CN112575240A

CN112575240A - Manufacturing method of compressor piston and compressor piston

Info

Publication number: CN112575240A
Application number: CN201910926171.XA
Authority: CN
Inventors: 李海成; 龙春仙
Original assignee: Anhui Meizhi Precision Manufacturing Co Ltd
Current assignee: Anhui Meizhi Precision Manufacturing Co Ltd
Priority date: 2019-09-27
Filing date: 2019-09-27
Publication date: 2021-03-30

Abstract

The application provides a manufacturing method of a compressor piston and the compressor piston, wherein the manufacturing method comprises the following steps: processing a nodular cast iron base material to form a piston semi-finished product; carrying out heat treatment on the piston semi-finished product, wherein the heat treatment comprises quenching treatment and low-temperature tempering treatment; and processing the piston semi-finished product after the heat treatment to form a piston finished product. By the mode, the piston which is lower in cost and meets the requirement of wear resistance can be provided.

Description

Manufacturing method of compressor piston and compressor piston

Technical Field

The application relates to the technical field of compressors, in particular to a manufacturing method of a compressor piston and the compressor piston.

Background

The piston is one of the key parts of the rotary compressor, and the rotation of the piston can drive the volume change of the refrigerant in the two cavities in the cylinder. The piston is always balanced with the front end of the sliding sheet, so that the piston is required to have high wear resistance, air tightness and small thermal expansion coefficient. Conventional pistons use gray cast iron containing the elements nicr-mo, and the wear resistance of the piston surface is generally increased by reducing or removing the elements nicr-mo from the nicr-mo gray cast iron and by improving the heat treatment process.

The inventor of the present application found that the conventional gray cast iron containing elements of nickel, chromium and molybdenum has a high cost per se in the long-term research process, and the subsequent process for improving the wear resistance of the gray cast iron further increases the cost of the gray cast iron. Therefore, there is a need for a piston that is less expensive and meets wear resistance requirements.

Disclosure of Invention

The technical problem that this application mainly solved provides a compressor piston's manufacturing method and compressor piston, can provide a lower and satisfy the required piston of wearability of cost.

In order to solve the technical problem, the application adopts a technical scheme that: provided is a method for manufacturing a compressor piston, including: processing a nodular cast iron base material to form a piston semi-finished product; carrying out heat treatment on the piston semi-finished product, wherein the heat treatment comprises quenching treatment and low-temperature tempering treatment; and processing the piston semi-finished product after the heat treatment to form a piston finished product.

Wherein the chemical components of the nodular cast iron base material comprise: c, carbon C: 3.0% -4.0%; silicon Si: 2.0% -3.0%; manganese Mn: less than or equal to 1.0 percent; phosphorus P: less than or equal to 0.1 percent; s, sulfur: less than or equal to 0.06 percent; magnesium Mg: 0.03% -0.06%; copper Cu: 0.5-0.8 percent, and the balance of Fe, wherein the percentage is the mass percentage.

Wherein the surface hardness of the piston semi-finished product and the piston finished product after heat treatment is within the range of 45HRc-58HRc, and/or the tensile strength is more than or equal to 400 MPa.

Wherein, the metallographic structure of the piston semi-finished product after heat treatment comprises: tempered martensite, spherical graphite, uniformly distributed carbides and residual austenite structure.

Wherein the metallographic structure of the piston semi-finished product which is not subjected to heat treatment comprises spherical graphite, pearlite and ferrite.

Wherein the spheroidization rate of the metallographic structure graphite of the piston semi-finished product which is not subjected to heat treatment is more than 70%.

Wherein the quenching temperature of the quenching treatment is 830-950 ℃, and/or the heat preservation time is 1-4 h, and/or the quenching liquid is oil or water.

Wherein the heat preservation temperature of the low-temperature tempering treatment is 180-200 ℃, and/or the heat preservation time is 2-6 h.

In order to solve the above technical problem, another technical solution adopted by the present application is: there is provided a compressor piston made by the method of manufacture described in any one of the above embodiments.

Wherein the compressor piston is applied in a rotary compressor.

