I have a design that requires steel bars that need to be as straight as possible and keep its shape over time. These bears are fairly long (about 50" and trying to reduce as much as I can with the length) and I am currently increasing the thickness to help the stiffness out. Since I have little knowledge in all the various types of steel, I was wondering if anyone knows any of type of steel to fit this job

The elastic modulus is essentially the same for all of the various structural steels. Austenitic stainless steel (3xx series) is slightly lower. Search the archives here if you would like a more detailed explanation.

Given that, maybe the best is the cheapest, you can use more of it:)

What is your performance specification?

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Basically the design is supposed to clamp a material that is being rolled for packaging. Once a roll is cut off a new roll will able to be stapled easier to the core since the clamp will hold each strand together.

We have a previous prototype that somehow was bent or warped during use and this new one needs to be straight to get a good enough grip on the material

Sounds like you need higher strength, that can be achieved with a harder steel.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

Stiffness is essentially the same for all structural steels. In other words, elastic deformation (deflection) will be equal.

What I think you may be asking for is higher yield strength, so that more stress can be sustained before permanent deformation happens. A wide range of strengths are available, and it is mainly just a cost issue.

The best way to achieve component stiffness for a given weight of bar is through design, or cross sectional shape. That is why H-beams and wide-flange beams are used to give maximum stiffness against vertical deflection.

Is this bar cantilevered? I know you said the bar bent, but depending how and what bent, the mounting can be responsible for unexpected flexibility.

The bar is not cantilevered. From what it looks like the bar bowed from being positioned at awkward angles under repeated use. But then again I was told our maintenance shop made it up with a basic drawing so that may explain some of it.