CN115747706A - Heat treatment method for pearlite heat-resistant steel - Google Patents

Heat treatment method for pearlite heat-resistant steel Download PDF

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CN115747706A
CN115747706A CN202211431318.6A CN202211431318A CN115747706A CN 115747706 A CN115747706 A CN 115747706A CN 202211431318 A CN202211431318 A CN 202211431318A CN 115747706 A CN115747706 A CN 115747706A
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gear
heat
treated
carbonitriding
processed
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徐峰
任长安
祝曼
侯晓鹏
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AECC Aero Engine Xian Power Control Technology Co Ltd
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AECC Aero Engine Xian Power Control Technology Co Ltd
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Abstract

The invention relates to a surface modification treatment method for a steel material, in particular to a heat treatment method for pearlite heat-resistant steel, which solves the technical problem that a 2Cr3WMoV material is difficult to meet the performance requirement of high-speed operation of an aircraft fuel accessory. The heat treatment method of the pearlite heat-resistant steel comprises the following steps: step 1: pre-treating, quenching and insulating the bar stock made of 2Cr3WMoV-1 material, and then carrying out air cooling or oil cooling; then tempering and heat preservation are carried out, and water cooling or oil cooling is carried out to obtain a bar stock with the hardness HRC less than or equal to 32; then processing the bar stock into a gear to be processed; then processing the bar stock into a gear to be processed; and 2, step: performing carbonitriding; and step 3: and performing sub-temperature quenching, cold treatment and tempering to finish the heat treatment of the gear to be treated, so that the pearlite heat-resistant steel has higher hardness and wear resistance.

Description

Heat treatment method for pearlite heat-resistant steel
Technical Field
The invention relates to a surface modification treatment method for a steel material, and particularly relates to a heat treatment method for pearlite heat-resistant steel.
Background
The 2Cr3WMoV-1 is a novel pearlite heat-resistant steel, is different from the 2Cr3WMoV chemical composition in GJB2294-1995 'aviation stainless steel and heat-resistant steel bar specification', is mainly reflected in the contents of C element, mn element, si element and Cr element, and the specific difference is shown in Table 1:
TABLE 1
Type of material C Mn Si Cr
2Cr3WMoV 0.16-0.24 0.25-0.6 ≤0.4 2.4-3.3
2Cr3WMoV-1 0.15-0.2 0.25-0.5 0.17-0.37 2.8-3.3
The 2Cr3WMoV material is mainly applied to forging gears to be processed, can achieve deep penetration layer, high hardness and wear resistance through a heat treatment method of carburizing and quenching, can meet the performance requirements of fuel accessories of aircraft engines, but is difficult to meet the performance requirements of high-speed operation of the fuel accessories of aircrafts. In the prior art, reports about solving related technical problems (hardness, wear resistance and the like) of the pearlite heat-resistant steel (namely 2Cr3 WMoV-1) through heat treatment are not found.
Disclosure of Invention
The invention aims to provide a heat treatment method of pearlite heat-resistant steel aiming at the technical problem that a 2Cr3WMoV material is difficult to meet the performance requirement of high-speed operation of an aircraft fuel accessory, so that the pearlite heat-resistant steel has higher hardness and wear resistance.
The conception of the invention is as follows:
selecting a round rod 2Cr3WMoV-1 which is superior to a 2Cr3WMoV material, strictly controlling the contents of C element, mn element, si element and Cr element in the round rod 2Cr3WMoV-1, changing a heat treatment method on the basis of optimizing the 2Cr3WMoV material, and adopting a pretreatment, two-stage carbonitriding and sub-temperature quenching method to form a carbonitriding layer with epsilon-nitrocarbon compounds on the surface of a gear processed by the round rod 2Cr3WMoV-1, wherein compared with a carburizing or/and nitriding chemical heat treatment, the gear processed by the round rod 2Cr3WMoV-1 has the characteristics of high wear resistance and small brittleness; meanwhile, the matrix crystal grains of the gear are refined to obtain a proper amount of distributed fine ferrite tissues, so that the matrix has higher toughness and meets the performance requirement of high-speed operation of the fuel accessory of the aircraft.
