ttl tur-iso manual 2010.04.07 eng in construction partial - hard metal

7/31/2019 Ttl Tur-Iso Manual 2010.04.07 Eng in Construction Partial - Hard Metal

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| 07th April 2010 | PA-E.Menezes1

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01. Introduction

Historical


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01. Introduction

Historical

The start of cutting material development coincided with the beginningof the industrial revolution in the 18th and 19th centuries, and beganto accelerate rapidly with the advent of the 20th century.

Up until the 19th century, the field of metalworking remainedrestricted to the work of the smith before mechanically poweredmachines became available.


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01. Introduction

Historical - Cutting Tools Development for Turning

100

26

15

63 1,5 1 0,95 0,9 0,85 0,80

20

40

60

80

100

120

1900 1910 1920 1930 1960 1970 1980 2000 2001 2006 2010

year

Cutting

time(min.)

A

B

C

D

E

F

G

High-carbon steel

High Speed Steel (HSS)

Cast alloy "Stellite" (50% hard carbides)

Hard metal - Cemented carbide

Indexable inserts

Coated cemented carbice inserts

Multi-coated cemented carbice inserts

A

B

C

DE F G


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01. Introduction

Historical - Cutting Tools Development for Turning

Machine tools developed rapidly in step with newly developed types ofcutting materials. At the start of the 20th Century, metal cutting wasstill a laborious affair. Alloyed and unalloyed carbon steel qualities were

the best cutting materials available at the time. Further development in the field of metallurgy culminated in the

emergence of high-performance high-speed steel with a hot hardnessof up to 600C. The nineteen-thirties saw the advent of the family ofhard metals. Cutting assignments which used to take 25 minutes couldnow be completed in just five minutes.

The first types of hard metal to be developed were pure tungstencarbide-cobalt compounds (K types). Further developments resulted insteel types of hard metal based on tungsten carbide in a first phaseand other complex carbides and the bonding metal cobalt as a thirdphase.

Hard metal coating, an important step in the development of cutting

materials, was initiated at the end of the sixties. These coatingsrepresented a milestone in the development of cutting materials whichwere both wear proof and simultaneously tenacious. Today, almost90% of all hard metals used for drilling, turning and milling operationsare coated.


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01. Introduction

Cutting tool materials for metal cutting

Source: Fachkunde Metal, Europa Lehrmittel

RubberDiamond

High-temperature

wearbe

havior

Cutting tool material toughness


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01. Introduction


Requirements in terms of cutting tool materials:

In the removal process, the cutting wedge material is called cutting toolmaterial.

During the cutting process, the cutting tool material is subject to highmechanical, thermal, chemical and abrasive stress.

In order to be resistant to the above indicated stress, the cutting tool materialshould feature the following properties:

Wear resistance:Capacity to resist abrasion,

Toughness: Extremely high bending strength/ transverse rupture strength

Red hardness: Capacity of retaining hardness and chemical resistance even with highcutting temperatures (turning, max.1100C)

The following cutting tool materials feature one or several of the above properties:

High-speed steel (HSS)

Tungsten carbide

Cermet

Cutting ceramics

Polycrystalline cubic boron nitride (PCBN)

Polycrystalline diamond (PCD)


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01. Introduction


Maximum permissible temperatureat the cutting edge

700C800C

900C

1300C 1400C

1500C

HSS Stellite Hardmetal

CeramicPCBNPCD

400

200

150

60 5030

1000 900

1500

2500

4000

7500

Toughness

,B

Hardn

ess,HV

HSS Stellite

Hard

metal

Ceramic

PCBN

PCD

C


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01. Introduction


25 30 35 40 45 50 55 60 65 70 HRc250 285 325 380 420 485 560 HB

860 970 1100 1290 1430 1670 200 N/mm2

Cutting tool material

Workpiece material hardness

PCBN

Ceramic

Carbide


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01. Introduction


Regarding to the metal cutting process, the question frequently arises:which cutting tool material is used for which work piecematerial? if the hardness and/or strength of work piece material

reaches the upper or lower limit of machinability. Another FAQ: does the cutting operation still make economic

sense or is it far beyond profitability due to the compromises andconcessions to be made such as high tool attrition and extendedproduction times.

