A heat treatment process for 20SiMn2MoVE lifting ring steel forgings

Abstract

This invention discloses a heat treatment process for 20SiMn2MoVE lifting ring steel forgings. It is the first to employ a composite heat treatment technology combining high-temperature normalizing, high-temperature tempering, and instantaneous quenching followed by high-temperature heating and holding, plus two low-temperature tempering processes. This ensures the overall quality of the forgings. Before high-temperature heating, a high-temperature anti-oxidation coating is applied to the surface of the lifting ring steel to prevent the formation of a thick oxide scale at high temperatures, thus improving the utilization rate of the forgings. High-temperature normalizing and tempering ensure the overall uniformity of the lifting ring steel forgings, achieving a good microstructure. Instantaneous quenching with high-temperature heating and short-term holding prevents the cooling effect of the forgings from being affected by temperature drops after quenching. Hot straightness testing effectively reduces or avoids straightening stress. Two low-temperature tempering processes not only stabilize the internal microstructure and remove stress, ensuring high strength and preventing deformation, but also enhance the thermal motion of hydrogen within the forgings, resulting in uniform hydrogen distribution and removal, and improved impact toughness.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology for metallic materials, and specifically relates to a heat treatment process for 20SiMn2MoVE lifting ring steel forgings that can not only effectively avoid or reduce the generation of surface oxide scale, improve the utilization rate of forgings, and save production costs, but also ensure the overall quality uniformity of forgings and obtain high strength, impact toughness, and internal stress removal. Background Technology

[0002] 20SiMn2MoVE material is an alloy structural steel containing elements such as C, Si, Mn, Mo, and V. It possesses high strength, high toughness, and good hardenability, enabling it to withstand significant tensile and impact forces at low temperatures for extended periods without deformation or fracture, effectively ensuring safety in use. Therefore, this material is widely used in products such as lightweight lifting rings, clamps, and perforators in oilfield drilling and hoisting systems. Currently, manufacturers typically use a direct annealing + quenching + tempering process when producing 20SiMn2MoVE lifting ring steel forgings. This process not only produces a large amount of oxide scale on the forging surface, reducing material utilization, but also results in uneven overall quality, leading to unstable mechanical properties and difficulty in achieving high strength and impact toughness. Consequently, it cannot guarantee safe use in harsh environments, affecting product quality. To address these issues, manufacturers generally resort to increasing allowances and rework, resulting in high production costs and a lack of market competitiveness. Therefore, a new heat treatment process is needed for quality control, ensuring the uniformity of lifting ring steel forging quality and achieving high strength and impact toughness. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a heat treatment process for 20SiMn2MoVE lifting ring steel forgings that can effectively guarantee the overall quality of the forgings. This process not only achieves high impact toughness under high strength but also effectively removes internal stress.

