The Research On Cored Wire Technology On The Production Of FCD700 Ductile Iron Camshaft

Camshaft is one of the most important parts of motorcar engine. It controls the function of air intake valve and exhaust valve, which not only affect the amount and precision of the air in-out, but also has key effects on ratio of combustion and energy-saving problem. Therefore only high hardness and wearable material could keep the engine accord with the design parameter, and indeed enhance the performance of auto engine. Ductile iron is often chosen as the material of a camshaft in automobile engine, because it has good shock absorption, high wearable performance, and strength as or higher than steel.FCD700 camshaft is a high strength ductile iron motor cast developed for 4G6 series engine in Harbin Dongan motor engine corporation. Pour over process has been used in spheroidisation and inoculation process for a long time. Although the technological conditions can satisfy the index requirements of camshaft, but it still involved a number of problems as the following: low spheroidisation rate and instability of spheroidal performance; severely chilling tendency; low utilization ratio of the returns and high production cost; more nodularizer addition; large fluctuation of residual Mg amount in pouring furnace; low percent recovery; high arc light and dust at field, bad work environment and hard labor condition. To resolve the problems above, increase the camshaft quality, reduce the producing cost, and improve work condition, in this paper, on the basis of theoretical analysis about cored wire technology in ductile cast iron production, reasons of the problems presents in former pour over process are analyzed, and rationality and feasibility of FCD700 ductile cast iron camshaft are verified. The scheme of replacement of pour over process by cored wire technology is made. Industrialization experiments are carried out, optical spectrum analysis sample, tensile sample, metallographic specimen were collected, and all the experiments results were analyzed.The result of industrialized experiments shows as the following: compared with the former pour over process, cored wire technology improved the cast part spheroidisation rate, and achieved better parameters such as the level of graphite spheroidisation size. It also improved the reliability of cast mechanical property effectively, achieved high spherodisation reliability and good repeatability. Cored wire technology need small amount Si-increment of melted iron, so large amount of returns is used, the producing cost is decreased, and the fluctuation of residual Mg percent can be adjusted flexibly. At the same time, environment effects and environment pollution of fume are eliminated in cored wire process spherodisation process, and the labor strength is reduced.