鋼材の溶接遅れ割れの研究(第 1 報) : 1 パスルート割れの防止

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The initiation and propagation of root cracks in steel weldments have been investigated by H-slit restraint cracking tests. The experimental variables examined in the tests are chemical compositions in steel in terms of P_CM (0.20 to 0.27), diffusible hydrogen in weld metal in terms of H_<JIS> (0.4 to 30ml/100gr), tensile restraint in terms of R_F (300 to 3,500kgf/mm・mm), ambient temperature (0,20 and 30℃) and groove shape (V, y and レ). It has been found that a root cracking tendency in root-pass welds may be given by the following parameter P_HM : P_HM=P_CM+0.075logH_JIS+0.15log (0.017K_t・σ_w) where, K_t・σ_w is a local stress at the weld root, K_t and σ_w being a notch stress concentration factor and an average stress of the weld metal, respectively. σ_w has been given by a function of plate thickness and R_F. Accoustic emission measurements have revealed that an incubation time for root cracking becomes shorter and that a velocity in crack propagation becomes higher as the P_HM value increases. With a decrease in an ambient temperature, a root cracking susceptibility has increased while a crack velocity decreasing unlike the case of increasing P_HM. The preheating temperature necessary for preventing root cracking in root-pass welds can be obtained by looking into t_100,the cooling time from the welding completion to 100℃, longer than (t_100)_cr given as : (t_100)_cr=10.5×10^4 (P_HM-0.276)^2 A relationship between t_100 measured at test plates and pheheating temperatures has been prepared for various plate thicknesses and heat-inputs.
社団法人溶接学会の論文
1979-12-05

鋼材の溶接遅れ割れの研究(第 1 報) : 1 パスルート割れの防止

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