Canadian Steel Charpy Values — CVN Requirements per CSA G40.21 and CSA S16
Complete reference for Charpy V-notch impact requirements for Canadian structural steel per CSA G40.21-18 and CSA S16-19. Covers 350WT toughness at -45 deg C, temperature zone classifications per NBCC 2020, energy requirements for all grades, test frequency, and fracture-critical applications in bridges and cold-weather structures.
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CSA G40.21 Charpy Requirements by Grade
Per CSA G40.21-18 Clause 7, Charpy V-notch testing is specified by the grade suffix. The "T" suffix (WT, AT, QT) indicates mandatory low-temperature toughness testing.
Standard CVN Requirements by Grade
| Grade | Test Temperature | Min Avg Energy | Min Single Energy | Test Orientation |
|---|---|---|---|---|
| 260W | Not required | — | — | — |
| 300W | Not required | — | — | — |
| 350W | Not required | — | — | — |
| 350WT | -45 °C | 27 J | 20 J | Longitudinal |
| 400W | Not required | — | — | — |
| 400WT | -45 °C | 27 J | 20 J | Longitudinal |
| 480W | -20 °C | 27 J | 20 J | Longitudinal |
| 480WT | -45 °C | 27 J | 20 J | Longitudinal |
| 700Q | -30 °C | 30 J | 24 J | Longitudinal |
| 350A | Not required | — | — | — |
| 350AT | -45 °C | 27 J | 20 J | Longitudinal |
350WT is the most commonly specified Charpy-tested grade in Canadian construction. It combines the standard 350W strength with guaranteed toughness at -45 deg C, making it suitable for all Canadian climate zones.
CSA S16-19 Temperature Zones
CSA S16-19 Clause 27.2 defines five temperature zones based on the January mean daily temperature from NBCC 2020 Appendix C:
| Zone | Temperature Range | Typical Locations | Charpy Test Temp Req |
|---|---|---|---|
| 1 | > -12 °C | Vancouver, Victoria, coastal BC | -12 °C |
| 2 | -12 to -23 °C | Toronto, Montreal, Ottawa, southern ON/QC | -23 °C |
| 3 | -23 to -34 °C | Calgary, Winnipeg, Edmonton, Regina | -34 °C |
| 4 | -34 to -43 °C | Saskatoon, Thunder Bay, Quebec City | -43 °C |
| 5 | < -43 °C | Yellowknife, Whitehorse, northern territories | -45 °C |
Member Categories (CSA S16 Clause 27.1)
CSA S16 classifies members into four categories for Charpy application:
| Category | Description | Examples | Charpy Required? |
|---|---|---|---|
| 1 | Tension members in connections | Gusset plates, splice plates, tension splices | Yes — full requirement |
| 2 | Primary tension members | Truss bottom chords, bracing ties, hangers | Yes — full requirement |
| 3 | Members with tensile stress under seismic | Seismic links, brace connections | Yes — per Seismic clause |
| 4 | Other members | Beams, columns, compression braces | Zone 3+ only |
For Categories 1 and 2, if stress ratio (Tf/Tr) > 0.3 at the serviceability limit state, Charpy testing per the temperature zone is mandatory.
Test Frequency Requirements
Per CSA G40.21-18 Clause 8.2, the Charpy test frequency depends on the grade:
| Grade | Test Frequency | Specimens per Test |
|---|---|---|
| WT grades | 1 test per 20 metric tons of each thickness | 3 specimens (average of 3) |
| AT grades | 1 test per 20 metric tons of each thickness | 3 specimens (average of 3) |
| Q grades | 1 test per 20 metric tons of each thickness | 3 specimens (average of 3) |
| 350W (special order) | As specified in purchase order | 3 specimens minimum |
Acceptance Criteria
Per CSA G40.21 Clause 8.3:
- The average energy of three specimens must equal or exceed the specified minimum
- No single specimen may be below the specified minimum single value
- If one specimen fails the single minimum, retest three additional specimens — the new average must exceed the specified minimum and no more than one specimen may be below
- If two or more specimens fail, the material fails the test and must be rejected
Charpy Requirements for Bridges (CSA S6)
CSA S6-19 (Canadian Highway Bridge Design Code) has more stringent Charpy requirements than CSA S16 for building structures:
| Component | Grade Requirement | Test Temp | Energy |
|---|---|---|---|
| Main tension members | 350WT minimum | -45 °C | 27 J |
| Main compression members | 350W minimum | N/A | Not required |
| Fracture-critical members | 350WT with enhanced CVN | -45 °C | 40 J |
| Welded splices in tension zones | Base metal 350WT | -45 °C | 27 J |
| Connection plates in tension | 350WT matching parent metal | -45 °C | 27 J |
| Transverse stiffeners (welded) | 350W minimum | Zone-specific | Per Clause 12 |
Fracture-critical members in bridges require a more stringent 40 J minimum at -45 °C compared to the 27 J standard for WT grades. This reflects the higher consequence of fracture in non-redundant bridge components.
