Steel sheet with excellent cold workability during forming and method for manufacturing the same

Abstract

The present invention provides a steel sheet having an excellent cold workability during forming and a method for producing the same. The steel sheet of the present invention is characterized in that: (a) the ratio of the number of carbides at the ferrite grain boundary to the number of carbides in the ferrite grain exceeds 1, (b) the ferrite grain diameter is 5 μm or more and 50 μm or less, (c) the in-plane anisotropy |Δr| of the r value is 0.2 or less, (d) the Vickers hardness is 100 HV or more and 150 HV or less, (e) the random intensity ratio of the {311} <011> orientation at the ½-thickness portion of the steel sheet is 3.0 or less.

Description

TECHNICAL FIELD[0001]The present invention relates to a steel sheet with excellent cold workability during forming and a method for manufacturing the sheet.BACKGROUND ART[0002]Automotive parts, knives, and other mechanical parts are manufactured through working processes such as punching, bending, and pressing. In the working processes, improvement of workability is required for a material carbon steel sheet, in order to improve product quality and stability and / or cost reduction.[0003]Generally, a carbon steel sheet is subjected to cold rolling and spheroidizing annealing, so as to produce a soft carbon steel sheet with excellent workability made of ferrite and spheroidized carbide. Many technologies for improving the workability of carbon steel sheets have been proposed so far.[0004]For example, Patent Document 1 discloses a high-carbon steel sheet for precision punching and a method for producing the sheet, wherein the sheet comprises, in terms of % by mass, C: 0.15 to 0.90%, Si:...

AI Technical Summary

Benefits of technology

The present invention allows for the creation of a steel sheet that can be easily worked into a desired shape.

Problems solved by technology

The carbides, even though capable of reducing hardness, deteriorate workability, which is disadvantageous in terms of workability.

The technologies described in Patent Documents 2 and 3 consider that the deterioration of workability is caused by the low carbide spheroidization ratio of carbides precipitated on the grain boundary, but do not take into account the problem of improving the spheroidization ratio of grain boundary carbides.

However, Patent Document 5 does not discuss what effect the aggregate structure has on the plastic anisotropy.

However, Patent Document 7 does not discuss what effect the aggregate texture has on the plastic anisotropy.

However, Patent Document 8 does not discuss what effect the aggregate texture has on the plastic anisotropy.