A heat treatment process for end tooth gauges

Abstract

This invention belongs to the field of metal heat treatment technology and discloses a heat treatment process for end-tooth gauges. First, 9CrWMn material is quenched and heated to a high temperature of 800–880°C. The quenching and holding time is determined based on the effective wall thickness of the end-tooth gauge and the heating equipment. Then, the quenched and held 9CrWMn material is rapidly transferred to isothermal quenching oil for isothermal quenching at a temperature of 190–230°C. After isothermal quenching, the 9CrWMn material is transferred to a cold environment for cooling for more than 2 hours. After cooling, the 9CrWMn material is returned to the isothermal quenching oil for tempering. The tempering oil temperature is the same as the isothermal quenching oil temperature in step two, and the tempering time is determined based on the effective wall thickness of the end-tooth gauge. Through the above process, 9CrWMn end tooth gauges with an effective wall thickness ≤40mm can be thoroughly quenched, with both the surface and core hardness ≥HRC62. At the same time, the parts do not crack during quenching. This invention can make the hardness of 9CrWMn after quenching reach up to HRC65~67, which can significantly improve the wear resistance and dimensional stability of the parts.

Description

Technical Field

[0001] This invention belongs to the field of metal heat treatment technology and relates to a heat treatment process for end tooth gauges. Background Technology

[0002] An end-tooth gauge is a measuring tool used to measure end teeth, typically manufactured from 9CrWMn material. Due to the structure of some end teeth, the effective thickness of the end-tooth gauge before quenching is ≥18mm, exceeding the hardenability of 9CrWMn, making the part unquenchable. Without changing the raw material, to ensure the dimensional stability of the end-tooth gauge, the quenching temperature is usually increased to improve the hardenability of the core structure. However, due to the gauge's own configuration, excessive quenching stress in areas with large curvature of the countersunk hole leads to cracking, ultimately rendering the end-tooth gauge unusable.

[0003] To date, no literature has reported that quenching of 9CrWMn end tooth gauges with an effective wall thickness ≥18mm can achieve a hardness difference ≤HRC1 between the core and the surface layer, without cracking. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a heat treatment process for end-tooth gauges, ensuring that when the gauge is made of 9CrWMn material with an effective thickness ≥18mm, it can be thoroughly hardened without cracking.

[0005] The technical solution of the present invention is as follows:

[0006] A heat treatment process for end-tooth gauges includes the following steps:

[0007] Step 1: The 9CrWMn material is quenched and heated to a high temperature of 800~880℃, and the quenching and holding time is determined according to the effective wall thickness of the end tooth gauge and the heating equipment.

[0008] Step 2: Quickly transfer the 9CrWMn material after quenching and heating to isothermal quenching oil for isothermal quenching. The isothermal quenching oil temperature is 190~230℃.

[0009] Step 3: After isothermal quenching, transfer the 9CrWMn material to a cold environment and cool it for more than 2 hours.

[0010] Step 4: After cooling, put the 9CrWMn material back into the isothermal quenching oil for tempering. The tempering oil temperature is the same as the isothermal quenching oil temperature 11 in Step 2, and the tempering time is determined according to the effective wall thickness of the end tooth gauge.

[0011] Furthermore, in step one, the specific relationship between the quenching heating temperature and the effective wall thickness of the end gear gauge is as follows: 800~830℃ for thicknesses below 18mm; 830℃ for thicknesses of 18~20mm; 840℃ for thicknesses of 20~25mm; 850℃ for thicknesses of 25~30mm; 860℃ for thicknesses of 30~35mm; and 870~880℃ for thicknesses of 35~40mm. This specific relationship between the quenching heating temperature and the effective wall thickness of the end gear gauge effectively ensures the quenching effect and prevents quenching cracks caused by oxidation and decarburization. If the temperature is outside this range, the 9CrWMn material will fail to meet the usage requirements or may crack during quenching; therefore, this relationship is crucial.

[0012] Furthermore, in step one, the 9CrWMn material is quenched and heated using a salt furnace or a protective atmosphere furnace.

[0013] Furthermore, when quenching 9CrWMn material using a salt furnace, the relationship between the holding time and the effective wall thickness of the end tooth gauge is as follows: 15 min for 18~20 mm; 17.5 min for 20~25 mm; 20 min for 25~30 mm; 22.5 min for 30~35 mm; and 25 min for 35~40 mm.

