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PE4652 Proses.Man.Lanjut

Material Benda Kerja dan Material Alat

Potong

TEKNIK DAN SISTEM PRODUKSI

Materi1 Pertimbangan Pemilihan Alat Potong

2 Material Alat Potong

3 Teknik Pembuatan Alat Potong Sisipan

4 Material Benda Kerja

5 Kerusakan Alat Potong

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Considerations of Cutting Tool Selections

MASUKAN

Pertimbangan

Pemilihan

Alat Potong

BATASAN

Proses Manufaktur, continuous vs inturrepted

Kondisi dan kapabilitas mesin perkakas (rigidity)

Persyaratan: geometry, finish, accuracy & permukaan

Workholding devices (rigidity)

JadwalProduksi waktu proses

Pemilihan alat potong material,

grade, bentuk dan geometri

Speed (rpm)

Feed

Depth of cut (doc)

Cutting fluids

Material benda kerja kekerasan,

komposisi & keadaan metalurgi

Jenis pemotongan roughing vs

finishing

Ukuran bagian& geometri - rigidity

Lot size small batch & mass

production

Machinability data tool life/specific

power

Kualitas dan kapabilitas yang diperlukan

Pengalaman perencana


Materi

1 Pertimbangan Pemilihan Alat Potong





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Cutting tool materials

Cutting Tool Materialrequirements :

Hard, to resist flank wear and deformation

Tough, to resist bulk breakage

Non-reactive with the workpiece material

Chemically stable, to resist oxidation and diffusion Resistant to sudden thermal changes.


Jenis-jenis Material Pemotong

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Perkembangan Alat Potong


Hard Cutting Materials I

Hardmetals:

o Uncoated hardmetal containing primarily tungstencarbide (WC)

o Uncoated hardmetal, also called cermet, containingprimarily titanium carbides (TIC) or titanium nitrides(TIN) or both.

o Hardmetals as above, but coated.

o

Cubic carbonitrides, as -phase, increase hothardness and to form gradients

o Gradients are used to combine improved plasticdeformation resistance with edge toughness

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Performance = f(composition & microstructure)

Composition: Amount of WC, TiC, TaC, NbC, Co, .

Microstructure: Carbide grain size & distribution,

cobalt mean free path

Straight WC-CoStraight WC-Co WC-(Ti,Ta,Nb)C-CoWC-(Ti,Ta,Nb)C-Co

Subtrat Cemented Carbide


Mikrostruktur Cemented Carbide

Elemen:

Alpha-phaseWC (tungsten carbide)

Gamma-phase(Ti,Ta,Nb)C(titanium, tantalum,niobium-carbides)

Beta-phaseCo (cobalt)

Hair diameter = 50-70 m

Cemented Carbideshard particles (carbides)in a binder matrix

The Bindermore Cobaltalso Nikel

Hard particles WC +fasa gamma (Ti, Ta, Nbcarbides & nitrides)

The gamma phase has abetter hot hardness and isless reactive at elevatedtemperatures

WC has a better abrasive wear resistance.

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Fundamental characteristics

Apart from the grain size of the WC, the amount of binder phase (cobalt) is animportant factor determining the characteristics of the carbide.

Amount of binder

Wear resistant

Toughness

WC grain size


Hot Hardness

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Classification - ISO

Increasing speed


Coating designMany factors influence the behavior of the insert:

Coating process Coating material Coating thickness Post treatment Surface morphology.

Wear resistance Toughness

ISO P01 P15 ISO P05 P30 ISO P10 P35 ISO P20 P45

o Thicker coatings mean more wearresistance

o Harder substrates mean more deformationresistance

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The Coating of Cemented Carbide

Al2O

3 Coating for chemical and thermal wearresistance.

TiCN MTCVD coating for mechanical wear

resistance

Functional gradient For optimized hardness and toughness.

Cemented carbide

Plastic deformation resistance.


