JOURNAL OF THE JAPAN WELDING SOCIETY
Online ISSN : 1883-7204
Print ISSN : 0021-4787
ISSN-L : 0021-4787
Study on Submerged Arc Welding for HT-80 Steel
Toshiro YoshidaHisahiro OnoeHideo KumabeHiroyuki Tsukui
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1963 Volume 32 Issue 12 Pages 1134-1142

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Abstract

This paper describes the results of a study on the determination of the most favorable welding procedures of submerged arc welding for an 80 kg/mm2 high strength steel.
When a basic bonded flux containing Mn-Ni-Mo alloying elements was used for submerged arc welding, visible cracks frequently appeared in weld metal. In this case, the lower the welding heat input, the higher the cracking susceptibility of weld metal. This would be due to the fact that an excessive nickel content of weld metal remained as the heat input was decreased.
On the other hand, in the transverse tension test of weld joint of HT-80 welded by using Mn-Ni-Mo bonded flux with the welding condition of more than 45, 000 Joules/cm in heat input, the fractured surfaces of H.A.Z. near the bond of weld were observed to be of cleavage type and moreover in this case the H.A.Z. had a poor notch toughness.
When using the Mn-Mo basic bonded flux (not containing Ni), although no visible crack was found in the weld metals deposited under various welding conditions, the notch toughness of H.A.Z. was also impaired if the welding was carried out with the heat input of over 45, 000 Joules/cm regardless of the alloying element of weld metal.
Through microscopic examination it was clarified that when the structure of H.A.Z. showed bainite more than 70% in area, the H.A.Z. resulted in a poor notch toughness.
In this connection it was observed that the smaller the cooling rate of welding, the larger the austenitic grains in H.A.Z. and also that the grains mainly contained a bainitic structure in the matrix and finally that such coarse grains seemed to cause a poor notch toughness of H.A.Z.

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