CLADDING TECHNOLOGY SHANXI CO., LTDResearch on Stainless Steel Strip Electrode Cladding Process
Literature Overview
Huang Siluo from Maoming Petrochemical Machinery Factory and He Xiang from Guangdong Yuehai Steel Cylinder Factory published this research in Welding in 1999. The study investigates the strip electrode cladding process for stainless steel overlays, addressing practical manufacturing challenges in the production of stainless steel lined pressure vessels and storage containers. This work represents a practical engineering approach to achieving uniform and high-quality stainless steel cladding layers using strip electrode technology.
Core Technical Content
Strip electrode cladding, also known as strip cladding or twin-wire strip welding, is a specialized cladding process that uses a continuous stainless steel strip as the filler material, with the strip fed into the arc alongside a consumable electrode. The process offers several advantages over conventional wire hardfacing: higher deposition rates, lower dilution from the base steel, and more uniform composition throughout the overlay thickness. The Maoming Petrochemical Machinery Factory application involved the cladding of carbon steel pressure vessels with stainless steel liners for chemical processing service.
Process Parameters and Configuration
The strip electrode cladding process employs a twin-wire configuration where the stainless steel strip and a consumable electrode are fed simultaneously into the arc. The strip thickness typically ranges from 1.5 to 3.0 mm, with a width of 15 to 25 mm. The process parameters are optimized to achieve a single-pass deposition thickness of 1.5 to 2.5 mm, with a travel speed of 150 to 300 mm/min and a current range of 300 to 500 A depending on the strip thickness and material.
| Process Parameter | Typical Range | Optimization Criteria |
|---|---|---|
| Strip thickness | 1.5-3.0 mm | Deposition thickness control |
| Strip width | 15-25 mm | Bead width and overlap |
| Current (DC+) | 300-500 A | Penetration and dilution |
| Travel speed | 150-300 mm/min | Deposition rate and quality |
| Shielding gas | Ar + 2-5% CO2 | Arc stability and cleanliness |
| Preheat temperature | 100-200°C | Stress relief and crack prevention |
| Interpass temperature | 150-250°C | Avoid excessive grain growth |
| Single pass thickness | 1.5-2.5 mm | Dilution control |
Microstructural Control and Dilution Management
The primary challenge in strip electrode cladding is controlling the dilution rate, which directly affects the corrosion resistance and mechanical properties of the overlay. The strip electrode process achieves lower dilution rates (typically 10-20 percent) compared to conventional wire hardfacing (20-35 percent) because the strip provides a larger volume of filler material that dilutes the base metal melt. The microstructure of the overlay consists of a fine-grained austenitic or austenitic-ferritic matrix with controlled grain boundary carbide precipitation.
The composition of the overlay is critical for ensuring adequate corrosion resistance. For 304 stainless steel cladding, the overlay composition should contain 18-20 percent chromium and 8-10 percent nickel to maintain a fully austenitic structure. The dilution from the base carbon steel introduces carbon and reduces the nickel content, which can lead to the formation of martensite or ferrite that degrades corrosion resistance. The strip electrode process mitigates this issue by providing a larger volume of stainless steel filler material.
Quality Control and Inspection
The quality of strip electrode cladding is assessed through several inspection methods. Visual inspection verifies the absence of surface defects such as cracks, porosity, and undercut. Magnetic particle testing (MT) or dye penetrant testing (PT) is used to detect surface and near-surface defects. Ultrasonic testing (UT) is employed to verify the bond strength between the overlay and the base steel, with a minimum bond strength requirement of 90 percent of the lower strength material. Radiographic testing (RT) may be used for critical applications to detect internal porosity or lack of fusion.
The mechanical properties of the overlay are verified through hardness testing, which should show uniform hardness across the overlay thickness. For 304 stainless steel cladding, the hardness should be in the range of 150-250 HV, with a maximum of 250 HV to ensure adequate ductility. Tensile testing of the overlay-base steel interface verifies the bond strength, which should exceed 90 percent of the base steel tensile strength.
Engineering Application and Performance
The strip electrode cladding process was successfully applied to the manufacture of stainless steel lined pressure vessels for chemical processing at the Maoming Petrochemical Machinery Factory. The cladding layer thickness was typically 3 to 6 mm, achieved in 2 to 4 passes depending on the required thickness. The service performance in chemical processing environments demonstrated excellent corrosion resistance, with no evidence of intergranular corrosion or pitting after 5 years of service in acidic environments.
The process offered significant economic advantages over solid stainless steel construction, with material cost reductions of 60-70 percent and weight reductions of 40-50 percent. The deposition rate of the strip electrode process (approximately 3-5 kg/h) was 2-3 times higher than conventional wire hardfacing, resulting in shorter production times and lower labor costs.
Key Reflections and Study Insights
The strip electrode cladding process represents an excellent example of process innovation that addresses practical manufacturing challenges. The key insight is that the process parameters must be carefully optimized to balance deposition rate, dilution control, and microstructural quality. The lower dilution rates achieved with strip electrode cladding are a direct result of the larger volume of filler material provided by the strip, which is a fundamental advantage over wire-based processes. The research demonstrates that process selection is as important as materials selection in achieving the desired performance of cladding applications, and that specialized processes such as strip electrode cladding can provide significant advantages for specific applications.