PRES SS Family Intro

7/29/2019 PRES SS Family Intro

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Introduction to the Family of

Stainless Steels


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Stainless Steels

u Definition Iron Alloy with >11% Cr

u Very Large Family - >100 Members

u Other Alloying Elements

Ni, Mo, N, Cu, Nb (Cb), Ti, C

u Metallurgy

Ferritic, Martensitic, Austenitic, Duplex, Super Ferritic, Martensitic are body-centered cubic

Austenitic is face-centered cubic

u Nickel-Rich Alloys


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Corrosion Resistant Alloys

Name UNS No. Alloy Group C (Max) N Cr Ni Mo Cu Fe Other PRE Cost Ratio

304 S30400 Austenitic 0.08 -- 18 8 -- -- Bal. -- 18 1.4 to 2

304L S30403 Austenitic 0.03 -- 18 8 -- -- Bal. -- 18 1.4 to 2

321 S32100 Austenitic 0.08 -- 17 9 -- -- Bal. Ti 17

347 S34700 Austenitic 0.08 -- 17 9 -- -- Bal. Cb 17

316 S31600 Austenitic 0.08 -- 16 10 2 -- Bal. -- 23 1.6 to 2.7

316L S31603 Austenitic 0.03 -- 16 10 2 -- Bal. -- 23 1.6 to 2.7

316Ti S31635 Austenitic 0.08 -- 16 10 2 -- Bal. Ti 0.7 23

SEA CURE S44660 Super Ferritic 0.03 -- 25 1 3 -- Bal. Cb+Ti 35

AL 29-4C S44735 Super Ferritic 0.03 -- 28 -- 3.6 -- Bal. Cb+Ti 40

AL 29-4-2 S44800 Super Ferritic 0.01 0.02 28 2 3.5 -- Bal. -- 40

Alloy 2205 S31803 Duplex 0.03 0.08 21 4.5 2.5 -- Bal. -- 31 2 to 4.5

Alloy 2205 S32205 Duplex 0.03 0.14 22 4.5 3 -- Bal. -- 34 2 to 4.5

Alloy 255 S32550 Duplex 0.04 0.1 24 4.5 2.9 1.5 Bal. -- 35 2.5

Alloy 2507 S32750 Super Duplex 0.03 0.24 24 6 3 -- Bal. -- 38 2.6 to 5.2

Zeron 100 S32760 Super Duplex 0.05 0.2 24 6 3 0.5 Bal. -- 37 3.5 to 6.5

Alloy 254 SMO S31254 Super Austenitic 0.02 0.18 19.5 17.5 6 0.5 Bal. -- 42 3.3 to 7.5

Alloy 20 Mo-6 N08026 Super Austenitic 0.03 0.1 22 33 5 2 Bal. -- 40 6

Alloy 28 N08028 Super Austenitic 0.03 -- 26 30 3 0.6 Bal. -- 36 3.3AL-6XN N08367 Super Austenitic 0.03 0.18 20 23.5 6 -- Bal. -- 42 3.3 to 7

904L N08904 Super Austenitic 0.02 -- 19 23 4 1 Bal. -- 32 3.2

Alloy926 N08926 Super Austenitic 0.02 0.15 19 24 6 0.5 Bal. -- 41 3.3 to 7.5

Alloy 1925hMo N08926 Super Austenitic 0.02 0.15 19 24 6 0.5 Bal. -- 41 3.3 to 7.5

Alloy 25-6MO N08926 Super Austenitic 0.02 0.15 19 24 6 0.5 Bal. -- 41 3.3 to 7.5

Alloy 654 SMO S32654 Super Austenitic 0.02 0.45 24 21 7 0.3 Bal. -- 53 4.5

Alloy G-30 N06030 Nickel Based 0.03 -- 28 Bal. 4 1 13 Cb W 41 10

Alloy 625 N06625 Nickel Based 0.1 -- 20 Bal. 8 -- 5 Cb 46 6.5

Alloy C-276 N10276 Nickel Based 0.01 -- 14.5 Bal. 15 -- 4 W 64 8 to 15

Nickel 200 N02200 Nickel Based 0.15 -- -- 99 -- -- -- -- 7.4 to 9

Monel 400 N04400 Nickel Based 0.3 -- -- 63 -- 28 -- -- -- 5.7 to 9

Alloy B3 N10665 Nickel Based 0.01 -- -- Bal. 26 -- -- -- -- 9 to 13


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How Does Stainless Steel

Corrode?