In order to solve the technical problems and realize the inventive concept, the invention adopts the technical scheme that:
the heat treatment method of the pearlite heat-resistant steel is characterized by comprising the following steps of:
step 1: pretreatment of
Quenching and insulating a bar stock made of a 2Cr3WMoV-1 material, and then carrying out air cooling or oil cooling; then tempering and heat preservation are carried out, water cooling or oil cooling is carried out, bar stock with the hardness HRC less than or equal to 32 is obtained, and finally the bar stock is processed into the gear to be processed;
and 2, step: carbonitriding
2.1 Determining a carbonitriding agent;
2.2 According to the penetrating agent in the step 2.1), calculating the ratio of carbon atoms to nitrogen atoms of the carbonitrided layer of the gear to be processed obtained in the step 1;
2.3 Carrying out two-stage carbonitriding on the gear to be treated obtained in the step 1 by utilizing the ratio of the carbonitriding agent in the step 2.1) to the carbon atoms and the nitrogen atoms in the step 2.2) to obtain the gear to be treated with the thickness of the carbonitriding layer of 0.35-0.5 mm;
and step 3: performing sub-temperature quenching, cold treatment and tempering
3.1 Carrying out sub-temperature quenching on the gear to be treated obtained in the step 2.2);
3.2 Carrying out cold treatment on the gear to be treated obtained in the step 3.1);
3.3 Tempering the gear to be treated obtained in the step 3.2) to finish the heat treatment of the gear to be treated.
Further, step 1 specifically comprises:
quenching a bar made of a 2Cr3WMoV-1 material at 1050 +/-10 ℃, preserving heat for 60-90min, and cooling in air or oil after preserving heat; air cooling or oil cooling, tempering at 700 +/-10 deg.c for 60-90min, water cooling or oil cooling to obtain bar with hardness HRC not higher than 32, and machining into gear to be treated.
Further, in the step 2.1), the carburizing agent comprises a carburizing agent, a diluent and ammonia gas;
the carburizing agent is C 3 H 8 The diluent is CH 3 OH。
Further, the step 2.2) specifically comprises the following steps:
2.2.1, calculating the content of carbon atoms in the carbonitrided layer;
setting the carbon potential in the carbonitriding furnace according to C 3 H 8 Flow determination CH 3 The flow of OH is calculated, and the carbon atom content in the carbonitrided layer of the gear to be processed obtained in the step 1 is calculated;
2.2.2 according to C in carbonitriding furnace 3 H 8 、CH 3 OH and NH 3 Calculating the content of nitrogen atoms in the carbonitrided layer of the gear to be treated obtained in the step 1 according to the gas volume;
2.2.3, obtaining the ratio of carbon atoms to nitrogen atoms of the carbonitrided layer according to the content of carbon atoms obtained in the step 2.2.1 and the content of nitrogen atoms obtained in the step 2.2.2.
Further, step 2.2.1 specifically comprises:
setting the carbon potential in the carbonitriding furnace to be 0.9 +/-0.1 percent and curing C 3 H 8 When the flow of the carbon dioxide is 0.3 +/-0.1L/min, controlling CH by the control mode of an oxygen probe and a carbon potential control instrument 3 The flow rate of OH is 0.7-1L/H, and the content of carbon atoms in the carbonitrided layer of the gear to be treated obtained in the step 1 is 0.8% -0.9%.
Further, step 2.2.2 specifically is:
2.2.2.1 determination of NH in carbonitriding furnace 3 Volume of gas in CH 3 The volume ratio of OH decomposition gas is 2.3%;
2.2.2.2 according to step 2.2.1 CH 3 OH flow rate is 0.7-1L/H and the volume ratio in the step 2.2.2.1 is 2.3%, and NH can be calculated 3 The flow rate of the carbon nitride is 0.43-0.61L/min, and the content of nitrogen atoms in the obtained carbonitrided layer is 0.3% -0.4%.
