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  Typical Si Mo Ductile Iron Chemical Mechanical Properties for Exhaust Manifold  
 

SiMo Ductile Iron is suitable for making various casting parts with high temperature resistance property, such as auto exhaust manifolds.

By increasing the Silicon and Molybdenum content of Ductile Iron, the heat resistance and strength at high temperatures will be increased significantly.

The following is the typical chemical composition:

C=3.2-3.8%, Si=4.0-5.0%, S < 0.02%, Mg=0.03-0.07%, Mo=0.5-1.5%

Physical properties depend on temperatures, the typical values are detailed in the table below:

Temperature oC

Tensile Strength N/mm2

0.2% Proof Stress N/mm2

Modulus of Elasticity N/m x 104

Hardness BHN

23

550

480

14.8

(200-240)

300

480

395

14

 

500

350

270

12

 

800

50

30

2.5

 

The main application for SiMo is in Automotive Exhaust and Turbocharger Systems, such as cast iron exhaust manifolds, but it is suitable for any high temperature application where both strength and ductility are required.

Machineability is similar to that of EN-GJS-500-7.

Typical Microstructure

The following photo is the typical microstructure of SiMo ductile iron. The black and round balls are the spheroidal graphite, the light yellow is the ferrite, the dark yellow is the pearlite.

Certian content of pearlite will increase its tensile strength and hardness. More spheroidal graphite balls will be good ductile iron.

Guideline Figures for Maximum Exhaust Manifold and Exhaust Gas Temperatures

Material Grade

Max. Manifold Temperature °C

Max. Exhaust Gas Temperature °C

EN-GJS-400-15

700

770

EN-GJS-SiMo (0.5% Mo)

750

820

EN-GJS-SiMo (1.0% Mo)

780

820

EN-GJS-SiMoNi

795

835

Ni Resist D-5S

870

950

 

 
 

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