CN109971923B - A kind of determination method of steel alloy water quenching technology - Google Patents

Abstract

The invention provides a method for determining the water quenching process of alloy steel, which is used to determine the water-air alternate time-controlled quenching and cooling process and the selection of the primary water quenching process for various materials; the method includes: S1: performing quenching and cooling on the workpiece Analysis, according to the distance between the required performance part of the workpiece and the position of the core, obtain the tissue composition of the required performance part; S2: Obtain the steel number and size range of the quenched and cooled workpiece, according to the steel number, size range and required performance part of the quenched and cooled workpiece , select the water-air alternate time-controlled quenching and cooling process or the one-time water quenching process; S3: implement the process through specific quenching and cooling operations according to the selected process. The invention can guide process designers to choose the correct alloy steel water quenching process, avoiding blindness in selecting the process.

Description

A method for determining the water quenching process of alloy steel

technical field

The invention relates to the field of steel heat treatment, in particular to a method for determining a water quenching process of alloy steel.

Background technique

Quenching and tempering is a traditional process, which heats alloy steel parts to the austenite zone, then quenches and cools to room temperature to obtain martensite or bainite structure, and then tempers at a suitable temperature to obtain tempered Martensite or tempered bainite structure. For alloy steel quenching, oil is generally used as the quenching medium to avoid cracking. The problem is that the mechanical properties of oil quenching are much lower than that of water quenching. At the same time, oil quenching has the risk of oil smoke pollution and fire. Therefore, water quenching of alloy steel parts is the future development direction.

After searching, it was found that the invention patent ZL 201310327206.0 is a method for formulating a water-air alternate time-controlled quenching and cooling process, which provides a method for formulating a water-air alternate time-controlled quenching and cooling process (hereinafter referred to as: ATQ process). The ATQ process divides the quenching and cooling into three stages: the first stage is the pre-cooling stage, the second stage is the water-air alternate quenching and cooling stage, and the third stage is the natural air cooling stage. In the second stage of water-air alternate quenching and cooling, the alloy steel is divided into a controlled cooling rate area and a slow cooling area along the section from the surface to the center, that is, the controlled cooling rate area is from the surface of the alloy steel part to the required performance part. , from the required performance part to the core is the slow cooling area; the purpose of controlled cooling rate zone cooling is to obtain the expected structure by controlling the cooling rate and then meet the mechanical performance requirements, and the purpose of slow cooling zone cooling is to avoid controlled cooling by slow cooling The martensite or bainite structure that has been transformed in the velocity region has been tempered due to excessive temperature rise.

After searching, it was found that the patent application 201910247450.3 is an optimization method for the water quenching process of alloy steel, and an optimization method for the water quenching process of alloy steel is given (hereinafter referred to as: one-time water quenching process or HTQ process). Process implementation steps:

Step 1: According to the performance requirements of the alloy steel parts, predict the structure and composition of the required performance parts;

Step 2: Determine the temperature to which the structure is to be cooled, that is, the predetermined temperature, by means of the isothermal transformation cooling curve of the alloy steel material;

Step 3: Divide the alloy steel part along the section from the surface to the center into a rapid cooling area and a slow cooling area relying on bulk heat transfer; wherein, the rapid cooling area is from the surface of the alloy steel part to the required performance part or a deeper part; the slow cooling zone is the required performance part or the deeper part to the center;

Step 4: Determine the water cooling time for the rapid cooling area to drop to the predetermined temperature by means of numerical simulation, and optimize the water cooling time in combination with the return temperature of the required performance part and the surface stress state;

According to the numerical simulation of the temperature change in the quenching and cooling process, analyze the temperature rise of the surface layer of alloy steel parts in the subsequent air cooling process, and determine the reduction of the rapid cooling area based on the principle that the return temperature of the performance part does not exceed the tempering temperature or the predetermined temperature. The water cooling time to the predetermined temperature; at the same time, according to the numerical simulation analysis of the surface stress state of the rapid cooling area before the water cooling time determined above, the pre-cooling time of the rapid cooling area before the rapid cooling and the time for the rapid cooling area to drop to the predetermined temperature are respectively adjusted. The water cooling time makes the tensile stress value of the surface layer lower than the breaking resistance of the material or presents a compressive stress state.

Step 5: Repeatedly optimize the pre-cooling time and the water-cooling time in the fourth step, and finally obtain the water-quenching process of the alloy steel, ie: the best pre-cooling time and the water-cooling time.

