CN109811295B - Vacuum carburizing furnace 750 ℃ low-temperature carburizing process for precision parts - Google Patents
Vacuum carburizing furnace 750 ℃ low-temperature carburizing process for precision parts Download PDFInfo
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Abstract
The invention relates to a low-temperature carburizing process at 750 ℃ for a vacuum carburizing furnace of a precision part, which can realize carburizing treatment on the metal part at the temperature of 750 ℃, the metal part treated by the carburizing process can obtain uniform carburized layer, higher quenching hardness and steeper carburized layer gradient, and the metal part can obtain lower brittleness after tempering treatment and bending test, the bending surface of the metal part has no surface peeling, stripping and fracture phenomena, the vacuum carburizing furnace using the process has no intergranular oxidation in the carburizing process of the metal part, can improve the fatigue resistance of workpiece materials, the surface of the carburized and quenched metal part has no black carbon deposit, is beneficial to subsequent electroplating processing, in addition, no point-shaped or block-shaped carbide and no residual austenite are seen in the carburization of the part produced by the vacuum carburizing furnace, the carburized layer and the matrix have good bonding strength and toughness and excellent tissue structure.
Description
Technical Field
The invention relates to a low-temperature carburizing process at 750 ℃ in a vacuum carburizing furnace for precision parts.
Background
The traditional vacuum carburizing furnace is widely applied to the manufacturing industry, and the carburizing process temperature of the traditional vacuum carburizing furnace is above 860 ℃. However, with the rapid development of science and technology, the carburizing process of the traditional vacuum carburizing furnace cannot meet the new requirements of modern industry, and some modern industrial products have the following new requirements on carburized metal parts: the method has the advantages that firstly, the manufacturing of the metal parts has higher precision requirement, for example, the deformation is required to be smaller after carburizing and quenching so as to keep higher dimensional precision or meet smaller tolerance requirement, the subsequent processing procedure is reduced, and the purpose of reducing the cost is achieved; and secondly, the surface of the metal part can be kept clean after carburizing, quenching and tempering so as to meet the requirement of subsequent electroplating. In order to overcome the defects of the problems, meet the requirements of the modern electronic industry on certain metal parts and reduce the deformation of carburizing and quenching, the applicant develops a low-temperature carburizing process at 750 ℃ for a vacuum carburizing furnace of precise parts, which can carry out vacuum carburizing and quenching treatment on SPCC materials at 750 ℃ so as to expect that the parts processed by the low-temperature carburizing and quenching process can realize smaller size deformation and have higher surface strength.
Disclosure of Invention
The invention aims to solve the technical problem of providing a low-temperature carburizing process at 750 ℃ for a vacuum carburizing furnace of precise parts, wherein the parts produced by adopting the process can realize smaller dimensional deformation and have higher surface strength, and the process solves the problems that the temperature of the carburizing process of the traditional vacuum carburizing furnace is over 860 ℃, the parts treated by adopting the carburizing and quenching process cannot realize smaller deformation, cannot keep higher dimensional precision or meet smaller tolerance requirements, cannot reduce subsequent processing procedures, cannot reduce cost, cannot keep the surfaces of metal parts clean after carburizing, quenching and tempering, cannot carry out vacuum carburizing and quenching treatment on SPCC materials at 750 ℃ and the like. The invention is realized by the following technical scheme:
a low-temperature carburizing process of a precision part at 750 ℃ in a vacuum carburizing furnace comprises the following steps of firstly placing a metal part into the vacuum furnace, then heating the vacuum furnace to a certain temperature and keeping the temperature constant, then inputting nitrogen into the vacuum furnace until the air pressure in the vacuum furnace reaches 100Pa pressure, and after the vacuum furnace works for a period of time at the constant temperature and the constant air pressure of 100Pa pressure, entering the next step of operation.
