AISI 410 stainless steel with good low-temperature toughness and manufacturing process thereof

Abstract

The application discloses a kind of AISI 410 stainless steel with good low-temperature toughness and manufacturing process, belong to martensitic stainless steel technical field, including the following steps: steel billet selection;Open billet;After the steel billet of open billet is placed in heating furnace and is heated in steps: furnace temperature is less than or equal to 280 DEG C, is heated to 603-608 DEG C when isothermal 2.5-3.2h, subsequent continues to heat to 1095-1100 DEG C, isothermal 2.5-3.2h;Finally heat to 1190-1210 DEG C and keep warm;Forging;Heat treatment quenching stage: heat to 1000-1015 DEG C, keep warm more than or equal to 5 h after, with furnace cooling to 963-970 DEG C, immerse in preheated 60-75 DEG C medium A and carry out quenching, when workpiece surface to 250-300 DEG C, transfer into mineral oil and cool to 45-55 DEG C.The application can significantly improve the low-temperature toughness of AISI 410 stainless steel, and ensure that material is high strength.

Description

Technical Field

[0001] This invention relates to the field of martensitic stainless steel technology, specifically to an AISI 410 stainless steel with good low-temperature toughness and its manufacturing process. Background Technology

[0002] Martensitic stainless steel is commonly used in the oil and gas industry due to its excellent high-temperature resistance, CO2 corrosion resistance, and high strength. The market demand for martensitic stainless steel valve bodies is showing a gradual upward trend. AISI 410 martensitic stainless steel is known for its high cost-effectiveness and high strength. However, it suffers from manufacturing difficulties, a tendency to crack after forging and heat treatment, and low impact absorption at -29℃.

[0003] To address the challenges in manufacturing AISI 410 stainless steel products, existing technologies have proposed numerous solutions related to forging and heat treatment. For example, patent CN201510549902.5 proposes a "refining + precision forging" process, enabling AISI 410SS martensitic stainless steel to achieve an average impact energy of 50 J at -29℃, but this still falls short of meeting the high toughness requirements of complex working conditions. Patent CN202411738267.0 proposes a "water quenching pretreatment + sub-temperature quenching" heat treatment method, which can increase the 0℃ impact value of 12Cr13 stainless steel to approximately 60 J, but its low-temperature impact performance improvement is limited, and the water quenching process easily generates significant phase transformation stress, increasing the risk of cracking. Patent CN202310854030.8 provides a heat treatment process for AISI 410 steel used in compressors, employing quenching + cryogenic treatment + low-temperature tempering + high-temperature tempering, achieving an impact energy of 88 J. However, the cryogenic treatment process increases equipment investment and production cycle, and the material temperature drops sharply to -50 to -160℃, which can easily generate new internal stress due to the large temperature gradient, further aggravating the risk of cracking after forging or heat treatment, which is not conducive to large-scale industrial application.

[0004] In summary, existing processes cannot simultaneously enable 410 stainless steel to possess properties such as high yield strength, excellent low-temperature toughness at -29℃, and low risk of forging / heat treatment cracking, thus failing to meet the stringent requirements of the petroleum and other industries for key components such as three-way valve bodies.

[0005] Based on this, the present invention designs an AISI 410 stainless steel with good low-temperature toughness and its manufacturing process to solve the above problems. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a subject matter.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A manufacturing process for AISI 410 stainless steel with good low-temperature toughness includes the following steps:

[0009] S1. Steel billet selection: The material composition meets the following requirements: C: 0.07-0.15%; Mn: 0.4-0.8%; P: ≤0.0020%; S: ≤0.0015%; Si: ≤0.5%; Cr: 11.50-13.50%; Ni: ≤0.75%; Mo: 0.15-0.22%; the remaining elements are Fe and other trace elements.

[0010] S2, roughing;

[0011] S3. Forging: The steel billet after roughing is placed in a heating furnace for stepped heating: the furnace loading temperature is ≤280℃, and the heating rate is controlled at ≤200℃ / h; when the temperature reaches 603-608℃, it is held isothermally for 2.5-3.2h, then the temperature continues to rise to 1095-1100℃, and the heating rate is controlled at ≤150℃ / h, and it is held isothermally for 2.5-3.2h; finally, the temperature is raised to 1190-1210℃ and held, and the heating rate is controlled at ≤100℃ / h; then forging is carried out.

