Method for processing mn-cr gear steel, gear steel, gear, end product

Abstract

The application relates to a processing method of MnCr gear steel, gear steel, a gear and an end product, and particularly relates to the field of gear steel, and the processing method comprises the following steps: sequentially performing rolling and heat treatment on a MnCr gear steel casting blank; the final rolling temperature of the rolling is 850-900 DEG C; the heat treatment comprises the following steps: sequentially performing heat preservation, first cooling and second cooling; the cooling rate of the first cooling is less than that of the second cooling. The processing method provided by the application can significantly reduce the bainite content of the core of the gear steel by performing a specific processing process on the MnCr gear steel casting blank, so that the hardness difference between the core and the surface is reduced, and the use performance of the gear steel is improved.

Description

Technical Field

[0001] This invention relates to the field of gear steel, specifically to a processing method for MnCr series gear steel, gear steel, gears, and end products. Background Technology

[0002] Currently, MnCr series low-carbon alloy gear steel is commonly used to machine automotive gearbox gears.

[0003] For example, CN107214485A discloses a manufacturing process for a high-wear-resistant automotive gear pair. The automotive gear pair is formed from 20MnCr5 steel. The gear pair includes a gear shaft workpiece and a gear ring workpiece. Taking advantage of the high strength and toughness of 20MnCr5 steel, the gear shaft workpiece and gear ring workpiece are formed by multiple stamping processes. Then, taking advantage of the good hardenability, small quenching deformation, and performance improvement through heat treatment of 20MnCr5 steel, a specific heat treatment combination process is applied to the gear shaft workpiece and gear ring workpiece to optimize the austenite grain structure within the workpiece.

[0004] CN116445807A discloses a narrow-hardenability, high-temperature carburizing MnCr gear steel, which contains Fe and unavoidable impurities, and also contains the following chemical elements in the following mass percentages: C: 0.175-0.195%, Si: 0.17-0.25%, Mn: 1.27-1.35%, S: 0.01-0.025%, Cr: 0.92-1.0%, Mo: 0.08-0.14%, Al: 0.01-0.03%, N: 0.008-0.014%, Nb: 0.008-0.025%. The manufacturing method includes the following steps: (1) smelting; (2) continuous casting; (3) heating: the ingot heating temperature is 1130-1250℃, and the holding time is 4-12h; (4) rolling: the ingot is processed into finished size by two-fire forming process, and then air-cooled or slowly cooled to room temperature in the heat preservation pit; (5) straightening.

[0005] However, in recent years, the requirements for automobile operating noise, vibration and acoustic roughness, fatigue strength, etc. have become increasingly stringent, and the performance indicators of gear steel have also become higher and higher. However, the core bainite of the current MnCr gear steel still has defects that are difficult to eliminate, resulting in poor mechanical properties of MnCr gear steel. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a processing method for MnCr gear steel, gear steel, gear, and end product, so as to solve the defect that the core bainite of MnCr gear steel is still difficult to eliminate, resulting in poor mechanical properties of MnCr gear steel.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for processing MnCr gear steel, the method comprising:

[0009] The MnCr series gear steel billets were rolled and heat-treated sequentially.

[0010] The final rolling temperature is 850-900℃;

[0011] The heat treatment includes: sequential heat preservation, first cooling, and second cooling;

[0012] The cooling rate of the first cooling is less than the cooling rate of the second cooling.

[0013] The processing method provided by this invention can significantly reduce the bainite content in the core of MnCr gear steel by performing a specific processing on the cast billet, thereby reducing the hardness difference between the core and the surface and improving the performance of the gear steel.

[0014] As a preferred technical solution of the present invention, the preheating of the rolling process includes: a preheating section, a heating section and a homogenizing section performed sequentially.

[0015] Preferably, the heat preservation temperature of the preheating section is 800-950℃.

[0016] Preferably, the heat preservation time of the preheating section is 70-90 minutes.

[0017] Preferably, the heat preservation temperature of the heating section is 1120-1270℃.

[0018] Preferably, the heat preservation time of the heating section is 70-90 minutes.

[0019] Preferably, the heat preservation temperature of the heat spreader is 1120-1250℃.

[0020] Preferably, the heat preservation time of the heat equalization section is 60-80 minutes.

