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Cast Iron Metal

16th July, 2025
Author: HULK Metal

We can tell from the name of cast iron that it is a raw material mainly used for foundry production. Cast iron refers to cast pig iron that is made by adding other metals, scrap steel, and recycled iron during the smelting process and adjusting its composition after smelting. Speaking of cast iron, we need to talk about pig iron first:

 

Pig iron is made by smelting iron ore, and it contains 2.11 - 6.69% carbon and other elements. Pig iron is brittle and hard, lacks toughness, and has almost no plastic deformation ability, so it cannot be processed by forging, rolling, drawing, and other methods. But pig iron can be used to make other raw materials such as steel and foundry pig iron. Therefore, pig iron can be divided into foundry pig iron and steelmaking pig iron according to the above uses. We habitually refer to steelmaking pig iron as pig iron and cast iron as cast iron.


Cast Iron Means:

Cast iron, also known as cast iron, is made by adding other metal elements, scrap steel, and recycled iron during the smelting process to adjust its composition and change its internal structure through forging, deterioration, spheroidization, and other methods. The carbon content of cast iron is above 2.11%. Industrial cast iron generally has 2.5% to 3.5% carbon content. In addition to carbon, cast iron also contains 1% to 3% silicon, manganese, phosphorus, sulfur, and other elements. The form of carbon in cast iron makes cast iron have unique properties. One of the classifications of cast iron we will talk about below is based on the form of carbon in the iron. Cast iron is primarily produced using casting processes to create iron castings with special shapes and properties. We have compiled an article about metal casting. You can click metal casting to see more.

 

Advantages and Disadvantages of Cast Iron:

With the development of science and technology, cast iron with many characteristics has been invented, such as cast iron with high wear resistance, high toughness and strength. Of course, no matter what kind of cast iron, they have common advantages and disadvantages.

 

Advantages of Cast Iron:


Durability:

Cast iron is especially durable and can withstand high temperatures and heavy loads. It's also resistant to scratches and other types of damage.

 

Heat Preservation:

Cast iron has excellent thermal conductivity and heat preservation performance. Cookware made of cast iron not only heats up quickly but also has a uniform overall temperature.

 

Wide Range of Applications:

cast iron can be used not only to make cookware but also to make industrial machinery. It can also be used to cast other structurally complicated, special size, and unique castings with performance requirements.

 

Save Money:

The acquisition cost of cast iron is cheaper than that of steel and copper, so cast iron is almost the best choice if there are no special requirements.

 

Non-stick Performance:

Specially processed cookware will have non-stick properties, allowing us to cook tastier food with less cooking oil, and it is easier to clean after use.

 

Disadvantages of Cast Iron:


Rust:

Cast iron requires regular maintenance to prevent rust and other types of damage.

 

Corrosion:

Cast iron is prone to react with acidic or alkaline substances, causing the surface of castings to corrode. So, when we use cast iron to make accessories or appliances, it is best to carry out the surface treatment.

 

Heats Up and Cools Down Slowly:

While cast iron is an excellent conductor of heat, it can take longer to heat up and cool down than other materials.

 

Brittleness:

Cast iron is brittle and may crack or break if dropped or subjected to extreme stress. This can be a disadvantage in some applications where durability is critical.

 

Application of Cast Iron:

Cast iron is a material with a wide range of uses. Here are some of the most common uses for cast iron:

 

Cookware:

Cast iron's excellent thermal insulation properties allow it to be used to make iron pots, oven trays, grills, etc.

 

Pipes and Fittings:

Because cast iron has excellent pressure and heat resistance, it is often used in manufacturing pipe fittings, cast iron pipes, etc.

 

Machine Components:

Because of its high strength and durability, cast iron is used to produce a variety of machine components, such as engine blocks, transmissions, and crankshafts.

 

Decorative Elements:

Cast iron has excellent casting properties, and we can use it to produce complex-shaped decorations, such as gates, railings, and lampposts.

 

Construction Materials:

Cast iron has high strength and wear resistance, and it is a better choice to use cast iron to produce manhole covers, drainage gratings, and gutters.

 

Agricultural Implements:

Cast iron is used in manufacturing agricultural implements and accessories such as plows, cultivators, and seeders and their accessories due to their durability and ability to withstand heavy loads.

 

Art Sculpture:

Cast iron is also used in art sculptures and monuments due to its ability to hold intricate details and resist weathering and corrosion when finished.