[0012] S4. Heat treatment quenching stage: The heating rate is controlled at ≤200℃ / h. The temperature is raised to 1000-1015℃ and held for ≥5 hours. Then, the workpiece is cooled in the furnace to 963-970℃ and immersed in a preheated medium A at 60-75℃ for quenching. When the surface temperature of the workpiece reaches 250-300℃, it is transferred to mineral oil and cooled to 45-55℃. Then, it is taken out and air-cooled. After that, tempering is performed. The medium A is a mixed aqueous solution of sodium nitrate, sodium nitrite, potassium nitrate and sodium chloride.

[0013] Furthermore, in step S1, the following condition must be met: 3 ≤ Ni / Mo ≤ 3.41.

[0014] Furthermore, in step S2, electroslag remelting electroslag ingots are selected as raw materials and forged into round billets through a billet-making process.

[0015] Furthermore, in step S3, forging specifically includes the following processes:

[0016] First forging: roughing, forging ratio ≥1.5, final forging temperature ≥800℃, furnace holding ≥1 h;

[0017] Second heat: drawing out, forging ratio ≥1.5, final forging temperature ≥800℃, and heat preservation in the furnace ≥1 h;

[0018] Third heat: drawing to shape, forging ratio ≥1.5, final forging temperature ≥850℃, air cooling.

[0019] Furthermore, in step S4, the medium A comprises the following raw materials by mass fraction: 10-14% sodium nitrate, 20-22% sodium nitrite, 15-20% potassium nitrate, 15-21% sodium chloride, and the remainder is water.

[0020] Furthermore, in step S4, tempering is performed within 12 hours after quenching.

[0021] Furthermore, in step S4, the tempering temperature is 680℃, and the tempering is followed by water cooling after ≥7 hours.

[0022] Furthermore, in step S3, the holding time at 1190-1210℃ is 1.2 min / mm.

[0023] To better achieve the objectives of this invention, this invention also provides an AISI 410 stainless steel with good low-temperature toughness prepared according to the manufacturing process described above.

[0024] Furthermore, AISI 410 stainless steel has an impact energy absorption capacity of >130 J at -29℃.

[0025] Compared to existing technologies, the advantages of this invention are as follows: This invention uses 410 stainless steel raw materials with low levels of impurities such as phosphorus and sulfur, and employs a segmented heating method in the forging heating process. This heating method avoids uneven internal structure caused by rapid heating; simultaneously, isothermal treatment at 603-608℃ helps alleviate raw material segregation, reduces anisotropy, and further reduces the risk of crack formation. In the heat treatment quenching stage, a liquid-liquid quenching method is used instead of water quenching pretreatment and deep cryogenic treatment: the workpiece is first immersed in a preheated 60-75℃ medium A and rapidly cooled to 250-300℃. Rapid cooling in the high-temperature zone obtains more dislocation-type martensite, improving the workpiece's strength and toughness. Subsequently, it is transferred to mineral oil and slowly cooled to 45-55℃. Slow cooling in the low-temperature zone alleviates the phase transformation internal stress generated during the martensitic transformation, avoiding the risk of cracking due to stress concentration. High-temperature tempering is performed within 12 hours after quenching to obtain tempered sorbite, improving the material's yield strength and toughness. This invention significantly improves the low-temperature toughness (impact energy at -29°C > 130 J) of AISI 410 stainless steel while ensuring high material strength, avoiding cracking during forging and heat treatment. This invention effectively improves the batch production yield of AISI 410 martensitic stainless steel three-way valve bodies, reduces production costs, and has significant economic benefits. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0027] Figure 1 Forging heating process diagram for a three-way valve body;

[0028] Figure 2 Example of forging process for a three-way valve body;

[0029] Figure 3 This is a heat treatment process diagram for a three-way valve body.

[0030] Figure 4 This is a metallographic diagram of the furnace-fed test block of Embodiment 3 of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Example 1: A manufacturing process for AISI 410 stainless steel with good low-temperature toughness, comprising the following steps:

[0033] S1. Steel billet selection: The material composition meets the following requirements: C: 0.07%; Mn: 0.8%; P: 0.0020%; S: 0.0015%; Si: 0.5%; Cr: 11.50%; Ni: 0.75%; Mo: 0.22%; the remaining elements are Fe and other trace elements;

[0034] In the billet composition design stage, the content of impurity elements must be strictly controlled. The billet material selected in S1 is an electroslag ingot with low Si, P, and S content, less impurity segregation, reduced cracking during forging, and improved low-temperature toughness. In addition, the appropriate addition of a small amount of Mo is beneficial to improving the tempering stability and corrosion resistance of the material and improving temper brittleness.

