Prediction on the Wear Resistance of Contact Tips for GMA Welding

Kim, Nam-Hoon; Kim, Hee-Jin; Kim, Hoi-Soo; Koh, Jin-Hyun

Journal of KWJS 2004;22(4):35-42.
Published online September 15, 2004.

[기술논문] GMA용접에서 콘택트팁의 내마모성에 대한 예측

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Prediction on the Wear Resistance of Contact Tips for GMA Welding

Nam-Hoon Kim, Hee-Jin Kim, Hoi-Soo Kim, Jin-Hyun Koh

Abstract

Contact tips are required to have a higher resistance to wear and thus to have an extended life time under the advanced GMA W welding process. Several requirements have been specified and employed by domestic industries for selecting their tips for such a purpose. However no attempt has been made to justify their requirements based on the experimental data of wear resistance or life time of contact tips. In this study, five different contact tips with three different compositions were employed for actual GMA welding up to 4 hours and were evaluated their wear resistance by measuring in every one hour the area of enlarged hole at the exit side. Experimental results clearly showed that the Cr-containing tips strengthened by precipitation hardening have much better resistance to wear than those made by work hardening. It was further noticed that Cr is an excellent alloying element for improving the wear resistance of contact tips only when it is in an properly aged condition. Initial hardness may play some role in the early stage of wear but not in the later stage of welding because the microstructure of tip changes significantly by the prolonged exposure to welding arc heat. Based on these results, critical review has been made on the current requirements employed by domestic industries. Of importance is that a new guideline has been confimled to be more reasonable.