Kent Henry
Former Technical Support Specialist
Electrical Apparatus Service Association, Inc.
St. Louis, MO
The paper "Welding Tips for the Service Center" by Kent Henry, presented at the EASA Convention 2009, provides comprehensive guidance on welding techniques and solutions for shaft repair in service centers. The focus is on minimizing turnaround time, reducing repair costs, and improving reliability for customers. Mechanical failures, particularly those involving shaft damage, are a significant cause of downtime and costs. Welding is the primary method for repairing worn or damaged shaft surfaces, and successful repairs depend on proper preparation, technique, and materials.
Henry discusses the importance of understanding basic metallurgy, including steel microstructures and the effects of heat treatment. Welding induces residual stresses and transforms microstructures in the heat-affected zone (HAZ), which can lead to brittle areas. Post-weld heat treatment (PWHT) is traditionally used to relieve stress and improve toughness, but it has disadvantages such as increased cost and downtime. An alternative method, temper bead welding (TBW), uses the heat from the welding process to stress relieve the HAZ.
The paper covers various welding methods, including stick welding (SMAW), TIG welding (GTAW), MIG welding (GMAW), flux cored arc welding (FCAW), and submerged arc welding (SAW). Proper storage of welding consumables, preheating, and maintaining interpass temperature are crucial to avoid hydrogen embrittlement and martensite formation. Techniques such as peening and vibratory stress relief can improve weld fatigue resistance.
Henry explains different TBW techniques, including the half-bead method, consistent layer method, and controlled deposition method. These techniques involve strategic placement of weld beads and controlled heat input to temper the HAZ and improve toughness. Weld toe tempering is also discussed as a method to reinforce the surface of the weld.
Preparation for welding includes cleaning, inspecting, and recording shaft dimensions, as well as preheating the entire rotor or armature assembly. Post-weld protection involves slow cooling to allow hydrogen diffusion and prevent rapid heat loss. Methods such as using a bake oven, mineral wool insulation, or burying the shaft in preheated sand are recommended.
The paper concludes by emphasizing the importance of good techniques, vigilant thermal control, and internal training programs to ensure repeatable weld repairs. Investing in these practices can reduce customer downtime, lower costs, and increase reliability.
Key Points Covered:
- Importance of minimizing turnaround time, reducing repair costs, and improving reliability
- Basic metallurgy and effects of heat treatment
- Various welding methods and their applications
- Proper storage, preheating, and maintaining interpass temperature
- Techniques to improve weld fatigue resistance
- Different temper bead welding techniques
- Preparation and post-weld protection methods
Key Takeaways:
- Successful welding repairs depend on proper preparation, technique, and materials.
- Understanding metallurgy and heat treatment is crucial for effective repairs.
- Proper storage and handling of welding consumables are essential to avoid hydrogen embrittlement.
- Preheating and maintaining interpass temperature prevent martensite formation and improve toughness.
- Temper bead welding techniques provide effective stress relief and improve weld quality.
- Slow cooling and post-weld protection are necessary to ensure the durability of repairs.
To read the full technical paper and view the slides, download the PDF below.
ANSI/EASA AR100
More information on this topic can be found in ANSI/EASA AR100- Section 2: Mechanical repair
Print
