What Is ASTM A108 Steel? A Comprehensive Guide

Steel is among the most versatile materials available – it is more durable and corrosion-resistant than iron, and its sleek, silver look is easy to clean and maintain. Before buying stainless steel, you must know how it is standardized. 

The American Society for Testing and Materials (ASTM) has some standards for steels, and one such standardization specification is the ASTM A108.

What is ASTM A108 Carbon Steel?

ASTM A108 is a set of specifications regarding physical, chemical, and mechanical properties for standardized steel. 

For example, it specifies that the chemical composition would include carbon, manganese, sulfur, phosphorus, and sometimes copper, nickel, and iron.  An alloy containing an element other than these, such as chromium, will not meet the specifications of ASTM A108. 

It mainly deals with cold-finished carbon and alloy steel that has been cold drawn, turned, ground, polished, hot wrought, cold rolled, and heat treated.

Note that carbon steels have carbon as the main alloyed element with iron, while alloyed steels contain other elements. 

Chemical Composition of ASTM A108 Steel


The exact chemical composition depends on the specific grade, but ASTM A108 steel generally has a medium range of carbon and an appreciable proportion of manganese. Trace amounts of sulfur and phosphorus are also present. You can also expect to find copper, nickel, and silicon, depending on the grade. 

The exact chemical composition depends upon the grade. For example, ASTM A108 grade 1018 has a carbon content of 0.15% to 0.20%, manganese content between 0.60% and 0.90%, and small, variable amounts of phosphorus and sulfur.

How Does the Chemical Composition of ASTM A108 Affect its Properties?

The carbon content affects the steel’s hardness and strength: the more carbon content there is, the stronger the steel will be.

Manganese also improves durability and hardness. However, excessive manganese can make your carbon steel brittle.

Phosphorus and sulfur improve machinability, but too much of them can cause brittleness; however, they make the steel prone to cracking.

Properties of ASTM A108 Steel

The properties of ASTM A108 steel are carefully specified:

1. Corrosion Resistance

As carbon steels, ASTM A108 steels do not resist corrosive forces much, as they do not contain significant amounts of corrosion-resistant materials like chromium.

2. Weldability

ASTM A108 steel has good weldability, but you require pre-weld and post-weld treatment, especially for the thicker sections. Without that, you risk cracking or distorting the steel.

3. Heat Resistance

ASTM A108 steel contains only carbon and manganese – not elements that withstand high temperatures like chromium or nickel. So, it does not have good heat resistance; you should use other steels for use in high-temperature environments.

4. Strength

Due to alloying with carbon and manganese, ASTM A108 is are high-strength steels. The exact hardness and strength depend on the steel grade.

5. Durability

ASTM A108 steel is very durable and can withstand mechanical stress. You can further improve its durability through heat treatment. 

Heat Treatment of ASTM A108 Steel

Heat Treatment of ASTM A108 Steel

Heat treatment can make ASTM A108 steel more durable. Here are some common heat treatments:

1. Annealing

In annealing, you heat the steel to a high temperature, retain it for some time,  and then slowly cool it back to room temperature. Doing so softens the steel and makes it tougher. You usually do this treatment for grade 1018. 

2. Quenching

In quenching, you heat the steel to a high temperature. After the heating process, you rapidly cool it in a liquid. Doing so induces martensitic structure in the steel, making it harder. This treatment is preferred for grades 4140 and 4340.

3. Tempering

You temper a quenched steel by heating it and maintaining the temerature for some time. The temperature for tempering is kept lower than annealing, and the resulting product is less soft. By this process, you reduce its brittleness while maintaining hardness. You can also induce different colors by tempering. 

4. Aging

Aging is a process similar to tempering, except that you hold the steel at a high temperature for an extended time. This allows the precipitation of small particles in the steel microstructure, improving its hardness.

Machinability of ASTM A108 Steel

Machinability refers to the ease through which you can shape or cut material using a machine. You’ll need your steel to be machinable to make complex parts. 

The machinability of ASTM A108 steels depends on the exact grade. Grades like 1018 and 1215 are highly machinable, but grades like 4140 and 1045 have poor machinability. 

