Our Duplex Fabrication Capabilities
Duplex stainless steels combine the strength of ferrite with the corrosion resistance of austenite in a roughly 50/50 microstructure. This balance gives duplex twice the yield strength of 316L at comparable corrosion resistance — but it also makes fabrication critical. Excessive heat input destroys the ferrite-austenite balance, and improper procedures can trigger sigma phase embrittlement or loss of pitting resistance.
Northern Manufacturing fabricates duplex with ASME BPVC Section IX qualified procedures, controlled interpass temperatures, and ferrite verification on every weldment. We provide complete fabrication from raw plate to finished, verified components.
Materials Handled
We have proven experience and qualified procedures for the full range of duplex grades:
- Lean Duplex: LDX 2101 — cost-effective alternative to 316L with higher strength and comparable corrosion resistance
- Standard Duplex: 2205 — the most widely used duplex grade, offering twice the yield strength of 316L with excellent chloride pitting resistance
- Super Duplex: 2507 — highest corrosion resistance in the duplex family, specified for severe chloride environments and elevated temperatures
Welding and Fabrication
Welding is the most critical step in duplex fabrication. The dual-phase microstructure that gives duplex its properties is also its vulnerability during thermal processing.
Strict heat input control. Too much heat shifts the ferrite-austenite balance toward ferrite, reducing corrosion resistance. Too little heat prevents sufficient austenite reformation. Our procedures maintain the narrow heat input band each grade requires.
Interpass temperature management. Duplex interpass temperature limits are more restrictive than austenitic grades. We monitor and enforce these limits on every pass to prevent sigma phase formation and preserve toughness.
Qualified welding procedures. All duplex welding procedures are qualified per ASME BPVC Section IX with ferrite measurement in the test coupons. Each WPS specifies heat input range, interpass temperature, shielding gas composition, and filler metal for the specific grade.
Forming, Rolling, and Finishing
Heavy forming and bending. Duplex requires higher forming forces than austenitic grades due to its superior yield strength. Our press brakes and tooling are rated for duplex thicknesses, and we apply grade-specific springback compensation.
Cylinder and shell rolling. Rolling duplex plate into cylinders and cones for pressure vessels and process equipment. Forming parameters are adjusted for each grade’s yield strength and work hardening behavior.
Pickling and passivation. Post-weld and post-forming pickling restores the passive layer disrupted by thermal processing. Our chemistry is formulated for duplex grades, which require different pickling parameters than austenitic stainless.
Why Choose a Duplex Fabrication Specialist
Choosing a fabricator for duplex steel is a critical extension of the engineering process. A non-specialist can introduce brittle intermetallic phases like sigma phase by failing to control thermal cycles during welding. This destroys the material’s toughness and corrosion resistance, creating a component that fails in the field.
We mitigate manufacturability risk. Our deep experience prevents the costly failures and delays that occur when fabricators cannot meet the tight tolerances and controlled thermal procedures duplex demands.
We guarantee metallurgical integrity. We enforce rigid controls over every thermal operation — from welding to hot forming — to prevent the formation of deleterious phases. Ferrite content is measured on production weldments, not just test coupons.
We deliver verifiable quality. As an ISO 9001:2015 certified and ASME-compliant fabricator, we provide the documentation and traceability your most critical quality audits require.
Quality Assurance
Our quality system incorporates duplex-specific inspection points at every stage:
- ASME code compliance — fabrication of pressure vessels and components in accordance with ASME BPVC
- Ferrite content measurement — calibrated testing on production weldments to verify the ferrite-austenite balance
- Positive Material Identification (PMI) — handheld PMI analyzers verify the grade of all incoming raw materials
- Comprehensive documentation — full packages including MTRs, ferrite test results, weld maps, and dimensional reports
Common Applications
- Chemical processing vessels and piping
- Oil and gas production equipment
- Desalination plant components
- Pulp and paper processing equipment
- Water and wastewater infrastructure
- Structural applications requiring high strength-to-weight ratio