Fundamentals of Plasma Arc Welding.
Abstract
A three-year study was made of physical phenomena underlying operation of the plasma-arc welding (PAW) process. Experimental methods were developed to measure plasma spectral intensities during welding, a mathematical method was perfected to compute plasma temperature distributions from the spectral data, and statistical methods were used to extract maximum information from the data and to infer improved values for four ARII transition probabilities. Welds in mild and stainless steels and in Ti-6Al-4V up to 12.7 mm thick were evaluated by metallography and/or by cyclic fatigue studies. At low stress concentration levels PAW was found to reduce cyclic crack growth rates in the weld metal compared to the parent metal. There appears to be evidence that plasma spectroscopy can aid in selection and control of welding parameters. The plasma temperature measurements clarify the mechanism whereby use of auxiliary ports in the PAW torch orifice cup reduces the width of a weld nugget. Simple plasmadynamic models were used to relate orifice geometry to plasma temperature and electrical resistance, and to weld quality, thus accounting for the observation that a convergent orifice enhances weld penetration, reduces weld width, and improves weld nugget geometry without causing double-arcing, while a divergent orifice (which simulates an eroded orifice cup) has the opposite, deleterious, effects. Nine documents are cited in which these results were reported and complete preprints of four journal articles not yet published are included as appendices. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1979
- Accession Number
- ADA074340
Entities
People
- C. B. Shaw Jr.