Year1
- 品牌：
- 进口/国产
- 规格：
- 齐全
- 厂家：
- 进口/国产
A general name for alloys mainly composed of iron, carbon and silicon. In these alloys, the carbon content exceeds the amount that can be retained in the austenite solid solution at the eutectic temperature. Cast iron is a general term for alloys mainly composed of iron, carbon and silicon. In these alloys, the carbon content exceeds the amount that can be retained in the austenite solid solution at the eutectic temperature.
Iron-carbon alloys with carbon content above. Industrial cast iron generally has a carbon content of ~. Carbon mostly exists in the form of graphite in cast iron, and sometimes in the form of cementite. In addition to carbon, cast iron also contains silicon, manganese, phosphorus, sulfur and other elements. Alloy cast iron also contains elements such as nickel, chromium, molybdenum, aluminum, copper, boron, and vanadium. 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. It has a high carbon content (~carbon mainly exists in the form of flake graphite, and the fracture surface is gray, referred to as gray iron. It has a low melting point (~℃) and small shrinkage when solidified. Its compressive strength and hardness are close to carbon steel, and it has good shock absorption. Used to manufacture machine tool beds, cylinders, boxes and other structural parts.
② White cast iron. The carbon and silicon content are low. The carbon mainly exists in the form of cementite, and the fracture surface is silvery white. It shrinks greatly during solidification. It is prone to shrinkage cavities and cracks. It has high hardness and brittleness and cannot withstand impact loads. It is mostly used as a blank for malleable iron and to make wear-resistant parts.
③ Malleable cast iron. Obtained from white cast iron after annealing, graphite Distributed in a clump-like shape, referred to as tough iron. Its structure and properties are uniform, wear-resistant, and has good plasticity and toughness. It is used to manufacture parts with complex shapes that can withstand strong dynamic loads.
④ Ductile iron. The gray Cast iron is obtained after spheroidizing treatment of molten iron. The precipitated graphite is in the shape of spheroids, referred to as ductile iron. It has higher strength, better toughness and plasticity than ordinary gray cast iron. It is used to manufacture internal combustion engines, automobile parts and agricultural machinery, etc. < br/> ⑤ Vermicular graphite cast iron. It is obtained by vermigating gray cast iron molten iron, and the precipitated graphite is in the shape of worms. The mechanical properties are similar to ductile iron, and the casting performance is between gray cast iron and ductile iron. Used for manufacturing Automobile parts.
⑥Alloy cast iron. Ordinary cast iron is obtained by adding appropriate amounts of alloying elements (such as silicon, manganese, phosphorus, nickel, chromium, molybdenum, copper, aluminum, boron, vanadium, tin, etc.). Alloying elements make cast iron The matrix structure changes, so that it has corresponding heat resistance, wear resistance, corrosion resistance, low temperature resistance or non-magnetic properties. It is used to manufacture parts for mining, chemical machinery, instruments, meters, etc.
Classification of cast iron
Classification method Classification name description
Fracture color classification
Gray cast iron Most or all of the carbon in this type of cast iron is in the form of free flake graphite, and its fracture is dark gray with a certain It has excellent mechanical properties and good cutting performance and is widely used in industry
White cast iron White cast iron is an iron-carbon alloy with no or almost no graphite in the structure. Its fracture surface is white and bright, hard and It is brittle and cannot be machined. It is rarely used directly in industry to make mechanical parts. Because of its high surface hardness and wear resistance, it is also called chilled cast iron or chilled cast iron
MaKou cast iron MaKou Cast iron is a kind of cast iron between white cast iron and gray cast iron. Its fracture surface is pitted with gray and white. It has poor performance and is rarely used.
