Steel plate is a flat steel for pouring steel water and pressed after cooling. The steel plate is divided into thickness, thin steel plates <4 mm (the thinnest 0.2 mm), thick steel plate 4 ~ 60 mm, and a thick steel plate 60 ~ 115 mm. The steel plate is divided by rolling, divided into hot rolling and cold rolling.
The steel type of thick steel plate is generally the same as the thin steel plate. In all aspects, in addition to bridge steel plates, boiler steel plates, automobile manufacturing steel plates, pressure vessel steel plates, and multi -layer high -pressure container steel plates are purely thick plates, some varieties of steel plates such as car beam steel plates (thickness 2.5 ~ 10 mm), pattern patterns Steel plates (2.5 ~ 8 mm thick), stainless steel plates, heat -resistant steel plates and other varieties are cross -plate.
In addition, the steel plate also has the material, not all steel plates are the same, the material is different, and the place where the steel plate is used is different.
Steel. Steel is made of steel water as the raw material. The steel water is used to pour it. After the steel water is cooled, the steel water is used to suppress the flat -shaped steel. The steel plates that we usually mention are almost all flat -shaped or rectangular. In fact, not only can it be directly suppressed by the machine, but also the wide steelband is cut directly. The thickness of the steel plate is not standardized, divided into thin steel plates, thick steel plates and thick steel plates. The thin steel plate is about 4mm, the thick steel plate is about 4 to 60mm, and the thick steel plate is mainly about 60 to 115mm.
The difference between the pickled plate used on sheet metal and the hot rolled plate
Acid washing plate: It is based on high -quality hot -rolled sheet as the raw material. After the acid washing unit removes oxidation layer, cut edges, after refined, the surface quality and use requirements (mainly cold -bending or stamping performance) Intermediate products between rolling plates
Hot -rolled plates: The strength is relatively low, and the surface quality is almost (aerobic, low degree of smoothness), but the plasticity is good. Generally, compared with the hot -rolled plates of the medium thick plate and the hot rolled plate:
The surface quality is good. Compared with ordinary hot -rolled plates, the hot -rolled pickled plate removes the surface of the surface of the iron, which improves the surface quality of the steel, and is convenient for welding, oil and paint.
High size and accuracy, after flatness, can change the plate shape to a certain extent, thereby reducing the deviation of unevenness. 3. Improve the surface smoothness and enhance the appearance effect
The effect of using hot plate on welding
- Point welding: Due to the oxygen skin on the surface, it must be removed before point welding. The specific yield strength needs to be welded
- Bolt welding: need to remove oxide, and the specific yield intensity needs to be welded
- Ordinary welding: large splashing, difficulty in deformation, difficult to polish welds, large deformation, and difficulty in plastic surgery; the yield strength of the same welding conditions will be increased
- Laser cutting: Laser cutting is large. It is not suitable for parts with high size requirements, which will have a great impact on later welding.
5, bending: cold bending or stamping performance is low, it is easy to produce bending cracks, easily reduce the service life of the product, and cause failure.
The impact of using hot plates on paint
Pre -treatment: Since there is a large amount of oxidative skin on the surface, the picking time is increased, and the pickling effect needs to be confirmed
Static powder spray: The surface is not good, which will not be conducive to spraying.
The hot -rolled plate is placed in the air, and it will be difficult to remove once rust.
The difference between cold -rolled steel plates and hot -rolled steel plates used on sheet metal
- There is a certain gloss on the surface of the cold -rolled plate. The hand does feel smooth, similar to the common steel cup that is used to drink water.
If the hot -rolled plate is not picked, it is similar to the surface of many ordinary steel plates on the market. The surface of the rusty is red, and the surface of the rusty is purple -black (iron oxide skin).
The performance advantage of cold -rolled plates and hot -rolled plates is:
(1) The accuracy is higher, and the thickness difference between cold rolling band steel does not exceed 0.01 ~ 0.03mm.
(2) The size is thinner, the thinnest of cold rolling can be rolled 0.001mm, and the hottest hot rolling can now reach 0.78mm.
(3) The surface quality is superior, and the cold -rolled steel plate can even produce the surface of the mirror surface; while the surface of the hot -rolled plate is oxygen, iron dioxide leather, hemp point and other defects.
(4)Cold -rolled plates can adjust their school -running performance such as tensile strength and process performance such as stamping performance. Cold rolls and hot rolling are two different types of steel rolling technologies. As the name suggests, cold rolling is to formulate it at room temperature. This steel has a large hardness. Hot rolling is the system at high temperature.
The hardness of the hot -rolled plate, easy processing, and good extension performance.
Cold -rolled plates have high hardness and are relatively difficult to process, but they are not easy to deform and have high strength.
