The bit contacts and breaks the rock mass during drilling, and will be subjected to huge impact loads and abrasive wear. The working conditions are extremely harsh, so the requirements for the bit body steel are also special. Requirements include: good dimensional stability and machinability; the material has high fatigue strength and wear resistance, and high air cooling hardenability; in the heat treatment state, the material has high plasticity, toughness, and hardness; in addition, it must have a high coefficient of linear expansion and tempering stability for tooth fixing, and high-strength physical properties to ensure high tooth fixing ability; it also needs a certain high-temperature strength and thermal stability to ensure the tooth fixing strength during use. In summary, the bit body material should be high-quality alloy steel with good thermal expansion, rigidity, toughness, machinability, and heat treatment properties.

(1) Strengthen the edge teeth, correctly select the tooth shape, tooth diameter, tooth height, wall thickness, etc.;

(2) Appropriate edge tooth inclination angle, generally 30°-35°;

(3) Increase the number of edge teeth or inner teeth where possible;

(4) Select high-toughness hard metal for edge teeth;

(5) Correctly select the interference fit of the teeth;

(6) Reasonable tooth arrangement, improved dust removal system, reduced repeated crushing, and strengthened the bit body to increase the wear resistance of the bit body.

Table 1 Matching Range of Rock Drill Impact Energy and Bit Diameter

Correct bit removal: It is strictly forbidden to remove the bit by hammering with a hand hammer, otherwise it will aggravate the bit expansion, cracking, waist breakage, tip breakage, and alloy tooth breakage. It is recommended to use a bit remover, which is beneficial to improving the bit life.

Reasonable bit sharpening: When drilling in soft or medium-hard rocks, ball tooth bits generally do not need to be sharpened. However, in rocks with high frontal abrasiveness, the alloy teeth of the bit wear out very quickly. When the worn flat reaches 2/3 of the tooth diameter, the bit stress deteriorates, and the drilling speed decreases. At this time, the bit must be sharpened. Timely sharpening of the bit helps to reduce surface cracks and prevent crack propagation.

Skilled operation of the rock drill by the operator, correct operation and use, such as slow advancement when opening holes, full-speed operation after the bit enters the rock mass, and preventing some alloy teeth from "air striking" hard rocks, causing a sharp increase in the stress on the alloy teeth; when connecting rods, keep the drill rod sleeve and drill tail concentric, tighten the threads, and do not hammer the drill when clamping the drill. Instead, use a small air intake valve, open the water valve, slowly advance, and constantly reciprocate to make the hole wall smooth, so that the drill can move freely, to prevent hard alloy pieces from breaking, drill tail breakage, sleeve cracking, drill rod breakage, and eliminate jamming accidents.

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