Rock drilling tools are necessary tool consumables in basic construction operations such as mining and tunneling. During use, they will be affected by the external environment, such as corrosion and wear. These problems will directly affect their service life and safety.
How does the corrosion damage process of rock drilling tools occur?
In the process of rock drilling tool manufacturing, such as forging, machining, heat treatment, etc., the non-uniform metallographic structure is produced in the temperature transition zone of the local hot working part. It causes certain tissue stress and residual tensile and compressive stress. Because of the influence of many factors, there are congenital metallurgical defects on the surface of the hollow steel. These metallurgical and processing defects are all soaked in mineral water, resulting in corrosion pits on its surface under the joint action of impact stress. The cyclic stress continues to act, and the bottom of the corrosion pit further forms a crack source, and cracks grow up. The two sides of the crack collide and rub with each other during the drilling. At the same time, the cracks formed first withstand the corrosion longer, the color is darker. The cracks formed later are corroded for a short time and have bright colors. Therefore, the fracture surface of the rock drilling tools generally presents the characteristics of conchoidal corrosion fatigue.
The above factors all affect the service life of rock drilling tools. Therefore, rock drilling tools should have excellent corrosion resistance under harsh environmental conditions, and the requirements for anti-corrosion technology are most important.
Methods of anti-corrosion treatment of rock drilling tools
1. Improve the smelting quality of hollow steel and reduce the non-metallic inclusions in the steel as much as possible.
2. Improve the rolling quality, reduce or eliminate various surface defects as much as possible, and promote the geometric structure, dimensional accuracy, and surface state of the hollow steel to meet the technical requirements.
3. Eliminate micro-cracks and adhesive to corrosive dirt on the inner wall of the flushing hole.
4. Carry out anti-corrosion treatment on the inner and outer surfaces of the rock drilling tools.
Anti-corrosion technology requirements for rock drilling tools
Material selection
Anti-corrosion materials for rock drill tools should have good corrosion, wear, and impact resistance.
Surface treatment
First of all, it is necessary to thoroughly clean the rock drilling tools to remove the dirt and impurities on the surface. Secondly, any burrs or unevenness on the surface need to be polished to improve the adhesion and appearance of the coating. After cleaning and grinding, plating and coating are required to improve the corrosion resistance of the surface. Once the surface is cleaned, anti-corrosion treatment must be carried out in time to ensure the anti-corrosion quality of rock drilling tools.
Anti-corrosion coating
When performing anti-corrosion treatment on the inner and outer surfaces of rock drilling tools, the primary purpose is to create a layer of coating on the inner and outer surfaces of the metal to isolate the metal from corrosive substances such as mineral water and avoid corrosion fatigue. Therefore, during the anti-corrosion operation, the anti-corrosion film must have sufficient strength and toughness. According to the actual use environment and requirements, select coating materials with excellent corrosion resistance.
Inspection and acceptance
Appearance inspection
Check whether the coating surface is flat and smooth and whether there are defects such as bubbles and cracks.
Corrosion resistance test
Test the corrosion resistance of the coating through a salt spray test, immersion test, and other methods.
Quality inspection
Conduct adhesion tests, abrasion resistance tests, impact resistance tests, and so on for the coating to ensure that the quality of the coating meets the requirements.
In short, the anti-corrosion process requirements of rock drilling tools are relatively high. It is necessary to select suitable materials, reasonable surface treatment and coating protection, and carry out strict inspection and acceptance. Only in this way can the safety and service life of rock drilling tools during use be ensured.
