ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed

Product Details:
Place of Origin: China
Brand Name: VANFORGE
Certification: ISO9001, ISO10012, ISO14001, OHSAS18001, ABS, BV, DNV, Lloyd, NK, PED
Payment & Shipping Terms:
Minimum Order Quantity: 1000 kg
Price: Negotiable
Packaging Details: Seaworthy package for export
Delivery Time: 45 days
Payment Terms: L/C, T/T
Supply Ability: 100 tons per month

Detail Information

Material: Austenitic Stainless Steels, Duplex Stainless Steels Process: Cold Rolled
Treatment: Bright Annealed Surface: BA Or On Request
Application: Petrochemical, Chemical, Paper And Pulp Feature: High Precision
Standard: ANSI, ASTM, ASME, EN, DIN, JIS, GOST
High Light:

ss sheet

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polished stainless steel sheet

Product Description

ASTM A240 S32750 cold rolled 2507 super duplex stainless steel flat sheet

 

UNS S32750 sheets and plates

 

UNS S32750 is a super-duplex (austenitic-ferritic) stainless steel for service in highly corrosive conditions. The grade is characterized by:

  • Excellent resistance to stress corrosion cracking (SCC) in chloride-bearing environments
  • Excellent resistance to pitting and crevice corrosion
  • High resistance to general corrosion
  • Very high mechanical strength
  • Physical properties that offer design advantages
  • High resistance to erosion corrosion and corrosion fatigue
  • Good weldability

Standards

  • UNS S32750
  • EN number 1.4410
  • EN name X 2 CrNiMoN 25-7-4
  • SS 2328

Product standards

  • Sheet and plate: ASTM A240

 

Approvals

  • Approved by the American Society of Mechanical Engineers (ASME) for use in accordance with ASME Boiler and Pressure Vessel Code, Section VIII, div. 1. There is no approval for UNS S32750 in the form of plate. However, according to the ASME paragraph UG-15 it is allowed to use the design values for seamless tube according to ASME Section VIII, div. 1 also for plate.
  • ISO 15156-3/NACE MR 0175 (Sulphide stress cracking resistant material for oil field equipment).

 

Chemical composition (nominal) %

C Si Mn P S Cr Ni Mo Others
max max max max max        
0.030 0.8 1.2 0.035 0.015 25 7 4 N=0.3

 

Mechanical properties

The following figures apply to material in the solution annealed condition. Tube and pipe with wall thickness above 20 mm (0.787 in.) may have slightly lower values. For seamless tubes with a wall thickness <4 mm we guarantee proof strength (Rp0.2) values that are 50 MPa higher than those listed below at 20°C (68°F) as well as those listed at higher temperatures. More detailed information can be supplied on request.

At 20°C (68°F)

 

Sheets with wall thickness max. 20 mm (0.79 in.).

Metric units

Proof strength, MPa

Tensile strength, MPa

Elongation, %

Hardness, HRC

Rp0.2a)

Rp1.0a)

Rm

Ab)

A2"

 

min.

min.

 

min.

min.

max.

550 640 800-1000 25 15 32

 

Imperial units
Proof strength, ksi Tensile strength, ksi Elongation, % Hardness, HRC
Rp0.2a) Rp1.0a) Rm Ab) A2" HRC
min. min.   min. min. max.
80 93 116-145 25 15 32

1 MPa = 1 N/mm2
a) Rp0.2 and Rp1.0 correspond to 0.2% offset and 1.0% offset yield strength, respectively.
b) Based on L0 = 5.65 √S0 where L0 is the original gauge length and S0the original cross-section area.

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 0

Figure 1. Comparison of minimum proof strength, 0.2% offset, of UNS S32750 and high alloy austenitic grades, for material in the solution annealed condition.

 

At high temperatures

If UNS S32750 is exposed to temperatures exceeding 250°C (480°F), for prolonged periods, 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. For example, heat exchanger tubes can be used at higher temperatures without any problems. Please contact Huahon for more information. For pressure vessel applications, 250°C (480°F) is required as a maximum, according to VdTÜV-Wb 508 and NGS 1609.