[0035] S2. Billeting: Select an electroslag remelted electroslag ingot weighing 520Kg as raw material and forge it into a round billet with a diameter of 300mm through the billeting process.

[0036] S3. Forging: The round billet after blanking is placed in a heating furnace for stepped heating: furnace loading temperature 280℃, heating rate controlled at 200℃ / h; when heated to 603℃, isothermal holding for 3 hours (hydrogen diffusion annealing process, to allow hydrogen atoms inside the billet to fully diffuse and escape, while eliminating structural stress, uniform billet temperature, and reducing subsequent deformation and cracking tendency), then continue heating to 1095℃, heating rate controlled at 150℃ / h, isothermal holding for 3 hours to avoid local temperature surges during subsequent heating; finally, heating to 1190℃ and holding (holding time: 1.2min / mm, holding time calculated by multiplying the effective thickness of the billet by 1.2), heating rate controlled at 100℃ / h to ensure uniform overall temperature of the billet; the specific forging process of the three-way valve body is as follows. Figure 2 As shown.

[0037] Forging specifically includes the following processes:

[0038] First forging: roughing, forging ratio 1.5, final forging temperature 800℃, and heat treatment in the furnace for 1.5 hours;

[0039] Second heat: drawing out, forging ratio 1.5, final forging temperature 800℃, and holding in the furnace for 1.5 hours;

[0040] Third heat: drawing to shape, forging ratio 1.5, final forging temperature 850℃, air cooling;

[0041] S4. Non-destructive testing. The forged structure is compact, and MT testing shows no microcracks on the surface.

[0042] S5. Heat Treatment Quenching Stage: The heating rate is controlled at 200℃ / h, reaching 1000℃. After holding at this temperature for 5 hours, the workpiece is furnace cooled to 970℃ and then immersed in preheated 60℃ medium A for quenching. (During this stage, a mixer needs to be started simultaneously at 950r / min to accelerate water flow, breaking the vapor film formed on the workpiece surface to ensure uniform quenching cooling rate and avoid insufficient local cooling affecting microstructure transformation). When the workpiece surface reaches 300℃, it is transferred to mineral oil for intercooling to 45℃, then removed and air-cooled. Tempering is performed within 12 hours after quenching to avoid cracking caused by excessive phase transformation stress. The tempering temperature is 680℃, and water cooling is performed after 7 hours of tempering. Tempering precipitates carbides, which helps improve the strength and impact toughness of the parts.

[0043] The medium A comprises the following raw materials by mass fraction: 10% sodium nitrate (NaNO3), 22% sodium nitrite (NaNO2), 15% potassium nitrate (KNO3), 21% sodium chloride (NaCl), and the remainder is water.

[0044] The heat treatment quenching stage employs a two-stage quenching method: first, the workpiece is immersed in preheated medium A and rapidly cooled to 300℃. Rapid cooling in the high-temperature zone yields a greater amount of dislocation-type martensite, improving the workpiece's strength and toughness. Subsequently, it is transferred to mineral oil and slowly cooled to 45℃. Slow cooling in the low-temperature zone alleviates the phase transformation stress generated during the martensitic transformation, avoiding the risk of cracking due to stress concentration. High-temperature tempering is performed within 12 hours after quenching to obtain tempered sorbite, improving the material's yield strength and toughness.

[0045] S6. Non-destructive testing. No cracks were found after MT testing following heat treatment.

[0046] The mechanical properties of the furnace-loaded test blocks were tested (GB / T 228.1-2021, GB / T 229-2020), and the results are shown in Table 1.

