A MICRO-COOLED HIGH-STRENGTH WELD FOR HEAVY TRANSPORT MEANS

Abstract

This paper focuses on the technical problem of repairing the main operating elements of heavy vehicles (semitrailers, dumps, and drums). If these vehicles are in service, significant changes in work schedules can occur, and costs can be generated immediately. Therefore, using the correct technology for repairs is crucial to minimizing financial and logistic difficulties. The article aims to analyze the mechanical properties of an MMA (Manual Metal Arc) welding (covered electrodes) joint made of Hardox 450 steel. This kind of material has a martensitic microstructure, which is difficult to weld because of changes in the components to the other ones during the joint process. Other inconveniences are related to the different chemical composition of steel and covered electrodes, their mechanical resistance, and thermodynamic conditions (consisting of the pre-heating temperature and the cross-pass temperature). Therefore, the joint quality should be determined using a few methods. In this case, NDT (magnetic and radiographic tests) and DT (microstructural analysis and static as well as fatigue tests) were used. All obtained results have enabled the proposed guides for the MMA welding of the steel grade. This is indicated as follows: (1) the method of bevelling the sheets before welding should be used, (2) pre-heating is necessary at temperature levels of 100 C and 125 C, and (3) the recommended interstitial temperature is between 170 C and 200°C.