 

Sheets with wall thickness max. 20 mm (0.79 in.)

Metric units
Temperature, °C Proof strength Rp0.2, MPa
  min.
50 530
100 480
150 445
200 420
250 405
300 395

 

Imperial units

Temperature, °F

Proof strength Rp0.2, ksi

 

min.

120 77.0
200 70.5
300 64.5
400 61.0
500 58.5
600 57.0

 

Impact strength

UNS S32750 possesses good impact strength. The ductile brittle transition temperature is below -50°C (-58°F). The impact strength of welded UNS S32750 is also good, although the values are lower than the base metal. The impact strength, if gas shielded arc weldments, is a minimum of 27 J (20 ft lb) at a temperature of -50°C (-58°F).

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 1

 

Figure 2. Typical impact energy curves for UNS S32750 using standard Charpy V specimens (average of 3 at each temp.). Parent metal samples taken in the longitudinal direction from 12 mm hot rolled and solution annealed (1075°C / 1965°F) sheet.

 

According to ASME B31.3 the following design values are recommended for UNS S32750:

Temperature

Stress

°F

°C

ksi

MPa

100 38 38.7 265
200 93 35.0 240
300 149 33.1 230
400 204 31.9 220
500 260 31.4 215
600 316 31.2 215

 

Physical properties

Density: 7.8 g/cm3, 0.28 lb/in.3

Specific heat capacity

Metric units Imperial units

 

Temperature, °C

J/(kg °C)

Temperature, °F

Btu/(lb°F)

20 490 68 0.12
100 505 200 0.12
200 520 400 0.12
300 550 600 0.13
400 585 800 0.14


Thermal conductivity
Metric units, W/(m°C)

Temperature, °C

20

100

200

300

400

UNS S32750 14 15 17 18 20
ASTM 316L 14 15 17 18 20


Imperial units, Btu/(ft h °F)

Temperature, °F

68

200

400

600

800

UNS S32750 8 9 10 11 12
ASTM 316L 8 9 10 10 12


Thermal expansion
UNS S32750 has a coefficient of thermal expansion close to that of carbon steel. This gives UNS S32750 definite design advantages over austenitic stainless steels in equipment comprising of both carbon steel and stainless steel. The values given below are average values in the temperature ranges.

Metric units, x10-6/°C

Temperature, °C

30-100

30-200

30-300

30-400

UNS S32750 13.5 14.0 14.0 14.5
Carbon steel 12.5 13.0 13.5 14.0
ASTM 316L 16.5 17.0 17.5 18

 

Imperial units, x10-6/°F

Temperature, °F

86-200

86-400

86-600

86-800

UNS S32750 7.5 7.5 8.0 8.0
Carbon steel 6.8 7.0 7.5 7.8
ASTM 316L 9.0 9.5 10.0 10.0

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 2

 

Figure 3. Thermal expansion, per°C (30-100°C, 86-210°F).

 

Resistivity

Temperature, °C

μΩm

Temperature, °F

μΩin.

20 0.83 68 32.7
100 0.89 200 34.9
200 0.96 400 37.9
300 1.03 600 40.7
400 1.08 800 43.2


Modulus of elasticity, (x103)

Metric units and imperial units

Temperature, °C

MPa

Temperature, °F

ksi

20 200 68 29.0
100 194 200 28.2
200 186 400 27.0
300 180 600 26.2

 

Corrosion resistance

General corrosion

UNS S32750 is highly resistant to corrosion by organic acids, e.g. experience less than 0.05 mm/year in 10% formic and 50% acetic acid where ASTM 316L has corrosion rate higher than 0.2 mm/year. Pure formic acid see Figure 4. Also in contaminated acid UNS S32750 remains resistant.

Figure 5 and Figure 6 show results from tests of UNS S32750 and various stainless steels and nickel alloys in acetic acid contaminated with chlorides which in practise are frequently present in processes.

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 3

Figure 4. Isocorrosion diagram in formic acid. The curves represent a corrosion rate of 0.1 mm/year (4 mpy) in stagnant test solution.

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 4

Figure 5. Corrosion rate of various alloys in 80% acetic acid with 2000 ppm chloride ions at 90°C.