Preferably, the vacuum furnace keeps the temperature at a constant temperature, then acetylene gas is input into the vacuum furnace in a pulse mode, the duration time of the acetylene gas pulse is 2 minutes, and the maximum pressure of the acetylene gas input into the vacuum furnace is 360 Pa; the method comprises the steps that acetylene gas is used as a carburizing medium to carburize a metal part in a vacuum furnace under the condition of constant temperature, so that the acetylene gas can be subjected to decomposition reaction with the surface of the metal part with certain temperature, carbon atoms can be left and enriched after the surface of the metal part is subjected to decomposition reaction, and carbon-containing saturated austenite can be formed after the metal part absorbs the carbon atoms and reaches certain concentration.
Preferably, in the third step, after the acetylene gas pulse is filled, the vacuum furnace keeps the temperature at a constant temperature, then nitrogen is input into the vacuum furnace for the second time, carbon atoms of carbon-containing saturated austenite on the surface of the metal part can be promoted to automatically diffuse into the metal part at the constant temperature along with the extension of the processing time in the vacuum furnace in a mode of maintaining the constant temperature, so that deep carburization is formed, the material state of the surface of the metal part can be changed from carbon-containing saturated austenite to carbon-containing unsaturated austenite, and the acetylene gas is input into the vacuum furnace in a pulse mode until the metal part adsorbs the carbon atoms again, so that the carbon-containing saturated austenite on the surface is formed, and the carbon-containing saturated austenite is diffused into the metal part again.
Preferably, in the fourth step, the vacuum furnace keeps the temperature at a constant temperature, then acetylene gas is input into the vacuum furnace for the second time, the vacuum furnace uses the acetylene gas as a carburizing medium, the surface of the metal part is continuously carburized again under a constant temperature environment and the same processing time, and the acetylene gas is stopped being conveyed into the vacuum furnace when the carbon-containing saturated austenite is formed on the surface of the metal part again. In the fourth step, the same processing time means a processing time of first feeding acetylene gas into the vacuum furnace.
Preferably, in the fifth step, the vacuum furnace keeps maintaining at a constant temperature, then nitrogen gas is fed into the vacuum furnace for the third time, the vacuum furnace keeps maintaining at a constant temperature to continuously promote the carbon atoms on the metal parts to be diffused again into the interior, that is, the vacuum furnace keeps at a constant temperature to diffuse the carbon atoms on the metal parts again for a period of time, and then the nitrogen gas feeding into the vacuum furnace is stopped.
Preferably, in the sixth step, the vacuum furnace keeps the temperature at a constant temperature, then acetylene gas is input into the vacuum furnace for the third time, the vacuum furnace uses the acetylene gas as a carburizing medium and continues to carry out vacuum carburization on the metal part under a constant temperature environment and the same processing time, and the acetylene gas is not conveyed into the vacuum furnace until the surface of the metal part forms carbon-containing saturated austenite again. In the sixth step, the same processing time means a processing time of first feeding the acetylene gas into the vacuum furnace.
Preferably, in the seventh step, the vacuum furnace keeps the temperature at a constant temperature, then nitrogen gas is fed into the vacuum furnace for the fourth time, and the vacuum furnace keeps the constant temperature to continuously promote the diffusion of the carbon atoms on the metal parts into the interior, that is, the vacuum furnace keeps the constant temperature to diffuse the carbon atoms on the metal parts for a while again, and then the nitrogen gas feeding into the vacuum furnace is stopped.
Preferably, in the step eight, the vacuum furnace keeps the temperature at a constant temperature, then acetylene gas is input into the vacuum furnace for the fourth time, the vacuum furnace takes the acetylene gas as a carburizing medium and continuously carburizes the metal part under a constant temperature environment and the same processing time, and the acetylene gas is not conveyed into the vacuum furnace until the surface of the metal part forms carbon-containing saturated austenite again. In the eighth step, the same processing time means a processing time of first feeding the acetylene gas into the vacuum furnace.
Preferably, in the ninth step, the vacuum furnace keeps the temperature at a constant temperature, then the nitrogen gas is fed into the vacuum furnace for the fifth time, the vacuum furnace keeps the constant temperature to promote the diffusion of the carbon atoms on the metal parts into the interior, and the vacuum furnace keeps the constant temperature to diffuse the carbon atoms on the metal parts again for a while, and then the nitrogen gas is stopped from being continuously fed into the vacuum furnace.
