METHOD OF THERMAL TREATMENT OF ITEMS MADE OUT OF LOW-CARBON AND MEDIUM-CARBON UNALLOYED AND LOW-ALLOYED STEEL Russian patent published in 2004 - IPC

FIELD: metallurgy; technologies of an induction high-heat treatment of items made out of low- and medium-carbon unalloyed and low-alloyed steel.

SUBSTANCE: the invention is dealt with technologies of an induction high-heat treatment of items made out of low- and medium-carbon unalloyed and low-alloyed steels. In particular, the invention may be used at an induction high-heat treatment of cylindrical items, rods, straps, bands, rolled section, pipes of different cross-section, including welded pipes. A problem solved by the offered invention is production of items with an optimal combination of strength and plastic properties by industrial method using the widespread industrial equipment of induction heating by a simple, cost-saving method. The technical result is solution of a problem - production of a fixed structure of items made out of low- and medium-carbon unalloyed and low-alloyed steels providing high plasticity at strength_} close to initial. The result is the method allows using minimum simple operations to produce the items of the given structure of material, that has increased strength and plasticity at least of no less than initial one. The result is achieved due to the induction heating of the items up to the temperature in the interval from (A_cl -75) °С up to (A_cl + 25) °С with speeds from 500 up to 1000 °С/s, then refrigeration is conducted with intensity of the heat sink of 20 000 - 40 000 W / m² * °C. As a result of such high-heat treatment the strength increases in 1.3 - 1.6 times as compared with the initial strength and more than in 1.5 time as compared with the strength of the prototype and practically does not become worse: the relative elongation for fivefold samples δ₅ is increased in 1.2 - 1.5 times or remains equal to the initial one. Due to found optimal combination of ranges of values of the thermal treatment main parameters it is possible to derive maximum advantages from the process of an incomplete conversion of the structures of the low- and medium-carbon unalloyed and low-alloyed steels in the temperature range from (A_cl -75) °С up to (A_cl + 25) °С.

EFFECT: the invention allows to produce items made out of low- and medium carbon steel with the given structure of material, that has an increased and strength, that are at least not low than initial strength.

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