4/1/2013
Stainless Steel
What is it and how is it made
Presented by:
Robert (Bob) Drab
Quality Manager
Corey Steel Company
Stainless Steel
What it is and how its made
• What we will talk about
– Define stainless steel
– What make a stainless steel stainless
– Discuss the many variations and their use
Discuss the many variations and their use
– How are stainless steels made
• Summarize
What is Stainless Steel
• Stainless Steels are iron based alloys with at least 11% chromium
• Other alloying elements are added to increase corrosion resistance in different environments
•
•
•
•
•
•
Nickel
Molybdenum
Manganese
Copper
Niobium
Titanium
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4/1/2013
What is Stainless Steel
How it works
Carbon and Alloy Steels
O2
Iron Oxide
Fe + C
Oxygen at the surface of the steel combines with the iron to first form FeO, a gray rust then will quickly combine
a gray rust, then will quickly combine with more oxygen to form the typical red rust – Fe2O3.
Stainless Steels
O2
Fe + Cr (12%)
Chromium oxide
(Depth : 1 nm)
Oxygen at the surface of the steel combines with Chrome to form chrome oxide.
What is Stainless Steel
• Just an important point – These materials are not stain proof; they are stain less
 Stainless steels can rust in a rain storm
• Martensitics are the worse, followed by ferritics and then austenitics
and then austenitics
– Grades like 303 (austenitic) will rust because of ferrite and martensite in the structure for machinability
What is Stainless Steel
• What do these elements do..
– Iron – Base metal
– Chromium – ferrite former ‐ forms basis of stainless steel –prevents corrosion
– Nickel – austenite former – improves oxidation & corrosion resistance
– Molybdenum –
l bd
h l
helps pitting corrosion, improves high temp strength
h h
h
– Manganese – same as nickel, combines with sulfur
– Carbon – increases strength
– Nitrogen – austenite former, increases austenite stability, increases strength
– Titanium/Columbium – stabilizes stainless – captures carbon
– Copper – typically used in age hardening reactions, can be an austenite stabilizer is 300 series
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What is Stainless Steel
Duplex
Corrosion Ressistance
+
Austenitic
Precipitation
Hardenable
a de ab e
Ferritic
Martensitic
Hardened &
Tempered
Annealed
-
-
+
Tensile Strength
What are Stainless Steels
410
431
.17C, 15Cr, 1.5 Ni
+Cr
4024
416
.13C, 12Cr
.1C, 12Cr
+C
+C
420A
420F
.2C, 12Cr
+C
.3C, 12Cr
+C
+C
, +C
r, +
M
o
430
.05C, 18Cr
+M
o
.4C, 12Cr
.46C, 15Cr, .5Mo, .1V
+S
.03C, 1.25Si,18Cr
.06C, 18Cr, 1.5Mo
+C
420D
.45C, 12Cr
+M
o
‐C, +Si
4118
.45C, 14Cr, .5 mo
+C, +Cr
, +M
o
1.0C, 17Cr, .5Mo
.03C, 18Cr, 8Ni, 3Cu
‐Cr Cr
+Ni, .03C, 16.5Cr, 10Ni, 2Mo
+C
+Ti
+N
304LN
304H
316H
.06C, 18Cr, 8Ni
.03C, 16Cr, 10Ni, 2Mo
304HN
.06C, 18Cr, 8Ni, .1N
4037
321
.03C, 17Cr, 9Ni, .2Ti
+C
.06C, 18Cr, 8Ni
18Cr‐2Mo
.03C, 18Cr, 1.5Mo
+C
440 Series
304Cu
+Cu
‐Cr +Ni, +Mo
316
.01C,1.5Si, 12Cr
+N
18Cr‐2Mo
.4C, 12Cr
304
12 Chrome
12 Chrome
‐Cr
C
+M
o
420C
.05C, 17Cr, 8Ni, 3Cu
.03C, 18Cr, 8Ni
+Si
430FR
302HQ
+Cu
‐C
+S
.03C, 18Cr, 8Ni
.05C, 18Cr
+C, ‐Mo, +V
4116
303
430F
.38C, 15Cr, 1Mo
4035
+Cr, +M
o
302
.05C, 17Cr, 8Ni
+Cu
+S
4122
To PH & Duplex Stainless Steels
+Cr +Ni
303UX
.03C, 18Cr, 8Ni, 1.4Cu
4104
.13C, 15Cr, .3Mo
+C
+S
420B
.3C, 12Cr
301
.05C, 16Cr, 6Ni
.05C, 11Cr
+S
+C
+Cr, +Ni
409
‐C
.1C, 12Cr
+C, +Cr, +Ni
Austenitic
Ferritic
Martensitic
+Cr +Ni, +Mo
317
316LN
+Ti
.03C, 16Cr, 10Ni, 2Mo
316Ti
.03C, 16Cr, 10Ni, 2Mo, .2Ti
.03C, 19Cr, 13Ni, 3Mo
.65C, 12Cr
347
.04C, 19Cr, 9Ni, .4Cb
+C
r +
Ni
, +C
b
What is Stainless Steel
•
•
Martensitic
– 410, 416, 420
– Heat treatable (similar to alloy steels)
– Low work hardening rate
– Moderate corrosion resistance
Austenitic
–
–
–
–
•
409, 430, 430F, 430FR
Non heat treatable
Non‐heat treatable
Low work hardening rate
Good corrosion resistance
303, 304/304L, 316/316L, 321
Non‐heat treatable
High work hardening rate
Very good corrosion resistance
Precipitation Hardenable
Duplex
– 2205, 2507, 329
– Non‐heat treatable
– Very high chrome, moderate‐low nickel
– Very high work hardening rate
– Great corrosion resistance
Great corrosion resistance
Ferritic
–
–
–
–
•
•
•
Super Austenitic
–
–
–
–
–
904L, UNS S31254, UNS S34565
Non‐heat treatable
Very high chrome, very high nickel
Very high work hardening rate
Great corrosion resistance
– 630, 631, 15‐5, A286
– Heat treatable (age hardening reaction)
– Moderate work hardening rate
– Very good corrosion resistance
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What is Stainless Steel
• Austenitics
