Production process for improving quality of 14Cr11MoV forging

Abstract

The invention discloses a production process for improving the quality of a 14Cr11MoV forge piece, which is used for the 14Cr11MoV forge piece of which the excircle diameter is less than or equal to phi 500mm. The production process comprises the following steps of: performing temperature control annealing, high-temperature quenching, primary high-temperature tempering and secondary high-temperature tempering, and controlling the temperature of the forge piece after the forging is finished, so that the quality of the 14Cr11MoV forge piece is improved. The phenomenon that the structure is thick or uneven due to overheating caused by long-time staying of the forge piece core at the high temperature is avoided; quenching cooling of a 6%-9% low-concentration aqueous solution and quenching cooling of N32 oil are combined, so that the uniformity of the overall quality of the forged piece after quenching cooling is guaranteed, the consumption of the aqueous solution is reduced, the production cost is reduced, and the environmental pollution is reduced; in combination with the martensite transformation point temperature of the 14Cr11MoV forge piece, an aqueous solution is adopted for cooling to be close to the martensite transformation point temperature, then cooling is conducted in an oil cooling mode, the structural stress of transformation from austenite to martensite is relieved, the forge piece cracking phenomenon is avoided, secondary high-temperature tempering is conducted by controlling the temperature rising speed, and therefore the 14Cr11MoV forge piece obtains high strength, plasticity and toughness; the internal stress is effectively removed, the stability of the forge piece is improved, and the overall quality is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat treatment of metal materials, and particularly relates to a production process for improving the quality of 14Cr11MoV forgings, which not only obtains good uniform refinement of the forging structure, but also avoids the phenomenon of cracking caused by the superposition of thermal stress and tissue transformation stress during the quenching process. Background Art

[0002] 14Cr11MoV material belongs to heat-resistant martensitic stainless steel, which has high thermal strength, good shock absorption and tissue stability. In addition, it has a small linear expansion coefficient and is not sensitive to temper embrittlement, and is a good blade material. Due to its high strength, good plasticity, strong ductility and excellent wear resistance, it is mainly used to manufacture bars, pipes, chemical equipment, mechanical parts, etc., and is widely used in industries such as chemical industry, petroleum, and aviation. At present, when producing products of this material, it is mainly used to produce forging products. This material has a high alloy content, the Cr alloy range is 10% - 11.5%, the V alloy range is 0.25% - 0.40%, and the Mo alloy range is 0.50% - 0.70%. During heat treatment production, due to improper control of the heat treatment process, it is easy to cause overheating of the forgings, resulting in phenomena such as coarse structure and quenching cracking, thereby causing certain waste losses. In order to improve the quality of 14Cr11MoV forging products and form stable batch production, a reasonable heat treatment process is urgently needed, which can effectively ensure product quality, meet production needs, and improve the delivery rate. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a production process for improving the quality of 14Cr11MoV forgings with significantly improved overall quality, which not only avoids overheating of the forging core resulting in coarse or uneven structure, slows down the tissue stress of austenite to martensite transformation, avoids phenomena such as forging cracking, but also reduces production costs and environmental pollution.

[0004] To achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions: A production process for improving the quality of 14Cr11MoV forgings, characterized in that it is carried out according to the following process: Step 1), controlled temperature annealing: After forging, the forgings are lifted to the cooling area for air cooling. When placing, the distance between the forgings should be greater than 1 meter. Air cool until the surface of the forgings reaches 550°C - 600°C, keep warm for 2h - 10h, then heat up to 840°C - 880°C at a heating rate of 10°C / h - 80°C / h, keep warm for 15h - 50h, and then cool down in the furnace at a cooling rate of ≤30°C / h until it is below 300°C and then take it out for air cooling until it reaches room temperature. After completing Step 1), prepare to load the forgings into the furnace and perform high-temperature quenching in the heating furnace; Step 2), High-temperature quenching: Load the forging into a heating furnace with a furnace temperature of ≤450°C, heat it up to 600°C - 700°C at a heating rate of 10°C / h - 100°C / h, hold for 2h - 5h, then heat it up to 980°C - 1020°C at full power heating rate, hold for 5h - 30h. After holding, take it out of the furnace for quenching and cooling. First, pre-cool in the air for 180s - 230s, then put the forging into an aqueous-based liquid with a concentration of 6% - 9% and an initial liquid temperature of 30°C - 50°C for cooling for 5min - 20min. During the cooling process, start the compressed air to stir the aqueous-based liquid. After cooling, lift the forging out of the aqueous-based liquid and transfer it to quenching oil with an initial temperature of ≤60°C for cooling for 30min - 200min. After completing Step 2), load the forging into a heating furnace with a furnace temperature of ≤450°C and perform a high-temperature tempering once; Step 3), First high-temperature tempering: Heat it up to 650°C - 750°C at a heating rate of 10°C / h - 100°C / h, hold for 5h - 30h, then take it out of the furnace and air-cool to room temperature. After completing Step 3), load the forging into a heating furnace with a furnace temperature of ≤450°C and perform a second high-temperature tempering; Step 4), Second high-temperature tempering: Heat it up to 620°C - 720°C at a heating rate of 10°C / h - 100°C / h, hold for 5h - 30h, then take it out of the furnace and air-cool to room temperature.

