11 300 series stainless steels a look at the grades, properties and applications
TRANSCRIPT
11
300 Series Stainless SteelsA look at the grades, properties and applications
2
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
3
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
4
Austenitic Stainless Steels
• A magnetic phase
• Can be estimated by
• Calculation diagrams
or
• MeasuredFerrite
Ferrite
About 10FN
It is not a chemical element!
5
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
6
Calculated by WRC 92
7
Fischer Feritscope
MAGNE-GAGE
Ferrite Number Measured on Actual Metal Specimen
8
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
9
• 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
10
300 Series Stainless “Groups”
Basic Cr NiCr Ni MoDissimilar Metal JoiningFully Austenitic
11
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
12
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
13
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)
14
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
15
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
16
Dissimilar Metal Joining
17
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
18
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.
19
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
20
Welding Fully Austenitic Stainless Steels
310, 320, 330, 385
No Ferrite
Susceptible to hot cracking – Centerline cracking
21
Reminder!
Ferrite – the up side
22
Fully Austenitic
23
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
24
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