The needle is reciprocating at high speed in the fiber web layer, and the frequency is usually between 600 and 2000 times/min. This requires the rigidity, toughness, elasticity and wear resistance of the needle body to be good. For different fiber weights, fiber sizes, and the use of various nonwovens, needle molding and heat treatment properties are also required. For example, if a synthetic leather base fabric is produced, the needle cannot be broken; and the needle for the needle-punched nonwoven fabric is generally required to be broken and not bendable. The broken needle is not required to break in the hook teeth to avoid damaging the surface of the fabric. Therefore, for different requirements of the needle, it is necessary to use different heat treatment processes to achieve the appropriate hardness and rigidity to meet the needs of production. Typical needle hardness: between HV600 - 680. The angle of the break should be different depending on the size of the needle: 20 or more needles, the break angle should be about 20°; the 22- 30 needle, the break angle 45°-65° is appropriate; the 32-36 needle break angle is 65 °-80° is suitable; the 38-42 needle break angle should be 80°-90°, or more than 90°. Nitriding treatment on the surface of the needle body can enhance the surface hardness, and the HRC can reach 63-65, which greatly enhances the wear resistance of the needle body and prolongs the service life.
The metallographic structure of the needle is an important indicator of the quality of the needle. Many domestic needle manufacturers, because the heat treatment process is not closed, the needle is not too brittle or too soft, no use value. Cheap purchases will seriously affect the quality of non-woven fabrics. Metallographic structure is best for tempered crypto-like martensite and small particle carbide.
The needles produced by Weston have no decarburization layer. Its mechanical properties are tough, wear-resistant, long service life and good needle toughness. Curved handle, tough and continuous. Computerized automatic vacuum nitriding heat treatment. Improve the surface hardness of the needle and enhance the wear resistance, the user reflects well.
