A4-70 stainless steel hex bolts are a highly sought-after fastener type in various industries due to their excellent mechanical properties, corrosion resistance, and durability. These bolts are especially prevalent in demanding environments such as wind towers, nuclear power plants, automotive manufacturing, construction, and electronics. Below is a detailed analysis of the specifications, grades, properties, and applications of A4-70 stainless steel hex bolts.

Specification of A4-70 Stainless Steel Hex Bolts

A4-70 hex bolts are made from high-quality stainless steel, specifically designed for high-strength and corrosion-resistant applications. These bolts are manufactured to international standards, including ISO 4017, DIN931, GB5783, and ASTM. The material used for these bolts typically includes various stainless steel alloys like SS304, SS316, SS316L, and others in the A2 and A4 series, with the A4-70 grade offering superior resistance to corrosion compared to A2-70.

The A4-70 hex bolts come in a wide range of sizes, from M2 to M100 in diameter and lengths ranging from 6mm to 500mm. They are available in multiple head types, including hex, square, round, hex flange, and flat, with several neck types like hex, square, triangular, and knurled. The bolts can be customized with different drive types such as Phillips, slotted, hex socket, Torx, and square slot, ensuring versatility for various applications.

Material and Properties of A4-70 Bolts

The A4-70 material, composed primarily of stainless steel alloys, provides outstanding resistance to corrosion, particularly in marine and other aggressive environments. The "A4" designation refers to stainless steel of the 316 grade, while the "70" signifies the bolt's strength (700 MPa minimum tensile strength). This combination of materials and strength ensures that A4-70 bolts can withstand harsh conditions, including exposure to seawater and industrial chemicals.

A4-70 stainless steel bolts exhibit excellent mechanical properties, including high tensile strength, which makes them ideal for heavy-duty applications. The material’s resistance to pitting, crevice corrosion, and stress corrosion cracking is a significant advantage, particularly in industries like aerospace, automotive, and chemical processing.

Surface Treatments for Enhanced Durability

To further enhance the durability and aesthetic appeal of A4-70 hex bolts, various surface treatments can be applied. These include passivation, anodizing, sand blasting, electroplating (zinc, nickel, black oxide, etc.), and hot-dip galvanizing. These finishes not only improve the corrosion resistance of the bolts but also help with their visual appearance and wear resistance. Surface coatings such as Teflon, cadmium, and zinc can also be used depending on the environmental conditions and specific requirements of the application.

Applications of A4-70 Stainless Steel Hex Bolts

Due to their superior properties, A4-70 hex bolts are used in a wide array of industries. They are commonly found in wind towers, nuclear power plants, railway systems, automotive manufacturing, and construction projects. These bolts are also crucial in the electronics industry, where high-strength, corrosion-resistant fasteners are needed for sensitive equipment.

Dimensions and Tolerances

A4-70 bolts are produced according to standard dimensions like ASME B18.6.3, ensuring compatibility with other fasteners in the same class. The bolts are precision-engineered with a tolerance of +/- 0.01mm to +/- 0.05mm, guaranteeing a tight fit and reliable performance in demanding applications. The production process involves several stages, including wire drawing, cold heading, tapping, heat treatment, and surface plating, all aimed at delivering high-quality fasteners.

Conclusion

A4-70 stainless steel hex bolts are an essential component in modern industrial applications, offering a blend of strength, corrosion resistance, and versatility. Their wide range of sizes, head types, and surface treatments makes them ideal for industries that require reliable and durable fasteners. Whether for wind towers, automotive manufacturing, or electronic equipment, A4-70 hex bolts ensure the longevity and safety of critical systems. By understanding the specifications, properties, and applications of these bolts, industries can make informed decisions to meet their specific needs.