At this stage, there is still a big gap between China's manufacturing industry and fasteners and the world's advanced level. The next 10 years will be a crucial period for China's manufacturing and fastener transformation and upgrading, from manufacturing to manufacturing countries.
Compared with the foreign level, there are still many gaps in the current fastener market demand. The specific performance is: low-end varieties, low levels, unstable quality, high early failure rate and poor reliability. In the introduction of technology, drawings and material components can be provided to China, but the heat treatment technology is strictly confidential. On the one hand, it lacks the support of national standards, on the other hand, the design specifications are almost harsh according to the requirements of foreign standards.
China's national economic construction is entering a new stage of development, infrastructure construction will be advanced to advanced stages (super high-rise buildings, large-scale high-performance steel structures, high-speed transportation networks, efficient transportation networks, efficient long-distance transportation pipelines, large ports and transportation hubs) Etc.), and advanced manufacturing represented by large aircraft, large-scale power generation equipment, automobiles, high-speed trains, large ships, and large-scale complete sets of equipment will also enter an important development direction. As a result, the 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. In order to improve the technical level of products, fastener enterprises must start with equipment improvement and technology improvement. Domestic host enterprises will not go far to import, which is a favorable trend of fastener enterprises in the current situation.
China's fastener companies now have no new advantages, and are the bottleneck restricting the fastener industry. In China, most of the characteristics of fastener enterprises, the importance of cold heading, cold extrusion, cold punching technology, engineers are proficient in mold design, often heavy cold processing, light heat treatment, some companies rely on external heat treatment to ensure shipment. The quality of fasteners cannot be guaranteed. In the long run, relying on external processing directly affects the innovation and development of fasteners.
However, the importance of heat treatment in China and some enterprises are not given due attention. In the relevant scientific research plans, development plans, project guidelines and subject setting, or lack of heat treatment, this situation needs to be reversed. At present, taking measures from different levels to promote the research of fastener heat treatment technology is of great significance for realizing the transformation of China from a fastener manufacturing country to a fastener manufacturing power.
The fasteners play a role in coupling, positioning and sealing in the mechanical components, wherein the bolts are used in the largest amount. The high-strength bolts have five performance grades, namely 8.8, 9.8, 10.9, 12..9 and 12..9. According to the technical requirements, these five grade bolts are heat treated. Heat treatment is to improve the overall mechanical properties of the bolt to meet the tensile strength and yield ratio specified by the product; the selection of materials is the basis for quality. Heat treatment technology is critical to high strength bolts, especially their inherent quality.
Heat treatment is the key technology to control fastener performance, ensure safety and reliability, and long life. It is the core element of the competitiveness of advanced materials and high-end machinery equipment. For example, bolt steel is a low-carbon, medium-carbon structural steel and a low-alloy structural steel with a carbon content of 0.20% to 0.55%. The performance of the material does not depend solely on its composition. The 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, a few parts. To date, the heat treatment profession has issued 83 national and industry standards for heat treatment, and more than 10 standards are pending approval. It is very necessary for the development of China's fastener industry, which not only shows the importance of heat treatment for fasteners, but also reflects the development of fasteners.
According to statistics, in the case of fastener failure, the cause of materials and heat treatment accounted for more than 80%. Although enterprises can produce according to GB/T3098.1-2010 standard, but the yield ratio, surface desorption, carbon addition, microstructure, impact toughness are often omitted indicators in the test, due to the existence of obvious quality hazards, It causes plastic deformation or fatigue fracture under the stress of alternating load, and such project and heat treatment process are closely related, that is to say, the anti-brittle technology of fasteners is inseparable from heat treatment.
Impact toughness is the ability of plastics to absorb energy during the whole process of plastic deformation and fracture. It is a 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 never leaks. . Therefore, the anti-brittle technology of fasteners is the crystallization of wisdom, and it is the core competitiveness of enterprises. Whoever has anti-brittle technology, its products can be upgraded, creating famous brands, and it has the advantage of car market standard parts for itself. The company creates wealth. Therefore, the anti-brittle technology is a new round of technology for fastener heat treatment, and is 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 fatigue failure problem is heat treatment technology. Heat treatment not only gives the material ultimate performance and endurance performance of high-strength bolts, but also guarantees the service of high-strength bolts. Therefore, heat treatment of fasteners is very important.
A technical seminar on the relationship between heat treatment process and metallographic inspection technology will be held at the Golden Spider Hangzhou Training Center, June 27-28, 2014. Why are some types of fasteners prone to early failure? Why is the cause of fastener damage not always as clear as we assumed? At the technical level, heat treatment technology and metallographic inspection, what can be done to reduce the liability claims brought by this? Zhang Zhangming, senior engineer, Zhang Gong has long been engaged in metal materials and metallurgical heat treatment processes in state-owned enterprises and private enterprises; He is good at the technical work of mechanical basic parts such as fasteners, has rich experience in heat treatment field, has certain unique views on the development and application of new materials and new processes, and has published more than 250 papers in national and provincial professional magazines. The achievement won the third prize of provincial technical achievements, and is a special consultant expert of Golden Spider Fastener Network.
Seminar content: relationship between heat treatment process and metallographic inspection technology
I. Annealing treatment of cold wire
1. Study on softening of cold-rolled wire rods 2. Structure, spheroidizing annealing and heat treatment relationship 3. Differences and processes of softening annealing, spheroidizing annealing and isothermal annealingSecond, the basis of metal materials and metal heat treatment process
1. Quenching temperature selection of medium and low carbon steel 2. Different points of heating of low alloy steel and carbon steelThird, the tempering heat treatment of fasteners
1. The importance of heat treatment of fasteners 2. The key to the tempering process for fasteners 3. New progress in hydrogen embrittlement researchFourth, quenched and tempered metallographic examination
1. Quenching and tempering organization rating chart and evaluation method 2. Identification of microstructureFifth, interpret the latest metallographic inspection standards for fasteners
1. New revision GB/T 13298-201X "Metal Microstructure Inspection Method"
2, the latest national standard GB/T226-201X "steel low-magnification structure and defect acid etching test method"
3, the latest national standard GB/T3098.2-201X "fastener mechanical performance nut" new standard will be released, emphasizing that the material requirements of grade 8 and above should have sufficient hardenability to ensure fastener thread The core of the cross section obtained about 90% of the martensite structure in the hardened state and before tempering.Sixth, the failure form and reasons of fasteners
1. The main form of failure 2. The form and judgment of micro-fracture 3. The cause of fastener failure 4. The relationship between electrolytic zinc plating and trivalent chromium passivationSeven, several cases of high-strength bolt breaks
(Golden Spider "Fasteners" quarterly editorial department)
relevant information:
Highly competitive energy-saving products in the heat treatment equipment industry may become a profit growth point
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