YSM - Leading Chinese excavator spare parts & machinery part supplier.
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YSM - Leading Chinese excavator spare parts & machinery part supplier.
(1) The greater the adhesive wear load and the higher the surface temperature, the more serious the adhesion phenomenon. For metal materials with a certain hardness, wear tests are performed under different pressures to obtain a graph of the relationship between wear rate and pressure. When the pressure reaches more than 1/3 of the hardness of the material, severe wear will occur. According to the stress distribution diagram, it can be seen that the maximum stress contact point is the maximum pressure, and its value is 884.4 MPa. Because the quenching hardness of the chain socket is HRC48~52, the corresponding hardness value is 4800MPa. Therefore, the pressure is far less than 1/3 of the material's hardness, so adhesive wear is not the main form of sprocket wear.
(2) Contact fatigue wear
The friction pair of the sprocket and the chain is an alternating contact stress, which is prone to fatigue pitting on the friction surface. The index for judging the contact fatigue strength of metals is the contact fatigue limit, that is, the maximum stress at which pitting corrosion does not occur under a certain number of stress cycles. The contact fatigue limit of 40Cr is σ0H=HRC17 +200 after surface quenching treatment, and σ0H=1016MPa is calculated. According to the stress distribution diagram, the maximum stress value of the sprocket socket is 884.4 MPa. Its value is very close to the allowable contact fatigue limit of the sprocket surface, and it is easier to cause pitting failure at the maximum stress. However, due to the poor lubrication conditions of the sprocket and the chain, pitting corrosion is too late to form and has caused wear. At this time, the main form of damage is wear rather than pitting. Contact fatigue wear is the main form of sprocket wear, which basically determines the service life of the sprocket.
(3) Abrasive wear
Because the chain inevitably comes into contact with pulverized coal, there is a small amount of pulverized coal on it, which is brought to the contact point of the sprocket chain socket. The pulverized coal contains a little sharp sand, which will cause the surface material of the sprocket to fall off during the friction process. This is abrasive wear. Abrasive wear is related to the hardness of the friction material and the hardness of the abrasive. From the graph of the influence of abrasive hardness on wear, it can be seen that when the abrasive hardness is close to the hardness of the friction material, it will cause high-speed wear of the friction material. Because the coal powder is mixed with a little sharp sand, this is also one of the main reasons for accelerating the wear of the sprocket.
