Aiming at X70 pipeline steel pipe,this paper establishes a heat source model of pipeline girth weld based on testing,and calculates welding heat cycle process by using numerical simulation software,and also determines variety process and distribution of temperature and stress in welding joint during welding,as well as magnitude and distribution of residual stress post-weld.

Adopting thermal simulation and micro analysis technology,it researched effect of welding thermal cycle on the HAZ structure and toughness for high Nb X70 grade pipeline steel.

Adopting simulation welding thermal cycle and thermoplastics tensile test,it studied welding crack sensitivity parameter of X70 grade pipeline steel,and judged welding thermal cycle sensitivity of X70 grade pipeline steel.

Metallurgical microstructure and fine structure in local brittle zone of in-service welding of X70 pipeline steel;

Cathodic polarization behavior of an X70 pipeline steel crevice in solution containing Cl~- and SO_4~(2-);

Static-recrystallization behavior of hot deformation austenite in X70 pipeline steel;

Effect of LF Feeding Si-Ca Wire on Modification of Inclusion in Pipeline Steel X70

The chemical composition and rolling technology of pipeline steel X70 were designed which was produced on 1880mm thin slab continuous casting and rolling line.