The yield strength of structural steel in Canada is usually 345 to 350 MPa (about 50,000 psi): 350 MPa for CSA G40.21 350W, used for HSS, channels, angles and plate, and 345 MPa (50 ksi) for ASTM A992 and CSA 345WM, the usual grades for wide-flange beams. Older and lighter grades are lower: 300W at 300 MPa and A36 at 250 MPa (36 ksi). All of them share the same stiffness, a Young's modulus of about 200 000 MPa, and a density of about 7850 kg/m³.
This guide gives the strength values by grade, the physical properties engineers use, and what each one means for a real beam or column.
Yield strength by grade
Yield strength is the stress at which steel stops springing back and starts to deform permanently. Design is based on the specified minimum for the grade, not on the test result for a particular batch.
| Grade | Standard | Minimum yield (MPa) | Minimum yield (psi) | Typical use |
|---|---|---|---|---|
| 350W | CSA G40.21 | 350 | about 50,800 | HSS, channels, angles, plate |
| 345WM | CSA G40.21 | 345 | 50,000 | W-beams and columns |
| A992 | ASTM | 345 | 50,000 | W-beams and columns |
| A572 Grade 50 | ASTM | 345 | 50,000 | Channels, angles, plate, H-piles |
| 300W | CSA G40.21 | 300 | about 43,500 | Plate, flat bar, light shapes |
| A36 | ASTM | 250 | 36,000 | Plate, bar, older buildings |
The psi figures for CSA grades are converted from MPa (1 MPa is about 145 psi); the ASTM grades are defined in ksi and converted the other way. For more on what each grade name means and which shape uses which, see our guide to structural steel grades in Canada.
Two points that trip people up:
- Yield strength belongs to the grade, not the shape. A W200x27 in A992 yields at 345 MPa; the identical shape in A36 yields at 250 MPa.
- The mill test report shows the actual yield, which is usually above the minimum. Designers still use the minimum, and a batch that happens to test high is still certified to its own grade.
Yield vs tensile strength
Tensile (ultimate) strength is the highest stress steel reaches before it necks and breaks. It is always higher than yield. A992, for example, has a minimum tensile strength of 450 MPa (65 ksi), and A36 a range of 400 to 550 MPa (58 to 80 ksi). The gap between the two is part of what makes steel forgiving: it yields, stretches and gives warning before it fractures.
Structural steel material properties
These are the general values used for carbon structural steel. Individual standards and design codes may round them slightly differently; the design code in use always governs.
| Property | Value | Imperial |
|---|---|---|
| Modulus of elasticity (Young's modulus), E | about 200 000 MPa (200 GPa) | about 29,000 ksi |
| Shear modulus, G | about 77 000 MPa (77 GPa) | about 11,200 ksi |
| Poisson's ratio | 0.3 | 0.3 |
| Density | about 7850 kg/m³ | about 490 lb/ft³ |
| Coefficient of thermal expansion | about 12 x 10⁻⁶ per °C | about 6.7 x 10⁻⁶ per °F |
| Melting range (carbon steel) | about 1425 to 1540 °C | about 2600 to 2800 °F |
What each property means in practice
Young's modulus is stiffness: how much steel stretches or bends under load before it yields. It is the number that controls deflection and floor bounce. Because it is essentially the same for every structural steel grade, a higher grade does not reduce sag. If a beam deflects too much, the fix is a deeper or heavier section or a shorter span.
Shear modulus governs twisting. It matters for torsion of open shapes such as W-beams and channels, and for lateral-torsional buckling.
Density turns sizes into weights. It is why plate weighs 7.85 kg per square metre per millimetre of thickness, and why the mass per metre printed in a W-shape name (the 27 in W200x27) is a reliable guide to its weight. Our structural steel size and weight chart puts it to work.