Further, step 2.2.3 specifically includes:
according to the carbon atom content of 0.8-0.9% in the step 2.2.1 and the nitrogen atom content of 0.3-0.4% in the step 2.2.2.2, the ratio of the carbon atoms to the nitrogen atoms of the carbonitrided layer is 2-3.
Further, the step 2.3) is specifically as follows:
2.3.1, in the first stage of carbonitriding, introducing C in the step 2.1) 3 H 8 、CH 3 OH and NH 3 Setting the carbon potential in the carbonitriding furnace to 0.9 +/-0.1 percent and NH 3 Controlling the flow rate to be 0.45-0.6L/min, heating the mixture to be 830 +/-10 ℃, preserving the heat for 55-75min, and infiltrating carbon atoms and nitrogen atoms into the gear to be processed obtained in the step 1 according to the proportion requirement obtained in the step 2.2.3 and the proportion of 2.5; the ratio is 2.5;
2.3.2 in the second stage of carbonitriding, the carbon potential in the carbonitriding furnace is reduced to 0.7 +/-0.1%, and NH 3 The flow rate of the gear is 0.45-0.6L/min, the heating temperature is 830 +/-10 ℃, and the temperature is kept for 20-40min, so that the gear to be treated with the carbonitrided layer with the thickness of 0.35-0.5mm is obtained.
Further, the step 3.1) specifically comprises:
putting the gear to be processed obtained in the step 2.3.2 into an atmosphere furnace, heating the atmosphere furnace to 700 +/-10 ℃, preserving heat for 2-3 hours, cooling the atmosphere furnace to below 300 ℃ and discharging; then transferring the gear to be treated into a salt furnace, heating the salt furnace to 870 +/-10 ℃, and preserving heat for 10-15min; finally, rotating the gear to be processed to a nitrate tank or an alkali tank, regulating the heating temperature of the nitrate tank or the alkali tank to 200 +/-20 ℃, cooling for 3-5min, and carrying out air cooling to obtain a carbonitriding layer with epsilon-nitrocarbon compounds on the gear to be processed;
or, putting the gear to be processed obtained in the step 2.3.2 into an atmosphere furnace, heating the atmosphere furnace to the temperature of 700 +/-10 ℃, preserving the temperature for 2-3 hours, cooling the atmosphere furnace to the temperature below 300 ℃, and discharging; then the gear to be treated is transferred into the salt furnace, the temperature of the salt furnace is heated to 900 +/-20 ℃, the heat preservation is carried out for 7-12min, and oil cooling is carried out after the heat preservation, so that the gear to be treated obtains a carbonitriding layer with epsilon-nitrocarbon compounds.
Further, the step 3.2) is specifically as follows:
putting the gear to be processed obtained in the step 3.1) into an ice cooler, adjusting the temperature of the ice cooler to be less than or equal to-75 ℃, preserving heat for 1-2h, and carrying out cold processing after heat preservation;
the step 3.3) is specifically as follows:
and (3) placing the gear to be treated obtained in the step (3.2) into a drying oven, setting the temperature of the gear to be treated to be 160 +/-10 ℃, keeping the temperature for more than or equal to 2 hours, and carrying out air cooling after keeping the temperature to obtain the gear to be treated with a carbonitrided layer of 0.35-0.5mm, a surface hardness of 56-62HRC, a center hardness of 35-43.5HRC and a carbide grade of less than or equal to 5, thereby completing the heat treatment of the gear to be treated.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
(1) The invention relates to a heat treatment method of pearlite heat-resistant steel, which utilizes a gear to be treated which is processed by a 2Cr3WMoV-1 material, changes the proportion of carbon atoms and nitrogen atoms of a carbonitrided layer of the gear to be treated through carbonitriding, then forms a carbonitrided layer with epsilon nitrocarbon compounds on the surface of the gear to be treated by implementing two-stage carbonitriding and adopting a method of sub-temperature quenching, and obtains high wear resistance and fatigue resistance; meanwhile, matrix grains of the gear to be processed are refined to obtain a proper amount of distributed fine ferrite tissues, so that the gear to be processed has higher toughness and small deformation, and can meet the performance requirement of high-speed operation of an aircraft fuel accessory.