 

Types of Cast Iron:

To help you better understand the classification of cast iron: we have specially compiled a table where you can see the information and introduction of different cast iron classifications. You can click on the name below to jump if you want to know more.

 

Cast Iron Type List：

Classification Method

Cast Iron Name

Cast Iron Explained

According to the Color of the Cast Iron Fracture

Gray Cast Iron

Most or all of the carbon in gray cast iron exists in the form of flake graphite in a free state, and its fracture is dark gray.

 

White Cast Iron

White cast iron is an iron-carbon alloy completely or almost completely free of graphite in the structure, and its fracture is bright white, which can be used to make steel or malleable cast iron.

Mottled Cast Iron

Mottled cast iron is a kind of cast iron between white cast iron and gray cast iron, and its fracture is gray and white pitted. It has poor performance and is rarely used.

According to the Chemical Composition of Cast Iron

Ordinary Cast Iron

Cast iron without any alloying elements, such as gray cast iron, malleable cast iron, ductile iron, etc.

Alloy Cast Iron

Some alloying elements are added to ordinary cast iron to improve some special properties of advanced cast iron. Such as various corrosion-resistant, heat-resistant, wear-resistant special performance cast iron.

According to the Casting Method and Microstructure of Cast Iron

Ordinary Gray Cast Iron

Most or all of the carbon in this cast iron exists in the form of flake graphite in a free state, and its fracture is dark gray. Its mechanical properties and cutting performance are quite satisfactory. The castings made of it are widely used in the craft.

Inoculated Cast Iron

It is obtained by the metamorphic treatment of gray cast iron, also known as metamorphic cast iron. The strength, plasticity, and toughness of inoculated cast iron are much better than ordinary gray cast iron, and the structure is more uniform. It is mainly used to manufacture large-scale castings with high requirements on mechanical properties and large changes in cross-sectional dimensions.

Malleable Cast Iron (Malleable Steel)

Malleable cast iron is made of a certain composition of white cast iron through graphitization annealing, which has higher toughness than gray cast iron, also known as ductile cast iron. It cannot be forged and is often used to make castings that withstand impact loads.

Nodular Cast Iron (Ductile Iron)

It is referred to as ductile iron. It is obtained by adding a certain amount of nodulizer and ink agent to the molten iron before casting to promote the crystallization of spherical graphite. Compared with steel, except for slightly lower plasticity and toughness, other properties are similar. It is an excellent material with the advantages of both steel and cast iron and is widely used in mechanical engineering.

Special Properties Cast Iron

This is a kind of cast iron with certain characteristics. According to different uses, it can be divided into wear-resistant cast iron, heat-resistant cast iron, and corrosion-resistant cast iron. Most of them are alloy cast iron and widely used in machinery manufacturing.

 

Gray Cast Iron:

Its carbon content is 2.7%~4.0%, its melting point is between 1145~1250℃, and its fracture is dark gray. Most or all of the carbon exists in the form of flake graphite in a free state. Gray cast iron consists of graphite and matrix. The matrix is ferrite, pearlite, or ferrite plus pearlite. Due to the presence of flake graphite, ordinary gray cast iron has excellent wear resistance, vibration damping, low-notch sensitivity, casting performance, and machinability. But it also has the disadvantages of low strength, low plasticity, and low toughness. We can use it to cast machine tool beds, cylinders, boxes, and other structural parts.

Gray cast iron can also be divided into four categories according to the matrix structure: ferrite matrix gray cast iron, pearlite-ferrite matrix gray cast iron, pearlite matrix gray cast iron, and inoculated cast iron. The carbon in gray cast iron consists of combined carbon (Fe3C) and graphite carbon. When the combined carbon is 0.8%, it belongs to pearlitic gray cast iron; when the combined carbon is less than 0.8%, it belongs to pearlitic-ferritic gray cast iron; when all the carbon exists in graphite state, it is ferritic gray cast iron.

 

Ferritic Gray Iron HT100:

Ferritic gray cast iron has many coarse graphite flakes distributed on a ferrite matrix. Because of its poor strength and hardness, it is rarely used, but it can also be used in unimportant castings with small loads and no special requirements for friction and wear, such as protective covers, covers, oil pans, handwheels, brackets, bottom plates, and heavy hammers, small handle, etc.

 

Pearlitic Gray Cast Iron HT200, HT250:

Pearlitic gray cast iron is uniform, and fine graphite flakes are distributed on the pearlite matrix. Its strength and hardness are relatively high. It can be used in manufacturing castings, such as cylinders, gears, frames, flywheels, beds, cylinder blocks, cylinder liners, pistons, gearboxes, brake wheels, coupling discs, medium-pressure valve bodies, bed, bodies, etc.

