阅读说明：本技术 一种改善20Cr13锻坯晶粒度的退火工艺 (Annealing process for improving grain size of 20Cr13 forging stock ) 是由 周鹏 雷冲 王雪松 张巧换 郑安雄 李占华 李玉标 双伟鹏 于 2021-04-09 设计创作，主要内容包括：本发明涉及一种改善20Cr13锻坯晶粒度的退火工艺,工艺如下：不完全退火：入炉温度≤450℃,以≤50～100℃/h升至550～700℃,以≥100℃/h升至800～900℃,以≤30℃/h随炉冷至350～-450℃,高温正火：以≤50～100℃/h升至550～700℃,以≥100℃/h升至1000～1060℃,保温出炉风冷,对锻坯大台阶风冷,两端小台阶空冷,小台阶降温至300～400℃后入炉,在300～400℃保温,低温正火：以≤50～100℃/h升至550～700℃,以≥100℃/h升至900～980℃,出炉风冷,对锻坯大台阶风冷,两端小台阶空冷,小台阶降至300～400℃入炉,在300～400℃保温,高温回火：以≤50～100℃/h升至680～730℃,以≤10～40℃/h冷至650～680℃,以≤50℃/h冷至≤300℃出炉冷至室温,使锻坯内部晶粒度明显改善,晶粒度由原来的1-2级改善到5-7级。(The invention relates to an annealing process for improving the grain size of a 20Cr13 forging stock, which comprises the following steps: incomplete annealing: the charging temperature is less than or equal to 450 ℃, the temperature is increased to 550-700 ℃ at the rate of less than or equal to 50-100 ℃/h, the temperature is increased to 800-900 ℃ at the rate of more than or equal to 100 ℃/h, the temperature is cooled to 350-450 ℃ along with the furnace at the rate of less than or equal to 30 ℃/h, and the high-temperature normalizing: raising the temperature to 550-700 ℃ at a speed of not more than 50-100 ℃/h, raising the temperature to 1000-1060 ℃ at a speed of not less than 100 ℃/h, keeping the temperature, discharging, air cooling large steps of the forging stock, air cooling small steps at two ends, cooling the small steps to 300-400 ℃, then feeding the small steps into a furnace, keeping the temperature at 300-400 ℃, normalizing at a low temperature: raising the temperature to 550-700 ℃ at a speed of not more than 50-100 ℃/h, raising the temperature to 900-980 ℃ at a speed of not less than 100 ℃/h, discharging the forging stock for air cooling, carrying out air cooling on a large step of the forging stock, carrying out air cooling on small steps at two ends, lowering the temperature of the small steps to 300-400 ℃, feeding the small steps into the furnace, carrying out heat preservation at 300-400 ℃, and carrying out high-temperature tempering: raising the temperature to 680-730 ℃ at a speed of less than or equal to 50-100 ℃/h, cooling to 650-680 ℃ at a speed of less than or equal to 10-40 ℃/h, cooling to 300 ℃ at a speed of less than or equal to 50 ℃/h, discharging from a furnace, and cooling to room temperature, so that the grain size in the forging stock is obviously improved, and the grain size is improved to 5-7 grade from the original 1-2 grade.)

1. An annealing process for improving the grain size of 20Cr13 forging stock is characterized in that: the annealing process is as follows:

step 1), incomplete annealing: the charging temperature is less than or equal to 450 ℃, the temperature is increased to 550-700 ℃ at the temperature increasing speed of less than or equal to 50 ℃/h-100 ℃/h, the temperature is maintained for 3-6 h, the temperature is increased to 800-900 ℃ at the temperature increasing speed of more than or equal to 100 ℃/h, the temperature is maintained for 5-20 h, the forging stock is charged into the furnace with the furnace cooling to 350-450 ℃ at the temperature of less than or equal to 30 ℃/h, and the step 1) is finished and the high-temperature normalizing is carried out after the forging stock is loaded into the furnace;

step 2), high-temperature normalizing: heating to 550-700 ℃ at a heating rate of less than or equal to 50 ℃/h-100 ℃/h, preserving heat for 3-6 h, heating to 1000-1060 ℃ at a heating rate of more than or equal to 100 ℃/h, preserving heat, taking out of the furnace for air cooling after 5-20 h, only carrying out air cooling on a large step in the middle of a forging blank by using an air blower, carrying out air cooling on small steps at two ends, cooling to the temperature of the small steps, lowering to 300-400 ℃, then feeding into the furnace, controlling the furnace temperature of the heating furnace to be 300-400 ℃, preserving heat for 5-15 h, and feeding the forging blank into the furnace for low-temperature normalizing after heat preservation;

