Why Do Gray Iron Castings Have a Hardness Problem?

As a material commonly used by cast iron manufacturers, gray cast iron has the characteristics of high wear resistance, high notch sensitivity and low shock absorption, and is widely used in the field of casting production. However, when casting iron castings, iron manufacturers will always face some unavoidable casting defects, and the problem of gray iron castings is a problem that needs to be solved urgently.

First of all, the chemical composition ratio in the molten metal is inappropriate, and the content of carbon and silicon is low. The production of gray iron castings should strictly control the content of silicon and carbon, under normal circumstances, the carbon content should be controlled between 2.9-3.5%, and the silicon content should be controlled between 1.5-2.4%. If the content of these two elements is too low, it will cause the ash casting to be too hard.

Secondly, the carbon element is not fully absorbed. When the gray cast iron manufacturer proportions the amount of metal raw materials, if the added carbon is not completely absorbed or the fluidity of the carburizer is poor, it will lead to high supercooling of the molten iron or uneven cooling temperature, which will cause the gray cast iron casting to be too hard.

Finally, the cause of the mold. If there is a defect in the mold, it will lead to poor fluidity of the molten iron and uneven cooling rate; If the air permeability of the mold is relatively poor, then there is no way for water vapor to overflow, which leads to the rapid cooling of some positions in water, resulting in an increase in the hardness of the casting; If the pouring time is too long, it will also lead to the failure of the inoculant, the charcoal in the molten iron will be burned, and the low silicon-carbon content will cause the hardness to increase.

The hard gray iron casting is caused by a variety of factors, which requires specific analysis of specific problems.

The above is Supreme Machinery Co., Ltd. according to the daily casting production experience, for you to sort out the relevant knowledge of the reasons for the gray iron castings, I hope to help you in the confusion of casting production!