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Stainless steel |
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Duplex & Super Dupex Steel |
Stainless steel, also known as inox steel is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass. Stainless steel does not stain, corrode, or rust as easily as ordinary steel .] It is also called corrosion-resistant steel or CRES when the alloy type and grade are not detailed, particularly in the aviation industry.
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| Benefits of Stainless Steel : |
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Corrosion Resistance |
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Fire And Heat Resistance |
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Hygiene |
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Aesthetic Appearance |
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Strength-To-Weight Advantage |
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Impact Resistance |
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Lower Total Life Cycle Cost |
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100%Recyclable |
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| Specification : |
| SS Round Bars as per ASTM A 484 |
| SS Forged Bars as per ASTM A 182 |
| SS pipe as per ASTM A 312 /249/270/269/213/358 |
| SS plate as per ASTM A 240 |
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| Grades – Chemical Composition and Equivalent Standards : |
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AISI ASTM |
EN DIN |
C % Max |
Mn % Max |
Si % Max |
S % Max |
P % Max |
Cr % Max |
Ni % Max |
Mo % Max |
Others % |
304 |
1.4301 |
0.08 |
2.00 |
1.00 |
0.030 |
0.045 |
18.00-20.00 |
8.00-11.00 |
- |
- |
310 |
1.4841 |
0.25 |
2.00 |
1.50 |
0.030 |
0.045 |
24.00-26.00 |
19.00-22.00 |
- |
- |
316 |
1.4401 |
0.08 |
2.00 |
1.00 |
0.030 |
0.045 |
16.00-18.00 |
10.00-14.00 |
2.00-3.00 |
- |
321 |
1.4541 |
0.08 |
2.00 |
1.00 |
0.030 |
0.045 |
17.00-19.00 |
9.00-12.00 |
- |
Ti : Min (5xC%) |
410 |
1.4006 |
0.15 |
1.00 |
1.00 |
0.030 |
0.040 |
11.50-13.50 |
- |
- |
- |
420 |
1.4021 |
0.15 Min |
1.00 |
1.00 |
0.030 |
0.040 |
12.00-14.00 |
- |
- |
- |
430 |
1.4016 |
0.12 |
1.00 |
1.00 |
0.030 |
0.040 |
16.00-18.00 |
- |
- |
- |
431 |
1.4057 |
0.20 |
1.00 |
1.00 |
0.030 |
0.040 |
15.00-17.00 |
1.25-2.50 |
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Duplex & Super Dupex Steel |
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Duplex alloys were originally created to combat corrosion problems caused by chloride-bearing cooling waters and other aggressive chemical process fluids.
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Called Duplex because of its mixed microstructure with about equal proportions of ferrite and austenite, duplex stainless steels are a family of grades, which range in corrosion performance depending on their alloy content. The chemical composition based on high contents of Cr and Mo, improves intergranular and pitting corrosion resistance, respectively. Additions of nitrogen can promote structural hardening by interstitial solid solution mechanism, which raises the yield strength and ultimate strength values without impairing toughness. Moreover, the two-phase microstructure guarantees higher resistance to pitting and stress corrosion cracking in comparison with conventional stainless steels. |
| The various Alloys |
| The development of the Duplex stainless steels has continued, graded for their corrosion performance depending on their alloy content. Today, modern duplex stainless steel can be divided into four groups: |
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| Composition of Duplex Stainless Steels : |
| The table lists the duplex stainless steels covered in ASTM specifications for plate, sheet, and bar products. |
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UNS Number
Duplex Grades |
Typeb |
C |
Mn |
P |
S |
Si |
Cr |
Ni |
Mo |
N |
Cu |
Other |
S31200 |
- |
0.030 |
2.00 |
0.045 |
0.030 |
1.00 |
24.0-26.0 |
5.5-6.5 |
1.20-2.00 |
0.14-0.20 |
- |
- |
S31260 |
- |
0.03 |
1.00 |
0.030 |
0.030 |
0.75 |
24.0-26.0 |
5.5-7.5 |
2.5-3.5 |
0.10-0.20 |
0.20-0.80 |
W0.10-0.20 |
S31803 |
- |
0.030 |
2.00 |
0.030 |
0.020 |
1.00 |
21.0-23.0 |
4.5-6.5 |
2.5-3.5 |
0.08-0.20 |
- |
- |
S32001 |
- |
0.030 |
4.0-6.0 |
0.040 |
0.030 |
1.00 |
22.0-23.0 |
1.00-3.00 |
0.60 |
0.05-0.17 |
1.00 |
- |
S32205 |
2205 |
0.030 |
2.00 |
0.030 |
0.020 |
1.00 |
19.5-21.5 |
4.5-6.5 |
3.0-3.5 |
0.14-0.20 |
- |
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S32304 |
2304 |
0.030 |
2.50 |
2.50 |
0.030 |
1.00 |
21.5-24.5 |
3.0-5.5 |
0.05-0.60 |
0.05-0.20 |
0.05-0.60 |
- |
S32520 |
- |
0.030 |
1.50 |
0.035 |
0.035 |
0.80 |
24.0-26.0 |
5.5-8.0 |
3.0-4.0 |
0.20-0.35 |
0.50-2.00 |
- |
S32550 |
255 |
0.04 |
1.50 |
0.040 |
0.030 |
1.00 |
24.0-27.0 |
4.5-6.5 |
2.9-3.9 |
0.10-0.25 |
1.5-2.5 |
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S32750 |
2507 |
0.030 |
1.20 |
0.035 |
0.020 |
0.80 |
24.0-26.0 |
6.0-8.0 |
3.0-5.0 |
0.24-0.32 |
0.50 |
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S32760 |
- |
0.030 |
1.00 |
0.030 |
0.010 |
1.00 |
24.0-26.0 |
6.0-8.0 |
3.0-4.0 |
0.20-0.30 |
0.50-1.00 |
c |
S32900 |
329 d |
0.06 |
1.00 |
0.040 |
0.030 |
0.75 |
23.0-28.0 |
2.5-5.0 |
1.0-2.0 |
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- |
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S32950 |
- |
0.03 |
2.00 |
0.035 |
- |
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- |
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- |
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| a BENEFITS |
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High strength |
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High resistance to pitting, crevice corrosion resistance. |
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High resistance to stress corrosion cracking, corrosion fatigue and erosion, |
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Good sulfide stress corrosion resistance, |
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Low thermal expansion and higher heat conductivity than austenitic steels, |
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Good workability and weldability, |
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High energy absorption. |
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