The above-mentioned patents do not specify what kind of hardenable alloy steel is suitable, what size range and workpieces require performance parts, that is, no strategy for selecting the above two processes is given.

Contents of the invention

In view of the defects in the prior art, the object of the present invention is to provide a method for determining the water quenching process of alloy steel.

In order to achieve the purpose of the above invention, the present invention provides a method for determining the water quenching process of alloy steel, which is used to determine the selection of the water-air alternate time-controlled quenching and cooling process and the primary water quenching process for various materials; the method includes:

S1: analyze the quenched and cooled workpiece, and obtain the tissue composition of the required performance part according to the distance from the center of the required performance part of the workpiece;

S2: Obtain the steel number and size range of the quenched and cooled workpiece, and select a water-air alternately controlled quenching and cooling process or a water quenching process according to the steel number, size range, and required performance parts of the quenched and cooled workpiece;

The scope of application of the water-air alternate time-controlled quenching and cooling process includes high-hardenability alloy steel and workpieces requiring high performance in the deep layer, and/or medium-low hardenability alloy steel and workpieces requiring high mechanical properties in the surface layer workpiece;

The scope of application of the primary water quenching process includes medium and low permeability alloy steels and workpieces requiring high performance in deep layers, and/or high hardenability alloy steels and workpieces requiring high mechanical properties in surface layers;

S3: Implement the process through specific quenching and cooling operations according to the selected process.

Preferably, according to the scope of application of the water-air alternating time-controlled quenching and cooling process, the high hardenability alloy steel material has sufficient hardenability characteristics, and through multiple water-air alternating processes, the required performance parts can reach The required organization; and/or using the low-hardenability alloy steel material with low hardenability and required performance parts on the surface layer, the surface layer can be obtained through the first immersion liquid to obtain the required structure, and then the air-water-air The function of alternating cooling is to ensure that the reheating temperature of the structure whose surface layer has undergone martensite or bainite transformation does not exceed its tempering temperature;

Obtain the specific steel grade, size range, and required performance parts of the quenched and cooled workpiece suitable for the water-air alternate time-controlled quenching and cooling process.

Preferably, the steel grade, size range, and required performance parts of the high-hardenability alloy steel that adopts the water-air alternate time-controlled quenching and cooling process and the workpiece that requires high performance in the deep layer are obtained, as shown in Table 1;

Preferably, the steel grade, size range, and required performance parts of the steel grade, size range, and required performance parts of the medium-low hardenability alloy steel that adopts the water-air alternate time-controlled quenching and cooling process and the workpiece that requires high mechanical properties at the surface position are obtained, as shown in Table 2;

steel number DI value (mm) (reference) Size range(mm) Performance area or requirement (R-radius) Product Category 42CrMo 112 φ200-300 0.2R from the surface axis 35CrMo 74 φ150-250 0.2R from the surface axis 40C 54 φ100-200 0.2R from the surface axis

.

Preferably, according to the scope of application of the one-time water quenching process, using a workpiece with a medium-low permeability alloy steel material with low hardenability, a relatively deep position and a small cross-sectional size, a longer time immersion solution is used to achieve the required Obtain the required structure in the performance part, and ensure that the reheating temperature of the structure that has undergone martensite or bainite transformation in the required performance part in the subsequent air cooling process does not exceed its tempering temperature; and/or use high hardenability materials, For workpieces that require performance on the surface and with small cross-sectional dimensions, the required structure can be obtained by immersing the required performance parts once, so as to ensure that the martensite or bainite transformation of the required performance parts will not be caused in the subsequent air cooling process The return temperature of the tissue exceeds its tempering temperature; at the same time, control the tissue transformation of the parts below the required performance, so as to obtain the pearlite structure as the best, and realize the stress distribution of thermal stress type, that is, the surface layer is compressive stress, and the core is tensile stress;

Obtain the steel grade, size range, and required performance parts of the quenched and cooled workpiece suitable for the primary water quenching process.

Preferably, the steel number, size range, and required performance parts of the steel grade, size range, and required performance parts of the medium-low-permeability alloy steel that adopts a water quenching process and the workpiece that requires high performance in the deep layer are obtained, as shown in Table 3;

steel number DI value (mm) (reference) Size range(mm) Performance area or requirement (R-radius) Product example 42CrMo 112 φ150-250 0.5R from the surface axis 35CrMo 74 φ100-200 0.5R from the surface axis 40C 54 φ80-150 0.5R from the surface axis

.

