LIGHT WEIGHT VEHICLE BODY CONSTRUCTION

IMPLICATION ON STAMPING

Presentation By : D G NAIK

AMS Conference

oVehicle Weight

oFactors Leading to Weight Increase

oNeed for Weight Reduction

oWays to Achieve

oMethodology

oChallenges

oSummary

CONTENT

Content

Vehicle Weight

Vehicle Weight is Governed by:

a) Body weight

b) Chassis

c) Drive line

d) Trims & others

Factors leading to Weight Increase

Factors Leading to Increase in Body Weight:

a) Crash & Safety requirements

b) Load carrying capacity

c) Emission Norms

d) Increasing Customer Needs

Crash & Safety Requirements

Offset Frontal Full Frontal Rear Impact

Side Impact Angular Frontal Pole Impact

Meeting crash requirements means increase in steel weight

Factors leading to Weight Increase

Higher Loading Capacity

Higher payload requirements means increase in steel weight

Factors leading to Weight Increase

Ongoing Stringent Emission Requirement

Need for weight reduction

Need for Weight Reduction

Need of Reduction in Body Weight:

a) Fuel economy

b) Vehicle cost

Need for Weight Reduction

Fuel Economy Use of High Strength Steel with reduced thickness

Weight Reduction leads to increased fuel economy

Need for Weight Reduction

Rs 80000 / Vehicle Rs 86000 / Vehicle

Cost Pressure Use of High Strength Steel with reduced thickness

Need of reduction

Sustaining cost pressure with change in material mix

Ways to achieve

Ways to achieve Light Weight Body requirements:

a) Reduction in number of parts

b) Use of Down Gauge Steels

c) Use of Lighter Material

Methodology

Methodology for Weight Reduction:

a) Use of Lower Gauge & High Strength Steel

b) Use of Tailor Welded Blanks

c) Use of Aluminium / SMC

Methodology for Weight Reduction

Material & Process

Process

Cold Form Hot Form Hydro Form

Methodology for Weight Reduction

Material & Process

Sr COLD FORMING HOT FORMING

1 Steel Stamped at Room Temperature Steel Stamped in hot condition @900 °C

2 Stamping possible on Conventional presses. Stamping requires special press & induction furnace & robots for part handling.

3 Stamping of steels up to 800 MPa UTS Stamping of Steels with UTS >800 Mpa.

4 Spring-back due to elastic recovery No Spring-back due metallurgical changes.

5 Post forming , trimming possible thro die route. Post forming , trimming thro die route is difficult (poor die cutting edge life). Recommend laser cutting.

6 Low Cycle time ( ~15 parts/min) High Cycle Time ( ~ 4 parts / min)

Sr COLD FORMING STEELS HOT FORMING STEELS

1 a) Low Carbon Steels: EDD 513 / IF EDD / D513 b) High Strength Steel: BH / IFHS / HSLA /E34 c) Ultra High Strength Steel : DP up to 500 Mpa

High & Ultra Strength Steel: DP beyond 500 MPa / TRIP / Boron / MART

o Design & Simulation Implications

• Reduced Formability

• Reduced elongation & tendency to Crack

• Residual stresses-Dimensional Instability

• Spring-back Compensation - iterative

COLD FORMING HOT FORMING

Process & Tooling Challenges

o Tryout & Tooling Cost Implications

• High spring-back leading to Panel Twist

• Special presses with high draw tonnage

• SKD 11 inserts in Dies with special coating

• High Tryout Time for Quality Loops

• High Tooling Cost

o Design & Simulation Implications

• Heat Flow Study

• Segmented Die construction

• Independent guiding & Cyl. for segments

o Tooling Cost Implications

• Special Press & Die

• Dies with internal cooling arrangement

• Induction Furnace with robotic blank handling

• Laser Cutting as separate set up

• High Tooling Cost & Processing Cost

Process & Tooling Challenges

Overcoming Challenges in Cold Forming:

