Production Welding Done Right
If you weld repair a part using the right material and the right techniques and you do proper heat treatment afterwards, the differences between welded and non-welded parts is negligible. But part of the issue is that not everyone does weld repair the right way, and many casting customers have had bad experiences at some point. In order to do production welding the right way, it takes a combination of process, experience and verification.
At Eagle Alloy, the weld repair process begins when inspectors recognize a weldable defect in a casting. The inspector marks that area and sends it to a welder down the production line. The welder then excavates the area using an ARC process until no trace of the defect remains. The next step depends on the type of alloy used for the part, and the rules are determined in advance. Metallurgists and quality control experts at the foundry decide on the rod to be used for each part, and the welder follows these instructions. When the welder finishes filling in the excavated area, he or she grinds the surface smooth and sends the part for heat treatment.
Heat treatment is a key aspect of the welding process. Some parts require full heat treatment, just like raw castings. Others will respond adequately to lower levels of heat treatment. Like choosing welding materials and processes, the correct heat treatment processes are determined for each part during the design phase.
When done right, heat treatment reduces internal stresses in the welded material and homogenizes the overall part. Through heat treatment, the welded portion bonds to the cast portion and takes on analogous mechanical and physical properties.
Potential Welding Issues
Fell right out of a casting like a filling out of a tooth. I can't tell you what specifically would go wrong to have a weld fall out of a cavity. it's an obvious lack of penetration, but I couldn't tell you what caused that lack of penetration
Surface finish, there may be a difference there. If we weld repair something, we grind it. They may see a difference in surface finish between the ground surface and the unground surface.
I don't think there's any kind of discoloration if it's done properly. As long as it's ground properly, they wouldn't really recognize any dimensional difference as long as it was done right. Machining. As long as it's heat-treated properly, the machine shops wouldn't notice any difference in hardenability or machineability.
Welding the Right Way
Certifications
Sometimes, some negotiations have gotten to the point to where the people say, "Fine. We will allow weld repair, but we want your welder to be certified to a level X."
We certify all of our welders to a boiler code, but some people will say that they want our welders certified to a higher level.
Standards
As a rule, weld repair is allowed. Then there are some customers who will put exceptions on their drawings. The vast majority of would, "Allows weld repair." But there's just been those occasions where it comes up where the drawing will restrict it or prohibit it.
ASTM guidelines for the identification of defects.