Kolisetty Alloy Castings - India  

Manufacturers of Alloy Steel Castings and Non Ferrous Castings Ranging 1 Kg to 300 Kgs.

Address: 16 H I.D.A., Balanagar, Hyderabad-37 India

Kolisetty Alloy CastingsContact Person : Address : 16-H, Ida, Balanagar ,Hyderabad - , Andhra Pradesh (India)Tel : 91-40-40073252/282/55997228/23077489Fax : 91-40-40073243/23077489/23176026

Mr. Veeraiah Kolisetty

16H, IDA, Balanagar, Rangareddy, Hyderabad, Andhra Pradesh, India Zip: 500037

91-40-40073282

9849017310

Mechanical properties of metals Stress Strain Shear strength An explanation of yield and deformation

 

Note

Whilst the materials considered are metals, the concepts of stress, strain, deformation, hardness, brittleness and ductility discussed below apply across the full materials spectrum, including polymers and ceramics.

 

 

Stress

When a material is subjected to an external force, it will either totally comply with that force and be pushed away, like a liquid or powder, or it will set up internal forces to oppose those applied from outside. Solid materials generally act rather like a spring – when stretched or compressed, the internal forces come into play, as is easily seen when the spring is released.

A material subjected to external forces that tend to stretch it is said to be in tension, whereas forces which squeeze the material put it in compression.

An important aspect is not so much the size of the force, as how much force is applied per unit of cross-sectional area. The term ‘stress’, symbol σ (Greek letter sigma), is used for the force per unit area, and has the units of pascals (Pa) with 1Pa being one newton per square metre.

Because the reference area is so large, it is normally necessary to use high multiples such as the megapascal (MPa = 106 Pa) and gigapascal (GPa = 109 Pa). However, when we bear in mind that, in electronics, the area over which forces are applied is generally very much smaller, it is useful to keep in mind that one MPa is equivalent to a force of 1 newton applied on a square millimetre of area.

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Strain

A material in tension or compression changes in length, and the change in length compared to the original length is referred to as the ‘strain’, symbol1 ε (Greek letter epsilon). Since strain is a ratio of two lengths it has no units and is frequently expressed as a percentage: a strain of 0.005 corresponds to a ½% change of the original length.

1 In some texts you may find η (Greek letter eta) used.

Hooke’s Law

As you know from a spring, if you gradually stretch it, the force needed increases, but the material springs back to its original shape when the force is released. Materials which react in the same way as a spring are said to be ‘elastic’. Typically if we measure the extension of different forces and plot the graph of this, we will find that the extension is proportional to the force applied. Materials that obey Hooke’s Law exhibit a linear relationship between the strain and the applied stress (Figure 1).

Figure 1: Stress-strain graph for an elastic solid

Many metals follow Hooke’s Law until a certain level of stress has been applied, after which the material will distort more severely. The point at which straight line behaviour ceases is called the limit of proportionality: beyond this the material will not spring back to its original shape, and is said to exhibit some plastic behaviour (Figure 2). The stress at which the material starts to exhibit permanent deformation is called the elastic limit or yield point.

Figure 2: Stress-strain graph for a typical metal

As Figure 2 shows, if the stress is increased beyond the yield point the sample will eventually break. The term (ultimate) tensile strength is used for the maximum value of tensile stress that a material can withstand without breaking, and is calculated at the maximum tensile force divided by the original cross-sectional area.

Note that there may be substantial differences between the stress at the yield point and on breaking – for example, one source quotes the ‘ultimate tensile strength’ for AISI304 stainless steel as 505 MPa, and the ‘yield tensile strength’ as 215 MPa. For most engineering purposes, metals are regarded as having failed once they have yielded, and are normally loaded at well below the yield point.

With some materials, including mild steel, the stress/strain graph shows a noticeable dip beyond the elastic limit, where the strain (the effect of the load) increases without any need to increase the load. The material is said to have ‘yielded’, and the point at which this occurs is the yield point. Materials such as aluminium alloys on the other hand don’t show a noticeable yield point, and it is usual to specify a ‘proof’ test. As shown in Figure 3, the 0.2% proof strength is obtained by drawing a line parallel to the straight line part of the graph, but starting at a strain of 0.2%.

