High-strength steel plate and manufacturing method thereof

A high-strength steel plate and manufacturing method technology, applied in the direction of manufacturing tools, coatings, furnace types, etc., can solve the problem that the processability is not comparable to that of polygonal ferrite, it is difficult to achieve high strength and processability at the same time, and the processability cannot be obtained And other problems, to achieve the effect of excellent extension flange, excellent ductility, and high use value

Active Publication Date: 2011-08-10
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, since the main phase is made of polygonal ferrite, it is difficult to simultaneously achieve high strength and workability with a tensile strength (TS) of 980 MPa or more
In addition, even if the workability of the hard phase itself is improved by forming carbides in the hard phase, it is not as good as the excellent level of workability of polygonal ferrite. Therefore, in order to achieve a tensile strength (TS) of 980MPa If the amount of polygonal ferrite is reduced for the above high strength, sufficient workability cannot be obtained.

Method used

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

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0124] Steel slabs obtained by smelting steel with the composition shown in Table 1 were heated to 1200°C, then hot-finished at 870°C, and the resulting hot-rolled steel sheets were coiled at 650°C, and then the hot-rolled steel sheets were pickled Thereafter, cold rolling was performed at a rolling reduction (rolling ratio) of 65% to obtain 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.

[0125] The cooling stop temperature T in Table 2 refers to the temperature at which the cooling of the steel sheet is stopped when the steel sheet is cooled from the annealing temperature.

[0126] In addition, hot-dip galvanizing treatment or alloying hot-dip galvanizing treatment is performed on a part of the cold-rolled steel sheet. Among them, the hot-dip galvanizing treatment is based on a coating bath temperature of 463°C and an adhesion amount (single surface) of 50g / m 2 condition...

Embodiment 2

[0152] Steel slabs obtained by smelting steel types a, b, c, d, and e shown in Table 4 were heated to 1200°C, then finished rolling at 870°C, and the resulting hot-rolled steel sheets were coiled at 650°C, followed by After the hot-rolled steel sheet was pickled, it was cold-rolled at a rolling reduction (rolling ratio) of 65% to obtain 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 5. Then, the heat-treated steel sheet was subjected to temper rolling with a rolling ratio (elongation) of 0.5%. In addition, A in Table 4 3 The point is obtained by the above formula, and the Ms point in Table 5 is the martensitic transformation initiation temperature of each steel type measured by the Foamaster test. In addition, in Table 5, Inventive Example 1 is an inventive example in which the first temperature range (cooling stop temperature) is lower than Ms-100°C, and Inventive Example 2 is...

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Abstract

Disclosed is a high-strength steel plate having superior ductility and stretch flangeability and a tensile strength (TS) of 980 MPa or higher, and having 0.17-0.73% C, 3.0% or less Si, 0.5-3.0 or less Mn, 0.1% or less P, 0.07% S, 3.0% or less Al, 0.010% or less N, and 0.7% or more Si + Al, an area ratio of martensite of 10-90% with respect to the entire steel plate composition, a residual austenite amount of 5-50%, and an area ratio of bainitic ferrite in the upper bainite of 5% or less with respect to the entire steel plate composition. Twenty-five percent or more of the aforementioned martensite is tempered martensite, and the total of the area ratio of the aforementioned martensite with respect to the entire steel plate composition, the aforementioned residual austenite amount and the area ratio of the aforementioned bainitic ferrite in the upper bainite with respect to the entire steel plate composition is 65% or more. The area ratio of polygonal ferrite with respect to the entire steel plate composition is 10% or less (including 0%), and the average amount of C in the aforementioned residual austenite is 0.70% or more.

Description

technical field [0001] The present invention relates to a high-strength steel sheet having a tensile strength (TS) of 980 MPa or more and excellent formability, especially ductility and stretch-flangeability, used in industrial fields such as automobiles and electric equipment, and a method for producing the same. Background technique [0002] In recent years, improving the fuel efficiency of automobiles has become an important issue from the viewpoint of global environmental protection. Therefore, studies are being actively conducted to reduce the weight of the vehicle body itself by reducing the thickness of vehicle body parts by increasing the strength of vehicle body materials. [0003] Generally, in order to increase the strength of a steel sheet, it is necessary to increase the ratio of hard phases such as martensite and bainite to the entire structure of the steel sheet. However, increasing the strength of the steel sheet by increasing the proportion of the hard phas...

Claims

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Application Information

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IPC IPC(8): C22C38/06C22C38/60C21D9/46
CPCC22C38/04C21D9/46C21D8/0205C23C2/02C23C2/28C21D6/00C21D2211/005C21D2211/001C21D2211/002C21D2211/008C22C38/06C21D8/04C22C38/02C22C38/001C21D1/19C21D1/25C23C2/024C23C2/0224C21D8/02
Inventor 松田广志船川义正田中靖
Owner JFE STEEL CORP
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