ImprovedLightweightManufacturingFlexibilitybyStampingofSelec<velyLaserHeatTreatedBoronSteelSheet

NaderAsnafi1,RogerAndersson2,Mar0nPersson3andMagnusLiljengren4

1VicePresident&CTEO,VAAutomo(ve,&ProfessorofMechanicalEngineering,ÖrebroUniversity,Sweden(nader.asnafi@oru.se,+46703110074)

2CEO,DurocSpecialSteel&SeniorResearchManager,SwereaMEFOS,Sweden3CEO,DurocLaserCoa(ng,Sweden4CEO,IndustrialDev.CentreinOlofström&Researcher,SwereaIVF,Sweden

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ImprovedLightweightManufacturingFlexibilitybyStampingofSelec<velyLaserHeatTreatedBoronSteelSheet

NaderAsnafi1,RogerAndersson2,Mar0nPersson3andMagnusLiljengren4

1VicePresident&CTEO,VAAutomo(ve,&ProfessorofMechanicalEngineering,ÖrebroUniversity,Sweden(nader.asnafi@oru.se,+46703110074)

2CEO,DurocSpecialSteel&SeniorResearchManager,SwereaMEFOS,Sweden3CEO,DurocLaserCoa(ng,Sweden4CEO,IndustrialDev.CentreinOlofström&Researcher,SwereaIVF,Sweden

Objec<vesandGoals

•  Greatermanufacturingflexibility•  Noprocess-boundequipment•  Lowercosts•  In-houseproduc<onoreasily/temporarilyoutsourcedproduc<on•  Reducedlead<me•  Greaterweightreduc<on

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Background= heat treated Selec<velaserorinduc0onheattreatmenttolocally

o  improve the blank formability and/or trimabilityAND/OR

o  reinforce the component to accomplish therequiredcomponentstrength/behaviour.

The size, posi0on and shape of this heat treatmentgrid is decided during the ini0al analysis of therequiredblankandcomponentproper0es.Heattemperatureexamples:

o Carbon&stainlesssteelsheet:925-1250°Co SheetAluminium/Automo0ve(5000-&6000-series):200-400°C

o SheetMagnesium:100-350°Co SheetTitanium:925°C

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CO2 Laser Heat Treatment/Hardening

Fiber Laser Heat Treatment/Hardening

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BackgroundPilotstudy

Material

C (%) min-max

Si (%) min-max

Mn (%) min-max

P (%) max

S (%) max

Cr (%) min-max

B (%) min-max

Boloc 02 0.20-0.25 0.20-0.35 1.00-1.30 0.030 0.010 0.140-0.260

0.0015-0.0050

Material Thickness (mm) Re (MPa) Rm (MPa) A80 (%)

Boloc 02 1.0 ca 340 ca 480 28

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Materials

FlexrailBlankShapeandSize500

107.79

118.12

Blankposi<oningsupport

350

Sheetmaterial=Boloc02Sheetthickness=1mm

Rollingdirec<on

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ExperimentalProcedureSelectedTestComponent-Flexrail

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ExperimentalProcedureTheFlexrailStampingTool/DieSet

Sheetmaterial=Boloc02Blanksize=350mmx500mmSheetthickness=1mm

500

350

25

25

20

20

20

Rollingdirec<on

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ExperimentalProcedureTheLaserPa]ern

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ExperimentalProcedureTheLaserPa]ern

Boron Steel Boloc02 Blank Manufacture Laser Heat Grid Laser Heat Grid

Flexrail produced?

Flexrail Property and Performance

Testing and Reporting

Production Process

Designation

Reference

GridTube

GridBlank

Yes

Yes

Yes

RapidLaser Yes

Laser speed = 500 mm/min

Laser speed = 1500 mm/min

Laser speed = 5000 mm/min

Room Temp. Stamping of the Flexrail

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ExperimentalProcedureFour(4)FlexrailProduc<on&Tes<ngRoutes

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GridBlank6,BP=90bar,

TrimmedBlank

GridBlank2,BP=100bar

GridBlank3,BP=90bar

GridBlank9,BP=90bar,

TrimmedBlank,1mmShimming

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ExperimentalProcedureStampingParameterSecng:GridBlankRoute–“Tryout”Flexrails

Boron Steel Boloc02 Blank Manufacture Laser Heat Grid Laser Heat Grid

Flexrail produced?