[0004] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A heat treatment process for 20SiMn2MoVE lifting ring steel forgings is implemented according to the following steps: Step 1) High-temperature normalizing: First, apply a high-temperature anti-oxidation coating to the entire outer surface of the lifting ring steel forging and let it dry. Then, put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature ≤650℃, and heat it to 920℃~960℃ at a heating rate of 10℃ / h~200℃ / h. Hold it at that temperature for 2h~15h. After holding, remove it from the furnace and air cool it to room temperature. After completing Step 1), prepare to perform high-temperature tempering. Step 2) High-temperature tempering: The lifting ring steel forging is placed into a horizontal heating furnace with a furnace temperature ≤450℃, and heated to 650℃~700℃ at a heating rate of 10℃ / h~200℃ / h. It is held for 5h~30h. After holding, it is taken out of the furnace and air-cooled to room temperature. After completing Step 2), it is ready to perform instantaneous quenching high-temperature heating. Step 3) Instantaneous quenching and high-temperature heating: First, apply a high-temperature anti-oxidation coating to the entire outer surface of the lifting ring steel forging and let it dry. Then, put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature ≤500℃ and heat it to 600℃~700℃ at a heating rate of 10℃ / h~200℃ / h, hold it for 0.5h~5h, then heat it to 900℃~920℃ at a heating rate of 10℃ / h~200℃ / h, hold it for 1h~15h, and then heat it to 925℃~950℃ at full power and hold it for 15min~60min. Then, take it out of the furnace and quench it. First, pre-cool it for 10s~180s, and then put the lifting ring steel forging into an aqueous solution with a concentration of 9%~11% and an initial liquid temperature of 15℃~40℃ for rapid cooling for 8min~60min. During the cooling process, compressed air needs to be turned on to stir the aqueous solution. After completing Step 3), prepare to perform a low-temperature tempering. Step 4) First low-temperature tempering: Put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature ≤150℃, heat it to 200℃~230℃ at a heating rate of 10℃ / h~50℃ / h, hold it for 10h~100h, and then take it out of the furnace for hot inspection of straightness. After completing Step 4), use the residual heat of the lifting ring steel for correction. Step 5) Residual heat correction: Place the lifting ring steel forging flat on the straightening machine, find the high and low points of the bent part and correct them. The straightness is corrected to ≤3mm. After correction, place the lifting ring steel forging flat in the air cooling area and air cool to room temperature. After completing Step 5), prepare for secondary low temperature tempering. Step 6) Secondary low-temperature tempering: The lifting ring steel forging is placed into a horizontal heating furnace with a furnace temperature ≤150℃, and heated to 200℃~230℃ at a heating rate of 10℃ / h~50℃ / h. It is held at this temperature for 2h~50h, and then removed from the furnace and air-cooled to room temperature.

[0005] Compared with the prior art, the process of this invention has the following advantages: 1. For the first time, a composite heat treatment technology of high-temperature normalizing + high-temperature tempering + instantaneous quenching, high-temperature heating and holding + two low-temperature tempering was adopted to ensure the overall quality of the forgings; 2. Apply a high-temperature anti-oxidation coating to the surface of the lifting ring steel before high-temperature heating to avoid the formation of a thick oxide scale on the surface at high temperatures, thereby improving the utilization rate of the forgings; 3. High-temperature normalizing followed by high-temperature tempering ensures a good microstructure for the overall uniformity of the lifting ring steel forgings; 4. By using instantaneous high-temperature heating and short-time heat preservation, the cooling effect of the forging is avoided when it is cooled after being taken out of the furnace. 5. The use of thermal straightness testing effectively reduces or avoids straightening stress; 6. The use of two low-temperature tempering processes not only stabilizes the internal structure of the forging and removes stress, ensuring high strength and preventing deformation, but also enhances the thermal motion of hydrogen inside the forging, uniformly distributes and removes hydrogen, and improves impact toughness.

[0006] The heat treatment process for 20SiMn2MoVE lifting ring steel forgings according to the present invention effectively ensures the overall quality of the forgings. It not only achieves high impact toughness under high strength performance, but also effectively removes internal stress, thus meeting market demands. Detailed Implementation

[0007] Example 1: A heat treatment process for 20SiMn2MoVE lifting ring steel forgings, comprising the following chemical composition by mass percentage: C=0.19%, Si=1.08%, Mn=2.43%, Cr=0.22%, S=0.002%, P=0.010%, Mo=0.37%, V=0.11%; Specifications: stepped shaft φ520*550mm (diameter*length) + φ115*6700mm (diameter*length) + φ510*430mm (diameter*length).

