CLADDING TECHNOLOGY SHANXI CO., LTDPractice and Application of Overlay Welding Repair for Profile BD Rollers
Literature Overview
This study documents the practical implementation of weld overlay repair on profile rolling mill rollers of the BD type, which are used in the production of structural steel sections. The rollers suffer from surface damage due to galling, spalling, and fatigue cracking during service, and conventional replacement is costly and time-consuming. The authors describe a systematic repair process involving surface preparation, multi-pass overlay welding with a nickel-based or high-chromium alloy, post-weld heat treatment, and dimensional restoration by grinding. The work provides a complete process window with specific welding parameters, consumable selection criteria, and quality assurance measures that can be directly applied in plant maintenance environments.
Process Description and Parameters
The repair process follows a disciplined sequence. First, the damaged surface is ground back to sound metal using a belt grinder or flap disc, removing all spalled material and ensuring a smooth transition between the repaired zone and the original surface. The surface is then cleaned with a wire brush and solvent to remove oxide and grease. A preheating temperature of 250 to 300 degrees Celsius is applied to reduce residual stress and prevent cracking in the base metal. The overlay is deposited using gas metal arc welding with a flux-cored wire or gas tungsten arc welding with a solid wire, depending on the required deposit thickness.
| Process Parameter | Value |
|---|---|
| Preheat Temperature | 250-300 C |
| Interpass Temperature | Maximum 300 C |
| Welding Current (GMAW) | 180-250 A |
| Arc Voltage | 22-28 V |
| Travel Speed | 150-250 mm/min |
| Wire Diameter | 1.2 mm |
| Shielding Gas | Ar 80% / CO2 20% |
| Number of Passes | 3-5 |
| Post-Weld Heat Treatment | 550-600 C for 2 h |
| Final Surface Finish | Ra 0.8-1.6 um |
The overlay alloy selected is a high-chromium austenitic composition containing 20 to 25 percent Cr and 10 to 15 percent Mn, providing excellent resistance to galling and adhesive wear. The multi-pass deposit builds up the material in thin layers, each approximately 2 to 3 mm in thickness, to ensure adequate fusion and minimize dilution with the base steel. After the final pass, the roller is heat treated to relieve residual stresses and temper any martensite formed during rapid cooling. The surface is then ground to the required dimensional tolerance of plus or minus 0.1 mm on diameter.
Quality Control and Defect Management
The repair process incorporates several quality control checkpoints. Visual inspection is performed after each pass to detect porosity, undercut, or incomplete fusion. Ultrasonic testing is applied to the full overlay thickness to identify subsurface cracks and lack of bond. Hardness testing is conducted at multiple locations across the repair zone to verify uniform hardness distribution within the specified range of 45 to 52 HRC. The study reports that the most common defects encountered are hot cracking in the first pass due to excessive sulfur and phosphorus in the base metal, and cold cracking in the heat-affected zone due to insufficient preheat. Countermeasures include strict control of preheat temperature, use of low-sulfur consumables, and limiting the hydrogen content in the shielding gas.
Engineering Insights
The practical value of this study lies in its emphasis on process discipline and repeatability. In plant maintenance settings, overlay repair is often performed under time pressure with limited access to laboratory facilities, which increases the risk of defects. The authors advocate for documented procedure sheets, operator training, and in-process monitoring as essential elements of a reliable repair program. The study also notes that the service life of a properly repaired roller can approach 80 to 90 percent of a new roller, making the economic case for repair rather than replacement in most cases. Engineers should note that the BD roller geometry, with its contoured working face, requires careful adjustment of the welding gun angle and travel speed to maintain consistent bead profile across the roller surface.
Conclusion
This study provides a comprehensive and practical framework for overlay repair of profile rolling mill rollers. The combination of appropriate alloy selection, controlled welding parameters, thorough preheating, and rigorous quality inspection yields reliable results that extend roller service life significantly. Engineers involved in rolling mill maintenance should adopt the systematic approach described here and adapt the process parameters to their specific roller dimensions and service conditions.