Coated Carbides cover the largest range of work piece materials,generally long chipping steels and their respective alloys.

The application ofceramic cutting tool material is very similar tothat of carbide when it comes to the machining ofshort-chippingcast materials.

Polycrystalline cubic boron nitride (PCBN) is used for machining

short-chipping cast iron and hard steels above 48HRc.


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01. Introduction


Source: Fachkunde Metal, Europa Lehrmittel

(approximately)

Other

Carbide

Ceramic

PCBN & PCD


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01. Introduction


Overview of cutting materials worldwide

Today, hard metals account for around half of the total consumption of cuttingmaterials, and have consequently assumed the role occupied by HSS in the

nineties.

There has been speculation over recent years about where hard metal will reachthe limits of its usefulness as a cutting material, and where the effects of coatingswill be exhausted.

It is frequently predicted that ceramic materials, cermets and new HSSdevelopments will take over many of the application fields currently dominated by

hard metals. However, in the meanwhile developments in the field of cuttingmaterials have shown that hard metals still continue to make continuous advancesas a cutting material.

The reason for this is the constant endeavour to achieve improved performance forcoated hard metal types and to improve wear resistance of the coatings usedrelative to the tenacity of the substrate.

The introduction of wide-ranging different new coated hard metal types in line withthe ISO classification system for workpiece material applications has also served toextend the field of application for carbides.

These objectives can only be achieved through specific research and developmentactivities.


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01. Introduction

Worldwide total production of indexable inserts distribution

Cermet

17%

Ceramic

10%

Coating

63%Carbide

10%

Coating

52%

Carbide

17%

Cermet

23%

Ceramic

8%

1998 2006

(Source: Ministry of Economy,Trade & Industry / JAPAN, 2006)

?


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01. Introduction

Worldwide potential - Indexable Tools Distribution Overview

Drilling

10%

Turning

65%

Milling

25%

ISO58%

Grooving

36%

Threading

7%

Indexable Tools Turning Tools

?


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02. Cemented carbide indexable inserts

Manufacture process


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Manufacture process

From powder to indexable insert

1

2

3

4

5

Tungsten core concentrate(scheelite, wolframite)

APT powder

(ammonium parawolframate)Tungsten oxide - powder

Tungsten - powder

Tungsten carbide - powder

1

23

4

5


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Manufacture process

Cobalt (CO)Binder

Tungsten carbide (WC)

Particles

Sinter areasWC-Co-Mixed crystals

Scanning electron microscope image


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Manufacture process

(Co/Ni) (WC) (TiC, TaC, NbC)


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Manufacture process

N

ano-materials

S

uperfine

U

ltrarfine

F

ine

sta

ndard


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Manufacture process

WC - Grain-size

Co-Binde

r-Quantity

WEA

RRE

SIST

ANCE

TENA

CITY


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Manufacture process / Main steps

TaC

NbCTiC

CoWC

Milling / BlendingMixing

Powdergranulation Pressing

SinteringGrindingCoating

VideoFrom powder to tool


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Manufacture process

3%-15%

BONDING AGENTMIXING CARBIDES

0%-25% Co = Cobalt

WC = Tungsten carbide

TiC = Titanium carbide

TaC = Tantalum carbide 3%-15%

HARD material + METAL bond = HARD METAL0%

-25% Co = Cobalt

Milling / BlendingMixing

Basic Elements

Milling and Granulation

Tungsten

Carbon

Mixing to a powder

Mixing Carburization1500-1800C

WC grain size0.6 6 m


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Manufacture process

Carburisation

Granulation Milling

Reduction

Mixing


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Manufacture process

Composition of press-ready powders

Hard metal can only be manufactured by means of powdermetallurgy.

