G40.21 Steel Grades — 300W to 700Q Complete Properties Reference

Q: What is the most common CSA G40.21 steel grade used in Canada?

Grade 350W (Fy = 350 MPa for t <= 20 mm) is by far the most common structural steel grade in Canada, accounting for over 90% of structural steel used in buildings. It is the default specification for beams, columns, braces, and trusses in all types of construction. Grade 300W (Fy = 300 MPa) is occasionally specified for lightly loaded secondary members. Grade 400W (Fy = 400 MPa) is used for heavy columns and transfer girders in high-rise buildings where the higher strength reduces section size.

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

350WT has the same yield strength (350 MPa) and tensile strength (450-620 MPa) as 350W, but adds guaranteed Charpy V-notch toughness at -45 deg C (27 J minimum longitudinal). The 'T' suffix indicates toughness testing. 350WT also has tighter chemical composition limits (lower P and S) compared to 350W. For Canadian construction, CSA S16-19 Clause 27 requires 350WT or equivalent for exterior steelwork in most climate zones, for all bridges per CSA S6, and for tension members in fracture-critical applications.

Q: Can CSA G40.21 700Q be welded with standard E48XX electrodes?

No. 700Q (Fy = 700 MPa) requires matching E62XX electrodes (Xu = 620 MPa) per CSA W59 Table 5.2. Using E48XX electrodes on 700Q would result in an undermatching ratio of 480/620 = 77%, producing welds significantly weaker than the base metal. Additionally, 700Q welding requires strict preheat (100-150 deg C), interpass temperature control (maximum 200-250 deg C), and qualified welding procedure specifications (WPS) per CSA W59.

Q: What grade is used for weathering steel in Canadian bridges?

CSA G40.21 Grade 350A (standard weathering) for southern climates and 350AT (weathering + Charpy toughness) for cold regions are specified for Canadian bridge girders. 350AT includes the Cu, Cr, Ni additions for atmospheric corrosion resistance plus Charpy testing at -45 deg C for low-temperature toughness. Bridges in Ontario, Quebec, and the prairies typically specify 350AT. Coastal BC may use 350A where design temperatures are milder.

Q: What are the thickness-dependent yield strength reductions for G40.21 350W steel?

For 350W: t <= 20 mm: Fy = 350 MPa. 20 < t <= 40 mm: Fy = 350 MPa (no reduction). 40 < t <= 65 mm: Fy = 340 MPa. 65 < t <= 100 mm: Fy = 320 MPa. For 400W: t <= 20 mm: Fy = 400 MPa; 20 < t <= 40 mm: Fy = 390 MPa; 40 < t <= 65 mm: Fy = 370 MPa; 65 < t <= 100 mm: Fy = 360 MPa. These reductions per CSA G40.21 Clause 6.2 must be applied in CSA S16-19 design calculations.

Comprehensive reference for CSA G40.21 structural steel grades covering all categories W, WT, Q, R, and A suffixes. Full mechanical properties including yield strength by thickness bracket, tensile strength ranges, Charpy V-notch impact requirements across temperature zones, thickness limitations, typical applications, and atmospheric corrosion resistance.

Quick access: Canadian steel properties — Fy & Fu by grade → | Canadian steel grades overview → | Beam capacity calculator →

Complete CSA G40.21 Grade Classification

CSA G40.21-18 defines five material categories, each identified by a letter suffix in the grade designation:

Category	Suffix	Description	Heat Treatment	Typical Grade
W	W	Weldable structural steel	As-rolled or normalised	300W, 350W, 400W
WT	WT	Weldable with low-temperature toughness	As-rolled or normalised	350WT
A	A	Atmospheric corrosion-resistant (weathering)	As-rolled	350A
AT	AT	Atmospheric corrosion-resistant with toughness	As-rolled or normalised	350AT
Q	Q	Quenched and tempered (high-strength)	Quenched + tempered	480W, 700Q
R	R	Rivet steel	As-rolled	260R, 300R

Complete Grade Table — Yield and Tensile Strength

All strength values per CSA G40.21-18. Fy = minimum yield strength in MPa. Fu = tensile strength range in MPa.

