In the engine system of a car, the camshaft is one of the very important accessories. Its main function is to control the closing and opening of the valve. When working, the camshaft not only needs to bear the extrusion stress from the connecting rod, but also is subjected to bending, torque And friction, over time, it will wear, deform, fatigue damage and fracture, therefore, a qualified camshaft must have high strength and hardness, good fatigue resistance, wear resistance and toughness. According to its characteristics, we choose medium carbon steel as the material for making camshafts. During production, they will be quenched with the help of high-frequency quenching equipment to further improve their technical performance.
During the heat treatment and quenching process of the camshaft, due to the relatively fast cooling speed after quenching, the temperature inside and outside the camshaft is different, and there is a certain temperature difference. At this time, thermal stress and tissue stress will be generated inside the camshaft. When it is large, it will cause cracks on its surface. In addition to this reason, if the raw materials for the production of the camshaft are unqualified or improperly selected; or the temperature is not suitable during the quenching process of the high-frequency quenching equipment, the operation method is incorrect; or the tempering after quenching is not timely, etc. will cause the camshaft Cracks appear on the surface. The reasons are different, and the cracking phenomena that may be caused are also different. The slight ones can be remedied, and the serious ones will cause the camshaft to be scrapped. Many experiments have allowed us to summarize several solutions. For example, if vertical cracks appear, we can use isothermal or graded methods during cooling to ensure that the camshaft will not be completely hardened, so as to further reduce its cracks. Tensile stress is generated inside, and the quenching treatment is completed before the camshaft is quenched; if there is a network of cracks, we can speed up or slow down the cooling rate when the high-frequency quenching equipment quenches the camshaft, and temper in time treatment to ensure the uniformity of the surface structure of the camshaft.
If the surface of the camshaft cracks during quenching and cooling, there may be a black oxide layer at the crack, there may be red rust, there may be cracks, and there may be protrusions Or uneven thickness, etc., these are caused during the forging or cooling process of the camshaft, so when we produce the camshaft, we must strictly follow the standard operation to avoid cracking on the surface.
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