Flexrail Property and Performance

Testing and Reporting

Production Process

Designation

Reference

GridTube

GridBlank

Yes

Yes

Yes

RapidLaser Yes

Laser speed = 500 mm/min

Laser speed = 1500 mm/min

Laser speed = 5000 mm/min

BP = 90 bar, Trimmed Blank, 1 mm Shimming

Room Temp. Stamping of the Flexrail

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ExperimentalProcedureFour(4)FlexrailProduc<on&Tes<ngRoutes

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ResultsandDiscussionFlexrailstampedaccordingtotheReferencetrack

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ResultsandDiscussion1mmthickBoloc02GridBlankLaserTreatedBoronsteelsheet

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ResultsandDiscussionTheGridBlankPlacedintheStampingToolPriortoForming

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ResultsandDiscussionStampingof1mmthickLaserTreatedGridBlankBoloc02@roomtemperature

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ResultsandDiscussionFlexrailstampedaccordingtotheGridBlanktrack

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ResultsandDiscussionFlexrailstampedaccordingtotheGridTubetrack

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ResultsandDiscussionLaserRobotPathGenera<onBasedontheScannedShapeofGridTubeFlexrail

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Results of the test run 12 - Sheet material = Boloc02 - Sheet thickness = 1 mm - Spot size and shape ≈ 5 mm - Laser speed = 25 mm/s - Laser effect = 32% - Temperature = 1500-1530° C - The sheet graphatized before laser processing - No cooling used at any time (except still air) - Measured case hardness ≈ 550 HV

Testrun12

laserproce

ssingparam

eterswere

selected

astheoper

a<onalpro

cessparam

eters

ResultsandDiscussionLaserProcessingParametersfortheGridTubeTrack(Determinedexperimentally)

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ResultsandDiscussionGridPa]ernApplica<ontotheFlexrailfollowingtheGridTubeTrack

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ResultsandDiscussionFlexrailProducedAccordingtotheGridTubeTrack

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ResultsandDiscussion1mmthickBoloc02RapidLaserTreatedBoronsteelsheet(Astrainmeasurementgridisalsoappliedtotheblank)

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ResultsandDiscussionFlexrailProducedAccordingtotheRapidLaserTrack

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Boron Steel Boloc02 Blank Manufacture Laser Heat Grid Laser Heat Grid

Flexrail produced?

Flexrail Property and Performance

Testing and Reporting

Production Process

Designation

Reference

GridTube

GridBlank

Yes

Yes

Yes

RapidLaser Yes

Laser speed = 500 mm/min

Laser speed = 1500 mm/min

Laser speed = 5000 mm/min

BP = 90 bar, Trimmed Blank, 1 mm Shimming

Room Temp. Stamping of the Flexrail

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ExperimentalProcedureFour(4)FlexrailProduc<on&Tes<ngRoutes

100%=100kN

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ResultsandDiscussionForming/StampingPunchForce

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100%=100kN

ResultsandDiscussionGeometricalShape/Springback

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A

C

X Y

Z

XA

Origo

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ResultsandDiscussionGeometricalShape/Springback

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ResultsandDiscussionGeometricalShape/Springback

RefGridBlank

GridTubeRapidLaser

Z

Origo

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ResultsandDiscussionGeometricalShape/Springback

RefGridBlank

GridTubeRapidLaser

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ResultsandDiscussionGeometricalShape/Springback

RefGridBlank

GridTubeRapidLaser

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ResultsandDiscussionGeometricalShape/Springback

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ResultsandDiscussionGeometricalShape/Springback

RefGridBlank

GridTubeRapidLaser

α (°) β (°)

SectionA-A Reference 7.19 16.95GridBlank 5.69 16.29GridTube 5.29 21.41RapidLaser 8.13 17.10

SectionB-B Reference 4.74 16.90GridBlank 3.25 15.40GridTube 5.76 20.60RapidLaser 6.63 15.47

SectionC-C Reference 9.18 17.45GridBlank 5.42 16.40GridTube 10.81 18.64RapidLaser 10.00 18.36

Longitudinal Transverse

- -

++

50 mm

ResultsandDiscussionFlexrailHardness(HV)

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ResultsandDiscussionFlexrailHardness(HV)

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ResultsandDiscussionFlexrailHardness(HV)

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ResultsandDiscussionFlexrailHardness(HV)

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ResultsandDiscussionFlexrailHardness(HV)

SummaryandConclusions •  It is possible to tailor boron steel sheet component properties by selective

laser heat treatment. This selected laser heat treatment can be conducted on the - blanks prior to stamping at ambient (room) temperature or - component after stamping at ambient (room) temperature.

•  The GridBlank production route, in which 1 mm thick blanks of Boloc 02 was - selectively laser heat treated, - allowed to cool down (still air cooling), - transported to the stamping plant where it was stamped at ambient (room) temperature,

yields the best component (flexrail) shape accuracy and the best hardness (700 HV) but required 41% higher maximum press force than the none laser heat treated Boloc 02.

•  The selective laser heat treatment of the sheet material (the blank) before stamping yields the most efficient and flexible route for large volume production.

The laser heat treatment can be conducted at the material supplier or at a supplier between the material supplier and the stamping plant or at the stamping plant. The existing press/stamping lines can be used as usual.

The investigation continues…

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