High-strength hot-rolled steel sheet having superior punchability and method for producing same

一种热轧钢板、制造方法的技术，应用在制造工具、金属轧制、化学仪器和方法等方向，达到有助于轻量化、冲裁加工性提高的效果

Active Publication Date: 2015-03-25
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In addition, in the technology described in Patent Document 2, the ferrite or bainitic ferrite phase is the phase with the largest area, and the hard second phase that adversely affects the hole expandability is limited to 3% or less

Method used

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  • High-strength hot-rolled steel sheet having superior punchability and method for producing same
  • High-strength hot-rolled steel sheet having superior punchability and method for producing same
  • High-strength hot-rolled steel sheet having superior punchability and method for producing same

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Embodiment

[0083] Molten steel having the composition shown in Table 1 was melted in a converter, and a billet (steel raw material) was produced by continuous casting. These slabs were heated under the conditions shown in Table 2, and subjected to rough rolling and finish rolling under the conditions shown in Table 2. And after finishing rolling, it was cooled under the conditions shown in Table 2, and coiled at the coiling temperature shown in Table 2 to obtain a hot-rolled steel sheet with a thickness shown in Table 2. It should be noted that cooling was started within 2 seconds after finish rolling was completed. Here, the first-stage cooling is represented by an average cooling rate from the finish rolling finish temperature to the cooling stop rate. In addition, the second-stage cooling is represented by the average cooling rate from the cooling stop temperature of the first-stage cooling to the coiling temperature.

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Abstract

A high strength hot rolled steel sheet having excellent blanking workability is provided. The composition contains C: 0.050 to 0.15%, Si: 0.1 to 1.5%, Mn: 1.0 to 2.0%, P: 0.03% or less, S: 0.0030% or less, Al: 0.01 to 0.08%, Ti: 0.05 to 0.15%, N: 0.005% or less, and the balance being Fe and unavoidable impurities. More than 95% of the microstructure is formed of a bainite phase in terms of area fraction. Average grain diameters of the bainite phase in a region having a thickness equal to 1 / 4 of the sheet thickness from the surface in the sheet thickness direction is 5 µm or less in an L-direction cross section and 4 µm or less in a C-direction cross section. The number of crystal grains extended in the rolling direction and having an aspect ratio of 5 or more is 7 or less in a sheet thickness center portion. As a result, the strength is increased to a tensile strength TS of 780 MPa or more, the blanked edge forms a fine and uniform ductile fracture surface, and a hot rolled steel sheet having excellent properties at blanked edges and excellent blanking workability is obtained.

Description

technical field [0001] The present invention relates to a high-strength hot-rolled steel sheet suitable as a raw material for running parts, structural parts, skeletons of automobiles, frame parts of trucks, etc., and particularly relates to improvement of punching workability. In addition, the "high strength" here refers to the case where the tensile strength TS is 780 MPa or more. Background technique [0002] In recent years, emission standards have been strengthened from the viewpoint of protecting the global environment. From this trend, there is particularly strong demand for improvement in the fuel efficiency of automobiles. Responding to such demands, the weight reduction of automobile bodies is directed, and the thinning of parts through high-strength raw materials is also rapidly progressing. In general, workability such as elongation and hole expandability tends to decrease with increasing strength. Therefore, when increasing the strength of raw materials, impr...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/00B21B3/00C21D9/46C22C38/14C22C38/58
CPCC21D9/46C22C38/14C22C38/002C22C38/005C21D6/00C22C38/12C22C38/04C22C38/44C21D2211/002C22C38/42C22C38/06C21D8/0226C22C38/02C21D8/005B32B15/013C22C38/16C22C38/08C22C38/001C22C38/18
Inventor 中岛胜己斋藤勇人船川义正森安永明村田贵幸
Owner JFE STEEL CORP
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