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Understanding The Differences Between Cast Iron VS Steel

Cast Iron VS SteelThe iron and steel casting market hit a whopping USD 145.97 billion in 2020 and is expected to grow at a rate of over 5.4% from 2021 to 2027? This impressive growth is primarily because of the widespread use of two key materials: cast iron and steel. To prove this, you can take a moment to look around, and you’ll notice that our world is essentially built from these two fundamental metals.

At first look, iron and steel castings might look similar, but if you dig deeper, you’ll discover a world of differences in their applications, production processes, and more. This contrast highlights the importance of understanding each material’s unique characteristics and how they shape our environment. So, let’s explore cast iron vs steel in detail.

 

What is Cast Iron?

Cast iron, a mix ferrous alloy mainly consisting of iron, carbon, and silicon, stands out for being really durable and great at holding heat. People have been using this metal for hundreds of years because it’s tough, and you can mold it into all sorts of detailed designs. The recipe for cast iron usually involves about 2-4% carbon and 1-3% silicon, and then iron makes up the rest.

Metal cast iron’s increased carbon content results in it solidifying as a mixed alloy, which means it has different types of microcrystalline structures within the material. The blend of this high level of carbon along with silicon is what makes cast iron so great for casting. This high carbon content gives cast iron its distinctive characteristics.

Cast Iron Parts3

 

What is Cast Iron Made of?

The making of cast iron involves melting pig iron, often along with quantities of scrap steel and iron, limestone, and carbon (usually in the form of coke) in a blast furnace. During this process, cast iron scrap or impurities are removed, and the right amount of carbon and silicon are added. The melted iron is then cast into different molds, forming a variety of shapes and products. Some of the different types of cast iron metal involve:

  • Gray Cast Iron
  • Ductile Cast Iron (Nodular Cast Iron)
  • White Cast Iron
  • Malleable Cast Iron
  • Compacted Graphite Iron (CGI)

Cast Iron Parts

What is Steel?

Steel, unlike cast iron, is an alloy primarily composed of iron and a much lower carbon content, typically less than 2%. This fundamental difference in composition gives steel distinct properties and a wide range of applications. Cast in steel is renowned for its strength and versatility, making it a cornerstone in construction, manufacturing, and numerous other industries.

Cast steel’s recyclability is a key attribute in today’s world, where sustainable practices are increasingly important. Steel doesn’t lose its strength or inherent properties, regardless of how many times it’s recycled. This aspect not only makes it an environmentally friendly choice but also a cost-effective one, as recycled steel maintains its quality and performance.

Carbon Steel Parts2

 

What is Steel Made Of?

Steel production involves refining iron ore in a blast furnace, where impurities are removed, and specific amounts of carbon are added. The procedure begins by transforming iron ore into liquid iron, which is subsequently processed into steel using either a basic oxygen furnace or an electric arc furnace. The carbon content is carefully controlled, with other elements like manganese, chromium, vanadium, and tungsten added to achieve various desired properties. Here are some of the most acclaimed types of steel:

  • Carbon Steel
  • Alloy Steel
  • Stainless Steel
  • Tool Steel
  • Structural Steel

Alloy Steel parts3

 

Difference Between Cast Iron and Steel

When choosing materials for construction, manufacturing, or everyday items, the debate often boils down to cast iron vs steel. Each metal boasts unique characteristics and advantages, making it suitable for specific applications. Below is a detailed comparison highlighting the cast iron and steel differences.

Tensile Strength

Tensile strength is the greatest amount of stress a material can endure under tension or pulling forces before it fails or fractures. Steel typically exhibits a higher tensile strength compared to cast iron. This difference arises from their distinct compositions and microstructures.

Steel that contains lower carbon content than cast iron, usually less than 2%. That’s why steel is more ductile and malleable, allowing it to withstand greater stress and strain before failing. On the other hand, cast iron, with a carbon content typically above 2%, has a relatively lower tensile strength.

Ductility

Ductility is the material’s ability to deform under tensile stress, commonly known as stretching or elongation, without breaking. In the context of steel vs. cast iron, steel generally exhibits superior flexibility compared to cast iron. Steel possesses a microstructure that allows it to deform considerably before fracturing.

That’s the reason steel is a ductile and malleable material. Conversely, cast iron tends to have much lower ductility. The excess carbon in thrown iron forms graphite flakes or cementite, which act as stress concentrators and significantly reduce their deformability.

Carbon Steel Parts

Melting Point

The melting point is a fundamental property that tells us the temperature at which a solid becomes a liquid. This property is crucial in metallurgy and manufacturing, affecting casting, forging, and welding processes. Steel typically has a higher melting point compared to cast iron.

The melting point of steel generally ranges from 1370°C to 1510°C (2500°F to 2750°F), depending on its specific composition and alloying elements. On the other hand, cast iron leads to a less tightly bonded atomic structure, allowing it to melt at the ranges between 1150°C and 1300°C (2100°F to 2370°F).

Machinability

When comparing cast iron vs steel in terms of machinability, cast iron generally offers superior ease of machining. It is known for its graphite flakes that act as a natural lubricant and facilitate the breaking of chips during the machining process. This characteristic not only reduces wear and tear on cutting tools but also allows for smoother and faster machining.

