Curved flat steel

[edinthecloudsParticipant @edintheclouds]

Hi,

I've purchased a 2' length of 3/8" x 1/8" flat steel, when I removed it from the wooded batten it had a slight curve/arc along the 2' length. I cut two 6" pieces normalised them to a bright cheery red. When they cooled both had a curve along their length greater than before.

I heated the remaining 12", when it cooled it too had a curve greater than before.

I think I'm wasting my time trying to straighten them. It would take a set of rollers to cold roll them flat/straight again.

Is this normal for small section steel?

Les

[edinthecloudsParticipant @edintheclouds]

[Anonymous]

Doesn't sound normal to me; was the strip cold drawn or sheared from sheet? Where was it purchased from?

Andrew

[edinthecloudsParticipant @edintheclouds]

The strip was cold drawn flat stock, from EKP supplies.

Les

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Les, if it was classed as flat, then I would have expected it to be reasonable flat as far as the eye can judge.

When heating cold drawn or rolled steel any where near red heat, it should be done totally uniformly, preferably in a furnace, otherwise the residual stresses induced during the cold working process will distort it because you will relieve the stresses on one side allowing the other side to pull it out of shape. It should then be allowed to cool uniformly also, as the contraction will be equal on all sides, but if one side is allowed to cool first, that will also distort the shape.

Regards Nick.

[JasonBModerator @jasonb]

What do you call a "slight curve" ? Allowable curve is 1.5-2.0mm over 1000mm.

Problem is if someone picks up a 3m length the wrong way it will bend under its own weight and won't spring back.

[edinthecloudsParticipant @edintheclouds]

Thanks JasonB,

I think your explaination is how the problem occured,

[Anonymous]

It is likely that a 3m length would be picked up in the middle, so the overhang becomes 1.5m, or about 59". The system is symmetric, so we can ignore one side. We then have a beam fixed at one end with a uniformly distributed load, ie, the weight of the material. A 59" length of 3/8" by 1/8" flat has a volume of 2.765 in³. Low carbon steel has a density of 0.283lb/in³, so the beam weighs 0.78267lb, uniformly distributed along the length. Maximum stress is at the support, and is given by Wl/2Z where Z is the section modulus. Assuming that the 3/8" dimension is horizontal this works out as 23642lb/in². The yield strength for low carbon steel (1018) is about 53000lb/in².

Andrew

[JasonBModerator @jasonb]

Andrew, thats why I said " if someone picks it up the wrong way" so assuming the right way is in the middle and the wrong way at one end while its still got a pile of other bits laying on it you could easily double your 23642lb/in2

[KWILParticipant @kwil]

Now now boys !!

[Neil WyattModerator @neilwyatt]

As long as the bar is flat stock the correct place to lift it is with the hands 0.553 of the bar length apart and equally spaced either side of the centre. This minimises the deflection, slightly wider to minimise the stress.

Neil

Edited By Neil Wyatt on 30/12/2014 14:19:48

[Gordon WParticipant @gordonw]

Not forgetting must be thin edge top and bottom.!

[JasonBModerator @jasonb]

Posted by Neil Wyatt on 30/12/2014 14:18:53:

As long as the bar is flat stock the correct place to lift it is with the hands 0.553 of the bar length apart and equally spaced either side of the centre. This minimises the deflection, slightly wider to minimise the stress.

Neil

Edited By Neil Wyatt on 30/12/2014 14:19:48

That handy as its 80mm less what I can reach finger tip to finger tip

Though would not want to try lifting a heavy bar like that

[Neil WyattModerator @neilwyatt]

It is handy though, as it applies to anything you want to lift/support with as little chance of distortion as possible – using a forklift or a fingers! Presumably it's also the best spacing for the legs of a lathe bed (ignoring the weight of the headstock) and I wonder if it determines the spacing of the uprights on the old Severn Bridge?

> Though would not want to try lifting a heavy bar like that

I initially read that as meaning you wouldn't want to lift the 3m of 1/8×3/8" bar… rather than 'lift a heavy bar in that way'.

Neil

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