 

Pearlitic-ferritic gray cast iron HT150:

Coarse graphite flakes are distributed on the mixed matrix of pearlite and ferrite. Although the strength and hardness of this cast iron are lower than the former, it can still meet the general performance requirements, and its castability and shock absorption is good and easy to smelt. It is the most widely used gray cast iron. It can be used to manufacture castings that bear medium loads, such as machine bases, brackets, boxes, tool holders, bed bodies, bearing housings, workbenches, pulleys, end covers, pump bodies, valve bodies, pipelines, flywheels, motors seat and so on.

 

Inoculant cast iron HT300, HT350:

Inoculated cast iron is obtained by the metamorphic treatment of gray cast iron, also known as metamorphic cast iron. The strength, plasticity, and toughness of inoculated cast iron are much better than ordinary gray cast iron, and the structure is more uniform. It mainly has high-load, wear-resistant, and high-air-tight castings, such as heavy-duty machine tools, shearing machines, presses, automatic lathe beds, machine bases, racks, high-pressure hydraulic parts, piston rings, and heavy-duty machine tools, gears, cams, bushings, crankshafts, cylinder blocks, cylinder liners, and cylinder heads of large engines.

 

White Cast Iron:

It is an iron-carbon alloy with no or almost no graphite in the structure. Its fracture is white and bright, hard and brittle, and cannot be cut. It is rarely used directly in the industry to make mechanical parts. After tempering at high temperatures, white cast iron has high strength and plasticity and can be cut, so white cast iron is only used to make wear-resistant agricultural tools, grinding balls, blades, pumps, rolls, etc. It is mainly used in producing malleable cast iron and as a raw material for steelmaking.

 

Malleable Cast Iron (Malleable Steel):

It is a high-strength cast iron obtained by graphitizing and annealing white cast iron. Its graphite is in the form of flocculent clusters, which has less splitting effect on the matrix. Compared with gray cast iron, malleable cast iron has better strength and plasticity, especially low-temperature impact performance, and better wear resistance and vibration damping than ordinary cast iron and carbon steel. One thing to note is that malleable cast iron cannot be forged. The matrix structure of malleable cast iron is different, and its performance is also other. Among them, black heart malleable cast iron has higher plasticity and toughness, while pearlitic malleable cast iron has higher strength, hardness, and wear resistance.

 

Advantages and Disadvantages of Malleable Cast Iron:


Advantages of Malleable Cast Iron:

Graphite in malleable cast iron is flocculent, with less content, less significant stress concentration, less effective load area for cast iron, a tensile strength of 300-700 MPa, and elongation of 2-12%. It has excellent machinability, oxidation growth resistance, and corrosion resistance.

 

Disadvantages of Malleable Cast Iron:

The as-cast structure of malleable cast iron is white, the fluidity of molten iron is poor, shrinkage cavities are prone to occur, and the tendency of hot cracking is relatively large, so it is generally only suitable for castings with less complicated shapes. In addition, since the annealing time increases with the increase of the wall thickness, and it is difficult to achieve complete annealing in the central part of the cast that is too thick, the wall thickness of white-heart malleable iron castings generally does not exceed 12 mm, and the wall thickness of black-heart malleable cast iron generally does not exceed 25 mm.

 

Applications of Malleable Cast Iron:

 

    Ferritic Malleable Cast Iron Applications:

It is widely used in wheels, differential housings, and chassis parts of automobiles and tractors wrenches in machine tool accessories, porcelain caps, wire clips, bowl head plates in power transmission lines, woolen machines in textile machinery, printing machine pan heads, and water and oil pipelines' elbows, tees, joints, and medium pressure valves.

    Pearlitic Malleable Cast Iron Applications: 

It is used for gas valve rockers, stoker parts, high-pressure joint valve bodies, automotive industry shift forks, differential gearboxes, etc.

White Heart Malleable Cast Iron Applications: 

It is used for auto parts hangers, steering column crowns, textile machine parts, etc.

 

Main Types of Malleable Cast Iron:

Whiteheart malleable iron, blackheart malleable iron, and pearlitic malleable iron. The detailed description is as follows:

 

White Heart Malleable Iron:

White-heart malleable cast iron is obtained by sealing white cast iron with low carbon and silicon content in an oxidizing medium and keeping it at a temperature of 950-1050°C for dozens of hours for decarburization annealing. The outer layer of its fibrous structure is ferrite, and a small amount of pearlite and flocculent graphite remains in the center. This structure makes its central fault appear white, hence the name. White heart malleable iron pipe fittings have good mechanical properties and welding properties.

