There are a wide variety of fasteners available. Understanding the difference between the types of steel used to make fasteners is a major consideration when selecting an appropriate fastener for your application. In this brief article, we take a look at the main steel types used to make nuts and bolts, and discuss their pros and cons.

Bolt-In Co Sunshine Coast is located on Wises Rd, Maroochydore on the Sunshine Coast QLD. Instore and online, we offer a wide range of high-quality nuts, bolts, fasteners, and balustrade supplies, backed up by great customer service and an experienced team. If you have any further questions, please don't hesitate to contact our team. 

What Steel are Fasteners Made From?

In different industries and manufacturing traditions around the world, specific fasteners have been developed to meet specific needs. Successful fasteners must be cost-effective as well as able to perform sufficiently well. Towards these goals, fasteners are made from steels or combinations of steels (alloys), specifically to create an optimal fastener for different applications. 

Examples of the types of steels used to make nuts and bolts include:

Carbon Steel - used in different amounts to achieve different grades of strength. For example, mild steel contains less carbon, and has a relatively low tensile strength. High tensile steel contains more carbon, with a relatively higher tensile strength. 

Alloy Steel - Chemical elements such as chromium, nickel, or molybdenum are added to carbon steel to create different properties, for example, corrosion resistance.

Stainless Steel - Stainless steel is an alloy that includes at least 10.5% chromium. This enhances its corrosion resistance. For this reason, stainless steel is useful on the Sunshine Coast which is largely exposed to a marine & coastal environment.

Titanium - Titanium fasteners are made with alloys that include titanium for light-weight, strong and hard nuts and bolts. 

What's the Best Type of Stainless Steel?

The best type of stainless steel - this depends on the intended application. For example, SS316 has more corrosion resistance than SS304, which in that regard makes it 'better' - but it also costs more. If your application doesn't require corrosion resistance, that just means you will be paying more money for something you don't need. 

Stainless steel fasteners are specifically made to fulfil an engineering requirement, and they have pros and cons in areas such as strength, corrosion resistance, and cost. Let's take a closer look at two popular types of stainless steel here on the Sunshine Coast: SS316 and SS304. 

Stainless Steel 316

Let's start with Stainless Steel 316, because on the Sunshine Coast, the proximity to the ocean often means corrosion resistance is an essential requirement. The photo above demonstrates Bolt-In Co SS316 wire rope in a balustrade solution by Swan Built Carpentry. SS316 has a high degree of corrosion resistance, making it suitable for applications on or near the coast, including the marine environment, and ideal for these types of project.

This corrosion resistance is achieved due to high levels of chromium, nickel and molybdenum. This combination ensures a long life in not only corrosive environments but also acidic and alkaline solutions, saltwater and chloride-containing environments. Here is an example of a concrete screw that we sell, made from SS316.

The inclusion of molybdenum is what separates SS316 from the next grade, SS304, which contains nickel and chromium (but not molybdenum). This inclusion enhances the corrosion resistance of SS316. However, SS316 products are generally more expensive. 

Interesting Fact: SS316 also comes in an 'L' variant: SS 316L. This L stands for 'low carbon'. The alloy of this variant includes less carbon than standard SS 316, and improves its weldability. 

Summary: If project is on or near the coast, or in a marine environment, SS316 is ideal for a long-lasting stainless steel fastener solution. 

Stainless Steel 304

Stainless Steel 304 is one of the most popular types of stainless steel. While its alloy includes nickel and chromium (like SS316) it does not include molybdenum. While SS304 does have some corrosion resistance, the absence of molybdenum in this alloy means it does not have the same capability as SS316 in a highly aggressive environment, such as a marine application. However, SS304 does generally come in at  a less expensive price point, making it a popular choice for many mainstream projects.

Other advantages of SS304 include high heat resistance, excellent formability, hygienic nature (easy to clean), and versatile, being used in a wide range of industries. 

Summary: For many projects, SS316 and SS304 steels may be used interchangeably. However, selecting the correct steel for your fasteners will ensure your project is optimised in terms of cost and outcome. 

Other Grades of Stainless Steel

Stainless steel comes in other grades apart from SS304 and SS316. Examples include SS430, SS201 and SS410. These varieties have different compositions, mechanical properties and benefits. We generally stock SS304 and SS316 as they are popular and cover a wide range of applications, including corrosion resistance, but if you're interested in other varieties, please ask our team.

Mild Steel

Mild Steel Nuts and Bolts are made up of a mild steel, also referred to as low carbon steel. This is due to the fact that compared to other types of steel, mild steel  contains a relatively low amount of carbon content (usually less than 0.3% by weight). It is 'milder' than other steels - less hard and strong. However, it is well-suited to a wide variety of engineering applications. Mild steel is popular due to its low cost and applicability to a wide range of applications. Mild steel is used in industries such as construction, furniture manufacture, household appliances and for low-tensile fastenings in machinery including automobiles. 

Mild Steel Fastener Advantages

Mild steel has several advantages that make it a suitable material for fasteners for a wide variety of applications. These include strength (though not as strong as high carbon or alloy steels, mild steel is sufficient for many tasks), ductility (high ductility means that mild steel can be stretched or bent without breaking, machinability (mild steel can be easily worked with), weldability (mild steel fasteners are highly weldable), availability, affordability and corrosion resistance (assuming a coating of zinc, epoxy or paint are used to protect the mild steel from corrosion.) 

High Tensile Steel

Tensile strength refers to how much stress can be sustained by a material before it breaks. High tensile steel bolts and fittings are utilised in applications when stress, such as tension is part of the equation. High tensile bolts are used in applications where durability is critical to firmly and safely hold components together.

High tensile fasteners are commonly used in the automotive industry, for example - think of all the vibration and movement inside a combustion engine. High tensile fasteners contain a relatively higher amount of carbon (usually between 0.5% and 0.8% by weight) and other alloying elements such as chromium, vanadium, or molybdenum, which in combination make them a stronger bolt than mild steel variants. 

High tensile steel bolts are the strongest bolts we sell.

What's the Strongest Bolt Grade?

The strongest generally available bolt grade is considered to be Grade 12.9. The grade is a metric bolt specification that defines the mechanical properties of the bolt, including its minimum tensile strength, yield strength, and elongation. Grade 12.9 bolts are made from alloy steel that has been quenched and tempered, resulting in a high-strength bolt that can withstand high stress and strain.

There's a great video about bolt strength here, if you'd like to learn more:

Galvanised Steel

We also sell galvanised steel fasteners. Galvanised steel fasteners are made by a manufacturing process where regular steel is dipped in zinc to form a protective coating. This coating creates a layer of protection against moisture and oxygen which protects the steel beneath. The benefits of galvanising steel include strengthening and corrosion resistance. Galvanised steel in a mild steel format is generally a less expensive option than stainless steel, but doesn't have the bright, clean look. It has more of a dull, dusty finish. (See picture above) Galvanised steel is commonly used in outdoor structures, construction, and in environments where corrosion resistance is critical.