A carbonitriding process for GCr15 parts

Abstract

The application provides a carbonitriding process for GCr15 parts, and steps are as follows: pre-oxidation, strong penetration, diffusion, quenching, hot cleaning, cold cleaning, cold treatment, tempering, taking out GCr15 parts, and air cooling after discharging. The application realizes continuous production by using a continuous mesh belt furnace production line with controllable atmosphere for carbonitriding, improves production efficiency, reduces labor intensity of workers, increases production capacity, reduces gap furnace opening and closing actions, reduces energy consumption, and saves at least 50% of cost compared with ordinary carbonitriding. In addition, carbon potential of each zone in the furnace can be controlled, so that quality stability is ensured. The surface hardness of the GCr15 parts obtained by the heat treatment process of the application can reach 62-65HRC, the core hardness is 61-64HRC, the carbide layer is less than 0.02mm, the carbonitriding layer is greater than 0.4mm, the surface carbon content is 1.15-1.5%, and the carbonitriding metallography can reach level 1.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology, and in particular to the carbonitriding process for GCr15 parts. Background Technology

[0002] As is well known, GCr15 is the most widely used high-carbon chromium bearing steel in the bearing industry. Many well-known domestic and international brands use this material in their small and medium-sized precision bearings, or bearings used under special operating conditions. They employ special heat treatment processes, such as carbonitriding and ultra-fine refining, to improve the surface hardness and wear resistance of the parts, thereby extending the bearing's service life. Traditional carbonitriding processes use a gap furnace, which requires frequent opening and closing, resulting in high labor intensity, low production efficiency, and inconsistent quality. Summary of the Invention

[0003] The purpose of this invention is to provide a carbonitriding process for GCr15 parts, which can solve the technical problems mentioned in the background art.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: a carbonitriding process for GCr15 parts, comprising the following steps:

[0005] (1) Pre-oxidation: GCr15 parts are pre-oxidized by heating in the front area of ​​the continuous mesh belt furnace production line under controlled atmosphere. The heating temperature is 450-650℃ and the time is 10-20min.

[0006] (2) Strong infiltration: GCr15 parts are subjected to strong infiltration treatment in the strong infiltration zone of the continuous mesh belt furnace production line with controlled atmosphere. The furnace temperature is maintained at 830-880℃ and the holding time is 120-300min. A high-speed stirring fan is added to the continuous mesh belt furnace with controlled atmosphere, which is directly facing the strong infiltration zone. The rotation of the high-speed stirring fan controls the uniform distribution of the atmosphere in the furnace, so that the carbon potential in the furnace in the strong infiltration zone is adjusted within 1.1-1.5%, and the ammonia flow rate is 0.2-1.0NL / min.

[0007] (3) Diffusion: GCr15 parts are diffused in the diffusion zone of the continuous mesh belt furnace production line with controlled atmosphere. The furnace temperature is maintained at 830-880℃. The diffusion time is 1 / 3-2 / 3 of the strong permeation time. A high-speed stirring fan is added to the continuous mesh belt furnace with controlled atmosphere, which is directly facing the diffusion zone. The high-speed stirring fan rotates to control the uniform distribution of the atmosphere in the furnace, so that the carbon potential in the diffusion zone is adjusted within 1.1-1.3%, and the ammonia flow rate is 0.2-1.0 NL / min.

[0008] (4) Quenching: The temperature of GCr15 parts is reduced to 820-840℃ in the cooling zone of the continuous mesh belt furnace production line with controlled atmosphere, and then they are put into the quenching tank of the continuous mesh belt furnace production line with controlled atmosphere for oil quenching, with the oil temperature controlled at 85-95℃.

[0009] (5) Hot cleaning: GCr15 parts are cleaned in the hot cleaning zone of the continuous mesh belt furnace production line under controlled atmosphere. Special cleaning agent is used, the cleaning temperature is 45-70℃, and the cleaning time is 10-20min.

[0010] (6) Cold cleaning: GCr15 parts are cleaned again in the cold cleaning zone of the continuous mesh belt furnace production line with controlled atmosphere. The cleaning temperature is 8-12℃ and the cleaning time is 5-10min.

[0011] (7) Cold treatment: Place the GCr15 parts in an industrial freezer for cold treatment. The cooling temperature is -30 to -70°C and the time is 40 to 60 minutes.

[0012] (8) Tempering: GCr15 parts are subjected to low-temperature tempering in the tempering zone of the continuous mesh belt furnace production line with controlled atmosphere. The furnace temperature is controlled at 150-230℃ and the time is 120-240min.

[0013] (9) Remove the GCr15 parts and air cool them after they are taken out of the furnace.

[0014] Preferably, the GCr15 parts are pre-cleaned and dried before pre-oxidation in step (1).

[0015] Preferably, the high-speed stirring fan rotates at 1000 r / min.

[0016] Preferably, the special cleaning agent is a bearing-specific cleaning agent.

