CLADDING TECHNOLOGY SHANXI CO., LTDManufacturing and Hard-Facing Cladding of CDG Roller Press Squeeze Rolls
Technical Background and Industry Context
The paper by Zou Wen, published in "New Century Cement Guide" in 2008, addresses the manufacturing and hard-facing cladding of squeeze rolls used in CDG (Cement Drum Grind) roller press systems. Roller presses are critical equipment in cement production, where two large steel rolls rotate in opposite directions to crush clinker or raw meal through intense pressure. The squeeze surfaces of these rolls are subjected to extreme combined loading: high contact pressure (often exceeding 30 MPa), abrasive wear from hard cement particles, thermal cycling, and occasional impact loading. The service life of squeeze rolls directly impacts production continuity and cost, making hard-facing cladding an essential surface engineering solution.
The author, representing the Chengdu Building Materials Industry Design and Research Institute, brings practical design experience to the problem, focusing on how cladding specifications and manufacturing methods translate into field performance.
Cladding Process Selection and Process Parameters
The study evaluates several hard-facing cladding processes for the squeeze roll surface, with particular emphasis on submerged arc welding (SAW) overlay and gas metal arc welding (GMAW) overlay. The following table presents the comparative analysis of applicable processes:
| Process | Typical Wire/Flux | Layer Hardness (HRC) | Layer Thickness | Advantages | Limitations |
|---|---|---|---|---|---|
| SAW overlay | E15CrMo-15 with flux | 45-55 | 3-6 mm per pass | High deposition rate, good penetration | Requires flat or cylindrical surface preparation |
| GMAW overlay | SS80 or hardfacing wire | 50-60 | 2-4 mm per pass | Flexible, portable | Lower deposition rate, higher spatter |
| Oxy-fuel overlay | Cast iron or alloy rod | 40-50 | 1-3 mm per pass | Simple equipment | Lower hardness, wide heat-affected zone |
| TIG overlay | Ni-based or Cr-based filler | 55-65 | 1-2 mm per pass | Precise control, clean weld | Very low deposition rate |
For CDG squeeze rolls, the study recommends a multi-layer SAW overlay approach using a Cr-Mo alloy steel wire with appropriate flux. The overlay layer composition should contain 2-4% Cr and 0.5-1.5% Mo to achieve a balance between hardness and toughness. The carbon content should be controlled between 0.3-0.6% to ensure sufficient carbide formation for wear resistance while maintaining adequate ductility to resist crack propagation.
Manufacturing Procedure and Heat Treatment
The manufacturing sequence for the cladded squeeze roll involves several critical steps. The base roll is typically made of medium carbon steel (such as 45 steel or 42CrMo) with a hardness of 220-260 HB after normalizing. The surface is machined to remove the oxide scale and prepare a uniform substrate. Preheating to 250-350°C is essential to prevent cold cracking in the weld metal, especially for thicker overlay layers.
The overlay welding is performed in multiple passes with interpass temperature control maintained below 300°C. After the overlay is complete, a stress-relieving heat treatment at 550-600°C for 2-4 hours is applied to reduce residual stresses and minimize the risk of post-weld cracking. The final hardness of the overlay surface should be verified by Rockwell C testing, with a minimum of 45 HRC required for adequate abrasive wear resistance in cement grinding service.
Defect Analysis and Countermeasures
The study identifies several common defects encountered during squeeze roll cladding and proposes countermeasures:
- Cracks at the weld root: Often caused by excessive preheat temperature or inadequate cleaning of the substrate surface. Countermeasure: ensure thorough grinding of the base metal to bare metal and maintain preheat within the specified range.
- Incomplete fusion between overlay layers: Results from insufficient arc travel speed or improper flux coverage. Countermeasure: optimize welding current and travel speed through procedure qualification testing.
- Surface porosity: Typically due to flux moisture or contaminated wire. Countermeasure: store flux in heated cabinets at 200-250°C and use new wire stock for each production run.
- Hardness unevenness: Caused by inconsistent dilution from the base metal across the roll circumference. Countermeasure: perform a first layer with higher alloy content wire to establish a consistent composition buffer.
Engineering Practice and Field Performance
The paper reports field data from cement plants where cladded squeeze rolls achieved service lives of 8-12 months compared to 3-5 months for uncladded rolls, representing a significant improvement in productivity and cost efficiency. The author emphasizes that the cladding specification must be tailored to the specific feed material characteristics: harder and more abrasive raw meal requires a higher carbon and chromium content overlay, while softer clinker can be adequately served by a lower-alloy overlay. Regular inspection of the overlay surface during planned maintenance intervals, including hardness mapping and crack detection by magnetic particle testing, is recommended to enable predictive maintenance scheduling.
Study Insights and Implications
This paper provides valuable practical guidance for engineers involved in surface engineering of heavy-duty grinding equipment. The emphasis on matching overlay composition to service conditions, rather than simply specifying maximum hardness, reflects mature engineering thinking. The study also highlights the importance of heat treatment as an integral part of the cladding process, not merely an optional finishing step. For organizations managing roller press maintenance programs, this research supports the development of standardized cladding specifications and inspection protocols that can be applied consistently across multiple production lines.