(2) According to the heat treatment method of the pearlite heat-resistant steel, the gear to be treated is processed by using the 2Cr3WMoV-1 material, and the volume ratio of the carburizing agent to the ammonia gas is reasonably determined, so that the gear to be treated is prevented from having black tissue defects and excessive retained austenite; the distribution of carbide and nitride of a carburized layer of the gear to be treated is improved, and unfavorable tissues are prevented, so that the carbonitrided layer of the gear to be treated can reach 0.35-0.5mm, the surface hardness reaches HRC56-62, and the center hardness reaches HRC35-43.5.
(3) The invention relates to a heat treatment method of pearlite heat-resistant steel, which utilizes a gear to be treated processed by a 2Cr3WMoV-1 material to ensure that the working rated rotating speed of an aircraft lubricating oil pump can reach 12100r/min, the rotating speed is high, the load is light, and the short-time high-speed stable operation is realized when the gear is applied to the aircraft lubricating oil pump.
Drawings
FIG. 1 is a pre-treatment process curve diagram of a gear to be treated in an embodiment of a heat treatment method of pearlite heat-resistant steel.
FIG. 2 is a graph showing a two-stage carbonitriding process performed on a gear to be treated in an embodiment of a heat treatment method for pearlite heat-resistant steel according to the present invention.
FIG. 3 is a process chart of tempering and sub-temperature quenching of a gear to be treated to obtain the HRC of the central hardness of the gear to be treated of 35-39 in the embodiment of the heat treatment method of pearlite heat-resistant steel.
FIG. 4 is a process chart of tempering and sub-temperature quenching of a gear to be treated to obtain a gear to be treated with a central hardness HRC of 39-45 in an embodiment of a heat treatment method of pearlite heat-resistant steel.
Detailed Description
A heat treatment method of pearlitic heat-resistant steel comprises the following steps:
step 1: pretreatment of
As shown in figure 1, quenching a bar stock made of 2Cr3WMoV-1 material at 1050 +/-10 ℃, preserving heat for 60-90min, and then carrying out air cooling or oil cooling; and then tempering is carried out, the tempering temperature is 700 +/-10 ℃, the temperature is kept for 60-90min, water cooling or oil cooling is carried out after the temperature is kept, a bar with the hardness HRC less than or equal to 32 is obtained, and finally the bar is processed into the gear to be processed.
Step 2: carbonitriding is carried out
Because 2Cr3WMoV-1 material contains more alloy elements, in order to avoid the gear to be processed which is processed by the bar material of the 2Cr3WMoV-1 material from generating black tissue defect, excessive retained austenite and reduced surface hardness, the volume ratio of the carburizing agent to the ammonia gas needs to be reasonably determined, so that the carbon atoms and the nitrogen atoms of the carbonitriding layer are infiltrated in a certain proportion, and the specific determination method comprises the following steps:
2.1 Determining a carbonitriding agent;
during carbonitriding, the permeating agent (gas) and ammonia (NH) are mixed 3 ) The volume ratio of (A) should be selected according to the material, the carburized layer structure, the performance and the carbonitriding temperature type of the part. In the implementation, the penetrating agent comprises a carburizing agent, a diluent and ammonia gas; preferably the carburizing agent is C 3 H 8 The diluent is CH 3 OH；
2.2 Calculating the ratio of carbon atoms to nitrogen atoms of the carbonitrided layer of the gear to be processed obtained in the step 1) according to the penetrating agent in the step 2.1);