Charpy Testing Procedure
The Charpy V-notch test per ASTM E23 involves:
- Specimen preparation: 10 mm × 10 mm × 55 mm bar with 2 mm deep V-notch at 45°
- Temperature conditioning: Specimen cooled to test temperature in a controlled bath
- Impact: 300 J capacity pendulum striker impacts at 5-5.5 m/s
- Energy measurement: Energy absorbed during fracture is read from the dial
- Fracture appearance: Lateral expansion and percent shear are also recorded
Temperature Shift Correction
For thicknesses exceeding the Charpy specimen size, CSA S16 permits a temperature shift correction:
Thickness correction (deg C) = 0.6 × (t - 10)
Where t = plate thickness in mm. This accounts for the increased constraint and stress triaxiality in thicker sections. For a 50 mm thick plate: shift = 0.6 × (50 - 10) = 24 °C. The Charpy test temperature must be reduced by this shift.
Correlation Between CVN Energy and Fracture Toughness
For CSA S16 design, the correlation between Charpy energy and fracture toughness (KIC) follows the Rolfe-Novak-Barson correlation for the transition temperature region:
KIC^2 / E = 0.64 × (CVN - 0.01 × Fy)
Where:
- KIC = plane strain fracture toughness (MPa√m)
- E = elastic modulus (200,000 MPa)
- CVN = Charpy energy at the service temperature (J)
- Fy = yield strength (MPa)
This correlation is used for fracture mechanics-based fatigue crack growth assessments per CSA S16 Clause 27.
Practical Application in Canadian Design
| Climate Zone | Typical Cities | Exterior Steel | Heated Interior Steel | Recommendation |
|---|---|---|---|---|
| 1 | Vancouver | 350WT or verify CVN | 350W | Standard 350WT for bridges |
| 2 | Toronto, Montreal | 350WT | 350W | 350WT for all exterior |
| 3 | Calgary, Winnipeg | 350WT | 350W | Verify zone temp carefully |
| 4 | Thunder Bay | 350WT at -45 °C | 350W | May need lower test temp |
| 5 | Yellowknife | 350WT at -45 °C | 350W | Arctic-specific WPS required |
For most Canadian building construction in Zones 2-3, specifying 350WT for all exterior steelwork and tension members provides a conservative approach without significant cost premium. The cost premium for 350WT over 350W is approximately 5-10% depending on mill and section size.
Frequently Asked Questions
What is the standard Charpy energy requirement for CSA G40.21 350WT steel? 350WT requires 27 J average minimum (20 J single minimum) at -45 °C, tested on longitudinal specimens per CSA G40.21-18 Clause 8. Three specimens are tested as a set. If one specimen fails the 20 J minimum, a retest set of three specimens is permitted where the new average must exceed 27 J and no more than one specimen may be below 20 J.
What temperature zone applies to Toronto for Charpy requirements? Toronto falls in Zone 2 per CSA S16-19 (-12 to -23 °C January mean daily temperature). The required Charpy test temperature for Zone 2 is -23 °C. However, specifying 350WT (tested at -45 °C) provides a significant safety margin and is common practice for exterior steelwork in Toronto and the GTA. For heated interior steelwork, standard 350W without Charpy testing is acceptable.
When is Charpy testing required for CSA S16 building structures? Charpy testing is required per CSA S16-19 Clause 27 for: (a) tension members and tension components of connections where the factored tensile stress exceeds 0.3 Fy at serviceability limit state, (b) members subject to tensile stress in Seismic Force Resisting Systems (SFRS) of moderate and high ductility, and (c) all members in Zones 3-5 where the calculated tensile stress exceeds 0.3 Fy. The test temperature must match the applicable temperature zone.
What is the cost premium for specifying 350WT over 350W? Typically 5-10% additional material cost for 350WT vs 350W. The premium reflects the tighter composition controls (lower C, P, S), additional Charpy testing per 20 metric tons, and mill quality assurance. For small quantities (< 5 tons), the premium may be higher. Most Canadian steel service centres stock common 350WT sections (W310-W920, HSS sections) as standard inventory, reducing lead time compared to special order.
Related Pages
- Canadian Steel Grades — CSA G40.21 Reference
- Canadian Steel Properties — Fy & Fu by Thickness
- Canadian Steel Chemical Composition
- CSA W59 Weld Inspection
- CSA S16 Beam Design
- CSA W59 Welding Procedure Specifications
- Canadian Seismic Design
This page is for educational reference. Charpy requirements per CSA G40.21-18 and CSA S16-19. Verify against the current edition of the code and project specifications. For fracture-critical and bridge applications, refer to CSA S6-19 which has additional requirements. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent PE/SE verification.
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