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Method for producing cold-rolled steel sheet, cold-rolled steel sheet, and vehicle member

A technology of cold-rolled steel sheet and manufacturing method, applied in the field of cold-rolled steel sheet, can solve the problems of inability to obtain corrosion resistance, failure to obtain high-strength cold-rolled steel sheet with corrosion resistance, improvement of corrosion resistance, etc., and achieve corrosion resistance after coating. Excellent chemical conversion treatment, improved corrosion resistance after painting, and excellent chemical conversion treatment

Active Publication Date: 2013-03-06
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] However, for the high-strength cold-rolled steel sheet described in Patent Document 1, even if the Si concentration on the surface of the steel sheet is reduced before cold rolling, since Si-containing oxides are formed on the surface of the steel sheet by annealing after cold rolling, it cannot be expected Corrosion resistance will be improved after painting
In addition, for the high-strength cold-rolled steel sheet described in Patent Document 2, although the corrosion resistance does not pose a problem in a corrosive environment such as the salt spray test specified in JIS Z2371, it is not a problem in the salt-warm water immersion test and the combined cycle corrosion test. In the severe corrosion environment such as the test, it is not possible to obtain sufficient corrosion resistance after painting
That is, high-strength cold-rolled steel sheets excellent in corrosion resistance after coating cannot be obtained only by reducing the Si concentration on the surface of the hot-rolled steel sheet or by reducing the linear oxides containing Si.

Method used

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  • Method for producing cold-rolled steel sheet, cold-rolled steel sheet, and vehicle member
  • Method for producing cold-rolled steel sheet, cold-rolled steel sheet, and vehicle member
  • Method for producing cold-rolled steel sheet, cold-rolled steel sheet, and vehicle member

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0093]Steel containing C: 0.125% by mass, Si: 1.5% by mass, Mn: 2.6% by mass, P: 0.019% by mass, S: 0.008% by mass, and Al: 0.040% by mass with the balance consisting of Fe and unavoidable impurities Steel raw material (steel billet) is produced by melting and continuous casting through ordinary refining processes such as a converter and degassing treatment. Next, after reheating the billet to a temperature of 1150-1170°C, hot rolling is performed with the finishing temperature set at 850-880°C, and coiled at a temperature of 500-550°C to form a plate Hot-rolled steel plate with a thickness of 3~4mm. Next, these hot-rolled steel sheets are pickled to remove scale, and then cold-rolled to produce cold-rolled steel sheets with a thickness of 1.8mm. Then, these cold-rolled steel sheets are heated to a soaking temperature of 750~780°C and kept After 40 to 50 seconds, perform continuous annealing at 20 to 30°C / second from the above soaking temperature to the cooling stop temperatu...

Embodiment 2

[0120] The steels A to Z having the composition shown in Table 3 were smelted and continuously cast through a common refining process such as a converter and degassing treatment to form a billet. These billets were hot-rolled under the hot-rolling conditions shown in Table 4 to produce hot-rolled steel sheets with a thickness of 3 to 4 mm, pickled to remove scale on the surface of the steel sheets, and then cold-rolled to obtain sheet thicknesses of 3 to 4 mm. 1.8mm cold-rolled steel plate. Next, these cold-rolled steel sheets were continuously annealed under the conditions shown in Table 4, then pickled under the conditions shown in Table 5, then pickled again, washed with water and dried, and subjected to elongation of 0.7%. Skin pass rolling to obtain No. 1~39 cold-rolled steel sheets.

[0121]

[0122]

[0123]

[0124]

[0125]

[0126] Test pieces were cut out from the above-mentioned cold-rolled steel sheets obtained in this way, and the surface coverage...

Embodiment 3

[0133]Steel containing C: 0.125% by mass, Si: 1.5% by mass, Mn: 2.6% by mass, P: 0.019% by mass, S: 0.008% by mass, and Al: 0.040% by mass with the balance consisting of Fe and unavoidable impurities Smelting and continuous casting are carried out to produce steel raw materials (billets). After reheating the slab to a temperature of 1150-1170°C, hot rolling is performed with the finish rolling temperature set at 850-880°C, and coiling is performed at a temperature of 500-550°C to produce a plate with a thickness of 3~ 4mm hot rolled steel plate. These hot-rolled steel sheets were pickled to remove scale, and then cold-rolled to obtain cold-rolled steel sheets with a thickness of 1.8 mm. Next, these cold-rolled steel sheets are heated to a soaking temperature of 750 to 780° C., held for 40 to 50 seconds, and then cooled from the above soaking temperature to a cooling stop temperature of 350 to 400° C. at a rate of 20 to 30° C. / second. Keep the continuous annealing for 100 to ...

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Abstract

Provided is a method for producing a cold-rolled steel sheet which exhibits excellent chemical conversion processability and corrosion resistance after coating in harsh corrosive environments such as in a warm salt water immersion test or a compound cyclic corrosion test, and comprises the steps of: pickling a cold-rolled steel sheet preferably containing 0.5 to 3.0 mass % of Si and subjected to continuous annealing after being cold-rolled, and removing an Si-containing oxide layer on the surface layer of the steel sheet; picking the cold-rolled steel again; and restricting the surface coverage of an iron-based oxide on the surface of the steel sheet to 40% or less, and more preferably restricting the maximum thickness of the iron-based oxide to 150 nm or less. Also provided are a cold-rolled steel sheet produced by means of the aforementioned method, and a vehicle member using said steel sheet.

Description

technical field [0001] The present invention relates to a method for manufacturing cold-rolled steel sheets, cold-rolled steel sheets, and automotive components. Specifically, the present invention relates to excellent chemical conversion treatability and excellent post-paint corrosion resistance as evaluated by a salt-warm water immersion test and a combined cycle corrosion test. A method for manufacturing a cold-rolled steel sheet, a cold-rolled steel sheet manufactured by the method, and an automobile component using the cold-rolled steel sheet. It should be noted that the cold-rolled steel sheet of the present invention can be suitably used as a high-strength cold-rolled steel sheet containing Si and having a tensile strength TS of 590 MPa or more. Background technique [0002] In recent years, there has been an urgent need to improve the fuel efficiency of automobiles from the viewpoint of protecting the global environment. In addition, from the viewpoint of ensuring t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23G1/08B21B3/02C21D9/46C22C38/00C22C38/02C22C38/58
CPCC23G1/086B21B3/02C21D8/0236C21D8/0278C22C38/02B21B45/0269C23G1/081C22C38/04C23G1/00C23G1/08C23G1/088C23G1/085C22C38/00C22C38/001C22C38/002C22C38/005C22C38/06C22C38/08C22C38/12C22C38/14C22C38/16C22C38/22C22C38/32C22C38/34C22C38/38Y10T428/26C21D9/46
Inventor 增冈弘之安藤聪山本俊佑
Owner JFE STEEL CORP
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