The principle of cold expansion and the superiority
2020-12-18 15:20:02
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The principle of cold expansion and the superiority
Source: China Bearing Network Time: 2018-01-21
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Although many domestic companies have added more and more attention to cold heading skills, they are subject to the original data quality, blank weight and precision, cold heading process and lack of cost-effective equipment; bearing ring cold heading skills have not been widely used; Therefore, we know the operating principle, process and the superiority of the cold expansion; it helps the company to make correct selection of the application of cold expansion.
First, the principle of cold rolling expansion 1, fine cold heading skills is the use of kneading and plastic deformation of the ring inversion parts at room temperature to obtain a cold forming method of the product parts. The main driving forming wheel forms the outer and outer shape; a driven forming mandrel to shape the inner and outer shapes; the mandrel and the workpiece are supported by the supporting wheel; when the workpiece is pressed; the rolling wheel drives the workpiece to rotate; the mandrel is in progress Kneading the workpiece under the advancement of the support wheel that is fixed to the equipment; then, the workpiece is crushed.
2. During the cold rolling period, the analysis is carried out in the cold rolling process; the pressure is not a constant; it follows the stroke of the feed; there is a significant period of time; the cold pressure and the stroke can usually be divided into three periods:
During the first deformation period, during the compression deformation, the rolling end is opened; the support wheel is arranged to feed the opening; the pressure of the crucible is necessary to overcome the deformation resistance inside the metal and the friction between the blank and the mold; so that all the metal lattices are completely pressed; Plastic deformation occurred at the beginning of the data; the helium pressure increased sharply.
During the period of stability and deformation during the second period, the support wheel is arranged to continue feeding; forcing the metal to continue to move. During this period; only the height of the blank is changed; the deformation zone is stable; the height of the plastic deformation zone is not changed with time; the pressure is not changed with the stroke Therefore, the height of the plastic deformation zone in this period is called the height of the stable plastic deformation zone. This height can be determined according to the principle that the steady pressure can occur when the pressure of the helium reaches a certain minimum value.
During the third period, when the residual thickness of the blank exceeds the height of the stable deformation zone; if the support wheel arrangement continues to move forward; the helium pressure rises sharply again.
It can be seen from the above analysis; when the second period is completed; if it is continuously pressed; the pressure is added sharply. Therefore, it is necessary to finish the pressing at this moment; otherwise, the mold or the boring machine is more likely to be damaged.
When the second period is over, the entire rolling process is completed; then; at this moment, the thickness of the residual material is equal to the height of the stable deformation zone. If the second period is completed, the pressure is continuously increased; at this moment, the pressure will rise sharply. The elevated value does not exceed the allowable unit pressure of the mold; and the thickness of the residual material is obtained according to this principle; thus, the talent of the mold data can be fully utilized; and the loss of the original data can be saved. The thickness should be less than the height of the stable deformation zone. Under normal circumstances, the pressure will be completed during the second period.
Second, the primary application of cold expansion and expansion 1, according to the application method is usually divided into two types of fine cold and rough.
The most used in foreign countries is rough. Usually, the shape is disorderly and the small-scale ferrules use more fine craftsmanship; the standard is larger (usually 308 or more), and the rough is used; SKF does not advocate the use of fine enamel.
The advantage of fine cold heading is that the channel and chamfer do not use the car; the downwind is the demand for the mold; the large deformation affects the grinding rate.
The rough advantage is simple manipulation; it does not affect the grinding power; the production layout is simple. The downwind is the lack of precision; the follow-up vehicle plus the work volume is large.
2. According to the blank type before cold heading, it is divided into forging piece cold forming and steel pipe ring cold rolling forming. The above two processes should be selected according to the user's practical conditions, economy, product demand, etc., but no matter which process is used; Raw material requirements, blank hardness, and blank component handling are all the same.
3, usually after cold forming, the need to carry out the full diameter; to ensure the accuracy of the ferrule.
Third, the advantages of cold expansion, superiority 1 Advantages 1) can reduce the cost of the original data; compared with the traditional method of turning processing; fine cold heading processing can improve the data saving rate by 10% to 15%,
2) Ability to complete the molding process of the messy appearance at one time; improve labor productivity,
3) It can improve the mechanical properties of the parts; after cold rolling deformation; the grain arrangement of the metal data is more and more fine; the metal flow line is unchanged; there is no blockage; the fatigue strength of the data is improved,
4) Cold expansion can reduce data consumption and shorten processing time; reduce production costs.
2, the lack of 1) the difficulty of processing the abrasive tools and the use of abrasive tools,
2) The process is difficult to grasp; the application is difficult,
3) The ferrule has a slight micro-crack appearance.
4) The shape error is relatively large (the larger the scale is, the larger the error is); the large deformation affects the subsequent grinding power,
5) The quality of the blank is high: the blank for cold heading should have a certain precision; the error of the blank component should not exceed 0.5%; the hardness requirement of the blank is even and common; there must be no cracks and significant decarburization.
6) Because there are no people in the country who have experienced process skills and operational protection; the company needs to explore the experience on its own; therefore, it is usually a long period of time from equipment introduction to sophisticated application.
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