8/12/2019 BS2L99 Alloy Detail

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BSL99 Aluminium Casting Alloy

BS2L99

ALUMINIUM CASTING ALLOY

(A1-Si7Mg0.3)

This alloy conforms to British standard 2L99. Castings are standardized in the solution treated and precipitationtreated condition.

CHEMICAL COMPOSITION

%

Copper 0.10 max.

Magnesium 0.20-0.45 (0.25-0.45)Silicon 6.5-7.5.Iron 0.20 max. (0.15)Manganese 0.10 max.Nickel 0.10 max.Zinc 0.10 max.Lead 0.05 max.Tin 0.05 max.Titanium 0.20 max.Aluminium RemainderOthers: each - (0.05)Others: total - (0.15)Figures in brackets are ingot compositions where they differ from the casting, single figures are maxima.

MECHANICAL PROPERTIES

SAND CAST CHILL CAST

0.2%. Proof Stress (N/mm_) 185 200Tensile Stress (N/mm_) 230 280Elongation (%) 2 5Impact Resistance Izod (Nm) - -Brinell Hardness 75 80Endurance Limit (5x108 cycles; N/mm_) 56 90Modulus of Elasticity (x10_ N/mm_) 71 71

Shear Strength (N/mm_) 160-180 170-200

The values in bold type are standardized properties for separately cast test samples produced to the requirements ofBS 4L 101; those in normal type are typical properties.

STRENGHT AT ELEVATED TEMPERATURES

The tensile properties of 2L99 alloy at elevated temperatures are influenced by the condition (heat treatment) of thecastings and the duration at the elevated temperature. For short term testing e.g., 30 minutes at temperature, theproperties fall only slowly and uniformly up to about 200 C at which temperature the strength is reduced byapproximately 20%.

Very prolonged heating (10,000 hours) results in a sharp loss of strength at about 135 C, and at 200 C, the strengthis less than half of that at room temperature.

8/12/2019 BS2L99 Alloy Detail

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BSL99 Aluminium Casting Alloy

PHYSICAL PROPERTIES

Coefficient of Thermal Expansion (per C at 20-100C) 0.000022Thermal Conductivity (cal/cm_/C at 25C) 0.36Electrical Conductivity (% copper standard at 20C) 39Density (g/cm_) 2.68Freezing Range (C)approx 615-550

MACHINABILITY

The heat-treated alloy has fairly good machining properties, but tools should preferably be of high speed steel, andmust be kept sharp. A moderately high rate of tool wear may be expected. Liberal cutting lubricant should beemployed.

CORROSION RESISTANCE

Resistance to corrosive attack by sea water and marine atmospheres is high.

ANODIZING

A protective anodic film can be obtained by either the sulphuric or chromic acid process but the grey opaquecharacter of the coatings of normal thickness precludes their colouring in light shades for decorative purposes.

CASTING CHARACTERISTICS

FLUIDITY Good, suitable for fairly thin castings.PRESSURE TIGHTNESS Good, suitable for castings required to be leak tight.HOT-TEARING Excellent. Problems due to hot tearing are seldom encountered.

TYPICAL POURING TEMPERATURE - 710 CThe practical temperature may range between 675-790 C, depending on the mould configuration.PATTERNMAKERS SHRINKAGE 1.3% OR 1/75

HEAT TREATMENT

BL 2L99 (fully heat treated) Heat for not less than 12 hours at 535-545C, quench in water at not less than 65C,orin a polymer quenchant not hotter than 30 C, followed by a precipitation treatment of not less than 4 hours at 150-160C and air cool.

APPLICATIONS

2L99 alloy is mainly used where good mechanical properties are required in castings of a shape or dimensions

requiring and alloy of excellent castability in order to achieve the desired standard of soundness. The alloy is alsoused where resistance to corrosion is an important consideration, particularly where high strength is required. It isused for aircraft pump parts, aircraft fittings and control parts, aircraft structures and engine controls.