[0047] Table 1 Results of mechanical property testing of the test blocks in the furnace

[0048] Performance testing Standard requirements Sampling location Test Results Does it meet the requirements? Yield strength / MPa ≥515 T / 4 longitudinal 530 yes Tensile strength / MPa ≥655 T / 4 longitudinal 708 yes Elongation / % ≥18 T / 4 longitudinal 27 yes Reduction of area / % ≥35 T / 4 longitudinal 75 yes -29℃ Impact Absorption Energy / J ≥27 T / 4 longitudinal 132，157，151 yes

[0049] Example 2: A manufacturing process for AISI 410 stainless steel with good low-temperature toughness, comprising the following steps:

[0050] S1. Steel billet selection: The material composition meets the following requirements: C: 0.15%; Mn: 0.4%; P: 0.0015%; S: 0.001%; ​​Si: 0.25%; Cr: 13.50%; Ni: 0.45%; Mo: 0.15%; the remaining elements are Fe and other trace elements;

[0051] In the billet composition design stage, the content of impurity elements must be strictly controlled. The billet material selected in S1 is an electroslag ingot with low Si, P, and S content, less impurity segregation, reduced cracking during forging, and improved low-temperature toughness. In addition, the appropriate addition of a small amount of Mo is beneficial to improving the tempering stability and corrosion resistance of the material and improving temper brittleness.

[0052] S2. Billeting: Select an electroslag remelted electroslag ingot weighing 520Kg as raw material and forge it into a round billet with a diameter of 300mm through the billeting process.

[0053] S3. Forging: The round billet after blanking is placed in a heating furnace for stepped heating: furnace loading temperature 270℃, heating rate controlled at 180℃ / h; when heated to 605℃, isothermal holding for 2.5h (hydrogen diffusion annealing process, to allow hydrogen atoms inside the billet to fully diffuse and escape, while eliminating structural stress, uniform billet temperature, and reducing subsequent deformation and cracking tendency), then continue heating to 1100℃, heating rate controlled at 135℃ / h, isothermal holding for 2.5h to avoid local temperature surges during subsequent heating; finally, heating to 1210℃ and holding (holding time: 1.2min / mm), heating rate controlled at 95℃ / h to ensure uniform overall billet temperature; the specific forging process of the three-way valve body is as follows. Figure 2 As shown.

[0054] Forging specifically includes the following processes:

[0055] First forging: roughing, forging ratio 1.8, final forging temperature 850℃, and heat treatment in the furnace for 1.2 h;

[0056] Second heat: drawing out, forging ratio 1.7, final forging temperature 850℃, and holding in the furnace for 1.2 h;

[0057] Third heat: drawing to shape, forging ratio 1.6, final forging temperature 880℃, air cooling;

[0058] S4. Non-destructive testing. The forged structure is compact, and MT testing shows no microcracks on the surface.

[0059] S5. Heat Treatment Quenching Stage: The heating rate is controlled at 180℃ / h, reaching 1015℃. After holding at this temperature for 5.5 hours, the workpiece is furnace cooled to 963℃ and then immersed in preheated 75℃ medium A for quenching. (During this stage, a mixer needs to be started simultaneously at 1000r / min to accelerate water flow, breaking the vapor film formed on the workpiece surface to ensure uniform quenching cooling rate and avoid insufficient local cooling affecting microstructure transformation). When the workpiece surface reaches 250℃, it is transferred to mineral oil for intercooling to 55℃, then removed and air-cooled. Tempering is performed within 12 hours after quenching to avoid cracking caused by excessive phase transformation stress. The tempering temperature is 680℃, and water cooling is performed after 8 hours of tempering. Tempering precipitates carbides, which helps improve the strength and impact toughness of the parts.

[0060] The medium A comprises the following raw materials by mass fraction: 14% sodium nitrate (NaNO3), 20% sodium nitrite (NaNO2), 20% potassium nitrate (KNO3), 15% sodium chloride (NaCl), and the remainder is water.

[0061] The heat treatment quenching stage employs a two-stage quenching method: first, the workpiece is immersed in preheated medium A and rapidly cooled to 250°C. Rapid cooling in the high-temperature zone yields a greater amount of dislocation-type martensite, improving the workpiece's strength and toughness. Subsequently, it is transferred to mineral oil and slowly cooled to 55°C. Slow cooling in the low-temperature zone alleviates the phase transformation stress generated during the martensitic transformation, avoiding the risk of cracking due to stress concentration. High-temperature tempering is performed within 12 hours after quenching to obtain tempered sorbite, improving the material's yield strength and toughness.

