Canadian Steel Properties — CSA G40.21 Yield & Tensile Strength by Grade

Q: What is the difference between 350W and 350WT in CSA G40.21?

350W is the standard weldable structural grade with Fy = 350 MPa and no guaranteed Charpy toughness. 350WT has the same strength properties but adds Charpy V-notch testing at -45 deg C (27 J minimum longitudinal). 350WT is required for exterior steelwork in most Canadian climate zones, for bridges per CSA S6, and for any tension member where fracture toughness is critical. The chemical composition of 350WT typically has tighter phosphorus and sulphur limits than 350W to ensure low-temperature toughness.

Q: Does CSA G40.21 350W have the same properties as ASTM A992?

They are very similar but not identical. 350W has Fy = 350 MPa vs A992 Fy = 345 MPa — a minimal difference. Both have Fu min = 450 MPa and similar CEV limits. The rolling practice and chemistry are essentially the same, and Canadian W shapes are often dual-certified. For CSA S16 design, use Fy = 350 MPa. For AISC 360 design, use Fy = 345 MPa. The key difference is the 'T' variant: CSA G40.21 provides 350WT with guaranteed -45 deg C Charpy, while A992 has no Charpy subgrade.

Q: What is the yield strength of CSA G40.21 350W in thicker plates?

For plates 20-40 mm thick, Fy = 350 MPa (no reduction). For 40-65 mm thick, Fy = 340 MPa. For 65-100 mm, Fy = 320 MPa. For 100-150 mm, Fy = 300 MPa. This thickness-dependent reduction applies to all CSA G40.21 grades and must be used in CSA S16-19 design calculations for member resistance per Clause 13.5.

Q: What is 700Q steel used for in Canadian construction?

700Q is a quenched and tempered high-strength steel with Fy = 700 MPa and Fu = 750-950 MPa. It is used in lightweight structural applications where weight reduction is critical: mobile equipment, military bridges, heavy equipment supports, and some crane runways. Due to its lower Fu/Fy ratio (1.07), it is not permitted in seismic force-resisting systems per CSA S16-19 Clause 27.1. Welding 700Q requires special procedures per CSA W59 with strict preheat and interpass temperature control.

Q: How do I determine required Charpy toughness for Canadian construction?

CSA S16-19 Clause 27.2 provides the procedure. Determine the minimum service temperature from NBCC 2020 Appendix C for your location. Apply a temperature adjustment based on member thickness and stress level. Select a G40.21 grade with Charpy test temperature below the adjusted value. For exterior steelwork in most of Canada (design temperature -35 deg C), 350WT (tested at -45 deg C) is appropriate. For heated interior steelwork, standard 350W without Charpy is typically acceptable.

Complete reference for CSA G40.21 structural steel mechanical properties. Yield strength Fy, tensile strength Fu, Charpy V-notch impact values, and chemical composition for all common Canadian steel grades used in structural engineering per CSA S16-19.

Quick access: Canadian steel grades guide → | CSA S16 design overview → | Beam capacity calculator →

CSA G40.21 Grade System Overview

CSA G40.21 (General Requirements for Rolled or Welded Structural Quality Steel) is the Canadian material standard for structural steel. The grade designation encodes yield strength, weldability, toughness, and corrosion resistance:

Number: Minimum yield strength in MPa (e.g., 350 = 350 MPa)
W: Weldable — guaranteed weldability with carbon equivalent value (CEV) limits
A: Atmospheric corrosion-resistant (weathering steel)
T: Toughness — Charpy V-notch tested at specified temperature
Q: Quenched and tempered — high-strength heat-treated steel

For example, 350WT means 350 MPa minimum yield, weldable, with low-temperature Charpy toughness. 700Q means 700 MPa minimum yield, quenched and tempered.

Complete G40.21 Grade Table — Fy and Fu

The following table presents yield strength and tensile strength for all commonly specified CSA G40.21 grades. All values per CSA G40.21-18.

Grade	Type	Fy (t <= 20 mm) MPa	Fu (t <= 20 mm) MPa	Fu/Fy Ratio	Comparable ASTM
260W	Weldable	260	410-550	1.58 min	A36
300W	Weldable	300	440-620	1.47 min	A572 Gr 42
350W	Weldable	350	450-620	1.29 min	A992 / A572 Gr 50
350A	Atmospheric	350	450-620	1.29 min	A588
400W	Weldable	400	480-650	1.20 min	A572 Gr 60
480W	Weldable (QT)	480	550-720	1.15 min	A572 Gr 65
700Q	Quenched & Tempered	700	750-950	1.07 min	A514
350WT	Weldable + Tough	350	450-620	1.29 min	—
350AT	Atmospheric + Tough	350	450-620	1.29 min	—

350W is the default structural grade in Canada for buildings. 350WT is required for exterior steelwork in most Canadian climate zones due to low-temperature toughness requirements.

