Elimination of Primary NbC Carbides in HSLA Steels for Oil Industry Tubular Goods

Two high-strength low-alloyed steels alloyed with various Nb contents were prepared using continuous casting (CC) technology. In the round Steel 30Nb CC billet, it was segregation of C and in central equiaxed zone that promoted precipitation primary NbC carbides at grain boundaries. After processing into seamless tubes, micron-sized located middle bands, surrounded by many nano-sized formed during post-solidification cooling and/or hot-piercing rolling. Even when content decreased down to 0.006 wt.%, there still coarse bands. However, no carbide found billet electroslag remelting Therefore, this study revealed a rapid solidification rate relatively effective eliminating compared merely decreasing content.