What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The process of removing iron oxide plate from cold heading steel wire rod is stripping and dephosphorization. There are two methods: mechanical dephosphorization and chemical pickling. Replacing the chemical pickling process of wire rod with mechanical phosphorus removal not only improves productivity, but also reduces environmental pollution. This phosphorus removal process includes bending method (the round wheel with triangular grooves is commonly used to repeatedly bend the wire rod), spray nine method, etc. The phosphorus removal effect is good, but the residual iron and phosphorus cannot be removed (the removal rate of iron oxide scale is 97%) ), especially when the iron oxide scale is very sticky, therefore, mechanical phosphorus removal is affected by iron scale thickness, structure and stress state. Carbon steel wire rods used for low strength fasteners (less than or equal to 6.8) High-strength bolts (greater than or equal to grade 8.8) use wire rods to remove all iron oxide scales after mechanical dephosphorization, and then go through a chemical pickling process for compound dephosphorization. For low carbon steel wire rods, the iron sheets left by mechanical dephosphorization are likely to cause uneven wear of grain draft. When the grain draft hole adheres to the iron sheet when the wire rod rubs against the external temperature, the surface of the wire rod produces longitudinal grain marks. More than 95% are caused by scratches on the surface of the steel wire during the drawing process. Therefore, the mechanical phosphorus removal method is not suitable for high-speed drawing.
Supporting T-bolts for pre-embedded channels, including hot-rolled pre-embedded channels, the lower part of the pre-embedded channel is provided with a longitudinal opening, and the head of the T-bolt enters from the opening and is clamped in the pre-embedded channel. There are plane teeth at the connection between the buried channel and the T-bolt, and the T-bolt has a tooth-shaped structure matched with the plane teeth. The direction of the teeth is parallel to the slotting direction, and the tooth-shaped cooperation achieves anti-slip effect. However, when the nut tightened on the T-bolt becomes loose, it will cause the T-bolt to move into the embedded channel and lose the toothed fit, thus changing the fixed position of the T-bolt in the embedded channel.
The process factors that affect the quality of high-strength fasteners include steel design, spheroidizing annealing, peeling and dephosphorization, drawing, cold heading, thread processing, heat treatment, etc., and sometimes the superposition of various factors.
Fasteners are a class of mechanical parts that are used for fastening connections and are widely used. It is used in a wide range of industries, including energy, electronics, electrical appliances, machinery, chemical industry, metallurgy, mold, hydraulic and other industries, in various machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, instruments, chemicals, instruments And supplies, etc., you can see all kinds of fasteners, which are widely used mechanical basic parts. In the fields of listed rails, construction machinery, etc., due to the harsh application environment, the requirements for fasteners are more stringent. If the fasteners are loosened, it may lead to serious consequences, resulting in a large amount of property damage, even serious life cost.
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