CLADDING TECHNOLOGY SHANXI CO., LTDZD Series Roller Press Surface Cladding Materials for Cement Industry Applications
Literature Overview and Industry Context
This 2005 publication by Xu Jian in the New Century Cement Guide addresses a highly specific and economically significant application of weld overlay technology: the surface cladding of roller press components used in cement grinding circuits. The roller press (also known as roll crusher or high-pressure grinding roll) has become the dominant comminution equipment in modern cement plants, replacing traditional ball mill circuits due to its superior energy efficiency. However, the extreme operating conditions in cement grinding—highly abrasive materials, compressive loads, and thermal cycling—impose severe demands on the roll surface, making overlay protection essential for economic operation.
The ZD series designation refers to a family of roller press models, and the study focuses on developing and characterizing overlay materials specifically suited for these applications. This represents a case study in application-driven overlay material development, where the material selection and process parameters are optimized for a specific service environment.
Service Environment Analysis and Material Requirements
Operating Conditions in Cement Roller Presses
The roller press surface is subjected to a complex combination of loading conditions:
| Condition | Typical Range | Effect on Surface |
|---|---|---|
| Compressive contact pressure | 100-250 MPa | Plastic deformation, work hardening |
| Abrasive particle size | 0.1-10 mm | Micro-cutting, ploughing |
| Sliding speed | 0.5-3.0 m/s | Friction heating, adhesive wear |
| Material temperature | 60-150°C | Thermal softening, oxidation |
| Load cycle frequency | 10-50 cycles/min | Fatigue, spalling |
| Abrasive material hardness | Mohs 6-8 (clinker, gypsum) | Severe abrasive wear |
Material Selection Criteria
Based on the service environment analysis, the overlay material must satisfy the following criteria:
- High hardness: Minimum 55-60 HRC for the as-deposited condition to resist abrasive wear
- Good toughness: Sufficient fracture toughness to prevent spalling under cyclic loading
- Wear-resistant microstructure: Carburide or carbide phases with appropriate size, shape, and distribution
- Bond strength: Adequate adhesion to the steel substrate to prevent delamination
- Thermal stability: Retention of hardness at operating temperatures up to 150°C
ZD Series Overlay Material System
Material Composition and Classification
The ZD series overlay materials are developed as a family of consumables with different compositions to address varying service conditions within the cement grinding circuit:
| Material Grade | Primary Alloying | Hardness (HRC) | Application |
|---|---|---|---|
| ZD-1 | Cr 12-14%, C 2.5-3.0% | 58-62 | General clinker grinding |
| ZD-2 | Cr 16-18%, C 3.0-3.5% | 60-64 | High-abrasion zones |
| ZD-3 | Cr 10-12%, Mo 2-3% | 55-58 | Mixed material handling |
| ZD-4 | Cr 14-16%, Nb 1-2% | 62-66 | Severe abrasive service |
Microstructural Design
The overlay microstructure is designed to achieve a balance between hardness and toughness through controlled carbide formation:
High-chromium martensitic structure (ZD-1, ZD-2): The overlay consists of a martensitic matrix with M₇C₃ and M₂₃C₆ chromium carbides. The carbides provide primary wear resistance through their high hardness (Vickers hardness of M₇C₃ is approximately 1800-2000 HV), while the martensitic matrix provides toughness and load-bearing capacity.
Chromium-molybdenum modified structure (ZD-3): The addition of molybdenum promotes the formation of MC-type carbides and improves the thermal stability of the martensitic matrix. This material is designed for applications where moderate hardness is acceptable but toughness is more critical.
Niobium-strengthened structure (ZD-4): Niobium addition promotes the formation of fine NbC carbides and improves the precipitation hardening response of the matrix. This provides the highest hardness in the series but requires careful process control to avoid excessive brittleness.
Process Parameters and Deposition Strategy
Multi-Pass Cladding Procedure
The recommended cladding procedure for ZD series roller press surfaces involves:
- Surface preparation: Grinding to remove oxide scale and provide a clean surface with Ra 12.5-25 μm
- Preheating: Induction or gas heating to 200-300°C to prevent cracking
- First pass (bond layer): Low-carbon, low-alloy deposit to ensure metallurgical bond with the substrate. Typical dilution: 20-30%.
- Intermediate passes: ZD series overlay material with controlled heat input. Typical dilution: 5-15%.
- Final pass (surface layer): ZD series material with minimum dilution. Typical dilution: 0-5%.
- Post-weld heat treatment: Optional tempering at 550-650°C for 2-4 hours to relieve residual stresses and optimize carbide distribution.
Process Parameters by Welding Method
| Parameter | SAW | GMAW | TIG |
|---|---|---|---|
| Current (A) | 300-450 | 180-280 | 80-150 |
| Voltage (V) | 28-35 | 22-30 | 12-18 |
| Travel speed (mm/min) | 200-400 | 150-350 | 80-200 |
| Wire/feed diameter (mm) | 1.6-2.4 | 1.2-1.6 | - |
| Gas flow (L/min) | - | 15-25 | 8-15 |
| Deposit thickness/pass (mm) | 2.0-3.5 | 0.5-1.2 | 0.3-0.6 |
Performance Evaluation and Field Results
Laboratory Test Results
| Test Method | ZD-1 | ZD-2 | ZD-3 | ZD-4 |
|---|---|---|---|---|
| Hardness (HRC) | 58-62 | 60-64 | 55-58 | 62-66 |
| Impact energy (J) | 25-35 | 18-28 | 35-50 | 12-22 |
| Bond strength (MPa) | 320-380 | 340-400 | 300-360 | 360-420 |
| Wear rate (mg/Nm) | 8-12 | 6-10 | 12-18 | 4-8 |
| Fatigue life (cycles) | 10⁶-10⁷ | 5×10⁵-5×10⁶ | 10⁷-10⁸ | 3×10⁵-3×10⁶ |
Field Performance Data
Based on industry reports and the principles established in this research, typical field performance of ZD series cladding on cement roller presses includes:
- Service life improvement: 3-5 times compared to uncladded steel surfaces
- Typical cladding thickness: 3-5 mm for standard service, 6-8 mm for severe service
- Recladding interval: 12-24 months depending on service conditions
- Cost per ton of cement produced: Reduction of 15-30% in grinding energy and equipment maintenance
Study Insights and Engineering Implications
This research exemplifies the application-driven approach to overlay material development, where the material system is designed from the ground up to address specific service conditions rather than adapting general-purpose materials to a specific application. This philosophy is critical for achieving optimal performance in demanding industrial applications.
The multi-grade material system (ZD-1 through ZD-4) reflects the understanding that cement grinding circuits present varying severity conditions across different components and operating zones. A single material cannot optimally address all conditions, and the development of a material family allows engineers to select the appropriate grade for each specific application.
An important practical consideration highlighted by this research is the role of post-weld heat treatment in optimizing overlay performance. While the as-deposited condition provides good wear resistance, tempering treatment can significantly improve toughness and reduce residual stresses without substantially compromising hardness. This heat treatment step should be considered as an integral part of the cladding process rather than an optional add-on.
The economic analysis implicit in this work demonstrates that overlay protection, while adding to the initial fabrication cost, provides significant lifecycle cost savings through extended service life and reduced downtime. For cement plants operating at high utilization rates, the return on investment for proper overlay protection is typically achieved within the first year of operation.
In conclusion, this study provides a comprehensive framework for overlay material selection and process optimization in cement roller press applications, demonstrating the value of application-specific material development and systematic process control in achieving reliable industrial performance.