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1.2GPa Tensile Strength

High Formability, Conventionally Stamped Steel Paul Villemonte

Nissan Technical Center, NA

Materials Engineering Dept.

Masahito Katsukura

Nissan Motor Co, Japan

Materials AE Dept.

Takaaki Kondo

Nissan Technical Center, Europe

Materials Engineering

1

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• INTRODUCTION (NISSAN’S APPROACH TO REDUCING C02)

• HIGH ELONGATION, 1.2GPa. DEV. (NEW MATERIAL DESCRIPTION)

• MICROSTRUCTURAL APPROACH AND STRENGTHENING MECHANISMS

• MECHANICAL PROPERTIES

• MANUFACTURING CAPABILITY

• APPLICATIONS

• FUTURE DIRECTION

AGENDA

2


Reduce CO2 emissions of new vehicles by 90% from 2000 Levels Achieve “CO2 concentration level of 450ppm” proposed by IPCC

80

0

20

2000 2010 2050 2030 2040

30% 90%

2005

CAFE※2

35%

Improvement

100

2020

2016

40

60

Long-term Vision for CO2 Emissions Reduction

Progress in NGP2016

Ratio of CO2 emissions

3


15% reduction of vehicle weight contributes to CO2 reduction of 5%

Society

Individuals

Vehicles

Triple-layered approach

・EV/HEV

・Engine/Transmission

・Idle stop

・Accessory loss

・Rolling resistance

・Air resistance

・Heat management

・Vehicle weight

- ECO Pedal

- Fuel consumption meter

- Eco drive advice

・ Supporting eco drive

・ Reduced traffic jam

- Sky Project - Star Wings

NISSAN’S APPROACH TO CO2

4


(Three Areas are Considered)

Nissan’s Approach TO BIW Weight Reduction

MATERIAL SUBSTITUTION

MANUFACTURING

MASS

REDUCTION

STRUCTURE RATIONALIZATION

HIGH STRENGTH MATERIALS

LOW SPECIFIC GRAVITY MATERIALS

JOINING

MOLDING

SHAPE OPTIMIZATION

INTEGRATION/SEPARATION OF FUNCTIONS

FUNCTION ALLOCATION

5


(WHY?) APPLY AHSS - MASS REDUCTION

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

Tensile Strength (MPa)

Part Thickness

20％

38％ 45％

COST

Cost and Mass Reduction can be Achieved by AHSS Application

6


1.2GPa T.S. HIGH ELONGATION

STEEL IS DEVELOPED

7


• HIGH ELONGATION 1.2GPa STEEL CAN BE APPLIED TO COMPLEX SHAPES • HIGH ELONGATION 1.2GPa STEEL HAS EQUAL OR BETTER BIAXIAL FORMABILITY THAN 980MPa MATERIAL

NISSAN & JAPANESE STEEL MAKERS DEVELOP 1.2GPa

440

MPa

980

590

MPa

780

MPa

980

MPa

1.2GPa

HE*

1.2GPa

*HE: High Elongation

Tensile Strength

Ductility

High Low

Next generation

High tensile

Strength Steel

Current

Status

High

Low SIMPLE

COMPLEX

8


MICROSTRUCTURE AND

STRENGTHENING MECHANISMS

9


HE 1.2GPa MICROSTRUCTURES – DP & TRIP

(DUAL PHASE)

Conventional material

Martensite and Bainite (Strength improvement)

Retained austenite (Improving formability)

Fine ferrite (Improving formability)

(COMPLEX PHASE)

Transformation induced plasticity

FERRITE

MARTENSITE

(TWO APPROACHES)

F

M


Dual Phase vs TBF Microstructure Mechanism of Steel

Hard area and soft area coexist.

Ferrite & Martensite

TRIP steel Retained AusteniteMartensite after force is applied.

