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A STUDY OF CASTING CHARACTERISTICS FOR “ DIE-CAST ALUMINUM ALLOY” ME8109: Casting And Solidification of Material Department of Mechanical & Industrial Engineering Graduate Program in Mechanical Engineering Ryerson University ME8109: Casting And Solidification of Material Submitted To: Dr. C.RAVINDRAN Prepared by: Anwar Hussain 1

A STUDY OF CASTING CHARACTERISTICS FOR “ DIE-CAST …rravindr/A Study of Casting Characteristics for Die... · A STUDY OF CASTING CHARACTERISTICS FOR “ DIE-CAST ALUMINUM ALLOY

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Page 1: A STUDY OF CASTING CHARACTERISTICS FOR “ DIE-CAST …rravindr/A Study of Casting Characteristics for Die... · A STUDY OF CASTING CHARACTERISTICS FOR “ DIE-CAST ALUMINUM ALLOY

A STUDY OF CASTING CHARACTERISTICS

FOR “ DIE-CAST ALUMINUM ALLOY”

ME8109: Casting And Solidification of Material

Department of Mechanical & Industrial Engineering

Graduate Program in Mechanical Engineering

Ryerson University

ME8109: Casting And Solidification of MaterialSubmitted To: Dr. C.RAVINDRAN

Prepared by: Anwar Hussain

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• CONTENTS:

• INTRODUCTION

• CAST ABILITY

• TYPE OF STANDARD DIE CAST ALUMINUM ALLOYS

• CHEMICAL COMPOSITION

• PHYSICAL AND MECHANICAL PROPERTIES

• CHARACTERISTICS OF DIE CAST ALUMINUM ALLOYS

CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

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• CHARACTERISTICS OF DIE CAST ALUMINUM ALLOYS

• COMPARISON DIFFERENT DIE CAST MATERIAL WITH DIE CAST AL-ALLOY

• DIE SOLDERING:

• SLUDGE FORMATION

• EFFECT OF HOLDING TEMPERATURES FOR SLUDGE FORMATION

• SLUDGE FORMATION FACTORS

• FLUDITY

• FACTORS WHICH EFFECT ON FLUDITY

• POROSITY

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

INTRODUCTION

Die casting technology is one of the mainly applied manufacturing practice

In the die casting process the molten metal is injected under pressure into the

hardened steel dies .

Different casting processes require the alloy to have different casting

characteristics. We will define here the different casting characteristics of die cast

AL- Alloy

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1) Cast ability

2) sludge Formation

3) Alloy fluidity

4) Machine ability

5) Die soldering

6) Porosity

7) Macro segregation

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

�Cast ability is the property of an alloy to be cast without formation of defects such as

cracks, segregations, pores or mis runs.

�Alloy dependent the phenomena that determine castability, fluidity, macro segregation,

hot tearing and porosity.

�Cast ability of aluminum alloys can also defined such as solidification path, dendrite

CASTABILITY:

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�Cast ability of aluminum alloys can also defined such as solidification path, dendrite

coherency, solidification shrinkage and inter dendrite permeability.

�The influence of alloy composition on fluidity, macro segregation, hot tearing and

porosity will be described. coherency, fluidity, permeability and shrinkage will be

presented

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

Aluminum die casting alloys are lightweight, offer good corrosion resistance, ease of

casting, good mechanical properties and dimensional stability. Although a variety of

aluminum alloys can be die cast from primary or recycled metal, designers select a

standard alloy listed below.

A360 -- Selected for best corrosion resistance and pressure tightness.

TYPE OF ALUMINUM DIE CASTING ALLOYS

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A360 -- Selected for best corrosion resistance and pressure tightness.

A380 -- The most common and cost effective of AL- die casting alloys. Provides the best

combination of utility and cost.

A383 & A384 -- These alloys are a modification of 380. Both provide better die filling

but with a moderate sacrifice in mechanical properties such as toughness.

A390 -- Selected for special applications where high strength, fluidity and wear-

resistance and bearing properties are required.

A413 (A13) -- Used for maximum pressure tightness and fluidity.

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

ALLOY

COMPOSITION (% max or range) A360 A380 A383 A384 A390 A413

(A13)

Silicon 9-10 7.5-9.5 9.5-11.5 10.5-12 16-18 11-13

( ALLOY – CHEMICAL COMPOSITION)

CHEMICAL COMPOSITION OF DIE CAST ALUMINUM ALLOYS

The following table will provide a general idea of the differences in different Aluminum Die

Cast alloys. This table will help us technical comparison in Al. alloys

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Silicon

Iron 1.3 1.3 1.3 1.3 1.3 1.3

Copper 0.6 3.4 2.3 3-4.5 4-5 1.0

Manganese 0.35 0.50 0.50 0.50 0.50 0.35

Magnesium 0.4-0.6 0.10 0.10 0.10 0.45-0.65 0.10

Nickel 0.50 0.50 0.30 0.50 0.10 0.50

Zinc 0.50 3.0 3.0 3.0 1.5 0.50

Tin 0.15 0.35 0.35 0.35 0.20 0.15

Titanium - - - - 0.20 -

Total others 0.25 0.50 0.50 0.50 0.20 0.25

Aluminum BAL. BAL. BAL. BAL. BAL. BAL.

