Welding in heat treat area...

[Steelforbrains]

We have a customer that wants us to fabricate some racks to hold aluminum wheels. The wheels are passing through heat treatment on these racks. They pass through an ovem at 1050F for 2 1/2 hours. They then go through a water quench with the water at 90F. The racks are roughly 6'x8'x8'. The main frame is 1"sqx12ga(0.105")wall tubing (A-500B). The shelves are constucted of 3/4" sq HR A36 bar. These shelves are cantilevered off of the tubing frame and joined via fillet welds.

I think that it is a poor design, and they have a lot of problems with their existing racks, but we are going to build them anyway. Does anyone have any recommendations on the type of wire/gas that we should be using for this application?

 

[metengr]

http://www.alcotec.com/default.html

 

[metengr]

Steelforbrains;

Oops, disregard that last post of mine. Entropy has started to set in. Can you provide more specifics on the actual problems with the current design - weld cracking or separation ???

 

[Steelforbrains]

They are having a lot of problems with the frames warping and welds cracking. The frames are completely welded and have a lot of tubing spreaders welded in but no diagonal bracing. I think that they need to utilize more bolted connections and have some expansion joints so that the steel is more free to expand and contract.

 

[metengr]

Based on your second post, I agree with you that the frame needs to be completely re-designed first, welding/bolted connection design would follow a close second.

 

[EdStainless]

A welded design may be OK, but it need less continuous welds. You are right, things need to be able to move around. If you don't allow the sructure to distort then it will try to tear itself apart.

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[rolledalloy]

Flexible racking is commonly used for heat treating applications. A common tray design is a serpentine grid

http://www.qual-fab.net/serpentine-trays.htm

These use flat bar and round bars to pin the rack together. As a result it can support a load, but the individual bars can expand and contract freely during each thermal cycle.