Low alloy steel for mfg. pipes used in oil drilling - where steel has very high resistance to stress corrosion cracking in acid oil or gas sources contg. sulphide(s)

摘要

Steel contains by wt. 0.15-0.5% C, 0.1-1% Si, 0.3-1.5% Mn, 0.003-0.1% Al, 0.0005-0.005% B, 0.003% max. N2, rest Fe and trace impurities. The steel is heated to between the Ac1 transformation point (Tl) and a temp. (T2) whic is 50 deg. C Ac3 transformation point, using an average heating speed of 1-30 deg. C/second. The steel is then quenched from a temp. between (T2) and the temp. (T3) at which crystal growth commences, followed by tempering at max. temp. (T1). The steel may also contain 0.05-1.5% Cr, 0.05- 1% Mo, 0.01-0.1% Nb, 0.01-0.1% V, 0.05-0.5% Cu.