MATERIAL
创建于05.29
The majority of industrial fasteners areproduced from aluminum, brass, certain synthetic non-metals, and various gradesof steel and stainless steel. In addition, metals such as titanium are alsovaluable for building fasteners, although they have very specific applicationsin a narrow range of fields. Generally, fastener materials are judged on theirmechanical properties, potential for post-fabrication treatments,cost-efficiency, and several other secondary criteria.
Steel Fasteners
Steel is the most commonly used material infastener production, constituting nearly 90 percent of all fastenersmanufactured annually. This metal’s popularity stems from its high degree offormability coupled with tensile strength and durability. Compared to othermetal stock, steel is also relatively inexpensive to fabricate. It isfrequently processed with zinc or chrome plating, but can also be formedwithout any surface treatments.Carbon steel is the most common type of steel used in fastenerproduction. Grades 2, 5, and 8 are typically the standard for carbon-steelbased screws and bolts, with alloyed carbon steel being a higher-end variationon these metals. Their mechanical strength ranges from approximately 50 ksi(kilo-pound per square inch) up to 300 ksi in a finished product. Materialproperties for these grades include:
- Grade 2: This is a low carbon category that features the least expensive, but also least durable, types of steel. Grade 2 material is highly workable, and forms the bulk of steel grade fasteners.
- Grade 5: Grade 5 steels are produced from unalloyed medium carbon groups, such as type 1038, and are usually work-hardened to improve their strength. This is the most common grade used in automotive applications.
- Grade 8: These steels are typically medium carbon alloys, such as types 4037 and 4340. They are work-hardened to a high degree, making them stronger and better-suited for mechanically straining applications, like vehicle suspension systems.
Alloy Steel:This is an alloy formed with high-strength carbon steel that can be thermallytreated up to 300 ksi. Alloy steel has low corrosion resistance and typicallybenefits from additional coating. These steels are extremely strong, but can berigid and brittle.
Stainless Steel Fasteners
Stainless steel is an alloy that combines the properties of low carbon grades withcertain percentages of chromium and nickel. Its chromium component lendsstainless steel a high degree of corrosion resistance that does not decreasefrom deformation or long-term use. However, the low carbon content prevents itfrom being effectively hardened, making the metal stronger than most grade 2steels, but weaker than many hardened grade 5 and 8 varieties. The finalstrength of most stainless steel grades ranges from around 70 to 220 ksi,depending on the ratio of metals in the alloy. Stainless steel fasteners arealso less magnetic than their standard steel counterparts. The two maincategories of stainless steel fastener materials are:
- Martensitic Stainless Steel: The martensitic group includes strong, durable stainless steels that can be further strengthened through heat treatments. They are more magnetic than other types of steel, but have lower corrosion resistance.
- Austenitic Stainless Steel: The vast majority of stainless steel fasteners are produced with metals from the austenitic family. Their high levels of chromium and nickel provide tough corrosion resistance and the ability to withstand considerable physical strain without fracturing, albeit at a higher cost than the martensitic varieties.