Coercimetric Technological and Acceptance Testing of Welded Joints to Ensure their Useful Life as Exemplified By Butt Welding of Rail Joints, including Subsequent Operational Diagnostics

摘要

It is the technology of performing weld joints (WJ) that determines its operational life. The main thing here is not provide just the usual today soundness but rather structural and phase uniformity of all metal constituents of WJ: weld, heat-affected areas and the base metal. This minimizes the initial unsoundness, while deformational uniformity of WJ is maximized and the time to occurrence of operational fatigue defects increases, durability is also maximized, not of the seam itself, but of the entire WJ, which, ideally, becomes identical to the base metal in its deformational and mechanical properties. The assessment of such uniformity of all areas of WJ at the production stage is carried out today sporadically by hardness testing. A much more efficient method here manifests itself, which is using coercive force, implemented in self-contained portable coercimeters with attached transducer, providing better usability and accuracy of assessment of the metal state to the desired depth, capability to operate in manual or automatic mode, while eliminating the need for surface grinding. Such monitoring may be performed point-wise or be continuous in time and space. On the example of welds in rail strings of continuous welded rails is shown imperfection of modern technologies of welding rails in terms of obtaining equally strong, uniform under deformations WJ, which is the case even with specialized rail welding companies. Such initial imperfections, later on add up with operational loads, which in certain actual cases, lead to accelerated fracture of the welded joint in the course of service. Operating coercimetric monitoring of welded rail joints makes it possible to identify such features of the newly welded joint. This allows adjusting the rail welding technology used now to increase useful life of the joints, reduce accidents at railways with the expected decrease in the number of proactive unjustified replacement of joints in service on suspicion of looming fracture. Coercimetric image of welded joints, whose metal has reached the limit after which begins its failure, is diagnostically much more accurate and adequate, than its similar flaw pattern, while allowing to form a forecast of residual life based on the current state.