steering components (light duty truck)

[tha89sx]

i was going to send out a steering arm from a 3/4 ton diesel pickup for material analysis, i was just wondering if someone could enlighten me so that i could save some time.

i suspect that the piece is forged, but i was wondering if the piece needs to be forged or not.

 

[CoryPad]

Usually a piece like that is forged. This is good for fatigue strength issues (uniform composition and microstructure, smooth grain flow, lack of porosity, lack of sharp edges or other stress concentrators, etc.). Pieces like this could be made from castings or sheet metal fabrications, but they would need to overcome the issues related to fatigue.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[patprimmer]

Forgings generally lack sharp detail as the metal does not flow as well as when cast.

Also forgings need to be struck in a way that the "hammers"? can strike and retract without getting stuck on any undercuts, so there will always be some draft angle apparent.

The parting line will be a blunt flat bump, not a sharp edge.

More complex shapes may be struck from different directions with different hammers to overcome the no undercuts problem in some cases.

To tell the difference between cast iron and steel, run a file over an edge. The steel will peel of shavings while the iron will powder.

Both tests are easier with experience or by direct comparison to known samples.

For detailed composition analysis you will need lab tests. In my lab days they would have used an Elmer Perkins atomic absorbtion spectrophotometer, but that was 30 or 40 years ago. Times may have changed.

Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dbooker630]

Most steering arms, especially if there some curvature to the design, will be forged. The arms are usually quench-and-tempered alloy steel and high wear areas may be induction hardened. If it is a straight arm it possibly could be made from bar stock provided the reduction ratio is high enough.

 

[Rob45]

Another simple way of distinguishing castings from forgings (but that wasn't the question, was it?) is to hit the suspect piece with a hammer, and listen to it.

Forgings ring, castings do not.

 

[patprimmer]

The OP triple posted slightly different but heavily overlapping questions.

The how to tell the difference was in another thread. I answered it all here to keep it in one place.



Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Tmoose]

I figure generally the geometry of a part can (and should) be changed to allow the use of any particular material. In fact, many of the part failures I've dealt with could easily have been avoided with slightly "better" geometry using the same old material. Airplanes can be made of wood or titanium. There are lots of strong, ductile casting matarials, but some weak brittle ones too.

Here is a picture of a cast nodular iron (ductile) claiming to be stronger than some unknown stock part .

http://www.rockstomper.com/images/products/axles/60knuckles/dedenbear/ded6005.jpg

the steering arm portion is faired smoothly and massively into the main knuckle.

Here is a picture of steering arm that needs to be a forging.

http://www.pozziracing.com/Media/camaro_outersteer_arm_short.jpg