CN111020459A

CN111020459A - Heat treatment method for small conical bearing

Info

Publication number: CN111020459A
Application number: CN201911379727.4A
Authority: CN
Inventors: 姜乐; 温博; 唐虎娇; 孙洪斌
Original assignee: Wafangdian Bearing Group National Bearing Engineering Technology Research Center Co Ltd
Current assignee: Wafangdian Bearing Group National Bearing Engineering Technology Research Center Co Ltd
Priority date: 2019-12-27
Filing date: 2019-12-27
Publication date: 2020-04-17
Anticipated expiration: 2039-12-27
Also published as: CN111020459B

Abstract

A heat treatment method of a small conical bearing. The invention belongs to the field of bearing heat treatment, and relates to a heat treatment method of a small conical bearing, which is mainly applied to application occasions with severe working conditions and requirements on high wear resistance, long service life and light weight. The method takes carburizing steel as a raw material, and refines the surface structure of the bearing through two carburizing processes and cooling processes, so that the bearing obtains higher surface hardness which can basically reach more than 65 HRC.

Description

Heat treatment method for small conical bearing

Technical Field

The invention belongs to the field of bearing heat treatment, and relates to a heat treatment method of a small conical bearing, which is mainly applied to application occasions with severe working conditions, high wear resistance, long service life and light weight.

Background

The common small-sized conical bearing generally uses high-carbon bearing steel as a raw material to carry out common heating quenching, but has the defects that the hardness is generally about 60HRC, the requirement of high wear resistance cannot be met, the structure formed after the common heating quenching is basically tensile stress, the common small-sized conical bearing is not impact-resistant, and the fatigue life of the bearing is not long.

Disclosure of Invention

In view of the above-described drawbacks of the prior art, an object of the present invention is to provide a heat treatment method for a small-sized conical bearing having an outer diameter of 60mm or less, which can improve the bearing hardness.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a heat treatment method for small-sized conical bearing includes such steps as carburizing bearing ring, discharging from furnace, air cooling, carburizing for the second time, quenching in salt bath, tempering, and air cooling to room temp.

Further, the first carburizing comprises a preheating process, a low-temperature nitrogen introducing process and a high-temperature carburizing process.

Further, the preheating process is preheating at 400 ℃ and heat preservation for 1 h.

Further, the low-temperature nitrogen introducing process comprises the following steps: heating to 800 +/-10 ℃, preserving the temperature for 5h, and introducing nitrogen at the flow rate of 8.0L/h.

Further, the high temperature carburization process is as follows: heating to 900 +/-10 ℃, keeping the carbon potential at 1.0%, keeping the temperature for 12h, and introducing nitrogen and propane, wherein the flow rate of the nitrogen is 4.0L/h, and the flow rate of the propane is 5.0L/h.

Further, the bearing ring is cooled to below 700 ℃ in the furnace discharging and air cooling process, an axial flow fan is used for spraying water mist for cooling, the water flow is 30L/h, and the cooling speed is higher than 80 ℃/h.

Further, the second carburizing process is as follows: heating to 900 +/-10 ℃, keeping the carbon potential at 1.0%, keeping the temperature for 5h, and introducing nitrogen and propane, wherein the flow rate of the nitrogen is 4.0L/h, and the flow rate of the propane is 5.0L/h.

Further, the temperature is reduced to 180 ℃ in the salt quenching process.

Further, the temperature is raised to 150 ℃ in the tempering process, and the temperature is kept for 4 hours.

Preferably, the equipment adopted in the carburizing process is an RTQF-11-ERM multi-purpose box furnace.

The invention has the beneficial effects that: the method takes carburizing steel as a raw material, and refines the surface structure of the bearing through two carburizing processes and cooling processes, so that the bearing obtains higher surface hardness which can basically reach more than 65 HRC.

Drawings

FIG. 1 is a process diagram of the present invention;

in the figure: t1 is room temperature part, T2 is first carburization process, T3 is air cooling process, T4 is second carburization process, T5 is salt bath quenching process, T6 is cleaning process, T7 is tempering process, T8 is air cooling process.

Detailed Description

In order to make the structure and function of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention.

Referring to the attached figure 1, the heat treatment method for the small conical bearing takes carburizing steel as a raw material and innovatively uses 20Cr steel as the raw material, thereby not only controlling the hardenability of the heat treatment process, but also reducing the cost of the raw material.

First, process method

1) For the conical bearing with large wall thickness difference, 10mm at the thickest part and 2mm at the thinnest part, in order to ensure that the thinnest part cannot penetrate, the carburizing speed of the first part of the carburizing process is strictly controlled, and the low temperature and low carbon potential are adopted to ensure that the first carburizing obtains a gentle carbon concentration gradient.

2) In order to obtain high surface hardness, the carburizing process comprises two times of cooling and surface tissue thinning, so that higher surface hardness can be obtained, and the surface hardness can basically reach more than 65 HRC.

3) Reduction of deformation

The carburized bearing must ensure uniform carburized layer distribution and small heat treatment deformation, and the heat treatment process mainly comprises two types, namely the diameter variation in the diameter direction and the axial taper.

a. Reducing the amount of diameter variation

The invention adopts two times of cooling in the carburizing process, wherein the first time adopts air cooling to avoid the structure stress deformation caused by a larger cooling speed, and the second time adopts salt quenching to ensure the uniformity of cooling and reduce the deformation caused by asynchronous structure transformation.

b. Reducing taper

In the beginning of designing the turning drawing, because the end with smaller wall thickness shrinks inwards too much, in order to avoid the taper after heat treatment, the size of the turning worker is artificially increased for the part with too much shrinkage, and thus the smaller taper can be ensured after heat treatment.

