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300 Series Stainless SteelsA look at the grades, properties and applications

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300 Series Stainless Steel Welding Consumables

“Austenitic Stainless Steels”

Iron Base (Fe) & Typically low Carbon (C)

Chromium (Cr) 15-30%

Nickel (Ni) 8-35%

Molybdenum (Mo) 0-5%

Mn, Si, Cu, Nb

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Stainless Steel Welding Alloys

308L

308H

308L(Si)

347

309L

309L(Si)

309LMo

316L

316L(Si)

317L

312

310

320LR

330

385

307

The Austenitic Grades:

Non-magnetic

May contain an

important magnetic

phase called ferrite

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Austenitic Stainless Steels

• A magnetic phase

• Can be estimated by

• Calculation diagrams

or

• MeasuredFerrite

Ferrite

About 10FN

It is not a chemical element!

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Austenitic Stainless SteelsFerrite

• Calculated using diagrams – based upon chemical

element percentages.

• WRC 92 (Welding Research Council, 1992)

Cr eq = Cr + Mo + .7Nb

Ferrite formers

Ni eq = Ni + 35C + 20N + .25Cu

Austenite formers

• Delong Diagram (introduced Nitrogen – 308/316)

• Schaeffler Diagram

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Calculated by WRC 92

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Fischer Feritscope

MAGNE-GAGE

Ferrite Number Measured on Actual Metal Specimen

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B.2 Effects of Ferrite

The most important effect of ferrite in nominally austenitic stainless steel weldments is the well-established

relationship between a reduced sensitivity to hot cracking and the presence of ferrite. The minimum

ferrite limit necessary to assure freedom from cracking depends, among other factors, on the weld metal

composition. The upper limit results from possible impairment of either mechanical or corrosion properties,

or both. The required amount of ferrite can be ascertained by adjusting the ration of ferrite formers (such

as chromium) to austenite promoters (such as nickel) within limits allowed by the applicable specification.

Ferrite in 300 Series Stainless

Ferrite – the up side

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• In High Temperature Applications, such as in refineries, >800F – Ferrite can transform to a brittle intermetallic phase – Sigma. The result is a lack of ductility.

• In Low Temperature Applications -320F – Ferrite can harm toughness

Controlled ferrite content is the key!

Intermetallic phasesFerrite – the down side

Ferrite in 300 Series Stainless

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300 Series Stainless “Groups”

Basic Cr NiCr Ni MoDissimilar Metal JoiningFully Austenitic

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Basic Cr Ni

18-8 Stainless 302/304 base metal

308 Family 19.5-22.0% Cr, 9.0-11.0% Ni308L less Carbon .03% max

308H more Carbon .04-.08%

308LSI more Silicon .65-1.00%

347 + Nb 10xC min to 1.0% max

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308L 304 joining GTAW, SAW, FCAW process

308H High Temp apps – hc Castings / Refineries

308LSI GMAW higher speed 304 joining

347 High Temp, minimize CrC precip

308L”CF” Low Temp –Cryo, LNG

Basic Cr Ni Applications

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Cr Ni Mo

16-18%Cr, 10-14%Ni, 2-3%Mo UNS S31630

Improved corrosion resistance – chlorides / pitting

308 Family 19.5-22.0% Cr, 9.0-11.0 Ni

316 Family 18.0-20.0% Cr, 11.0-14.0%Ni,2.0-3.0%Mo316L less Carbon .03% max

316LSI more Silicon .65-1.00%

317L +Ni (13.0-15.0), +Mo (3.0-4.0)

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Food processing, salt water316L 316 joining GTAW, SAW, FCAW process

316LSI GMAW higher speed 316 joining

316L”CF” Low Temp –Cryo, LNG coastal areas, ocean transport

317L Upgrade to 316L for additional corrosion protection

Basic Cr Ni Mo Applications

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Dissimilar Metal Joining

Carbon Steel to Stainless - Dilution308 Family 19.5-22.0% Cr, 9.0-11.0 Ni316 Family 18.0-20.0% Cr, 11.0-14.0Ni, 2.0-3.0Mo309L Types 308 +Cr +Ni

23.0-25.0%Cr, 12.0-14.0% Ni

312 308 ++ Cr 28.0-32.0%Cr, 8.0-10.5% Ni

18 8 Mn (307) 5.0-8.0Mn, 17-20Cr, 7-10Ni23 12 2 L (309LMo) 309L plus 2.0-3.5% Mo

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Dissimilar Metal Joining

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Dissimilar Metal Joining

CenterlineHot Crack

Minimize dilution of carbon steel

to prevent centerline cracking (lack of ferrite)

In cases of high dilution, 312 may be the best choice

PWHT / Stress Relief can make

high ferrite welds brittle – might be a factor

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Alert

• Not all AWS ER309LSi wires are the same.

• For Hot Mills / Rolling HRAP rod with high ferrite content is difficult. Higher scrap, higher cost…..

• Premium brands like Lincoln Bluemax 309LSi have higher min FN levels

• Bluemax may work where other 309LSi brands will not.

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Specialty Grades

310 27%Cr 21% Ni

330 16%Cr 35%Ni

320LR 20%Cr 34%Ni 2.5%Mo 3.4%Cu

385 21%Cr 25%Ni 4.6%Mo 1.6%Cu

Applications

High heat

Severe corrosion

Heat treat furnace components, baskets

Chemical containment tanks

Fully Austenitic

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Welding Fully Austenitic Stainless Steels

310, 320, 330, 385

No Ferrite

Susceptible to hot cracking – Centerline cracking

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Reminder!

Ferrite – the up side

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Fully Austenitic

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Welding Fully Austenitic Stainless Steels

310, 320, 330, 385

No Ferrite

320LR “Low Residual” reduces crack sensitivity (less C, Si, P, S)

No preheat

Maximum interpass temperature of 212°F (100°C)

Low heat input No weaving

Small weld puddle

Make an “ugly weld” with more reinforcement, convex fillet not concave fillet Electrodes with -15 or -16 coatings, not -17

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Summary

• 300 Series StainlessUnderstanding starts with 18-8 and add on

Understand “ferrite” is important

Understand properties and applications change with sometimes small adjustments to composition