Service HotlineIn the manufacture of fasteners, the correct selection of fastener materials is an important part, because the performance of fasteners is closely related to its materials. If the material is improperly or incorrectly selected, the performance may not meet the requirements, the service life may be shortened, or even accidents or processing difficulties may occur, and the manufacturing cost will be high. Therefore, the selection of fastener materials is a very important link. Cold heading steel is a steel for fasteners with high interchangeability produced by cold heading forming process. Because it is formed by metal plastic processing at room temperature, each part has a large amount of deformation and a high deformation speed. Therefore, the performance requirements of cold heading steel raw materials are very strict. On the basis of long-term production practice and user research, combined with GB/T6478-2001 Technical Conditions for Cold Heading and Cold Extrusion Steel GB/T699-1999 High-Quality Carbon Structural Steel and target JISG3507-1991 Cold Heading Characteristics of Carbon Steel Wire Rod for Steel, taking the material requirements of grade 8.8 and grade 9.8 bolts and screws as an example, the determination of various chemical elements. If the C content is too high, the cold formability will be reduced; if it is too low, the mechanical properties of the parts cannot be met, so it is set at 0.25% - 0.55%. Mn can improve the permeability of steel, but adding too much will strengthen the matrix structure and affect the cold forming performance; when the part is quenched and tempered, it has the tendency to promote the growth of austenite grains, so it should be appropriately improved on the basis of international standards. 0.45 % - 0.80 %. Si can strengthen the ferrite and reduce the cold formability. SP is an impurity element, and their existence will cause segregation along the grain boundary, resulting in the embrittlement of the grain boundary and damage to the mechanical properties of the steel. It should be reduced as much as possible. B. The maximum value of boron content is 0.005%, because although boron element can significantly improve the permeability of steel, it will also increase the brittleness of steel. Excessive boron content is very unfavorable for workpieces such as bolts, screws and studs that require good comprehensive mechanical properties.
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.
The screw is a fairly common structure in the technical field of machine parts assembly, and it mainly uses the mutual engagement characteristics of male and female threads to achieve the purpose of pressing the workpiece. At present, there are many kinds of screws on the market, and their functions are also very different. However, a stud and a rotating part by which the stud is rotated are the same basic structure.
A nut provided by Yueluo. The nut is in the shape of a sleeve and has a threaded section inside. An annular groove is set on the inner wall of one end of the threaded section. The notch of the groove points to the hole core. The hole diameter at the groove notch at the front end is larger than the nominal size of the thread segment or the hole diameter at the groove notch at the rear end in the screwing direction is smaller than the nominal size of the thread segment.
Material broadcast Cross recessed screws are made of iron and stainless steel. Iron cross recessed screws are also called carbon steel screws. Stainless steel cross recessed screws include stainless steel SUS201 and stainless steel SUS304, and stainless steel SUS316 cross recessed screws.
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