The drill rod is limited by the diameter of the hole in the drilling and blasting project, and its cross-sectional area is small. The elongated rod is subjected to high frequency and high impact rock drill under the condition of severe wear and corrosive medium. Apply cyclic stresses such as pulling, pressing, bending, and twisting. Depending on the load size and rock solidity conditions, the rock drilling life often ranges from a dozen hours to more than one hundred hours. It is the most demanding condition, short service life and technical content of all human mechanical tools. Engineering tools that are expensive and expensive for basic industries.
Therefore, in order to improve the service life of the drill rod and reduce the cost of the drill loss, we must not only consider the product itself, but also analyze the external conditions of the product, because the manufacturer produces qualified solder products, a high The life cycle of the quality drill rod has gone through several processes: steel making – continuous casting round billet – drilling – core – blanking – rolling – core pulling – forming – forging – machining – heat treatment – surface strengthening – finishing – Anti-corrosion treatment – inspection – marking factory, any abnormality in any link can determine the length of the life of the drill rod. Although the manufacturer strictly checks and monitors each link in real time, it produces high-quality drill rods; however, 80% of the quality of the drill rods depends on the environment and users.
As a user of each tool, it is hoped that the minimum cost will be used to obtain the maximum profit, which requires the reduction of the loss of the tool; therefore, the manufacturer and the user of the tool should cooperate closely to discuss the improvement of the rock drilling tool. The service life is jointly proposed.
1. From the user’s point of view, the choice of the drill product should have the following characteristics:
(1) High-quality soldering products: It is usually required that the solder tail products have a high life to reduce the time for disassembling and replacing the solder tails. The requirements for the drill rod and the drill bit are also quite high, because the drill rod fracture not only loses the drill rod, the drill bit, but also causes the waste hole. Due to the high degree of automation of the hydraulic rock drilling rig, the operator does not need to pay a large labor intensity in normal production, and disassembling the replacement of the shank, salvaging the broken drill rod or grinding the boring head not only wastes man-hours but also increases the operation. Labor intensity and labor costs. Therefore, when selecting a soldering product, the user pays attention not only to the price of the product but also to the quality of the product.
(2) Optimal rock drilling rate: In the trolley operation, except for the labor compensation and the purchase cost of the drill, the other working hours cost is regarded as the fixed cost, and the cost of the drilling tool is high in the rock drilling operation. Therefore, increasing the rock drilling speed means lowering the construction cost, so the user attaches great importance to increasing the rock drilling speed.
(3) The minimum blasthole skewness: In the medium-deep hole rock blasting, the blasthole deflection means that the charge is reduced and the blast hole spacing is shortened, which leads to a decrease in the amount of mining. Therefore, the user Straightness is very high and is usually controlled within a small error range. The main cause of the deflection of the blasthole is the hole error during drilling, the calibration of the blasthole error and the flatness error generated during the rock drilling process. In the full hydraulic rock drilling rig or computer controlled hydraulic drilling rig rock drilling The first two errors can be basically eliminated, and the blast hole deflection is the main reason due to the structure of the drill product. As the depth of the hole is deepened, the degree of deflection will be intensified, eventually causing the waste hole, reducing or eliminating the blast hole. The best way to deflect is to use a guided rock drill.
2. Analysis of causes of loss of soldering tools
(1) The drill set is different
The different ends between the drill tail, the connecting sleeve and the drill rod cause the bending deformation of the drill, resulting in stress, which causes the joint of the drill set to not cooperate, causing the joint to be loose.
(2) Propulsion pressure
?? The pressure is too low, so that the rock penetration efficiency is reduced, causing the combination to loosen, causing the energy loss transmitted by the drill set, causing great stress, causing instantaneous contact and separation of the contact joint end face. The performance of insufficient propulsive pressure is that the brazing material is hot, the joint is “squeaky”, the overheating makes the thread wear abnormally, and the melting pit appears.
If the pressure is too high, the bit rotation speed is low, there is a risk of stuck drilling, and the bending stress of the drill pipe increases.
(3) Impact pressure
If the impact pressure is not properly adjusted, it will directly affect the speed of rotation, the efficiency of rock drilling and the life of the tool.
(4) Swing speed
The speed of rotation should match the diameter of the drill bit and the impact frequency of the rock drill. The larger the drill bit, the lower the swing speed and the higher the swing speed will damage the periphery of the drill bit.
