Quenched and tempered steel wire with superior cold forging characteristics
a technology of cold forging characteristics and tempered steel wire, which is applied in the direction of heat treatment equipment, furnaces, manufacturing tools, etc., can solve the problems of low productivity, high energy loss, and deterioration of working conditions, and achieve the effect of superior cold forging characteristics
Inactive Publication Date: 2005-10-06
SAMHWA STEEL
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Benefits of technology
"The present invention provides a method for manufacturing quenched and tempered steel wire with superior cold forging characteristics. This is achieved by conducting a quenching process and a tempering process before the cold forging process, which eliminates the need for additional heat treatment. The technical effect is improved manufacturing efficiency and quality."
Problems solved by technology
(1) A spheroidizing annealing process of steel wire for a long period leads to high energy loss and low productivity.
In addition, working conditions deteriorate where the steel wire is subjected to heat treatment in a manufacturing place.
Where the heat treatment is subcontracted to an outside manufacturer, costs for heat treatment and labor for managing delivery schedules are increased, thereby complicating overall process management.
Method used
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Embodiment Construction
[0017] Since a quenched and tempered steel wire has high strength, a desired product cannot be manufactured merely by subjecting such a steel wire to a cold forging process. Therefore, as a result of lots of studies to manufacture a variety of complicated machine structural parts from high strength steel wire by a cold forging process, the present inventors have found that superior cold forging characteristics can result when a quenched and tempered steel wire having tensile strength of 700-1300 Mpa has percent spheroidization of carbides deposited therein of 30% or more, as observed by a transmission electron microscope.
[0018] In other words, when the percent spheroidization of the deposited carbides in the steel wire quenched and tempered to have tensile strength of 700-1300 Mpa before the cold forging process is not less than 30%, the steel wire has superior cold forging characteristics even though being high in strength. Thus, a cold forging process may be efficiently performed...
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Abstract
Disclosed is a quenched and tempered steel wire with superior cold forging characteristics, consisting essentially of 0.1-0.5 wt % of C, 1.0 wt % or less of Si, 0.2-2.5 wt % of Mn, 0.03 wt % or less of P, and 0.03 wt % of S, with the balance being Fe and inevitable impurities, which has tensile strength of 700-1300 Mpa and percent spheroidization of carbides of at least 30%. Such quenched and tempered steel wire, which is subjected to a quenching and tempering processes by high frequency induction heating in a short period, without a spheroidizing annealing process needing a long period, has forging characteristics equal or superior to those of spheroidizing annealed steel wire, thus increasing productivity. Therefore, the quenched and tempered steel wire is applicable to make various bolts and shafts as parts for machine structures requiring high strengths.
Description
TECHNICAL FIELD [0001] The present invention relates to steel wires or steel rods, suitable for use in manufacturing various parts for machine structures, such as bolts and shafts, having relatively high strength. More specifically, the present invention is directed to a quenched and tempered steel wire with superior cold forging characteristics, characterized in that additional heat treatment, such as quenching and tempering, is not performed after a cold forging process by maintaining a new factor affecting the cold forging characteristics of the steel wire in a predetermined range. BACKGROUND ART [0002] In general, parts for machines with relatively high tensile strength between 700 and 1300 Mpa, for example, hexagonal headed bolts, U-shaped bolts, ball studs, shafts, etc., are obtained by subjecting steel wires or steel rods (hereinafter, referred to as ‘steel wire’) to a cold forging process. Specifically, the parts are manufactured in such a way that steel wire is heated at ab...
Claims
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IPC IPC(8): C21D1/18C21D1/42C21D9/00C21D9/52C22C38/00C22C38/02C22C38/04C22C38/38
CPCC21D1/18C21D1/42C22C38/04C21D9/525C22C38/02C21D9/0093Y02P10/25
Inventor AHN, SOON-TAE
Owner SAMHWA STEEL