Figure 3: Stress-strain graph for an aluminium alloy

Self Assessment Question

You are designing a part with a retention clip which has to spring into place after being pressed into position. By making reference to their stress-strain curves, explain why you would expect steel to be a better choice than aluminium for this application.

go to solution

Young’s modulus

As you will appreciate from the shapes of Figure 2 and Figure 3, the slope of the stress/strain graph varies with stress, so we generally take only the slope of the initial straight-line portion. The stress/strain ratio is referred to as the modulus of elasticity or Young’s Modulus. The units are those of stress, since strain has no units. Engineering

materials frequently have a modulus of the order of 109Pa, which is usually expressed as GPa. Some approximate figures for typical electronic materials are given in Table 1.

Table 1: Tensile strength and Young’s modulus for selected materialsmaterial tensile strength MPa modulus of elasticity GPa

304 stainless steel 500 200copper 270 12096% alumina 200 340aluminium 90 70Sn63 solder 35 30epoxy resin 40 3silicone rubber 10 0.003

Quote

Stress is what happens to you from outside; strain is what you feel. Engineers should never say that ‘they feel stressed’, even if they have reached their yield point!

Compression

The compressive strength is the maximum compressive stress that a material can withstand without being crushed. Both strengths have the same unit as stress, and are typically millions of Pa. For most engineering materials, Young’s Modulus is the same in compression as in tension.

Hardness

Hardness is another measure of the ability of a material to be deformed. There are many different tests for this, but all measure the resistance of a material to indentation, applying a known force to a tool of defined radius which is very much harder than the material being tested. Empirical hardness numbers are calculated from measurements of the dimensions of the indentation.

Figure 4: The Rockwell R hardness test

The principle of one of the simpler tests, the Rockwell R2 test, can be seen in Figure 9. A specimen at least ¼ inch (6.4 mm) thick is indented by a ½ inch (12.7 mm) diameter steel ball. A small load is applied, the apparatus is zeroed, and then a larger load is applied and removed. After a short time with the preload still applied, the remaining indentation is read from the scale.

2 As with many standard tests, the units used are American! We have kept kgf to help you gauge the magnitude of the force involved: 1 ‘kilogramforce’ = 9.81N.

For metal measurements, there are alternative Rockwell tests, with different test heads and different loads. You will also find Brinell hardness numbers (BHN), derived from a test which uses a 10mm tungsten carbide ball. Brinell testing is sometimes preferred as it covers a wider hardness range than the Rockwell tests.

There is unfortunately little correlation between different hardness tests, but there is reasonable correlation between the hardness results and the tensile strength, at least for given families of alloys. Note that the correlation is to tensile strength rather than yield strength, because plastic deformation takes place during the hardness measurement.

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Shear strength

Subjected to forces which cause it to twist, or one face to slide relative to an opposite face, a material is said to be in shear (Figure 5). Compared to tensile and compressive stress and strain, the shear forces act over an area which is in line with the forces.

Figure 5: Shear stress applied to an object

The force per unit area is referred to as the shear stress, denoted by the symbol τ (Greek letter tau), where

Its unit is the pascal (Pa), where force is measured in newtons (N) and area in square metres.

When shear stress is applied, there will be an angular change in dimension, just as there is a change in length when materials are under tension or compression. Shear strain, denoted by the symbol γ (Greek letter gamma), is defined by

where the angular deformation, symbol φ (Greek letter phi) is expressed in radians. The last approximate equality results from the fact that the tangent of a small angle is almost the same as the angle expressed in radians. This is the reason why some texts give the radian as the unit of strain. Both shear strain and angular deformation are ratios, so have no units. However, it is not unusual for shear strain to be quoted in %, as with tensile strain.

Shear stresses are most evident where lap joints are fastened together and forces applied to pull them apart, but are also seen when rods are twisted, or laminated boards bent.

The shear strength of a material is the maximum stress that it can withstand in shear before failure occurs. For example, punching, cropping and guillotining all apply shear stresses of more than the maximum shear stress for that material.

As with Hooke’s Law for tensile stress, most metals have a shear stress which is proportional to the shear strain. And in a similar way to Young’s modulus, the gradient of the graph is referred to as the shear modulus or modulus of rigidity. Again the SI unit3 for shear modulus is the pascal (Pa).

