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High-strength cold-rolled steel plate and manufacturing method thereof

A technology of cold-rolled steel sheet and manufacturing method, applied in the field of cold-rolled steel sheet and its manufacturing, capable of solving problems such as insufficient corrosion resistance and poor surface appearance of cold-rolled steel sheet

Active Publication Date: 2013-09-11
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the inventors of the present invention have further studied the appearance and corrosion resistance of cold-rolled steel sheets and found that the appearance of the surface of cold-rolled steel sheets may become poor and the corrosion resistance may become insufficient even if only the hot-rolling conditions are specified.

Method used

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  • High-strength cold-rolled steel plate and manufacturing method thereof
  • High-strength cold-rolled steel plate and manufacturing method thereof
  • High-strength cold-rolled steel plate and manufacturing method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0161] Using a cold-rolled steel sheet containing 1.2% by mass Si and 2.0% by mass Mn, degreasing, annealing, and pickling were performed under the following conditions to obtain steel sheets with different precipitation forms of Si-containing oxides.

example 1

[0163] Degreasing: immerse in 5% (mass %, hereinafter the same for aqueous solution) sodium hydroxide aqueous solution at 60°C for 30 seconds → wash with water → dry

[0164] Annealing: 3% hydrogen-containing inert gas environment, dew point -20°C, heating at 870°C×200s

[0165] Pickling; immerse in 3% hydrochloric acid aqueous solution at 60°C for 5 seconds → wash with water → dry

[0166] (Example 2 of the present invention)

[0167] Degreasing: Soak in 5% sodium hydroxide aqueous solution at 60°C for 30 seconds → wash with water → dry

[0168] Annealing: 3% hydrogen-containing inert gas environment, dew point -15°C, heating at 870°C×200s

[0169] Pickling; immerse in 3% hydrochloric acid aqueous solution at 60°C for 5 seconds → wash with water → dry

Embodiment 2

[0190] Using a cold-rolled steel sheet containing 1.5% by mass of Si and 1.8% by mass of Mn, it was degreased by immersing it in a 5% sodium hydroxide aqueous solution at 60°C for 30 seconds, washed with water, and dried. After that, as shown in Table 2 , annealed at 840°C for 120 seconds in a 3% hydrogen-containing inert gas environment with different dew points, and then pickled with 3% hydrochloric acid aqueous solution at 60°C for 5 seconds, washed with water, and dried to prepare the test material.

[0191] These test materials were cut in a direction perpendicular to the surface of the steel plate, and the cross-section including the vicinity of the surface was observed by TEM in the same manner as in Example 1 above. That is, for each test material, five samples including samples for TEM observation with a steel plate surface length of 10 μm or more were prepared, observed at a magnification of 60,000, and the amount of Si-containing oxide in the steel plate surface leng...

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Abstract

The invention provides a steel plate containing C, Si and Mn, and particularly relates to a high-strength cold-rolled steel plate and a manufacturing method thereof. In case of a high Si content, the high-strength cold-rolled steel plate can be well subjected to phosphate treatment, has favorable appearance with no tiny dents on the surface, and has excellent corrosion resistance. Therefore, when a cross section in a direction perpendicular to the surface of the steel plate is observed through an electron microscope at a multiplying factor of 50000 times or above, the ratio of Si-containing oxide on the surface of the steel plate having a length of 10mu m, based on the average value of five points randomly selected, is 80% or below.

Description

technical field [0001] The present invention relates to a high-strength steel sheet used in steel sheets for automobiles, etc., and particularly relates to a cold-rolled cold-rolled steel sheet that ensures excellent phosphate treatment properties even with a large Si content, high strength, and excellent corrosion resistance with a good surface appearance Steel plate and its manufacturing method. Background technique [0002] In recent years, for the purpose of preventing global warming, CO 2 As measures against emissions, setting new targets for improving vehicle fuel efficiency and introducing a preferential tax system for vehicles with low fuel efficiency will increase the need for improvement in vehicle fuel efficiency. The weight reduction of automobiles is effective as a means for improving fuel efficiency, and from the viewpoint of such weight reduction, higher tension of the material is strongly demanded. On the other hand, since steel sheets for automobiles are s...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/04C21D8/02
Inventor 内海幸博村上俊夫梶原桂池田贡基桥本郁郎井户秀和野村正裕嘉村学大宫良信
Owner KOBE STEEL LTD
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