Effect of alloying of the seam metal on the properties of weldments in invar alloys

Abstract

1. Alloys of iron with 36–42% Ni have good weldability and high physicomechanical properties at 4.2–293°K. 2. To increase the resistance of weld seams to hot cracking and porosities it is necessary to use filler wire alloyed with as much as 3.5% Mn, 1.5% Ti, and 4% Mo. Higher strength of welds is achieved by combined alloying with these elements and chromium (up to 5%). 3. An increase of the coefficient of thermal expansion to 4–5·10−6 deg−1 leads to thermal stresses near 5.0 kg/mm2 during thermal cycling in the range of 4.2–293°K. 4. In welded joints of Invar and stainless steel of the 18/8 type stresses around 40.0 kg/mm2 occur during thermal cycling, which amounts to 0.5σ0.2 of the weld metal at 4.2°K.