Hydraulic rock drill jumbo is a rock drilling machine widely used in large-scale infrastructure construction projects. During the rock drilling operation, its main consumable parts are drill bits, drill rods, and shank adapters. Among them, the drill rod is the most important part of rock drilling tools, and it is a kind of slender rod that is subject to complex alternating stress such as tension, compression, torsion, bending as well as wear and corrosion, and transmits dynamic energy in the form of high-frequency stress waves, so the requirements are strict for its performance and quality. So, what problems should be noted in the production of drill rods for hydraulic rock drill jumbo?
Material selection
Quality of steel
The quality of hollow steel is one of the main reasons affecting the unsatisfactory service life of drill rods. Therefore, the quality of drill rod steel is directly related to the service life of drill rods. Drill rod is a tool that works under dynamic load conditions and must have high fatigue resistance, wear resistance, and impact resistance. These properties are related to the steel type, the purity of steel, and the uniformity of structure.
Strength and toughness: drill rods should ensure strength and toughness while withstanding high-impact loads. Therefore, choosing the appropriate material is crucial.
Corrosion resistance: since the drill rod works underground or in a humid environment, its material should have good corrosion resistance.
Manufacturing processability: when choosing materials, it is also necessary to consider their processability and welding performance.
Structural design
The structural design of the drill rod has an essential impact on its performance. First, it is necessary to ensure that the shape and size of the drill rod meet the engineering requirements. Secondly, the wall thickness and thread of the drill rod should be designed reasonably to improve the strength and wear resistance of the drill rod. In addition, we should pay attention to the heat treatment process of the drill rod to enhance its hardness and impact resistance.
Reasonable design and structural optimization
The design of the drill rod should fully consider its stress characteristics and working environment. Reasonable structural design can improve the bearing capacity and service life of the drill rod. For instance, utilizing a variable cross-section design can decrease the weight of the drill rod and enhance its stability when subjected to impact loads. Furthermore, optimizing the design of the connection part can lessen stress concentration and the likelihood of fracture. Additionally, it’s critical to consider the compatibility between the drill rod and the rock drill to ensure optimal performance when used together.
Production process
Reasonable production processes and manufacturing technology are the guarantees of product quality. At the same time, manufacturers should also pay attention to the upsetting extrusion process, end groove and stress ring, thread processing, heat treatment process, and anti-corrosion process in production.
Upsetting extrusion process
The R38 thread of drill rod for hydraulic drill jumbo requires full upsetting, a straight inner hole, and no sudden change in the joint. If necessary, the bore should be machined. If the straightness of the bore fluctuates greatly during upsetting or the transition of the joint is not good, it will affect the service life of drill rod.
End groove and stress ring
Some drill rods are designed with a flushing groove on the end of the rod and a stress ring in the transition area at the root of thread. The flushing groove can make high-pressure water enter the thread surface to cool and prevent rock dust from entering the thread. In addition to meeting the needs of high-speed machining threads, the stress ring is also conducive to increasing the flexibility of drill rod and relieving the bending stress load.
Thread processing
The rate of thread root fracture failure at the end of the connection with drill bit is larger when drill rod is used. In cases where the hollow steel is not ideal, manufacturers should pay more attention to the quality of the threads’ machining. A reasonable tool should be selected to implement high-precision machining of the thread surface and improve the thread surface quality.
Heat treatment process
The purpose of heat treatment is to maximize the potential of the material, and further exploration of carburizing process and surface quenching process is very beneficial to improve the service life of drill rods.
Anti-corrosion process
The anti-corrosion process for drill rods with a length of more than 3m is to spray paint but not to deal with the water holes. Some manufacturers use overall oil immersion treatment for shorter drill rods. In general, the coating adhesion performance and anti-corrosion performance of these two methods are not very satisfactory. It is necessary to explore the process of choosing reasonably priced low-thickness chemical anti-corrosion coatings and treating both the inside and outside surfaces of drill rods.
Quality inspection and testing
Quality inspection and testing are necessary links to ensure the quality of drill rods. In production, strict quality inspection of the drill rod should be carried out, including dimensional inspection, non-destructive testing, and mechanical property testing. In addition, environmental adaptability tests and life prediction tests should also be conducted to ensure the performance of the drill rod in actual use.
Dimensional accuracy: ensure that the diameter, length, and other dimensions of the drill rod meet the design requirements to ensure smooth installation and avoid problems during use.
Surface quality: the surface of the drill rod should be smooth and free of scratches, burrs, and other defects to reduce wear and resistance during use.
Non-destructive testing: perform non-destructive testing on the drill rod, such as ultrasonic flaw detection and radiographic flaw detection to discover and eliminate possible internal defects.
Mechanical property testing: conduct tensile, impact, hardness, and other tests on the drill rod to ensure that its mechanical properties meet the design requirements.
Anti-corrosion treatment: perform effective anti-corrosion treatment on the drill rod, such as coating, plating, etc., to improve its corrosion resistance.
Conclusion
During the operation of hydraulic rock drill jumbos, the drill rod is one of the core components, and its performance and status are directly related to the rock drilling efficiency, equipment service life, and operation safety. Therefore, it is essential to pay attention to the drill rod during production. Every step, from material selection and quality control to design and structural optimization to the production process, must be handled with care. Only by paying full attention to solving these problems can we ensure that the drill rod maintains an efficient and stable operating state in a complex and changeable operating environment and provides strong support for mining, tunneling, and infrastructure construction. In short, the production of drill rods for hydraulic rock drill jumbos is a complex and rigorous process that requires strict control from all links. Only through scientific and reasonable manufacturing methods and strict quality control systems can high-quality and high-reliability drill rods be produced to provide a solid guarantee for the stable operation of hydraulic rock drill jumbos.
