Zhuojin Pipe Fitting Co., LtdArgon Arc Overlay Welding of Aluminum Bronze
Literature Overview
This 1997 paper by Ma Yan and Feng Wenjie from CITIC Heavy Machinery Company, published in Welding (Issue 10, pages 28-29), documents the development and implementation of an argon arc overlay welding process for aluminum bronze deposits on various carbon and alloy steel components used in rolling mill and leveling mill applications. The project involved cooperation with a Japanese company for the production of 1450 mm rolling mill and 1750 mm leveling mill equipment, with a total overlay welding requirement of 600 kg of wire and factory acceptance inspection by the foreign partner.
Application Context
The paper describes overlay welding requirements for critical components in rolling mill and leveling mill equipment:
| Component Type | Base Material | Overlay Requirement |
|---|---|---|
| Roll chocks | Q235, 25 steel | Wear-resistant bore surface |
| Roll necks | 35, 45 steel | Corrosion-resistant surface |
| Bearing housings | 35CrMo | Wear-resistant contact surfaces |
| Gear housings | 40CrMnMo | Sealing surface protection |
The aluminum bronze overlay provides:
- Excellent wear resistance in sliding contact applications
- Good corrosion resistance in humid or chemical environments
- Low coefficient of friction against steel mating surfaces
- Good thermal conductivity for heat dissipation
- Non-galling properties to prevent seizure in tight-fitting assemblies
Process Development
Material Selection
The aluminum bronze overlay material is typically a Cu-Al-Ni system alloy (such as C95400 or equivalent Chinese grade QAl10-4-4). Key properties include:
| Property | Aluminum Bronze (C95400) | Base Steel (Q235) |
|---|---|---|
| Tensile strength (MPa) | 550–620 | 370–500 |
| Hardness (HB) | 120–160 | 120–140 |
| Thermal expansion (10⁻⁶/K) | 17 | 12 |
| Thermal conductivity (W/m·K) | 45 | 50 |
| Coefficient of friction (vs. steel) | 0.15–0.25 | 0.4–0.6 |
Welding Process Parameters
The GTAW (argon arc) overlay welding process was optimized with the following parameters:
| Parameter | Value | Notes |
|---|---|---|
| Welding current | 150–250 A | Depends on deposit thickness |
| Arc voltage | 18–22 V | Maintains stable arc |
| Travel speed | 80–150 mm/min | Controls heat input |
| Wire feed speed | 4–6 m/min | For wire feed GTAW |
| Shielding gas flow | 15–20 L/min | Pure argon |
| Torch angle | 80–90° | Perpendicular to surface |
| Standoff distance | 8–12 mm | Constant during welding |
Surface Preparation
Proper surface preparation is critical for successful aluminum bronze overlay welding:
- Mechanical cleaning: Grinding or shot blasting to remove scale, rust, and contaminants.
- Chemical cleaning: Solvent cleaning to remove oil and grease.
- Preheating: 100–200°C for carbon steel base metals to reduce cracking susceptibility.
- Surface activation: Final cleaning with emery cloth immediately before welding.
Quality Requirements
The paper specifies stringent quality requirements for the overlay deposits:
- Surface roughness: Ra 1.6 μm after post-weld machining
- Defect limits: No cracks, incomplete fusion, porosity, or slag inclusions > 0.5 mm
- Bond strength: Adequate metallurgical bonding between overlay and base metal
- Dimensional accuracy: Within specified tolerances after machining
- Visual appearance: Smooth, uniform bead profile
Defect Prevention and Control
The development of a complete overlay welding process required systematic identification and prevention of potential defects:
| Defect | Cause | Prevention |
|---|---|---|
| Cracking | High cooling rate, hydrogen | Preheat, low-hydrogen consumables |
| Porosity | Contaminated surface, insufficient shielding | Thorough cleaning, adequate gas flow |
| Incomplete fusion | Low heat input, poor wetting | Increase current, proper surface preparation |
| Excessive dilution | High heat input, thin deposit | Optimize parameters, multi-pass technique |
| Spatter | High travel speed, poor technique | Reduce speed, maintain proper angle |
Engineering Practice Integration
The project involved close coordination with the Japanese partner company, with factory acceptance inspection (FAI) requirements. Key aspects of the engineering practice include:
- Procedure qualification: A complete welding procedure specification (WPS) was developed and qualified according to applicable standards.
- Welder qualification: Operators were trained and qualified on the specific process parameters.
- In-process inspection: Visual examination of each bead, with periodic hardness testing and non-destructive examination.
- Final inspection: Post-machining dimensional verification and surface finish measurement.
- Documentation: Complete quality records including material certificates, process parameters, inspection results, and acceptance documentation.
Study Reflections
This paper illustrates the practical challenges of developing and implementing overlay welding processes for international joint ventures. The requirement for 600 kg of aluminum bronze overlay wire represents a significant production volume, requiring careful planning of consumable supply, equipment capacity, and quality control resources.
The cooperation with a Japanese company and factory acceptance inspection requirements reflect the quality standards expected in international equipment manufacturing. The successful completion of this project demonstrates China's growing capability in advanced welding technology and quality management.
For contemporary engineers, this paper serves as a practical reference for aluminum bronze overlay welding applications. The process parameters and quality control approaches described remain relevant for similar applications in heavy machinery, mining equipment, and marine engineering.
The key lesson is that successful overlay welding requires a systematic approach encompassing material selection, process development, quality control, and documentation. Each aspect must be carefully managed to ensure the overlay deposit meets the required performance criteria for its intended application.