Selecting the Right Tool Steel for Your Metalforming ... Selecting the Right Tool... · 1 Choosing the right steel for your metalworking applications Patricia Miller, Senior Technical

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Choosing the right steel for your metalworking applications

Patricia Miller, Senior Technical Manager,

©2015 Bohler-Uddeholm

Selecting the Right Tool Steel for

Your Metalforming Application.

Patricia Miller,

Senior Technical Manager




Application

Work materials

Failure mechanism of tooling steel

Production method of the tooling steel

Serial length

Complexity of geometry

What parameters drive your tooling material choice?

2




Application

Work materials

Failure mechanism of tooling steel

Production method of the tooling steel

Serial length

Complexity of geometry

What parameters drive your tooling material choice?




Cold Work Applications

3




Overview of Today’s

Working Materials




Grades with good ductility Copper and copper derivatives

Aluminum

Mild steel

Stainless steel

Grades with less ductility

Cold rolled steels

Spring steels

Hard materials

Grades with higher abrasive nature

Electrical steels

Ceramics

Hard metals

Common Work Materials

4




Work Material Comparisons: Cold Forming and Stamping

0

10

20

30

40

50

60

200 400 600 800 1000 1200 1400

Form

abili

ty, A

80

(%)

Mild Steel

HSLA

DP-steel

Trip-steel

Mart. steel

Bake Hardenable

IF

MPa

58 87 116 145 174 203 KSI 29

~125HB ~180HB ~22HRC ~33HRC ~38HRC ~44HRC

70

Boron - steel

High Strength

Stainless Steel




30% martensite

70% ferrite

50% martensite

50% ferrite

100% martensite

Du

400 600 800 1000 1200 1400 Strength MPa

Dual Phase Alloys

5




Third Generation Developments: Sheet Metal Grades




M 1400 MPa

800 MPa

500 MPa

280 MPa

Shock wave during breakthrough

High force

Punch diameter: Ø 4.80 mm (0.19”)

Die clearance: 10%

Sheet thickness: 1 mm (0.039”)

Influence of Sheet Material Strength

6




Introduction to

Tooling Failure Types




Tool Steel Failure Mechanisms

7




Wear (abrasive or adhesive)

Results in a material loss and is related to the sheet material type,

the application and the process conditions

Abrasive Wear Adhesive Wear

Failure Mechanisms in Cold Work




Material is lost because of friction between tooling and work material

This is a predictable failure

Solutions for Abrasive Wear

Abrasive wear resistance is normally base on hardness and / or carbide volume of the tooling material

Tooling material

Surface Treatments

Abrasive Wear

8




Volume fraction and type of primary alloy carbide

in the heat treated microstructure:

Distribution of primary carbides

Size of primary carbides (severe abrasion only)

Hardness , quality and type of heat treatment

Chromium carbide (M7C3) 66-68 HRC

Molybdenum carbide (M6C) 72-74 HRC

Tungsten carbide (M6C) 72-74 HRC

Vanadium carbide (MC) 82-84 HRC

Wear Resistance is a function of…




Normally referred to as micro-welding of tooling material to work material.

Tooling material is pulled out.

Is often misdiagnosed as abrasive wear.

Solutions to Adhesive Wear:

Tooling material, improving chipping resistance.

Pull-out

Adhesive Wear

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Is related to the stresses in the process and the fatigue resistance of

the tool material.

Chipping

D2

Uddeholm Vanadis® 4 Extra

SuperClean

Chipping




Occurs if the process stresses are higher than the compressive

strength of the tool steel.

Plastic Deformation

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Occurs when the process stresses, and presence of an existing crack

result in a stress level higher than the toughness of the tooling

material.

Cracking




Is a physical and/or chemical adhesion of the work material to the tool surface.

The severity of galling depends on the surface finish and chemical composition of the tool steel and work material.

Proper use of surface treatments can also reduce galling.

Galling

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Identify the dominating failure mechanism.

Select a tool steel with better resistance to the

dominating failure mechanism.

Goal: Reliable and economical production:

The choice will depend on the steel’s inherent

capabilities and its production method.

