CLADDING TECHNOLOGY SHANXI CO., LTDSubmerged Arc Weld Overlay Device for Roll Press Squeeze Rolls
Literature Overview
This 2019 study by Wang Yinjun, Huang Quanxin, Huang Xiang, Jiang Sheming, and Zhang Qifu from the Central Iron and Steel Research Institute (Advanced Metallic Materials Coating National Engineering Laboratory), Shanghai Meishan Iron and Steel Co., Ltd., and Guangxi No. 1 Industrial School presents a submerged arc welding (SAW) overlay device specifically designed for roll press squeeze rolls. Roll press squeeze rolls are critical components in steel rolling mills, subjected to extreme mechanical loading, abrasion, and thermal cycling. The development of a dedicated SAW overlay device addresses the specific challenges of overlaying large-diameter cylindrical rolls in a manufacturing environment, ensuring consistent quality and productivity.
Core Technical Analysis
The submerged arc welding overlay of squeeze rolls presents unique challenges due to the large diameter, rotational symmetry, and demanding service conditions of these components. The SAW process is well-suited for this application due to its high deposition rate, deep penetration, and excellent slag protection. However, the development of a specialized device is necessary to accommodate the large geometry and ensure uniform overlay coverage.
Device Configuration and Design Features
The SAW overlay device for squeeze rolls incorporates several key design features:
| Feature | Description | Function |
|---|---|---|
| Rotating chuck | Holds and rotates the roll | Enables uniform circumferential coverage |
| Multi-wire system | Two or more wires for high deposition rate | Increases productivity |
| Slag shield | Flux coverage for protection | Prevents oxidation, stabilizes arc |
| Positioning system | Precise wire-to-roll alignment | Ensures uniform weld geometry |
| Cooling system | Water or air cooling of the roll | Controls temperature, reduces distortion |
| Monitoring system | Real-time parameter monitoring | Ensures process stability |
Process Parameters for Squeeze Roll Overlay
The overlay process parameters are optimized for the specific application of squeeze rolls:
| Parameter | Typical Value | Rationale |
|---|---|---|
| Welding current | 600–1200 A | High deposition rate for productivity |
| Arc voltage | 28–38 V | Controls penetration and dilution |
| Travel speed | 200–500 mm/min | Balances deposition rate and quality |
| Wire diameter | 1.6–3.2 mm | Accommodates high current |
| Flux composition | High-silica or low-silica | Controls slag properties and weld metal quality |
| Wire composition | High-chromium iron or high-carbon iron | Provides wear resistance |
| Preheat temperature | 100–300°C | Reduces cracking susceptibility |
| Interpass temperature | < 300°C | Controls microstructure and residual stresses |
| Number of passes | 3–8 | Achieves required overlay thickness |
Overlay Layer Microstructure and Properties
The overlay layer for squeeze rolls is designed to provide high wear resistance while maintaining adequate toughness to resist impact and thermal shock:
| Property | Target Value | Testing Method |
|---|---|---|
| Hardness | 400–550 HV | Vickers hardness test |
| Tensile strength | 600–800 MPa | Tensile test |
| Impact energy | > 30 J at 20°C | Charpy V-notch test |
| Dilution rate | < 30% | Optical emission spectrometry |
| Bond strength | > 0.8 × base metal strength | Peel test or tensile bond test |
| Wear resistance | > 3× base metal | Pin-on-disk test |
Comparison of Overlay Processes for Squeeze Rolls
| Process | Deposition Rate (kg/h) | Dilution (%) | Hardness (HV) | Cost | Applicability |
|---|---|---|---|---|---|
| Submerged arc welding | 50–150 | 20–40 | 350–500 | Low | Large rolls, high productivity |
| Gas metal arc welding | 10–30 | 15–35 | 300–450 | Moderate | Medium rolls, flexible |
| Flame spraying | 20–60 | N/A (no dilution) | 250–400 | Moderate | Thin overlays, low-stress areas |
| Electroslag welding | 100–300 | 30–50 | 300–450 | Low | Very large rolls, high thickness |
| Laser cladding | 5–20 | 5–15 | 400–600 | High | Precision overlays, small areas |
Engineering Practice Integration
The development of the SAW overlay device has significant implications for the maintenance and productivity of steel rolling mills. Key engineering considerations include:
- Overlay thickness design — The overlay thickness must be sufficient to provide the required wear life while minimizing the weight and cost of the overlay. A typical overlay thickness for squeeze rolls is 10–25 mm, depending on the severity of service conditions.
- Grinding after overlay — After overlay welding, the roll surface must be ground to achieve the required surface finish and dimensional accuracy. The grinding allowance must be included in the overlay thickness design.
- Heat treatment after overlay — Post-weld heat treatment may be required to relieve residual stresses and improve the toughness of the overlay layer. The heat treatment parameters must be carefully controlled to avoid softening the overlay or introducing new defects.
- Quality assurance — The overlay process must be accompanied by a comprehensive quality assurance program that includes material verification, process parameter monitoring, in-process inspection, and final testing.
- Life prediction — The service life of the overlay layer should be predicted based on the wear rate under specific service conditions. This prediction should be used to schedule preventive maintenance and overlay renewal.
Key Questions and Reflections
A critical question arising from this research is how to optimize the overlay process for specific service conditions. The wear mechanism in squeeze rolls may vary depending on the material being rolled, the rolling temperature, and the rolling speed. Understanding the dominant wear mechanism is essential for selecting the appropriate overlay composition and process parameters.
Another important consideration is the effect of thermal cycling on the overlay layer. Squeeze rolls experience significant temperature variations during operation, which can induce thermal fatigue cracking in the overlay layer. The thermal fatigue resistance of the overlay layer should be evaluated during process development and qualification.
Study Insights and Implications
This research demonstrates that the development of specialized equipment for SAW overlay of squeeze rolls can significantly improve the productivity and quality of the overlay process. The key insight is that the overlay process must be tailored to the specific geometry and service conditions of the component, rather than applying a generic process to all applications. This approach ensures that the overlay layer provides optimal performance while minimizing costs and downtime.
The study also highlights the importance of collaboration between research institutions, equipment manufacturers, and end users in the development of specialized welding equipment. The integration of advanced materials knowledge, process engineering, and practical manufacturing experience is essential for developing effective solutions for challenging industrial applications. Future research should focus on further optimizing the overlay process parameters, developing new overlay compositions, and integrating real-time monitoring and control systems to improve the consistency and reliability of the overlay process.