Selecting Wear Blocks for Heavy Equipment: Hardness, Toughness, and Welding Installation Best Practices

Heavy machinery operates in highly demanding environments where wear liners are subjected to a combination of two destructive forces: abrasion and impact.

Selecting the right wear material is a balancing act. If the wear liner is too hard, it will be brittle and shatter under impact. If it is too soft, it will wear away rapidly under abrasion, leading to frequent maintenance shutdowns.

This guide provides a technical framework for evaluating the Hardness vs. Toughness trade-off, maps different wear block types to specific equipment zones, and details the welding installation procedures required to prevent cracking.

1. The Hardness-Toughness Trade-off in Wear Materials

In materials science, hardness (resistance to scratching/indentation) and toughness (resistance to fracture under impact) are generally inversely proportional.

To specify the correct wear block, engineers must evaluate the operating environment:

• High Impact / Low Abrasion: For example, primary crusher jaws or hopper walls receiving large boulders. Here, work-hardening manganese steel is preferred because it deforms and hardens under impact.
• Extreme Abrasion / Low-to-Medium Impact: For example, sand chutes, dredge pump liners, or excavator bucket shrouds. In these zones, bi-metallic wear blocks (700 HB) or tungsten carbide wear blocks are ideal because they resist micro-scratching.

2. Equipment Mapping: Where to Position Wear Blocks

To maximize wear life while controlling costs, plants utilize a “zoned” approach, placing different wear shapes in specific high-wear areas.

3. Welding Installation Guide for Bi-Metallic Wear Blocks

Since bi-metallic wear blocks consist of an ultra-hard white iron layer vacuum-brazed to a mild steel backing plate, incorrect welding procedures will cause thermal shock, resulting in cracks that propagate through the wear layer.

Follow this step-by-step engineering procedure to ensure a secure, crack-free installation:

Step 1: Surface Preparation

• Clean the target surface (bucket or chute steel) to remove rust, paint, grease, and moisture.
• Grind the area flat. Any air gaps beneath the wear block’s mild steel backing plate will cause bending stresses during operation, leading to bond failure.

Step 2: Preheating Requirements

• While the mild steel backing plate does not require preheating, the heavy equipment structure (often high-strength low-alloy steel like Q345 or Hardox) does.
• Preheat the parent metal to 100°C to 150°C (212°F to 300°F) around the weld zone to prevent hydrogen-induced cracking in the heat-affected zone (HAZ).
• WARNING: Never apply direct heat to the white iron wear layer. Only heat the parent steel structure.

Step 3: Welder Settings & Consumables

• Welding Process: Shielded Metal Arc Welding (SMAW / Stick) or Gas Metal Arc Welding (GMAW / MIG) is recommended.
• Consumables: Use low-hydrogen electrodes such as E7018 (or wire equivalents like E71T-1).
• Current: Keep the heat input as low as possible. Use a welding current of 120A to 140A for a 3.2mm electrode.

Step 4: Welding Sequence

1. Tack Welding: Tack weld the wear block at the center of both sides.
2. Stitch Welding: Weld from the center outward to the corners. Avoid continuous high-heat passes; instead, use intermittent stitch welds to minimize thermal accumulation.
3. Weld Size: A fillet weld size of 6mm to 8mm is typically sufficient. Do not overweld, as excessive weld volume increases shrinkage stresses.

Welding Sequence (Stitch from Center Outward):
       [ Corner 3 ] <======= [ Tack Center ] =======> [ Corner 1 ]
       [ Corner 4 ] <======= [ Tack Center ] =======> [ Corner 2 ]

Step 5: Post-Weld Cooling

• Allow the welded assembly to cool slowly in still air.
• Never quench the welds with water or force-cool them with compressed air. Rapid cooling will induce thermal shock, instantly cracking the 700 HB white iron wear layer.

Conclusion: Optimize Your Wear Life with VOTNE

Proper selection and correct installation are the keys to maximizing the return on your wear liner investment. At VOTNE, our wear blocks are engineered with a ductile Q235 steel backing that makes welding straightforward and safe. By following our thermal management and welding guidelines, you can eliminate installation cracks and ensure your equipment stays in the field longer.

Contact our engineering team today for custom layout drawings, welding support, or to request a quote.

• Email: engineering@votne.com
• Technical Support: Fill out our Contact Form to consult with a B2B parts specialist.