Steel material for high-strength pipe expansion with excellent pipe expandability and crush resistance, expanded steel pipe, and manufacturing method thereof

摘要

There are provided an expandable high-strength steel material and an expanded high-strength steel pipe having excellent expandability and collapse resistance, and methods for manufacturing the expandable high-strength steel material and the expanded high-strength steel pipe. The expandable high-strength steel material including, by weight, manganese (Mn): 12% to 18%, carbon (C): 0.3% to 0.6%, and a balance of iron (Fe) and inevitable impurities, wherein the carbon (C) and the manganese (Mn) satisfy the following condition: 23≦35.5C+Mn≦38. Before being expanded, the expandable high-strength steel material has an austenite single phase microstructure, and after being expanded, the expandable high-strength steel material has a microstructure including 5 area % to 50 area % martensite and 50 area % to 95 area % austenite.