What is Mild Steel? Everything You Need to Know?

What is Mild Steel? Everything You Need to Know?

Mild steel offers incredible properties, making it easy to weld, bend, and shape according to any requirements. This versatility makes it highly popular across various industries.

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Ease in machining and welding makes mild steel one of the most popular forms of steel available.

In this guide, we will break down EVERYTHING about mild steel, including:

Without further ado, let's get started.

What is Mild Steel?

Mild steel is a type of carbon steel with a low carbon content, typically up to 2.1%. This low carbon content makes it more ductile and malleable while retaining significant iron properties.

Carbon Content

Low carbon steels, such as mild or soft steel, have a carbon content ranging between 0.05% to 0.25%. This low percentage makes them highly adaptable for various applications. Multiple grades of mild steel exist with carbon content up to 0.25%, along with other alloying elements to enhance properties like wear resistance, tensile strength, and corrosion resistance.

Elemental Additions

The properties of mild steel can be enhanced using elements like silicon, molybdenum, chromium, copper, nickel, vanadium, and aluminum. Impurities like sulfur and phosphorus are kept in controlled proportions.

Comparing Mild Steel to Higher Carbon Steel

While mild steel has higher tensile strength compared to higher carbon steel, it will deform rather than break under load. This absence of crystal deformation due to lower carbon content makes mild steel valuable across different industries.

Manufacturing Process of Mild Steel

Three primary steps are involved in producing mild steel:

Primary Steelmaking

This step involves mixing iron ore with lime and coal, then heating in a blast furnace with capacities ranging from 100 to 400 tons. Lime serves as a flux, creating a protective layer over the molten metal.

Modern steelmaking methods utilize BOS (Basic Oxygen Furnace) or EAF (Electric Arc Furnace). The BOS method introduces oxygen to the molten metal, reducing carbon content to around 1.5%. The EAF process introduces scrap steel through high-power electric arcs, improving the steel's overall quality.

Secondary Steelmaking

This step further reduces carbon content by adding various alloy elements. Furnaces manipulate conditions by altering temperature and pressure. Processes such as degassing, CAS-OB, ladle injection, ladle furnace, and stirring are used to achieve different types of mild steel.

Mild Steel Casting & Primary Forming

Once the desired carbon content and added elements are achieved, the molten metal is poured into molds. Once solidified, the steel is cut into specific shapes like billets, blooms, and slabs. Hot rolling improves surface quality.

Secondary Forming

This step refines mild steel, enhancing its mechanical properties and shaping it into its final form. Techniques like machining, cold rolling, coating, surface treatment, and tempering are used.

Common Grades of Mild Steel

EN 1.0301

This grade contains 0.1% carbon, 0.4% manganese, and 0.4% silicon, with small amounts of other elements like aluminum, copper, chromium, and nickel. It is equivalent to AISI 1008, AISI C10, and AISI DC01 and is commonly used in furniture, appliances, and the automotive industry.

EN 1.1121

This grade features 0.08% to 0.13% carbon and 0.3% to 0.6% manganese, equivalent to AISI 1010. It is widely used in the automotive industry.

EB 1.0402

This grade has 0.18% to 0.23% carbon and 0.3% to 0.6% manganese, equivalent to AISI 1020 and AISI C22. It is suitable for hydraulic parts and camshafts.

Chemical Properties

Mild steel typically features very low carbon content, usually not exceeding 0.25%. However, it may contain other elements like cobalt, chromium, copper, sulfur, phosphorus, aluminum, nickel, molybdenum, and manganese.

Adding chromium enhances corrosion resistance and overall hardness. In its pure form, mild steel easily corrodes. Exposure to chromium develops a protective layer of chromium oxide, preventing corrosion and offering additional protection.

• Iron: 98.81% to 99.26%
• Carbon: 0.14% to 0.20%
• Manganese: 0.60% to 0.90%
• Phosphorus: <= 0.04%
• Sulfur: <= 0.05%

Physical Properties

Mild steel's low carbon content makes it highly machinable and easy to weld. However, its strength is lower compared to high or medium-carbon steel. The density and weight of mild steel are also lower, and it has a significantly lower melting point compared to other carbon steels.

Mild steel's physical properties are impressive, making it increasingly popular in various industries. Key properties include:

• High impact strength.
• High tensile strength.
• Excellent weldability and ductility.
• Magnetic, due to ferrite content.
• Cold-forming capabilities.
• Poor heat treatment suitability for physical property enhancement.
• Almost impossible to harden through quenching and heating.
• Corrosion-prone if not properly coated.
• Cost-effective compared to other steels.

Mild Steel Strength, Density & Melting Point

Mild steel has high impact and tensile strength due to its low carbon content. With a density of approximately 0.248 pounds per cubic inch and a melting point of 2570°F, it is highly malleable and resists breakage under pressure, deforming or bending instead.

