HIGH-STRENGTH STEEL FOR SEAMLESS, WELDABLE STEEL PIPES

摘要

A low-alloy steel containing, by weight percent, C 0.03-0.13%, Mn 0.90-1.80%, Si = 0.40%, P = 0.020%, S = 0.005%, Ni 0.10- 1.00%, Cr 0.20-1 .20%, Mo 0.15-0.80%, Ca = 0.040%, V = 0.10%, Nb= 0.040%, Ti < 0.020% and N = 0.01 1 % for making high-strength, weldable steel seamless pipe, characterized in that the microstructure of the alloy steel is a mixture of bainite and martensite and the yield stress is at least 621 MPa (90 Ksi). It is a second object of the present invention to provide a high- strength, weldable steel seamless pipe, comprising an alloy steel containing, by weight percent, C 0.03-0.13%, Mn 0.90-1.80%, Si < 0.40%, P = 0.020%, S < 0.005%, Ni 0.10-1.00%, Cr 0.20-1.20%, Mo 0.15-0.80% , Ca = 0.040%, V <; < 0.10%, Nb < 0.040%, Ti < 0.020% and N < 0.01 1 % also characterized in that the microstructure of the alloy steel is predominantly martensite and the yield stress is at least 690 MPa (100 ksi).