Effects of alloying elements on the formation of hydrogen blowholes during solidification of steel and cast iron

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The effects of Al, Ti, Bi, Te and S on the formation of hydrogen blowholes have been investigated by the technique of solidifying molten Fe-C-Si alloys in quartz tubes. This technique was employed to control the hydrogen content in the melts immediately before solidifying and to eliminate the influence of mold conditions.First, the effects of Al, Ti, Bi, Te and S have been investigated on condition that these elements are not oxidized.The results obtained are as follows; 1.The Al addition had no influence on the blowhole formation in white iron. On the other hand, the Al Addition reduced the tendency of blowhole formation in gray iron.2.The addition of Ti had no influence on the blowhole formation in white iron.3.In the case of gray iron with Ti contents in the 0.091% to 0.108%, intermediate Al contents of 0.046% to 0.124% increased the tendency of blowhole formation and Al contents over 0.230% had no influence on the blowhole formation as compared with Ti- free samples.4.The addition of Bi, Te and S increased the tendency of blowhole formation in white iron.In addition, the molten Fe-C-Si alloys were treated with a gas mixture of H_2, Ar and H_2O by bubbling through the melts for purposes of investigating the effect of oxidation of Al in the melts. The water vapor pressure of this gas mixture was established at about 10^<-4> atm, and thermodynamic consideration indicated that only Al was oxidized by this treatment.The results of this treatment of the melts are as follows; 1.The treatment increased the tendency of blowhole formation in gray iron in the concentration range of 0.05-0.4%Al.2.The treatment had no influence on the blowhole formation in gray iron, when the concentration of Al was 0.05-0.23%Al and the concentration of Ti was 0.1%. However, a part of solidifying melts came out of quartz tubes.