Zhuojin Pipe Fitting Co., LtdSurfacing Technology for Roller Press Squeeze Rolls
Literature Overview
The paper by Zhao Yunfeng and Li Wenqing, published in Welding in 2000, addresses the surfacing technology for squeeze rolls used in roller presses within the cement industry. Although the paper is brief, it addresses a critical engineering challenge: the restoration and enhancement of wear-resistant surfaces on large-diameter rolls that undergo severe abrasion and impact during cement clinker grinding operations.
Technical Context
Roller presses are essential equipment in modern cement manufacturing, where two large steel rolls compress clinker material to reduce particle size efficiently. The squeeze rolls are subjected to extreme operating conditions including high compressive loads, abrasive contact with hard cement clinker, and thermal cycling. The surfacing of wear-resistant materials onto the roll surface is a standard maintenance practice to extend roll life and reduce replacement costs.
Surfacing Process Considerations
| Parameter | Typical Range | Rationale |
|---|---|---|
| Surfacing Material | High-Cr cast iron, martensitic stainless steel | Abrasion and impact resistance |
| Preheat Temperature | 200-300 °C | Reduce residual stress, prevent cracking |
| Interpass Temperature | Below 150 °C | Control HAZ hardness |
| Surfacing Layers | 2-3 layers | Achieve required thickness and hardness |
| Post-Weld Treatment | Stress relief annealing | Reduce residual stress |
The selection of surfacing materials for cement roller press squeeze rolls typically involves high-chromium cast irons (such as Cr20 or Cr26 grades) or martensitic stainless steels, chosen for their excellent abrasion resistance and hardness. The high carbon and chromium content promotes the formation of hard carbides that resist the abrasive action of cement clinker.
Welding Challenges on Large Rolls
Surfacing large-diameter rolls presents unique challenges. The substantial mass of the roll creates significant thermal mass effects, meaning that heat input during welding can lead to severe thermal gradients and residual stresses. The curvature of the roll surface also complicates weld access and bead placement, particularly for the lower portion of the roll where gravity and accessibility are concerns. Multi-pass welding with careful control of heat input and interpass temperature is essential to prevent cracking and to achieve uniform hardness across the surfacing layer.
Engineering Practice Implications
In cement plant maintenance operations, the surfacing of squeeze rolls is typically performed in-situ or in a specialized workshop. The process requires careful planning of weld sequence to minimize distortion, particularly for large rolls where even small angular distortions can affect roller press operation. The surfacing layer thickness is typically designed to allow for multiple regrinding operations during the roll's service life, with each regrinding removing a small amount of material to restore surface finish.
The choice between manual arc welding (SMAW) and automated belt electrode surfacing depends on the roll size, required surfacing area, and production schedule. For large rolls requiring extensive coverage, belt electrode surfacing offers higher deposition rates, while manual welding provides greater flexibility for complex geometries and repair work.
Study Insights and Reflections
This paper, while concise, highlights the practical importance of surfacing technology in heavy industrial equipment maintenance. The cement industry's demand for cost-effective roll maintenance drives continuous improvement in surfacing processes, materials, and inspection methods. Engineers working in this area should focus on optimizing the balance between surfacing hardness and toughness to prevent both abrasive wear and impact spalling, and should implement rigorous non-destructive testing protocols to detect subsurface defects that could lead to premature failure.