Blank Raw Material

Blank Holder Punch/ Die Cutting Element

UTS < 600 MPa FGS 600 FGS 600 + Small Inserts in Z Type Steel

Z 160 CDV12 Z160CDV12 + TiN

High Strength Steel – UTS <800

FGS 600 FGS 600 + Small Inserts in Z Type Steel

Z 160 CDV12 (Steel with 8% Cr)

UTS > 800 FGS 600 + Small Inserts in Z Type Steel

FGS 600 + Small Inserts in Z Type Steel

Z 160 CDV8.4 (Steel with 8% Cr)

Die Steel Materials

Upper Die – Made in M15 casting • To have easy modifications (weld/machine) in Q-

loops • 30% cost of actual SKD11 inserts • Faster modification cycle ( no annealing required )

Upper Die – Final SKD11 inserts • Final casting shape ( after Q-loop) is scanned for machining of inserts • Die Design made modular to accommodate the SKD11 inserts by removal of M15 casting in the UDIE cavity

Excessive Spring Back with High Strength Steel

1. Cheaper M15 casting used

for Die proving

2. After proving, SKD11 inserts

fitted

Overcoming Challenges in Cold Forming:

Overcoming Challenges in Cold Forming:

Change in Die Design Concept Active Bead for High Strength Steel

Shape set

Section AA:

No Shape set

Set beads function as draw bead

Shape Set beads function as stop bead at end of draw

Tool open

o Design

No Spring-back zone Spring-back zone

Hydro Forming :

o Process

o Applications

Faxial Faxial

P

Hydro Forming

Die Holding Press : 1000~3000T

Fluid Pressure @ 900 Bar

Tailor Welded Blanks

Tailor Welded Blank –

Differential thickness material

Single Piece same thickness

Without Tailor Welded blanks With Tailor Welded blanks

No Hinge Reinforcement Hinge Reinforcement

Panel – 0.8 thick Panel – 1.6 thick

Panel – 0.8 thick

Tailor Welded Blank

Use of Aluminium:

o Usage of Aluminum Alloy • Wax Coated blanks ( have shelf life) • Riveted Joints for fastening • Low BIW Weight • Used in Premium segment vehicles

• In raw material cost, aluminum is 3 times

more expensive than steel.

• In conversion cost, aluminum is 2 times

more expensive than steel.

• In assembly, aluminum is 20 to 30% more

expensive than steel.

• In total, an aluminum structured vehicle is

estimated at 60 to 80% more expensive

than a conventional steel design.

Aluminium Body Panels

Summary:

1. Why Light Weighting of Vehicle Body ?

• Regulatory requirements – Crash /Safety / Emission • Customer Demand – Cost & Fuel Economy

2. How is this Possible ?

• Use of Lighter materials – Aluminium • Use of High Strength Steel with reduced thickness. • Use of Ultra High Strength Steel with reduced thickness & geometry. • Tailor Welded Blank – Differential thickness material (eliminate part/s)

3. What are the Challenges ?

• Aluminium panels – cost goes up (both material + process).

• High Strength Steel panels – Formability of part, Die design & its material.

• Ultra High Strength Steel panels – Press & Process needs change Specialized process (hot forming), Spl dies & Equipment.

This means auto makers will have to invest in advanced

equipment and technologies to further improve upon the market

requirements.

The technology of producing light weight vehicle bodies will build

position of advantage in current market competition.

The requirements are demanding, however there is a way.

The challenges may be many, but the advantages are more.

WHAT IS THE IMPLICATION ON LIGHT WEIGHT VEHICLE BODY

Summary:

END OF PRESENTATION

AMS Conference

Coil Blank Furnace Robot Press

For homogeneous austenitic microstructure

Around 3 sec blank transfer

Austenite transforms into Martensitic microstructure

cooling rate 80 deg C/sec (4 sec)

10 min / 900 deg C

Hot Forming

o Process

o Applications

Coil Blank Furnace Robot Press

For homogeneous austenitic microstructure

Around 3 sec blank transfer

Austenite transforms into Martensitic microstructure

cooling rate 80 deg C/sec (4 sec)

10 min / 900 deg C

Hot Forming

o Process

o Applications