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New Trends in Processing and Applicationof Tool Steels for Cold Forming

- Tool Steels, Heat Treatment, Application Examples -

Peru Nov. 2007

Dipl.-Wirt. Ing. Andreas HungerDörrenberg Edelstahl GmbH Engelskirchen Germany

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Content

1. Introduction

2. Requirements on tool steels

3. Tool steels and factors of influece on micostructure

4. Effect of heat treatment on properties of cold work steel s

5. Application examples

6. Conclusion

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Example of use high strength materials shown at the BMW 5th series

2476-9

1980 1985 1990 1995 2000 2005

20

40

60

Per

cent

age

of h

igh

stre

ngth

s m

ater

ials

[%]

E28

E34

E39

E60

Quelle: BMW AG

15%23%

62%

Aluminium

Standard sheets

High strengths sheets (Rm > 320MPa)

5th series BMW (E60)

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-5

0

5

10

15

20

0 0,2 0,4 0,6 0,8 1

Cutting way [mm]

Cut

ting

forc

e [k

N]

ZStE180

TRIP700

Load of punching tools using different sheet materials

Punching : Oval-Punch (8x16mm)Clearens: 10 %Cutting edge: small radius

ZStE180Tensile strength: 332 MPaCutting force: 5,16 kN

TRIP 700Tensile strength: ~850 MPaCutting force: 17,62 kN

2477-9

Quelle: IFU-Stuttgart

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adhesive wear

separation of adhesive junctions

abrasive wear

cutting crackingploughing

Typical wear of sheet-metal forming tools

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Requirements on cold work steelsrequired properties for use:• high compressive strength• high hardness• high tensile strength• sufficient toughness to avoid brittle spontaneous fracture

and increase fatigue life• high resistance against abrasive wear• low adhesion properties (transfer of material)

required properties for production:• good castability• good formability• good machinability• good hardenability• good dimensional stability

1802-7

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CP4M0,6% C5,0% Cr

CPOH1,0% C8,0% Cr

Structure comparison1.2080/D3 - 1.2379/D2 - CP4M - CPOH - WP7V

2489-9

1.2080/D32,0% C

12,0% Cr

1.2379/D2 1,6% C

12,0% Cr

WP7V0,5% C7,8% Cr

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Hardness of different carbides

0

500

1000

1500

2000

2500

3000

3500

Har

dnes

s [H

V

0,05

]

Scatter value

Ti V Nb W Mo Cr FeElement

MC MC MC MC M6C M7C3 M3CType

2351-9

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Properties and classification of cold work steels

2009-8

42 6646 50 54 58 62hardness in HRc

wea

rre

sist

ance

toug

hnes

s

tough hard rich incarbides

wear resistance

toughness

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Cold work tool steels2010-8

C

0,45

0,60

0,50

0,90

1,00

1,00

1,20

1,55

2,10

Si

0,45

0,70

0,30

0,30

0,30

1,10

0,30

0,25

0,25

Mn

0,30

0,30

0,30

2,00

0,60

0,30

0,30

0,30

0,30

Cr

1,40

1,00

7,80

0,40

5,00

8,00

12,0

12,0

12,0

Mo

0,20

-

1,50

-

1,00

2,50

1,40

0,80

-

V

-

0,20

1,50

0,15

0,30

0,30

1,70

1,00

-

W

-

2,00

-

-

-

2,50

-

0,80

Ni

4,00

-

-

-

-

-

-

-

standard chemical compositionmaterial tempering behaviour

+ add.

1.2767 1.2550 WP7V

1.2842 1.2363 CPOH

CPR 1.2379 1.2436

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Micro structure of cold work tool steels from different production methods

2193-8

Powder metallurgyD2 / PM 1.2379

ForgedD2 / 1.2379

CastD2 / 1.2382

50µm

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Structure of a cast ingot

2059-9

Ingot

Ingot centersegregation

Ingot mould

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Crack propagation in steels with distributed or connected carbides

F

distributed carbides carbide network

F

crack

Berns et al.