u General Corrosion

u Occluded Cell Corrosion (Pitting, Crevice

Corrosion, Deposit Corrosion)u Stress Corrosion Cracking

u Intergranular Corrosion


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General Corrosion

u Oxidizing Power Below the Required Level

to Passivate

u

In such a case, SS corrodes like carbon steelu This situation is fairly easy to avoid


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Oxidizing Power vs. Corr. Rate

SS in Dilute Sulfuric Acid

Co

rrosion

Rate

O x i d i z e r A d d e d


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Occluded Cell Corrosion

u Chloride is the Usual Cause

u Mechanism

u

Crevice Corrosion, Deposit Corrosionu Pitting

u Pitting is Different because of theRequirement for Initiation

u Once initiated, pitting progresses just likecrevice corrosion


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Occluded Cell Corrosion

Mechanism


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Stress Corrosion Cracking

u Requires tensile stress + Specific Environment

u Chloride or hot, strong caustic

u Increased Risk at Higher Temp., Stress Level,

chloride level, Lower pHu Empirical Correlations

u Corrective Actions

Modify Environment

Relieve Stress

Change Alloy - Higher Ni content or Duplex


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Chloride SCC Limits 304, 316

SCC Limits - 304/316

0.1

1

10

100

1000

10000

0 50 100 150 200 250 300 350

Process Inlet Temperature C

C

hloridesppm

McIntyre - All Data

Sakai - 3 Year Data

Sakai - 6 Year DataSakai - Shell Side

Sakai - Tube Side


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Intergranular Corrosion

u Occurs In Specific Environments, in Presence of

Grain Boundary Precipitates

u Precipitates Form in 800 to 1600 F Range

u Area parallel to weldment most Common

u Weld Decay

u Corrective Actions Lower Carbon in Alloy, Add

Ti or Nb to Alloy, Quench Anneal after Welding

u Unusual with Modern Alloys Tend to be Low C


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Examples

u SS in Sea Water

u SS in Cooling Tower Water

u Corrosion Under Insulationu SS Polymer Reactor

u SS in HCN Stripper Column


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The Rules

Use of Common SS in Sea Water

u Dont

u If Unavoidable, and Tmax >60 C, to have achance of success

Sterilize Water

Water on Tube Side

Horizontal Exchanger

Water Velocity (Actual), Continuous, High asPossible, Definitely >6 ft/sec


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The Rules

Use of Common SS in CTW

u Use 316 or 316L

u Mount Exchanger Horizontal

u Water on Tube Side if Possible

u Keep Water Flow Continuous, Velocity High

u If Exchanger Must be Vertical, Water on Shell

Side

Vent Top Tube Sheet

If Process T>60 C, Use a Better Alloy


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Water In

Water Out

Process In

Process Out

Hot Process

Inlet

Water

Level

Concentration and

deposition at interfaceon hot wall causespitting, crevice corrosionand/or stress corrosioncracking.

Tube SheetVent

Figure 2-7 The Problem with Vertical, Shell Side Water Exchangers

The Problem with Vertical,

Shell- Side Water Exchangers


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Corrosion Under Insulation


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Absorber/Stripper System


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Polymer Treatment Reactor


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Common Austenitic Stainless

Steels

Name UNS No. C (Max) Cr Ni Mo Fe Other PRE Cost Ratio

304 S30400 0.08 18 8 -- Bal. -- 18 1.4 to 2304L S30403 0.03 18 8 -- Bal. -- 18 1.4 to 2

321 S32100 0.08 17 9 -- Bal. Ti 17

347 S34700 0.08 17 9 -- Bal. Cb 17

316 S31600 0.08 16 10 2 Bal. -- 23 1.6 to 2.7

316L S31603 0.03 16 10 2 Bal. -- 23 1.6 to 2.7316Ti S31635 0.08 16 10 2 Bal. Ti 0.7 23

PRE is Pitting Resistance Equivalent. PRE=Cr+3.3*Mo+13*N

Cost Ratio is Approximate Ratio of Fabricated Cost to Carbon Steel


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Super Austenitic Stainless Steels

Name UNS No. C (Max) N Cr Ni Mo Cu Fe PRE Cost Ratio

Alloy 254 SMO S31254 0.02 0.18 19.5 17.5 6 0.5 Bal. 42 3.3 to 7.5

Alloy 20 Mo-6 N08026 0.03 0.1 22 33 5 2 Bal. 40 6Alloy 28 N08028 0.03 -- 26 30 3 0.6 Bal. 36 3.3

AL-6XN N08367 0.03 0.18 20 23.5 6 -- Bal. 42 3.3 to 7

904L N08904 0.02 -- 19 23 4 1 Bal. 32 3.2

Alloy926 N08926 0.02 0.15 19 24 6 0.5 Bal. 41 3.3 to 7.5Alloy 1925hMo N08926 0.02 0.15 19 24 6 0.5 Bal. 41 3.3 to 7.5

