Additional Filler Wire Submerged Arc Hardfacing of 12Cr2Mo1V Steel Boss on Hydrogenation Reactor Shells

Literature Overview

This 2024 paper by Wang Xuejiao et al., published in "Pressure Vessel," addresses a significant manufacturing challenge in the fabrication of hydrogenation reactors: the efficient hardfacing of 12Cr2Mo1V steel boss (raised area) on reactor shells. The authors, from ERIC (Deyang) Heavy Equipment Co., Ltd., investigated the feasibility of using additional filler wire submerged arc welding (SAW) to replace the conventional single-wire SAW method, which suffers from low manufacturing efficiency. The study is particularly timely given the growing demand for hydrogenation reactors in petrochemical and hydrogen energy industries.

Core Technical Findings

The research demonstrates that the additional filler wire SAW method (two-gun, six-wire configuration) is technically feasible and offers substantial productivity improvements while maintaining full compliance with material performance requirements:

Additional Filler Wire SAW Process Configuration

The additional filler wire SAW process differs from conventional single-wire SAW in that one or more additional filler wires are introduced into the molten weld pool through the arc zone without being directly melted by the arc. The additional wires are heated by the arc and the molten pool, and their molten metal merges with the primary weld pool. This configuration allows for:

1. Higher deposition rates without proportionally increasing thermal input
2. More uniform chemical composition of the weld metal
3. Reduced dilution from the base metal
4. Improved weld geometry with fewer passes

Metallurgical Considerations for 12Cr2Mo1V Steel

12Cr2Mo1V is a Cr-Mo-V alloy steel used for high-pressure hydrogen service at elevated temperatures (typically 400-550°C). The key metallurgical challenges include:

• Temper embrittlement susceptibility: The presence of Cr, Mo, and V promotes temper embrittlement in the 370-570°C range, which is why the embrittlement resistance test (VTr54+3ΔVTr54) is specified
• Low-temperature toughness: Hydrogenation reactors may experience cold start-up conditions, requiring adequate -30°C impact toughness
• Hydrogen-induced cracking (HIC): In hydrogen service, susceptibility to HIC and SOHIC (stress-oriented hydrogen-induced cracking) must be considered
• Creep strength: At operating temperatures, creep resistance is essential for long-term structural integrity

The achievement of -30°C Charpy KV₂ values ≥54 J demonstrates that the additional filler wire method produces weld metal with adequate low-temperature toughness, which is critical for safe operation during cold start-up and shutdown cycles.

Embrittlement Resistance Evaluation

The temper embrittlement evaluation criterion VTr54+3ΔVTr54 ≤ 0°C is a stringent requirement that ensures the material does not exhibit significant ductile-to-brittle transition temperature shift during tempering. The ΔVTr54 represents the shift in the 54 J transition temperature after tempering at 540°C for 400 hours. A value of ≤0°C indicates that the temper embrittlement shift is minimal, which is essential for the long-term reliability of the reactor boss.

Engineering Practice Integration

Manufacturing Efficiency Analysis

The 200%-250% improvement in production efficiency is remarkable and has significant economic implications. For a typical hydrogenation reactor with multiple bosses, the time savings can translate to:

• Reduced shop floor space utilization time
• Lower labor costs
• Shorter project schedules
• Reduced energy consumption per unit of weld metal deposited

Process Development Methodology

The study follows a rigorous qualification testing approach consistent with ASME Section IX and NB/T 47014:

1. Pre-qualification: Literature review and consumable selection
2. Procedure qualification: Welding procedure specification (WPS) development
3. Mechanical testing: Tensile, bend, impact, and embrittlement testing
4. Metallographic examination: Microstructure and defect assessment
5. Non-destructive testing: RT or UT for volumetric defect detection
6. Final approval: Comparison of results with acceptance criteria

Quality Control Framework

For production implementation, the following quality control measures are recommended:

Key Questions and Reflections

The study successfully demonstrates the technical feasibility of additional filler wire SAW for 12Cr2Mo1V boss hardfacing. However, several questions remain for further investigation:

1. How does the additional filler wire method affect hydrogen diffusion and susceptibility to delayed hydrogen cracking in the heat-affected zone?
2. What are the long-term creep properties of the weld metal and HAZ under hydrogenation service conditions (400-550°C, high hydrogen partial pressure)?
3. How does the process scale to larger diameter reactors with thicker wall sections?
4. What are the implications for post-weld heat treatment (PWHT) parameters?

The study's emphasis on green manufacturing and energy efficiency is particularly commendable, as it aligns with the industry's growing commitment to sustainable manufacturing practices. The reduction in manufacturing time directly translates to lower energy consumption and reduced carbon emissions per unit of product.

Study Insights and Implications

This research represents a significant advancement in heavy equipment manufacturing technology, demonstrating that productivity improvements can be achieved without compromising material performance. The additional filler wire SAW method provides a practical solution to the bottleneck of boss hardfacing in hydrogenation reactor fabrication. For pressure vessel engineers and manufacturing managers, this study provides the technical basis for adopting this process, subject to appropriate qualification testing per applicable codes and standards. The findings also suggest that similar efficiency gains may be achievable for other Cr-Mo alloy steel applications in the pressure vessel and piping industries.