CLADDING TECHNOLOGY SHANXI CO., LTDWear-Resistant Cladding of Sintered Hot Ore Crushed Tooth Rollers
Literature Overview
This study note examines the weld overlay cladding technology applied to tooth rollers used in sintered hot ore crushing operations. Tooth rollers in mineral processing plants are subjected to severe abrasive and impact loading conditions, where the sintered ore particles — often angular and hard — cause rapid wear of the tooth surfaces. The literature reviewed focuses on selecting appropriate cladding materials, optimizing the welding process parameters, and evaluating the service life improvement achieved through the cladding treatment.
Core Technical Points
The key challenge in cladding tooth rollers for sintered ore crushing lies in balancing hardness, toughness, and wear resistance. Conventional steel rollers typically exhibit hardness below 250 HV, leading to wear rates exceeding 0.5 mm per thousand operating hours under hot sintered ore conditions. The cladding materials discussed in the literature include high-chromium cast irons (Cr15, Cr20, Cr26), martensitic stainless steels (410, 440C), and tungsten carbide composite alloys. The most commonly adopted approach involves multi-layer cladding, where a transition layer is applied first to ensure metallurgical compatibility between the base steel and the hardfacing overlay.
| Cladding Material | Typical Hardness (HV) | Wear Resistance Index | Impact Toughness (J/cm²) |
|---|---|---|---|
| Cr15 High-Chromium Iron | 600–700 | 3.2 | 8–12 |
| Cr26 High-Chromium Iron | 650–750 | 4.1 | 6–10 |
| 440C Martensitic SS | 500–580 | 2.8 | 15–22 |
| WC-Co Composite | 800–950 | 5.5 | 3–6 |
Process Parameters and Layer Design
The cladding process typically employs submerged arc welding (SAW) or flux-cored arc welding (FCAW) for the transition layer, followed by multiple layers of hardfacing material. The recommended process window includes a preheating temperature of 200–300 °C to minimize hydrogen-induced cracking in the base metal, an interpass temperature maintained between 150–250 °C, and a post-weld cooling rate controlled to avoid excessive residual stress. The cladding thickness is generally designed at 8–15 mm for tooth rollers, with a minimum effective layer thickness of 3 mm above the dilution zone.
A critical aspect highlighted in the literature is the dilution rate. For the first overlay layer, dilution can reach 40–60%, significantly reducing the hardness of the deposited metal. To counteract this, the literature recommends either a two-step approach — first applying a compatible transition alloy such as Stellite 6 or a 309L stainless steel — or using a thicker first pass with higher current to increase the dilution zone volume while maintaining adequate bonding.
Defect Analysis and Countermeasures
Common defects observed in cladding tooth rollers include surface cracks, undercut, porosity, and incomplete fusion at the toe of the weld bead. Surface cracks are particularly prevalent when using high-carbon or high-chromium overlay materials due to the formation of brittle martensite and carbide networks. The following countermeasures are recommended:
- Preheating the base metal to 250–300 °C to slow the cooling rate and promote tempering of martensite.
- Using low-hydrogen flux and properly dried welding consumables to prevent porosity.
- Applying a peening operation between passes to relieve residual tensile stress and introduce beneficial compressive stress.
- Conducting magnetic particle inspection (MT) after each layer to detect surface cracks early.
Engineering Practice Insights
In practical field applications, tooth rollers cladded with Cr26 high-chromium iron have demonstrated service life improvements of 3–5 times compared to uncladded baseline rollers. However, the effectiveness depends heavily on the welding procedure qualification and the quality of post-weld heat treatment. A recommended PWHT at 550–600 °C for 2 hours per inch of thickness can significantly improve toughness without substantially reducing hardness. Metallographic examination of successfully cladded rollers shows a clear three-zone structure: a dilution zone with reduced hardness, a transition zone with mixed microstructure, and a full-property overlay zone with the desired carbide distribution.
Study Reflections
The literature reinforces the principle that cladding design must be considered as a system rather than a simple surface treatment. The selection of overlay material, the design of the transition layer, the control of process parameters, and the post-weld treatment all interact to determine the final performance. Engineers should always consider the specific service environment — including temperature, impact severity, and abrasive particle characteristics — when designing the cladding scheme. The cost-benefit analysis should also account for the downtime savings achieved through extended service life, which often justifies the higher initial cladding cost.