CN110643905B - Heat treatment method for large-diameter high-carbon chromium stainless steel forging with uniformly distributed pearlite - Google Patents
Heat treatment method for large-diameter high-carbon chromium stainless steel forging with uniformly distributed pearlite Download PDFInfo
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Abstract
The invention relates to a heat treatment method for uniform distribution of pearlite of a large-diameter high-carbon chromium stainless steel forging, which comprises the steps of heating and preserving heat of a G102Cr18Mo forging meeting the requirement in smelting analysis, heating to 1050-1060 ℃ for temperature equalization, preserving heat, discharging from a furnace, cooling to 600-650 ℃, feeding into a heating furnace at 650 ℃, then cooling to 500-550 ℃ for temperature equalization, preserving heat for homogeneous carbon distribution, heating to 650 +/-10 ℃ for performance tempering, discharging from the furnace, cooling to 200 ℃ for air cooling. According to the invention, the homogeneous pearlite structure can be obtained on the martensitic stainless steel material by heating and controlling the temperature and cooling in stages and carrying out carbon distribution at 500-550 ℃. The large-diameter G102Cr18Mo high-carbon chromium mushroom head stainless steel forging produced by the method has high mechanical property index, and fine grained pearlite structures are uniformly distributed; the technical requirements of GB/T3086-2008 standard are met; can meet the technical requirements of the gate construction of large hydropower stations.
Description
Technical Field
The invention relates to a heat treatment method, in particular to a heat treatment method for uniformly distributing pearlite of a large-diameter high-carbon chromium stainless steel forging. The large-diameter high-carbon chromium stainless steel forging is a G102Cr18Mo high-carbon chromium stainless steel forging with the nominal diameter or the effective section diameter of more than 160 mm.
Background
The G102Cr18Mo high-carbon chromium stainless steel material has good corrosion resistance, high temperature resistance and low temperature resistance. The highest using temperature can reach 427 ℃, and the lowest using temperature can reach below-253 ℃.
The G102Cr18Mo high-carbon chromium stainless steel is developed by adding Mo on the basis of 9Cr18 steel, and has higher hardness and tempering resistance than 9Cr18 steel. The critical points (approximate values) of the steel are AC1: 815-865 ℃, Ar1: 665-765 ℃, Ms:145 ℃. The steel is spherical pearlite and carbide after being completely annealed, but has low hardness and strength indexes, and is easy to form chain or net-shaped carbide; the traditional normalizing and tempering process is adopted, and bainite and martensite low-temperature transformation structures and the like are easily formed due to good hardenability. Therefore, a pearlite structure with high hardness and uniform distribution is obtained on a G102Cr18Mo steel forging with a large section diameter, and the difficulty is high by adopting a traditional method.
The G102Cr18Mo mushroom head stainless steel is developed and applied to the manufacture of hydraulic engineering gates, and is mainly applied to the hydraulic gates by using 35CrMo materials at home. The G102Cr18Mo mushroom head stainless steel consists of a hemisphere and a columnar platform. If the diameter of the hemisphere is S phi 1200mm, the height of the columnar platform is 200mm, the diameter of the platform is phi 1400mm, and the effective section diameter is 800 mm.
Disclosure of Invention
The invention aims to provide a heat treatment method for uniformly distributing pearlite of a large-diameter high-carbon chromium stainless steel forging with uniformly distributed fine-grained pearlite structures and without twin carbide.
