CLADDING TECHNOLOGY SHANXI CO., LTDApplication of Hardfacing in the Cement Industry
Literature Overview
This 2005 study by Zhang Kunmou from Kunshan Huifeng Wear-Resistant Industry Co., Ltd., published in the journal "China Cement," documents the application of hardfacing technology in the cement industry. The cement industry is characterized by severe abrasive wear from raw materials, clinker, and finished products, making hardfacing one of the most effective solutions for extending component life.
Core Technical Content
The cement industry employs hardfacing on a wide range of components including ball mill liners, grinding rods, fan blades, chutes, hoppers, and conveyor wear plates. The abrasive materials in cement production include limestone, clay, shale, gypsum, and clinker, all of which have high hardness and angularity, causing rapid wear of unprotected steel components.
The study categorizes hardfacing alloys used in cement applications into three groups:
| Alloy Group | Typical Composition | Hardness (HRC) | Application |
|---|---|---|---|
| High-carbon martensitic | Fe-3C-12Cr-2V | 55–65 | Mill liners, grinding rods |
| High-chromium castable | Fe-3C-26Cr | 55–60 | Chutes, hoppers |
| Carbide composite | Fe-2C-6Cr-3Mo + WC/Co | 60–70 | Fan blades, wear plates |
Application Cases
The study presents several case studies of hardfacing applications in cement plants:
Ball mill liners: Hardfacing with Fe-3C-12Cr-2V alloy increased liner life from 6 months to 18 months, reducing maintenance costs by 60%. The overlay thickness was 6–8 mm, applied using submerged arc welding (SAW) with a single-layer, multi-pass technique.
Fan blades: Centrifugal fans in cement kiln systems experience erosion from fly ash and clinker particles. Hardfacing with a carbide composite alloy (Fe-2C-6Cr-3Mo + WC/Co) increased blade life from 3 months to 12 months. The overlay was applied using gas metal arc welding (GMAW) with a wire feed rate of 6–8 m/h.
Chutes and hoppers: These components experience impact and sliding wear from clinker. Hardfacing with high-chromium alloy (Fe-3C-26Cr) increased life from 4 months to 14 months. The overlay was applied using flux-cored arc welding (FCAW) with a 1.6 mm wire diameter.
Process Parameters and Quality Control
The study provides recommended process parameters for each application:
| Parameter | Ball Mill Liners | Fan Blades | Chutes |
|---|---|---|---|
| Welding process | SAW | GMAW | FCAW |
| Wire diameter | 1.6 mm | 1.2 mm | 1.6 mm |
| Current | 200–250 A | 120–160 A | 180–220 A |
| Voltage | 28–32 V | 22–26 V | 26–30 V |
| Travel speed | 200–300 mm/min | 150–250 mm/min | 200–300 mm/min |
| Interpass temperature | <200 °C | <150 °C | <200 °C |
| Overlay thickness | 6–8 mm | 3–5 mm | 4–6 mm |
Quality control includes visual inspection, ultrasonic testing (UT) for bond strength, and hardness testing. The bond strength between the overlay and substrate should be verified by a bend test or tensile test, with acceptance criteria of no delamination or cracking at the fusion boundary.
Engineering Practice Implications
The cement industry presents unique challenges for hardfacing:
- High abrasion severity: Cement materials are among the most abrasive encountered in industry, requiring hardfacing alloys with hardness above 55 HRC.
- Impact loading: Components such as mill liners and fan blades experience impact loading in addition to abrasion, requiring alloys with adequate toughness.
- High temperature: Kiln systems operate at temperatures up to 400 °C, requiring alloys with thermal stability.
- Large component size: Ball mill liners and fan blades are large components, requiring careful control of thermal distortion during overlay welding.
The study recommends a systematic approach to hardfacing in cement applications:
- Identify the wear mechanism (abrasion, impact, erosion, or combination).
- Select the appropriate alloy based on hardness, toughness, and thermal stability requirements.
- Design the overlay geometry to minimize stress concentration and maximize wear resistance.
- Apply the overlay using the recommended welding process and parameters.
- Inspect and test the overlay for quality and bond strength.
Key Questions and Reflections
One question that arises is the economic justification of hardfacing versus replacement. The study demonstrates that hardfacing can extend component life by 3–6 times, but the initial cost of hardfacing must be weighed against the cost of frequent replacement. In most cement applications, hardfacing is economically justified when component life is extended by more than 2 times.
Another reflection is the importance of surface preparation. The base metal surface must be clean and free of scale, rust, and paint before hardfacing. Inadequate surface preparation can lead to poor bond strength and premature overlay failure. The study recommends grinding or shot blasting the surface to a near-white finish before welding.
Study Insights and Reference Value
This study provides a comprehensive overview of hardfacing applications in the cement industry, with practical case studies and process parameters. The data on component life extension and cost savings provide strong evidence for the economic benefits of hardfacing.
The study also highlights the importance of alloy selection based on the specific wear mechanism. Not all hardfacing alloys are suitable for all cement applications, and engineers must carefully match the alloy to the service conditions. The case studies demonstrate that proper alloy selection and process control can dramatically extend component life and reduce maintenance costs.
For engineers involved in cement plant maintenance, this study serves as a practical guide to hardfacing technology. The recommended process parameters and quality control procedures can be directly applied to production environments. The study also reinforces the principle that hardfacing is a cost-effective solution for extending the life of wear-critical components in abrasive service.