EPNM 2012 Metallurgical Considerations in Hot Metalworking Bi-Metal Materials John Banker Vice...
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Transcript of EPNM 2012 Metallurgical Considerations in Hot Metalworking Bi-Metal Materials John Banker Vice...
EPNM 2012EPNM 2012
Metallurgical Considerations in Hot Metalworking Bi-Metal
Materials
John BankerVice President Customers & Technology
Dynamic Materials CorporationBoulder, CO, USA
EPNM 2012EPNM 2012Introduction
Explosion Welding is a proven, robust technology for manufacture of flat clad plates and concentric cylinders
Fabrication of these clad components into industrial equipment often requires high temperature metalworking operations
Controlling these procedures to simultaneously assure metallurgical quality of the cladding layer, base layer and interface in the fabricated equipment can be challenging
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Hot Cylinder Forming
Commonly used for clad steel >100mm thick
Typically performed at approximately-650 C to 900 CDependent upon steel composition and thickness
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Hot Head Forming
Commonly used for clad steel >25 mm tk
Typically performed at approximately-500C to 1100 C Dependent upon clad combination, steel type, and thickness
EPNM 2012EPNM 2012Hot Plate Rolling“Bang and Roll”
Typically used to produce clad plates <20 mm tk from thicker clad slabs
Performed at approximately-750 C to 1150 C Dependent upon clad combination, steel type, and thickness
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Base Metal Metallurgical Concerns
Steels are the dominant clad base metalSteel is selected for mechanical
strength and toughnessBase metal must meet Specification
Requirements after hot working, heat treating, and all fabrication work (UTS, YS, Impacts, etc)
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Typical Steel Hot Working Ranges
Figure 4. Iron-Carbon Phase Diagram
Typical Structural Steel Carbon Level
Austenitic Hot Working Range
Ferritic Hot Working Range
EPNM 2012EPNM 2012Typical Steel Heat Treatments to
Achieve Required Properties
900
650
20
Tem
pera
ture
(°C
)
Time (min)
Austentize
Water Quench Cooling + Temper
Normalize (still air cooling)
EPNM 2012EPNM 2012Cladding Metal Metallurgical Concerns
Corrosion Resistant Alloy (CRA) cladCladding metal is selected for specific corrosion
resistanceCladding metal is rarely considered in design
strength calculationsHigh temperature operations must be controlled
to assure corrosion performanceKey Factors: temperature, time at temperature,
heating and cooling rates Time-Temperature-Sensitization Curves show
relationships of Corrosion Properties vs Heat Treatments
EPNM 2012EPNM 2012CRA Groups from Hot Working
Perspective
Stainless Steels:Basic austenitic stainless steels- 304, 316, 321,
347, 317Super austenitic stainless steels- >= 5% MoDuplex stainless steels
Nickel Alloys Reactive metals- Ti & Zr Refractory metals – Ta & Nb
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Secondary Phases of Concern in Stainless Steels and Nickel Alloys
(Cr,Fe,Mo)23C6 600 – 950° C Cubic
(Cr,Fe,Mo,Cb)6C 600 – 950° C Cubic
(Cr,Fe,Mo)7C6 950 - 1050° C Orthorhombic
Nitrides (Cr,Fe)2N 650 – 950° C Hexagonal
Sigma σ (Cr,Fe,Mo,Ni) 550 – 1050° C Tetragonal
Laves η (FeCr)2(Mo,Nb,Ti,Si) 550 – 900° C Hexagonal
Chi χ Fe36Cr12Mo10 600 – 900° C Cubic
Carbides
Phase Composition Temperature Range Structure
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Austenitic Stainless SteelsCarbide Formation Major Concern
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Increased Alloying – Other Phases
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Duplex Stainless Steels
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Nickel Alloys
Some Alloys Very Slow or No High Temperature Sensitization Nickel 200: Unalloyed NiAlloy 400: 60 Ni – 40 CuAlloy 625: 61 Ni + 22 Cr + 4 Fe + 3.6 Cb + 9
MoAlloy 825: 42 Ni – 22 Cr – 32 Fe + 2.2 Cu + 3
Mo
Others Complex secondary phase development- Example Alloy C Family
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Nickel Alloy C Family Ni-Cr-Mo
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Nickel Alloy C Family Ni-Cr-Mo (alt)
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Reactive & Refractory Metals
Commonly used Reactive and Refractory metals exhibit no significant phase changes that affect corrosion performanceTitanium alloys Grades 1, 2, 16, 17 Zr alloys 700 & 702Tantalum and Ta-2.5W
EPNM 2012EPNM 2012Effects of Hot Working on Clad
Interface Properties
Stainless Steels & Nickel AlloysDiffusion w/in +/- 0.5mm of interfaceNo continuous brittle intermetallics
formedSlight decrease in shear strength due
to recovery of Cold Work at interfaceInterface retains toughnessExtremely difficult to disbond
EPNM 2012EPNM 2012Reactive Metal Clad InterfaceConcerns during Hot Working
Ti-Fe, Zr-Fe form several brittle intermetallic compounds
Exposure to Elevated Temperatures can Degrade Clad Interface Properties
EPNM 2012EPNM 2012Shear Strength of Titanium-Steel
EPNM 2012EPNM 2012Larson-Miller Parameter
Titanium – Steel Clad
EPNM 2012EPNM 2012Shear Strength of Zirconium-Steel
EPNM 2012EPNM 2012Reactive Metal Clad Steel
Hot Working Considerations
Optimum temperature range for Heat Teating and Hot Working Reactive Metal Clad is between 550oC – 700oCAvoid unacceptable degradation of interface
propertiesReduction in base metal yield strength at
forming temperatureBelow steel lower critical temperature
• Minimize changes to base metal structure and mechanical properties
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EPNM 2012EPNM 2012Typical Segmental Ti Clad Head9 m Diameter x (80 + 3) thick
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Hot Working Refractory Alloy Clad
TantalumReadily oxidizes in air above 300C Cold working is typicalIf hot working is mandatory, tantalum must be protected from airSome success with encapsulation in steel
EPNM 2012EPNM 2012Bang & Roll
Stainless Steels & Nickel Alloys Typical rolling at 1100 C to 900 C Single slab rolling for clad thickness <10% of total
thickness Pack rolling for greater clad % Reliable clad thickness uniformity Reliable product yields Some cladding alloys not possible to achieve both
cladding metal and base metal propertiesExamples: Duplex, Some C-family alloys
EPNM 2012EPNM 2012Bang & Roll
Titanium – Steel Clad Considerable tonnage of titanium clad has been produced
by single slab Bang & Roll Slabs up to 150mm thick, rolled product down to 5mm
thick Good thickness uniformity and rolling control up to 15%
clad ratio Difficult to achieve both good bond strength AND base
metal of Pressure Vessel Quality Test work by Hardwick indicates that a Nb interlayer may
allow higher temperature rolling, possibly reducing the steel quality issues
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Conclusions
Explosion Clad plates can be formed and fabricated into reliable industrial equipment by Hot Metalworking
With Proper Selection of Alloys & Procedures, no compromise inCladding Metal Corrosion PropertiesBase Metal Mechanical PropertiesClad bond quality
With the Wrong Procedures, it is easy to make expensive trash quickly