[0008] The heat treatment process is as follows: Step 1) High-temperature normalizing: First, apply a high-temperature anti-oxidation coating to the entire outer surface of the lifting ring steel forging and let it dry. Then, put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature of 282℃, raise the temperature to 940℃ at a heating rate of 100℃ / h, hold it at that temperature for 2.5h, and then remove it from the furnace and air cool it to room temperature. Step 2) After Step 1) is completed, perform high-temperature tempering: put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature of 170℃, heat it to 680℃ at a heating rate of 100℃ / h, hold it at that temperature for 6 hours, and then remove it from the furnace and air cool it to room temperature. Step 3) After step 2) is completed, first apply a high-temperature anti-oxidation coating to the entire outer surface of the lifting ring steel forging and let it dry. Then, put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature of 230℃ and perform instantaneous quenching high-temperature heating: heat up to 650℃ at a heating rate of 100℃ / h, hold for 0.5h, then heat up to 910℃ at a heating rate of 100℃ / h, hold for 2h, then heat up to 930℃ at full power and hold for 30min. Then, take it out of the furnace for quenching and cooling. First, pre-cool for 120s, then put the lifting ring steel forging into an aqueous solution with a concentration of 9.8% and an initial liquid temperature of 31℃ for rapid cooling for 12min. During the cooling process, the compressed air agitator needs to be turned on to stir the aqueous solution. Step 4) After step 3) is completed, perform a low-temperature tempering: put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature of 102℃, heat it to 210℃ at a heating rate of 30℃ / h, hold it at that temperature for 24h, and then take it out of the furnace for hot inspection of straightness. Step 5) After step 4) is completed, perform residual heat correction: place the lifting ring steel forging flat on the straightening machine, find the high and low points of the bent part and correct them, and straighten the straightness to 2.7mm. After correction, place the lifting ring steel forging flat in the air cooling area and air cool to room temperature. Step 6) After step 5) is completed, perform a second low-temperature tempering: put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature of 98℃, heat it to 210℃ at a heating rate of 30℃ / h, hold it at that temperature for 10h, and then take it out of the furnace and air cool it to room temperature.

[0009] After production according to the above heat treatment process, the mechanical properties are qualified, and the test results are shown in Table 1: Table 1 Test Results Technical Requirements Rp0.2 yield strength ≥ 1375 MPa Rm tensile strength ≥ 1050 MPa A% elongation ≥ 10% Z% reduction of area ≥ 40% KV8 (Impact Energy) (-20℃, ≥20J) Actual testing 1490 1140 15% 52% 24 / 26 / 25 After being produced by the heat treatment process of 20SiMn2MoVE lifting ring steel forgings according to the present invention, the steel exhibits high strength and high impact toughness.

[0010] Example 2: A heat treatment process for 20SiMn2MoVE lifting ring steel forgings, comprising the following chemical composition by mass percentage: C=0.19%, Si=1.09%, Mn=2.41%, Cr=0.23%, S=0.002%, P=0.011%, Mo=0.37%, V=0.10%; Specifications: stepped shaft φ520*550mm (diameter*length) + φ115*6700mm (diameter*length) + φ510*430mm (diameter*length).

[0011] The heat treatment process is as follows: Step 1) High-temperature normalizing: First, apply a high-temperature anti-oxidation coating to the entire outer surface of the lifting ring steel forging and let it dry. Then, put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature of 275℃, raise the temperature to 940℃ at a heating rate of 100℃ / h, hold it at that temperature for 2.5h, and then remove it from the furnace and air cool it to room temperature. Step 2) After Step 1) is completed, perform high-temperature tempering: put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature of 220℃, heat it to 680℃ at a heating rate of 100℃ / h, hold it at that temperature for 6 hours, and then remove it from the furnace and air cool it to room temperature. Step 3) After step 2) is completed, first apply a high-temperature anti-oxidation coating to the entire outer surface of the lifting ring steel forging and let it dry. Then, put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature of 237℃ and perform instantaneous quenching high-temperature heating: heat up to 650℃ at a heating rate of 100℃ / h, hold for 0.5h, then heat up to 910℃ at a heating rate of 100℃ / h, hold for 2h, then heat up to 930℃ at full power and hold for 30min. Then, take it out of the furnace for quenching and cooling. First, pre-cool for 130s, then put the lifting ring steel forging into an aqueous solution with a concentration of 9.8% and an initial liquid temperature of 33℃ for rapid cooling for 12min. During the cooling process, the compressed air agitator needs to be turned on to stir the aqueous solution. Step 4) After step 3) is completed, perform a low-temperature tempering: put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature of 87℃, heat it to 210℃ at a heating rate of 30℃ / h, hold it at that temperature for 24h, and then take it out of the furnace for hot inspection of straightness. Step 5) After step 4) is completed, perform residual heat correction: place the lifting ring steel forging flat on the straightening machine, find the high and low points of the bent part and correct them, straighten the straightness to 3.0mm, and after correction, place the lifting ring steel forging flat in the air cooling area and air cool to room temperature. Step 6) After step 5) is completed, perform a second low-temperature tempering: put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature of 85℃, heat it to 210℃ at a heating rate of 30℃ / h, hold it at that temperature for 10h, and then remove it from the furnace and air cool it to room temperature.