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Influence of carbide structure on the toughness of a steel

2166-8

Tou

ghne

ss

Carbide size T

ough

ness

Carbide amount

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Atomising plant

892-4

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Hot isostatic pressing

gas atomised powder

vacuum pump

Argon under pressure

filling capsules evacuating and welding of capsules HIP-cycle Removing the capsule

Illustration of production steps for hip-process

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Comparison conventional - powder metallurgical

2091-8.0

1.3344

64 HRc14 J

3585 MPa7,2

PMD 23

64 HRc43 J

5350 MPa9,8

hardnesscharpy notch (ISO-U) impact value

bend fracture strengthgrinding ratio

1,304,206,405,003,10rest

CCrWMoVFe

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Impact Toughness: Standard- compared to PLUS-material

0

5

10

15

20

25

1.2379 Standard(transversal)

1.2379 Standard(longitudinal)

1.2379 Plus (transversal)

Impa

ct v

alue

s in

J

60 HRc 58 HRc

1.2379 conventionell: specimen taken f r om Ø70mm at 1/ 4 D

1.2379 P lus: specimen taken f r om Ø207mm, cor e

All samples unnotched

All samples har dened at 1050 °C and secondar y temper ed

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Properties and classification of conventional cold work tool steels

2009-8

42 6646 50 54 58 62Hardness in HRc

Wea

r re

sist

ance

Tou

ghne

ss

tough hard rich incarbides

wear resistance

toughness

PM-Materials

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Dörrenberg Edelstahl PM-Tool Steels

0,302,508,001,00CPOHPLUS

1,905,06,404,000,901.3343PLUS

0,900,8012,001.551.2379PLUS

4,001,508,001,50PMD V4

5,005,0012,204,201,60PMD T15

9,751,205,252,45PMD 10

High-speed-steels

3,105,006,404,201,30PMD 23

4,004,505,804,201,35PMD M4

Martensitic-Stainless steel5,800,5017,502,20PMD440

Cold-work-steels9,001,305,251,80PMD 9

8,003,105,006,404,201,30PMD 30

CoVMoWCrC

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Dörrenberg Edelstahl PM-Tool Steels

standard HSS flat, standard dies, EDM-blocks, (M2)1.3343PLUS

standard cold work steel1.2379PLUS

very tough cold work steelCPOHPLUS

HSS with good thermal stability, improved wear resista nce, forchipping and cold forging

PMD 52

HSS with good thermal stability, for cold forging, chi ppingPMD 30

standard HSS flat, sheet metal forming, fine blanking , cold formingPMD M4

standard HSS round, standard dies, chippingPMD 23

stainless including carbides, food processing, plastic processingPMD 440

exeptionally high wear resistant cold work steel, with hi gh V-contentPMD 10

wear resistant cold work steel, increeased V-content, go od toughnessPMD V4

propertiesgrade

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Advantages of powder metallurgical tool steels

• good machinability

• good grindability

• good polishability

• high degree of purity

• high toughness

• high compressive strength

• high wear resistance

• structure with less segregations

• isotropic change in dimension

1948-4

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Principles of tempering behaviour

1803-7

+ Cr, Mo, V, W

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Advantages of secondary hardenable steels

Due to the high tempering temperatures these materials are most suited for the following process es:

� PVD-coating� CVD-coating� Nitriding� EDM� Grinding

The typical properties are:

� High toughness and high hardness� Dimensional adjustments possible

2232-9

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Heat treatment process

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Influence of tempering on micro structureand mechanical properties (grade DE - CPR)

1979-8.0

hardened58 HRc

impact value:

2 x tempered63 HRc

13 J

1 x tempered61 HRc

11 J

annealed25 HRc

3 x tempered63 HRc

28 J

40 µm

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Influence of the heat treatment of the carbide structure (material: PMD M4 / 62 HRc)

2763-9

20 µm20 µm

Globular carbide structure

Optimized heat treatment

Coagulation of carbides

Long austenitizing time

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Example for the use of PM- tool steel

Nummer

Quelle:

~ 20.000 piecesLife Time:

1.2379 plasma nitridedNht.~0,1mm

Material :

massive abrasive wear, evoked by hard powderparticles

Cause for theFailure:

57,5 HRCHardness:

160 x 100 x 105 mmDimensions:

pressing tool for brakelining production

Application:

Solution: Changing material to highwear resitant special steelPMD 10 ~62HRC

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Example for the use of PM tool steel

2788-0

use:

material:

hardness:

problem:

forming die

1.3343

62,0 - 62,5 HRC

insufficient toughness, crackpropagation along the carbides

10 mm

500 µm

solution: material change toPMD M4 with ca. 62 HRC

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Example of use: Coining punches

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Example for the use of PM tool steel

2760-9

Use:

Material:

Hardness:

Reason for failure:

⇒⇒⇒⇒

Coining punch

1.2379

59,5 - 60,0 HRC

Low toughness and compressive strength

Material change to PMD M4(62 ± 1 HRC)

20 mm

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Example for the use of PM tool steel

2759-9

Perforating knife

1.2067

63,5 HRC

Cracking in the cutting tees, less toughness

Material change to PMD23(64 ± 1 HRC)

20 mm

Use:

Material:

Hardness:

Reason for failure:

⇒⇒⇒⇒

2 mm

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Example for the use of PM tool steel

2757-9

Use:

Material:

Hardness:

Reason for failure:

⇒⇒⇒⇒

Cutting punch

1.2379

62,5 - 63,0 HRC

Less toughness

Changing material to PMD30 (63 – 64 HRC)

50 µm

10 mm

40 mm

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Comparison of lifetime 1.2379 ⇒ PMD23

0

20.000

40.000

60.000

80.000

100.000

Num

ber o

f pie

ces

1.2379 PMD23

Wire cuttingProduction way

Cold workWorking area

~20.000 pieces>60.000 pieces

Lifetime:1.2379 / 59 HRcPMD23 / 61 HRc

16MnCr5, ~600 MPa,5 mm, bright

Sheet material

142 x 76 mmdimensions

Precision blankingTool

2764-9

50 mm

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Comparison of lifetime 1.3343 ⇒ PMD10

0

50.000

100.000

150.000

Num

ber o

f pie

ces

1.3343 PMD10

Wire cuttingProduction way

Cold workWorking area

400.000 pieces>1.200.000 pieces

Life time:1.3343 / 63 HRcPMD10 / 63 HRc

Cupper, ca. 680 MPa, 0,2 mm, bright

Sheet material

ca. 13,5 × 4 mmdimensions

Blanking tool(high speed blanking)

Tool

30 mm

2761-9

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Economic calculation

16MnCr5

Material:

79,7 %Economic advantage [%]K:

0,0410,202Tool cost per punched part (I : C)J:

3.240,--1.210,--Total tool cost until failure (F + H)I:

2.700,--810,--Total cost of regrinding and changing tools (B x G)H:

270,--270,--Cost for the regrinding including changing toolsG:

540,--400,--Total tool cost (D + E)F:

140,--10,--Cost of the tool materialE:

400,--390,--Production cost of the toolsD:

€€Economy

80.0006.000Total parts per tool (A x B)C:

103Number of regrindingsB:

8.0002.000Produced parts before regrindingA:

PMD M4; 61 HRc1.2379; 59 HRcResult:

12.000/Month8,0 mm~ 600 N/mm²Precision blanking punch

Parts per Month:Thickness:Tensile Strength:Type of Tool:

1895-7

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Factors influencing tool life

1421-4

tool steelproduction

process

tool steelformingprocess

toolmaterial

geometry ofthe tool

toolmanufacturing

heattreatment

surfacefinishing

bondingstrength

second heattreatmentend finish

formingmaterial

formingprocess

lubricant

lubricantsupply

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Conclusion

�advantageous tool steel selection provides a lot of possibilities

�a) to improve the lifetime of toolsb) to increase the efficiency and to reduce the total costs

�The heat treatment process is an importent device to achieverequired micro structure and needed properties

The ideal prerequisites for later surface coatings should be accomplished during the stage of construction by advantageous tool steel selection, heat treatment,

dimensioning and design!

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Thank you for your attention

Milling cutterDE-PMD30 + PVD-TiN66,5 – 67,5 HRc