CLADDING TECHNOLOGY SHANXI CO., LTDResearch on Cladding of Rolling Rolls in Mining Engineering Applications
Literature Overview and Context
This 2002 publication by Ji Hailing, Li Xianghai, and Wang Huaiyu from the Technical Department of the Fifth Division, China Railway 13th Bureau, addresses the application of weld overlay techniques on rolling rolls used in mining and geological exploration engineering. Published in the Western Exploration Engineering journal, this work sits at the intersection of surface engineering and heavy-duty industrial equipment maintenance. The authors investigated overlay welding methods suitable for the harsh operating conditions encountered in mining roll applications, where abrasive wear, impact loading, and corrosive environments demand exceptional surface hardness and toughness.
Core Technical Content and Process Parameters
The fundamental challenge in roll cladding lies in balancing surface hardness against substrate toughness. Rolling rolls in mining applications typically experience severe abrasive wear from ore particles and rock fragments, necessitating overlay layers with hardness exceeding 50 HRC. The authors examined several overlay approaches including multi-layer welding strategies to manage residual stress and prevent cracking at the weld interface.
| Parameter | Typical Range | Rationale |
|---|---|---|
| Overlay layer hardness | 50-60 HRC | Abrasive resistance against ore particles |
| Number of overlay passes | 2-4 layers | Stress management and dilution control |
| Interpass temperature | 150-250°C | Prevent cold cracking in high-carbon overlay |
| Preheat temperature | 200-350°C | Reduce thermal gradient in roll body |
| Dilution rate target | <25% | Maintain overlay composition integrity |
| Cooling rate control | Controlled by interpass temp | Avoid martensitic transformation cracking |
The study emphasized that the base material of mining rolls is typically medium-carbon steel or low-alloy steel, which presents challenges for achieving high-hardness overlay layers without excessive dilution. The authors proposed using high-carbon, high-chromium consumables such as Cr-C system hardfacing alloys to achieve the required surface properties.
Engineering Practice and Defect Analysis
In practice, the most common defects observed in roll cladding include hot cracking in the overlay layer, lack of fusion at the interface, and undercutting at the roll edge. The authors identified that hot cracking occurs primarily when the carbon equivalent of the overlay material exceeds 0.6%, particularly in austenitic or high-martensitic compositions. Countermeasures included reducing the welding current, increasing the number of thinner layers, and maintaining adequate interpass temperatures.
Key Defects and Countermeasures
| Defect Type | Root Cause | Countermeasure |
|---|---|---|
| Hot cracking | High carbon equivalent, high restraint | Reduce welding current, add thin layers |
| Lack of fusion | Insufficient heat input, surface contamination | Preheat substrate, clean surface thoroughly |
| Undercut at edge | Poor travel technique at roll perimeter | Use backing bar or edge pre-welding |
| Porosity | Flux moisture, inadequate shielding | Dry flux, ensure proper gas coverage |
The engineering significance of this work lies in its practical orientation toward field repair of mining equipment. The authors demonstrated that proper preheating and post-weld heat treatment (PWHT) at 500-550°C for 2 hours per 25 mm of roll thickness could effectively relieve residual stresses and prevent delayed cracking during service.
Study Insights and Implications
This literature provides valuable insight into the practical challenges of applying overlay welding to cylindrical components with high geometric constraints. The mining engineering context adds another dimension — the rolls must withstand not only wear but also impact from large rock fragments. The authors' approach of combining high-hardness overlay with controlled residual stress management represents a mature engineering philosophy that remains relevant in contemporary practice. The work also highlights the importance of understanding the specific service conditions when selecting overlay materials, as generic hardfacing alloys may not provide optimal performance in all mining applications.