1. Cold rolled plate, grade SPCC. The most basic sheet metal material is widely used. It is used as a substrate for other materials and is more likely to rust.


2. Electro-galvanized sheet, grade SECC, is widely used for cold-plated substrate electroplating, which is the result of chemical reaction.


3. Hot-dip galvanized sheet, grade SGCC, is widely used. It is a product obtained by using a cold plate as a substrate to be heated in a molten zinc solution to form a zinc layer. The production process belongs to a physical change process.


4. Hot-rolled plate, grade SPHC, belongs to the low-end material and is easy to rust. The thickness is thicker and generally more than 3mm. Usually used as a hinge product.


5.SD steel plate is a plate with excellent rust and corrosion resistance. This material is used for the mounting bracket of the air conditioner outdoor unit.


6. Stainless steel and stainless steel, stainless steel shell processing typical grades SUS304 and SUS430, belonging to alloy materials. It has good rust and corrosion resistance and a beautiful surface. Usually used to make appearance parts, such as the door of the refrigerator and the cooktop of the gas stove.


7. Aluminized zinc plate, which seems to belong to a kind of electro-galvanized plate, but has a metal aluminum element than the electro-galvanized plate, so the surface is relatively smooth and beautiful, and is often used to make appearance parts, such as the back plate of a certain type of refrigerator.


8. Aluminum or aluminum alloy plates, also known as aluminum sheets. Low density and anti-corrosion, typical products: refrigerator water tray and evaporator fins.


2. The price of sheet metal materials


price comparison:


In the case of the same thickness:


Hot rolled sheet<Cold rolled sheet<Hot zinc plate<Electric zinc plate<SD steel plate<v<stainless steel


The same material, the greater the thickness, the lower the processing price of the sheet metal shell.


Among the cost of sheet metal parts, material costs account for 60-70%, sometimes higher.


Therefore, it is necessary to design a reasonable structure. It is also necessary to improve the material utilization rate. If the material utilization rate is low, it may happen that the product price is lower than the scrap price.


Third, the purpose of steel surface treatment  


Since some sheet metal materials do not have rust and corrosion resistance, they are subjected to surface treatment to achieve the purpose.


There are two main types of surface treatment:


1. Improve the service life of the product in harsh environments.


Refers to: rust and corrosion resistance.


2. To get the desired surface effect or function.


Refers to: to meet the appearance requirements of the product.


4. Surface treatment process commonly used for steel plates


Electroplated zinc
: It is the process of forming a uniform, dense, well-bonded metal or alloy deposit on the surface of the part by electrolysis.


Compared to other metals, zinc is a relatively inexpensive and easily plateable metal that is a low value corrosion resistant plating. It is widely used to protect steel parts, especially to prevent atmospheric corrosion, and is used for decoration. Plating techniques include slot plating (or rack plating), barrel plating (for small parts), automatic plating and continuous plating (for wire and strip).


Domestic classification by electroplating solution can be divided into four categories:


Cyanide galvanizing


Since (CN) is highly toxic, environmental protection imposes strict restrictions on the use of cyanide in electroplating zinc, and continuously promotes the development of cyanide and substituted cyanide electroplating zinc plating system, requiring the use of low cyanide (microcyanide) plating solution. . After electroplating with this process, the product quality is good, especially for color plating, and the color is kept good after passivation.


Zinc galvanizing


This process is derived from the cyanide galvanizing. At present, there are two major factions in China, namely: a) "DPE" series of Wuhan Material Protection Institute; b) "DE" series of broadcasting and television institutes. Zinc galvanizing, which is an alkaline additive; pH is 12.5~13. With this process, the plating lattice structure is columnar and has good corrosion resistance and is suitable for color galvanizing.


Chloride galvanizing


This process is widely used in the electroplating industry, accounting for up to 40%. After passivation (blue) can be zinc-chromic (comparable to chrome), especially after the addition of water-soluble varnish, it is difficult for laymen to identify whether it is galvanized or chrome-plated. This process is suitable for white passivation (blue, silver).


Sulfate zinc plating


 
This process is suitable for continuous plating (wire, strip, simple, coarse and large zero, parts). low cost.


The electro-galvanizing industry belongs to the polluting industry. Although it is widely used and low in cost, electro-galvanized products do not meet ROHS standards, so electroplating products should not be used in product design.


1. Chrome plating:The process principle is the same as galvanizing.


Compared with traditional electro-galvanizing: chrome coating has strong corrosion resistance, 7-10 times of galvanizing, and the surface is beautiful, but the cost is high.


At present, the most advanced chrome plating process is called DACROMET. The Chinese name is Dakoro. It is a revolutionary high-tech metal surface treatment process with no pollution.


2.Dusting
: The powder is polarized and uniformly attached to the surface of the opposite polarity product under the action of the electric field force. Belongs to physical changes.


Principle of dusting process:


Electrostatic powder spraying: mainly by polarizing the coating (powder) through the electrode, and then carrying the opposite charge on the object to be sprayed, and the powder uniformly adheres to the surface of the object under the action of the electric field force.


Characteristics of the dusting process:


Powder electrostatic spraying will not cause atmospheric pollution. The powder can be recycled to reduce the cost of material consumption. The coating film has superior acid resistance, alkali resistance, salt corrosion resistance and high adhesion.


3. Electrophoresis: Electrophoretic coating under the action of the yin and yang electrodes, the charged coating ions move to the surface of the product and deposit to form a coating. Belongs to chemical changes.


The principle of electrophoresis:


The electrophoretic coating is applied to the electrodes at the yin and yang electrodes, and the charged coating ions move to the cathode and form an insoluble matter with the alkaline action generated on the surface of the cathode to deposit on the surface of the workpiece. 


Characteristics of electrophoretic surface treatment process:


The electrophoretic paint film has the advantages of fullness, uniformity, smoothness and smoothness of the coating. The hardness, adhesion, corrosion resistance, impact performance and permeability of the electrophoretic paint film are obviously superior to other coating processes.


Common electrophoresis colors are mostly black, and other colors are also available.


4. DipThe product is heated in a molten material, and the heated metal is combined with the surrounding molten material to form a surface material having a certain thickness. Belongs to physical changes.


Process principle of dip:


Metal dip coating is a new type of technical treatment process for metal surface anti-corrosion. Dipping is a heating process, metal preheating, dip coating and solidification. During dipping, the heated metal sticks to the surrounding material. The hotter the metal, the longer the dipping time and the thicker the material.


Process characteristics of dip:


Wide range of applications: rich in color, good protection, excellent cold insulation and acid and alkali resistance.



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