2.2.1, calculating the content of carbon atoms in the carbonitrided layer;
setting the carbon potential in the carbonitriding furnace to be 0.9 +/-0.1 percent and curing C 3 H 8 When the flow of the carbon dioxide is 0.3 +/-0.1L/min, controlling CH by the control mode of an oxygen probe and a carbon potential control instrument 3 The flow rate of OH is 0.7-1L/H, and the carbon atom content in the obtained carbonitrided layer is 0.8-0.9%；
2.2.2 according to C in carbonitriding furnace 3 H 8 、CH 3 OH and NH 3 Calculating the content of nitrogen atoms in the carbonitrided layer according to the gas volume;
2.2.2.1 general reaction of NH 3 The gas volume accounts for 2-12% of the gas volume in the carbonitriding furnace, and the method determines NH in the carbonitriding furnace 3 Volume of gas in CH 3 The volume ratio of OH decomposition gas is 2.3%;
2.2.2.2 according to step 2.2.1 CH 3 OH flow is 0.7-1L/H and the volume ratio in the step 2.2.2.1 is 2.3%, NH can be calculated 3 The flow rate of (c);
in this embodiment, CH 3 When the OH flow rate was 1L/H, the flow rate of the generated decomposition gas was 26.7L/min, and NH was found 3 The flow rate is 26.7 × 2.3% =0.61L/min; in actual production of CH 3 OH flow rate is 0.7-1L/H, then NH 3 A flow rate of
NH 3 Minimum flow rate: 0.7X 0.61=0.43L/min
NH 3 Maximum flow rate: 1 × 0.61=0.61l/min
As the minimum scale of the flowmeter of the floater is 0.05L/min, the flowmeter is convenient for field operation, and therefore, NH is controlled by the flowmeter of the floater 3 The flow rate of (A) is 0.45-0.6L/min.
According to calculated NH 3 The flow rate is 0.43-0.61L/min, and the content of nitrogen atoms in the carbonitriding layer is 0.3% -0.4%.
2.2.3, according to the content of carbon atoms in the step 2.2.1 of 0.8-0.9 percent and the content of nitrogen atoms in the step 2.2.2.2, the ratio of the carbon atoms to the nitrogen atoms of the carbonitrided layer is 2-3.
2.3 2Cr3WMoV-1 material contains many kinds and high content of carbide-forming elements, and C is added to avoid the occurrence of unfavorable structures such as network, block and horn in the carbonitrided layer of the gear to be treated 3 H 8 、CH 3 OH and NH 3 According to the proportion of carbon atoms and nitrogen atoms in the step 2.2.3, the gear to be treated obtained in the step 1 is subjected to two-stage carbonitriding to obtain the gear to be treated with the carbonitriding layer thickness of 0.35-0.5mm, and the gear to be treated hasThe body is shown in figure 2:
2.3.1 in the first stage of carbonitriding, C in the step 2.1) is introduced into a carbonitriding furnace under the action of high carbon potential and high temperature 3 H 8 、CH 3 OH and NH 3 Performing forced infiltration on the gear to be treated for a long time by keeping the temperature for a long time, so that carbon atoms and nitrogen atoms infiltrate into a matrix of the gear to be treated according to a certain proportion, wherein in the embodiment, the proportion of the carbon atoms to the nitrogen atoms is preferably 2.5; setting the carbon potential in the carbonitriding furnace to be 0.9% +/-0.1% and NH 3 The flow rate is 0.45-0.6L/min, the heating temperature is 830 +/-10 ℃, the temperature is kept for 55-75min, carbon atoms and nitrogen atoms are infiltrated into the gear to be treated obtained in the step 1, and a high-concentration carbonitriding layer with the thickness of 0.35-0.4mm is obtained;
2.3.2 in the second stage of carbonitriding, the carbon potential in the carbonitriding furnace is reduced to 0.7 +/-0.1%, NH 3 The flow rate is 0.45-0.6L/min, the heating temperature is 830 +/-10 ℃, and the temperature is kept for 20-40min, so that the gear to be treated with the carbonitriding layer with the thickness of 0.35-0.5mm is obtained.
