Long ago, people only had the concept of iron, because there was no strict definition between steel and iron. Even now entering the era of highly developed information technology, ordinary people will not be too clear about the specific quantitative distinction between steel and iron. Now let's share the difference between pig iron and steel for you. I hope it can help you.
What are the differences between steel and pig iron
In fact, what people usually call iron is pig iron. Pig iron and steel are alloy of iron and carbon (with a small amount of Mn, Si, P, s and other components). In modern times, people call those with carbon content of 0.02-2% as steel, those with carbon content of 2-4.5% as pig iron, and those with carbon content of & lt; 0.02% as pure iron (industrial pure iron).
Pure iron has good ductility and weldability, but its strength and hardness are poor. In addition to the application in the electrical industry, there are few applications in other fields.
Pig iron has high strength and hardness, but it has poor ductility and willfulness, poor weldability and brittleness. Widely used as raw materials for casting and steelmaking.
With the increase of carbon content, the strength and hardness of Fe3C solid melt increase, while the plasticity and impact toughness decrease.
Application prospect of steel: steel has good physical, chemical and mechanical properties, and can be deep processed by drawing, pressing, rolling, punching and drawing. Its application is very wide.
Different applications require different properties of steel, so different requirements are put forward for steel production. Many important fields, such as petroleum, chemical industry, aerospace, transportation, agriculture, national defense and so on, need a large amount of steel of various types, and our daily life is inseparable from steel. In short, steel will still be the most widely used structural material and the most important functional material in the 21st century.
The difference between grey cast iron and pig iron
cast iron
Iron carbon alloy with more than 2% carbon content. Generally, the carbon content of industrial cast iron is 2% - 4%. Carbon in cast iron is mostly in graphite form, sometimes in cementite form. In addition to carbon, cast iron also contains 1% - 3% 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.
Cast iron can be divided into:
① gray cast iron. The carbon content is high (2.7% ~ 4.0%). The carbon mainly exists in the form of flake graphite, and the fracture is gray, which is called gray iron for short. It has low melting point (1145-1250 ℃), small shrinkage during solidification, close to carbon steel in compressive strength and hardness, and good shock absorption. Used to manufacture machine bed, cylinder, box and other structural parts.
② white cast iron. The content of carbon and silicon is low, the carbon is mainly in the form of cementite, and the fracture is silvery white. It is easy to produce shrinkage cavity and crack. High hardness and brittleness, unable to bear impact load. It is mainly used as the blank of malleable cast iron and wear-resistant parts.
③ malleable cast iron. After annealing of white cast iron, graphite is distributed in floccules, which is called ductile iron for short. Its structure and properties are uniform, wear-resistant, with good plasticity and toughness. It is used to manufacture parts with complex shape and strong dynamic load.
④ ductile iron. After spheroidizing the gray cast iron, the graphite is spheroidal, which is called nodular iron for short. Compared with ordinary gray cast iron, it has higher strength, better toughness and plasticity. It is used to manufacture internal combustion engine, auto parts, agricultural machinery, etc.
⑤ vermicular cast iron. The graphite of gray cast iron is vermicular after it is vermiculated. The mechanical properties are similar to that of nodular cast iron, and the casting properties are between gray cast iron and nodular cast iron. Parts used to make cars.
⑥ alloy cast iron. Ordinary cast iron is obtained by adding some alloy elements (such as silicon, manganese, phosphorus, nickel, chromium, molybdenum, copper, aluminum, boron, vanadium, tin, etc.). Alloy elements make the matrix structure of cast iron change, so it has the corresponding characteristics of heat resistance, wear resistance, corrosion resistance, low temperature resistance or non magnetism. It is used to manufacture spare parts of mining, chemical machinery, instruments and meters, etc.
Classification of cast iron
According to the color of the fracture (1) gray cast iron, most or all of the carbon in this cast iron exists in the form of free state flake graphite, and its fracture is dark gray, with certain mechanical properties and good cutting properties, which is widely used in industry
1. Other names and common names of pig iron: Definitions
Pig iron is an iron carbon alloy with a carbon content of more than 2%. Industrial pig iron generally has a carbon content of 2.5% - 4%, and contains elements such as C, Si, Mn, s, P, etc. it is a product smelted by iron ore through blast furnace. According to the different forms of carbon in pig iron, it can be divided into steel-making pig iron, casting pig iron and nodular iron.
Properties of pig iron: pig iron is hard, wear-resistant and castable, but pig iron is brittle and cannot be forged.
2. Properties, brief introduction and application of various pig irons
The carbon in pig iron is mainly in the form of iron carbide. Its section is white, usually called white iron. This kind of pig iron is hard and brittle, and is generally used as raw material for steelmaking.
The carbon in cast pig iron exists in the form of flake graphite. Its fracture is gray, which is also called gray iron. Because of its soft graphite and lubricity, cast pig iron has good cutting, wear resistance and casting properties. But its strength is not enough, so it can not be forged and rolled. It can only be used to make all kinds of castings, such as casting all kinds of machine bed, iron pipe, etc.
Carbon in nodular cast iron exists in the form of spherical graphite. Its mechanical properties are much better than that of gray iron and close to that of steel. It has excellent casting, machining and wear resistance, and has certain elasticity. It is widely used in the manufacture of crankshaft, gear, piston and other high-grade castings as well as a variety of mechanical parts.
In addition, there are also pig iron with high silicon, manganese, nickel or other elements, called alloy pig iron, such as ferrosilicon and ferromanganese, which are often used as raw materials for steelmaking. The properties of steel can be improved by adding some alloy pig iron.