[0062] S6. Non-destructive testing. No cracks were found after MT testing following heat treatment.

[0063] The mechanical properties of the furnace-loaded test blocks were tested, and the results are shown in Table 2.

[0064] Table 2 Results of mechanical property testing of the furnace-loaded test blocks

[0065] Performance testing Standard requirements Sampling location Test Results Does it meet the requirements? Yield strength / MPa ≥515 T / 4 longitudinal 541 yes Tensile strength / MPa ≥655 T / 4 longitudinal 723 yes Elongation / % ≥18 T / 4 longitudinal 26 yes Reduction of area / % ≥35 T / 4 longitudinal 73 yes -29℃ Impact Absorption Energy / J ≥27 T / 4 longitudinal 145，158，149 yes

[0066] Example 3: A manufacturing process for AISI 410 stainless steel with good low-temperature toughness, comprising the following steps:

[0067] S1. Steel billet selection: The material composition meets the following requirements: C: 0.09%; Mn: 0.55%; P: 0.013%; S: 0.001%; ​​Si: 0.001%; ​​Cr: 12.50%; Ni: 0.55%; Mo: 0.18%; the remaining elements are Fe and other trace elements.

[0068] In the billet composition design stage, the content of impurity elements must be strictly controlled. The billet material selected in S1 is an electroslag ingot with low Si, P, and S content, less impurity segregation, reduced cracking during forging, and improved low-temperature toughness. In addition, the appropriate addition of a small amount of Mo is beneficial to improving the tempering stability and corrosion resistance of the material and improving temper brittleness.

[0069] S2. Billeting: Select an electroslag remelted electroslag ingot weighing 520Kg as raw material and forge it into a round billet with a diameter of 300mm through the billeting process.

[0070] S3. Forging: The round billet after roughing is placed in a heating furnace for stepped heating: the furnace loading temperature is 275℃, and the heating rate is controlled at 185℃ / h; when the temperature reaches 608℃, it is held isothermally for 3.2h (hydrogen diffusion annealing process, which allows hydrogen atoms inside the billet to fully diffuse and escape, while eliminating structural stress, uniformizing the billet temperature, and reducing the tendency for subsequent deformation and cracking), then the temperature is continued to rise to 1098℃, with the heating rate controlled at 150℃ / h, and held isothermally for 3.2h to avoid local temperature surges during subsequent heating; finally, the temperature is raised to 1200℃ and held (holding time: 1.2min / mm), with the heating rate controlled at 100℃ / h to ensure uniform temperature of the billet; the specific forging process of the three-way valve body is as follows. Figure 2 As shown.

[0071] Forging specifically includes the following processes:

[0072] First forging: roughing, forging ratio 1.5, final forging temperature 800℃, and holding in the furnace for 1 hour;

[0073] Second heat: drawing out, forging ratio 1.5, final forging temperature 800℃, and holding in the furnace for 1 hour;

[0074] Third heat: drawing to shape, forging ratio 1.5, final forging temperature 850℃, air cooling;

[0075] S4. Non-destructive testing. The forged structure is compact, and MT testing shows no microcracks on the surface.

[0076] S5. Heat Treatment Quenching Stage: The heating rate is controlled at 200℃ / h, reaching 1010℃. After holding at this temperature for 5 hours, the workpiece is furnace cooled to 965℃ and then immersed in preheated 70℃ medium A for quenching. (During this stage, a mixer needs to be started simultaneously at 980r / min to accelerate water flow, breaking the vapor film formed on the workpiece surface to ensure uniform quenching cooling rate and avoid insufficient local cooling affecting microstructure transformation). When the workpiece surface reaches 290℃, it is transferred to mineral oil for intercooling to 50℃, then removed and air-cooled. Tempering is performed within 12 hours after quenching to avoid cracking caused by excessive phase transformation stress. The tempering temperature is 680℃, and water cooling is performed after 7 hours of tempering. Tempering precipitates carbides, which helps improve the strength and impact toughness of the parts.

[0077] The medium A comprises the following raw materials by mass fraction: sodium nitrate (NaNO3) 13%, sodium nitrite (NaNO2) 21%, potassium nitrate (KNO3) 16%, sodium chloride (NaCl) 18%, and the remainder is water.