Preferably, step ten and finally, the vacuum furnace uses oil as a quenching medium to carry out continuous quenching on the metal part for a period of time so as to enable the metal part to reach the required structure and hardness for production.
Preferably, in the first step, the heating to a certain temperature means heating to 750 ℃, and the working period means working for 30 minutes.
Preferably, the constant temperature is 750 ℃ in the first to ninth steps.
Preferably, in the first step, the third step, the fifth step, the seventh step and the ninth step, each nitrogen gas input means inputting nitrogen gas into the vacuum furnace until the pressure in the vacuum furnace reaches 100 Pa.
Preferably, in the second, fourth, sixth and eighth steps, the maximum pressure of acetylene gas fed into the vacuum furnace is 360 Pa.
Preferably, in step two, step four, step six and step eight, the time for carburizing is set to 2 minutes.
Preferably, in step three, the time for diffusion is set to 6 minutes; in the fifth step, the diffusion for a period of time means diffusion for 10 minutes; in step seven, the time of diffusion is set to 15 minutes; in step nine, the diffusion for a second time is 20 minutes.
Preferably, in the step ten, the continuous quenching time is 10 minutes.
The invention has the beneficial effects that: 1. the invention can realize the carburization treatment of the metal part at the temperature of 750 ℃, the metal part treated by the carburization process can obtain a uniform carburized layer, higher quenching hardness and steeper carburized layer gradient, the metal part can obtain lower brittleness after tempering and bending test, the bending surface of the metal part has no surface peeling or stripping phenomenon, and the metal part has no fracture phenomenon after being bent for 90 degrees.
1. The vacuum carburizing furnace using the process does not generate intergranular oxidation in the carburizing process of the metal parts, not only can improve the fatigue resistance of workpiece materials, but also can avoid secondary processing of the metal parts under certain conditions, so that the cost can be reduced; and the surface of the metal part after carburization and quenching can not generate black carbon deposition, thereby being beneficial to the subsequent electroplating processing.
2. The carburized layer of the part produced by the method has no point or block carbide and no residual austenite, and has excellent structure; the carburized layer obtained by the process has good bonding strength and good toughness with a matrix, and is beneficial to service.
Drawings
For ease of illustration, the present invention is described in detail by the following preferred embodiments and the accompanying drawings.
Fig. 1 is an enlarged view of a bent portion structure of a metal part produced by a vacuum carburizing furnace at a low temperature of 750 ℃ by a carburizing process for precision parts according to an embodiment.
Fig. 2 is an enlarged view of a bent portion structure of a metal part produced by a vacuum carburizing furnace at a low temperature of 750 ℃ in a precision part according to the second embodiment, the bent portion structure being subjected to 90-degree bending detection.
Fig. 3 is an enlarged state diagram of a carburized layer and a matrix metallographic structure of a metal part produced by a vacuum carburizing furnace low-temperature carburizing process at 750 ℃ of a precision part according to the first embodiment.
FIG. 4 is an enlarged view of the carburized layer and the matrix metallographic structure of a metal part subjected to a carburized layer metallographic structure test in a vacuum carburizing furnace for precision parts according to the second embodiment, wherein the carburized layer and the matrix metallographic structure are produced by a low-temperature carburizing process at 750 ℃.
FIG. 5 is an enlarged view of the intergranular oxidation test of a metal part produced by the vacuum carburizing furnace at a low temperature of 750 ℃ carburizing process for precision parts according to the first embodiment.
FIG. 6 is an enlarged view of the intergranular oxidation test of a metal part produced by the vacuum carburizing furnace at a low temperature of 750 ℃ carburizing process for a precision part according to the second embodiment.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The first embodiment is as follows:
a low-temperature carburizing process at 750 ℃ for a vacuum carburizing furnace of precision parts comprises the steps of firstly placing metal parts into the vacuum furnace, heating the vacuum furnace to 750 ℃, then inputting nitrogen into the vacuum furnace until the air pressure in the vacuum furnace reaches 100Pa, and stopping inputting nitrogen into the vacuum furnace after the vacuum furnace continuously works for 30 minutes at 750 ℃ and 100 Pa.
