Super Ferritic Stainless Steel (UNS #S44660)
Chemical Composition
|
Element
|
Percent
|
|
Chromium
|
25.0-28.0
|
|
Molybdenum
|
3.0-4.0
|
|
Nickel
|
1.0-3.5
|
|
Manganese
|
1.00 max
|
|
Silion
|
1.00 max
|
|
Carbon
|
0.030 max
|
|
Nitrogen
|
0.040 max
|
|
Phosphorous
|
0.040 max
|
|
Sulfur
|
0.030 max
|
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Titanium + Niobium
|
0.020-1.00
|
|
Iron
|
0.020-1.00
|
Description
The ferritic structure of UNS #S44660 stainless-steel provides a high strength/low work hardening material with sensible malleability.
These properties enable high style stress limits with sensible fabrication characteristics. due to the nickel addition,UNS #S44660 contains a lower ductile-to-brittle transition temperature than similar ferritic steels while not nickel additions.
Applications
This kind of alloy is specifically designed for applications wherever chloride elicited indentation, crevice, and stress corrosion cracking is also encountered.
UNS #S44660 stainless-steel is employed in electrical power plant condensers and BOP exchangers, numerous heat exchangers in chemical, organic compound, and processing applications, chemical process heat exchangers and flue gas handling systems like the secondary heat exchangers in high potency furnaces. The yank Gas Association has approved UNS #S44660 for flue gas atmospheric phenomenon applications. UNS #S44660 stainless-steel has higher resistance to general corrosion over a broader vary of conditions than the solid solution untainted steels.
|
Welded Super Ferritic Stainless Steel (UNS #S44660) as per ASTM/ASME A/SA268 |
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O.D/W.T (mm) |
12.7 |
15.9 |
17.2 |
19.05 |
22.0 |
25.4 |
26.7 |
31.8 |
38.1 |
|
0.4 |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
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0.5 |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
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|
0.6 |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
|
0.7 |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
|
0.8 |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
|
0.9 |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
|
1.0 |
|
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
|
1.1 |
|
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
|
1.2 |
|
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☆ |
☆ |
☆ |
☆ |
☆ |
☆ |
|
1.5 |
|
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☆ |
☆ |
☆ |
☆ |
☆ |
|
1.8 |
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☆ |
☆ |
☆ |
|
2.0 |
|
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☆ |
☆ |
|
2.5 |
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☆ |
☆ |
Corrosion Resistance
Resistance to a number of strong acids was evaluated using the Materials Technology Institute of the Chemical Process Industries procedures. Representative data are given below.
|
Acid
Solution
|
Temperature
|
Type
304
|
Type
316
|
|
|
|
˚F
|
˚C
|
Corrosion Rate—MPY*
|
|||
|
0.1% Hydrochloric
|
212
|
100 B
|
17.4
|
2.08
|
0.23
|
|
1.0% Hydrochloric
|
210
|
99 B
|
|
|
0.68
|
|
1.0% Hydrochloric
+ 3% FeCl3
|
167
|
75
|
|
|
2.27**
|
|
10% Sulfuric
|
215
|
102 B |
|
|
1.05
|
|
60% Sulfuric
|
244
|
118 B
|
|
|
>1000
|
|
93% Sulfuric
|
171
|
77
|
|
78.0
|
10.0
|
|
50% Phosphoric
|
228
|
109 B
|
2.46
|
3.87
|
1.78
|
|
10% Nitric
|
219
|
104 B
|
0.37
|
0.96
|
0.46
|
|
65% Nitric
|
241
|
116 B
|
3.34
|
3.95
|
1.20***
|
|
60% Nitric + 2% HCL
|
235
|
113 B
|
|
|
4.18***
|
|
80% Acetic
|
217
|
103 B
|
17.0
|
|
0.02
|
|
100% Acetic
|
243
|
117 B
|
0.39
|
0.54
|
0.44
|
|
50% Acetic + 50% Anhyd
|
164
|
73
|
0.40
|
|
1.60
|
|
50% Formic
|
221
|
105 B
|
|
|
0.89
|
|
10% Oxalic
|
216
|
102 B
|
|
|
1.31
|
|
55% NaOH
+ 8% NaC
+3% NaClO3
|
210
|
99
|
|
6.1
|
<0.1
|
|
50% NaOH
|
289
|
143
|
|
15.0
|
1.0
|
* Corrosion-rate in mils per year— evaluated over a ninety six hour time period.
