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All About Mild Steel

Picture of Dean McClements
Written by
Aaron Lichtig
Updated by
 3 min read
Published October 24, 2022
Updated August 30, 2024

Learn more about mild steel and how it's used in manufacturing.

Common mild steel Galvalume roof - Image Credit: Shutterstock/Hamid Rustanto

Mild steel, also known as low-carbon steel, is one of the most widely used steels. It is used in the construction and automotive industries, and for fencing, signs, and other applications. Generally speaking, it has good weldability, machinability, and ductility.  Mild steel is primarily characterized by having a carbon content of less than 0.2 % by weight. The 4-digit AISI (American Iron and Steel Institute) classification codes for mild steel start with "10" and end with two digits that are less than 20, indicating the approximate carbon content of the steel in hundredths.

This article will explore the chemical composition, mechanical properties, grades, and characteristics of mild steel.

What is Mild Steel?

Mild steel is an iron alloy with carbon as its main alloying element. It is one of the most widely used forms of steel and can be applied to a range of general-purpose applications. Mild steel owes its popularity to its adequate strength at low cost, in addition to its excellent machinability and weldability. Various grades of mild steel have differing amounts of carbon with higher carbon contents wrestling in increased strength at the expense of ductility. In some cases, additional alloying elements are added to improve properties such as tensile strength, corrosion resistance, and wear resistance.

steel bars
Steel bars

Mild steel is made up of an iron (Fe) base with the addition of small amounts of carbon. Low-carbon steel is typically defined as having less than 0.2 % carbon by ASM International. Different grades of mild steel are defined by their differing levels of carbon. Another common alloying element is manganese (Mn).

Grades of Mild Steel

There are many different grades of mild steel that you could use. Mild steels classified according to the AISI (American Iron and Steel Institute) numbering system will all begin with “10” as their first two digits signifying their low carbon content. Low-carbon steel, and by extension mild steel, will have the final 2 digits of the designation as any number less than 20 (approximate carbon content multiplied by 100). Most mild steel has low (<1%) quantities of phosphorus and sulfur and these elements are actively limited as they are considered impurities. Some common grades are listed in Table 1 below:

Table 1: Mild Steel Grades
ClassificationApproximate EquivalentsKey Points
Classification

AISI 1008

Approximate Equivalents

DIN 1.0204

Key Points

Excellent cold formability

Classification

AISI 1010

Approximate Equivalents

DIN 1.0301

Key Points

Low strength, used for magnet cores

Classification

AISI 1015

Approximate Equivalents

DIN 1.0401

Key Points

Wear-resistant, good machinability

Classification

AISI 1018

Approximate Equivalents

DIN 1.0419

Key Points

Excellent for carburizing applications, good machinability

Classification

AISI 1020

Approximate Equivalents

DIN 1.0044

Key Points

A good balance of strength and ductility,

Industrial Applications of Mild Steel

Mild steel is a general-purpose material that can be found in most industries. Some typical applications include: car bodies, furniture, wire, rebar, and fasteners. Higher strength mild steel is used for structures and storage tank plating.

Steel plates
Steel plates

Mechanical Properties of Mild Steel

The mechanical properties of some of the common types of mild steels are listed in Table 2 below:

Table 2: Mild Steel Properties
Type of Mild SteelModulus of Elasticity (GPa)Brinell HardnessUltimate Tensile Strength (MPa)Yield Strength (MPa)Elongation at Break (%)Steel Density kg/m3
Type of Mild Steel

AISI 1008

Modulus of Elasticity (GPa)

200

Brinell Hardness

95

Ultimate Tensile Strength (MPa)

340

Yield Strength (MPa)

285

Elongation at Break (%)

20

Steel Density kg/m3

7.87

Type of Mild Steel

AISI 1010

Modulus of Elasticity (GPa)

205

Brinell Hardness

105

Ultimate Tensile Strength (MPa)

365

Yield Strength (MPa)

305

Elongation at Break (%)

20

Steel Density kg/m3

7.87

Type of Mild Steel

AISI 1015

Modulus of Elasticity (GPa)

205

Brinell Hardness

111

Ultimate Tensile Strength (MPa)

385

Yield Strength (MPa)

325

Elongation at Break (%)

18

Steel Density kg/m3

7.87

Type of Mild Steel

AISI 1018

Modulus of Elasticity (GPa)

205

Brinell Hardness

126

Ultimate Tensile Strength (MPa)

440

Yield Strength (MPa)

370

Elongation at Break (%)

15

Steel Density kg/m3

7.87

Type of Mild Steel

AISI 1020

Modulus of Elasticity (GPa)

186

Brinell Hardness

121

Ultimate Tensile Strength (MPa)

420

Yield Strength (MPa)

350

Elongation at Break (%)

15

Steel Density kg/m3

7.87

Type of Mild Steel

S275 J0

Modulus of Elasticity (GPa)

205

Brinell Hardness

121

Ultimate Tensile Strength (MPa)

430 - 580

Yield Strength (MPa)

275

Elongation at Break (%)

21

Steel Density kg/m3

7.85

Type of Mild Steel

S355 J0

Modulus of Elasticity (GPa)

210

Brinell Hardness

146

Ultimate Tensile Strength (MPa)

510 - 680

Yield Strength (MPa)

355

Elongation at Break (%)

20

Steel Density kg/m3

7.80

Table Credit: matweb.com

The Chemical Composition of Mild Steel

Table 3 below lists the secondary elements present in the various grades of mild steels:

Table 3: Mild Steel Chemical Composition
ClassificationCarbon Content (% Weight)Secondary Alloying Elements (% Weight)
Classification

AISI 1008

Carbon Content (% Weight)

<0.1

Secondary Alloying Elements (% Weight)

0.3 to 0.5 Mn; 0.04 P; 0.05 S

Classification

AISI 1010

Carbon Content (% Weight)

0.08 to 0.13

Secondary Alloying Elements (% Weight)

0.3 to 0.6 Mn; 0.04 P; 0.05 S

Classification

AISI 1015

Carbon Content (% Weight)

0.13 to 0.18

Secondary Alloying Elements (% Weight)

0.3 to 0.6 Mn; 0.04 P; 0.05 S

Classification

AISI 1018

Carbon Content (% Weight)

0.14 to 0.2

Secondary Alloying Elements (% Weight)

0.6 to 0.9 Mn; 0.04 P; 0.05 S

Classification

AISI 1020

Carbon Content (% Weight)

0.17 to 0.23

Secondary Alloying Elements (% Weight)

0.3 to 0.6 Mn; 0.04 P; 0.05 S

Classification

S275

Carbon Content (% Weight)

0.18

Secondary Alloying Elements (% Weight)

1.5 Mn; 0.030 P; 0.030 S; 0.012 N; 0.55 Cu

Classification

S355

Carbon Content (% Weight)

0.2

Secondary Alloying Elements (% Weight)

1.6 Mn; 0.030 P; 0.030 S; 0.012 N; 0.55 Cu

Table 3: matweb.com

Summary

To learn more about mild steel and all the ways that you can use it in manfacturing, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to get a quote today.

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Picture of Dean McClements
Dean McClements
Dean McClements is a B.Eng Honors graduate in Mechanical Engineering with over two decades of experience in the manufacturing industry. His professional journey includes significant roles at leading companies such as Caterpillar, Autodesk, Collins Aerospace, and Hyster-Yale, where he developed a deep understanding of engineering processes and innovations.

Read more articles by Dean McClements

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