阅读说明：本技术 一种超高硬度齿轮渗碳淬火工艺 (Carburizing and quenching process for ultrahigh-hardness gear ) 是由 费斌 黄丰 吴嘉铭 那刚 周秋晨 朱圣伟 堵瑞麟 邬晓龙 张伟 刘艳 于 2020-12-21 设计创作，主要内容包括：本发明提出了一种超高硬度齿轮渗碳淬火工艺,包括以下步骤：S1.区域划分：根据材料硬度划分为A、B、C三个位置区域；S2.一次渗碳：将B、C位置区域进行防渗保护后,将A位置区域进行渗碳；S3.二次渗碳：将B位置区域脱去保护后,将A、B位置区域进行渗碳；S4.三次渗碳：将C位置区域脱去保护后,将A、B、C位置区域进行渗碳淬火,得到产品；计算方式为：L-2＝6/5L-L-1；其中L-1＝已渗的深度,L＝要求的深度,取平均值,L-2＝本次补渗的深度。采用本发明渗碳工艺后得到的产品具有更高的硬度和力学性能,且工作温度更高,可在320℃以下使用。(The invention provides a carburizing and quenching process for an ultrahigh-hardness gear, which comprises the following steps of: s1, area division: a, B, C three position areas are divided according to the hardness of the material; s2, primary carburization: after the B, C position area is subjected to seepage-proofing protection, carburizing the A position area; s3, secondary carburization: after the B site region is deprotected, the A, B site region is carburized; s4, third carburizing: after the C position area is unprotected, the A, B, C position area is carburized and quenched to obtain a product; the calculation method is as follows: l is 2 ＝6/5L‑L 1 (ii) a Wherein L is 1 The mean value of the depth of penetration and L is the desired depth 2 The depth of this time of replenishing infiltration. The product obtained by adopting the carburizing process has higher hardness and mechanical property, and higher working temperature, and can be used below 320 ℃.)

1. A carburizing and quenching process for an ultrahigh-hardness gear is characterized by comprising the following steps:

s1, area division: dividing the material into A, B, C three position areas according to the hardness of the 16Cr3NiWMoVNbE material;

s2, primary carburization: after the B, C position area is subjected to seepage-proofing protection, carburizing the A position area;

s3, secondary carburization: after the B site region is deprotected, the A, B site region is carburized;

s4, third carburizing: after the C position area is unprotected, the A, B, C position area is carburized and quenched to obtain a product;

the calculation method is as follows: l is₂＝6/5L-L₁(ii) a Wherein L is₁The mean value of the depth of penetration and L is the desired depth₂The depth of this time of replenishing infiltration.

2. The carburizing and quenching process for ultra-high hardness gear according to claim 1, wherein the method for dividing the regions in step S1 is: dividing the gear cone surface S1.1-1.2 and HV0.6 which is more than or equal to HRC60 into an A position area; dividing S0.8-0.9 and HV0.5 which are more than or equal to HRC60 on the outer circular surface of the gear into a B position area; the C position area is divided by S0.4-0.5, HV0.2 ≥ HRC60 on the inner circular surface of the gear.

3. The ultra-high hardness gear carburizing and quenching process according to claim 1, characterized by comprising the steps of: the anti-seepage protection method is to plate copper locally.

4. The carburizing and quenching process for the ultra-high hardness gear according to claim 3, wherein the local copper plating method is to evenly coat natural beeswax on the area needing the anti-seepage protection in advance, and after the natural beeswax is solidified, the local copper plating is carried out on the surface.

5. The carburizing and quenching process for the ultra-high hardness gear according to claim 4, wherein the deprotection method comprises removing natural beeswax with boiled water and brushing clean.

6. The ultra-high hardness gear carburizing and quenching process according to claim 1, wherein the carburizing process comprises three stages of feeding and vacuumizing, stage temperature rising and pulse carburizing.

7. The carburizing and quenching process for the ultra-high hardness gear according to claim 1, wherein the chemical components of the 16Cr3NiWMoVNbE material are as follows by mass fraction: 0.12 to 0.17 percent of C, 0.25 to 1.7 percent of Si, 0.2 to 1.0 percent of Mn, 2.0 to 3.0 percent of Cr2, 1.2 to 2.5 percent of Ni1.0 to 1.4 percent of W, 0.4 to 0.6 percent of Mo0.3 to 0.6 percent of V, 0.1 to 0.2 percent of Nb0.015 percent or less of P, 0.01 percent or less of S, 0.015 percent or less of Cu and the balance of Fe.

