Abstract
A new process of hot water quenching from low austenitizing temperature was explored for steel wires. It is pointed out that the operation of lead patenting of steel wires at high heating temperature (1 1931 223 K) is not a optimising process. Higher austenitizing temperatures of lead patenting are caused by lower cooling power of lead liquid. The possibility using lower austenitizing temperatures in patenting of steel wires was proposed by means of theoretical analysis. The effect of austenitizing temperature on mechanical properties and microstructures of the hot water quenched steel wires was studied in detail. Austenitizing temperature of steel wires during patenting can be reduced to conventionally used heating temperature (Ac3+20?30K) in heat treatment by enhancing the cooling rate. When performing single-step hot water quenching in pure boiling water, the strength and ductility are arised with a increase in austenitizing temperature ; when the austenitizing temperature exceeds a certain valure (Tm), brittle fracture of wires would be occur for producing martensite. Tm is a lowest austenilizing temperature, at which mechanical properties obtained by hot water quenching is similar to that of lead patented steel wire, under a given cooling rate, and Tm of various diameters of steel wires falls with increasing the cooling rate. A new technique-Complex Water Bath Processing has been developed, which can make the heating temperature reduce to 1073?1093 K for intermediate heat treatment (normalizing) and to 1093?1123 K for final heat treatment (patenting) in wire production. The quality of the complex water bath processed wires can fully attain the level of lead patented wires, and the strengths of wires in diameter of more than 5 mm φ may be even higher than that for lead patented wires.
