Girth-welding process for a pipe and a high cellulose type coated

Abstract

Chemical compositions of a base metal and a high cellulose type welding electrode are regulated within predetermined ranges, so that the chemical composition of the weld metal obtained from the welding can be regulated within a predetermined range. Particularly, with respect to the weld metal, the Mo content (Mo)1 in the weld metal and the Mo content (Mo)2 in the base metal are regulated such that the difference between the both contents .DELTA.Mo (=(Mo)1-(Mo)2) is 0.03% or more, and PCM is 0.30% or less, where PCM is defined as follows: PCM=(C)+(Si)/30+(Mn)/20+(Cu)/20+(Ni)/60+(Cr)/20+(Mo)/15+(V)/10+5(B). Here, (M) denotes a content (weight %) of a component M in the weld metal. On the other hand, a coating flux of the high cellulose type coated electrode contains relative to the total amount of the coating flux, 0.1 to 7.0% of MgO, 7 to 25% of iron oxides (in FeO equivalent), 8 to 19% of TiO.sub.2, 10 to 30% of SiO.sub.2 and 5 to 27% of Mn, and a core wire and/or the coating flux includes 0.06 to 1.10% of Mo relative to the total amount of the welding electrode. A ratio of the weight of the coating flux to the weight of the welding electrode being 0.10 to 0.19. By this, preferential corrosion resistance, toughness and crack resistance can be improved in the weld metal of a girth weld zone of a pipe which might be exposed in a corrosion environment containing CO.sub.2.