Cermet

A cermet is a cemented carbide with titanium based hardparticles

o TiC and nickelo titanium carbonitride Ti(C,N), (Ti,Nb,W)(C,N)o W-rich cobalt binder

Cermets have :

High flank and crater wear resistance

High chemical stability and hot hardness

Low tendency for built-up edges to form

Low tendency for oxidation wear

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sumber : L.A. Dobrzaski et.al.,2010


Hard Cutting Materials II

Ceramics:o Oxide ceramics containing primarily aluminium oxide

(Al2O3).

o Mixed ceramics containing primarily aluminium oxide(Al2O3) but containing components other than oxides

o Nitride ceramics containing primarily silicon nitride(Si3N4).

o Ceramics as above, but coated

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Ceramics

Oxide ceramics are aluminium oxide based (Al2O3), with added

zirconia (ZrO2) for crack inhibition. This generates a material that ischemically very stable, but which lacks thermal shock resistance

Mixed ceramics are particle reinforced through the additionof

cubic carbides or carbonitrides(TiC, Ti(C,N)). This improves

toughness and thermal conductivity.

Whisker-reinforced ceramics use silicon carbide whiskers (SiCw)

to increase toughness and enable the use of coolant

Silicon nitride ceramics (Si3N4) , their elongated crystals form a

self-reinforced material with high toughness

Sialon (SiAlON) grades combine the strength of a self-reinforcedsilicon nitride network with enhanced chemical stability


Hard Cutting Materials III

Superhard Cutting Materials :

o Diamond

Polycrystalline diamond

o Boron nitride

Cubic boron nitride

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Polycrystalline cubic boron nitride, CBN

CBN is manufactured through high temperature and pressure to bond

the cubic boron crystals together with a ceramic or metal binder. Therandomly oriented particles form a very dense polycrystalline structure.

The actual CBN crystal is similar to that of synthetic diamond.

Amorphous BN

powder

crystalline

h-BN

c-BN

Heating nitrogen flow

above 1500 C

Annealing higher

temperatures

pressures above 5 GPa


Polycrystalline diamond, PCD

PCD is a composite of diamond particles sintered together with ametallic binder

As a cutting tool, it has good wearresistance but it lacks chemicalstability at high temperatures anddissolves easily in iron

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Materi







The development of cutting tool material

Indexableinserts

First coatedinsert

Thick aluminumoxide coating

Functionalgradients

New generationcoatings

A new insertgeneration

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Powder Production


Pressing powder compacts

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Sintering the pressed inserts

Sintering phase consists of the following phases:o Loading trays of inserts into a sintering furnace.o The temperature is raised to ~1400 C.

o This process melts the cobalt and the cobalt acts as a binder

o The insert will shrink 18% in all directions during the sintering phase; this corresponds to about50% in volume

1. Unsintered insert2. Sintered insert3. Coated insert

32

1


Different types of grinding operations

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CVD Chemical Vapor Deposition

The process is carried out at approx. 900 C for 30 hours.Thickness is approx 2-12 microns.

The advantages of CVD coatings:

The ability to making thick coatings.Ability to make even coating

thickness.Very good adherence/bonding to the

carbide substrate.Very good wear resistance. Possibility to make oxide coatings


PVD Physical Vapor DepositionPhysical Vapor Deposition (PVD) coatings are formed at relatively low temperatures (400-600 C). The most common source is titanium (Ti).The coating thickness is in the range of 2-6 microns.The most common PVD layers today are TiN, Ti(C,N), (Ti,Al)N, (Ti,Al,Cr)N, also aluminumoxides

The advantages of PVD coatings:

PVD provides good edge line toughness. PVD coatings can maintain a sharp

cutting edge. PVD can be used on brazed tips. PVD can be used on solid carbide tools

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Materi







Berkenaan dengan machinabilityKlasifikasi Material menurut ISO

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Machinability definition

Three main factors that must be identified in order to determine a materialsmachinability:

1. Classification of the workpiece material from a metallurgical/mechanical pointof view.

2. The cutting edge geometry to be used, on the micro and macro levels.

3. The cutting tool material (grade) with its proper constituents, e.g. coatedcemented carbide, ceramic, CBN, or PCD, etc.


Standar Internasional

DIN ( Jerman ) - Deutsche Industrie Normung

JIS ( Jepang ) -

AISI-SAE ( Amerika ) - American Iron and Steel Institute

BS ( Inggris )

AFNOR ( Perancis ) - Assocaition Francaise de Normalisation

SS ( Swedia )

UNE ( Itali )

GB ( China ) - Guojia Biaozhun

Nippon Kgy Kikaku

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Steel

Definition

Steel is the largest workpiece material group in the metalcutting area.