[0014] Furthermore, when quenching 9CrWMn material using a protective atmosphere furnace, the relationship between the holding time and the effective wall thickness of the end tooth gauge is as follows: 100 min for 18~20 mm; 110 min for 20~25 mm; 120 min for 25~30 mm; 130 min for 30~35 mm; and 140 min for 35~40 mm.

[0015] Furthermore, in step two, after the quenching and holding period, the time interval between transferring the 9CrWMn material to the isothermal quenching oil should not exceed 20 seconds. This is also the key to achieving the technical effect of this invention, which can utilize the homogeneous synchronous nucleation characteristics of martensite transformation at high temperatures to improve the hardenability of 9CrWMn material. However, if this time is exceeded, the internal and external temperatures of the 9CrWMn material will no longer meet the corresponding requirements, which will prevent the effective and comprehensive improvement of hardenability.

[0016] Furthermore, in step two, the specific relationship between the isothermal quenching oil temperature and the effective wall thickness of the end gear gauge is as follows: 170~190℃ for thicknesses below 18mm; 190℃ for thicknesses of 18~20mm; 200℃ for thicknesses of 20~25mm; 210℃ for thicknesses of 25~30mm; 220℃ for thicknesses of 30~35mm; and 230℃ for thicknesses of 35~40mm. This relationship is also key to achieving the technical effect of this invention.

[0017] Furthermore, in step two, the isothermal quenching time is 0.5 to 4.0 hours.

[0018] Furthermore, in step three, the freezing temperature is below -40℃ and the freezing time is greater than 2 hours.

[0019] Furthermore, the relationship between the tempering and heat preservation time and the effective wall thickness of the end tooth gauge is as follows: 270 min for 18~20 mm; 300 min for 20~25 mm; 330 min for 25~30 mm; 360 min for 30~35 mm; and 390 min for 35~40 mm.

[0020] Compared with the prior art, the advantages of the present invention include the following:

[0021] 1. Through the above process, 9CrWMn end tooth gauges with an effective wall thickness ≤40mm can be hardened through, and the surface and core hardness are both ≥HRC62. At the same time, the parts do not crack during quenching.

[0022] 2. This invention can make the hardness of 9CrWMn after quenching reach up to HRC65-67, which can significantly improve the wear resistance and dimensional stability of the parts. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this invention, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the end tooth gauge. Detailed Implementation

[0025] This section describes embodiments of the present invention, used to explain and illustrate the technical solutions of the present invention. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0026] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating directions or positional relationships, are given in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or device referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include more than one of those features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integrated connections; they can refer to mechanical connections or point connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] A heat treatment process for end-tooth gauges includes the following steps:

[0029] Step 1: The 9CrWMn material is quenched and heated to a high temperature of 800~880℃, and the quenching and holding time is determined according to the effective wall thickness of the end tooth gauge and the heating equipment.

[0030] Step 2: Quickly transfer the 9CrWMn material after quenching and heating to isothermal quenching oil for isothermal quenching. The isothermal quenching oil temperature is 190~230℃.

[0031] Step 3: After isothermal quenching, transfer the 9CrWMn material to a cold environment and cool it for more than 2 hours.

[0032] Step four: After cooling, place the 9CrWMn material back into the isothermal quenching oil for tempering. The tempering oil temperature is the same as the isothermal quenching oil temperature in step two, and the tempering time is determined according to the effective wall thickness of the end tooth gauge.

[0033] In step one, the specific relationship between the quenching heating temperature and the effective wall thickness of the end gear gauge is as follows: 800~830℃ for thicknesses below 18mm; 830℃ for thicknesses of 18~20mm; 840℃ for thicknesses of 20~25mm; 850℃ for thicknesses of 25~30mm; 860℃ for thicknesses of 30~35mm; and 870~880℃ for thicknesses of 35~40mm. This matching relationship between the quenching heating temperature and the effective wall thickness of the end gear gauge effectively ensures the quenching effect and prevents quenching cracks caused by oxidation and decarburization. If the temperature is outside the specified range, the 9CrWMn material will fail to meet the usage requirements or may crack during quenching; therefore, this relationship is crucial.

[0034] In step one, the 9CrWMn material is quenched and heated using a salt furnace or a protective atmosphere furnace.

[0035] When quenching 9CrWMn material using a salt furnace, the relationship between the holding time and the effective wall thickness of the end tooth gauge is as follows: 15 min for 18~20 mm; 17.5 min for 20~25 mm; 20 min for 25~30 mm; 22.5 min for 30~35 mm; and 25 min for 35~40 mm.

