The thermal conductivity of molybdenum is about twice that of iron, and the specific heat is about half that of iron. There is, therefore, a rapid rise in temperature of molybdenum and alloys on either side of a weld.

High energy inputs are required to raise the metal at the joint to its melting point without developing a wide heat affected zone.

Molybdenum and molybdenum alloys cannot be heat treated to enhance their inherent properties; the most useful mechanical properties are developed by strain-hardening or cold-working.Weld metal is always cast and the cold-worked metal on either side of the weld will recrystallize whenever it attains temperatures above 1370 ℃. The wider the high temperature zone on either side of the weld, the greater will be the volume of recrystallized metal and the lower will be the strength of the assembly.

Uniform preheating and postheating will minimize thermal gradients and also lower the flow stress of the metal to permit its accommodation to thermal gradients and fluctuations associated with the welding process.

Like other body-centered cubic metals, molybdenum exhibits a ductile-to-brittle transition temperature. The ductile-to-brittle transition temperature is raised substantially by stress concentrations, by increased rates of strain, by such complex distributions of stress as those generated by the contraction of the metal in the weld zone during cooling after welding and by recrystallization of the cold-worked structure. There is, therefore, a high propensity for molybdenum welds to crack during cooling and under external biaxial stresses at room temperature following welding.

Zhengzhou Sanhui Co., Ltd has beening dealing in refractory metals for over 24 years, including titanium, niobium, molybdenum and others. Sanhui is the pioneer of argon arc welding machine and Alibaba 10 years’golden supplier.