SAF®32760+ Bar

Grade characteristics

Excellent

• Resistance to stress corrosion cracking in chloride-bearing environments
• Resistance to pitting and crevice corrosion

Very high

• Mechanical strength

High

• Resistance to general corrosion
• Resistance to erosion corrosion and corrosion fatigue

Good

• Weldability

Material designations

• UNS: S32760
• EN Number: 1.4501
• EN Name: X2CrNiMoCuWN25-7-4

Product standards

• ISO 17781:2017:QL1
• IOGP S-563:2018
• ASTM A-479 / ASME SA-479
• ASTM A-276 / ASME SA-276
• EN 10088-3
• EN 10088-5 (D≤160 mm / D≤6.30”)
• NORSOK M-630 2020 Rev.7, MDS D57 Rev.6
• NACE MR0175 / ISO 15156-3
• NACE MR0103 / ISO 17945-1
• ISO 14067:2018 (CO2e)

Chemical composition and mechanical properties only:

• EN 10222-5
• EN 10272
• ASTM A-182 / ASME SA-182

Approvals

• Pressure Equipment Directive / PED (2014/68/EU)
• ISO17782:2018, NORSOK M650 Ed. 4
• DNV approved manufacturer

Climate change impact

Carbon footprint / CO2e data (kg/ton) and Life Cycle Assessment report is available for these products in the range of D 75-180 mm (D3.00”-7.00”).

Material Test Certificate

According to EN 10204/3.1

Chemical composition (nominal)

Chemical composition (nominal) %

C	Si	Mn	P	S	Cr	Ni	Mo	N	W	Cu
≤0.03	≤1.0	≤1.0	≤0.030	≤0.010	25.5	7	3.8	0.26	0.7	0.8

Applications

SAF®32760+ is a super-duplex stainless steel specially designed for service in aggressive chloride-containing environments.

Typical applications are:

• Oil and gas industry
• Seawater cooling
• Salt evaporation industry
• Desalination plants
• Geothermal wells
• Refineries and petrochemical plants
• Mechanical components requiring high strength
• Pulp and paper industry
• Chemical processing

Corrosion resistance

General corrosion

SAF®32760+ is highly resistant to corrosion by organic acids, e.g. formic and acetic acid. It is suitable for use at high concentrations and temperatures, where austenitic stainless steels corrode at a high rate.

Resistance to inorganic acids is comparable to that of high alloy austenitic stainless steels in certain concentration ranges.

Stress corrosion cracking

SAF®32760+ has excellent resistance to chloride-induced stress corrosion cracking.

Pitting and crevice corrosion

The pitting and crevice corrosion resistance of a stainless steel is primarily determined by the content of chromium, molybdenum and nitrogen. An index for comparing the resistance to pitting and crevice corrosion is the PRE number (Pitting Resistance Equivalent).

The PRE is defined as, in weight-% PRE = %Cr + 3.3x%Mo +16x%N

For duplex stainless steels the pitting corrosion resistance is dependent on the PRE-value in both the ferrite phase and the austenite phase, so that the phase with the lowest PRE-value will be limiting for the actual pitting corrosion resistance.

The minimum PRE-value for SAF®32760+ is 41.

This is significantly higher than e.g. the PRE-values for other duplex stainless steels of the 25Cr type which are not "super-duplex". As an example UNS S31260 (25Cr3Mo0.2N) has a PRE-value of typically 38.

Erosion corrosion and corrosion fatigue

The superior mechanical properties combined with the improved corrosion resistance of SAF®32760+ result in excellent resistance to both erosion corrosion and corrosion fatigue compared to standard austenitic stainless steels.

Units

Metric units apply. Imperial for reference.

Forms of supply

Dimensions and finishes

SAF®32760+ bar steel is stocked in a number of sizes.

The standard size range for stock comprises 20-180 mm (0.79-7.08”)

Solid round bar is supplied in solution annealed, quenched and peel-turned condition.

Lengths

Bars are delivered in random lengths of 3-7 m (9.84-22.96 ft.), depending on diameter.

Tolerances

Straightness

Surface condition

Manufacturing

All products are made at the Alleima Tube AB integrated production facility in Sandviken, Sweden.

