CLADDING TECHNOLOGY SHANXI CO., LTDDevelopment of Welding Electrodes for Corrugated Roll Cladding
Literature Overview
This study addresses the critical challenge of developing specialized welding electrodes for the cladding repair and maintenance of corrugated rolls used in paper and packaging industries. Corrugated rolls operate under extreme conditions involving high contact pressure, friction, moisture, and chemical attack from paper pulp. The base material is typically a high-carbon steel or medium-carbon steel with a hardness range of 250–320 HB, and the working surface undergoes periodic wear that necessitates periodic cladding repair to restore dimensional accuracy and surface quality. The research focuses on electrode composition design, welding process optimization, and the relationship between electrode chemistry and the resulting overlay microstructure and wear resistance.
Core Technical Analysis
The key innovation in this work lies in the systematic approach to electrode flux composition and core wire chemistry tailored specifically for corrugated roll applications. Traditional general-purpose stainless steel or high-carbon electrodes often produce overlay layers with excessive hardness (exceeding 550 HV), leading to poor grindability and excessive wear on grinding wheels. Conversely, overly soft overlays (below 280 HV) fail to resist the abrasive and adhesive wear mechanisms prevalent in corrugating operations.
The electrode design targets a balanced microstructure with a hardness of 320–380 HV in the as-welded condition, which provides sufficient wear resistance while maintaining good machinability. The alloying strategy involves controlled addition of Cr (8–12%), Mo (1–2%), and V (0.3–0.5%) in the core wire, combined with a flux that promotes controlled dilution and grain refinement. The flux composition is designed to ensure stable arc burning, low spatter, and adequate deoxidation to prevent porosity in the overlay.
| Parameter | Target Range | Measurement Method |
|---|---|---|
| Overlay hardness (as-welded) | 320–380 HV | Vickers microhardness |
| Dilution rate | 25–35% | Optical emission spectroscopy |
| Overlay thickness per pass | 2.5–3.5 mm | Micrometer measurement |
| Interpass temperature | 150–250 °C | Infrared pyrometer |
| Arc voltage | 22–28 V | Digital multimeter |
| Welding current | 180–240 A | Ammeter |
| Cr content in overlay | 10–14% | OES analysis |
| Mo content in overlay | 1.5–2.5% | OES analysis |
Welding Process Optimization
The welding process parameters were optimized through orthogonal experimental design (L9 orthogonal array) to minimize defects while maximizing overlay quality. The base metal of the corrugated roll is typically preheated to 150–200 °C to reduce the risk of cold cracking in the HAZ. The interpass temperature must be carefully controlled—exceeding 300 °C leads to excessive grain growth and softening of the previous weld pass, while too low a temperature promotes martensitic transformation and increases residual stress.
A critical finding is that the electrode depositing rate and dilution control are strongly influenced by the welding angle. For corrugated rolls, the rolling surface is curved, and the electrode must be deposited in a multi-pass pattern following the roll's helical corrugation. The recommended technique involves a weave pattern with a frequency of 3–5 weaves per 100 mm of travel, ensuring uniform coverage of the corrugation peaks and valleys.
Common Defects and Countermeasures
| Defect Type | Root Cause | Countermeasure |
|---|---|---|
| Porosity | Flux moisture absorption | Pre-dry flux at 300 °C for 2 h |
| Cracking in overlay | Excessive dilution from base | Increase electrode alloying content |
| Undercut | Excessive arc length | Reduce arc length to 2–3 mm |
| Excessive hardness | High cooling rate | Increase preheat temperature |
| Poor surface finish | Spatter accumulation | Adjust current to 200–220 A |
Engineering Practice Integration
In practice, the cladding of corrugated rolls requires special consideration for the roll's operational geometry. The corrugation profile means that the electrode must be applied in a way that maintains the precise corrugation dimensions after grinding. Typically, an overbuild of 0.5–1.0 mm above the nominal surface is applied before final grinding to the required profile. The electrode must therefore be deposited with a controlled build-up rate to avoid excessive material waste and to minimize grinding time.
The study also highlights the importance of post-weld cooling control. Rapid air cooling after welding can induce martensitic transformation in the overlay, leading to high hardness and potential cracking. Controlled cooling in a low-temperature furnace (150–200 °C, held for 1 h) is recommended to temper the overlay and reduce residual stress without significantly reducing hardness.
Study Insights
The research demonstrates that electrode development for specialized applications requires a holistic approach that considers not only the overlay's wear properties but also the processability, grindability, and dimensional stability of the deposited layer. The corrugated roll application is particularly demanding because the overlay must survive repeated grinding cycles during maintenance without exposing the base metal or developing surface cracks. The systematic approach to flux and core wire design, combined with rigorous process parameter optimization, provides a replicable methodology for developing electrodes for other specialized roll applications such as calender rolls and embossing rolls.