step 3), low-temperature normalizing: heating to 550-700 ℃ at a heating rate of less than or equal to 50 ℃/h-100 ℃/h, preserving heat for 3-6 h, heating to 900-980 ℃ at a heating rate of more than or equal to 100 ℃/h, preserving heat, taking out of the furnace for air cooling after 5-20 h, only carrying out air cooling on a large step in the middle of a forging blank by using an air blower, carrying out air cooling on small steps at two ends, cooling to the temperature of the small step, reducing the temperature of the small step to 300-400 ℃, entering the furnace, controlling the furnace temperature of the heating furnace to 300-400 ℃, preserving heat for 5-15 h, and directly carrying out high-temperature tempering after heat preservation;

step 4), high-temperature tempering: heating to 680-730 ℃ at a heating rate of less than or equal to 50 ℃/h-100 ℃/h

And keeping the temperature for 20-40 h, keeping the temperature, cooling the temperature to 650-680 ℃ along with the furnace at a cooling speed of less than or equal to 10 ℃/h-40 ℃/h, keeping the temperature for 40-100 h, cooling the temperature to less than or equal to 300 ℃ along with the furnace at a cooling speed of less than or equal to 50 ℃/h, and taking out of the furnace and air cooling the temperature to room temperature.

2. The annealing process for improving the grain size of 20Cr13 forging stock according to claim 1, wherein the annealing process is characterized in that

In the following steps: the process is suitable for round rods or step shafts with the outer circle diameter phi of 500-phi 1000mm, and the grain size inside the forged blank of 20Cr13 produced according to the process is improved from the original coarse grade of 1-2 to the fine grade of 5-7.

Technical Field

The invention belongs to the technical field of heat treatment of metal materials, and particularly relates to an annealing process capable of improving the grain size of a 20Cr13 forging stock, which can effectively improve the product quality.

Background

In actual production, due to the fact that the Cr alloy component in the 20Cr13 steel is high, surface cracking is easy to occur in the forging process to cause waste products, production operation is not easy to control, and particularly, the production process is a round bar or step shaft forging blank with the excircle diameter of phi 500 mm-phi 1000 mm. Therefore, in order to ensure the surface quality of the forging stock, multiple times of heating forging is adopted in the forging process, the forging stock is continuously heated and insulated at high temperature, the grain size inside a workpiece is large, the grain size of the forging stock is usually 1-2 grade, and if the conventional annealing process is adopted: the single annealing and high-temperature tempering within the range of 820-880 ℃ or the double annealing process within the range of 820-880 ℃ is carried out twice, so that the effect of improving the grain size of the forging stock cannot be effectively achieved. Therefore, aiming at a round bar or step shaft forging stock with the excircle diameter of phi 500 mm-phi 1000mm, an annealing process capable of effectively improving the coarse grain size of the forging stock is urgently needed.

Object of the Invention

The invention aims to overcome the defects in the prior art and provide an annealing process for improving the grain size of a 20Cr13 forging stock, which can effectively improve the problem of coarse grain size of the 20Cr13 forging stock and refine the grains of the forging stock to improve the product quality.

Disclosure of Invention

In order to achieve the purpose, the invention adopts the following technical scheme:

an annealing process for improving the grain size of 20Cr13 forging stock specifically comprises the following steps:

step 1), incomplete annealing: the charging temperature is less than or equal to 450 ℃, the temperature is raised to 550-700 ℃ at the temperature raising speed of less than or equal to 50 ℃/h-100 ℃/h, the temperature is maintained for 3-6 h, the temperature is raised to 800-900 ℃ at the temperature raising speed of more than or equal to 100 ℃/h, the temperature is maintained for 5-20 h, the forging stock is charged into the furnace with the furnace cooling to 350-450 ℃ at the temperature of less than or equal to 30 ℃/h, and the step 1) is executed to load the forging stock into the furnace for high-temperature normalizing;

step 2) high-temperature normalizing: heating to 550-700 ℃ at a heating rate of less than or equal to 50 ℃/h-100 ℃/h, keeping the temperature for 3-6 h, heating to 1000-1060 ℃ at a heating rate of more than or equal to 100 ℃/h, keeping the temperature, taking out of the furnace for air cooling after keeping the temperature for 5-20 h, only carrying out air cooling on a large middle step of the forging stock by using an air blower, carrying out air cooling on small steps at two ends, cooling to 300-400 ℃ and then putting into the furnace, controlling the furnace temperature of the heating furnace at 300-400 ℃, keeping the temperature of the forging stock for 5-15 h, and putting the forging stock into the furnace for low-temperature normalizing after keeping the temperature;

