高マンガン鋼クロッシングの溶接

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The austenitic manganese steel crossing was welded with an electrode of 16Mn-16Cr whose deposited metal was composed of γ and several per cent α. But the intergranular microfissures were found on the surface of the weld metal in several months after welding. Most of cracks were found in 1st and 2nd layer welded onto the manganese steel, whose weld metal changed into γ structure through dilution of base metal.It was considered that the crack was stress corrosion crack due to residual stress and corrosive agent in atmosphere. The effective treatments to prevent the crack are:(1) The groove face of the manganese base metal was first welded with ferritic metal such as 25Cr-4Ni as a buttering, and the weld metal was turned into α+γ. Then the remainder was welded with an electrode of 16Mn-16Cr.(2) The welded zone was stress-relieved at the temperature less than 400°C.(3) The welded zone was shot blasted.These treatments were applied on the two sets of austenitic manganese crossing. Accordingly there have been no cracks for the past 6 years since it was practically used.
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