Although the screw seems to be a small and insignificant part, but it is indispensable for large national heavy weapon and small household items. Then do you know how screws are made?
General screw manufacturing requires six steps.
The first step to select the wire
according to the production of screws of different diameters to choose different diameters of wire as raw materials.
The second step, rough drawing processing treatment.
First, the wire is heated and held for a period of time and then slowly cooled to adjust the crystalline organization. reduce the hardness of the wire, eliminate particles, in order to improve the wire room temperature processability. this step we call annealing.
Next is the pickling phosphate, remove the wire surface oxide film. the metal surface will form a phosphate film, with this layer of phosphate film, the wire can be more easily processed into shape. and can also reduce wire drawing, and cold heading and other subsequent processing, the tooling of the scrap and loss. Simply put, the purpose of rough drawing is to remove the oxidized skin of the wire in the production and storage process. after the rough drawing process, the surface of the wire will show the original color of metal.
The third step is the fine drawing process
This step requires the wire to be drawn to the appropriate thickness according to the product requirements.
Then you can move to the fourth step, the forming process, which can be roughly divided into three steps.
The first step is cold heading, where the cold heading machine cuts the wire to the required length and punches out the nut and logo.
The second step is tail clamping, which is a critical step to create a dovetail shape that can penetrate the steel plate.
This is the third step, thread rolling, also called tooth grinding. Through the interaction of the movable and fixed plates, the threads are produced from the semi-finished product. At this point, a screw is basically formed.
The fifth step, the heat treatment process, is divided into five stages.
The first step is cleaning,which removes grease from the surface of the screw.
The second step is high-temperature carburizing, which is the core of the entire heat treatment process, to allow carbon atoms to penetrate into the surface layer of the screw to increase its hardness.
The third link is quenching, the carburized screw will be quenched at high temperature, which can form a layer of crystals on the surface of the screw to achieve the final hardness requirements.
The fourth stage is to clean off the quenching oil from the surface of the screw.
The fifth link is low temperature tempering, which aims to reduce the core hardness of the screw. Because if the core hardness is too high, it will cause the screw to break, and after the low-temperature tempering of the screw will be more tough.
After the completion of the first five, the screws will generally be sent into the laboratory, after testing various parameters, will come to the last stop, surface treatment
surface treatment to alleviate the corrosion of the screw body to prevent the screw rust, extend the service life, but also to achieve aesthetic effects. Generally this step takes 1.5-2 hours, and finally according to the type of screws will be boxed factory, a small screw is born.
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