[0078] The heat treatment quenching stage employs a two-stage quenching method: first, the workpiece is immersed in preheated medium A and rapidly cooled to 290°C. Rapid cooling in the high-temperature zone yields a greater amount of dislocation-type martensite, improving the workpiece's strength and toughness. Subsequently, it is transferred to mineral oil and slowly cooled to 50°C. Slow cooling in the low-temperature zone alleviates the phase transformation stress generated during the martensitic transformation, avoiding the risk of cracking due to stress concentration. High-temperature tempering is performed within 12 hours after quenching to obtain tempered sorbite, improving the material's yield strength and toughness.

[0079] S6. Non-destructive testing. No cracks were found after MT testing following heat treatment.

[0080] The mechanical properties of the test blocks were tested, and the results are shown in Table 3.

[0081] Table 3 Results of mechanical property testing of the test blocks in the furnace

[0082] Performance testing Standard requirements Sampling location Test Results Does it meet the requirements? Yield strength / MPa ≥515 T / 4 longitudinal 553 yes Tensile strength / MPa ≥655 T / 4 longitudinal 739 yes Elongation / % ≥18 T / 4 longitudinal 25 yes Reduction of area / % ≥35 T / 4 longitudinal 71 yes -29℃ Impact Absorption Energy / J ≥27 T / 4 longitudinal 142，155，153 yes

[0083] Comparative Example 1: The difference from Example 3 is as follows: S1. Steel billet selection: The material composition meets the following requirements: C: 0.09%; Mn: 0.55%; P: 0.024%; S: 0.013%; Si: 0.041%; Cr: 12.50%; Ni: 0.55%; Mo: 0.18%; the remaining elements are Fe and other trace elements. Everything else is the same as in Example 3. It can be seen that the content of inclusions (P, S, Si) is slightly higher.

[0084] The mechanical properties of the furnace-loaded test blocks were tested, and the results are shown in Table 4.

[0085] Table 4 Results of mechanical property testing of the test blocks in the furnace

[0086] Performance testing Standard requirements Sampling location Test Results Does it meet the requirements? Yield strength / MPa ≥515 T / 4 longitudinal 519 yes Tensile strength / MPa ≥655 T / 4 longitudinal 687 yes Elongation / % ≥18 T / 4 longitudinal 28 yes Reduction of area / % ≥35 T / 4 longitudinal 74 yes -29℃ Impact Absorption Energy / J ≥27 T / 4 longitudinal 48，54，48 yes

[0087] Comparative Example 2: Unlike Example 3, in step S3, the round billet after roughing is placed in a heating furnace for stepped heating: the furnace loading temperature is 275℃, and the heating rate is controlled at 210℃ / h; when the temperature reaches 650℃, it is held isothermally for 3.2h (hydrogen diffusion annealing process, which allows hydrogen atoms inside the billet to fully diffuse out, while eliminating structural stress, uniformizing the billet temperature, and reducing subsequent deformation and cracking tendency), then the temperature continues to rise to 1150℃, the heating rate is controlled at 180℃ / h, and it is held isothermally for 3.2h to avoid local temperature surges during subsequent heating; finally, the temperature is raised to 1200℃ and held (holding time: 1.2min / mm), the heating rate is controlled at 120℃ / h to ensure uniform overall temperature of the billet; the specific forging process of the three-way valve body is the same as in Example 3.

[0088] The mechanical properties of the furnace-loaded test blocks were tested, and the results are shown in Table 5.

[0089] Table 5 Results of mechanical property testing of the furnace-loaded test blocks

[0090] Performance testing Standard requirements Sampling location Test Results Does it meet the requirements? Yield strength / MPa ≥515 T / 4 longitudinal 535 yes Tensile strength / MPa ≥655 T / 4 longitudinal 712 yes Elongation / % ≥18 T / 4 longitudinal 27 yes Reduction of area / % ≥35 T / 4 longitudinal 42 yes -29℃ Impact Absorption Energy / J ≥27 T / 4 longitudinal 112，105，123 yes

[0091] Comparative Example 3: Unlike Example 3, in step S5, the heat treatment quenching stage: the heating rate is controlled at 200℃ / h, reaching 1010℃, and held for 5 hours. Then, it is furnace cooled to 980℃ and immersed in unheated medium A for quenching (at this stage, a mixer needs to be started simultaneously at 980r / min to accelerate water flow, breaking the vapor film formed on the workpiece surface to ensure uniform quenching cooling rate and avoid insufficient local cooling affecting microstructure transformation). When the workpiece surface reaches 350℃, it is transferred to mineral oil for intercooling to 50℃, then removed and air-cooled. Tempering is performed within 12 hours after quenching to avoid excessive phase transformation stress causing cracking. The tempering temperature is 680℃, and water cooling is performed after 7 hours of tempering. Tempering precipitates carbides, which helps improve the strength and impact toughness of the parts.

