Effect of modifying additions on the impact toughness of welded joints in low‐carbon steels produced with electrodes with a basic coating

Abstract

To cite this article: V B Pen'kov , G V Kamenetskaya & Yu V Poletaev (2001) Effect of modifying additions on the impact toughness of welded joints in low-carbon steels produced with electrodes with a basic coating, Welding International, 15:12,[983][984][985] The construction of surface structures in the climatic regions with low temperatures is associated with the problem of ensuring the service reliability of welded joints. In addition to the parameters determined by strength calculations, for these objects it is important to evaluate the brittle fracture resistance of welded joints.From the set of the mechanical characteristics, determined on standard specimens, the impact toughness at the minimum service temperature is of special importance from the viewpoint of ensuring the brittle fracture resistance of metal.The service reliability of welded joints depends greatly on the properties of welded metals and, consequently, the standard documents control the minimum permissible values. For example, according to GOST 9467-75 standard, the impact toughness of specimens with a sharp notch (type IX according to GOST 6996-66) should not be lower than 35.4J/cm 2 .One of the methods of improving the quality and mechanical characteristics of metals is the introduction of various amounts of microadditions of alloying elements (modification agents), for example, rare-earth elements (REM) or compounds of these elements. Theoretical and experimental data have been obtained indicating the positive effect of REM additions on the structure and properties of different metals and alloys, including on the impact toughness of welded joints at subzero temperatures. 1 " 9 ; However, the currently available data on the effect of modification agents on the mechanical properties of welded metals, produced with electrodes with a basic coating, do not: make it possible to evaluate unambiguously the strength of this effect because these data have been obtained on the electrode coatings of different composition and in a wide range of the welding conditions. 6 " 11 It is well-known that the technology of welding with coated electrodes and metallurgical special features of these electrodes greatly affect the brittle fracture susceptibility of welded joints. 11 ' 12 A review of the investigations carried out in these areas shows that the experimental conditions were different, mainly the amount and combinations of added modification agents, the composition of coatings and heat input in welding, complicating the analysis and comparison of the results.The aim of this work was to compare the effect of various REMs on the impact toughness of welded metals at subzero temperatures produced with electrodes with a basic coating at different values of heat input in welding.The practice of metallurgy and development of welding materials shows that high and stable values of the mechanical properties of low-carbon steels, including the metal deposited with electrodes with a basic coating, are ensured in the complex deoxidation and the following level of...