[Technology] Frequently Asked Questions! Summary of the attributes of excavator support wheels and analysis of the causes of damage---Quanzhou excavator guide wheels
Spindle spindle material is 50Mn high quality carbon structural steel, C content is 0.48%~0.56%, Si content is 0.17%~0.37%, Mn content is 0.7%~1.0%, S content is less than 0.035%, P content is less than 0.035% , Cr content is less than 0.25%, Ni content is less than 0.30%, Cu content is less than 0.25%. Among them, Mn is an important element in alloy steel, which can improve the forgeability and plasticity of steel, and can ensure that the material has sufficient toughness and wear resistance. After heat treatment, 50Mn steel has higher strength and hardness, excellent hardenability, deeper hardened layer, finer pearlite structure and better mechanical properties. ---Quanzhou excavator guide wheel
The spindle design standard requires that the depth T of the hardened layer is 2~7mm, and the quenching hardness is 50~62HRC, as shown in Figure 3.
The wheel track surface of the wheel body support wheel is subjected to frequent impact loads and is prone to extrusion deformation, which makes the wheel body track surface extend into a conical shape. In order to improve the stress condition, we have lengthened the track surface of the wheel body, and designed the transition between the track surface and the wheel waist as an inclined surface to improve the supporting capacity of the track surface. The shaded part shown in Figure 4 is the extended track surface and transition Incline.
In order to improve the wear resistance of the roller body, the wheel body material is 40Mn2 alloy structural steel. The C content is 0.37% to 0.44%, the Si content is 0.17% to 0.37%, the Mn content is 1.4% to 1.8%, the P content is less than 0.030%, and the S content is less than 0.030%.
The wheel body is formed by forging, and the roughness of the wheel body is quenched and tempered after forming, with a hardness of 26~32HRC, in order to maintain the high strength, plasticity, toughness and comprehensive mechanical properties of the wheel body. The surface of the wheel body is quenched to improve the hardness and wear resistance of the track surface of the roller. The quenching hardness is 50~58HRC, and the depth of the hardened layer is 6~12mm, so that the rail surface hardness is basically close to the chain rail link hardness (48~58HRC). ---Quanzhou excavator guide wheel
The size and surface roughness of the ring groove of the sealing O-ring should meet the design requirements, the mating surface should be chamfered, and the burrs and sharp edges should be cleaned.
Floating seal rubber ring and O-shaped sealing ring should be made of high-quality nitrile rubber. The inner diameter, wire diameter, elasticity, hardness (Shore), and surface finish should meet the standards. Before assembly, the above items should be inspected one by one before they are qualified. Put into assembly.
If the floating seal ring does not cover the ring groove of the floating seal ring, or does not adhere to the floating seal ring, the floating seal ring will exert uneven pressure on the floating seal ring. Uneven pressure will increase local blade surface wear when the floating seal ring rotates, resulting in oil leakage of the floating seal ring. If the edge of the O-ring seal is cut badly when assembling the inner and outer covers, the half of the O-ring is stuck outside the ring groove, or is twisted when installed in the ring groove, the sealing performance or service life of the O-ring seal will be reduced. Sometimes, if the airtightness check pressure does not reach a certain value, no leakage will be detected, and no leakage will occur after oil filling. However, after the excavator has been working for a certain period of time, the friction of the various components of the roller will increase, and the internal cavity pressure will rise to a certain value. , There will be leakage. If you continue to use it after a leak occurs, the floating oil seal will leak seriously. ---Quanzhou excavator guide wheel
Clearance The gap between the main shaft of the roller and the sleeve on the wheel body is 0.2~0.4mm, there should be no blocking when rotating, the sealing performance is good, and there is no oil leakage.
For lubrication, use an oiler to fill the roller with gear oil, and if necessary, increase the viscosity of the lubricating oil. Before adding gear oil, drain the failed gear oil first, and then add new gear oil into the oil plug hole until the oil flows out. When adding lubricating oil, unscrew the screw plug at the shaft end, put the end of the lubricating nozzle of the lubricator against the inner shoulder of the oil passage, and inject oil into the oil passage. When installing the oil plug, a torque wrench is required to control the tightening torque of the oil plug within the range of 157~255Nm.
2. Analysis of the cause of damage
This article takes a 20t excavator from a certain manufacturer as an example to analyze the cause of damage to its supporting wheels. We inspected the partially damaged support wheels of the excavator and found that the main faults were mainly damage to the main shaft and wheel body and oil leakage. Among them, the heavy-damaged main shaft of the supporting wheel appears to hold the shaft, causing the entire supporting wheel to be unable to rotate. Now we will analyze it separately. ---Quanzhou excavator guide wheel
(1) Spindle damage
There are two reasons for the analysis of the oil leakage of the supporting roller: one is that the supporting roller is soaked in water for a long time during the operation of the excavator, causing the floating seal ring and the O-ring ring groove to be corroded; the second is the construction in muddy water in winter. Cause the floating seal ring to freeze and fail. ---Quanzhou excavator guide wheel