Secondary quenching system for reducing thermal expansion amount of 20Cr piston pin

Abstract

The utility model discloses a secondary quenching system for reducing the thermal expansion amount of a 20Cr piston pin, which relates to the technical field of quenching and comprises a mounting base provided with a quenching mechanism convenient for secondary quenching of the piston pin. The quenching mechanism comprises a gantry support, a heat treatment furnace and a quenching pool, the heat treatment furnace is fixedly mounted at the upper end of the mounting base, and the quenching pool is fixedly mounted at the upper end of the mounting base. The secondary quenching process is adopted, the surface of the piston pin can obtain higher hardness and strength through secondary quenching, a hard carbonitriding compound layer is formed on the surface after carbonitriding, the martensite structure is further refined through secondary quenching, the bearing capacity of the material is enhanced, the swelling capacity of the material is reduced, and the service life of the material is prolonged. And in actual use, the influence of environment temperature is smaller, and the use is more stable.

Description

Technical Field

[0001] The utility model relates to the technical field of quenching, in particular to a secondary quenching system for reducing the thermal expansion of a 20Cr piston pin. Background Art

[0002] The piston pin is a cylindrical pin installed on the piston skirt. Its middle part passes through the small end hole of the connecting rod. It is used to connect the piston and the connecting rod, and transmit the gas force borne by the piston to the connecting rod. It plays a key role in the energy conversion and transmission process of the internal combustion engine. During the operation of the internal combustion engine, the high temperature generated by the combustion of the fuel will be transmitted to the piston pin. Under heating conditions, the piston pin will have a certain amount of thermal expansion. If its expansion exceeds the matching size with the small end of the connecting rod, it will accelerate the wear of the piston pin.

[0003] The existing piston pin quenching process is carbonitriding → direct oil quenching → low-temperature tempering → cold treatment (keeping at -60℃ for 120 minutes) → secondary low-temperature tempering → cold treatment (for heats that fail the thermal stability test).

[0004] However, during the implementation of the above technical solution, at least the following technical problems were found: the existing piston pin quenching process is to use oil quenching after carbonitriding. After quenching, the piston pin is tested by metal image. The carburized layer contains 5%-10% retained austenite. In order to reduce the content of retained austenite, a cold treatment process is used to transform the retained austenite into a martensite structure. This process has a long production cycle, high production costs, and a low pass rate in thermal stability tests. Utility Model Content

[0005] (1) Technical problems solved

[0006] In view of the shortcomings of the existing technology, the utility model provides a secondary quenching system for reducing the thermal expansion of 20Cr piston pins, which solves the technical problems of the existing piston pin quenching process, which is oil quenching after carbonitriding. The piston pin after quenching is subjected to metal image detection and the carburized layer contains 5%-10% retained austenite. In order to reduce the content of retained austenite, a cold treatment process is adopted to transform the retained austenite into martensite structure. This process has a long production cycle, high production cost and low thermal stability test pass rate.

[0007] (2) Technical solution

[0008] In order to achieve the above objectives, the present invention is implemented through the following technical solutions:

[0009] A secondary quenching system for reducing the thermal expansion of a 20Cr piston pin comprises a mounting base, the mounting base being provided with a quenching mechanism for facilitating secondary quenching of the piston pin, the quenching mechanism comprising a gantry support, a heat treatment furnace and a quenching pool, the heat treatment furnace being fixedly mounted on the upper end portion of the mounting base, the quenching pool being fixedly mounted on the upper end portion of the mounting base, a low-temperature tempering furnace being also fixedly mounted on the upper end portion of the mounting base, electric slide rails being provided on both side ends of the mounting base, the gantry support being fixedly mounted on the electric slide rails, a drive motor being provided on the gantry support, a hoist being provided on the gantry support, a furnace door being provided on the side end portion of the heat treatment furnace, and a temperature control device being provided on the circumferential end portion of the heat treatment furnace.

