An Overview of Types of Low Carbon Steel
What Is Low Carbon Steel?
Low carbon steel—also known as mild steel—is one of the most widely used metal types in modern manufacturing. Its versatility, affordability, and ease of processing make it a staple across industries from automotive to construction.
Carbon Content and Basic Characteristics
Low carbon steel typically contains less than 0.25% carbon by weight, with the most common range between 0.05% and 0.20%. This low carbon content gives the material:
- High ductility: It can be bent, shaped, and formed easily.
- Excellent weldability: It doesn’t harden during welding, reducing the risk of cracking.
- Good machinability: Easily cut, drilled, or milled using standard tools.
- Affordable cost: Compared to alloyed or stainless steels.
However, the low carbon content also results in relatively lower tensile strength and wear resistance, which limits its use in high-stress or high-load applications unless treated or alloyed.
Comparison with Medium and High Carbon Steel
| Property | Low Carbon Steel | Medium Carbon Steel | High Carbon Steel |
|---|---|---|---|
| Carbon Content | 0.05%–0.25% | 0.25%–0.60% | 0.60%–1.0% |
| Strength | Low | Medium | High |
| Ductility | High | Medium | Low |
| Weldability | Excellent | Good | Poor |
| Applications | Structural parts, sheet metal, automotive panels | Shafts, axles, forging | Springs, cutting tools |
Low carbon steel is preferred when formability, weldability, and cost are prioritized over hardness and tensile strength.
Common Forms: Sheet, Plate, Bar, Pipe
Low carbon steel is available in a wide variety of forms to suit different manufacturing processes:
- Sheet: Thin and lightweight, used for automotive panels, enclosures, appliances.
- Plate: Thicker than sheet, ideal for structural applications, machinery bases.
- Bar: Available in round, square, or flat sections; commonly used for shafts, brackets, fasteners.
- Pipe and Tube: Used in plumbing, low-pressure fluid systems, and structural supports.
Each form can be hot rolled or cold rolled depending on dimensional and surface finish requirements.
Classification of Low Carbon Steel Types
Low carbon steel, also known as mild steel, is categorized in multiple ways based on its chemical composition, processing method, and end-use applications. Understanding these classifications helps manufacturers and engineers choose the right grade for machining, forming, or fabricating specific parts.
By SAE/AISI Grade
The SAE-AISI system is one of the most commonly used classification standards. It identifies carbon steels by a four-digit number, where the first two digits indicate the alloying element (typically “10” for plain carbon steels) and the last two digits represent the approximate carbon content.
| Grade | Carbon Content (%) | Key Characteristics | Common Uses |
|---|---|---|---|
| AISI 1006 | ~0.06% | Very soft, high ductility, excellent for deep drawing | Automotive body panels, wire products |
| AISI 1008 | ~0.08% | Good formability, low strength | Cold headed fasteners, rivets |
| AISI 1010 | ~0.10% | Balanced formability and strength | Stampings, structural shapes |
| AISI 1018 | ~0.15–0.20% | Excellent machinability and weldability | Shafts, gears, pins |
| AISI 1020 | ~0.18–0.23% | Higher strength, good weldability | Machinery parts, tubing |
These grades are widely available, affordable, and suitable for high-volume production processes such as stamping, forging, and CNC machining.
By Processing Method
The performance of low carbon steel can vary significantly depending on whether it is cold-rolled, hot-rolled, or annealed. Here’s how each type differs:
Hot Rolled Low Carbon Steel
- Manufacturing: Rolled at high temperatures (>1700°F)
- Surface: Rougher finish, with scale
- Strength: Slightly lower dimensional accuracy but cost-effective
- Applications: Structural beams, railroad tracks, agricultural equipment
Cold Rolled Low Carbon Steel
- Manufacturing: Further processed at room temperature after hot rolling
- Surface: Smooth finish, tighter tolerances
- Strength: Increased strength and hardness due to strain hardening
- Applications: Furniture, appliances, precision parts
Annealed Low Carbon Steel
- Process: Heat treated to soften the metal after cold working
- Benefit: Improved ductility and machinability
- Applications: Deep drawing, complex bending operations
By Application-Based Categorization
Certain low carbon steel types are tailored for specific industries or functional requirements:
1. Structural Grades
These grades offer a balance of strength and formability and are often used in construction and manufacturing:
- Example: ASTM A36 – widely used structural steel with low carbon content.
