Stahlwerke Peine-salzgitter Ag

Hans Paulitsch

Constantin M Vlad

Gerhard Kiefer

Ullrich Koch

Alfred Babilon

Kurt Koerfer

A cooling arrangement, especially but not exclusively suited for cooling rolled stock such as wires and bars, has two end members provided with axially aligned passages through which a workpiece can travel. The end members are connected by an annularly arranged series of bars between which spaces are left free so that cooling fluid admitted into contact with the workpiece can rapidly flow off again. The space surrounded by the bars converges in the direction of travel of the workpiece. Upstream of one end member is provided a fluid admitting element formed with a workpiece guide passage which is divergent-convergent as considered in the travel direction of the workpiece. A fluid inlet arrangement has an inner wall bounding the passage and provided with circumferentially spaced slot-shaped openings which communicate with the divergent part and extend toward the convergent part, and an outer wall surrounding the inner wall and bounding with the same an annular fluid chamber from which the slot-shaped openings receive fluid.

Cooling arrangement

A cooling arrangement, especially but not exclusively suited for cooling rolled stock such as wires and bars, has two end members provided with axially aligned passages through which a workpiece can travel. The end members are connected by an annularly arranged series of bars between which spaces are left free so that cooling fluid admitted into contact with the workpiece can rapidly flow off again. The space surrounded by the bars converges in the direction of travel of the workpiece.

A steel wire after coming from the mill is brought to a temperature between 850.degree. and 910.degree. C. This is followed by multi-stage water-cooling of the wire in such a manner that the surface of the wire is cooled to below the martensite start temperature while austenite is retained in the core of the wire. The heat retained in the core of the wire serves to partially temper the martensite formed at the surface of the wire. The wire is coiled while the temperature remains substantially constant so that the retained austenite in the core of the wire undergoes an isothermal transformation to fine pearlite. The heat of transformation serves to complete tempering of the martensite. After coiling, the wire is air-cooled to room temperature. The final wire exhibits a structure consisting of an outer layer of tempered martensite and a core of fine pearlite. This structure imparts excellent cold-working characteristics to the wire.

Method of making a steel wire adapted for cold drawing

A steel wire is rolled while in the austenitic range. Thereafter, the wire is cooled to a temperature between 850.degree. and 910.degree. C. This is followed by multi-stage water-cooling of the wire in such a manner that the surface of the wire is cooled to below the martensite start temperature while austenite is retained in the core of the wire. The latter cooling step brings the temperature of the surface of the wire to below the martensite start temperature in approximately 0.2 seconds. The heat retained in the core of the wire serves to partially temper the martensite formed at the surface of the wire. The wire is then coiled while the temperature remains substantially constant so that the retained austenite in the core of the wire undergoes an isothermal transformation to fine pearlite. The heat of transformation serves to complete tempering of the martensite. After coiling, the wire is air-cooled to room temperature and exhibits a structure consisting of an outer layer of fully tempered martensite and a core of fine pearlite. This structure imparts excellent cold-working characteristics to the wire since both the tempered martensite and the fine pearlite may be readily cold-drawn and, in addition, the tempered martensite at the surface of the wire possesses great strength which enables the stresses generated during cold-working to be transmitted along the wire. The reduction of area of the wire during cold-working may amount to 85 percent and more.

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Salzgitter-Lebenstedt, Germany

Hans Paulitsch