Every processing process of bearing forgings is indispensable.

Dec 13, 2024

1. Raw material preparation

The processing of bearing forgings begins with the selection of high-quality steel. Commonly used raw materials include high-carbon chromium steel, carburized steel, etc. These materials have good wear resistance and strength and can meet the use requirements of bearings in various mechanical equipment.

After the raw materials enter the factory, they must first be inspected to ensure that the quality of the steel meets the production standards. After passing the inspection, the steel is cut into billets suitable for forging. During the cutting process, the quality of the blanks must be controlled to avoid axial movement and warping of the bar material to ensure the smooth progress of the subsequent forging process.

2. Heating and forging

Preheating

The billet needs to be preheated before entering the forging to reduce deformation resistance, improve plasticity, and prevent cracking. The preheating temperature is usually determined according to the type of material and forging requirements.

Forging

Forging is a key link in the processing of bearing forgings. During the forging process, the billet is shaped into a preliminary bearing shape by free forging or die forging. It is usually done on forging equipment (such as air hammers, steam-air hammers, crank presses, flat forging machines reamers, etc.).

The forging process can be divided into the following steps:

Upsetting: The blank is placed on the forging equipment, and the pressure of the hammer or hydraulic press causes the metal to flow and eliminate internal defects while increasing the diameter of the blank.

Punching: Punching holes in the upsetting blank to prepare for the subsequent separation of the inner and outer rings.

Separation of inner and outer rings: The blank is separated into the inner and outer rings through further forging and punching.

For large bearing forgings, after hot forging, the inner and outer diameters need to be expanded by hot rolling to reach the specified size. There are many types of hot rolling equipment, and the processing method usually includes rolling the main roller and the mandrel in the thickness direction of the outer and inner rings and rolling the outer and inner rings with two conical pressure rollers in the height direction.

For small and medium-sized bearing forgings, the mother-and-child ring forging method can be used; that is, the inner and outer rings are forged at the same time to reduce the forging process. This method is suitable for matching inner and outer rings. The gap between the inner and outer rings after forging is very small, and the outer ring needs to be further expanded by cold rolling.

3. Rolling and shaping

Rolling is a process that thins the wall thickness of the ring blank on a special reamer to expand the inner and outer diameters at the same time and obtain the required end face shape. The rolling process is widely used in the forging production of bearing rings. It can improve the geometric accuracy and dimensional accuracy of the ring forgings, eliminate the wall thickness difference, and make its shape as close to the finished shape of the ring as possible.

The ring, after rolling, also needs to be shaped to improve the accuracy further. The shaping process usually includes sizing and end face shaping to ensure that the aperture roundness and end face flatness of the ring meet the design requirements.

4. Heat treatment

Heat treatment is an indispensable part of the bearing forging process. Through heat treatment, the organizational structure of forgings can be improved, the hardness and wear resistance can be increased, the organization can be stabilized, and the internal stress can be reduced.

The heat treatment process usually includes the following steps:

Spheroidizing annealing: After forging, the forgings are subjected to spheroidizing annealing to improve the cutting performance of the material. During the spheroidizing annealing process, the cementite (Fe3C) precipitated in the pre-treatment spheroidizing annealing is dissolved into the matrix, the austenite of solid carbon is rapidly cooled, and martensite transformation occurs, resulting in high hardness.

Quenching: The forgings are heated to the quenching temperature and then rapidly cooled to improve the hardness and wear resistance. The quenching medium is usually oil quenching or air quenching.

Tempering: The quenched forgings are heated to the tempering temperature, kept warm for some time, and then cooled to stabilize the organization, reduce internal stress, and maintain a certain hardness.

5. Grinding and cleaning

Grinding

The forgings after heat treatment need to be ground to remove the oxide scale and deformation layer generated during the heat treatment process while ensuring that the dimensional accuracy and surface roughness of the forgings meet the requirements. The grinding process usually includes steps such as rough grinding, fine grinding and super fine grinding.

Cleaning

After the forging is ground, it is necessary to clean it to remove impurities such as grease, dirt and scale on the surface of the forging. Cleaning methods include horizontal drum cleaning and shot blasting drum cleaning. The surface of the forging after cleaning should be clean, bright and flawless.

6. Quality inspection and packaging

Quality inspection

Comprehensive quality inspection of the completed bearing forgings is an important part of ensuring product quality. The quality inspection content includes dimensions, shape, hardness, surface quality and other aspects. During the inspection process, various measuring tools and inspection equipment are usually used, such as micrometers, vernier calipers, hardness testers, etc.

Packaging and storage

Qualified bearing forgings need to be rust-proofed and then packaged in the prescribed manner. Packaging materials usually use cartons, woven bags, etc., to ensure that the forgings are not damaged during transportation and storage. The storage environment should be dry and ventilated to avoid moisture and corrosion.

7. New technologies and development trends

With the continuous advancement of science and technology and the development of the bearing manufacturing industry, the processing technology of bearing forgings is also constantly innovating and improving. The following are some new technologies and development trends:

Cold rolling technology and high-speed upsetting: Cold rolling technology originated from Japan and Germany, and high-speed upsetting represents the most advanced level in my country. These technologies can significantly improve forging efficiency and product quality.

Near-net-shape plastic processing technology: By optimizing the forging process and die design, the near-net-shape processing of forgings can be achieved, the amount of subsequent machining can be reduced, and the material utilization rate can be improved.

High-frequency induction heating: The high-frequency induction heating method is used to improve the heating efficiency and heating quality and reduce energy consumption and environmental load.

Automation and intelligence: In the forging production process, automation equipment and intelligent control systems are introduced to realize the automation and intelligent control of the production process and improve production efficiency and product quality.

The processing process of bearing forgings is a complex and sophisticated process involving multiple links such as raw material preparation, heating and forging, rolling and shaping, heat treatment, grinding and cleaning, quality inspection and packaging. By strictly controlling the process parameters and operation procedures of each step, we can ensure the production of high-quality bearing forgings that meet the use requirements of various mechanical equipment. At the same time, with the continuous emergence of new technologies and the continuous changes in development trends, the processing technology of bearing forgings will continue to innovate and improve, injecting new vitality into the development of the bearing manufacturing industry.