2. Automotive Grades
Optimized for press forming and spot welding:
- Example: SAE 1006 and 1008 – ideal for body panels due to deep drawability.
3. Deep Drawing Grades
Designed for maximum ductility and minimal cracking under tension:
- Example: AISI 1006 DDQ (Deep Drawing Quality) – used in cookware, sinks, and complex automotive shapes.
4. Free-Machining Grades
Some low carbon steels are enhanced with elements like sulfur to improve machinability:
- Example: 12L14 – although slightly higher in carbon, often considered for fast-turn CNC parts requiring fine finishes.
Pro Tip: How to Read a Steel Grade
For example, AISI 1018 breaks down as:
- 10 → Plain carbon steel
- 18 → ~0.18% carbon content
The higher the last two digits, the stronger (but less ductile) the material tends to be.
Summary Table: Low Carbon Steel Classification Overview
| Classification Basis | Example Types | Highlights |
|---|---|---|
| SAE/AISI Grades | 1006, 1010, 1018, 1020 | Standardized carbon levels |
| Processing | Hot Rolled, Cold Rolled, Annealed | Impacts surface finish & mechanical strength |
| Application Use | Structural, Automotive, Drawing Grades | Tailored to industry needs |
Key Properties of Low Carbon Steel
The properties of low carbon steel make it suitable for a broad range of fabrication processes. While it lacks the hardness of high-carbon alloys, its unique balance of mechanical and working properties makes it a practical material for everyday industrial use.
Mechanical Properties (e.g. Tensile Strength, Hardness)
- Tensile Strength: Typically ranges from 350–550 MPa depending on grade and processing.
- Yield Strength: Generally lower, around 250 MPa, allowing for easy forming.
- Hardness: Measured on the Brinell scale, low carbon steel usually rates around 120–180 HB.
- Elongation: High elongation (often >25%) makes it ideal for stamping and drawing.
These properties can be slightly improved through cold working or surface treatments, though they remain relatively soft compared to high-carbon or alloy steels.
Weldability and Machinability
One of the biggest advantages of low carbon steel is its outstanding weldability:
- No preheating needed
- Minimal risk of cracking or distortion
- Compatible with MIG, TIG, stick welding
Its machinability is also excellent, particularly for grades like AISI 1018, which are commonly used in CNC turning, drilling, and milling.
Free-machining variants such as 12L14 (with added lead) offer superior performance for high-volume production, though they’re technically considered “resulfurized” steels.
Surface Finish and Corrosion Resistance
Low carbon steel is not corrosion-resistant by itself due to the lack of chromium or other alloying elements. To enhance performance:
- Surface finishes like powder coating, painting, or galvanizing are often applied.
- Cold rolled low carbon steel typically has a smoother, shinier finish.
- Hot rolled steel may appear dull and scaled but is more cost-effective for structural use.
For outdoor or moist environments, protective finishing is essential to prevent rust and degradation.
Heat Treatment Compatibility
Unlike high carbon steel, low carbon steel has limited response to traditional heat treatments like quenching and tempering due to its lower carbon content. However, certain treatments can still be beneficial:
- Case Hardening (Carburizing): Increases surface hardness while maintaining a ductile core.
- Annealing: Enhances ductility and relieves internal stress after cold working.
- Normalizing: Refines grain structure, improving strength and toughness uniformly.
These methods are especially useful when combining formability with localized surface wear resistance.
