A metal product heat treatment process

Abstract

The application provides a metal product heat treatment process, which comprises the following steps: pre-treating a metal product to reduce internal stress of the metal product, so as to minimize deformation; and adopting nitrogen gas for air quenching in a sectional quenching mode, so that the internal stress of the metal product can be better released, quenching cracking and micro-cracks of the metal product in the quenching process can be avoided, and the hardness and toughness of the workpiece material can be improved; and the nitrogen gas is used for air quenching, so that the surface oxidation and decarburization of the metal product are avoided, and the performance of the workpiece is not reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat treatment, in particular to a metal product heat treatment process. BACKGROUND

[0002] The heat treatment process determines the mechanical properties of the material, and the heat treatment processes of different materials are not the same. Different heat treatment processes of the same material will also cause a large gap in the mechanical properties of the material itself. The heat treatment process is affected by factors such as material and part processing. The general heat treatment process of the material is to pretreat first, then quench and finally temper. The quenching stage is the most important stage. The control of quenching temperature is a double-edged sword. Increasing the quenching temperature will increase the hardness of the material, but at the same time it will also reduce the toughness and ductility of the material. Therefore, the control of the quenching temperature is particularly important in the quenching stage. Secondly, if the workpiece cannot release stress in the quenching stage, the workpiece is prone to quenching cracking and micro-crack, which seriously affects the service life of the tool.

[0003] However, in the existing heat treatment process, one-time quenching treatment is usually used, but it cannot release the stress of the workpiece well. Although the existing technology also uses multiple quenching treatments for steel, it cannot well control the temperature of each quenching, resulting in that the stress of the workpiece cannot be well released, and repeated heating causes serious oxidation and decarburization on the surface of the workpiece, causing the performance of the workpiece to decrease. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a metal product heat treatment process to solve the above problems.

[0005] The present application adopts the following scheme:

[0006] The present application provides a metal product heat treatment process, comprising the following steps:

[0007] S1: pretreatment; at least one pretreatment is performed on the metal product to preliminarily eliminate the internal stress of the metal product;

[0008] S2: quenching treatment; the pretreated metal product is heated to a first temperature range and kept for a period of time in the first temperature range, and then nitrogen gas is input to quench the metal product for the first time; when the temperature of the metal product drops to a second temperature range, the nitrogen gas input is stopped, and the metal product is kept for a period of time in the second temperature range; then nitrogen gas is input to quench the metal product for the second time, and when the metal product drops to a third temperature range, the nitrogen gas input is stopped, and the metal product is kept for a period of time in the third temperature range; finally, nitrogen gas is continuously input to quench the metal product for the third time until the temperature of the metal product reaches room temperature;

[0009] S3: tempering treatment; at least one tempering treatment is performed on the quenched metal product.

[0010] Further, the temperature of the metal product is detected by an external infrared thermal imager in step S2.

[0011] Further, in step S2, after the metal product is kept at the first temperature range for a period of time, the quenching furnace is first pumped to 2 Pa and then nitrogen is inputted.

[0012] Further, the input speed of nitrogen in the first gas quenching and the third gas quenching in step S2 is 15-20 m / s.

[0013] Further, in step S2, the metal product is kept at the second temperature range for 25-35 min.

[0014] Further, the input speed of nitrogen in the second gas quenching in step S2 is 10-15 m / s.

[0015] Further, in step S2, the metal product is kept at the third temperature range for 25-35 min.

[0016] By adopting the technical scheme, the following technical effects can be achieved:

[0017] The present application provides a metal product heat treatment process, which first reduces the internal stress of the metal product by pretreating the metal product, thereby minimizing deformation, and then uses nitrogen for gas quenching by segmental quenching, which can control the quenching temperature of the metal product by controlling the input of nitrogen, so that the internal stress of the metal product can be better released, avoiding quenching cracking and micro-cracks of the metal product during quenching, thereby improving the hardness and toughness of the workpiece material; at the same time, using nitrogen for gas quenching avoids the oxidation and decarburization of the metal product surface, which causes the performance of the workpiece to decline. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor.

