HEAT TREATMENT METHOD OF WELDED JOINTS OF LOW CARBON FERRITE-PEARLITE STEELS Russian patent published in 2007 - IPC C21D9/50 C21D1/30 

FIELD: heat treatment of welded joints, namely joints of welded structures operating at lo temperatures.

SUBSTANCE: method comprises steps of slow cooling of welded joint together with furnace during three stages. At first stage cooling is realized only till temperature exceeding less than 150 C temperature value of starting formation of coherent to matrix tertiary cementite. At second stage accelerated cooling is realized at rate 30 - 50 m/h till temperature 250 ± 50°C and then welded joint is cooled in air. In such case tertiary cementite at stage of beginning its formation has small size and in the result stresses between matrix and reinforcing phase are occurred to be weak. It allows eliminate embitterment of welded joint. Low rate of cooling allows eliminate warping of welded structures.

EFFECT: increased cold resistance of zone of thermal influence of welded joints due to slow cooling of welded joint together with furnace during three stages.

1 ex, 2 tbl