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  BS 2789 900/2 Ductile Cast Iron  
 

BS 2789 900/2 is a ductile iron material grade used in UK, also equal to ISO grade 900-2, China QT900-2, Euro EN-GJS-900-2.

According to the standard of BS 2789, this material grade requires Tensile Strength min. 900 MPa, Yield Strength min. 600 MPa, Elongation min. 2%, Hardness(BHN) 302~359. The matrix structure is tempered martensite.

In standard BS 2789, there is no requirement to the chemical composition, so the iron foundry could adjust their chemical composition as their experience, but the mechanical properties as above are the necessary requirement.

The typical properties of BS 2789 900/2 SG iron is equal to ISO 1083/JS/900-2 SG iron as following:

Characteristic

Unit

Material designation

ISO 1083/JS/900-2

Shear strength

N/mm2

810

Torsional strength

N/mm2

810

Modulus of elasticity E (tension and compression)

GN/ m2

176

Poisson's Ratio v

-

0,275

Fatigue limit (Wöhler)c (rotating bending) unnotchedd (ø10,6mm)

N/mm2

304

Fatigue limit (Wöhler)c (rotating bending) notchede (ø10,6mm)

N/mm2

182

Compression strength

N/mm2

-

Fracture toughness KIC

MPa·√m

14

Thermal conductivity at 300°C

W/(K·m)

31,1

Specific heat capacity 20°C to 500°C

J/(kg·K)

515

Linear expansion coefficient 20°C to 400°C

μm/(m·K)

12,5

Density

kg/dm3

7,2

Maximum permeability

μH/m

501

Hysteresis loss(B=1T)

J/m3

2700

Resistivity

μΩ·m

0,54

Predominant structure

 

tempered martensite

c  Fatigue limit test pieces.

d  Unnotched – In annealed ferritic spheroidal graphite cast iron the fatigue limit is about 0,5 x tensile strength in spheroidal graphite cast iron with a tensile strength of 370 N/mm2. The ratio decreases with increase in tensile strength until, in pearlitic and quenched and tempered spheroidal graphite cast iron, the fatigue limit is approximately 0,4 x tensile strength. The ratio decreases further when tensile strength exceeds 740 N/mm2.

e  Notched – For a test piece of 10,6 mm diameter at notch with a circumferential 45° V-notch having a radius of 0,25 mm, the fatigue limit of annealed spheroidal graphite cast iron decreases to a value of about 0,63 x fatigue limit of unnotched test pieces in spheroidal graphite cast iron with a tensile strength of 370 N/mm2. This figure decreases as the tensile strength of a ferritic spheroidal graphite cast iron increases. In spheroidal graphite cast iron with intermediate strengths and in pearlitic spheroidal graphite cast iron and quenched and tempered spheroidal graphite cast iron, the fatigue limit of notched test pieces is approximately 0,6 x the fatigue limit of unnotched test pieces.

 

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