8. The carburizing and quenching process for the ultra-high hardness gear according to claim 1, wherein the quenching method is vacuum oil quenching, the quenching temperature is 750-.

9. The carburizing and quenching process for ultra-high hardness gears according to claim 1, wherein any one or more of steps S2-S4 is/are repeated.

10. The carburizing and quenching process for the ultra-high hardness gear according to claim 1, wherein the surface hardness of the product is HRC60-64, the core hardness is HRC42-46, and the tensile strength is 1270-1350 MPa; the yield strength is 1130-1210 MPa; elongation after fracture is 10-15%; the reduction of area is 50-60%.

Technical Field

The invention relates to the technical field of vacuum carburization, in particular to a carburizing and quenching process for an ultrahigh-hardness gear.

Background

The 16Cr3NiWMoVNbE steel belongs to super-grade high-quality steel and has good hardenability, high toughness and plasticity and high tensile strength. After surface carburization and subsequent heat treatment, the surface has very high hardness and strength, the core has good toughness and plasticity, and meanwhile, the alloy has good forging and cutting processing properties, the use temperature can reach 350 ℃, and the alloy has good comprehensive properties and becomes a representative of a new generation of aviation gear materials. The 16Cr3NiWMoVNbE alloy has complex components, adopts a traditional well carburizing furnace and an atmosphere carburizing furnace to carry out carburizing treatment, has the defects of difficult accurate control of the carburizing process, long carburizing time, large energy consumption, serious oxidation in a carburized layer, poor size and distribution uniformity of carbide in the carburized layer and difficult uniform carburization for components with complex shapes.

At present, no standard carburizing process for 16Cr3NiWMoVNbE steel exists in China, so that the process for carburizing meeting the requirements is the key problem at present. Chinese patent CN106319436A, vacuum carburizing furnace and carburizing method using the same, describes a device and process of a vacuum carburizing furnace, mainly focuses on the introduction of mechanical design, device structure and arrangement of the carburizing furnace, proposes an example of a production flow of a low-pressure vacuum carburizing furnace, and does not mention a specific carburizing process.

A control method of a low-pressure vacuum carburization process is related to multiple patent applications, such as a Chinese patent with the publication number of CN103556106A, a preparation method of a high-temperature vacuum carburization layer of a 1Cr17Ni2 alloy material, a Chinese patent with the publication number of CN107829064A, a vacuum carburization heat treatment process of a 12CrNi3A material, a Chinese patent with the publication number of CN102899603A, a low-pressure vacuum carburization method of an M50NiL material and the like, but the methods are respectively specific to different carburization materials and are not suitable for 16Cr3NiWMoVNbE materials with complex components.

Chinese patent CN105386043A, "a method for preventing tip over-penetration of narrow-toothed parts made of 16Cr3NiWMoVNbE material", proposes an atmosphere carburizing method in which partial copper plating changes primary carburization into secondary carburization by changing the traditional heat treatment process. The method can effectively prevent the excessive penetration of the tooth tops of the narrow-tooth parts made of the 16Cr3NiWMoVNbE materials, but because the process adopts atmosphere carburization, local copper plating and twice carburization, the process is too complicated, the process is not well controlled, the production process time is long, and the problems that the size and the distribution of carbide in a carburized layer are difficult to control exist.

The Chinese patent with publication number CN105296718A, "a heat treatment method for improving the hardness of the center of 16Cr3NiWMoVNbE steel after carburization", introduces an air cooling annealing process added before the commonly adopted heat treatment system: annealing is carried out at 720-750 ℃ for 4-20 hours. The process can fully separate out and spheroidize carbide, and the hardness value of the core part of the part meets the process requirement. The patent mainly focuses on the introduction of a carburizing process route, does not provide a carburizing production example of 16Cr3NiWMoVNbE steel, does not provide a concrete carburizing process for the 16Cr3NiWMoVNbE steel, and lacks a control method for key carburizing process parameters such as strong carburizing, diffusion concentration and the like.

Chinese patent publication No. CN102912282A, "secondary carburization process of 16Cr3NiWMoVNbE material", proposes a method of performing secondary carburization on a part by first protecting a non-carburized part, carburizing a carburized surface required for deep layer, continuously processing a part after carburization to form a carburized layer position required for shallow carburized layer depth, and then protecting other parts except the carburized part. The patent emphasizes on introducing a secondary carburization process of different parts of a part, adopts a traditional atmosphere carburization mode, and does not relate to how to solve the problems of long carburization time, high energy consumption, serious oxidation in a carburized layer and poor size and distribution uniformity of carbide in the carburized layer.