[0036] When quenching 9CrWMn material in a protective atmosphere furnace, the relationship between the holding time and the effective wall thickness of the end tooth gauge is as follows: 100 min for 18~20 mm; 110 min for 20~25 mm; 120 min for 25~30 mm; 130 min for 30~35 mm; and 140 min for 35~40 mm.

[0037] In step two, after the quenching and holding period, the time interval between transferring the 9CrWMn material to the isothermal quenching oil should not exceed 20 seconds. This is also the key to achieving the technical effect of this invention, which can utilize the homogeneous synchronous nucleation characteristics of martensite transformation at high temperatures to improve the hardenability of 9CrWMn material. However, if this time is exceeded, the internal and external temperatures of the 9CrWMn material will no longer meet the corresponding requirements, which will prevent the effective and comprehensive improvement of hardenability.

[0038] In step two, the specific relationship between the isothermal quenching oil temperature and the effective wall thickness of the end gear gauge is as follows: 170~190℃ for thicknesses below 18mm; 190℃ for thicknesses of 18~20mm; 200℃ for thicknesses of 20~25mm; 210℃ for thicknesses of 25~30mm; 220℃ for thicknesses of 30~35mm; and 230℃ for thicknesses of 35~40mm. This relationship is also key to achieving the technical effect of this invention.

[0039] In step two, the isothermal quenching time is 0.5 to 4.0 hours.

[0040] In step three, the freezing temperature is below -40℃ and the freezing time is greater than 2 hours.

[0041] The relationship between tempering and heat preservation time and effective wall thickness of end tooth gauge is as follows: 270 min for 18~20 mm; 300 min for 20~25 mm; 330 min for 25~30 mm; 360 min for 30~35 mm; and 390 min for 35~40 mm.

[0042] Another embodiment of the present invention will be described below.

[0043] The technical solution of this invention is to adopt isothermal quenching and utilize the homogeneous synchronous nucleation characteristics of martensite transformation at high temperature to improve the hardenability of 9CrWMn material.

[0044] To prevent the end teeth manufactured by 9CrWMn from cracking due to oxidation and decarburization during quenching, a salt furnace or protective atmosphere furnace is used for heating, with a heating temperature of (830~870)℃. The relationship between quenching heating temperature and wall thickness is shown in Table 1 below.

[0045] Table 1: Relationship between quenching heating temperature and effective wall thickness of 9CrWMn end tooth gauge

[0046]

[0047] The end teeth manufactured by 9CrWMn and the quenching and holding times are shown in Table 2 below.

[0048] Table 2: Correspondence between quenching heating and holding time and effective wall thickness for 9CrWMn end tooth gauges

[0049]

[0050] After the quenching and heat preservation is completed, the 9CrWMn end tooth gauge is transferred to the isothermal quenching oil bath within ≤20s for isothermal quenching.

[0051] The isothermal quenching oil temperature is (190~230)℃. The specific isothermal quenching oil temperature and effective wall thickness correspondence is shown in Table 3.

[0052] Table 3: Correspondence between isothermal quenching oil temperature and effective wall thickness for 9CrWMn end tooth gauges

[0053]

[0054] The isothermal quenching time is (0.5~4.0) h.

[0055] After isothermal quenching, within ≤4 hours, remove the 9CrWMn end tooth gauge from the isothermal quenching oil and transfer it to a chiller for chilling.

[0056] The freezing temperature is ≤-40℃, and the freezing time is ≥2h.

[0057] After cooling, tempering should be performed within ≤4 hours.

[0058] The tempering temperature is the isothermal quenching oil temperature, and the tempering time is reasonably selected based on the thickness of the 9CrWMn end tooth gauge, as shown in Table 4 below.

[0059] Table 4: Correspondence between tempering holding time and effective wall thickness for 9CrWMn end tooth gauges

[0060]

[0061] The technical advantages of this invention are as follows: Through the above-described process, 9CrWMn end-tooth gauges with an effective wall thickness ≤40mm can be thoroughly hardened, achieving a surface and core hardness ≥HRC62, while preventing cracking during quenching. This invention can achieve a maximum hardness of HRC65-67 for 9CrWMn after quenching, significantly improving the wear resistance and dimensional stability of the parts.

[0062] A certain specification of end-tooth gauge, with an effective wall thickness of 29mm, was quenched at 840℃ for 2 hours, then oil-quenched at 55℃, followed by ice cooling at -70℃ for 1.5 hours, and finally tempered at 200℃ for 4 hours. The core hardness of the end-tooth gauge was only HRC52, while the surface hardness reached approximately HRC60. To improve the core hardness, the quenching temperature was increased to 880℃. However, quenching cracks appeared in the inner hole of the end-tooth gauge, rendering the product undeliverable. (See part drawing). Figure 1 As shown.