Chemical composition
Ordinary cast iron refers to Cast iron containing any alloying elements, such as gray cast iron, malleable cast iron, ductile iron, etc. Alloy cast iron is a high-grade cast iron prepared by adding some alloying elements to ordinary cast iron to improve certain special properties. Such as various Cast iron with special properties of corrosion resistance, heat resistance and wear resistance
Production method and structural performance classification
Ordinary gray cast iron, see gray cast iron
Inoculation cast iron is based on gray cast iron and processed by modification. It is also called modified cast iron. Its strength, plasticity and toughness are much better than ordinary gray cast iron, and its structure is also more uniform. Mainly used to manufacture large castings that require high mechanical properties and large changes in cross-sectional dimensions
Malleable cast iron Malleable cast iron is made of white cast iron with a certain composition and graphitized annealing. It has higher toughness than gray cast iron and is Called ductile cast iron. It cannot be forged and is often used to make castings that can withstand impact loads
Ductile iron is referred to as ductile iron. It is obtained by adding a certain amount of nodularizing agent and inking agent to the molten iron before casting to promote the crystallization of spheroidal graphite. Compared with steel, except for slightly lower plasticity and toughness, its other properties are similar. It is an excellent material that combines the advantages of steel and cast iron. It is widely used in mechanical engineering
Special performance cast iron This is a kind of cast iron with certain Characteristics of cast iron, according to different uses, can be divided into wear-resistant cast iron, heat-resistant cast iron, corrosion-resistant cast iron, etc. Most of them belong to alloy cast iron and are widely used in machinery manufacturing
Cast iron heat treatment process
Stress relief annealing Due to the uneven wall thickness of the casting, effective stress and structural stress will be generated during the heating, cooling and phase transformation processes. . In addition, large parts are prone to residual stress after machining, and all these internal stresses must be eliminated. The usual heating temperature for stress relief annealing is ~℃ and the holding time is ~, and then furnace cooling (gray iron) or air cooling (ductile iron). Using this process can eliminate the internal stress of the casting, but the cast iron structure will not change. If the temperature exceeds ℃ or the holding time is too long, it will cause graphitization and reduce the strength and hardness of the casting.
High-temperature graphitization annealing to remove cast iron white spots
When castings are cooled, white spots often occur on the surface layer and thin sections. The white structure is hard and brittle, has poor processing performance and is easy to peel off. Therefore, annealing (or normalizing) must be used to eliminate the white structure. The annealing process is to heat to ℃ and keep warm, then cool the furnace to ℃ and then leave the furnace for air cooling. During the high-temperature insulation period, free cementite and eutectic cementite decompose into graphite and graphite. During the subsequent cooling process, secondary cementite and eutectoid cementite also decompose, and the graphitization process occurs. Due to the decomposition of cementite, the hardness decreases, thereby improving the machinability.
Normalizing Iron
The purpose of normalizing ductile iron is to obtain the pearlite matrix structure, refine the grains, and uniform the structure to improve the mechanical properties of the casting. Sometimes normalizing is also the structural preparation for surface quenching of ductile iron. Normalizing is divided into high-temperature normalizing and low-temperature normalizing. The high-temperature normalizing temperature generally does not exceed ~℃, and the low-temperature normalizing temperature is generally heated to the refractory temperature range ~℃. After normalizing, four people are generally required to handle it to eliminate the internal stress generated during normalizing.
Quenching and tempering of iron
In order to improve the mechanical properties of ductile iron, castings are generally heated to above ~°C (representing the final temperature formed during heating) and then quenched in oil to obtain a martensite structure. In order to Appropriately reduce the residual stress after quenching. Generally, tempering should be performed after quenching. The low-temperature tempered structure is tempered martensite plus residual bainite plus spherical graphite. This structure has good wear resistance and is used for applications requiring high wear resistance. properties, high-strength parts. The medium-temperature tempering temperature is ℃. The structure after tempering is tempered troostite plus spherical graphite. It is suitable for thick parts that require good wear resistance, certain effective stability and elasticity. Related to Xiangyun Company More talents are concentrated in the Steel Talent Network. The high temperature tempering temperature is ℃, and the structure after tempering is tempered Soxhlet plus spherical graphite. The one with good combination of toughness and strength is ℃. The structure after tempering is tempered Soxhlet. Adding spherical graphite, it has a good combination of toughness and strength, so it is widely used in production.
Multi-temperature quenching of iron
Ductile iron can obtain high strength after isothermal quenching, and at the same time it has better Plasticity and toughness. The selection of heating temperature for multi-temperature quenching mainly considers the complete transformation of the original structure without residue, and also avoids grain growth. The heating temperature is generally used above ~ ℃, and the isothermal treatment temperature is ~ ℃ to ensure that comprehensive Mechanical properties of lower bainite structure. After isothermal quenching of rare earth magnesium aluminum ductile iron~,~,~. However, it should be noted that a tempering process is added after isothermal quenching.
Surface quenching
In order to improve certain Surface quenching can be used to improve the surface hardness, wear resistance and fatigue strength of castings. Both gray cast iron and ductile iron castings can be surface quenched. Generally, high (medium) frequency induction heating surface quenching and electrical contact surface quenching are used.
Learn heat treatment
For castings that require surface wear resistance, oxidation resistance, and corrosion resistance, chemical heat treatment processes similar to steel can be used, such as gas soft chlorination, chlorination, boronization, sulfurization, etc.
Gray cast iron
China
Japan
Korea
United States
United States
Ductile iron
China
Japan
South Korea< br/> United States
United States
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