Alloy 25-6MO N08926 0.02 0.15 19 24 6 0.5 Bal. 41 3.3 to 7.5

Alloy 654 SMO S32654 0.02 0.45 24 21 7 0.3 Bal. 53 4.5

PRE is Pitting Resistance Equivalent. PRE=Cr+3.3*Mo+13*NCost Ratio is Approximate Ratio of Fabricated Cost to Carbon Steel


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Some Nickel Based Alloys

Name UNS No. C (Max) Cr Ni Mo Cu Fe Other PRE Cost Ratio

Alloy G-30 N06030 0.03 28 Bal. 4 1 13 Cb W 41 10

Alloy 625 N06625 0.1 20 Bal. 8 -- 5 Cb 46 6.5

Alloy C-276 N10276 0.01 14.5 Bal. 15 -- 4 W 64 8 to 15

Nickel 200 N02200 0.15 -- 99 -- -- -- -- 7.4 to 9

Monel 400 N04400 0.3 -- 63 -- 28 -- -- -- 5.7 to 9Alloy B3 N10665 0.01 -- Bal. 26 -- -- -- -- 9 to 13



F i i & D l S i l


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Ferritic & Duplex Stainless

Steels

Name UNS No. Alloy Group C (Max) N Cr Ni Mo Cu Fe Other PRE Cost Ratio

SEA CURE S44660 Super Ferritic 0.03 -- 25 1 3 -- Bal. Cb+Ti 35AL 29-4C S44735 Super Ferritic 0.03 -- 28 -- 3.6 -- Bal. Cb+Ti 40

AL 29-4-2 S44800 Super Ferritic 0.01 0.02 28 2 3.5 -- Bal. -- 40

Alloy 2205 S31803 Duplex 0.03 0.08 21 4.5 2.5 -- Bal. -- 31 2 to 4.5

Alloy 2205 S32205 Duplex 0.03 0.14 22 4.5 3 -- Bal. -- 34 2 to 4.5

Alloy 255 S32550 Duplex 0.04 0.1 24 4.5 2.9 1.5 Bal. -- 35 2.5Alloy 2507 S32750 Super Duplex 0.03 0.24 24 6 3 -- Bal. -- 38 2.6 to 5.2

Zeron 100 S32760 Super Duplex 0.05 0.2 24 6 3 0.5 Bal. -- 37 3.5 to 6.5




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Nomenclature

u Trade Names Carpenter 20Cb3, etc.

u Common Names - Alloy Chemistry Only

AISI 304, 316, 310, etc. Chemistry only

UNS S30400, S31600, S31000

u Specifications - Chemistry + Mechanical +Manufacture

ASTM A-249-02 Alloy Base + Product Form + Year

N l M S


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Nomenclature Many Systems

Example UNS S30400, 304 SS

u Trade Names

EN 1.4301, 3R12, 5R10, B8, B8A, Polarit 725,15 more

u Specifications AMS 27

ASME 13

ASTM 51 SAE 3

Ch f M d S l Mill


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Changes from Modern Steel Mill

Practices

u Tighter Control of Alloy Chemistry

+/- 0.2% now vs. 0.5% then

u Raw Material Recycled Scrap now vs. orethen

u Annealing Practices Shorter time attemperature and slower quench now

u Pickling Practices Spray and Flush nowvs. Immersion then

R lt f Ch i Mill


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Result of Changes in Mill

Practices

u Desired Alloy Content at Low End of Spec.

u Unspecified Elements Can Be Present

May Change Corrosion Resistanceu Annealing May Not Be Fully Effective

u Pickling Practice May Create a Thin

Surface Layer of Low Alloy Content MayAllow Corrosion to Initiate


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Summary

u SSs are Commonly and Successfully Used

u SSs Can and Do Fail

u Failure Risk Can be Minimized by ProperSelection Procedures

u Resources

In-House Experts

Consultants

Suppliers


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Alloying Elements

u Ferrite Formers vs. Austenite Formers

u Ferrite Formers

Cr Resistance to oxidizers, Pitting, HighTemperature

Mo Resistance to Corrosion, especially

Pitting

Ti, Nb Control Carbide Ppt., tendency

toward intergranular corrosion


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Alloying Elements, Cont.

u Austenite Formers

Nickel Conveys Resistance to SCC

Carbon Higher level improves high temp. strength,

but can contribute to intergranular corr Manganese

Nitrogen Improves resistance to pitting

u Misc.

S, Se Improve Machinability, but hurt corr.

Restistance

Documents

PRES SS Family Intro