Because the carbonitriding of the first section is strong carburizing, the carbon concentration on the surface of the carburized layer is about 0.9% + -0.1%, the carbon potential is reduced to 0.7 +/-0.1% in the second section, and a short-time trace infiltration method is adopted, so that on one hand, carbon atoms and nitrogen atoms on the surface of the carburized layer are diffused to the core part of the gear to be processed, the concentration gradient is gradually slowed down, the distribution of carbide and nitride of the carburized layer of the gear to be processed is improved, and unfavorable tissues are prevented from occurring; on the other hand, trace carbon atoms and nitrogen atoms permeate into the part with low local content of the gear to be treated, so that the phenomenon that a permeating layer generates soft spots is avoided.
And step 3: tempering and sub-temperature quenching
In GJB2294-1995, the specification of stainless steel and heat-resistant steel bars for aviation use, the quenching temperature of 2Cr3WMoV is 1030-1080 ℃, and the quenching temperature recommended by the 2Cr3WMoV-1 material standard is 900-950 ℃. Based on the carbonitriding quenching process for common structural steel and stainless steel in combination with standard requirements, the invention selects a sub-temperature quenching method, namely 870 +/-10 ℃ or 900 +/-20 ℃, to form a carbonitriding layer with epsilon-nitrocarbon compounds on the surface of the gear to be processed, thereby obtaining higher wear resistance than a carburized layer, simultaneously refining matrix grains of the gear to be processed, obtaining a proper amount of distributed fine ferrite tissues, obtaining higher toughness and reducing the deformation of the gear to be processed.
3.1 Placing the gear to be processed obtained in the step 2.3.2 into an atmosphere furnace, heating the temperature of the atmosphere furnace to 700 +/-10 ℃, preserving the temperature for 2-3 hours, cooling the atmosphere furnace to below 300 ℃ and discharging the gear as shown in figure 3; then transferring the gear to be treated into a salt furnace, heating the salt furnace to 870 +/-10 ℃, and preserving heat for 10-15min; finally, rotating the gear to be treated to an alkali tank and also to a nitrate tank, regulating the heating temperature of the alkali tank or the nitrate tank to 200 +/-20 ℃, cooling for 3-5min, and carrying out air cooling to obtain a carbonitrided layer with epsilon-nitrocarbon compounds on the gear to be treated, wherein the central hardness HRC is 35-39;
or, as shown in fig. 4, in order to improve the central hardness of the gear to be processed, the gear to be processed obtained in step 2.3.2 can be placed into an atmosphere furnace, the temperature of the atmosphere furnace is heated to 700 +/-10 ℃, the temperature is kept for 2-3 hours, and the gear to be processed is discharged after being cooled to below 300 ℃; and then transferring the gear to be treated into a salt furnace, heating the salt furnace to 900 +/-20 ℃, preserving heat for 7-12min, and carrying out oil cooling after heat preservation to ensure that the gear to be treated obtains a carbonitrided layer with epsilon nitrocarbon compounds, and the central hardness HRC is 39-45.
3.2 Putting the gear to be processed obtained in the step 3.1) into an ice cooler, adjusting the temperature of the ice cooler to be less than or equal to-75 ℃, preserving heat for 1-2h, and carrying out cold processing after heat preservation.
3.3 In the drying oven of the gear to be processed obtained in the step 3.2), the temperature is set to be 160 +/-10 ℃, the heat preservation time is more than or equal to 2 hours, air cooling is carried out after heat preservation, and the gear to be processed with the carbonitrided layer of 0.35-0.5mm, the surface hardness of 56-62HRC, the center hardness of 35-43.5HRC and the carbide grade of less than or equal to 5 grade is obtained, so that the gear to be processed has higher wear resistance and toughness, has small deformation and can meet the performance requirement of high-speed operation of fuel accessories of an aircraft.

