Ni-Cr 鋼 (SNC22) および Si-Mn 鋼 (SM50B) の溶接性(<特集>溶接部の組織とじん性)

概要

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Weldability as related to the heat-affected onzes of the steels, Ni-Cr(SNC22) and Si-Mn (SM50B) were investigated by making the SH-CCT diagram, V-charpy impact and micro-tensile test of synthetic HAZ specimens and the slit type cracking test. The results of these test are summalized as follows. (1) The impact value of synthetic heat-affected zone changes according to a cooling time. Regions of cooling time (800∿500℃) to obtain the highest impact value are less than 15sec for steel SNC22 and 11∿21sec for steel SM50B. (2) The impact value of synthetic HAZ after postheating (600℃, 2hrs) is remarkably improved when the cooling time of the thermal cycle is less than 10sec (100% martensite) for SNC22 and more than 21sec (bainite+Ferrite) for SM50B. (3) In multi-pass weld joint test, the effect of cooling time (800∿500℃) after welding on the impact value of the HAZ agrees well with the tendency in the result of the thermal cycle test. (4) In the slit type cracking test, when the amount of the bainite structure of the HAZ is approximately more than 45% for SNC22 and more than 65% for SM50B, the HAZ cracking can be prevented even if wet covered electrode (12ccH_2/100g) is used. (5) When the slit type cracking test specimens were welded by the TIG welding process, the HAZ cracking cannot be recognized even under no preheating conditions for each kinds of the test steels.
社団法人溶接学会の論文
1981-01-05