High-Strength Wear-Resistant Alloy Overlay Welding on Sintering Machine Tail Scraper

Literature Overview

This technical paper published in Sintering and Pelletizing (2011, Vol. 36, No. 2) by Han Shicheng and colleagues from Jinan Iron and Steel Group Ironmaking Plant documents the practical application of high-strength wear-resistant alloy overlay welding on sintering machine tail scrapers. The paper reports that the overlay welding treatment extended the scraper service life to 18–24 months, substantially reducing spare parts consumption and maintenance costs. As an engineer familiar with the demanding wear conditions in iron and steel production, I find this case particularly relevant to the broader challenge of extending the service life of wear-critical components through surface engineering.

Application Background and Wear Mechanisms

The sintering machine tail scraper operates under severe abrasive and adhesive wear conditions:

• Direct contact with sintered ore material containing hard mineral particles
• Continuous sliding motion against the sinter belt
• High temperatures from the hot sinter material
• Significant lateral forces from material discharge
• Variable loading conditions depending on feed material characteristics

The original scraper material, typically a carbon or low-alloy steel, wears rapidly under these conditions, necessitating frequent replacement. The overlay welding approach addresses this by creating a hard, wear-resistant surface layer on the scraper body while retaining the toughness of the base material.

Overlay Welding Design Considerations

The paper emphasizes several key design principles for the overlay welding application:

The emphasis on "reasonable arrangement of wear layer structure and force direction" is particularly important. This indicates that the engineers considered not only the hardness of the overlay material but also the mechanical design of the scraper to ensure that the overlay layer experiences compressive rather than tensile stresses during operation.

Performance Results

The reported improvement in service life from the original baseline to 18–24 months represents a significant enhancement. While the paper does not specify the original service life, typical unhardened scrapers in sintering applications may last only 3–6 months before requiring replacement or repair.

The benefits achieved include:

• Substantial reduction in spare parts consumption
• Decreased maintenance and downtime costs
• Improved production continuity
• Reduced environmental impact from fewer scrapped components

Metallurgical and Process Considerations

For the overlay welding of high-strength wear-resistant alloys on iron and steel equipment, several technical factors are critical:

• Preheating: Adequate preheating (typically 200–300°C for medium carbon steels) is essential to reduce hydrogen-induced cracking risk and control cooling rates.
• Heat input control: Excessive heat input can dilute the overlay deposit and reduce its hardness; insufficient heat input can result in poor bonding.
• Interpass temperature: Maintaining interpass temperature below a specified limit (typically 250°C) prevents excessive softening of the previous pass.
• Post-weld treatment: Stress relief annealing may be required to reduce residual stresses in the base metal.
• Layer design: Multiple layers with varying compositions can optimize the hardness-toughness gradient between the overlay and base metal.

Engineering Practice Integration

The sintering machine scraper overlay welding case illustrates several principles of practical surface engineering:

1. The overlay layer must be designed not only for hardness but also for the specific wear mechanism—abrasive wear in this case requires high hardness with adequate toughness.
2. The mechanical design of the component should be considered in conjunction with the surface treatment to ensure the overlay layer is loaded in the most favorable manner.
3. Economic analysis should compare the cost of overlay welding repair against replacement, considering both material costs and downtime costs.
4. The overlay welding procedure must be qualified and documented to ensure consistent results across multiple repair operations.

Study Insights

This paper, while concise, demonstrates the practical value of surface engineering in extending the service life of critical wear components. The extension from a presumably short service life to 18–24 months represents a substantial improvement that directly impacts production economics. The emphasis on both the overlay material properties and the mechanical design of the scraper component reflects a mature engineering approach that considers the interaction between surface treatment and component design.

From my experience with similar applications in mining and steel industries, I would add that the long-term success of overlay welding depends not only on the initial quality of the weld but also on the condition monitoring and maintenance practices. Regular inspection of the overlay surface for spalling, cracking, or excessive wear is essential to detect degradation before it leads to component failure. The overlay weld interface is a potential failure location, particularly if the bonding quality is insufficient or if the thermal cycling during operation causes fatigue cracking at the interface.

The case also highlights the importance of standardizing overlay welding procedures for repeatable results. When multiple scrapers are repaired over time, consistency in welding parameters, preheating, and post-weld treatment is essential to ensure uniform performance across all repaired components.