Claims (10)

1. A heat treatment method for pearlite heat-resistant steel is characterized by comprising the following steps:
step 1: pretreatment of
Quenching and insulating a bar stock made of a 2Cr3WMoV-1 material, and then cooling in air or oil; then tempering and heat preservation are carried out, water cooling or oil cooling is carried out to obtain a bar stock with the hardness HRC less than or equal to 32, and finally the bar stock is processed into a gear to be processed;
and 2, step: carbonitriding
2.1 Determining the carbonitriding agent;
2.2 According to the penetrating agent in the step 2.1), calculating the ratio of carbon atoms to nitrogen atoms of the carbonitrided layer of the gear to be processed obtained in the step 1;
2.3 Carrying out two-stage carbonitriding on the gear to be treated obtained in the step 1 by utilizing the ratio of the carbonitriding agent in the step 2.1) to the carbon atoms and the nitrogen atoms in the step 2.2) to obtain the gear to be treated with the thickness of the carbonitriding layer of 0.35-0.5 mm;
and 3, step 3: performing sub-temperature quenching, cold treatment and tempering
3.1 Carrying out sub-temperature quenching on the gear to be treated obtained in the step 2.2);
3.2 Carrying out cold treatment on the gear to be treated obtained in the step 3.1);
3.3 Tempering the gear to be treated obtained in the step 3.2) to finish the heat treatment of the gear to be treated.
2. The heat treatment method of pearlitic heat resistant steel according to claim 1, wherein step 1 is specifically:
quenching a bar made of a 2Cr3WMoV-1 material at 1050 +/-10 ℃, preserving heat for 60-90min, and cooling in air or oil after preserving heat; air cooling or oil cooling, tempering at 700 +/-10 deg.c for 60-90min, water cooling or oil cooling to obtain bar with hardness HRC not higher than 32, and machining into gear to be treated.
3. A heat treatment method of pearlitic heat resistant steel according to claim 1 or 2, characterized in that: in the step 2.1), the penetrating agent comprises a carburizing agent, a diluent and ammonia gas;
the carburizing agent is C 3 H 8 The diluent is CH 3 OH。
4. A heat treatment method for pearlite heat-resistant steel according to claim 3, wherein step 2.2) is specifically:
2.2.1, calculating the content of carbon atoms in the carbonitriding layer;
setting the carbon potential in the carbonitriding furnace according to C 3 H 8 Flow determination CH 3 OH flow, and calculating the carbon atom content in the carbonitrided layer of the gear to be processed obtained in the step 1;
2.2.2 according to C in carbonitriding furnace 3 H 8 、CH 3 OH and NH 3 Calculating the content of nitrogen atoms in the carbonitrided layer of the gear to be treated obtained in the step 1 according to the gas volume;
2.2.3, obtaining the ratio of carbon atoms to nitrogen atoms of the carbonitrided layer according to the content of carbon atoms obtained in the step 2.2.1 and the content of nitrogen atoms obtained in the step 2.2.2.
5. The heat treatment method of pearlitic heat resistant steel according to claim 4, wherein step 2.2.1 is specifically:
setting the carbon potential in the carbonitriding furnace to be 0.9 +/-0.1 percent and curing C 3 H 8 When the flow rate of the carbon dioxide is 0.3 +/-0.1L/min, the CH is controlled in a control mode of an oxygen probe and a carbon potential control instrument 3 The flow rate of OH is 0.7-1L/H, and the content of carbon atoms in the carbonitrided layer of the gear to be treated obtained in the step 1 is 0.8% -0.9%.
6. The heat treatment method of pearlitic heat resistant steel according to claim 5, wherein step 2.2.2 is specifically:
2.2.2.1 determination of NH in carbonitriding furnaces 3 Volume of gas in CH 3 The volume ratio of OH decomposition gas is 2.3%;
2.2.2.2 according to step 2.2.1 CH 3 OH flow rate is 0.7-1L/H and the volume ratio in the step 2.2.2.1 is 2.3%, and NH can be calculated 3 OfThe amount is 0.43-0.61L/min, and the content of nitrogen atoms in the obtained carbonitriding layer is 0.3% -0.4%.
