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Hot-rolled steel sheet and manufacturing method thereof

A hot-rolled steel plate and manufacturing method technology, applied in the direction of manufacturing tools, heat treatment furnaces, heat treatment equipment, etc., can solve problems such as cracks, gaps, and mold temperature rise on the punching end surface, and achieve excellent elongation flangeability and punching performance Effect

Active Publication Date: 2020-06-23
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In the actual mass production of parts, due to the temperature rise of the die caused by continuous stamping and the wear of the die, the gap between the punched parts often changes, and when there is a gap change, sometimes cracks, gaps, etc. occur on the punched end surface.

Method used

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  • Hot-rolled steel sheet and manufacturing method thereof
  • Hot-rolled steel sheet and manufacturing method thereof
  • Hot-rolled steel sheet and manufacturing method thereof

Examples

Experimental program
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Effect test

Embodiment

[0138] Molten steel having the composition shown in Table 1 was smelted and continuously cast by a generally known method to produce a steel billet (steel material) with a wall thickness of 300 mm. These steel billets are heated to the temperature shown in Table 2, carry out rough rolling, end finish rolling with the temperature shown in Table 2, after finishing rolling, carry out cooling with the average cooling rate of Table 2, in the coiling shown in Table 2 Coiling was performed at a high temperature to obtain a hot-rolled steel sheet having a thickness of 3.2 mm. Further, these hot-rolled steel sheets were pickled by a generally known method, and annealed under the conditions shown in Table 2 in a continuous annealing line. In addition, some steel sheets are subjected to hot-dip galvanizing treatment in a continuous annealing production line, and further alloying treatment to produce hot-dip galvanized steel sheets and alloyed hot-dip galvanized steel sheets.

[0139] ...

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Abstract

The present invention provides a hot-rolled steel sheet having a predetermined composition and a structure in which the sum of the area ratios of a tempered bainite phase and a tempered martensite phase is 70% or more, and a method for producing the same. , and the sum of the area ratios of the coarse pearlite phase, martensite phase, and retained austenite phase is 10% or less, and the tempered bainite phase and tempered martensite phase have laths with an average width of 1.0 μm or less As a substructure, the ratio of Fe-based carbides with an aspect ratio of 5 or less among the Fe-based carbides precipitated inside the lath and at the lath boundary is 80% or more. MC-type carbides with an average particle size of 20 nm or less, and the average dislocation density of the hot-rolled steel sheet is set to 1.0×10 14 m ‑2 Above and 5.0×10 15 m ‑2 the following.

Description

technical field [0001] The present invention relates to structural steel materials such as transportation machinery parts represented by automobiles, construction steel materials, etc., which have high strength with a tensile strength (TS) of 780 MPa or more, and have excellent stretch flangeability and punching A hot-rolled steel sheet excellent in durability and production stability, and a method for producing the same. Background technique [0002] From the viewpoint of protecting the global environment, in order to reduce CO 2 Emissions, weight reduction while maintaining the strength of the car body, and improvement of the fuel efficiency of the car are often regarded as important issues in the car industry. In order to reduce the weight of the automobile body while maintaining the strength of the automobile body, it is effective to reduce the thickness of the steel sheet by increasing the strength of the steel sheet as a raw material for automobile parts. For example...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/00C21D9/46C22C38/14C22C38/60
CPCC22C38/00C22C38/14C22C38/60C21D8/0226C21D8/0273C22C38/001C22C38/002C22C38/02C22C38/04C22C38/06C22C38/08C22C38/10C22C38/12C22C38/16C22C38/22C22C38/28C22C38/38C21D2211/002C21D2211/004C21D2211/008C21D1/25C21D8/0263C21D9/46C21D6/02C21D8/0205C21D6/005C21D6/008
Inventor 田中孝明木津太郎丰田俊介
Owner JFE STEEL CORP