Welding and manufacturing process of pipelines is mainly organized with root-pass welding and fill-pass welding. Of them, root-pass welding is very difficult to automatize, compared to normal welding, and it doesn't guarantee high welding quality. Root-pass welding quality can be represented by back-bead width and back-bead height, and there are a variety of studies to predict back-bead geometry, currently. In this study, a variety of welding experiments were carried out to optimize root-pass welding process using GMA process. Based on the experimental results, optimal welding conditions were selected after analyzing correlation between welding parameters and back-bead geometry. Then, effectiveness of empirical models developed was compared and analyzed, and optimized empirical models were finally developed for predicting back-bead by analyzing the main effect of each factor which affects back-bead geometry and their influence on interaction.

Abstract
 1. 서론
 2. 용접실험 및 결과
  2.1 용접 실험 준비
  2.2 실험 설계
  2.3 실험 결과
 3. 수학적 모델 개발 및 최적조건 선정
  3.1 수학적 모델 개발
  3.2 최적 조건선정
 4. 결론
 참고문헌

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