structural welds between steel and cast steel - cwa acs by the canadian welding bureau (cwb) for...

Structural Welds BetweenSteel and Cast Steel

MissionWe simplify the design and enhance the performance of structures by enabling Architects and Engineers to use cast steel connections.

We take pride in collaborating in the creation of safer, innovative, and more beautiful built environments.

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TYK WELD

Stress Concentration Factor

6Conventionally Fabricated Connection

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Butt WELD

Stress Concentration Factor

7Connection with cast steel node

T, Y, or K with CJP groove weldsStress Category DT

Butt splices, CJP groove weldsStress Category C1

T, Y, or K with CJP groove weldsStress Category DT

Butt splices, CJP groove weldsStress Category C1

T, Y, or K with CJP groove weldsStress Category DT

Butt splices, CJP groove weldsStress Category C1

Local connection limit states often govern member selection in conventionally fabricated connections, driving up tonnage

Cast nodes reduce tonnage in HSS structures

Standardized cast steel fittings:

- Simplified fabrication

- Improved structural performance

- Improved aesthetics

Non-Destructive Examination of Steel Castings• Radiographic Testing• Ultrasonic Testing• Magnetic Particle Inspection• Visual Examination

• Acceptance Criteria are based on predefined “Levels”, each of which correlates to allowable indication size and distribution, which in turn correlates to the structural efficacy of the casting

• Areas of castings which have indications that exceed Acceptance Criteria are weld repaired and re-examined to confirm conformance to specification, prior to final heat treat

Weldability of Cast Steels

• Welding is an integral part of the steel casting manufacturing process -> steel castings AREweldable

• Mechanical properties are achieved in castings via chemistry and heat treatment– a casting typically requires more alloying than a rolled

steel product having similar mechanical properties

Graville Diagram – Susceptibility to Hydrogen Induced Cracking

Zone I – Easily WeldableZone II – WeldableZone III – Difficult to Weld

• Should consider weldability when selecting cast steel grade• The stipulation of supplemental chemical requirements above those listed in

the specified ASTM standard is sometimes necessary

Other factors affecting welds to steel castings

Casting indications that may affect welding:• Non-metallic inclusions• Porosity• Chemical segregation

All of these issues can be fully mitigated with appropriate casting design:• Part shaping and orientation in the mold• Riser contact locations• Non-destructive examination criteria• Adequate preparation of surfaces to be welded

Code-Related Challenges for Castings in Building Structures

• There are currently no Cast Steel Grades listed as Prequalified Base Metals in CSA W59 nor AWS D1.1

• This does not mean that castings can’t be used in building structures!

• This does put some additional burden on steel fabricators incorporating castings to building structures

Suggested Contract Document Verbiage

“For welds applied to be applied between rolled steel elements and steel castings, the steel fabricator shall produce a Welding Procedure Specification (WPS) accepted by the Canadian Welding Bureau (CWB) for each welding position, welding process, electrode manufacturer, filler metal trade name for the electrode type selected, and for all essential variable changes in the Procedure Qualification Record (PQR) that exceed allowable tolerances.”

WPS/PQR Development and Testing

Cast Steel Grades in Structural Welding Codes

• Many cast steel grades are listed as prequalified base materials in American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) Section IX

• Steel Founders’ Society of America (SFSA) is currently lobbying the American Welding Society (AWS) to add a selection cast steel grades to the list of prequalified base metals in AWS D1.1

• Incorporation of cast steel grades as prequalified base metals will also be proposed to CSA W59

Questions?

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