 |
|||||||||||||||
|
Hydrogen Induced Cracking-Resistant Steel Plates Sumitomo started research earlier, and has continued it in earnest, on mechanism of and counter-measures against hydrogen induced cracking under humid hydrogen sulfide environment. Such research was started in the course of the development of materials for line-pipes used for sour gas and/or sour oil, and achieved results are ranked in the top level of world research in this area. As a result, Sumitomo's hydrogen induced cracking resistant plate, "CR5" was developed and commercialized, aimed at application for oil refining facilities. CR50 is produced by treating 40 and 50 kg/mm2 strength class plates as countermeasures to prevent hydrogen induced cracking, such as reducing quantity of inclusions, shape control of inclusions and addition of infinitesimal amount of elements to inhibit hydrogen penetration into a plate.
It was known for a long time since the old days that cracks occur under humid environment containing hydrogen sulfide. Mechanisms for such cracks are classified into the following two categories. (1) Sulfide stress corrosion cracking (SSC) It occurs when external stress (working stress, residual stress) is working on steel, and propagates to the vertical direction to axial stress. It is also called Sulfide Stress Cracking (SC). (2) Hydrogen induced cracking (HIC) It occurs under a condition without external stress. The cracking is parallel to the plate surface and propagates stepwise to the thickness direction with time. Surface swelling due to occurrence of cracks on the surface or immediately beneath the surface is called blistering. |
|||||||||||||||
|
|||||||||||||||
