Application of Hard Surfacing Wear-Resistant Lining Plates in Electric Shovel Buckets

Literature Overview

This 2011 paper by Wang Hui and colleagues from Shandong Borun Industrial Technology Co., Ltd. examines the application of hard surfacing wear-resistant lining plates on electric shovel bucket bodies in open-pit mining operations. The study demonstrates that composite surfacing of wear-resistant lining plates on the bucket interior significantly improves wear resistance and overall service life, while also reducing maintenance difficulty and costs. The work addresses a critical economic challenge in mining operations: the frequent replacement and repair of shovel buckets due to abrasive wear from ore and rock.

Core Technical Analysis

Wear Mechanisms in Electric Shovel Buckets

Electric shovel buckets in open-pit mining are subjected to multiple wear mechanisms simultaneously:

The bucket body, particularly the interior surfaces, experiences the most severe abrasive wear. The typical service life of an unprotected carbon steel bucket in aggressive mining conditions may be only 500-2000 operating hours, depending on the abrasiveness of the material being mined.

Hard Surfacing Lining Plate Design

The hard surfacing lining plate approach involves:

1. Plate fabrication: Wear-resistant plates are fabricated from high-carbon, high-chromium steel or similar alloy with a hardness of HRC 55-70. The plates are typically 10-20 mm thick with a designed profile that matches the bucket interior geometry.
2. Surface preparation: The bucket interior is prepared by machining or grinding to remove scale and ensure a clean, flat surface for welding attachment.
3. Welding attachment: The lining plates are attached to the bucket body using a combination of:

• Fillet welds along the plate edges for structural attachment
• Surfacing welds on the plate surface for additional wear resistance
• Possibly a backing layer to minimize dilution from the base steel

1. Multi-layer construction: In high-wear areas, multiple layers of hard surfacing may be applied to build up the required thickness and hardness profile.

Material Selection for Hard Surfacing

The selection of hardfacing consumables for mining applications requires balancing hardness (wear resistance) with toughness (impact resistance):

The choice of consumable depends on the specific mining conditions. For ore with high silica content (highly abrasive), harder consumables with higher carbide content are preferred. For impact-heavy operations, tougher consumables with better spalling resistance are more appropriate.

Process Development and Quality Control

The application of hard surfacing lining plates requires careful process development:

Welding Process Parameters

Quality Control Protocol

For mining equipment, the quality control protocol is somewhat less stringent than for pressure vessels but still essential:

1. Visual inspection: All welds must be free from cracks, excessive porosity, and incomplete fusion.
2. Hardness verification: The surfacing layer must achieve the specified hardness range; hardness mapping across the weld cross-section verifies the transition zone.
3. Impact testing: Drop hammer or Charpy V-notch testing on test coupons verifies that the surfacing does not compromise the structural integrity of the bucket.
4. Field performance monitoring: Service life tracking provides the ultimate validation of the surfacing process.

FMEA for Surfacing Application

Economic Analysis and Engineering Practice

The economic case for hard surfacing lining plates is straightforward and compelling:

• Service life extension: Hard surfacing typically extends bucket life by 3-5 times compared to unprotected carbon steel.
• Maintenance reduction: Longer service intervals reduce downtime for bucket replacement, which is critical in continuous mining operations.
• Cost per ton mined: Despite the initial investment in surfacing, the cost per ton of material mined is significantly reduced due to extended bucket life.
• Safety improvement: Stronger, more wear-resistant buckets reduce the risk of catastrophic failure during operation.

The paper's recommendation for widespread adoption is well-founded. In open-pit mining operations where shovel availability directly impacts production rates, the investment in hard surfacing lining plates pays for itself within the first few months of operation.

Study Insights and Reflections

This paper, while focused on a specific application, illustrates a fundamental principle in materials engineering: the strategic application of expensive materials in the most critical areas provides the best cost-benefit ratio. Rather than fabricating the entire bucket from wear-resistant alloy (which would be prohibitively expensive), the hard surfacing approach applies the wear-resistant material only where it is needed—the interior surfaces subject to abrasive wear. This philosophy of selective material application is consistent with the approach taken in hydrogenation reactor internals and corrosion-resistant piping, where expensive alloys are applied as overlays or linings rather than as the base material.

The paper also highlights the importance of considering the full lifecycle of a component, not just its initial fabrication cost. In mining operations, where equipment availability is directly tied to revenue, the extended service life provided by hard surfacing translates directly into improved profitability. For engineers involved in mining equipment design and maintenance, this paper provides a clear demonstration that investing in proper surfacing technology is one of the most effective ways to improve equipment reliability and reduce operating costs. The success of this approach in one mining operation should encourage its adoption across the industry, with appropriate modifications for specific operating conditions and material types.