Yield Strength by Thickness

Per CSA G40.21 Clause 6.2, the specified minimum yield strength decreases as section thickness increases. This is critical for heavy column sections, base plates, and thick built-up girders.

Grade	t <= 20 mm	20 < t <= 40 mm	40 < t <= 65 mm	65 < t <= 100 mm	100 < t <= 150 mm
260W	260	260	250	230	210
300W	300	300	280	270	250
350W	350	350	340	320	300
350A	350	350	340	320	300
400W	400	390	370	360	340
480W	480	460	430	410	—
700Q	700	670	630	590	—
350WT	350	350	340	320	300

For a W310x129 column with flange thickness exceeding 20 mm in Grade 350W, the design yield strength Fy = 350 MPa (flange thickness 20.3 mm, still within 20-40 mm bracket). For a heavy built-up girder with 50 mm flange plates in 350W, Fy = 340 MPa — a 3% reduction that must be accounted for in moment and compression resistance calculations per CSA S16-19 Clause 13.5.

Tensile Strength Ranges

The tensile strength Fu is specified as a range in CSA G40.21. The minimum Fu is used for bolt bearing and net section fracture calculations per CSA S16-19 Clause 13.11.

Grade	Fu min (MPa)	Fu max (MPa)	Fu/Fy Actual (t=20mm)	Notes
260W	410	550	1.58	High ductility, secondary members
300W	440	620	1.47	Good ductility, general framing
350W	450	620	1.29	Standard structural, good ductility
350A	450	620	1.29	Weathering, same strength as 350W
400W	480	650	1.20	Higher strength, reduced ductility
480W	550	720	1.15	Quenched & tempered
700Q	750	950	1.07	High strength, limited ductility
350WT	450	620	1.29	Same as 350W + Charpy

The Fu/Fy ratio is important for seismic design. CSA S16-19 Clause 27.1 requires a minimum Fu/Fy ratio of 1.20 for members in ductile seismic force-resisting systems. Grade 350W (Fu/Fy = 1.29) meets this requirement. Grade 700Q (Fu/Fy = 1.07) does not, so it is restricted to non-seismic applications.

Charpy V-Notch Impact Requirements

Charpy V-notch (CVN) testing is specified by grade suffix. Only the "T" suffix grades (350WT, 350AT) and the quenched and tempered grades (480W, 700Q) have guaranteed Charpy requirements per CSA G40.21.

Grade	Test Temperature	Min Energy (Longitudinal)	Min Energy (Transverse)
300W (non-T)	Not specified	—	—
350W (non-T)	Not specified	—	—
350WT	-45 deg C	27 J	20 J
350AT	-45 deg C	27 J	20 J
400W (non-T)	Not specified	—	—
480W	-20 deg C	27 J	20 J
700Q	-30 deg C	30 J	22 J

For fracture-critical members and tension components in welded built-up girders, CSA S16-19 Clause 27.2 imposes additional Charpy requirements beyond the base material standard. The minimum service temperature (from NBCC 2020 Appendix C climatic data) governs the required test temperature.

Charpy Temperature Adjustment for Design

Per CSA S16-19 Clause 27.2.2, the Charpy test temperature T_test shall be:

T_test = T_service + delta_T

Where delta_T depends on member thickness and stress level. For a 50 mm thick tension flange in a welded girder at -35 deg C service temperature, the required Charpy test temperature may be -45 deg C — which drives the specification of 350WT over 350W.

Chemical Composition

CSA G40.21 specifies ladle analysis limits for each grade. The following values are maximum percentages unless noted.

Element	300W	350W	350A	400W	480W	700Q
Carbon, C (max %)	0.23	0.22	0.20	0.23	0.22	0.18
Manganese, Mn (max %)	1.50	1.50	1.25	1.50	1.50	1.50
Silicon, Si (max %)	0.40	0.40	0.40	0.40	0.40	0.40
Phosphorus, P (max %)	0.04	0.04	0.04	0.04	0.04	0.025
Sulphur, S (max %)	0.05	0.05	0.05	0.05	0.05	0.025
Copper, Cu (min %)	—	—	0.25-0.40	—	—	—
Chromium, Cr (min %)	—	—	0.40-0.65	—	—	—
Nickel, Ni (min %)	—	—	0.25-0.40	—	—	—

Carbon Equivalent Value (CEV)

Weldability is quantified by the carbon equivalent value per CSA G40.21:

CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

Typical CEV values for Canadian structural steel:

Grade	Typical CEV (t <= 40 mm)	Maximum CEV (by agreement)
300W	0.35-0.40	0.45
350W	0.38-0.43	0.48
400W	0.40-0.46	0.50
480W	0.42-0.48	0.52
700Q	0.45-0.55	0.60

CEV governs preheat requirements per CSA W59 (Welded Steel Construction). For 350W sections up to 25 mm thickness, CEV below 0.45 typically requires no preheat with low-hydrogen electrodes. For thicker sections or higher CEV, Table 5.2 of CSA W59 specifies minimum preheat temperatures.

