Fasteners are manufactured from a wide variety of materials: carbon steel, stainless steel, alloy steel, brass, bronze, aluminum alloys, nickel alloys, titanium alloys, plastics, and other high performance specialty materials. When selecting materials, engineers need to consider: strength, stress, ductility, corrosive environments, cost, weight, magnetism, electrical conductivity, coatings/plating, reusability, life expectancy, etc.
In the global fastener market, more than 90% of fasteners are made from steel because of its strength, ease of processing and low cost. Common types of steel include mild steel, medium carbon steel, and alloy steel.
Carbon Steel
- Low carbon steel: carbon content ≦ 0.25%, grades ANSI 1006, 1008, 1010, 1015, 1018, 1022, 1035, etc.. Mainly used for 4.8 grade bolts and 4 grade nuts, small screws and other products without hardness requirements. (Note: Drill nails are mainly made of 1022 material.)
- Medium carbon steel: carbon content of 0.25-0.45%, grade AISI 1035, CH38F, 1039, 40ACR and so on. Mainly used for grade 8 nuts, grade 8.8 bolts and grade 8.8 hexagonal products.
| Material Type | Material Grade | Carbon Content | Mechanical Properties | Features |
|---|---|---|---|---|
| Low Carbon Steel | Q195, Q235, A36; AISI grades 1006, 1008, 1010, 1015, 1018, 1022, 1035. | ≦ 0.25% | 60,000 psi to 80,000 psi ( 410MPa to 550MPa) | Easy processing, good plasticity, low strength, low cost. |
| Medium Carbon Steel | 35#, 45#, 40Mn, CH38F, 40ACR, S35C, S45C; AISI grades 1541, 1038, 5132, 5135. | 0.25–0.60% | 100,000 psi to 120,000 psi. (690MPa to 830MPa) | High strength, moderate toughness, adjustable quality. |
Coil used for carbon steel fasteners
| # | Fastener Types | Available Materials |
|---|---|---|
| 1 | Grade 4.8 hex bolts | 1008K, 1010, 1015K |
| 2 | Grade 6.8 hex bolts | 1032, 1035, 1040, CH38F, 1039 |
| 3 | Grade 8.8 hex bolts | 1035ACR(<M10), 1040ACR(>M12), CH38F, 1045ACR, 1039, 10B21, 10B33, 10B38 |
| 4 | Grade 8.8 hex socket bolts | CH38F, 1039, 10B21(M10-M12), 10B33(M14), 10B38(M12-M24), 10B21 |
| 5 | Grade 10.9 hex bolts | 1045ACR, 10B38 |
| 6 | │Grade 8│nuts | 1008K, 1010 |
| 7 | Grade 8 nuts | 1015(M＜16), CH38F(M≧16) |
| 8 | Grade 10 nuts | CH38F, 1039, 10B21, 10B33 |
| 9 | Grade 12 nuts | 1039, 10B21, 10B33, 10B38 |
| 10 | Carriage screws | 1008, 1010, 1015 |
| 11 | Hexagonal flange bolts | CH38F, 1039, 10B21, 10B33, 10B38 |
| 12 | hexagonal wood screw | 1008K, 1010 |
| 13 | Self-tapping screws, wall panel screws, drill screws, plywood screws | 1018, 1022, CH22A |
| 14 | Machine screws, furniture screws | 1008, 1010 |
Carbon Steel Material Strength Grades
| ISO Strength Grade | Tensile Strength Rm (MPa) | Yield Strength Re (MPa) | Characteristics | Typical Applications |
|---|---|---|---|---|
| 4.6 | ≥ 400 | ≥ 240 | General low-carbon steel, good ductility, low strength | Furniture screws, electronic components |
| 5.6 | ≥ 500 | ≥ 300 | Slightly stronger, low cost | Light-duty structures, civilian installations |
| 5.8 | ≥ 500 | ≥ 400 | Moderate load capacity, suitable for medium-strength connections | Electrical cabinets, general supports |
| 6.8 | ≥ 600 | ≥ 480 | Intermediate type, cost-effective | Building structures |
| 8.8 | ≥ 800 | ≥ 640 | Main grade of medium-strength bolts | Mechanical joints, industrial bolts |
| 10.9 | ≥ 1000 | ≥ 900 | High-strength alloy steel (tempered) | Engineering machinery, vehicle chassis |
| 12.9 | ≥ 1200 | ≥ 1080 | Ultra-high strength, lower ductility | Stamping dies, aerospace structures |
Alloy Steel
Alloying elements (chromium / molybdenum / manganese / nickel / boron / titanium) are added to carbon steels to increase the special properties of the steel. The Cr-Mo alloy system is the main alloying material for fasteners.
| Types | Grades | Mechanical Properties | Features |
| Chrome-Molybdenum | 35CrMo, 40Cr, 42CrMo, ANSI 4140, SCM435. | 8.8, 10.9, 12.9 (ISO), Grade 5, 8 (SAE). | High tensile, corrosion resistant |
Various elements of steel properties:
- Carbon (C): improves the strength of steel parts, especially their heat treatment properties, but as the carbon content increases, the plasticity and toughness decreases and affects the cold heading properties and welding properties of steel parts.
- Manganese (Mn): to improve the strength of the steel, and to a certain extent to improve the hardenability. That is, in the quenching increased hardening penetration strength, manganese can also improve the surface quality, but too much manganese on the ductility and weldability is unfavorable. However, too much manganese is detrimental to ductility and weldability, and affects the control of the coating during plating.