Steels can be non-hardened, or hardened and tempered witha common hardness up to 400 HB.

Steel is an alloy with iron as the major component (Fe-based).

Unalloyed steels have a carbon content lower than 0.8%, andare composed solely of iron (Fe), with no other alloyingelements.

Alloyed steels have a carbon content that is lower than 1.7 %and alloying elements such as Ni, Cr, Mo, V and W.

Low alloyed steels have alloying elements less that 5%.

High alloyed steels have more than 5% alloying elements.


Steel

Machinability in general

The machinability of steel differs, depending on alloyingelements, heat treatment and manufacturing process(forged, rolled, cast, etc.).

In general, chip control is relatively easy and smooth.

Low carbon steels produce longer chips that are sticky andrequire sharp cutting edges.

Specific cutting force kc1: 1400-3100 N/mm2.

Cutting forces, and thus the power required to machinethem, remain within a limited range.

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The ISO nomenclature in the ISO-P area

Operations and working conditions

Internal and external finishing turning; high cutting speed; small chip

area; good surface finish; narrow tolerances; no vibrations

Turning; copying; threading; milling; high cutting speed; small tomedium chip area

Turning; copying; medium cutting speed; facing with small chiparea; medium to difficult conditions

Turning; milling facing; medium to low cutting speed; medium tolarge chip area; includes operations with tough conditions

Turning; facing; milling; cutting; grooving; low cutting speed; largechip area; large possible chip angle; very tough conditions

When very high toughness in the tool is needed in turning, facing,

grooving, cutting, low cutting speed, large chip area, large possiblechip angle, extremely tough conditions

S P C Co Cr Mn Mo Ni N Si Wc V

Meningkatkan

Mampu putus tatal X

Kemampuan mempertahankan daya

potongX X

Kekuatan tarik X X X X X X X X X X X

Sifat liat X X

Sifat tahan aus X X X

Kekerasan X* X X X X X X X

Ketahanan thd temperatur tinggi X X X X X X

Kedalaman kekerasan X X X

Sifat simpan kekerasan X X

Elastisitas X

Batas luluh X X X X X

Ketahanan thd korosi X X X X

Menurunkan

Sifat mampu mesin X X X X X XSifat liat X

Sifat mulur X X X X X X

Kepekaan thd panas lanjut X X X

kekuatan kejut takikan X

Kekuatan tumbuk X

Sifat mampu las X X X

Sifat mampu tempa X X X X X

Sifat mampu bentuk X X X X X

Pengaruh Elemen Paduan

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Stainless steel

Definition

An alloy with the element iron (Fe) as the major constituent.

Has a chrome content which is higher than 12%

Has a generally low carbon content (C 0.05 %).

Various additions of Nickel (Ni), Chromium (Cr), Molybdenum (Mo),Niobium (Nb) and Titanium (Ti), supply different characteristics,such as resistance towards corrosion and strength at hightemperatures.

Chrome combines with oxygen (O) to create a passivating layer of

Cr2O3 on the surface of the steel, which provides a non-corrosiveproperty to the material.


Stainless Steel Clasification

40

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Identification of material group


Stainless steelMachinability in general

Long-chipping material.

Chip control is fair in ferritic/martensitic materials, becoming morecomplex in the austenitic and duplex types.

Specific cutting force: 1800-2850 N/mm2.

Machining creates high cuttting forces, built-up edge, heat and work-hardened surfaces.

Higher nitrogen (N) content austenitic structure, it increases strength andprovides some resistance against corrosion, but lowers machinability,

while the deformation hardening increases. Additions of Sulphur (S) are used to improve machinability.

High C-content (>0.2%) provides relatively large flank wear.

Mo and N decrease machinability, however, they provide resistance to acidattacks and contribute to high temperature strength.

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Machinability


Cast Iron

Definition

There are 5 main types of cast iron :

Grey Cast Iron (GCI),

Malleable Cast Iron (MCI),

Nodular Cast Iron (NCI),

Compacted Graphite Iron (CGI)

Austempered Ductile Iron (ADI).

