Duplex - New Promo Sheet 2012

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DUPLEXSTAINLESS STEEL

High performance laser fused Structural Sections



Duplex High performance laser fused Structural Sections

Introduction

Stainless steels are used predominantly for their corrosion resistance in moderate to highly aggressive

environments. For construction purposes, carbon steel normally is the common choice due to low cost,

long experience, applicable design rules and a large variety of strength classes. However, differentstainless steel types can also provide a very wide range of mechanical properties and they have the

advantage of no need for surface protection. Duplex stainless steels in particular, with twice themechanical strength of conventional austenitic and ferritic stainless steels, have a potential for use in

constructions. Since the introduction of this family of steels about seventy years ago, they have beenused widely.

Duplex has been used or is being considered as substitutes for stainless steel types 304L, 316L, 904L or

254SMO depending from environment and corrosion aspects. Some examples of industry end uses arestructural supports for offshore oil & gas industry, chemical process industry, desalination and watertreatment, chemical tankers, architecture, building & construction, pulp and paper industry, pollution

control, etc. The list keeps growing as more industries become aware of the advantages of Duplex.

Laser fusion of structural sections in Duplex

Laser fusion of Duplex differs substantially from the

process used for austenitic stainless steel grades. While theprocess parameters vary only slightly, the big differencelies in the microstructure that results from the ultra-rapid

cooling of the weld pool.

It is characteristically for duplex grades to roughly have a

50% austenitic and 50% ferritic microstructure. The

alloying elements are balanced in order to achieve thisdistribution after a classical solution annealing treatment.

There is a certain variance in the distribution and up to a65:35 ratio in favour of one or the other of the two

microstructures is considered normal.

During laser fusion the base material melts and thensolidifies extremely rapidly. The cooling speed normally is

in excess of 500°C/s, which means that the segregations

found with conventional welding methods are totallyavoided when using laser fusion. On the other hand, this

same rapid cooling rate could cause a preference for the

ferritic microstructure if not counterbalanced. Fig. 2 – Laser fused Duplex beam

Corrosion resistance of structural sections in Duplex

Thanks to technical improvements in this field, today the classical balanced duplex microstructure isachieved without the necessity of a final solution annealing. In an “as welded” condition the corrosion

resistance of the weld and heat affected zone of a Duplex structural sections produced by laser fusion is

equivalent to a hot rolled or extruded structural section.

Duplex resistance to localized corrosion, such as pitting and crevice attack is extremely performing. A

numerical relationship between pitting resistance and alloying content has been developed to comparestainless steels (Fig.1). This is known as pitting resistance equivalent number or PREN (PREN = Cr + 3.3x %Mo + 16 x




Fig.1 - Pitting and crevice corrosion resistance

Chemical analysis PREN

Grade type (EN)C

maxCr Ni Mo N

max average

304L (1.4307) 0,03 17,5-19,5 8,0-10,0 --- 0,11 18

316L (1.4404) 0,03 16,5-18,5 10,0-13,0 2,0-2,5 0,11 24

904L (1.4539) 0,02 19,0-21,0 24,0-26,0 4,0-5,0 0,15 36

254 SM0 (1.4547) 0,02 19,5-20,5 17,5-18,5 6,0-7,0 0,25 >40

2101 (1.4162) 0,04 21,0-22,0 1,35-1,7 0,1-0,8 0,25 26

2304 (1.4362) 0,03 22,0-24,0 3,5-5,5 0,1-0,6 0,20 26

2205 (1.4462) 0,03 21,0-23,0 4,5-6,5 2,5-3,5 0,22 35

2507 (1.4410) 0,03 24,0-26,0 6,0-8,0 3,0-4,5 0,35 >40

Mechanical properties of structural sections in Duplex

Fig. 3 – Crash test on laser fused beam

Laser fused structural sections have a monolithic structure

with a controlled area of heat input and a small, barelynoticeable seam at the juncture of the components.

Extensive destructive testing has shown that the fracturepoints in laser fused sections rarely lie in the weld area

itself. External stresses and loads applied to the sections

are transmitted to the neighbouring parent material, whichthen fails according to its own mechanical characteristics

(Fig. 3).The mechanical characteristics of the weld and heat

affected zone of laser fused structural sections in Duplexare no constraint in industrial applications.