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 5

 

Figure 6. Corrosion rate of various alloys in concentrated acetic acid with 200 ppm chloride ions.

Practical experience with UNS S32750 in organic acids, e.g. in teraphthalic acid plants, has shown that this alloy is highly resistant to this type of environment. The alloy is therefore a competitive alternative to high alloyed austenitics and nickel alloys in applications where standard austenitic stainless steels corrode at a high rate.

 

Resistance to inorganic acids is comparable to, or even better than that of high alloy austenitic stainless steels in certain concentration ranges. Figures 7 to 9 show isocorrosion diagrams for sulphuric acid, sulphuric acid contaminated with 2000 ppm chloride ions, and hydrochloric acid, respectively.

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 6

Figure 7. Isocorrosion diagram in naturally aerated sulphuric acid. The curves represent a corrosion rate of 0.1 mm/year (4 mpy) in a stagnant test solution.

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 7

Figure 8. Isocorrosion diagram, 0.1 mm/year (4 mpy) in a naturally aerated sulphuric acid containing 2000 ppm chloride ions.

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 8

Figure 9. Isocorrosion diagram in a hydrochloric acid. The curves represent acorrosion rate of 0.1 mm/year (4 mpy) in stagnant test solution.

 

Pitting and crevice corrosion

The pitting and crevice corrosion resistance of stainless steel is primarily determined by the content of chromium, molybdenum and nitrogen. The manufacturing and fabrication practice, e.g. welding, are also of vital importance for the actual performance in service.

 

A parameter for comparing the resistance to pitting in chloride environments is the PRE number (Pitting Resistance Equivalent).
The PRE is defined as, in weight-%)
PRE = %Cr + 3.3 x %Mo + 16 x %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. In UNS S32750 the PRE value is equal in both phases, which has been achieved by a careful balance of the elements.

 

The minimum PRE value for UNS S32750 seamless tubes is 42.5. 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 minimum PRE-value of 33.

One of the most severe pitting and crevice corrosion tests applied to stainless steel is ASTM G48, i.e. exposure to 6% FeCI3 with and without crevices (method A and B respectively). In a modified version of the ASTM G48 A test, the sample is exposed for periods of 24 hours. When pits are detected together with a substantial weight loss (>5 mg), the test is interrupted. Otherwise the temperature is increased by 5 °C (9 °F) and the test is continued with the same sample. Figure 11 shows critical pitting and crevice temperatures (CPT and CCT) from the test.

 

Potentiostatic tests in solutions with different chloride contents are presented in Figure 11. Figure 12 shows the effect of increased acidity. In both cases the applied potential is 600 mV vs SCE, a very high value compared with that normally associated with natural unchlorinated seawater, thus resulting in lower critical temperatures compared with most practical service conditions.

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 9

Figure 10. Critical pitting and crevice temperatures in 6% FeCl3, 24h (similar to ASTM G48).

 

The scatter band for UNS S32750 and 6Mo+N illustrates the fact that both alloys have similar resistance to pitting, and CPT-values are within the range shown in the figure.

 

Tests were performed in natural seawater to determine the critical crevice corrosion temperature of samples with an applied potential of 150 mV vs SCE. The temperature was raised by 4°C (7oF) steps every 24 hours until crevice corrosion occurred. The results are shown in the table below.

Alloy

CCT (°C)

UNS S32750 64
6Mo+N 61

 

In these tests the propagation rates of initiated crevice corrosion attacks, at 15-50°C (59-122°F) and an applied potential of 150 mV vs SCE were also determined. These were found to be around ten times lower for UNS S32750 than for the 6Mo+N alloy.

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 10

Figure 11. Critical pitting temperatures (CPT) at varying concentrations of sodium chloride, from 3 to 25% (potentiostatic determination at +600 mV SCE with surface ground with 600 grit paper).

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 11

Figure 12. Critical pitting temperatures (CPT) in 3% NaCl with varying pH (potentiostatic determination at +600 mV SCE with surface ground with 600 grit paper).

