Zhuojin Pipe Fitting Co., LtdSurface Overlay Welding for Side Press Module Performance Enhancement
Literature Overview
The paper by Wang Guanghuan, Lin Tao, Jiang Guangbiao, and Li Xiaobing, published in Materials for Mechanical Engineering (Volume 33, Issue 5, 2009, pages 59–61), investigates the application of surface overlay welding to improve the performance and service life of side press modules used in hot rolling mills. The study examines the mechanical properties, high-temperature hardness, and high-temperature oxidation resistance of the overlay weld metal, as well as the microstructure of the overlay layer. The results demonstrate that surface overlay welding can significantly extend the service life of side press modules and replace imported modules at a lower cost.
Core Technical Analysis
Application Background and Failure Mode
Side press modules are critical components in hot rolling mills, where they are subjected to extreme mechanical loading, high temperatures (typically 600–800°C), and severe oxidation. The primary failure mode of conventional side press modules is surface degradation due to the combined effects of:
- High-temperature oxidation: Formation of oxide scales that spall off, leading to material loss.
- Thermal fatigue: Repeated heating and cooling cycles cause cracking at the surface.
- Abrasive wear: Contact with hot steel strips causes material removal.
- Adhesive wear: Transfer of material between the module surface and the steel strip.
The conventional material for side press modules is typically a high-temperature alloy steel or a cast alloy, which provides adequate strength but limited resistance to the combined degradation mechanisms. The overlay welding approach addresses this limitation by applying a wear-resistant, oxidation-resistant alloy layer on the surface of the module.
Overlay Welding Process and Material Selection
The paper describes the use of surface overlay welding to deposit a wear-resistant alloy layer on the side press module. The overlay material is selected to provide the following properties:
| Property | Requirement |
|---|---|
| High-temperature hardness | Maintain hardness above 30 HRC at 600°C |
| High-temperature oxidation resistance | Minimum oxide scale thickness at 800°C for 100 hours |
| Microstructure | Tempered sorbite + small amount of ferrite |
| Ductility | Adequate to prevent cracking during thermal cycling |
The overlay process is designed to achieve a uniform layer thickness of 3–5 mm on the working surface of the module. The welding parameters are optimized to minimize the dilution of the base material into the overlay and to ensure a metallurgically sound bond between the overlay and the base.
Microstructure and Property Analysis
The paper reports the following findings from the microstructural and property analysis:
- Microstructure: The overlay weld metal exhibits a tempered sorbite microstructure with a small amount of retained ferrite. This microstructure provides a good balance of strength and ductility, which is essential for resisting thermal fatigue cracking.
- High-temperature hardness: The overlay layer maintains a hardness of approximately 35 HRC at 600°C, which is significantly higher than the base material (approximately 20 HRC at the same temperature). This indicates that the overlay material provides effective resistance to abrasive and adhesive wear at operating temperatures.
- High-temperature oxidation resistance: The overlay layer shows a significantly reduced oxide scale thickness compared to the base material after exposure at 800°C for 100 hours. This indicates that the overlay material forms a protective oxide scale that limits further oxidation.
- Mechanical properties: The overlay layer exhibits improved ductility compared to the base material, which is beneficial for resisting thermal fatigue cracking.
Performance Comparison and Application Results
The paper compares the performance of the overlay-welded modules with both conventional domestic modules and imported modules:
| Metric | Conventional Domestic Module | Overlay-Welded Module | Imported Module |
|---|---|---|---|
| Service life (hours) | Baseline | Significantly extended | Comparable to overlay |
| High-temperature hardness | Lower | Higher | Comparable |
| Oxidation resistance | Poor | Good | Good |
| Cost | Low | Moderate | High |
The field trial results demonstrate that the overlay-welded modules achieve a service life comparable to imported modules while being significantly more cost-effective. This represents a successful technology transfer from imported to domestically produced components.
Engineering Practice Integration
The successful application of surface overlay welding to side press modules demonstrates the versatility of this technology for improving the performance of hot-section components in steel mills. The key engineering considerations are:
- The overlay material must be selected to match the specific service conditions (temperature, load, oxidation environment).
- The overlay thickness must be sufficient to provide the required service life, but not so thick as to cause cracking during thermal cycling.
- The welding parameters must be optimized to achieve a sound bond between the overlay and the base material, with minimal dilution.
- The overlay-welded module must be inspected for defects (cracks, porosity, lack of fusion) before being put into service.
Study Insights and Implications
This paper provides a clear demonstration of the economic and technical benefits of surface overlay welding for improving the performance of hot-section components. The key insight is that overlay welding can be used to create a functionally graded component, with a wear-resistant, oxidation-resistant surface and a strong, ductile base. This approach is particularly effective for components that are subject to combined mechanical and thermal degradation mechanisms. For engineers involved in steel mill maintenance and component design, this paper offers a validated approach to extending component life and reducing costs. The broader implication is that surface overlay welding is a versatile technology that can be applied to a wide range of industrial components, from steel mill equipment to power generation components.