3 You are very likely to find Young’s modulus and shear modulus quoted in psi (pounds force per square inch) or kpsi (thousands of psi). To convert to MPa, multiply the figure in kpsi by 6.89. Watch the units! You should also expect there to be very wide variations in the figures quoted, as these depend critically on alloy composition and work hardening (for metals), on purity (for ceramics) and on formulation (for polymers). Table 2: Shear strength and shear modulus for selected materials

material shear strength MPa modulus of rigidity GPa96% alumina 330   304 stainless steel 186 73copper 42 44aluminium 30 26Sn63 solder 28 6epoxy resin 10 – 40  

Self Assessment Question

Hybrid microcircuits are typically made on a substrate of 96% alumina. How would you expect their mechanical characteristics, such as strength and hardness, to differ from equivalent circuits made on an FR-4 laminate?

go to solution

Stiffness

The stiffness of a material is an important aspect of PCB design, being the ability of the material to resist bending. When a board is bent, one surface stretches and the inside of the radius is compressed. The more a material bends, the more the outer surface stretches and the internal surface contracts. A stiff material is one that gives a relatively small change in length when subject to tension or compression, in other words, a small value of strain/stress.

However, on the basis that stiff = good, a natural feeling that this should be a larger figure means that we actually quote the ratio of stress/strain. So a stiff material has a high value of Young’s modulus. From Table 1 you will be aware of the very wide range of properties in electronic materials. Note that the metals in this list are much stiffer than polymers, but well below the stiffness of a typical ceramic. However, this stiffness is

accompanied by extreme brittleness. One of the features of a metal is that it is unlikely to shatter, as would a piece of glass or ceramic, but it will show permanent deformation when forces are applied – ask any car body shop!

Elongation

The stress-strain graph of a brittle material (Figure 6) shows that very little plastic deformation occurs before the point at which the stress is sufficient to induce failure. A brittle test piece after fracture will be almost the same length as it started. However, a ‘ductile’ material, such as copper will stretch a great deal before it finally breaks. Try stretching a piece of copper wire, and you will know that it stretches by 10-20% before the weakest point in the wire ‘necks’ and the wire breaks. The percentage elongation of a material is used as a measure of its ductility.

Figure 6: Brittle and ductile materials compared

Self Assessment Question

Explain why it is important for an FR-4 laminate that glass-reinforced epoxy has a Young’s Modulus less than that of solder and that copper is a ductile material.

go to solution

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An explanation of yield and deformation

The block slip model (Figure 7) is used to explain the elastic and plastic behaviour of metals. A metal is viewed as blocks of atoms which can move relative to each other. When stress is applied, these blocks become displaced until, when the yield stress is reached, large blocks of atoms slip past each other. The plane along which movement occurs is called the slip plane.

Figure 7: The block slip model, showing behaviour of metals under stress

Slip lines do not cross from one grain to another, but are confined by the grain boundaries (Figure 8). The bigger the grains, the more slippage and the greater the plastic deformation which occurs. Materials with a fine grain structure are therefore less ductile and more brittle – each slip process is confined and not allowed to spread.

Figure 8: Grain boundaries modifying behaviour during deformation

The effect of temperature

Figure 9 shows how the strength and hardness of a metal varies with temperature: note that the temperature is measured on the Kelvin scale, whose origin is absolute zero (–273ºC). Provided that the curves are scaled correctly, and referenced to the melting temperature of the material (Tm), this is actually a generic relationship: the pattern follows

a similar pattern for most metals, reducing to zero at the melting point, and reducing markedly as that temperature is approached.

Figure 9: Strength/hardness of a metal related to its melting temperature

Metallurgists refer to the idea of a ‘homologous temperature’, where the actual temperature of a material is expressed as a fraction of its melting temperature expressed in Kelvin. Solder (m.pt 183°C = 456K) at 0.85Tm or 115ºC (= 388K), would thus be expected to have comparable properties to copper (m.pt 1085°C = 1358K) at 0.85Tm or 881ºC (= 1154K).

In electronics applications, where circuits typically operate over a –55ºC®+125ºC range, eutectic tin-lead (Sn63) solder is working at 0.48®0.87Tm. From this we can deduce that solder will have limited mechanical strength (as a bulk material) and be within the ‘creep range’. This is borne out by the comparatively low values for tensile strength, shear strength and modulus of elasticity which are given in Table 1 and Table 2.