In one embodiment, the vacuum furnace is kept at a constant temperature of 750 ℃, then acetylene gas is input into the vacuum furnace, the maximum pressure of the acetylene gas is maintained at 360Pa, so that the acetylene gas can generate decomposition reaction with the surface of the 750 ℃ metal part under the condition of the constant temperature, carbon atoms are left and gradually enriched after the decomposition reaction of the surface of the metal part, carbon-containing saturated austenite is formed after the surface of the metal material absorbs the carbon atoms, and the carbon atoms after the austenitization can be diffused into the workpiece body and form deep carburization. In this step, the acetylene gas is introduced for 2 minutes, which enables the surface of the metal part to form a sufficient amount of carbon-containing saturated austenite.
In one embodiment, in the third step, the vacuum furnace is kept at the constant temperature of 750 ℃, then, nitrogen is input into the vacuum furnace for the second time, the pressure of the nitrogen is maintained at 100Pa, the carbon atoms on the surface of the metal part can be promoted to diffuse into the metal part by maintaining the constant temperature of 750 ℃ in the vacuum furnace, and after the diffusion process is maintained for 6 minutes, the nitrogen is stopped from being continuously conveyed into the vacuum furnace.
In one embodiment, the vacuum furnace keeps the temperature at 750 ℃ continuously, then acetylene gas is input into the vacuum furnace for the second time, the pressure of the acetylene gas is maintained at 360Pa, the vacuum furnace uses the acetylene gas as a carburizing medium and carries out vacuum carburizing on the surface of the metal part for 2 minutes again under the constant temperature environment at 750 ℃ so as to promote the surface of the metal material to absorb carbon atoms and form carbon-containing saturated austenite, and then the acetylene gas is stopped from being conveyed into the vacuum furnace.
In one embodiment, in the fifth step, the vacuum furnace keeps the temperature at 750 ℃ continuously, then nitrogen is input into the vacuum furnace for the third time, the pressure of the nitrogen is maintained at 100Pa, the vacuum furnace keeps the temperature at 750 ℃ continuously to promote the carbon atoms on the metal part to diffuse into the metal part, and the nitrogen is stopped from being continuously transmitted into the vacuum furnace after the carbon atoms continuously diffuse for 10 minutes.
In one embodiment, in the sixth step, the vacuum furnace keeps the temperature at a constant temperature of 750 ℃, then acetylene gas is input into the vacuum furnace for the third time, the pressure of the acetylene gas is maintained at 360Pa, the vacuum furnace uses the acetylene gas as a carburizing medium and performs vacuum carburizing on the surface of the metal part for 2 minutes again in a constant temperature environment of 750 ℃ so as to promote the surface of the metal material to absorb carbon atoms and form carbon-containing saturated austenite, and then the acetylene gas is stopped from being conveyed into the vacuum furnace.
In one embodiment, in the seventh step, the vacuum furnace keeps the temperature at 750 ℃ continuously, then, nitrogen is input into the vacuum furnace for the fourth time, the pressure of the nitrogen is maintained at 100Pa, the vacuum furnace keeps the temperature at 750 ℃ continuously to promote the diffusion of the carbon atoms on the metal part into the metal part, and the nitrogen is stopped from being continuously transmitted into the vacuum furnace after the diffusion is continuously performed for 15 minutes.
In one embodiment, in the step eight, the vacuum furnace keeps the temperature at 750 ℃ continuously, then acetylene gas is input into the vacuum furnace for the fourth time, the pressure of the acetylene gas is maintained at 360Pa, the vacuum furnace uses the acetylene gas as a carburizing medium and carries out vacuum carburizing on the surface of the metal part for 2 minutes again in the constant temperature environment at 750 ℃ so as to promote the surface of the metal material to absorb carbon atoms to form carbon-containing saturated austenite, and then the acetylene gas is stopped from being conveyed into the vacuum furnace.
In one embodiment, in the ninth step, the vacuum furnace keeps the temperature at 750 ℃, then the nitrogen gas is fed into the vacuum furnace for the fifth time, the nitrogen gas pressure is maintained at 100Pa, the vacuum furnace keeps the temperature at 750 ℃ to continuously promote the carbon atoms on the metal part to diffuse into the metal part, and after the diffusion is continued for 20 minutes, the nitrogen gas is stopped being continuously fed into the vacuum furnace.
