Zhuojin Pipe Fitting Co., LtdWear-Resistant Cladding of Coal Gangue Molding Plates
Literature Overview
This 1997 paper published in Hot Working Technology by Ying Pengzhan, Ge Changlu, and Liu Fabing from China University of Mining and Technology investigates the application of wear-resistant overlay welding on coal gangue molding plates used in brick-making machinery. The study introduces the performance characteristics of the wear-resistant overlay welding electrodes, the cladding process parameters, and presents hardness and wear resistance analysis of the overlay layer. Industrial application results demonstrate a 13.37-fold increase in average service life. This research is directly relevant to engineers working on surface engineering solutions for heavy-duty industrial components subjected to severe abrasive wear.
Core Technical Findings
The coal gangue molding plate is subjected to severe abrasive wear from the friction and impact of coal gangue material during the pressing and molding process. The conventional carbon steel construction of these plates results in rapid wear and frequent replacement, leading to high maintenance costs and production downtime. The application of wear-resistant overlay welding provides a cost-effective solution by restoring and enhancing the surface properties of the worn components.
Overlay Performance Results
| Metric | Before Cladding | After Cladding | Improvement |
|---|---|---|---|
| Average service life | Baseline | 13.37 times baseline | 13.37x |
| Surface hardness | ~150-200 HV (base steel) | 500-600 HV (overlay layer) | ~3x increase |
| Wear resistance | Poor | Excellent | Dramatic improvement |
The wear-resistant overlay welding electrodes used in this study were specifically formulated to provide high hardness and wear resistance while maintaining adequate ductility to prevent cracking during welding and service. The overlay layer typically contains hard carbide phases such as Cr7C3, Cr3C, and Fe3C distributed in a tough matrix, providing a combination of hardness and toughness that resists both abrasive and adhesive wear mechanisms.
Cladding Process Parameters
| Parameter | Typical Value | Rationale |
|---|---|---|
| Electrode type | Heavy coated low-hydrogen or cellulose type | Adequate penetration and arc stability |
| Preheating temperature | 150-250°C | Reduce hydrogen cracking risk in low-alloy steel substrate |
| Interpass temperature | 200-300°C | Maintain ductility and prevent cracking |
| Welding current | 200-300 A | Ensure adequate penetration for bonding |
| Welding speed | 200-400 mm/min | Balance deposition rate and heat input |
| Number of passes | 2-3 layers | Achieve sufficient overlay thickness (3-5 mm) |
Wear Mechanism Analysis
The wear resistance of the overlay layer is attributed to the presence of hard carbide phases that resist abrasive material removal. The coal gangue material contains hard mineral particles such as quartz and feldspar that act as abrasive agents. The hard carbide phases in the overlay layer are harder than these abrasive particles, preventing their penetration into the matrix and reducing material removal rates. The tough matrix surrounding the carbides provides support and prevents crack initiation and propagation, ensuring that the overlay layer maintains its integrity under cyclic loading conditions.
Engineering Practice Implications
The 13.37-fold improvement in service life demonstrated in this study represents a compelling economic case for the application of wear-resistant overlay welding in heavy-duty industrial components. Several practical considerations arise:
- Cost-benefit analysis: The cost of overlay welding is significantly lower than the cost of manufacturing new components from wear-resistant materials. For components with large surface areas or complex geometries, overlay welding provides a practical solution that would be economically prohibitive with alternative approaches.
- Process qualification: The cladding process must be qualified through mechanical testing and field trials before widespread implementation. The hardness profile, bond strength, and wear resistance should be verified through standardized testing procedures.
- Maintenance integration: Overlay welding can be integrated into scheduled maintenance programs, allowing components to be restored to service condition during planned shutdowns rather than requiring emergency replacement.
- Substrate preparation: The surface of the worn component must be properly prepared before overlay welding. This includes removal of old oxide layers, rust, and contaminated material through grinding or shot blasting. The substrate should be cleaned and degreased to ensure proper arc stability and weld quality.
Common Defects and Prevention
| Defect | Cause | Prevention |
|---|---|---|
| Cracking | Excessive carbon content, hydrogen embrittlement | Use low-hydrogen electrodes, control interpass temperature |
| Porosity | Contaminated surface, moisture in electrodes | Proper surface preparation, electrode storage |
| Incomplete fusion | Insufficient heat input, improper welding angle | Increase current, optimize welding technique |
| Excessive dilution | High heat input, excessive penetration | Reduce heat input, use multiple thin layers |
Study Insights and Reflections
This paper provides a practical demonstration of the economic and technical benefits of wear-resistant overlay welding for heavy-duty industrial components. The 13.37-fold improvement in service life is remarkable and underscores the significant potential of surface engineering to extend component life and reduce maintenance costs.
The coal gangue molding plate application is representative of a broader class of industrial components subjected to severe abrasive wear, including conveyor belt pulleys, crusher hammers, and mining equipment components. The overlay welding approach demonstrated in this study can be adapted to these applications with appropriate selection of overlay materials and process parameters.
From a metallurgical perspective, the effectiveness of the overlay layer depends on the hardness contrast between the overlay and the abrasive material. The coal gangue contains hard mineral particles that are effectively resisted by the hard carbide phases in the overlay. Engineers should always consider the hardness and composition of the abrasive material when selecting overlay materials, as the overlay must be harder than the abrasive to provide effective protection.
In summary, this literature provides a compelling case study for the application of wear-resistant overlay welding in heavy-duty industrial components, demonstrating substantial improvements in service life and providing practical process guidelines for implementation in similar applications.