From raw materials, melting, hot working, heat treatment to finishing and testing.

Heat treatment

Solution annealing

Slow heating up to 1000°C (1830°F). Annealing at 1050-1125°C (1920-2060°F), followed by quenching in water.

Microstructure

In the solution annealed and quenched condition SAF®32760+ has an austenitic-ferritic microstructure, which is free from grain boundary carbides and intermetallic phases. The ferrite content is 35 – 55%.

Mechanical properties

Tensile strength at 20°C (68°F)

The following values apply to material in the solution annealed and quenched condition. More detailed information can be supplied on request.

1 MPa = 1 N/mm2
R_p0.2 corresponds to 0.2% offset yield strength.
Based on L0 = 5.65√S0 , where L0 is the original gauge length
and S0 the original cross-section area.

Figure 1. Comparison of proof strength.

Impact strength

SAF®32760+ possesses good impact strength, both at room temperature and at low temperatures.

The Alleima bar stock program guarantees the following

Impact strength (Charpy-V longitudinal) at -50°C / -58°F.

ISO17781 QL1
D≤180 mm  85J average / 65J single
(D≤7.08”) (62.7 ft-lb average / 47.9 ft.lb single)

The impact strength at “RT” / 20°C (68°F) is min 100J average / 70J single ( 73 ft.lb average / 51 ft.lb single ).

At higher temperatures

SAF®32760+ is exposed for prolonged periods to temperatures exceeding 250°C (480°F), the microstructure changes which results in a reduction in impact strength. This does not necessarily affect the behavior of the material at the operating temperature.

More detailed information can be supplied on request.

Hardness

Max. 271 HBW

Physical properties

Density

7.8 g/cm³, 0.28 lb/in³

Specific heat capacity

500 J/(kg °C) at 20°C, 0.12 Btu/(lb °F) at 68°F

Thermal conductivity

Thermal expansion

SAF®32760+ has a coefficient of thermal expansion close to that of carbon steel. This gives SAF®32760+ definite design advantages over austenitic stainless steels in equipment comprising both carbon steel and stainless steel. The values given below are average values in the temperature ranges.

Metric units, x10^-6/°C

Imperial units, x10^-6/°F

Figure 2. Thermal expansion

Resistivity

0.8 μΩm at 20°C, 31.5 μΩin. at 68°F

Modulus of elasticity, (x10³)

Metric units; Imperial units

Welding

The weldability of SAF^®32760+ is good. Suitable methods of fusion welding are manual metal-arc welding (MMA/SMAW) and gas-shielded arc welding, with the TIG/GTAW method as first choice.

For SAF®32760+, heat input of 0.2-1.5 kJ/mm and interpass temperature of <150°C (300°F) are recommended. Preheating and post-weld heat treatment are normally not necessary.

Recommended filler metals

GTAW/TIG welding

ISO 14343 S 25 9 4 N L / AWS A5.9 ER2594 (e.g. Exaton 25.10.4.L)

MMA/SMAW welding

ISO 3581 E 25 9 4 N L R / AWS A5.4 E2594-16 (e.g. Exaton 25.10.4.LR)

ISO 3581 E 25 9 4 N L B / AWS A5.4 E2594-15 (e.g. Exaton 25.10.4.LB)

Machining

General

Machining is an expression used for a number of subtractive manufacturing methods.
Mainly turning, milling, drilling. But also other operations like cutting, boring, grinding, reaming and tapping.

For solid bars the initial operations primarily are cutting and external turning to prepare a blank for component manufacturing.

Stainless steels

Materials within the ISO-M material area can be challenging to machine.

The materials vary a lot within the ISO-M group, but in general presents difficult chip control, high cutting forces and tool wear.

In order to get as efficient function and tool life as possible, dedicated cutting tools and strategies to be used.

Getting started

To get it right, the first thing is to know the material to be machined.

As the material properties are input to the selection of start values.

• ISO material group
• Condition/heat treatment
• Actual hardness of the material lot

Consult your cutting tool supplier for start recommendations, since the choice of cutting tools and machine tool set the direction for which start values to use.