Conventional deformation control includes uniformity of temperature rise and fall, and a method is generally adopted: 1. the charging mode is controlled, and the uniformity of temperature rise is ensured; 2. when cooling, the medium is stirred uniformly, and the uniformity of the cooling speed is ensured. However, in conventional free quenching, it was found that even though these two methods are well controlled, our effect is not achieved. Because the product is too thin and only 1 mm, and is subjected to heat treatment for many times, and cold and heat are alternated for many times, the structural stress and the thermal stress are both larger.

Disclosure of Invention

The invention aims to provide a carburizing and quenching process for an ultrahigh-hardness gear, wherein a product obtained by adopting the carburizing process has better hardness and mechanical property, the surface hardness is HRC60-64, the core hardness is HRC42-46 and the tensile strength is 1270-; the yield strength is 1130-1210 MPa; elongation after fracture is 10-15%; the reduction of area is 50-60%, and the working temperature is higher, and the product can be used below 320 ℃.

The technical scheme of the invention is realized as follows:

the invention provides a carburizing and quenching process for an ultrahigh-hardness gear, which comprises the following steps of:

s1, area division: dividing the material into A, B, C three position areas according to the hardness of the 16Cr3NiWMoVNbE material;

s2, primary carburization: after the B, C position area is subjected to seepage-proofing protection, carburizing the A position area;

s3, secondary carburization: after the B site region is deprotected, the A, B site region is carburized;

s4, third carburizing: after the C position area is unprotected, the A, B, C position area is carburized and quenched to obtain a product;

the calculation method is as follows: l is₂＝6/5L-L₁(ii) a Wherein L is₁The mean value of the depth of penetration and L is the desired depth₂The depth of this time of replenishing infiltration.

As a further improvement of the present invention, the method for dividing the area in step S1 is: dividing the gear cone surface S1.1-1.2 and HV0.6 which is more than or equal to HRC60 into an A position area; dividing S0.8-0.9 and HV0.5 which are more than or equal to HRC60 on the outer circular surface of the gear into a B position area; the C position area is divided by S0.4-0.5, HV0.2 ≥ HRC60 on the inner circular surface of the gear.

As a further improvement of the invention, the anti-seepage protection method is local copper plating.

As a further improvement of the invention, the method for plating copper locally is to uniformly coat natural beeswax on the area needing anti-seepage protection in advance, and after the natural beeswax is solidified, plating copper locally on the surface.

As a further improvement of the invention, the method for removing the protection is to remove the natural beewax by boiled water and brush the beewax clean.

As a further improvement of the invention, the carburizing process comprises three stages of feeding and vacuumizing, stage temperature rising and pulse carburizing.

Specifically, the method comprises the following steps of vacuumizing: cleaning the surface of the sample to remove oil stains and dirt, and vacuumizing a hearth after feeding, wherein the absolute pressure is 5-30 Pa; step heating: heating and preserving the temperature of the sample along with the furnace in stages, and finally enabling the carburizing temperature to reach 800-; pulse carburizing: and setting the process control conditions of the strong penetration concentration value Uhigh, the diffusion concentration value Ulow, the pulse period and the time.

As a further improvement of the invention, the chemical components of the 16Cr3NiWMoVNbE material are calculated by mass fraction: 0.12 to 0.17 percent of C, 0.25 to 1.7 percent of Si, 0.2 to 1.0 percent of Mn, 2.0 to 3.0 percent of Cr2, 1.2 to 2.5 percent of Ni1.0 to 1.4 percent of W, 0.4 to 0.6 percent of Mo0.3 to 0.6 percent of V, 0.1 to 0.2 percent of Nb0.015 percent or less of P, 0.01 percent or less of S, 0.015 percent or less of Cu and the balance of Fe.

As a further improvement of the invention, the quenching method is vacuum oil quenching, the quenching temperature is 750-.

As a further improvement of the present invention, any one or more of the steps S2-S4 are repeated.

As a further improvement of the invention, the surface hardness of the product is HRC60-64, the core hardness is HRC42-46, and the tensile strength is 1270-1350 MPa; the yield strength is 1130-1210 MPa; elongation after fracture is 10-15%; the reduction of area is 50-60%.