 

The grades of white heart malleable cast iron are KTB380-04, KTB380-12, KTB400-05, and KTB450-07. Due to the complex smelting process of white heart cast iron, it is rarely used in mechanical manufacturing. So, it is limited to the manufacture of thin-walled castings and castings that do not require heat treatment after welding.

 

Black Heart Malleable Iron:

Black-heart malleable cast iron is to put white cast iron with low carbon and silicon content in a neutral medium for graphitization treatment, and then obtain two kinds of black-heart malleable cast iron by two types of processes: the first one is: keep several After ten hours, cool in the furnace to 720-740°C and keep warm for more than ten hours, and finally get ferrite black-centered malleable cast iron with ferrite matrix and flocculent graphite; the second is after holding for ten hours at 850-950°C Take it out of the furnace and cool it in the air to get pearlite black-heart malleable cast iron with pearlite matrix and flocculent graphite.

 

Grades and applications of black heart malleable cast iron:

Brands: KTH300-06, KTH330-08, KTH350-10, KTH370-12. Black heart malleable cast iron is used for manufacturing pipe fittings, low-pressure valves, rear axle housings of automobile tractors, steering mechanisms, machine tool parts, etc.

 

Pearlitic Malleable Cast Iron:

Pearlitic malleable cast iron is malleable cast iron whose metal matrix structure is mainly pearlite (> 70%), and the shape of pearlite has two types: flake and granular. Pearlitic malleable cast iron has high strength, certain toughness and hardness, and good wear resistance. After quenching heat treatment, its hardness can reach HRC50, and its wear resistance can reach the level of some low alloy steels.

 

Ductile Cast Iron (Ductile Iron):

It is obtained by adding a certain amount of nodularizing and blackening agents to the molten iron before casting to make the graphite inside the cast iron appear spherical. Compared with steel, except for slightly lower plasticity and toughness, other properties are close, and it is an excellent material that combines the advantages of steel and cast iron.

Elemental composition of ductile iron: carbon content 3.0-4.0%, silicon content 1.8-3.2%, manganese, phosphorus, sulfur total not more than 3.0%, and the appropriate amount of spheroidizing elements such as rare earth and magnesium.

 

Advantages and Disadvantages of Ductile Iron:

 

Advantages of Ductile Iron:

Ductile iron has high strength, plasticity, toughness, wear resistance, severe thermal and mechanical shock resistance, high or low-temperature resistance, corrosion resistance, and dimensional stability. The elongation of ductile iron can reach 17%, and the tensile strength can reach 800 N/mm2.

 

Disadvantages of Ductile Iron:

Shrinkage porosity

Ductile iron castings may often have defects such as shrinkage cavities and shrinkage porosity due to poor feeding.

stomatal defect

During the production process of ductile iron castings, subcutaneous pores may occur.

 

Grades and Applications of Ductile Iron:

Grades

matrix tissue type

Application

QT400-18

Ferritic

These three kinds of ductile iron are mainly used to produce parts that withstand shock and vibration: Such wheels of automobiles and push-pull machines, drive axle housings, differential housings, shift forks, agricultural machinery parts, medium and low-pressure valves, upper and lower water and gas transmission pipelines, high and low-pressure cylinders on compressors, motor casings, gearboxes, flywheel casings, etc.

QT400-15

Ferritic

QT450-10

Ferritic

QT500-7

Ferrite + Pearlite

The ductile iron of QT500-7 is mainly used to produce machine mounts, transmission shafts, flywheels, motor frames, oil pump gears for internal combustion engines, bearing bushes for railway locomotives, etc.

QT600-3

Pearlite + Ferrite

These three kinds of ductile iron are mainly used to manufacture parts with heavy loads and complex stress: such as crankshafts, connecting rod camshafts, cylinder liners of automobiles and tractors, spindles of some grinding machines, milling machines, lathes, worms and worm gears of machine tools, rolling mill rolls, large-type gears, main shafts of small water turbines, cylinder blocks, large and small rollers of bridge cranes, etc.

QT700-2

Pearlite

QT800-2

pearlite or tempered structure

QT900-2

Bainite or Tempered Martensite

 QT900-2 ductile iron is mainly to produce high-strength gears, such as spiral bevel gears for automobile rear axles, large-type reducer gears, internal combustion engine crankshafts, camshafts, etc.

