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4130 "Heat Treating" (Larger than 0.120" wall)

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Nate Palsa View Drop Down
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    Posted: Jan/08/2016 at 6:21pm
Hey everyone,

This forum has been immensely helpful to me in the past few years and so first and foremost, Thank You!

Quick question however;

I will be manufacturing some spherical bearing cups to accept the 1" bearings used in our front lower control arms. The attachment type used involves welding this 0.875" tall cup to a connecting plug which then adapts to the control arm tubing. The cup is 1.375" in diameter giving a thickness of 3/16" and it welds to the adapter which narrows to 3/8" at the connection.

I have machined a test cup from some some of that butter known as 1018 steel and am happy with the product but I know these cups are most often made from 4130. My concern (without having done any destructive testing yet) is that the 1/16" lip used to retain the bearing will be in danger of failing if not made from 4130.

My other concern is that since the 4130 is thick enough to require post weld processing or stress relief, would it be just as likely to fail if this heat treating was skipped?

Just looking for a few opinions before I machine all of the pieces out of one material or another.

Thanks everyone!
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drvr5 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote drvr5 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/08/2016 at 8:17pm
What are the forces you expect to see on that lip? It might be the wrong size by an order of magnitude either way, but there is no way to tell without knowing the loading condition.
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Nate Palsa View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nate Palsa Quote  Post ReplyReply Direct Link To This Post Posted: Jan/09/2016 at 12:59am
The design of this part was actually based on a nearly identical part offered by a company that was nice enough to provide specific dimensions for cup OD, height and lip ID as well as the bearing size it is made for so the dimensions for a 1" OD bearing were used to generate a part that should be very similar to a commercially available part which is stated by the company to be made from 4130.

As for loading, the we have been using the "Structural Consideraions for a Baja SAE Chassis" paper as a guideline as well as information found on here. Given the load reported in the paper and considering a safety factor with the motion ratio of the control arm, we were figuring a value of 2000lbs at the bearing surface.

Apologies for seeming a bit lazy for not running FEA on this component, but I was looking for some advice on the effects of skipping a heat treatment on 4130 vs using a material with an appreciably lower yield strength. We will likely be machining these components very soon so I will run some quick FEA as well as destructively test this 1018 steel mockup tomorrow to verify and if both show a large factor of safety, I will continue using the low carbon components.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote drvr5 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/09/2016 at 9:54am
Skipping the heat treat will give you very different strengths throughout the part as you move from the weld through the heat affected zone. It won't be weaker than 1018, and most Baja designs won't be affected by skipping the heat treat.

For the thickness, you need to run the trig to see what your force vector is to see if it is adequate.
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