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ã€China Aluminum Industry Network】 (1) The preparation of scale zinc aluminum powder is divided into wet grinding and dry grinding. Wet grinding process shown in Figure 1, dry grinding process shown in Figure 2.
In the grinding process, the wet grinding method adds additives, stearic acid, and 2008 solvent gasoline to prevent zinc oxide from separating from the air in order to prevent oxidation of the zinc aluminum flakes. However, after grinding, the oil that is to be thoroughly cleaned is removed. The process problems, and the high oil content will seriously affect the quality of zinc-chromium coating, so the wet grinding method inherently has insurmountable defects.
At present, the world's more advanced technology and better quality scale zinc aluminum powder is the use of more advanced gas protection dry ball mill method, the metal powder is injected into the inert gas gas during ball milling to protect the gas phase to avoid oxidation of the zinc aluminum sheet. In addition, the metal powder does not contain oil after forming and does not require a degreasing process, thus ensuring the quality of the zinc aluminum sheet.
(2) Surface Modification of Zinc-Aluminum Flake When Grinding Because the metal powder has high activity, easy to agglomerate, affect the performance and quality of the powder, it needs to be dispersed, in addition to the need to change the properties of the metal powder and on the surface. The coating treatment is performed to achieve the purpose of preventing oxidation and corrosion, and the physical and chemical methods are used for surface treatment of the metal powder to purposely change the physical and chemical properties of the surface.
1 chemical method. When the metal powder is ground, a small amount of surface active agent, namely grinding aid, is added, and it can be adsorbed on the surface of the material particles, and the mechanical effect is produced through physical and chemical actions, so as to play the role of lubrication, surface wetting, and improvement of the powder. Dispersibility, improve its surface gloss and flatness, improve the durability of the powder.
2 physical law. With the effect of crushing mechanical forces, the effect of modification can be promoted. During the comminution process, a large amount of mechanical energy is applied, and in addition to being consumed in grain refinement, part of it is used to change the crystal lattice and surface properties of the particles, thereby exhibiting activity. Surface chemical modification and mechanical force modification will also promote crushing and grinding. It is of great significance to squash zinc aluminum powder crushing and sheeting.
(3) Typical process parameters of wet grinding method 1 The raw material is 200 mesh spherical zinc powder.
2 The total amount of ball and raw zinc powder accounts for 30% to 40% of the drum volume.
3 Grinding aid octadecanoic acid glycerin is added in an amount of 3% to 5% of the weight of the raw zinc powder.
It can be consolidated in the material, by its own thread, will be consolidated body [Drill-drill, extrusion,"out of the corresponding thread, make it close to each other.
Self tapping screw is a kind of screw with a drill bit, through the construction of special power tools, drilling, tapping, fixing, locking once completed. The self tapping screw is mainly used for the connection and fixing of some thin plate parts, such as the connection of Color Steel Plate and color steel plate, the connection of Color Steel Plate and Purlin, wall beam, etc. . Self-tapping Screws are often exposed to the outside world and have strong corrosion resistance of their own. The rubber sealing ring ensures that the screws are impervious to water and have good corrosion resistance.
Self tapping screws are usually described by three parameters: screw diameter series, number of threads per inch and screw length. There are 10 and 12 grades of screw diameter, the corresponding screw diameter is 4.87 mm and 5.43 mm, and the number of threads per inch is 14,16 and 24 grades. The more threads per inch, the stronger the self-drilling ability.
Tapping screws, self drilling screws,non metallic or softer metal
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