How to identify cast iron vs cast steel

Cast steel (cast steel) is steel used for casting castings. A type of casting alloy. Cast steel is divided into three categories: cast carbon steel, cast low alloy steel and cast special steel.

1. Cast carbon steel

Cast steel with carbon as the primary alloying element and containing a small amount of other elements. Cast low-carbon steel contains less than 0.2% carbon, cast medium-carbon steel contains 0.2% to 0.5% carbon, and cast high-carbon steel contains more than 0.5% carbon. With the increase in carbon content, the strength and hardness of cast carbon steel increase. Cast carbon steel has high strength, plasticity, toughness, and low cost. It is used in heavy machinery to manufacture parts that bear heavy loads, such as rolling mill frames, hydraulic press bases, etc.; it is used on railway vehicles to manufacture parts that bear large forces and impacts, such as bolsters, side frames, wheels and hooks.

2. Cast low alloy steel

Cast steel containing alloy elements such as manganese, chromium, and copper. The total amount of alloy elements is generally less than 5%, has a more significant impact on toughness, and can obtain better mechanical properties through heat treatment. Cast low alloy steel has better performance than carbon steel, can reduce the weight of parts, and increases service life.

3. Cast special steel

Alloy cast steel is refined to meet unique needs, with a wide variety of varieties, usually containing one or more high amounts of alloy elements to obtain specific unique properties.

For example, high manganese steel containing 11% to 14% manganese can withstand impact wear and is mainly used for wear-resistant parts of mining machinery and engineering machinery; various stainless sheets of steel with chromium or chromium-nickel as the main alloying elements are used for parts working under corrosive or high-temperature conditions above 650°C, such as valve bodies, pumps, containers for chemical industry, or turbine housings of large-capacity power stations.

Although both are iron-carbon alloys, they have different metallographic structures after crystallization due to the various percentages of chemical elements such as carbon, silicon, manganese, phosphorus, and sulfur. They show many differences in mechanical properties and process properties.

For example, in the casting state, the elongation, cross-sectional shrinkage, and impact toughness of cast iron are lower than those of cast steel; the compressive strength and shock absorption performance of cast iron are better than those of cast steel; the liquid fluidity of gray cast iron is better than that of cast steel, and it is more suitable for casting thin-walled castings with complex structures; in the bending test, cast iron is brittle fracture, and cast steel is bending deformation. And so on. Therefore, they are respectively suitable for casting parts with different requirements.

How to distinguish cast iron from cast steel in actual production life:

1. Brightness: Cast steel is shiny, cast iron is dark and gray, and the gray iron and ductile iron in cast iron are different. Ductile iron is brighter than gray iron.

2. Particles: Cast steel is very dense, and the particles are generally invisible to the naked eye. Both gray iron and ductile iron can see particles, and gray iron particles are more considerable.

3. Sound.: The collision of cast steel parts is “just,” which is different from the sound of cast iron parts.

4. Gas cutting: The surface of cast steel parts is rough, and the riser and gate area are large, so they must be removed by gas cutting. Ductile iron cannot be cut by gas cutting.

5. Toughness: The toughness of cast steel is close to that of steel plate, while the toughness of ductile iron is slightly inferior. Thin-walled parts can reach 20-30 degrees of bending, and gray cast iron has no toughness.

6. The difference between malleable cast iron and ductile iron: The hardness, wear resistance and tensile strength of ductile iron are much greater than those of malleable cast iron parts, and the tensile strength can reach 1000MPa. Ductile iron can be used to make various high-strength structural parts such as engine crankshafts and gears. Malleable cast iron and ductile iron can be distinguished by listening to the sound. Malleable cast iron has a sharp and short sound; ductile iron has a loud sound and a long echo.

Although both are iron-carbon alloys, they have different metallographic structures after crystallization due to the various percentages of chemical elements such as carbon, silicon, manganese, phosphorus, and sulfur. They show many differences in mechanical properties and process properties. For example, in the casting state, the elongation, cross-sectional shrinkage, and impact toughness of cast iron are lower than those of cast steel. The compressive strength and shock absorption performance of cast iron are better than those of cast steel. Gray cast iron has better liquid fluidity than cast steel and is more suitable for casting thin-walled castings with complex structures. In the bending test, cast iron fractures brittlely and cast steel deforms by bending. And so on. Therefore, they are respectively suitable for casting parts with different requirements.