The Effects of Solidification Conditions on ZDT, ZST and Hot Cracking in Weldments of AISI 309LSi

• Main Authors: EN-Jen Shu, 蘇晏正
• Other Authors: Dong-Yih Lin
• Format: Others
• Language: en_US
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/72476998450674663936

碩士 === 義守大學 === 材料科學與工程學系 === 88 === In this study were the ZDT and ZST of AISI 309LSi stainless steel by solidification rates of 10℃/min, 30℃/min and 60℃/min investigated. Also the influence of melt quantity on the ZDT and ZST was studied with varied diameters of samples from 6mm, 10mm to 20mm. Goal of this study is to know hot cracking that occurred in austenitic stainless steels during solidification or welding. A Gleeble 2000 hot tensile test machine was used for these hot tensile tests. The test results indicated that ZDT and ZST decreased and the crack sensitivity temperature range(△T) was extended with the increasing of cooling rate. Additionally, ZDT and ZST decreased with the increasing of melt quantity of material. Moreover, the sensitivity of hot cracking by different melt quantity of samples was also investigated by Spot-Varestraint test with different welding time. This experiment proved the maximum cracking sensitivity by solidification while welding time was 6 seconds. The location of hot crack corresponds to the crack sensitive region(△T) between ZDT and ZST. A minimumδ-ferrite content was observed on welded sample. As welding time was longer than 6 seconds the hot cracking sensitivity decreased due to the backfill of liquid in cracks. This research indicated that the crack sensitivity in semi-solid phase of AISI 309LSi is related to the ZDT, ZST and the crack sensitive temperature range △T.