The purpose of the invention is realized by the following steps: the heat treatment method for the uniform distribution of pearlite of the large-diameter high-carbon chromium stainless steel forging, wherein the large-diameter high-carbon chromium stainless steel forging is a G102Cr18Mo high-carbon chromium stainless steel forging with the nominal diameter or the effective section diameter of more than 160 mm;
the chemical components of the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging, wt, are as follows by smelting analysis: 0.95 to 1.10 percent of C, 0.20 to 0.78 percent of Si, 0.20 to 0.78 percent of Mn, 0.005 to 0.034 percent of P, 0.003 to 0.028 percent of S, 16.02 to 17.95 percent of Cr, 0.40 to 0.70 percent of Mo, 0.03 to 0.25 percent of Ni and 0.03 to 0.24 percent of Cu. The heat treatment comprises the following specific steps:
1) putting the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging into a heating furnace, heating to 600-650 ℃ at the speed of 45-55 ℃/h, and preserving heat, wherein the heat preservation time is calculated according to 10h/100 mm; then raising the temperature to 1050-1060 ℃, and then carrying out temperature equalization and heat preservation, wherein the temperature equalization time is calculated according to 2h/100mm, and the heat preservation time is 1/2 of the temperature equalization time;
the 100mm refers to the effective section diameter of the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging;
2) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging subjected to temperature equalization and heat preservation in the step 1), and air-cooling to 600 ℃;
3) placing the large-diameter G102Cr18Mo high-carbon chromium stainless steel forged piece subjected to air cooling in the step 2) into a heating furnace at 650 ℃, cooling to 500-550 ℃ along with the furnace, and performing homogeneous carbon distribution, wherein the heat preservation time is calculated according to 1h/100 mm; then raising the temperature to 650 +/-10 ℃ for temperature equalization and heat preservation, wherein the temperature equalization time is calculated according to 3.0h/100mm, and the heat preservation time is 1/2 of the temperature equalization time; cooling to 200 ℃ along with the furnace;
the 100mm refers to the effective section diameter of the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging;
4) and (3) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging which is cooled to 200 ℃ along with the furnace in the step 3), and air-cooling to obtain the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging which has uniformly distributed pearlite structures and does not have harmful twin carbide.
The invention adopts a heat treatment method of temperature control and cold control to the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging; and (3) carrying out homogeneous carbon distribution by adopting heat preservation at a medium temperature range of 500-550 ℃ to ensure that carbides are fully precipitated and a low-temperature transformation structure is cut off. Thus obtaining the homogeneously distributed fine grain pearlite structure on the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging.
The invention solves the problem that harmful twin carbide is easy to appear in the production of large-diameter G102Cr18Mo high-carbon chromium stainless steel, and solves the problem that manufacturers with the nominal diameter or effective diameter larger than 160mm cannot keep any performance index.
The large-diameter G102Cr18Mo high-carbon chromium stainless steel forging subjected to heat treatment of the invention has the tensile strength of 590-835 MPa and the Brinell hardness HB of the body of 250-300. The performance index can meet the GB/T3086-2008 standard technical requirement corresponding to the effective diameter section of 5-160 mm which is only produced by few bearing manufacturers at home at present.
The invention has strong operability, not only refines the crystal grains, but also can control the appearance of low-temperature bainite or martensite transformation structure, avoids harmful reticular carbide structure and completely obtains good pearlite high-temperature transformation structure with comprehensive mechanical properties. The obtained large-diameter G102Cr18Mo steel has high hardness and corrosion resistance, and can be used for manufacturing bearings and gate parts which work in a corrosive environment and in a non-lubricating strong oxidizing atmosphere; the method is increasingly applied to the navigation and hydraulic engineering industries, and has wide application prospect.
The large-diameter G102Cr18Mo mushroom head stainless steel processed by the method can meet the technical requirements of the large hydropower station water gate mushroom head forge piece.
Drawings
FIG. 1 is a diagram showing a homogeneous distribution pearlite structure by heat treatment in example 1,
FIG. 2 is a diagram showing a pearlite structure in a homogeneous distribution by heat treatment in example 2,
FIG. 3 is a diagram of a homogeneously distributed pearlite structure by heat treatment in example 3,
FIG. 4 is a drawing showing a structure of tempered martensite heat-treated in comparative example 1,
FIG. 5 is a graph of a white network carbide + black pearlite structure heat-treated by comparative example 2.
Detailed Description
The large-diameter G102Cr18Mo high-carbon chromium stainless steel forging meeting the requirements of smelting analysis is firstly placed into a heating furnace, the heating is carried out at the heating speed of 45-55 ℃/h to 600-650 ℃, the heat preservation is carried out, the temperature is raised to 1050-1060 ℃, the heat preservation is carried out, the forging is discharged from the furnace and cooled to 600-650 ℃, the forging is heated to 650 ℃, the heating furnace is then carried out after the forging is heated to 500-550 ℃, the heat preservation is carried out, the homogeneous carbon distribution is realized, the temperature is raised to 650 +/-10 ℃ for performance tempering, the forging is then discharged from the furnace and cooled to 200 ℃, and the G102Cr18Mo high-carbon chromium stainless steel forging with the pearlite distributed homogeneously is obtained.
