Abstract
Thermomechanically processed steels are materials of great mechanical properties connected with more than good weldability. This mixture makes them interesting for different types of industrial applications. When creating welded joints, a specified amount of heat is introduced into the welding area and a so called heat-affected zone (HAZ) is formed. The key issue is to reduce the width of the HAZ, because properties of the material in the HAZ are worse than in the base material. In the paper, thermographic measurements of HAZ temperatures were presented as a potential tool for quality assuring the welding process in terms of monitoring and control. The main issue solved was the precise temperature measurement in terms of varying emissivity during a welding thermal cycle. A model of emissivity changes was elaborated and successfully applied. Additionally, material in the HAZ was tested to reveal its properties and connect changes of those properties with heating parameters. The obtained results prove that correctly modeled emissivity allows measurement of temperature, which is a valuable tool for welding process monitoring.
Highlights
Elaboration of new materials is a task that is demanded by constantly developing industries
Because of the emissivity variation during the thermal cycle, it was necessary to find a way of temperature correction for the proper assessment of one of the heat-affected zone (HAZ)’s properties, namely maximum heating temperature and cooling time t8/5
The paper presents results of research devoted to finding the method of monitoring of a weld joint during the welding process
Summary
Elaboration of new materials is a task that is demanded by constantly developing industries. Reducing the thickness of metal sheets produced in the process of thermomechanical rolling (thermomechanical controlled processing—TMCP) for the automotive industry, shipbuilding, oil industry, and many branches of civil engineering led to a reduction in the cost with simultaneous preservation of all mechanical properties of material. This type of steel is characterized by high strength combined with high toughness, high resistance against cold cracks, great formability, and low carbon content or equivalent (CE). The obtained results have proven that the proposed method has the potential to be applied in manufacturing processes to achieve optimal functional properties of welded joints
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