The Distinction of Steel and Cast Iron and How to Distinguish

1. The Distinction of Steel and Cast Iron and How to Distinguish The essential difference between cast iron and cast steel lies in the difference of chemical composition. In engineering, it is generally believed that it is iron if containing over 2% carbon and it is steel if containing below the same volume. Because of difference in volume of elements causes differences of structure property. Generally speaking, the plasticity and toughness of steel is better, which shows in the elongation, cross-section shrinkage and impact toughness. While iron is hard and brittle. Cast iron contains more than 2% Carbon. Industrial cast iron generally contains 2%-4% of Carbon. Carbon exists with the form of graphite in the cast iron in and sometimes exists in the form of cementite. Apart from Carbon, cast iron also contains 1% to 3% of Silicon, Manganese, Phosphorus, Sulfur and other elements. Alloy cast iron also contains Nickel, Chromium, Molybdenum, Aluminum, Copper, Boron, Vanadium and other elements. Carbon and Silicon are the main elements that affect the microstructure and properties of cast iron.

2. Cast iron can be divided into three kinds. The first kind is gray cast iron with high volume of carbon (2.7% -4.0%), mainly in the form of flake graphite, which shortly is named as gray iron because its fracture surface is grey. It has low melting point (1145 ~ 1250 ℃), small solidification shrinkage, tensile strength and hardness close to carbon steel, with good shock absorption. The second is white cast iron, which contains less Carbon (mainly in the form of cementite) and Silicon, with silver-white fracture surface. It has good solidification shrinkage, which easily results in shrinkage, cracks. Besides it is too brittle with high hardness to bear the impact load. The third is malleable cast iron made from white cast iron after annealing treatment. Its graphite exists in flocculent distribution. It is briefly called tough iron, with uniform structure property, wear resistance, good plasticity and toughness. Cast steel china is used for casting cast steel, a kind of cast alloy. Cast steel is divided into cast carbon steel, casting low alloy steel and casting special steel.

3. For Cast carbon steel, Carbon is the main alloying element with a small amount of other elements. If containing below 0.2% of Carbon, it is low carbon cast steel; if containing 0.2% - 0.5% of Carbon, it is middle carbon cast steel; if containing over 0.5% of Carbon, it is high carbon cast steel. With the increase of carbon content, the strength of cast carbon steel increases and so does its hardness. Cast carbon steel has much higher strength, plasticity and toughness and its cost is low so that it is widely used for making heavy-loaded parts for heavy machinery For low alloy cast steel, it contains Manganese, Chromium, Copper and other alloy elements (generally less than 5%) with greater impact toughness. It can get better mechanical properties by heat treatment. Casting low-alloy steel has better usage performance than carbon steel, which can reduce the weight of part and increase service life of parts.

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