zO8gKQ03RrSrO0eY20Ww Duplex Materials Peter Weis
TTMA Report Duplex Materials
NTTC - 2013 Peter Weis Chief Engineer Polar Tank Trailer
Presentation Objectives: • What are Duplex SS materials? • What makes them relevant? • DOT Special Permits • Welding Duplex Material
What is Duplex Stainless Steel? Austenite
Ferrite
• T316, T304 • High Toughness (fracture resistance) • Good Weldability
• Kitchen Appliances, Mufflers
Plus
• Low Toughness • Limited Weldability
• Good Formability
• Stress Corrosion Cracking resistant
• Higher Thermal Expansion
• Higher thermal conductivity
• Non-magnetic
• Magnetic
Even better when mixed!
What is Duplex SS?
Duplex Class • 2101, 2205, and other grades
Lean Duplex - LDX 2101 21% Chrome, 1% Nickel
• High Toughness • High Strength • Acceptable Weldability
Duplex - 2205 (plus two)
• Acceptable Formability
22% Chrome, 5% Nickel
• Lower Thermal Expansion
What is Duplex SS?
Can this structure be preserved in a welded joint?
Microstructure ≈ 50% Ferrite/50% Austenite
What is Duplex SS? History: Duplex
2205 Duplex (a “standard” duplex”) emerged in the 1980’s
Most common “Duplex” material
2205 Duplex was used on some tankers in the 1980’s for it’s thermal properties
Uncommon in our industry.
Lean Duplex
“Lean” refers to a lower level of Nickel and Molybdenum vs. Duplex
Competitor to T304 and T316 (in cost and corrosion resistance)
Commonly used in stationary pressure vessels, including API 650, and ASME Code cases
Several Lean Duplex tankers have been built under DOT Special Permit
Relevance? What makes Duplex Relevant to our Industry? 1. Higher Strength 2. Increased Corrosion Resistance 3. Better Thermal Stability 4. Price
1) Relevance: Higher Strength Alloy
Mechanical Properties (KSI) Yield
Tensile
T304
30
75
T316
30
75
LDX 2101 (Lean Duplex)
65
94
2205 Duplex (plus two)*
65
95
*2205/2205+2 is often dual certified (31803/32205)
2101 and 2205 are about 25% stronger than T316
1) Relevance: Higher Strength 7000 Gallon DOT 407 DOT Minimum Thickness Alloy
Minimum Thickness (in) Top/Sides
Bottom
Heads
T304
0.115
0.115
0.115
T316(L)
0.115
0.115
0.115
LDX 2101 (Lean Duplex)
0.090
0.090
0.095
2205 PLUS TWO (32205)
0.093
0.093
0.095
Shells can be thinner (as allowed by DOT Special Permit):
2) Relevance: Corrosion Resistance For Increased Corrosion Resistance Increase chromium (Cr) Increase molybdenum (Mo) Increase nitrogen (N)
•
Chromium – corrosion resistance
•
Molybdenum – chloride pitting resistance
•
Nickel – ductility, toughness, high temperature strength
•
Nitrogen – strength, pitting resistance
Bold items are important for corrosion resistance
2) Relevance: Corrosion Resistance Chemical Composition %
Alloy
Chrome
Molybdenum
Nickel
Nitrogen
T304
18
0
8
0.06
T316(L)
17
2
11
0.06
LDX 2101 (Lean Duplex)
21
0.3
1.5
0.22
2205 Duplex (plus two)*
21-23
3-3.5
5
.14-.20
*2205/2205+2 is often dual certified (31803/32205)
•
Chromium – corrosion resistance
•
Molybdenum – chloride pitting resistance
•
Nickel – ductility, toughness, high temperature strength
•
Nitrogen – strength, pitting resistance
2) Relevance: Corrosion Resistance - comparison “Pitting Resistance Equivalent Number” Higher is better
PRE = %Cr + 3.3x%Mo + 16x%N Alloy
PRE
T304
18
T316(L)
23
LDX 2101 (Lean Duplex)
23
2205 Duplex PLUS TWO (32205)
35
2205 Duplex is significantly more resistant to pitting than T316L.
2) Relevance: Corrosion Resistance - comparison Both Duplex types are more resistant to “Crevice Corrosion” Crevice Corrosion can occur in: • A Poorly finished surface • Poorly penetrated weld • Entrapment of product due to poor design
3) Relevance: Thermal Stability Duplex = 7.5 x 10-6 in/in/ OF T316 = 8.9 x 10-6 in/in/ OF Lower is better
Duplex has less thermal expansion (both types). • Less likely to buckle due to heat • Less likely to buckle due to thermal shock • Less likely to warp during welding (partly due to it’s higher strength)
4) Price • Duplex price fluctuations differ vs. T316 SS Due to differences in composition, as shown below 2101 Lean Duplex can be cheaper than T316 (but not currently) 2205 Duplex is more expensive than T316 Chemical Composition % Alloy Chrome
Molybdenum
Nickel
T316(L)
17
2
11
LDX 2101 (Lean Duplex)
21
0.3
1.5
During periods of fluctuating commodity prices, Lean Duplex can be cheaper than T316.