step 3), low-temperature normalizing: heating to 550-700 ℃ at a heating rate of less than or equal to 50 ℃/h-100 ℃/h, preserving heat for 3-6 h, heating to 900-980 ℃ at a heating rate of more than or equal to 100 ℃/h, preserving heat, taking out of the furnace for air cooling after 5-20 h, only carrying out air cooling on a large step in the middle of a forging blank by using an air blower, carrying out air cooling on small steps at two ends, cooling to the temperature of the small steps, reducing to 300-400 ℃, entering the furnace, controlling the furnace temperature of the heating furnace at 300-400 ℃, preserving heat for 5-15 h, and directly carrying out high-temperature tempering after heat preservation;

step 4), high-temperature tempering: heating to 680-730 ℃ at a heating rate of less than or equal to 50 ℃/h-100 ℃/h, preserving heat for 20-40 h, cooling to 650-680 ℃ along with the furnace at a cooling rate of less than or equal to 10 ℃/h-40 ℃/h after preserving heat, preserving heat for 40-100 h, cooling to less than or equal to 300 ℃ along with the furnace at a cooling rate of less than or equal to 50 ℃/h, and taking out of the furnace and air-cooling to room temperature.

The process is suitable for round rods or step shafts with the outer diameter phi of 500-phi 1000mm, and the grain size inside the forged blank of 20Cr13 produced by the process is improved from the original coarse grade of 1-2 to the fine grade of 5-7.

Compared with the prior art, the process provided by the invention provides an annealing process for improving the grain size of 20Cr13 forging stock, and has the following advantages:

1. the incomplete annealing process and the high-temperature normalizing, low-temperature normalizing and high-temperature tempering processes are effectively combined, and the grain size refinement and homogenization in the forging stock can be ensured through repeated structure transformation.

2. The forging stock produced by the conventional annealing process is prevented from only playing a spheroidizing role and not thinning the internal grain size.

3. By adopting the method, the internal structure of the forging stock can be effectively improved, the internal stress is removed, and the forging stock is prevented from cracking.

The 20Cr13 forged blank produced by the method has the advantages that the grain size inside the forged blank is obviously improved, and the grain size is improved from the original coarse grade 1-2 to the fine grade 5-7. The method can effectively improve the coarseness of the grain size of the 20Cr13 forging stock, refine the grains of the forging stock, and meet the market demand, and the grain size of the forging stock is more than or equal to grade 4.

Detailed Description

Example 1: an annealing process for improving the grain size of 20Cr13 forging stock:

steel grade: 20Cr13, chemical composition: 0.2% for C, 0.38% for Si, 0.63% for Mn, 12.5% for Cr, 0.47% for Ni, 0.0026% for S, 0.012% for P, and 0.08% for Mo.

Specification: 520 x Φ 320mm +1020 x Φ 570mm +790 x Φ 290 mm.

Grain size of the forging stock: 1-2 stages

The annealing process comprises the following steps:

step 1), incomplete annealing: the charging temperature is less than or equal to 450 ℃, the temperature is increased to 650 ℃ according to the speed of less than or equal to 80 ℃/h, the temperature is maintained for 3h, the full power is increased to 860 ℃ for heat preservation, the temperature is maintained for 14h, and then the furnace is cooled to less than or equal to 450 ℃ along with the furnace;

step 2), after the step 1), loading the forging stock into a heating furnace, and performing high-temperature normalizing: the charging temperature is less than or equal to 450 ℃, the temperature is increased to 650 ℃ according to the speed of less than or equal to 80 ℃/h, the temperature is maintained for 3h, then the full power is increased to 1000 ℃ for heat preservation, the temperature is maintained for 14h, then the forging stock is taken out of the furnace for air cooling, only the large step in the middle of the forging stock is air cooled by adopting an air blower, the small steps at the two ends are air cooled, the temperature is reduced to 300-350 ℃ when the small steps are cooled, the forging stock is charged into the furnace, and the temperature of the furnace is maintained for 9h at 350-400 ℃;

