evaluation of sheet metal covers to improve tool life in ... of sheet metal...evaluation of sheet...

Evaluation of Sheet Metal Covers to

Improve Tool Life in Forging

Prof. Dr.-Ing. L. Schaeffer*, J. Zottis, Dr. Ing. A. Brito,

Laboratório de Transformação Mecânica – UFRGS

Prof. Dr.-Ing. G. Hirt, M. Wolfgarten*, Y. Yu

Institut für Bildsame Formgebung – RWTH Aachen

University

*Presenting authors

Motivation

Tooling costs stand up to 15-35% of total costs

Main failure of forging die: abrasive wear

Most failures appear on the surface

Method of surface protection

– Surface treatment (Nitriding, PVD…)

– Coating

– Die insert

Tool repair and exchange is still required

To protect forging tool, decrease tooling costs

Inspired by the exchangeable cutting tool insert

For Making the surface of forging die

“exchangeable”

Wear

Mechanial

fatigue

Plastic

deformation

Thermal

fatigue

Failures

Out of use

Hot forging die Forging

Traditional forging

Motivation

Inexpensive and easy-to-exchange sheet metal

as a protective die cover

Die cover concept

– Failures will only affect die covers

– Can be exchanged quickly

– Thermal load will be reduced

– Economical

Fix the die cover Forging

Take out forging

pieces

Take out the die cover

after N forging pieces

Out of use

Recycle use

Forging die

Forging with die covers

Motivation

Conclusions from the previous project stage

Materials were selected based upon their mechanical and

thermal properties.

Different geometries were developed to define the

application range of this concept.

The protection effect of die covers was proved both by

simulations and experiment.

Two geometries were validated by experiment and the die

cover reached 10 forging cycles.

Open questions:

– Wrinkling and thinning problems

– Application on more complex geometries

Objectives of the 2nd phase

Investigation of possibilities to improve the boundary

conditions

– Influence of the friction coefficient on the tensile stresses

within the die cover

– Test of enhanced sheet fixation

Development of a suitable die geometry

– Investigation of 3D geometries

– Investigation of axisymmetric geometries

Investigation of multi-stage forging processes

– Analysis of multi-stage forging process with reduced

tangential movement in forging stages

– Investigation of the “finisher” step

General information

Publications

– Publications in Journals:

First experimental and numerical study on the use of sheet metal die covers for wear

protection in closed-die forging (Key Engineering Materials Vols 651-653 (2015) pp 266-271)

Estudo da aplicabilidade de máscaras metálicas de DP600 em superfícies de matrizes de

forjamento (Revista Ferramental. ed 66, p27-32. Curitiba, 2016)

– Conference Proceedings:

Influence of the Die Geometry on the Application of a Sheet Metal Cover for Wear Protection

in Closed Die Forging (35th SENAFOR)

Influence of Die Geometry and Material Selection on the Behavior of Protective Die Covers

in Closed-die Forging (ESAFORM 2016)

Characterization of DP600 Sheet Mechanical Properties and Anisotropy (15th ENEMET –

ABM)

Study of DP600 metallic mask applicability in forging die surface (36th SENAFOR)

Temperature influence on DP600 sheet hardness to metallic mask application in Hot Forging

(36th SENAFOR)

Hot Forging Process Analysis Using a Metallic Mask as Surface Coating (22th Cbecimat)

General information

Work missions

– Brazil: Prof. Dr.-Ing. L. Schaeffer

– Germany: M. Wolfgarten, Y. Yu

Student missions

– Brazil: Master Student A-K. Haussmann

– Germany: Doctoral Student J. Zottis; Master Student T. M. Ivaniski

Post-Doctor

– Prof. Dr. Eng. A. Brito (Brazil Germany)

Students

– Bachelor students: A. Seeliger and N. Adrian (Germany); A. Rosiak, G. Graziottin and

H. Kemmerich (Brazil)

– Master students: E. Segebade, S. Böhnke (Germany), T. M. Ivaniski (Brazil)

– Doctoral students: Y. Yu (Germany); L. de L. de Costa (Brazil), J. Zottis (Brazil Germany)