 

The corrosion resistance of UNS S32750 in oxidising chloride solutions is illustrated by critical pitting temperatures (CPT) determined in a 'Green death' -solution (1% FeCI3 + 1% CuCl2 +11% H2SO4 + 1.2% HCI) and in a 'Yellow death' -solution (0.1 % Fe2(SO4)3 + 4% NaCl + 0.01 M HCI). The table below shows CPT-values for different alloys in these solutions. It is clear that the values for UNS S32750 are on the same level as those for the nickel alloy UNS N06625. The tests demonstrate a good correlation with the ranking of alloys for use as reheater tubes in flue gas desulphurisation systems.

 

Critical pitting temperature (CPT) determined in different test solutions.

Alloy

Critical pitting temperature (CPT), °C
'Green death'

'Yellow death'

UNS S32750 72.5 >90
6Mo+N 70 >90
UNS N06625 67.5 >90
ASTM 316 <25 20

 

Stress corrosion cracking

UNS S32750 has excellent resistance to chloride induced stress corrosion cracking (SCC).

 

The SCC resistance of UNS S32750 in chloride solutions at high temperatures is illustrated in Figure 13. There were no signs of SCC up to 1000 ppm Cl-/300°C and 10000 ppm Cl-/250°C.

 

UNS S32750 U-bend specimens exposed for 1000 hours in hot brine (108°C, 226°F, 25% NaCl) showed no cracking.
The threshold stress for UNS S32750 in 40% CaCl2 at 100 °C (210 °F) and pH = 6.5 is above 90% of the tensile strength for both parent metal and welded joints

 

Figure 14 shows the result of testing in 40% CaCl2 at 100 °C (210 °F) acidified to pH = 1.5. Acidifying of the standard test solution to pH = 1.5 lowers the threshold stress for UNS S32205/31803, but not for UNS S32750. This applies to both parent metal and welded joints.

 

The threshold stress for both parent metal and welded joints of UNS S32750 in boiling 45% MgCl2 , 155°C (311°F) (ASTM G36), is approximately 50% of the proof strength.

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 12

Figure 13. SCC resistance in oxygen-bearing (abt. 8 ppm) neutral chloride solutions. Testing time 1000 hours. Applied stress equal to proof strength at testing temperature.

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 13

Figure 14. Results of SCC tests with constant load in 40% CaCl2, pH=1.5, at 100 °C (210°F) with aerated test solution.

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 14

Figure 15. Constant load SCC tests in NACE solution at room temperature (NACE TM 0177).

 

Figure 15 shows the results of SCC tests at room temperature in NACE TM0177 Test solution A (5% sodium chloride and 0.5% acetic acid saturated with hydrogen sulphide). No cracking occurred on UNS S32750, irrespective of the applied stress.

In aqueous solutions containing hydrogen sulphide and chlorides, stress corrosion cracking can also occur on stainless steels at temperatures below 60 °C (140 °F). The corrosivity of such solutions is affected by acidity and chloride content. In direct contrast to the case with ordinary chloride-induced stress corrosion cracking, ferritic stainless steels are more sensitive to this type of stress corrosion cracking than austenitic steels.

 

In accordance with ISO 15156/NACE MR 0175 solution annealed and liquid quenched wrought UNS S32750 is suitable for use at temperatures up to 450 °F (232 °C) in sour environments in oil and gas production, if the partial pressure of hydrogen sulphide does not exceed 3 psi (0.20 bar).

UNS S32750, with a maximum hardness of 32 HRC, solution annealed and rapidly cooled, according to NACE MR0103, is suitable for use in sour petroleum refining.
 

Intergranular corrosion

UNS S32750 is a member of the family of modern duplex stainless steels whose chemical composition is balanced to give quick reformation of austenite in the high temperature heat affected zone of a weld. This results in a microstructure that provides the material with good resistance to intergranular corrosion. UNS S32750 passes testing to ASTM A262 Practice E (Strauss test) without reservation.

