1. 1 plate classification and name

Plate refers to various shapes of semi-finished products, such as thin plate, medium plate, thick plate, narrow band, belt and so on.

According to thickness: thick plate (above 4mm), medium plate (3-4mm) and thin plate (below 3mm).

According to the rolling state: hot rolled steel plate, cold rolled steel plate.

Production process of cold-rolled steel plate (Baosteel): ore → blast furnace ironmaking → converter steelmaking → continuous casting (slab) → hot tandem rolling → pickling → cold tandem rolling → continuous annealing (-hot dip galvanizing) → coiling/other (electro-galvanizing/longitudinal cutting/transverse cutting/)

Production technology of hot rolled steel plate (Baosteel): ore → blast furnace ironmaking → converter steelmaking → continuous casting (slab) → descaling → finishing rolling → cooling → coiling → hot rolled coil (-cold rolling) → straightening/longitudinal shearing/transverse shearing.

1.2 alloy and alloy steel

The steel we usually use is actually an iron-carbon alloy, and carbon permeates into the iron matrix to form a solid solution. According to the carbon content, it can be divided into three types: low, medium and high carbon steel.

Undoubtedly, alloy steel has infiltrated or dissolved other metal elements in iron base, thus improving the plasticity of steel, such as 08al and other plates, mainly Al and Fe alloys. This combination greatly improves the plasticity of the plate and can adapt to the deformation of cold stamping.

1.3 influence of sheet material on cold stamping

(1) Thickness tolerance of steel plate

Tolerance of steel plate thickness refers to the deviation that the actual thickness of steel plate exceeds the allowable standard, which not only affects stamping cracking, surface wrinkling, parts springback, but may even cause major die accidents. This is one of the three major factors that affect the success or failure of stamping.

The fluctuation of steel plate thickness tolerance actually affects the pressure exerted by the die on the parts and the difficulty of metal flow, thus affecting the stamping cracking and wrinkling of the parts.

(2) Surface defects of steel plate

According to the regulations, there must be no cracks, scars, folds, bubbles, delamination, interlayer and other defects on the surface of hot rolled steel plate that are harmful to use. However, minor and local defects such as pits, depressions and scratches with a depth (or height) not exceeding half of the thickness tolerance are allowed, and the minimum thickness of the steel plate is guaranteed.

The existence of any surface defects of cold-rolled and hot-rolled steel plates, especially those exceeding the allowable standards, will directly affect the stamping cracking of parts, painting quality and body appearance quality.

1.4 chemical composition of steel plate

(1) carbon. Carbon is one of the most basic elements in steel, which improves the strength of steel plate, especially the tensile strength.

(2) silicon. Silicon can improve the strength of cold-rolled steel plate.

(3) manganese. It can prevent excessive oxidation of steel and edge cracking of cold rolled steel plate.

(4) phosphorus. It has good cold rolling annealing function. However, phosphorus has cold brittleness, which also has an adverse effect on welding performance.

(5) sulfur. Elements harmful to stamping.

(6) aluminum. Prevent steel plate from aging. As a strong deoxidizer, it is beneficial to deep drawing performance.

1.5 indicates the main mechanical properties of the steel plate;

A strength: the ability of metal materials to resist deformation and fracture under external force. Yield strength and tensile strength are extremely important strength indexes and important basis for selecting metal materials. Strength is expressed by stress, that is, the load (external force) that can be borne per unit area, and the commonly used unit is MPa.

B yield strength: the phenomenon that the metal sample continues to deform without increasing the load in the tensile test is called "yield". The stress when the yield phenomenon occurs, that is, the stress at the beginning of plastic deformation, is called the yield point, which is expressed by the symbol σs and the unit is MPa. Generally, when a material reaches the yield strength, it begins to be accompanied by permanent plastic deformation, so it is a very important index.

C tensile strength: the maximum stress that a metal sample can bear before it breaks in the tensile test, which is expressed by the symbol σb, and the unit is MPa.

D. Elongation: the percentage of the increased length of the gauge part of the metal to the original gauge length after the specimen is broken in the tensile test is called elongation. Represented by the symbol δ. Elongation reflects the plasticity of materials, and the greater the elongation, the greater the plasticity of materials.