(5) Swing pressure
Normal swing pressure is very important. It not only provides proper anti-card protection for the drill pipe, but also guarantees a certain amount of swing pressure. The increase of the rotary pressure is the key factor to maintain the tightness of the drill set. The tightness is not enough, which often causes the joint to heat up, the surface of the thread peels off, and the thread is worn or even broken early.
(6) Improper use
After use, the combination of the drill will shorten the service life of the drill if it is used together with the new drill. In addition, the alignment will be misaligned, the thread will have sediment, and the thread will not damage the drill when the thread is connected. “Air strike” damage to the drill is the most serious and should be avoided as much as possible.
3. Relationship between rock drilling parameters and rock drilling effect:
Impact pressure: The higher the pressure, the higher the piston speed and the greater the energy generated. When the drill bit is in good contact with the complete hard rock, the shock wave energy can be utilized to the maximum. Conversely, when the drill bit and the rock are not in good contact, the energy cannot pass away from the drill to the rock and is reflected back to the drill chain as a tension wave. Only when drilling on a rock that is hard enough can the maximum energy per impact be utilized. In order to reduce energy reflection when drilling soft rock, the impact pressure or energy must be reduced. The greater the impact pressure given, the greater the stress in the cross section of the drill pipe. In order to make the life of the drill rod and the shank as long as possible, it must be ensured that the working pressure is matched with the drill chain at any time.
Propulsion pressure: The purpose of propulsion is to make the drill bit and the rock in close contact, while the drill bit can also rotate. Propulsion must be reasonably matched to the impact pressure. The correct propulsive force can make the drilling the most economical; the pushing pressure is too low, the penetration speed is reduced and the threaded joint of the drilling tool is loose; the noise of the connecting sleeve overheating and generating the clucking indicates that the propulsion pressure setting is too low; if the connecting part Continued drilling after loosening will increase the energy loss, and the temperature of the connecting sleeve will be too high, which will cause the threaded joint of the drilling tool to ablate and break. If the propulsive force is too large, the rotation speed will decrease, the penetration rate will also decrease and the card will be brought. Danger of drilling; there is also the risk of borehole deflection because the propulsive force is too large and the drill chain tends to bend.
Swing speed: The purpose of the slewing is to turn the drill bit to a new position for the next impact. When using a cylindrical tooth drill, the circumference between the two impacts is about 10 mm. Therefore, the speed must be adjusted according to the impact frequency and the diameter of the drill. The larger the drill diameter, the lower the speed should be. Excessive speed can cause excessive wear on the teeth of the drill bit;
|Pressure range||Impact range||General value|
|Impact pressure||high||160-220 bar||180 bar|
|low||110-150 bar||120 bar|
|Advancing pressure||high||70-90 bar||80 bar|
|low||40-50 bar||40 bar|
|Swing pressure||40-60 bar||50 bar|
|Buffer pressure||40-60 bar||45 bar|
|Rotating speed||D51-89mm bits||110-150 /min||110 /min|
4. During the use of the drill, the following points should be noted:
(1) Before entering the pole, adjust the appropriate impact pressure, propulsion pressure, swing speed and buffer pressure according to different geological rock layers, and adjust the pressure values to match the geological rock layers and rock hardness between the pressure values.
(2) When punching, the drill set should be concentric, avoiding bending deformation of the drill tail, the drill rod and the drill bit.
(3) Avoid the phenomenon of empty play, stop the punching immediately after the air strike, and avoid excessive damage to the drill.
(4) After the drill rod is punched, each of the drill rods that are retracted should be coated with cooling lubricant in the threaded end of the drill rod and the quick interface. After the drilling of the blasting hole is completed, the threaded joint of the drill rod is heated. There are some gravel blocks and mineral water, and the cooling oil is applied to lubricate, cool down, prevent corrosion and improve the wear resistance of the thread.
(5) During the process of retracting, try to avoid repeated vibrations (this operation is one of the most serious causes of damage to the drill pipe). When the threaded joint of the drill rod is difficult to loosen, the first time is threaded. Inject the lubricating oil, then retract the rod or loosen the vibrating rod to reduce the direct damage to the thread of the drill rod during the vibrating process. When the vibrating rod is used, the rock drill will transmit the impact pressure of nearly 200 bar, and the continuous action of the high frequency impact pressure Underneath, causing stress concentration, repeated vibrations lead to high temperature and high heat will cause cold welding spot burning at the threaded end of the drill rod, that is, ablation pit, and even reach the melting temperature of the metal to form an etch pit, thereby forming a fatigue source leading to early failure of the drill rod.