[0005] The present invention is applicable to 14Cr11MoV forgings with an outer diameter of ≤φ500mm. It not only avoids overheating in the core of the forging, resulting in coarse or uneven structure, slows down the structure stress during the transformation from austenite to martensite, and avoids phenomena such as forging cracking, but also reduces production costs and environmental pollution. Compared with the existing technology, the process of the present invention has the following advantages: 1. After forging, by controlling the temperature of the forging, it avoids the overheating in the core of the forging at high temperature for a long time, resulting in coarse or uneven structure; 2. By combining quenching and cooling with a low-concentration aqueous solution of 6% - 9% and N32 oil quenching and cooling, it not only ensures the uniformity of the overall quality of the forging after quenching and cooling, but also reduces the consumption of the aqueous solution, reduces production costs and environmental pollution; 3. Combining with the martensite transformation point temperature of 14Cr11MoV forgings, first cool with an aqueous solution to near the martensite transformation point temperature, and then cool with oil cooling, which slows down the structure stress during the transformation from austenite to martensite and avoids forging cracking; 4. By controlling the heating rate for the second high-temperature tempering, the 14Cr11MoV forgings obtain higher strength, plasticity, and toughness, and effectively remove internal stress, improving the stability of the forgings. The overall quality of the 14Cr11MoV forgings produced according to the present invention is improved, meeting the market use requirements. Specific embodiments

[0006] Example 1: A production process for improving the quality of 14Cr11MoV forgings. Steel type: 14Cr11MoV, Chemical composition: C = 0.12%, Si = 0.34%, Mn = 0.41%, Cr = 10.48%, Ni = 0.35%, S = 0.002%, P = 0.015%, Mo = 0.54%, V = 0.35%. Specification: Φ420*Φ265*4660mm. The heat treatment process is as follows: Step 1), controlled-temperature annealing: After forging, lift the forgings to the cooling area for air cooling. When placing, the distance between forgings is 1.5 meters. Air cool until the surface of the forgings reaches 575°C, hold for 2 hours, then heat up to 860°C at a heating rate of 80°C / h, hold for 25 hours, and then cool with the furnace at a cooling rate of 30°C / h until the temperature is below 291°C and then take out for air cooling until room temperature; Step 2), after step 1) is executed, load the forgings into a heating furnace with a furnace temperature of 288°C and perform high-temperature quenching: Heat up to 650°C at a heating rate of 80°C / h, hold for 2 hours, then heat up to 1000°C at full power heating rate, hold for 6 hours, and then take out for quenching and cooling. First, pre-cool in the air for 220 seconds, and then put the forgings into an aqueous-based liquid with a concentration of 8.1% and an initial liquid temperature of 37°C for cooling for 8 minutes. During the cooling process, turn on the compressed air to stir the aqueous-based liquid. After cooling, lift the forgings out of the aqueous-based liquid and transfer them to quenching oil with an initial temperature of 41°C for cooling for 40 minutes; Step 3), after step 2) is executed, load the forgings into a heating furnace with a furnace temperature of 255°C and perform a first high-temperature tempering: Heat up to 700°C at a heating rate of 80°C / h, hold for 8 hours, and then take out for air cooling until room temperature; Step 4), after step 3) is executed, load the forgings into a heating furnace with a furnace temperature of 229°C and perform a second high-temperature tempering: Heat up to 670°C at a heating rate of 80°C / h, hold for 7 hours, and then take out for air cooling until room temperature.

[0007] Table 1 Test results Technical requirements Surface hardness: 200 - 255 HB Grain size ≥ Grade 4 Actual detection 234 / 229 / 231 Grade 7 - 6 After production by the production process for improving the quality of 14Cr11MoV forgings of the present invention, the test results of surface hardness and grain size are qualified, meeting the technical requirements of customers.

