CLADDING TECHNOLOGY SHANXI CO., LTDApplication of Strip Electrode Hardfacing Technology
Literature Overview
This 2010 article, published in the journal "Welding Machine" (电焊机), presents the application of strip electrode hardfacing technology by Martin Kubenka, Gabriella Galazzi, and Solveig Rigdal from ESAB Welding and Cutting Products (Shanghai) Co., Ltd. The paper provides practical insights into the use of strip electrode welding for hardfacing applications, emphasizing the process advantages, typical applications, and technical considerations for successful implementation.
Process Description
Strip electrode hardfacing utilizes a continuous metal strip (typically 3-25 mm wide and 0.5-2.0 mm thick) as the filler material, fed into the arc along with a flux or gas shielding. The process combines features of submerged arc welding and gas metal arc welding, offering very high deposition rates while maintaining good deposit quality.
Process Configuration
| Configuration | Description | Application |
|---|---|---|
| Open strip electrode (OEW) | Strip fed into open arc with gas shielding | Flat and horizontal surfaces |
| Submerged strip electrode (SSEW) | Strip fed under flux layer | Large area coverage, thick deposits |
| Combined strip electrode | Multiple strips fed simultaneously | Very thick deposits, rapid buildup |
Technical Advantages
Strip electrode hardfacing offers several significant advantages over conventional hardfacing processes:
| Advantage | Comparison to Conventional Processes |
|---|---|
| Deposition rate | 5-10 times higher than solid wire GMAW |
| Productivity | Reduced labor cost per unit area |
| Dilution control | Lower dilution than electrode processes |
| Deposit thickness | Capable of building 10-50 mm in single pass |
| Cost efficiency | Lower cost per kg of deposited material |
| Surface preparation | Less demanding than laser or PTA processes |
Typical Process Parameters
| Parameter | Range | Notes |
|---|---|---|
| Strip width | 6-25 mm | Wider strips for higher deposition rate |
| Strip thickness | 0.5-2.0 mm | Thicker strips for deeper penetration |
| Current | 200-600 A | DCEN polarity typically used |
| Voltage | 20-35 V | Depends on strip geometry |
| Travel speed | 100-400 mm/min | Higher speeds for thinner deposits |
| Strip feed speed | 0.5-2.0 m/min | Synchronized with travel speed |
| Shielding gas | CO2, Ar+CO2, or flux | Selection based on alloy system |
| Preheat temperature | 100-300°C | Depends on base material and alloy |
| Interpass temperature | 150-350°C | Maintain to prevent cracking |
Alloy Systems for Strip Electrode Hardfacing
The following alloy systems are commonly available as strip electrodes:
| Alloy System | Composition Type | Typical Hardness (HV) | Applications |
|---|---|---|---|
| Low-alloy steel | Fe-Cr-Mo | 300-450 | General wear protection |
| Medium-alloy steel | Fe-Cr-Mo-V | 450-600 | Moderate wear conditions |
| High-alloy steel | Fe-Cr-Mo-W | 600-800 | Severe abrasion |
| High-speed steel | Fe-Cr-W-V-Co | 800-1100 | Cutting and forming tools |
| Cobalt-based | Co-Cr-W | 400-600 | High-temperature wear |
| Nickel-based | Ni-Cr-B-Si | 400-500 | Corrosive wear environments |
| Cast iron | Fe-C-Si | 250-400 | Repair of cast iron components |
Industrial Applications
The paper documents several successful industrial applications of strip electrode hardfacing:
Mining Industry
- Crusher jaw plates: Deposition of 20-30 mm of high-carbon chrome alloy, extending service life by 5-10 times
- Conveyor rollers: Hardfacing of contact surfaces to reduce wear and improve material handling
- Drill collars: Application of cobalt-based alloys for improved wear resistance in drilling operations
Cement Industry
- Kiln shell repair: Building up worn areas to restore original dimensions
- Slide gate liners: Hardfacing of wear surfaces to extend replacement intervals
- Fan blades: Protection of leading edges and pressure surfaces
Power Generation
- Boiler tube repair: Restoration of wall thickness in worn areas
- Air preheater elements: Protection against abrasive wear from flue gas
- Steam turbine components: Application of nickel-based alloys for improved thermal fatigue resistance
Chemical Processing
- Pump impellers: Hardfacing of wear surfaces with corrosion-resistant alloys
- Valve trim: Application of cobalt-based alloys for combined wear and corrosion resistance
- Heat exchanger tubes: Repair of worn tube ends and connections
Quality Considerations
Successful strip electrode hardfacing requires attention to several quality factors:
- Surface preparation: Thorough cleaning and grinding of base material to remove scale, rust, and contaminants
- Preheating: Controlled preheating to reduce residual stress and prevent cracking
- Wet-out layer: Application of a compatible wet-out layer when hardfacing dissimilar materials
- Interpass temperature control: Maintaining appropriate interpass temperature to ensure proper microstructure
- Post-weld heat treatment: Stress relief annealing when required by the application
- Inspection: Visual, MT, and UT inspection of completed hardfacing work
Defect Analysis and Prevention
| Defect Type | Cause | Prevention |
|---|---|---|
| Cracking | High residual stress, hydrogen | Proper preheat, controlled cooling |
| Porosity | Inadequate shielding, contaminated surfaces | Clean surfaces, proper gas flow |
| Lack of fusion | Insufficient heat input, poor surface prep | Adequate current, proper preparation |
| Excessive dilution | High heat input, thin strip | Lower current, thicker strip |
| Spalling | Poor bond strength, residual stress | Stress relief, proper alloy selection |
| Hardness variation | Inconsistent process parameters | Stable process control |
Process Optimization Strategies
The authors recommend the following strategies for optimizing strip electrode hardfacing:
- Multi-pass strategy: Using multiple passes with different strip compositions to achieve graded properties
- Pattern welding: Using weave patterns to ensure uniform coverage and stress distribution
- Temperature monitoring: Using infrared thermometers to maintain interpass temperatures within specified ranges
- Process parameter stability: Maintaining consistent current, voltage, and travel speed throughout the operation
- Documentation: Recording all process parameters and inspection results for quality traceability
Study Insights
This paper provides practical guidance for engineers considering strip electrode hardfacing for industrial applications. The key insight is that strip electrode welding represents a productive and cost-effective solution for many hardfacing applications, particularly where thick deposits are required or where productivity is a critical factor.
However, engineers must recognize the limitations of the process. Strip electrode hardfacing deposits may exhibit coarser microstructures compared to more refined processes such as laser cladding or PTA welding. The process is also less suitable for complex geometries and thin sections where heat input must be carefully controlled.
For organizations considering the adoption of strip electrode hardfacing, a thorough process qualification program is essential. The qualification should include mechanical testing, hardness verification, and wear testing under representative service conditions. Qualified personnel and proper equipment maintenance are also critical to achieving consistent results.
The paper reinforces the principle that the optimal hardfacing process is determined by the specific application requirements, including wear mechanism, service environment, component geometry, and production constraints. Engineers should evaluate all available hardfacing options and select the process that best meets the application requirements while considering cost, productivity, and quality factors.