The heat treatment process of bearing rollers and the importance of introduction

Nov 10, 2023

Bearing rollers are an essential part of roller bearings, and the heat treatment of rollers plays a vital role in improving the performance and quality of bearings. Through a reasonable heat treatment process, the roller's wear, fatigue, and corrosion resistance can be enhanced, the contact performance can be optimized, and friction loss can be reduced. It helps improve bearing life, stability, and reliability, reduces maintenance costs, and improves mechanical equipment's operating performance. Therefore, it is essential to pay enough attention to the heat treatment of rollers during the bearing manufacturing process. Here are five main areas where roller heat treatment is necessary and its impact.

Enhanced wear resistance: The heat treatment of the roller can improve its surface's hardness and wear resistance, thereby extending the service life of the roller. The increase in hardness can reduce the friction and wear of the roller during the rolling process and prevent early failure.

Improve fatigue resistance: Heat treatment can refine the grains of the rollers and eliminate internal stress, thereby improving the fatigue resistance of the rollers. It helps reduce fatigue crack formation and expansion of rollers under cyclic pressure and improves bearing reliability.

Enhanced corrosion resistance: Heat treatment can improve the oxidation and corrosion resistance of the rollers, preventing them from being corroded and oxidized during operation. It helps improve bearing durability and reliability.

Optimize contact performance: The heat treatment of the roller can improve its contact performance with the bearing seat and increase the adhesion and friction coefficient of the contact surface, thereby enhancing the stability and accuracy of the bearing.

Reduce friction loss: Through appropriate heat treatment, the surface roughness of the roller can be optimized, and the friction loss between it and the bearing seat can be reduced, thereby improving the efficiency and service life of the bearing.

The heat treatment process of bearing rollers includes quenching, tempering, surface strengthening treatment, etc.

Quenching: Quenching is one of the critical processes in the heat treatment of bearing rollers. Its primary purpose is to improve the hardness and wear resistance of the rollers. Quenching treatment generally includes the following steps:

Preheating: Put the roller into the preheating furnace and heat it to a specific temperature so that the surface and core of the roller reach a particular gradient of temperature.

Heating: Put the preheated roller into the furnace and heat it to the quenching temperature, which varies according to the material and specifications.

Insulation: Maintain the quenching temperature for a certain period to heat the surface and core of the roller fully.

Quenching: Rapidly cooling the roller to room temperature to harden the surface of the roller.

Commonly used quenching media include oil, water, brine, etc. After quenching, the hardness of the rollers is significantly increased, and the wear resistance is improved.

Tempering

Tempering is another essential process in the heat treatment of bearing rollers. Its primary purpose is to eliminate the internal stress generated during the quenching process, reduce the hardness, and improve the toughness and impact resistance of the rollers. Tempering treatment generally includes the following steps:

Put the quenched roller into the tempering furnace and heat it to the tempering temperature, which generally varies according to the material and specifications.

Insulation: Keep at the tempering temperature for a certain period to fully heat the surface and core of the roller.

Cooling: Cool the roller to room temperature to obtain the tempered structure.

Tempering treatment can choose different tempering temperatures and times according to additional requirements to achieve the best comprehensive mechanical properties. After tempering, the hardness of the roller will be reduced, but the toughness will be improved.

Post-processing steps after tempering include cleaning, grinding, correction, etc. The purpose of post-processing is to remove oxide scale, impurities, etc., on the surface of the roller and perform accuracy correction on the roller to ensure its geometric accuracy and motion accuracy. Testing rollers' surface quality and hardness is essential to ensure they meet design and process standards.

Surface strengthening treatment

Surface strengthening treatment is one of the essential means to improve the surface hardness and wear resistance of bearing rollers. Commonly used surface-strengthening treatment methods include carburizing, nitriding, carbonitriding, etc.

Carburization

Carburizing refers to the process of infiltrating low-carbon carbon atoms into the surface of the roller to harden the surface layer and thereby improve wear resistance. Carburizing treatment generally includes the following steps:

Put the quenched roller into the carburizing furnace and heat it to the carburizing temperature.

Pour the carburizing agent into the furnace to absorb carbon atoms on the roller surface.

Keep warm for a certain period to harden the surface layer of the roller fully.

Cool to room temperature to obtain the carburized structure.

After carburizing treatment, the surface hardness of the roller will be significantly increased, and the wear resistance will also be improved. However, defects such as cracks are prone to occur during the carburizing process, and care needs to be taken to control the carburizing temperature and time.

Nitriding

Nitriding is the process of hardening the surface layer of the roller by infusing nitrogen atoms, which improves its wear and corrosion resistance. Nitriding treatment generally includes the following steps:

Put the quenched roller into the nitriding furnace and heat it to the nitriding temperature.

Pour ammonia or other nitrogen sources into the furnace to absorb nitrogen atoms on the roller surface.

Keep warm to harden the roller's surface layer for a certain period.

Cool to room temperature to obtain the nitrided structure.

After nitriding treatment, the surface hardness of the roller will be higher than that of carburizing therapy, and the wear and corrosion resistance will be further improved. However, cracks and other defects are also prone to occur during the nitriding process, so attention needs to be paid to controlling the nitriding temperature and time.

Carbonitriding

Carbonitriding hardens roller surfaces by infiltrating carbon and nitrogen atoms, enhancing wear and corrosion resistance. Carbonitriding treatment generally includes the following steps:

Put the quenched roller into the carbonitriding furnace and heat it to the carbonitriding temperature.

Introduce the carbon and nitrogen sources into the furnace so that the roller surface absorbs carbon and nitrogen atoms simultaneously.

Keep warm to harden the roller's surface layer for a certain period.

In short, the heat treatment process of bearing rollers is one of the critical links in the bearing manufacturing process. It is necessary to strictly control the heating temperature, speed, holding time, cooling rate, and other process parameters. At the same time, it is essential to select appropriate heat treatment processes and equipment according to different materials and process requirements to ensure the best performance and quality of the rollers.