[0021] As a preferred embodiment of the present invention, the initial rolling temperature is 1100-1150℃.

[0022] Preferably, the rolling process controls the single-pass pressing amount to be 10-15 mm.

[0023] As a preferred embodiment of the present invention, the heating rate of the heat preservation is ≤80℃ / h.

[0024] Preferably, the insulation temperature is 740-760℃.

[0025] Preferably, the heat preservation time is 3.5-7 hours.

[0026] As a preferred technical solution of the present invention, the first cooling method includes: furnace cooling.

[0027] Preferably, the endpoint temperature of the first cooling is 430-450°C.

[0028] As a preferred technical solution of the present invention, the second cooling method includes: air cooling.

[0029] Preferably, the endpoint temperature of the second cooling is 10-40°C.

[0030] Secondly, the present invention provides a gear steel, which is obtained by processing using the processing method described in the first aspect.

[0031] As a preferred embodiment of the present invention, the gear steel comprises, by weight percentage:

[0032] C 0.17-0.22%, Si 0.1-0.3%, Mn 1-1.3%, P≤0.035%, S 0.025-0.035%, Cr 0.9-1.1%, Ni≤0.3%, Al 0.03-0.05%, O≤0.02%, N 0.007-0.015%, H≤0.0002%, balance Fe and unavoidable impurities.

[0033] Thirdly, the present invention provides a gear, which is manufactured from gear steel as described in the second aspect.

[0034] Fourthly, the present invention provides a terminal product, the terminal product comprising: the gear as described in the third aspect.

[0035] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0036] The processing method provided by this invention, through the design of the heat treatment process and the combination of specific heat preservation and cooling processes, can significantly reduce the bainite content in the gear steel core and increase the surface hardness, thereby significantly reducing the hardness difference between the core and the surface, reducing deformation in subsequent cold working processes, thus improving the performance of gear steel and ensuring the high efficiency of gear processing.

[0037] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0038] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0039] Currently, MnCr-based low-carbon alloy gear steel is commonly used for machining automotive gearbox gears. However, in recent years, due to increasingly stringent requirements for automotive operating noise, vibration and acoustic roughness, and fatigue strength, the performance indicators of gear steel have become increasingly demanding. However, the core bainite in current MnCr-based gear steel remains difficult to eliminate, resulting in poor mechanical properties. Therefore, this invention optimizes the machining process of MnCr-based gear steel to eliminate the bainite in the gear steel core, thereby ensuring the performance of MnCr-based gear steel. Specifically, the following is a detailed explanation:

[0040] I. This embodiment provides a processing method for MnCr series gear steel, the processing method including:

[0041] The MnCr series gear steel billets were rolled and heat-treated sequentially.

[0042] The final rolling temperature is 850-900℃;

[0043] The heat treatment includes: sequential heat preservation, first cooling, and second cooling;

[0044] The cooling rate of the first cooling is less than the cooling rate of the second cooling.

[0045] In this invention, the MnCr gear steel billet is obtained by following conventional smelting processes in the art.

[0046] In this invention, the final rolling temperature is 850-900℃, for example, it can be 850℃, 855℃, 860℃, 865℃, 870℃, 875℃, 880℃, 885℃, 890℃, 895℃ or 900℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also acceptable.

[0047] In this invention, heat treatment can be implemented by selecting appropriate equipment according to conventional requirements in the field, such as a box furnace.

[0048] In this invention, a cutting process can also be performed during rolling and heat treatment. For example, the length is arranged closely on the cooling bed, and after being placed on the cooling bed, it is rapidly stepped. The shearing temperature is 690℃-750℃ (the tail shear is greater than 650℃). After shearing, it is collected using a rapid collection device and the temperature is maintained at 590℃-630℃. Then, it is cooled to room temperature and heat-treated.

[0049] The preheating process of the rolling process includes a preheating section, a heating section, and a homogenizing section, which are carried out sequentially.