[0019] Fig. 1 is a heat treatment process diagram of the M42 high-speed steel drill bit of the first embodiment of the present application;

[0020] Fig. 2 is a heat treatment process diagram of the NM360 steel plate of the second embodiment of the present application;

[0021] Fig. 3 is a material performance comparison chart after heat treatment of M42 high-speed steel drill bit and NM360 steel plate. DETAILED DESCRIPTION

[0022] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0023] EMBODIMENT

[0024] In combination with Figs. 1-3 The present embodiment provides a metal product heat treatment process, taking M42 high-speed steel drill bit heat treatment as an example one, including the following steps:

[0025] S1: pretreatment; the M42 high-speed steel drill bit is placed in a high-temperature box furnace for twice preheating treatment, to preliminarily eliminate the internal stress of the metal product; first heated to 550℃ at a heating rate of 10℃ / min in the box furnace and kept for 100min, then continuously heated to 870℃ and kept for 70min.

[0026] S2: quenching treatment; the metal product after pretreatment is continuously heated to 1160℃ in the box furnace, which is the austenitizing temperature, and kept for 1h at 1160℃. Then the box furnace is first pumped to 2Pa, and nitrogen is input to the metal product for the first gas quenching, and the flow rate of nitrogen is set to 20m / s; the surface temperature of the sample is detected by an infrared thermal imager, and when the temperature of the metal product drops to 630℃, the nitrogen input is stopped, and the temperature is kept at 630℃ for 30min; then nitrogen is input at a flow rate of 15m / s for the second gas quenching of the metal product, and when the metal product drops to 260℃, the nitrogen input is stopped, and the temperature is kept at 260℃ for 30min; finally, nitrogen is input at a flow rate of 15m / s for the third gas quenching of the metal product until the temperature of the metal product drops to 25℃;

[0027] S3: tempering treatment; the metal product after quenching treatment is subjected to three times of tempering treatment in a box resistance furnace, the tempering temperature is set to 500℃, 550℃ and 600℃, each temperature is kept for 1h, and the metal product needs to be cooled to room temperature after each tempering before the next tempering.

[0028] The heat treatment of the NM360 steel plate is taken as Example Two:

[0029] S1: pretreatment; the NM360 steel plate is placed in a high-temperature box furnace for one time of pretreatment to preliminarily eliminate the internal stress of the metal product; the box furnace is heated to 940℃ at a heating rate of 50℃ / min and kept for 60min.

[0030] S2: quenching treatment; the box furnace is first pumped to 2Pa, nitrogen gas is input to quench the metal product for the first time, the flow rate of the nitrogen gas is set to 20m / s; the surface temperature of the sample is detected by using an infrared thermal imager, when the temperature of the metal product drops to 8000℃, the nitrogen gas input is stopped, and the temperature is kept at 800℃ for 30min; then the nitrogen gas is input again at a flow rate of 20m / s to quench the metal product for the second time, when the temperature of the metal product drops to 600℃, the nitrogen gas input is stopped, and the temperature is kept at 600℃ for 30min; finally, the nitrogen gas is input at a flow rate of 20m / s to quench the metal product for the third time until the temperature of the metal product drops to 25℃;

[0031] S3: tempering treatment; the metal product after quenching treatment is subjected to three times of tempering treatment in a box resistance furnace, the tempering temperature is set to 200℃, 425℃ and 575℃, each temperature is kept for 1h, and the metal product needs to be cooled to room temperature after each tempering before the next tempering.

[0032] The following is a comparative example of conventional heat treatment:

[0033] Comparative Example One:

[0034] S1: pretreatment; the M42 high-speed steel drill bit is placed in a high-temperature box furnace for two times of preheating treatment. First, the box furnace is heated to 550℃ at a heating rate of 10℃ / min and kept for 100min, and then heated to 870℃ and kept for 70min.

