METHOD AND LINE FOR THERMAL PROCESSING OF STEEL STRIP Russian patent published in 2003 - IPC

FIELD: metallurgy. SUBSTANCE: method involves heating and holding steel strip at austenitization temperature; providing two-staged cooling in heated liquid and in air to martensite transition of austenite; providing heating and isothermal holding until martensite is converted into troostite-corbite; performing final cooling of continuously moving steel strip. Method is characterized in that steel strip is heated and held for 3.5-13 min, stepped cooling is performed in heated liquid by immersing steel strip for 1-3.5 min followed by cooling in air for 3-11.2 min. Isothermal holding is carried out for 1.3-4 min while steel strip is pressed between heated plates. Cooling liquid has high specific conductivity. Line has successively arranged unwinding device, steel strip heating oven, stepped quenching device, isothermal holding device for steel strip sliding between heated metal plates, and winding device. Isothermal holding device has pairs of plates adapted for raising steel strip under predetermined specific pressure providing resistance against movement of steel strip and, as a result, reduced warpage thereof. Pulling device is positioned downstream of isothermal holding device to provide pulling of steel strip at constant speed, with specific tension changeable during replacement of steel strip being less than half the ultimate strength of steel strip having temperature equal to that at outlet end of said plates. Method and line are used for producing steel strip for manufacture of cutting tool, in particular, saw bands and disks from thermally processed 0.9-3.2 mm thick and 36-410 mm wide strip. EFFECT: improved physico-mechanical characteristics of steel strip, homogeneous structure of material, increased efficiency of production line. 6 cl, 2 dwg