In one embodiment, step ten and finally, the metal part is quenched by the vacuum furnace for 10 minutes by using quenching oil as a quenching medium, so that the metal part can reach the required texture and hardness for production.
Example two:
a low-temperature carburizing process of a precision part at 750 ℃ in a vacuum carburizing furnace comprises the following steps of firstly placing a metal part into the vacuum furnace, then heating the vacuum furnace to 750 ℃, keeping the temperature constant, then inputting nitrogen into the vacuum furnace until the air pressure in the vacuum furnace reaches 100Pa pressure, and after the vacuum furnace works for 30 minutes at 750 ℃ and 100Pa pressure, entering the next step of operation.
In one embodiment, the vacuum furnace is kept at a constant temperature of 750 ℃ continuously, then acetylene gas is input into the vacuum furnace, the acetylene gas is input into the vacuum furnace in a pulse mode, the pulse time of the acetylene gas is 2 minutes, and the maximum pressure of the acetylene gas input into the vacuum furnace is kept at 360 Pa; the vacuum furnace is used for carburizing the metal parts by taking acetylene gas as a carburizing medium under the condition of keeping the constant temperature of 750 ℃, so that the acetylene gas can generate decomposition reaction with the surface of the metal parts at 750 ℃, carbon atoms can be left and enriched after the decomposition reaction of the surface of the metal parts, and carbon-containing saturated austenite can be formed after the metal parts absorb the carbon atoms and reach certain concentration.
In one embodiment, in the third step, after the acetylene gas pulse inflation is finished, the vacuum furnace keeps the temperature continuously at the constant temperature of 750 ℃, then nitrogen is input into the vacuum furnace for the second time, the pressure of the nitrogen is maintained at 100Pa, carbon atoms of carbon-containing saturated austenite on the surface of the metal part are automatically diffused into the metal part along with the extension of the processing time in the vacuum furnace in a mode of maintaining the constant temperature of 750 ℃, so that deep carburization is formed, the material state of the surface of the metal part can be changed from carbon-containing saturated austenite to carbon-containing unsaturated austenite, and the acetylene gas is input into the vacuum furnace in a pulse mode until the metal part adsorbs the carbon atoms again to form carbon-containing saturated austenite on the surface and diffuses into the interior of the metal part again.
In one embodiment, the vacuum furnace keeps the temperature at 750 ℃ continuously, then acetylene gas is input into the vacuum furnace for the second time, the pressure of the acetylene gas is maintained at 360Pa, the vacuum furnace uses the acetylene gas as a carburizing medium and continuously carburizes the surface of the metal part for 2 minutes at 750 ℃ continuously, and the acetylene gas is stopped being conveyed into the vacuum furnace when the surface of the metal part forms carbon-containing saturated austenite again.
In one embodiment, in the fifth step, the vacuum furnace keeps the temperature at 750 ℃, then nitrogen is input into the vacuum furnace for the third time, the pressure of the nitrogen is maintained at 100Pa, the vacuum furnace keeps the temperature at 750 ℃ to continuously promote the carbon atoms on the surface of the metal part to diffuse into the metal part again, namely the vacuum furnace keeps the temperature at 750 ℃ to diffuse the carbon atoms on the surface of the metal part again for 10 minutes, and then the nitrogen is stopped being continuously transmitted into the vacuum furnace.
In one embodiment, in the sixth step, the vacuum furnace keeps the temperature at 750 ℃ continuously, then acetylene gas is input into the vacuum furnace for the third time, the pressure of the acetylene gas is maintained at 360Pa, the vacuum furnace uses the acetylene gas as a carburizing medium and continues to carry out vacuum carburizing on the metal part at 750 ℃ for 2 minutes, and the acetylene gas is not conveyed into the vacuum furnace until the surface of the metal part forms carbon-containing saturated austenite again.
