Introduction to shell mold casting

Shell casting process is a kind of forging method in which the shell shape is put into the barrel, steel shot is added around the barrel to strengthen the shell shape, and then molten iron is poured.Casting is to rely on steel shot to cool, cooling rate is faster, permeability is good, steel shot acceptance is good, equipment investment is small, die consumption is slow, die change is easy.The production process of shell type filled steel shot is shown in figure 2.

Sand-coated iron forging is a kind of forging technology which is formed by covering a thin layer of sand on the inner cavity of metal mold (called iron mold), which is evolved from metal mold forging and shell forging, so it has advantages of metal mold forging and shell forging, and overcomes the disadvantages of white mouth structure of metal mold casting.Germany, the former Soviet union and other countries in the 1960s began to use the sand-clad iron forging in forging production, mainly used for the production of nodular iron crankshaft, brake hub, brake disc, cylinder liner, bomb shell, tank track and electromechanical base (more than 30 kinds of casting).The research on the utilization of sand-coated iron forging in China started from the beginning of the 29th century to 1979. Zhejiang electric machinery research institute and yongkang factory cooperated with each other, and the process was first applied to the batch forging production of S195 crankshaft castings, and a victory was achieved in the production of six-cylinder crankshaft.The obvious characteristic of shell mold casting process is that it can control the change of the thickness of the sand layer and the thickness of the iron mold.Also can form the premise of solidification at the same time, the manipulation of the graphitization contraction of ductile iron, iron the characteristics of high stiffness, enrich the manipulation of the ductile iron graphitization contractions occur from feeding, and make the casting riser forging is realized. Therefore, sand type iron forging of the point is: should be in accordance with the differences of iron casting wall thickness to select the suitable thickness and coating type, in order to obtain the required cooling rate.At present, nearly 100 enterprises in the world have made use of the iron-type sand-covered forging process to produce more than 30 kinds of castings such as ductile iron crankshaft, camshaft, balance shaft, pressure-resistant valve body, cylinder liner and wear-resistant gear plate.At present, the problem of iron process is: the cost of tooling is higher, and the point is difficult;The general problem of iron type is difficult to resolve.Production line of the machine and active degree is not high.The production process of sand - coated iron process.

The shell thickness is very important to the material uniformity of the guaranteed casting, so the mold layout and mold manufacturing accuracy are very high.For the sand-free box does not fill the steel shot process, because the shell shape to accept the effect of high temperature liquid iron, so the shell shape shell thickness should be a little thicker.