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High-strength steel sheet and process for production thereof

A technology of high-strength steel plate and manufacturing method, which is applied in the direction of manufacturing tools, coatings, furnace types, etc., can solve the problems of reduced formability, etc., and achieve the effects of excellent processability, cost reduction, and process reduction

Active Publication Date: 2010-12-29
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, since the increase in the strength of the steel sheet reduces the formability, the development of a material that has both high strength and excellent formability is desired.

Method used

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  • High-strength steel sheet and process for production thereof
  • High-strength steel sheet and process for production thereof
  • High-strength steel sheet and process for production thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0118] Hereinafter, the present invention will be further described through examples, but the following examples do not limit the present invention. Furthermore, structural changes made within the scope of the gist of the present invention are included in the scope of the present invention.

[0119] Steel slabs with various compositions shown in Table 1 were heated to 1250°C, then hot-finish rolled at 880°C, and the resulting hot-rolled steel sheets were coiled at 600°C, and then the hot-rolled steel sheets were pickled and placed in Cold rolling was performed at a rolling reduction rate of 65% to produce a cold-rolled steel sheet having a thickness of 1.2 mm. The obtained cold-rolled steel sheets were heat-treated under the conditions shown in Table 2. None of the samples in the same table were quenched.

[0120] Hot-dip galvanizing is performed at a plating bath temperature of 463°C and an adhesion weight (per single side) of 50g / m 2 (Double-sided plating) under the condi...

Embodiment 2

[0135] The steel slabs having the compositions shown in steel grades A, C and F in Table 1 are heated to 1250°C, and then the hot-rolled steel sheets after hot finish rolling at 880°C are coiled at 600°C, and then the hot-rolled steel sheets are pickled After that, it was cold-rolled at a rolling reduction rate of 65% to produce a cold-rolled steel sheet with a thickness of 1.2 mm. The obtained cold-rolled steel sheets were heat-treated under the conditions shown in Table 4.

[0136] Regardless of the presence or absence of plating, the obtained steel sheets were subjected to temper rolling at a rolling ratio (elongation) of 0.3%.

[0137] The steel sheets obtained above were evaluated by the same method as in Example 1. The results are shown in Table 5.

[0138] Sample Nos. 24 to 27 all use suitable steel, but the cooling rate of the heat treatment is outside the range specified by the present invention, so the steel structure and the number of iron carbides are not within ...

Embodiment 3

[0142] Heat the steel slabs with the composition shown in the steel types P, C and F in Table 1 to 1250°C, and then coil the hot-rolled steel sheet after hot-rolling at 880°C at 600°C, and then pickle the hot-rolled steel sheet , cold rolled at a rolling rate of 65%, and made into a cold-rolled steel plate with a thickness of 1.2mm. The obtained cold-rolled steel sheets were heat-treated under the conditions shown in Table 6. Regardless of the presence or absence of plating, the obtained steel sheets were subjected to temper rolling at a rolling ratio (elongation) of 0.3%. In addition, in Table 6, Nos. 28, 30, and 32 represent the same samples as Nos. 4, 6, and 11 shown in Table 2, respectively.

[0143] The steel sheets obtained above were evaluated by the same method as in Example 1. In addition, in the self-tempered martensite, the number of precipitated iron carbides of 0.1 μm or more and 0.5 μm or less per 1 mm 2 Medium is 5×10 2 The amount of self-tempered martensite...

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Abstract

Disclosed are an ultra-high-strength steel sheet having both a tensile strength of as high as 1400MPa or above and excellent formability and an advantageous process for manufacturing the same. A high-strength steel sheet having both a composition which contains by mass C: 0.12 to 0.50%, Si: 2.0% or less, Mn: 1.0 to 5.0%, P: 0.1% or less, S: 0.07% or less, Al: 1.0% or less, and N: 0.008% or less with the balance being Fe and unavoidable impurities, and a structure which comprises, in terms of area fraction, autotempered martensite: 80% or more, ferrite: less than 5%, bainite: 10% or less, and retained austenite: 5% or less and in which the average number of precipitated iron carbide particles of 5nm to 0.5[mu]m in the autotempered martensite is 5OE04 or above per mm2.

Description

technical field [0001] The present invention relates to a high-strength steel sheet having an excellent formability and a tensile strength of 1400 MPa or more used in industrial fields such as automobiles and electric appliances, and a method for producing the same. In addition, the high-strength steel sheet of the present invention includes a steel sheet that has been subjected to hot-dip galvanizing or galvannealing on the surface of the steel sheet. Background technique [0002] In recent years, improving the fuel efficiency of automobiles has become an important issue from the viewpoint of protecting the global environment. Therefore, studies are being actively conducted to reduce the weight of the vehicle body itself by increasing the strength of the vehicle body material to achieve thinning. However, since the increase in the strength of steel sheets reduces the formability, development of materials having both high strength and excellent formability has been desired....

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/60C21D9/46C23C2/06C23C2/28
CPCC21D2211/008C22C38/06C21D8/04C23C2/02C23C2/28C22C38/02C21D1/18C22C38/04C23C2/06C22C38/001C23C2/024C23C2/0224C22C38/60C23C2/29C21D9/46
Inventor 松田广志水野玲子船川义正田中靖
Owner JFE STEEL CORP
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