I. Classification of Common Materials for Fasteners

Currently, standard fasteners on the market mainly include four types of materials: carbon steel, stainless steel, brass, and aluminum alloy.

1. Carbon Steel

Carbon steel is classified into low-carbon steel, medium-carbon steel, high-carbon steel, and alloy steel based on its carbon content.

1.1 Low-carbon steel

With a carbon content of C% ≤ 0.25%, it is commonly referred to as "A3 steel" in China and basically as 1008, 1015, 1018, 1022, etc., overseas. It is mainly used for products with no hardness requirements, such as 4.8-grade bolts, Grade 4 nuts, and small screws.

1.2 Medium-carbon steel

With a carbon content of 0.25% < C% ≤ 0.60%.

1.3 High-carbon steel

With a carbon content of C% > 0.60%, it is rarely used in the current market.

1.4 Alloy steel

Alloying elements are added to plain carbon steel to enhance specific properties of the steel, such as 35, 40CrMo, SCM435, and 10B38. Fasson 12.9-grade screws mainly use SCM435 chromium-molybdenum alloy steel, whose main components include C, Si, Mn, P, S, Cr, and Mo.

2. Stainless Steel

Stainless steel is mainly categorized as follows:

Austenitic stainless steel (18% Cr, 8% Ni): Features good heat resistance, corrosion resistance, and weldability (e.g., A1, A2, A4).
Martensitic stainless steel (13% Cr): Has poor corrosion resistance but high strength and good wear resistance (e.g., C1, C2, C4).
Ferritic stainless steel (18% Cr): Offers good cold-heading performance and better corrosion resistance than martensitic stainless steel.

3. Copper

Commonly used materials are brass and copper-zinc alloys. In the market, H62, H65, and H68 copper are mainly used for standard fasteners.

4. Aluminum Alloy

Aluminum alloy has low density but high strength, close to or exceeding that of high-quality steel. It has good plasticity and can be processed into various profiles. With excellent electrical conductivity, thermal conductivity, and corrosion resistance, it is widely used in industry, second only to steel in usage.

5. Alloy Steel (Narrowly Referring to Chromium-Molybdenum Alloy Steel, e.g., SCM435)

II. Common Materials for Fasteners

(I) Carbon Steel, Alloy Steel, and Special Steel

1. Bolts, screws, Studs

Grades 3.6, 4.6, 4.8, 5.6, 5.8, and 6.8 generally use carbon steel and do not require heat treatment.
Grades 8.8 and 9.8 typically use low-carbon alloy steel or medium-carbon steel, followed by quenching and tempering.
Grade 10.9 usually uses low/medium-carbon alloy steel or alloy steel, with quenching and tempering.
Grade 12.9 mainly uses alloy steel, processed by quenching and tempering.

2. Nuts

Grades 4, 5, and 6 generally use carbon steel or free-cutting steel, without heat treatment.
Grades 8 and 9 typically use medium-carbon steel, followed by quenching and tempering.
For Grades 10 and 12, alloying elements may be added if necessary to improve mechanical properties, followed by quenching and tempering.

3. Set screws

Grade 14H generally uses carbon steel without heat treatment.
Grades 22H and 33H usually use carbon steel, processed by quenching and tempering.
Grade 45H typically uses alloy steel, with quenching and tempering.

4. Self-tapping screws / Drill Tail Screws

Medium-carbon steel such as SWRCH22A is generally used, with surface carburizing treatment.

5. Flat Washers

HV140 flat washers generally use low-carbon steel.
HV300 flat washers typically use medium-carbon steel, requiring heat treatment.

6. Elastic Washers

Spring steel such as 70, 65Mn, or 60Si2Mn is generally used, processed by quenching and tempering.

7. Tooth-shaped / Serrated lock washers, Saddle-shaped / Wave-shaped Elastic Washers

65Mn is generally used.

8. Pins

Carbon steel 35# is commonly used, with quenching and tempering to HRC 28-38; 45# is used with quenching and tempering to HRC 38-46.
Alloy steel 30CrMnSiA is used, with quenching and tempering to HRC 35-41.
Special steels such as 1Cr13/2Cr13, Cr17Ni2, and 1Cr18Ni9Ti are also used.

(II) Stainless Steel

1. Grades, Types, and Applications of Stainless Steel

Grade	Type	Applications
1Cr18Ni9Ti	Austenitic	Most widely used; suitable for food, chemical, pharmaceutical, and atomic energy industries.
0Cr25Ni20	Austenitic	Furnace materials; materials for automobile exhaust purification devices.
1Cr18Ni9	Austenitic	High strength after cold working; used for architectural decorative components.
0Cr18Ni9	Austenitic	Most widely used as stainless heat-resistant steel; suitable for food equipment, general chemical equipment, and atomic energy industry.
00Cr19Ni10	Austenitic	Used for outdoor machinery, building materials, heat-resistant parts, and parts difficult to heat-treat in chemical, coal, and petroleum industries with high requirements for intergranular corrosion resistance.
0Cr17Ni12Mo2	Austenitic	Suitable for seawater and other media; mainly used as pitting corrosion-resistant materials for photography, food industry, coastal facilities, ropes, CD rods, bolts, and nuts.
00Cr17Ni14Mo2	Austenitic	Ultra-low carbon steel of 0Cr17Ni14Mo2; used for products with special requirements for intergranular corrosion resistance.
1Cr18Ni12Mo2Ti	Austenitic	Used for equipment resistant to sulfuric acid, phosphoric acid, formic acid, and acetic acid, with good intergranular corrosion resistance.
0Cr18Ni12Mo2Ti	Austenitic	Same as above.
0Cr18Ni10Ti	Austenitic	Ti addition improves intergranular corrosion resistance; not recommended for decorative components.
0Cr16Ni14	Austenitic	Non-magnetic stainless steel; used for electronic components.
0-1Cr20Ni14Si2	Austenitic	Has high high-temperature strength and oxidation resistance; sensitive to sulfur-containing atmospheres, with embrittlement tendency due to precipitated phases at 600-800°C; suitable for stress-bearing furnace components.
1Cr17Ni7	Austenitic	Suitable for high-strength components and materials for railway passenger carriages.
00Cr18Ni5Mo3Si2	Austenitic + Ferritic	Good stress corrosion cracking resistance and high strength; suitable for chloride-containing environments, used in refining, fertilizer, papermaking, petroleum, and chemical industries for manufacturing heat exchangers, condensers, etc.
00Cr12Ti	Ultra-pure Ferritic	Used for stamping parts in washing machines and decorative purposes.
0Cr17(Ti)	Ferritic	Used for automobile muffler pipes and decorative purposes.
0Cr13Al	Ferritic	No significant hardening when cooled from high temperatures; used as steam turbine materials, quenching parts, and composite steel.
1Cr17	Ferritic	General-purpose steel with good corrosion resistance; used for interior architectural decoration, heavy oil components, household appliances, and home appliance parts.
0Cr13	Ferritic	Used for parts requiring high toughness and impact resistance, such as turbine blades, structural frames, bolts, and nuts.
1Cr13	Martensitic	Has good corrosion resistance and machinability; used for general purposes, cutting mechanical parts, oil refining equipment, bolts, nuts, pump rods, and tableware.
2Cr13	Martensitic	High hardness in quenched state with good corrosion resistance; used for steam turbine blades and tableware (knives).

Common Materials for Fasteners