Some factors affecting an ASTM A108 steel machinability include:

  • Composition: Elements like phosphorus, sulfur, and lead improve machinability. 
  • Heat Treatment: Annealed or soft-tempered steels are more machinable than hard-tempered steels.
  • Hardness: Generally, the harder your workpiece is, the less machinable it will be.

Wondering how to improve the machinability of ASTM A108 steel? Follow these tips:

  • Proper Lubrication: If your material isn’t machinable, lubricate it using a cutting fluid like oil.
  • Tool and Parameter Selection: Optimize your cutting tool and parameters like cutting force for your workpiece. 
  • Heat Treatment: Annealing or soft-tempering your steel will make it more machinable. 

Surface Finish of ASTM A108 Steel

Surface finish refers to the quality and appearance of the steel surface after it is processed. It has an important role both in aesthetics and properties.

A good surface finish will make your steel bar shiny, sleek, and aesthetic. It will also reduce wear by removing surface contaminants and improve corrosion resistance. And it reduces the chances of surface cracks and increases the steel’s fatigue strength.

Here are some surface finish techniques for ASTM A108:

  • Machining: You can use machining strategies like cutting and drilling to scrap away unneeded material at the surface.
  • Polishing: You can do mechanical or electrochemical polishing to get a mirror-like surface.
  • Passivation: In passivation, you immerse your workpiece in certain chemicals like nitric oxide to coat it with a passive oxide layer. This increases corrosion resistance. 

Welding of ASTM A108 Steel

Welding of ASTM A108 Steel

ASTM A108 is generally weldable, but you require pre-welding and post-welding treatments to prevent cracking. The weldability depends upon the specific ASTM A108 grade; some may be less weldable due to their microstructure.


You must select the proper technique for your steel alloy; common options include:

  • Gas tungsten arc welding. 
  • Gas metal arc welding.
  • Shielded metal arc welding.
  • submerged arc welding.

Remove any contaminants from the surface and pre-heat the steel before the job. And after welding, inspect for any defects like cracks or porosity. Perform the required post-welding treatment like annealing or stress-relieving. 

Make sure you conduct a quality control test like dye penetration or x-ray inspection to ensure no cracks. 

Applications of ASTM A108 Steel

ASTM A108 is a versatile steel class with applications in different industries. Some of these applications are: 

  • Aerospace Industry: High-strength grades of ASTM A108 steel are used to manufacture structural components and landing gears.
  • Automotive Industry: Due to its machinability, you can make gears and axles from ASTM A108 steel. However, choose the grades that have good wear resistance.
  • Chemical Processing Industry: You can make valves in the chemical industry from ASTM A108, which is highly machinable. 
  • Construction Industry: Durable grades of ASTM A108 can be used to make fasteners and nuts for the construction industry.
  • Medical Devices Industry: As it is highly machinable, you can use ASTM A108 for surgical instruments requiring precision in their manufacture. 
  • Food Processing Industry: You can use ASTM A108 to make mixers and storage tanks in the food industry as it is hygienic. 

ASTM A108 Steel Grades

ASTM A108 has up to 39 different grades. Some of these include:

  • Grade 1018: This low carbon grade has excellent machinability. You use it in parts that require high accuracy, like bolts.
  • Grade 1045: This medium carbon steel has high toughness and strength. You use it in gears, axles, and other parts that require strength.
  • Grade 4140: This low alloy steel has high toughness and strength. You use it where you require good wear resistance, like heavy machinery parts.
  • Grade 4340: This grade is tough and has excellent fatigue resistance. Its applications include aircraft parts and other machinery operating in extreme conditions requiring durability.

Advantages and Disadvantages of ASTM A108 Steel

ASTM A108 has several benefits and limitations. We discuss them here, starting with the pros:


ASTM A108 steel has many advantages:

  • High Strength: Many grades of ASTM A108, like 4140 and 4340, have high strength.
  • Machinability: ASTM A108 grades like 1018 have excellent machinability.
  • Affordability: ASTM A108 standardized steels are generally affordable and cheap.


Be mindful of these limitations of ASTM A108:

Corrosion Susceptibility: ASTM A108 grades generally aren’t very corrosion resistant, but you can get oxide coatings to make them less susceptible to corrosion.

Limited Temperature Range: ASTM A108 is unsuitable for applications requiring high temperatures.