[0050] The heat preservation temperature of the preheating section is 800-950℃, for example, it can be 800℃, 815℃, 830℃, 845℃, 860℃, 875℃, 890℃, 905℃, 920℃, 935℃ or 950℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0051] The heat preservation time of the preheating section is 70-90 minutes, for example, it can be 70 minutes, 72 minutes, 74 minutes, 76 minutes, 78 minutes, 80 minutes, 82 minutes, 84 minutes, 86 minutes, 88 minutes or 90 minutes, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0052] The heat preservation temperature of the heating section is 1120-1270℃, for example, it can be 1120℃, 1135℃, 1150℃, 1165℃, 1180℃, 1195℃, 1210℃, 1225℃, 1240℃, 1255℃ or 1270℃, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0053] The holding time of the heating section is 70-90 minutes, for example, it can be 70 minutes, 72 minutes, 74 minutes, 76 minutes, 78 minutes, 80 minutes, 82 minutes, 84 minutes, 86 minutes, 88 minutes or 90 minutes, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0054] The heat preservation temperature of the heat spreader is 1120-1250℃, for example, it can be 1120℃, 1133℃, 1146℃, 1159℃, 1172℃, 1185℃, 1198℃, 1211℃, 1224℃, 1237℃ or 1250℃, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0055] The heat preservation time of the heat-spreading section is 60-80 minutes, for example, it can be 60 minutes, 62 minutes, 64 minutes, 66 minutes, 68 minutes, 70 minutes, 72 minutes, 74 minutes, 76 minutes, 78 minutes or 80 minutes, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0056] The initial rolling temperature is 1100-1150℃, for example, it can be 1100℃, 1105℃, 1110℃, 1115℃, 1120℃, 1125℃, 1130℃, 1135℃, 1140℃, 1145℃ or 1150℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0057] The rolling process controls the single-pass pressing amount to be 10-15mm, for example, it can be 10mm, 10.5mm, 11mm, 11.5mm, 12mm, 12.5mm, 13mm, 13.5mm, 14mm, 14.5mm or 15mm, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0058] The heating rate of the heat preservation is ≤80℃ / h, for example, it can be 80℃ / h, 78℃ / h, 76℃ / h, 74℃ / h, 72℃ / h, 70℃ / h, 68℃ / h, 66℃ / h, 64℃ / h, 62℃ / h or 60℃ / h, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0059] The insulation temperature is 740-760℃, for example, it can be 740℃, 742℃, 744℃, 746℃, 748℃, 750℃, 752℃, 754℃, 756℃, 758℃ or 760℃, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0060] The heat preservation time is 3.5-7 hours, for example, it can be 3.5 hours, 3.85 hours, 4.2 hours, 4.55 hours, 4.9 hours, 5.25 hours, 5.6 hours, 5.95 hours, 6.3 hours, 6.65 hours or 7 hours, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0061] The first cooling method includes: furnace-side cooling.

[0062] The endpoint temperature of the first cooling is 430-450℃, for example, it can be 430℃, 432℃, 434℃, 436℃, 438℃, 440℃, 442℃, 444℃, 446℃, 448℃ or 450℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0063] The second cooling method includes air cooling.

[0064] The endpoint temperature of the second cooling is 10-40℃, for example, it can be 10℃, 13℃, 16℃, 19℃, 22℃, 25℃, 28℃, 31℃, 34℃, 37℃ or 40℃, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0065] II. This embodiment provides a gear steel, which is obtained by processing the gear steel using the processing method of the present invention.

[0066] The gear steel, by mass percentage, comprises:

[0067] C 0.17-0.22%, Si 0.1-0.3%, Mn 1-1.3%, P≤0.035%, S 0.025-0.035%, Cr 0.9-1.1%, Ni≤0.3%, Al 0.03-0.05%, O≤0.02%, N 0.007-0.015%, H≤0.0002%, balance Fe and unavoidable impurities.