– Potable water, city atmospheres, food industry, chemical industry (sulfuric, phosphoric, organic), chlorides (salt, bleach), high temperature (8‐900F) , surgical/body parts, fittings, automotive sensors
g,
• Ferritics
– Solenoid valves/injectors, house appliances, oil burner nozzels
• Martensitics
– Pumps, valves, surgical tools, oil field parts, fittings, fasteners, spray nozzles
What is Stainless Steel
• Precipitation Hardenable
– Pumps, valves, surgical tools, oil field parts, fasteners, performance bicycle parts, automotive sensors
• Duplex
p
– Fuel rail parts, pumps for specialized acids
What is Stainless Steel
• Stainless steels were developed to resist corrosion
 The manufacturing to a part were more difficult than carbon steels
• Producers found ways to ease manufacturability
 Especially machinability
Especially machinability
 Increasing machinability has negative effects
– Weldability
– Corrosion resistance
– mechanical properties
• Designers need to be aware
 Need to understand the grade
 Need to balance costs
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Stainless Steels – How its Made
Melt in Arc Furnace
Starts with Scrap
The Melting Process
Remove Slag
Stainless Steels – How its Made
VOD
The Refining Process
Vacuum Degas
Final Ladle Treatment
AOD
Stainless Steels – How its Made
Vertical Caster
VAR
ESR
Ingot/Electrode Mold Casting
Optional
Horizontal Curve Mold Caster
The casting process
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4/1/2013
Stainless Steels – How its Made
The cogging process
Bloom
Press
Coil
Hot Roll
Bar
Billet
Rotary Forge
Stainless Steels – How its Made
Purpose
1) Put Cr back into solution
2) Soften
3) Condition Structure (PH)
Note: Can bypass annealing by:
1) Slow cooling
2) Direct water quench
The annealing process
Stainless Steels – How its Made
Martensitics handled differently than austenitics and ferritics
The annealing process
• Martensitics are slow cooled
• Austenitics and ferritics are water quenched
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Stainless Steels – How its Made
At this stage – The materials could be sold as is:
1) Billets and bar
2)
•
as treated
•
pickled •
ground – billets only
Coils
•
pickled
p
•
as treated
•
turned
Hot Finish Goods
OR
Bars and coils continue to cold finishing
Stainless Steels – How its Made
Wire Coil Finish Goods
Cold Draw
Coil to Coil
Cold Draw
Coil to Bar
Cold Draw
Bar to Bar
STRAIGHTENING
Galet hyperbolique
Barre à dresser
Hot Roll Bar
Avance hélicoïdale
Galet cylindrique
Bar Finish Goods
PEELING ‐ TURNING
Plaquettes carbure en rotation
GRINDING ‐ POLISHING
Galets entraîneurs
Galet d’entraînement
Meule
Barre à rectifier
Barre à écroûter
Avance hélicoïdale
Support en bronze
Stainless Steels – How its Made
Coil Finish Goods
• Spring Wire
• Escomatic Wire
• Cold Heading Wire
• Fine wire
• Shape Wire
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Stainless Steels – How its Made
Bar Finish Goods
• Machining bar
• Forge bar
• Shaped bar
• Shaft/Pump quality
Stainless Machining Bar
• Sold as annealed stock
– Cold drawing can follow annealing
• Sold to ASTM A484 size tolerances in US, ISO tables in Europe
– No standard grind tolerance in US system – ½ or ¼ tolerance
– Europe uses ISO table for ground stock, h, j, k
 Standard CD tolerance about equivalent to ISO J10
• End chamfering is available
• Cut lengths available
– Usually not able to re‐chamfer
Stainless Machining Bar
Other important Information
• ASTM Spec do not necessarily reflect reality
– Tensile values for cold drawn product will be much higher ASTM Mins
– Even hot rolled bars are higher then specs
• Be careful of datasheet values
– These are “typical” values, not absolute
• The letter behind the grade –
The letter behind the grade i.e. 304L
i e 304L
– “L” = low carbon
– “H” = high carbon
– “N” = increased nitrogen or nitrogen strengthen
– “LN” = low carbon, increased nitrogen
– “Se” = selenium addition
• European designation
• X5 CrNi 18‐10
1.4301
Nickel content
Chromium content
Carbon content x100
(ex : C=0,05%)
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4/1/2013
Summary
• Stainless is a difficult material to machine
• Stainless machinability not easily defined
– Many families
• There are many ways to produce bar
• It is important to marry tooling with grade
– Geometry/Grade/Coating
Stainless Steel
What it is and how its made
• What we talked about
– Define stainless steel
– What make a stainless steel stainless
– Discuss the many variations and their use
Discuss the many variations and their use
– How are stainless steels made
Thank‐you
y
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