The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 25, 1997
Filed:
Sep. 11, 1996
Naoki Yoshinaga, Futtsu, JP;
Kohsaku Ushioda, Futtsu, JP;
Osamu Akisue, Futtsu, JP;
Yoshikazu Matsumura, Futtsu, JP;
Kunio Nishimura, Kitakyusyu, JP;
Nippon Steel Corporation, Tokyo, JP;
Abstract
The present invention provides a cold-rolled steel sheet and a hot-dip galvanized steel sheet having good bake hardenability, non-aging properties at room temperature and good formability and a process for producing the same. An extra low carbon steel or an extra low carbon steel containing at least one element selected from Ti and Nb is annealed at a temperature of not lower than the AC.sub.3 transformation point to bring the structure after annealing to a structure of low-temperature transformation products. This makes it possible to provide a steel sheet that has a combination of high paint-bake hardenability and non-aging properties at room temperature and is excellent also in formability in respect of average r value (deep drawability) and elongation (punch stretchability). In particular, with respect to paint-bake hardenability, a BH property on a high level up to about 10 kgf/mm.sup.2 can be imparted according to need, and it is possible to provide a cold-rolled steel sheet and a hot-dip galvanized cold-rolled steel sheet that also have a non-aging property at room temperature.