Cast iron is a Fe-C composition with a relatively high percentage of Si(1-3%). Carbon content is over 2%, which is the maximum solubilityof C in the austenitic phase. Cr (Chromium), Mo (Molybdenum) and V(Vanadium) form carbides, which increase strength and hardness, butlower machinability.

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Cast Iron


Short-chipping material with good chip control in most conditions.Specific cutting force: 790 1350 N/mm2.

Machining at higher speeds, especially in cast irons with sand inclusions, createsabrasive wear.

NCI, CGI and ADI require extra attention due to the different mechanicalproperties and the presence of graphite in the matrix, compared to normal GCI.

Cast irons are often machined with negative type of inserts, as these providestrong edges and safe applications.

The carbide substrates should be hard and the coatings should be of thickaluminium oxide types for good abrasive wear resistance.

Cast irons are traditionally machined dry, but can also be used in wetconditions, mainly to keep the contamination of dust from carbon and iron to a

minimum. There are also grades available that suit applications with coolantsupply


Cast Iron

The austempering heat treatment converts ductile iron, (NCI), into austemperedductile iron (ADI).

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Non-ferrous materials

Definition:

This group contains non-ferrous, soft metals with hardnesses under130 HB, except for high strength bronzes (>225HB)

Aluminium (Al) alloys comprising less than 12-13% silicon (Si)represent the largest part

MMC: Metal Matrix Composite: Al + SiC (20-30%)

Magnesium based alloys

Copper, electrolytic copper with 99.95% Cu

Bronze: Copper with Tin (Sn) (10-14%) and/or aluminium (3-10%)

Brass: Copper (60-85%) with Zinc (Zn) (40-15%)


Non-ferrous materials

Machinability of aluminium

Long-chipping material

Relatively easy chip control, if alloyed

Pure Al is sticky and requires sharp cutting edges and high Vc

Specific cutting force: 350700 N/mm

Cutting forces, and thus the power required to machine them,are low.

The material can be machined with fine-grained, uncoatedcarbide grades when the Si-content is below 7-8%, and withPCD tipped grades for Aluminium with higher Si-content.

Over eutectic Al with higher Si-content > 12% is very abrasive.

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Heat Resistant Super Alloys (HRSA) and Titanium

Definition

The ISO S group can be divided into heat resistant super alloys(HRSA) and titanium.

HRSA materials can be split into three groups: Nickel-based, iron-based and cobalt-based alloys.

Condition: Annealed, solution heat treated, aged, rolled, forged,cast

Properties: Increased alloy content (Co more so than Ni), resultsin better resistance to heat, increased tensile strength and highercorrosive resistance

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The physical properties and machining behavior of each variesconsiderably, due both to the chemical nature of the alloy and theprecise metallurgical processing it receives during manufacture.

Annealing and aging are particularly influential on the subsequentmachining properties.

Difficult chip control (segmented chips)

Specific cutting force: 24003100 N/mm2 for HRSA and 13001400N/mm2 for titanium

Cutting forces and power required are quite high



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Hardened steel

Definition

This group of materials contains hardened and tempered steels withhardnesses >45 68 HRC.

Common steels include carburizing steel (~60 HRc), ball bearingsteel (~60 HRc) and tool steel (~68 HRc). Hard types of cast ironsinclude white cast iron (~50 HRc) andADI/Kymenite (~40 HRc).Construction steel (4045 HRc), Mn-steel and different types of

hardcoatings, i.e. stellite, P/M steel and cemented carbide alsobelong to this group.

Typically hard part turning fall within the range of 5568 HRC.

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Hardened steel

Machinability

Hardened steel is the smallest group from a machining point of viewand finishing is the most common machining operation. Specific cuttingforce: 25504870 N/mm2. The operation usually produces fair chipcontrol. Cutting forces and power requirements are quite high.

The cutting tool material needs to have good resistance to plasticdeformation (hot hardness), chemical stability (at high temperatures),mechanical strength and resistance to abrasive wear. CBN has thesecharacteristics and allows turning instead of grinding.

Mixed or whisker reinforced ceramic are also used in turning, when theworkpiece has moderate surface finish demands and the hardness is toohigh for carbide. Cemented carbide dominates in milling and drillingapplications and is used up to approx. 60 HRc.


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