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Methodology to Eliminate Automotive Forged Component Distortion

Manish Mehta1 and B. Lynn Ferguson2

1National Center for Manufacturing Sciences (NCMS)2Deformation Control Technology, Inc. (DCT)

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Outline

Quantitative Measurement of Steel Transformation (QMST)

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• Background & Rationale• Project Accomplishments• New Collaboration Opportunities• Case Studies in Distortion Modeling

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Heat Treatment of Forged Steel

• Produces – Hardness, Strength and Toughness– Dimensional Change (Size and Shape)– Residual Stress

• Surface Compression is Beneficial• Surface Tension is Detrimental

• Correcting Distortion Problems or Poor Residual Stress State Results in Added Manufacturing Process Cost– Finish Machining, Grinding– Straightening, Bending– Shot Peening, etc.

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• ASTM A-1033 Standard Practice (A01.13)– Obtaining and Archiving Quantitative Steel Transformation

Kinetic Data and Thermal Strain Data. – Quantitative Dilatometry– Complete Set of Data for SAE 1050 and SAE 8620

• Jointly Addresses Needs of Value Chain to Predict:– Microstructure– Properties– Distortion and Dimensional Change

QMST Project Accomplishments

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• American Axle & Mfg.• Caterpillar• DaimlerChrysler• Deere and Co.• Deformation Control

Technology, Inc.• Dynamic Systems, Inc.• Ford Motor Co.• GKN, Inc.• Ispat Inland Steel• MacSteel• Metaldyne

• North Star Steel• Thyssen Krupp Stahl• Timken Steel Corp.• Torrington• Oak Ridge National

Laboratory• Sandia National Laboratory• Colorado School of Mines• NIST• TRC- NCMS• American Iron and Steel

Institute• U.S. Dept. of Energy

QMST Participants

Technical Manager: Dr. Tom Oakwood

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• Lack of Standard Procedures for Collection, Analysis, Reporting of Steel Transformation Data and Transformation Strain Data

• Available Data is Limited and Qualitative–Meant for Use as Guidelines, NOT Modeling – Hinders Realization of Key Benefits of Modeling

• Product Quality Assurance, Energy Savings, Lean Manufacturing, Waste Reduction

QMST Rationale

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0

100

200

300

400

500

600

700

800

1 10 100 1000 10000Time (s)

Tem

pera

ture

(o C

)

F

P

B

M

Typical CCT Diagram for Steel

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-0.002

0

0.002

0.004

0.006

0.008

0.01

0.012

0 100 200 300 400 500 600 700 800 900

Temperature, Deg. C

Lin

ear

Str

ain

Transformation Data

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• Resistance Heating and High Speed Quench Dilatometers

• Determination of Ac1 and Ac3

• Thermal Cycles– Isothermal Transformation– Continuous Cooling Transformation

• Metallographic Procedures• Data Format and Reporting Procedures

ASTM A-1033 Standard

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• Improved Product Consistency and Quality• Improved Process Efficiency Through Standardization• Reduction in Testing Trials• Reduction in Non-Conforming Materials and Parts• Reduction in Non-Value Added Operations• Reduction in Manufacturing and Energy Costs• Supports Lean Production

Steel Supply Chain Benefits

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• ~19M Tons of Carbon and Alloy Steel Per Year That is Thermally Processed

[Source: 2002 AISI Steel Shipment Data]

• The Biggest Single Contributor to Energy Consumption Was During Heat-up for Rolling, Forging, Heat Treatment, etc.

Projected Impact on US Industry

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New Collaboration Opportunities

• Populate Transformation Database Using ASTM A1033• Extend Distortion Modeling Studies to Additional Parts• Develop Standardized Test Procedures for Phase

Transformation Measurement Under Austenite Deformation Conditions

• Contact:– David Anderson, AISI, (248) 945-4764,

andersnd@autosteel.org– Manish Mehta, NCMS, (734) 995-4938,

manishm@ncms.org

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Distortion Case Studies:Steel Phase Transformation Kinetics

B. Lynn FergusonDeformation Control Technology, Inc.

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Computer-Based Approach to Heat Treat ModelingQMST Project

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Dilatometry Curves (MMC Continuous Cooling)

Data from Oak Ridge National Laboratory QMST Project Sponsored by AISI, DOE, TRC/NCMS

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Heat treating processes:• Heat up• Carburize• Quench

Material:• Carburized 8620 Steel

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Marine Crankshaft : Temperature AnimationDimensional Change is Magnified x25

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Marine Crankshaft : Austenite AnimationDimensional Change is Magnified x25

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Marine Crankshaft : Final Length Dimensional Changex25

mm

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Automotive Transmission Shaft

• 8620 Steel • Carburized• Quenched(Austempered)

Requirements• hardness• toughness• fatigue strength• straightness

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Carbon Profile, weight fraction

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Austenite Volume Fraction - Animation

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Minimum Principal Stress, MPa

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Minimum Principle Stress, MPa

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Bainite Distribution

Martensite Distribution

Carburized and Austempered 8620 Shaft

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Summary

• Phase Transformations of Steel Directly Affect Part Performance

• Phase Transformations of Steel Directly Affect Process Economics

• Once Kinetics are Quantified, Computer-based Simulations Can Be Run for Purposes of Prediction, Process Modifications or New Product Development

• Phases Formed and Distribution• Residual Stress

• Correcting for Distortion• Scrap / Rework