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Characteristics of slotted drill pipe for integral spiral drill pipe
Release time:
2018-05-11
Author:
Source:
When the welded spiral drill pipe is drilled into the soft coal seam with wind pressure, the spiral wing is easy to crack, desoldering and wear-resistant, which leads to the problems of difficult hole formation and even scrapping. The spiral groove is processed in the thick-walled pipe by milling chips, the drill pipe joint is improved, the thread is surface treated, and the integral spiral drill pipe is developed. The field test results show that the integral spiral drill pipe has good comprehensive mechanical properties, strong hole-forming ability and long service life, which can not only replace the welded spiral drill pipe for wind pressure drilling in soft coal seam, but also replace the regular outer flat drill pipe for rock drilling.
For welding typeauger drill pipeWhen drilling into soft coal seam with wind pressure, the spiral wing is prone to cracking, desoldering and wear-resistant, resulting in problems such as difficulty in forming holes or even scrapping. Spiral grooves are machined in thick-walled pipes by milling chips, drill pipe joints are improved, thread surface treatment is carried out, and integral type is developed.auger drill pipe. The field test results show that the integral spiral drill pipe has good comprehensive mechanical properties, strong hole-forming ability and long service life, which can not only replace the welded spiral drill pipe for wind pressure drilling in soft coal seam, but also replace the regular outer flat drill pipe for rock drilling.
Problems encountered in drilling soft coal seam
Soft coal seam refers to the coal seam with coal hardness coefficient f<1, which has the characteristics of soft coal, poor permeability, high gas content and high pressure. In the process of gas drainage drilling construction, accidents such as injection hole, hole collapse and holding drilling are easy to occur, which leads to problems such as shallow drilling depth, low hole formation rate and poor gas drainage effect [1], which have become the problems to be solved urgently in coal mine safe and efficient mining.
In the long-term drilling practice, some domestic coal mining enterprises have carried out the test and application of soft coal seam air drilling technology. After using the wide wing spiral drill pipe with wind pressure drilling technology, the hole depth and hole rate of soft coal seam have been greatly improved, and the wind pressure air drilling technology has become an effective and feasible drilling construction technology in soft coal seam.
At present, wide-wing spiral drill pipe is widely used in China, and spiral wings are mostly processed by hot melt welding. This processing method requires a high level of welding technology, and the controllability and stability of welding quality in the actual processing process are poor. Affected by the level of welding process, it is inevitable to produce "over welding" or "off welding" and other problems. "over-welding" will cause damage to the rod body, and fracture is prone to occur along the welding seam between the spiral fin and the rod body during use. "off-welding" is the fall-off of the spiral fin when the drill pipe is used due to substandard welding quality. In addition, hot melt welding has high requirements on the material of the rod body and the spiral fin. In order to ensure good welding between the spiral blade and the drill pipe body, the material properties of the two need to be optimized. If selected at will, in addition to the abnormal phenomena such as over-welding and desalding, it will also cause the drill pipe spiral fin to wear too fast, which greatly reduces the service life of the drill pipe.
Manufacturing Process of Integral Spiral Drill Pipe
This kind of drill pipe adopts the whole milling method to mill out the thick-walled pipe. The development and application of the integral spiral drill pipe have certain parameters of the spiral groove, thus forming the spiral wing. Due to the use of CNC milling machine processing, can effectively control the spiral groove machining accuracy, the formation of the spiral wing and rod body as a whole, its material and drill pipeThe parent material is the same, and the wear resistance is greatly improved, which completely solves the problems of traditional welded spiral drill pipe over-welding, poor welding, and rapid wear of spiral fins.
Features of integral spiral drill pipe
1) The applicability of full hydraulic drilling rigs in regular coal mines, that is, the use of drill pipes does not require modification of existing drilling rigs, and will not increase drilling construction procedures and labor intensity of workers;
2) The single-head, double-head or triple-head spiral milling groove shall be arranged in the axial direction of the drill pipe to ensure not only the overall strength of the drill pipe, but also the ability of the drill pipe to stir powder and discharge powder.
3) The joint adopts double-top structure and adopts trapezoidal tooth type. The tensile strength and torsional strength are increased by 30% and 40% respectively compared with the regular drill pipe. Considering the use of rapid hole-protecting screen technology in soft coal seam, the joint is designed with regular diameter and large diameter.
4) The main parameters of spiral milling groove are milling groove depth, width and milling groove structure. The depth and width of the milling groove refer to the welded wide-fin spiral drill pipe fin, and the milling groove angle adopts arc transition to reduce stress concentration.
5) The joint adopts friction welding technology. The technology has the characteristics of high quality, high efficiency, energy saving and no pollution, high degree of mechanization and high production efficiency.
6) The joint adopts heat treatment process to heat treat the weld heat-affected zone to improve its comprehensive mechanical properties.
7) The integral spiral drill pipe adopts ordinary tempering heat treatment process.
8) The threaded surface treatment joint is the weak link of the drill pipe, and the joint buckle is the most common failure form. The surface hardness of the thread of the integral spiral drill pipe can reach HRC45-50 after surface hardening treatment, which is about 50% higher than the HRC30-35 hardness before surface treatment, which greatly improves the anti-galling performance and wear resistance of the thread.
Key words:
Yiguang Science and Technology Integral Spiral Drill Pipe
