Zhuojin Pipe Fitting Co., LtdHardfacing Applications in the Cement Industry
Literature Overview
This 2005 paper by Zhang Kunmou from Kunshan Huifeng Wear-Resistant Industrial Co., Ltd., published in China Cement (Vol. 12, pp. 86–87), documents the evolution and practical deployment of hardfacing technology in cement production facilities since the 1980s. The article traces how high-chromium cast iron and martensitic overlay systems have become indispensable for protecting grinding mill components, kiln wear parts, and material handling equipment against abrasive degradation. The paper is situated within the CLC classification TQ172.6 (cement manufacturing equipment), reflecting its strong industrial application orientation rather than pure metallurgical research.
Core Technical Content
Historical Development of Hardfacing in Cement
The cement industry has undergone significant transformations since the 1980s, and hardfacing technology has evolved in parallel to address increasingly demanding abrasion conditions. Early applications relied predominantly on high-chromium cast iron (Cr > 10%) overlays applied via submerged arc welding or flux-cored wire processes. Over time, the industry shifted toward higher-chromium formulations (Cr content up to 28–32%) and martensitic steel systems to achieve better combinations of hardness, toughness, and impact resistance.
The key materials discussed include:
| Material Type | Typical Composition | Hardness (HRC) | Key Application |
|---|---|---|---|
| High-Cr Cast Iron | Cr 20–32%, C 2.5–4% | 58–65 | Ball mill liners, bucket elevator buckets |
| Martensitic Steel | Cr 6–12%, C 0.5–1.0% | 45–58 | Mill rings, chutes, transfer hoppers |
| High-Alloy Steel | Ni, Mo, V additions | 50–62 | High-temperature wear zones |
Energy Savings and Economic Rationale
A critical insight from this paper is the direct correlation between hardfacing technology and energy conservation in cement production. By extending the service life of mill liners and grinding components through hardfacing, operators reduce downtime for replacement and minimize the energy losses associated with frequent mill stops and restarts. The paper emphasizes that hardfacing is not merely a wear-protection strategy but an integral component of overall energy efficiency in the cement production chain.
Engineering Practice Insights
Ball Mill Liner Hardfacing
The ball mill is the primary application cited. In a typical cement grinding circuit, the mill liners experience severe three-body abrasion from the interaction between grinding media (steel balls) and the mill shell. Without hardfacing, plain carbon steel liners may last only 3–6 months in a raw mill circuit. With appropriate high-chromium cast iron overlay, service life can be extended to 12–18 months or more.
Key process parameters for ball mill liner hardfacing typically include:
- Preheat temperature: 200–300°C for medium-carbon steel substrates
- Interpass temperature: maintained below 350°C to prevent temper embrittlement
- Welding current (SMAW): 180–250 A depending on electrode diameter
- Travel speed: controlled to maintain a narrow weld bead for uniform hardness
- Number of passes: typically 2–3 layers, with the final layer providing the full-hardness surface
Common Defects and Countermeasures
| Defect Type | Root Cause | Countermeasure |
|---|---|---|
| Cracking in overlay | High carbon equivalent of substrate | Increase preheat, use low-hydrogen consumables |
| Porosity | Flux contamination, inadequate shielding | Clean base metal thoroughly, use flux-cored wire with controlled shielding gas |
| Excessive dilution | Wide weld bead, low travel speed | Reduce current, increase travel speed, use multiple narrow passes |
| Soft spots | Incomplete melting of previous layer | Maintain consistent interpass temperature, ensure proper overlap |
Study Insights and Reflections
Having worked extensively with overlay welding processes across multiple industries, I find this paper particularly valuable for its practical orientation and economic framing. The author correctly identifies that the decision to hardface is not purely metallurgical but must be evaluated within the total cost of ownership framework. In cement plants, where grinding represents 30–40% of total energy consumption, even modest extensions in liner life translate into significant energy savings.
One area I would supplement from my own experience is the importance of weldability assessment for the base material. Many cement mill shells are fabricated from low-carbon steel (Q235 or Q345 equivalent), which is generally weldable, but older equipment may contain higher carbon equivalents or impurities that complicate the overlay process. A systematic weldability evaluation following ISO 9506 or ISO 17637 procedures should always precede large-scale hardfacing campaigns.
The paper also touches on the evolution of consumables from the 1980s to the mid-2000s, which mirrors the broader trend in wear-resistant overlay technology from simple high-carbon/high-chromium systems toward more sophisticated multi-component alloys with tailored microstructures. This evolution is documented more comprehensively in later literature, including the work reviewed in Topic 4 of this study set, which examines modern overlay consumables on low-alloy steel substrates.
In summary, this paper serves as a foundational reference for understanding the industrial adoption of hardfacing in cement manufacturing, with particular emphasis on the economic and energy-saving rationale that drives technology selection in this sector.