The chemical components wt% of the G102Cr18Mo high-carbon chromium stainless steel forging used in the invention are as follows by smelting analysis: 0.95 to 1.10 percent of C, 0.20 to 0.78 percent of Si, 0.20 to 0.78 percent of Mn, 0.005 to 0.034 percent of P, 0.003 to 0.028 percent of S, 16.02 to 17.95 percent of Cr, 0.40 to 0.70 percent of Mo, 0.03 to 0.25 percent of Ni and 0.03 to 0.24 percent of Cu.
The 100mm refers to the effective cross-sectional diameter of the material forging for heat treatment.
The air cooling refers to discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging, and naturally cooling the forging in the air at room temperature.
And the furnace cooling means that the large-diameter high-carbon chromium stainless steel forging is placed in a heating furnace which is subjected to heat preservation, the furnace door is closed, and the furnace is slowly cooled under the condition of not heating.
The present invention is described in detail below with reference to specific examples.
Example 1, chemical composition%, wt, of a large diameter G102Cr18Mo high carbon chromium stainless steel mushroom head forging, melting analysis is as follows: 1.01 percent of C, 0.62 percent of Si, 0.61 percent of Mn, 0.024 percent of P, 0.005 percent of S, 16.82 percent of Cr, 0.40 percent of Mo, 0.14 percent of Ni and 0.08 percent of Cu.
The large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging consists of a hemisphere and a columnar platform, wherein the diameter of the hemisphere is S phi 1200mm, the height of the columnar platform is 200mm, the diameter of the columnar platform is phi 1400mm, and the effective section diameter of the platform is 800 mm. The heat treatment comprises the following specific steps:
1) putting the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging into a heating furnace, heating to 650 ℃ at the speed of 50 ℃/h, and preserving heat for 80 h; then heating to 1050 ℃, and then carrying out temperature equalization and heat preservation for 16h, wherein the heat preservation time is 8 h;
2) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging subjected to temperature equalization and heat preservation in the step 1), and air-cooling to 600 ℃;
3) placing the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forge piece subjected to air cooling in the step 2) into a heating furnace at 650 ℃, cooling to 530 ℃ along with the temperature of the heating furnace, and preserving the heat for 8 hours to perform homogeneous carbon distribution; then heating to 650 +/-10 ℃ for temperature equalization and heat preservation, wherein the temperature equalization time is 24 hours and the temperature equalization time is 12 hours; cooling to 200 ℃ along with the furnace;
4) and (3) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging cooled with the furnace in the step 3), and air-cooling to obtain the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging with uniformly distributed pearlite structures as shown in the figure 1.
The applicant has carried out mechanical property tests on the large-diameter G102Cr18Mo mushroom head forgings subjected to heat treatment in the embodiment, and the sampling positions of the mechanical property are as follows: cutting a ring on the table surface with the diameter phi 1400 of the mushroom head after rough machining and sampling. The mechanical performance index is as follows: σ b 677MPa, bulk brinell hardness HB: 269. 272, 270, the metallographic structure is fine pearlite uniformly distributed (see fig. 1). The strength performance index of the large-diameter G102Cr18Mo mushroom head forging subjected to heat treatment in the embodiment meets the technical requirements of GB/T3086-2008 standard corresponding to an effective nominal diameter section of 5-160 mm, the Brinell hardness meets the hardness index of 250-300 of the hydraulic engineering mushroom head, and twin-crystal carbide is avoided.
Example 2, chemical composition%, wt, of a large diameter G102Cr18Mo high carbon chromium stainless steel mushroom head forging, melting analysis is as follows: 0.95 percent of C, 0.78 percent of Si, 0.20 percent of Mn, 0.034 percent of P, 0.028 percent of S, 17.95 percent of Cr, 0.70 percent of Mo, 0.25 percent of Ni and 0.24 percent of Cu.
