At this stage, there is still a big gap between my country's manufacturing and fasteners and the world's advanced level. The next 10 years will be a critical period for my country's manufacturing and fasteners to transform and upgrade, from a manufacturing power to a manufacturing power.
Compared with the current fastener market demand and foreign level, there is still a big gap, which is manifested in: few high-end varieties, low level, unstable quality, high early failure rate and poor reliability. In the imported technology, the drawings and material components can be provided to my country, but the heat treatment technology is strictly kept secret.
my country's national economic construction is entering a new stage of development, and infrastructure construction will develop to an advanced stage (super high-rise buildings, large-scale high-performance steel structure buildings, high-speed transportation networks, efficient transportation networks, efficient long-distance transmission pipelines, large ports and transportation hubs. etc.), and advanced manufacturing represented by large aircraft, large power generation equipment, automobiles, high-speed trains, large ships, and large complete sets of equipment will also enter an important development direction. As a result, fasteners will enter an important stage of development. The development history of developed countries shows that the use of high-strength fasteners will increase rapidly after fully entering the development stage dominated by advanced manufacturing. If fastener companies want to improve the technical level of their products, they must start from equipment improvement and technology improvement. Domestic host companies will not go to far to import. This is a favorable trend for fastener companies in the current situation.
Chinese fastener enterprises now have no new advantages, which is the bottleneck restricting the power of fasteners. Compared with the characteristics of most fastener companies in my country, they attach great importance to cold heading, cold extrusion and cold stamping technology. Engineers are proficient in mold design, often heavy cold processing and light heat treatment. Some enterprises rely on external heat treatment to ensure shipments. The quality of fasteners cannot be guaranteed. In the long run, relying on external processing will directly affect the innovation and development of fasteners.
However, at present, the importance of heat treatment has not received due attention in my country and some enterprises, and there is a lack of heat treatment content in relevant scientific research plans, development plans, project guidelines and discipline settings. This situation needs to be reversed urgently. At present, taking measures from different levels to promote the research on fastener heat treatment technology is of great significance for the realization of my country's transformation from a fastener manufacturing country to a fastener manufacturing power.
Fasteners play the role of connection, positioning and sealing in mechanical components, among which bolts are used the most. High-strength bolts have five performance levels, namely 8.8, 9.8, 10.9, 12..9 and 12..9. According to technical requirements, these 5 grades of bolts are subject to heat treatment. Heat treatment is to improve the comprehensive mechanical properties of the bolt to meet the specified tensile strength and yield ratio of the product; the selection of materials is the basis for quality assurance. Heat treatment technology is very important for high strength bolts, especially its intrinsic quality.
Heat treatment is a key technology to control the performance of fasteners, ensure safety, reliability and long life, and is the core element of the competitiveness of advanced materials and high-end machinery and equipment. For example, bolt steel is low and medium carbon structural steel and low alloy structural steel with a carbon content of 0.20% to 0.55%. The performance of a material is not simply determined by its composition. Heat treatment can greatly improve the performance of the material and give full play to the potential of the material.
Do a good job of heat treatment, and a few parts are topped. So far, 83 national and industrial standards for heat treatment have been promulgated and implemented in the professional field of heat treatment, and there are more than 10 standards to be submitted for approval. It is very necessary for the development of my country's fastener industry, which not only shows the importance of heat treatment to fasteners, but also reflects that the development of fasteners is also inseparable from heat treatment.
According to statistics, in the case of fastener failure, the reasons for material and heat treatment account for more than 80%. Although enterprises can produce according to GB/T3098.1-2010 standard, the yield strength ratio, surface decarburization, microstructure, and impact toughness are often omitted indicators in testing. Due to the obvious hidden quality problems, Causes plastic deformation or fatigue fracture under the stress of alternating load, and such items are closely related to the heat treatment process, that is to say, the anti-brittle fracture technology of fasteners is inseparable from heat treatment.
Impact toughness is the ability of fasteners to absorb energy during the plastic deformation and fracture process. It is the comprehensive performance of strength and plasticity. It is still an important research topic in domestic fasteners, while foreign heat treatment toughness technology is confidential and will never be leaked. . Therefore, the anti-brittle fracture technology of fasteners is the crystallization of wisdom and the core competitiveness of enterprises. Whoever has the anti-brittle fracture technology can upgrade its products, create a famous brand, and have the advantage of dividing up the automotive standard parts market. businesses create wealth. Therefore, the anti-brittle fracture technology is a new round of technology for fastener heat treatment and the cornerstone of the transformation and upgrading of the fastener industry.
The main failure mode of high-strength bolts is fatigue, which is characterized by sudden failure without significant deformation. The key to solving the problem of fatigue failure is heat treatment technology. Heat treatment not only imparts the ultimate performance of the material and the ultimate service performance of the high-strength bolt, but also provides a guarantee for the service of the high-strength bolt. Therefore, fastener heat treatment is very important.