Heat treated m. steel frame

By - Date 09-21-2000 18:30

I plan on welding some 1/4" mild steel bars to a light duty tractor frame but some people have told me not to put down too much heat while welding (and consequently not to get 100% penetration) because the frame was heat-treated during the manufacturing process. What does heat treating have to do with the welding process. I want very strong welds but according to several people I can't put down sufficient heat to get it. I planned on using .035 e70s-6 wire, 80/20 Ar/Co2, and my Millermatic 185(195amps). I do not know what particular heat treating method was used on the frame but i would like to find out what I should do about this because people have said the same about my 1/2 ton Ford pick-up truck's frame (yet I've seen people repair their light-duty truck frames in the field with a simple stick welder and never have problems down the road.) Thanks for any info and sorry my entry was so long.

By RonG

Date 09-22-2000 00:17

It is true that welding on a vehicle frame is not a good idea but there are techniques that can help, like useing diamond shaped fish plates, never weld straight across the frame or any other structual iron.

Frames generaly are tempered and welding destroys the temper and leaves a heat affected zone (HAZ)that may be prone to cracking.

In my contruction working years we repaired many cracked frames by covering them with a diamond fish plate (after welding the crack) for reinforcment. The fish plate should be longer than tall and if possible do not tie the welds together in the center of the frame.

If you put a good fish plate on then you can weld to it with out weaking the frame any more.

Now! I have been around a few Tractors and the "Frame" consisted of an Engine block, Transmission and Axel housing. Just where are you wanting to weld because all of the above are usually Cast Iron.

By - Date 09-26-2000 15:11

Should I go ahead and use my 240 amp mig welder (b/c of a smaller haz than my stick welder)? What do you mean by not tying in the welds at the center of the frame? Should I preheat the area to be reenforced? Any more specific info on welding truck frames would be greatly appreciated. thanx.

By RonG

Date 09-26-2000 17:13

I am not sure of your concept of 100% penetration. I was thinking more in the terms of a lap joint.You sure dont want to burn thru your frame.The MIG should be fine. I dont recall but if you are useing flux core even better.

It seems to me you should be thinking in terms of Amount and Direction of load.
Stop welding short of the conners in the middle of the frame. (you are weaking the stuctural integrity of the frame when you weld on it) "Dont weld all the way across the frame"

Unless its a cold rainy day I would only preheat enough to remove moisture. 300 deg F. Tack your fish plate in place. Weld one leg and let it cool before welding the next leg which should be opposite (180 deg) of the one you welded last.

The point is if you have to weld to the frame use a large enough fish plate to allow plenty of suface area of weld to be strong enough to take what ever load. Think in terms of square inches and pounds per square inch. That "70" in you filler material is 70,000 psi tensil. Then attach your load to the fish plate, that you can do what ever you want to with out doing more damage to your frame.

Also to keep down cold cracking (from hydrogen) you need to remove oil, grease, paint, rust and dirt.
And if it is a cold and rainy day have some insulation handy to let it cool a little slower.

By - Date 09-26-2000 22:03

Thanks, I got a little confused at first. Two more things, why is flux-cored wire better for this particular application (I have heard of slag inclusion occuring as result of using flux-core) Also, can you give me any suggestions or info on "boxing" a CJ Jeep frame or adding crossmemebers? Many people have said that this particular vehicle needs frame reenforcing (at least from the bellhousing up) i appreciate all the information and I'm sure you can tell that i am novice.

By RonG

Date 09-27-2000 02:16

I would guess that most likely the frame is a "Channel" and has 3 sides if you add a 4th side then you have a box. You would be welding to the open lip of the channel and that should not do harm.
I can't say about the cross member, That may involve some tricky fiting. Are there skid plates under the engine and transmission? If you go under them you loose a lot of ground clearance and you surely dont want to connect to them.

By - Date 09-27-2000 16:25

Can you recommend any specific procedures I should follow when boxing the frame? Also, there are skid plates galore but some people have recommended adding crossmembers to the rear 1/3 of the frame for more "lateral" stregth (I guess they have experienced some frame twisting when they put a lot of torque to the rear wheels and hit a boulder at the same time or something). Would it be easier to just bolt them in? Thanks again for your time.