed.

7. A high-strength 1Cr11Ni2W2MoV steel, characterized in that: The hot-rolled piece of 1Cr11Ni2W2MoV steel is prepared according to the heat treatment method of high-strength 1Cr11Ni2W2MoV steel according to any one of claims 1-6.

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