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Hot-rolled steel plate exhibiting excellent cold workability and excellent surface hardness after working

A technology of surface hardness and hot-rolled steel plate, which is applied in the field of hot-rolled steel plate, can solve the problems of low cost and achieve the effects of reduced deformation resistance and extended life

Inactive Publication Date: 2015-09-09
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0010] However, there is a problem with this technology that nitriding treatment is required after cold working, and sufficient cost reduction cannot be achieved.
[0012] However, in this hot-rolled steel sheet, N is limited to an extremely low content as a harmful element, and it is completely different from the hot-rolled steel sheet of the present invention that utilizes N actively.

Method used

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  • Hot-rolled steel plate exhibiting excellent cold workability and excellent surface hardness after working
  • Hot-rolled steel plate exhibiting excellent cold workability and excellent surface hardness after working
  • Hot-rolled steel plate exhibiting excellent cold workability and excellent surface hardness after working

Examples

Experimental program
Comparison scheme
Effect test

preparation example Construction

[0121] [Preparation of molten steel]

[0122] Regarding the content of N in the molten steel, it can be determined by adding a raw material containing N compounds to the molten steel during smelting with a converter, and / or controlling the atmosphere of the converter to N 2 atmosphere to adjust.

[0123] [heating]

[0124] Heating before hot rolling is performed at 1100 to 1300°C. In this heating, high-temperature heating conditions are required in order to dissolve as much N as possible without forming N compounds. A preferable lower limit of the heating temperature is 1100°C, and a more preferable lower limit is 1150°C. On the other hand, temperatures higher than 1300°C are operationally difficult.

[0125] [hot rolled]

[0126] Hot rolling is performed so that the finish rolling temperature may be 880° C. or higher. If the finish rolling temperature is too low, the ferrite transformation will occur at a high temperature, the precipitated carbides in the ferrite will b...

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Abstract

This hot-rolled steel plate has: a plate thickness of 3 to 20mm; a composition which contains, in mass%, up to 0.3% (exclusive of 0%) of C, up to 0.5% (exclusive of 0%) of Si, 0.2 to 1% of Mn, up to 0.05% (exclusive of 0%) of P, up to 0.05% (exclusive of 0%) of S, 0.01 to 0.1% of Al and 0.008 to 0.025% of N with the balance consisting of iron and unavoidable impurities and which satisfies two relationships, namely, the content of solid-soluted N ≥ 0.007% and 10C+N≤3.0 (wherein C and N represent the contents of C and N respectively); and a structure which contains, in area fraction with respect to the whole structure, less than 20% of pearlite with the balance being ferrite and in which the mean grain diameter of the ferrite is 3 to 35μm. The hot-rolled steel plate exhibits good cold workability during cold working, and exhibits a prescribed surface hardness after the working.

Description

technical field [0001] The present invention relates to a hot-rolled steel sheet that exhibits good cold workability during working and a predetermined surface hardness after working. Background technique [0002] In recent years, from the viewpoint of environmental protection, in order to improve the fuel efficiency of automobiles, there has been an increasing demand for the reduction of the weight of various parts of automobiles, such as transmission parts such as gears and casings, that is, higher strength. soaring. In order to meet such demands for weight reduction and high strength, generally used steel materials are steel materials obtained by hot forging bar steel (hot forging materials). In addition, in order to reduce CO in the parts manufacturing process 2 emissions, so far, the demand for cold forging of parts such as gears processed by hot forging is also increasing. [0003] Then, cold working (cold forging) has the advantages of high productivity, dimensiona...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/60C21D8/02C21D9/46
CPCC22C38/02C22C38/04C21D9/46C21D8/02C22C38/60C21D2211/009C21D2211/005C22C38/06C21D8/0226C22C38/004C22C38/002C22C38/001C22C38/26C22C38/16C22C38/08
Inventor 梶原桂
Owner KOBE STEEL LTD
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