E strain hardening index n: the slope of the actual stress-strain curve of tensile steel. Its physical significance lies in that the high value of n indicates that the deformation of the material is easy to spread to the low deformation zone during the forming process, which makes the strain distribution more uniform and reduces the local deformation concentration phenomenon, so the value of n is very important for deep drawing and bulging.

F. R value of plastic strain ratio: R value indicates the strain ratio between width direction and thickness direction when the steel plate is stretched. The greater the R value, the less the possibility of deformation in the thickness direction of the steel plate (the less the possibility of cracking) and the better the stamping performance.

1.6 surface quality of steel plate

Level code characteristics

A few scratches, indentations, pits, roll marks, oxidation colors and other defects are allowed on the surface of FB (O3), which does not affect the formability and adhesion of the coating and coating.

Advanced finish surface FC (O4) products have two good surfaces, one has no obvious defects visible to the naked eye, and the other must at least meet the requirements of FB.

The good side of ultra-high-grade finished surface FD (O5) products must not have any defects, that is, it cannot affect the appearance quality after painting, and the appearance quality after electroplating, and the other side must at least reach FB level.

2. Stamped steel plates shall meet the following three basic quality requirements:

(1) has good surface quality.

The surface of the material should be smooth, without delamination and mechanical damage, rust, scale and other attachments.

(2) Strict thickness dimension tolerance.

The thickness tolerance of materials shall conform to national standards.

(3) Excellent deep drawing performance (complex grade yield 130- 190), stamping grade (yield 180-230) and ordinary grade (yield 220-245).

The material should have good plasticity, low yield ratio, large thickness direction coefficient, yield limit and elastic modulus.

Generally, metal materials begin to deform plastically after yielding, but the tensile strength has not yet come out. After constant stretching, they will reach the maximum stress point. When the material is stretched to the maximum force (tensile strength), the force begins to decrease until it breaks. The smaller the yield ratio, the later the necking, the larger the yield ratio, the faster the necking and the faster the rupture. )

What is the thickness direction coefficient? What effect does it have on stamping process?

Due to factors such as ingot crystallization and fiber structure in the process of plate rolling, the plasticity of plate will be different due to different directions, which is called plastic anisotropy of plate. Anisotropy includes anisotropy in thickness direction and plate plane. The anisotropy in the thickness direction is represented by the direction coefficient r of the plate thickness. The greater the R value, the harder it is for the plate to become thinner during deformation. It is the premise of analyzing the deformation degree of stamping parts, carrying out process design and formulating process regulations. If the shape of the sheet metal is appropriate, it can not only obviously improve the uneven distribution of deformation along the sheet metal, but also increase the forming limit and reduce the lug height and trimming margin. In addition, for some parts directly formed after blanking, if the accurate shape and size of the sheet metal can be given, the number of die trial and die adjustment can be reduced, thus shortening the production cycle and improving productivity.

3. Steel plate for cold stamping

Most of the plates used in cold stamping process are cold-rolled plates.

Cold-rolled sheet is favored by cold stamping because of its smooth surface and high dimensional accuracy. Different countries and regions have different names (or brands) of thin plates, but their organizational structure and physical and chemical properties are similar. At present, most brands used in stamping workshops are st series, such as St 13, St 14, St 16, etc. The materials of the same brand will be subdivided because of different stamping properties. Generally, it can be divided into F grade, HF grade and ZF grade. F, H and Z are the initial letters of the multiple, extremely multiple and most multiple levels of Chinese Pinyin, which can be seen at a glance. It is used for complex stamping parts, very complex stamping parts and the most complex stamping parts respectively. The properties of the above-mentioned St series plates are basically the same as those of domestic 08Al series plates, and they are all 08AL series ultra-low carbon alloy steels in essence. The following table shows the mechanical performance parameters of common automobile steel belts:

4. Material consumption quota

The material consumption quota of stamping parts refers to the material weight of a certain specification required for a single product. Material consumption quota can be calculated according to the following formula:

Q0=Q 1+Q2

Among them:

Q0—— Material consumption quota for stamping parts of a single product.

Q1-weight of stamping parts of single product

Q2—— Theoretical waste weight consumed by stamping parts of a single product. In the stamping workshop, for incoming materials, it is the package material, Q2 is the weight of a single blank, and for incoming materials, it is the coil material, Q2 is the average weight of a single blank after the head and tail of the coil material are removed.

