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AUTOMOBILE STEEL WHEELSThe Road to Dual Phase

Thomas HeckHayes Lemmerz International


AUTOMOTIVE STEEL WHEELSThe Road to Dual Phase

• Automotive Wheels Have Been Manufactured From Many Materials Through Out The History Of The Automobile:

• Wood• Steel (Casting, Sheet or Wire)• Aluminum (Casting, Forging, or Sheet)• Magnesium• Composites (FRP)• Combinations of the Above



• From The Early Days Steel Has Been A Predominant Choice For Wheel Materials:

Pressed Steel Wheel

Circa 1910

Early Wire Wheel

Circa 1920



• The Age of Steel (1935 – 1980s): During This Period Steel Wheels Dominated The Automobile. By 1935 Wheel Diameters Had Decreased From 36” To 16” And Rim Widths Increased From 3”to 6”. The Processes Of Stamping The Center (Disc) And Rolling The Rim Were Well Suited For High Volume Low Cost Production.



• Hot Rolled Low Carbon Steel Grades Were Predominant For Wheels Prior To The 1970s And Continue To Be Used Primarily on Rims Today:

• Discs: • Rimmed 1012/1015 HRLC

• High Formability – Low Alloyed Outer Surface• Converted to Continuous Cast 1012/1015 HRLC

• Rims: • Mechanically Capped 1008/1010 HRLC• Converted to Continuous Cast 1008/1010 HRLC

• Still the Predominant Steel Alloy for Rims



• The Early To Mid 1970s Brought The Need To Reduce Weight And Led To The Introduction Of Higher Strength Steels Into Wheels:

• North America: 955X / 960Y HSLA Grades• Precipitation Hardening w/Cb Additions for Grain Refinement

• Europe: Dual Phase Grades• DP550 – Initially Si Chemistry

• Japan: SAPH 45 – 60 HSLA Grades• C-Mn Grades with Improved Formability



• This Demand For Higher Strength Steels Along With A Need To Maintain Formability Led To The 1st Attempted Use Of Dual Phase Steel For Wheels In North America:

• Mid 1970s – SAE980X Continuously Annealed Dual Phase• Motor Wheel Corporation: AMC Wheel• Kelsey Hayes: Cadillac Wheel

• Both Attempts Discontinued – Production Steel Problems• Material Property Inconsistencies• Surface Cosmetics due to High Si Levels



• The 980X Experience Resulted In North American Wheel Manufacturers And OEMs Reluctant To Pursue Dual Phase Steel For Wheels:

• Micro-Alloyed HSLAs became the Standard for North American Light Weight Steel Wheel Applications

• Dual Phase / Bainitic Steels became the Standard for European Light Weight Steel Wheel Applications



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Disc Europe Disc NorthAmerica

2002 MY Steel Grade Usage - Automotive Wheels

Bainitic(HR45-60)Dual PhaseHSLAHRLC



• Renewed Interest in Dual Phase:• Aluminum Wheel Penetration

• Advantages of Styling and Weight• Need for Improved Formability

• High Vent Wheel Development• Renewed Need for Weight Reduction• Dual Phase Development for Ford “Impact” Program• Development of Cr Based DP Chemistry

• Increased Availability



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%Aluminum %Steel

Wheel Material Usage 1980 - Present



• 1999: Hayes Lemmerz Began An Investigative Study Into Utilizing Dual Phase In Steel Wheels:• Trial DP Steels from 7 Global Suppliers:

• 2 North American• 1 South American• 2 European• 2 Asian

• Chemistry:• Si (4 Suppliers)• Cr (3 Suppliers)


Attributes Evaluated (Dual Phase vs HSLA):

Fatigue StrengthHigher Base Tensile Strength

87 ksi min. vs 75 ksi min.Greater Work HardeningPaint Bake Hardening

FormabilityLower Yield to Tensile Ratio

0.60 - 0.70 Typical vs 0.80 – 0.90




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Production060 HSLA

Supplier #1Si=1.2%

Supplier #2Si=1.0%

Supplier #3Si=1.1%

Supplier #4Si=0.2%

Supplier #5Si=.02%

Supplier #6Si=1.1%

Dual Phase Supplier - Si Level

Average Rotary Fatigue Life Comparison15x6 Drop Center Wheel



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Production - 060 HSLA Supplier #4 - Si .02% Supplier #5 - Si 1.1%Dual Phase Supplier - Si Level

Average Rotary Fatigue Life Comparison15x7 Full Face Wheel



Wohler Curve Comparison – Dual Phase vs HSLA



• Evaluation Results: Benefits Confirmed

• Fatigue Performance Improvement• Typically 50% or Greater Increase

• Allows for 10% Gauge/Mass Reduction

• Formability• Reduced Forming Scrap• Reduced Leuder (Strain) Lines



• Evaluation Results: Concerns• Cosmetics

• “Tiger” (Silicon) Stripes• Formability

• Higher Work Hardening (n-values)

• Redesigned Die Operations

• More Forming Up Front

• Consistency

• Heat to Heat Variation (1970’s Experience)

• Availability and Cost



• Going Forward:

• 2006 MY Production Dual Phase Programs• Flex Wheel Programs

• Cr Chemistry Dual Phase Specified• 2 Suppliers Identified

• Additional Steel Suppliers to be Evaluated



• I’d Like to Acknowledge the Following Contributors:• Steel Companies:

