liquefaction vs welding

liquefaction

noun
  • Process of being, or state of having been, made liquid (from either a solid or a gas) 

  • The liquid or semiliquid that results from this process. 

welding

noun
  • joining two materials (especially two metals) together by applying heat, pressure and filler, either separately or in any combination, or 

  • binding together inseparably; uniting closely or intimately. 

How often have the words liquefaction and welding occurred in a corpus of books? (source: Google Ngram Viewer )