Investigation of 3D geometries

Comparison of 2D die cover and 3D die cover

2D die cover

– Easy to form

– Wrinkling and thinning problems

– Material of billet flows around the die cover

3D die covers

– Need more complex manufacture process

– More stable2D die cover 3D die cover

Billet

Die cover

Forging die

Problem of 2D die cover

Material flows around the die cover 2D die cover 3D die cover

Two ideas to explore 3D die covers

From existed sheet metal parts to forging parts

– Advantages: die cover manufacture process already existed

From the geometry to the manufacture of die cover


Square flange

Cross forging



From existed sheet metal parts to forging parts

– Cross die

Material flow mainly perpendicular to forging direction

1 2

3 4

Forming progress Material flow

Cross sheet part

Cross forging part


Experimental validation

– Material: 22MnB5

– Die covers manufactured by deep drawing

Drawing depth: 30 mm

– Heat treatment

Heating above 830°C, then cooling

-0.34

0.26

mm

0

Comparison of the die cover before and after heat treatment

0

200

400

600

800

1000

0 200 400 600T

em

pera

ture

in

°C

Time in s

900°C

Heat treatment curve

Deep drawing



– Billet: C45

– Dimension: 50*50*75 mm

– Lubricant: graphite

– 10 forging cycles

Lubrication Positioning billet Forging Taking off billet

2 s5s10 s 34 s

Waiting

30 s30s

Forging process

0

200

400

600

800

1000

1200

1400

1600

1800

0 0,5 1 1,5 2

Fo

rce

in

KN

Time in s

experiment

simulation



From the existed sheet metal part to the forging part

– Cross die

Maximum stress: 1372 MPa

0

700

1400

Von Mises stress

Unit: MPa

Maximum point

1372 MPa

Stress distribution Press force



– 10 forging cycles

– Stable state: 350°C to 450°C

Conclusions

– The 3D die covers are more stable than the 2D die covers

– The die cover made by 22MnB5 has more than 10 cycles

service life

– Easy to put in and take off is possible in this case

– More cases with similar material flow ways can be explored

as the applications

Die covers before and

after heat treatment

Die covers before and

after 10 forging cycles

Idea two: from the geometry to the manufacture of die

cover

Idea of how to design the new geometry

– Keeping the cross section same with 2D geometries

– Considering the limitation of manufacture methods (deep

drawing and incremental forming)

– Nonaxisymmetrical

2D geometries in phase 1 3D geometries design The selected 3D geometry

Supporting tool for incremental forming



New 3D geometry

– Press force: 270 t

– Maximum stress: 1292 MPa

– Die cover manufacture: incremental forming

– Material: 22MnB5

0

700

1400

Von Mises stress

Unit: Mpa

Stress distribution Incremental forming of die cover

X: 15.6727

Y: 4.96127e+06

Investigation of axisymmetric geometries

– Numerical investigation to determine suitable geometries

– Investigation of manufacturing strategies for the die cover

– Evaluation of die wear by forging experiments

3D axisymmetric geometries

– Forging force analysis

– Billet size

– Experimental plan


Gear Blanks

Ø150x50 mm

Numerical evaluation – billet size

Axisymmetric geometry


– Numerical simulation results

Using a sheet metal as a die cover – 22MnB5

Without die cover

– Maximum temperature of the lower die on surface decrease

from 640°C to 320°C

– von Mises stresses decrease from 700 MPa to 380 MPa.


Die cover (22MnB5 with 1.5 mm thickness) after one forging cycle

Temperature (°C)

Temperature (°C)

Without Die Cover

Without Die Cover

With Die Cover

With Die Cover

Stress – Effective (MPa)

Stress - Effective (MPa)

Investigation of manufacturing strategies for the die cover

– Incremental Sheet Forming

Different materials

DP600

22MnB5 (before treatment)

DC04

Manufacturing of a supporting tool (forging tool)

Process parameters:

Offset = 0.5 mm (Z)

Velocity = 4000 m/s

Tool size

1st 20 mm

2nd 10 mm

Die cover measurements:

3D scan

Optical 3D (ARGUS 5M)


First Path – tool 20 mm

Second Path – tool 20 mm

ab

c d

Holder

Sheet

material

Supporting

tool

Final Geometry – tool 10 mm

Incremental Sheet Forming

– Equipment: Amino

– Fixation

Bottom of Supporting tool

Structure for lateral stability


FixationMaterial thickness samples

DC04 1mm 3

1.5mm 3

DP600 1mm 3

22MnB5-coated (before quenching) 1mm 6

1.5mm 3

Samples number of manufactured covers

with different thickness.

Incremental Sheet Forming

– Equipment: Amino

– Manufacturing steps:

First path with 20 mm of tool diameter

Second path with 10 mm of tool diameter


ISF Process Final Step

Manufactured Die Cover

3D die covers measurements

– A PDA grid pattern or mesh printed by Laser on the bottom

surface of sheet metal before incremental forming process

(ISF).

– Optical 3D measurement system (ARGUS 5M) was used to

evaluate the final thickness of the manufacture die cover.

– For the DP600 formed material, can be observed higher

reduction in the die cover walls.

– ISF process could provide an accurate final geometry.



– Experimental plan


1. Forging Experiment Set and lubrication

2. HeatingBillet – 45 min

Dies – 20 min

3. Billet Transfer ~ 30 s

4. Positioning and Start ~ 10 s

5. Forging Operation 15 mm (stroke Z)

6. Extraction and lubrication ~ 60 s

Cover Materials

DC04

22MnB5

DP600

Forging cycle for each cover sample N = 4

Test of enhanced sheet fixation

Test of enhanced sheet fixation

– High temperature glue (long curing time)

– Mechanical fixing

Mechanical fixations

Fixation effect in simulation Holder used as a

mechanical fixation

Holder

Die cover

Lower die

Fixation

Fixation

Outlook

Investigation of possibilities to improve the boundary

conditions

– To validate the friction results in experiment using different

topography

Development of a suitable die geometry

– To explore the max service life of die cover in different

geometries

– Evaluation of die wear

Investigation of multi-stage forging processes

– Analysis of multi-stage forging process with reduced

tangential movement in forging stages

– Investigation of the “finisher” step

Different topography

Thank you for your attention!

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