Metal treatment – Process of modifying or maintaining internal physical... – Producing or treating layered – bonded – welded – or...
Patent
1996-10-18
1999-09-21
Wyszomierski, George
Metal treatment
Process of modifying or maintaining internal physical...
Producing or treating layered, bonded, welded, or...
148603, 420126, 420127, C21D 802
Patent
active
059548967
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a cold rolled steel sheet and a galvanized steel sheet, for use in automobiles, domestic electric appliances, building materials and the like, and a process for producing the same and, in particular, a process for producing said steel sheets from a cold rolled steel strip or a galvanized steel strip having improved homogeneity in workability.
BACKGROUND ART
Ultra low carbon steel sheets, by virtue of excellent workability, have been extensively used in applications such as automobiles (Japanese Unexamined Patent Publication (Kokai) No. 58-185752).
In order to further improve the workability, various studies have been made on the compositions of ultra low carbon steels and their production processes.
For example, Japanese Unexamined Patent Publications (Kokai) No. 3-130323, No. 4-143228, and No. 4-116124 disclose that excellent workability can be provided by minimizing the content of C, Mn, P and other elements in an ultra low carbon steel with Ti added thereto. In the inventions described therein, however, no mention is made of an improvement in the yield in the end portions in the widthwise direction and longitudinal direction of the steel strip (coil). Further, the techniques disclosed therein, unlike the technique according to the present invention, do not positively utilize Ti and Nb carbosulfides, Ti carbide and the like.
Japanese Unexamined Patent Publications (Kokai) No. 3-170618 and No. 4-52229 describe a reduction in a variation of properties of materials. According to the inventions described herein, however, the reduction ratio in finish hot rolling should be large, and, at the same time, an enhanced coiling temperature after the hot rolling is necessary, resulting in application of large load to the step of hot rolling.
The effect of the present invention can be attained also in P- or Si-strengthened high-strength cold rolled steel sheets possessing good workability. Representative techniques on these steel sheets are disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) Nos. 59-31827 and 59-38337, Japanese Examined Patent Publication (Kokoku) No. 57-57945, and Japanese Unexamined Patent Publication (Kokai) No. 61-276931. In these techniques, however, no device for improving the yield in the end portions in the widthwise direction and longitudinal direction of the coil is provided. Further, the techniques disclosed therein, unlike the technique according to the present invention, do not positively utilize Ti and Nb carbosulfides.
For ultra low carbon steels with Ti or a combination of Ti and Nb added thereto, it is common practice to coil a steel strip, after hot rolling, at an elevated temperature. According to this method, the coiling at an elevated temperature causes C to be precipitated as TiC or NbC, resulting in reduced C in solid solution, which in turn ensures good properties after cold rolling and annealing. Since, however, the end portions in the widthwise direction and the end portions in the longitudinal direction of hot rolled coils are very rapidly cooled during and after coiling, the precipitation of TiC and NbC is unsatisfactory, leading to deteriorated properties in these portions. For this reason, in fact, the end portions of hot rolled sheets or cold rolled sheets are, in many cases, cut off, increasing the production cost of the ultra low carbon steel.
DISCLOSURE OF THE INVENTION
An object of the present invention is to solve the above problems and to provide a cold rolled steel sheet which has been improved in homogeneity in workability, that is, is much less likely to cause a deterioration of properties in the end portions in the widthwise direction and longitudinal direction of the coil.
In the prior art, the amount of C, M, N, P and other elements added has been minimized from the viewpoint of improving the absolute value of indexes of workability, such as elongation and r value. However, no studies have been made on a reduction in the amount of C in solid solution by taking advantage of the prec
REFERENCES:
patent: 4473414 (1984-09-01), Irie et al.
patent: 5133815 (1992-07-01), Hashimoto et al.
patent: 5356493 (1994-10-01), Tsuyama et al.
patent: 5690755 (1997-11-01), Yoshinaga et al.
patent: 5846343 (1998-12-01), Yasuhara et al.
Katsumi Yamada, "Precipitation Behavior of Ti-S-C in Ultra-Low-Carbon Steels," Material and Process 6(6) (1993) Katsumi Yamada, Masakazu Niikura P. 1710.
Hashimoto Natsuko
Koyama Kazuo
Suehiro Masayoshi
Yoshinaga Naoki
Nippon Steel Corporation
Wyszomierski George
LandOfFree
Cold rolled steel sheet and galvanized steel sheet having improv does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cold rolled steel sheet and galvanized steel sheet having improv, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cold rolled steel sheet and galvanized steel sheet having improv will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-76359