Application of H22 Integral Drill Steel

1.Preface
In the past, the drilling team of Henan Geological Bureau purchased carbon steel or alloy steel drill steel and processed the drill rods by themselves. Due to the lack of talents and equipment for specialized production, the latest scientific and technological achievements and comprehensive quality management could not be adopted. As a result, the processed drill rods were of poor quality, causing the drill rods to be prone to fatigue fracture, short service life, and the drill tail to be hard or soft, increasing the failure rate of rock drills and the consumption of accessories; the water needle often broke; the drill tip was easy to break, and it did not match well with the drill head cone hole, and the drill head was often damaged or lost, etc. From July to August 1981, the workers used the H22 55SiMnMo Integral Drill Steel produced by Guiyang Steel Plant provided by the drill head research group of Wuhan Institute of Geology, and the feedback was very good. It not only saved steel and resources for the country, but also brought new prosperity to the modernization of my country's rock drilling tool industry.

2.H22 55SiMnMo Integral Drill Steel
The 55SiMnMo Integral Drill Steel produced by Guiyang Steel Plant and Xinfu Steel Plant is one of the scientific research achievements of the Drilling Steel Technical Working Group and Drilling Steel Technical Cooperation Group of the Ministry of Metallurgy over the past decade. It combines my country's resource conditions and absorbs advanced foreign experience. It has stable quality and has become a representative product that marks the development level of my country's drill steel industry.  

H22 Integral Drill Steel were awarded the title of Guizhou Province's high-quality products in 1979, and their life indicators have entered the ranks of international advanced levels. In 1979, a large number of comparative tests were conducted in the hard granite of f=12~16 in Xihuashan Tungsten Mine in Jiangxi Province, and the results showed that the average drilling life of H22 55SiMnMo drill rods was 169.2 meters, which was 66.5% higher than the average life of Japanese drill rods of 104 meters.

In May 1981, according to a report by Hong Kong Lidian Trading Company, the product "has been certified by international product inspection agencies such as Japan and Hong Kong, and its quality has reached international standards, and both the testing and use departments are satisfied."

Compared with the drill rods processed by themselves, the domestic mining departments that use H22 Integral Drill Steel can reduce the consumption of drill rods by 50~70%; the consumption of rock drill spare parts is reduced by more than 50%; the rock drilling time can be shortened by 20~30%; and the labor intensity of workers is also greatly reduced. Therefore, H22 drill rod has been well received by domestic users.

3.Rock drilling
Time: July 16 to August 28, 1981.

Location: Yangping mining area, vein 5, Xiaoqinling gold mine, Lingbao, Henan.

The rocks are fine-grained mylonitic granite, biotite hornblende gneiss, siliceous quartz and gold-bearing quartz veins, with an average sub-VII to VIII grade, f=10~14, and a uniaxial compressive strength of R=1275.8 kg cm². The tunnel section is 2x1.8 m².

Use 7655 rock drill and FL140 air leg to advance.

Use self-made T8 carbon drill rod and H22 55SiMnMo Integral Drill Steel from Guiyang Steel Plant (in order to match the new drill head, a fine turning drill tip is used: the tip diameter is ∅18.5~19 mm, the insertion depth is 32~36 mm; the tip surface finish is ▽5, no longer heat treated; a 0.1~0.15 mm thick copper liner is installed between the drill tip and the drill head cone hole). The drill bits are new horseshoe, cross (II) and ball-tooth types produced by Chengdu Prospecting Machinery Factory, with diameters of ∅40 and ∅42 mm. The working air pressure is 5~6 kg/cm². The sliding hammer drill unloader of the Institute of Geology is used. The rock driller level is 2~4.

4.Result analysis
As shown in Figure and Table 2, the 14 homemade carbon steel drill rods have not been used up (the 14 carbon steel drill rods were scrapped after only five days of drilling). The minimum rock drilling life of the Integral Drill Steel is 85.25 meters/rod, and the maximum is 484.92 meters/rod (still not broken), which is expected to exceed 500 meters/rod. The average life has exceeded 256.97 meters/rod, which is 5~6 times that of the homemade carbon steel drill rods. The consumption of drill steel per meter of tunnel has also been reduced to less than 0.48 kg/m, which is only 15~25% of the homemade steel drill.

If the unit price of H22 55SiMnMo Integral Drill Steel is 3843 yuan/ton and the unit price of processed homemade carbon steel drill rods is 1500 yuan/ton, the purchase of one ton of Integral Drill Steel and the processing of five tons of carbon steel drill rods are compared. The cost of drill steel consumption alone can save the country 3657 yuan.

After having a good drill rod, there is still the problem of tool matching and careful use. This application would not have been possible without high-quality new drill bits, reasonable methods for connecting and removing the drill tips, careful management of the drill rods (anti-rust, anti-bending, anti-surface damage, anti-clogging of water holes, and anti-loss), and timely repair of broken tips. From the perspective of improving service quality and sales services of manufacturers, we suggest: (1) In order to match the parameters of the new drill bits and the tapered hole insertion depth provided by international standards and facilitate the use of drill removers, the drill tips of H22 Integral Drill Steel should not be roughened. They can be processed by fine turning or fine grinding before overall heat treatment, and then surface hardening treatment can be performed. At the same time, the diameter of the small end of the drill tip should be changed from ∅21 mm to ∅18.5~19 mm; (2) In order to facilitate users, a system of recycling and repairing broken drill rods (changing long drills to short drills) and only charging processing fees should be established.