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

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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

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
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Example Embodiment

[0123] (Example 1)

[0124] The steel slab obtained by smelting the steel with the composition shown in Table 1 is heated to 1200°C, then hot-finished at 870°C, the resulting hot-rolled steel sheet is coiled at 650°C, and then the hot-rolled steel sheet is pickled After that, cold rolling was performed at a rolling rate (rolling rate) of 65% to produce a cold-rolled steel sheet having a thickness of 1.2 mm. The obtained cold-rolled steel sheet was 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, some cold-rolled steel sheets are subjected to hot-dip galvanizing or galvanizing. Among them, the hot-dip galvanizing treatment is based on the bath temperature of 463℃ and the adhesion amount (single surface) of 50g / m 2 The conditions for implementing double-sided plating. In...

Example Embodiment

[0151] (Example 2)

[0152] The slabs obtained by smelting the steel types a, b, c, d, and e shown in Table 4 were heated to 1200°C, and then finally rolled at 870°C. The resulting hot-rolled steel sheet was coiled at 650°C, and then After pickling the hot-rolled steel sheet, it was cold-rolled at a rolling rate (rolling rate) of 65% to produce a cold-rolled steel sheet with a thickness of 1.2 mm. The obtained cold-rolled steel sheet was heat-treated under the conditions shown in Table 5. Then, the steel sheet after the heat treatment was subjected to pass rolling with a rolling rate (elongation) of 0.5%. In addition, A in Table 4 3 The point is obtained by the above-mentioned formula, and the Ms point in Table 5 is the martensitic transformation start temperature of each steel type measured by the Fomasta test. In addition, in Table 5, invention example 1 is an invention example in which the first temperature range (cooling stop temperature) is lower than Ms-100°C, and inventi...

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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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