CLADDING TECHNOLOGY SHANXI CO., LTDResearch on Fan Blade Manufacturing Using Overlay Welded Composite Steel Plate
Literature Overview
This 1998 study by Yan Zhixing and Meng Zhaohong from the Process Institute of the Chinese Academy of Agricultural Machinery investigates the manufacturing of fan blades using overlay welded composite steel plate. Published in the journal Fan Technology, the research addresses the challenge of producing high-performance fan blades that combine the strength of structural steel with the wear resistance of overlay materials, particularly for agricultural and industrial fan applications.
Technical Background and Design Requirements
Fan blades are subjected to complex loading conditions including centrifugal forces, aerodynamic loading, and occasional impact from foreign objects. In agricultural applications, fan blades are also exposed to abrasive dust and particulate matter that accelerates wear. The use of overlay welded composite steel plate offers an economical solution to these challenges by combining a tough structural steel substrate with a hard, wear-resistant overlay layer.
Material Selection Criteria
| Component | Material | Key Properties |
|---|---|---|
| Substrate Plate | Q345R, 16MnR, 15CrMoR | Strength, toughness, formability |
| Overlay Layer | High-carbon steel, martensitic stainless steel | Hardness, wear resistance |
| Bonding Method | ESW, SAW, GMAW overlay | Bond strength, process efficiency |
Composite Steel Plate Manufacturing Process
The manufacturing of overlay welded composite steel plate for fan blades involves several critical steps:
Substrate Plate Preparation
The substrate plate must meet the requirements of GB/T 713 for pressure vessel steel or equivalent standards. The plate thickness is typically 6–12 mm for fan blade applications, with a maximum width determined by the blade geometry. Surface preparation includes machining, grinding, or shot blasting to a surface roughness of Ra 3.2–6.3 μm.
Overlay Welding Process
The overlay welding process can be performed using several methods, each with distinct advantages:
| Process | Advantages | Limitations | Typical Layer Thickness |
|---|---|---|---|
| ESW (Electroslag Welding) | High deposition rate, uniform layer | Limited to horizontal position | 2.0–5.0 mm |
| SAW (Submerged Arc Welding) | Good penetration, moderate rate | Flux management required | 1.5–4.0 mm |
| GMAW (Gas Metal Arc Welding) | Flexible, good control | Lower deposition rate | 1.0–3.0 mm |
| FCAW (Flux-Cored Arc Welding) | High deposition rate, good quality | Flux cored wire cost | 1.5–3.5 mm |
Process Parameters for Fan Blade Application
| Parameter | Recommended Value | Rationale |
|---|---|---|
| Heat Input | 20–30 kJ/mm | Balance penetration and dilution |
| Travel Speed | 100–200 mm/min | Control bead geometry |
| Wire Diameter | 1.6–2.4 mm | Deposition rate optimization |
| Shielding Gas | CO2 or Ar+CO2 | Arc stability and penetration |
| Preheat Temperature | 100–200 °C | Reduce HAZ cracking risk |
| Interpass Temperature | 150–250 °C | Control cooling rate |
Fan Blade Fabrication from Composite Plate
After the composite steel plate is manufactured, fan blades are fabricated through the following steps:
- Cutting: The composite plate is cut into blade blanks using flame cutting, plasma cutting, or waterjet cutting. The cutting method must be selected to minimize damage to the overlay layer.
- Forming: Blade blanks are formed using press braking or rolling to achieve the required aerodynamic profile. The forming process must be controlled to prevent cracking of the overlay layer.
- Machining: Final dimensions are achieved through milling, drilling, or grinding. The overlay layer thickness must be verified after machining to ensure adequate wear protection.
- Heat Treatment: Stress relief at 550–600 °C for 2 hours reduces residual stresses from forming and welding.
- Inspection: Non-destructive testing and dimensional verification ensure quality.
Performance and Quality Assessment
Mechanical Properties
The composite steel plate fan blades exhibit improved performance compared to conventional single-material blades:
| Property | Conventional Blade | Composite Blade |
|---|---|---|
| Substrate Yield Strength (MPa) | 345 | 345 |
| Overlay Hardness (HV) | N/A | 400–550 |
| Bond Strength (MPa) | N/A | 200–300 |
| Fatigue Life (cycles) | Baseline | 1.5–2.0× Baseline |
Wear Performance
In accelerated wear testing simulating agricultural fan operating conditions, composite blades demonstrated a wear rate reduction of 50–65% compared to conventional blades. The overlay layer provided effective protection against abrasive wear from dust and particulate matter.
Defect Analysis and Countermeasures
Common defects in overlay welded composite steel plate include:
- Lack of fusion: Caused by inadequate heat input or poor surface preparation. Prevented by ensuring proper preheating and surface cleaning.
- Cracking in the overlay layer: Resulting from high carbon content and rapid cooling. Addressed by controlling interpass temperature and using appropriate filler metals.
- Uneven overlay thickness: Due to inconsistent welding parameters. Corrected by automated welding or skilled manual technique.
- Overlay spalling during forming: Caused by excessive forming strains. Prevented by controlling forming angles and using warm forming when necessary.
Quality control should include visual inspection, magnetic particle testing, ultrasonic testing for bond quality verification, and hardness mapping to ensure overlay uniformity. The overlay thickness should be verified at multiple locations using ultrasonic testing or metallographic examination.
Study Insights and Engineering Recommendations
This research demonstrates that overlay welded composite steel plate is a viable and economical technology for fan blade manufacturing. The combination of structural steel strength and overlay wear resistance provides significant performance advantages without the cost of using fully alloyed materials. Engineers should adopt a systematic approach to process development, using design of experiments (DOE) methods to optimize welding parameters for specific blade geometries and service conditions. The PDCA cycle is recommended for continuous improvement of the manufacturing process. The economic benefits of composite blade technology are substantial, with estimated cost reductions of 30–50% compared to fully alloyed blade materials while providing equal or superior performance. Future development should focus on automated overlay welding systems and advanced monitoring techniques for real-time quality control.