What is SiMo (Silicon Molybdenum)?


The properties of S.G Iron can be modified to give superior heat resistance characteristics by adding up to 5% Silicon and 1.5% Molybdenum. The material is used in turbo housings, manifolds and other cast turbo chrager parts which require high ductility, oxidation resistance, heat resistance, impact resistance and dimensional stability.

 

 

The microstructure of SiMo iron

 

Typical mechanical properties at elevated temperatures, see table below.

 

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

Temperature

°C

Tensile Strength

N/mm²

0.2% Proof Stress

N/mm²

Modulus of Elasticity

N/m x 10⁴

Hardness

BHN

23 550 480 14.8 (200-400)
 300  480  395  14  
 500  350  270  12  
 800  50  30  2.5  

 

Guideline Figures for Maximum 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