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Nov. 21, 2013

Development of New Auto Steels and Application Technology

Jae-Bok NAMPOSCO Technical Research Lab.

worldsteel / CISA China Automotive Steel Conference

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POSCO Automotive Steel

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Steel GradeProduct

- Sales in 2003 to 2012 has been increasing by CAGR of 11.7%. - In 2012, total sales is 7.3 million tons including 62% overseas sales. - High strength steel and AHSS are occupied with 44.7% of total sales

Sales in 2003~2012 Sales Mix in 2012

HSS+AHSS : 44.7%Coated Product : 33.5%0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

Sale

s o

f A

utom

otiv

e St

eels

, mill

ion

ton

Automotive Steels in POSCO

Introduction POSCO Automotive SteelPOSCO Automotive Steel

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Development of AHSS

Conventional AHSS- DP, TRIP, CP, Mart, HPF- TSxEl < 25,000 MPa·%

eXtra-AHSS (X-AHSS)- Giga duplex, Light weight steel- 25,000 < TSxEl < 50,000 MPa·%

Ultra-AHSS (U-AHSS)- TWIP steel- TSxEl > 50,000 MPa·%

IF

Mild

BH

CommercializedDevelopedDeveloping

Status

DP/CPTRIPMartHPFTWIPDuplex/Lightweight

AHSS grade

Elon

gatio

n (%

)

Tensile strength (MPa)

X-AHSS : eXtra-Advanced HSS / U-AHSS : Ultra-Advanced HSSRef : Ohjoon Kwon, Kwang Geun Chin et al : Materials Science Forum, Volume THERMEC 2009, p.136

Banana Diagram

POSCO Automotive SteelPOSCO Automotive Steel

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GA 490DP for Door Outer – World First Production（2005）

[ Improvement of dent resistance ][ Weight reduction ]

Requirement : Surface quality, Dent resistance, Stiffness

[ Door outer, 0.7t GA 490DP ] [ Removal of Body panel reinforcement sealer ]

16

17

18

340BH

Wei

ght (

kg)

490DP

- 7%0.75mm

0.7mm

05

10152025

340BH

Den

t loa

d (k

gf)

490DP

+ 53%

Body panel reinforcement sealer

Replacement of 340BH steel by 490DP steelWeight reduction 7%, improvement of dent resistance 53%

490DP Steel for Outer Panel POSCO Automotive SteelPOSCO Automotive Steel

Applications

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Trial for hood outer : 21% weight reduction (0.7t 340BH 0.55t 590DP) Trial for fender at Japanese automobile company shows good formability

Japanese Car, FenderGA 590DP (0.55t)

Small Sedan, Hood outerGA 590DP (0.55t)

[ Hood outer using GA 590DP of 0.55mm thickness ]

GA 590DP for Closure Parts

590DP Steel for Outer Panel POSCO Automotive SteelPOSCO Automotive Steel

Applications

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GI

Grade Class YS (MPa) TS (MPa) El (%) r

340E CR/EG ≥167 ≥ 340 ≥ 32 1.75GI/GA

340ES CR/EG ≥180 ≥ 340 ≥ 35 2.25GI/GA

High elongation and excellent r-value suitable for outer parts requiring strength & formability

340E Steel on Korean OEM’s SIDE OTR PNL

World’s first commercial application

Weight Reduction 7% (EDDQ 0.7t 0.65t)

We have 340ES for better than 340E

[ One Piece Side Outer (domestic company) ]

Super Formable IF HSS

IF HSS (E/ES-class)

POSCO Automotive SteelPOSCO Automotive Steel

Application

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Bending direction

Spec.(R/t)

Bendability ( GA980DP: 2.0t)R/t 0.5R 1.0R 1.5 2.0 2.5 3.0

L ≤ 2.5 1.5 X X △ △ △ OC ≤ 2.5 1.3 △ △ O △ O O

[ Cross section of spot welded GA980DP steel ] [ Floor panel tunnel (GI 980DP) ]

[ Back side bracket (CR 980DP) ]

