Abstract
It has been confirmed that the precipitated carbides in 18 Cr-8 Ni stainless steels play an important role in determining the creep rupture strength. The finer the dispersion of the carbides is, the higher rises the rupture strength. The small amounts of titanium and niobium, especially when both the elements coexist, have been found to be effective controlling elements to obtain a fine dispersion of the carbides. The addition of titanium and niobium of the order of 0.1% to 18 Cr-8 Ni stainless steel will considerably increase its creep rupture strength. To 18 Cr-10 Ni-2 Mo steel, also, small addition of titanium and niobium together with boron and nitrogen will have an effect of preventing abnormal decrease in creep rupture strength, and of giving the steel such high rupture strength as 18.5kg/mm2 at 700°C-1000hr.
