Production Practice of Hydrogen-induced Cracking Resistant High-strength X65 Pipeline Steel

With average [S] of 0.033%(in the range of 0.028%~0.039%),and average [P] of 0.133%(in the range of 0.129%~0.138%) in molten iron to be fed into converter,X65 pipeline steel was successfully produced through dephosphorization by double slag process in converter,modification of ladle slag during tapping,application of double-deck high alkalinity covering agent in tundish,control of LF slag composition,and casting protection with argon.The average [N],T and [P] in the strands were controlled at 0.0035%,0.001 4%,0.002 3%,and 0.009 8% respectively.Inclusions in the strand were rated below 0.5 with total amounts of 0.004 4%.These globular inclusions were small in size and number,exhibiting satisfied internal quality.The mechanical properties of the trial-produced steel achieved the desired effect,and could fully meet the requirements of standards and users.