The large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging consists of a hemisphere and a columnar platform, wherein the diameter of the hemisphere is S phi 800mm, the height of the columnar platform is 200mm, the diameter of the columnar platform is phi 1000mm, and the effective section diameter is 600 mm. The heat treatment comprises the following specific steps:
1) putting the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging into a heating furnace, heating to 600 ℃ at the speed of 50 ℃/h, and preserving heat for 60 h; then heating to 1050 ℃, and then carrying out temperature equalization and heat preservation for 12h, wherein the heat preservation time is 6 h;
2) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging subjected to temperature equalization and heat preservation in the step 1), air-cooling and cooling to 600 ℃;
3) placing the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forge piece subjected to air cooling in the step 2) into a heating furnace at 650 ℃, cooling to 500 ℃ along with the temperature of the heating furnace, and preserving heat for 6 hours to carry out homogeneous carbon distribution; then heating to 650 +/-10 ℃ for temperature equalization and heat preservation, wherein the temperature equalization time is 18 hours and the temperature equalization time is 9 hours; cooling to 200 ℃ along with the furnace;
4) and (3) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging which is cooled to 200 ℃ along with the furnace in the step 3), and air-cooling to obtain the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging with uniformly distributed pearlite structures as shown in the figure 2.
The applicant has carried out mechanical property tests on the large-diameter G102Cr18Mo mushroom head forgings subjected to heat treatment in the embodiment, and the sampling positions of the mechanical property are as follows: cutting a ring on a platform surface with the diameter phi of 1000 of the mushroom head after rough machining and sampling. The mechanical performance index is as follows: σ b 688MPa, bulk brinell hardness HB: 275. 271, 273, the metallographic structure is fine pearlite distributed uniformly (see fig. 2). The strength performance index of the large-diameter G102Cr18Mo mushroom head forging subjected to heat treatment in the embodiment meets the technical requirements of GB/T3086-2008 standard corresponding to an effective nominal diameter section of 5-160 mm, the Brinell hardness meets the hardness index of 250-300 of the hydraulic engineering mushroom head, and twin-crystal carbide is avoided.
Example 3, chemical composition%, wt, of a large diameter G102Cr18Mo high carbon chromium stainless steel mushroom head forging, melt analysis is as follows: 1.10 percent of C, 0.20 percent of Si, 0.78 percent of Mn, 0.005 percent of P, 0.003 percent of S, 16.02 percent of Cr, 0.70 percent of Mo, 0.03 percent of Ni and 0.03 percent of Cu.
The large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head consists of a hemisphere and a columnar platform, wherein the diameter of the hemisphere is S phi 1200mm hemisphere, the height of the columnar platform is 200mm, the diameter of the columnar platform is phi 1400mm, and the effective section diameter is 800 mm. The heat treatment comprises the following specific steps:
1) putting the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging into a heating furnace, heating to 650 ℃ at the speed of 50 ℃/h, and preserving heat for 80 h; then heating to 1050 ℃, and then carrying out temperature equalization and heat preservation for 16h, wherein the heat preservation time is 8 h;
2) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging subjected to temperature equalization and heat preservation in the step 1), air-cooling and cooling to 600 ℃;
3) placing the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forge piece subjected to air cooling in the step 2) into a heating furnace at 650 ℃, cooling to 550 ℃ along with the temperature of the heating furnace, and preserving heat for 8 hours to perform homogeneous carbon distribution; then heating to 650 +/-10 ℃ for temperature equalization and heat preservation, wherein the temperature equalization time is 24 hours and the temperature equalization time is 12 hours; cooling to 200 ℃ along with the furnace;
4) and (3) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging which is cooled to 200 ℃ along with the furnace in the step 3), and air-cooling to obtain the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging with uniformly distributed pearlite structures shown in the figure 3.
The applicant has carried out mechanical property tests on the large-diameter G102Cr18Mo mushroom head forgings subjected to heat treatment in the embodiment, and the sampling positions of the mechanical property are as follows: cutting a ring on the table surface with the diameter phi 1400 of the mushroom head after rough machining and sampling. The mechanical performance index is as follows: σ b 685MPa, bulk brinell hardness HB: 275. 272, 275, the metallographic structure is a uniformly distributed fine pearlite (see fig. 3). The strength performance index of the large-diameter G102Cr18Mo mushroom head forging subjected to heat treatment in the embodiment meets the technical requirements of GB/T3086-2008 standard corresponding to an effective nominal diameter section of 5-160 mm, the Brinell hardness meets the hardness index of 250-300 of the hydraulic engineering mushroom head, and twin-crystal carbide is avoided.
In order to confirm that the technical scheme of the invention is a necessary technical scheme, the applicant makes a comparative experiment, which specifically comprises the following steps:
the chemical components of the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging in percentage by weight are as follows by smelting analysis: 1.02% of C, 0.61% of Si, 0.59% of Mn, 0.021% of P, 0.005% of S, 16.82% of Cr, 0.49% of Mo, 0.12% of Ni and 0.08% of Cu.
