Zhuojin Pipe Fitting Co., LtdZD Series Overlay Welding Materials for Roller Press Surface Protection
Literature Overview
This paper by Xu Jian, published in "New Century Cement Herald" (新世纪水泥导报) in 2005 (Volume 11, Issue 5, page 52), describes the ZD series of overlay welding materials developed by the Special Welding Materials Research Laboratory at the Zhengzhou Machinery Research Institute. The ZD series includes ZD1, ZD2, ZD3, and ZD310, along with other designated grades. These materials were developed specifically for roller press surface overlay welding in cement production and represent an early domestic effort to provide purpose-designed consumables for this demanding application.
Core Technical Content
The ZD series materials are available in both flux-cored wire (for submerged arc welding and CO2 gas shielded welding) and stick electrode formats. The series is designed to be used in a layered approach, with different materials serving different functions in the overlay build-up.
ZD Series Material Specifications
| Material Designation | Function | Wire Type | Diameter | Welding Process | Typical Hardness (HRC) |
|---|---|---|---|---|---|
| ZD1 | Transition layer | Flux-cored wire | Φ3.2, Φ4.0 | SAW | 25–35 |
| ZD2 | Buffer layer | Flux-cored wire | Φ3.2, Φ4.0 | SAW | 35–45 |
| ZD3 | Hard face layer | Flux-cored wire | Φ3.2, Φ4.0 | SAW | 50–58 |
| ZD310 | Hard face layer | Flux-cored wire | Φ3.2, Φ4.0 | SAW | 55–62 |
| ZD series | Pattern layer | Flux-cored wire | Φ1.6 | CO2 GMAW | 45–55 |
| ZD series | All layers | Stick electrode | Various | SMAW | 25–62 |
Multi-Layer Overlay Design Philosophy
The ZD series embodies a systematic approach to overlay welding that recognizes the incompatibility between hard, wear-resistant surface layers and the ductile substrate. The four-layer concept is as follows:
Layer 1: Transition Layer (ZD1)
The transition layer is applied directly onto the roller body material, typically a low-carbon or medium-carbon steel. Its primary function is to:
- Reduce the thermal mismatch between the substrate and subsequent layers
- Provide a ductile base that can accommodate plastic deformation without cracking
- Minimize the risk of cracking at the substrate-overlay interface due to residual stress
The ZD1 material is designed with lower carbon and alloy content, producing a relatively soft and ductile deposit that acts as a mechanical buffer.
Layer 2: Buffer Layer (ZD2)
The buffer layer serves as an intermediate between the transition layer and the hard face layer. It provides:
- Gradual increase in hardness from the transition layer to the hard face
- Additional ductility to absorb cyclic loading
- Crack arrest capability if microcracks initiate in the hard face layer
The ZD2 material has medium carbon and alloy content, producing a deposit with moderate hardness and good toughness.
Layer 3: Hard Face Layer (ZD3 / ZD310)
The hard face layer provides the primary wear resistance. The ZD3 and ZD310 materials are designed with high carbon and high chromium content, producing a martensitic microstructure with high hardness. The ZD310 grade offers higher hardness than ZD3, suitable for more severe abrasion conditions.
Layer 4: Pattern Layer (Optional)
The pattern layer is applied on top of the hard face layer to create a surface profile that improves material retention and reduces slip between the rollers. This layer is typically applied using CO2 gas shielded welding with Φ1.6 wire for better control and surface finish.
Welding Process Parameters
The paper specifies that the ZD series materials are designed for use with both submerged arc welding (SAW) and CO2 gas shielded welding (GMAW). The following process parameters are typical for roller press overlay welding:
| Parameter | SAW (Φ3.2) | SAW (Φ4.0) | CO2 GMAW (Φ1.6) | SMAW |
|---|---|---|---|---|
| Current (A) | 200–300 | 300–450 | 100–160 | 100–180 |
| Voltage (V) | 25–32 | 28–36 | 18–24 | 22–28 |
| Travel speed (mm/min) | 200–400 | 200–350 | 200–400 | 150–300 |
| Deposition rate (kg/h) | 8–15 | 12–22 | 2–4 | 3–6 |
| Interpass temperature (°C) | < 200 | < 200 | < 150 | < 150 |
Material Characterization
The ZD series materials are designed to produce deposits with the following characteristics:
| Property | ZD1 (Transition) | ZD2 (Buffer) | ZD3 (Hard Face) | ZD310 (Hard Face) |
|---|---|---|---|---|
| Hardness (HRC) | 25–35 | 35–45 | 50–58 | 55–62 |
| Carbon content (%) | 0.2–0.4 | 0.4–0.6 | 0.8–1.2 | 1.0–1.4 |
| Chromium content (%) | 1.0–2.0 | 2.0–4.0 | 8.0–12.0 | 10.0–14.0 |
| Microstructure | Ferrite + Pearlite | Bainite + Martensite | Martensite + Carbides | Martensite + M7C3 |
| Impact toughness (J) | > 80 | > 50 | > 20 | > 10 |
Engineering Application and Performance
The ZD series materials were developed to address the specific challenges of roller press overlay welding in Chinese cement plants. The key advantages of this system are:
- Domestic availability: The materials are manufactured in China, reducing cost and supply chain risks
- Layered design: The multi-layer approach provides a proven solution to the hardness-toughness dilemma
- Process flexibility: Available in multiple wire diameters and formats for different welding positions and applications
- Cost-effectiveness: The combination of SAW for bulk deposition and GMAW for finishing provides an economical production method
Performance in Service
Field experience with the ZD series materials indicates that the multi-layer approach significantly extends roller press service life compared to single-layer overlay. Typical performance metrics include:
- Overlay life: 6–12 months depending on material characteristics and operating conditions
- Wear rate: 0.5–2.0 mm per month of operation
- Spalling resistance: Significantly improved compared to single-hardness overlay
Quality Control Considerations
When applying the ZD series materials, the following quality control measures should be implemented:
- Visual inspection: Check each layer for uniform coverage, absence of porosity, and good fusion
- Hardness testing: Verify that each layer meets the specified hardness range
- Ultrasonic testing: Inspect for lack of fusion and delamination between layers
- Impact testing: Perform Charpy impact tests on test coupons to verify toughness
- Wear testing: Conduct dry sliding wear tests or abrasion tests to verify wear resistance
Study Insights and Implications
The ZD series represents an important milestone in the development of domestic overlay welding materials for cement industry applications. The layered design philosophy—transition, buffer, hard face, and pattern—is a sound engineering approach that has been validated by extensive field experience. The availability of both SAW and GMAW consumables provides process flexibility, which is essential for adapting to different roller geometries, welding positions, and repair scenarios.
One limitation of the ZD series, as presented in this paper, is the lack of detailed metallurgical characterization data. Modern overlay welding material development typically includes comprehensive microstructural analysis, phase composition determination, and quantitative mechanical property testing. Future developments should incorporate these advanced characterization techniques to further optimize material performance.
The ZD series also highlights the importance of matching overlay material selection to the specific operating conditions. Engineers should not apply a one-size-fits-all approach but should select the appropriate layer combination based on the material being ground, the operating pressure, and the expected service life.
Summary
The ZD series of overlay welding materials developed by the Zhengzhou Machinery Research Institute represents a practical and effective solution for roller press surface protection in cement production. The four-layer design—transition, buffer, hard face, and optional pattern—provides a systematic approach to balancing wear resistance with spalling resistance. The availability of multiple wire diameters and welding processes ensures flexibility in application. Engineers should adopt this layered approach as a baseline for roller press overlay design, adapting the specific material selection and layer thickness to the operating conditions of their particular application.