Study of Mechanical Properties and Microstructure of Welded Joints Made of Structural High-Strength Steel S690QL of Russian and Foreign Production

Abstract

Steel S690QL is intended for welded heavily loaded structures: lifting beams, traverses, trailers for heavy haulers, and others. This work presents the results of a study on the mechanical properties and microstructure of S690QL steel produced in Russia and abroad, as well as the ductile properties of welded samples at different temperatures. Atomic emission spectroscopy methods, tensile testing, impact toughness testing, and microstructural analysis were used. Hardness was determined using the Vickers method. It was established that the chemical composition of both steels is practically identical. The impact toughness values of samples made from domestic S690QL exceed those of the foreign counterpart, particularly in the metal that has not undergone welding processes (the impact toughness for Russian steel in this zone was 200 J/cm² at –40°C, which exceeds that of the foreign steel in the same zone by almost 80%). The brittle–ductile transition temperatures for the weld joint zones of Russian S690QL were determined. For the zones of melted metal and thermal influence, this temperature was –40°C. In all zones of the weld seam of the test welded joints made from both steels, a similar microstructure was observed. The hardness in the studied samples showed close values and similar variations across the zones of the weld joints. The obtained results can be used in machine engineering for the certification and design of welded structures, primarily for the Arctic zone.