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Home > Haisen Blog > Basic knowledge of cold heading

  • Cold heading: It is to use the plasticity of metal to apply pressure or cold drawing by cold mechanics to achieve the purpose of solid metal deformation.

    The forging method of thickening the top of a bar or wire at room temperature is also called cold extrusion.

    is mainly used to make parts such as bolts, nuts, nails, rivets and steel balls.

    The optional metal materials are not carbon steel, but also copper, aluminum, alloy steel, stainless steel and titanium alloy, etc. The material utilization rate can reach 80-90%. Continuous, multi-station, automated production is realized through a dedicated cold heading machine (the world's largest cold heading machine exhibition-Shanghai Fastener Professional Exhibition June 2015). Cutting, heading, accumulation, forming, chamfering, thread rolling, diameter reduction and trimming can be completed in sequence on the cold heading machine. The cold heading machine has high production efficiency, up to 300 pieces per minute.

    |Is the hex head of the screw cold-headed?

    Most of them are produced by the cold heading process, because this process saves time and materials and has a low price.

    Small batches of special or special bolts with hexagon heads are milled after turning.

    The forming of the hexagonal head of the bolt cannot be generalized. There are cold heading, hot piercing, and the finished product directly after upsetting, and also the machining after upsetting and all machining.

    |How is the thread made?

    Single piece and small batch can be processed by die threading, lathe picking, whirlwind milling and other methods. This method is low in efficiency, waste materials are generated, and raw materials are wasted.

    When a large number of light bolts (cold heading) and wool bolts (hot hitting) need to be threaded, it is necessary to use a thread rolling machine to thread the thread. The efficiency is high and there is almost no waste. At the Shanghai Fastener Exhibition, you can find the world's top thread rolling machine manufacturer.

    The production of ordinary screws is basically divided into two processes, the first is the head forming, cold heading, warm heading or red punching process; the second is thread rolling, which is based on the previous process, the threaded part is manufactured. Most screws must undergo surface treatment and heat treatment before they leave the factory.

    |Example: The complete manufacturing process of 8.8 grade hexagonal head galvanized bolts

    Wire annealing---pickling---drawing---heading---rubbing teeth---heat treatment---plating---packing


    Annealing: A process of metal heat treatment to control the hardness of the wire itself. Generally use high temperature spheroidizing annealing furnace.

    Pickling: is to wash away the rust and impurities on the surface of the wire.

    Wire drawing: refers to cold drawing the wire to the diameter you need to produce the bolt.

    Cold heading wire: wire after drawing, pickling or heat treatment, also called cold-bonding wire, finished screw wire.

    Heading: It is the name of the process of cold heading forming and extruding the bolt head. Usually, the manufacture of bolts with a diameter larger than M24 (or 1 inch) does not use the cold extrusion process.

    Thread rolling or rolling: thread rolling machine or thread rolling machine.

    Heat treatment: heat and heat in an industrial furnace to finally cool down, change the metal crystal structure, and reach the corresponding performance level of the fastener.

    Electroplating: A type of surface treatment, usually galvanized on the surface to achieve general anti-corrosion purposes.
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