Further comprising:

1. a normalizing and tempering process is carried out on the pre-heat treatment to ensure a tissue preparation before the final heat treatment,

2. in the cold working procedure, after the large allowance cutting, the stress relief procedure is immediately carried out to ensure that the stress minimum state distribution is reached before the final heat treatment,

3. when the temperature rises, the steel is preheated firstly when the steel has elasticity, and the temperature is equalized by about 700 ℃ in the heating process, and finally the steel is heated to the carburizing temperature, so that the temperature difference between the inside and the outside of the steel is smaller and more uniform when the temperature rises;

4. during cooling, the temperature of the medium is increased, and the thermal stress is continuously reduced on the premise of not influencing the structure performance; 5. and when the steel is stably tempered, a special flat plate is adopted to reduce the deformation.

The invention has the following beneficial effects: compared with the low-carbon alloy steel such as 20CrMnTi and the like of the original gear material, the invention adopts the new material 16Cr3NiWMoVNbE low-carbon high-alloy carburizing steel, and has the advantages that: 1. the service temperature of the product is obviously improved, and the product can adapt to more environments; 2. the hardness of the surface and the core is high, and the strength is improved; 3. the tissue is more stable at normal temperature; 4. all the indexes of mechanical property are excellent.

The product obtained by adopting the carburizing process has better hardness and mechanical property, the surface hardness is HRC60-64, the core hardness is HRC42-46 and the tensile strength is 1270-; the yield strength is 1130-1210 MPa; elongation after fracture is 10-15%; the reduction of area is 50-60%, and the working temperature is higher, and the product can be used below 320 ℃.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a distribution diagram of three carburizations of a gear according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

At present, the carburizing process of more than 80 percent of shaft and gear parts adopts a controllable atmosphere heat treatment technology, and has the problems of poor surface performance, serious deformation, energy consumption, row amplification and the like. Compared with the disadvantage of atmosphere carburization, the low-pressure vacuum carburization is to load the workpiece into a vacuum furnace, vacuumize and heat the workpiece to purify the furnace, introduce hydrocarbon (such as acetylene) to carburize the workpiece after reaching the carburization temperature, cut off the carburizing agent after a certain period of time, and then vacuumize the workpiece to diffuse the workpiece. The components are simple and do not contain oxygen, so that the problems of environmental pollution and internal oxidation are solved; the carburizing temperature is higher than that of the traditional atmosphere carburizing, so that the carburizing period is greatly shortened; safe operation and excellent integration performance with other devices. Particularly, the alloy shows excellent performance in specific fields, such as long oil nozzle needle valve bodies of blind hole parts, thin-layer carburization of pin shaft parts and the like. It is difficult to carburize these parts with a generally controlled atmosphere, but vacuum carburization can be easily solved.

The vacuum carburizing process is the most advanced carburizing process at present, can realize the non-intergranular oxidation and the precise control of the depth of a carburized layer, and meets the repeatability in a low error range and the selectivity of the surface carbon concentration. With the rail connection between various industries and the world in China, higher requirements are put forward on the part processing precision, and the vacuum carburizing technology with high efficiency, energy conservation and small pollution has wide application prospect at present with resource shortage and increasingly serious environmental pollution. Aiming at the control problem that a plurality of process parameters are comprehensively considered in the process of carrying out the low-pressure vacuum carburization on a 16Cr3NiWMoVNbE aviation material with complex components, a series of heat treatment procedures can be reasonably formulated to ensure the depth, hardness and uniformity of a carburized layer, wherein the heat treatment procedures comprise the control of key technical parameters such as high-temperature pretreatment temperature, vacuum carburization pressure and time, quenching temperature, ice-cooling treatment temperature and time, medium-temperature tempering temperature and the like, and especially the setting of process parameters such as a strong carburization concentration value U high, a diffusion concentration value U low, a pulse period and time and the like in the carburization process is more important.

Example 1

The steps of the carburizing and quenching process example of the ultra-high hardness gear are as follows: the 16Cr3NiWMoVNbE steel comprises 0.12 percent of C, 0.25 percent of Si, 0.2 percent of Mn, 2.0 percent of Cr, 1.2 percent of Ni, 1.0 percent of W, 0.4 percent of Mo0.3 percent of V, 0.1 percent of Nb0.015 percent or less of P, 0.01 percent or less of S, 0.015 percent or less of Cu and the balance of Fe. The preset depth of the infiltrated layer in the embodiment is 0.75 mm.