CR/GI/GA 980DP with good bendability Reduce the strength difference between phases Improvement of bendability Low Ceq decreasing welding nugget hardness Increase of ductility ratio

POSCO Automotive SteelPOSCO Automotive Steel980DP Steel

Applications

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GA 1180CP for Reinforcement Parts

[ Rocker Outer (Domestic company) ]

Material Change (EG 590TRIP GA 1180CP steel) Achieve 33% of weight reduction First commercial production in the world

Martensite Ferrite

Bainite

[ Microstructure ]

Suppress ferrite and promote bainite transformation High YR, excellent bending property

High YR Bendability Spot weldability Zn coatability

YS ≥ 850 MPa, TS ≥ 1180 MPa

Bending radius ≤ 3 x thickness Low Ceq and Si content

1180CP

Requirement Devloping Target

POSCO Automotive SteelPOSCO Automotive Steel1180CP Steel

Applications

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< Mechanical properties >

Safety regulation for frontal small overlap crash test : 25% offset collision introduced by IIHS So, rocker or side sill becomes more and more

important where anti-corrosion is also significant

* cf. www.iihs.org

[ Rocker Outer (Domestic company)]

GI 1470Mart for Reinforcement Parts

Rocker Outer Bumper Beam

First commercial production in the world

YS (MPa) TS (MPa) T-El (%) YR Bendability(1）

≥ 1050 ≥ 1470 ≥ 5 > 0.71 ≤ 6

1) Bendability = Min. corner radius / Thickness

POSCO Automotive SteelPOSCO Automotive SteelGI 1470Mart

Applications

Commercialization of the world 1st GI 1470 Martensitic steel

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TWIP Steels (U-AHSS) Characteristics High Mn austenitic steel work-hardened by twinning High energy absorption by excellent strain hardening rate Very high strength-ductility combination (1000MPa, 65%) Commercialization : Cold rolled product, 2011~ (POSCO, World First) Developing high YS TWIP steels (900, 1100, 1300, 1500, 1700 grades)

[Bumper Beam, Commercialized product (’12) ]

[ Wheel, Chassis with TWIP steel ]

High TS, High El : Bumper, member etc. Commercialized Bumper of European Vehicle

(28% weight reduction, 22% cost saving) High HER, High El : Wheel, Low arm etc

- Low arm : 540MPa FB (4 Ops) 980MPa TWIP (2 Ops)

POSCO Automotive SteelPOSCO Automotive Steel

Applications

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Part development of BIW (body in white) and Chassis

The red colored parts are made from TWIP steel through collaboration with customers.

POSCO Automotive SteelPOSCO Automotive SteelTWIP Steels (U-AHSS)

Lower Arm

Wheel Disc & Rim

Spring Stopper

Front Cross Member

Recently, the number of chassis application is increasing as the advantage becomesapparent with TWIP steel. .

BIW Chassis

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0

200

400

600

800

1000

1200

1400

0 20 40 60 80

Elo

ngat

ion

(%)

Tensile Strength (MPa)0

10

20

30

40

50

60

70

600 800 1200400 1000 1400

LC

BH

200

CP, MART

★

★

★

★

★

HPF

★ : Commercial, ★ : Developed

Stre

ss (M

Pa)

Strain (%)

900TWIP900_HY TWIP

1000_HY TWIP

1200_HY TWIP

900TWIP

980TWIP

900_HY TWIP

1000_HY TWIP

1200_HY TWIP

To meet the customers needs for high YS TWIP steels, POSCO developed three grades, 900_HY, 1000_HY and 1200_HY, which is utilized work hardening by skin pass rolling .

