Toyoyuki Sato

Study of wind-toughness of metal arc welding with reference to multi-pass weld metal quality

Abstract The maximum cause to make mechanical toughness of a weld metal reduce in process management is known to be a mixture of nitrogen including in the atmosphere by breaking the shield condition. Mixture of the atmosphere is prevented by blowing the shielding gas such as carbon dioxide, argon, and this mixture to the arc and the molten pool in gas metal arc welding, but it is easily affected by wind. Therefore, it has been recommended conventionally that wind velocity should be controlled to less than 2.0 m/s. But it is thought that this recommendation value is unsuitable to produce multi-pass weld metal with high mechanical and porosity toughness properties because this was provided from examination results by only consideration of porosity toughness of single-pass weld metal but non-consideration mechanical toughness. In this paper, the shielding condition is evaluated not only chemical analysis and mechanical properties of multi-pass weld metal in some velocity wind environment but also visualizing varied shielding gas behaviour by the Schlieren method. As a result, it is necessary to control the wind velocity to less than 0.5 m/s to produce multi-pass weld metal with good properties. And the calculated velocity of shielding gas should be controlled to more than twice the wind velocity.

Measurement of molten pool temperature distribution by UV thermal radiation

Summary Accurate measurement of temperature is an increasingly important aspect of modern production processes. The radiation thermometer, requiring no physical contact with the object being measured, is available for such temperature measurement. It is reported, however, that the IR radiation thermometer has led to significant errors in molten pool temperature measurements where the emissivity is variable. It is evident from Plancks law of radiation that the luminance temperature (measured by radiation thermometry) approaches the true temperature of an object when the measurement wavelength is shorter than IR. This paper describes an investigation of molten pool temperature measurement by UV thermal radiation. In the experiments, stainless steel (SUS304) and mild steel are melted by GTA (gas tungsten arc or TIG) or a laser beam, and the temperature distribution of the molten pool is measured with a UV sensor (CCD camera, image intensifier, and interference filter). The results show that the melting poin...