 

Compacted Graphite Cast Iron:

Compacted graphite cast iron's graphite form is worm-like between flake graphite and spherical graphite, so its mechanical properties are also between ordinary gray cast iron and nodular cast iron. The chemical composition (%) of vermicular graphite cast iron is usually: C3.5~3.9, Si2.2~2.8, Mn0.4~0.8, P<0.06, S<0.06, R (rare earth) 0.04~0.06. Its physical and casting properties are superior to ductile iron and close to ordinary gray cast iron. Vermicular graphite cast iron is a new type of engineering structural material with excellent mechanical properties, thermal conductivity, and low section sensitivity.

 

Casting Performance of Compacted Graphite Cast Iron:

(1) Vermicular graphite cast iron with rare earth has good fluidity. Vermicular iron and gray cast iron has similar fluidity at the same carbon equivalent.

(2) The shrinkage of vermicular iron is also between gray cast iron and ductile iron, and the gating system can be designed according to gray cast iron. We need to use the nodular iron casting and feeding system to replace compacted graphite cast iron if complex castings with high compactness requirements and big wall thickness differences.

(3) Vermicular iron has the good properties of gray cast iron and ductile iron, and its tensile strength and yield strength are higher than gray cast iron, which is equivalent to ferritic ductile iron. The thermal conductivity is close to that of gray cast iron, so the casting process is convenient and easy. The compacted graphite cast iron parts yield is high.

(4) Vermicular iron has good anti-growth and anti-oxidation properties. The wear resistance of vermicular iron is more than 2.2 times that of GB HT300 and one time higher than that of high-phosphorus cast iron and similar to that of phosphorus copper titanium cast iron.

 

Cast Iron Parts Casting Services:

Iron castings casting service refers to the service that the foundry factory uses sand casting, investment casting, lost foam casting, and other processes to produce iron castings according to your requirements. The following types of services are generally available:

 

1. Foundries that can only provide one type of casting service:

This kind of foundry will be polarized: one is that the large scale does not accept small orders. But the production efficiency is fast and the lead time is very short. And the quality of cast iron parts is very high, which also means that the price is relatively high. If you have a huge order, and the foreign trade department of this foundry can provide you with excellent sales service, then you can rest assured to hand over the order to them. The other is that the scale is small and can only be molded manually and it can only provide casting services for iron castings with a longer delivery cycle and higher cost performance. This kind of foundry has a fatal disadvantage. That is, they are rarely equipped with a foreign trade service team, and you may need to spend more energy to track the production progress of the order. If the order in your hand is small, the quantity of each purchase is also small. And you have enough energy to communicate directly with the factory. Then the service that this kind of foundry can provide you will be your best choice.

 

2. A casting service provider that does not have its factory but works closely with

foundries and can provide comprehensive services such as procurement, quality inspection, and freight.

They can help you find a more suitable iron-casting foundry according to your needs. They can measure the production capacity of the foundry to complete the order faster with less cost under the premise of ensuring the quality of cast iron parts. This kind of casting service provider is more like your office in China to help you handle orders and various matters of goods in China.

 

3. Unique foundry service factories also cooperate with other foundries to form a complete foundry service system.

This is similar to the first one just mentioned. They will have their service department provide a relatively good service.

 

These three casting service providers have their advantages and disadvantages. We can make a comprehensive comparison and choose the one that is more suitable for us.

 

We are a well-known iron casting service provider in China. Although we do not have a factory, we can provide you with professional and comprehensive services to ensure the quality and quantity of your orders, complete production in China faster, and deliver faster into your hands. You can contact us anytime if you need such cast iron casting services. We will formulate a complete production solution according to your requirements. Let you enjoy more thoughtful service while buying better iron parts.



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Our cast iron production is supported by advanced factories specializing in different manufacturing processes. These include sand casting factories, precision machining workshops, heat treatment plants, and surface finishing factories. Each is equipped with skilled teams and modern equipment to ensure consistent quality and efficiency. Close collaboration between these factories allows us to handle projects from mold making to final assembly, ensuring your cast iron products meet both technical and aesthetic standards.

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Our Quality Control Center in China is equipped with a full range of advanced testing instruments and staffed by experienced inspectors. We implement strict quality control procedures to thoroughly check the dimensions, shape, and performance of your custom metal parts. A comprehensive inspection report can be provided for every order. Kindly contact our sales manager if you would like to schedule a visit to our quality control center.

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