A Complete Guide to Forging Process of Bearing Rings

In the realm of mechanical manufacturing, although bearing rings are small components, they hold a significant position. They act as the "joints" of machinery, ensuring the smooth operation of various mechanical devices. Today, let's delve into the forging process of bearing rings and see how it has been continuously optimized over time, providing solid support to the mechanical manufacturing industry.

Bearing Rings: The Key "Joints" of Mechanical Operation

Bearing rings, which may appear to be ordinary annular parts, actually play a crucial role. They have one or several raceways and are the core components of radial rolling bearings. In the world of mechanical manufacturing, they are omnipresent and widely used in all kinds of mechanical equipment. Why are they so widely applied? The key lies in their three major advantages: ease of assembly and disassembly, axial fixation, and axial position adjustment. These features enable mechanical equipment to operate more flexibly and efficiently during maintenance, repair, and operation.

The structure of bearing rings is diverse, including tapered inner rings, tapered outer rings, double-row tapered inner rings, and double-row tapered outer rings. Different structural forms meet the diverse needs of various mechanical equipment in terms of load capacity, operating precision, and spatial layout. It can be said that bearing rings are like "Transformers" in the mechanical world, capable of transforming into the most suitable form according to different tasks.

Bearing Ring Forging Overview

The forging process of bearing rings is a topic that is both ancient and full of novelty. It is ancient because its traces can be found early in the long history of industrial development. As early as ancient times, people had already begun to use simple forging techniques to manufacture some metal tools and parts. The forging process of bearing rings has gradually developed in this historical inheritance. It is novel because it has never stopped improving and optimizing. With the continuous progress of science and technology, new materials, new equipment, and new process concepts are constantly emerging. The forging process of bearing rings is also constantly absorbing these fresh elements and rejuvenating itself.

Optimizing the forging process of bearing rings has many benefits. On the one hand, it can reduce process machining costs and lower production costs. For enterprises, this means stronger market competitiveness and higher economic benefits. On the other hand, the optimized process can improve the quality of the forged bearing rings. Higher quality means longer service life, higher reliability, and better performance, which is crucial for the stable operation of mechanical equipment.

Bearing Ring Forging Process

The production process of bearing rings can be divided into four stages: forging, heat treatment, monitoring of grinding processes, and marking management. These four stages are closely linked, and each link has a crucial impact on the final product quality. The focus of this article is to deeply analyze the core link of the forging process.

During the forging process, some problems may arise, such as overheating, overburning, and the formation of a network of carbides. These problems may sound technical, but their impact on the toughness and strength of the rings is very real. Overburning can make the metal grains coarse, reducing the material's toughness; overheating can change the internal structure of the metal, affecting its performance; and the formation of a network of carbides can weaken the metal's strength. Therefore, we must always be vigilant and strictly control the processing temperature, cyclic heating, and post-forging cooling conditions. Especially for larger rings, when the temperature after final forging is still above 700°C, they must not be stacked. Otherwise, the heat cannot be dissipated in time, which may lead to a series of quality problems.

Taking the forging of tapered roller bearing rings as an example, we can more intuitively understand the current status of bearing ring forging technology in our country. At present, the single-squeeze and single-squeeze-expansion processes are widely used in China to produce tapered roller bearing rings. This is especially true for the forging of medium and large-sized tapered roller bearing ring forgings. Specifically, a section of material is heated and then roughly processed, followed by squeeze preforming, core cutting and hole expansion forming, and finally, the outer ring of the tapered roller bearing is obtained after the sizing process. If the inner ring is to be produced, the method is basically the same, except that the sizing process is omitted at the end. Although this process is relatively mature, there is still room for improvement and optimization in the face of increasingly fierce market competition and ever-increasing quality requirements.

Bearing Ring Forging Process Design Principles

The design of the forging process for bearing rings needs to follow three basic principles. These principles are like a "compass" in the design process, guiding the correct direction of process design.