Fabrication of ASTM A108 Steel

Fabrication of ASTM A108 Steel

Fabrication refers to creating usable products from raw steel sheets. You can fabricate machinable steel by cutting, bending, or transforming it into a product in other ways.

Common fabrication methods include: 

  • Cutting: You can cut an ASTM A108 steel sheet in several ways, like plasma cutting and shearing.
  • Machining: You can conveniently drill or mill ASTM A108 steel with conventional machines.
  • Forming: You can form ASTM A108 steels in different shapes by stamping, rolling, or bending.
  • Welding: It is possible to weld ASTM A108 using different welding techniques.

However, remember that many issues can arise during ASTM A108 fabrication. It is prone to warping or getting a distorted structure when welded. Also, some grades can easily crack if you don’t give them pre-treatment. 

Maintenance of ASTM A108 Steel

You can extend the life of ASTM A108 steel grades through proper maintenance practices.

You should thoroughly inspect your ASTM A108 parts to ensure they aren’t corroded or cracked so that you can replace them in time. Also, clean them regularly and effectively with appropriate cleaning techniques and store them away from abrasive materials and harsh chemicals. Lubricate moving parts to prevent.

To clean an ASTM A108 part, you just need a cloth, water, and detergent; avoid using steel wool or other abrasive cleaners. You can use nonabrasive cleaners like vinegar for persistent stains. 

Make sure to dry the surface properly to avoid rust. 

Use different steel protection techniques, such as applying a protective coating like black oxide or wax. Doing so will provide corrosion resistance. Don’t expose it to humid conditions for too long; store it in a dry and well-ventilated area. 

Comparison of ASTM A108 Steel with other Stainless Steel Grades

ASTM A108 is a carbon and alloy steel specification; some stainless steel grades fall under this specification. Other stainless steel grades include austenitic, ferritic, martensitic, and duplex stainless steel.

Both duplex and austenitic stainless steel are more expensive than ASTM A108 SS grades but offer better corrosion resistance. Austenitic steels are also more tolerant of higher temperatures. 

In contrast, ASTM A108 is more cracking-resistant than ferritic stainless steel. ASTM A108 is also more machinable than martensitic stainless steel, which is brittle and less flexible. 


ASTM A108 is a standard specification for cold-finished carbon and alloy steels. It has over 39 grades that also include some stainless steel grades. The properties of ASTM A108 steel generally depend upon the specific grade you’re using.

ASTM A108 comprises iron alloyed with carbon and manganese, with other elements present in some grades. It is generally very machinable, and some grades offer durability and toughness too. You can also easily weld and fabricate it, but you must apply pre- and post-weld treatments.

Contact us today for a quote for an ASTM A108 grade of your choice!


1. Is ASTM A108 steel magnetic?

ASTM A108 is a standard specification that includes different grades of steel. Some of them may be magnetic, while others are not. Carbon steel is generally magnetic, while the magnetism of alloyed steel depends on its constituent elements. We recommend you double-check whether the grade you want to use is magnetic. 

2. What are the different ASTM A108 Steel types?

ASTM A108 steels are generally of two types: carbon and alloy steels. Carbon steels are further classified based on their carbon content, such as low-carbon steels or medium-carbon steels. On the other hand, alloy steels have iron alloyed with many other elements, such as chromium, molybdenum, nickel, or silicon.  

3. How does ASTM A108 steel affect the environment?

ASTM A108 production involves high temperatures, which require burning fossil fuels. The production process also releases pollutants like greenhouse gases. 

However, ASTM A108 is recyclable and has a long life cycle, reducing the need to manufacture ASTM A108 steel from scratch. By recycling ASTM A108, we also reduce waste generation. More energy-efficient technologies will also make the process more efficient and reduce the negative environmental impact of ASTM A108 in the future. 

4. What are the future prospects in manufacturing processes for ASTM A108 Steel?

The future of ASTM A108 steel is promising in the industry. There is an increasing demand for carbon and alloy steel, promoting growth opportunities for ASTM A108 steel. New steel grades are also being continuously developed.

In the future, the ASTM A108 production process will likely be more sustainable through energy-efficient technologies. We can also expect new technologies like additive manufacturing to play a role in steel manufacturing. 

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