Rock-drilling cemented carbide is a tool material widely used in mining, tunneling, oil drilling, and other fields. The choice of its grade directly affects the performance and service life of the tool. Therefore, when selecting a rock drilling carbide grade, we must comprehensively consider several factors to ensure that the most suitable tool material is selected.
Selection of cemented carbide grades
Hardness
Hardness is one of the significant factors in the selection of cemented carbide grades. Different grades of cemented carbide have different hardnesses, so we need to choose the appropriate hardness according to your usage needs. Generally speaking, the higher the hardness, the better the wear resistance and the brittleness. Therefore, when selecting the appropriate hardness of a tool, it is essential to consider the environment and operational conditions it will be subjected to.
Toughness
Toughness is another important performance indicator of cemented carbide. A carbide with good toughness is less likely to crack or fracture during impact and bending. Therefore, when selecting a carbide grade, the working environment and conditions of the tool need to be considered to ensure that the tool has sufficient toughness.
Wear resistance
Wear resistance refers to the ability of cemented carbide to resist wear. When selecting a carbide grade, you need to consider the working environment and conditions of the tool, as well as the friction between the tool and rocks or other materials. Generally speaking, carbide with good wear resistance is better able to resist wear and thus extend the tool’s service life.
Corrosion resistance
In specific working environments, cemented carbide may be corroded by corrosive substances. Therefore, when selecting a carbide grade, its corrosion resistance requires consideration. Generally speaking, carbide with good corrosion resistance can better resist the erosion of corrosive substances, thereby extending the tool’s service life.
Based on the above content, the selection of rock-drilling cemented carbide grades can start with impact rock-drilling cemented carbide and oil-drilling cemented carbide.
Impact rock drilling cemented carbide
According to different rock properties
Impact rock drilling requires carbides with good toughness because of impact loads. According to different rock hardness, YG6, YG8, YG8C, YG11C, YG13C, YG15 and other carbide grades are used. If the rock hardness and the impact load are large, high Co and coarse grain carbides should be selected. On the contrary, if the rock hardness and the impact load are small, medium cobalt and coarse-grained carbides should be selected.
According to the different impact energy of rock drills
Rock drill bit is born to cyclic stresses such as alternating tensile, compressive, bending, torsion, and stress corrosion during drilling. The working conditions of drill bit are very harsh. For extremely tough rocks and rock drills with high-impact energy, the focus should be on toughness, and carbide with high cobalt content should be used. For medium-hard, hard, hard and brittle rocks with high abrasiveness, the focus should be on wear resistance, and carbide with low cobalt content should be used.
When the impact energy is small, the specific power required to break the rock increases. Within a certain range, the impact energy increases, and the specific power required to crush the rock decreases. The stronger the rock, the higher the specific power at the same impact energy. In the case of higher impact energy, weaker rocks, or hard and brittle rock, the button bit has better adaptability than the chip bit. If the impact energy is too large, the rock will be crushed excessively and cause energy loss.
According to the different shape of rock drill bits
The surrounding carbide of the chip bit has a long rock drilling stroke and a large area, so the peripheral carbide wears faster than the central carbide and is easy to break. Moreover, the loading area of the chip bit carbide on the rock is small, and the boundary line is short, so the impact load per unit area is large.
The gauge buttons and middle buttons of button bit are reasonably distributed, the chiseling borne by each button is more balanced, and the wear is more even. The button bit carbide has a large loading area on the rock, a long boundary line, and a small impact load per unit area. Therefore, the binder content can be lower than that of chip bit when designing the carbide of button bit, and the WC grain can be finer.
Button bit is suitable for use with rock drills with high-impact energy. The impact energy of pneumatic rock drill is not enough, the drilling speed is not as fast as that of chip bit, and the ability to resist radial wear is not as good as that of chip bit. Because the impact energy of hydraulic rock drill is high, button bit should be used mainly. For tough rocks with serious abrasiveness, service life span of button bits is often not as long as that of chip bits.
Cemented carbide for oil drilling
The most important thing about cemented carbide for oil drilling is that the carbide is damaged at the bottom of the well. Therefore, it is desired that carbide has wear resistance based on better toughness. High cobalt and coarse-grain carbides should be designed and selected. Such as YG8C, YG11C, YG13C, etc.
In addition, the following should be paid attention to when choosing cemented carbide grades.
1. The physical properties of the rock, such as hardness, abrasiveness, grain size, and its characteristics (compactness and fissures, etc.).
2. Rock drill model.
3. The method of breaking rocks (including air pressure, etc.).
4. Equipment capacity.
In summary, selecting a rock drilling carbide grade requires considering several factors to ensure the selection of the most suitable tool material. During the selection process, it is necessary to fully understand the fundamental performance and engineering requirements of rock drilling cemented carbide, consider economic benefits and environmental protection, refer to manufacturer recommendations and experience selection, and conduct test verification and evaluation effects.