The large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging consists of a hemisphere and a columnar platform, wherein the diameter of the hemisphere is an S phi 1200mm hemisphere, the columnar platform is a platform with the height of 200mm and the diameter of phi 1400mm, and the effective section diameter is 800 mm. The heat treatment comprises the following specific steps:
1) putting the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging into a heating furnace, heating to 650 ℃ at the speed of 50 ℃/h, and preserving heat for 80 h; then heating to 1050 ℃, and then carrying out temperature equalization and heat preservation for 16h and 8 h;
2) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging subjected to temperature equalization and heat preservation in the step 1), and air-cooling to room temperature;
3) placing the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging which is air-cooled to room temperature in the step 2) into a heating furnace, raising the temperature from the room temperature to 650 +/-10 ℃, and carrying out temperature equalization and heat preservation for 24 hours and 12 hours; cooling to 200 ℃ along with the furnace.
4) And (3) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging which is cooled to 200 ℃ in the furnace in the step 3), and air-cooling. A large diameter G102Cr18Mo high carbon chromium stainless steel mushroom head forging of tempered martensite structure as shown in fig. 4 can be obtained.
The large-diameter G102Cr18Mo mushroom head forging subjected to heat treatment in the comparative example is directly air-cooled to room temperature in the step 2), is not placed in a 650 ℃ heating furnace in the step 3), is cooled to 530 ℃ along with the temperature of the furnace, and is subjected to heat preservation for 8 hours for homogeneous carbon distribution; the temperature is directly increased to 650 +/-10 ℃, so the mechanical performance indexes of the heat-treated large-diameter G102Cr18Mo mushroom head forging are as follows: σ b 911MPa, bulk brinell hardness HB: 342. 345 and 357, and the metallographic structure is a tempered martensite structure. The strength and the hardness are overproof, and the metallographic structure is a tempered martensite structure and does not meet the technical requirements of GB/T3086-2008 standard corresponding to an effective nominal diameter section of 5-160 mm.
The chemical composition percent wt of the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging of the comparative example 2 and the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging is as follows in smelting analysis: 1.04 percent of C, 0.560 percent of Si, 0.59 percent of Mn, 0.023 percent of P, 0.005 percent of S, 16.98 percent of Cr, 0.47 percent of Mo, 0.16 percent of Ni and 0.13 percent of Cu. The heat treatment comprises the following specific steps:
1) putting the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging into a heating furnace, heating to 650 ℃ at the speed of 50 ℃/h, and preserving heat for 80 h; and then raising the temperature to 1050 ℃, and then carrying out temperature equalization and heat preservation for 16h and 8 h.
2) And (3) cooling the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging subjected to temperature equalization and heat preservation in the step 1) to room temperature along with a furnace.
3) Placing the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forge piece air-cooled to room temperature in the step 2) into a heating furnace, heating to 650 +/-10 ℃, and carrying out uniform temperature and heat preservation for 24 hours and 12 hours; cooling to 200 ℃ along with the furnace.
4) And (3) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging which is cooled to 200 ℃ in the furnace in the step 3), and air-cooling. A large diameter G102Cr18Mo high carbon chromium stainless steel mushroom head forging of white reticulated carbide + black pearlite structure as shown in fig. 5 can be obtained.
The comparative example 2 is different from the examples 1, 2 and 3 in that a furnace cooling to room temperature process is adopted in the step 2), namely the step 2) is carried out for temperature equalization after 1050 ℃, heat preservation is carried out, then furnace cooling is directly carried out to room temperature, homogeneous carbon distribution is not carried out by adopting medium temperature section heat preservation at 500-550 ℃, and low-temperature transformation structure is cut off to ensure the full precipitation of carbide; therefore, the mechanical properties of the heat-treated large-diameter G102Cr18Mo mushroom head forging are as follows: σ b ═ 567MPa, bulk brinell hardness HB: 220. 222 and 230, the metallographic structure is a large reticular carbide plus annealed pearlite structure, and the strength and the hardness are lower than the standard. The method does not meet the technical requirements of GB/T3086-2008 standard corresponding to the effective nominal diameter section of 5-160 mm, and harmful large-scale net-shaped carbide appears.
