The mutual relationship between the static welding behavior and physical characteristics of contact materials has been obtained with an X-Y recorder and an oscilloscope for various metals and alloys.
Light welding or sticking occurs at the softening temperature of the material in the contact area, and heavy welding occurs at its melting temperature. The temperature of the contact area which has influence on the welding behavior is correlated to the current density in the contact area. The I⁄d is given by
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where I is the contact current, d is the diameter of the circular contact area, T is the maximum temperature in the contact area, T_r is room temperature, ρ_r is the electrical resistivity at room temperature, α is the temperature coefficient of electrical resistivity, and L is the Wiedemann-Franz constant and is equal to 2.45×10⁻⁸ (V/deg)².
The higher the melting temperature or the larger the temperature coefficient of electrical resistivity of the contact material, the more hardly the contact area can attain its melting state.
It is considered that the stationary melting state cannot exist in the static contact area.