[0008] Example 2: A production process for improving the quality of 14Cr11MoV forgings. Steel type: 14Cr11MoV, Chemical composition: C = 0.13%, Si = 0.34%, Mn = 0.40%, Cr = 10.52%, Ni = 0.34%, S = 0.002%, P = 0.015%, Mo = 0.55%, V = 0.35%. Specification: Φ420*Φ265*4660mm. The heat treatment process is as follows: Step 1), controlled temperature annealing: After forging, the forgings are lifted to the cooling area for air cooling. When placing, the distance between forgings is 1.2 meters. Air cool until the surface of the forgings reaches 560°C, hold for 2 hours, then heat up to 860°C at a heating rate of 80°C / h, hold for 25 hours, then cool in the furnace at a cooling rate of 30°C / h until it is below 285°C and then take out for air cooling until it reaches room temperature; Step 2), after step 1) is executed, load the forgings into a heating furnace with a furnace temperature of 325°C and perform high-temperature quenching: Heat up to 650°C at a heating rate of 80°C / h, hold for 2 hours, then heat up to 1000°C at full power heating rate, hold for 6 hours, then take out for quenching and cooling. First, pre-cool in the air for 220 seconds, then put the forgings into an aqueous-based solution with a concentration of 8% and an initial liquid temperature of 38°C for cooling for 8 minutes. During the cooling process, start the compressed air to stir the aqueous-based solution. After cooling, lift the forgings out of the aqueous-based solution and transfer them to quenching oil with an initial temperature of 41°C for cooling for 40 minutes; Step 3), after step 2) is executed, load the forgings into a heating furnace with a furnace temperature of 278°C and perform a first high-temperature tempering: Heat up to 700°C at a heating rate of 80°C / h, hold for 8 hours, then take out for air cooling until it reaches room temperature; Step 4), after step 3) is executed, load the forgings into a heating furnace with a furnace temperature of 221°C and perform a second high-temperature tempering: Heat up to 670°C at a heating rate of 80°C / h, hold for 7 hours, then take out for air cooling until it reaches room temperature.

[0009] Table 2 Test Results Technical requirements Surface hardness: 200 - 255 HB Grain size ≥ Grade 4 Actual detection 221 / 225 / 227 Grade 6 After being produced by the production process for improving the quality of 14Cr11MoV forgings of the present invention, the test results of surface hardness and grain size are qualified, meeting the technical requirements of customers.

Claims

1. A production process for improving the quality of 14Cr11MoV forgings, characterized by: It is carried out according to the following process: Step 1), temperature-controlled annealing: After forging, the forgings are hoisted to the cooling zone for air cooling. The distance between the forgings should be greater than 1 meter. Air cool until the surface of the forgings reaches 550℃~600℃, keep warm for 2h~10h, then heat up to 840℃~880℃ at a heating rate of 10℃ / h~80℃ / h, keep warm for 15h~50h, then cool to below 300℃ with the furnace at a cooling rate of ≤30℃ / h, take out of the furnace and air cool to room temperature. After completing step 1), prepare to load the forgings into the furnace and perform high-temperature quenching in the heating furnace; Step 2), high temperature quenching: put the forging into a heating furnace with a furnace temperature of ≤450℃, heat it to 600℃~700℃ at a heating rate of 10℃ / h~100℃ / h, keep it warm for 2h~5h, then heat it to 980℃~1020℃ at a full power heating rate, keep it warm for 5h~30h, take it out of the furnace for quenching and cooling, first pre-cool it in the air for 180s~230s, then put the forging into a water-based liquid with a concentration of 6%~9% and an initial liquid temperature of 30℃~50℃ for cooling for 5min~20min, turn on compressed air to stir the water-based liquid during the cooling process, after cooling, lift the forging out of the water-based liquid and transfer it to the quenching oil with a starting temperature of ≤60℃ for cooling for 30min~200min, and after executing step 2), put the forging into a heating furnace with a furnace temperature of ≤450℃ for a high temperature tempering; Step 3), primary high temperature tempering: heat up to 650℃~750℃ at a heating rate of 10℃ / h~100℃ / h, keep warm for 5h~30h, then take out of the furnace and air cool to room temperature. After step 3), put the forging into a heating furnace with a furnace temperature of ≤450℃ for secondary high temperature tempering; Step 4), secondary high temperature tempering: heat up to 620℃~720℃ at a heating rate of 10℃ / h~100℃ / h, keep warm for 5h~30h, then take out of the furnace and air cool to room temperature.

2. A production process for improving the quality of 14Cr11MoV forgings according to claim 1, characterized in that: Suitable for 14Cr11MoV forgings with outer diameter ≤φ500mm.