Tungsten Carbide Mining Button Process

During the brazing of tungsten carbide mining button, the size of welding gap is the key factor that will affect the density and strength of weld line. If the gap is too narrow, it will hinder the inflow of the solder; if the gap is too wide, it will destroy capillary action so that the solder can not fill the gap. 

The brazing of the mining button is to weld the xenogeneic material of steel and tungsten carbide. Given that the tungsten carbide coefficient of linear expansion is 1Π2~1Π3 of steel, the gap of brazing should be smaller than that of steel welding. Through the experiments of several sets of different weld gaps, the test results show that the appropriate gap generally ranges from 0.08 mm to 0.15 mm. In addition, it is best to use a tapered alloy head and a tapered mining button bore to ensure the uniformity of weld gap around the carbide tip.

At present, there are two kinds of the production process of domestic mining button:

(1) the machine-shaping of the mining button → the brazing of tungsten carbide → the heating in the salt bath furnace → nitrate isothermal hardening → tempering

(2) the machine-shaping of the mining button → the heating in the salt bath furnace →nitrate isothermal hardening → rinsing → the brazing of tungsten carbide → tempering

The order of the first type of production process is the brazing of tungsten carbide, the heating in the salt bath furnace and nitrate isothermal hardening. It guarantees the hardness of mining button. But the tungsten carbide has gone through heating twice during the process of brazing and the process of nitrate isothermal hardening. Its head has been embrittled so that the service life of mining button will be greatly shortened owing to the cracking of tungsten carbide and the welding between alloy head and mining button. 

The order of second type is nitrate isothermal hardening and the brazing of tungsten carbide. Although the quality of weld line and alloy head can be guaranteed, the hardness of mining button head decreases so that the wear resistance of the mining button head greatly decreases as well. As a result, during the use of mining button, the alloy head has been detached in advance and the service life of button is shortened.

Therefore, a vacuum furnace brazing and heat treatment should be simultaneously used for heating so that the brazed mining button can go through the process of hardening directly. This process has some obvious features which are listed as below:

(1) The vacuum furnace brazing can prevent the brazing surface from contacting with air which will lead to oxidation during the process of brazing.

(2) The brazed mining button are directly quenched without air cooling, avoiding the second heating and improving the overall mechanical properties of the button.

The vacuum furnace brazing process of the mining button:

Rinsing the mining button part which needs to be brazed, solder and tungsten carbide tip→ drying → filling with the solder and loading the tungsten carbide tip → loading the mining button into jig → heating in the furnace → cooling

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