Help understanding alloys

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I'm new to welding and trying to understand how to avoid overheating metals containing different alloys. For example when welding metal containing a low expansion alloy like this http://www.nealloys.com/36_alloy_invar.php how can overheating be avoided? Would techniques differ when using a crystalline metal?
Reply:Invar 36 is a 36% Ni-based alloy.  For pressure vessel work, Section IX ASME governs.  Uncertain as to our application.  Disagree with the above link that Alloy 36 will not react to thermal expansion heat.  Even quartz react to heat, albeit to a lesser degree.  The literature states TIG with Inconel Filler Metal 92 or Hastelloy W.   Welding 304SS (18/8-based alloy) would be a warm-up to working with Alloy 36.  Avoid overheating?  Fit up, HAZ control, and hood time.  Access link for additional commentary on Invar 36:  http://www.nickelinstitute.org/~/Med...rvice_410_.pdf"Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi