10 03 iehk- gkn presentation
TRANSCRIPT
Grain Stabilized 16-20 MnCr5 for Inner Races & Tripods
OverviewNithin SHARMA | 10/03/2015
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Content
Introduction
Process flow for Inner Races (IR) & Tripods
Industrial Experience
Potential Improvements
Draft Plan for Master Thesis
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INTRODUCTION
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Continuous Velocity Joints (CVJ) [Fixed Joints]
Fixed Ball AC Joint
Fixed Ball Joint UF
Fixed Joint countertrack
Inner Races
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Continuous Velocity Joints (CVJ) [Plunging Joints]Tripod GI
Tripod AARiTrunion
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Why Nb Steels?
Nb has threefold influence on Mechanical properties of Steel:• Grain size refinement during Thermo Mechanical Treatment hot forming• Lowers the, Austenite Ferrite transition temperature• Precipitation hardening
Problems with Nb steels:• Clealiness
These effects are used in low, medium and high carbon engineering steels for different automotive applications
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Problem Statement
Grain Size Scale ASTM
Coarse Fine
Coarse grain formation in the Heat Treated Cold & Warm forged, Case Carburized components (IR & Tripods )
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Inner Race
Location Grain Size
Sphere Core ASTM 3 - 4
Location Grain Size
Track Vertex Case ASTM 7 - 8
Coarse Grains
Inner Race
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Tripod
Coarse Grains
ASTM 3-4
Trunion
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PROCESS FLOW
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State of the Art in GKN Driveline (Forming Process)
Inner Races
LEG(Spain)
TRI(Germany)
OLE(France)
PRESTA(Lichtenstein)
AC Warm Cold
UF Cold
DO
Tripods LEG TRI OLE PRESTA
AAR WarmGIiGI3
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State of the Art in GKN Driveline (Process Flow IR & Tripods)
Material
Cropping
Annealing
Shotblasting
Inner Races Tripods
• The steel bar is pushed through the driver until the length stop. The mobile blade is moved cropping the steel bar into billets
• Shear deformations are introduced during cropping.• Annealing Temperatures : ? (unknown)
• Ensures removal of scale, after forging and HT related to forged parts
16 MnCr5/ 20 MnCr5 16 MnCr5 (AAR) / 20 MnCr5 (GI)
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State of the Art in GKN Driveline (Process Flow IR & Tripods)
Coating
Preforming
Stress Relief • Process time and temperature is dependent on material specification.?
(Unknown)
Coating
• The preforms are loaded into a drum. The drum is submerged into a series of baths in order to clean the pieces and coat them with phosphate and soap
• Pickling, Rinse, Phosphate, Rinse in neutraliser, Soap
Inner Races Tripods
Forming at room temperature
Warm forming at temperature 925º C
NA X NA
Shotblasting
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State of the Art in GKN Driveline (Process Flow IR & Tripods)
Weight grading
Final forming
Case carburising
Inner Races Tripods
Forged at room temperature
NA
X NA
Shotblsting
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State of the Art in GKN Driveline (Process Flow IR)
Material
SB;CO
SB;CO;WG
Annealing
Preforming
Stress Relief
CP
Final forming
Case carburising
CP: CroppingSB: ShotblastingCO: CoatingWG: Weight grading
Temp Involved Strain Involved
Tem
pera
ture
Time
Temper 165 -190ºC, 1-2 hrs
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State of the Art in GKN Driveline (Process Flow Tripods)
Material
SB
SB;CO
Material
Annealing
Preforming
Stress Relief
Case carburising
CP
CP: CroppingSB: ShotblastingCO: Coating
Temp Involved Temp + Strain
Involved
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INDUSTRIAL EXPERIENCE
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Industrial Experience: MS43 (16MnCr5) steel with Nb
Increase in Nb results in decrease of C = High volume fraction of Nb[C,N]
Tem
pera
ture
Time
1 hour, 900 - 920º C
Heat Up
Air Cool
Final forming
Case carburising
Normalizing
0.05% Nb addition to 0.14% C, prevents coarse grain formation, for joints treated with inter stage annealing or normalizing treatments
Addition of Al formed coarse AlN precipitates, therefore a controlled TMT in hot rolling can ensure that Al addition to be utilized to form maximum volume fraction of AlN in fine form in the as rolled bar
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Industrial Experience:16MnCr5 steel with Nb in Auburn Hills= 16MnCr5
Al/N2 ratio of 2:1 is preferred
Nb[C,N] present in the solution is more effective than AlN (since the later forming coarse precipitates)
Ressistance of coarse grain formation ~ Vf of Nb [C,N]
Proposed to increase times in carburising furnace temperature
For maximum volume of [C,N] modifications on Temperatures of Roll Mill & Slab soaking can be done
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Industrial Experience:16MnCr5 steel with Nb in Auburn Hills
Location Grain Size
Sphere Core ASTM 3 - 4
Location Grain Size
Track Vertex Case ASTM 7 - 8
Inner Race
Coarse Grains
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POTENTIAL IMPROVEMENTS
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Potential Improvements
Grain size is influenced by processing conditions
Important to understand the process chain from end to end
Need quantitative data for process steps like :
* Temperature & time;
* Microstructure study; TEM observations
* Degree of deformation and strain induced during forging;
* Microstructure study (Grain Size); TEM observations (Precipitates Size)
When informed with all process parameters, simulate the kinetics of AlN/ Nb(C,N) precipitates using MATCALC, THERMOCALC software and try to validate
- reduces time and cost
- greater flexibility
Annealing
Preforming
Stress Relief
Final forming
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PLAN FOR MASTER THESIS
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Which Process Flow?
* Tripods warm forged
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Which Simulation Software?
MATCALC
Precipitation kinetics can be studied with this software
Optimal processing parameters may be defined, leading to optimal particle pinning and thus inhitbited grain coarsening
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Probable procedure followedSimulation of the precipitate evolution as function of chemical composition and thermo-mechanical processing in terms of mean radius volume fraction by MATCALC
Comparison of experimentally investigated precipitation sizes and validation of simulation parameters
Evaluation of the Zener force according to precipitate size and volume
Optimization of the processing parameters in order to achieve maximum Zener forces
Note: The above following approach was followed by Patrick Fayek, Thomas Petermann and Dr Prahl at IEHK, Aachen on the project titled „ Simulation of Precipitate and Grain-Size Evolution in Case Carburizing Steels“.
Chemical Composition TMT Processing
MATCALC
Precipitate size distribution Precipitate volume fraction
Zener Force
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THANK YOU!