Before explaining the types of sheet metal, let us first understand what is sheet metal?
What Is Sheet Metal?
Sheet metal is a processing technology and has not yet had a relatively complete definition.
According to a definition in a professional journal, it can be defined as:
Sheet metal is a comprehensive cold working process for metal sheets (usually below 6mm), including shearing, punching/cutting/, folding, riveting, splicing, forming (such as car body) etc.
Its remarkable feature is the same thickness of the same part.
Types of Sheet Metal
Commonly used sheet metal materials can be divided into two categories, which are:
- Galvanized steel
- Stainless steel
Galvanized steel can be mainly divided into:
- Electro-galvanized sheet
- Hot-dipped metallic-coated sheet
Let’s compare the above two galvanized sheets of steel through a table.
|Electro-galvanized sheet (EG/SECC)||Hot-dipped metallic-coated sheet (GI)|
|Base metal||Cold rolled annealed steel||Cold rolled hard steel plate|
|Zinc plating||Hard plating for thick||Hard plating for thin|
|Plating surface||The zinc layer is adsorbed on the surface of the steel, and the surface is smooth and free of zinc spangle.||Solidified structure of zinc layer, may have zinc spangle or not.|
|Plating organization||Pure zinc coating||The outermost layer is pure zinc and the inner layer is iron-zinc alloy.|
|Mechanical performance||Same as the base metal||After annealing, it has age hardening; the material is soft.|
|Max material thickness||Common material thickness can be seen||0.6-1.5mm|
|Corrosion resistance||Thin coating, poor||The plating is thick and good. Can be added with anti-fingerprint coating|
It is a general term for stainless acid resistant steel which resistance to atmospheric, acid, alkali, salt and other media corrosion
To achieve stainless corrosion resistance, the amount of chromium (Cr) should not less than 13%;
In addition, nickel (Ni) or molybdenum (Mo) may be added to increase the effect.
Due to the different types and contents of alloys, there are many types.
Stainless steel features
Good corrosion resistance, good brightness, high strength; with a certain elasticity; expensive.
Stainless steel material properties
Ferritic stainless steel
It has a high content of Cr and has good properties and high-temperature oxidation resistance.
Austenitic stainless steel
Typical grades like Cr18Ni9 and Cr18Ni9T1.
Non-magnetic, good corrosion resistance, good temperature strength and high-temperature oxidation resistance, good plasticity, good impact toughness, no gap effect, excellent weldability, and therefore widely used.
Such steels generally have low strength, low yield strength, and cannot be strengthened by heat treatment. But after cold pressing, the tensile strength is high and the elasticity is improved.
However, its strength obtained by cold drawing at high temperatures is easily weakened and should not be used to withstand high loads.
Martensitic stainless steel
Typical grades like 2Cr13 and GX-8.
With magnetic property; has excellent shock absorption and good thermal conductivity; has high strength and yield limit. After heat treatment and strengthening, it has good comprehensive mechanical properties.
Because of the high carbon content, it needs to be tempered after welding to eliminate stress.
It’s mainly used for load-carrying parts.
Characteristics of sheet metal
Sheet metal has the characteristics of light weight, high strength, conductive (can be used for electromagnetic shielding), low cost, and good mass production performance.
It has been widely used in the fields of electronic appliances, communications, automobile industry, medical devices, etc.
For example, in computer cases, mobile phones, MP3, sheet metal is an indispensable component.
With the more and more extensive application of sheet metal, the design of sheet metal parts has become a very important part in the process of product development.
Mechanical engineers must master the design skills of sheet metal parts, so that the designed sheet metal can not only meet the requirements of product function and appearance, but also make the stamping die manufacturing simple and low-cost.
Main applications of sheet metal
There are many sheet metal materials suitable for stamping processing.
Sheet metal materials widely used in the electronic and electrical industry include:
- Ordinary cold rolled sheet (SPCC)
SPCC refers to the continuous rolling of steel ingots into steel coils or sheets of required thickness by cold rolling mill.
The surface of SPCC is not protected.
