Material and process
The challenges of machining Duplex and Super Duplex
Duplex and Super Duplex combine high strength with corrosion resistance. Machining can involve high cutting forces, heat and work-hardening. Stable workholding, suitable cutting parameters and effective chip removal are important.
The exact grade determines the approach. Welding requires attention to heat input and preservation of the material structure. Agree the grade, operating environment and required testing in advance; suitability is assessed for each component.
Technical starting points
Material suitability and execution criteria
Exact grade, operations and documentation are agreed for your component. The material examples below do not represent a stock list.
- Grades and condition
- 2205 occurs under UNS S31803 and UNS S32205; Super Duplex 2507 under UNS S32750. State the prescribed standard, product form and exact designation. These examples do not constitute a general supply or machining guarantee.
- Operations
- CNC milling, turning and drilling are adapted to the grade. Any welding requires prior confirmation of the applicable procedure, qualifications and required inspections.
- Material certificates
- State whether EN 10204 3.1 or 3.2 is required. Availability, inspection stages and the link between the heat or batch number and the component are agreed before procurement and production.
- Application and environment
- For components in corrosive process environments or seawater, medium, temperature, loading and design conditions are decisive. A sector name alone does not establish material selection or product suitability.
In practice
Lifting and tilting yoke for a container
A custom lifting and tilting yoke for a 6.5-tonne container, developed by Douna with positive-fit lifting points and self-locking mechanisms.
Machines, welding and inspection
Explore the resources for your production route. The suitable machine, welding procedure and inspection approach are established for each workpiece.
Hedelius ACURA 85
Automated five-axis CNC milling for controlled precision work. Explore the key specifications, suitable workpieces and its role in the complete production route.
Measuring equipment and range
Coordinate critical features, measuring conditions and reporting with the drawing.
More about materials and machining
Machining duplex and super duplex: long components, deep channels and residual stress
Machining duplex and super duplex requires control of cutting forces, residual stress and chip evacuation. Two practical examples show why the machining sequence matters.
CNC milling: design, workholding and manufacturability
What is CNC milling and what makes a part suitable for it? Explore internal corners, tool access, workholding and the choice between 3 and 5 axes.
Questions about material and supply
Frequently asked questions about material management
Can you supply material with a 3.1 certificate and heat numbers?
State the required certificate type and traceability requirement in the enquiry. Availability of the material certificate and preservation of the link between heat and component are confirmed in advance. A 3.2 document needs additional arrangements for independent inspection; it is not an automatic retrospective alternative.
Can I supply my own material, forging or casting?
Provide material data, condition, starting form and available allowance. Technical assessment establishes the suitable machining route and incoming inspection. Customer-supplied material is not automatically suitable for the final geometry.
Does experience with stainless steel 316 establish suitability for Super Duplex?
Stainless steel 316 and Super Duplex have different structures and different machining and welding conditions. A stainless steel case is therefore not evidence for the same execution in Super Duplex. Exact grade, tooling strategy, procedure and inspection require separate assessment.
What should be agreed about cross-contamination and cleanliness?
Specify the required surface condition and any cleanliness criteria. Fixture cleaning, dedicated tools, storage and handling may be relevant. Applicable measures and inspections are established for the order.