CLADDING TECHNOLOGY SHANXI CO., LTDResearch on Cladding Materials and Processes for Coal Crusher Teeth Rings
Literature Overview
The study by Pei Haixu, Wang Sheng, and Fan Ling from the 52nd Research Institute of China North Industries Group (2003) addresses a critical engineering problem in coal preparation plants: the rapid abrasive failure of coal crusher teeth rings. These components operate under extreme conditions involving high-impact abrasion against hard coal and rock, making conventional carbon steel structures wholly inadequate. The research systematically evaluates cladding materials and welding processes specifically tailored for this severe service environment, published in the journal Ordnance Materials Science and Engineering.
Core Technical Content
The fundamental challenge with coal crusher teeth rings lies in balancing three competing requirements: surface hardness exceeding 60 HRC to resist abrasive wear, sufficient core toughness to absorb impact loads without catastrophic fracture, and reliable metallurgical bonding between the cladding layer and the base steel substrate. The researchers investigated multiple overlay strategies including submerged arc welding (SAW) with multi-layer schemes, electroslag welding (ESW) for thick deposits, and flux-cored arc welding (FCAW) for localized repair applications.
The material selection focused on high-chromium white cast iron compositions containing 12-18% Cr and 2.5-3.5% C, which form a high volume fraction of Cr7C3 carbides responsible for exceptional wear resistance. However, the brittleness of these carbides necessitates careful process control to prevent cracking during solidification and cooling.
| Parameter | Specification | Rationale |
|---|---|---|
| Cladding hardness | 60-68 HRC | Adequate wear resistance against coal and rock |
| Base steel | Q345R or similar | Sufficient impact toughness at operating temperature |
| Dilution rate | < 25% | Maintains carbide content and hardness in surface layer |
| Preheat temperature | 200-300°C | Reduces cooling rate and minimizes cracking risk |
| Interpass temperature | < 250°C | Controls microstructure evolution and residual stress |
| Post-weld treatment | 550-600°C × 2h | Stress relief without significant hardness reduction |
Process Analysis and Engineering Practice
The SAW multi-layer cladding approach proved most cost-effective for production-scale manufacturing. The first layer (bonding layer) typically uses a nickel-based or austenitic stainless steel filler such as ENi-CrMo or E309 to bridge the metallurgical incompatibility between the ferritic-pearlitic base steel and the brittle high-chromium cladding. This bonding layer prevents microcracking at the interface caused by differential thermal expansion coefficients.
Subsequent cladding layers use high-chromium iron wire or flux-cored wire with controlled composition. The dilution rate is the single most critical process variable; exceeding 25% dilution from the base steel significantly reduces the volume fraction of hard carbides and consequently degrades wear life. Achieving low dilution requires careful control of heat input, typically maintained between 15-25 kJ/mm, and proper joint preparation with adequate root opening.
A common defect observed in field applications is interfacial delamination caused by excessive cooling rates or inadequate preheating. The researchers emphasized the importance of maintaining interpass temperatures below 250°C to avoid the formation of coarse martensite and retained austenite in the bonding layer, which would compromise bond strength. Post-weld stress relief treatment at 550-600°C for 2 hours is mandatory to reduce residual stresses that can lead to delayed cracking under cyclic loading.
Key Insights and Reflections
This research demonstrates that successful cladding of coal crusher teeth rings is not merely a matter of selecting a hard overlay material but rather a holistic engineering approach integrating material design, process optimization, and heat treatment. The emphasis on dilution control reflects a broader principle in weld overlay engineering: the as-deposited microstructure is always a compromise between the intended cladding composition and the inevitable mixing with base material. Understanding this compromise and managing it through process variables is the essence of practical cladding engineering. The work, though published in 2003, remains highly relevant given the continued demand for cost-effective wear part solutions in mining and coal handling industries.