Cemented carbide is an important part of rock drill bits and is known as "industrial teeth" due to its high hardness, strength, wear resistance, and corrosion resistance.
Commonly used cemented carbides include tungsten-cobalt, tungsten-titanium-cobalt, and tungsten-titanium-tantalum (niobium), each category has a variety of grades. Due to the ever-changing rocks, the variety of rock drills, and the extremely harsh working environment, it is impossible to use only one grade of cemented carbide.
Cemented carbides suitable for rock drilling must be resistant to damage under impact load and have high wear resistance. The correct selection of cemented carbide grades is one of the important factors to ensure the effective use of cemented carbide rock drilling tools. Therefore, the following points should be paid attention to when choosing cemented carbide grades:
- Physical and mechanical properties of rocks, such as hardness, abrasiveness, particle size, and characteristics.
- Rock drill model.
- The method of breaking rocks.
- Equipment capacity
In addition, the inserting, welding, and grinding of cemented carbide for rock drilling tools is an important process. If mishandled, it is easy to produce an insert detached from the slot, insert shattered, cracks, debris, and other defects, so that the service life of cemented carbide tools is reduced.
Matters needing attention when using cemented carbide for rock drilling tools - The inserting methods used for button alloys are hot inserting, hot pressing, and cold pressing. When inserting teeth, strictly control the interference and clearance between the teeth and holes according to the process requirements, finely grind the column teeth, and eliminate the grinding stress before inserting the teeth.
- Due to the difference in thermal conductivity and thermal expansion coefficient between cemented carbide and shell material, improper handling during welding is prone to cracks. It is suggested that the welding gap should be controlled between 0.3~0.4 mm, and the shell should be placed in an incubator for slow cooling after welding.
- The surface of cemented carbide should be cleaned before welding and sandblasting and roller grinding can be used. The grinding process must be carried out under strictly controlled tumbling process conditions, otherwise, the products with edges and corners are prone to fall off the edge. It is best to use an organic solvent such as gasoline or anhydrous ethanol as a cleaning agent to clean the cemented carbide, and weld immediately after cleaning.
- When grinding the edge surface of the shell, a green silicon carbide grinding wheel is used and cooled with water.
The cemented carbide used in rock drilling tools should have good toughness. Choosing the cemented carbide grades reasonably and strictly following the precautions in use can effectively extend the service life of rock drilling tools.