Quenched and tempered steel wire with excellent cold forging properties

Abstract

Steel wires and steel rods with excellent cold forging properties and used in a manufacture of various machine components, which have relatively high strengths, are disclosed. The steel wires are produced by maintaining a product (n×YS) of a yield strength (YS) and a work hardening coefficient (n) obtained by a tensile test of the steel wire within a range of 4.0-11.0 kgf/mm 2 , without a need of additional quenching and tempering treatments after cold forging. There is no need to perform heating for spheroidizing annealing for a long time, and it is possible to produce quenched and tempered steel wires having excellent cold forging properties by quenching and tempering treatments in a short period of time.

What is claimed is:  
     
         1 . A method for providing steel wire that can be cold forged without prior spherodizing annealing comprising: 
 providing a specimen of steel wire;    heating the specimen;    quenching the specimen;    tempering the specimen;    calculating values of a work hardening coefficient (n), yield strength (YS) and the product n×YS for the specimen;    comparing the calculated value of n×YS to a known range defining steel wire with excellent cold forging properties.    
     
     
         2 . The method of  claim 1 , wherein the step of heating the specimen is performed at a temperature between 880° C. and 1300° C.  
     
     
         3 . The method of  claim 2 , wherein the step of heating the specimen occurs during a time period of approximately 40 seconds.  
     
     
         4 . The method of  claim 1 , wherein the step of tempering the specimen is performed at a temperature between 200° C. and 750° C.  
     
     
         5 . The method of  claim 4 , wherein the step of tempering the specimen occurs during a time period of approximately 40 seconds.  
     
     
         6 . The method of  claim 1 , further comprising the step of drawing the specimen after the tempering step.