What is a Hot-Rolled Steel Section?
Hot rolled sections are produced by steelmakers where the molten steel is cast into a steel ‘blank’ approximating the shape of the finished product, the blank is then re-heated in a re-heating furnace and drawn through a series of carefully calibrated rollers to the final shape. The beams are then straightened, cut into standard lengths, cooled, and prepared for shipment.
The dimensions for hot-rolled steel sections are determined by the width and profile of the mill rolls which are constant for the designated ‘Nominal Size’ therefore the internal dimensions will remain constant while variations in ‘unit mass’ manifest in the thicknesses of the flange and web of the section affecting the overall profile dimensions.
Standard hot-rolled section profiles include -I- / -H- / -C- / -L- shapes, the finished dimensions and tolerances of which are determined by UK, European, US, and International standards.
Flanges may be either ‘Parallel’ or ‘Taper’ with parallel flanges being increasingly popular.
Taper flanges require tapered washers in order to make connections, and as the taper angle varies widely (between 4 and 9 degrees) they can be a nuisance. However, the taper flange is usually thicker (and heavier) than its parallel flange counterpart and is thus more resistant to deformation.
They are generally used for single-span applications
In the United Kingdom, the steel shapes are still rolled to imperial dimensions (BS4-1) and have simply been converted to metric equivalents, hence the section sizes appear a little odd, for example 16” = 406.4 mm
To a great extent, UK section sizes (BS4-1) are compatible to the American Standard (ASTM A 6/A 6M-12)
The larger Universal Beams (1016) are rolled to American Standards (ASTM A 6/A 6M-12)
Rolled steel angles and parallel flange channels however are rolled to true metric sizes in accordance with European standards (EN 10056-1:1998)
In Europe, the parallel flange steel shapes are rolled to European standards (EN and DIN) with the exception of:
Extra-Wide Flange Beams (HL), Wide Flange Columns (HD), Wide-Flange Bearing Piles (HP), and small Taper-Flange Channels, which are rolled to American standards (ASTM A 6/A 6M-12)
In the United States steel sections (which are referred to as ‘Shapes’) are rolled to imperial dimensions and are still referred to in inches, though, like the UK sections the dimensions are, in certain regions, quoted in metric units.
American -I- and -H- sections are not separated into Beams and Columns as is practiced in the UK and Europe, instead they are collectively termed as ‘Wide-Flange Beams’ and designated (W)
The notation used to identify hot rolled sections varies around the world:
In the United Kingdom steel sections are commonly specified with a code according to their nominal depth, width, unit mass, and designation. Therefore, a 254 x 146 x 31 UB would be a Universal Beam (UB) of approximately 254 mm in depth and a flange width of approximately 146 mm with a nominal mass of 31 kg/m.
In Australia, like the United Kingdom, steel sections are specified as Universal sections, but are identified in a slightly different manner; the same beam would be referred to as: 254-UB-31
In the United States steel sections are specified according to their designation, approximate depth, and unit mass in imperial units, therefore a W10 x 22 would be a Wide Flange Beam with an approximate depth of 10 inches and a nominal mass of 22 lbf/ft.
In Canada, which uses the same steel sections as the United States, steel sections are identified in the same manner except in metric units. Therefore, the W10 x 22 would be referred to as W250 x 33
Steel Sections or Shapes – Serial Size v Actual Size
Steel sections are often identified by their Nominal, or Serial size, which in almost every case differs from the actual size, and this is a very important issue for the steel draftsman. Steel section tables always list the steel sections in groups according to their serial size, for example:
254 x 146 x 31
254 x 146 x 37
254 x 146 x 43
This group represents the 254 x1 46 range; the difference is in the unit mass. In consulting the tables, it will be found that the actual sizes for these Universal Beams are:
251.5 x 146.1 x 31.3 kg/m
256.0 x 146.4 x 37.2 kg/m
259.6 x1 47.3 x 43.2 kg/m
So, it’s evident that the unit mass determines the actual size of the section, this is because of the manner in which hot rolled sections are formed. The unit mass differences are made up by the thicknesses of the flange and web of the section, the heavier the beam, the thicker the flange and web. It will be found that the inside dimension between the flanges remains constant (due to the roller settings) while the additional material in the web is reflected in the overall depth. In large sections, the overall depth of the beam will vary significantly.
It’s been a general practice over the years for nominal section sizes to be identified on the layout and design drawings, while the details should reflect the true sizes, especially where tolerances are tight. The true unit mass will assist in mass calculations.
United Kingdom Shape Designations
|I||UB||Universal Beam||Parallel||UB 127 /940
BS EN 10056:1999
ASTM A 6/A 6M - 12
|RSJ||Rolled Steel Joist||Taper||BS4-1:2005 / BS EN 10056:1999|
|H||UC||Universal Column||Parallel||BS4-1:2005 / BS EN 10056:1999|
|UBP||Universal Bearing Pile||Parallel||BS4-1:2005 / BS EN 10056:1999|
|C||RSC||Rolled Steel Channel||Taper||BS4-1:1993 / BS EN 10056:1999|
|PFC||Parallel Flange Channel||Parallel||BS4-1:2005 / BS EN 10056:1999|
|L||RSA-e||Rolled Steel Angle
|RSA-u||Rolled Steel Angle
European Shape Designations
|I||IPE||European I Beam||Parallel||EN 19-57|
|IPN||European Standard Beam||Taper||DIN 1025-1|
|HE||European Wide Flange Beam||Parallel||EN 53-62|
|HL||European Extra Wide Flange Beam||Parallel||ASTM A 6/A 6M-12|
|H||HD||Wide Flange Columns||Parallel||ASTM A 6/A 6M-12|
|HP||Wide Flange Bearing Piles||Parallel||ASTM A 6/A 6M-12|
|C||UPE||Parallel Flange Channel||Parallel||DIN 1026-2:2002-10|
|UPN||European Standard Channel||Taper||DIN 1026-1:2009|
|U||Taper Flange Channels (small)||Taper||ASTM A 6/A 6M-12|
|L||L||Equal Leg Angle||Parallel||EN 10056-1:1998|
|L||Unequal Leg Angle||Parallel||EN 10056-1:1998|
American Shape Designations
|I||W||American Wide Flange Beam||Parallel||ASTM A 6/A 6M-12|
|S||American Standard Beam||Taper||ASTM A 6/A 6M-12|
|H||HP||American Wide Flange Bearing Piles||Parallel||ASTM A 6/A 6M-12|
|C||C||American Standard Channel||Taper||ASTM A 6/A 6M-12|
|MC||American Channel||Taper||ASTM A 6/A 6M-12|
|L||L||American Equal Leg Angle||Parallel||ASTM A 6/A 6M-12|
|American Unequal Leg Angle||Parallel||ASTM A 6/A 6M-12|