Weldability problems in jack-up rigs arise principally in leg construction where particularly high-strength steels (690 N mm−2 yield) are used for chords and racks. Attainment of mechanical properties is not usually difficult, although procedural trials are advisable.
Of potential fabrication problems, hydrogen cracking (heat-affected zones or weld metal) is of greatest concern, and consideration of solidification cracking is advisable. Lamellar tearing is not generally a problem with modern steels, and the risk of stress-relief cracking will be confined to the limited number of joints which can be heat-treated.
Fatigue cracking is probably the major cause of service failure of jack-up rigs, and the use of high-strength steels, which permits higher static stress limits, can exacerbate this problem. Hydrogen-induced stress corrosion can also occur, either due to cathodic polarisation or corrosion, particularly in the presence of H2S in foul sea-water. For this reason weld hardness limits need to be maintained. 相似文献
A study was performed on TMCP (thermo-mechanical control process) - manufactured high-tensile steel plates with yield point of 40 kgf/mm2 (YP40), which were recently developed for use in ship production and whose ease of shop fabrication is almost equal to that of the well-proven ship high-tensile steel plates (HT50) with yield points at 32 and 36 kgf/mm2 levels.
The authors' study addressed the performance required of the YP40 TMCP high-tensile steel for ship applications, including strength characteristics of base metal and high-heat-input welded joints, and also shop fabrication methods suitable to this material. 相似文献