[0017] Preferably, ammonia pipelines and oxygen probes are installed in both the strong permeation zone and the diffusion zone of the controlled atmosphere continuous mesh belt furnace production line.

[0018] Compared with existing technologies, the advantages of this invention are as follows: This invention uses a continuous mesh belt furnace production line with a controlled atmosphere to achieve continuous carbonitriding, thereby improving production efficiency, reducing labor intensity, increasing capacity, reducing the frequency of furnace opening and closing, reducing energy consumption, shortening time, and saving at least 50% in cost compared to ordinary carbonitriding. Furthermore, the carbon potential in each zone of the furnace can be controlled, thus ensuring stable quality. GCr15 parts obtained through the heat treatment process of this invention can achieve a surface hardness of 62-65 HRC, a core hardness of 61-64 HRC, a carbide layer of less than 0.02 mm, a carbonitrided layer of greater than 0.4 mm, a surface carbon content of 1.15-1.5%, and a carbonitriding metallographic grade of 1. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the controllable atmosphere continuous mesh belt furnace production line of the present invention. Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0021] like Figure 1 As shown, this invention provides a carbonitriding process for GCr15 parts, the steps of which are as follows:

[0022] (1) Pre-oxidation: GCr15 parts are pre-oxidized by heating in the front zone 1 of the continuous mesh belt furnace production line under controlled atmosphere. The heating temperature is 450-650℃ and the time is 10-20min, which can accelerate the carbonitriding speed.

[0023] (2) Strong infiltration: GCr15 parts are subjected to strong infiltration treatment in the strong infiltration zone 2 of the continuous mesh belt furnace production line with controlled atmosphere. The furnace temperature is maintained at 830-880℃ and the holding time is 120-300min. A high-speed stirring fan 9 is added to the continuous mesh belt furnace with controlled atmosphere, which is directly facing the strong infiltration zone. The high-speed stirring fan 9 rotates to control the uniform distribution of the atmosphere in the furnace, so that the carbon potential in the furnace in the strong infiltration zone is adjusted within 1.1-1.5%, and the ammonia flow rate is 0.2-1.0NL / min.

[0024] (3) Diffusion: GCr15 parts are diffused in the diffusion zone 3 of the continuous mesh belt furnace production line with controlled atmosphere. The furnace temperature is maintained at 830-880℃. The diffusion time is 1 / 3-2 / 3 of the strong diffusion time. A high-speed stirring fan 9 is added to the continuous mesh belt furnace with controlled atmosphere, which is directly opposite the diffusion zone. The high-speed stirring fan 9 rotates to control the uniform distribution of the atmosphere in the furnace, so that the carbon potential in the diffusion zone is adjusted within 1.1-1.3%. The ammonia flow rate is 0.2-1.0 NL / min, which can accelerate the diffusion and increase the carbon and nitrogen diffusion layer.

[0025] (4) Quenching: The temperature of GCr15 parts is reduced to 820-840℃ in the cooling zone 4 of the continuous mesh belt furnace production line with controlled atmosphere, and then they are put into the quenching tank 5 of the continuous mesh belt furnace production line with controlled atmosphere for oil quenching. The oil temperature is controlled at 85-95℃ to reduce workpiece deformation.

[0026] (5) Hot cleaning: GCr15 parts are cleaned in the hot cleaning zone 6 of the continuous mesh belt furnace production line under controlled atmosphere to remove oil stains from the surface of GCr15 parts. Special cleaning agent is used, the cleaning temperature is 45-70℃, and the cleaning time is 10-20min to increase the cleaning effect.

[0027] (6) Cold cleaning: GCr15 parts are cleaned again in the cold cleaning zone 7 of the continuous mesh belt furnace production line with controlled atmosphere. The cleaning temperature is 8-12℃ and the cleaning time is 5-10min. This allows the residual austenite that did not have time to transform into martensite during quenching to continue to transform into martensite, thereby reducing the content of residual austenite and increasing the precision of GCr15 parts.

[0028] (7) Cold treatment: Place the GCr15 parts in an industrial freezer for cold treatment. The cooling temperature is -30 to -70°C and the time is 40 to 60 minutes to further reduce the content of residual austenite.

[0029] (8) Tempering: GCr15 parts are subjected to low-temperature tempering in tempering zone 8 of the continuous mesh belt furnace production line with controlled atmosphere. The furnace temperature is controlled at 150-230℃ and the time is 120-240min to increase the hardness and wear resistance of GCr15 parts.

[0030] (9) Remove the GCr15 parts and air cool them after they are taken out of the furnace.

[0031] Preferably, before the pre-oxidation in step (1), the GCr15 parts are pre-cleaned and dried to remove surface impurities.

[0032] Preferably, the high-speed stirring fan 9 rotates at 1000 r / min, which can ensure the uniformity of carbon potential and ammonia gas in the furnace of the continuous mesh belt furnace production line with controlled atmosphere.

