Material selection for sheet metal design
Sheet metal materials are the most commonly used materials in product structure design. Understanding the comprehensive properties of materials and knowing how to select materials correctly will have an important impact on product cost, product performance, product quality and processing technology. The main principles for selecting sheet metal materials are as follows:
- 1 Choose common metal materials and reduce the variety of material specifications;
- 2 In the same product, reduce the variety of materials and plate thickness specifications as much as possible;
- 3 On the premise of ensuring the function of the parts, try to use cheap materials to reduce material costs;
- 4 For cabinets and some large plug-in boxes, full consideration needs to be given to reducing the weight of the entire machine;
- 5 In addition to ensuring the function of the parts, it is also necessary to consider that the stamping performance of the material should meet the processing requirements.
🔧 Today, we will briefly introduce various commonly used materials in sheet metal processing.
(1) Cold rolled plate SPCC
SPCC refers to the continuous rolling of steel ingots into steel plate coils or sheets of required thickness through a cold rolling mill. There is no protection on the surface of SPCC. It is easily oxidized when exposed to the air. Especially in humid environments, the oxidation rate accelerates and dark red rust appears. The surface must be painted, electroplated or otherwise protected during use.
(2) Electro-galvanized steel sheet SECC
The base material of SECC is ordinary cold-rolled steel coils. After degreasing, pickling, electroplating and various post-processing processes in the continuous electro-galvanizing production line, it becomes an electro-galvanized product. SECC not only has the mechanical properties and similar processability of general cold-rolled steel sheets, but also has superior corrosion resistance and decorative appearance. It is highly competitive and substitutable in the markets of electronic products, home appliances and furniture. For example, SECC is commonly used in computer cases.
(3) Hot-dip galvanized steel sheet SGCC
SGCC hot-dip galvanized steel coil refers to a semi-finished product that is hot-rolled, pickled or cold-rolled. It is cleaned, annealed, and immersed in a molten zinc bath with a temperature of about 460°C to coat the steel sheet with a zinc layer. It is then tempered, leveled, and chemically treated. SGCC material is harder than SECC material, has poorer ductility (avoid deep drawing design), thicker zinc layer, and poorer weldability.
(4) Aluminum-zinc clad plate
The aluminum-zinc alloy coating of aluminum-zinc-clad panels is composed of 55% aluminum, 43.4% zinc and 1.6% silicon solidified at a high temperature of 600°C to form a dense quaternary crystal protective layer with excellent corrosion resistance. The normal service life can reach 25 years, which is 3-6 times longer than galvanized panels and equivalent to stainless steel. The corrosion resistance of aluminum-zinc clad panels comes from the barrier layer protection function of aluminum and the sacrificial protection function of zinc. When zinc provides sacrificial protection on trimmed edges, scratches and abraded parts of the plating, aluminum forms an insoluble oxide layer and exerts a barrier protection function.
(5) Stainless steel SUS304
SUS304 is one of the most widely used stainless steels. Because it contains Ni (nickel), it has better corrosion resistance and heat resistance than steel containing Cr (chromium). It has very good mechanical properties, no heat treatment hardening phenomenon, and no elasticity.
(6) Stainless steel SUS301
The content of Cr (chromium) is lower than that of SUS304, and its corrosion resistance is poor. However, after cold working, it can obtain good tensile strength and hardness in stamping processing, and has good elasticity. It is mostly used for springs and EMI prevention.
(7) Copper and copper alloy plates
There are two main types of commonly used copper and copper alloy plates, red copper T2 and brass H62, which are mainly made of conductive materials. The surface treatment is nickel plating, chromium plating or no treatment, which is costly.
Red copper T2 is the most commonly used pure copper, with a purple appearance, also known as red copper. It has high electrical conductivity, thermal conductivity, good corrosion resistance and formability, but its strength and hardness are much lower than brass, and the price is also very expensive. It is mainly used for electrical conductivity, thermal conductivity and corrosion components of durable consumer goods. It is generally used for parts in power supplies that need to carry large currents.
Brass H62 is a high-zinc brass with high strength and excellent cold and hot workability. It is easy to be used for various forms of pressure processing and cutting processing. It is mainly used for various deep drawing and bending stress-bearing parts. Its conductivity is not as good as that of copper, but it has better strength and hardness, and the price is relatively moderate. When meeting the conductive requirements, brass H62 should be used instead of copper as much as possible, which can greatly reduce material costs, such as busbars. At present, most of the conductive sheets of busbars are made of brass H62, which has been proven to fully meet the requirements.
(8) Aluminum plate
Aluminum plate is one of the most widely used and most economical materials. The current production and usage of aluminum (in terms of tons) is second only to steel, making it the second largest metal used by humans. Aluminum plates have been used in many industries due to their low density, light weight, corrosion resistance and other advantages.
The 5000 series aluminum alloy is mainly used for sheet metal structural parts. The 5000 series aluminum plate belongs to the more commonly used alloy aluminum plate series. The main other elements are magnesium. The magnesium content is between 3-5%, and it can also be called aluminum-magnesium alloy. The main features are: low density, high tensile strength and high elongation. The density is lower than other series of aluminum alloys. The processing technology is continuous casting and rolling, which belongs to the hot-rolled aluminum plate series. Mainly in my country, the 5000 series aluminum plate is one of the more mature aluminum plate series.
5052 is often used. It has good molding performance, corrosion resistance, weldability, fatigue strength and moderate static strength. It is used to manufacture aircraft oil pipes, fuel tanks and sheet metal parts of transportation vehicles and ships.
The 6000 series aluminum alloy is mainly used for machined parts. Unlike the 5000 series, the 6000 series alloy is added with silicon element, so that the hardness of the 6000 series aluminum alloy is greatly improved and the machining performance is very good. It is also suitable for applications with high requirements on corrosion resistance and oxidation resistance. Easy to layer, high strength and corrosion resistance. What I often use is 6061 aluminum alloy, which is used for machined parts and has good cutting performance (5000 series is not good).
The aluminum plate has a white luster and its surface is easily oxidized and corroded, so the surface is often covered with a PVC protective film.
Surface treatment: It can be sandblasted, brushed, or polished first, then anodized (non-conductive, can be dyed in various colors); chromate oxidation (also called conductive oxidation, available in primary color and golden yellow).