STRUCTURAL-PHASE STATE AND METAL FRACTURE SURFACE OF WELDS MADE WITH THE USE OF NEW MATERIALS BASED ON TECHNOGENIC RAW MATERIALS

Abstract

The structural-phase state and the metal fracture surface of 09G2S steel welds made using new welding materials based on technogenic raw materials of metallurgical production (silica manganese slag and aluminum electrofilter dust) were studied by scanning and transmission electron microscopy methods. The production of welded joints was carried out in laboratory conditions using welding wire of the Sv-08GA brand on the equipment of the scientific and production center "Welding Processes and Technologies" of SibSIU. Quantitative analysis of the parameters of the structure and dislocation substructure of the weld metal was performed, using the equipment of the Institute of High-current Electronics SB RAS (Tomsk). The contributions of scalar and excessive dislocation density to the strength of the weld metal are estimated. It is established that the main metal phase of the studied welds (regardless of the introduction of the additive) is a solid solution based on α-iron (ferrite, BCC crystal lattice, α-phase). In addition to α-iron, particles of iron carbide (cementite) and (mainly in the sample without additives) iron silicide of the composition Fe3S are present in the weld metal. Analyzing electron microscopic images of the structure of the weld metal, it was noticed that the narrowest contours are formed at the interfacial boundaries of the inclusion – matrix. Such inclusions detected by transmission electron microscopy methods may be cementite particles located in the volume and at the boundaries of ferrite grains, and iron silicide particles of rounded (spherical) shape located in the volume of ferrite grains. It is revealed that the inclusions of the second phase present in the weld metal are stress concentrators and can be centers of microcrack nucleation under mechanical action on the material.