Copper, on the other hand, has a much higher melting point, so foils are working at only 0.16®0.29Tm, and their properties are little affected by temperature.

Exercise

This is something to think about! What is the ‘creep range’ mentioned in the diagram? And does failure ever happen at lower stress conditions?

For answers to those questions you will have to wait until you study the unit on Stress and its effect on materials. Or you might like to glance ahead at that section now.

go to Stress unit

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Author: Martin Tarr

 

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence.

Terms and conditions apply.

 

 Aluminium Alloys - Aluminium 6082 Properties, Fabrication and Applications, Supplier Data by Aalco

Topics Covered

Background

Chemical Composition of Aluminium alloy 6082

Properties of Aluminium alloy 6082

Mechanical Properties of Aluminium alloy 6082

Physical Properties of Aluminium alloy 6082

Alloy Designations

Fabrication of Aluminium alloy 6082

Welding

Fabrication Response

Temper

Applications of Aluminium alloy 6082

Supplied Forms

Background

Aluminium alloy 6082 is a medium strength alloy with excellent corrosion resistance. It has the highest strength of the 6000 series alloys. Alloy 6082 is known as a structural alloy. In plate form, Aluminium alloy 6082 is the alloy most commonly used for machining. As a relatively new alloy, the higher strength of Aluminium alloy 6082 has seen it replace 6061 in many applications. The addition of a large amount of manganese controls the grain structure which in turn results in a stronger alloy.

In the T6 and T651 temper, Aluminium alloy 6082 machines well and produces tight coils of swarf when chip breakers are used.

Chemical Composition of Aluminium alloy 6082

Table 1. Typical chemical composition for aluminium alloy 6082

Element % Present

Si 0.7 to 1.3%

Fe 0.5%

Cu 0.1%

Mn 0.4 to 1.0%

Mg 0.6 to 1.2%

Zn 0.2%

Ti 0.1%

Cr 0.25%

Al Balance

Properties of Aluminium alloy 6082

Mechanical Properties of Aluminium alloy 6082

Table 2. Typical mechanical properties for aluminium alloy 6082

Temper O T4 T6/T651

Proof Stress 0.2% (MPa) 60 170 310

Tensile Strength (MPa) 130 260 340

Shear Strength (MPa) 85 170 210

Elongation A5 (%) 27 19 11

Hardness Vickers (HV) 35 75 100

Physical Properties of Aluminium alloy 6082

Table 3. Typical physical properties for aluminium alloy 6082

Property Value

Density 2.70 g/cm3

Melting Point 555°C

Modulus of Elasticity 70 GPa

Electrical Resistivity 0.038x10-6 Ω.m

Thermal Conductivity 180 W/m.K

Thermal Expansion 24x10-6 /K

Alloy Designations

Aluminium alloy 6082 also corresponds to the following standard designations and specifications:

AA6082 HE30

DIN 3.2315 EN AW-6082

ISO: Al Si1MgMn A96082

Fabrication of Aluminium alloy 6082

Welding

Aluminium alloy 6082 has very good weldability but strength is lowered in the weld zone. When welded to itself, alloy 4043 wire is recommended. If welding Aluminium alloy 6082 to 7005, then the wire used should be alloy 5356.

Fabrication Response

Table 4. Typical fabrication response for aluminium alloy 6082

Process Rating

Workability - Cold Good

Machinability Good

Weldability – Gas Good

Weldability – Arc Good

Weldability – Resistance Good

Brazability Good

Solderability Good

Temper

The most common tempers for Aluminium alloy 6082 are:

         O – annealed wrought alloy

         T4 – Solution heat treated and naturally aged

         T6 – Solution heat treated and artificially aged

         T651 - Solution heat treated, stress relieved by stretching and then artificially aged

Applications of Aluminium alloy 6082

Aluminium alloy 6082 is typically used in:

         High stress applications

         Trusses

         Bridges

         Cranes

         Transport applications

         Ore skips

         Beer barrels

         Milk churns

Supplied Forms

Aluminium alloy 6082 is available from Aalco in the following forms with a T6 temper:

         Square bar

         Square box section

         Rectangular box section

         Channel

         Tee section

         Equal angle

         Unequal angle

         Flat bar

         Tube

         Sheet

Aalco also supply Aluminium alloy 6082-T651 as:

         Plate

         Shate

         Sheet

Aluminum 6061-T6; 6061-T651

Subcategory: 6000 Series Aluminum Alloy; Aluminum Alloy; Metal; Nonferrous Metal

Close Analogs:

Composition Notes: Aluminum content reported is calculated as remainder.Composition information provided by the Aluminum Association and is not for design.

