You will need to be more specific. Welding is a broad category. Underwater pipe welding versus ship or pipe welders... the salaries will vary.
The American Welding Society has a page that cites welding salaries by state/community. It is a few years old at this point, but it should give you an idea of the range. Broadly, the answer is "about $30 an hour"... and it appears the number of jobs is growing, especially if you are willing to move to follow the work.