In the production process of steel castings, many workers will encounter the appearance of steel castings subsurface blowhole. There are many reasons for the blowhole, the improper casting of a certain step in the whole casting process may lead to the formation of blowhole. In this paper, the causes and preventive measures of blowhole are analyzed in detail from the aspects of raw material, steel melting and sand mixing.

1. Raw materials

(1). It is banned to use raw materials with high contents of Ti (Ti), aluminum (AI) and high alloy steel, stainless steel.

(2). The raw metrials with rust, oxidation, oil, coal, waste sand should be cleaned up before use.

(3). The raw metrials which moisture should be dried before use.

(4). Prohibit to use the iron sheet (pipe) thinner than 3mm.

(5). The length of raw materials must be controlled at around 300-400mm.

2.  Steel melting

(1). The raw materials loaded into furnace must be compacted as far as possible to reduce space, in order to reduce the absorption and oxidation of molten steel.

(2). In the process of steel melting in each furnace, clear the slag at least 2-3 times, and then cover the liquid steel.3, The waiting time for molten steel is not more than 10-15 minutes, otherwise, the quality of molten steel will seriously deteriorate, and become "stagnant water".4.  It is banned to use substandard carburizing agent.3. mixed sand1, Strictly control the sand moisture which is should not greater than 3.5%.

(3). Control sand permeability in 130-180, wet compression strength in 120-140KPa, compaction rate in 35-38%, and sand surface hardness of >90.

(4). Use high quality bentonite and pulverized coal.

(5). At the end of each day, reclaim the excess sand, and thoroughly clean and clean sand mixer.

CHAENG (Great Wall Steel Casting) is one of the largest steel casting factoires in the middle China. It has advanced pocessing equipment and makes opmization in casting process to provide high quliaty large steel castings.
E-mail: casting@chaeng.co