 

Erosion corrosion

The mechanical properties combined with corrosion resistance give UNS S32750 a good resistance to erosion corrosion. Testing in sand containing media has shown that UNS S32750 has an erosion corrosion resistance better than corresponding austenitic stainless steels. Figure 16 below shows the relative mass loss rate of the duplex UNS S32750, Sandvik SAF 2205 and an austenitic 6Mo+N type steel after exposure to synthetic seawater (ASTM D-1141) containing 0.025-0.25% silica sand at a velocity of 8.9-29.3 m/s (average of all tests is shown).

 

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 15

Figure 16. Relative mass loss rate after testing of the resistance aginst erosion corrosion.

 

Corrosion fatigue

Duplex stainless steels which have a high tensile strength usually have a high fatigue limit and high resistance to both fatigue and corrosion fatigue.

 

The high fatigue strength of UNS S32750 can be explained by its good mechanical properties, while its high resistance to corrosion fatigue has been proven by fatigue testing in corrosive media.

 

Heat treatment

The tubes are normally delivered in heat treated condition. If additional heat treatment is needed due to further processing the following is recommended.

 

Solution annealing

1050-1125°C (1920-2060°F), rapid cooling in air or water.

Welding

The weldability of UNS S32750 is good. Suitable welding methods are manual metal-arc welding with covered electrodes or gasshielded arc welding. Welding should be undertaken within the heat input range of 0.2-1.5 kJ/mm and with an interpass temperature of 150°C (300°F) maximum.

Preheating or post-weld heat treatment is not necessary.

 

Fabrication

Bending

The starting force needed for bending is slightly higher for UNS S32750 than for standard austenitic stainless steels (ASTM 304L and 316L).

If the service conditions are on the limit of the stress corrosion resistance of UNS S32750 heat treatment is recommended after cold bending. For pressure vessel applications in Germany and the Nordic countries heat treatment may be required after cold deformation in accordance with VdTÜV-Wb 508 and NGS 1609. Heat treatment should be carried out by solution annealing (See under Heat treatment) or resistance annealing.

Hot bending is carried out at 1125-1025°C (2060-1880°F) and should be followed by solution annealing.

 

Expanding

Compared to austenitic stainless steels, UNS S32750 has a higher proof and tensile strength. This must be kept in mind when expanding tubes into tubesheets. Normal expanding methods can be used, but the expansion requires higher initial force and should be undertaken in one operation. As a general rule, tube to tubesheet joints should be welded if the service conditions include a high chloride concentration, thus limiting the risk of crevice corrosion.

 

Machining

Being a two-phase material (austenitic-ferritic) UNS S32750 will present a different tool wear profile from that of single-phase steels of type ASTM 304L. The cutting speed must therefore be lower than that recommended for ASTM 304L. It is recommended that a tougher insert grade is used than when machining austenitic stainless steels, e.g. ASTM 304L.

 

Applications

UNS S32750 is a duplex stainless steel especially designed for service in aggressive chloride-containing environments. Typical applications are:

Typical applications for UNS S32750
Oil and gas exploration
and production
Chloride-containing environments such as seawater handling and process systems. Hydraulic and process fluid tubes in umbilicals
Seawater cooling Tubing for heat exchangers in refineries, chemical industries, process industries and other industries using seawater or chlorinated seawater as coolant
Salt evaporation Evaporator tubing for production of corrosive salts, e.g. chlorides, sulphates and carbonates
Desalination plants Pressure vessels for reverse osmosis units, tube and pipe for seawater transport, heat exchanger tubing
Geothermal wells Heat exchangers in geothermal exploitation units, systems exposed to geothermal or high salinity brines, tubing and casing for production
Oil refining and petrochemical and gas processing Tubes and pipes where the process environment contains a high amount of chlorides, or is contaminated with hydrochloric acid
Pulp and paper production Material for chloride-containing bleaching environments
Chemical processing Organic acid plants, also when process solutions are contaminated with e.g. chlorides
Mechanical components requiring high strength Propeller shafts and other products subjected to high mechanical load in seawater and other chloride-containing environments
Desulphurisation units As reheater tubes in flue gas desulphurisation systems. The good mechanical and corrosion properties make UNS S32750 an economical choice in many applications by reducing the life cycle cost of equipment.

 

Production process

ASTM A240 UNS S32750 Data Sheet SCC High Mechanical Strength Bright Annealed 16


 

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