[0010] Preferably, an exhaust mechanism is fixedly installed on the side end of the quenching tank, and a stirring mechanism is provided on the inner side wall of the quenching tank.

[0011] Preferably, a control panel is provided at the side end of the low-temperature tempering furnace.

[0012] (3) Beneficial effects

[0013] 1. This device is equipped with a secondary quenching process, which can make the piston pin surface obtain higher hardness and strength. After carbonitriding, a hard carbonitride layer is formed on the surface. The secondary quenching further refines the martensite structure, enhances the material's load-bearing capacity, and reduces its expansion. In actual use, it is less affected by the ambient temperature and is more stable.

[0014] 2. This device greatly reduces production costs, shortens production cycles, and uses a secondary quenching process, eliminating the need for cold treatment and secondary tempering, thereby improving the efficiency of piston pin production and providing high practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and to implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings.

[0016] Figure 1 This is a structural diagram of the installation base of the utility model;

[0017] Figure 2 This is a structural diagram of the gantry bracket of the utility model;

[0018] Figure 3 This is a structural diagram of the heat treatment furnace of the utility model;

[0019] Figure 4 This is a structural diagram of the low-temperature tempering furnace of the utility model.

[0020] Legend: 1. Mounting base; 11. Electric slide rail; 2. Gantry bracket; 21. Lifter; 22. Drive motor; 3. Heat treatment furnace; 31. Temperature control equipment; 32. Furnace door; 4. Quenching tank; 41. Exhaust mechanism; 5. Low-temperature tempering furnace; 51. Control panel. DETAILED DESCRIPTION

[0021] The embodiment of the present application provides a secondary quenching system for reducing the thermal expansion of a 20Cr piston pin, thereby effectively solving the existing piston pin quenching process. The system uses oil quenching after carbonitriding. After quenching, the piston pin is subjected to metal image inspection, and the quenched layer contains 5%-10% residual austenite. In order to reduce the content of residual austenite, a cold treatment process is used to transform the residual austenite into a martensite structure. This process has the technical problems of a long production cycle, high production cost, and a low pass rate in thermal stability tests. The present device is provided with a secondary quenching process. The secondary quenching can make the piston pin surface obtain higher hardness and strength. After carbonitriding, a hard carbonitride layer is formed on the surface, and the secondary quenching further refines the martensite structure, enhances the material's bearing capacity, and reduces its expansion. In actual use, it is less affected by the ambient temperature and is more stable to use.

[0022] Example

[0023] like Figure 1 、 Figure 2 、 Figure 3 and Figure 4 The technical solution in the embodiment of the present application is to effectively solve the existing piston pin quenching process, which is to use oil quenching after carbonitriding. After quenching, the piston pin is subjected to metal image detection. The carburized layer contains 5%-10% retained austenite. In order to reduce the content of retained austenite, a cold treatment process is used to transform the retained austenite into a martensite structure. The process has a long production cycle, high production cost, and a low pass rate in the thermal stability test. The overall idea is as follows: A secondary quenching system for reducing the thermal expansion of a 20Cr piston pin includes a mounting base 1, and the mounting base 1 is provided with a mounting base 1 for facilitating secondary quenching of the piston pin. The quenching mechanism includes a gantry support 2, a heat treatment furnace 3 and a quenching pool 4. The heat treatment furnace 3 is fixedly mounted on the upper end of the mounting base 1, the quenching pool 4 is fixedly mounted on the upper end of the mounting base 1, and a low-temperature tempering furnace 5 is also fixedly mounted on the upper end of the mounting base 1. Both ends of the mounting base 1 are provided with electric slide rails 11, the gantry support 2 is fixedly mounted on the electric slide rails 11, the gantry support 2 is provided with a drive motor 22, and the gantry support 2 is also provided with a hoist 21. When the piston pin on the workpiece rack is transferred, it can be achieved by the cooperation of the gantry support 2, the hoist 21 and the drive motor 22;

[0024] A furnace door 32 is provided at the side end of the heat treatment furnace 3, and a temperature control device 31 is provided at the circumferential end of the heat treatment furnace 3. First, carbonitriding is performed. The heat treatment furnace 3 is used to precisely control parameters such as the temperature, carbon potential, and nitrogen potential in the heat treatment furnace 3. The workpiece holder is lifted by the lifter 21 to place the piston pin into the heat treatment furnace 3 for treatment. The carbonitriding time depends on the size and shape of the piston pin and the required depth of the carburized layer.