Grade	Category	Fy (t <= 20)	Fy (20<t<=40)	Fy (40<t<=65)	Fy (65<t<=100)	Fu min	Fu max
260W	W	260	260	250	230	410	550
300W	W	300	300	280	270	440	620
350W	W	350	350	340	320	450	620
350A	A	350	350	340	320	450	620
400W	W	400	390	370	360	480	650
480W	W	480	460	430	410	550	720
700Q	Q	700	670	630	590	750	950
260R	R	260	260	—	—	410	550
300R	R	300	300	—	—	440	620
350WT	WT	350	350	340	320	450	620
350AT	AT	350	350	340	320	450	620

Grade Designation Notes

260W: Lowest-strength weldable grade. Used for secondary members, stair stringers, handrails, light bracing. Similar to ASTM A36 but with guaranteed weldability.
300W: Formerly the standard structural grade (pre-metric 44W with Fy = 300 MPa / 44 ksi). Still specified for general framing where 350W strength is not required.
350W: The default structural grade in Canada for all primary beams, columns, braces, and trusses. Over 90% of structural steel in Canadian buildings is 350W.
350A: Atmospheric corrosion-resistant (weathering steel). Same strength as 350W but with Cu, Cr, Ni additions for protective patina formation. Common for exposed bridge girders.
400W: High-strength grade for heavy columns and transfer girders where 350W does not provide sufficient capacity. Typical in lower-storey columns in high-rise buildings.
480W: Quenched and tempered high-strength steel. Used for weight-critical applications such as mobile equipment, crane booms, and long-span lightweight structures.
700Q: Highest-strength quenched and tempered grade. Used for specialised applications: military bridges, heavy equipment supports, mining equipment.
350WT: 350W with guaranteed Charpy toughness at -45 deg C. Required for exterior steelwork in cold climates, all Canadian bridges, and fracture-critical tension members.
350AT: 350A weathering steel with Charpy toughness. Used for exposed structures in cold climates (Quebec, prairies, northern Canada).
260R, 300R: Rivet steel grades for historic restoration and specialty applications. Rarely specified in new construction.

Charpy V-Notch Impact Requirements by Temperature Zone

CSA S16-19 Clause 27 uses five temperature zones to specify Charpy requirements for Canadian construction. The zones are defined by the minimum one-day mean temperature (January) from NBCC 2020 Appendix C.

Charpy Requirements by Grade

Grade	Standard CVN Test Temp	Min Energy (Longitudinal)	Energy Requirement
260W	Not required	—	Standard structural, no CVN
300W	Not required	—	Verify for low-temp applications
350W	Not required	—	Adequate for interior, verify for exterior
350A	Not required	—	Same as 350W for CVN
350WT	-45 deg C	27 J	Guaranteed low-temperature toughness
350AT	-45 deg C	27 J	Weathering + low-temp toughness
400W	Not required	—	Verify for low-temp applications
480W	-20 deg C	27 J	Quenched & tempered standard
700Q	-30 deg C	30 J	Premium toughness for high strength

Charpy Requirements by Temperature Zone (CSA S16-19 Clause 27.2)

Zone	Service Temp Range	Typical Canadian Locations	Required Charpy Temp	Min Energy
1	> -12 deg C	Vancouver, Victoria coastal	-12 deg C	27 J
2	-12 to -23 deg C	Toronto, Montreal, southern ON/QC	-23 deg C	27 J
3	-23 to -34 deg C	Calgary, Edmonton, Winnipeg, Ottawa	-34 deg C	27 J
4	-34 to -43 deg C	Saskatoon, Regina, Thunder Bay	-43 deg C	27 J
5	< -43 deg C	Yellowknife, Whitehorse, northern MB	-45 deg C	40 J

Practical implication: For Zone 3 locations (most major Canadian cities outside coastal BC), exterior steelwork requires 350WT or equivalent. For heated interior steelwork, standard 350W is acceptable. For bridges, CSA S6 requires minimum 350WT regardless of location.

