smelting vs soldering

smelting

noun
  • The process of melting or fusion, especially to extract a metal from its ore. 

soldering

noun
  • A method of joining two metallic surfaces by melting an alloy between them. 

  • A soldered joint. 

  • An instance of soldering. 

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