A, carbide head embrittlement
1, carbide head of quality problems, domestic cemented carbide graphite impurity is contained in the head, uneven distribution of grain size, cracks were found to exist in the part of the carbide, under the action of impact load, the cutting blade in high stress state, when faced with hard coal and rock, high pressure stress exceeds the ultimate strength of the cemented carbide occurs brittle fracture. If Co elements content in cemented carbide is insufficient, lead to insufficient toughness, under the action of impact load, carbide cutter head is also easy to brittle fracture.
2, qian welding residual stress is big, the domestic cutter tooth with copper zinc solder, the welding temperature is above 920 degrees Celsius, hard alloy, solder and the expansion coefficient difference between base metal, the three kinds of different degree of material shrinkage when cooling, with copper maximum shrinkage, findings and the substrate metal carbide minimum, this inevitably in cemented carbide and solder, solder and substrate metal between the large tensile stress, resulting in a decline in weld strength and cutting by powerful impact load, cause carbide head embrittlement.
Second, the tooth wear
1, the abrasive wear. Domestic some alloying elements content in alloy can not meet the requirements, graphite impurities, uneven distribution of grain size, porosity, organization is not uniform, this is the main cause of cemented carbide head wear; The tooth body material quality performance is not stable, improper heat treatment process control is the cause of the tooth body wear.
Caused by 2, red hardness, low wear and tear. Red hardness refers to the props material's ability to maintain high hardness at high temperature. Carbide can theoretically in 800-1000 ℃ high temperature to keep high hardness, but as a result of domestic cemented carbide production there are some realistic problems makes the red hardness of low. When cutting tooth cutting coal and rock, the surface temperature of the cutting tools can reach 600-600 ℃, its hardness fell by around 50%, material softening of accelerated the tooth wear.
Third, carbide head easy to fall off.
Due to welding and shape design, alloy head loss.