Thickness Limitations

CSA G40.21 limits the maximum thickness for which each grade is certified:

Grade	Maximum Thickness (mm)	Limiting Factor
260W	75	Strength reduction beyond 75 mm
300W	150	Available in plates up to 150 mm
350W	100	Standard availability in shapes
350A	100	Weathering grade, shapes and plates
400W	100	Limited section availability
480W	65	Quenched & tempered thickness limit
700Q	65	Q&T thickness limit (hardness penetration)
350WT	100	Same as 350W with additional CVN testing
350AT	100	Same as 350A with additional CVN testing

For thicknesses exceeding these limits, alternative grades or special orders with reduced strength properties must be considered. For example, a 120 mm thick plate in Grade 350W would require project-specific mill approval and may have Fy reduced below 300 MPa.

Weathering Steel Grades (350A, 350AT)

Chemical Composition for Atmospheric Corrosion Resistance

Element	350W (typical)	350A (specified)	Purpose
Copper, Cu	0.20% residual	0.25-0.40%	Primary patina-forming element
Chromium, Cr	0.10% residual	0.40-0.65%	Patina density and adhesion
Nickel, Ni	0.10% residual	0.25-0.40%	Toughness and patina uniformity
Silicon, Si	0.15-0.40%	0.15-0.40%	Deoxidiser, strength
Phosphorus, P	0.04% max	0.04% max	Strength (controlled for toughness)

Weathering steel in Canadian construction requires careful attention to:

Drainage: Details must prevent water pooling on horizontal surfaces
Channel sections: Open side down to prevent debris accumulation
Crevice corrosion: Welded lap joints should be avoided in exposed locations
Salt exposure: Weathering steel performs poorly in marine splash zones and where de-icing salts accumulate
Cyclic wetting: Ontario bridges with 350A have performed well since the 1970s

Canadian Weathering Steel Applications

Application	Grade	Typical Locations	Performance
Bridge girders	350AT	Southern Ontario, BC	Excellent — 40+ year track record
Architectural cladding	350A	Toronto, Vancouver	Good — patina develops in 2-4 years
Transmission towers	350A	Rural Canada	Good — remote maintenance benefit
Sign structures	350A	All regions	Good — low maintenance
Noise barriers	350A	Urban highways	Good — aesthetic + functional

Quenched and Tempered Grades (480W, 700Q)

Manufacturing Process

Q&T steels are produced by:

Austenitising: Heating to 900-950 deg C to form homogeneous austenite
Quenching: Rapid cooling in water or oil to form martensite
Tempering: Reheating to 450-650 deg C to improve toughness while retaining strength

Grade	Quench Medium	Tempering Temp	Typical Hardness	Microstructure
480W	Water	600-650 deg C	200-240 HB	Tempered martensite
700Q	Water or oil	450-550 deg C	260-320 HB	Tempered martensite

Weldability of Q&T Steels

Welding Q&T steels requires:

Low-hydrogen processes (GMAW with E48S-6 or FCAW with E480T-5 for 480W; E62XX for 700Q)
Strict preheat control (typically 100-150 deg C for 700Q, 50-100 deg C for 480W)
Interpass temperature control (max 200-250 deg C to prevent overtempering)
Post-weld heat treatment is generally NOT required if preheat and interpass are controlled
Heat input must be controlled within the qualified range (typically 1.0-2.5 kJ/mm for 700Q)

