CLADDING TECHNOLOGY SHANXI CO., LTDApplication of Multi-Functional Roller Body Cladding Equipment in Rolling Mills
Literature Overview
This 2005 publication by Wang Yinjun from the Technical Center of Baosteel Meishan Iron and Steel Co., Ltd. documents the development and industrial deployment of a multi-functional roller body cladding (weld overlay) system specifically designed for hot rolling mill work rolls. The work addresses a long-standing challenge in the steel industry: the premature wear and damage of work rolls during the hot rolling process, which leads to reduced productivity, increased downtime, and elevated replacement costs. The paper reports on the engineering design, process parameter optimization, and field trial results of a cladding system capable of applying wear-resistant and corrosion-resistant overlay coatings onto cylindrical roller surfaces with high geometric accuracy and metallurgical bond quality.
Core Technical Content
The multi-functional roller body cladding equipment integrates several welding processes into a single automated system, allowing operators to select the most appropriate overlay method depending on the required surface hardness, wear resistance, and roller geometry. The system typically incorporates submerged arc welding (SAW) for bulk deposition of the base overlay layer, followed by surface finishing using gas metal arc welding (GMAW) or plasma transferred arc (PTA) techniques to achieve the final surface quality and hardness profile.
The key engineering innovation lies in the multi-axis positioning system that accommodates the large diameter and length of hot mill work rolls, which typically range from 500 mm to 800 mm in diameter and 1200 mm to 2000 mm in effective length. The cladding system must maintain precise wire feed control, travel speed synchronization, and arc stability over the entire cylindrical surface, including the critical shoulder regions where the roll body meets the journal.
Typical Process Parameters
| Parameter | Range | Notes |
|---|---|---|
| Base substrate | 42CrMo or 50CrVA | Normalized condition |
| Overlay layer | Cr-Mo-V hardfacing alloy | 55-60 HRC target hardness |
| SAW wire diameter | 1.6-2.4 mm | Solid wire or flux-cored |
| SAW current | 400-600 A | DC, electrode positive |
| Travel speed | 150-350 mm/min | Depends on wire diameter |
| Layer thickness | 2-4 mm per pass | Multi-pass buildup |
| Interpass temperature | < 250 °C | Controlled to prevent cracking |
| Preheating temperature | 150-250 °C | Uniform across roller surface |
Metallurgical Considerations
The bond strength between the overlay layer and the base roll material is critical for the service life of the cladded roller. The dilution rate between the base metal and the overlay alloy directly affects the final hardness and wear resistance of the surface layer. For hot rolling applications, a dilution rate of 15-25 percent is generally acceptable, as excessive dilution reduces the hardness below the required threshold, while insufficient dilution may lead to cracking at the bond interface due to thermal stress during cooling.
The residual stress distribution in the cladded roller is another critical factor. The multi-pass cladding process introduces complex residual stress patterns that can affect the dimensional stability of the roller during subsequent grinding and dressing operations. Post-weld heat treatment (PWHT) at 580-620 °C for 2-4 hours is typically applied to relieve these stresses and stabilize the microstructure.
Engineering Practice and Field Results
The field trials conducted at Baosteel Meishan demonstrated significant improvements in roller service life compared to conventional hardbanding methods. The multi-functional system allowed for in-situ repair of damaged rollers without complete removal from the mill line, reducing downtime by approximately 60 percent. The overlay layer hardness achieved values in the range of 55-62 HRC, providing excellent resistance to the abrasive and adhesive wear mechanisms prevalent in hot rolling operations.
The system also enabled the application of different overlay compositions to different zones of the roller surface, optimizing wear resistance where it is most needed while maintaining adequate toughness in regions subject to impact loading. This zonal cladding strategy represents a significant advancement over uniform cladding approaches used in earlier generations of roller repair systems.
Study Insights and Reflections
This work exemplifies the integration of welding process technology with mechanical engineering to solve a specific industrial problem. The multi-functional approach—combining multiple welding processes in a single system—reflects the philosophy of flexibility and adaptability that is essential in industrial applications where production conditions vary. The success of this system at a major steel production facility validates the technical approach and provides a reference framework for similar roller cladding applications in other rolling mills worldwide.