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The car is called "a machine that changes the world." Because the auto industry has a strong industrial relationship, it is considered as an important symbol of a country's economic development level. This chapter uses four chapters to discuss the four major processes of the car. Stamping process as the top priority of the four major processes, but also the first of the four major processes, let's take a look.
First, concept
1, stamping concept
Stamping is the method of forming and processing a workpiece (stamped part) of a desired shape and size by applying an external force to a plate, a strip, a pipe, and a profile by means of a press and a die to cause plastic deformation or separation. Stamping and forging are plastic processing (or pressure processing), collectively known as forging. Stamped blanks are mainly hot-rolled and cold-rolled steel sheets and strips. Of the steel in the world, 60 to 70% are sheet metal, most of which are stamped and finished.
The car's body, chassis, fuel tanks, radiators, boiler steam drums, container shells, motor cores, and electrical appliances are all stamped. There are also a large number of stamping parts in products such as instrumentation, household appliances, bicycles, office machinery, and household utensils.
2, stamping process features
A. Stamping is a processing method with high production efficiency and low material consumption. The stamping process is suitable for the production of large-volume parts, facilitates mechanization and automation, and has high production efficiency. At the same time, stamping production can not only strive to produce less scrap and no waste, but even in some cases there are edges. The remaining material can also be fully utilized.
B. It is easy to operate and does not require operators to have a high level of skills.
C, stamped parts generally do not need to be machined again, with high dimensional accuracy.
D, stamping parts have better interchangeability. Stamping processing stability is better, the same batch of stampings. Can be used interchangeably without affecting assembly and product performance.
E. Since the stamped part is made of sheet material, its surface quality is good, providing convenient conditions for subsequent surface treatment processes (such as electroplating, painting).
F, stamping processing can obtain high strength, high stiffness and light weight parts.
G. Stampings produced in mass with molds are inexpensive.
H. Stamping can create complex parts that are difficult to machine with other metal processing methods.
3, stamping process introduction
The mechanical steering system uses the driver's physical strength as a steering power source, and all mechanical transmission structures are mechanical. The mechanical steering system is composed of three parts: steering mechanism, steering gear and steering transmission.
A, separation process
The sheet material is separated along a certain contour line under external force to obtain finished products and semi-finished products with a certain shape, size and cut-off surface quality. Separation conditions: The stress inside the deformed material exceeds the strength limit σb.
a. Blanking
Punching along the closed curve with the punch, the punched part is the part. Used to make various shapes of flat parts.
b. Punching
Punching along a closed curve with a die, the part that is washed down is scrap. There are several types of punching, side punching, and hanging punching.
c. Trimming
The edge of the formed part is trimmed or cut into a certain shape.
d. Separation
Punches along the non-closed curve with a die create a separation.
When the left and right pieces are molded together, the separation process is used more often.
B, forming process
The blank is plastically deformed without breaking to obtain finished and semi-finished products of a certain shape and size.
Forming conditions: yield strength σS <material internal stress <intensity limit σb.
a.
The blank blank is formed into various open hollow parts.
b. Flanging
The edge of the sheet or semi-finished product is formed into a standing edge by a certain curvature along a certain curve.
c. Shaping
A forming method used to increase the dimensional accuracy of a formed part or to obtain a small fillet radius.
d.
An upright edge is made on a pre-punched sheet or semi-finished product or unpunched sheet.
e. Bend
By bending the sheet material into various shapes along a straight line, parts with extremely complex shapes can be machined.
4, stamping process flow chart
Two: stamping die
The mold is known in Japan as "the driving force behind entering an affluent society," and in Germany it is called "the emperor in the metal processing industry." The level of mold design and manufacturing technology is an important indicator of the level of product manufacturing in a country.
A, mold classification
According to the working principle can be divided into:
B, the basic structure of the mold
The die is usually composed of two parts, the upper and the lower die (convex, die)
Composition: 1 work section, 2 guides, 3 positions, 4 stops, 5 spring elements, 6 lifts and flips
Three: stamping equipment
1. Press
A. According to the bed structure, the presses can be divided into two kinds: open presses and closed presses.
Open-type presses are open on three sides, the bed is C-shaped, poor rigidity, generally used for small presses;
The front and back sides of the closed press are open on both sides, the bed is closed, and the rigidity is good. It is generally used for large and medium-sized presses.