DOT Special Permits for Duplex Materials What are they? 1. Allows for materials that are not otherwise authorized in the regulations. 2. Allows these materials to be thinner due to higher strength. 3. Granted to each manufacturer individually.
Why are they necessary? 1. Some materials aren’t ASME recognized (1998 A99 ASME Code) 2. Many of these materials have been newly developed since 1998.
Responsibilities: Unique to this permit DOT Special Permit documents can be easily obtained: Google search “ Polar DOT-SP 14573”, or “Brenner DOT-SP 14467”
•
•
TESTING PER SECTION 180 •
Requirements are the same as any 400 series tank
•
Training is required for each “Hazmat Employee”
•
Must be able to calibrate the thickness tester, etc.
MARKING •
•
Must be marked on both sides with Permit number
REPAIR •
Requires a qualified weld procedure
Welding
1. Not as “forgiving” as austenitic stainless steel 2. Establish good procedures, and stick to them 3. 2209 filler for both types (high nickel input) 4. Require the use of filler wire (2205) 5. Proper shielding gasses are important 6. Very rapid quench results in high ferrite content
Weld spatter
Stud welds
Pipes (orbital)
Welding Consequences of Improper welding? 1. Weld may not have good corrosion resistance 2. Weld may be out of “duplex” phase (30% to 70% is optimal).
Positives/Negatives of Duplex Materials Positives:
Positives:
2101 Lean Duplex • Thinner shell/lighter • Resistant to Heat Buckling • Price (variable)
2205 Duplex • Thinner shell/lighter • Resistant to Heat Buckling • Corrosion resistance
Negatives: • • • • •
New Availability of Material Reduced formability Less forgiving to underdeveloped welding processes Finding Qualified Repair Shops
NTTC - 2013 Peter Weis Chief Engineer Polar Tank Trailer
Presentation Objectives: • What are Duplex SS materials? • What makes them relevant? • DOT Special Permits • Welding Duplex Material
What is Duplex Stainless Steel? Austenite
Ferrite
• T316, T304 • High Toughness (fracture resistance) • Good Weldability
• Kitchen Appliances, Mufflers
Plus
• Low Toughness • Limited Weldability
• Good Formability
• Stress Corrosion Cracking resistant
• Higher Thermal Expansion
• Higher thermal conductivity
• Non-magnetic
• Magnetic
Even better when mixed!
What is Duplex SS?
Duplex Class • 2101, 2205, and other grades
Lean Duplex - LDX 2101 21% Chrome, 1% Nickel
• High Toughness • High Strength • Acceptable Weldability
Duplex - 2205 (plus two)
• Acceptable Formability
22% Chrome, 5% Nickel
• Lower Thermal Expansion
What is Duplex SS?
Can this structure be preserved in a welded joint?
Microstructure ≈ 50% Ferrite/50% Austenite
What is Duplex SS? History: Duplex
2205 Duplex (a “standard” duplex”) emerged in the 1980’s
Most common “Duplex” material
2205 Duplex was used on some tankers in the 1980’s for it’s thermal properties
Uncommon in our industry.
