all-about-high-strength-fasteners

All about High-Strength Fasteners - Materials | Types | Applications

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What are high-strength fasteners?

In simple words, high-strength fasteners are hardware devices like bolts, nuts, screws, and rivets built to withstand extreme atmospheric conditions like-

  • Corrosion due to chemical exposure
  • High temperatures 
  • Rusting due to exposure to moisture

These types of fasteners are mainly used for critical applications in aerospace equipment, petrochemical processing, mining, oil & gas, or the marine industries. Logically, these industries require to work with materials with the highest tensile strength to function correctly. Hence, it is only natural that these fasteners are made from only the most advanced alloys available on the market.

Materials and Applications

There are many alloys in a range of thicknesses, shapes, sizes, and tempers that are used to create high-strength fasteners for carrying out critical applications. Some of these high strength materials are as follows-

1. Precipitation Hardening (PH) Alloys

This variety of alloy is in high demand today. The alloy is different from other grades of stainless and nickel-based alloys since it contains small amounts of copper, aluminum, phosphorous, and/or titanium. 

PH alloys undergo cold forming during their soft solution annealed condition. Post fabrication, the parts are then tested to age-hardening, in which the added elements precipitate as hard intermetallic compounds. These compounds significantly increase hardness and strength.

PH alloys, despite their more complex metallurgy, cost less than non-age-hardenable alloys. Also, their performance is substantially higher and their corrosion resistance is decreased or increased during the aging cycle.

Some of the PH alloys are A-286 iron base alloy, 17-7 PH, Inconel 718, Waspalloy, and L-605

Applications: PH Alloys are mostly applied in aerospace and other high-technology industries owing to their high strength. They are also used for making gears, high-strength shafts, valves, important engine components, turbine blades, molding dies, and nuclear waste casks.

2. Titanium alloys

Titanium has a higher tensile strength making it resistant to higher temperatures, seawater exposure, and galvanic corrosion. Titanium fasteners have both physical and mechanical properties thermal conductivity, proof stress, creep resistance, electrical conductivity, yield strength, tensile strength, electrical resistivity, density, and melting point which help fight against corrosion and high temperatures. 

Applications: Titanium Fasteners are suitably applied in industries like offshore oil drilling, pharmaceuticals, petrochemical, power generation, power plant, transportation, gas processing, food processing, heat exchanger, condensers, paper industry, pulp industry, transportation, and the specialty chemical industry as well.

3. Nickel Alloys

Nickel Alloy Fasteners are designed from nickel along with additional content like chromium, copper, and iron. These grades of fasteners are heat and corrosion resistant making them suitable for wide use in various applications. Nickel Alloy fasteners possess low thermal expansion and exhibit predictable and uniform expansion over certain temperature ranges. 

Applications: Nickel alloys are applied in important industries like marine and saltwater equipment, pump and valve components, as well as on equipment and components exposed to chemicals, acids, and other corrosive materials.

4. High Strength Stainless Steels

Stainless Steel fasteners are distinguished by their resistance to corrosion, aesthetic appearance, and cost-effectiveness. As compared to carbon and/or alloy steel fasteners, stainless steel fasteners have medium strength and high corrosion resistance. Stainless steel fasteners are commonly used without coating since they have a high aesthetic value. Stainless Steel alloys are categorized into three main groups-

  • Martensitic
  • Austenitic
  • Ferritic

Some fasteners for advanced high strength steel alloys are made from- ASTM A193, ASTM A194, ASTM A320, ASTM F593, ASTM F594, and BS EN ISO 3506-1. 

Applications:  Stainless steel fasteners like high-strength bolts and high-strength screws can provide high strength and excellent fatigue properties. The distinguished properties of a stainless steel ally make it a perfect fit for marine applications, subject to vibration and dynamic loads, like propulsion systems and offshore wind turbines.

5. Super Alloys

After developing a commercially viable stainless steel alloy, metallurgists kept looking for a much stronger material that had a higher resistance to corrosion for high-temperature applications. Stainless steel had its limitations in its strength capabilities, which led to experimentation with alloys and then the discovery of superalloys.

Superalloys exhibit superior strength mechanically along with creep resistance at temperatures as high as 1000 degrees Fahrenheit and above. These types of alloys also exhibit good surface stability, as well as corrosion and oxidation resistance. Superalloys fall into three basic groups-

  • Iron-nickel-base superalloys like Invar 36
  • Nickel-base superalloys like Inconel and Monel; and 
  • cobalt-base superalloys like FSX-414, Jetalloy, and Ultimet

Applications: Superalloys find their applications in high-exposure industries like-

  • Aircraft gas turbines
  • Steam turbine power plants
  • Reciprocating engines
  • Metal processing
  • Medical applications
  • Space vehicles
  • Heat-treating equipment
  • Nuclear power systems
  • Chemical and Petrochemical industries
  • Pollution control equipment
  • Metals processing mills
  • Coal gasification and liquefaction systems

 

So, which industry do you require fasteners for? 

If your industry is subject to harsh surroundings and work routines then you surely are in need of high tensile bolts made from high-end bolts material, as well as high strength screws. KG Lilly is a manufacturer of some of the best and custom-made high-strength bolts and high-strength screws in the USA. For more details visit the website or contact us.

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