It is easy to be oxidized when exposed to the air.
Especially in the humid environment, the oxidation speed is accelerated and dark red rust appears.
The surface shall be painted, plated or otherwise protected during use.
- Galvanized steel plate SECC
The base material of SECC is general cold-rolled steel coil.
After degreasing, pickling, electroplating and various post-treatment processes in the continuous electro galvanized production line, it becomes an electro galvanized product.
SECC not only has the mechanical properties and similar processability of general cold rolled steel sheet, but also has excellent corrosion resistance and decorative appearance.
It is highly competitive and substitutable in the market of electronic products, household appliances and furniture.
For example, SECC is commonly used in computer chassis.
- Hot dip galvanized steel plate (SGCC)
Hot dip galvanized steel coil refers to the semi-finished products after hot-rolled pickling or cold rolling, which are washed and annealed, immersed in the molten zinc bath at a temperature of about 460 ° C, and then plated with zinc layer, and then subjected to tempering, leveling and chemical treatment.
SGCC material is harder than SECC material, with poor ductility (avoid deep drawing design), thicker zinc layer and poor weldability.
- Stainless steel SUS301
The content of Cr (chromium) is lower than that of SUS304, and the corrosion resistance is poor.
However, good tensile force and hardness can be obtained after cold processing, and the elasticity is good.
It is mainly used for elastic spring and anti EMI.
- Stainless steel SUS304
It is one of the most widely used stainless steels.
Because it contains Ni (nickel), it has better corrosion resistance and heat resistance than the steel containing Cr (chromium).
It has very good mechanical properties, no heat treatment hardening phenomenon and no elasticity.
Sheet metal process
Generally speaking, the basic equipment of sheet metal process includes shearing machine, CNC punching machine, laser cutting machine, plasma cutting machine, water jet cutting machine, press brake machine, drilling machine and various auxiliary equipment such as uncoiler, leveling machine, deburring machine and spot welding machine.
Generally, the most important four steps of sheet metal process are shearing, punching / cutting / folding / rolling, welding, surface treatment, etc.
Sometimes, sheet metal is also called “plate metal”.
Generally, some metal sheets are plastically deformed by manual or die stamping to form the desired shape and size, and further more complex parts can be formed by welding or a small amount of mechanical processing.
For example, chimneys, sheet metal furnaces and automobile shells commonly used in the family are sheet metal parts.
Metal plate processing is called sheet metal processing.
Specifically, for example, the use of plates to make chimneys, iron drums, oil tanks, ventilation pipes, elbow heads, round places, funnel shapes, etc. the main processes are cutting, bending and bucking, bending and forming, welding, riveting, etc., which requires certain geometric knowledge.
Sheet metal parts are thin sheet hardware parts, that is, parts that can be processed by stamping, bending, stretching and other means.
A general definition is – parts with constant thickness during processing.
The corresponding parts are cast parts, forged parts, machined parts, etc. for example, the iron shell outside the automobile is a sheet metal part, and some kitchen utensils made of stainless steel are also sheet metal parts.
Modern sheet metal technology includes: filament power winding, laser cutting, heavy processing, metal bonding, metal drawing, plasma cutting, precision welding, roll forming, metal sheet bending, die forging, water jet cutting, precision welding, etc.
The surface treatment of sheet metal parts is also a very important part of the sheet metal processing process, because it can prevent parts from rusting and beautify the appearance of products.
The surface pretreatment of sheet metal parts is mainly used to remove oil stain, oxide scale, rust, etc. it prepares for the surface post-treatment, and the post-treatment mainly includes spraying (baking) paint, spraying plastic and plating anti rust layer.
In the 3D software, Solidworks, UG, Pro / E, SolidEdge, Topsolid, CATIA, etc. all have sheet metal parts, which are mainly used to obtain the data required for sheet metal parts processing (such as unfolding drawings, bending lines, etc.) through the editing of 3D graphics and to provide data for CNC punching machine / laser, plasma, water jet cutting machine (laser, plasma, waterjet cutting machine) / combination machine and CNC bending machine.