Large Gray Iron Plates for Workholding
Made by Dandong Foundry

We made these large plates for our client in USA. Their material is Gray Iron Class 35, with Brinell hardness BH 160-220. Their weights are from 60kg to 300kg per piece. Two front and back surfaces need to be grinded to Rz3.2. This is very smooth as mirror. There is no any sand holes or air holes on any surfaces or inside. This requirement is very high. These plates must be stress released by electric oven/furnace. Otherwise, the inside stress will cause the tiny deformation in the future. During machining, you have to machine them step by step. If you machine too much allowance in one time, the machining will cause the deformation, and this plate will be failed. Moreover, you have to find a large surface-grinding machine / flat grinder to grind it by one time.

As for the casting process, the resin sand molding process will be necessary since the resin sand moulding can effectively prevent the deformation during cooling period.

Our iron foundry has produced these plates for over two years. Actually, we have not made them very well yet. We have not reduced the defective rates to low yet. This is also because of the typical shortcoming for sand castings. You never can prevent the air holes, sand holes and small shrinkage. We have bought a portable X-ray detector to check the inside shrinkage and sand holes, but we can not completely prevent the inside flaws.