tool and die design for deep drawing ahss - autosteel

Institute for Metal Forming TechnologyProf. Dr.-Ing. Dr. h.c. Klaus Siegert

Prof. Dr.-Ing. Dr. h.c. Klaus SiegertDipl.-Ing. M. Vulcan

Tool and Die Design for Deep Drawing AHSS

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Stuttgart UniversityInstitute for Metal Forming Technology

High Strength Steel Sheets

Cushion Systems and Die Design

Stretch Drawing of Flat Parts

Controllable Draw Beads

Summary

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1975 1975 1980 1980 1985 1985 1990 1990 1995 1995 20002000

Source: ThyssenDevelopment of High Strength Steels

Increase of strength by microstructural changeMultiphase Steel

Concerted control of grain refining by addingTitanium

Isotropic Steel

Solid solution hardeningHigher-Strength IF-Steel

Diffusion of interst. N und C to increase the yield strength

Bake Hardening Steel

Embedding hard martensite parts in ferritic matrixDual Phase Steel

Solid solution hardening by adding phosphorusPhosphorus-Alloyed Steel

Hardening by carbides of micro alloy elements Ti, Nb, V

Micro-Alloyed Steel

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El

onga

tion

atFr

actu

reA

80 (%

)

Tensile Strength Rm (MPa)

50

0

10

20

30

40

60

200 300 400 500 600 700 800 900

TRIP - SteelTRIP 700TRIP 800

IF- SteelIF 180IF 260

Bake Hardening -

SteelHSLA 180BHHSLA 300BH

Micro AlloyedHSLA 260HSLA 420

Phosphoralloyed

HSLA 220PHSLA 300P

1000 1100

IsotropicHSLA 220iHSLA 280i

Complex-Phase -Steel

CP-W 800CP-W 1000

Martensite-Steel

MS-W 1000MS-W 1200

Dual-PhaseSteel

DP 500DP 600

Comparison of Different Steel Grades

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Source: IFU

Flow Curves of Actual Sheet Metals

FePO4

200

500

0,10

700

kf

900

[N/mm²]

0,150 gϕ

100

300

400

600

IF 260

DP 500DP 600

TRIP 700

0,05Logarithmic True Strain

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Source: Birzer

0,923574381DP 600

rm = 1,530400320280220HSLA 220 BH

10869567DP 800

0,7613501150MS 1200

14903793CP 800

0,820-30850680TRIP 700

16735583DP 700

High and Advanced High Strength Steels

rm = 1,326480400360300HSLA 300 BH

rm = 1,428440360320260HSLA 260 BH

rm = 1,932380300240180HSLA 180 BH

High Strength Bake-Hardening Steels

90°45°0°maxminmaxmin

R-ValueElong. at Fracture A80 in %

UTS in MPaYield Strength in MPa

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Summary

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GripperBlankholder

Hydraulic ValvesPunch

Frame

Source: T. Krockenberger, IFU

Test Equipment for Stretch Drawing followed by Deep Drawing

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Test Equipment for Stretch Drawing followed by Deep Drawing,Installed in Single Acting Hydraulic Press at IFU

Source: T. Krockenberger, IFU

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Source: D. Vlahovic, IFU

First Stage: Clamping the Sheet

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Second Stage: Predefined Stretching of the Sheet

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Third Stage: Tool Closing

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Last Stage: Deep Drawing of the Sun Roof Panel

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Principal Strain after Deep Drawing


Results FEM Process Simulation

Principal Strain after Pre-Stretching

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Summary

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Springback Reduction:

Increased Wall Stresses in the Straight Sides by Driving the Active Drawbeads Upwards.

