Weld Cold Cracking in HAZ of Engineering Carbon and Low Alloy Steel (Report IV) : Susceptibility and Crack Free Condition to Quenching Crack Type Cold Cracking under Various Cooling Conditions(Materials, Metallurgy & Weldability)

概要

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For fifteen kinds of commercial steels with phosphorus content about 0.012-0.026wt.% to be susceptible to quenching crack type cold cracking in weld HAZ, the variation in hardness, fracture stress and their correlations were studied by the simulated cold cracking test under the various cooling conditions. Consequently, the crack free condition was attributed to hardness and fracture stress. The fracture stress has an excellent correlation with the fraction of intergranular fracture which indicates the cold cracking susceptibility of quenching crack type. The hardness has a good correlation with the fraction of intergranular fracture, too. However, the fraction of intergranular fracture within Hv600 to 700 is largely influenced by cooling rate, i.e., the fracture stress is remarkably improved by decreasing the cooling rate, although the loss of hardness is little. It was thought that this type of cold cracking is avoidable by adoption of the materials or welding conditions giving the maximum hardness in HAZ less than about Hv600 or the fracture stress more than about 95OMPa.
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