High-strength steel plate

一种高强度钢板、抗拉强度的技术，应用在炉子类型、炉、热处理炉等方向，能够解决烘烤硬化量预应变依赖性小、烘烤硬化性高、烘烤硬化量大等问题，达到烘烤硬化性优异的效果

CN112204162AActive Publication Date: 2021-01-08NIPPON STEEL CORP
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2021-01-08

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Abstract

Provided is a high-strength steel plate which exhibits a large amount of bake-hardening and highly uniform bake-hardening properties, and contains, in mass%, C in the amount of 0.13-0.40%, Si in the amount of 0.500-3.000%, Mn in the amount of 2.50-5.00%, P in the amount of 0.100% or less, S in the amount of 0.010% or less, Al in the amount of 0.001-2.000%, and N in the amount of 0.010% or less, with the remainder constituting Fe and impurities, wherein: the martensite content by area ratio is at least 95%, and remaining structures occupy an area ratio of 5% or less; the ratio C1 / C2 of the upper-limit value C1 (mass%) of the Si concentration in a thickness direction cross-section to the lower-limit value C2 (mass%) thereof is 1.25 or less; the number density of precipitates exhibiting a major axis dimension of 0.05-1.00[mu]m, inclusive, and an aspect ratio of at least 1:3 is 30 per um2 or higher; and the tensile strength of the plate is 1,300 MPa or higher.
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Description

Technical field

[0001] The present invention relates to a high-strength steel sheet. Specifically, it relates to a high-strength steel sheet having a tensile strength of 1300 MPa or more and excellent bake hardenability suitable for structural members such as automobiles used mainly by press working.

[0002] This application claims priority based on Japanese Patent Application No. 2018-141244 for which it applied to Japan on July 27, 2018, and uses the content here.Background technique

[0003] In recent years, in order to protect the global environment, the fuel efficiency of automobiles is required to be improved. In automobile steel sheets, further increase in strength is required to reduce the weight of the car body and ensure safety. If the strength of the steel sheet is increased, the ductility generally decreases, so cold forming becomes difficult. Therefore, a material that is relatively soft and easy to form during forming processing, and has a high strength after forming, that is, ...

Examples

Embodiment 1

[0163]Next, an embodiment of the present invention will be described. The conditions in the examples are an example of conditions used to confirm the practicability and effects of the present invention, and the present invention is not limited to this example of conditions. The present invention can adopt various conditions as long as it does not deviate from the gist of the present invention and achieves the purpose of the present invention.

[0164]A slab having the chemical composition shown in Table 1 was produced. After the slab was heated at 1300°C for 1 hour, rough rolling and finish rolling were performed under the conditions shown in Table 2 to obtain a hot-rolled steel sheet. After that, the hot-rolled steel sheet was pickled, and cold-rolled at the reduction ratio shown in Table 2 to obtain a cold-rolled steel sheet. Next, annealing and heat treatment were performed under the conditions shown in Table 2. In addition, each temperature shown in Table 2 is the surface temperatu...