Picking the right welding rod

I'm getting ready to fix my flatbed car hauler. Several years ago a drunk lady in a mini van hit the back of my parked trailer and ramped herself up and got stuck on it.
Damage wasn't all that bad but the left side is about 3 inches lower than the right. The trailer pulls straight and works fine. The trailer's main 3x5x1/4" angle iron frame is bent (warped really) in several places. I'm thinking about welding a 2x4x1/4" rec. tube into the angle iron frame. The radius of the inside of the angle is the same as the radius of the tube. Should fit great. I have a 225 amp AC buzz box, and in the past have burned a lot of 6013 with it. What kind of rod would work best. Should I weld an inch and skip 5 inches. I don't want to overweld.
Any suggestions or comments would be appreciated.
Thanks, Chuck in Phoenix
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I'd suggest that you really need to straighten the frame out before you start adding more sttel. Plus it would seem to me that the fitup between the warped old steel and the straight new steel would not be very good.
While I really 6013 for new work, this job sounds like you may have some painted or rusty steel, poor fitup (gaps), and out of position welding. Try some 6011 or upgrade and use some 7018AC for extra strength. If the new material is really just a stiffener, a 1" in 4"to 6" stitch weld should be fine. I'd tend to make the 1" a bit longer to ensure that you have a good arc established and are getting good penetration.
Chuck wrote:

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Stitch welding is wise. If you can chain the high corner down and jack the low corner up before you install the tube the frame should end up straight afterward. Jack it up a little extra :')) Unless you have access to a floor that has anchor points it will be difficult to do what I mentioned. A tube frame work is much more resistant to twisting than angle iron. Randy

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