7. The heat treatment method for pearlite heat-resistant steel according to claim 6, wherein step 2.2.3 is specifically:
according to the carbon atom content of 0.8-0.9% in the step 2.2.1 and the nitrogen atom content of 0.3-0.4% in the step 2.2.2.2, the ratio of the carbon atoms to the nitrogen atoms of the carbonitrided layer is 2-3.
8. The heat treatment method of pearlitic heat resistant steel according to claim 7, wherein step 2.3) is specifically:
2.3.1, in the first stage of carbonitriding, introducing C in the step 2.1) 3 H 8 、CH 3 OH and NH 3 Setting the carbon potential in the carbonitriding furnace to 0.9 +/-0.1 percent and NH 3 The flow rate of the gear to be processed is controlled to be 0.45-0.6L/min, the heating temperature is 830 +/-10 ℃, the temperature is kept for 55-75min, and carbon atoms and nitrogen atoms are infiltrated into the gear to be processed obtained in the step 1 according to the proportion requirement obtained in the step 2.2.3 and the selection proportion of 2.5; the ratio is 2.5;
2.3.2 in the second stage of carbonitriding, the carbon potential in the carbonitriding furnace is reduced to 0.7 +/-0.1%, NH 3 The flow rate of the gear is 0.45-0.6L/min, the heating temperature is 830 +/-10 ℃, and the temperature is kept for 20-40min, so that the gear to be treated with the carbonitrided layer with the thickness of 0.35-0.5mm is obtained.
9. The heat treatment method for the pearlite heat-resistant steel according to claim 8, wherein the step 3.1) is specifically as follows:
putting the gear to be processed obtained in the step 2.3.2 into an atmosphere furnace, heating the atmosphere furnace to 700 +/-10 ℃, preserving heat for 2-3 hours, cooling the atmosphere furnace to below 300 ℃ and discharging; then transferring the gear to be treated into a salt furnace, heating the salt furnace to 870 +/-10 ℃, and preserving heat for 10-15min; finally, rotating the gear to be processed to a nitrate tank or an alkali tank, regulating the heating temperature of the nitrate tank or the alkali tank to 200 +/-20 ℃, cooling for 3-5min, and carrying out air cooling to obtain a carbonitriding layer with epsilon-nitrocarbon compounds on the gear to be processed;
or, putting the gear to be processed obtained in the step 2.3.2 into an atmosphere furnace, heating the atmosphere furnace to the temperature of 700 +/-10 ℃, preserving the heat for 2-3 hours, cooling the atmosphere furnace to the temperature below 300 ℃ and discharging; and then transferring the gear to be treated into a salt furnace, heating the salt furnace to 900 +/-20 ℃, preserving heat for 7-12min, and carrying out oil cooling after heat preservation to ensure that the gear to be treated obtains a carbonitrided layer with epsilon nitrocarbon compounds.
10. The heat treatment method of pearlitic heat resistant steel according to claim 9, wherein step 3.2) is specifically:
putting the gear to be processed obtained in the step 3.1) into an ice cooler, adjusting the temperature of the ice cooler to be less than or equal to-75 ℃, preserving heat for 1-2h, and carrying out cold processing after heat preservation;
the step 3.3) is specifically as follows:
and (3) placing the gear to be treated obtained in the step (3.2) into an oven, setting the temperature of the gear to be treated to be 160 +/-10 ℃, keeping the temperature for more than or equal to 2 hours, and performing air cooling after heat preservation to obtain the gear to be treated with a carbonitrided layer of 0.35-0.5mm, a surface hardness of 56-62HRC, a center hardness of 35-43.5HRC and a carbide grade of less than or equal to 5 grade, thereby completing the heat treatment of the gear to be treated.
CN202211431318.6A 2022-11-15 2022-11-15 Heat treatment method for pearlite heat-resistant steel Pending CN115747706A (en)

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