In one embodiment, in the seventh step, the vacuum furnace keeps the temperature at 750 ℃ continuously, then nitrogen is input into the vacuum furnace for the fourth time, the nitrogen pressure is maintained at 100Pa, the vacuum furnace keeps the temperature at 750 ℃ to continuously promote the diffusion of the carbon atoms on the surface of the metal part into the metal part, that is, the vacuum furnace keeps the temperature at 750 ℃ to diffuse the carbon atoms on the surface of the metal part for 15 minutes again, and then the nitrogen is stopped being continuously input into the vacuum furnace.
In one embodiment, in the step eight, the vacuum furnace keeps the temperature at the constant temperature of 750 ℃, then acetylene gas is input into the vacuum furnace for the fourth time, the pressure of the acetylene gas is maintained at 360Pa, the vacuum furnace uses the acetylene gas as a carburizing medium and continuously carburizes the metal part for 2 minutes under the constant temperature environment of 750 ℃, and the acetylene gas is not conveyed into the vacuum furnace until carbon-containing saturated austenite is formed on the surface of the metal part again.
In one embodiment, the vacuum furnace keeps the temperature at 750 ℃, then the nitrogen gas is fed into the vacuum furnace for the fifth time, the nitrogen gas pressure is maintained at 100Pa, the vacuum furnace keeps the temperature at 750 ℃ to continuously promote the diffusion of the carbon atoms on the surface of the metal part into the metal part, and the vacuum furnace keeps the temperature at 750 ℃ to diffuse the carbon atoms on the surface of the metal part for 20 minutes again before stopping feeding the nitrogen gas into the vacuum furnace.
In one embodiment, step ten and finally, the vacuum furnace uses oil as a quenching medium to continuously quench the metal part for 10 minutes so as to enable the metal part to reach the required texture and hardness for production.
Referring to fig. 1 to 2, the metal parts produced in the first and second embodiments of the present invention were subjected to 90-degree bending test (metallographic test), respectively, and it can be seen from fig. 1 to 2 that the infiltrated structure at the bent portion of the metal parts produced in the first and second embodiments maintained the original structural characteristics after bending, the surface peeling or peeling did not occur on the bent surface of the metal parts, and the fracture did not occur on the metal parts bent at 90 degrees. In addition, the metal part treated by the carburizing process can obtain a uniform carburized layer, higher quenching hardness and a steeper carburized layer gradient, and the metal part can obtain lower brittleness after tempering and bending tests.
Referring to fig. 3-4, the metal parts produced by the first and second embodiments of the invention are respectively subjected to carburized layer and matrix metallographic structure detection, as can be seen from fig. 3-4, the metallographic structures of the metal parts produced by the first and second embodiments of the invention do not have point-like or block-like carbide and residual austenite, the metallographic structures are excellent, and the carburized layer and the matrix of the parts produced by the invention have good bonding strength and good toughness, thereby being beneficial to service.
Referring to fig. 5 to 6, the metal parts produced by the first and second embodiments of the present invention were subjected to intercrystalline oxidation tests after shallow carburizing and quenching, respectively, and as can be seen from fig. 5 to 6, no intercrystalline oxidation was observed, and even though the vacuum carburizing furnace using this process did not cause intercrystalline oxidation during the carburizing of the metal parts, it could not only achieve an improvement in fatigue resistance of the workpiece material, but also eliminate secondary working of the metal parts in some cases, enabling a reduction in cost; the surface of the metal part after carburization and quenching can not generate black carbon deposition, thereby being beneficial to the subsequent electroplating processing.
The metal parts produced by the first embodiment and the second embodiment of the invention are subjected to a Vickers hardness test, the surface hardness value of the metal parts produced by the first embodiment after carburizing and quenching treatment is 776HV50gf, and the surface hardness value of the metal parts produced by the second embodiment after carburizing and quenching treatment is 813HV50gf, namely, the surface hardness value of the metal parts produced by the invention after carburizing and quenching treatment is 776HV50gf or more, and the HV50gf refers to a microhardness test result, which proves that the metal parts produced by the invention can obtain higher quenching hardness.
