Repair techniques and methods for three-wheeled bulldozers

The three wheels and the belt of a bulldozer are consumable parts. According to their designed service life and construction conditions, their service life is limited to a certain period, which is often much shorter than the normal service life or major overhaul period of other parts of the bulldozer. For the three-wheeled parts of imported large bulldozers, if the method of discarding the old and replacing them is adopted, the price is relatively high, the maintenance cost is too large, and the residual value of the old parts is also wasted. If reasonable repair methods can be adopted, the update cost can be significantly reduced, and its service life can be guaranteed. At the same time, it is also much more cost-effective in terms of performance and price compared to using imported non-original factory parts or domestic parts. The following is a brief introduction to the repair process, equipment and effect of the three-wheel belt of Caterpillar bulldozers:

1. The methods and techniques of restoration

The wear in the three-wheel belt mainly refers to the rolling and sliding wear between the track surface and the outer housing of each wheel, as well as between the track pin sleeve and the teeth of the drive wheel. Analysis shows that when the surface wear reaches the limit, most of the internal shaft parts, being in a sealed and lubricated state, have not yet failed. At this point, if the worn surface can be welded and repaired to restore it to its original size, the service life of the three-wheel belt can be extended.

Before welding repair, rust removal treatment should be carried out on the worn surface first. Then heat and preheat them to around 250 tons to eliminate the pressure on these workpieces during use. Internal stress generated by impact; Next, apply a base layer of 105 B flexible welding wire (to increase the welding strength), usually 2 to 3 layers, and fill in the remaining dimensions with 104 welding wire. During the welding repair process, the welding current and wire feeding speed should be selected based on the size of the wheel and the thickness of the track to ensure the quality and appearance of the welding repair. The welded workpiece needs to be kept warm (especially in winter), but no surface treatment is required (as the selected solder is very close to the performance of the original component and can reach the surface hardness of the original component).

It is worth noting that for the three-wheel area where the wear amount has not reached 70% of the wear limit or exceeds 120%, it is not recommended to use the surfacing welding method for repair. This is because at this time, the workpiece either has not completely worn off the surface hardened layer or has other phenomena, reducing the success rate of welding.

For components like wheels and chain links that wear along the circumferential surface, surfacing welding can be adopted for repair. For parts like the track pin sleeve that are locally worn in a sector area less than 180º, the process of turning over the sleeve can be adopted to reuse them. In most cases, the external wear rate of the pin sleeve is always faster than that of the chain link (the wear rate ratio of the two is approximately 2:1), especially when the pin sleeve reaches the wear limit and the hardened layer has been worn out. If it is used continuously, the wear rate will accelerate, and the remaining service life will be very short. At this time, the possibility of oil loss of the oil-lubricated chain track increases. That is to say, the chance of pin wear increases. Therefore, when it approaches the wear limit, timely rotation of the pin sleeve, replacement of the seal and oiling can double the service life of the pin sleeve, thereby making more effective use of the residual value of the chain link and the pin.

2 Main repair equipment

The main repair equipment includes track surface and three-wheel surfacing welding machines as well as track disassembly and assembly machines. These machines can perform surfacing welding on worn surfaces to restore them to their original dimensions and disassemble and assemble the tracks that have been welded for repair or require the rotation of pin sleeves, thus realizing the mechanization of track plate disassembly and assembly. These devices have a high degree of automation and strong reliability, and can achieve batch repair. At present, Beijing, Guangzhou, Jiangsu, Inner Mongolia and Shanxi and other places have all introduced these devices from the United States or Japan. Users can send them for repair nearby.

3 Quality and effect analysis

After being repaired through processes such as welding and sleeve turning, the service life of the three-wheeled belt can reach 80% to 90% of that of new products, and the average repair cost is only 30% of that of new products. The repair cycle is shorter than that of imported new products. Therefore, repairing the three-wheel area when it has just reached or slightly exceeded the wear limit can be regarded as a relatively good renewal method.