Second, carburizing process

Carburizing equipment: RTQF-11-ERM multipurpose box type furnace

Carburizing atmosphere: nitrogen and propane are introduced at a lower temperature to soften and accelerate carbon atoms to penetrate into the surface of the workpiece; propane is passed at normal carburizing temperature to provide activated carbon atoms as a carburizing atmosphere.

A first part:

1. preheating at 400 ℃, keeping the temperature for 1h, mainly acting as activating the surface of the workpiece at low temperature, improving the surface activity of the workpiece, improving the carburizing efficiency, preparing for carburizing, and reducing the deformation by releasing the stress of the part through preheating.

2. Keeping the temperature at 800 +/-10 ℃ for 5 hours, introducing nitrogen with the flow rate of 8.0L/h, softening the surface of the workpiece in advance, preparing for rapid carburization, ensuring that carbon atoms rapidly permeate the surface of the workpiece in a large amount, ensuring that the carbon content is more than 0.9 percent, ensuring that the layer depth is more than 0.3mm, ensuring that the surface and the subsurface of the part have higher strength, and improving the fatigue life of the part to a certain extent by permeating trace active nitrogen atoms into the surface of the part.

3. 900 +/-10 ℃, 1.0 percent of carbon potential, 12 hours, 4.0L/h of nitrogen flow and 5.0L/h of propane flow.

4. Discharging and air cooling, wherein the cooling speed is ensured to be more than 80 ℃/h, namely, the surface of the part is ensured not to generate reticular carbide, the deformation of the part can be reduced, and the diameter variation is basically not more than 0.10 mm.

A second part:

1. the surface carburization is carried out at 900 +/-10 ℃, the carbon potential is 1.0 percent and 5 hours, the nitrogen flow is 4.0L/h and the propane flow is 5.0L/h, the purpose of surface carburization is to improve the surface carbon content, finally the surface carbon content is ensured to be 1.15 +/-0.05 percent, the later quenching hardness is improved, and the surface wear resistance and the fatigue life of the part are further improved.

2. Taking out of the furnace, carrying out salt bath quenching, wherein the temperature of salt solution is 180 ℃, the quenching time is 20min, the stirring speed is 300 r/min, taking out of the quenching tank, carrying out hot cleaning, and the temperature of cleaning solution is 70 ℃, drying, then entering a tempering furnace, and carrying out quenching for 4h at 150 ℃.

The above list is only the preferred embodiment of the present invention. It is obvious that the invention is not limited to the above embodiments, but that many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.

Claims

1. A heat treatment method for a small-sized conical bearing is characterized in that a bearing ring is carburizing steel, the bearing ring is taken out of a furnace for air cooling after being carburized for the first time, then carburized for the second time, taken out of the furnace for salt bath quenching, tempered and finally air cooled to room temperature.

2. The heat treatment method for the miniature conical bearing as set forth in claim 1, wherein the first carburization includes a preheating process, a low-temperature nitrogen-introducing process and a high-temperature carburization process.

3. The heat treatment method for the miniature conical bearing as set forth in claim 2, wherein the preheating process is preheating at 400 ℃ and holding for 1 hour.

4. The heat treatment method for the miniature conical bearing as set forth in claim 2, wherein the low temperature nitrogen introduction process is as follows: heating to 800 +/-10 ℃, preserving the temperature for 5h, and introducing nitrogen at the flow rate of 8.0L/h.

5. The heat treatment method for the miniature conical bearing according to claim 2, wherein: the high-temperature carburization process is as follows: heating to 900 +/-10 ℃, keeping the carbon potential at 1.0%, keeping the temperature for 12h, and introducing nitrogen and propane, wherein the flow rate of the nitrogen is 4.0L/h, and the flow rate of the propane is 5.0L/h.

6. The heat treatment method for the miniature conical bearing according to claim 1, wherein: and in the discharging and air cooling process, the bearing ring is cooled to below 700 ℃, and the cooling speed is higher than 80 ℃/h.

7. The heat treatment method for the miniature conical bearing according to claim 1, wherein: the second carburizing process is as follows: heating to 900 +/-10 ℃, keeping the carbon potential at 1.0%, keeping the temperature for 5h, and introducing nitrogen and propane, wherein the flow rate of the nitrogen is 4.0L/h, and the flow rate of the propane is 5.0L/h.

8. The heat treatment method for the miniature conical bearing according to claim 1, wherein: and discharging from the furnace, carrying out salt bath quenching, wherein the temperature of salt solution is 180 ℃, the quenching time is 20min, the stirring speed is 300 r/min, discharging from a quenching tank, carrying out hot cleaning, and the temperature of cleaning solution is 70 ℃, drying, and then, feeding into a tempering furnace for tempering.

9. The heat treatment method for the miniature conical bearing according to claim 1, wherein: and in the tempering process, the temperature is increased to 150 ℃, and the temperature is kept for 4 hours.

10. The heat treatment method for the miniature conical bearing according to claim 1, wherein: the equipment adopted in the carburizing process is an RTQF-11-ERM multi-purpose box furnace.