3 ways to produce self-drilling anchor bars
Self drilling anchor systems are advanced anchoring systems, composed of high-strength fully threaded self-drilling anchor bars, anchor bits, anchor couplers, anchor nuts, anchor plates, and other necessary components. These systems can simultaneously execute drilling and grouting functions in loose soil and fractured rock.
The crucial component of the self-drilling anchoring system is the self drilling anchor bars, which is divided into R thread and T thread. R-type threads feature continuous corrugated profiles, typically designed according to ISO 10208 or ISO 1720 standards, with common sizes being R25, R32, R38, R51, etc. T-type threads are usually based on internal designs of each manufacturer and do not conform to any international standard, with common sizes including T30, T40, T52, T73, T76, T103, T111, etc.
There are 3 ways to produce self -drilling anchor bars: cold rolling, hot rolling, and warm rolling.
1. Cold Rolling
Widely used in European countries, this process employs low-carbon alloy steel pipes as raw material. Low-carbon alloy steel pipes inherently has lower hardness and strength but better plasticity, allowing it to be rolled at room temperature without heating. This rolling process refines the grain structure. As heating is not required, this method is more energy-efficient and environmentally friendly, and the quality is relatively stable. However, since it does not undergo heat treatment, the strength of the self-drilling anchor bars primarily depends on the strength of the steel pipes. To achieve adequate load capacity (mainly tensile and yield strength), these self-drilling anchor bars must maintain sufficient thickness, meaning a relatively heavier weight per meter or larger section area.
2. Hot Rolling
Evolving from cold rolling process, hot rolling is mainly used in countries like China, Turkey, Iran, and India. The self-drilling anchor bars formed by hot rolling generally use medium-carbon alloy steel pipes. Unlike cold rolling, hot rolling requires the raw material to be heated above the phase transition temperature (around 1000℃) before rolling, followed by rapid water cooling, essentially an incomplete quenching process. While this method enables the production of stronger self-drilling anchor bars with thinner steel tubes, it compromises the ductility of the self-drilling anchor bars. The self-drilling bars are stronger but less plastic and more brittle with a lower elongation rate. Furthermore, the equipment used in this process is often primitive, and due to large temperature variances in the environment, it’s challenging to control the exact temperature changes, leading to inconsistent dimensions and quality of the self-drilling anchor bars. If the quality requirement for self-drilling anchor bars is not high,, hot rolling can be economically beneficial for use in temporary support project, but is unsuitable for permanent project.
3. Warm Rolling
Warm rolling is an intermediary process between cold and hot rolling, usually also utilizing medium-carbon steel pipe as the raw material. This method requires heating the raw material to about 500℃ for rolling. It optimizes the properties of the steel pipe, balancing and ensuring strength while also achieving good ductility of the self-drilling anchor bars. Additionally, as the heating temperature is not very high, the dimensional control of the self-drilling anchor bars is more precise, and the quality is stable. Thus, warm rolling allows for an excellent balance between the toughness and ductility of self-drilling anchor bars, achieving superior overall mechanical properties.
As a professional manufacturer with over 20 years of production experience, Sinodrills possesses 8 full automated self-drilling anchor bars production lines. Our self-drilling anchor bars are dimensionally precise and consistently high-quality, ensuring strength and excellent toughness, fully reaching European standards, in some aspects even exceeding European standards. Our products are now widely used in railway, tunnel, rock bolting, infrastructure, and mining projects across Europe!
Anchor down your next project with Sinodrills’ self -drilling anchor systems!