The sourcing of raw materials and the energy-intensive processingmethods help to make hard metal raw materials relatively expensive.

Some hard metal manufacturers start their production process withtungsten carbide powder in different grit sizes, others prefer toproduce not only the carbide but also the metal from chemically puretungsten compounds. Depending on the required hard metal type, the

necessary quantities of tungsten carbide with a defined grit sizecharacteristic, complex carbides of a defined composition and cobaltare precisely weighed and prepared for milling.

The wet milling method used exclusively today serves to transform thepowder constituents into an ultra-finely dispersed conglomerate. Afterthe milling process, the wet sludge is passed through a sieve and themilling fluid and powder separated. As filling the press mould when

using automatic pressing processes calls for particularly goodpourability in the powder, the dried powder must subsequently betransformed into granulate. The pressing agent (e.g. 1-2% paraffinwax) is generally added during the course of drying.


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Porosity = 50%Shrinkage factor = 17%-20%

Pressed microstructure

PressingFilling

Pressing agent = 1-2% paraffin

Pressing


Manufacture process


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Manufacture process

Pressing of (hard metal) powder

The manufacture of indexable inserts for metal cutting or other moulded partsmade of hard metal begins with moulding by hand (hand forming) or mouldingusing pressing dies. The efficient method of moulding is direct pressing inpressing dies in high-speed automatic mechanical or hydraulic presses. The fillingof press moulds naturally calls for powders with particularly good pouringproperties.

As a result of pressing in single or double-sided automatic presses, the blank isgiven its basic shape, but not the measurements it is required to demonstrate inits sintered state. This type of compact has a porosity (shrinkage) of appr.50 % by volume, which disappears completely after the sintering process.The linear shrinkage factor for the width, height and length dimension isbetween 17 and 20%.

These dimensions must be taken into consideration as early as the design of thepress dies (male and female die).

As the carbides used (WC, Ti, Ta, Nb) do not have plastic deformation capability,the pressing forces are between 1.5 1.8 tons per cm2 (150 180 MPa). The

benefit of the pressing method for producing hard metals is the ability for directmoulding and also the achievable piece numbers at between 15 and 20 strokes perminute. Alternative methods are: Injection moulding, extrusion pressing, coldisostatic pressing.


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Manufacture process

1350C-1500C

Sintering

N


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Manufacture process

Hard metal sintering

Sintering requires first and foremost precise temperature regulation,process sequence times and a suitable atmospheric environment in

order to complete the enormous transformation from a porous powdercompact to a dense hard metal blank and so to the best possiblecutting material available.

The compacts prepared ready for sintering on graphite plates areplaced in the sintering oven. Initially during the heating-up process,the compacts reach the critical range at which the pressing aid

(paraffin) is expelled. The sintering process must be preciselytemperature and time controlled in order to ensure that theproduced carbide demonstrates the required characteristics.

During the sintering process, a reaction occurs which is called liquidphase sintering, meaning that on reaching the relevant prescribedsintering temperature of 1350 to 1500C, the bonding agent (cobalt) is

melted and a not insignificant quantity of carbide has dissolved.

The capillary forces which occur during sintering cause the pores toclose, while the powder grains join primarily as a result of diffusion.

ON


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Manufacture process

1000C 1000C

Grinding the contact surfaces

Cutting pressure

Cutting pressure

Support

Support

TION


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Manufacture process

Grinding the contact surfaces

Special grinding machines are generally used to grind the contactsurfaces (face grinding) of indexable inserts. On these machines, the

two face surfaces are ground between two diamond grinding wheelsinclined slightly towards each other, whereby the indexable inserts areembedded in steel cages.

