Flange Nuts

Flange nuts and general hexagon nuts have the same size as screw threads, but compared with hexagon nuts, it is gaskets and nuts that are integrated. There is an anti-skid insection on the bottom, which increases surface area contacts of nuts and workpieces and is stronger than the combination of ordinary nuts and washers. Generally, the specifications of common flange nuts are generally below M20, because most of the flange nuts are used on pipes and flanges, so the specifications of flange nuts are less than those of nuts due to the constraints of the workpiece. Most of the flange nuts above M20 are flat flanges, that is, there is no insection on the flange surface. Most of these nuts are used in some special equipment and special places, and the general manufacturers do not have them in stock.
 
Because the flange nut is small and irregular and screw threads are required for some of them, there are some obvious defects in hot-dip galvanizing.
 
1. It is difficult to twist the screw thread after plating. After hot-dip galvanizing, the residual zinc stuck in the screw thread is not easy to remove, and the thickness of the zinc layer is uneven, which affects the fitness of the threaded parts. The external thread of the fastener should be processed or rolled according to the standard before hot-dip galvanizing, while the internal thread can be processed before or after hot-dip galvanizing. However, in practical applications, customers often require that both internal and external threads have a galvanized layer, so people use various measures to solve the problem of hot-dip galvanizing of threaded fittings, such as reserving a large fit clearance; centrifugal throwing and other methods. Deliberately increasing the nut diameter or reserving a fit clearance beyond the range can easily reduce the fit strength, which is not allowed for high-strength fitness.
 
2. The high operating temperature of hot-dip galvanizing will reduce the mechanical strength of high-strength flange nuts. After hot-dip galvanizing of grade 8.8 bolts, the strength of some threads is lower than the standard requirement; the strength of bolts above grade 9.8 after hot-dip galvanizing cannot meet the requirements.
 
3. The working environment is poor and the pollution is serious. The hot-dip galvanizing of fasteners is carried out at high temperatures. When the solvent is dried and the workpiece to be galvanized is dipped into the pool, strong irritating hydrogen gas will be precipitated; the zinc pool is kept at high temperatures for a long time, and the surface of the zinc pool will produce zinc vapor; the atmosphere of the whole working environment is bad. Although there are many defects in hot-dip galvanizing of fasteners, it has been highly praised in the departments of electric power, communication and transportation due to the thick coating of hot-dip galvanizing, good bonding strength and good long-term corrosion effect. With the great development of electric power and transportation in China, the development of hot-dip galvanizing of flange nuts will be promoted; therefore, it is necessary to develop automatic centrifugal throwing equipment, improve the hot-dip galvanizing of fasteners, and it is very important to improve the quality of hot-dip galvanized coatings of fasteners.

 

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