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Hydrogen in Steelmaking

OR many years steel producers have been concerned 
with the problem of hydrogen in steel. The pres- 
ence of hydrogen in excess of its solubility at the melting point 
may cause bleeding and unsoundness in ingots and castings. In 
fully-killed steels the hydrogen content which causes such 
unsoundness depends on the alloy content, and may range 
from 6 to 12 parts per million. • It is also recognized that even 
smaller contents of hydrogen, down to I or 2 paits per million, 
may play a part in causing other defects such as flakes and hair- 
line cracks, and generally lowered ductility. Table I and Fig. I 
show typical data on these effects of hydrogen in steel.l•2 Small 
amounts of hydrogen pose a problem of special importance in 
such products as large forgings where maximum properties 
are desired. 
It is possible to remove hydrogen from solid steel by suitable 
heat treatment because of its relatively high rate of diffusion 
in steel. However, the effectiveness of heat treatment dimin-

ishes rapidly as the cross-section of the steel parc treated in- 
creases. The time required to reduce the hydrogen content to 
an acceptable level increases approximately as the square of 
the diameter of the section. If heating for 4 days is required 
for a section 10 inches in diameter, heating for about i 6 days 
will be required for a 2()-inch diameter section. Thus, large 
forgings may require excessively protracted heating periods. 
For this reason the importance of keeping the hydrogen content 
of the steel as low as possible while it is still liquid becomes 
evident.

The purpose of this paper is to discuss what is known about 
the effects of steelmaking operations on the hydrogen content 
of the liquid steel. The discussion emphasizes the following 
points: