Strengthening Button Methods of Tungsten Carbide Button Bit

Strengthening button method of tungsten carbide button bit refers to how to fix the button on the bit in order to support it and guarantee that the displacement and detachment of the button won’t happen during rock drilling.

There are three current methods of strengthening teeth: welding method, cold fixing method, and hot inserting method.

The welding method is the earliest used strengthening teeth method. It is relatively simple. It mainly determines the size of the perforations and tungsten carbide button by welding the gap. According to the structure of the bit, the perforations are drilled on the bit body. And then the brazing or silver welding method can be adopted to weld the button on the bit body. The requirement for the drilling precision and the size of button are not high. There are three disadvantages of this method. Firstly, the operation is relatively difficult. Secondly, it is easily to leave the crater which will affect the appearance. Thirdly, the welding strength is low and the durability of the bit is low. This method is mostly adopted to produce tapered hole joint button bit in minor diameter, which has been gradually eliminated.

At present, the cold fixing method is adopted by most of enterprises. The main point of this method is to calculate the fit clearance between the perforation and the tungsten carbide button according to the yield-limit of steel of the bit and press the button into perforation under an interference fit by using external force. Its advantages are that the method is easy to master and the production efficiency is relatively high. But its disadvantage is the stability. When the button is pressed into the perforation, the button and bit are easily damaged by external force. The service life is limited, especially the late life is poor. The phenomenon of detachment of teeth and broken teeth is easy to occur. It is mainly used on the strengthening teeth of threaded connection button bit which is with low demand or not used for repeated grinding.

The hot inserting method is not only easy to operate but also has a good stability because it has small impact on the button and bit which are not basically damaged. As for the use of the threaded joint button bit with higher requirement, we suggest adopting method. It selects the alloy steel with better thermal expansibility and tenacity as the bit steel. Under the same heating condition and an appropriate interference fit, it is easy to press the button into the bit perforation. When it is cooled to normal temperature and the steel body shrinks, the process of strengthening button is completed.

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