1. Principle of Constant Weight

This principle may sound simple, but in practice, it requires consideration of many factors. First, the weight of the forgings involved in the forging process must be equal. However, in actual production, there will be some weight loss of the forgings during the forging process. This requires us to consider the actual conditions of fire loss, forging allowance, and dimensional tolerance in advance and to allocate the weight reasonably. At the same time, since different temperatures can affect the size of the forgings, we also need to accurately design the process (die) dimensions under different conditions to ensure the pass rate of the forged products. Only by grasping these two points can we ensure the success of the bearing ring forging process design.

2. Principle of Forging Defect Control

No forging process is completed in one step; it involves multiple working processes. In each process, some forging defects may occur, such as burrs, pits, and fillets. If these defects are not properly rounded during the forging process, they will be "copied" to the final forged product, directly affecting the quality of the forging. Therefore, during the forging process, we should try to ensure that the blank conditions are good and that the forging deformation is sufficient. In this way, through multiple forging deformations, various defects in the blank can be reduced.

The blank undergoes multiple deformations during the forging process and eventually becomes the finished product. If the various parts of the blank deform disproportionately, various forging defects will occur, such as burrs, pits, fillets, and scale. In addition, internal stresses caused by processing deformation lead to out-of-round deformation, and the quality of the finished product will inevitably be substandard. If this defective finished product is subjected to subsequent machining such as turning and grinding, the precision of the bearing ring will be greatly affected. Therefore, controlling forging defects during the forging process is crucial.

3. Principle of Specificity

The forging process of bearing rings has its own particularities. Taking the design of the double-expansion process for inner and outer rings as an example, it generally involves nine processes: cutting, heating, upsetting and cutting, hole expansion and flattening, outer ring expansion, sizing, inner ring preforming, bottom cutting, and inner ring expansion. Among them, the cutting process is the key process of the double-expansion process. It determines the initial blank conditions for the forging of the inner and outer rings, the weight distribution of the inner and outer rings, the flattening amount of the outer ring, and the expansion ratio. It plays a crucial role in the final formed forging.

The expansion ratio is closely related to the production rhythm. The selection of the expansion ratio directly determines the unit time for single-piece production of the hole-expanding machine. In a production line where the press and the hole-expanding machine are connected, it is crucial to the production quota. Therefore, the determination of the expansion ratio must be the minimum value. The larger the expansion ratio, the stronger the ability to eliminate blank defects, and the more dense the internal structure of the forged part formed after sufficient rolling and expansion. However, due to the constraints of multiple parameters, the expansion ratio cannot be infinitely large. On the contrary, the smaller the expansion ratio, the weaker the ability to eliminate blank defects, the higher the requirements for the previous process of imitation, and the increased consumption. Therefore, the range of the expansion ratio is generally suitable between 1.2 and 1.6.

The selection of the flattening amount is also very important. The larger the flattening amount, the greater the appearance defects formed on the surface of the blank after hole expansion and flattening, which requires a larger expansion ratio for sufficient rolling and expansion to eliminate defects. The smaller the flattening amount, the smaller the appearance defects formed on the surface of the blank after hole expansion and flattening, but a smaller flattening amount is not sufficient to eliminate the end plane defects formed by cutting and does not meet the requirements of hole expansion. Therefore, the range of the flattening amount is generally between 15% and 25% Cn (Cn is the width of the outer ring forging, including half tolerance). The combined selection of the expansion ratio and the flattening amount should not only meet the above requirements respectively, but also conform to the law of linear proportional distribution in their respective values.

Summary

The optimization of the forging process of bearing rings is an ongoing process. It is not only related to product quality and production efficiency but also directly affects the competitiveness of the entire mechanical manufacturing industry. By strictly following the principles of constant weight, forging defect control, and specificity, we can ensure the scientific and rational nature of the forging process. At the same time, with the continuous progress of science and technology, the application of intelligent forging technology, the exploration of new materials and processes, and the implementation of green forging concepts all provide broad space for the future development of forging processes.