At present, China is the world's largest producer of fasteners, but it has been facing claims due to quality issues. Among them, a large proportion of cases of quality problems in fastener products due to poor steel quality. China's fastener steel still needs to expand production on the premise of meeting strict quality standards.
In recent years, Chinese fastener companies have been sued by customers for product quality, and in these incidents, it is largely due to the poor use of fastener steel.
At present, there are roughly over 40000 types and millions of sizes of fasteners both domestically and internationally. Their usage occasions and environments are ever-changing. Fasteners, as connectors for the host and components, together with the host, bear various requirements for the basic performance of the main body and the basic functions of the components.
Tested together with the host in various harsh service environments. There are various occasions such as high temperature, high pressure, low temperature, vibration, corrosion, heavy load, alternating stress, shear and torsion resistance. For example, the fasteners used for connecting certain parts of spacecraft must first withstand the tests of high temperature, high pressure, and vibration, and then undergo the tests of preventing pre tightening failure under sudden temperature changes, low temperature, and weightlessness conditions after entering orbit. The probability of accidents or disasters caused by the failure and damage of fasteners is very high. So the materials used for manufacturing fasteners must be carefully selected in advance. Currently, commonly used materials include titanium alloy, steel, copper, aluminum, nylon, and other metallic and non-metallic materials.
The steel used for fasteners (including alloy steel, low alloy steel, and carbon steel) has excellent toughness and plasticity, which determines its adaptability to various processing processes and also has good strength. Especially after specific heat treatment, it can achieve the expected better comprehensive mechanical properties.
Steel (wire or bar) is a finished product for the steel factory, and it cannot be fully inspected before leaving the factory. Moreover, some are still destructive test items, and factory inspection can only be spot checks. For fastener manufacturers, it is the production of raw materials, and when using these materials to manufacture fasteners, it is equivalent to 100% inspection of the materials. Users in certain specific situations now require fastener manufacturers to provide "zero defect" fastener products. Therefore, in addition to strict quality control of various processes implemented by manufacturers during the production process, careful and scientific inspection of various quality indicators is carried out before leaving the factory. The quality of the selected raw materials plays a decisive role in the final quality of the fastener product.
Many performance and quality indicators of fasteners are provided by the base material. Even for the generally required quantity of commodity fasteners, due to the application of advanced technologies such as high-speed cold heading and fully automatic continuous heat treatment production lines, there are also high requirements for the hardness of raw material cold heading wire rods, the mass fraction of chemical composition, and the uniformity of raw material strip performance.