Preferably, the steel number, size range, and required performance parts of the high-hardenability alloy steel that adopts a water quenching process and the workpiece that requires high mechanical properties at the surface position are obtained, as shown in Table 4;

steel number DI value (mm) (reference) Size range(mm) Performance area or requirement (R-radius) Product Category 40CrNiMo 132 φ100-200 0.2R from the surface axis 34CrNiMo6 165 φ150-300 0.2R from the surface axis

.

Compared with the prior art, the present invention has the following beneficial effects:

The alloy steel water quenching process selection strategy provided by the invention can guide process designers to choose the correct process method, and avoid blindness in selecting the process method. For example: for 34CrNiMo6 material, shafts with a diameter of φ400mm, it is required to obtain martensite + bainite structure at a position 0.5 radius away from the surface. Stress increases the risk of cracking; for 42CrMo materials, shafts with a diameter of φ200mm are required to obtain the best performance at a position 0.2 radius away from the surface. In the quenching cooling process, the performance cannot meet the performance requirements because the average cooling rate at the position 0.2 radius from the surface is too low. Therefore, it will be a meaningful work for craftsmen to select the process method before designing the specific process with reference to the data provided by the patent of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Example 1

This embodiment provides a method for determining the water quenching process of alloy steel; it is used to determine the selection of the water-air alternate time-controlled quenching and cooling process and the primary water quenching process for various materials; the method includes:

S1: Analyze the quenched and cooled workpiece, and obtain the tissue composition of the required performance part according to the distance from the core of the required performance part of the workpiece;

S2: Obtain the steel grade and size range of the quenched and cooled workpiece. According to the steel grade, size range and required performance parts of the quenched and cooled workpiece, select the water-air alternately controlled quenching and cooling process or the one-time water quenching process;

The scope of application of the water-air alternate time-controlled quenching and cooling process includes high-hardenability alloy steel and workpieces requiring high performance in the deep layer, and/or medium-low hardenability alloy steel and workpieces requiring high mechanical properties in the surface layer;

The scope of application of the primary water quenching process includes alloy steels with medium and low permeability and workpieces requiring high performance in deep layers, and/or alloy steels with high hardenability and workpieces requiring high mechanical properties in surface layers;

S3: Implement the process through specific quenching and cooling operations according to the selected process.

As a preferred embodiment, according to the scope of application of the water-air alternate time-controlled quenching and cooling process, the high hardenability alloy steel material has sufficient hardenability characteristics, and through multiple water-air alternate processes, the required performance parts Reach the required organization; and/or use the low hardenability alloy steel material with low hardenability and the required performance part on the surface layer to achieve the required structure on the surface layer through the first immersion, and then alternate air-water-air The function of cooling is to ensure that the return temperature of the structure whose surface layer has undergone martensite or bainite transformation does not exceed its tempering temperature.

Obtain the specific steel grade, size range, and required performance parts of the quenched and cooled workpiece suitable for the water-air alternate time-controlled quenching and cooling process.

(1) The scope of application of the water-air alternately controlled quenching and cooling process (ATQ process)

① High hardenability alloy steel and workpieces requiring high performance in deep positions, see Table 1.

Table 1

*For the calculation of DI value, see "ASTM A255-10(2014) Standard Test Methods for Determining Hardenability of Steel", where DI value is only used as a relative index to measure the hardenability of the material.

The process design principle in Table 1: take advantage of the characteristics of sufficient hardenability of the material, through multiple water-air alternating processes, so that the required performance parts can reach the required structure.

②Medium and low hardenability alloy steel and workpieces requiring high mechanical properties at the surface, see Table 2.

Table 2

The process design principle in Table 2: Since the hardenability of the material is not high and the required performance part is on the surface layer, the surface layer can obtain the required structure through the first immersion, and the effect of the subsequent air-water-air alternate cooling is not to cause the surface layer The reheating temperature of the structure that has undergone martensite or bainite transformation exceeds its tempering temperature.

Table 1 and Table 2 give the steel grades, size ranges and required performance parts suitable for ATQ process.

