Bending Reinforcement bars

[demsha]

Hello All,

Is there any standard or specification available for bending reinforcement bars? Is it OK to use welding torch? Is there any damaged to the material?
The material is CSA G30.18 Gr. 400 Mpa. Pictures from field indicates that welder has used the torch and darkened (black) areas appear in the bended region

Thanks in advance

 

[Goahead]

You may wish to see (no promotion intended)

http://www.arcreo.com.au/bending-reinforcement-shape

Hoping this helps,

http://www.welding-advisers.com/

 

[TXStructural]

Steel reinforcement is cold bent in the US, and in every other market that I have investigated. The odd appearance of bends is due to the spalling of hematite and magnetite iron oxides which form on the hot-rolled bar as it cools in air. These oxides are brittle and break away from the bar surface during bending.

There are reasons hot bending could be used, but it not common, and can negatively affect the mechanical properties of the steel. It also adds significant cost to an inexpensive process. Bend diameters are limited by codes (ACI 318 in the US). There are also bend diameters/radii in the relevant ASTM standards for our market here, however these are for bend testing bars for acceptance and should never be used for fabrication.

 

[LittleInch]

Is it ok to use welding torch - NO
Is there any damage to the material - almost certainly YES. Heating re-bar is one thing, but without proper control over the cooling, which is very unlikley, extreme brittleness / hardness can develop and the re-bar just snaps. To get it soft enough to bend by hand - otherwise I asusme they wouldn't have done it - needs red hot metal.

Sounds like time to fire the person responsible and then cut the affected bars off and start again or you risk collapse of your structure - your call.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[TXStructural]

Heating bars to 1100-1500F is the standard method for bending large bars in place for field repair. There will be difficulty in doing this properly, and rebar should be air cooled (not liquid quenched). But this is a method of last-resort, for field repair, not for routine bending. The difference being that factory production of bends needs to be economical, rapid, and repeatable, but field repair requires extraordinary measures and allows the corresponding risks.