[0068] In this invention, the carbon element in the gear steel is 0.17-0.22% by mass, for example, it can be 0.17%, 0.175%, 0.18%, 0.185%, 0.19%, 0.195%, 0.2%, 0.205%, 0.21%, 0.215%, or 0.22%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0069] In this invention, the Si element in the gear steel is 0.1-0.3% by mass, for example, it can be 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28% or 0.3%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0070] In this invention, the Mn element in the gear steel is 1-1.3% by mass, for example, it can be 1%, 1.03%, 1.06%, 1.09%, 1.12%, 1.15%, 1.18%, 1.21%, 1.24%, 1.27% or 1.3%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0071] In this invention, the phosphorus (P) element in the gear steel is ≤0.035% by mass percentage. For example, it can be 0.035%, 0.0335%, 0.032%, 0.0305%, 0.029%, 0.0275%, 0.026%, 0.0245%, 0.023%, 0.0215%, or 0.02%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0072] In this invention, the sulfur element in the gear steel is 0.025-0.035% by mass percentage, for example, it can be 0.025%, 0.026%, 0.027%, 0.028%, 0.029%, 0.03%, 0.031%, 0.032%, 0.033%, 0.034% or 0.035%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0073] In this invention, the Cr element in the gear steel is 0.9-1.1% by mass, for example, it can be 0.9%, 0.92%, 0.94%, 0.96%, 0.98%, 1%, 1.02%, 1.04%, 1.06%, 1.08% or 1.1%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0074] In this invention, the Ni element in the gear steel is ≤0.3% by mass percentage. For example, it can be 0.3%, 0.271%, 0.242%, 0.213%, 0.184%, 0.155%, 0.126%, 0.097%, 0.068%, 0.039%, or 0.01%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0075] In this invention, the Al element in the gear steel is 0.03-0.05% by mass percentage, for example, it can be 0.03%, 0.032%, 0.034%, 0.036%, 0.038%, 0.04%, 0.042%, 0.044%, 0.046%, 0.048% or 0.05%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0076] In this invention, the oxygen element in the gear steel is ≤0.02% by mass percentage. For example, it can be 0.02%, 0.01812%, 0.01624%, 0.01436%, 0.01248%, 0.0106%, 0.00872%, 0.00684%, 0.00496%, 0.00308%, or 0.0012%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0077] In this invention, the nitrogen element in the gear steel is 0.007-0.015% by mass, for example, it can be 0.007%, 0.0078%, 0.0086%, 0.0094%, 0.0102%, 0.011%, 0.0118%, 0.0126%, 0.0134%, 0.0142%, or 0.015%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0078] In this invention, the hydrogen element in the gear steel is ≤0.0002% by mass percentage. For example, it can be 0.0002%, 0.000192%, 0.000184%, 0.000176%, 0.000168%, 0.00016%, 0.000152%, 0.000144%, 0.000136%, 0.000128%, or 0.00012%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0079] III. This embodiment provides a gear, which is processed using the gear steel of the present invention.

[0080] In this invention, a gear refers to a mechanical component with teeth on its rim that can continuously mesh to transmit motion and power. Gears can be classified by shape as cylindrical gears, bevel gears, non-circular gears, racks, and worm gears; or by tooth line shape as spur gears, helical gears, herringbone gears, and curved gears.

[0081] IV. This embodiment provides a terminal product, which includes: the gear of the present invention.

[0082] In this invention, the end products containing gears can be gearboxes (planetary gear sets, synchronizer gears), differentials (hypoid gears), engine timing systems, and vehicles containing at least one of the aforementioned products, as well as speed reducers, metallurgical and mining equipment, home appliances, and agricultural machinery such as harvesters and seeders.

[0083] V. To illustrate the superior properties of the gear steel obtained by the processing method of MnCr gear steel provided by the present invention, the following examples are used for explanation:

[0084] The mass percentage composition of the MnCr series gear steel billets used in the following examples is as follows:

[0085] C 0.18%, Si 0.25%, Mn 1.14%, P 0.02%, S 0.03%, Cr 1.05%, Ni 0.08%, Al 0.038%, O 0.0012%, N 0.011%, H 0.00012%, balance Fe and unavoidable impurities.

[0086] Example 1

[0087] This embodiment provides a method for machining MnCr gear steel, the method comprising:

[0088] The MnCr series gear steel billets were rolled and heat-treated sequentially.

[0089] The preheating process for rolling includes: a preheating section, a heating section, and a soaking section performed sequentially; the holding temperature of the preheating section is 850℃; the holding time of the preheating section is 80 min; the holding temperature of the heating section is 1150℃; the holding time of the heating section is 80 min; the holding temperature of the soaking section is 1150℃; the holding time of the soaking section is 70 min; the initial rolling temperature is 1130℃; the final rolling temperature is 860℃; and the single-pass reduction is controlled at 12 mm during rolling.

