The rock drill bit is subjected to impact and rotation to break the rock under the action of the rock drill, with high impact frequency and high rotation torque, the working conditions are harsh, and the consumption is large. There are many kinds of rock drill bits, and the button bit has the characteristics of high rock breaking efficiency, effective elimination of rock breaking blind area at the bottom of rock hole, avoiding repeated rock chip breaking, and unlimited lower limit of rock drill bit diameter, etc., which are in use in construction projects. However, in the actual rock drilling process, the tooth loss phenomenon of the button bit happens from time to time, which can seriously affect its working performance and service life. We can determine the best tooth-fixing scheme through research on the tooth-fixing process of the button bit to improve its quality and prolong service life.
Of course, the solid tooth process is not the only factor that determines the service life of rock drill bits. In the face of harsh rock drilling conditions, the material of the rock drill bit is also important, which requires the steel material of the bit to have high plasticity, toughness, and hardness in the heat treatment state, high fatigue strength, and wear resistance, high air cooling hardenability, as well as relatively simple heat treatment process, and the cost should not be too high. The material used in the drill bit is mainly Cr-Ni type high-quality steel, of which 45CrNiMo1V steel has a long multi-impact fatigue life, superior tensile strength, and better wear resistance, so it is suitable as the steel for the shell of the threaded connection button bit for hydraulic drilling vehicles.
The button bit made of heat-treated 45CrNiMo1V is a high-quality drill widely used in the mining industry. They are subjected to a rigorous process to ensure that they have the necessary strength and durability. The carbides on the bit are designed to be sharp and strong, so they can easily break through rock formations while retaining their shape over time.
Fixing process
There are three fixing processes for 45CrNiMo1V button bits: cold pressing, hot pressing, and hot inserting.
Cold pressing
Cold pressing is to determine the processing size of the tooth hole according to the size and interference of the carbide button and the amount of interference, to drill and ream the corresponding tooth hole in the rock drill bit, and to force the carbide button into the tooth hole through the method of interference fit by external force on the cold pressing gear at room temperature, using the power generated by the elastic deformation of the shell steel to fasten the carbide buttons.
Hot pressing
According to the size and interference of the carbide button, the tooth hole processing size of the rock drill bit is determined by hot pressing, and the corresponding tooth holes are drilled and reamed; the rock drill bit is heated to a suitable temperature (must be lower than the annealing temperature of the shell steel to ensure that the rock drill bit does not soften and anneal), and the carbide button is pressed into the corresponding hole by external force on a dedicated tool for fixing teeth and cooled to room temperature. The hot pressing method uses the elastic deformation force of the shell metal material to fasten the carbide button.
Hot inserting
Hot inserting is to heat the drill bit first and keep it warm for some time so that its tooth hole expands and the carbide button can be set into the corresponding tooth hole by a slight external force and then cooled to room temperature on the slow cooling table.
Comparison and selection of different fixing processes
When selecting the fixing process of the 45CrNiMo1V button bit, overall considerations need to be made based on the specific use occasions and requirements. Although cold processing is low-cost and easy to operate, the fixing strength is relatively low, and it is suitable for some occasions that do not require high fixing strength. Hot pressing can boost the strength of fixing and lower the chances of tooth loss, but it comes at a hefty price and demands specific equipment and operational expertise. The hot-mounted fixing process can achieve a seamless connection between the alloy teeth and the bit body, significantly improving the fixing strength, and is suitable for occasions that require high fixing strength.
In addition to the choice of the fixing process, it is also necessary to pay attention to the interference between the carbide buttons and the bit body. The interference refers to the difference between the diameter of the carbide buttons and the diameter of the reserved hole in the bit body. Appropriate interference can ensure the tight combination between the carbide buttons and the bit body and improve the strength of the solid teeth. However, if the interference amount is too much or too little, it’ll impact the effectiveness of the fixing. Therefore, when selecting the fixing process, it is necessary to determine the appropriate interference amount based on the actual situation.
The influence of the fixing process on the service life of drill bits
The fixing process significantly influences the lifespan of the 45CrNiMo1V button bit. Employing an appropriate fixing process can greatly enhance the fixing strength and the longevity of the bit. At the same time, by optimizing the stress distribution between the carbide buttons and the bit body and reducing the occurrence of tooth loss, the working performance and stability of the drill bit can also be improved. Therefore, in practical applications, we should choose the appropriate fixing process and parameters according to the specific use occasions and requirements.
Conclusion
The fixing process of the 45CrNiMo1V button bit is one of the key factors affecting its service life and working performance. By choosing the appropriate cementing process and taking effective measures to optimize the cementing process, the performance and service life of 45CrNiMo1V button bits can be significantly improved to meet various engineering requirements. At the same time, strengthening quality inspection and control is also one of the essential measures to ensure product quality.
