A. M. Kulkarni, M. S. Patil, Essar Steel Limited, Surat, India; J. M. Gray, Microalloying International Inc., Houston, TX
Resistance to hydrogen induced cracking is an essential requirement of API line-pipe steel used for sour service applications. The resistance to HIC can be improved by having minimum level of the center-line segregation in as-cast slabs. Essar Steel Ltd. has made trial heats with the philosophy of using minimal amounts of alloying elements (manganese and carbon) having tendency for center-line segregation during continuous casting. Sulphur levels have also been slightly relaxed. The current paper compares the test results obtained in these trial heats with regard to segregation levels, mechanical properties and resistance to HIC with those in heats made with the conventional alloy design suitable for sour service applications.
Summary: There is growing requirement of line-pipe steel with improved resistance to hydrogen induced cracking. Elements like carbon and manganese have a strong tendency to segregate at the center-line of as-cast slabs. Alloy design with reduced manganese levels have given encouraging results when compared to conventional alloy design practice.