[0063] Therefore, we readjusted the process parameters as follows:

[0064] The 9CrWMn end-tooth gauge was quenched at 850℃ and held in a protective atmosphere furnace for 120 minutes. Within 10 seconds, it was transferred to an isothermal quenching oil bath at 210℃ for 2 hours. Within 2 hours after isothermal quenching, the 9CrWMn end-tooth gauge was removed from the isothermal quenching oil and transferred to a -80℃ cryostat for 2 hours. Within 2 hours after cryostating, the end-tooth gauge underwent tempering at 210℃ for 330 minutes.

[0065] Following the above process route and parameters, the end tooth gauges manufactured from 9CrWMn material have a surface and core hardness of HRC65-67. After isothermal quenching, no cracks appeared, and the residual austenite content was ≤3.5%, which met the design and process requirements and enabled the smooth transfer and delivery of end tooth gauge products between processes.

Claims

1. A heat treatment process for end-tooth gauges, characterized in that, Includes the following steps: Step 1: The 9CrWMn material is quenched and heated to a high temperature of 800-880℃, and the quenching and holding time is determined according to the effective wall thickness of the end tooth gauge and the heating equipment. Step 2: Quickly transfer the 9CrWMn material after quenching and heating to isothermal quenching oil for isothermal quenching. The isothermal quenching oil temperature is 190-230℃. Step 3: After isothermal quenching, transfer the 9CrWMn material to a cold environment and cool it for more than 2 hours. Step 4: After cooling, put the 9CrWMn material back into the isothermal quenching oil for tempering. The tempering oil temperature is the same as the isothermal quenching oil temperature in Step 2, and the tempering time is determined according to the effective wall thickness of the end tooth gauge. In step one, the specific relationship between the quenching heating temperature and the effective wall thickness of the end gear gauge is as follows: below 18mm, 800~830℃; 18~20mm, 830℃; 20~25mm, 840℃; 25~30mm, 850℃; 30~35mm, 860℃; 35~40mm, 870~880℃. In step two, after the quenching and heat preservation are completed, the time interval between transferring the 9CrWMn material to the isothermal quenching oil shall not exceed 20 seconds.

2. The heat treatment process for an end-tooth gauge according to claim 1, characterized in that, In step one, the 9CrWMn material is quenched and heated using a salt furnace or a protective atmosphere furnace.

3. The heat treatment process for an end-tooth gauge according to claim 2, characterized in that, When quenching 9CrWMn material using a salt furnace, the relationship between the holding time and the effective wall thickness of the end tooth gauge is as follows: 15 min for 18-20 mm; 17.5 min for 20-25 mm; 20 min for 25-30 mm; 22.5 min for 30-35 mm; and 25 min for 35-40 mm.

4. The heat treatment process for an end-tooth gauge according to claim 2, characterized in that, When quenching 9CrWMn material in a protective atmosphere furnace, the relationship between the holding time and the effective wall thickness of the end tooth gauge is as follows: 100 min for 18-20 mm; 110 min for 20-25 mm; 120 min for 25-30 mm; 130 min for 30-35 mm; and 140 min for 35-40 mm.

5. The heat treatment process for an end-tooth gauge according to claim 1, characterized in that, In step two, the specific relationship between the isothermal quenching oil temperature and the effective wall thickness of the end gear gauge is as follows: 170-190℃ for thicknesses below 18mm; 190℃ for thicknesses of 18-20mm; 200℃ for thicknesses of 20-25mm; 210℃ for thicknesses of 25-30mm; 220℃ for thicknesses of 30-35mm; and 230℃ for thicknesses of 35-40mm.

6. The heat treatment process for an end-tooth gauge according to claim 1, characterized in that, In step two, the isothermal quenching time is 0.5 to 4.0 hours.

7. The heat treatment process for an end-tooth gauge according to claim 1, characterized in that, In step three, the freezing temperature is below -40℃ and the freezing time is greater than 2 hours.

8. The heat treatment process for an end-tooth gauge according to claim 1, characterized in that, The relationship between tempering and heat preservation time and effective wall thickness of end tooth gauge is as follows: 270 min for 18-20 mm; 300 min for 20-25 mm; 330 min for 25-30 mm; 360 min for 30-35 mm; and 390 min for 35-40 mm.

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