Common Applications of Low Carbon Steel
Low carbon steel is one of the most widely used materials in manufacturing due to its affordability, ductility, and versatility. From structural frameworks to intricate stamped parts, its applications span across almost every major industry.
Automotive Components (Panels, Fasteners, etc.)
The automotive industry is a major consumer of low carbon steel, especially for non-critical structural parts where formability and cost-efficiency are key.
- Body panels: Grades like AISI 1006 and 1008 are deep-drawing quality and used for hoods, doors, and roofs.
- Fasteners: Screws, bolts, and clips are commonly made from AISI 1018 due to its strength and machinability.
- Chassis brackets and supports: Easily formed and welded into complex shapes.
Low carbon steel is ideal for components that require high volume production and excellent surface finish after painting or coating.
Construction (Beams, Plates, Wire)
In construction, low carbon steel provides a reliable and cost-effective solution for load-bearing and structural applications.
- Beams and columns: ASTM A36 (a low carbon structural grade) is widely used in commercial and industrial buildings.
- Reinforcing mesh and bar ties: Malleable yet strong, easily shaped on-site.
- Plates and flat stock: Used for gussets, frames, supports, and other fabrication tasks.
Its weldability is particularly advantageous in structural assembly, and its surface can be galvanized for corrosion protection.
Metal Stamping and Forming
Because of its excellent ductility and low yield strength, low carbon steel is a top material choice for stamping and forming operations.
- Consumer appliances: Internal brackets, panels, and reinforcement structures.
- Electrical enclosures and housings: Formed into protective covers or boxes.
- Toolboxes and cabinetry: Precision-formed parts using deep-draw quality grades.
Cold-rolled low carbon steel sheets are favored for applications requiring smooth surfaces and tight dimensional tolerances.
Pipes and Tubing for Low-Pressure Use
Low carbon steel is commonly used in the production of pipe and tubing, particularly for low-pressure or non-corrosive environments.
- Furniture tubing: Lightweight and easy to weld into frames.
- Conduits: Protect electrical wiring in commercial and residential installations.
- Low-pressure fluid transport: Ideal for water lines, HVAC, and general piping where corrosion resistance is not critical.
Hot-dip galvanizing or painting is often applied to extend the service life of these components.
How to Choose the Right Low Carbon Steel Type
Selecting the proper low carbon steel grade involves evaluating your application needs, forming or welding requirements, and overall budget. Making the right choice ensures part performance, manufacturability, and cost-efficiency.
Based on Intended Application
Choose steel grades based on the mechanical performance and design purpose:
| Application | Recommended Grade | Reason |
|---|---|---|
| Deep drawing | AISI 1006 / 1008 | High ductility, minimal cracking |
| Machined parts | AISI 1018 | Excellent machinability, tighter tolerances |
| Structural support | ASTM A36 / AISI 1020 | Higher strength, good weldability |
| Decorative components | Cold-rolled low carbon | Smooth surface finish |
Based on Forming and Welding Requirements
| Process | Ideal Characteristics | Suggested Grades |
|---|---|---|
| Stamping/Deep Drawing | High elongation, low yield strength | AISI 1006, 1008 |
| Cold Forming/Bending | High ductility | AISI 1010, 1018 |
| Welding | Low carbon content, minimal hardening | AISI 1018, ASTM A36 |
If post-welding strength or wear resistance is needed, case hardening can be applied to low carbon steel parts.
Based on Cost and Availability
- Budget-conscious projects may favor hot-rolled grades like A36 or 1020, which are readily available and inexpensive.
- For tighter tolerances and cosmetic surfaces, cold-rolled low carbon steel offers better results at slightly higher cost.
- Consider material availability in your region and compatibility with local fabrication standards.
Low Carbon Steel in Custom Metal Fabrication
Low carbon steel is one of the most flexible and cost-effective materials used in custom metal fabrication. Its mechanical properties and broad compatibility with industrial processes make it a go-to option for CNC machining, welding, and stamping operations.
