Interesting. In dutch we use 'solderen' vs 'lassen', in German they use 'schweizen' and 'loten'.

English has a third term like that as well called 'brazing', then there is silver solder (a high temperature version of soldering), in dutch we'd call that 'hardsolderen', whereas what the English call brazing we call oxy-acetyleen lassen (which is more of a process name by virtue of naming the ingredients).

Soldadura autogeno and Soldadura en el arco (sp?) are what I think the modifiers used in Spanish to indicate brazing and (arc) welding.