Submerged Arc Overlay Welding Repair of 2-Ton Steam Hammer Anvil Base

Literature Overview

This paper by Zhou Hongbo, Li Zhisheng, and Yang Peizhen from Dalian Steel Plant, published in Welding (1990, No. 3, pp. 22-23), documents the repair of a critical component in heavy forging equipment: the anvil base (anvil seat) of a 2-ton steam hammer. The anvil base is subjected to extreme conditions—repeated impact loading at elevated temperatures, thermal cycling, and creep deformation—resulting in severe metal loss at the dovetail interface. The authors describe a transition from manual arc overlay welding to submerged arc overlay welding (SAW), achieving a fivefold improvement in productivity while maintaining repair quality. This is a significant engineering achievement that demonstrates the advantages of mechanized welding processes in heavy industrial repair applications.

Core Technical Analysis

Service Conditions and Failure Mechanism

The 2-ton steam hammer is a primary forging equipment used in the steel plant's forging production line. The anvil base (anvil seat) is the foundation upon which the die is mounted, and it directly receives the impact energy from each forging stroke. The service conditions are extremely severe:

• Impact loading: Each forging stroke delivers a hammer blow of approximately 2 tons of energy, resulting in peak contact pressures exceeding 1000 MPa at the die-anvil interface.
• Thermal cycling: The heated workpiece (forged at 1100-1200°C) transfers heat to the anvil, creating thermal gradients of several hundred degrees across the anvil thickness.
• Creep deformation: Under sustained high temperature and stress, the metal at the dovetail interface undergoes time-dependent plastic deformation (creep), gradually wearing away the metal.
• Thermal fatigue: The repeated heating and cooling cycles induce thermal fatigue cracks, which propagate and eventually lead to metal loss.

The failure mode described in the paper is a combination of creep and thermal fatigue, resulting in progressive metal loss at the dovetail interface. In severe cases, metal detaches in blocks, rendering the anvil unusable.

Comparison of Repair Methods

The paper provides a compelling comparison between manual arc overlay welding and submerged arc overlay welding for this repair application:

The dramatic improvement in productivity (5×) is primarily due to the high deposition rate and deep penetration of submerged arc welding. The mechanized nature of SAW also ensures consistent weld quality, which is critical for a component subjected to severe cyclic loading.

Welding Procedure for SAW Repair

The submerged arc overlay welding procedure for the anvil base involves the following steps:

1. Surface preparation: Remove all loose metal, scale, and debris from the dovetail interface. Grind the surface to bare metal, creating a slight undercut groove (5-8 mm deep, 15-20 mm wide) to ensure adequate fusion.
2. Preheating: Preheat the anvil to 300-400°C using induction heating or gas torches. This reduces the cooling rate and minimizes the risk of cracking in the heat-affected zone. The base material of the anvil is typically a medium-carbon steel (such as 45 steel or 50 steel) or a low-alloy steel, which requires preheating to prevent cold cracking.
3. Welding parameters: Typical SAW parameters for this application include:

• Welding current: 600-800 A (DC, electrode positive)
• Welding voltage: 28-35 V
• Travel speed: 300-500 mm/min
• Wire diameter: 3.2-4.0 mm
• Flux: Rutile-type or basic-type flux (e.g., HJ431 or HJ430)

1. Multi-pass welding: The overlay is deposited in multiple passes to build up the required thickness. The first pass ensures good fusion with the base, while subsequent passes refine the microstructure and achieve uniform hardness. The total overlay thickness is typically 15-25 mm, depending on the severity of metal loss.
2. Interpass temperature control: Maintain interpass temperature between 200-350°C to prevent excessive grain growth and maintain the desired microstructure.
3. Post-weld heat treatment: Temper the repaired anvil at 550-600°C for 2-4 hours to relieve residual stresses and improve toughness.

Material Selection for Overlay

The selection of overlay material for the anvil base repair is critical and must consider the following requirements:

• High hardness: To resist impact and abrasion during forging operations.
• Good toughness: To withstand repeated impact loading without brittle fracture.
• Creep resistance: To resist time-dependent deformation at elevated temperatures.
• Thermal fatigue resistance: To withstand repeated thermal cycling without cracking.

Typical overlay materials for this application include:

For the 2-ton steam hammer anvil, a Cr-Mo-B or Cr-Mo-V type overlay material is typically selected to provide a good balance of hardness and toughness under the severe impact loading conditions.

Engineering Practice Insights

This paper highlights several important lessons for heavy industrial repair welding:

First, the transition from manual to mechanized welding can dramatically improve productivity and quality in large-scale repair applications. The 5× improvement in productivity reported in this paper is not unusual for SAW versus SMAW in heavy deposit applications. Engineers should always evaluate the feasibility of mechanized welding processes for large repair jobs, as the initial setup time is quickly offset by the higher deposition rates.

Second, the quality of the repair is critical for the long-term reliability of the component. The anvil base is a safety-critical component, and any failure could result in significant downtime or safety incidents. The consistent weld quality achieved with SAW, combined with proper preheating and post-weld heat treatment, ensures that the repair meets the required performance standards.

Third, the paper demonstrates the importance of systematic approach to repair welding. The authors did not simply apply a different welding process; they developed a complete repair procedure including surface preparation, preheating, welding parameters, and post-weld treatment. This systematic approach is essential for successful repair of heavily loaded components.

Key Questions and Reflections

One question that arises from this study is the long-term performance of the SAW-repaired anvil compared to the original new anvil. The paper mentions that several anvils were repaired and used successfully, but detailed long-term performance data (such as number of forging strokes before failure, wear rate comparison, etc.) would be valuable for engineers making repair decisions. The microstructure of the SAW overlay, with its characteristic grain structure and possibly different grain size compared to the original forging, could affect the long-term fatigue and creep performance.

Another consideration is the feasibility of applying this technique to larger steam hammers (such as 5-ton or 10-ton units) where the repair areas are even larger and the loading conditions are more severe. The basic principles would remain the same, but the welding parameters and procedures would need to be adjusted for the larger scale and more demanding service conditions.

Study Insights and Implications

This paper is a classic example of how welding technology can be effectively applied to extend the service life of critical industrial equipment. The transition from manual to submerged arc overlay welding represents a significant engineering improvement that delivers both productivity gains and quality benefits. For engineers working in heavy forging, steel production, and other industries where large components are subjected to severe impact and thermal loading, this paper provides a valuable reference for developing efficient repair procedures. The key insights are: (1) mechanized welding processes offer substantial advantages for large-scale repair applications, (2) systematic approach to repair welding (including proper material selection, process parameters, and heat treatment) is essential for long-term reliability, and (3) the economic benefits of repair welding over component replacement can be substantial, making it a cost-effective maintenance strategy.