Compared with the strength, hardness and metallographic structure data of the examples 1, 2 and 3 and the comparative examples 1 and 2, the cooling control and temperature control mode of the invention after the temperature is raised to 1050-1060 ℃ is very important. If the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging is cooled to room temperature by air according to the traditional normalizing process, the quenching phenomenon is easy to occur when the cooling speed is too high (seen in a comparative example), and a bainite and martensite structure is formed; complete annealing by high temperature furnace cooling is easy to form harmful net carbonization because of too slow cooling speed (seen in comparison example).
The method adopts the medium-temperature section of 500-550 ℃ for heat preservation, and performs homogeneous carbon distribution to ensure the full precipitation of carbide and cut off the low-temperature transformation structure. Therefore, the invention can completely avoid the chain or net carbide of the large-diameter G102Cr18Mo high-carbon chromium stainless steel mushroom head forging, and can obtain high-temperature stable pearlite structure on the large casting and forging, namely refined crystal grains; the strength and hardness indexes are guaranteed to meet the technical requirements of GB/T3086-2008 standard corresponding to the effective nominal diameter section of 5-160 mm, and the technical requirements of large mushroom head gates used in hydraulic engineering are completely met.
Claims (3)
1. The heat treatment method for the uniform distribution of pearlite of the large-diameter high-carbon chromium stainless steel forging is characterized by comprising the following steps of: the large-diameter high-carbon chromium stainless steel forging is a G102Cr18Mo high-carbon chromium stainless steel forging with the nominal diameter or the effective section diameter of more than 160 mm;
the chemical composition wt% of the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging is as follows: 0.95 to 1.10 percent of C, 0.20 to 0.78 percent of Si, 0.20 to 0.78 percent of Mn, 0.005 to 0.034 percent of P, 0.003 to 0.028 percent of S, 16.02 to 17.95 percent of Cr, 0.40 to 0.70 percent of Mo, 0.03 to 0.25 percent of Ni and 0.03 to 0.24 percent of Cu;
the heat treatment comprises the following specific steps:
1) putting the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging into a heating furnace, heating to 600-650 ℃ at the speed of 45-55 ℃/h, and preserving heat, wherein the heat preservation time is calculated according to 10h/100 mm; then raising the temperature to 1050-1060 ℃, and then carrying out temperature equalization and heat preservation, wherein the temperature equalization time is calculated according to 2h/100mm, and the heat preservation time is 1/2 of the temperature equalization time;
the 100mm is a reference unit of converting the effective section diameter of the G102Cr18Mo high-carbon chromium stainless steel forging into the heat preservation and temperature equalization time of the forging;
2) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging subjected to temperature equalization and heat preservation in the step 1), and air-cooling to 600 ℃;
3) placing the large-diameter G102Cr18Mo high-carbon chromium stainless steel forged piece subjected to air cooling in the step 2) into a heating furnace at 650 ℃, cooling to 500-550 ℃ along with the furnace, and performing homogeneous carbon distribution, wherein the heat preservation time is calculated according to 1h/100 mm; then raising the temperature to 650 +/-10 ℃ for temperature equalization and heat preservation, wherein the temperature equalization time is calculated according to 3.0h/100mm, and the heat preservation time is 1/2 of the temperature equalization time; cooling to 200 ℃ along with the furnace;
the 100mm is a reference unit of converting the effective section diameter of the G102Cr18Mo high-carbon chromium stainless steel forging into the heat preservation and temperature equalization time of the forging;
4) and (3) discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging which is cooled to 200 ℃ along with the furnace in the step 3), and air-cooling to obtain the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging which has uniformly distributed pearlite structures and does not have harmful twin carbide.
2. The heat treatment method for large-diameter high-carbon chromium stainless steel forgings with uniformly distributed pearlite according to claim 1, is characterized in that: and in the step 2) and the step 4), air cooling refers to discharging the large-diameter G102Cr18Mo high-carbon chromium stainless steel forging, and placing the forging in the air space at room temperature for natural cooling.
3. The heat treatment method for large-diameter high-carbon chromium stainless steel forgings with uniformly distributed pearlite according to claim 1, is characterized in that: and 3) furnace cooling, namely placing the large-diameter high-carbon chromium stainless steel forging into the heating furnace with the heat preservation completed, closing the furnace door, and slowly cooling without heating.
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