The main difference between cast iron and iron steel valves is the difference in carbon content, which directly affects the strength and plasticity of steel.

Different carbon contents

Cast iron is an iron-carbon alloy with a carbon content of 2% or more.

Carbon steel, also called carbon steel, contains less than 2% carbon WC iron-carbon alloy. Carbon steel in addition to carbon generally contains a small amount of silicon, manganese, sulfur, phosphorus According to the use of carbon steel can be divided into three categories of carbon structural steel, carbon tool steel, and free-cutting structural steel. Carbon structural steel is also divided into two types of structural steel for construction and machine building Carbon steel can be divided into low carbon steel (WC≤0.25%), medium carbon steel (WC0.25%--0.6%), and high carbon steel (WC>0.6%) According to the phosphorus, the sulfur content of carbon steel can be divided into ordinary carbon steel (containing phosphorus, sulfur higher) The higher the carbon content in general carbon steel, the higher the hardness and strength, but the lower the plasticity.

Cast iron 

Cast iron can be divided into :

1. gray cast iron

2. white cast iron

3. malleable cast iron

4. ductile iron

5. peristaltic cast iron

6. alloy cast iron

Generally, we say cast iron valves are made of ductile iron, which is obtained by spheroidizing gray cast iron, and the graphite precipitated is spherical, referred to as ductile iron. Higher strength, better toughness, and plasticity than ordinary gray cast iron.

Application of cast iron valves: for example, we often see valves for conveying water pipes, the valves are then painted black on the surface, these valves are cast iron valves.

Cast Steel

Steel is used to pour castings. A type of casting alloy. Cast steel is divided into 3 categories: casting carbon steel, casting low-alloy steel, and casting special steel; casting carbon steel. Cast steel with carbon as the main alloying element and contains a small number of other elements. Containing less than 0.2% carbon for casting low carbon steel, carbon 0.2% to 0.5% for casting carbon steel, carbon greater than 0.5% for casting high carbon steel. As the carbon content increases, the strength of cast carbon steel increases, the hardness increases. Cast carbon steel has high strength, plasticity, and toughness, lower cost, used in the manufacture of heavy machinery to bear large loads of parts, such as rolling mill frame, hydraulic base, etc.; in railroad vehicles for the manufacture of large forces and impact parts such as rocking pillows, side frames, wheels, and hooks, etc.

Comparison

From the above material characteristics, cast iron is more rigid than cast steel, brittle than cast steel, and cast steel has better plasticity and toughness than cast iron, so cast iron is generally used in low-pressure pipelines, but also can only be applied to the top of the pipeline at room temperature, because the rise in pressure or temperature means that the valve will have a certain amount of trace deformation, which is detrimental to cast iron valves 

Compared to cast iron valves cast steel valves can be used in pipelines with higher pressure or temperature.

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