A carburizing and quenching process for thin-walled parts

Abstract

The present invention relates to the field of heat treatment technology, and specifically to a carburizing and quenching process for thin-walled parts, which can reduce the deformation of thin-walled parts, prevent penetration, shorten the process cycle and improve product performance, and comprises the following steps: (1) applying an anti-seepage material to the thin-walled part of the part and placing it in a carburizing furnace, wherein the carbon potential in the furnace is set to be maintained at 0.3%-0.4%, and the temperature is raised after the carbon potential reaches the set value, and the temperature of the carburizing furnace is raised to 925°C-935°C for insulation and preheating treatment; (2) performing a strong carburizing treatment first, which lasts for 7h-9h, and the carbon potential is maintained at 1 .08%-1.18%; after the strong carburizing is completed, diffusion carburizing is carried out, and the carbon potential is maintained at 0.88%-0.98%, and the diffusion carburizing time lasts for 2h-3h; then the carbon potential is maintained at 0.70%-0.80%, and the furnace is slowly cooled for 1h; then the carbon potential is maintained at 0.55%-0.65%, and the furnace is slowly cooled in the outer chamber for 1h, and then the temperature is raised to 845℃-855℃, and the temperature is kept at this temperature for 1h, and the carbon potential is maintained at 0.75%; (3) quenching; (4) low-temperature tempering; (5) cold treatment; (6) cleaning; (7) secondary low-temperature tempering; (8) air cooling.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment, in particular to a carburizing and quenching process for thin-walled parts. Background Art

[0002] The more commonly used materials for heavy-load shafts are Cr, Cr-Mn, and Cr-Mo carburizing steels. These steels have good wear resistance and fatigue resistance after carburizing and quenching, and can well meet work requirements.

[0003] With the development of science and technology, people have a high degree of direction in the use of machinery, and the development and application of shaft parts are also diverse. However, if the wall thickness of the same axis is different and the heat treatment process is not appropriate, it will cause large deformation, penetration of thinner parts, etc., resulting in substandard performance of parts and even cracking and breakage. Summary of the Invention

[0004] In order to solve the problem that existing processes may cause deformation or even penetration of thin-walled parts, the present invention provides a carburizing and quenching process for thin-walled parts, which can reduce the deformation of thin-walled parts, prevent penetration, shorten the process cycle and improve product performance.

[0005] The technical solution is as follows: a carburizing and quenching process for thin-walled parts, characterized in that it includes the following steps:

[0006] (1) Apply anti-seepage material to the thin-walled part of the part and put it into the carburizing furnace. The carbon potential in the furnace is set to maintain at 0.3%-0.4%. When the carbon potential reaches the set value, the temperature starts to rise. The temperature of the carburizing furnace is raised to 925℃-935℃ for insulation and preheating treatment;

[0007] (2) First, perform a strong carburizing treatment for 7h-9h, and keep the carbon potential at 1.08%-1.18%; after the strong carburizing, perform diffusion carburizing, and keep the carbon potential at 0.88%-0.98% for 2h-3h; then keep the carbon potential at 0.70%-0.80%, and slowly cool it in the furnace for 1h; then keep the carbon potential at 0.55%-0.65%, and slowly cool it in the outer chamber for 1h, then heat it to 845℃-855℃, keep it warm for 1h, and keep the carbon potential at 0.75%;

[0008] (3) Quenching: Quenching is carried out in the outer chamber of the carburizing quenching furnace, using austempering oil at a temperature of 110 °C for 50 min;

[0009] (4) Low temperature tempering: transfer the parts to a low temperature tempering furnace, maintain the furnace temperature at 205°C-215°C for 30 minutes, and then air cool;

[0010] (5) Cold treatment: transfer the parts to a deep freezer, treat the parts at -85±5℃ for 2h, then take them out and return them to the temperature for 45-60min;

[0011] (6) Cleaning: Use a mixture of detergent and water to clean the parts;

[0012] (7) Secondary low-temperature tempering: transfer the parts to a low-temperature tempering furnace and maintain the furnace temperature at 205°C-210°C for 90 minutes;

[0013] (8) Air cooling.

[0014] It is further characterized in that in step (3), oil quenching and spraying are combined.

[0015] After adopting the present invention, the carburizing time is shortened by utilizing one-time strong carburizing and diffusion carburizing, which can prevent the metal hardness from being too low due to too long heating time and reduce wear resistance. After carburizing, the furnace is cooled, which can make the structure more uniform and the grains refined, effectively eliminate internal stress and reduce deformation tendency; deep cooling and low-temperature tempering transform the supercooled austenite into martensite, thereby improving the hardness, wear resistance and fatigue strength of the parts; and then using austempering oil, oil quenching and spraying in combination, the parts have a faster cooling rate in the medium temperature zone, while the cooling rate in the low temperature zone is not too fast, which can reduce the risk of part deformation, prevent penetration in thinner parts of the parts, shorten the process cycle and improve product performance. DETAILED DESCRIPTION