In contrast, steel, with its lower carbon content (usually less than 2%) and absence of graphite flakes, presents more challenges in machining. The lack of natural lubrication and chip-breaking features in steel leads to increased tool wear and a requirement for slower machining speeds to maintain precision.

Cast Iron3

Corrosion Resistance

In the context of cast iron vs steel, particularly concerning corrosion resistance, each material exhibits distinct characteristics. The structure of cast iron, especially grey cast iron, which contains graphite flakes, tends to be more susceptible to rust and corrosion. The graphite present in cast iron can encourage galvanic corrosion, where graphite acts as a cathode and iron as an anode, accelerating the rusting process.

However, cast steel, mainly stainless steel varieties, exhibits significantly higher corrosion resistance than cast iron. It’s because of the presence of chromium, which, when added in sufficient amounts (at least 10.5%), leads to forming a thin, stable, and adherent chromium oxide layer on the surface.

Weight

In comparing cast iron vs steel regarding weight, cast iron, with a specific gravity ranging from about 7.0 to 7.8, is generally considered heavier than steel on a volume-to-volume basis. This higher density in cast iron is primarily due to its high carbon content, typically over 2%. On the other hand, steel typically has a specific gravity of around 7.85.

Despite being slightly higher than the upper range of cast iron’s specific gravity, steel is often considered lighter in practical applications. This is because steel, with a carbon content usually less than 2%, has a less dense microstructure than cast iron.

Tool Steel Parts2

Here is a comprehensive table to explain the differences between cast iron and steel in a more straightforward manner:

Factors

Cast Iron Steel

Carbon content

Iron with 2-4% carbon, 1-3% silicon Iron with 0.1-2% carbon

Tensile Strength

Compressive strength is high; brittle under tension High tensile strength; less brittle
Ductility Generally low (except for ductile cast iron)

High, especially in low-carbon steels

Machinability Easier to machine

Harder to machine

Corrosion Resistance

Less Generally higher

Weldability

Poor Generally good
Weight Heavier

Lighter

Cost Generally cheaper

More expensive

Melting Point Lower

Higher

 

Key Applications of Iron Casting vs Steel

Casting iron and steel are essential metals that play a huge part in our everyday lives and have done so for a long time. They form the core of many modern inventions and buildings around us. These metals are the reason we have tall buildings that shape our cities and the reliable pots and pans we use in our kitchens. Now, let’s explore their critical applications in more detail.

Applications of Cast Iron

  • Construction and Infrastructure: Cast iron’s compressive strength makes it ideal for constructing structures like bridges, pipes, and culverts.
  • Automotive Industry: Gray CI casting is extensively used in the automotive industry, particularly for making engine blocks and cylinder heads.
  • Machinery and Tools: Due to its excellent wear resistance and machinability, cast iron is often used in machine tools and heavy truck frame rail blanks.
  • Cookware: The excellent heat retention and even heating properties of cast iron make it a favourite for cookware like skillets, pans, and Dutch ovens.

Cast Iron Parts4

Applications of Steel

  • Construction and Building: Steel is used in everything from skyscrapers’ structural framework to concrete reinforcing bars.
  • Transportation: Steel is a primary material in manufacturing automobiles, ships, and trains due to its strength and durability.
  • Infrastructure: Steel is widely used in infrastructure projects, including bridges, tunnels, and railways.
  • Medical Applications: Stainless steel, known for its corrosion resistance and hygienic properties, is extensively used in surgical instruments, implants, and equipment due to its ability to be sterilized without degrading.
  • Consumer Goods: Steel is used in various household items, including appliances, tools, and furniture.

Stainless Steel Parts4

 

Choosing Between Cast Iron and Steel

When you’re trying to choose between cast iron and steel for a project, there are a few essential things to think about to make sure you’re picking the right one. Let’s start with the cost. Usually, cast iron won’t hit your wallet as hard as steel, which is why a lot of people go for it when they’re watching their budget. On the other hand, steel might cost you more at first, but it tends to last longer and doesn’t need as much care and attention down the line. This means that, in the long haul, steel could actually be the wiser choice money-wise.

Performance requirements are another critical consideration. If you need something that’s really strong and can handle a lot of pressure or weight, steel is usually your go-to. It’s super versatile and rugged, making it perfect for jobs that will put it under a lot of stress, like building skyscrapers or bridges or driving cars. CI material, while strong, is more brittle and is better suited for applications where this brittleness is not a liability, such as in heavy machinery or cookware.

Environmental impact and sustainability are also increasingly important considerations. Steel has a significant advantage in this area, as it is one of the most recycled materials in the world. The recycling process for steel casting is also more energy-efficient than cast iron, making it a more sustainable choice for environmentally conscious projects.

Ductile Cast Iron Tubes

 

Final Thoughts

In wrapping up our exploration of the cast iron vs. steel debate, you’ve likely developed a preference based on each material’s distinct characteristics and applications. However, selecting the right material is just the beginning. The next crucial step is finding the right partner for metal casting services that can handle both prototyping and production with expertise.

So don’t wait; consult JIAHUI today because we are amongst the top manufacturers in the market that bring high precision, capacity, and quality control. With JIAHUI, every decision counts in this journey, from selecting the perfect material to seeing your project come to fruition. Remember that the possibilities are endless with the right materials and partners.

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