Key Words: al6061, UNS A96061; ISO AlMg1SiCu; Aluminium 6061-T6, AD-33 (Russia); AA6061-T6; 6061T6, UNS A96061; ISO AlMg1SiCu; Aluminium 6061-T651, AD-33 (Russia); AA6061-T651

Component    Wt. %

Al 95.8 - 98.6  

Cr 0.04 - 0.35  

Cu 0.15 - 0.4  

Fe Max 0.7  

Component    Wt. %

Mg 0.8 - 1.2  

Mn Max 0.15  

Other, each Max 0.05  

Other, total Max 0.15  

Component    Wt. %

Si 0.4 - 0.8  

Ti Max 0.15  

Zn Max 0.25  

Material Notes: Information provided by Alcoa, Starmet and the references. General 6061 characteristics and uses: Excellent joining characteristics, good acceptance of applied coatings. Combines relatively high strength, good workability, and high resistance to corrosion; widely available. The T8 and T9 tempers offer better chipping characteristics over the T6 temper.

Applications: Aircraft fittings, camera lens mounts, couplings, marines fittings and hardware, electrical fittings and connectors, decorative or misc. hardware, hinge pins, magneto parts, brake pistons, hydraulic pistons, appliance fittings, valves and valve parts; bike frames.

Data points with the AA note have been provided by the Aluminum Association, Inc. and are NOT FOR DESIGN.

Physical Properties Metric English Comments

Density 2.7   g/cc 0.0975 lb/in³  AA; Typical

Mechanical Properties

Hardness, Brinell 95 95  AA; Typical; 500 g load; 10 mm ball

Hardness, Knoop 120 120  Converted from Brinell Hardness Value

Hardness, Rockwell A 40 40  Converted from Brinell Hardness Value

Hardness, Rockwell B 60 60  Converted from Brinell Hardness Value

Hardness, Vickers 107 107  Converted from Brinell Hardness Value

Ultimate Tensile Strength 310   MPa 45000 psi  AA; Typical

Tensile Yield Strength 276   MPa 40000 psi  AA; Typical

Elongation at Break 12   % 12 %  AA; Typical; 1/16 in. (1.6 mm) Thickness

Elongation at Break 17   % 17 %  AA; Typical; 1/2 in. (12.7 mm) Diameter

Modulus of Elasticity 68.9   GPa 10000 ksi  AA; Typical; Average of tension and compression. Compression

modulus is about 2% greater than tensile modulus.

Notched Tensile Strength 324   MPa 47000 psi  2.5 cm width x 0.16 cm thick side-notched specimen, Kt = 17.

Ultimate Bearing Strength

607   MPa 88000 psi  Edge distance/pin diameter = 2.0

Bearing Yield Strength 386   MPa 56000 psi  Edge distance/pin diameter = 2.0

Poisson's Ratio 0.33 0.33  Estimated from trends in similar Al alloys.

Fatigue Strength 96.5   MPa 14000 psi  AA; 500,000,000 cycles completely reversed stress; RR

Moore machine/specimen

Fracture Toughness 29   MPa-m½ 26.4 ksi-in½  KIC; TL orientation.

Machinability 50   % 50 %  0-100 Scale of Aluminum Alloys

Shear Modulus 26   GPa 3770 ksi  Estimated from similar Al alloys.

Shear Strength 207   MPa 30000 psi  AA; Typical

Electrical Properties

Electrical Resistivity 3.99e-006   ohm- cm

3.99e-006 ohm-cm  AA; Typical at 68°F

Thermal Properties

CTE, linear 68°F 23.6   µm/m-°C 13.1 µin/in-°F  AA; Typical; Average over 68-212°F range.

CTE, linear 250°C 25.2   µm/m-°C 14 µin/in-°F  Estimated from trends in similar Al alloys. 20-300°C.