[0025] After the workpiece is taken out of the heat treatment furnace 3, it is naturally cooled in the air for quenching. When the workpiece is cooled in the air, the surface temperature drops rapidly, a phase transformation occurs, and a martensite structure is formed. Air cooling quenching can make the workpiece surface obtain a certain hardness and strength. However, due to the relatively slow cooling rate, some residual austenite may be present. The workpiece that has been air-cooled and quenched is placed in the heat treatment furnace 3 again for heating. The heating temperature is determined according to the workpiece material and process requirements, and is generally slightly lower than the carbonitriding temperature.

[0026] An exhaust mechanism 41 is fixedly installed at the side end of the quenching tank 4. A stirring mechanism is provided on the inner side wall of the quenching tank 4. The heated workpiece is quickly placed in the quenching tank 4 filled with 10%-15% salt water for quenching. Salt water, as a quenching medium, has a high cooling rate and can quickly cool the workpiece surface to form a martensite structure. Compared with air cooling quenching, salt water quenching can more effectively reduce the content of retained austenite and improve the hardness and strength of the workpiece.

[0027] A control panel 51 is provided at the side end of the low-temperature tempering furnace 5. The quenched workpiece is placed in the low-temperature tempering furnace 5 for low-temperature tempering. The tempering temperature and time are controlled by the control panel 51. The tempering time should ensure that the workpiece structure is fully stable, eliminate quenching stress, and improve the toughness and dimensional stability of the workpiece.

[0028] In response to the problems existing in the prior art, the utility model provides a secondary quenching system for reducing the thermal expansion of a 20Cr piston pin. The device is equipped with a secondary quenching process, which can enable the piston pin surface to obtain higher hardness and strength. After carbonitriding, a hard carbonitride layer is formed on the surface, and the secondary quenching further refines the martensitic structure, enhances the material's bearing capacity, and reduces its expansion. In actual use, it is less affected by the ambient temperature and is more stable to use.

[0029] Working principle:

