Submerged Arc Weld Overlay Repair of a 2-Tonne Steam Hammer Anvil

Literature Overview

This 1990 study by Zhou Hongbo, Li Zhisheng, and Yang Peizhen from Dalian Iron and Steel Works documents the submerged arc welding (SAW) overlay repair of a 2-tonne steam hammer anvil, a heavy industrial forging component subjected to extreme impact and fatigue loading. The study represents early Chinese engineering practice in the repair of heavy-duty equipment through weld overlay technology, providing valuable historical context and practical lessons for modern repair engineering.

Core Technical Content

A 2-tonne steam hammer anvil is a massive forging that receives repeated impact loads from the hammer ram during forging operations. Over time, the anvil surface suffers from fatigue cracking, surface damage, and dimensional wear, necessitating repair or replacement. Weld overlay repair offers a cost-effective alternative to complete replacement, particularly when the base material remains structurally sound.

Process Design for Heavy-Duty Overlay Repair

The repair of a steam hammer anvil presents unique challenges due to the massive section thickness, the requirement for high impact resistance, and the severe service conditions:

1. Surface preparation: The damaged surface must be thoroughly ground to remove cracks, decarburized layers, and surface defects. Any detected cracks must be fully removed by grinding or machining, followed by proof testing to confirm crack removal.
2. Preheating: Given the carbon equivalent of the base material and the thick section, preheating to 200–300°C is essential to prevent cold cracking. The preheat temperature must be maintained throughout the welding operation.
3. Welding parameters: Submerged arc welding is selected for its high deposition rate and deep penetration, which are critical for building up substantial overlay thickness efficiently. Typical parameters include:

• Current: 500–700 A
• Voltage: 28–35 V
• Travel speed: 150–250 mm/min
• Flux coverage: Continuous, with adequate flux depth (≥ 25 mm)

1. Multi-pass welding: The overlay is built up in multiple passes, with each pass carefully controlled to minimize thermal stress and ensure uniform microstructure. The interpass temperature must be maintained between 200–300°C.
2. Post-weld heat treatment: Stress relief at 600–650°C is typically required to relieve residual stresses and improve the toughness of the overlay and HAZ.

Microstructural and Mechanical Property Considerations

The overlay material selection is critical for ensuring that the repaired anvil can withstand the severe impact and fatigue loading of service. Common overlay materials for steam hammer anvils include:

The as-welded microstructure of the overlay typically consists of martensite and bainite, which provide high hardness but may be susceptible to cracking under impact loading. Post-weld heat treatment (tempering) is therefore essential to transform the microstructure to tempered martensite, improving toughness while maintaining adequate hardness.

Defect Analysis and Quality Control

Quality control for the repair includes:

• Visual inspection of all weld surfaces for defects.
• Magnetic particle testing (MT) for surface and near-surface cracks.
• Ultrasonic testing (UT) for internal defects and bond quality.
• Hardness testing across the overlay and HAZ to verify microstructural integrity.
• Proof load testing to confirm structural adequacy before returning the anvil to service.

Engineering Practice and Lessons Learned

The repair of heavy industrial components such as steam hammer anvils represents a practical application of weld overlay technology in situations where complete replacement is economically or logistically impractical. The key lessons from this case study include:

1. Thorough damage assessment: Before initiating repair, the extent of damage must be fully characterized through non-destructive testing and dimensional measurement. Hidden cracks or subsurface defects must be detected and addressed.
2. Process qualification: The welding procedure must be qualified through coupon testing that simulates the base material, section thickness, and service conditions. This ensures that the repair procedure produces acceptable results.
3. Post-weld treatment: Stress relief and tempering are not optional—they are essential for ensuring the long-term reliability of the repair. Skipping or inadequately performing these steps can lead to premature failure.
4. Documentation: Complete documentation of the repair, including pre-repair condition, repair procedure, inspection results, and post-repair testing, is essential for traceability and future maintenance planning.

Study Insights and Reflections

This 1990 study, while predating many modern welding technologies, captures fundamental principles of weld overlay repair that remain relevant today. The challenges of repairing heavy-duty components—managing residual stresses, ensuring adequate toughness, and achieving reliable bond strength—are timeless engineering problems that require careful process design and rigorous quality control.

The practical insight is that weld overlay repair is not merely a technical exercise but a systematic engineering process that requires integration of metallurgical understanding, process engineering, quality assurance, and economic analysis. The success of the repair depends on every element of this system, from the initial damage assessment to the final proof test.

For modern engineers, this study serves as a reminder that while technology has advanced—offering processes such as laser cladding, plasma arc welding, and advanced metallurgical modeling—the fundamental principles of sound engineering practice remain unchanged. The repair of heavy industrial components continues to demand the same level of rigor, attention to detail, and respect for metallurgical fundamentals that characterized the work documented in this 1990 study.