Development of TWIP steels with High YS

POSCO Automotive SteelPOSCO Automotive SteelTWIP Steels (U-AHSS)

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0 10 20 300

200

400

600

800

1000

1200

Stre

ngth

(MP

a)

Strain(%)

CR 980 Duplex

YS (MPa) TS (MPa) El (%) TSxEl (MPa%)

980 DP 780 1040 11 11440

980 Duplex 937 1033 28 28924

X-AHSS grade!! (TS X El ≥ 25,000MPa%)

Austenite

Ferrite

Characteristics Medium Mn addition increase of austenite stability High TS strength, yield ratio and elongation with a large amount of austenite Duplex microstructure of ultra-fine retained austenite and ferrite

< Mechanical Properties >

< Microstructure >

Medium Mn TRIP steel (X-AHSS) POSCO Automotive SteelPOSCO Automotive Steel

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POSCO Application Technology

New Forming Technology

Lightweight Solutions for Chassis

POSCO Lightweight Body Concept

Electric Power Train

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Implementation : Multi-strength HPF, TWB HPF to enhance the ductility in sepecific area

[ Conventional Design ]

② HSS 380Y

① HSS 590③ HSS 590

Laser weldingHPF1470(1.5GPa)

CHSP340Y(0.6GPa)

HPF1470(1.5GPa)

HPF1470(0.6GPa)

Multi-strength HPF

TWB HPF

(1 Piece Blank)

(TWB Blank)

Tailored Hot Press Forming

POSCO Application Tech.POSCO Application Tech.New Forming Technology

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POSCO’s own FE Program (Shape-MDRF) : Reduction of Calculation Time with High Accuracy

Unique Solution for the Prevention of Distortion: Incremental Counter Forming Method [Conventional Product]

(Uniform Section)[PosRollForm Product]

(Variable Section)

[PBC-EV PosRollForm Part]Side Sill Floor Cross Member

[PosRollForm Test Facility]

Concept : Producing Variable Sectional Profile usingLinear & Rotational Movement of Stands”

PosRollForm (Multi-Directional Roll Forming)

POSCO Application Tech.POSCO Application Tech.New Forming Technology

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Removing reinforcement (bracket) for a lightweight torsion beam Design Optimization and Advanced Manufacturing by Hydroforming Technology New Concept : Bended and Expanded Beam for Structural Performance

FB780 One-piece Beam

Project on Torsion Beam Axle Development

PI

Proto Beam – Hydro forming

Design OptimizationWeight Down+Bracket Removing

Original Beam

Optimized H/F beamWeld Durability Analysis

Durability Test

Torsion Beam Axle

Lightweight Solution for Chassis POSCO Application Tech.POSCO Application Tech.

17

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Die design & Forming Analysis

TWIP980 – Rim Bead Optimization TWB Disk

Structural / Durability analysis

Styled Steel wheel

TWIP980 Wheel Rim HB780 Wheel Disk

Lightweighting by Shape Optimization and Advanced Manufacturing Technology New Concept : High Stiffness Rim (TWIP980 steel + Hydroforming)

TWB Disk (HB780 steel- 3.6t / 3.2t)

Styled Steel Wheel

POSCO Application Tech.POSCO Application Tech.Lightweight Solution for Chassis

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To integrate POSCO’s steel products & application tech. to provide Cost Efficient Steel Solutions for electric vehicle to our customers

To identify Requirements of New Steel Grades and New Opportunities for Steel

Dimensions

PBC-EV : POSCO Body Concept-Electric Vehicle

Overall Length 4320mm, Wheelbase 2750mm,Width 1830mm, Height 1550mm

CFD Based Styling for OptimalAerodynamic Design High Roof Package for Maximizing

Passenger/Battery Spaces Detachable Rear Battery Package

[ Computational Fluid Dynamic (CFD) simulation ]

[ Final Styling ]

Cd = 0.285

Separated Air FlowSurface Streamline

POSCO Body Concept : PBC-EV POSCO Application Tech.POSCO Application Tech.

Objectives

Styling & Packages

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AHSS = 65.0 %UHSS(≥1GPa) = 45.4 %

Steel Grades(As % of Body Weight)

* Body Weight : Without Bumper Impact Beam

Body Weight : 218 kgWeight Reduction : 26.4%

DP490/590/780,

15.6%

DP980,

9.3%

TRIP590,1.6%

TRIP980,1180,

3.3%

TWIP980,

10.4%DUPLEX3.9%

CP1180/1470,

10.3%

HPF1470/2000,

8.2%

Mg(Sheet),2.0%

MILD,2.5%

E-ES/C/R Class,

32.9%

ETC, 0.53%

PBC-EV Base Model

Weight Reduction : 26.4%

Performance : [Crash] 5 Star & Good Safety Rating, No Battery Damage[Stiffness] Static Bending/Torsion > 15000, Dynamic Bending/Torsion = 51.2/47.4Hz

POSCO Application Tech.POSCO Application Tech.

