The drill rod is the core product of rock drilling tools and one of the main consumption tools of rock drilling equipment. It is mainly used in the mining and construction of railways, highways, canals, dams, and other projects. Its manufacturing material is hollow steel. Due to the different needs of rock drilling, hollow steel has various types.

1. Classified by section shape

There is hollow steel with round, regular hexagon, regular octagon, flat octagon, rectangle, round with ears, diamond, square, and cross-section.

Among them, rectangular hollow steel is specially used for making flexible drill rods. This drill rod is used in a very narrow working space. Because of its rectangular cross-section, the drill rod made of it can drill rock under a certain deflection,  thus solving the difficulty of the narrow working space.

The hollow steel with round ears and diamond section is used to manufacture coal drill pipes for coal mining. Hollow steels with other sectional shapes are used for rock drilling operations under normal conditions. Customers can choose drill rods according to application conditions and rock characteristics. After long-term drilling practice, hollow steel is mainly hexagonal and circular in section shape.

2. Classified by use

A. Hollow steel for manufacturing down-the-hole drill rods

For rock drilling operations with rock hole depth below 8m, most drilling works are carried out by single drill rods. Therefore,  from the stiffness, the effect of discharging powder, drilling speed, and other aspects of the drill rod, the hollow steel for such purposes adopts a regular hexagonal section. Because of the wide application range of DTH rock drilling, the requirements for drilling equipment, and other rock drilling conditions are low, hollow steel occupies a large proportion in drilling and blasting engineering, accounting for more than 70% of the total hollow steel consumption.

B. Hollow steel for the manufacturing of threaded extension rods for drilling medium and deep rock holes

For the rock drilling operation of drilling deep rock holes of more than 8m, it is necessary to drill by connecting multiple drill rods. Hollow steel with a circular section is often used to solve the connection structure and roll thread at both ends. To reduce the single weight of the drill rod and improve the power transfer efficiency of the rock drill, hollow steel with a normal hexagonal section is also used when the strength and stiffness permit. The amount of this kind of hollow steel accounts for about 20%-30% of the whole.

C. Hollow steel for manufacturing special purpose drill rods

Such as flexible drill rods, coal drill rods, etc., the amount of which is less.

3. Classification by steel type

So far, dozens of hollow steel grades have been used at home and abroad. If classified by steel type, there are only carbon steel and alloy steel. This is closely related to drilling conditions and use requirements.

The above is all the introduction of hollow steel types. No matter how they are classified, they are inseparable from specific drilling conditions and use requirements. With the continuous development of the market, people will have new demands. In this process, hollow steel will get new development, let us wait and see.