1. Introduction to embossing process and embossing process:
Imprinting and embossing processes are widely used on sheet metal parts, including label pasting position indication, product code, production date, version, manufacturer code, and even patterns. These two processes can be used for processing.
① Imprinting process
Embossing is to change the thickness of the material, fill the extruded material in the undulating mold cavity, and form undulating patterns or words on the parts.
Generally, it is carried out in a closed mold to prevent metal from being squeezed out of the mold cavity; For relatively large parts or parts with special shape, trimming can be carried out in the open die. To ensure good surface quality of parts, the blanks shall be annealed, pickled, sandblasted, etc. before forming.
② Embossing process
Embossing process is similar to embossing, except that the deformation depth is small and the pressure required is also small. Embossing method: when the depth h ≤ (0.3~0.4t), it shall be carried out on the smooth concave die; When the depth h>0.4t, it is carried out on the female die with the corresponding groove matched with the male die. The width of the female die is larger than that on the male die, and the depth is shallower than that on the male die.
2. Metal material:
SPCC: steel plate is generally used, and the surface needs electroplating or coating treatment.
SECC: galvanized steel plate, the surface has been subject to acid salt treatment and fingerprint prevention treatment.
SUS301: elastic stainless steel.
SUS304: stainless steel.
3.The chemical composition of the galvanized steel plate surface ------ base material (steel), zinc coating or nickel zinc alloy coating, soldering acid salt layer and organic chemical film layer.
The organic chemical film layer can resist fingerprint and white rust on the surface, resist corrosion and have better paint baking performance.
① Galvanizing method of SECC:
Hot dip galvanizing method: continuous galvanizing method, in which coiled steel plates are continuously immersed in the plating bath with zinc dissolved; With the sheet zinc plating method, the sheared steel plate is immersed in the plating tank, and there will be zinc flakes after plating.
Electroplating method: electrochemical electroplating, with zinc sulfate solution in the plating tank, zinc as the anode, and the original steel plate as the cathode.
② General problems of galvanized steel plate:
4. White rust --- white powdery rust with zinc hydroxide as the main component due to condensation or wetting by water. (will lead to product quality deterioration)
5. Red rust --- black tea powder like rust with ferric hydroxide as the main component due to condensation or wetting by water.
6. Uneven soldering acid --- yellow tea island shape or line shape pattern, but the corrosion resistance is no problem.
7. Alternative corrosion protection: when the zinc surface is cut and exposed to the surface of the steel plate substrate, we do not have to worry about the rust problem of the galvanized steel plate cutting edge.
③ Paint baking treatment of galvanized steel plate:
8. Pretreatment
As zinc is a highly active metal, proper chemical conversion treatment such as phosphate treatment is required before baking. There are two kinds of phosphate treatment agents, one for iron and the other for zinc.
9. Degrease
Use weak base, organic solvent, neutral lotion or detergent, and avoid acid or strong base degreaser. The water film test can be used to confirm whether the water after the test is polluted and whether the water film on the surface of the test object is uniform.
10. Baking varnish
The paint selectivity of galvanized steel sheet is stricter than that of cold-rolled steel sheet. The use of water primer can ensure strong paint adhesion.
