Zhuojin Pipe Fitting Co., LtdLarge-Area Wear-Resistant Alloy Overlay Cladding Plate Surfacing Technology and Its Applications
Literature Overview
This paper by Qian Qiang, Bao Xiaobing, Cui Rong, and Huang Wenzhe from the Harbin Welding Research Institute, published in the journal "Welding" (1990, Issue 3, pp. 1-5), provides a comprehensive review of large-area wear-resistant alloy overlay cladding plate surfacing technology. The study covers the characteristics of the submerged arc welding process with powder filler metal, the selection of surfacing materials, and practical applications in industrial production. This early work laid important groundwork for the development of overlay cladding technology in China and reflects the state of the art at the time of publication.
Core Technical Content
The paper focuses on the submerged arc welding (SAW) process using powder filler metal as the primary method for producing large-area wear-resistant alloy overlay cladding plates. This approach combines the advantages of submerged arc welding, including high deposition rate, deep penetration, and excellent weld quality, with the versatility of powder filler metals, which allow for precise composition control of the deposited overlay layer.
The basic process involves welding a wear-resistant alloy layer onto a structural steel base plate. The overlay layer provides wear resistance, while the base plate provides structural strength and toughness. The key technical challenge is achieving a sound metallurgical bond between the overlay layer and the base plate, while also managing the dilution of base metal into the overlay layer to ensure the required hardness and wear resistance.
Submerged Arc Welding with Powder Filler Metal
The submerged arc welding process uses a flux-cored wire or self-shielded wire in conjunction with a granular flux. When powder filler metal is used, the consumable consists of a wire core and a coating of alloy powder, or a wire is fed through a flux powder mixture. This approach offers several advantages for overlay welding applications:
| Feature | Description | Engineering Significance |
|---|---|---|
| Deposition rate | 5-20 kg/h | High productivity for large-area cladding |
| Dilution rate | 5-25% (adjustable) | Controls overlay composition |
| Weld width | 20-60 mm | Efficient coverage of large surfaces |
| Layer thickness | 3-8 mm per pass | Fewer passes needed for target thickness |
| Weld defects | Low porosity rate | Flux provides good shielding |
| Cost per unit area | Relatively low | Economical for large production runs |
The powder filler metal allows for the production of overlay alloys with compositions that would be difficult or impossible to achieve with solid wire electrodes. The powder can contain hardening elements such as chromium, tungsten, molybdenum, cobalt, and carbon in precise proportions, enabling the production of overlay layers with specific hardness and wear resistance characteristics.
Surfacing Material Selection
The selection of wear-resistant overlay materials depends on the specific wear mechanism encountered in the application. The paper discusses several material systems commonly used for overlay cladding:
| Material System | Typical Hardness (HRC) | Wear Mechanism | Application Examples |
|---|---|---|---|
| Cr-C (High Carbon Chromium) | 55-65 | Abrasive wear | Mining equipment, conveyor components |
| Cr-Co (Cobalt-based) | 45-55 | High-temperature wear | Hot working tools, die casting |
| Cr-Mo (Chromium-Molybdenum) | 40-50 | Impact and abrasion | Mining buckets, crusher parts |
| Ni-Cr (Nickel-Chromium) | 50-60 | Severe abrasive wear | Cement mills, grinding media |
| Fe-Cr-C (Iron-Chromium-Carbon) | 55-65 | General abrasive wear | Industrial wear plates |
The dilution of base metal into the overlay layer is a critical factor in determining the final properties of the cladding. For high-carbon chromium overlays, dilution can reduce the carbon content below the level needed for martensite formation, resulting in lower hardness. Strategies to minimize dilution include using a transition layer with composition intermediate between the base plate and the final overlay, using higher welding speeds, and employing multiple thin passes instead of fewer thick passes.
Production Applications
The paper documents several industrial applications of the large-area overlay cladding technology. These applications span multiple industries, including mining, cement, power generation, and material handling. The common thread across these applications is the need for components that experience severe abrasive wear and require periodic replacement or repair.
In the mining industry, overlay cladding plates are used for conveyor chutes, hopper liners, and crusher components. The overlay layer extends the service life of these components by a factor of 3-10 times compared to unclad carbon steel, significantly reducing maintenance costs and downtime. In the cement industry, grinding mill liners and mill shells benefit from overlay cladding that resists the abrasive action of cement clinker and grinding media.
The production of large-area cladding plates requires careful process control to ensure uniform overlay thickness, consistent hardness, and sound metallurgical bonding across the entire surface area. Quality control measures include visual inspection, magnetic particle testing for surface and near-surface defects, ultrasonic testing for subsurface defects, and hardness testing at multiple locations across the cladded surface.
Key Technical Insights
The paper highlights several important technical considerations that remain relevant in modern overlay welding practice. First, the selection of the base plate material is critical. The base plate must have adequate toughness to support the hard overlay layer without cracking during service. Low-carbon steels such as ASTM A36 or A516 Gr. 70 are commonly used as base plates, with the selection depending on the required mechanical properties and service conditions.
Second, the welding procedure qualification is essential for ensuring consistent overlay quality. The welding procedure specification (WPS) must define the welding parameters, including current, voltage, travel speed, wire feed rate, and preheat temperature, as well as the sequence of welding passes and the required interpass temperature. The welder performance qualification must demonstrate the welder's ability to produce sound overlay welds with the required properties.
Third, the post-welding treatment can significantly affect the final properties of the overlay layer. Some overlay alloys require heat treatment to achieve the target hardness and wear resistance. For example, high-carbon chromium overlays may require austenitizing and quenching to transform the as-deposited structure to martensite. Other overlays may require stress relief to reduce residual stresses that could lead to cracking during service.
Summary
This early but influential paper provides a valuable overview of large-area wear-resistant overlay cladding technology, covering the process fundamentals, material selection, and industrial applications. The submerged arc welding process with powder filler metal remains one of the most economical and productive methods for producing overlay cladding plates, and the principles discussed in this paper continue to guide modern practice. Engineers involved in wear-resistant component design and manufacturing should study this work to understand the historical development of overlay technology and the fundamental principles that underpin its successful application. The emphasis on process control, material selection, and quality assurance remains as relevant today as it was when the paper was published.