In the use of surface hydraulic rock drilling jumbos, an MF rod is a common type of rock drilling tool. It has good adaptability, can adapt to different drilling operation requirements, and improves the efficiency and quality of drilling. However, because of the harsh service conditions of the drill rod, coupled with irregular use causing premature failure of the rods, failure analysis of the rods and development of precautions for standardized use are necessary to improve the MF rod process and provide standards for drill truck operators to standardize the use of drill rods.
What is a surface hydraulic rock drilling jumbo?
The most used type of rock drilling jumbo is the surface hydraulic rock drilling jumbo, which adopts the crawler-type walking mechanism, a single-arm drilling device, and provides hydraulic power and compressed air with the accompanying diesel engine as the power system. The hydraulic surface rock drilling jumbo adopts the extension rod set, with a set of six drill rods connected for rock drilling. The drilling jumbo has an automatic drill rod replacement mechanism, which can quickly and conveniently load and unload drill rods. It usually uses compressed air to discharge rock powder, and the drilling jumbo is equipped with dust collection equipment. It is widely used in large and medium-sized open-pit mining, quarry, road, and railway construction, water conservancy and hydropower construction sites, and various infrastructure construction projects.
Failure Mode of MF Rod Used in Surface Hydraulic Rock Drilling Jumbo
In drilling a rock hole, the drill rod connects the drill bit and the shank adapter and transmits energy to break the rock. After continuous drilling and use, various forms of failure of the drill rod can occur. Its failure forms mainly include wear of the internal and external threads, external thread fracture, internal thread longitudinal cracking, and rod body fracture. These different forms of rod failure will cause the drill bit or rod to fall into the rock hole and cannot be removed, resulting in waste holes and lost bits, reducing the productivity of rock drilling operations, increasing production costs, and making it difficult to bring the high efficiency of the hydraulic drilling jumbo into play.
Therefore, to improve and maximize the performance and service life of the drill rod of the surface hydraulic drilling jumbo, the following matters should be noted during the rock drilling process of the drill rod.
Precautions when using MF rods for surface hydraulic rock drilling jumbos
1. During the rock drilling process of the drill rod, lubricating oil is used when the internal and external threads are connected, which can lubricate and reduce wear, cool down, clean, rust and corrosion, shock absorption, stress dispersion and buffering on the internal and external threads, to reduce the internal and external thread surface ablation and wear, to avoid premature failure of internal and external threads. Moreover, drilling jumbo operators should take good care of the drill rod to avoid severe mechanical damage and wear on the surface.
2. In the surface quality control, strengthen the billet grinding and skinning process to clean up the surface defects of the billet as much as possible without generating new overheating or over-burning flaws to ensure the surface quality of the hollow steel.
3. Take effective guarantee measures in heat treatment and machining quality. Heat treatment quality should control the level of martensite, retained austenite, and reticular carbide, and the hardness distribution from the surface infiltrated layer to the matrix should be reasonable. The machining quality should control the matching tolerance of internal and external threads to avoid difficulties in loading and unloading, and the surface roughness must meet the requirements and avoid serious tool marks.
4. Forging quality problems of the internal thread of the drill rod (forging cracks, poor structure after forging, appearance defects) is the factor that causes internal thread failure. Therefore, there should not be forging cracks, overheating, overburning, folding, or other quality problems.
5. MF rod quality problems, MF rod internal and external thread connection, in the process of use, with the gradual wear of the internal and external threads, the internal and external threads with the gap gradually increased, under the action of tensile and compressive stress internal and external the threads “serial movement”, the frictional heat generation of the internal and external thread contact surfaces is intensified, and “hard points” and “jamming” are found, resulting in excessive force at the contact between the internal and external threads instantly. At the same time, when it is difficult to unload the rod, the drill truck operator usually starts the rock drill to “empty” the drill rod, making the internal and external threads loose, which will cause damage to the drill rod.
To sum up, production quality and use quality are the keys to determining the service life of MF rods. Therefore, in the manufacturing process of MF rods, it is necessary to strictly control the quality of smelting and rolling, machining, and heat treatment of drill rod raw materials. In addition, the extensive use of the drill rod will cause mechanical damage, resulting in rapid failure of the drill rod. Therefore, to standardize the use.