Specific Heat Capacity 0.896   J/g-°C 0.214 BTU/lb-°F  

Thermal Conductivity 167   W/m-K 1160 BTU-in/hr-ft²-°F

 AA; Typical at 77°F

Melting Point 582 - 652 °C 1080 - 1205 °F  AA; Typical range based on typical composition for wrought

products 1/4 inch thickness or greater; Eutectic melting can be

completely eliminated by homogenization.

Solidus 582   °C 1080 °F  AA; Typical

Liquidus 652   °C 1205 °F  AA; Typical

Processing Properties

Solution Temperature 529   °C 985 °F  Aging Temperature 160   °C 320 °F  Rolled or drawn products; hold at

temperature for 18 hr

Aging Temperature 177   °C 350 °F  Extrusions or forgings; hold at temperature for 8 hr

References for this datasheet.

Some of the values displayed above may have been converted from their original units and/or rounded in order to display the information in a consistant format. Users requiring more precise data for scientific or engineering calculations can click on the property value to see the original value as well as raw conversions to equivalent units. We advise that you only use the original value or one of its raw conversions in your calculations to minimize rounding error. We also ask that you refer to MatWeb's disclaimer and terms of use regarding this information. MatWeb data and tools provided by MatWeb.com, a product of Automation Creations, Inc.

 

Material Specifications

Contents:

Aluminum Alloy Specifications

Mechanical PropertiesPhysical PropertiesChemical Specifications

Magnesium Alloy Specifications

Mechanical PropertiesPhysical PropertiesChemical Specifications

Zinc Alloy Specifications

Mechanical PropertiesPhysical PropertiesChemical Specifications

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*Note: 6061T-6 is listed for reference only and is not

an alloy that is die cast by Simalex*Aluminum Mechanical Properties

ALLOY 343 AL 360 AL 383 AL *6061T-6

Tensile Strength (ksi)

35 44 45 45

Yield Strength (ksi)

20 25 22 40

Elongation (% in 2")

6 4 3.5 17

Shear Strength (ksi)

N/A 28 N/A 28

Hardness (Brinell) N/A 75 75 30

Aluminum Physical Properties

ALLOY 343 AL 360 AL 383 AL*6061T-

6

Density (lb./ci) N/A 0.095 0.099 0.098

Melting Point (°F) N/A 1105 1080 1206

Electrical Conductivity (% IACS)

N/A 29 23 43

Coefficient of Thermal Expansion (68-212°F)

(µin/in/°F x 10E-6)N/A 11.6 11.7 13.1

Aluminum Chemical Specifications (Per ASTM) (% by weight)

ALLOY 343 AL 360 AL 383 AL *6061T-6

Zn 1.2 to 1.9 0.1 max. 3.0 max. 0.25 max.

Mg 0.1 max. 0.4 to 0.6 0.1 max. 0.8 to 1.2

Cu 0.5 to 0.9 0.6 max. 2.0 to 3.0 0.15 to 0.4

Fe 0.9 max. 2.0 max. 1.3 max. 0.7 max.

Cr 0.1 max. - 0.15 max. .04 to 0.35

Si 6.7 to 7.7 9.0 to 10.0 9.5 to 11.5 0.4 to 0.8

Mn 0.5 max. 0.1 max. 0.5 max. 0.15 max.

Sn 0.5 max. 0.1 max. 0.15 max. -

Ni - 0.5 max. 0.3 max. -

Al Remainder Remainder Remainder Remainder

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Zinc Mechanical Properties

ALLOY No. 3 Zinc ZA-12

Tensile Strength (ksi) 41 58

Yield Strength (ksi) - 46

Elongation (% in 2") 10 6

Shear Strength (ksi) 31 43

Hardness (Brinell) 82 105

Zinc Physical Properties

ALLOY No. 3 Zinc ZA-12

Density (lb./ci) 0.240 0.218

Melting Point (°F) 728 810

Electrical Conductivity (%IACS) 27 28

Coefficient of Thermal Expansion (68-212°F)(µin/in/°F)

15.2 12.9

Zinc Chemical Specifications (Per ASTM) (% by weight)

ALLOY No. 3 Zinc ZA-12

Al 3.5 to 4.3 10.5 to 11.5

Mg 0.02 to 0.05 0.015 to 0.03

Cu 0.25 max. 0.5 to 1.25

Fe 0.1 max. 0.075 max.

