Hot-rolled steel sheet having excellent surface hardness after carburizing heat treatment and excellent drawability

A technology of tensile workability and surface hardness, used in heat treatment furnaces, heat treatment equipment, manufacturing tools, etc., can solve the problems of unclear improvement effect, unresearched, no mention of cold workability, etc., to achieve extended life and difficult to crack. , the effect of improving the deformation ability

Inactive Publication Date: 2016-06-08
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0024] However, the hot-rolled steel sheet (carburized steel strip) disclosed in the above-mentioned Patent Document 7 is excellent in surface hardness after carburizing heat treatment, but it does not mention drawing workability, nor does it mention cold workability at all, and its improvement effect is unclear.
[0025] As mentioned above, there has been little research so far on hot-rolled steel sheets that have both drawability and surface hardness after carburizing heat treatment.

Method used

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  • Hot-rolled steel sheet having excellent surface hardness after carburizing heat treatment and excellent drawability
  • Hot-rolled steel sheet having excellent surface hardness after carburizing heat treatment and excellent drawability
  • Hot-rolled steel sheet having excellent surface hardness after carburizing heat treatment and excellent drawability

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Experimental program
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Effect test

preparation example Construction

[0128] [Preparation of molten steel]

[0129] First, predetermined alloy elements are added in a predetermined order to molten steel in which the dissolved oxygen amount and the total oxygen amount have been adjusted, whereby desired oxides can be formed. Especially in the present invention, it is extremely important to adjust the total oxygen amount after adjusting the dissolved oxygen amount so as not to form coarse oxides.

[0130] The so-called dissolved oxygen means free oxygen that does not form oxides but exists in molten steel. The term "total oxygen" means all the oxygen contained in molten steel, that is, the sum of free oxygen and oxygen forming oxides.

[0131] First, the dissolved oxygen content of molten steel is adjusted to a range of 0.0010% to 0.0060%. When the amount of dissolved oxygen in the molten steel is less than 0.0010%, the amount of dissolved oxygen in the molten steel is insufficient, so a predetermined amount of Al—O-based oxides cannot be secure...

Embodiment

[0160] Steel with the composition shown in Table 1 below was melted by vacuum melting, cast into a steel ingot with a thickness of 120 mm, and hot-rolled under the conditions shown in Table 2 below to produce a hot-rolled steel sheet. In addition, in any of the tests, the cooling after the stop of rapid cooling was performed under the following conditions: slow cooling at a cooling rate of 10°C / s or less for 5 to 20 seconds.

[0161] Using a vacuum furnace (capacity 150 kg), the test steel containing the chemical composition shown in Table 1 was melted, cast into a 150 kg ingot, and cooled. When the test steel is smelted in a vacuum furnace, elements other than Al, REM, and Ca are adjusted for composition, and at least one element selected from C, Si, and Mn is used for deoxidation to adjust the dissolved oxygen content of molten steel. Stir the molten steel whose dissolved oxygen content has been adjusted for about 1 to 10 minutes to float and separate oxides in the molten st...

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Abstract

A hot-rolled steel sheet that has a sheet thickness of 2-10 mm and that contains specific amounts of C, Mn, Al, and N, the remainder comprising iron and unavoidable impurities. With regard to all crystal grains that exist at a depth of t/4 (t being sheet thickness), the average grain diameter of all of the crystal grains is 3-50 [mu]m, the area ratio of crystal grains that have a sheet-plane orientation that is within 10 DEG of a (123) plane is 20% or more, and the total area ratio of crystal grains that, in the rolling direction, have a crystal direction that is within 10 DEG of a <001> direction and crystal grains that, in the rolling direction, have a crystal direction that is within 10 DEG of a <110> direction is 25% or less.

Description

technical field [0001] The present invention relates to a hot-rolled steel sheet that exhibits good cold workability in working before heat treatment, and exhibits a predetermined surface hardness after carburizing heat treatment, and exhibits desired hardness even at a place deep from the surface, specifically In terms of steel materials used as various structural parts, especially in order to improve wear resistance and fatigue resistance, surface hardening is carried out through carburizing and quenching or carbonitriding and quenching. Hot-rolled steel sheets are useful as raw materials for texturized parts, for example, hot-rolled steel sheets are useful as raw materials for clutches, dampers, gears, and the like used in various parts of automobiles. In addition, in the following description, the case where it is applied to clutches is representatively selected for description, but the present invention is of course not limited to such manufacturing, but can be used as a ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00B21B3/00C22C38/06C22C38/60C21D8/02C21D9/46
CPCC21D1/06C21D8/0205C21D8/0226C21D8/0263C21D8/0273C21D8/0278C21D8/0463C21D8/0473C21D9/46C21D2201/05C21D2211/005C21D2211/009C22C38/00C22C38/001C22C38/002C22C38/005C22C38/02C22C38/04C22C38/06C22C38/08C22C38/12C22C38/14C22C38/38C22C38/42C22C38/50C22C38/52C22C38/58C22C38/60C23C8/22
Inventor 梶原桂土田武广
Owner KOBE STEEL LTD
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