As a preferred embodiment, according to the scope of application of the primary water quenching process, using a workpiece with a medium-low permeability alloy steel material with low hardenability, a relatively deep position and a small cross-sectional size, a longer time immersion To obtain the required microstructure in the required performance parts, ensure that the reheating temperature of the martensite or bainite transformation in the required performance parts in the subsequent air cooling process does not exceed its tempering temperature; and/or use high quenching For non-resistant materials, workpieces with required performance parts on the surface layer and small cross-sectional size, the required structure can be obtained by one-time immersion, so as to ensure that martensite or bainite in the required performance parts will not be caused in the subsequent air cooling process The return temperature of the bulk-transformed tissue exceeds its tempering temperature; at the same time, control the tissue transformation of the parts below the required performance, so as to obtain the pearlite structure as the best, and realize the stress distribution of thermal stress type, that is, the surface layer is compressive stress, and the core is tensile stress;

Obtain the steel grade, size range, and required performance parts of the quenched and cooled workpiece suitable for the primary water quenching process.

(2) The scope of application of the primary water quenching process (HTQ process)

① Alloy steel with medium and low permeability and workpieces requiring high performance in deep positions, see Table 3.

table 3

steel number DI value (mm) (reference) Size range(mm) Performance area or requirement (R-radius) Product example 42CrMo 112 φ150-250 0.5R from the surface axis 35CrMo 74 φ100-200 0.5R from the surface axis 40C 54 φ80-150 0.5R from the surface axis

The process design principle in Table 3 is: for workpieces with low material hardenability, required performance parts at relatively deep positions, and small cross-sectional dimensions, the required microstructure can be obtained at the required performance parts by immersion for a long time, and then During the air cooling process, it will not cause the return temperature of the structure that has undergone martensite or bainite transformation in the required performance part to exceed its tempering temperature.

② High hardenability alloy steel and workpieces requiring high mechanical properties at the surface, see Table 4.

Table 4

The process design principle in Table 4 is: for high-hardenability materials, workpieces with required performance parts on the surface layer and small cross-sectional size, the required microstructure can be achieved at the required performance parts through one-time immersion, and the key point is to ensure the subsequent air cooling During the process, the return temperature of the structure that has undergone martensite or bainite transformation in the required performance part does not exceed its tempering temperature; at the same time, the structure transformation of the part below the required performance is controlled to obtain the pearlite structure. The stress distribution of thermal stress type, that is, the surface layer is compressive stress, and the core is tensile stress.

Table 3 and Table 4 give the steel grades, size ranges and required performance parts suitable for HTQ process.

Other materials, dimensions and required performance parts not listed in Table 1-4 can be compared with the data in the table to select similar conditions. The hardenability of the material can be determined by comparing the DI value.

As a preferred embodiment: the medium used in this embodiment is water, and it should also include the use of other media, such as: salt water, various water-soluble media, etc.

As a preferred embodiment: the medium used in this embodiment is water, and the cooling method can be water immersion, water spray or spray.

Example 2

Based on the determination method of a water quenching process of alloy steel in the above-mentioned embodiment 1, the quenching and cooling object adopted in this embodiment is: P20 material (material DI value=270mm) with a thickness of 350mm, and it is required to obtain martensite and bainite along the cross section organization, while the uniformity of hardness along the section is less than ±2.5HRC.

First, analyze the quenching and cooling object: the workpiece requires martensite and bainite structure and hardness uniformity <±2.5HRC along the section.

Secondly, according to the alloy steel water quenching process selection strategy given in Example 1 above, it is determined that the workpiece is within the condition range of P20 in Table 1, so the water-air alternate time-controlled quenching cooling process (ATQ process) should be selected.

Finally, design the process according to the ATQ process design method and implement the process through specific quenching and cooling operations.

The principle of process design: in order to ensure the uniformity of hardness, the goal should be to obtain the same structure. It is easier to obtain martensitic structure on the surface, but it is more difficult to obtain the core. Therefore, the cooling rate of the surface layer should be controlled in the formulation of the quenching cooling process. Try to obtain bainite structure in the surface layer as well.

The selection strategy of alloy steel water quenching process can guide process designers to choose the correct process and avoid blindness in process selection.

Example 3

Based on the determination method of an alloy steel water quenching process in the above-mentioned embodiment 1, the quenching and cooling object adopted in this embodiment is: a shaft with a diameter of φ250mm, the material is 42CrMo (DI value=112mm), and it is required to be obtained at a distance of 0.8R from the center. best mechanical properties.

First, analyze the quenching and cooling object: the workpiece requires a position 0.8R away from the core (that is, a position 25mm away from the surface) to obtain a mixed structure of martensite and bainite.

Secondly, according to the alloy steel water quenching process selection strategy given in Example 1 above, it is determined that the workpiece is within the condition range of 42CrMo in Table 2, so the ATQ process should be selected.

