Most likly a high carbon, & heat treated for stress relief. (DO NOT WELD!)

Hello Brian, the gentleman in his post stated that truck frames are made of high carbon steel and possibly heat treated and stress relieved. This is certainly the case for a great many of the truck frames that are out there. A good many of them are also made of heat treated Aluminum. Any of these types of frames are not designed to be welded on and in most cases they will have warning labels posted all over on them saying so. Another thing to consider when working with semi tractor frames is that they do not want you to drill holes in the flanges of any frames, the webs are generally considered okay when you are adding accessories but not the flanges. If you run into a frame that is considered weldable and you are considering stretching the frame then you should use a diagonal type splice joint and also use a tight fitting sleeve that fits the inside of the frame rail and extends beyond the splice sight, once the sleeve is in place it should be bolted in through the flange. Truck frames are designed to be somewhat flexible, that is why the majority of components that make them up are either bolted, riveted, or Huck fasteners are used to put them together. If they were welded they would constantly be breaking welds due to the tortional forces and vibration that the truck sees in service. What this all really boils down to in a lot of cases is how willing you are to be liable for the work that you do on a frame. If it is your own personal truck then you can make the judgement call on how comfortable you are with the repair quality and the DOT may also have some comment regarding this. If it is someone elses truck I would be a whole lot more careful about how far you stick your neck out to try to help them out. In a lot of cases the only solution for repairing frame damaged trucks is to replace the entire rail. Hope this helps, regards, aevald

Welding on a truck frame is dicey business. Call the manufacturer for recommendations. If that fails, you can remove a small piece of the frame and send it out for a chemical analysis. The cost is around $75. It may be well worth the cost to have peace of mind. Assuming the frame is high strength steel, make sure you tell the lab that you need to know the carbon, chrome, manganese, chrome, nickel, silicon, phosphorus, sulfur, vanadium, and boron content. You can use those values to calculate the preheat requirements using the method in the annex of AWS D1.1 or other carbon equivalency formula available from other sources. I would imagine the steel may be a quench and tempered high strength steel. Use stringer beads, with a temper bead, and maintain a low interpass temperature (100 to 150 degrees F above the preheat temperature). Any welding should utilize low hydrogen practices, and if you are using SMAW, make sure the low hydrogen electrodes are "fresh".

Perhaps the best way to remove the sample from the frame is to use a hole saw or Hougen type drill that removes a "slug". Drill the hole through the web where is is least likely to reduce the usefulness of the frame.

I tend to agree that the best weld is no weld on a quench and tempered high strength truck frame. Think liability and the ramifications if the frame fails in service and someone is seriously hurt or killed as a result of your work.

Best regards - Al

I just happened to come upon Your question, so Better late than never...  When We made them at Dana Corp they were made of 1027 modified. Unfortunatly I don't  know just what the modified includes, but they were water quenched from above critical, I don't recall if they were tempered.