[0016] A carburizing and quenching process for thin-walled parts, comprising the following steps:

[0017] (1) After applying anti-seepage material on the thin-walled part of the part, place it in the carburizing furnace. The anti-seepage material is KT-908 type paint from Zhejiang Huangyan Special Coating Factory. The carbon potential in the furnace is set to maintain at 0.3%-0.4% to establish a stable atmosphere, reduce the temperature difference between the inside and outside of the part, make the structure uniform, and reduce deformation. After the carbon potential reaches the set value, the temperature begins to rise, and the temperature of the carburizing furnace is raised to 925℃-935℃ for insulation and preheating treatment;

[0018] (2) First, perform a strong carburizing treatment for 7h-9h, and keep the carbon potential at 1.08%-1.18%; after the strong carburizing, perform diffusion carburizing, and keep the carbon potential at 0.88%-0.98%, and the diffusion carburizing time lasts for 2h-3h; then keep the carbon potential at 0.70%-0.80%, and slowly cool it with the furnace for 1h; then keep the carbon potential at 0.55%-0.65%, and slowly cool it with the furnace in the outer chamber for 1h, then heat it to 845℃-855℃, keep it warm for 1h, and keep the carbon potential at 0.75%; using one-time strong carburizing and diffusion carburizing can shorten the carburizing time, prevent the metal hardness from being too low due to long heating time, and reduce wear resistance; after carburizing, use furnace cooling to make the structure more uniform and refine the grains, effectively eliminate internal stress and reduce deformation tendency;

[0019] (3) Quenching: Quenching is carried out in the outer chamber of the carburizing quenching furnace, using austempering oil, the temperature is set to 110 ° C, oil quenching and spraying are combined, and the total duration is 50 minutes; this method can make the parts cool faster in the medium temperature zone and cool relatively slowly in the low temperature zone, which can shorten the time difference between the outside and inside of the parts to transform into martensite, while reducing thermal stress and structural stress, which is conducive to reducing deformation tendency;

[0020] (4) Low temperature tempering: Transfer the parts to a low temperature tempering furnace, maintain the furnace temperature at 205°C-215°C for 30 minutes, and then air cool. Low temperature tempering can further stabilize the part structure and reduce the workpiece stress.

[0021] (5) Cold treatment: transfer the parts to a deep freezer, treat the parts at -85±5℃ for 2h, then take them out and return them to the temperature for 45-60min; this can effectively reduce the retained austenite content and improve the surface hardness and wear resistance;

[0022] (6) Cleaning: Use KZ ULTRA CLEANER 4921 cleaning agent mixed with water at a ratio of 1:117, at a temperature of 70°C ± 10°C, for 40-60 minutes.

[0023] (7) Secondary low-temperature tempering: transfer the parts to a low-temperature tempering furnace and maintain the furnace temperature at 210°C for 90 minutes to further eliminate stress and stabilize the size;

[0024] (8) Air cooling.

[0025] By utilizing the solution of the present invention, the deformation of thin-walled parts can be reduced, the process cycle can be shortened, and the parts produced by using the process have good microstructure and mechanical properties.

Claims

1. A carburizing and quenching process for thin-walled parts, characterized in that: It includes the following steps: (1) Apply anti-seepage material to the thin-walled part of the part and put it into the carburizing furnace. The carbon potential in the furnace is set to maintain at 0.3%-0.4%. When the carbon potential reaches the set value, the temperature starts to rise. The temperature of the carburizing furnace is raised to 925℃-935℃ for insulation and preheating treatment; (2) First, perform a strong carburizing treatment for 7h-9h, and keep the carbon potential at 1.08%-1.18%; after the strong carburizing, perform diffusion carburizing, and keep the carbon potential at 0.88%-0.98% for 2h-3h; then keep the carbon potential at 0.70%-0.80%, and slowly cool it in the furnace for 1h; then keep the carbon potential at 0.55%-0.65%, and slowly cool it in the outer chamber for 1h, then heat it to 845℃-855℃, keep it warm for 1h, and keep the carbon potential at 0.75%; (3) Quenching: Quenching is carried out in the outer chamber of the carburizing quenching furnace, using austempering oil at a temperature of 110 °C for 50 min; (4) Low temperature tempering: transfer the parts to a low temperature tempering furnace, maintain the furnace temperature at 205°C-215°C for 30 minutes, and then air cool; (5) Cold treatment: transfer the parts to a deep freezer, treat the parts at -85±5℃ for 2h, then take them out and return them to the temperature for 45-60min; (6) Cleaning: Use a mixture of detergent and water to clean the parts; (7) Secondary low-temperature tempering: transfer the parts to a low-temperature tempering furnace and maintain the furnace temperature at 205°C-210°C for 90 minutes; (8) Air cooling.

2. The carburizing and quenching process for thin-walled parts according to claim 1, characterized in that: In step (3), oil quenching and spraying are combined.