Zhuojin Pipe Fitting Co., LtdWear-Resistant Surfacing of Spiral Conveyor Blades
Literature Overview
This technical paper by Ma Tiantian and Wang Bingjun from Tangshan Sanyou Chemical Engineering Design Co., Ltd. addresses the practical engineering challenge of extending the service life of spiral conveyor blades through wear-resistant surfacing technology. Published in Soda Industry journal, Issue 1, 2018, the study provides a systematic analysis of blade wear mechanisms and proposes optimization strategies for surfacing material selection and process parameters.
Analysis of Wear Mechanisms
Spiral conveyor blades in chemical processing environments are subjected to multiple simultaneous wear mechanisms that significantly limit their service life. The following table summarizes the primary wear modes and their relative contributions:
| Wear Mechanism | Relative Contribution | Operating Conditions |
|---|---|---|
| Abrasive wear | 50-60% | Continuous sliding contact with conveyed material |
| Adhesive wear | 15-20% | High contact pressure, insufficient lubrication |
| Corrosive wear | 15-20% | Exposure to chemical by-products and moisture |
| Fatigue wear | 10-15% | Cyclic loading during conveying operations |
The spiral blade geometry creates complex stress states, with the leading edge experiencing the highest contact pressures and sliding velocities. The curvature of the blade introduces additional bending stresses that compound the surface degradation mechanisms.
Surfacing Material Selection Strategy
The study proposes a systematic approach to surfacing material selection based on the specific operating conditions encountered in soda production processes:
Material Options Evaluated
| Surfacing Material | Typical Hardness (HRC) | Wear Resistance Rating | Cost Factor | Recommended Application |
|---|---|---|---|---|
| High carbon martensitic steel (Cr12MoV) | 55-60 | Good | Low | General abrasive wear |
| High chromium cast iron (Cr20) | 58-62 | Very good | Moderate | Severe abrasive wear |
| Nickel-based alloy (Stellite 6) | 40-45 | Excellent (corrosive environments) | High | Corrosive + abrasive combined wear |
| Carbide-composite overlay | 65-70 | Outstanding | High | Extreme abrasive conditions |
Process Selection Criteria
The selection of surfacing process depends on the blade geometry, production volume, and required surface quality:
- Flame spray welding: Suitable for thick overlay layers (3-5mm), provides good dilution control, economical for large production volumes.
- SMAW surfacing: Portable and flexible, suitable for field repair operations, moderate deposition rates.
- Oxy-fuel gas surfacing: High deposition rates, suitable for flat blade surfaces, limited applicability to curved geometries.
- Submerged arc surfacing (SAW): Excellent surface quality, high deposition efficiency, requires specialized equipment.
Engineering Practice Recommendations
Based on the comprehensive analysis of blade wear conditions and available surfacing technologies, the following optimization strategy is recommended:
Pre-Surfacing Preparation
- Remove all existing worn material to establish a sound base metal surface.
- Grind the surface to be free of oxides, scale, and embedded foreign material.
- Preheat the blade to 150-200°C to reduce hydrogen absorption and improve wetting.
Surfacing Process Parameters
- For martensitic steel overlays: maintain interpass temperature below 250°C to ensure proper hardening.
- For high chromium iron overlays: control cooling rate to prevent excessive cracking in the brittle carbide-rich microstructure.
- For nickel-based alloy overlays: ensure complete melting of each pass to achieve proper alloy dissolution and bonding.
Post-Surfacing Treatment
- Allow controlled cooling in still air to minimize residual stresses.
- Perform visual and magnetic particle inspection to detect surface cracks and defects.
- Measure overlay thickness and hardness at representative locations to verify specification compliance.
Key Questions and Reflections
The paper addresses an important practical problem but would benefit from more quantitative data regarding the actual service life extension achieved. Engineering decisions regarding surfacing investment require economic justification, and the ratio of additional surfacing cost to extended service life should be clearly established. Furthermore, the study does not address the effect of surfacing layer thickness on blade balance and dynamic performance, which is a critical consideration for high-speed spiral conveyor operations.
The interaction between surfacing layer properties and the conveyed material characteristics deserves more detailed investigation. Different chemical products (soda ash, caustic soda, carbonate solutions) present distinctly different wear and corrosion challenges, and a single surfacing solution may not be optimal for all operating conditions within a chemical processing plant.
Study Insights and Implications
This study provides a practical framework for approaching the wear-resistant surfacing of spiral conveyor blades in chemical processing environments. The systematic analysis of wear mechanisms, material selection criteria, and process parameters offers valuable guidance for engineers responsible for equipment reliability and maintenance planning. The key insight is that effective surfacing requires matching the overlay material properties to the specific combination of wear mechanisms present in the operating environment, rather than applying a universal solution. This approach to surface engineering—tailoring material and process to specific service conditions—represents best practice in wear protection engineering and should guide future optimization efforts for material handling equipment in chemical processing industries.