Lean Duplex
“Lean” refers to a lower level of Nickel and Molybdenum vs. Duplex
Competitor to T304 and T316 (in cost and corrosion resistance)
Commonly used in stationary pressure vessels, including API 650, and ASME Code cases
Several Lean Duplex tankers have been built under DOT Special Permit
Relevance? What makes Duplex Relevant to our Industry? 1. Higher Strength 2. Increased Corrosion Resistance 3. Better Thermal Stability 4. Price
1) Relevance: Higher Strength Alloy
Mechanical Properties (KSI) Yield
Tensile
T304
30
75
T316
30
75
LDX 2101 (Lean Duplex)
65
94
2205 Duplex (plus two)*
65
95
*2205/2205+2 is often dual certified (31803/32205)
2101 and 2205 are about 25% stronger than T316
1) Relevance: Higher Strength 7000 Gallon DOT 407 DOT Minimum Thickness Alloy
Minimum Thickness (in) Top/Sides
Bottom
Heads
T304
0.115
0.115
0.115
T316(L)
0.115
0.115
0.115
LDX 2101 (Lean Duplex)
0.090
0.090
0.095
2205 PLUS TWO (32205)
0.093
0.093
0.095
Shells can be thinner (as allowed by DOT Special Permit):
2) Relevance: Corrosion Resistance For Increased Corrosion Resistance Increase chromium (Cr) Increase molybdenum (Mo) Increase nitrogen (N)
•
Chromium – corrosion resistance
•
Molybdenum – chloride pitting resistance
•
Nickel – ductility, toughness, high temperature strength
•
Nitrogen – strength, pitting resistance
Bold items are important for corrosion resistance
2) Relevance: Corrosion Resistance Chemical Composition %
Alloy
Chrome
Molybdenum
Nickel
Nitrogen
T304
18
0
8
0.06
T316(L)
17
2
11
0.06
LDX 2101 (Lean Duplex)
21
0.3
1.5
0.22
2205 Duplex (plus two)*
21-23
3-3.5
5
.14-.20
*2205/2205+2 is often dual certified (31803/32205)
•
Chromium – corrosion resistance
•
Molybdenum – chloride pitting resistance
•
Nickel – ductility, toughness, high temperature strength
•
Nitrogen – strength, pitting resistance
2) Relevance: Corrosion Resistance - comparison “Pitting Resistance Equivalent Number” Higher is better
PRE = %Cr + 3.3x%Mo + 16x%N Alloy
PRE
T304
18
T316(L)
23
LDX 2101 (Lean Duplex)
23
2205 Duplex PLUS TWO (32205)
35
2205 Duplex is significantly more resistant to pitting than T316L.
2) Relevance: Corrosion Resistance - comparison Both Duplex types are more resistant to “Crevice Corrosion” Crevice Corrosion can occur in: • A Poorly finished surface • Poorly penetrated weld • Entrapment of product due to poor design
3) Relevance: Thermal Stability Duplex = 7.5 x 10-6 in/in/ OF T316 = 8.9 x 10-6 in/in/ OF Lower is better
Duplex has less thermal expansion (both types). • Less likely to buckle due to heat • Less likely to buckle due to thermal shock • Less likely to warp during welding (partly due to it’s higher strength)
4) Price • Duplex price fluctuations differ vs. T316 SS Due to differences in composition, as shown below 2101 Lean Duplex can be cheaper than T316 (but not currently) 2205 Duplex is more expensive than T316 Chemical Composition % Alloy Chrome
Molybdenum
Nickel
T316(L)
17
2
11
LDX 2101 (Lean Duplex)
21
0.3
1.5
During periods of fluctuating commodity prices, Lean Duplex can be cheaper than T316.
DOT Special Permits for Duplex Materials What are they? 1. Allows for materials that are not otherwise authorized in the regulations. 2. Allows these materials to be thinner due to higher strength. 3. Granted to each manufacturer individually.
Why are they necessary? 1. Some materials aren’t ASME recognized (1998 A99 ASME Code) 2. Many of these materials have been newly developed since 1998.
Responsibilities: Unique to this permit DOT Special Permit documents can be easily obtained: Google search “ Polar DOT-SP 14573”, or “Brenner DOT-SP 14467”
•
•
TESTING PER SECTION 180 •
Requirements are the same as any 400 series tank
•
Training is required for each “Hazmat Employee”
•
Must be able to calibrate the thickness tester, etc.
MARKING •
•
Must be marked on both sides with Permit number
REPAIR •
Requires a qualified weld procedure
Welding
1. Not as “forgiving” as austenitic stainless steel 2. Establish good procedures, and stick to them 3. 2209 filler for both types (high nickel input) 4. Require the use of filler wire (2205) 5. Proper shielding gasses are important 6. Very rapid quench results in high ferrite content
Weld spatter
Stud welds
Pipes (orbital)
Welding Consequences of Improper welding? 1. Weld may not have good corrosion resistance 2. Weld may be out of “duplex” phase (30% to 70% is optimal).
Positives/Negatives of Duplex Materials Positives:
Positives:
2101 Lean Duplex • Thinner shell/lighter • Resistant to Heat Buckling • Price (variable)
2205 Duplex • Thinner shell/lighter • Resistant to Heat Buckling • Corrosion resistance
Negatives: • • • • •
New Availability of Material Reduced formability Less forgiving to underdeveloped welding processes Finding Qualified Repair Shops
