The cutting pick is part of a mining and excavating machine, mainly used for coal mining and excavation of roadways, tunnels, ground trenching, and other projects. Since it is one of the most consumed accessories in mining equipment, improving the service life of the cutting pick can help improve the mining efficiency.
Brazing and heat treatment
The coal mining cutting pick is consisted of cemented carbide head and a skirt body, which are brazed and welded together. Brazing quality affects the service life of cutting picks, and the shear strength of the weld after brazing should meet the requirements of the cutting pick. When brazing, the temperature is generally required to be 25-50℃ higher than the melting point of brazing material. If the temperature is too high, it will easily cause defects such as overburning and corrosion of the cemented carbide head. If the temperature is too low, it is easy to make brazing difficult and produce defects, and the weld quality is not guaranteed. Brazing material selection of copper-based brazing material most, and copper-based brazing temperature in the range of the phase change of alloy steel, the use of residual heat after welding can be heat treatment of the cutting picks. Therefore, choose the brazing material liquid phase line temperature or brazing temperature higher than the heat treatment heating temperature of the skirt body material, after brazing, the trunnion can be heat treated in the heating, improve the performance of the skirt body material and increase the service life of the trunnion. If the liquid phase line temperature of brazing material or brazing temperature is lower than the heat treatment heating temperature of the skirt body, the heat treatment of cutting picks cannot be carried out again to avoid affecting the shear strength of the brazed seam of cutting picks.
Surface modification of cutting picks
An effective measure to improve the service life of the cutting pick is to modify the surface of cutting pick face to improve its impact resistance and wear resistance performance. The main methods for the surface modification of the cutting pick are thermal spraying of the main wear parts, plasma beam surface metallurgy, laser coating, and surfacing of wear-resistant alloy, etc.
Thermal Spray Technology
Thermal spraying technology is a surface processing technology that uses a heat source to heat the spraying material to a molten state and blows it through the airflow to make it atomized and sprayed to the surface of the part at high speed to form a spraying layer. With this technology, a layer of high hardness wear-resistant alloy is spray-welded on the head of the pick body. The alloy layer has good metallurgical combination with the pick body of cutting picks, which has the advantages of impact resistance and high wear resistance. Its service life is about 0.5-1.0 times higher than the traditional inlaid carbide cutting picks.
Plasma beam surface metallurgy
Plasma beam surface metallurgy is to use the high temperature of the plasma beam to form a molten pool of similar size to the beam diameter on the surface of the truncated tooth in rapid sequence and to feed the alloy powder into the plasma beam or the molten pool simultaneously. The coating is bonded to the substrate metallurgically. The plasma beam surface metallurgy on the pick body of cutting picks has obtained a 3-4mm wear-resistant layer, which has increased the service life by more than two times compared with the same type of cutting picks produced by the traditional process.
Laser coating
Laser coating technology is to use laser high-energy beams to quickly heat the coating material on the surface of cutting picks so that the coating material can melt on the surface layer of skirt body, and achieve rapid solidification through the skirt body cooling effect, to obtain a coating with high hardness, wear resistance, and impact resistance. The cladding material mainly uses impact-resistant and wear-resistant materials. The thickness of the cladding layer is 0.2-2.0mm at one time, and the service life after cladding is 6-7 times higher than that of ordinary cutting picks.
Surfacing technology
The surfacing welding technology is to surface a layer of wear-resistant materials such as high-alloy electrodes (wires) containing chromium, tungsten, molybdenum, vanadium, and other elements on the part of the skirt body covered with cemented carbide, generally along the circumferential direction of the trunnion cladding cemented carbide part of a circular belt with a width of about 20-30mm, using the high hardness of the cladding layer alloy to improve the wear resistance and service life of the trunnion.
