№65-09

Metallographic analysis of potential areas of destruction initiation of the zone of thermal impact of low-carbon steels after laser welding

D. Laukhin¹, O. Beketov ², Y. Slupska², E. Babenko², N. Rott¹, V. Dytiuk¹

¹ Dnipro University of Technology, Dnipro, Ukraine

² State Higher Educational Establishment «Prydniprovska State Academy of Civil Engineering and Architecture», Dnipro, Ukraine

Coll.res.pap.nat.min.univ. 2021, 65:88-98

https://doi.org/10.33271/crpnmu/65.088

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ABSTRACT

Purpose. To find out dangerous areas of the zone of thermal impact on the basis of the research of welding joint structure formation after laser welding of low-carbon structural steels 09Mn2Si, 10CrNiCu, 10Mn2VNb.

The methods. In research are  used methods of studying the structure and fine structure of materials, namely raster electron microscopy using a scanning electron microscope РЕМ-106И.

Findings. The work investigates the detection of dangerous areas of the zones of thermal impact on the basis of the research of welding joint structure formation after laser welding of low-carbon steels 09Mn2Si, 10CrNiCu, 10Mn2VNb. The complex of studies carried out showed that the welded joint is structurally divided into several zones. At the same time, metallographic analysis showed that in the zones of the welded joint there is a conglomerate of structures, which contains components characteristic both for metal in the cast state and for metal after accelerated cooling.

The originality. The established dependences show that the significant differences in structural state were found out on the boundary between the joint and the zone of thermal impact (the boundary between areas 1 and 2). It means that in this area a significant increase in the level of microstrength will be observed, comparing to the other joint areas. Taking into account the width of this zone, it should be stressed that the concentration of mechanical strength will occur in a relatively narrow zone of the welding joint. As a result, this zone will be a potential place for the accumulation of defects and will significantly influence the mechanical properties of the whole joint.

Practical implimintation. Improving the results obtained and conducting new research on this topic will allow the development of improved modes of welding of high-strength steels, taking into account the structural state and operating conditions of rolled metal.

Key words: Laser welding, low-carbon steel, welding joint structure, structural components, welding joint zones

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