ME8109: Casting And Solidification of Material
A STUDY OF CASTING CHARACTERISTICS
FOR “ DIE-CAST ALUMINUM ALLOY”
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
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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS
•
CONTENTS:
•
INTRODUCTION
•
CAST ABILITY
•
TYPE OF STANDARD DIE CAST ALUMINUM ALLOYS
•
CHEMICAL COMPOSITION
•
PHYSICAL AND MECHANICAL PROPERTIES
•
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
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
CASTABILITY:
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
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
TYPE OF ALUMINUM DIE CASTING 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.
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 wearresistance 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
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
( ALLOY – CHEMICAL COMPOSITION)
ALLOY
COMPOSITION (% max or range)
A360
A380
A383
A384
A390
Silicon
9-10
7.5-9.5
9.5-11.5
10.5-12
16-18
A413
(A13)
11-13
Iron
Copper
Manganese
Magnesium
1.3
1.3
1.3
1.3
1.3
1.3
0.6
3.4
2.3
3-4.5
4-5
1.0
0.35
0.50
0.50
0.50
0.50
0.35
0.4-0.6
0.10
0.10
0.10
0.45-0.65
0.10
Nickel
Zinc
Tin
Titanium
Total others
Aluminum
0.50
0.50
0.30
0.50
0.10
0.50
0.50
3.0
3.0
3.0
1.5
0.50
0.15
0.35
0.35
0.35
0.20
0.15
-
-
-
-
0.20
-
0.25
0.50
0.50
0.50
0.20
0.25
BAL.
BAL.
BAL.
BAL.
BAL.
BAL. 6
CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS
PHYSICAL AND MECHANICAL PROPERTIES
ALLOY
A384
A390
A413
(A13)
45
48
40.5
42
22
3.5
80
25
24
1—2.5
35
19
0.097
20
0.098
0.099
19
3.5
120
29
2.0
20
0.096
1000-1100
960-1080
960-1080
945-1200
1065-1080
0.23
11.8
0.23
11.7
0.23
11.5
0.23
11.3
0.23
11.7
0.23
10.3
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
PROPERTIES
Ultimate tensile strength (ksi)
Tensile yield strength (ksi)
Elongation (% in 2" G.L.)
Hardness (HB)
Shear strength (ksi)
Charpy impact strength(ft.lb)
Fatigue strength (ksi)
Density (lb./in.3)
Melting range (oF) approx.
Specific heat (Btu/lb .o F)
Coefficient of thermal
expansion
Thermal conductivity (Btu/ft
hr. oF)
A360
A380
46
47
24
3.5
75
26
4.2
18
0.095
23
3.5
80
27
3.5
20
0.098
1035-1105
A383
85
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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS
CHARACTERISTICS OF DIE CAST ALUMINUM ALLOYS
(1-most desirable; 4–least desirable)
ALLOY
CHARACTERISTICS
Resistance to Hot Cracking
Pressure Tightness
Polishing
Fluidity
Corrosion Resistance
Machine-ability
Strength at Elev. Temp.
Anti-Die Soldering Tend.
Electroplating
Anodizing Appearance
A360
A380
A383
A384
A390
A413
(A13)
2
1
3
2
3
2
3
3
1
4
2
2
3
2
4
2
2
1
1
4
2
1
3
2
2
2
-
2
2
3
1
4
3
1
2
2
4
-
1
1
4
1
2
4
2
2
3
4
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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS”
COMPARISON THE PROPERTIES OF DIFFERENT DIE CAST MATERIAL WITH DIE CAST
AL-ALLOY
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
3.50
15
3.0
10
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
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
Elongation, pct in 2 in.
Hardness (Brinell)
Electrical conductivity,
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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:
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
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
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.
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
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STAGE VI ==> Merging and straightening of erosion pits and inter metallic phases.
CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS
EFFECT OF VARIOUS ELEMENTS ON THE INTERMEDIATE LAYER THICKNESS.
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
Manganese
1—3%
Same as above
Beryllium
0.3—2%
Alloy layer reduces by 7%
Copper
----
Free Nitrogen
No effect
0.002---0.055% Alloy layer thickness reduces by about
70%.
Chromium
2—20%
Alloy layer reduction by about 60%
Titanium
0.1%
Silicon
-----
Alloy layer decreases by 85%
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)
(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
TEMPERATURE VERSUS SLUDGE FACTOR FOR SPECIFIC ALLOY
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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS
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.
• 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 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.
Lf =
CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS
FLUDITY LENGTH DEPENDENT
VARIABLE (Lf)
Lf =
= (C’/H)
Lf
a
C’
TO
∆T
ρ’
VO
H
h
T
Tm
T’
Final length , fluidity
Channel Radius
Specific Heat of Liquid Metal
Ambient environmental Temperature (room temperature)
Superheat Temperature
Density of metal
Velocity of metal flow
Heat of Fusion of metal
Heat transfer coefficient of metal interface
Time average melt temperature in the fluidity test
Metal melting temperature
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
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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CASTING CHARACTERISTICS FOR “DIE-CAST ALUMINUM ALLOYS
THANK YOU &
Question
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