[0030] When the user quenches the piston pin, the process is carried out according to the following steps: carbonitriding → air cooling quenching → heating in the furnace → secondary quenching (10%-15% brine) → low temperature tempering. First, carbonitriding is carried out. A heat treatment furnace 3 is used to precisely control the temperature, carbon potential, nitrogen potential and other parameters in the heat treatment furnace 3. The workpiece holder is lifted by the lifter 21 to place the piston pin into the heat treatment furnace 3 for treatment. The carbonitriding time depends on the size, shape and required depth of the penetration layer of the piston pin. After the workpiece is taken out of the heat treatment furnace 3, it is naturally cooled in the air for quenching. When the workpiece is cooled in the air, the surface temperature drops rapidly, a phase transformation occurs, and a martensitic structure is formed. Air cooling quenching Air quenching can make the surface of the workpiece obtain a certain hardness and strength, but due to the relatively slow cooling rate, it may cause the existence of some residual austenite. The workpiece that has been air-cooled quenched is placed in the heat treatment furnace 3 for heating again. The heating temperature is determined according to the workpiece material and process requirements. It is generally slightly lower than the carbonitriding temperature. The heating time must ensure that the workpiece can be evenly heated to the set temperature so that the structure is fully austenitized. The heated workpiece is quickly placed in the quenching pool 4 filled with 10%-15% salt water for quenching. Salt water, as a quenching medium, has a higher cooling rate, which can quickly cool the surface of the workpiece and form a martensitic structure. Compared with air quenching, salt water quenching can In order to more effectively reduce the content of retained austenite and improve the hardness and strength of the workpiece, the quenched workpiece is placed in a low-temperature tempering furnace 5 for low-temperature tempering. The tempering temperature and time are controlled by a control panel 51. The tempering time must ensure that the workpiece structure is fully stable, the quenching stress is eliminated, and the toughness and dimensional stability of the workpiece are improved. When the piston pin on the workpiece rack is transferred, it can be achieved by the gantry bracket 2, the hoist 21 and the drive motor 22. The existing piston pin quenching process is to quench with oil after carbonitriding. The quenched piston pin is tested by gold image. The carburized layer contains 5%-10% retained austenite. In order to reduce the content of retained austenite, a cold treatment process is adopted to make the retained austenite The remaining austenite is transformed into martensite structure. This process has a long production cycle, high production cost, and a low pass rate in the thermal stability test. This device is equipped with a secondary quenching process. The secondary quenching can make the piston pin surface obtain higher hardness and strength. After carbonitriding, a hard carbonitride layer is formed on the surface, and the secondary quenching further refines the martensite structure, enhances the material's bearing capacity, and reduces its expansion. In actual use, it is less affected by the ambient temperature and is more stable to use. This device greatly reduces production costs and shortens production cycles. The secondary quenching process does not require cold treatment and secondary tempering, which improves the efficiency of piston pin production and is highly practical.

[0031] Finally, it should be noted that: apparently, the above embodiments are merely examples for clearly illustrating the utility model, and are not limited to the implementation. For ordinary skilled persons in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the implementation. The obvious changes or variations derived therefrom are still within the protection scope of the utility model.

Claims

1. A secondary quenching system for reducing the thermal expansion of a 20Cr piston pin, comprising a mounting base (1), characterized in that: The mounting base (1) is provided with a quenching mechanism for facilitating secondary quenching of the piston pin; The quenching mechanism comprises a gantry support (2), a heat treatment furnace (3) and a quenching pool (4); the heat treatment furnace (3) is fixedly mounted on the upper end of the mounting base (1); the quenching pool (4) is fixedly mounted on the upper end of the mounting base (1); and a low-temperature tempering furnace (5) is also fixedly mounted on the upper end of the mounting base (1).

2. A secondary quenching system for reducing thermal expansion of a 20Cr piston pin according to claim 1, characterized in that: Both side ends of the mounting base (1) are provided with electric slide rails (11), and the gantry bracket (2) is fixedly mounted on the electric slide rails (11).

3. A secondary quenching system for reducing thermal expansion of a 20Cr piston pin according to claim 2, characterized in that: A driving motor (22) is provided on the gantry support (2), and a hoist (21) is also provided on the gantry support (2).

4. A secondary quenching system for reducing thermal expansion of a 20Cr piston pin according to claim 3, characterized in that: A furnace door (32) is provided at a side end portion of the heat treatment furnace (3).

5. A secondary quenching system for reducing thermal expansion of a 20Cr piston pin according to claim 4, characterized in that: A temperature control device (31) is provided at the circumferential end of the heat treatment furnace (3).

6. A secondary quenching system for reducing thermal expansion of a 20Cr piston pin according to claim 5, characterized in that: An exhaust mechanism (41) is fixedly installed on the side end of the quenching tank (4), and a stirring mechanism is provided on the inner side wall of the quenching tank (4).

7. A secondary quenching system for reducing thermal expansion of a 20Cr piston pin according to claim 6, characterized in that: The inner side wall of the quenching tank (4) is provided with a stirring mechanism.

8. A secondary quenching system for reducing thermal expansion of a 20Cr piston pin according to claim 7, characterized in that: A control panel (51) is provided at a side end portion of the low-temperature tempering furnace (5).

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