** Pitting.
*** Welded UNS #S44660 showed sensible performance within the gas tests. However, caution ought to be exercised in mistreatment any atomic number 22 stable alloy in extremely oxidizing environments.
B — Boiling
Acid atmospheric phenomenon Resistance
Heat recovery systems area unit notably at risk of severe corrosion caused by acid condensates within the atmosphere. the method of condensation and evaporation concentrates acids and chlorides, increasing the corrosive attack at the atmospheric phenomenon purpose|temperature|saturation point} or water boiling point. UNS #S44660 stainless-steel has the potential to resist most of those corrodents.
Seawater Corrosion Resistance
UNS #S44660 stainless-steel was developed specifically to resist localized indentation and crevice corrosion in aggressive chloride solutions, like brine. In comparative accelerated laboratory
and crevice corrosion testing, UNS #S44660 ranks way superior to the common primary solid solution unblemished steels like sorts 304 & 316.
Testing Results
In natural brine at close temperature, many tests have shown no attack in over ten years. Today, varied powerhouse condensers have over twenty five years of exposure. underneath identical conditions, kind 316 full-fledged a .039 in. crevice corrosion attack. In areas wherever organic pollution is gift (which will decay to provide gas sulfide), UNS #S44660 stainless-steel resulted in considerably higher corrosion resistance than the copper alloys, like copper-nickel.
Chloride Stress-Corrosion Cracking Resistance
Like most alternative totally ferritic unblemished steels, UNS #S44660 stainless-steel has glorious resistance to chloride-induced stress-corrosion cracking. once stressed to ninetieth of its yield strength and placed during a 212˚F (100˚C) four-hundredth CaC12 resolution, UNS #S44660 unblemished failed to crack even once a 5000 hour exposure. kind 316L unblemished cracks among four hundred hours underneath identical conditions. UNS #S44660 U-Bend specimens exposed to 1500 ppm binary compound at 212˚ F (100˚C) conjointly failed to crack. Like alternative unblemished steels, UNS #S44660 isn\'t proof against stress corrosion in four-hundredth Mg chloride resolution (boiling) at 284˚F (140˚C).
Erosion-Corrosion Resistance
UNS #S44660 exhibits glorious resistance to all or any kinds of erosion. it's not full of high water velocities, which can result from either tube blockage or mechanical style, nor by steam or impingement erosion. during a wear-erosion check mistreatment silicon oxide sand and water occurrence on varied unblemished steels, it shows solely twenty fifth of the burden loss of kind 316.
Galvanic Corrosion
Whenever the tubes and also the tubesheet of a device or condenser area unit of dissimilar materials and up-to-date with conductive water (usually quite 1000ppm dissolved solids), there\'s a clear stage of galvanic corrosion of the opposite alloy.
UNS #S44660 incorporates a high conductor potential in brine, creating it terribly noble or electrode. it's slightly below atomic number 22, gold and Pt, and is a lot of noble than the copper alloys, copper-nickel or steel within the galvanic series. Therefore, there's a clear stage of galvanic attack to the fabric that's lower within the galvanic series. Thus, if UNS #S44660 tubes area unit used with a brass tubesheet in brine, the brass tubesheet will pit within the ligament section between the tubes. Covering the tubesheet with associate degree epoxy-type coating or mistreatment associate degree affected voltage electrode protection system typically protects the tubesheet. If a electrode protection system is employed, the voltage ought to be maintained a lot of positive than -0.800 volts as measured against a customary mercurous chloride conductor to stop generation of gas, which might cause gas embrittlement.
