Structure of joints of medium-carbon steel after friction welding and surfacing
One of the main tasks of modern materials science is to increase the resource and reliability of equipment. In the extractive industries, the construction of oil and gas wells is associated with significant wear on the outer surface of the drilling tool, especially at horizontal intervals, therefore, various surfacing technologies are used to repair drill pipes, both restoration of the outer diameter and lengthening of tool joints. During welding to lengthen the tool joint, the deposited layer overlaps the friction and HAZ (heat affected zone) welding areas on the upset part of the pipe and the joint. The effect of surfacing on the base metal and the weld, in this case, is not well understood. This work is aimed at determining the role of surfacing in the formation of the structure and mechanical properties of low-alloy pearlitic steels. The structure of the surfacing, the HAZ of the surfacing, the friction welding zone, the overlap of the HAZ of the surfacing and the HAZ of the weld were investigated. A weak effect on the mechanical properties of the overlapping zones is shown The mechanical properties before and after creating the joints were almost the same. The sizes of grains and interlamellar distances are determined. The dimensions of the structural elements, the plates at the second (outer) layer of the surfacing are almost one and a half times smaller than the dimensions of the laths and the inter-plate distance in other areas of the products, but the lamellar structure of pearlite was preserved, there are few ferrite fields. This means that it is possible to use the construction of drill pipes made of pearlitic medium-carbon low-alloy steels in the case of friction welding.