Guideline: σWall< 0,8 σFracture

SafetyFactor

σFracture

σz, Wall, Basic

σz, Wall, Drawbead

Safety Distance

Desired Wall Stress DistributionSource: S. Beck, IFU

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Safety Distance

Additional Force by IncreasedBlankholder Force and/orIncreased Drawbead Height

Intention: Improved Wall Quality by Introducing Additional Forces

Desired Punch Force TrajectorySource: S. Beck, IFU

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Side Wall Stress SensorSource: S. Beck, IFU

Elastic Hinge

Load Cell

Force in theSheet

Vertical Force Horizontal Force

in the Sheet(Restraining Force)

Side Wall StressSensor

Punch

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Drawbead 3 Connected

Drawbead 4

Drawbead 1

Drawbead 2

Optional

Sensor

Position of the Wall Stress Sensors and Position of the DrawbeadsSource: S. Beck, IFU

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Stroke in mm

Stre

ssin

N/m

m2

0

50

100

150

200

250

300

350

0 20 40 60 80 100 120

Stress 1Stress 2Stress 3Stress 4

Stress at Fracture

Side Wall Stress vs. Stroke for Constant Draw Bead HeightsQuelle: S. Beck, IFU

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R

r = 1/R

Curvature of the Side Wall for Variable Draw Bead Heights vs. StrokeSource: S. Beck, IFU

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Springback Phenomena when Drawing U-ProfilesSource: M. Beth

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Sidewall of the Part, drawn without Drawbeads

Sidewall of the Part, drawn with Controllable Drawbeads

Surface Quality with and without Controllable Drawbeads(Measured with the System Diffracto)

Source: S. Beck, IFU

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Summary

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Design of Conventional Draw Dies

Box-Profile

C-Profile

Source: M. Häussermann, IFU

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Blankholder Pressure by the Box-Profile

Blankholder Pressure: 4 ... ... 0 N/mm24 ...4 ... ... 0 N/mm... 0 N/mm22


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Principle of the Segment-Elastic Blankholder

Draw Ring

Blankholder

Blank

FPin FPin FPin

Locally increased Blankholder Pressure

FPin, increased


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Prismatc DesignedDraw Ring

Return StrokeCylinders

Segment-Eelastic Blankholder

Servo Valves

Hydraulic Cylinders

Guide

Punch

StrokeMeasurement

Bottom Plate


Draw Die with Segment-Elastic Blankholder,Prismatic Designed Draw Ring and 10-Point

Cushion System Integrated into the Die

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Hydraulic Multipoint Cushion System in the Die


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Normal Pressure: 4,5 ... ... 0 N/mm2


EqualPin Forces

Increase of100% in theMiddle Area

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Optimization of the Cushion Pin Forces

2 kN90 kN 98 kN

52 kN

24 kN

13 kN99 kN102 kN7 kN

43 kN

Total Blankholder Force 530kN Good Part with 68 mm Draw Depth


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Punch

Blankholder

Cables and sensors

Valves

18 Nytrogen Cylinders

Source: D. Haller, IFU

Die for the Deep Drawing of Longitudinal Beams with Cushion

System integrated into the Die

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Source: D. Haller, IFU

Die for the Deep Drawing of Longitudinal Beams with Cushion

System integrated into the Die

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Experimental Die

Source: J. Hengelhaupt, IFU


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MOOG Controller Units

HydraulicHMI

HYDACPowerUnit

Main MobileHydraulic Unit

Cooling System

10 Point Flexible Binder Die

2 x Return Tank Units 2 x Bladder Accumulators Station(each 1 x 60 bar and

2 x 10 bar)

IFUHMI

20.000 kNHydraulic Press at

the IFU

PressHMI

Source: IFU

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Source: M. Vulcan, IFUControl system with Touch Screen to Adjust

the Blankholder Pressure Area by Area

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Source: IFU

Design of Closed Loop Control of the BHF

Nominal Value

Stroke

Controller

Cushion System integratedinto the Die

Segment-elasticBlankholder

Actual Values

Ram

Upper Binder

MeasuringFrictionForce andWrinkleHeight

Friction Force versus the StrokeMax. Wrinkle Height

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Tool and Die Design for

Deep DrawingAHSS

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w w w . a u t o s t e e l . o r g

Great Designs in Steel is Sponsored by:•AK Steel Corporation•Dofasco Inc.

•Severstal North America Inc.•United States Steel Corporation

•Mittal Steel Company•Nucor Corporation

tool and die design for deep drawing ahss - autosteel

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