• Hardness Brinell (Knoop, Rockwell B, & Vickers): 126 (145, 71, & 131)
• Ultimate Tensile Strength (Yield): 63800 PSI (53700 PSI)
• Elongation @ Break (within 50mm): 15%
• Ductility: High
• Machinability: 78% (based on 100% machinability of AISI 1212 steel)
• Weldability: Instant welding (but not recommended when carburized or nitrided)
• Corrosion Resistance: High with alloying
• Affordability: Cheaper than most steels
• Magnetism: Yes
• Cutting: Flame, disc, and plasma cutting
• Hardening/Strengthening: Impossible through quenching or heating
• Heat Resistivity: High (up to 540°C/ 1000°F)

Mild steel is widely used in various industries for numerous purposes, being the most common type of metal seen around homes and workplaces.

Applications of Mild Steel

Construction

Certain grades of mild steel, known as structural steels, offer excellent load-bearing capabilities. They meet wind and seismic requirements and are resistant to corrosion and fire, making them an affordable choice compared to other steel types.

Machinery Applications

Mild steel is commonly used in manufacturing automobiles and machinery. It works well with coatings and cutting techniques and exhibits excellent weldability, making it ideal for panels and frames.

Poles and Pipelines

With its high ductility, mild steel is ideal for pipelines and poles, easily handling extreme weather conditions.

Cookware and Cutlery

Chefs now prefer mild steel cutlery over stainless steel due to its ease of cleaning, higher temperature tolerance, and non-stick properties.

Fencing

Mild steel is easily shaped and offers great visual appeal, making it a top choice for fencing.

Product Forms Available of Mild Steel

Mild steel comes in various forms, including sheets, box sections, channels, angles, flats, squares, hexagons, rounds, tubes, T-sections, pipes, mesh, threaded bars, telescopic tubes, and half-round molds. This makes it suitable for multiple applications based on needs and requirements.

Its wide range of applications also means there are various surface finishes available for different aesthetic and usage requirements. Mild steel is prone to rusting and corrosion due to oxidation, similar to wrought iron. Various surface finishes prevent this oxidation and keep the metal safe.

– Priming

Priming involves painting the metal with zinc phosphate paint, which acts as an active rust-resistant coating. Zinc phosphate interferes with anode formation on the metal’s surface by hydrolyzing water to produce zinc and phosphate ions, disrupting corrosion. The paint must be applied in layers to a thickness of around 125 microns. Suitable for indoor use, it does not perform well under extreme conditions.

– Galvanizing

Galvanizing coats the steel with zinc by dipping it into molten zinc. Upon cooling, zinc reacts with the steel to form zinc carbonate, creating galvanized steel. This protective layer prevents atmospheric exposure and acts as a sacrificial layer, corroding the zinc first to protect the steel beneath. Galvanizing works well for outdoor applications, handling harsh weather conditions effectively.

– Intumescent Coating

Intumescent coatings resemble paints but act as insulators at temperatures around 200–250°C by undergoing a complex chemical reaction. The coating swells and forms a low-conductivity layer, protecting the steel. Intumescent coatings come in thick and thin films. Thick films suit hydrocarbon and offshore industries, while thin, water- or solvent-based films are used for building fire protection. These coatings make mild steel fire-resistant.

Pros & Cons of Using Mild Steel

Pros:

• Mild steel is lightweight compared to other steel types.
• It is cost-effective in comparison to other carbon steels.
• It is more malleable and ductile than other steels.
• Mild steel is easier to recycle than other steel forms.
• It is versatile and can be used for various purposes.

Cons:

• Mild steel cannot be heat treated.
• It does not handle high-stress applications well and deforms easily.

Frequently Asked Questions

Can you harden mild steel?

Yes, mild steel can be hardened by increasing its carbon content. However, it is difficult due to the steel's initial low carbon processing to reduce oxidation risks.

Is mild steel alloy steel or pure metal?

Mild steel is not a pure metal; it contains a high percentage of iron, along with other elements like carbon, nickel, and chromium. In its pure form, it is primarily iron.

How is mild steel different from high carbon steel and medium carbon steel?

Mild steel has lower carbon content (0.05% to 0.25%) compared to medium and high carbon steels, which have higher carbon percentages.

Is mild steel stronger than stainless steel?

Strength can be context-dependent. Mild steel is more ductile and malleable than stainless steel, making it less prone to breakage but more likely to bend or deform. Stainless steel, with higher carbon content, is more brittle but has better corrosion resistance.

Final Thoughts

Given its high ductility and malleability, mild steel is suitable for a variety of applications. Its physical properties make it ideal for different industries, offering high machinability and weldability. Mild steel's low carbon content can be enhanced with alloys for better wear and corrosion resistance. Its ease of handling makes it one of the most versatile metals available.

Mild steel is a highly practical choice thanks to its adaptability and extensive range of uses. The addition of various alloys can enhance its properties, making it is a staple in myriad manufacturing processes.

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