Roll Formed Angle Strength

Among engineers and buyers, there are some misconceptions that the strengths of mill angle iron and roll formed angle meet the same parameters when made to the same gage, leg length, and using the same type of material. The purpose of this page is to assist engineers in the decision-making process when they are faced with the choice of which one to use.

Shapes produced by rolling steel billet in a heated plastic state, or hot mill angle iron shapes, are better for structural purposes, and are commonly produced with ASTM A36 and ASTM A588 material grades.

ASTM A36 is a low carbon steel similar to the A1008 steel that is commonly available as commercial quality cold rolled steel. ASTM A588 is a high strength low alloy material that is usually sold in sheet form similar to Cor-Ten steels.

Dimensionally, the differences between a hot mill product and a cold rolled product are as follows:

1. The outside corners of a hot mill product will usually have square corners, whereas the cold roll formed product will have rounded corners which are a product of the inside radius (usually 1T or greater) plus material thickness and stretch.
2. The web of channels and the legs of channels and angles will have a taper with a hot mill product, whereas the cold formed product is a uniform thickness.
3. The outside leg edges of a hot milled steel product will be rounded whereas the cold formed product will be square due to the fact that the edges are slit from coil.

There is a significant advantage to using cold finished product when there is to be subsequent fabrications such as holes, notches, and miters, etc. The flatness and consistent thickness inherent in cold formed products allow for the accurate location of fabricated features, something that is difficult to achieve with hot milled products. These features can often be imparted to the material in the “flat” state prior to forming using a pre-notch process that allows roll formers to combine operations that otherwise would have to be done as discrete secondary operations using a hot rolled process if, depending on the secondary operation in question, it can be done at all. The rigidity of a roll formed section may be assumed to be close between hot milled and cold formed parts of a similar gage, or when the median measured thickness of the hot mill product is similar to that of the cold formed product.

In summary, gage for gage and dimension for dimension, the cold roll formed process offers roll formed angles with similar strength and rigidity, but more flexibility, making them preferable when compared to angle iron made with the hot rolling process. Please contact success@samsonmail.com for more information about this subject if you are considering the use of angle iron or hot rolled (structural) angle.