Method for Steel Selection in Cold Work Applications




Today’s Tool Steel Options

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Heat Treatment Machining

ESR Re-Melting EAF Vacuum-De-Gassing Ladle Furnace Uphill Casting

Melting Shop

Stock Forging Plant Rolling Mill

Inspection &

Testing Customer

Conventional / Ingot Steel Production




High Reduction Forging

Breakdown of the solidification structure to

obtain a fine-grained austenite and freedom from

carbide networks.

Tool Steel Production: Hot Working

13




D2 Structures: Can be very different from each manufacturer




Punch made from standard D2 – premature failure

Starting material: bar rd. 33 mm

Tool Failure: D2

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Controlled Carbide distribution with Bohler K110

Bar rd. 33 mm, Direction: Longitudinal / Magnification: x 100

Standard Grade 1.2379

Carbide Distribution




The most popular tool steels for blanking; trim, forming

and calibration dies:

AISI A2: 5 % Chromium steel, air hardening, general

purpose, hardness is 58-62 HRC.

AISI D2: 12 % Chromium steel, air hardening, high wear

resistance, hardness of 60-62 HRC.

These grades are not always suitable for demanding

coldwork applications.

Not easy to salvage when chipping, wear, or galling take

place.

The cold work tooling environment: Conventional Grades

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The Goal: Extend the life of the tool first by minimizing failure

modes like chipping so that we can address the wear failure modes.

Time for crack initiation

Time for crack

propagation

Tool lifetime

Tool with poor

surface finish

Tool with

EDM-surface layer

Tool material with

carbide stringers




Electroslag remelting

The small amount of liquid metal solidifies much faster than a large steel melt which gives:

Less time for carbide growth during solidification.

improved homogeneity and smaller carbides.

The remelting takes place under a liquid active slag layer which removes inclusions.

Consumable

Water Cooled Mold

Molten Slag

ESR’ed Ingot

Remelting under protected

atmosphere

Conventional Tool Steel Production with Secondary Melting

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More consistent structure in the steel

More consistent to machine.

Easier and more consistent to heat treat.

Much higher toughness and more uniform in all directions.

Permits new grade development

Allows for high temperature tempered grades to replace older

versions.

Better stability in operation.

Easier to coat.

Greater versatility in the types of coatings to use.

More uniform wear rates, with less chipping.

Benefits of Re-Melted Steel




Conventional Produced and Remelted

Bohler W360 Isobloc®:

An ESR produced very high toughness hot work tool steel, high temperature tempered to 54-56 HRC.

Uddeholm Caldie®: An ESR produced high toughness medium wear resistance tool steel. With a typical working hardness of 58-62HRC and high temperature tempering.

Readily weldable and coatable.

Bohler K340 Ecostar®/Isodur®: A medium toughness good wear resistance tool steel. With a typical working hardness of 58-64HRC and high temperature tempering. Use instead of M2, M4, D2.

Quick overview of BU Tooling Materials for High Strength Work Materials

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8 Trim dies in Caldie

PVD TiCN coated

DP 600 sheet;

1.8 mm (0.071”) thick

Production since 2005:

800,000 parts/die with no downtime.

In total, over 2.5 millions parts have

been produced.

Results from Production Tools




Photo Micrographs are at 500x

AISI D2 8% Cr Steel ESR

Microstructure Comparison

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8 T heat size

Large Tundish with

ESH and EMS

Fine powder

gas atomization Direct capsule filling without

extra powder handling

Cold Load

Hot Unload

HIP

Powder Metallurgical (PM) Steel Production

PM PRODUCTION ROUTE




Advantages to Tool Users

Wider selection of grades that can have better wear characteristics.

Less variation in performance.

Reduced risk of cracking and chipping failures.

Reduced risk of fatigue failures.

Longer tool life

Less Downtime and Maintenance = Improved Profitability

Powder Metallurgical Steel Advantages

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More uniform response during tool making with regards to:

More consistent machinability/grindability.

Reduced risk of problems during EDM.

Reduced risk of problems during polishing.

Improved adherence of surface coatings.

Powder Metallurgical Steel Advantages

Advantages to Tool Makers




PM 4V Conventional Steel (AISI D2)

Improvements in Cleanliness Bohler-Uddeholm

PM Standard Market PM

Powder Metallurgical Production Process

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Surface polished to Ra 0.029 µm

Dense distribution of very low

friction* nitro-carbides (M(N,C) to

support the work material.