• USS / National Steel• Kobe• Usinor• Usiminas

• Personnel• Alan Coleman (Hayes Lemmerz)• Mike Miller (Hayes Lemmerz)• Hayes Lemmerz Sedalia, MO Plant• Chuck Gregoire (National Steel)• Weiping Sun (National Steel)• Dave Ruhno (USS)• Garth Lawrence (Smithers Scientific)


DEVELOPMENT OF HIGH CHROME

DUAL PHASE FERRITE-MARTENSITE

STEEL FOR WHEELS APLICATION

João Alfredo GrittiArvinMeritor


AUTO INDUSTRY DEMAND FOR WHEELS IN THE LAST 7 YEARS

• Cost Reduction

• Weight Reduction

• Durability (+ fatigue)

• Appearance

• Better Uniformity

• Increase in Size


ARVINMERITOR STEEL APPLICATION

– Until 1986• Mild Steel - Carbon/Manganese

Y. S. = 240 MPa Minimum (35 ksi) T. S. = 350 MPa Minimum (50 ksi)

for disc and rim application



– End of the 1980’s• High Strength Low Alloy - T. S. = 450 MPa (65 ksi) for disc and rim application (similar SAE J1392 050 YK)

• Hardening and grain size refining through precipitation of a very fine carbonitrides in the ferritic matrix.


– 1992 / TWO POSSIBILITIES•Continue to increase T. S. through the precipitation hardening (Nb - Nb + Ti Microalloys).

Limitation: poor formability

•To develop the hardening by a phase transformation produced by a controlled cooling at the hot rolled mill with high formability.



– BAINITIC STEEL (SIMILAR SAE J1392 070XF)•HSLA development - T. S. = 550 MPa (80 Ksi) for disc and rim application•Transformation hardening steel (Japanese Concept) 5% weight reduction for disc application (compared to Nb Microalloyed)

•Improved formability, weldability and behavior at the hole expansion test. Very good fatigue performance.

– Application: Toyota, DaimlerChrysler and Honda



– 1994 / DUAL PHASE STEEL DEVELOPMENT•Hardening through a martensite phase produced by a controlled cooling at the hot rolled mill, for disc application.

•Dual Phase is currently used by Japanese and Germany Industries which reduced the disc weight 5 to 8 % (compared to Bainitic Steel).

– Limitation: Maximum Thickness 4.5 mm•Only for Disc Application•Surface Quality (Red Scale)•Simple Design Application



DUAL PHASE STEEL

Microstructure 4% nital - 500x


DUAL PHASE STEEL

Microstructure Metabissulphite - 500 X


Chemical Composition

DUAL PHASE STEEL

Material (Wt %)

C Mn Si P S Al Cr Ca Nb

Dual Phase Steel 0,08 1,14 0,97 0,015 0,003 0,030 0,10 0,0014 ---

Bainitic Steel 0,08 1,40 0,12 0,015 0,002 0,025 --- 0,0014 0,030

Nb Microalloy 0,10 0,55 0,02 0,016 0,008 0,045 --- --- 0,023


DUAL PHASE STEEL

Typical ResultsMaterial YS TS YS/TS El (%)

(MPa) (MPa) (GL: 50 mm)

Dual Phase Steel 390 (57 ksi) 650 (95 ksi) 0,60 26

Bainitic Steel 480 (69 ksi) 596 (86 ksi) 0,80 25

Nb Microalloy 390 (57 ksi) 488 (71 ksi) 0,79 31

Mechanical Properties


Thickness: 3.80 mm

USI-RW-600DP

B10%=105.310 ciclosDual Phase Steel

USI-RW-550

B10%=32.447 ciclosBainitic Steel

USI-RW450B10%=23.229 ciclosNb Microalloy

FATIGUE BEHAVIOR DP STEEL WITH Si


Wheel DesignWheel 6 J x 15H2

PRODUCT APPLICATION DAIMLER CHRYSLER WHEEL


6 J x 15 CH WHEEL

FATIGUE BEHAVIORDP STEEL AND Nb Microalloy


RED SCALE


– 1999 / DUAL PHASE HIGH CHROME •Hardening through a martensite phase produced by a controlled cooling at the hot rolled mill, for disc application.

– Material developed to eliminate red scale

– Limitation: Maximum Thickness 4.5 mm•Only for Disc Application•Simple Design Application



Chemical Composition


Material (Wt %)

C Mn Si P S Al Cr Ca N

Dual Phase Si 0,08 1,14 0,97 0,015 0,003 0,030 0,10 0,0014 0,0047

Dual Phase Cr 0,07 1,20 0,03 0,060 0,002 0,025 0,58 0,0023 0,0054



Typical ResultsMaterial YS TS YS/TS El (%)

(MPa) (MPa) (GL: 50 mm)

Dual Phase Si 390 (57 ksi) 650 (95 ksi) 0,60 26

Dual Phase Cr 402 (59 ksi) 637 (93 ksi) 0,63 25

Mechanical Properties


FATIGUE BEHAVIOR DPSTEEL THICKNESS 3.80mm



Application of HSLA material provides the following possibilities in terms of weigh reduction.

RIM Nb Microalloy Bainitic Steel10%

Bainitic Steel DP with Cr5 to 8%

DISC Nb Microalloy Bainitic Steel5 to 8%



Tensile Strength (MPa)

350 400 450 500 550 600 650 700

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Q1 Meritor GradeC - Mn - Steel

Q4 Meritor GradeNb Microalloy

Q7 Meritor GradeBainitic Steel

Q8 Meritor GradeDual Phase Steel


THANK YOU!



Sponsored by: American Iron and Steel Institute

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