Threaded drill rod includes extension drill rod, light extension drill rod, drifter rod, MF rod, etc.
In the process of drilling, whether horizontal operation, vertical operation or oblique operation, the drill rod often works in different bending states due to the change of bit thrust, rock heterogeneity or cracks and holes. If the bending state is serious or the elasticity of the rod is not good, it will cause the rod bending and fracture and early failure. Therefore, the drill rod must have good elasticity.
The threaded structure at both ends of the threaded drill rod is an important part of connecting the whole drilling tool strings and transmitting rock drilling stress. The analysis shows that the threaded part is often the most important part of the failure of the threaded drill rod, and its failure mechanism is the result of fretting wear and impact wear. Therefore, the wear resistance of the threaded part is often the decisive factor to determine the service life of the threaded bit.
The fracture of drill rod is mainly fatigue fracture. The main reason is that the drill rod must bear the high-frequency impact force and axial thrust of the drill bit. In addition, the drill rod is a slender rod. During oblique operation and horizontal operation, the drill rod often produces bending stress due to the influence of the weight of the drill tools. Therefore, the threaded rod material must have high fatigue strength and fracture toughness.
At present, dry drilling is mostly used in open-pit drilling, and wet drilling is mostly used in underground drilling. Most drill rods are with wet drilling. The joint action of high frequency and high stress and water (often acidic water) corrosion on the inner hole of the screw is the main factor causing the fatigue fracture in the screw. Therefore, the threaded drill rod must have good waterproof and anti-corrosion ability.
Threaded drill rod as extension drill rod, drifter rod, MF rod must have high fatigue strength, fracture toughness, elasticity, wear-resistance, and corrosion resistance. The threaded drill rod is a slender rod, which is not suitable for complex heat treatment. Only through the best heat treatment process can comprehensive properties be obtained, such as high fatigue strength, fracture toughness, elasticity, wear resistance and corrosion resistance, and so on.