Design Results

POSCO Body Concept : PBC-EV

Steel Grades

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Cost Efficient Manufacturing

Manufacturing Process(As % of BIW Structure Mass)

Roll Forming + Forming = 41.2 %(Including PosRollForm)

POSCO Application Tech.POSCO Application Tech.POSCO Body Concept : PBC-EV

Manufacturing Process

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World 1st Body Concept for Electric VehicleBy Steel Company

Weldability Test Assembly

Prototyping

Ductile Zone Hard Zone

Transition line

Weld-line

CHSP340Y HPF1470Process Design &

Formability Analysis

Process Optimization &Prototyping

POSCO Application Tech.POSCO Application Tech.POSCO Body Concept : PBC-EV Demonstration

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1. Solution for RCAR Test 2.1%2.4%

※ Max. Effective Plastic

Strain < 0.03

RCAR Front/Rear Structural Test (CAE Result)

• Additional Lightweight by Structure Improvement and Increase of HPF Parts (HPF ratio in BIW : 8.2 17.1%)

2. Extra Lightweight Model

• Torsional Stiffness Improvement : 50.0% (17.2 25.8 kN/deg)

3. High Torsional Stiffness Model

Modified Parts

Design Modification for Extra Lightweight

FinalWeight Savings

30%

218kg 216kg207kg

25.8

17.4%

50%

17.2 20.2

PBC-EV Base Extra Light. High Stiff.

Torsional Stiffness (kN/deg)

Analysis of Strain Energy& Thickness Sensitiveness

LH : 2.3%1.9%• Effective Solution for RCAR Structural Tests

POSCO Application Tech.POSCO Application Tech.POSCO Body Concept : PBC-EV Upgraded Models

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Products

Applications to EV (Electric Vehicle)

POSCO EPT Applications

100kW EPT – PMSM, PCU100kW EPT – PMSM, PCU

High Performance and Reliability : PMSM EPT System with High Power Density & High Efficiency

CompactHigh Power Density

Light WeightKey Factor for EV

Low CostOptimized Design

Easy InstallationParts Integration

60kW EPT – PMSM, PCU60kW EPT – PMSM, PCU

• EV Conversion for EPT Test- Various Performance Evaluations- Road Driving Test

• Mid-size EV Buildup with Customer• Small Size EV Development in Consortium

* PMSM : Permanent Magnet Synchronous Motor

EPT (Electric Power Train) POSCO Application Tech.POSCO Application Tech.

POSCO EPT system

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100kW T-N characteristic

Tor

que

(Nm

)

Motor Speed (rpm)

Pow

er (k

W)Max Power

Continuous Power

Max Torque

Cont. Torque

100kW output

60kW is available stably for whole speed range

T-N Curve Efficiency Map

- Motor Type : Interior Permanent Magnet- Max. Power : 100kW@5,600rpm/90sec- Continuous Power : 60kW@0~12,000rpm- Max. Torque : 320Nm/90sec- Cooling : Water (65 , 12ℓ/min)- Power Density : 1.6kW/kg

Major Specifications

100kW PMSM (L 286mm H 325mm Stator Dia. 260mm, Weight 62kg)100kW PMSM (L 286mm H 325mm Stator Dia. 260mm, Weight 62kg)

Performance

* Avg. 95% efficiency in most

frequent usable operating

** Avg. efficiency (UDDS LA4mode) :

92%

POSCO Application Tech.POSCO Application Tech.

100kW PMSM

EPT (Electric Power Train)

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POSCO Global R&D Network

POSCO has been developing new advanced materials and application technologies for vehicle lightweighting

POSCO develops new technologies, utilizing external as well as internal resources for customer value creation

Concluding Remarks