STEEL MATERIAL WITH HIGH RESISTANCE TO INITIATION OF DUCTILE CRACKS FROM ZONE SUBJECTED TO WELDING HEAT IMPACT, AND BASIC MATERIAL, AND THEIR PRODUCTION METHOD Russian patent published in 2013 - IPC C22C38/60 C22C38/06 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: slab with the following composition, wt %: C: from 0.02 to 0.2, Si: from 0.01 to 0.5, Mn: from 0.5 to 2.5, P: 0.05 or less, S: 0.05 or less, Al: 0.1 or less, N: 0.01 or less, the rest is Fe and inevitable impurities, it is heated to 1000°C or above. Rolling is performed till plate is obtained in such a way that reduction ratio of rolling in temperature range of 900°C or above was 50% or more, and final temperature of rolling was within range from point Ar₃ to Ar₃-50°C. Then cooling with water is started at temperature within range from point Ar₃-10°C to Ar₃-70°C and cooling with water is finished at temperature of 500°C or below. Plates have microstructure in position ¼ of their thickness containing ferrite as soft phase and bainite, martensite or mixed bainite/martensite component as hard phase, part per square of hard phase from 50 to 90% and average aspect ratio of ferrite grains of 1.5 or more.

EFFECT: improving resistance to initiation of ductile cracks both of basic metal and of zone subjected to welding heat impact.

5 cl, 4 dwg, 4 tbl, 1 ex