Pan head screws in accuracy classes A and B (elevated and normal) produced according to the requirements of the standard with a diameter of one to twenty millimeters. Screw GOST 17473-80 has two versions - with a straight and cross recess.
screws with a cross slot provides the best alignment of the axes of the mounting holes, screw, screwdrivers, which guarantees high quality connections, its strength and reliability.
Screws GOST 17473-80 have found their application for connecting individual elements to metal structures, in which the mounting holes are not through, and the deaf. During installation, the products can be equipped with spring, flat or lock washers.
Protective coatings are applied to the fasteners to harden the surface of the hardware and increase the service life of the joints..
In the process of galvanizing, low-grade coating, subject to destruction, acting as an anode, while the screw body retains its structure, being the cathode.
Modern production uses several methods to protect hardware from corrosion.:
- galvanizing;
- oxidation;
- phosphating.
In the galvanizing process, the steel surface is covered with a layer of zinc by one of two methods - hot galvanizing and cold galvanizing. (electrolytic).
In the hot dip galvanizing process, products are immersed in a bath of molten zinc., whose temperature can reach 48000FROM. When using this method, the applied layer has an uneven thickness, which has a direct impact on build quality. The cold galvanizing method reduces zinc consumption and improves the quality of the coating. The result is an even layer., thick 35 m.
To strengthen the zinc film and prevent its loosening, the products are passivated in solutions of zinc and chromic acid., which reliably protects against mechanical damage.
During the oxidation process, the products are immersed in a solution, and under the influence of high temperatures, their surface is covered with oxide films. Upon completion of the process, the hardware is additionally coated with grease or mineral oil..
Phosphating process provides products with high corrosion resistance, antistatic, adhesive and anti-friction properties. This is achieved thanks to, that iron phosphate is not oxidized.
The quality of the coating depends on the size of the crystal lattice of the film - the more reliable the connection, the stronger it is.
