Effect of carbonates on welding properties of low hydrogen electrode

• Main Authors: Chia-Ming Chang, 張家銘
• Other Authors: 吳威德
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/22971912833106867323

碩士 === 國立中興大學 === 材料工程學系所 === 94 === Shielded metal arc welding flux was a multi-composition system. Therefore, it was difficult that investigated into the effect of the compositions for welding properties. In this study, various contents of carbonates, MgCO3, Na2CO3, K2CO3 and BaCO3, respectively, were added to investigate the bead shape, droplet size, and mechanical properties. It examined the effect of carbonates for bead shape and droplet size by automatic welding and droplet collection method, separately. The results showed that MgCO3, Na2CO3 and BaCO3 increased the surface tension of the molten metal, but K2CO3 reduced the surface tension. The surface tension of the molten metal influenced on the width and height of bead . The surface tension increasing, not only bead width decreased, but bead height increased. In addition, droplet size increased with surface tension increased. Adding higher ionization potential carbonates in the welding flux made the penetration depth decease. Phase identification was performed by X-ray diffraction analysis. It was found that BCC structure existed in all weld metal. Optical microscope was carried out to observe metallography. The microstructure included of the primary ferrite (grain boundary ferrite and intragranular polygonal ferrite), the ferrite with second phase, and acicular ferrite. Adding carbonates resulted in the variation of heat input to transfer microstructure. So far as mechanical properties were concerned, the addition of carbonates affected hardness, tensile, and impact properties. MgCO3 and Na2CO3 diminished the welding quality. Oppositely, K2CO3 and BaCO3 improved mechanical properties.