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Fasteners are made from a wide variety of materials, with the selection depending on the application's requirements for strength, corrosion resistance, temperature tolerance, weight, cost, and electrical conductivity. The main categories and typical materials are as follows:

I. Ferrous Materials (Most Common)

This is the most widely used category, accounting for over 80% of the fastener market.

1. Carbon Steel

Low Carbon Steel:e.g., Q235 (A3 steel), SWRCH10A/18A (wire rod). Offers lower strength but good plasticity. Used for general-purpose, low-strength fasteners.

Medium Carbon Steel: e.g., Grade 35, Grade 45 steel. Can achieve good comprehensive mechanical properties after heat treatment (quenching and tempering). Used for medium-strength bolts and nuts.

Alloy Steel / Medium Carbon Alloy Steel:e.g., 35CrMo, 42CrMo, SCM435, 40Cr. The addition of elements like chromium and molybdenum significantly enhances strength, toughness, and hardenability. Used for high-strength fasteners in critical applications like automotive engines and construction machinery.

Boron Steel:e.g., 10B21, 10B33. Contains trace amounts of boron to improve hardenability at a relatively low cost. Widely used for automotive bolts.

2. Stainless Steel

Austenitic Stainless Steel: The most common type; non-magnetic with excellent corrosion resistance.

    A2 (304): General-purpose, resistant to atmospheric corrosion.

    A4 (316): Contains molybdenum, resistant to corrosion from acids, alkalis, and chlorides ("marine grade").

Martensitic Stainless Steel: e.g., 410, 420. Can be strengthened by heat treatment, offering higher strength but lower corrosion resistance than austenitic steels. Some grades are magnetic.

Ferritic Stainless Steel: e.g., 430. Offers moderate corrosion resistance, mainly used for decorative purposes or in general environments.

II. Non-Ferrous Materials

1. Copper and Copper Alloys

Brass:Aesthetically pleasing with good electrical conductivity. Used in electronics, decorative applications, and low-strength corrosion-resistant situations.

Bronze:Wear-resistant, used for special bearings or components resistant to seawater corrosion.

Pure Copper:Excellent electrical conductivity, used for electrical connections.

2.Aluminum and Aluminum Alloys

Advantages: Lightweight (approx. 1/3 the density of steel), resistant to atmospheric corrosion (forms a protective oxide layer), good thermal and electrical conductivity.

Grades: e.g., 5052, 6061, 7075 (high-strength aerospace aluminum).

Applications: Aerospace, electronic equipment, lightweight structures.

III. High-Temperature / Special Alloys

Used in extreme environments.

1. Nickel-Based Alloys: e.g., Inconel 600/718, Monel 400/K500. Offer exceptional high-temperature resistance and corrosion resistance (to acids, alkalis, seawater). Used in aerospace, chemical, and marine engineering.

2. Titanium and Titanium Alloys:e.g., TC4 (Ti-6Al-4V). Feature very high strength-to-weight ratio, are lightweight, offer excellent corrosion resistance and good biocompatibility. Used in aerospace, medical implants, and high-performance racing. Cost is high.

IV. Other Materials

1. Plastics / Polymers:e.g., Nylon (PA6, PA66), Polypropylene (PP), Polyetheretherketone (PEEK). Provide insulation, are lightweight, chemically resistant, and non-magnetic, but have lower strength. Used in electronics, food/medical industries, and corrosive environments.

2. Special Materials and Coatings:

Base materials can undergo surface treatments to enhance performance. Examples include zinc plating, Dacromet coating, hot-dip galvanizing, and phosphating to improve rust resistance; carburizing/nitriding to increase surface hardness.

Composite material fasteners are also under development.