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

ALLOY

PROPERTIESA360 A380 A383 A384 A390 A413

(A13)

Ultimate tensile strength (ksi) 46 47 45 48 40.5 42

Tensile yield strength (ksi) 24 23 22 24 35 19

Elongation (% in 2" G.L.) 3.5 3.5 3.5 1—2.5 3.5

Hardness (HB) 75 80 80 85 120

Shear strength (ksi) 26 27 25 29

PHYSICAL AND MECHANICAL PROPERTIES

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Shear strength (ksi) 26 27 25 29

Charpy impact strength(ft.lb) 4.2 3.5 2.0

Fatigue strength (ksi) 18 20 19 20 20

Density (lb./in.3) 0.095 0.098 0.097 0.098 0.099 0.096

Melting range (oF) approx. 1035-1105 1000-1100 960-1080 960-1080 945-1200 1065-1080

Specific heat (Btu/lb .o F) 0.23 0.23 0.23 0.23 0.23 0.23

Coefficient of thermal

expansion

11.8 11.7 11.5 11.3 11.7 10.3

Thermal conductivity (Btu/ft

hr. oF)

65.3 55.6 55.6 56 78.6 67.7

Electrical conductivity (% IACS) 29 31 23 23 25 31

Modulus of elasticity (106 psi) 10.3 10.3 10.3 10.3 11.9 10.3

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

ALLOYA360 A380 A383 A384 A390 A413

(A13)

Resistance to Hot Cracking 2 2 - 2 - 1

Pressure Tightness 1 2 2 2 - 1

CHARACTERISTICS OF DIE CAST ALUMINUM ALLOYS (1-most desirable; 4–least desirable)

CHARACTERISTICS

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Pressure Tightness 1 2 2 2 - 1

Polishing 3 3 - 3 - 4

Fluidity 2 2 1 1 - 1

Corrosion Resistance 3 4 3 4 - 2

Machine-ability 2 2 2 3 - 4

Strength at Elev. Temp. 3 2 2 1 - 2

Anti-Die Soldering Tend. 3 1 2 2 - 2

Electroplating 1 1 - 2 - 3

Anodizing Appearance 4 4 - 4 - 4

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS”

Aluminum Brass Magnesium Zinc

Tensile strength, psi x 1000 47 55 34 41

Yield strength, psi x 100 (0.2 pct offset) 23 30 23 —

Shear strength, psi x 1000 28 37 20 31

Fatigue strength, psi x 1000 20 25 14 7

COMPARISON THE PROPERTIES OF DIFFERENT DIE CAST MATERIAL WITH DIE CAST

AL-ALLOY

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Elongation, pct in 2 in. 3.50 15 3.0 10

Hardness (Brinell) 80 91 63 82

Specific gravity 2.71 8.30 1.80 6.60

Weight, lb/cu. in. 0.098 0.305 0.066 0.24

Melting point (liquid), °F 1100 1670 1105 728

Thermal conductivity, CG5 0.23 0.21 0.16 0.27

Thermal expansion, in./in./°F x 106 12.1 12.0 15.0 15.2

Electrical conductivity, 27 20 10 27

Modulus of elasticity, psi x 106 10.3 15 6.5 —

Impact strength (Charpy), ft/lb 3.0 40 2.0 43.0

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

�Die Soldering is the result of an interface reaction between molten aluminum and the die

material during the impact of the high-velocity molten aluminum onto the die surface and the

DIE SOLDERING:

�sticks to the surface of the die material and remains there after the ejection of the cast part.

�Die soldering is referred to the phenomenon that molten aluminum

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material during the impact of the high-velocity molten aluminum onto the die surface and the

intimate contact between alloy and die at high temperature

�When molten aluminum enters in the die with a high velocity and destroys the protective film

(coating and lubricant) on the die surface. the molten aluminum comes in contact with the virgin

die surface. iron in the die dissolves into the molten aluminum and a layer of inter metallic phases

is formed. A soldering layer is formed over this intermediate layer at an atomic level, which is

difficult to prevent

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

DIE SOLDERING:There are several classes of process parameters that influence die

soldering. These are under :

•Temperature of the metal and die.

•Nature and constituents of casting alloy and inter metallic layers.

•Die Lubrication and coating.

•Nature of the die and operating parameters.

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•Nature of the die and operating parameters.

THE MECHANISM OF DIE SOLDERING OCCURS IN SIX STAGES:

STAGE I ==> Erosion of grain boundaries on the die surface

STAGE II ==> Pitting of the die surface

STAGE III ==> Formation of iron-aluminum compounds

STAGE IV ==> Formation of pyramid shaped inter metallic phases

STAGE V ==> Adherence of aluminum onto the pyramids of inter metallic phases

STAGE VI ==> Merging and straightening of erosion pits and inter metallic phases.