B. According to the type of drive slide force, presses can be divided into: mechanical presses and hydraulic presses
2. Winding line
3. Shears
Shears are mainly used to trim straight edges of various sizes of sheet metal.
The transmission form is mechanical and hydraulic.
Four: stamping materials
Stamping material is an important factor affecting the quality of parts and mold life. Currently, stampable materials include not only low-carbon steels but also stainless steel, aluminum and aluminum alloys, copper and copper alloys.
Steel plate is currently the most widely used raw material for automobile stamping. At present, new materials such as high-strength steel plates and sandwiched steel plates are increasingly used in automobile bodies as body weight requirements are reduced.
1 steel plate performance requirements
A, with good mechanical properties and greater ability to deform.
The mechanical properties of metal materials refer to tensile strength, yield strength, elongation, hardness, and plastic strain ratio.
High plastic strain ratio r value (anisotropic properties)
High work hardening index n value;
High elongation δ;
Low yield ratio (σs/σb);
Low ageing index.
B. Good surface quality
The surface of the steel plate must not have obvious defects such as scars, cracks, inclusions, and scratches. The inner panel of the car body is allowed to have defects that do not affect the formability and paint adhesion, such as small bubbles, small scratches, small roll marks, minor scratches and slight oxidation color; the outer plates must meet the quality of FD (O5) The level, ie, the better side of both sides, must not have any imperfections, ie it must not affect the appearance quality after painting or the appearance quality after plating, and the other side should meet the requirements of FB (O3).
2. Steel plate classification
A. According to thickness: thick plate (4mm or more), medium plate (3-4mm), thin plate (3mm or less) automotive body stamping parts mainly in thin plate
B. According to the state of rolling: hot-rolled steel plate, cold-rolled steel plate
Hot rolling is to soften the alloy at a temperature higher than the recrystallization temperature of the alloy and then press the material into a thin section or a cross section of the steel billet with a pressure roller to deform the material, but the physical properties of the material do not change. Hot-rolled sheet has poor toughness and surface smoothness, and the price is low. The hot rolling process is rough and the steel cannot be rolled thin.
Cold rolling is a process in which a material that has been hot-rolled, except the pitting and oxidation removal process, is further pressed with a press roller at a temperature lower than the recrystallization temperature of the alloy to recrystallize the material. After repeated cold-pressing-recrystallization-annealing-cold pressing (reversing 2 to 3 times), the metal in the material undergoes a molecular-level change (recrystallization), and the physical properties of the formed alloy change. Therefore, the surface quality is good, the finish is high, and the product dimensional accuracy is high. The performance and organization of the product can meet some special requirements for use.
Cold-rolled steel plates mainly include cold-rolled carbon steel plates, cold-rolled low-carbon steel plates, cold-rolled steel plates for stamping, and high-strength cold-rolled steel plates.
Cold-rolled carbon steel plate
S is the abbreviation of Steel Steel, P is the abbreviation of Plate Plate, the third letter C is the abbreviation of Cold, and N means that non-timeliness needs to be guaranteed.
Cold rolled low carbon steel
Five: inspection tools
The gage is a special inspection device for measuring and evaluating the dimensional quality of parts.
In automobile manufacturing, special inspection tools are widely used as main testing means for large stampings, interior parts, welding subassemblies with complex geometries, simple small stampings, interior trims, etc. , Used to control the product quality between processes.
The inspection tool detection has the advantages of rapidness, accuracy, intuition, and convenience, and is particularly suitable for the needs of mass production.
The inspection tool often consists of three parts:
1 Skeleton and base section;
Type 2 body part;
3 function pieces (function pieces include: quick chuck, positioning pin, detection pin, movable gap slider, measurement table, profile card, etc.).
Source: Easy car network, Baidu Encyclopedia
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