The beneficial effect of this application is: the compressor piston is made of nodular cast iron, the nodular cast iron has the advantages of good casting performance, shock resistance and wear resistance, and the cost of the compressor piston is lower than that of a traditional gray cast iron piston; after quenching treatment and low-temperature tempering treatment, the hardness of the nodular cast iron is improved, and the wear resistance of the nodular cast iron is further improved, so that the wear resistance requirement of the piston for the compressor can be met.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts. Wherein:

FIG. 1 is a schematic flow chart illustrating one embodiment of a method for manufacturing a piston for a compressor according to the present application;

FIG. 2 is a schematic structural view of an embodiment of a piston of the compressor of the present application;

fig. 3 is a schematic structural diagram of an embodiment of a compression mechanism of a rotary compressor.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Referring to fig. 1, fig. 1 is a schematic flow chart illustrating an embodiment of a method for manufacturing a piston of a compressor according to the present application, the method including:

s101: and processing the nodular cast iron base material to form a piston semi-finished product.

Specifically, spheroidal graphite cast iron is cast iron in which carbon obtained by spheroidization and inoculation is precipitated as spheroidal graphite, and has good castability, wear resistance, and machinability. The nodular cast iron has excellent mechanical property and technological property, and the mechanical property can be further improved through heat treatment, so that the nodular cast iron can be used for manufacturing parts with larger load and more complex stress, such as a compressor piston, or a crankshaft, a connecting rod, a gear, a machine tool spindle and the like.

In one embodiment, the chemical composition of the nodular cast iron base material used in the above step S101 includes: c, carbon C: 3.0% -4.0% (e.g., 3.2%, 3.5%, 3.8%, etc.); silicon Si: 2.0% -3.0% (e.g., 2.2%, 2.5%, 2.7%, etc.); manganese Mn: less than or equal to 1.0% (e.g., 0.7%, 0.5%, 0.2, etc.); phosphorus P: 0.1% or less (e.g., 0.08, 0.05, etc.); s, sulfur: less than or equal to 0.06% (e.g., 0.05%, 0.03%, etc.); magnesium Mg: 0.03% -0.06% (e.g., 0.04%, 0.05%, etc.); copper Cu: 0.5% -0.8% (e.g., 0.6%, 0.7%, etc.), and the balance being Fe, wherein the above percentages are mass percentages.

Wherein carbon C in the nodular cast iron base material is an element necessary for crystallizing and precipitating the spheroidal graphite, and the carbon content in the range of 3.0% to 4.0% causes the spheroidal graphite to crystallize and precipitate. Silicon Si is an element necessary for crystallizing and precipitating spherical graphite, and the silicon content in the range of 2.0% to 3.0% is advantageous for crystallizing and precipitating spherical graphite and can suppress generation of scum defects and floating of graphite. Manganese Mn is an element having an effect of making graphite fine and strengthening a pearlite structure, and the manganese Mn in the range of not more than 1.0% is advantageous for exerting its effect. Magnesium Mg is an element necessary for obtaining spherical graphite, and magnesium Mg in the above-mentioned range of 0.03% to 0.06% is advantageous for achieving the object, and can suppress dross defects, void defects, shrinkage cavities, white spots, and the like. Copper Cu can suppress carbides, and is advantageous for obtaining spheroidal graphite. Phosphorus P and sulfur S are inevitable impurities in the nodular cast iron, and the content of the phosphorus P and the sulfur S can be reduced as much as possible.

Further, the step S101 specifically includes: spheroidizing the molten metal, wherein the spheroidizing has the effect of making the graphite spherical during the crystal growth to improve the appearance of the base material and improve the mechanical property of the casting; pouring molten metal into a casting mold, and adding an inoculant for inoculation, wherein the inoculation aims at eliminating white cast, increasing eutectic clusters and graphite nodules, refining, eliminating segregation, eliminating the tendency of crystal supercooling and the like, and the inoculant can be Si-Fe and the like; after cooling, a semi-finished piston is obtained from the casting mould.

S102: and carrying out heat treatment on the piston semi-finished product, wherein the heat treatment comprises quenching treatment and low-temperature tempering treatment.

Specifically, in the present embodiment, the metallographic structure of the non-heat-treated piston semi-finished product provided in step S101 is composed of spheroidal graphite and a matrix structure including pearlite and ferrite; wherein, ferrite is a single-phase structure, is a gap solid solution formed by dissolving carbon in alpha-Fe, and has low strength and hardness, but good plasticity and toughness; pearlite is a two-phase structure, a mechanical mixture of ferrite and cementite, which is a metal compound formed by iron and carbon and has the chemical formula of Fe₃And C, the pearlite strength and the hardness are high. The non-heat-treated piston semi-finished product having the above-described metallographic structure can balance strength and plasticity by ferrite and pearlite.