- Nickel (Ni): improve the strength of steel, improve the toughness at low temperatures, improve resistance to atmospheric corrosion, and can ensure stable heat treatment effect, reduce the role of hydrogen embrittlement.
- Chromium (Cr): can improve hardenability, improve wear resistance, improve corrosion resistance, and is conducive to maintaining strength at high temperatures.
- Molybdenum (Mo): can help control the hardenability, reduce the susceptibility of steel to temper brittleness, and have a great impact on improving the tensile strength at high temperatures.
- Boron (B): improves hardenability and helps to make mild steels respond as expected to heat treatment.
- Alum (V): austenite grain refinement, improve toughness.
- Silicon (Si): to ensure the strength of steel parts, appropriate content can improve the plasticity and toughness of steel.
Stainless Steel
Stainless steel standard parts characterized by corrosion resistance, aesthetics, hygiene, but its strength, hardness is normally equivalent to carbon steel (6.8 level), so the stainless steel products should not be impact, knocking, pay attention to the maintenance of its surface finish, precision, and can not be used with carbon steel products as casually applying force, but also can not be applied to the force is too large.
Stainless steel add 10.5% chromium element, the formation of chromium oxide protective film on the surface of the steel, in order to effectively block the contact between the steel and the air, so that the oxygen in the air can not enter the steel to produce a chemical reaction, to achieve the effect of rust prevention.
| Types | Grades | Features |
| Austenitic Stainless Steel | AISI grades 302, 303, 304, 304L, 316, 347, 348. | 18%Cr, 8%Ni; Non-magnetic, easy to form, cold forming, good weldability. |
| Martensitic Stainless Steel | AISI grades 410, 416, 420, 431. | 12%-18%Cr; Magnetic, high strength, good abrasion resistance. |
| Ferritic Stainless Steel | 430，C1，C2，C4 | 12-30%Cr; good forging properties, strong magnetism, and is resistant to rust and pitting. |
| Duplex Stainless Steel | S31803 / S32205，1.4462，2507（S32750），2205，2.5-7Ni，23-30cr，Zeron 100 | Stainless steel material with austenitic + ferritic duplex organization, high yield strength, superb resistance to pitting corrosion, resistance to chloride stress corrosion cracking. |
Chemical composition of 300 series austenitic stainless steel:
304M, 304HC, 316 three materials is the most widely used austenitic stainless steel material. The obvious difference of each material is: after cold working, the magnetic properties of the material are 316<304HC<304M. 316 material is resistant to chemical corrosion, pore corrosion and seawater corrosion resistance is relatively good compared to 304M and 304HC.
304M slightly magnetic after cold working (1.6u-2.0u or so); 304HC magnetic (1.01u-1.6u or so); 316 material magnetic after cold working is less than 1.01u. All materials have good ductility, easy to cold working molding, tensile strength, yield strength, can meet the requirements. (Ts tensile strength min 700N/mm, Ys yield strength min 450N/mm)
| Grade | C | Si | Mn | P | S | Ni | Cr | Mo | Cu |
|---|---|---|---|---|---|---|---|---|---|
| 304M | ≦ 0.06 | ≦ 1.0 | ≦ 2.0 | ≦ 0.045 | ≦ 0.03 | 8.91 – 10.0 | 18.0 – 20.0 | 0 | 0 |
| 316 | ≦ 0.03–0.06 | ≦ 1.0 | ≦ 2.0 | ≦ 0.045 | ≦ 0.03 | 10.0 – 14.0 | 16.0 – 18.0 | 2.0 – 3.0 | 0 |
| 304HC | ≦ 0.08 | ≦ 1.0 | ≦ 2.0 | ≦ 0.045 | ≦ 0.03 | 8.0 – 10.5 | 17.0 – 19.0 | 0 | 1.0 – 3.0 |
Chemical composition and stainless steel properties
- Carbon C can increase the hardness and strength, the content is too high will reduce its ductility and corrosion resistance.
- Chromium Cr can increase corrosion resistance, oxidation resistance, make the grain refinement, increase strength, hardness and wear resistance.
- Nickel Ni can increase high temperature strength, corrosion resistance, reduce the rate of cold work hardening.
- Molybdenum Mo increases strength and has excellent corrosion resistance to oxides and seawater.
- Copper Cu facilitates cold working and molding, and reduces magnetism.
Copper Alloy
Copper. Commonly used alloy materials are brass, silicon bronze, aluminum bronze, phosphor bronze, manganese bronze. Mainly used H62, H65, H68, C260 (70/30) copper as standard parts
| Silicon bronze | Salt spray resistant, non-magnetic |
| Brass | An alloy of copper (Cu) + zinc (Zn), usually containing between 5% and 45% zinc. |
High Performance Nickel Alloys
| Types | Mechanical Properties | Features |
|---|---|---|
| Nickel-copper alloy | 80,000 psi (550 MPa) | Excellent strength, toughness, and ductility, and performs well in extreme high and low temperature conditions. |
| Nickel-copper-aluminum alloy | 1130,000 psi (896 MPa | Excellent performance and oxidation resistance |
Titanium Alloy
| Material | Grades | Mechanical Properties | Features |
|---|---|---|---|
| Titanium | Gr1, Gr2, Gr5, etc | 150,000psi（1034 MPa） | Ultra-light, high strength, high temperature resistant, non-magnetic. |
Aluminum Alloy
| Material | Grades | Mechanical Properties |
|---|---|---|
| Aluminum Alloy | AL6061, AL6063, AL6082, AL7075, AL5052, A380, etc. | 13,000psi(90MPa) to 60,000psi(414MPa) |