Production Process of Hexagonal Bolts

Raw Material Selection

High - quality carbon steel, alloy steel, or stainless - steel wires are chosen as the raw materials. The selection depends on the intended application of the bolts. For example, carbon steel is suitable for general - purpose applications, while stainless steel is used when corrosion resistance is required. The raw material wires should meet specific chemical composition and mechanical property standards.

Cold Heading

The selected wire is fed into a cold - heading machine. In this machine, the wire is cut into specific lengths. Then, powerful punches and dies are used to shape the cut - off wire segments into the basic form of the bolt head. The cold - heading process deforms the metal at room temperature, which not only improves the mechanical properties of the metal, such as increasing its strength and hardness, but also efficiently creates the characteristic hexagonal shape of the bolt head.

Thread Rolling

After the bolt head is formed, the bolt shank is processed for threading. This is typically done using thread - rolling machines. The bolt blank is placed between two dies with the reverse - image of the desired thread pattern. As the dies rotate and move towards each other, they press and roll the surface of the bolt shank, creating the threads. Thread rolling is preferred over cutting threads as it results in stronger threads by work - hardening the surface of the metal.

Heat Treatment (Optional)

For bolts that require enhanced mechanical properties, such as higher strength or toughness, heat treatment is carried out. This usually involves processes like quenching and tempering. The bolts are heated to a specific temperature and then rapidly cooled (quenching) in a suitable medium, such as oil or water. After quenching, they are reheated to a lower temperature and held for a certain period (tempering) to relieve internal stresses and adjust the hardness and toughness to the desired levels.

Surface Treatment

Surface treatment is an important step to protect the bolts from corrosion and improve their appearance. Common surface treatment methods include electro - plating (such as zinc - plating), hot - dip galvanizing, and black - oxide coating. Electro - plating involves depositing a thin layer of metal (e.g., zinc) onto the bolt surface through an electrochemical process. Hot - dip galvanizing immerses the bolts in a bath of molten zinc, creating a thick, durable zinc - iron alloy layer. Black - oxide coating forms a thin, black, protective oxide layer on the surface of the bolts.

Quality Inspection

Multiple inspection procedures are carried out at different stages of production. Visual inspection is done to check for any surface defects, such as cracks, burrs, or uneven plating. Dimensional inspection is performed using precision measuring tools, like calipers and gauges, to ensure that the bolts meet the required size specifications for the head, shank, and thread. Mechanical property tests, such as tensile tests and hardness tests, are also conducted to verify that the bolts have the appropriate strength and hardness for their intended use. Only bolts that pass all these inspections are considered suitable for packaging and distribution.

Packaging

Finally, the are packaged. They are usually grouped by size, grade, and surface treatment type. Packaging materials may include plastic bags, cardboard boxes, or wooden crates, depending on the quantity and destination of the bolts. Appropriate labels are attached to the packages, indicating information such as the bolt size, material, grade, and surface treatment to facilitate identification and inventory management.

Hebei Sanwei Fasteners Co., Ltd.'s production base is located in Hebei, China, covering an area of 33,000 square meters with a building area of approximately 30,000 square meters. Sanwei established its own research and development center, increased investment in new development and technological innovation, marking the transformation from a traditional manufacturing enterprise to a technology-driven enterprise. Expanding overseas markets, products successfully exported to overseas countries such as, and overseas offices were set up, further enhancing the brand's international influence. Stable Maturity Period: Sanwei continuously optimized its industrial structure, deepened with upstream and downstream partners in the industry chain, forming a complete industrial chain integrating raw material supply, design and research, production processing, and sales service. 

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