[0033] Preferably, the special cleaning agent is a bearing-specific cleaning agent, which has a good cleaning effect.

[0034] Preferably, ammonia pipelines and oxygen probes 10 are installed in both the strong permeation zone 2 and the diffusion zone 3 of the controlled atmosphere continuous mesh belt furnace production line to achieve precise control of carbon and nitrogen and ensure the quality of GCr15 parts.

[0035] The above heat treatment process was used to perform carbonitriding treatment on the inner rings of models 6001, 6202, and 6306ZZ. The products have small heat treatment deformation, uniform carbonitrided layer quality, fine and dispersed surface carbides, and good heat treatment processability.

[0036] This invention utilizes a controlled atmosphere continuous mesh belt furnace production line for carbonitriding to achieve continuous production, improving production efficiency, reducing labor intensity, increasing capacity, reducing frequent furnace opening and closing operations, reducing energy consumption, shortening time, and saving at least 50% in cost compared to ordinary carbonitriding. Furthermore, the carbon potential in each zone of the furnace can be controlled, thus ensuring stable quality. GCr15 parts obtained through the heat treatment process of this invention can achieve a surface hardness of 62-65 HRC, a core hardness of 61-64 HRC, a carbide layer of less than 0.02 mm, a carbonitrided layer of greater than 0.4 mm, a surface carbon content of 1.15-1.5%, and a carbonitriding metallographic grade of 1.

[0037] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. Other modifications can be easily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A carbonitriding process of a GCr15 part, characterized in that, The steps are as follows: (1) pre-oxidation: the GCr15 parts are heated and pre-oxidized in the pre-position area of the continuous mesh belt furnace production line in a controllable atmosphere, the heating temperature is 450-650 DEG C, and the time is 10-20 min; (2) strong penetration: the GCr15 parts are treated by strong penetration in the strong penetration area of the continuous mesh belt furnace production line in a controllable atmosphere, the furnace temperature is maintained at 830-880 DEG C, the holding time is 120-300 min, the high-speed stirring fan opposite to the strong penetration area is added on the continuous mesh belt furnace in a controllable atmosphere, the high-speed stirring fan rotates to control the uniform distribution of the atmosphere in the furnace, the carbon potential in the strong penetration area is adjusted to 1.1-1.5%, and the ammonia gas amount is 0.2-1.0 NL / min; (3) diffusion: the GCr15 parts are diffused in the diffusion area of the continuous mesh belt furnace production line in a controllable atmosphere, the furnace temperature is continuously maintained at 830-880 DEG C, the diffusion time is 1 / 3-2 / 3 of the strong penetration time, the high-speed stirring fan opposite to the diffusion area is added on the continuous mesh belt furnace in a controllable atmosphere, the high-speed stirring fan rotates to control the uniform distribution of the atmosphere in the furnace, the carbon potential in the diffusion area is adjusted to 1.1-1.3%, and the ammonia gas amount is 0.2-1.0 NL / min; (4) quenching: the temperature of the GCr15 parts is reduced to 820-840 DEG C in the cooling area of the continuous mesh belt furnace production line in a controllable atmosphere, and then the GCr15 parts are put into the oil quenching tank of the continuous mesh belt furnace production line in a controllable atmosphere for oil quenching, and the oil temperature is controlled at 85-95 DEG C; (5) hot cleaning: the GCr15 parts are cleaned in the hot cleaning area of the continuous mesh belt furnace production line in a controllable atmosphere, a special cleaning agent is used, the cleaning temperature is 45-70 DEG C, and the cleaning time is 10-20 min; (6) cold cleaning: the GCr15 parts are cleaned again in the cold cleaning area of the continuous mesh belt furnace production line in a controllable atmosphere, the cleaning temperature is 8-12 DEG C, and the cleaning time is 5-10 min; (7) cold treatment: the GCr15 parts are put into an industrial freezer for cold treatment, the cooling temperature is minus 30 to minus 70 DEG C, and the time is 40-60 min; (8) tempering: the GCr15 parts are tempered at low temperature in the tempering area of the continuous mesh belt furnace production line in a controllable atmosphere, the furnace temperature is controlled at 150-230 DEG C, and the time is 120-240 min; (9) the GCr15 parts are taken out and air-cooled.

2. The process for carbonitriding GCr15 parts according to claim 1, characterized in that: Before step (1) pre-oxidation, the GCr15 parts are pre-cleaned and dried.

3. The carbonitriding process of GCr15 parts according to claim 1 or 2, characterized in that: The rotating speed of the high-speed stirring fan is 1000 r / min.

4. The carbonitriding process of GCr15 parts according to claim 1 or 2, characterized in that: The special cleaning agent is a bearing special cleaning agent.

5. The process for carbonitriding GCr15 parts according to claim 1 or 2, characterized in that: The ammonia gas pipeline and oxygen probe are installed on the strong penetration area and the diffusion area of the continuous mesh belt furnace production line in a controllable atmosphere.

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