Ok to heat and bend a pitman arm?

340mopar said
Steering parts are just forged steel, there is nothing special about them. They are heated when they are formed. We weld our own spring hangers on our cars that attach our suspension parts and this is different how? It is not, it is the same thing. If done right there is of no issue. To remove king pins & bushings in semis it is common practice to use lots of heat and these trucks haul over 80,000lbs, no big deal.

Chuck

When you forge form a piece of metal you realign the grain structure to follow the shape of the part. This is why a forged metal part is stronger than a cast part or one machined from a lump of metal.

When you heat a peice of steel up to it's red hot so you can bend it the grain structure will re-align it self into a more random pattern which reduces the strength of the part. Basically you have negated all the benifits of the forging process. Depending on the actual make up of the alloy if you do not cool it properly or peform the proper heat treatment after the heating you can cause carbon to parcipitate into the boundaries between the grain structure which makes the material very brittle and causes intergranual stress corrosion. You now have further reduced the parts ability to perform it's function. I have seen high strength alloy bolts have the heads just pop off sitting in the box because of improper heat treatment.

To say heating and bending a part like a pitman is no big deal without knowing all the details about the design and function is akin to saying playing Russion Roulette is no big deal without knowing if there are bullets in the gun.

My 30+ years as an engineer would look at a pitman arm and say it is a forged part because it's a convienent and cost effective way to make it more than the strength derived from forging. But I am not sure, and if the choice is between denting a header tube and potentially creating an unsafe part I would dent the tube.

Citing the heavy truck practice as justification is reckless. When a structural part is designed, a safety factor is built in. The heating on the big truck is likley reducing the overall strength but there may be a much larger safety factor that in the end your margin is still acceptable. Where as in car parts there is much more of a concern for reduced weight for performance & economy and the safety factor may not be as big. The heating could reduce the strength to a point of where no margin is left.

Before doing anything like this you need to understand what the potential consequences are and decide if you want to take the risk.