The contact surfaces of the indexable inserts, which can be a one ortwo-sided version, are ground firstly in order to guarantee theprecision of the tool (centre height) and more importantly to

ensure improved heat dissipation during the metal cuttingprocess.

Hard metal is a poor conductor of heat, i.e. the entire metal cuttingenergy (heat) is stored primarily in the hard metal. During the metalcutting process turning, for example, when working with theparameters of an HC- P10 type, metal cutting temperature levels of1000C are reached close to the cutting edge radius.

In most clamping systems used for turning, bilaterally ground carbidebottom support are integrated in order to improve the dissipation ofheat.

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Manufacture process

Honing the cutting edges

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Manufacture process

Honing the cutting edges

By pressing and sintering in the press mould, a precision-sintered hardmetal blank has been created in its basic shape and with its finish-

sintered cutting edges and corner radii. However, due to the manufacturing process, at the precision

sintered cutting edges there is a slight burr formation which isdangerous for the subsequent metal cutting process.

The cutting edges should be protected for the metal cutting process.

Chamfering or rounding in order to stabilize the cutting edgeswas a customary practice as far back as soldered hard metal tools.

Most indexable inserts have corner-rounded cutting edges. Thistreatment of the sintered blank by means of brushing or blastingproduces a rounding effect and stabilizes the cutting edge.

Depending on the size of the indexable insert, the cutting edge radius,

hard metal sort and application conditions during metal cutting, therounding effect is between 10 m and 100 m.

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Manufacture process - Coating process

PhysicalVapourDeposition

ChemicalVapourDeposition

Coating

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Coating of hard metals

Modern coated hard metal types have improved substantially in termsof their reliability and efficiency since the introduction of the firstcoated hard metals (around 1970).

The underlying concept of an extremely tenacious core (substrate)surrounded by an extremely hard coating has meant a radicalincrease in both cutting speeds and also the service life of tools overrecent decades.

Today, coated indexable inserts are always amongst the first choicewhen it comes to metal cutting operations involving the drilling,turning or milling of steel or cast materials, stainless and hightemperature resistance steels.

The most frequently used coating processes are:

CVD (Chemical Vapour Deposition)

PVD (Physical Vapour Deposition)

thicker CVD coatings are used predominantly for drilling, turning andmilling, due to their higher stock removal rates

while thinner PVD coatings offer benefits where metal cuttingoperations call for sharp coated cutting edges or particularly hightenacity.

STRUCTIO

N


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Plasma-activatedT: 400 500 C

Low coating temperaturePress. inh. stress, high toughnessMicrocrystalline Smooth surfaceLayer thickness: 1 6 m

h

PVD

Coating the whole surface areaAdherence by the coatingTensile strength (layer)High-temperature wear resistanceLayer thickness: 3 25 m

h

CVD

Thermally activatedT: 800 1050 C

NSTRUCTI

ON


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CVD PVD

1 m 1 m

ONSTRUCT

ION


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How do you see if a insert is PVD or CVD coated?

Uncoated in the bore

PVD coating

Coated also in the bore

CVD coating

CONSTRUC

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Monolayer

crack crack

crack in the

substrate

PVD coating: TiB 4500HV from Cemecon



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INCONST


ISO materials machining groups

General catalogue 2007 / Page 24 / 26

page 798-803

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INCONS


ISO materials machining groups

There are many different workpiece materials on the market. Most ofthem can be machined without difficulty.

In accordance to ISO, the workpiece materials are divided into six

main machining groups; in addition, they have been assigneddifferent colors in order to simplify both the handling and theapplication of the materials.

In order to define the appropriate starting speed related to theindividual workpiece materials, the main machining groups are dividedinto sub-groups and classified in accordance to the treatment

condition, strength and/or hardness of workpiece material. In addition, the main machining groups are marked with the former

carbide designation symbols (P,M,K).

