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High-strength cold-rolled steel sheet and manufacturing method therefor

A technology of cold-rolled steel sheet and manufacturing method, which is applied in the field of high-strength cold-rolled steel sheet and its manufacture, can solve the problem of reduced reactivity between steel sheet and chemical conversion treatment solution, and achieves good chemical conversion treatment property, stable manufacturing, and excellent corrosion resistance. sexual effect

Pending Publication Date: 2020-03-31
JFE STEEL CORP
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The lowering of the temperature of the chemical conversion treatment liquid lowers the reactivity between the steel sheet and the chemical conversion treatment liquid, so it is required to improve the chemical conversion treatment property

Method used

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  • High-strength cold-rolled steel sheet and manufacturing method therefor
  • High-strength cold-rolled steel sheet and manufacturing method therefor
  • High-strength cold-rolled steel sheet and manufacturing method therefor

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0082] As the test material, a continuous annealing material (cold-rolled steel sheet) having the component composition and tensile strength TS shown in Table 1 was used. These steel sheets were pickled, washed with water, and dried under the conditions shown in Table 2 and Table 3, and then subjected to temper rolling with an elongation of 0.7% to produce high-strength cold-rolled steel sheets No. 1 to 33. It should be noted that the Fe of the pickling solution 3+ The ion concentration is adjusted by the method described above.

[0083] A test piece was collected from each manufactured steel plate, and 5 locations on the surface of the test piece selected arbitrarily were analyzed in the depth direction by glow discharge emission spectroscopy (GDS), and it was investigated whether Al, Si, Mn, and O were displayed. The peaks of Al, Si, Mn, and O are evaluated as "existence (remaining) of oxide layer", and the cases where none of the peaks appear are evaluated as "absence" (Remai...

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Abstract

Provided is a high-strength cold-rolled steel sheet to which Cu is added to improve delayed fracture resistance characteristics, which has good chemical conversion treatability during low-temperaturechemical conversion treatment and for which excellent post-painting corrosion resistance and delayed fracture resistance characteristics can be attained. The high-strength cold-rolled steel sheet contains at least one of Si, Mn, and Al and 0.05-0.25 mass% of Cu, wherein: the steel structure is a recrystallized structure; no oxide layer containing at least one of Al, Si, and Mn is present on the surface of the steel sheet; and cross-sectional coverage by a deposited metal Cu on the steel sheet surface is 30% or less. A film of a pickling liquid on the surface of the steel sheet reacts with thesteel sheet between a period after pickling until washing with water causing Cu to be eluted from the steel plate and deposited on the surface of the steel plate. This deposited metal Cu lowers the chemical conversion treatability, and so, by keeping the cross-sectional coverage by this deposited metal Cu to a low level, chemical conversion treatability can be improved.

Description

Technical field [0001] The present invention relates to a high-strength cold-rolled steel sheet used in automobile structural members, reinforcement members, etc., and a manufacturing method thereof. Background technique [0002] Regarding cold-rolled steel sheets used in the automotive field, from the viewpoint of anti-rust properties, coating is often applied after the base treatment for coating, and in order to obtain excellent corrosion resistance after coating, cold rolling is required The steel plate has good chemical conversion treatment properties. In addition, in recent years, from the viewpoint of improving fuel efficiency, thinning of steel sheets has been promoted for the purpose of reducing the weight of the vehicle body. Along with this, there has been a demand for higher strength of cold-rolled steel sheets. However, there is a problem that the delayed fracture resistance property (delayed fracture resistance property) is reduced due to the increase in strength. I...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23G1/08C22C38/00C22C38/16
CPCC22C38/00C22C38/16C23G1/08
Inventor 增冈弘之古谷真一竹山隼人松崎晃
Owner JFE STEEL CORP
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