Applications by Grade

Grade	Typical Applications	Design Fy (MPa)	Max Thickness
260W	Purlins, girts, light framing, stairs, handrails	260	75 mm
300W	Secondary beams, bracing, light columns, platforms	300	100 mm
350W	Primary beams, columns, braces, trusses, general framing — default structural grade	350	100 mm
350A	Exposed bridge girders, architectural framing, signage structures	350	100 mm
400W	Heavy columns (W360x110+), transfer girders, long-span beams	400	100 mm
480W	Lightweight structures, mobile equipment, crane runways	480	65 mm
700Q	Heavy equipment supports, military bridges, specialty applications	700	65 mm
350WT	Exterior steel in cold climates, Arctic structures, bridges	350	100 mm

For most building structures designed to CSA S16-19, Grade 350W in thickness up to 20 mm (Fy = 350 MPa) is the most economical choice. Grade 400W becomes economical for heavily loaded columns where the 14% increase in yield strength (400 vs 350 MPa) reduces the required section mass.

Ductility Requirements

CSA S16-19 Clause 27.1.1 requires that steel used in seismic force-resisting systems meet minimum elongation requirements:

Minimum elongation in 200 mm: 20% for W shapes and plates
Fu/Fy ratio minimum: 1.20
Maximum Fy / specified Fy: 1.30

Grade 350W meets all three requirements, making it suitable for ductile moment frames, concentrically braced frames (CBFs), and eccentrically braced frames (EBFs) per CSA S16-19 Clause 27.

Grade 700Q does not meet the Fu/Fy ratio requirement (1.07 < 1.20) and is therefore restricted to non-seismic applications or systems where expected ductility demands are low.

Frequently Asked Questions

What is the difference between 350W and 350WT in CSA G40.21? 350W is the standard weldable structural grade with Fy = 350 MPa and no guaranteed Charpy toughness. 350WT has the same strength properties but adds Charpy V-notch testing at -45 deg C (27 J minimum longitudinal). 350WT is required for exterior steelwork in most Canadian climate zones, for bridges per CSA S6, and for any tension member where fracture toughness is critical. The chemical composition of 350WT typically has tighter phosphorus and sulphur limits than 350W to ensure low-temperature toughness.

Does CSA G40.21 350W have the same properties as ASTM A992? They are very similar but not identical. 350W has Fy = 350 MPa vs A992 Fy = 345 MPa — a minimal difference. Both have Fu min = 450 MPa and similar CEV limits. The rolling practice and chemistry are essentially the same, and Canadian W shapes are often dual-certified. For CSA S16 design, use Fy = 350 MPa. For AISC 360 design, use Fy = 345 MPa. The key difference is the "T" variant: CSA G40.21 provides 350WT with guaranteed -45 deg C Charpy, while A992 has no Charpy subgrade.

What is the yield strength of CSA G40.21 350W in thicker plates? For plates 20-40 mm thick, Fy = 350 MPa (no reduction). For 40-65 mm thick, Fy = 340 MPa. For 65-100 mm, Fy = 320 MPa. For 100-150 mm, Fy = 300 MPa. This thickness-dependent reduction applies to all CSA G40.21 grades and must be used in CSA S16-19 design calculations for member resistance per Clause 13.5.

What is 700Q steel used for in Canadian construction? 700Q is a quenched and tempered high-strength steel with Fy = 700 MPa and Fu = 750-950 MPa. It is used in lightweight structural applications where weight reduction is critical: mobile equipment, military bridges, heavy equipment supports, and some crane runways. Due to its lower Fu/Fy ratio (1.07), it is not permitted in seismic force-resisting systems per CSA S16-19 Clause 27.1. Welding 700Q requires special procedures per CSA W59 with strict preheat and interpass temperature control.

How do I determine required Charpy toughness for Canadian construction? CSA S16-19 Clause 27.2 provides the procedure. Determine the minimum service temperature from NBCC 2020 Appendix C for your location. Apply a temperature adjustment based on member thickness and stress level. Select a G40.21 grade with Charpy test temperature below the adjusted value. For exterior steelwork in most of Canada (design temperature -35 deg C), 350WT (tested at -45 deg C) is appropriate. For heated interior steelwork, standard 350W without Charpy is typically acceptable.

This page is for educational reference. All material property data per CSA G40.20/G40.21-18. Verify properties against current mill certificates before procurement or design. For fracture-critical members, follow CSA S16-19 Clause 27 material selection procedures. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent PE/SE verification.