[0090] The heat treatment includes: sequential holding, first cooling, and second cooling; the cooling rate of the first cooling is less than the cooling rate of the second cooling; the heating rate of the holding is 60℃ / h; the holding temperature of the holding is 750℃; the holding time of the holding is 5h; the first cooling is furnace cooling; the final temperature of the first cooling is 440℃; the second cooling is air cooling; the final temperature of the second cooling is 20℃.

[0091] Example 2

[0092] This embodiment provides a method for machining MnCr gear steel, the method comprising:

[0093] The MnCr series gear steel billets were rolled and heat-treated sequentially.

[0094] The preheating process for rolling includes: a preheating section, a heating section, and a soaking section performed sequentially; the holding temperature of the preheating section is 900℃; the holding time of the preheating section is 85 min; the holding temperature of the heating section is 1200℃; the holding time of the heating section is 75 min; the holding temperature of the soaking section is 1200℃; the holding time of the soaking section is 75 min; the initial rolling temperature is 1140℃; the final rolling temperature is 880℃; and the single-pass reduction is controlled at 13 mm during rolling.

[0095] The heat treatment includes: sequential holding, first cooling, and second cooling; the cooling rate of the first cooling is less than the cooling rate of the second cooling; the heating rate of the holding is 70℃ / h; the holding temperature of the holding is 755℃; the holding time of the holding is 5.5h; the first cooling is furnace cooling; the final temperature of the first cooling is 435℃; the second cooling is air cooling; the final temperature of the second cooling is 30℃.

[0096] Example 3

[0097] This embodiment provides a method for machining MnCr gear steel, the method comprising:

[0098] The MnCr series gear steel billets were rolled and heat-treated sequentially.

[0099] The preheating process for rolling includes: a preheating section, a heating section, and a soaking section performed sequentially; the holding temperature of the preheating section is 800℃; the holding time of the preheating section is 70 min; the holding temperature of the heating section is 1120℃; the holding time of the heating section is 70 min; the holding temperature of the soaking section is 1120℃; the holding time of the soaking section is 60 min; the initial rolling temperature is 1100℃; the final rolling temperature is 850℃; and the single-pass reduction is controlled at 10 mm during rolling.

[0100] The heat treatment includes: sequential holding, first cooling, and second cooling; the cooling rate of the first cooling is less than the cooling rate of the second cooling; the heating rate of the holding is 80℃ / h; the holding temperature of the holding is 740℃; the holding time of the holding is 3.5h; the first cooling method includes: furnace cooling; the final temperature of the first cooling is 430℃; the second cooling method includes: air cooling; the final temperature of the second cooling is 10℃.

[0101] Example 4

[0102] This embodiment provides a method for machining MnCr gear steel, the method comprising:

[0103] The MnCr series gear steel billets were rolled and heat-treated sequentially.

[0104] The preheating process for rolling includes: a preheating section, a heating section, and a soaking section performed sequentially; the holding temperature of the preheating section is 950℃; the holding time of the preheating section is 90 min; the holding temperature of the heating section is 1250℃; the holding time of the heating section is 90 min; the holding temperature of the soaking section is 1250℃; the holding time of the soaking section is 80 min; the initial rolling temperature is 1150℃; the final rolling temperature is 900℃; and the single-pass reduction is controlled at 15 mm during rolling.

[0105] The heat treatment includes: sequential holding, first cooling, and second cooling; the cooling rate of the first cooling is less than the cooling rate of the second cooling; the heating rate of the holding is 70℃ / h; the holding temperature of the holding is 760℃; the holding time of the holding is 7h; the first cooling method includes: furnace cooling; the final temperature of the first cooling is 450℃; the second cooling method includes: air cooling; the final temperature of the second cooling is 40℃.

[0106] Example 5

[0107] The only difference from Example 1 is that the initial rolling temperature is 1080°C.

[0108] Example 6

[0109] The only difference from Example 1 is that the insulation temperature is 700°C.

[0110] Example 7

[0111] The only difference from Example 1 is that the insulation temperature is 800°C.

[0112] Example 8

[0113] The only difference from Example 1 is that the final temperature of the first cooling is 480°C.

[0114] Example 9

[0115] The only difference from Example 1 is that the second cooling method is oil cooling.

[0116] Comparative Example 1

[0117] The only difference from Example 1 is that the final rolling temperature is 800°C.

