Tack Welding Pads to Chain Links: Best Practices and Considerations

[MikePhua]

Tack welding pads to chain links is a common practice in the heavy equipment industry, particularly in the maintenance and repair of track-driven machines like bulldozers, excavators, and other tracked vehicles. This technique involves welding wear pads or track shoes to the individual chain links of a track assembly to extend the life of the track and improve performance in specific applications. Understanding how to execute this process properly is essential for ensuring that the welds are secure and reliable.
The Importance of Tack Welding Pads to Chain Links
Tracked machines, such as excavators and bulldozers, rely on a robust track system to provide mobility on rugged terrains. The track consists of continuous chains made up of interlocking links, which are fitted with pads that come into direct contact with the ground. Over time, these pads wear down due to constant friction with rough surfaces, and this is where tack welding comes into play.
Welding pads to chain links serves several purposes:

• Extend Track Life: Wear pads prevent excessive wear on the track and the individual chain links, reducing the need for costly track replacements.
  
• Improve Traction: The pads are designed with specific materials and shapes that enhance grip, offering better traction in particular environments like muddy, rocky, or icy surfaces.
  
• Cost-Effectiveness: By welding pads to the chain links, operators can repair and maintain their equipment more affordably, instead of purchasing new, expensive tracks.
  

Materials and Tools Used for Tack Welding

1. Wear Pads:
   Wear pads, often made from high-strength steel or composite materials, are welded to the track links. These pads may feature a hardened surface to withstand abrasive conditions. The material used for the wear pad should be compatible with the track material to ensure good adhesion during welding.
   
2. Welding Rods/Consumables:
   The choice of welding rod or consumable is crucial for ensuring strong and durable welds. For tack welding on steel tracks, electrodes such as E7018 (for mild steel) or E11018 (for high-strength steel) are commonly used. The welding material should be chosen based on the track material and the environmental conditions the machine will operate in.
   
3. Welding Machine:
   A reliable welding machine is required for tack welding, typically a stick welder or MIG welder. The machine should have adjustable amperage settings to ensure the right amount of heat is applied for the welding process. Some specialized equipment like flux-cored welding machines can also be used for outdoor or rough environments.
   
4. Track Shoes:
   Track shoes are the pads that are welded to the chain links. These shoes come in various designs, including single or double grousers, depending on the required traction. The shoes are often designed to be replaceable but may need welding when they become worn or damaged.
   

Step-by-Step Guide to Tack Welding Pads to Chain Links

1. Preparation of the Track and Pad:
   Before beginning the welding process, ensure that both the track links and the pads are clean. Dirt, rust, and oil must be removed from the surfaces to be welded. A wire brush, grinder, or chemical cleaner can be used to prepare the surfaces. Ensuring that these surfaces are clean helps to avoid poor adhesion and weak welds.
   
2. Positioning the Wear Pads:
   Once the track and wear pads are cleaned, position the pad against the chain link in the desired location. Make sure the pad is aligned properly to ensure even wear over time. The pads should be centered and positioned securely so they do not shift during the welding process.
   
3. Tack Welding the Pad:
   Begin by making small tack welds at the four corners of the pad to secure it in place. These tacks should be made with low amperage to avoid excessive heat buildup, which could distort the chain link. The goal of the tack welds is to hold the pad in place while you complete the final welds.
   
4. Complete the Welds:
   Once the pad is tacked in place, increase the amperage to make the final welds. Use a continuous welding motion, ensuring the weld penetrates deeply into both the pad and the chain link for a strong bond. Ensure that the weld is uniform and covers all the edges of the pad. It’s important to maintain a steady pace to avoid overheating the materials, which can lead to warping or cracking.
   
5. Post-Weld Cleaning and Inspection:
   After welding, the joint should be cleaned to remove slag and any residual contaminants. Inspect the weld for any cracks, gaps, or weak points. A visual inspection is often sufficient, but non-destructive testing methods such as ultrasonic testing can be used for critical welds.
   
6. Final Adjustments and Testing:
   After completing the welds, check the track to ensure that the pads are securely attached and positioned correctly. Run the machine at low speeds initially to ensure that the pads do not shift and that the track performs as expected.
   

Common Challenges in Tack Welding Track Pads

1. Heat Distortion:
   One of the biggest challenges when tack welding pads to chain links is managing the heat to prevent warping or distortion of the track. To minimize heat distortion, welding in smaller sections or using intermittent tacking can help. It's also important to allow the material to cool gradually rather than quenching it too quickly.
   
2. Inconsistent Weld Penetration:
   Inconsistent penetration can occur if the amperage is too low or if the welding technique is incorrect. This can result in weak welds that may fail under stress. To avoid this, always ensure that the appropriate amperage is set for the material thickness and that the welding is done evenly.
   
3. Pad Positioning:
   Improperly positioned pads can cause uneven wear on the track, reducing its effectiveness. It's essential to carefully align the pads and ensure they are centered and level before welding.
   
4. Welding Contaminants:
   Contaminants like rust, oil, or dirt on the track or the pad can lead to poor weld quality. It’s essential to clean all surfaces thoroughly before beginning the welding process. Contaminants can cause porosity in the welds, weakening the joint.
   

Maintenance and Inspection After Tack Welding
After the pads are welded, it’s important to inspect the track regularly. Look for signs of excessive wear, cracks, or loose pads. Regular maintenance and timely repairs will ensure that the tack-welded pads continue to perform optimally.

1. Visual Inspection:
   Look for signs of cracking or any areas where the pads may have begun to lift or separate from the track. Inspect the welds for any visible damage or degradation.
   
2. Track Tension and Alignment:
   Check the track tension to ensure that it is within the manufacturer’s recommended range. Proper tension is crucial for the longevity of both the track and the welded pads.
   
3. Lubrication:
   Periodically lubricate the track assembly and ensure that all moving parts are properly greased to reduce friction and wear.
   

Conclusion
Tack welding pads to chain links is a valuable technique for extending the life of tracked vehicles and improving their performance in challenging conditions. By following proper procedures, selecting the right materials, and performing regular maintenance, operators can ensure the durability and reliability of their equipment. Tack welding provides an affordable, effective way to repair and maintain track systems without the need for costly full track replacements. With careful execution and attention to detail, tack welding can significantly enhance the functionality of heavy equipment in demanding work environments.