Effect of Alloying Elements and Processing Parameters on the Properties of Cold-rolled IF Steel Sheets

摘要

In order to produce a high resistance to SWE as well as high r-value steel, extra-low carbon Ti-added IF steels with different amount of carbon were tested in this investigation. The results obtained in this study can be summarized as follows: 1. R-value contour lines in precipitation map shows that decreasing carbon content, increasing titanium content or decreasing SRT increase r-value. 2. SWE-temperature contour lines in precipitation map shows that decreasing carbon content, increasing titanium content or increasing SRT increase SWE-temperature. 3. Increasing coiling temperature or increasing cold reduction increase r-value. The later factor also decrease Δr value, especially in Ti+Nb steel. 4. Low SRT steel has a high grain boundary binding strength and a low material strength, thus results in a low SWE-temperature. 5. Low CT steel has both a high grain boundary binding strength and a material strength, which causes the SWE-temperature similar to that of the high CT steel. Therefore, coiling temperature gives little effect on SWE-temperature. 6. Increasing cold reduction decreases Ar value, thus decreases earing height, which decreases the work hardening. As a result, low SWE-temperature is obtained in high cold reduction steel. 7. A high resistance to SWE as well as high r-value steel can be obtained by using extra-low carbon Ti+Nb IF steel with proper processing.