Thermal expansion matters on long or exposed steel. A 30 m steel member that warms by 40 °C grows by about 14 mm (30 000 mm x 12 x 10⁻⁶ x 40). Long canopies, exterior frames and buildings with long runs of steel may need slotted connections or expansion joints so that movement does not crack finishes or overload connections.
Melting point is mostly a curiosity for structural purposes. Steel loses much of its strength and stiffness at temperatures far below melting, so fire safety depends on keeping the steel cool enough, not on keeping it from melting. See structural steel fireproofing in Ontario.
How strong is structural steel?
Some ways to picture it:
- A 100 mm² piece of 350W steel (a 10 mm by 10 mm square bar) starts to yield in tension at about 35 kN, the weight of roughly 3.5 tonnes hanging from it.
- Steel is strong in both tension and compression. Concrete is strong only in compression, which is why concrete needs rebar. Our comparison of structural steel vs rebar covers how the two steels differ.
- Strength is rarely the only limit. Slender columns buckle well below their yield strength, and long beams are often sized by deflection or by sideways buckling of the compression flange. That is why design is done member by member to CSA S16, not by dividing a load by the yield strength.
Design under CSA S16 multiplies the steel's resistance by a resistance factor below 1.0 and compares it with factored loads from the building code, so the yield strength is one input among several.
Ductility, toughness and weldability
Three other properties matter for structural work even though they rarely appear as a single number on drawings:
- Ductility is the ability to stretch a long way after yielding without breaking. It lets steel structures redistribute load and give visible warning before failure, and it is essential in seismic design.
- Toughness is resistance to brittle fracture, especially in the cold. It is measured by Charpy impact tests. In CSA G40.21, grades with a T (such as 350WT) are impact tested, and they are specified for bridges, crane girders and some cold-exposed members.
- Weldability depends on chemistry, mainly carbon and alloy content. The W in 350W stands for weldable. Higher-strength and hardened steels need more careful welding procedures, and steel of unknown grade in an existing building may need testing before anything is welded to it.
Properties of existing and unknown steel
Renovation projects often meet steel with no paperwork. Older buildings may contain A36 or earlier grades, and very old buildings may even contain wrought iron. An engineer will usually either assume a conservative yield strength or have samples tested before relying on that steel or welding to it. Never assume an old beam is 350W just because it looks like a modern W-shape.
For new steel, ask for the mill test reports when the project needs them. They list the grade certification, chemistry and measured yield and tensile strength for each heat.
Steel supplied to the grade you need
We supply and fabricate beams, posts, plates, channels and lintels to the grades on your drawings, with in-house shop drawings, CWB certified welding and delivery across the GTA and Ontario. If you are not sure what grade your drawings call for, send them and we will go through them with you; substitutions still go to your designer. Request a quote, or browse our steel products.
Frequently asked questions
What is the yield strength of structural steel in MPa?
It depends on the grade. Canadian 350W has a minimum yield of 350 MPa, ASTM A992 and CSA 345WM 345 MPa, 300W 300 MPa, and ASTM A36 250 MPa. Most beams, columns and HSS in Canada today are in the 345 to 350 MPa range.
What is the yield strength of structural steel in psi?
A992 and A572 Grade 50 steel have a 50,000 psi (50 ksi) minimum yield. CSA 350W works out to about 50,800 psi, 300W to about 43,500 psi, and A36 to 36,000 psi.
What is Young's modulus of structural steel?
About 200 000 MPa (200 GPa, or 29,000 ksi). It is essentially the same for every structural steel grade, which is why a higher grade makes a beam stronger but not stiffer.
What is the density of structural steel?
About 7850 kg per cubic metre (490 lb per cubic foot). That works out to 7.85 kg per square metre of plate for every millimetre of thickness.
What is the melting point of structural steel?
Carbon steels melt over a range of roughly 1425 to 1540 °C (about 2600 to 2800 °F), depending on composition. Steel loses much of its strength long before it melts, which is why fire protection is designed around temperature, not melting.
