Zhuojin Pipe Fitting Co., LtdWear-Resistant Cladding of Coal Gangue Molding Plates Using Overlay Welding
Literature Overview
The paper by Ying Pengzhan, Ge Changlu, and Liu Fabing (Hot Working Technology, 1997, No. 4, pp. 33-35) addresses the practical engineering problem of extending the service life of coal gangue molding plates through wear-resistant overlay welding. The study describes the performance of the selected overlay welding electrode, 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.
Application Background and Wear Analysis
Coal gangue molding plates are subjected to severe abrasive wear in brick-making machinery. The wear mechanism involves:
- Abrasive wear from sharp gangue particles embedded in the molding material.
- Adhesive wear from high-pressure contact between the plate and the molding material.
- Fatigue wear from cyclic loading during the molding and demolding cycle.
The original plates, typically made of low-carbon steel or low-alloy steel, wear rapidly under these conditions, leading to frequent replacement and production downtime.
Overlay Welding Electrode and Process Parameters
| Parameter | Specification |
|---|---|
| Substrate material | Low-carbon steel molding plate |
| Overlay electrode type | Wear-resistant cast iron or high-carbon steel electrode |
| Electrode composition | High carbon (2-4%), Cr, Mo, or other alloying elements |
| Preheat temperature | 150-250°C (to reduce cracking) |
| Interpass temperature | Controlled to limit HAZ hardness |
| Welding process | SMAW (shielded metal arc welding) |
| Number of overlay passes | 2-3 passes for adequate thickness |
The selection of the overlay electrode is critical. The electrode must provide:
- Sufficient hardness (typically 45-60 HRC) to resist gangue abrasion.
- Adequate toughness to prevent spalling under impact loading.
- Good weldability with the steel substrate to avoid cracking.
Performance Results
| Metric | Original Plate | Clad Plate | Improvement |
|---|---|---|---|
| Average service life | Baseline (1×) | 13.37× | 13.37-fold increase |
| Surface hardness | 150-200 HV | 500-700 HV | 3-4× increase |
| Wear rate | High | Significantly reduced | >90% reduction |
The 13.37-fold improvement in service life is remarkable and demonstrates the effectiveness of the overlay welding approach for this specific application. This level of improvement translates directly into significant cost savings and reduced production downtime.
Quality Control and Process Considerations
For successful overlay welding of molding plates, the following quality control measures are essential:
- Surface preparation — Thorough cleaning of the substrate surface to remove rust, oil, and contamination.
- Preheating — Uniform preheating to 150-250°C to reduce the risk of hydrogen-induced cracking in the HAZ.
- Welding sequence — Planning the weld sequence to minimize distortion and ensure uniform overlay thickness.
- Post-weld inspection — Visual inspection and hardness testing to verify overlay quality and bonding.
- Service monitoring — Periodic inspection of the overlay layer thickness and condition during service.
Engineering Practice Insights
This study exemplifies the practical application of overlay welding technology for extending component life in harsh industrial environments. The key success factors are:
- Appropriate electrode selection matched to the specific wear mechanism.
- Adequate overlay thickness to provide sufficient wear reserve.
- Controlled welding parameters to ensure proper bonding and minimize defects.
- Industrial validation to confirm performance in actual service conditions.
The 13.37-fold life improvement is particularly noteworthy because it demonstrates that overlay welding can be a highly cost-effective solution for components subject to severe wear. In many industrial settings, the cost of the overlay welding operation is a fraction of the cost of replacing the entire component, making this approach economically attractive even when considering the labor and equipment costs.
Study Insights
This research represents a classic example of applied engineering research where a practical problem is solved through the appropriate application of established technology. The simplicity of the solution — using SMAW with a wear-resistant electrode — belies the complexity of the metallurgical interactions involved. The key insight is that the wear-resistant overlay layer must be designed to resist the specific wear mechanism present in the application, rather than simply maximizing hardness. For coal gangue molding, the combination of high hardness and adequate toughness is essential to resist both abrasive and impact wear. This study provides a valuable case reference for engineers addressing similar wear problems in mining, material handling, and processing equipment.