CLADDING TECHNOLOGY SHANXI CO., LTDApplication of Lincoln Wire in Composite Cladding of Billet Continuous Casting Rolls
Literature Overview
This study examines the practical application of Lincoln Electric welding consumables in the composite cladding repair and fabrication of billet continuous casting rolls. Continuous casting rolls operate under extreme conditions involving cyclic thermal loading, molten steel contact, mechanical wear from the solidifying shell, and corrosive attack from slag and flux. The roll surface must therefore exhibit high thermal fatigue resistance, wear resistance, and thermal conductivity, while the roll body must provide adequate structural strength. The composite cladding approach combines a wear- and corrosion-resistant surface layer with a tough, ductile substrate, and the selection of welding consumables is critical to achieving the required metallurgical compatibility and joint integrity.
Core Technical Points
Selection of Welding Consumables
The study evaluates specific Lincoln Electric wire electrodes designed for overlay applications on continuous casting rolls. These consumables are typically based on nickel-based or cobalt-based systems with controlled chromium, tungsten, and molybdenum additions to provide thermal fatigue resistance and wear resistance. The Lincoln wires are selected to match the dilution characteristics of the base roll material, which is commonly a ductile iron or low-carbon steel roll shell. The key advantage of using purpose-designed overlay wires is the ability to control the deposited metal composition independently of the base metal, ensuring that the final overlay alloy falls within the specified range even at dilution levels of 15-25%.
| Consumable Type | Base Alloy System | Typical Composition (wt%) | Application |
|---|---|---|---|
| Lincoln Nickel-Based Wire | Ni-Fe-Cr | Ni balance, Cr 25-30, Fe 10-15 | Thermal fatigue resistant cladding |
| Lincoln Hardfacing Wire | Co-Cr-W | Co balance, Cr 25-30, W 5-8 | High wear resistance zones |
| Lincoln Stainless Wire | Cr-Ni austenitic | Cr 20-25, Ni 18-22 | Corrosion resistant transition layer |
Welding Process Parameters
The overlay welding is typically performed using flux-cored arc welding or submerged arc welding for high deposition rates. The process parameters are optimized to control the dilution ratio, which is the most critical factor determining the final overlay composition. A dilution ratio of 10-15% is generally acceptable for nickel-based systems, while cobalt-based systems can tolerate higher dilution up to 20-25% due to their wider solidification range. The welding parameters include a current of 300-500 A, voltage of 28-36 V, and travel speed of 300-600 mm/min, depending on the wire diameter and the required bead profile.
Microstructural Analysis
The overlay microstructure consists of a dendritic primary phase of austenite or austenite-ferrite, with interdendritic carbides of the M7C3 or M23C6 type in nickel-based systems and M6C carbides in cobalt-based systems. The grain structure at the fusion boundary is columnar and can extend up to 100-200 μm into the overlay layer. The heat-affected zone in the base metal exhibits grain growth and possible martensitic transformation if the base is a low-carbon steel with a carbon equivalent exceeding 0.40%. Post-weld heat treatment at 800-900 °C for 2-4 hours is required to temper any martensite formed in the HAZ and to homogenize the carbide distribution in the overlay.
Engineering Practice and Quality Control
Defect Analysis and Countermeasures
The most common defects encountered in continuous casting roll cladding are porosity, hot cracking, and lack of fusion at the fusion boundary. Porosity is primarily caused by gas pickup from contaminated base metal or flux, and can be mitigated by thorough surface cleaning and the use of low-hydrogen consumables. Hot cracking is associated with the segregation of low-melting-point phases at the interdendritic regions and can be controlled by adjusting the carbon and sulfur content of the deposited metal. Lack of fusion at the fusion boundary is the most critical defect, as it directly compromises the bond strength between the overlay and the base metal, and can be prevented by ensuring adequate preheating (200-300 °C) and proper welding technique.
The non-destructive testing protocol for cladded casting rolls includes magnetic particle inspection of the surface and near-surface regions, ultrasonic testing of the bond strength, and hardness mapping across the overlay thickness. The bond strength is verified by sectioning representative specimens and performing a three-point bend test in accordance with ASTM A263 or equivalent standards. The minimum acceptable bond strength is typically 250 MPa for nickel-based overlays and 300 MPa for cobalt-based overlays.
Performance in Service
Field experience indicates that properly cladded continuous casting rolls achieve a service life of 3-5 times that of uncladded rolls. The thermal fatigue resistance of the nickel-based overlay is attributed to the fine-grained austenitic structure with dispersed carbides, which provides adequate creep resistance at the elevated temperatures encountered during casting (up to 1500 °C at the roll surface). The wear resistance is enhanced by the hard carbide phases that resist abrasion from the solidifying steel shell. The study confirms that the Lincoln wires deliver consistent performance across multiple production runs, with low variability in overlay composition and mechanical properties.
Study Insights and Reflections
The practical application of specialized welding consumables in continuous casting roll cladding illustrates the importance of consumable-process-structure-property integration in industrial welding. The selection of Lincoln wires is not merely a matter of brand preference but reflects a systematic approach to consumable qualification that includes composition control, dilution prediction, and mechanical property verification. For engineers involved in cladding design, this study reinforces the principle that the welding consumable must be qualified under conditions that replicate the actual production environment, including the specific base metal composition, the welding process parameters, and the post-weld heat treatment schedule.
The study also highlights the value of field feedback in consumable development. The continuous casting industry has accumulated decades of experience in overlay welding, and this empirical knowledge has been incorporated into the design of modern consumables. Engineers should actively participate in consumable qualification programs and maintain detailed records of service performance to contribute to the ongoing improvement of cladding technologies.