The invention can realize the carburizing and quenching treatment of the metal parts at the temperature of 750 ℃, the metal parts treated by the carburizing process can obtain uniform carburized layers, higher quenching hardness, steeper carburized layer gradient and good appearance, and the bending test is carried out on the metal parts after the carburizing and quenching treatment after the tempering treatment, so that the carburized layers of the metal parts have good adhesive force, the bending surface of the metal parts can not be peeled or stripped, and the metal parts can not be fractured after being bent at 90 degrees, thereby showing that the metal parts obtained by the process have good toughness; the vacuum carburizing furnace does not generate intercrystalline oxidation in the carburizing and quenching process of the metal parts, so that the fatigue resistance of the metal parts can be improved, and black carbon deposition is not generated on the surface of the workpiece after carburizing and quenching, thereby being beneficial to subsequent electroplating production; metallographic examination proves that the carburized layer of the metal part obtained by carburizing the metal part at the temperature of 750 ℃ is uniform, no point-shaped or block-shaped carbide and no residual austenite are seen in the structure of the carburized layer, and the carburized layer and a matrix have good bonding strength and good toughness.
The present invention is not limited to the above-mentioned preferred embodiments, and any other products similar or identical to the present invention, which can be obtained by anyone based on the teaching of the present invention, fall within the protection scope of the present invention.
Claims (6)
1. A low-temperature carburizing process at 750 ℃ for a vacuum carburizing furnace of SPCC material precision parts is characterized by comprising the following steps: the low-temperature carburizing process at 750 ℃ of the vacuum carburizing furnace for the SPCC material precision parts comprises the following steps:
firstly, placing a metal part into a vacuum furnace, heating the vacuum furnace to a certain temperature, keeping a constant temperature state, then inputting nitrogen into the vacuum furnace until the air pressure in the vacuum furnace reaches 100Pa pressure, and enabling the vacuum furnace to work for a period of time at the constant temperature and the constant air pressure of 100Pa pressure, and then entering the next step of operation;
continuously keeping the temperature of the vacuum furnace at a constant temperature, then inputting acetylene gas into the vacuum furnace, inputting the acetylene gas into the vacuum furnace in a pulse mode, wherein the duration time of acetylene gas pulse is 2 minutes, and the maximum air pressure of the acetylene gas input into the vacuum furnace is 360 Pa; the method comprises the following steps that acetylene gas is used as a carburizing medium to carburize a metal part in a vacuum furnace under the condition of constant temperature, so that the acetylene gas can be subjected to decomposition reaction with the surface of the metal part with certain temperature, carbon atoms can be left and enriched after the surface of the metal part is subjected to decomposition reaction, and carbon-containing saturated austenite can be formed after the metal part absorbs the carbon atoms and reaches certain concentration;
thirdly, after the acetylene gas pulse inflation is finished, continuously preserving heat of the vacuum furnace at a constant temperature, then, inputting nitrogen into the vacuum furnace for the second time, and promoting carbon atoms of carbon-containing saturated austenite on the surface of the metal part to automatically diffuse into the metal part at the constant temperature along with the extension of the processing time in the vacuum furnace in a constant temperature maintaining mode so as to form deep carburization, so that the material state of the surface of the metal part can be changed from carbon-containing saturated austenite to carbon-containing unsaturated austenite until the acetylene gas is input into the vacuum furnace in a pulse mode again for the next time, so that the metal part forms carbon-containing saturated austenite on the surface after adsorbing the carbon atoms again and diffuses into the inside again;
continuously preserving heat of the vacuum furnace at a constant temperature, then inputting acetylene gas into the vacuum furnace for the second time, continuously carburizing the surface of the metal part in the vacuum furnace by taking the acetylene gas as a carburizing medium under a constant temperature environment and the same processing time, and stopping conveying the acetylene gas into the vacuum furnace when the surface of the metal part forms carbon-containing saturated austenite again;
step five, continuously preserving heat of the vacuum furnace at a constant temperature, then inputting nitrogen into the vacuum furnace for the third time, continuously promoting the carbon atoms on the metal parts to diffuse inwards again by the vacuum furnace in a constant temperature keeping mode, namely stopping continuously conveying the nitrogen into the vacuum furnace after the carbon atoms on the metal parts are diffused again for a period of time under the constant temperature condition of the vacuum furnace;
