I'm looking for some web based or Power Point welding engineering information, free information of course.  I downloaded a link that was posted her previously, but was wondering if there was some more Power Point info that someone had laying around they would like to give up.  I am pretty familiar with most basic metallurgy and would like to know some more about joint design, the whys of using specific metal combinations, filler metal, specific shielding gases, PWHT, etc....  Basically more info on why certain materials and processes and gases and fillers are used and what effects they have.