Finally, design the process according to the ATQ process design method and implement the process through specific quenching and cooling operations. Its process design principle: Due to the limitation of hardenability of 42CrMo material, in order to obtain the required structure at this position, it needs to be cooled below the Ms point (martensite start temperature) within the time of pearlite transformation incubation period, which requires To achieve this goal during the first immersion process, the role of the subsequent air-water-air alternate cooling is not to cause the return temperature of the surface layer that has undergone martensite or bainite transformation to exceed its tempering temperature .

Adopting the alloy steel water quenching process selection strategy can guide process designers to choose the correct process and avoid blindness in process selection.

Example 4

Based on the determination method of an alloy steel water quenching process in the above-mentioned embodiment 1, the quenching and cooling object adopted in this embodiment is: a shaft with a diameter of φ150mm, the material is 35CrMo (DI value=74mm), and it is required to be obtained at a distance of 0.5R from the center. best mechanical properties.

First, analyze the quenching and cooling object: the workpiece requires a position 0.5R away from the core (that is, a position 37.5mm away from the surface) to obtain a mixed structure of martensite and bainite. Due to the limitation of the hardenability of the 35CrMo material, in order to obtain the required structure at this position, it needs to be cooled below the Ms point (martensitic transformation temperature) within the time of the pearlite transformation incubation period, which requires an immersion solution process to achieve this goal.

Secondly, according to the alloy steel water quenching process selection strategy given in Example 1 above, it is determined that the workpiece is within the condition range of 35CrMo in Table 3, so the HTQ process should be selected.

Finally, design the process according to the HTQ process design method and implement the process through specific quenching and cooling operations. Its process design principle: For workpieces with low material hardenability, deep position and small cross-sectional size, the required performance parts can be obtained by immersion for a long time, and in the subsequent air cooling process In order not to cause the reheating temperature of the structure that has undergone martensite or bainite transformation in the required performance parts to exceed its tempering temperature.

Adopting the alloy steel water quenching process selection strategy can guide process designers to choose the correct process and avoid blindness in process selection.

Example 5

Based on the determination method of an alloy steel water quenching process in the above-mentioned embodiment 1, the quenching and cooling object adopted in this embodiment is: a shaft with a diameter of φ200mm, the material is 34CrNiMo6 (DI value=165mm), and it is required to be obtained at a place 0.8R away from the center. best mechanical properties.

First, analyze the quenching and cooling object: the workpiece requires a position 0.8R away from the core (that is, a position 20mm away from the surface) to obtain a mixed structure of martensite and bainite.

Secondly, according to the alloy steel water quenching process selection strategy given in Example 1 above, it is determined that the workpiece is within the condition range of 34CrNiMo6 in Table 4, so the HTQ process should be selected.

Finally, design the process according to the HTQ process design method and implement the process through specific quenching and cooling operations. The process design principle: due to the high hardenability of the 34CrNiMo6 material, the incubation period for pearlite transformation is longer, and the pre-cooling time can be extended in the process design (from the time when the workpiece is transferred from the heating furnace to the end of the immersion quenching and cooling of the workpiece Time), that is, cooling to the austenite-to-pearlite transformation temperature (Ar1), the pre-cooling time for the piece to cool to the Ar1 temperature is 420s. Then achieve the required structure through one immersion, the principle of determining the time of one immersion is: (a) ensure that the structure that has undergone martensite or bainite transformation in the required performance part will not be caused in the subsequent air cooling process (b) Control the structural transformation of parts below the required performance, so as to obtain the pearlite structure as the best, and realize the stress distribution of thermal stress type, that is, the surface layer is compressive stress, and the core is tensile stress .

Adopting the alloy steel water quenching process selection strategy can guide process designers to choose the correct process and avoid blindness in process selection.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (5)

