Lean duplex has become more commonly used to counteract the strong price fluctuations typical seen in stainless steel grades. Lean duplex has a significant lower level of nickel compared to a typical stainless steel grade (such as 304/316) – resulting in more price stable alloy.
In addition to higher price stability, lean duplex offers a unique combination of corrosion resistance, mechanical strength and ease of processing, making it the ideal choice for a wide range of industrial applications.
In this post we will explore the main characteristics of this material and its most common applications.
Characteristics of Lean Duplex:
Lean Duplex owes its name to its balanced chemical composition resulting in a micro structure in range of 50/50 of austenite/ ferrite.
Another distinctive feature of Lean Duplex is its excellent corrosion resistance. In fact, lean duplex alloys are particularly suitable for applications in corrosive environments. They also offer excellent mechanical strength, making them suitable for applications where a combination of strength and corrosion resistance is required, as they retain good mechanical properties.
Last but not least, Lean Duplex is known for its ease of machining and welding. These alloys can be machined with the same methods used for austenitic stainless steels, thus allowing for the same flexibility in forming and implementations.
Common applications of Lean Duplex:
Marine industry: maritime applications, such as offshore platforms and ships, benefit from the corrosion resistance of Lean Duplex in aggressive saline environments.
Oil and gas industry: these alloys are used typically for structures and pipe support elements and other equipment in oil and gas extraction and transportation operations.
Food and pharmaceutical industry: due to their corrosion resistance and ease of cleaning, Lean Duplex alloys are often used in food and pharmaceutical production equipment.
Construction and architecture: Lean Duplex alloys are also used in the construction of buildings in proximity of seas and oceans or structures, like bridges and walkways, that are exposed to strong winds.
Montanstahl and Lean Duplex:
Given all the characteristics just listed, the demand for this material is increasing significantly in the stainless steel market. In fact, Montanstahl has been carrying out an increasing number of large projects requiring the use of Lean Duplex.
For example, for the construction of a 15-metre long bridge, we designed hollow sections of 250x250x15 mm with lengths of 6 metres in Lean Duplex grade 1.4362/ EDX 2304 as per standard EN 10088.
With the current means of production, Montanstahl is able to weld on one side with a guaranteed minimum penetration of 10 mm.
The customer clearly expressed the need for 15 mm thick tubular profiles (see drawing) that would guarantee full penetration of the joint.
In this case, we partnered with a leader in conventional welding (MIG MAG) to complete the desired welding.
This innovative combination allowed us to produce welded tubulars in a hybrid manner: 10 mm joints welded with laser technology (including WPS and WPQR) and remaining thickness welded with more conventional methods.
The result was outstanding: the welds showed zero defects in the contact phase between the two different production technologies and Montanstahl was able to supply the desired custom solution to the customer.
Qualifications obtained by Montanstahl:
For the continuous supply of Lean Duplex 1.4362/EDX 2304 steel profiles, it was necessary to qualify Montanstahl according to NORSOK, a prerequisite for entering the North Sea offshore market.
In close cooperation with the customer, we understood the requirements and developed a tailor-made procedure to meet all the stringent requirements of this specific application, and so obtained the required qualification.
In the field of oil platform structures, nowadays Montanstahl regularly supplies structural profiles such as beams, angles and U-beams, in the Lean Duplex grade 1.4362, which has recently established itself as the most suitable steel grade for this type of application.
In conclusion, Lean Duplex is a class of stainless steel alloys that offers an exceptional combination of corrosion resistance, mechanical strength and machinability. These alloys are widely used in many industries where durability and equipment performance are critical.