/002.HTM (Ba Li color board standard), which is more suitable?

Shaping common sense

A, the composition of the general mold:

1. Working parts: the parts that complete the stamping work; Include parts such as punches and dies.

2. Positioning piece: it is to ensure good guidance and control the feeding distance during feeding; It mainly includes locating pins, locating pins, side blades and other parts.

3. Stamping, discharging and ejecting parts: the function of these parts is to ensure the removal of parts and waste after the stamping process is completed; It mainly includes unloading plate, ejector, pneumatic ejector and so on.

4. Guiding part: it is to ensure the accurate guidance when the upper die and the lower die move relatively, so that there is a uniform gap between the male die and the female die, and the quality of stamping parts is improved; Comprise a guide post, a guide sleeve, a guide plate and other parts.

5. Installation and fixation of parts: the function of these parts is to integrate the above four parts, ensure the relative position between parts, and enable the mold to be installed on the press; Comprise an upper template, a lower template, a die handle, a fixed plate, a backing plate, a screw, a cylindrical pin and that like.

6. Buffer components: including unloading spring, polyurethane rubber, nitrogen cylinder, etc.

7. Safety components and other auxiliary components: mainly including safety side pins, safety screws, working limiters, storage limiters, loading and unloading racks, garbage slides, lifting rods, lifting lugs, etc.

Safety side pin: the main function is to prevent the fastening screw of the upper die platen from loosening or breaking, which will cause the platen to fall off and cause great losses to personnel and tooling.

Storage limiter: the main function is to prevent the elastic element of the mold from failing due to long-term pressure, and to prevent the long-term contact of the cutting edge from affecting the service life of the cutting edge. (Polyurethane rubber is generally used)

Work limiter: the main function is to limit the feeding depth of punch and die.

Second, the factors affecting the life of the mold:

1. Influence of stamping process and die design and measures to improve die life;

(1) Influence of cold stamping raw materials. For example, the thickness tolerance of raw materials does not meet the requirements, the material performance fluctuates, the surface quality is poor, and it is unclean. ;

A. Strictly check the brand, thickness and surface quality of raw materials before stamping.

B. ensure the surface quality and cleanliness of materials.

(2) The influence of layout and wrapping:

Layout method and overlap value have great influence on the life of die. Unnecessary reciprocating feeding layout and too small overlapping value are often the important reasons for the die to wear too fast and gnaw away the punch and die.

(3) The influence of mold guiding structure and guiding accuracy:

Necessary and reliable guidance is very effective for reducing the wear of working parts and avoiding the biting of convex and concave dies.

(4) Influence of geometric parameters of the mold:

The shape, gap and fillet radius of the convex-concave die not only have great influence on the forming of stamping parts, but also on the wear of the die.

2. The influence of mold materials:

The material properties and heat treatment quality of the die are the most important factors affecting the life of the die.

3. The influence of die hot working and surface strengthening.

4. The influence of mold processing technology:

The surface roughness of the die after machining has a great influence on the life of the die, so the machining process should be selected reasonably according to the situation of the parts.

5. The influence of the accuracy and stiffness of the press.

6. The influence of the use, maintenance and maintenance of the mould.

7. Proper use, maintenance and storage of molds is an important aspect to improve the life of molds. It includes the correct installation and adjustment of the mold; Pay attention to keep the mold clean and lubricated reasonably; Prevent wrong feeding and repeated feeding; Strictly control the depth of the punch into the concave die, and control the position of the bottom dead center of the upper die during the process of correcting bending and shaping; Timely grinding and polishing, etc.

Three, the basic requirements for the performance of cold stamping die steel:

1. has high hardness and strength, which ensures that the mold is compression-resistant, wear-resistant, deformation-free and adhesion-free;

2. It has high wear resistance, so as to ensure that the shape and size tolerance of the mold will change within a certain range during long-term work, and it will not fail due to excessive wear;

3. It has enough toughness to prevent the mold from brittle fracture under impact load;

4. The deformation of heat treatment is small, which ensures that the mold will not be scrapped due to excessive deformation during heat treatment;

5. It has high thermal hardness to ensure that the die will not soften due to temperature rise during high-speed stamping or heavy-duty stamping.