Preparation before Welding of Tungsten Carbide and Steel(1)
a) The inspection for the crack, bent, concave or convex etc defectiveness on tungsten carbide surface have to be taken, and the welding surface must be flat. If the welding surface is sphere or rectangle shape, which must be comply with a certain geometry shape .To keep a good connecting between tungsten carbide and substrate is the condition to reach a good brazing quality.
b) The sand-blasting process has to be taken on the tungsten carbide, if not sand-blasting equipment, you can hold the tungsten carbide parts with hand on the rotating green SiC grinding wheel to grind out the oxidized layer and black letters on the welding surface. The tungsten carbide could not be wetted by the brazing alloy if do not remove the oxidized layer. The experience has shown that the oxidization layer and black letters on the brazing surface have to be treated with sand-blasting ,otherwise, the cemented carbide is unavailable to be wetted by brazing alloy ,meanwhile the black letters still exist in the brazing joint ,resulting in reduction of welding area and causing desoldering problem.
c) When clean the brazing surface of cemented carbide, it is better that do not use the chemical-mechanical grinding or electrolytic grinding process, as these ways are depending on corrosion of the binding agent (Cobalt) on the surface of tungsten carbide to expedite grinding and improve grinding efficiency, on the contrary, if the cobalt is eroded, the brazing alloy will be very hard to wet the cemented carbide and lead to desoldering phenomenon. In the special case ,if the brazing surface of the cemented carbide has to be treated in the mentioned methods or EDM process, you have to resand-blasting or grind out the surface with SiC grinding wheel on the tungsten carbide .The cemented carbide treated with sand-blasting could not cleaned with gasoline and alcohol so as to off oil dirt.
