The weldability of 9Cr-1Mo-Nb-V steel was studied using casting, forging and heavy section pipe.
The obtained results are as follows;
(1) Minimum preheating temperature to prevent cold cracking in y groove restraint specimen is about 200°C, which is lower than the values estimated from the chemistry of 9Cr-1 Mo-Nb-V steel used and ordinary 2.25Cr-1Mo steel.
(2) The degrease in susceptibility of the cold cracking of weldments made with electrode of matching composition can be interpreted by cosidering relief of thermal shrinkage caused by martensitic transformation of weld metals which, then, lowers degree of residual stress in restraint condition.
(3) The susceptibility to hot cracking is the same or less than that of Type 304 stainless steel and far less than that of Type 316 or Type 347 stainless steel.
(4) Long time heating embrittlement phenomenon was not observed for 9Cr-1 Mo-Nb-V welded joints under the condition of 600°C for 5000 hours.
(5) Newly developed 9Cr-1 Mo-Nb-V casting shows sufficient weldability for welding production.
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