May 8, 2007
Q: I am building a 400-gallon paint tank and I'm having trouble with leaks when using gas metal arc welding (GMAW). I'm using a welding machine running on 440. My best results come when running hot 19.5 on the heat and about 21/2 on wire speed. I am using a trimix gas and 0.035-inch 308 wire. The welds look pretty but are not leakproof. It takes three weeks of 10-hour days to make the paint tanks with GMAW, and it could take twice as long using shielded metal arc welding (SMAW). Any advice or tips are welcome.
A: This sounds like a heck of a project. Here are a few questions: What is the base material type and thickness (type of stainless)? Is it a fillet, edge, or butt joint? What are the wire feed speed (WFS), voltage, and shielding gas flow rate?It sounds like you are using a fairly common machine, on which that 21/2 on the wire feeder typically equates to 175 to 200 inches per minute (IPM). You should measure the actual WFS output of your machine. To run "hot," use your current 0.035-dia. 308L electrode, and set the weld parameters as follows:
These settings will increase weld speed significantly, but you might need some practice to adjust to the speed.
If your base material is thicker than 3/16 inch, then these parameters should work for you, but keep in mind I'm giving this advice without knowing your specific welding requirements. Before you start welding, you should always develop a Procedure Qualification Record (PQR) and Welding Procedure Specification (WPS).
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