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Taper drill rod H22*108, H25*159 (55SiMnMo)
- Shank size: H22*108, H25*159
- Length: 400,800,1600,1800,2400,3200mm etc.
- Taper Degree: 7°, 11°, 12°.
- Materials: 55SiMnMo
- 1. Hollow Drill Steel Rolled :
- 2. Steel Making Process with Electric Furnace :
- 3. The raw material is free from radioactivecontamination :
- 4. Material free from mercury contamination :
- 5. No welding or weld repair:
Rock drilling tools Tapered Drill Rod is to provide a hexagonal chuck section to provide leverage for the rotation chuck bushing. It usually has a forged collar to maintain the proper shank striking face position in the rock drill, and a tapered drill bit end. Tapered steel lengths are measured from the collar to the bit end. Holes are usually drilled in 0.6 m increments to accommodate the air leg feed length. The drilled steel is extracted and followed with a slightly smaller diameter rock drill bit on the next steel length in the sequence.
Carburization is a process used to harden the entire tapered drill rod surface both internally and externally to strengthen and extend the life of the tapered drill rod.
Shank Hexagon: 19*108 mm, 22*108mm, 25*108 mm, 25*159 mm; 6, 7, 11, 12 degree taper in most lengths, taper degree of drill steel is mostly imports for excellent drilling productivity.
For drilling medium-hard to hard and abrasive rock formations, taper angles of 11 and 12-degrees are normally used on modern drill rigs, like our model no. PD-Y58 crawler hydraulic rock drill. Also for Y6, Y10, Y24, YT24, Mobile rock drills pneumatic and hydraulic. For low impact rock drills and softer rock formations, a narrow tape range of 7 degrees is used, such as Indian, Saudi’s granite and marble quarry. A comprehensive range of taper button bits, cross bits and chisel bits with 6, 7, 11, 12 degree taper, drill hole diameter: 28mm-57mm.
Tapered rod insert to tapered drill bits:
Steel for Tapered Drill Rods and Integral Drill Rods
Tapered connection drill rods and integral drill rods generally refer to those made of H22 and H25 hexagonal hollow steel billets, which are suitable for short-hole drilling operations with small pneumatic or hydraulic rock drills.
Integral drill rods are those with cemented carbide inserts on the head, and they are widely used in both developed and some developing countries. The head of a tapered connection drill rod is conical, and it can only perform drilling work when connected and matched with a drill bit with a tapered hole. Almost all short-hole drilling operations in China adopt tapered connection drill rods, which are also applied in Canada and some other developed countries.
The most widely used steel grade for such drill rods abroad is 95CrMo, which belongs to the alloy tool steel category, with 95Cr and other grades in the same category. Alloy structural steel grades include 40SiMnCrNiMo, 38CrNi3Mo, 38SiCrV, 40MnMo, etc. A few countries also use spring steel such as 55Si2Mn and carburized steel such as 18CrNi3Mo. After long-term screening in China, 55SiMnMo, a type of spring steel, is regarded as an ideal steel grade. T8 and T8Cr steels, which were widely used in the early days, have now been basically phased out.
The main requirements for steel grades of tapered drill rods and integral drill rods are as follows:
- High fatigue strength combined with good toughness.
- Low notch sensitivity and low fatigue crack growth rate.
- Capable of achieving a hardness of around HRC 40 under controlled rolling and controlled cooling or normalized conditions to ensure the elasticity of the drill rod; reaching a hardness of HRC 50–54 after quenching and tempering to prevent the drill shank from mushrooming or bursting under the impact of the rock drill piston.
- Low decarburization tendency during heating.
For more details please watch PDF online: Tapered Drill Rod for Small Hole Drilling Catalogue
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