Cd 0.004 max. 0.006 max.

Si 0.003 max. 0.003 max.

Zn Remainder Remainder

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Magnesium Mechanical Properties

ALLOY AZ91D

Tensile Strength (ksi) 33

Yield Strength (0.2% offset)

23

Elongation (% in 2") 3

Shear Strength (ksi) 20

Hardness (Brinell) 63

Magnesium Physical Properties

ALLOY AZ91D

Density (lb./ci) .065

Melting Point (°F) N/A

Electrical Conductivity (%IACS) 11.2

Coefficient of Thermal Expansion (68-212°F)(µin/in/°F)

14.4

Magnesium Chemical Specifications (Per ASTM) (% by weight)

ALLOY AZ91D

Al 8.5-9.5

Zn 0.45-0.9

Mn 0.15 min.

Si 0.02 max.

Cu 0.015 max.

Ni 0.001 max.

Fe 0.005 max.

Fe/Mn 0.032 max.

Others 0.01 max.

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Premium Quality H-13 Steel

Contents:

Product Summary

Key Benefit

Specifications

Chemical CompositionHardnessMicrocleanlinessUltrasonic QualityImpact Capability TestingGrain SizeAnnealed MicrostructureAcknowledgments

 

Product Summary

Tooling materials to be used in the construction of a die casting die for casting Aluminum, Magnesium and ZA alloys, should be high quality tool steel such as Premium Quality H-13 especially for part designs with critical features or if high production runs are being contemplated.

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Key Benefit

Longer die life.

Premium Quality H-13 will yield a higher resistance to heat checking, cracking and die wear caused by the thermal shock associated with the die casting process.

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Specifications

Chemical Composition 

Chemical composition (% by weight) of Critical Alloying Elements and Impurities (ASTM A-681 sec. 6) 

ELEMENT MIN. MAX.

CARBON 0.37 0.42

MANGANESE 0.20 0.50

PHOSPHORUS 0 0.025

SULFUR 0 0.005

SILICON 0.80 1.20

CHROMIUM 5.00 5.50

VANADIUM 0.80 1.20

MOLYBDENUM 1.20 1.75

  Hardness 

Hardness (ASTM A-681 sec. 7):Annealed hardness, as received, shall not exceed 235 Brinell (BHN). A steel specimen having a thickness no greater than one inch shall exhibit a minimum hardness of 50 HRC, when air cooled, after heating for 30 minutes at 1850°F in a protective atmosphere, or when using a non-protective atmosphere, insure the sample has appropriate oversize allowance.

 Microcleanliness 

Microcleanliness (ASTM A-681 S2.1): The permissible limits of microcleanliness (severity levels of non-metallic inclusion content) shall be determined by ASTM E-45, Method A (latest revision). Plate III should be used to obtain rating increments of 0.5. The maximum allowable limits are: 

INCLUSIONS

TYPE THIN HEAVY

A (sulfide) 1.0 0.5

B (aluminate) 1.5 1.0

C (silicate) 1.0 1.0

D (globular oxides) 2.0 1.0

  Ultrasonic Quality 

Ultrasonic Quality (ASTM A-681 S1.1): Appropriate ultrasonic inspection techniques shall be performed to assure soundness. All blocks shall be free from internal defects such as stringers, oxides, porosity, bursts, heavy segregation, etc. as indicated by ultrasonic testing. Ultrasonic examination of the original steel stock shall be conducted in accordance with ASTM recommended practices A388 and E114 (latest Revision). Acceptance criteria are as agreed upon supplier and vendor.

 

Impact Capability Testing 

Impact Capability Testing: Impact capability testing covers all mill product forms with a thickness greater or equal to 2 1/2 inches. Specimen blanks shall be removed from the short transverse orientation corresponding to the center location of the parent block of steel. A minimum of one set (i.e. 3) of impact specimens shall be tested per lot of material produced. A lot shall consist of all the product of a single ingot, which is forged or rolled via a common procedure to one size and annealed in a single furnace charge. Multiple starting ingots, variations in forging or rolling size or procedure, or variations in annealing furnace charge shall require additional sets of tests. 

