Aluminum alloy pipe for rock drill
Aluminum alloy pipes for rock drills are core components of rock drilling equipment, primarily used in the manufacture of impact pistons, cylinders, and gas pipelines. They require high strength, wear resistance, and lightweight properties, playing a key role in mining, tunnel construction, and construction rock drilling. Commonly used materials include high-strength aluminum alloys such as 2A12, 6061-T6, and 7075-T6. 2A12 aluminum alloy contains 4.0-5.0% copper, boasts a tensile strength of ≥420 MPa, and excellent impact toughness, making it suitable for impact pistons. 6061-T6, containing magnesium and silicon, offers a balanced balance of strength and corrosion resistance, making it suitable for cylinders. 7075-T6, containing 5.1-6.1% zinc, boasts a tensile strength of ≥500 MPa and is suitable for high-pressure gas pipelines. The pipes typically have an outer diameter of 20-80 mm, a wall thickness of 3-10 mm, an internal bore precision of H8, and a surface roughness of Ra ≤ 0.8 μm to ensure a precise fit between the piston and cylinder.
The production process for aluminum alloy tubes for rock drills requires a balance between strength and dimensional accuracy. First, high-quality aluminum alloy ingots (purity above 99.7%) are selected and homogenized (450-500°C for 6-8 hours) to eliminate compositional segregation. During the hot rolling process, the ingots are heated to 400-450°C and perforated to form rough tubes with an outer diameter 10-15mm larger than the finished product. Cold drawing or cold rolling is a key process, employing multiple passes with a deformation of 15-25% per pass. Carbide dies are used to ensure inner bore precision, and the cold drawing speed is 5-8m/min. For high-strength alloys such as 7075, intermediate annealing (300-350°C) is required to prevent cracking. The finished tubes undergo solution treatment (water quenching at 500-550°C) and artificial aging (120-180°C), achieving a hardness of HB120-150. Ultimately, it must pass water pressure test (≥30MPa no leakage), non-destructive testing (eddy current testing) and impact test (impact energy ≥25J) to ensure quality.
In the mining sector, aluminum alloy pipes for rock drills offer significant lightweighting advantages. The impact pistons of down-the-hole rock drills in large open-pit mines utilize 2A12 aluminum alloy pipes with diameters of 50-80mm, resulting in a 40% weight reduction compared to steel pistons. Energy consumption for rock drills at one mine has been reduced by 15%, and the equipment lifespan has been extended to 800 hours per unit. The cylinders of underground rock drills utilize 6061-T6 aluminum alloy pipes with wall thicknesses of 5-8mm, which are resistant to hydraulic oil corrosion. This has helped extend the downtime of rock drills on a tunnel project to 300 hours. The gas lines of small handheld rock drills utilize 7075-T6 aluminum alloy pipes with outer diameters of 20-30mm and compressive strength of ≥60MPa, improving the portability of equipment for a construction team by 30%.
Tunnel construction and stone processing place stringent demands on the fatigue resistance of aluminum alloy pipes. The impact pipes of shield tunneling machines’ rock drilling equipment utilize 2A12 aluminum alloy pipes. Shot peening increases surface hardness by 20%, resulting in a fatigue life of 100,000 impacts. This reduced equipment maintenance costs for a subway tunnel project by 25%. The pistons of rock drills used in granite mining are made of 7075-T6 aluminum alloy pipes, chrome-plated (5-10μm thick) for enhanced wear resistance. This has extended the piston replacement cycle at a stone processing plant to 150 hours. The guide pipes of micro-tunnel boring machines utilize 6061-T6 aluminum alloy pipes, with a straightness of ≤0.1mm/m, ensuring drilling accuracy (deviation ≤5mm). This has improved the construction accuracy of a municipal project by 20%.
As rock drilling equipment evolves towards higher efficiency and energy conservation, the performance of aluminum alloy pipes continues to improve. A manufacturer has developed a gradient-strengthened aluminum alloy pipe (2A12 inner layer + 7075 outer layer), which maintains both impact toughness and improved wear resistance. This has resulted in a 50% increase in piston life for a heavy-duty rock drill. For humid mining environments, a corrosion-resistant aluminum alloy pipe (with added chromium and nickel) has been developed, offering salt spray resistance for ≥1000 hours. This has reduced the rust rate of equipment at a coal mine by 60%. Using high-pressure forming technology, the pipe achieves H7-level dimensional accuracy, improving assembly efficiency for a rock drill manufacturer by 30%. In the future, with the development of new energy rock drilling equipment, aluminum alloy pipes will develop towards higher strength (≥600MPa) and lighter weight (density ≤2.7g/cm³), supporting the industry’s green transformation.
