Abstract
The minor alloying element in steel, such as sulfur has been of great concern in welding, because sulfur is an element that significantly changes the weld penetration. To analyze the "minor element effect" experimentally, accurate information on the molten pool, such as temperature or fluid flow, is essential. The radiation thermometer is commonly used to obtain the temperature field of the object. However, the emissivity problem occurs in measuring temperature of molten metals. The emissivity fluctuation causes a noticeable error in temperature indicated by radiation thermometers. As described in the previous paper, the UV (ultra-violet) radiation thermometer is useful to solve the emissivity problem.
In the present paper, the influence of sulfur content on temperature field of molten pool is discussed. In order to avoid interference from arc plasma, the measurement was carried out from the bottom side. It was found that temperature distribution was asymmetrical, and minor changes in sulfur content can change molten pool formation. As a result, it was made clear that changes in sulfur content also affected temperature field of molten pool.