The method comprises the following steps:

s1, area division: a, B, C three position areas are divided according to the hardness of the material; dividing the gear cone surface S1.1-1.2 and HV0.6 which is more than or equal to HRC60 into an A position area; dividing S0.8-0.9 and HV0.5 which are more than or equal to HRC60 on the outer circular surface of the gear into a B position area; dividing S0.4-0.5 and HV0.2 which are more than or equal to HRC60 on the inner circular surface of the gear into a C position area;

s2, primary carburization: after the B, C position area is subjected to seepage-proofing protection, carburizing the A position area;

s3, secondary carburization: after the B site region is deprotected, the A, B site region is carburized;

s4, third carburizing: after the C position area is unprotected, the A, B, C position area is carburized and quenched to obtain a product;

the anti-seepage protection method is to plate copper locally, wherein natural beeswax is uniformly coated on the area needing anti-seepage protection in advance, and after the natural beeswax is solidified, the surface is plated with copper locally.

The deprotection method comprises removing natural Cera flava with boiled water and cleaning.

The carburizing process comprises three stages of feeding and vacuumizing, stage heating and pulse carburizing, and specifically comprises the following steps: cleaning the surface of the sample to remove oil stains and dirt, and vacuumizing a hearth after feeding, wherein the absolute pressure is 5 Pa; step heating: heating and preserving the temperature of the sample along with the furnace in stages, and finally enabling the carburizing temperature to reach 800 ℃; pulse carburizing: and setting the process control conditions of the strong penetration concentration value Uhigh, the diffusion concentration value Ulow, the pulse period and the time.

The calculation method is as follows: l is₂＝6/5L-L₁(ii) a Wherein L is₁The mean value of the depth of penetration and L is the desired depth₂The depth of this time of replenishing infiltration.

Analyzing the carburized sample, wherein the surface hardness is HRC60, the core hardness is HRC42, and the tensile strength is 1270 MPa; the yield strength is 1130 MPa; elongation after fracture 10%; reduction of area 50%, working temperature: below 320 ℃.

Example 2

The steps of the carburizing and quenching process example of the ultra-high hardness gear are as follows: the 16Cr3NiWMoVNbE steel comprises 0.17 percent of C, 1.7 percent of Si, 1.0 percent of Mn1, 3.0 percent of Cr3, 2.5 percent of Ni2, 1.4 percent of W, 0.6 percent of Mo0, 0.6 percent of V, 0.2 percent of Nb0, less than or equal to 0.015 percent of P, less than or equal to 0.01 percent of S, less than or equal to 0.015 percent of Cu and the balance of iron. The preset depth of the infiltrated layer in the embodiment is 0.9 mm.

The method comprises the following steps:

s1, area division: a, B, C three position areas are divided according to the hardness of the material; dividing the gear cone surface S1.1-1.2 and HV0.6 which is more than or equal to HRC60 into an A position area; dividing S0.8-0.9 and HV0.5 which are more than or equal to HRC60 on the outer circular surface of the gear into a B position area; dividing S0.4-0.5 and HV0.2 which are more than or equal to HRC60 on the inner circular surface of the gear into a C position area;

s2, primary carburization: after the B, C position area is subjected to seepage-proofing protection, carburizing the A position area;

s3, secondary carburization: after the B site region is deprotected, the A, B site region is carburized;

s4, third carburizing: after the C position area is unprotected, the A, B, C position area is carburized and quenched to obtain a product;

the anti-seepage protection method is to plate copper locally, wherein natural beeswax is uniformly coated on the area needing anti-seepage protection in advance, and after the natural beeswax is solidified, the surface is plated with copper locally.

The deprotection method comprises removing natural Cera flava with boiled water and cleaning.

The carburizing process comprises three stages of feeding and vacuumizing, stage heating and pulse carburizing, and specifically comprises the following steps: cleaning the surface of the sample to remove oil stains and dirt, and vacuumizing a hearth after feeding, wherein the absolute pressure is 30 Pa; step heating: heating and preserving the temperature of the sample in stages along with the furnace, and finally enabling the carburizing temperature to reach 1050 ℃; pulse carburizing: and setting the process control conditions of the strong penetration concentration value Uhigh, the diffusion concentration value Ulow, the pulse period and the time.

The calculation method is as follows: l is₂＝6/5L-L₁(ii) a Wherein L is₁The mean value of the depth of penetration and L is the desired depth₂The depth of this time of replenishing infiltration.

Analyzing the carburized sample, wherein the surface hardness is HRC64, the core hardness is HRC46, and the tensile strength is 1350 MPa; the yield strength is 1210 MPa; elongation after fracture 15%; reduction of area 60%, working temperature: below 320 ℃.

