Zhuojin Pipe Fitting Co., LtdPowder-Adding Strip Electrode Submerged Arc Overlay Welding Process
Literature Overview
The paper by Ma Hongze, Jiang Lipeng, Yu Jianrong, Huang Wenzhe, and Qian Qiang, published in Welding (1998, No. 12, pp. 16-19), presents a systematic study of the powder-adding strip electrode submerged arc overlay welding process. The authors, from Beijing Institute of Petrochemical Technology and the Harbin Welding Research Institute, address a specific metallurgical challenge inherent in conventional strip electrode submerged arc welding: the difficulty of roll-forming strip electrodes with high alloy content.
Core Technical Content
Conventional strip electrode submerged arc welding offers exceptional deposition rates, making it highly attractive for overlay applications requiring thick deposits. However, when alloy content in the strip electrode exceeds certain thresholds, the metallurgical properties of the strip become incompatible with the cold rolling process used to manufacture the electrode. High-carbon and high-alloy steels are difficult to roll into thin strip form without cracking, and the resulting strip may have poor surface quality.
The powder-adding technique elegantly solves this problem by:
- Using a low-alloy or mild steel strip electrode that is easily roll-formed into thin, uniform strips
- Introducing high-alloy powder into the arc zone through a separate feed mechanism
- Achieving high alloy content in the weld metal through dilution of the added powder into the molten pool
This approach combines the high deposition efficiency of strip electrode SAW with the metallurgical flexibility of powder metallurgy.
Process Parameter Optimization
The authors employed orthogonal experimental design to systematically optimize the process parameters. The key variables investigated include:
| Parameter | Range Studied | Effect on Quality |
|---|---|---|
| Travel speed | 0.5-2.0 m/min | Affects dilution rate and bead geometry |
| Powder feed rate | 1.0-4.0 kg/min | Controls alloy content in deposit |
| Powder particle size | 0.5-1.5 mm | Influences melting rate and distribution |
| Arc voltage | 25-40 V | Determines heat input and penetration |
| Strip electrode thickness | 1.0-2.0 mm | Affects deposition rate and stability |
| Powder-to-strip ratio | 0.5:1 to 3.0:1 | Controls final alloy composition |
The orthogonal experimental design allowed the authors to identify the interaction effects between parameters and determine the optimal parameter combination for achieving desired overlay properties.
Metallurgical Considerations
The powder-adding strip electrode SAW process creates a unique metallurgical environment:
- Dilution control: The alloy content in the final deposit depends on the relative melting rates of the strip and powder, which are influenced by arc characteristics and powder characteristics.
- Microstructure development: The cooling rate and thermal cycle determine the microstructure of the overlay, which directly affects wear resistance and toughness.
- Alloy segregation: The powder-adding technique may result in non-uniform alloy distribution if parameters are not carefully controlled.
- Inclusion formation: Powder particle size and composition affect the formation of oxide and sulfide inclusions in the weld metal.
Comparative Analysis with Conventional Processes
| Process | Deposition Rate | Alloy Flexibility | Cost | Equipment Complexity |
|---|---|---|---|---|
| Strip electrode SAW | Very high | Limited by strip rollability | Moderate | Low |
| Powder-adding strip SAW | High | High (powder composition) | Moderate-High | Medium |
| Powder-adding FCAW | Moderate | High | High | Medium |
| Electrode arc overlay | Low-Moderate | Moderate | Low-Moderate | Low |
| GMAW overlay | Low | High | High | Medium |
Engineering Applications and Practice
The powder-adding strip electrode SAW process is particularly suitable for:
- Large-scale overlay applications requiring thick deposits on heavy components
- High-alloy overlays where conventional strip electrodes cannot be manufactured
- Industrial repair operations where high deposition efficiency reduces repair time
- Wear-resistant surface engineering for mining, cement, and power generation equipment
From a practical standpoint, the process requires careful attention to:
- Powder feed system reliability and consistency
- Powder storage and handling to prevent contamination
- Process parameter monitoring and control
- Quality assurance through periodic metallographic examination
Study Insights and Implications
This 1998 paper represents an important contribution to the field of overlay welding technology, demonstrating how process innovation can overcome fundamental metallurgical limitations. The use of orthogonal experimental design for parameter optimization reflects rigorous engineering methodology and provides a reproducible framework for process development.
The powder-adding technique essentially decouples the metallurgical requirements of the overlay from the mechanical requirements of the electrode form. This conceptual separation is powerful and has implications beyond this specific application. Engineers should consider this approach when facing similar constraints in other welding applications where material properties and manufacturing constraints are in conflict.
The process remains relevant today, particularly for industrial repair applications where deposition efficiency is critical and high-alloy overlays are required. The fundamental principles established in this paper continue to inform modern powder-adding welding technologies.