| ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ KAWASAKI STEEL TECHNICAL REPORT No.1 ( September 1980 ) ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ |
| Development of Steels Resistant to Hydrogen Induced Cracking in Wet Hydrogen Sulfide Environment
Yoichi Nakai, Hayao Kurahashi, Toshihiko Emi, Osamu Haida |
| Synopsis : Factors influencing the occurrence of Hydrogen Induced Cracking (HIC) in steel plates for linepipe use have been investigated by means of ultrasonic C-scanning of plate specimens preliminarily immersed into synthetic sea water saturated with H2S. The cracks were most frequently observed in the area corresponding to A- and V-segregates of mother ingots, initiating at elongated MnS inclusions and propagating along anomalous structure in which Mn and P were segregated. The rest area was rather in-susceptible to HIC. The occurrence of HIC in the former area was slightly decreased but could not be prevented even by decreasing average S content of the plates as low as 0.001wt%. The addition of copper markedly reduced the rate of hydrogen permeation, but hardly prevented the formation of HIC. Heat treatments to improve the solute segregation in slabs or to make the structure in plates homogeneous helped decreasing the susceptibility to HIC. The treatments, however, were impracticable for commercial control- rolled plates. An effective means to overcome these difficulties has been found by strictly controlling the ratio of effective cerium or calcium to sulfur in the melt (atomic ratio1.5) and preventing the reoxidation of the two elements during the teeming of the melt. Resulting plates subjected to controlled rolling have been highly resistant or totally insusceptible to HIC, exhibiting no defect on the C-scanning. |
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