Further, the above-mentioned non-heat-treated piston semi-finished product has a graphite spheroidization rate of a metallographic structure of 70% or more (for example, 80%, 90%, etc.), and the above-mentioned graphite spheroidization rate of 70% or more can improve the impact strength, fatigue property, corrosion resistance, and wear resistance of the spheroidal graphite cast iron.

In a specific application scene, the metallographic structure of the non-heat-treated piston semi-finished product comprises spherical graphite, a bullseye structure and ferrite, wherein the graphite spheroidization rate is more than 80%, and the ferrite content is less than 25%; wherein the bullseye structure is a structure similar to bullseye shape formed by surrounding ferrite around spherical graphite, and pearlite around the periphery of the ferrite, the ferrite content in the bullseye structure is below 25% (e.g. 5%, 10%, etc.), and the ferrite content in the whole metallographic structure is below 25% (e.g. 20%, 15%, etc.). The piston semi-finished product with the metallographic structure and without heat treatment has good strength and hardness performance, is beneficial to preparing a wear-resistant piston, and is particularly suitable for pistons for rotary compressors.

In another embodiment, the metallographic structure of the piston semi-finished product after the heat treatment in step S102 includes: tempered martensite, spherical graphite, uniformly distributed carbides and residual austenite structures; the tempered martensite is a complex phase structure formed by desolventizing the carbon in the form of transition carbide and dispersed with extremely fine transition carbide sheets (the interface with the matrix is a coherent interface) in a solid solution matrix (the crystal structure is changed into body-centered cubic), has high hardness and high wear resistance, and has improved toughness due to reduced internal stress. The carbide is a binary compound consisting of metal or nonmetal and carbon, can be granular and uniformly distributed in a metallographic structure, and can improve the comprehensive mechanical property of the nodular cast iron. The retained austenite structure is a portion that is not transformed during quenching, and is associated with a quenching treatment process, such as a holding temperature at the time of quenching, a cooling rate, and the like. The residual small amount of austenite structure has certain toughness, exists between tempered martensite with high strength in a film shape or a block shape, can release stress at the tip of a crack, increases energy required by crack propagation, can effectively prevent crack propagation, and improves the overall strength and the toughness to a certain extent.

In another embodiment, the quenching process in step S102 includes: firstly, heating a piston semi-finished product to a temperature above a eutectoid temperature, and preserving heat for a period of time, wherein a nodular cast iron base material is austenitized; and then rapidly cooling the steel plate to a bainite transformation region in the quenching liquid at a cooling speed which is higher than that of pearlite formation for isothermal treatment, wherein an austenitizing part is transformed into bainite at the moment, and the strength and the toughness of the bainite are higher. In the present embodiment, the quenching temperature of the quenching treatment is 830 to 950 ℃ (i.e., the temperature is increased to a temperature higher than the eutectoid temperature in the above process), for example, 870 ℃, 900 ℃, or the like; and/or the holding time is 1h-4h, such as 2h, 3h and the like; and/or the quenching liquid is oil or water. The strength, hardness and wear resistance of the nodular cast iron are improved after the quenching process.

Because the piston semi-finished product is rapidly cooled in the quenching treatment, internal stress can appear in the piston semi-finished product, the plasticity and the toughness are reduced, in order to further improve the comprehensive performance of the piston semi-finished product, the piston semi-finished product is subjected to low-temperature tempering treatment after the quenching treatment, and the low-temperature tempering technological process comprises the following steps: and (3) reheating the quenched piston semi-finished product to a proper temperature, preserving heat for a plurality of times, and then slowly or rapidly cooling. In this embodiment, the temperature of the low temperature tempering treatment is 180 ℃ to 200 ℃, for example, 190 ℃; and/or the incubation time is 2h to 6h, e.g., 3h, 4h, 5h, etc. The number of times of the low-temperature tempering treatment may be one or more.

Further, in the above embodiment, the surface hardness of the piston semi-finished product after heat treatment is in the range of 45HRc-58HRc (e.g., 48HRc, 50HRc, 55HRc, etc.), and/or the tensile strength is not less than 400MPa (e.g., 450MPa, 500MPa, 550MPa, etc.). The hardness and tensile strength indicate that the piston semi-finished product after heat treatment has better wear resistance.

