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Steel wire with excellent cold forging characteristics and manufacturing process thereof

A manufacturing method and technology of steel wire, applied in the direction of manufacturing tools, furnace types, furnaces, etc., can solve the problem of high deformation resistance, and achieve the effect of improving deformation capacity, product yield and productivity

Active Publication Date: 2013-09-11
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When the structure is such a fine structure before annealing, the ferrite particles do not become coarse after annealing, and the deformation resistance is high, so there is a problem that the die load increases during cold forging

Method used

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  • Steel wire with excellent cold forging characteristics and manufacturing process thereof
  • Steel wire with excellent cold forging characteristics and manufacturing process thereof
  • Steel wire with excellent cold forging characteristics and manufacturing process thereof

Examples

Experimental program
Comparison scheme
Effect test

no. 1 approach

[0044] Hereinafter, the metal structure of the steel wire excellent in cold forgeability according to the first embodiment of the present invention will be described.

[0045] (metal structure)

[0046] The metal structure of the steel wire of the present embodiment is substantially composed of ferrite particles and spherical carbides. When a bainite structure and a martensite structure are included in the metal structure, deformation resistance increases and ductility decreases, thereby deteriorating cold forgeability. Therefore, it is preferable not to contain these structures. "The metal structure is substantially composed of ferrite particles and spherical carbides" means that more than 97% of the area ratio of the metal structure is ferrite particles and spherical carbides. In other words, if the area ratio is less than 3%, then The existence of bainite or martensite is allowed.

[0047] (Average particle size of ferrite particles)

[0048] Coarsening of ferrite partic...

no. 2 approach

[0117] Hereinafter, a method for producing a steel wire having excellent cold forgeability according to a second embodiment of the present invention will be described in detail.

[0118] The steel wire manufacturing method of this embodiment includes at least a heating step, a hot rolling step, a first cooling step, a second cooling step, a holding step, a wire drawing step, and an annealing step. Hereinafter, each step will be described in detail.

[0119] (heating process)

[0120] In the heating step, a steel slab containing the component composition described in the first embodiment is prepared and heated to 950° C. or higher and 1300° C. or lower.

[0121] (hot rolling process)

[0122] In the hot rolling process, the heated slab is hot rolled at a rolling finish temperature equal to or higher than the Ar1 temperature (° C.) to manufacture a rolled wire rod. When the rolling completion temperature is lower than the Ar1 temperature (° C.), the ferrite grains are miniatu...

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Abstract

Provided is a steel wire that has a component composition, by mass, of 0.25-0.60 % C, 0.01-0.40 % Si, 0.20-1.50 % Mn, and a maximum of 0.20% Cr, 0.030% P, 0.040% S, 0.010% N and 0.0040% O. The remainder is comprised of iron and unavoidable impurities. The steel wire has a metal structure that is effectively formed from ferrite grains and carbide spheres where the average diameter of the ferrite grains is greater than or equal to 15 µm, the average diameter of the carbide spheres is average diameter of less than or equal to 0.8 µm, the largest diameter being less than or equal to 4.0 µm and the number of carbide spheres that are 1 mm2 each being 0.5 x 106 x C% - 5.0 x 106 x C%. Amongst the carbide spheres, the greatest separation between carbide spheres with a diameter of greater than or equal to 0.1 µm is less than or equal to 10 µm.

Description

technical field [0001] The present invention relates to a steel wire that is used as a raw material for mechanical parts such as bolts, screws, and nuts, and is formed by cold forging or roll forming, and a manufacturing method thereof. In particular, the present invention relates to a steel wire having excellent cold forgeability capable of suppressing forming cracks and a method for producing the same. In addition, the steel wire which is the object of this invention also includes the "steel bar coil" which coiled the hot-rolled steel bar. [0002] This application claims priority based on Japanese Patent Application No. 2010-045621 for which it applied in Japan on March 2, 2010, and uses the content here. Background technique [0003] Because cold forging has excellent dimensional accuracy and productivity of finished products, there is an increasing tendency to switch from conventional hot forging to cold forging when forming mechanical parts such as steel bolts, screws...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/00C21D8/06C22C38/18C22C38/54
CPCC21D9/5732C22C38/02C21D1/607C21D8/065C21D1/32C22C38/04C21D2211/005C22C38/001C21D2211/003C22C38/18
Inventor 小此木真山崎真吾大羽浩细川浩一富泽秀世
Owner NIPPON STEEL CORP