Choosing the Materials of Fasteners
The type of material chosen by different industries is diverse when it comes to choosing fasteners. This is an essential factor owing to the elements that the fasteners have to be exposed to like the external environment and corrosive elements in it. That is why fasteners, whether bolts, rivets, screws, or clamps, are created with a wide variety of specifications to uphold their purpose.
Generally, the market has a bulk production of fasteners created for industrial purposes made from various metals like titanium, aluminum, synthetic non-metals, steel, or brass to meet specific applications in a range of fields. But sometimes, to meet a specific requirement, customized fasteners are produced too.
Fastener materials need to be judged based on their mechanical properties, cost-efficiency, and many other criteria. Hence, it is crucial to select the suitable material for your particular application. To help you choose the right fasteners for your use, here are some things that you need to know about.
1. The overall strength
When we talk about the overall strength of a fastener's material, this is calculated in ‘pounds per square inch’ or ‘PSI.’ Speaking of which, pure steel and low carbon steels possess the lowest acceptable proof stress, somewhere around 60,000 PSI. Steel is one of the common materials that is used for producing fasteners, and it constitutes approximately 90% of all fasteners that are manufactured in a year.
Steel fasteners are obtainable in many grades; however, only four grades of this material are in high demand in many industries. These grades of steel fasteners are as follows-
Grade 2 Steel Fasteners:
This is a standard type of hardware-grade steel that is used for light industrial applications. This grade of steel is also used by many for DIY home projects.
Grade 5 Steel Fasteners:
The production of this grade of steel fasteners has to undergo a number of treatments so that the strength is enhanced. Usually, fasteners of this material are used in the automotive industry.
Grade 8 Steel Fasteners:
Fasteners of this grade are stronger than grade 5 steel fasteners. These fasteners are considered high-tensile and are mostly used in challenging industrial applications like large trucks, tractors, and even tanks. It is also used for machinery, pumps, vessels, and valves. Grade 8 steel fasteners have a minimum tensile strength of 150,000 PSI.
Other than graded steel, fasteners are also made from alloy steel. Alloy steel fasteners are made in diverse alloy types giving them the strength and resistance that is required in high demanding industries. These fasteners have extra strength due to heat treatment but are also brittle as compared to fasteners of other materials.
Other than that, fasteners are also produced from superalloys that have a tensile strength that exceeds 250,000 PSI. Superalloy fasteners are devised for suiting extreme applications like building rockets and space probes.
2. Resistance from Corrosion
Corrosion happens when a metal interacts with the chemicals in the environment. Oxidation is one of the most common types of corrosion, which happens when a metal reacts to the oxygen in the air and forms rust. Most metal fasteners are prone to rust and corrosion. Hence, to prevent this from happening, metal fasteners are covered with a protective coating. This coating can differ from one another as per the requirement of an industry’s application. Some of the common types of plating that are used for metal fasteners are as follows:
This type of plating offers high anti-corrosion properties. A chrome-plated metal surface offers sturdiness and durability, which means a longer life for your metal fasteners even under the most severe situations and harsh environments. Mostly purchased for their appearance, chrome-plated metal fasteners are not cost-efficient, and that is a big disadvantage.
This is one of the most excellent forms of plating for metal fasteners that are sustainable for outdoor and industrial applications. However, it must be kept in mind that zinc-plated fasteners are not ideal for marine environments.
This method of proofing metal fasteners from corrosion is the most common. Hot-dip galvanizing is one of the oldest methods used to prevent metals from corroding. The metal used for the process is mostly layers of zinc-iron alloy layers, which are harder than the base metal. Metal fasteners that undergo hot-dip galvanizing are more resilient due to the thick coating of zinc. hot-dip galvanized metal fasteners are useful if used in coastal environments.
3. The temperature of the Work Environment
It must always be kept in mind that fasteners are not only used for simple projects. Sometimes most of them have to be exposed to environments at high temperatures. In such cases, the metal fasteners used must be sustainable and sturdy so that performance is not affected. The extreme heat of 1000 degrees Fahrenheit and above can cause poorly chosen metal fasteners to melt, rust, or corrode. It might also cause their expansion, thus pushing pressure on the holes it was driven into, which might loosen the screws when the environment is cooler.
Some strong alloys that you can choose from to work within high-temperature industries are as follows.
Stainless Steel 309 and 310
They are higher in chromium and nickel content. The 310 stainless steel provides extra corrosion resistance, which makes it ideal for use in salty environments.
Stainless Steel 630
It is an extra hard alloy, a state that is achieved by cold working and aging at low temperatures. It is one of the most common alloys used in high-temperature environments for its sturdy features.
It is an alloy that contains chrome, nickel, and iron. The metal can withstand oxidation at high temperatures but begins to break down at 1,300 Fahrenheit and above.
It can be used for environments with temperatures between 1,300-and 1800 degrees.
So these were some tips on choosing the right type of materials for fasteners. Ensure to cross-check them all and save yourself time and money for the long run.
Kenneth G Lilly has been a provider of customized fasteners for over 60 years. It provides ASTM-grade materials that take into account its material, size range, proof load, minimum yield strength, and minimum tensile strength.