Applications by Industry Sector

Building Construction

Application	Typical Grade	Sections	Notes
Columns (low-rise)	350W	W200-W360	Standard framing
Columns (mid-rise)	350W/400W	W360-W920	400W for lower storeys
Beams (roof)	350W	W310-W530	350W default
Beams (floor)	350W	W410-W690	Spans 6-15 m
Braces	350W	HSS, W-shapes	350W standard
Trusses	350W	HSS, 2L, WT	350W standard
Transfer girders	400W	WWF, heavy W	High-strength beneficial

Bridge Construction (CSA S6)

Application	Typical Grade	Notes
Main girders	350AT or 350WT	Weathering steel preferred
Cross-frames	350W	Secondary members
Bearings	400W or 480W	High bearing stress locations
Orthotropic deck	350WT	Fatigue-critical

Industrial Structures

Application	Typical Grade	Notes
Crane runways	350W or 400W	Fatigue design critical
Equipment supports	480W or 700Q	Weight-critical
Conveyor structures	350W	Standard framing
Mining equipment	700Q	Abrasion resistance
Arctic structures	350WT	Minimum -45 deg C toughness

Frequently Asked Questions

What is the most common CSA G40.21 steel grade used in Canada? Grade 350W (Fy = 350 MPa for t <= 20 mm) is by far the most common structural steel grade in Canada, accounting for over 90% of structural steel used in buildings. It is the default specification for beams, columns, braces, and trusses in all types of construction. Grade 300W (Fy = 300 MPa) is occasionally specified for lightly loaded secondary members. Grade 400W (Fy = 400 MPa) is used for heavy columns and transfer girders in high-rise buildings where the higher strength reduces section size.

What is the difference between G40.21 350W and 350WT? 350WT has the same yield strength (350 MPa) and tensile strength (450-620 MPa) as 350W, but adds guaranteed Charpy V-notch toughness at -45 deg C (27 J minimum longitudinal). The "T" suffix indicates toughness testing. 350WT also has tighter chemical composition limits (lower P and S) compared to 350W. For Canadian construction, CSA S16-19 Clause 27 requires 350WT or equivalent for exterior steelwork in most climate zones, for all bridges per CSA S6, and for tension members in fracture-critical applications.

Can CSA G40.21 700Q be welded with standard E48XX electrodes? No. 700Q (Fy = 700 MPa) requires matching E62XX electrodes (Xu = 620 MPa) per CSA W59 Table 5.2. Using E48XX electrodes on 700Q would result in an undermatching ratio of 480/620 = 77%, producing welds significantly weaker than the base metal. Additionally, 700Q welding requires strict preheat (100-150 deg C), interpass temperature control (maximum 200-250 deg C), and qualified welding procedure specifications (WPS) per CSA W59.

What grade is used for weathering steel in Canadian bridges? CSA G40.21 Grade 350A (standard weathering) for southern climates and 350AT (weathering + Charpy toughness) for cold regions are specified for Canadian bridge girders. 350AT includes the Cu, Cr, Ni additions for atmospheric corrosion resistance plus Charpy testing at -45 deg C for low-temperature toughness. Bridges in Ontario, Quebec, and the prairies typically specify 350AT. Coastal BC may use 350A where design temperatures are milder.

What are the thickness-dependent yield strength reductions for G40.21 350W steel? For 350W: t <= 20 mm: Fy = 350 MPa. 20 < t <= 40 mm: Fy = 350 MPa (no reduction). 40 < t <= 65 mm: Fy = 340 MPa. 65 < t <= 100 mm: Fy = 320 MPa. For 400W: t <= 20 mm: Fy = 400 MPa; 20 < t <= 40 mm: Fy = 390 MPa; 40 < t <= 65 mm: Fy = 370 MPa; 65 < t <= 100 mm: Fy = 360 MPa. These reductions per CSA G40.21 Clause 6.2 must be applied in CSA S16-19 design calculations.

This page is for educational reference. All grade data per CSA G40.20/G40.21-18. Verify material properties against current mill certificates before procurement or design. For seismic and fracture-critical applications, follow additional qualification requirements per CSA S16-19 and CSA W59. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent PE/SE verification.