[0012] After production according to the above heat treatment process, the mechanical properties are qualified, and the test results are shown in Table 2: Table 2 Test Results Technical Requirements Rp0.2 yield strength ≥ 1375 MPa Rm tensile strength ≥ 1050 MPa A% elongation ≥ 10% Z% reduction of area ≥ 40% KV8 (Impact Energy) (-20℃, ≥20J) Actual testing 1510 1210 16% 52% 25 / 23 / 25 After being produced by the heat treatment process of 20SiMn2MoVE lifting ring steel forgings according to the present invention, the steel exhibits high strength and high impact toughness.

Claims

1. A heat treatment process for 20SiMn2MoVE lifting ring steel forgings, characterized in that: The process is implemented according to the following steps: Step 1) High-temperature normalizing: First, apply a high-temperature anti-oxidation coating to the entire outer surface of the lifting ring steel forging and let it dry. Then, put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature ≤650℃, and heat it to 920℃~960℃ at a heating rate of 10℃ / h~200℃ / h. Hold it at that temperature for 2h~15h. After holding, remove it from the furnace and air cool it to room temperature. After completing Step 1), prepare to perform high-temperature tempering. Step 2) High-temperature tempering: The lifting ring steel forging is placed into a horizontal heating furnace with a furnace temperature ≤450℃, and heated to 650℃~700℃ at a heating rate of 10℃ / h~200℃ / h. It is held for 5h~30h. After holding, it is taken out of the furnace and air-cooled to room temperature. After completing Step 2), it is ready to perform instantaneous quenching high-temperature heating. Step 3) Instantaneous quenching and high-temperature heating: First, apply a high-temperature anti-oxidation coating to the entire outer surface of the lifting ring steel forging and let it dry. Then, put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature ≤500℃ and heat it to 600℃~700℃ at a heating rate of 10℃ / h~200℃ / h, hold it for 0.5h~5h, then heat it to 900℃~920℃ at a heating rate of 10℃ / h~200℃ / h, hold it for 1h~15h, and then heat it to 925℃~950℃ at full power and hold it for 15min~60min. Then, take it out of the furnace and quench it. First, pre-cool it for 10s~180s, and then put the lifting ring steel forging into an aqueous solution with a concentration of 9%~11% and an initial liquid temperature of 15℃~40℃ for rapid cooling for 8min~60min. During the cooling process, compressed air needs to be turned on to stir the aqueous solution. After completing Step 3), prepare to perform a low-temperature tempering. Step 4) First low-temperature tempering: Put the lifting ring steel forging into a horizontal heating furnace with a furnace temperature ≤150℃, heat it to 200℃~230℃ at a heating rate of 10℃ / h~50℃ / h, hold it for 10h~100h, and then take it out of the furnace for hot inspection of straightness. After completing Step 4), use the residual heat of the lifting ring steel for correction. Step 5) Residual heat correction: Place the lifting ring steel forging flat on the straightening machine, find the high and low points of the bent part and correct them. The straightness is corrected to ≤3mm. After correction, place the lifting ring steel forging flat in the air cooling area and air cool to room temperature. After completing Step 5), prepare for secondary low temperature tempering. Step 6) Secondary low-temperature tempering: The lifting ring steel forging is placed into a horizontal heating furnace with a furnace temperature ≤150℃, and heated to 200℃~230℃ at a heating rate of 10℃ / h~50℃ / h. It is held at this temperature for 2h~50h, and then removed from the furnace and air-cooled to room temperature.

2. The heat treatment process for 20SiMn2MoVE lifting ring steel forgings according to claim 1, characterized in that: The 20SiMn2MoVE lifting ring steel forging comprises the following chemical composition by mass percentage: C = (0.17~0.23)%, Si = (0.9~1.2)%, Mn = (2.2~2.6)%, Cr < 0.3%, S ≤ 0.01%, P ≤ 0.02%, Mo = (0.3~0.4)%, V = (0.05~0.12)%; the balance is iron.