The cast iron vs malleable iron will be discussed in this article. When selecting the proper material for a given task, it is vital to comprehend the difference between various types of metals. Cast iron and malleable iron are two used materials. With knowledge of their respective properties and functions, you will be able to make an informed choice of which one to use. This will help you determine which metal is ideal for your project.

What Is Cast Iron?

A category of iron alloys known as “cast iron” generally comprises 2% to 4% carbon. It may even reach 5%, depending on the specific variety of cast iron. Various waste metals and alloys are combined with smelted iron ore or pig iron to produce them. Cast or pour the molten substance afterward. It retains its strength while solidifying into the shape of the mold. Due to its high carbon ratio, unique erosion resistance, and strength are characteristics of cast iron.

Types Of Cast Iron 

The following four materials are classified as cast iron: grey, white, malleable, and ductile.

1. Grey Cast Iron

Composition:

• 1-3% silicon, rest iron
• 5-4% carbon

Grey cast iron is not used to produce malleable fittings or cast iron. The gray shade emitted by the fractures of grey cast iron is the source of its WS40 (top)-1 designation. Due to its weight, grey cast iron is the most utilized, and the most used released WTCC-6-CI material.

Grey cast iron possesses strength like that of low or medium-carbon steel. Moreover, it is weaker tensile strength and impact resistance. Seals and well caps are ordinary objects fabricated from grey cast iron.

2. White Cast Iron

Composition:

• 3%-L8 silicon, rest iron
• 8-3.2% carbon

Both cast iron and malleable iron fixtures were fabricated from white cast iron. The uniform white surface of white cast iron is due to the cementous substance present in it. For many structural applications, white cast iron is excessively brittle.

Still, its good hardness and abrasion resistance can be used in many applications. These include the backhoe’s digging bucket and lifter bars in ball mills. This material is also relatively low-cost.

3. Malleable Cast Iron

Composition:

• 3%-1.8 silicon, rest iron
• 8 -3.2% carbon

2-BLB-1512Malleable iron starts as white iron casting. However, it was treated at a temperature of roughly 1,650°F, 900°C. Malleable iron contains blunter boundaries than flakes. Grey cast iron can cause problems with stress concentration, but this iron doesn’t. Comparable properties can be found in malleable iron and mild steel.

2-BLB-1512 After heating to about 1,650°F (900°C), malleable iron transforms from its original state into white iron casting. The lack of flakes in malleable iron prevents stress concentration issues that might arise from grey cast iron. A lot of the characteristics of mild steel are shared by malleable iron.

4. Ductile Cast Iron

Composition:

• 6% to 2.8% silicon, 3% to 4% Carbon, and the rest iron
• A meager amount of sulfur and phosphorus

The development of ductile cast iron occurred very recently. A tiny quantity of magnesium is included. While both ductile iron and malleable iron have comparable properties, they allow for the casting of bigger components, while the latter has the most allowed sectional size. Pitless spools, well seals, and well caps are coated with blue electrostatic epoxy paint. It helps to make them corrosion-resistant.

What Is Malleable Iron?

Annealing is the thermal process by which malleable iron is produced. Workability and flexibility are both enhanced, while carbon content is decreased using this technique. Various cast irons, including white cast iron with a high carbon content, are first cast. The transformation of carbon into graphite occurs when it is heated for a long time to a temperature below its melting point.

Nodules or spheres, the end product of this process, make cast iron so pliable. When metal is annealed, its brittleness decreases, making it more resistant to cracks. It allows for shaping and bending without fracturing.

Types Of Malleable Iron:

• Pearlitic
• Blackheart
• Whiteheart

Cast Iron Vs. Malleable Iron

• Differences in Formation

The initial step in producing malleable iron is the rapid cooling of cast iron to produce white cast iron, thereby inhibiting the deposition of graphite particles. Using particular substances, the white cast iron is heated for extended periods. Throughout these intervals, a portion of the carbon present in the iron undergoes decomposition and starts to separate from the metal, transforming into graphite particles. Further addition of liquid metal is required to prevent fractures caused by volume loss. This process yields malleable iron.

Utilizing a bloomery furnace, one can produce cast iron. The metal is never transformed into a liquid state by melting iron in a bloomery furnace via direct reduction. Gray cast iron is created when the iron incorporates an adequate amount of carbon when the furnace temperature exceeds the limit set for other varieties of iron casting. As it cools, graphite particles are produced.

• Carbon Ratio

Malleable iron comprises carbon ranging from 0.08% to 0.20% by weight. In contrast, cast iron has a higher carbon content than malleable iron. The carbon content of the substance varies between 2 and 4.5 percent.

• Properties

For intricate designs, such as malleable iron pipe fittings, malleable iron is easier to manipulate. Cast iron is more recognized for its castability, which refers to its capacity to be easily poured into molds. It does not require cooling due to its low melting point.

Cast Iron Advantages

The pros of cast iron are as follows.

• Materials composed of cast iron (Grey Cast Iron) are machinable.
• It possesses excellent casting properties.
• Cast iron possesses a compressive strength that is three to five times greater than that of steel.
• Cast iron possesses exceptional corrosion resistance.
• It possesses low-pressure concentration and resistance to deformation.

Cast Iron Disadvantages 

The following disadvantages pertain to cast iron.

• Cast iron is exceptionally brittle.
• Machining is not possible with white cast iron.
• Its resistance to impact is inadequate, and its weight-to-strength ratio is high.
• Machinability is weak.

Advantages of Malleable Cast Iron

When is malleable cast iron appropriate for a given application? When these benefits are required:

• A ductile material is well-suited for applications requiring substantial machining during refining. Its tensile strength, elasticity, and impact resistance are lower than ductile iron’s. However, it can still be machined without fracturing.
• It can be hammered and flattened, in contrast to certain cast irons, which would fracture or shatter.
• Robust as gray cast iron.
• Excellent resistance to impacts at low temperatures.

Disadvantages of Malleable Cast Iron 

There are disadvantages to the physical properties of malleable cast iron. Always be aware of a material’s drawbacks:

• Shrinks due to volume loss when cooled. This occurs to some degree with all cast irons and all materials, but it is especially evident with malleable cast iron.
• Corrosion resistance is low.
• It is less durable than steel or ductile cast iron.
• It can become brittle at high temperatures, rendering it susceptible to splitting. Thus, it should not be used for high tensile or compressive strength applications.

Summary

Knowing each element of facts ensures that the proper material is utilized. However, each material has specific applications in which it functions effectively. Malleable iron is used in the plumbing industry, where it has gained considerable popularity.