The effect of Nb and Al on the transformation temperatures on heating was determined for the high strength steel (low-alloy steel with C content up to 0.20%). The relation of chemical composition of steel to the beginning-temperature (A
S) and the end-temperature (A
f) of transformation was well expressed by the following empirical formula.
A
S=747.7+(17.6×%Si)-{23.0×%(Cu+Ni)}+(24.1×%Cr)
+(22.5×%Mo)-(39.7×%V)-(11.6×%Mn)+(31.9×%Zr)
Add -2.9 for boron containing steel.
A
f=937.2-(476.5×%C)+(56.0×%Si)-(19.7×%Mn)-(16.3×%Cu)
-(26.6×%Ni)+(38.1×%Mo)+(124.8×%V)+(136.3×%Ti)
-(4.9×%Cr)+(35.0×%Zr)
The variation in transformation temperatures due to the variation in the alloy content other than Nb and Al was evaluated from the above equation and the effect of Nb and Al was obtained.
With 0.03% Nb, As was raised about 10°C, while there was no change in A. With soluble Al content of 0.03%, both A
S and A
f were raised about 10°C.
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