Panfilov A. Technology and materials for automatic wear-resistant arc surfacing of thin steel sheets

The dissertation for awarding the degree of Doctor of Philosophy in the field of 132 "Materials science" (13 Mechanical engineering). Dniprovsky State Technical University, Kamyanske, 2021. The object of the research is the processes that occur in different methods of arc surfacing of thin steel sheets and plates with flux-cored wires. The subject of the research is technologies and materials for surfacing the parts operating in conditions of intensive abrasive wear. Machines and mechanisms operating in conditions of intensive abrasive wear are widely used in the mining and metallurgical industries. Such machines and mechanisms include sheet structures and parts. Wear-resistant bimetallic sheets are widely used in order to increase the service life of such parts as lining elements. The technologies and materials that are currently used allow the production of similar sheets with a base metal thickness of ≥ 6 mm and a total thickness of ≥ 8… 10 mm. Existing technologies and materials are not suitable for surfacing sheets of smaller thickness. The main problem of existing surfacing technologies is significant penetration of the base metal and the risk of burnings-through. Describes the surfacing materials and equipment that are used in the performance of work; methods of research of chemical composition, structure of the applied metal and its wear resistance at abrasive wear are resulted; the developed methods of experimental estimation of influence of methods and modes of arc surfacing by powder wires of different diameters on penetration of base metal, its share in surfaced metal, quality of weld surfaced formation. The third section is devoted to the study of the influence of different methods of arc surfacing with flux-cored wire on different surfaced rollers and the stability of the surfacing process. The study was performed using a computer information and measurement system (CIMS). It is established that the geometric dimensions of the rollers and the penetration of the base metal are most significantly affected by the submerged arc surfacing modes. This method provides the widest range of voltage deviations ΔUT = ± 2 V from the optimal process voltage UT that provides good formation of the surfaced rollers. Open arc surfacing with self-protective flux-cored wire provides minimal penetration during surfacing of samples with a flat or cylindrical surface among the studied methods of arc surfacing. At the same time the minimum possible penetration (≈ 1,5 mm) at qualitative formation of the surfaced rollers provides the use of self-protective flux-cored wire of Ø1,8 mm. It is established that a threefold increase in the rate of energy input (decrease in the surfacing rate) doubles the penetration depth of the base metal. The geometric dimensions of the surfaced rollers also increase. Significantly less rate of energy input affects the share of the base metal in the surfaced metal. The fourth section presents the results of experiments of improving the composition and studying the properties of self-protective flux-cored wire, as well as additional application of alloying and modifying components to surfaced rollers. PP-AN192s (PP-NP-150H5T4M) Ø1.8 mm self-protective flux-cored wire was chosen for wear-resistant arc surfacing of thin steel sheets. The composition of the gas-slag part of the wire charge on the basis of CaO + TiO2 + MgO + CaF2 + Al2O3 slag system was developed. This composition of the charge allows achieving the degree of assimilation of titanium by surfaced metal at the level of 55 ... 65%. For comparison: when surfacing with the same wire under the AN-26 flux, the absorption of titanium does not exceed 40%. The conditions for obtaining arc surfacing layers of variable composition and properties, which is important given the reduction of residual stresses and deformations in thin sheet elements, are determined. The scheme of surfacing on a layer of alloying charge is chosen as a basis. The results of the study of the influence of the introduction of the SiO2 aerosil modifying component on the hardness and structure of the rollers are presented. The wear resistance at abrasive wear of 150Х5Т4М metal surfaced with PP-AN192s self-protective flux-cored wire is determined. It is established that the wear resistance of 150Х5Т4М surfaced 150Х5Т4М metal is not inferior to the high-alloyed 400Х30М metal surfaced with Hardface hc о flux-cored wire. The high wear resistance of the surfaced 150Х6Т4М metal is explained by the ability of the alloy matrix to retain titanium carbonitrides that have a high wear resistance. The technique and technology of wear-resistant surfacing of St3 δ = 3 mm steel sheets with PP-AN192s Ø1.8 mm self-protective flux-cored wire was developed. According to the research results, the Technological instruction for wear-resistant arc surfacing with powder wire of steel sheets with a thickness of ≤ 5 mm was developed.