Many deep lubricant reservoirs.

* Much lower friction coefficient than the carbides in our other PM steels.

New PM Technology: PM + Nitrogenated Powders




Powder Metallurgy with Uddeholm SuperClean Technology

Uddeholm Vanadis® 4 Extra SuperClean:

High toughness with good wear resistance PM tool steel. Typically hardness range of 58-64HRC with high temperature tempering.

Uddeholm Vanadis® 8 SuperClean: New Development for Trials PM steel, used in applications where abrasive wear resistance is critical. Typical hardness range is 58-62 HRC.

Uddeholm Vancron® 40 SuperClean:

Medium toughness with excellent resistance to galling. Typical hardness range 58-65HRC, with heat treatment similar to Vanadis 23.

Quick Overview of Tooling Materials

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Uddeholm Vanadis® 4 Extra SuperClean




Forming Die for Producing a Bolt Fastener

Part

Vancron 40 coated with PVD Coating by Thermo Tech produced

500,000 parts and still running customer commented that the insert still looks GREAT!

Produced part

Bolt fastner part for Mid Sized trucks.

Sheet Steel

Uncoated HSLA Steel, Hytens 55 ksi,

Rm=350 MPa, HRPO t=5 mm

Tool Steel and Production Conditions

Uncoated Vancron 40 and D2 TD Coated

Dimension: 3.50 x 4.00 x 5.00”

Hardness: 60 HRC

Surface Roughness: Ra=0,1 um ?

Lubrication: 10% Oil Emulsion

Press speed: 60 parts/min

Galling / flaking of TD

coating on D2

Case Study: Vancron® 40 SuperClean

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Application: Forming

Company: Presstran

Type of tool: Bolt Fastener

Work material: HSLA Hytens 55 ksi Thickness: 5mm

Process:

Case Study: Vancron® 40 SuperClean




Powder Metallurgy with Bohler MICROCLEAN ® Technology

K890 MICROCLEAN®:

Extremely high toughness in a PM tool steel: 3 Percent Vanadium Grade.

S693 MICROCLEAN®:

Good combination of wear resistance and ductility in a PM steel: high carbon PM M4.

K294 MICROCLEAN®:

Very high wear resistance in PM steel: a third generation PM A11.

S390 MICROCLEAN®:

Modified PM T15 with extremely high hardness capabilities and compressive strength.

Quick overview of Tooling Materials

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Putting it all Together




Does your tool steel source produce the grades they

supply to you?

Do you know how the steel is being produced?

Do they address your concerns and provide corrective

action when you need it?

Do they create new grades to address your current and

future concerns?

Supplier’s contribution:

• Premium Grade Tool Steel

• Application-Designed Steel

• Full Technical Service

Critical questions…..just as with your work materials

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47

UDDEHOLM VANADIS 8

SUPERCLEAN

General Comparison: Abrasive Wear Resistance vs. Toughness




Bohler W360 Isobloc®

Uddeholm Caldie®

Bohler K340 Ecostar®/Isodur®

Uddeholm Vanadis® 4 Extra

Hardness

Chipping

Resistance

Tool Steels for Good Chipping Resistance

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Abrasive Wear

Uddeholm Vanadis® 8 SuperClean

Bohler K294 MICROCLEAN®

Adhesive Wear

Uddeholm Vanadis® 4 Extra SuperClean or

Uddeholm Caldie®

Combination

Bohler K340 Ecostar®/Isodur®

Uddeholm Vancron® 40 SuperClean

Tool Steels Used for Wear Resistance





Uddeholm Vanadis® 8 SuperClean

Uddeholm Vancron® 40 SuperClean

Add coatings when needed!

Improved

Galling

Resistance

Tool Steels Used for Galling Resistance

26





Bohler S693 MICROCLEAN®

Bohler S390 MICROCLEAN®

Tool Steels for High Compressive Strength




Total Tooling Economy: Bring all of your costs to the surface

27




Upgrading Your Tooling Performance with

Application Specific Heat Treatment and

Coatings.

Please join us for our next webinar in early 2016




Questions?

Selecting the Right Tool Steel for Your Metalforming ... Selecting the Right Tool... · 1 Choosing the right steel for your metalworking applications Patricia Miller, Senior Technical

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