Why It’s Popular in CNC Machining, Welding, and Stamping
Low carbon steel is favored by metal fabricators for several key reasons:
- Excellent machinability: Grades like AISI 1018 allow for tight tolerances and smooth surface finishes with minimal tool wear.
- Superb weldability: The low carbon content minimizes the risk of cracking, distortion, or heat-affected zones during MIG, TIG, or arc welding.
- Ideal for high-speed stamping: High ductility and uniform thickness make it suitable for progressive die stamping and deep drawing.
Its ability to be processed in high volumes at low cost makes it the material of choice for industries that value efficiency and repeatability.
Examples from CSMFG: Common Parts We Fabricate
At CSMFG, we regularly use low carbon steel to produce a wide variety of components tailored to customer specifications. Typical parts include:
- Brackets and support frames – For machinery, vehicles, or enclosures
- Mounting plates and flanges – CNC-machined with tight tolerances
- Fasteners and pins – Cold-headed or turned from 1018 steel
- Sheet metal enclosures – Stamped, formed, and coated
- Tubular structures – For furniture, racks, or automotive applications
We can deliver fully finished parts with secondary processes such as tapping, bending, powder coating, or galvanizing to meet exact design and durability requirements.
Surface Finishing Options for Low Carbon Steel (Powder Coating, Painting, Galvanizing)
While low carbon steel lacks natural corrosion resistance, it can be protected and enhanced through various surface finishes:
- Powder Coating: Durable, chip-resistant, and available in many colors. Ideal for equipment housings, consumer products, and outdoor applications.
- Painting: A cost-effective option for both decorative and protective purposes. Often used on structural steel and fabricated parts.
- Galvanizing (Hot-Dip or Electro): Provides superior corrosion protection by applying a zinc coating. Commonly used in construction, piping, and outdoor metal frameworks.
CSMFG offers all three finishing options in-house or through qualified partners, ensuring a one-stop solution from raw material to finished product.
FAQ About Low Carbon Steel Types
Is 1018 steel stronger than 1020?
Generally, AISI 1020 steel has a slightly higher carbon content than 1018, which results in:
- Higher tensile and yield strength
- Slightly lower ductility and machinability
However, both grades are similar in overall behavior, and 1018 is often preferred for machining, while **1020 suits structural applications requiring added strength.
Which low carbon steel is best for welding?
AISI 1018 and ASTM A36 are both excellent for welding. Their low carbon content reduces the risk of brittleness or cracking during weld cooling. For critical welds, 1018 offers:
- More consistent chemistry
- Better predictability in precision welding
Can low carbon steel be hardened?
Low carbon steel cannot be through-hardened via traditional heat treatment due to its low carbon percentage. However, it can be case hardened using methods like:
- Carburizing
- Nitriding
These processes increase surface hardness while maintaining a tough, ductile core—ideal for wear-resistant components such as bushings, gears, and pins.
What is the cheapest type of low carbon steel?
Hot-rolled AISI 1006 or 1008 are among the most affordable types due to:
- Minimal alloy content
- High availability
- Simple processing
These grades are commonly used in low-stress applications such as wire products, stampings, and sheet metal components.
Conclusion: Find the Right Low Carbon Steel for Your Project
Low carbon steel offers a wide spectrum of grades and processing options to suit nearly any manufacturing need. Whether you need:
- High ductility for forming
- Strong weldability for assembly
- Machinability for custom parts
…there’s a suitable low carbon steel solution for you.
At CSMFG, we provide end-to-end custom fabrication services, from material sourcing and machining to finishing and inspection. With a deep understanding of steel grades and manufacturing processes, we help customers optimize performance, control costs, and reduce lead times.
Contact us today to get a quote for your low carbon steel part — and discover why global manufacturers trust CSMFG for precision and reliability.