step six, continuously preserving heat of the vacuum furnace at a constant temperature, then inputting acetylene gas into the vacuum furnace for the third time, taking the acetylene gas as a carburizing medium in the vacuum furnace, continuously performing vacuum carburization on the metal part under a constant temperature environment and the same processing time, and stopping conveying the acetylene gas into the vacuum furnace until carbon-containing saturated austenite is formed on the surface of the metal part again;
step seven, the vacuum furnace keeps the temperature at a constant temperature, then nitrogen is input into the vacuum furnace for the fourth time, the vacuum furnace continuously promotes the carbon atoms on the metal parts to diffuse inwards in a constant temperature keeping mode, namely the vacuum furnace stops continuously conveying the nitrogen into the vacuum furnace after the vacuum furnace diffuses the carbon atoms on the metal parts for a period of time again under the constant temperature condition;
step eight, continuously preserving heat of the vacuum furnace at a constant temperature, then, inputting acetylene gas into the vacuum furnace for the fourth time, taking the acetylene gas as a carburizing medium in the vacuum furnace, continuously carburizing the metal part under the constant temperature environment and the same processing time, and stopping conveying the acetylene gas into the vacuum furnace until the surface of the metal part forms carbon-containing saturated austenite again;
step nine, the vacuum furnace keeps the temperature at a constant temperature, then nitrogen is input into the vacuum furnace for the fifth time, the vacuum furnace continuously promotes the carbon atoms on the metal parts to diffuse inwards in a constant temperature keeping mode, and the vacuum furnace stops continuously conveying the nitrogen into the vacuum furnace after the carbon atoms on the metal parts are diffused again for a period of time under the constant temperature condition;
step ten, finally, continuously quenching the metal part for a period of time by using oil as a quenching medium in the vacuum furnace so that the metal part can reach the tissue and hardness required by production;
in the first step, heating to a certain temperature means heating to 750 ℃, and working for a period of time means working for 30 minutes;
in steps one through nine, the constant temperature is 750 ℃;
the vacuum carburizing furnace 750 ℃ low-temperature carburizing process for the SPCC material precision part can perform carburizing treatment on the metal part at the temperature of 750 ℃, the carburized layer of the metal part has good adhesive force, the bending surface of the metal part cannot be peeled or peeled off, and the metal part cannot be broken after being bent at 90 ℃; the vacuum carburizing furnace does not generate intercrystalline oxidation in the carburizing and quenching process of the metal parts, so that the fatigue resistance of the metal parts can be improved, and black carbon deposition is not generated on the surface of the workpiece after carburizing and quenching, thereby being beneficial to subsequent electroplating production; the metal part carburized by adopting the vacuum carburizing furnace of the SPCC material precision part carburizing process at the low temperature of 750 ℃ is uniform, no point-shaped or block-shaped carbide and no residual austenite are seen in the carburized layer structure, and the carburized layer and a matrix have good bonding strength and good toughness.
2. The vacuum carburizing process at 750 ℃ for the SPCC material precision parts according to claim 1, characterized in that: in the first step, the third step, the fifth step, the seventh step and the ninth step, each nitrogen gas input means inputting nitrogen gas into the vacuum furnace until the pressure in the vacuum furnace reaches 100 Pa.
3. The vacuum carburizing process at 750 ℃ for the SPCC material precision parts according to claim 1, characterized in that: in the second step, the fourth step, the sixth step and the eighth step, the maximum pressure of acetylene gas fed into the vacuum furnace each time is 360 Pa.
4. The vacuum carburizing process at 750 ℃ for the SPCC material precision parts according to claim 1, characterized in that: in step two, step four, step six and step eight, the time for carburizing was set to 2 minutes.
5. The vacuum carburizing process at 750 ℃ for the SPCC material precision parts according to claim 1, characterized in that: in step three, the diffusion time is set to 6 minutes; in the fifth step, the diffusion for a period of time means diffusion for 10 minutes; in step seven, the time of diffusion is set to 15 minutes; in step nine, the diffusion for a second time is 20 minutes.
6. The vacuum carburizing process at 750 ℃ for the SPCC material precision parts according to claim 1, characterized in that: in step ten, the continuous quenching time is quenching for 10 minutes.
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