凝固組織を有するNi合金の高温延性

Ni合金およびオーステナイト系ステンレス鋼多層溶接金属部のミクロ割れについて(第2報)

抄録

Hot ductility behaviour was investigated for 17 kinds of Nickel alloy weld deposits. The used specimens were prepeared from weld deposits made in the form of pads on Type 304 steel plate using covered electrodes. Then, plastic strains were applied to the specimens in the heating and cooling process of weldsimulation thermal cycle, and critical enforced strain (εHC) capable of initiating cracking were measured. The obtained results are as follows:
(1) Cracking occurs along grain boundary of dendrite when the plastic strain exceeding εHC values was applied to weld metal specimen.
(2) When the testing temperature becomes over 1100°C, weld deposits tend to indicate extremely low values.
(3) Hot ductility, i.e. ego value, depends markedly on the chemical compositions.
(4) The following equation may predict hot ductility behaviour.
εHC₁₂₀₀=20[C] -0.5[Mo] -0.5[Nb] -5[T] +2.8
When the εHC₁₂₀₀ value is over 2, the weld deposit exhibits excellent hot ductility.