[0035] S2: quenching treatment; the M42 high-speed steel drill bit after pretreatment is continuously heated to 1160℃ in the box furnace, which is the austenitizing temperature, and kept at this temperature for 1h. Quenching treatment is then performed for 2h.

[0036] S2: Tempering treatment; The M42 high-speed steel drill bit after quenching is tempered three times in a box-type resistance furnace. The tempering temperature is set to 500, 550 and 600℃, and each temperature is held for 1 hour. Each tempering needs to be cooled to room temperature before the next tempering.

[0037] Comparative Example 2:

[0038] S1: Pretreatment; The NM360 steel plate is placed in a high-temperature box furnace for a pretreatment. The plate is heated to 940°C at a heating rate of 50°C / min and held for 1 hour.

[0039] S2: Quenching treatment; then quenching treatment is performed for 1.5 hours.

[0040] S3: Finally, three tempering treatments are carried out in a box-type resistance furnace. The tempering temperatures are set to 200, 425 and 575°C, and each temperature is maintained for 1 hour. Each tempering process must be cooled to room temperature before the next tempering is carried out.

[0041] like Fig. 2 As shown, compared with conventionally heat-treated drill bits, the metal product heat treatment process of this invention first pre-treats the metal product to reduce internal stress, thereby minimizing deformation. Then, it uses a segmented quenching method with nitrogen gas quenching. By controlling the nitrogen input, the quenching temperature of the metal product can be controlled, allowing for better release of internal stress and preventing quenching cracks and microcracks during the quenching process, thus improving the hardness and toughness of the workpiece material. Simultaneously, nitrogen gas quenching avoids surface oxidation and decarburization of the metal product, preventing performance degradation. Therefore, the mechanical properties of the tool after this heat treatment process are significantly better than those of tools treated with conventional heat treatment.

[0042] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention.

[0043] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] In addition, the terms "first", "second", etc. are used only for the purpose of description and do not imply or imply relative importance or imply the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0045] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above-mentioned terms in the present application can be understood according to the specific circumstances.

[0046] In the present application, unless otherwise explicitly specified and limited, the first feature "on" or "under" the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the first feature "on", "above" and "above" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

Claims

1. A metal article heat treatment process, characterized by, The method comprises the following steps: S1: pretreatment; The metal product is pretreated at least once to preliminarily eliminate the internal stress of the metal product; S2: quenching treatment; The pretreated metal product is heated to a first temperature range, and is kept in the first temperature range for a period of time, and then is subjected to first gas quenching by inputting nitrogen; when the temperature of the metal product drops to a second temperature range, the input of nitrogen is stopped, and the metal product is kept in the second temperature range for a period of time; Then the metal product is subjected to second gas quenching by inputting nitrogen, and when the temperature of the metal product drops to a third temperature range, the input of nitrogen is stopped, and the metal product is kept in the third temperature range for a period of time; finally, the metal product is subjected to third gas quenching by continuously inputting nitrogen until the temperature of the metal product drops to room temperature; S3: tempering treatment; the metal product after the quenching treatment is subjected to at least one tempering treatment.

2. The metal article heat treatment process of claim 1, wherein, In step S2, the temperature of the metal product is detected by an external infrared thermal imager.

3. The metal article heat treatment process of claim 1, wherein, In step S2, after the metal product is kept in the first temperature range for a period of time, the quenching furnace is first pumped to 2 Pa and then the input of nitrogen is performed.

4. The metal article heat treatment process of claim 1, wherein, In step S2, the input speed of nitrogen in the first gas quenching and the third gas quenching is 15-20 m / s.

5. The metal article heat treatment process of claim 4, wherein, In step S2, the metal product is kept in the second temperature range for 25-35 min.

6. The metal article heat treatment process of claim 1, wherein, In step S2, the input speed of nitrogen in the second gas quenching is 10-15 m / s.

7. The metal article heat treatment process of claim 6, wherein, In step S2, the metal product is kept in the third temperature range for 25-35 min.

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