การประเมินความต้านทานการแตกร้าวขณะแข็งตัว ในเนื้อเชื่อมภายใต้เส้นโค้งความเหนียว ณ อุณหภูมิสูง

Abstract

This research aims to evaluate weld solidification cracking resistance based on high temperature ductility curve. This approach is able to elucidate the essential factors, namely solidification cracking temperature range (SCTR), critical strain, solidification cracking susceptibility during welding. Two (2) kinds of the weld metals were investigated as a hardfacing MSG 6 GZ-60 and a high strength AWS ER70S-6. Experiments were divided into two (2) parts. Firstly, trans-varestaint test was carried out in order to determine maximum crack length in SCTR. Solidification cracking were stimulated through immediately bending during GTAW welding. Bending strain levels of 0.7-4.1% were employed. Secondly, cooling rate during welding was measured so as to estimate a certain temperature value at the cracking tip. From the relationships between maximum cracking during SCTR and critical strain levels could establish the high temperature ductility curve. It was found that the hardfacing weld metal MSG 6 GZ-60 produced the longest crack. In addition, the high strength weld metal AWS ER70S-6 induced more cracking distributions on entire strain levels. Based on high temperature ductility curve, cracking susceptibility considered through the extensive SCTR, as well as the critical strain, it indicated the most susceptibility, namely MSG 6 GZ-60 and AWS ER70S-6 respectively. Those results was reasonably related to their metallurgical weld morphology.