What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The drawing process has two purposes, one is to modify the size of the raw materials; the other is to obtain basic mechanical properties of the fasteners through deformation and strengthening. For medium carbon steel, medium carbon alloy steel also has another purpose, that is, to make the wire rod. The flaky cementite obtained after controlled cooling is cracked as much as possible during the drawing process to prepare for the subsequent spheroidization (softening) annealing to obtain granular cementite. However, some manufacturers arbitrarily reduce the drawing in order to reduce costs. The excessive reduction rate increases the work hardening tendency of the wire rod, which directly affects the cold heading performance of the wire rod. If the distribution of the reduction ratio of each pass is not appropriate, it will also cause torsional cracks in the wire rod during the drawing process. In addition, if the lubrication is not good during the drawing process, it can also cause regular transverse cracks in the cold drawn wire rod. The tangential direction of the wire rod and the wire drawing die is not concentric at the same time when the wire rod is rolled out of the die, which will cause the wear of the unilateral hole pattern of the wire drawing die to aggravate, make the inner hole out of round, and cause uneven drawing deformation in the circumferential direction of the wire. The roundness of the steel wire is out of tolerance, and the cross-sectional stress of the steel wire is not uniform during the cold heading process, which affects the cold heading pass rate. During the drawing process of the wire rod, the excessive surface reduction ratio will deteriorate the surface quality of the steel wire, while the too low surface reduction ratio is not conducive to the crushing of the flaky cementite, and it is difficult to obtain as much granular cementite as possible. , that is, the spheroidization rate of cementite is low, which is extremely unfavorable to the cold heading performance of the steel wire. For the bar and wire rod produced by the drawing method, the partial surface reduction rate is directly controlled within the range of 10%-15%.
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.
Contents of the utility model The purpose of Guangdong Yueluo Hardware Industry Co., Ltd. is to provide a hexagon socket head screw that is easy to disassemble and assemble. In order to achieve the above purpose, the technical scheme adopted by the present invention is as follows: a hexagon socket screw, which includes a cylindrical screw head and a cylindrical screw below the screw head, the screw is provided with threads, and an integrated screw is designed between the screw head and the screw. The circular skirt pad has a hexagonal depression along the axial direction on the screw head, and is characterized in that two symmetrical flat grooves are opened on the upper part of the side wall of the hexagonal depression of the screw head, and the lines of the two flat grooves overlap. Guangdong Yueluo Hardware Industry Co., Ltd.'s socket head screws are compared with ordinary socket head screws. A notch is designed in the inner hexagon space at the top of the screw. In terms of tool use, it can be avoided that the socket head screws must be equipped with the corresponding socket head tools. disadvantages. The improved hexagon socket screw can not only use the matching hexagon socket tool, but also use the traditional flat-blade screwdriver, which is more convenient to use.
Principles of stainless steel screw material selection: The selection of stainless steel materials is mainly considered from the following five aspects. 1. Requirements on mechanical properties, especially strength, of stainless steel screw materials; 2. Requirements on corrosion resistance of materials by working conditions; 3. Heat resistance of materials by working temperature (high temperature strength, oxidation resistance) 4. Requirements for material processing performance in terms of production technology; 5. Other aspects such as weight, price, procurement and many other factors must be considered.
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