METHOD FOR PREVENTION OF COLD CRACKS DEVELOPMENT IN WELDED JOINTS FROM CARBONACEOUS AND LOW-ALLOYED STEELS IN PROCESS OF WELDING AT SPECIFIED MODES Russian patent published in 2010 - IPC B23K31/12 

FIELD: technological processes.

SUBSTANCE: invention relates to the field of welding equipment, namely to assessment of requirements to chemical composition of carbonaceous and low-alloyed steels, which provide for absence of inclination to development of cold cracks and required complex of mechanical characteristics of welded joint in process of welding performance at specified modes. Previously for group of steels of selected class, critical speeds of metal cooling are detected in near-seam section of welded joint in the range of temperatures of 800 - 500°C, which correspond to limit permissible value of inclination index of each steel from the group to development of cold cracks in near-seam section of welded joint. As specified index, maximum permissible percentage of martensite is used in structure of near-seam section of welded joint or limit permissible value of hardness of near-seam section of welded joint. Values of equivalent carbon are detected for each steel, and curve of dependence is built between critical speeds of cooling and equivalent carbon for specified group of steels. Value of cooling speed of near-seam section of welded joint that corresponds to specified method and modes of welding is entered into produced curve, and critical value of equivalent carbon is identified for steels of specified group of selected class. For welding at specified mode steels are used, equivalent carbon of which does not exceed a certain critical value.

EFFECT: high reliability of cold cracks development prevention with achievement of specified mechanical properties of metal in near-seam section of welded joint.

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