The intensity of the hot rolled plate is relatively low, and the surface quality is almost (aerobic, low in smoothness), but the plasticity is good, generally a medium thick plate, cold -rolled plate: high strength, high hardness high surface smoothness, generally thin plate, can be used as stamping for stamping, can be used as stamping for stamping, which can be used as stamping. plate.
Hot -rolled steel plates, mechanical properties are far less than cold processing, and they are also more than forging processing, but they have good toughness and ductility.
Cold -rolled steel plates have a certain degree of processing hardening and low toughness, but they can achieve a good flexion and use it to be used to cold -bent spring pieces and other parts. At the same time Foresignability, accidents are prone to accidents when the load exceeds the load.
In terms of definition, it is difficult to deform at room temperature at room temperature and is not easy to process. Generally, it is heated to 1100-1250 ° C for rolling. This rolling process is called hot rolling. Most steel is rolled in hot rolling methods. However, because the surface of steel is easy to generate iron oxide skin at high temperature, the surface of hot -rolled steel is rough and the size fluctuates large, so steel with a smooth surface, accurate size, and good mechanical properties are required. Production of rolling methods.
Rolling at room temperature is generally understood as cold rolling. From the perspective of metal science, the boundary between cold and hot rolling should be distinguished by crystallizing temperature. That is, the rolling of the re -crystallization temperature is cold rolled, and the rolling of the crystal temperature is hot rolled. The re -crystallization temperature of the steel is 450 ~ 600 ° C.
Hot rolling, as the name suggests, the temperature of the rolling parts is high, so the deformation resistance is small, which can achieve a large deformation. Take the rolling of the steel plate as an example. Generally, the thickness of the casting blank is about 230mm, and after rolling and refined rolling, the final thickness is 1 ~ 20mm. At the same time, due to the small ratio of the steel plate, the size and accuracy of the size are relatively low, it is not easy to occur on the plate -shaped problem, mainly to control the convexity. For organizations, it is generally implemented by controlling rolling control, that is, controlling the rolling temperature, the final rolling temperature, and the curling temperature of the refined rolling to control the micro -organization and mechanical performance of the steel with steel.
Cold rolling, usually there is no heating process before rolling. However, because the thickness of the steel is small, it is easy to occur. Moreover, after the cold rolling, it is the finished product. Therefore, in order to control the size accuracy and surface quality of the steel, many very cumbersome craftsmanship is adopted.
The cold -rolled production line is long, with many equipment and complex craftsmanship. With the improvement of the user’s steel size accuracy, plate shape and surface quality requirements, the control model, L1 and L2 systems, and plate -shaped control methods of cold rolling units are relatively hot rolled. Moreover, the temperature of rolls and steel is one of the more important control indicators.
In terms of cold -rolled products and hot -rolled products, it is the difference between the upper and lower processes. Hot -rolled products are the raw materials for cold rolled products. The rolling machine, rolling, are all cold processing, mainly to roll the thick specifications into thin-specifically cold-rolled plates, usually like a 3.0mm hot-rolled plate rolling machine to produce 0.3-0.7mm The main principle of cold rolling rolls is forcibly deformed with the principle of squeezing.
Hot rolled
advantage:
Fast speed of molding, high yield, and no damage coating can be made into a variety of section forms to meet the needs of the use conditions; cold rolling can cause large plastic deformation of steel, thereby improving the yield point of steel.
shortcoming:
- Although it has not been compressed during the molding process, there is still residual stress in the cross section, which will inevitably affect the characteristics of the overall and local flexion of steel;
- Cold -rolled steel styles are generally the cross section of the opening, making the free rigidity of the cross -section lower. It is prone to twist when bending, and it is easy to twist and flexion when compression, and the resistance resistance is poor;
- Cold rolling molding steel wall thickness is smaller, and there is no thickening at the corner of the plate connection. The ability to withstand localized concentration loads is weak.
Cold rolling
advantage:
It can destroy the casting organization of steel ingots, refine the grains of steel, and eliminate the defects of microstrip organizations, so that the steel tissue is dense and the mechanical properties are improved. This improvement is mainly reflected in the direction of rolling, so that the steel is no longer the same -sex body to a certain extent; the bubbles, cracks and loose air bubbles formed during pouring can also be welded under high temperature and pressure.
shortcoming:
- After the heat rolled, non -metallic mixed materials (mainly sulfides and oxides, and silicate) inside the steel are pressed into thin slices and layered phenomena. The performance of the stratification of the steel is greatly deteriorated along the thick direction, and the layer tears may occur during weld shrinkage. The local strain induced by welding seams often reaches several times the yield point strain, which is much larger than the strain caused by loads;
- Remnant stress caused by uneven cooling. The residual stress is the stress that the internal self -balance is balanced without external forces. The hot -rolled steel of various sections has such residual stress. The larger the size of the general steel section, the greater the residual stress. Although the residual stress is self -balanced, it still has a certain impact on the performance of the steel component under external force. Such as deformation, stability, and anti -fatigue may produce adverse effects.