[0092] The mechanical properties of the furnace-loaded test blocks were tested, and the results are shown in Table 6.

[0093] Table 6 Results of mechanical property testing of the furnace-loaded test blocks

[0094] Performance testing Standard requirements Sampling location Test Results Does it meet the requirements? Yield strength / MPa ≥515 T / 4 longitudinal 522 yes Tensile strength / MPa ≥655 T / 4 longitudinal 675 yes Elongation / % ≥18 T / 4 longitudinal 23 yes Reduction of area / % ≥35 T / 4 longitudinal 45 yes -29℃ Impact Absorption Energy / J ≥27 T / 4 longitudinal 82，87，93 yes

[0095] Comparative Example 4: Unlike Example 3, in step S3, the round billet after roughing is placed in a heating furnace for stepped heating: the furnace loading temperature is 275℃, and the heating rate is controlled at 210℃ / h; when the temperature reaches 650℃, it is held isothermally for 3.2h (hydrogen diffusion annealing process, which allows hydrogen atoms inside the billet to fully diffuse out, while eliminating structural stress, uniformizing the billet temperature, and reducing subsequent deformation and cracking tendency), then the temperature continues to rise to 1150℃, the heating rate is controlled at 180℃ / h, and it is held isothermally for 3.2h to avoid local temperature surges during subsequent heating; finally, the temperature is raised to 1200℃ and held (holding time: 1.2min / mm), the heating rate is controlled at 120℃ / h to ensure uniform overall temperature of the billet; the specific forging process of the three-way valve body is the same as in Example 3. Step S5, Heat Treatment Quenching Stage: The heating rate is controlled at 200℃ / h, reaching 1010℃. After holding at this temperature for 5 hours, the workpiece is furnace cooled to 980℃ and then immersed in unheated medium A for quenching (during this stage, a mixer needs to be started simultaneously at 980r / min to accelerate water flow, breaking the vapor film formed on the workpiece surface to ensure uniform quenching cooling rate and avoid insufficient local cooling affecting microstructure transformation). When the workpiece surface reaches 350℃, it is transferred to mineral oil for intercooling to 50℃, then removed and air-cooled. Tempering is performed within 12 hours after quenching to avoid cracking caused by excessive phase transformation stress. The tempering temperature is 680℃, and water cooling is performed after 7 hours of tempering. Tempering precipitates carbides, which is beneficial for improving the strength and impact toughness of the parts. The remaining steps are the same as in Example 3.

[0096] The mechanical properties of the test blocks were tested, and the results are shown in Table 7.

[0097] Table 7 Results of mechanical property testing of the furnace-loaded test blocks

[0098] Performance testing Standard requirements Sampling location Test Results Does it meet the requirements? Yield strength / MPa ≥515 T / 4 longitudinal 516 yes Tensile strength / MPa ≥655 T / 4 longitudinal 650 no Elongation / % ≥18 T / 4 longitudinal 19 yes Reduction of area / % ≥35 T / 4 longitudinal 38 yes -29℃ Impact Absorption Energy / J ≥27 T / 4 longitudinal 25，27，23 no

