Bearing data and the development direction of heat treatment

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Bearing data and the development direction of heat treatment

Source: China Bearing Network Time: 2013-05-09

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First, improve the exercise skills and improve the cleanliness and uniformity of steel compared with industrial developed countries; China's bearing steel oxygen content has been close to foreign leading level; but the inclusions and carbide scale and dispersion uniformity, composition uniformity and foreign There is still a large distance; for example, large-scale inclusions and carbides, uneven basic components constitute black and white areas; the quality of the bearing parts is congenitally insufficient; severely affects the life, reliability and consistency of the bearing.
In addition; the presence of large-scale inclusions on the rolling touch surface also severely reduces the appearance accuracy; the noise of the bearing is added. To this end; the bearing profession should negotiate with the metallurgical profession; promote the metallurgical profession on the basis of further reducing the oxygen content; , rolling skills, inclusion handling and testing skills; such as improving electromagnetic mixing during continuous casting, adding Dalian casting billet scale, strengthening high-temperature dispersion annealing, etc.; to improve the scale and uniformity of inclusions and carbides .
Second, the development and implementation of new steel varieties are not the same as the demand for bearings, following the miniaturization, light weight and high speed of the main engine; the operating environment of the bearings is more and more diversified; the demand for bearings is becoming more and more stringent; There are steel grades that are not satisfactory or can not be satisfied with the main bearing requirements of the bearings; for this reason; the development and implementation of new materials should be actively carried out. For example, the development of high-hardenability steel for heavy-duty bearings, heavy loads and clean smooth conditions or Bearing steel used under small and light weight conditions, high carbon steel and carburized steel for bearings used under polluted conditions, bearing steel for quasi-high temperature (operating temperature below 200 °C) and bearing steel for special conditions ( Stainless steel, high temperature steel).
Third, the discussion and implementation of the new process of heat treatment. The bainite quenched bainite austempering bearing has good impact toughness and external compressive stress; whether it is cracking during installation, it is still the tendency of the casing to block the block and the inner casing to break. The 铱 档 档 鲎 鲎 鲎 因而 因而 因而 因而 因而 因而 因而 因而 因而 因而 因而 因而 因而 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承 轴承The bearing used. The process is compared with other life extension methods; the process is simple; the cost is low. In these years; China has developed a new steel grade GCr18Mo bainite quenching special steel; to promote the application of bainite quenching on large-scale bearing parts In view of the many advantages of the process; advocated in the use of bearings with harsh conditions (large impact load, poor smoothness, etc.) or high reliability of demand; and further study the wear resistance and fatigue life after bainite treatment .
2. The external carbonitriding Luoyang Bearing Research Institute started the martensitic stress quenching of bearing steel in the 1980s; after special carbonitriding quenching of high carbon chromium bearing steel parts; progressing the appearance of residual austenite The content of the body; improve the external stress state; greatly improve the carbonitriding of the gearbox; improve the residual austenite content on the surface without reducing the appearance hardness; to improve the fatigue life and reliability of the bearing under the condition of smooth pollution Sex.
Fourth, the appearance of modification skills through the appropriate appearance of the surface to improve the appearance of the function; to meet the functional requirements of the bearing under special conditions. For example, using the vapor deposition technique to coat the bearing raceway with diamond coating can achieve the effect of friction reduction and wear resistance. Greatly improve the wear life and precision of the bearing. It can be used in household appliances bearings and computer hard disk drive bearings. Apply thermal coating skills to coat alumina ceramic materials on the outer cylinder surface of the bearing outer ring; Electrical insulation function; avoid electric shock; improve the life and reliability of the motor bearing, in the bearing parts surface sulfur or accumulation of M0S2 can reach the anti-friction smoothing effect.
5. Heat treatment equipment and related skills1. The atmosphere and control are heated by a controlled atmosphere heated to a precise control of the carbon potential and nitrogen potential; the function of the parts after heat treatment is improved; the disadvantages of heat treatment such as decarburization, cracking, etc. are greatly reduced. Contact heat treatment quenching deformation control skills ; can reduce the finishing allowance after heat treatment; improve the utilization rate of data and machining power; together improve the appearance of bearing parts after finishing; such as the carbon content, arrangement, hardness and stress status of the surface.
2. Automation and intelligence are based on the application requirements, data, and layout dimensions of the parts; the use of physical metallurgical knowledge and leading computer simulation and testing skills; optimization of process parameters; the ability to reach the required functions or maximize the potential of data, and On the one hand, it is the automation degree and stability of the advanced heat treatment; it is sufficient to ensure the stability of the optimized process; the quality of the finished product is very disproportionate. The mechanical equipment hospital faded.
Sixth, deformation and dimensional stability Martensite quenching process; because the parts of the parts are not evenly cooled; inevitably present thermal stress and arrange stress to cause deformation of the part. Quenching of the parts after quenching (including scale changes and shapes Change) is affected by many factors; it is a problem of proper clutter; such as the shape and scale of the part, the uniformity of the original arrangement, the roughing condition before quenching (the size of the feed amount during turning, the residual stress of machining, etc.), The heating rate and temperature during quenching, the placement method of the workpiece, the oil inlet method, the characteristics of the quenching medium and the circulation method, and the temperature of the medium all affect the deformation of the part. The deformation should be discussed with detailed equipment and products; Deformation method; such as rotary quenching, die quenching, control part oiling method, etc.; reduce heat treatment deformation; improve processing power and part function.
After martensite quenching; the dimensional stability of the part is mainly affected by the following three different transformations: carbon migration from the martensite lattice constitutes ε-carbide, residual austenite differentiation and composition of fe3c; Superimposed on each other. Between 50 and 120 ° C; because of the deposition of ε-carbide; incurs the volume shrinkage of the part. 懔慵 After 150 ° C tempering, this transformation has been completed; its scale in the future use of parts The effect of stability can be neglected, between 100 and 250 ° C; residual austenite differentiation; transformation to martensite or bainite; will accompany the volume increase, above 200 ° C; ε-carbide carburization Body transformation; incurs a reduction in the volume of parts. The study indicates that the remaining austenite is also differentiated at the external load effect or at a lower tempering temperature (even at room temperature); it causes a change in the size of the part. Therefore; in practical use; The heating temperature of the bearing parts should be higher than the operating temperature of 50 °C; the parts with higher requirements for dimensional stability should be reduced as much as possible of the retained austenite; and the dimensional stability, accuracy and life of the storage and operation should be improved. Number and reliability.
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