step 3), after the step 2), loading the forging stock into a heating furnace, and performing low-temperature normalizing: heating to 650 ℃ at a speed of less than or equal to 80 ℃/h, preserving heat for 3h, then heating to 980 ℃ at full power, preserving heat for 14h, taking out of the furnace, air-cooling, only carrying out air-cooling on a large step in the middle of the forging stock by adopting an air blower, carrying out air-cooling on small steps at two ends, cooling to 300-350 ℃ until the temperature of the small steps is reduced to 300-350 ℃, and putting into the furnace, and preserving heat for 9h at the furnace temperature of 350-400 ℃;

step 4), after the step 3), loading the forging stock into a heating furnace, and performing high-temperature tempering: heating to 680 ℃ at a speed of less than or equal to 80 ℃/h, preserving heat for 20h, preserving heat at a speed of less than or equal to 30 ℃/h, cooling to 650 ℃ along with the furnace, preserving heat for 54h, cooling to less than or equal to 300 ℃ along with the furnace at a speed of less than or equal to 30 ℃/h, discharging, and air cooling to room temperature.

After the forging stock is produced according to the annealing process, the grain size detection of the forging stock meets the requirement of being more than or equal to grade 4.

After the production according to the heat treatment process, the detection results are shown in table 1:

TABLE 1 test results

After the annealing process for improving the grain size of the 20Cr13 forging stock is produced, the performance and grain size detection results meet the requirements and are delivered successfully.

Example 2: an annealing process for improving the grain size of 20Cr13 forging stock.

Steel grade: 20Cr13

Chemical components: 0.18% of C, 0.36% of Si, 0.61% of Mn, 12.29% of Cr, 0.48% of Ni,

S＝0.0021％，P＝0.013％，Mo＝0.07％。

specification: 550 + 340mm +1160 + 700mm +680 + 340mm stepped axis.

Grain size of the forging stock: 1-2 stages.

The annealing process comprises the following steps:

step 1), incomplete annealing: the charging temperature is less than or equal to 450 ℃, the temperature is increased to 650 ℃ according to the speed of less than or equal to 80 ℃/h, the temperature is maintained for 3h, the full power is increased to 860 ℃ for heat preservation, and the temperature is cooled to less than or equal to 450 ℃ along with the furnace at the speed of less than or equal to 30 ℃/h after the heat preservation for 14h and then is charged into the furnace;

step 2), after the step 1), loading the forging stock into a heating furnace, and performing high-temperature normalizing: the charging temperature is less than or equal to 450 ℃, the temperature is increased to 650 ℃ according to the speed of less than or equal to 80 ℃/h, the temperature is maintained for 3h, the full power temperature is increased to 1000 ℃ for heat preservation, the temperature is maintained for 14h, then the forging stock is taken out of the furnace for air cooling, only the large step in the middle of the forging stock is subjected to air cooling by adopting an air blower, the small steps at two ends are subjected to air cooling, the temperature is reduced to 300-350 ℃ when the small steps are cooled, the forging stock is charged into the furnace, and the temperature of the furnace is maintained for 9h at 350-400 ℃;

step 3), after the step 2), loading the forging stock into a heating furnace, and performing low-temperature normalizing: heating to 650 ℃ at a speed of less than or equal to 80 ℃/h, preserving heat for 3h, then heating to 980 ℃ at full power, preserving heat for 14h, taking out of the furnace, air-cooling, only carrying out air-cooling on a large step in the middle of the forging stock by adopting an air blower, carrying out air-cooling on small steps at two ends, cooling to 300-350 ℃ until the temperature of the small steps is reduced to 300-350 ℃, and putting into the furnace, and preserving heat for 9h at the furnace temperature of 350-400 ℃;

step 4), after the step 3), loading the forging stock into a heating furnace, and performing high-temperature tempering: heating to 680 ℃ at a speed of less than or equal to 80 ℃/h, preserving heat for 20h, preserving heat at a speed of less than or equal to 30 ℃/h, cooling to 650 ℃ along with the furnace, preserving heat for 54h, cooling to less than or equal to 300 ℃ along with the furnace at a speed of less than or equal to 30 ℃/h, discharging, and air cooling to room temperature.

After the forging stock is produced according to the heat treatment process, the grain size detection of the forging stock meets the requirement of being more than or equal to grade 4.

After the production according to the heat treatment process, the detection results are shown in table 2:

TABLE 2 test results

After the annealing process for improving the grain size of the 20Cr13 forging stock is produced, the performance and grain size detection results meet the requirements and are delivered successfully.