When the above-mentioned heat-treated piston semifinished product was subjected to a heat deformation test under a condition of keeping it at 170 ℃ for 24 hours, it was found that the dimensional change was 0.01% or less. The test results show that the thermal stability of the piston semifinished product obtained by this heat treatment is high.

S103: and processing the piston semi-finished product after heat treatment to form a piston finished product.

Specifically, the heat-treated piston semi-finished product may be subjected to a finishing process to form a piston finished product.

The method for manufacturing a piston for a compressor provided by the present application is further described below in a specific embodiment.

Firstly, roughly processing a nodular cast iron casting with the model of QT600/QT500 into a piston semi-finished product; then quenching the semi-finished piston product, wherein the quenching temperature is 860 ℃, and the heat preservation time is 60 min; then, carrying out low-temperature tempering treatment on the piston semi-finished product, wherein the heat preservation temperature is 200 ℃, the heat preservation time is 180min, and the surface hardness of the heat-treated piston semi-finished product is 55 HRc; and finally, performing finish machining on the heat-treated piston semi-finished product to form a piston finished product.

Referring to fig. 2-3, fig. 2 is a schematic structural view of an embodiment of a piston of a compressor according to the present application, and fig. 3 is a schematic structural view of an embodiment of a compression mechanism of a rotary compressor. The compressor piston is manufactured by the manufacturing method in any one of the above embodiments, the specific shape of the compressor piston 100 is not limited in the present application, and the compressor piston 100 provided in the present application may be applied to a rotary compressor, a reciprocating compressor, and the like.

The following description will be made by taking a rotary compressor as an example. The rotary compressor, which may be generally used in an air conditioner, a refrigerator, or the like, includes a housing, and a motor part and a compression mechanism 10 disposed in the housing, wherein the motor part is used to output a rotational power, and the compression mechanism 10 and the motor part perform a motion transmission via a crankshaft. The compression mechanism 10 includes a piston 100 that eccentrically rotates by being driven by a crankshaft, and a cylinder 102 that engages with the piston 100, and a compression chamber 104 is formed between an inner peripheral surface of the cylinder 102 and an outer peripheral surface of the piston 100. A sliding piece mounting groove (not marked) is formed in the cylinder 102, a sliding piece 106 is movably arranged in the sliding piece mounting groove, and a front end a of the sliding piece 106 extends out of the sliding piece mounting groove and abuts against the outer peripheral surface of the piston 100 so as to divide the compression cavity 104 into an air suction cavity and an air exhaust cavity. Since the piston 100 and the front end a of the sliding vane 106 always abut against each other, the piston 100 provided by the present application is required to have high wear resistance.

In one embodiment, the compressor piston 100 is made of nodular cast iron, and the chemical composition of the nodular cast iron includes: c, carbon C: 3.0% -4.0% (e.g., 3.2%, 3.5%, 3.8%, etc.); silicon Si: 2.0% -3.0% (e.g., 2.2%, 2.5%, 2.7%, etc.); manganese Mn: less than or equal to 1.0% (e.g., 0.7%, 0.5%, 0.2, etc.); phosphorus P: 0.1% or less (e.g., 0.08, 0.05, etc.); s, sulfur: less than or equal to 0.06% (e.g., 0.05%, 0.03%, etc.); magnesium Mg: 0.03% -0.06% (e.g., 0.04%, 0.05%, etc.); copper Cu: 0.5% -0.8% (e.g., 0.6%, 0.7%, etc.), and the balance being Fe, wherein the above percentages are mass percentages.

Wherein carbon C in the nodular cast iron base material is an element required for crystallizing and precipitating the spheroidal graphite, and the content of the carbon C in the range of 3.0-4.0% causes the spheroidal graphite to crystallize and precipitate. Silicon Si is an element necessary for crystallization of spherical graphite, and the content of silicon Si in the range of 2.0% to 3.0% is advantageous for crystallization of spherical graphite and can suppress generation of scum defects and floating of graphite. Manganese Mn is an element having an effect of making graphite fine and strengthening a pearlite structure, and the manganese Mn in the range of not more than 1.0% is advantageous for exerting its effect. Magnesium Mg is an element necessary for obtaining spherical graphite, and magnesium Mg in the above-mentioned range of 0.03% to 0.06% is advantageous for achieving the object, and can suppress dross defects, void defects, shrinkage cavities, white spots, and the like. Copper Cu can suppress carbides, and is advantageous for obtaining spheroidal graphite. Phosphorus P and sulfur S are inevitable impurities in the nodular cast iron, and the content of the phosphorus P and the sulfur S can be reduced as much as possible.