The cutting tool material manufacturers have developed suitablecutting tool materials for these main machining groups:

P= long-chipping steel M= stainless austenitic steelK= short-chipping cast iron N= nonferrous material

S= difficult cutting properties H= hard workpiece material

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ISO Workpiece Material Groups

ISO material groups

Psteel

MStainless

steel

KCastiron

NNon-ferrous

metals

SHeat-ResistantSuper Alloys

HHard

materials

Steel is the largestmaterial group in themetal cutting area, fromunalloyed to high-alloyded materials,including steel castingsand ferritic andmartensitic stainlesssteels.The machinability is

normally good, butdiffers a lot depending onmaterial hardness,carbon content, etc.

Stainless steels arematerials alloyed with aminimum of 12%chromium; other alloysmay include nickel andmolybdenum. Differentconditions, such asferritic, martensitic,austenitic andaustenitic-ferritic

(duplex), create a largefamily. For these typesthe cutting edges areexposed to a great dealof heat, notch wear andbuilt-up edge

Cast iron, is a short-chipping type of material.Grey cast irons (GCI)and malleable castirons (MCI) are quiteeasy to machine, butnodular cast irons(CGI) andaustempered castirons (ADI) are more

difficult. All cast ironscontain SiC, which is veryabrasive to the cuttingedge

Non-ferrous metals aresofter metals, such asaluminium, copper,brass, etc. Aluminiumwith a Si-content of 13%is very abrasive.Generally high cuttingspeeds and long tool lifecan be expected forinserts with sharp edges.

Heat-Resistant SuperAlloys include a greatnumber ofhigh-alloyediron, nickel, cobalt andtitanium basedmaterials. They aresticky, create built-upedge, harden duringworking (workhardening), and generate

heat. They are verysimilar to the ISO M areabut are much moredifficult to cut, andreduce the tool life of theinsert edges.

Hard materials groupincludes steels with ahardness between 45-65HRc and also chilledcast iron around 400-600 HB. The hardnessmakes them all difficultto machine. Thematerials generate heatduring cutting and are

very abrasive for thecutting edge.

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INCO



The metal cutting industry produces an extremely wide varietyof components machined from many different materials.

Each material has its own unique characteristics that are

influenced by the alloying elements, heat treatment, hardness,etc.

These combine to strongly influence the choice of cutting toolgeometry, grade and cutting data.

Therefore, workpiece materials have been divided into six

major groups, in accordance with ISO-standard and each grouphas unique properties regarding machinability

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General catalogue 2007 / Page 798-803

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IN

02. Cutting tool material - indexable inserts

ISO grade designation

ISO P M K N S H

0105

10

1520

25

30

35

40

INCREASEWEAR

RESISTANCE

INCREASE

THOUGHNESS

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Application tables - Turning grades

General catalogue 2007 / Page 66

W A P 1 0

Cutting / Turning

Wear resistance / toughness

Main application

Coating (X = PVD)

WALTER

Old designation key

W P P 1 0

Turning (0), Boring (5)Grooving/Parting off (3)

Wear resistance / toughness2nd main application

1st main application

WALTER

W S M 3 3

W K P 3 5

New designation key

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Application tables - Turning grades

ISO P M K N S H

01 WPP 01 WXN 10* WPP 01*05 WPP 05 WK 1 WCB 30

10WPP 10

WAK 20*

(WAM 10)

WSM 10

WAK 10new

WPP 05*

WCB 50*

WXN 10

(WK 1*)

WS 10

WSM 10

WCB 50

1520

WPP 20

WSM 20*

(WAM 20)

WSM 20

WAK 20

WSM 10

WPP 10*

WSM 20

25

30WPP 30

(WAM 30)

WSM 30

WAK 30

WPP 20*WSM 30 WAK 10*

35

40 WAK 30*

INCREASEWEAR

RESISTANCE

INCREASE

THOUGHNESS

* => Secondary application() => old grade

ttl tur-iso manual 2010.04.07 eng in construction partial - hard metal

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