Metal sheet fabrication is called sheet metal fabrication. For instance, when making chimneys, iron buckets, oil tanks and oil cans, ventilation ducts, elbows, reducers, round tops and square bottoms, funnel-shaped structures, etc. from sheet materials, the main processes include shearing, bending and flanging, bending and forming, welding, riveting, etc., which require certain geometric knowledge. Sheet metal parts are thin plate hardware parts, which can be processed by stamping, bending, stretching, etc. A general definition is that they are parts whose thickness remains unchanged during the processing. Correspondingly, there are castings, forged parts, machined parts, etc.
Material selection
The materials commonly used in sheet metal processing include cold-rolled sheets (SPCC), hot-rolled sheets (SHCC), galvanized sheets (SECC, SGCC), copper (CU), brass, red copper, beryllium copper, aluminum sheets (6061, 5052, 1010, 1060, 6063, hard aluminum, etc.), aluminum profiles, and stainless steel (mirror finish, brushed finish, matte finish). Depending on the different functions of the product, other materials are selected. Generally, it is necessary to consider the product's application and cost.
(1) Cold-rolled sheet SPCC, mainly used for electroplated and painted parts, has low cost, is easy to form, and the material thickness is ≤3.2mm.
(2) Hot-rolled sheet SHCC, with material T≥3.0mm, is also used for electroplating and baking varnish parts. It has a low cost but is difficult to form and is mainly used for flat parts.
(3) Galvanized sheets SECC and SGCC. SECC electrolytic plates are divided into N material and P material. N material is mainly not surface-treated and has a high cost, while P material is used for spray-painted parts.
(4) Copper The main conductive material is used, and its surface treatment is nickel plating, chromium plating, or no treatment at all, which is costly.
(5) Aluminum plate: Generally, surface chromate (J11-A) is used for oxidation (conductive oxidation, chemical oxidation), which is costly. Silver and nickel plating are options.
(6) Aluminium profiles. Materials with complex cross-sectional structures are widely used in various types of boxes. The surface treatment is the same as that of aluminum plates.
(7) Stainless steel. It is mainly used without any surface treatment and has a high cost.
Common materials
Galvanized steel sheet SECC
The base material of SECC is common cold-rolled steel coil. After going through degreasing, pickling, electroplating, and various post-treatment processes on the continuous electro-galvanizing production line, it becomes an electro-galvanized product. SECC not only possesses the mechanical properties and similar processability of general cold-rolled steel sheets, but also has superior corrosion resistance and decorative appearance. It has great competitiveness and substitutability in the markets of electronic products, household appliances, and furniture. For example, SECC is commonly used in computer cases.
Ordinary cold-rolled sheet SPCC
SPCC refers to the continuous rolling of steel ingots through a cold rolling mill into steel sheet coils or sheets of the required thickness. The surface of SPCC has no protection at all. It is extremely prone to oxidation when exposed to the air, especially in a humid environment, where the oxidation rate accelerates, resulting in dark red rust. When in use, the surface should be painted, electroplated, or otherwise protected.
Hot-dip galvanized steel sheet SGCC
Hot-dip galvanized steel coil refers to the semi-finished products after hot-rolled pickling or cold rolling, which are cleaned and annealed, then immersed in a molten zinc bath at about 460°C to coat the steel sheet with a zinc layer, and finally undergo quenching and tempering, leveling, and chemical treatment. SGCC material is harder than SECC material, has poorer ductility (avoid deep drawing design), a thicker zinc coating, and poorer weldability.
Stainless steel SUS304
One of the most widely used stainless steels, due to its Ni (nickel) content, is more corrosion-resistant and heat-resistant than steel containing Cr (chromium), and has excellent mechanical properties. There is no hardening phenomenon after heat treatment, and it has no elasticity.
Stainless steel SUS301
The content of Cr (chromium) is lower than that of SUS304, and its corrosion resistance is relatively poor. However, after cold working, it can achieve excellent tensile strength and hardness in stamping processing, with good elasticity. It is mostly used in spring sheets, springs, and EMI protection.