Roll Forming of Advanced High- Strength Steels/media/Files/Autosteel/Great Design… ·  · 2011-10-26w w w . a u t o s t e e l . o r g Roll Forming of Advanced High-Strength Steels

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

Roll Forming of Advanced High-Strength Steels

Heinrich Weber – Dreistern / Germany

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

Topics.1 Company profile

2 Drivers and constraints for use of AHSS

3 Critical parameters

4 Applications

5 New process concepts

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

Company Profile.Location: Schopfheim / Germany Telford (PA) / USAOutput: 50 lines per yearCore Competencies:

Roll formingWeldingCuttingPunching

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

Next topic.1 Company profile

2 Drivers and constraints for use of AHSS

3 Critical parameters

4 Applications

5 New process concepts

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

Drivers & Constraints Using AHSS.

Investment Cost Process Design & Parameters

Material Characteristics

Minimal RadiiSpring BackYield PointElongation Variation

Vehicle Requirements

DesignSafetyFuel Consumption

Driving Performance Cost

Car Body Requirements

CostWeightCrash PerformanceStiffness Manufacturing

Processes

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

Process Characteristics.

Continuous forming process at room temperature

Plastic deformation of metal strip by paired roll sets

Integration of pre and post operations (Cutting, punching, notching, welding and bending) results in reduction of total process costs

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

Characteristics of roll formed parts.Complex open and closed sections

Variable lengths with no additional tooling costs

Short lead times

Lower part costs (compared with pressings)

Limited 3D forming

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

Next topic.1 Company profile

2 Drivers and constraints for use of AHSS

3 Critical parameters

4 Applications

5 New process concepts

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

Some critical parameters.

Part design:Bending radius, sheet metal thickness, …

Machine:

Spring back compensation, number of stand, machine cost, tool cost, …

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

Bending Radius.

Steel suppliers recommend min. inner Radius Ri = 6 – 9 x t (sheet metal thickness) for AHSS.

Up to Ri = 1 x t is achievable provided sufficient residual formability.

Mild SteelRi = 0

AHSSRi = 1 x t

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

Strip metal thickness.

Tensile strength 1100 MPa

Elongation 2%

Ri = 6 x t

t = 1,9 mm cracking at 60 ⁰

t = 2,2 mm cracking at 30°.2,2

1,9

30°

60°

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

Compensating excessive spring back.

AHSS requires much higher over bending.

Varying material characteristics may require adjusting over bending rates.

Roll forming allows easy adjustments

Mild SteelRe = 280 MPa

AHSSRe = 800 MPa

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

Forming Stand Count.

20%

30%

40%

50%

60%

70%

80%

90%

100%

250 350 450 550 650 750 850 950 1050 1150 1250Rp0.2 [Mpa]

Reduction of forming stand count in theory.

Only slight reduction recommended in order to minimize machine size, crack risk and tool wear.

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

Tolerances.

Minimal stretch during roll forming results in a more accurate pre punch pattern.

Improved profile straightness

Easy compensation of varying material characteristics (e.g. spring back)

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

Machine costs.

1,0

2,0

3,0

4,0

5,0

6,0

200 300 400 500 600 700 800 900 1000 1100 1200

Yield Strength [MPa]

Rel

ativ

e M

achi

ne C

ost

t = 1.0 mm

t = 2.0 mm

t = 3.0 mm

Yield strength

Forming forces

Machine size

Investment costs

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

1,0

1,5

2,0

2,5

3,0

3,5

4,0

200 300 400 500 600 700 800 900 1000 1100 1200

Yield Strength [MPa]

Rel

ativ

e To

olin

g C

ost [

-]

Tool costs.

t = 1.0 mm

t = 2.0 mm

t = 3.0 mm

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

Next topic.1 Company profile

2 Drivers and constraints for use of AHSS

3 Critical parameters

4 Applications

5 New process concepts

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

Application example “Rocker”

Source: Volkswagen, GermanyLead timePerformance

Material utilizationTool cost

12 months3 months12 parts / minute30 parts / minute

70 %95 %800.000 $130.000 $PressedRoll formed

Open sectionLength 1000 mmWeight 3.5 kg

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

Application example “Rail Side Roof Member”

Source: Volkswagen, Germany

Lead timePerformance

Material utilization

Tool cost

12 months3 months7 parts / minute7 parts / minute

70 %95 %

2 x 1,300.000 $ (2 parts)200.000 $

PressedRoll formed

Closed SectionLength 3500 mmWeight 4.3 kg

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

Manufacturing process.1 Strip feeding

2 Straightening

3 Pre punching

4 Seam preparation

5 Roll forming

6 Laser Welding

7 Seam monitoring

8 Post punching / cutting

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

Next topic.1 Company profile

2 Drivers and constraints for use of AHSS

3 Critical parameters

4 Applications

5 New process concepts

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

Composite profile concept.

Two components being formed and welded in-line.

Differing thickness

Differing materials

Complex sections become practical

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

Composite profile process.

Simultaneous forming of two metal strips

Simultaneous Laser welding of two seams with one laser

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

Variable cross sections.Expanding the degree of freedom for profile designers.

New technology based on proven components

Simple concept using tailored strips.

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

AHSS for roll form intensive structures.Reliable process for precise AHSS parts

Almost 100 % material utilization

Variable lengths with no additional tooling costs

Superior welding speed and quality

Low capital investment and tooling cost

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

Thank you.

Further information: [email protected]@dreistern.com