[0118] Comparative Example 2

[0119] The only difference from Example 1 is that the first cooling method is air cooling.

[0120] Comparative Example 3

[0121] The only difference from Example 1 is that the second cooling method is furnace cooling.

[0122] Comparative Example 4

[0123] The only difference from Example 1 is that the first cooling method is oil cooling.

[0124] The performance of the gear steels obtained in the above embodiments and comparative examples was analyzed, and the results are shown in Table 1 below.

[0125] Table 1

[0126]

[0127] In the table: Hardness testing is conducted according to GB / T 231.1-2018 Metallic Materials Brinell Hardness Test - Part 1: Test Method. The core refers to the area extending outward from the geometric center of the bar cross section to a radius of 30%-50%, specifically the 50% area. This is the core area where the bar solidifies last, cools the slowest, and deforms the least during solidification, rolling, and heat treatment.

[0128] As shown in Table 1, the solution provided by this invention can significantly improve the problem of uneven hardness distribution in the bar cross-section by optimizing the process, so that the hardness of both the core and the surface is within a reasonable and stable process range, with small data dispersion and higher product quality stability. The optimized process effectively reduces the excessive hardness of the bar core, narrows the core-to-surface hardness gradient, and eliminates the structural defect of "hard core and soft surface" in conventional processes, greatly improving the uniformity of the bar cross-section structure. The optimized hardness matching relationship is more suitable for the actual service conditions of the bar, solving the problems of insufficient core toughness and easy cracking, and improving the shortcomings of surface strength and wear resistance. The comprehensive mechanical properties and service reliability of the product are significantly better than those of products made with conventional processes. The surface hardness of the product is ≥175HB, and the core hardness is ≥213HB. Under the preferred scheme, the surface hardness and core hardness are even closer, with the surface hardness ≥187HB and the core hardness ≥213HB.

[0129] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0130] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0131] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for processing MnCr gear steel, characterized in that, The processing method includes: The MnCr series gear steel billets were rolled and heat-treated sequentially. The final rolling temperature is 850-900℃; The heat treatment includes: sequential heat preservation, first cooling, and second cooling; The cooling rate of the first cooling is less than the cooling rate of the second cooling.

2. The processing method as described in claim 1, characterized in that, The preheating of the rolling process includes: a preheating section, a heating section, and a soaking section performed sequentially; Preferably, the heat preservation temperature of the preheating section is 800-950℃; Preferably, the heat preservation time of the preheating section is 70-90 minutes; Preferably, the heat preservation temperature of the heating section is 1120-1270℃; Preferably, the heat preservation time of the heating section is 70-90 minutes; Preferably, the heat preservation temperature of the heat spreader is 1120-1250℃; Preferably, the heat preservation time of the heat equalization section is 60-80 minutes.

3. The processing method as described in claim 1, characterized in that, The initial rolling temperature is 1100-1150℃; Preferably, the rolling process controls the single-pass pressing amount to be 10-15 mm.

4. The processing method as described in claim 1, characterized in that, The heating rate of the insulation is ≤80℃ / h; Preferably, the insulation temperature is 740-760℃; Preferably, the heat preservation time is 3.5-7 hours.

5. The processing method as described in claim 1, characterized in that, The first cooling method includes: furnace cooling; Preferably, the endpoint temperature of the first cooling is 430-450°C.

6. The processing method as described in claim 1, characterized in that, The second cooling method includes: air cooling; Preferably, the endpoint temperature of the second cooling is 10-40°C.

7. A gear steel, characterized in that, The gear steel is obtained by processing using the processing method described in any one of claims 1-6.

8. The gear steel as described in claim 7, characterized in that, The gear steel comprises, by mass percentage: C 0.17-0.22%, Si 0.1-0.3%, Mn 1-1.3%, P≤0.035%, S 0.025-0.035%, Cr 0.9-1.1%, Ni≤0.3%, Al 0.03-0.05%, O≤0.02%, N 0.007-0.015%, H≤0.0002%, balance Fe and unavoidable impurities.

9. A gear, characterized in that, The gear is manufactured from the gear steel as described in claim 7 or 8.

10. A terminal product, characterized in that, The end product includes: the gear as described in claim 9.

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