1. A method for determining alloy steel water quenching process is characterized in that: it is used to determine the selection of water-air alternately controlled time quenching cooling process and primary water quenching process for determining various materials; said method comprises: S1: Analyze the quenched and cooled workpiece, and obtain the tissue composition of the required performance part according to the distance from the core of the required performance part of the workpiece; S2: Obtain the steel grade and size range of the quenched and cooled workpiece. According to the steel grade, size range and required performance parts of the quenched and cooled workpiece, select the water-air alternately controlled quenching and cooling process or the one-time water quenching process; The scope of application of the water-air alternate time-controlled quenching and cooling process includes high-hardenability alloy steel and workpieces requiring high performance in the deep layer, or medium-low hardenability alloy steel and workpieces requiring high mechanical properties in the surface layer; The scope of application of the primary water quenching process includes medium and low permeability alloy steels and workpieces requiring high performance in deep layers, or high hardenability alloy steels and workpieces requiring high mechanical properties in surface layers; in: According to the scope of application of the water-air alternating time-controlled quenching and cooling process, the high hardenability alloy steel material has sufficient hardenability characteristics, and through multiple water-air alternating processes, the required performance parts can reach the required structure. or utilize the low hardenability of the low-hardenability alloy steel material and the required performance position on the surface layer, realize the surface layer to obtain the required structure through the first immersion, and the effect of the alternate cooling of air-water-air afterwards is Ensure that the return temperature of the structure that has undergone martensite or bainite transformation on the surface does not exceed its tempering temperature; obtain the specific steel number, size range, and requirements of the quenched and cooled workpiece suitable for the water-air alternate controlled quenching and cooling process performance part; According to the scope of application of the one-time water quenching process, use the workpiece with low hardenability of medium and low-permeability alloy steel materials, the required performance parts are at a relatively deep position and the cross-sectional size is not large, and use a longer time immersion to achieve the required performance parts. For the required structure, ensure that the return temperature of the structure that has undergone martensite or bainite transformation in the required performance part in the subsequent air cooling process does not exceed its tempering temperature; or, using high hardenability materials, the required performance part is in the For workpieces with small surface and cross-sectional dimensions, the required structure can be obtained in the required performance part through one-time immersion, so as to ensure that the structure that has undergone martensite or bainite transformation in the required performance part will not be returned to temperature during the subsequent air cooling process The temperature exceeds its tempering temperature; at the same time, control the structural transformation of the parts below the required performance, so as to obtain the pearlite structure as the best, and realize the stress distribution of thermal stress type, that is, the surface layer is compressive stress, and the core is tensile stress; The steel grade, size range, and required performance parts of the quenched and cooled workpiece in the water quenching process; S3: Implement the process through specific quenching and cooling operations according to the selected process. 2. The method for determining the water quenching process of a kind of alloy steel according to claim 1, characterized in that: the high hardenability alloy steel and the workpiece requiring high performance in the deep layer position are obtained by adopting the water-air alternately controlled quenching and cooling process The steel grade, size range and required performance parts are shown in Table 1; steel number DI value (mm) Size range (mm) Performance area or requirement (R-radius) Product Category 40CrNiMo 132 φ200-400 0.5R from the surface axis 34CrNiMo6 165 φ250-500 0.5R from the surface axis P20 (3Cr2Mo) 270 Thickness 300-500 full section plastic mold steel 718 (3Cr2MnNiMo) 425 Thickness 500-1100 full section plastic mold steel H13 535 Thickness 350-700 full section Hot work die steel . 3. The method for determining the water quenching process of a kind of alloy steel according to claim 1, characterized in that: obtain the medium and low hardenability alloy steel and require the surface layer position to have high mechanical properties by adopting water-air alternate quenching and cooling process The steel grade, size range, and required performance parts of the workpiece are shown in Table 2; steel number DI value (mm) Size range (mm) Performance area or requirement (R-radius) Product Category 42CrMo 112 φ200-300 0.2R from the surface axis 35CrMo 74 φ150-250 0.2R from the surface axis 40C 54 φ100-200 0.2R from the surface axis . 4. the determination method of a kind of alloy steel water quenching process according to claim 1, it is characterized in that: obtain the steel grade of the medium and low permeability alloy steel that is suitable for adopting a water quenching process and the workpiece that requires high performance in the deep layer position, The size range and required performance parts are shown in Table 3; steel number DI value (mm) Size range (mm) Performance area or requirement (R-radius) Product example 42CrMo 112 φ150-250 0.5R from the surface axis 35CrMo 74 φ100-200 0.5R from the surface axis 40C 54 φ80-150 0.5R from the surface axis . 5. The method for determining a water quenching process for alloy steel according to claim 1, characterized in that: obtain the steel number of the high hardenability alloy steel suitable for the primary water quenching process and the workpiece that requires the surface layer to have high mechanical properties , size range, and required performance parts, as shown in Table 4; steel number DI value (mm) Size range (mm) Performance area or requirement (R-radius) Product Category 40CrNiMo 132 φ100-200 0.2R from the surface axis 34CrNiMo6 165 φ150-300 0.2R from the surface axis .