Samples shall be machined to appropriate oversize, and heat treated as follows:

Austenite (protective atmosphere or use adequate oversize in a non-protective atmosphere) at 1875°F for 30 minutes, and oil quench. Minimum double temper to achieve resultant 44/46 HRC.

 

Following heat treating, the samples shall be machined to finish size as follows:

Charpy V-notch as per ASTM A-370, latest revision. 

7 x 10 mm unnotched.- adjacent sides shall be at 90 degrees +/- 10 minutes.- cross section dimensions shall be +/- 0.100 mm (0.004 in.)- length of specimen shall be 55 +/- 1 mm (2.165 +/- 0.040 in.)- surface finish shall be 63 micro inch (1.6 micro meter) max. on the 55 x 10 mm faces and 125 micro inch (3.2 micro meter) max. on the 55 x 7 mm faces. 

Triplicate testing shall be conducted at room temperature on test machines that meet the calibration requirements of ASTM E-23 or ISO 148/R442 (latest revision). The tup shall strike the center of one of the 55 x 10 mm faces on the 7 x 10 mm unnotched impact specimens. Testing shall yield the following specified values.

Acceptance Criteria (ft. lbs.)

Test Specimen AverageMinimum

Single Value

Charpy V-notch 8 6

7 x 10 mm unnotched 125 70

  Grain Size 

Grain Size: The Shepherd Fracture Grain Size shall be predominantly No.7 or finer when made on a hardened (air cooled after heating for 30 minutes at 1850°F, in a protective media or using an appropriately oversize sample in a non-protective media) and untempered specimen taken from a representative sample.

 

Annealed Microstructure 

Annealed Microstructure: The annealed microstructure of the as-received steel shall consist essentially of a ferritic matrix with homogeneous distribution of spheroidized carbides when examined at 500X, after being polished and etched with 4% Nital. The annealed microstructure shall also be free of excessive banding. 

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Acknowledgments:

The specifications and attributes from the preceding paragraphs was obtained from "PREMIUM QUALITY H-13 STEEL ACCEPTANCE CRITERIA FOR PRESSURE DIE CASTING DIES" by the NADCA DIE MATERIALS COMMITTEE. NADCA Product # 207-90.

NADCA Die Materials Committee

2000 N. Fifth Ave. River Grove, IL 60171 Tel: 1-847-452-0700

ASTM standards A-388, A-681, A-370, E-23, E-45, E-112 and E-114 may be obtained from:

ASTM Sales Department 1916 Race Street Philadelphia, PA 19103 Tel: 1-215-299-5400

ISO Standards 148 and R442 may be obtained from:

ISO Central Secretariat 1, Rue de Varembe CH-1211 Geneve 20 Switzerland/Suisse

 

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Tool Steel H11 

Principal Design Features

This alloy is one of the Hot Work, Chromium type tool steels. It is relatively low in carbon content and has good toughness and deep hardens by air quench from heat treatment.

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Applications

H11 is often used for highly stressed structural parts such as aircraft landing gear. It resists softening at temperatures up to 1000 F while retaining good ductility and toughness even at strength levels on the order of 275 ksi.

Machinability

Machinability is reasonably good, approximately 75% that of the W group water hardening low alloy tool steels.

Forming

Forming characteristics of H11 are good by conventional methods. It also may be formed by forging and machining.

Welding

H11 is a readily weldable alloy by conventional methods.

Heat Treatment

Preheat to 1500 F and then heat to 1850 F and hold for 15 to 40 minutes. Air cool (air quench).

Forging

Forge at 2050 F down to 1700 F. Do not forge below 1650 F.

Hot Working

No data given. The alloy may be hot worked by "Forging".

Cold Working

Cold working may readily be accomplished on H11 by conventional methods.

Annealing

Anneal at 1600 F and slow cool at 40 F per hour or less in the furnace.

Aging

Not applicable to this alloy.

Tempering

Temper at 1000 F to 1200 F for Rockwell C hardness of 54 to 38. Double tempering for one hour each time at the selected tempering temperature is recommended.

Hardening

See "Heat Treatment" and "Tempering".

Other Comments

H11 provides good toughness with high strength even at elevated temperature.

Density: 0.281

Specific Gravity: 7.8

Melting Point: 2600

MoETensile: 29

 

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