Internal quality control of chilled cast iron camshaft casting

The chilled cast iron camshaft uses the chilling effect of the formed chill on the high temperature molten iron to obtain a certain thickness of white layer and transition zone from the surface to the center of the cam lift section, while the rest parts maintain the gray cast iron structure. Because of the advantages of chilled cast iron camshaft, such as good wear resistance of cam surface, keeping the mechanical strength of gray cast iron at journal and center, direct grinding of cam after casting, high production efficiency and low cost, this material is widely used in most car engine camshaft at home and abroad.

The internal quality technical indexes of chilled cast iron camshaft mainly include: chemical composition, matrix hardness, cam tip hardness, chilled layer depth (hereinafter referred to as cold depth), microstructure, tensile strength, etc. To control the internal quality of chilled cast iron camshaft is the basis to ensure the quality and performance of finished camshaft.

At present, the domestic production of chilled cast iron camshaft blank is completed by professional casting company or professional foundry. It is not too difficult to produce the blank that meets the requirements of technical conditions for automobile engine camshaft, but it is not easy to produce 100% qualified products in batch. Especially with the development of car engine technology, the camshaft, as one of the core components of the engine, has put forward higher requirements. As the case of customer a and customer B described in this paper, the internal quality technical requirements of camshaft are obviously higher than the requirements recommended in “technical conditions for camshaft of automobile engine”. Through the strict control of chemical composition, matrix hardness, cam tip hardness, depth of cold shock layer, metallographic structure and tensile strength, the internal quality pass rate of customer a and customer B products is more than 99.7%.

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