[0099] This invention uses 410 stainless steel raw materials with low levels of impurities such as phosphorus and sulfur, and employs a segmented heating method in the forging heating process. This heating method avoids uneven internal structure caused by rapid heating; simultaneously, isothermal treatment at 603-608℃ helps alleviate raw material segregation, reduces anisotropy, and further reduces the risk of crack formation. In the heat treatment quenching stage, a split-liquid quenching method is used instead of water quenching pretreatment and deep cryogenic treatment: the workpiece is first immersed in a preheated medium A at 60-75℃ and rapidly cooled to 250-300℃. Rapid cooling in the high-temperature zone obtains more dislocation-type martensite, improving the workpiece's strength and toughness. Subsequently, it is transferred to mineral oil and slowly cooled to 45-55℃. Slow cooling in the low-temperature zone alleviates the phase transformation internal stress generated during the martensitic transformation, avoiding the risk of cracking due to stress concentration. High-temperature tempering is performed within 12 hours after quenching to obtain tempered sorbite, improving the material's yield strength and toughness. This invention significantly improves the low-temperature toughness (impact energy at -29°C > 130 J) of AISI 410 stainless steel while ensuring high material strength, avoiding cracking during forging and heat treatment. This invention effectively improves the batch production yield of AISI 410 martensitic stainless steel three-way valve bodies, reduces production costs, and has significant economic benefits.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A manufacturing process of an AISI 410 stainless steel having good low temperature toughness, characterized in that, It comprises the following steps: S1, billet selection: material composition meets: C: 0.07-0.15%; Mn: 0.4-0.8%; S: ≤0.0015%; Si: ≤0.5%; Cr: 11.50-13.50%; Ni: ≤0.75%; Mo: 0.15-0.22%; the rest elements are Fe and other trace elements; P：≤0.0020%； S2, cogging; S3, forging: the cogged billet is placed in a heating furnace for stepwise heating: furnace charging temperature ≤280℃, the heating rate is controlled to be ≤200℃ / h; when the temperature is increased to 603-608℃, isothermal holding for 2.5-3.2h, then continues to increase the temperature to 1095-1100℃, the heating rate is controlled to be ≤150℃ / h, isothermal holding for 2.5-3.2h; finally, the temperature is increased to 1190-1210℃, the heating rate is controlled to be ≤100℃ / h; then, forging is carried out; S4, quenching stage of heat treatment: the heating rate is controlled to be ≤200℃ / h, the temperature is increased to 1000-1015℃, after holding for ≥5h, the furnace is cooled to 963-970℃, and then immersed in preheated medium A of 60-75℃ for quenching; when the surface of the workpiece is 250-300℃, it is transferred into mineral oil for cooling to 45-55℃, and then taken out for air cooling; then, tempering is carried out; the medium A is a mixed aqueous solution of sodium nitrate, sodium nitrite, potassium nitrate and sodium chloride. In step S1, it meets: 3 ≤ Ni / Mo ≤ 3.

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2. The manufacturing process of AISI 410 stainless steel with good cryogenic toughness according to claim 1, characterized in that, In step S2, electroslag remelted ingot is selected as raw material, and is processed into round billet through cogging process.

3. The manufacturing process of AISI 410 stainless steel with good cryogenic toughness according to claim 1, characterized in that, In step S3, the forging specifically comprises the following procedures:

4. The manufacturing process of AISI 410 stainless steel with good cryogenic toughness according to claim 1, characterized in that, First fire: roughing, forging ratio ≥1.5, final forging temperature ≥800℃, return to furnace and holding for ≥1h; Second fire: elongation, forging ratio ≥1.5, final forging temperature ≥800℃, return to furnace and holding for ≥1h; Third fire: elongation to forming, forging ratio ≥1.5, final forging temperature ≥850℃, air cooling. In step S4, the medium A comprises the following raw materials in mass fraction: sodium nitrate 10-14%, sodium nitrite 20-22%, potassium nitrate 15-20%, sodium chloride 15-21%, and the rest is water.

5. The manufacturing process of AISI 410 stainless steel with good cryogenic toughness according to claim 1, characterized in that, In step S4, the tempering is carried out within 12h after quenching.

6. The manufacturing process of AISI 410 stainless steel with good cryogenic toughness according to claim 1, characterized in that, In step S4, the tempering temperature is 680℃, and water cooling is carried out after holding for ≥7h.

7. The manufacturing process of AISI 410 stainless steel with good cryogenic toughness according to claim 1, characterized in that, In step S3, the holding time when the temperature is increased to 1190-1210℃ is 1.2min / mm.

8. The process for manufacturing AISI 410 stainless steel with good cryogenic toughness according to claim 1, characterized in that, 9. An AISI 410 stainless steel with good low-temperature toughness prepared by the manufacturing process according to any one of claims 1-8. The AISI 410 stainless steel has impact absorption energy of-29℃ >130 J.

10. The good low temperature toughness AISI 410 stainless steel according to claim 9, characterized in that, ​

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