All Duplex grades feature significantly better mechanical properties than common austenitic stainless

steels (see Fig. 4). Wear resistance and especially fatigue strength, which becomes an important

material property in structures where dynamic loads are present, are all closely related to yieldstrength.

Fig. 4 – Mechanical properties according to EN 10088

Tensile StrengthR m N/mm2

Yield StrengthR e 0.2% N/mm2

ElongationA5%

HardnessBrinell

Grade type (EN) Min. Min. Min. Max.

316L (1.4404) 500 200 45 217

2101 (1.4162) 650 450 30 290

2304 (1.4362) 630 400 25 290

2205 (1.4462) 640 460 25 290

2507 (1.4410) 730 530 20 290




Cost saving potential of structural sections in Duplex

The higher yield properties of Duplex are therefore an advantage for structural applications (seeEurocodes for the design of steel structural). In the specific case of sections like beams, channels or

angles, Duplex offer a huge cost saving potential by using lighter sections without decreasing the

structural performance. The following charts show the cost saving potential of structural sections made

of Duplex type 2205 compared to structural sections in type 316L. Figure 6 shows the improvedbuckling load of Duplex compared to standard austenitic stainless steel. E.g. in case of a 12 feet longW8x48 beam, Duplex 2205 can bear a 55% higher load compared to the same beam size in type 316L.

Fig. 6

This means that Duplex can reduce, under the same buckling load, the weight of an austenitic stainlesssteel section by e.g. 35% using a W8x31 beam instead of a W8x48 at a bar length of 10 feet (Fig. 7).

Fig. 7 316L

316L

2205

2205

-- W8x48 2205

-- W8x48 316L




The following chart (Fig. 8) clearly shows the advantages of higher yield properties in structural

sections based on single span performance. E.g. a W8x15 in Duplex achieves the same structuralperformance like an W8x28 in standard austenitic stainless steel.

Fig. 8

This means that, under the same span load, the material saving potential of Duplex is 50% compared

to austenitic stainless steel beams on a bar length of 16 feet (Fig. 9). By comparing the tension tie ofDuplex 2205 with type 316L the material saving is as well 50% by using lighter section with the same

structural performance (Fig 10).

Fig. 9 Fig. 10

W8x24*

2205

W8x24*

2205

W8x24*

316L

W8x24*

316L

2205

316L




Available structural sections in Duplex

The following structural sections are all available laser fused:

• Equal angles• Unequal Angles• Channels• H – Beams • I – Beams• Tees

Standards & approvals

• ASTM A240 - Plate, sheet &

strip• ASTM A276 - Bars & shapes• ASTM A479 - Bars for boilers

and other pressure vessels• ASME Code Case 2418 - Plate,

sheet and strip• EN 10088(1-5) – European

standards for stainless steelfor general and construction

Conclusions

Switching to smart alloys like Duplex offers economic value in terms of reduced raw material surcharge

as well as improved mechanical properties.Structural sections like beams, channels and angles made of Duplex achieve higher performance at a

lower cost. Duplex sections satisfy the needs of the engineers and designers for light and cost-effectivestructures in stainless steel, which fulfil at the same time the criteria of safety and durability.



Europe:Montanstahl AG fon +41 91 6416800

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Switzerland

North America:Stainless Structurals, LLC fon +1 904 781 6447

590 Beautyrest Avenue fon +1 877 739 6057 (Toll free)Jacksonville fax +1 904 781 6444

32254 - Florida [email protected]

Asia:Stainless Structurals Asia Pte. Ltd. fon +65 6793 2282

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Information given in this brochure may be subject to alterations without notice. Care has been taken to ensurethat the contents of this publication are accurate but Stainless Structurals LLC. and its affiliated companies donot accept responsibility for errors or for information which is found to be misleading. Suggestions for ordescriptions of the end use or application of products or methods of working are for information only andStainless Structurals LLC. and its affiliated companies accept no liability in respect thereof. Before using

products supplied or manufactured by the company the customer should satisfy himself of their suitability.

Documents

Duplex - New Promo Sheet 2012