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Zinc Plated half thread Mushroom Head Square Neck Carriage Bolt DIN603,M 6 /8
Diameter range (mm)：M5-M24，3/16-1'Length range (mm)：16-600，1''-2'
The friction coefficient control of electrogalvanized high toughness galvanized bolts should be carried out from two levels: the control of bolt body characteristics and the control of the whole process of tightening.
According to the different diameter, pitch diameter, compressive strength level, passivation layer, galvanized thickness and surface treatment of the connecting piece, the bolt tightening experiment is comprehensively carried out to obtain the friction coefficient range under different loads. In order to better set the detection scope of friction coefficient and control the consistency of bolt friction coefficient, different bolts do not use friction coefficient to fine manage and set torque.
For the control of the bolt body, among many factors, the passivation layer has a greater impact on the friction coefficient of the bolt. The reliability of controlling the passivation layer to improve the friction coefficient of high toughness galvanized bolts is also the most significant. It is very difficult to accurately control the galvanized coating.
At the same time, the passivation solution is the final solution of the bolt surface. In the whole process, if only the thickness of the passivation layer is controlled, it is difficult to control the passivation layer. To some extent, controlling the thickness of the passivation layer can fill the gap of the electroplating process layer. Therefore, the friction coefficient control of galvanized bolts should focus on the passivation solution, which can directly affect the accuracy of control. Size of friction coefficient.
According to the technicality that can be used at this stage, the friction coefficient of high toughness galvanized bolts solved by Grade C chromate is very different from that of electrogalvanized high toughness bolts solved by Grade D chromate. However, the range of friction coefficient of the same electrogalvanized high toughness bolts solved by chromate is relatively stable, and the range of friction coefficient of bolts solved by different chromates does not cross.
The coefficient of friction of galvanized bolts with Grade C chromate solution is 0.28 to 0.36, and the coefficient of friction of galvanized bolts with Grade D chromate solution is 0.18 to 0.25. Therefore, there is no difference in the passivation layer of galvanized high toughness bolts at this stage. It is unreasonable to use the same torque to tighten the bolts with Grade C chromate and Grade D chromate, and it is also very bad to control the preload.
