Various strengthening techniques are applied to the surface of rock drilling tools to improve their durability and service life. One common technique is the application of heat treatment methods, such as quenching and tempering, to enhance the hardness and toughness of steel. In addition, the coating is also one of the commonly used surface strengthening technologies, such as chromium, nickel, tungsten, and other metal materials, which can make rock drilling tools more wear-resistant and corrosion-resistant during work. Advanced technologies, such as laser and electrochemical treatment, can be utilized to strengthen the surface of rock drilling tools, thereby further improving their performance and service life. However, the utilization of strengthening technology is dependent on equipment. Therefore, what is the surface strengthening equipment for rock drilling tools?

Shot blasting machine

There are two kinds of shot blasting surface strengthening mechanical equipment commonly used by rock drilling tool manufacturers. One is the mechanical centrifugal shot blasting machine, which uses the centrifugal force of the impeller rotation to throw out the projectile; the other is the air-operated shot blasting machine, which uses compressed air to shoot out the projectile from the nozzle. The advantages of the former are high efficiency, convenient adjustment, stable work, and easy automation. The disadvantage is the high investment in equipment, not easy to deal with the complex shape of the parts. The latter has the advantages of simple and flexible equipment and can spray complex surfaces and internal cavities. The disadvantage is low efficiency and high energy consumption. The shot blasting equipment used for surface peening of rock drilling tools is usually mechanical centrifugal shot blasting machines.

Projectile for shot blasting

Shot peening projectiles should have a spherical shape. In the case of ensuring a certain impact toughness, the higher the hardness, the better. Commonly used projectile materials include steel and cast iron, with a projectile diameter of 0.8-1.2mm, according to the different requirements of the projectile size. If the projectile diameter is too small, it may not provide sufficient strengthening effect. On the other hand, if the diameter is too large, it will result in a rough surface on the rock drilling tool and create a deep strengthening layer, ultimately reducing its surface fatigue strength.

Projectiles can be purchased directly from professional factories that manufacture iron or steel shots. Shot hardness to HRC45~50 is appropriate, high hardness shot peening effect is good, but easy to break, low service life.

During the shot blasting process, the quality of the shot blasting is affected due to the crushing and wear of the steel shot. For this reason, new steel shots need to be replaced or supplemented. The diameter and geometric shape of the steel shot should meet the technical requirements, accounting for more than 80% of the quality assurance process for shot blasting. It is a crucial step in ensuring high-quality shot blasting.

Rolling strengthening equipment

It is a thread-rolling device installed on an ordinary lathe, which is suitable for local strengthening of the external thread surface of the thread-matching drilling tool. It can perform not only continuous rolling strengthening on the external thread surface but also local rolling strengthening on the bottom, root, transition groove, eccentric groove, and so on. Its pressure head can be a spherical surface or a circular arc surface.