CLADDING TECHNOLOGY SHANXI CO., LTDProperties of Hard Cladding Wear-Resistant Plates and Application in Coal Preparation Plant Chutes
Literature Overview and Context
The study by Wang Meng, Liu Shuliang, and Tang Linlin, published in 2010 in the Journal of Coal Processing and Comprehensive Utilization, examines the properties of hard cladding wear-resistant plates and their application in coal preparation plant chutes. Coal preparation plants process raw coal through crushing, washing, screening, and dewatering operations, and the chutes and transfer points are subjected to severe abrasive wear from coal particles, water, and slurry. The study evaluates hard cladding overlay technology as a solution to extend the service life of chute components and reduce maintenance costs.
Core Technical Points
Wear Environment in Coal Preparation Plant Chutes
Coal preparation plant chutes operate under the following conditions:
- Material being conveyed: Coal particles (size 0–100 mm), water, and coal-water slurry
- Impact velocity: 5–25 m/s depending on chute angle and height
- Sliding abrasion: Coal particles slide along chute surfaces under gravity
- Abrasive particle hardness: Coal itself is relatively soft (2–3 Mohs), but impurities such as quartz, pyrite, and shale can reach 6–7 Mohs
- Environmental factors: Moisture, temperature (20–80°C), and occasional chemical exposure (acids from pyrite oxidation)
The dominant wear mechanism is a combination of sliding abrasion and impact erosion, with abrasive particles acting as the primary wear agents. The presence of water can exacerbate wear through hydrodynamic effects and can also cause corrosion of unprotected steel surfaces.
Hard Cladding Wear-Resistant Plate Properties
The study evaluates several types of hard cladding wear-resistant plates:
| Plate Type | Overlay Composition | Hardness (HRC) | Wear Rate (mg/1000m) | Impact Toughness (J) |
|---|---|---|---|---|
| High-carbon martensitic | C 2.0–2.5%, Cr 5–8% | 55–60 | 8–12 | 15–25 |
| High-chromium cast iron | C 2.5–3.5%, Cr 25–30% | 58–62 | 5–8 | 10–20 |
| Chromium carbide composite | Cr7C3 particles in martensitic matrix | 60–65 | 3–6 | 8–15 |
| Tungsten carbide composite | WC particles in iron matrix | 62–68 | 2–4 | 5–12 |
| Stellite overlay | Co-Cr-W alloy (Stellite 6 equivalent) | 40–45 | 6–10 | 20–30 |
The selection of overlay type depends on the specific wear conditions, required service life, and economic constraints. For coal preparation plant chutes, the high-carbon martensitic and chromium carbide composite overlays offer the best balance of wear resistance, toughness, and cost.
Cladding Process and Fabrication Details
The hard cladding wear-resistant plates are typically fabricated using the following processes:
| Process | Typical Application | Key Characteristics |
|---|---|---|
| Submerged arc welding (SAW) | Large plate areas, heavy overlay | High deposition rate, good penetration, low cost |
| Flux-cored arc welding (FCAW) | Medium areas, complex shapes | Good deposition rate, flexible positioning |
| Plasma transferred arc (PTA) | Precision overlay, thin layers | Low dilution, smooth surface, high quality |
| Laser cladding | Thin, high-quality overlay | Very low dilution, excellent metallurgical bond |
Typical fabrication parameters for SAW cladding of wear-resistant plates:
- Electrode wire: High-carbon alloy wire (C 2.0%, Cr 8%, Mo 1.5%, V 0.5%)
- Flux: HJ431 or equivalent rutilic flux
- Current: 500–700 A
- Voltage: 30–36 V
- Travel speed: 150–250 mm/mm
- Preheat: 100–150°C
- Interpass temperature: < 250°C
- Number of passes: 2–3 layers
- Total overlay thickness: 6–12 mm
- Final hardness: 55–60 HRC
Application Design for Chute Components
The study provides specific design guidance for applying hard cladding plates to chute components:
- Chute walls: Apply wear-resistant plates to the full sliding surface, with overlap joints of 50–100 mm to prevent material ingress behind the plate.
- Chute corners and bends: These are high-wear areas where impact and abrasion combine. Use thicker overlay (10–15 mm) and consider angled plate installation to deflect material flow.
- Transfer points: Where material drops from one level to another, impact wear is dominant. Use impact-resistant overlay compositions with higher toughness.
- Fastening method: Wear-resistant plates are typically bolted to the base structure with stainless steel bolts and lock washers. Bolt spacing should be 100–150 mm on center, with additional fasteners at corners and edges.
- Edge treatment: Plate edges should be chamfered or rounded to prevent material accumulation and edge wear.
Performance Monitoring and Maintenance
The study recommends the following performance monitoring approach:
- Initial baseline measurement: Measure plate thickness at multiple points immediately after installation.
- Periodic thickness measurement: Monitor thickness at 1–3 month intervals using ultrasonic thickness gauges.
- Wear rate calculation: Calculate wear rate as (initial thickness - current thickness) / operating hours.
- Replacement criteria: Replace or re-clad when remaining overlay thickness falls below 50% of original thickness or when base material is exposed.
- Service life prediction: Based on wear rate data, predict remaining service life and schedule preventive maintenance.
Engineering Practice Integration
The application of hard cladding wear-resistant plates in coal preparation plant chutes offers significant operational and economic benefits:
- Service life extension: From 3–6 months (bare steel) to 12–24 months (hard cladding plates), representing a 3–5× improvement.
- Reduced maintenance downtime: Fewer chute replacements mean fewer plant shutdowns.
- Lower total cost of ownership: Despite higher initial cost, the extended service life results in lower annual maintenance expenditure.
- Improved safety: Reduced frequency of hot work and hot plate replacement improves workplace safety.
- Environmental compliance: Reduced material spillage from worn chutes improves environmental performance.
A comprehensive FMEA analysis for chute wear-resistant plate installation:
| Failure Mode | Cause | Effect | Detection | Prevention |
|---|---|---|---|---|
| Plate spalling | Poor bond, thermal shock | Material loss, base exposure | Visual, UT | Proper preheat, qualified WPS |
| Bolt loosening | Vibration, thermal cycling | Plate displacement | Visual, torque check | Lock washers, regular inspection |
| Edge wear | Material impact at edges | Progressive edge erosion | Visual, thickness measurement | Edge protection, chamfering |
| Base corrosion | Water ingress behind plate | Base material degradation | Visual after plate removal | Sealing, drainage provisions |
| Overlay cracking | Thermal stress, impact | Wear rate acceleration | MT, visual | Tough overlay composition, PWHT |
Study Insights and Reflections
This study by Wang Meng and colleagues provides a practical and well-documented evaluation of hard cladding wear-resistant plates for coal preparation plant applications. The systematic approach to material selection, process qualification, and performance monitoring is exemplary of good engineering practice. The data on wear rates and service life improvements are directly useful for maintenance planning and budget forecasting. One notable observation is that the selection of overlay material must balance wear resistance against toughness—a harder overlay may resist abrasion better but is more susceptible to impact spalling in high-impact areas. The study's emphasis on proper fastening and edge treatment reflects practical experience with field failures caused by attention to detail. For engineers working in coal preparation, mining, and bulk material handling, this study provides a solid technical foundation for implementing wear-resistant cladding solutions. The findings are transferable to similar applications in mineral processing, power plant coal handling, and aggregate processing industries.