Ferrite Martensite Austenite Martensite

DP steel

11


Deformation behavior of retained austenite phase

12

Blue: bcc (ferrite + banite) Red: fcc (retained austenite)

=2 μm; Phase map; Step=0.05 ｵm; Grid227x170

fcc：6.4%

ε= 0％


fcc：3.3%

ε= 5％


fcc：2.3%

ε= 13％

X

Y

Z

Decreased Retained Austenite Existence until late deformation

((RETAINED AUSTENITE REMAINS AT HIGH DEFORMATION)

TRIP EFFECT

12


ENERGY ABSORPTION(STRENGTH vs THICKNESS)

13

15 %

Drop weight test results


THE TRIP EFFECT RESULTS IN ADDED ENERGY ABSORPTION PROVIDING ADDITIONAL STRENGTH

AND CRITICAL ENERGY ABSORPTION


MECHANICAL PROPERTIES

15


60 0

500

1000

1500

Mild

Steel

440MPa

590MPa

980MPa

NEW 1.2GPa

with high

formability

10 20 30 40 50

1.2GPa

Advanced High Tensile Strength Steel (AHSS)

Mechanical Properties Stress (MPa)

Strain (％)

MATERIAL STATUS T.S. (MPa) Y.S.(MPa) %ELONG LAMBDA(%)

1.2GPa SPEC. SPECIFICATION 1180 Min. 850 Min. 14 Min. 30 Min.

980MPa DP SPECIFICATION 980 Min. 600 Min. 10 Min. --

16


MANUFACTURING CAPABILITY

17


FLD SHOWS NEW HIGH ELONGATION 1.2GPa MATERIAL CONTAINS BIAXIAL

FORMABILITY EQUAL OR BETTER THAN THE 980MPa DP MATERIAL

MANUFACTURING CAPABILITY – FORMING

(TRIP MATERIAL)

⑤ ⑥

① ② ③

④

⑦ ⑧


MANUFACTURING CAPABILITY – FORMING

PART SHAPE & SPRING BACK

980MPa DP HE 1.2GPa

■ After spring back ■ Before spring back

19


BEFORE WELD

TEMPER PULSE

AFTER GRAIN

REFINEMENT

Current condition Optimized condition

Reduce stress concentration of nugget

by extending heat-affected zone (HAZ)

Cross Tensile Strength is

Increased dramatically


NISSAN 1.2GPa APPLICATIONS

21


590MPa

780MPa

980MPa

Die Quench (1350MPa)

TARGET PARTS/GRADES TO APPLY 1.2 GPa MATERIAL

普通材48%

590M Pa15%

780M Pa3%

980M Pa9%

1350M Pa4%

その他3%アルミ

2%

under590M Pa16%

Mild steel

AL

Other

s

BIW material mass ratio

22


NISSAN APPLIES NEW 1.2GPa

MATERIAL TO Q50

1. FIRST APPLICATION OF 1.2GPa MATERIAL REDUCES MASS BY – 11 KG 2. NEXT STEP IS TO INCREASE APPLICATION OF AHSS

WORLD FIRST

-11 KG MASS

Reinf. Ctr Pillar

23


INCREASE APPLICATION OF 1.2GPa

FUTURE APPLICATION

- 15.9 -15.9

-15.9 kg


FUTURE DIRECTION

25


Increased Application of Advanced High Strength Steels Globally

FUTURE AHSS RATIO： CURRENT AHSS RATIO：

STRATEGY – APPLY AHSS EXTENSIVELY

26


Cum. Weight Reduction

Steel

Al & Mg

・Closure Panels

・Chassis

・P/T Parts etc.

Plastics ・FDR, Back Door etc.

High Tensile

Strength Steel

• BIW

• Chassis

• Forged Parts

for P/T

Light Metals & Plastics

Cum

. C

ost

FUTURE DIRECTION

Cost Reduction for Expanding Application - Material

- Assembly

Structural

Integration

Structure

Expand HTSS

application

NEW 1.2GPa

APPLICATION

27


NISSAN’S REQUEST TO STEEL CO.’S

PLEASE DEVELOP HE 1.2GPa FOR OEMS IN NORTH AMERICA

28


North American

Light Vehicle Metallic Material Trends

Great Designs in Steel is Sponsored by:

Use your web-enabled device to download the presentations from today’s event

PRESENTATIONS WILL BE AVAILABLE MAY 16

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