In yet another embodiment, the compressor piston 100 has a surface hardness in the range of 45HRc-58HRc (e.g., 48HRc, 50HRc, 55HRc, etc.), and/or a tensile strength ≧ 400MPa (e.g., 450MPa, 500MPa, 550MPa, etc.).

In yet another embodiment, the metallographic structure of the compressor piston 100 comprises: tempered martensite, spherical graphite, uniformly distributed carbides and residual austenite structures; the tempered martensite is a complex phase structure formed by desolventizing the carbon in the form of transition carbide and dispersed with extremely fine transition carbide sheets (the interface with the matrix is a coherent interface) in a solid solution matrix (the crystal structure is changed into body-centered cubic), has high hardness and high wear resistance, and has improved toughness due to reduced internal stress. The carbide is a binary compound consisting of metal or nonmetal and carbon, can be granular and uniformly distributed in a metallographic structure, and can improve the comprehensive mechanical property of the nodular cast iron. The retained austenite structure is a portion that is not transformed during quenching, and is associated with a quenching treatment process, such as a holding temperature at the time of quenching, a cooling rate, and the like. The residual small amount of austenite structure has certain toughness, exists between martensite with high strength in a film shape or a block shape, can release stress at the tip of a crack, increases energy required by crack propagation, can effectively prevent crack propagation, and improves the overall strength and the toughness to a certain extent.

In summary, the material forming the compressor piston 100 of the present application is nodular cast iron, which has the advantages of good casting performance, shock resistance and wear resistance, and the cost is lower than that of the conventional gray cast iron piston; after quenching treatment and low-temperature tempering treatment, the hardness of the nodular cast iron is improved, and the wear resistance of the nodular cast iron is further improved, so that the wear resistance requirement of the piston for the compressor can be met.

The above description is only for the purpose of illustrating embodiments of the present application and is not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings of the present application or are directly or indirectly applied to other related technical fields, are also included in the scope of the present application.

Claims

1. A method of manufacturing a compressor piston, comprising:

processing a nodular cast iron base material to form a piston semi-finished product;

carrying out heat treatment on the piston semi-finished product, wherein the heat treatment comprises quenching treatment and low-temperature tempering treatment;

and processing the piston semi-finished product after the heat treatment to form a piston finished product.

2. The manufacturing method according to claim 1,

the chemical components of the nodular cast iron base material comprise: c, carbon C: 3.0% -4.0%; silicon Si: 2.0% -3.0%; manganese Mn: less than or equal to 1.0 percent; phosphorus P: less than or equal to 0.1 percent; s, sulfur: less than or equal to 0.06 percent; magnesium Mg: 0.03% -0.06%; copper Cu: 0.5-0.8 percent, and the balance of Fe, wherein the percentage is the mass percentage.

3. The manufacturing method according to claim 1, wherein the surface hardness of the piston semi-finished product and the piston finished product after the heat treatment is within a range of 45HRc-58HRc, and/or the tensile strength is not less than 400 MPa.

4. The manufacturing method according to claim 1, wherein the metallographic structure of the piston semi-finished product after the heat treatment comprises: tempered martensite, spherical graphite, uniformly distributed carbides and residual austenite structure.

5. The manufacturing method according to claim 4, wherein the metallographic structure of the piston semi-finished product that has not been heat-treated includes spheroidal graphite, pearlite, and ferrite.

6. The manufacturing method according to claim 5,

the graphite spheroidization rate of the metallographic structure of the piston semi-finished product which is not subjected to heat treatment is more than 70%.

7. The manufacturing method according to claim 1, wherein the quenching temperature of the quenching treatment is 830-950 ℃, and/or the holding time is 1-4 h, and/or the quenching liquid is oil or water.

8. The manufacturing method according to claim 1, wherein the low-temperature tempering treatment is performed at a holding temperature of 180 ℃ to 200 ℃ and/or for a holding time of 2h to 6 h.

9. Compressor piston, characterized in that it is manufactured with the manufacturing method according to any one of claims 1 to 8.

10. The compressor piston as recited in claim 9, wherein the compressor piston is utilized in a rotary compressor.