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

The effects of alloy composition on the die soldering for the A 380 type alloys and effects of some

key elements on the growth of the intermediate layer between the tool steel surface and the

soldered Aluminum.

ELEMENTS AMOUNT EFFECT

Nickel 0.5% Alloy Layer thickness increases

by about 50% at 720-730°C

EFFECT OFVARIOUS ELEMENTS ON THE INTERMEDIATE LAYER THICKNESS.

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Manganese 1—3% Same as above

Beryllium 0.3—2% Alloy layer reduces by 7%

Copper ---- No effect

Free Nitrogen 0.002---0.055% Alloy layer thickness reduces by about

70%.

Chromium 2—20% Alloy layer reduction by about 60%

Titanium 0.1% Alloy layer decreases by 85%

Silicon ----- Alloy layer thickness decreasesas

Silicon content increases

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS”

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

SLUDGE

• Sludge is made up of primary crystals containing Al, Si, Fe, Mn, Cr, Mg,

etc. and having high melting temperature and high specific gravity.

• Factors that affect sludge formation:

•Alloy composition .

•Melting and holding temperatures

• Cooling rate

•Sludge factor (SF)

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•Sludge factor (SF)

(SF) = (1 x wt % Fe) + (2 x wt%Mn) + (3 x wt % Cr

With an increase in cooling rate, the size of the sludge particles and the volume

fraction of sludge decrease

,Sludge formed at the low cooling rate as large platelets, and polyhedral particles.

At the high cooling rate, SLUDGE is in the form of platelets and

star-like particles

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

EFFECT OF HOLDING TEMPERATURES

Relation of sludge forming temperature with Fe

content:

Temperature (°C) = 645.7 + 34.2 (%Fe)2

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TEMPERATURE VERSUS SLUDGE FACTOR FOR SPECIFIC ALLOY

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

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�When the alloys solidify at low cooling rate, holding

at 670°C and 720°C does not affect sludge formation.

� When the alloys solidify at high cooling

rate,more sludge was found in A380 alloy

afterholding at 670°C

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

SLUDGE FORMATION FACTORS:

� In 380 type alloys, the sludge phases are mainly Fe-rich compounds

consisting of Al, Fe, Mn, Cr, Ni.

• Alloys with higher SF have a higher tendency to form sludge and form larger

volume fraction of sludge.

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• The morphology of sludge is influenced by the Fe:Mn: Cr ratio and by the

cooling rate.

• Slow cooling favours formation of sludge.

• Holding at 670°C (~1240°F) and 720°C (1328°F) does not affect sludge

formation in all the alloys solidify slowly.

• When cooling fast, more sludge formed in A380 alloy after holding at 670°C

than at 720°C.

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS”

FLUIDITY:

�Fluidity is a material’s ability to flow into and fill a given cavity, as

measured by the dimensions of that cavity under specific conditions.

The length of molten liquid metal that can flow through a given

mould before freezing

Fluidity is heavily dependent on heat flow during solidification. Fluidity is heavily dependent on heat flow during solidification.

�Fluidity of Al- Alloy depends on lubricant coatings, alloying

additions, head pressure, and temperature of molten metal.

Increasing the solidification range results in decreasing fluidity

FACTORS WHICH EFFECT ON FLUDITY:

•Alloy chemical composition play a important role in die filling

that is the fluidity of molten metal.

•Alloying Elements that lean to form high temperature

compounds, e.g., Fe, Mn, Cr, and Mg, tend to decrease fluidity.

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

Lf=

= (C’/H)

Lf =

Lf Final length , fluidity

a Channel Radius

FLUDITY LENGTH DEPENDENT

VARIABLE (Lf)

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a Channel Radius

C’ Specific Heat of Liquid Metal

TO Ambient environmental Temperature (room temperature)

∆T Superheat Temperature

ρ’ Density of metal

VO Velocity of metal flow

H Heat of Fusion of metal

h Heat transfer coefficient of metal interface

T Time average melt temperature in the fluidity test

Tm Metal melting temperature

T’ Temperature of superheated metal entering flow channel

Critical solid concentration required to stop flow in mushy alloy.

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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

POROSITY:

�Hydrogen gas dissolve in the liquid molten aluminum alloy from the atmosphere. Its

solubility varies directly with temperature and the square root of pressure.

�During the cooling and solidification of molten aluminum, dissolved hydrogen in excess of

the extremely low solid solubility may precipitate in molecular form, resulting in the

formation of primary and / or secondary voids

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formation of primary and / or secondary voids

�There are two types of hydrogen porosity occur in the die cast.

�One is the inter-dendritic porosity, which is encountered when hydrogen

contents are sufficiently high that hydrogen rejected at the solidification due to

high pressures above atmospheric.

�Secondary (micron-size) porosity occurs when dissolved hydrogen contents

are low, and void formation is characteristically critical.

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THANK YOU &

CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS

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THANK YOU & Question