Marine Fouling
All metals foul in brine over time. as a result of most unblemished steels don't contain copper, that dissolves and forms copper ions that area unit toxic to marine growth, fouling could occur earlier.
The tendency for marines fouling of all materials are often decreased by chlorination, mechanical cleansing or high water speed.
UNS #S44660 unblemished, by virtue of its erosion resistance, is ideally suited to either mechanical cleansing or high water speed. In softer copper alloys, these ways will cause severe wear.
Sulfide indentation Attack
Pitting corrosion within the presence of sulfur compounds and bound microorganism in impure brine could occur with copper-nickel, aluminum-brass and alternative alloys high in copper. UNS #S44660 isn't attacked by these sulfur compounds and also the associated microorganism.
Manganese microorganism Attack
Manganese are often extracted from bound waters by bound kinds of microorganism and deposited on device surfaces as hydrous manganous compound. within the presence of halogen, this compound are often modify to the salt and also the halogen reduced to the halogen particle. This reaction will cause indentation within the three hundred Series unblemished steels and Admiralty Metal. UNS #S44660 is actually proof against this reaction owing to its terribly high resistance to indentation.
Ammonia Attack
Copper-base alloys area unit terribly at risk of ammonia attack leading to accelerated general corrosion, indentation attack, or ammonia-induced stress corrosion crack. UNS #S44660 like alternative unblemished steels is actually proof against ammonia attack.
Physical Properties
UNS #S44660 stainless-steel incorporates a range of enticing physical properties, together with low thermal growth, sensible thermal physical phenomenon, and a high modulus that provides high stiffness. High stiffness permits less vibration than with alternative engineering materials. The thermal growth coefficients area unit kind of like those of steel and not up to those of the primary solid solution stainless-steel or copper alloys. The thermal physical phenomenon is analogous to atomic number 22 and better than the primary solid solution unblemished steels of high nickel alloys. The passive corrosion resistant film is very skinny, that permits sensible heat transfer performance.
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Comparative Properties of Various Alloys
|
|||
|
|
Ti Gr.2
|
90-10 Cu/Ni
|
UNS 44660
|
|
Yield Strength* (ksi)
|
40
|
15
|
65
|
|
Tensile Strength* (ksi)
|
50
|
40
|
85
|
|
Elongation* (%)
|
20
|
25
|
20
|
|
Elastic Modulus (PSI x 106)
|
15.5**
|
18
|
31.5
|
|
Density (lb/in3)
|
0.16
|
0.32
|
0.278
|
|
Expansion Coefficient
(in/in-˚Fx106)
|
4.7
|
9.5
|
5.38
|
|
Thermal Conductivity
(Btu/hr-ft2-˚F/ft)
|
12.6
|
26
|
10.1
|
|
Specific Heat(Btu/lb-˚F)
|
0.124
|
0.092
|
0.12
|
|
Fatigue Endurance(ksi)
|
16
|
25
|
35
|
* Minimum ASTM price
** most ASTM price
Vibration Resistance
Because of its terribly high modulus of physical property, UNS #S44660 stainless-steel is extremely proof against wave fatigue harm. For the aim of comparison, the subsequent minimum tube wall would be needed to stop vibration harm underneath identical conditions of rotary engine exhaust steam speed, steam density, tubes support spacing, and tube diameter:
Mechanical Properties
The close temperature strength of UNS #S44660 stainless-steel is maintained over the temperature vary encountered by most device applications. UNS #S44660 is approved for ASME Boiler and Pressure Vessel Code construction Section VIII, Division I. The allowable stresses for each sheet and tube area unit well beyond those of lower alloy ferritic and primary solid solution unblemished steels. This issue will turn out substantial savings through reduced section thickness or higher in operation pressures. associate degree higher temperature limit of 500˚F is obligatory to avoid danger from 885˚F embrittlement that could be a characteristic of all ferritic steels that contain quite twelve-tone music metal.
Key Words: Stainless Sheet 304, aceroinoxidable，Stainless Steel Plates, Super Ferritic Stainless Steel