Example 3

The steps of the carburizing and quenching process example of the ultra-high hardness gear are as follows: the 16Cr3NiWMoVNbE steel comprises 0.15 percent of C, 1.2 percent of Si, 0.8 percent of Mn, 2.5 percent of Cr, 2 percent of Ni, 1.2 percent of W, 0.5 percent of Mo0.5 percent of V, 0.15 percent of Nb0.15 percent of P, less than or equal to 0.01 percent of S, less than or equal to 0.015 percent of Cu and the balance of Fe. In this embodiment, the preset depth of the infiltrated layer is 0.75-0.9 mm.

The method comprises the following steps:

s1, area division: a, B, C three position areas are divided according to the hardness of the material; dividing the gear cone surface S1.1-1.2 and HV0.6 which is more than or equal to HRC60 into an A position area; dividing S0.8-0.9 and HV0.5 which are more than or equal to HRC60 on the outer circular surface of the gear into a B position area; dividing S0.4-0.5 and HV0.2 which are more than or equal to HRC60 on the inner circular surface of the gear into a C position area;

s2, primary carburization: after the B, C position area is subjected to seepage-proofing protection, carburizing the A position area;

s3, secondary carburization: after the B site region is deprotected, the A, B site region is carburized;

s4, third carburizing: after the C position area is unprotected, the A, B, C position area is carburized and quenched to obtain a product;

the anti-seepage protection method is to plate copper locally, wherein natural beeswax is uniformly coated on the area needing anti-seepage protection in advance, and after the natural beeswax is solidified, the surface is plated with copper locally.

The deprotection method comprises removing natural Cera flava with boiled water and cleaning.

The carburizing process comprises three stages of feeding and vacuumizing, stage heating and pulse carburizing, and specifically comprises the following steps: cleaning the surface of the sample to remove oil stains and dirt, and vacuumizing a hearth after feeding, wherein the absolute pressure is 20 Pa; step heating: heating and preserving the sample in stages along with the furnace, and finally enabling the carburizing temperature to reach 950 ℃; pulse carburizing: and setting the process control conditions of the strong penetration concentration value Uhigh, the diffusion concentration value Ulow, the pulse period and the time.

The calculation method is as follows: l is₂＝6/5L-L₁(ii) a Wherein L is₁The mean value of the depth of penetration and L is the desired depth₂The depth of this time of replenishing infiltration.

Analyzing the carburized sample, wherein the surface hardness is HRC62, the core hardness is HRC44, and the tensile strength is 1300 MPa; the yield strength is 1170 MPa; elongation after fracture of 12%; reduction of area 55%, working temperature: below 320 ℃.

Comparative example

Raw materials: 20CrMnTi and other low-carbon alloy steels.

The conventional process comprises the following steps: in the traditional controlled atmosphere carburization process, the two-stage process is difficult to realize the control of the hardness gradient of the carburized layer, even under the condition of the multi-stage process, as the carbon potential adjustment needs longer response time, the carburization time is too long, the carburized layer tissue is difficult to control, network carbide is often formed, the hardness distribution fluctuation is larger, and the generation of the network carbide at the crystal boundary further prevents the activated carbon from diffusing to the inside of the material, so that the depth of the carburized layer cannot be ensured. Therefore, for a complex component system material, such as the material indicated in example 1, the conventional controlled atmosphere carburizing period is long, the energy consumption is high, and the goal of accurately controlling the hardness gradient of a carburized layer is difficult to achieve.

Analyzing the carburized sample, wherein the surface hardness is HRC58, the core hardness is HRC35, and the tensile strength is 1080 MPa; the yield strength is 850 MPa; elongation after fracture 10%; reduction of area 45%, working temperature: below 220 c, excess temperature reduces the strength, thereby reducing contact fatigue strength and bending fatigue strength.

Compared with the prior art, compared with the low-carbon alloy steel such as the original gear material 20CrMnTi and the like, the invention adopts the new material 16Cr3NiWMoVNbE low-carbon high-alloy carburizing steel, and has the following advantages: 1. the service temperature of the product is obviously improved, and the product can adapt to more environments; 2. the hardness of the surface and the core is high, and the strength is improved; 3. the tissue is more stable at normal temperature; 4. all the indexes of mechanical property are excellent.

The product obtained by adopting the carburizing process has better hardness and mechanical property, the surface hardness is HRC60-64, the core hardness is HRC42-46 and the tensile strength is 1270-; the yield strength is 1130-1210 MPa; elongation after fracture is 10-15%; the reduction of area is 50-60%, and the working temperature is higher, and the product can be used below 320 ℃.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.