METHOD OF PEARLITE STEEL STEAM PIPELINES AND THEIR WELDED BUTTS HOLLOW PIECES RECOVERING THERMAL TREATMENT Russian patent published in 1997 - IPC

FIELD: thermal treatment of metals, method is used to recover structure and operational properties of hollow pieces of steam pipelines and their welded butts together with welded seams zones mainly maid of low-carbon and low-alloyed pearlite steels. SUBSTANCE: aim is to increase service life of steam pipelines and their welded butts hollow pieces with simultaneous decrease of treatment costs. Aim is realized as follows: before treatment beginning temporal supports are mounted on steam pipeline and suspensions are cyclically heated. Heating temperature in cycles is varied in all cycles except the last one. Heating is exercised up to 1000 - 1100 C and in the last cycle - up to 880 - 1050 C. In process of heating and cooling adjustment of tensions in pieces of steam pipelines and their welded joints is exercised using changes of loadings on temporal supports and suspensions and suspensions by changing their length. Method allows to exercised treatment without steam pipeline dismantling of steam pipeline, to carry out cooling operation in cycle of steam pipeline blowing through by compressed gas or air, to exercise holding in last cycle during cooling under temperature equal to temperature of tempering with duration equal to duration of tempering and carrying out tempering after cooling in last cycle. EFFECT: increased effectiveness in steam pipeline hollow pieces properties recovery. 7 cl