Cold rolling is only used to produce small sections and sheets. Cold rolling refers to the processing of steel sheets or steel strips into various types of steel at room temperature by cold drawing, cold bending, cold drawing, and another cold working. Advantages: fast forming speed, high output, without damaging the coating, can be made into a variety of cross-section forms to meet the needs of the use conditions; cold rolling can make the steel produce large plastic deformation, thereby improving the yield of the steel point. Disadvantages: Although there is no hot plastic compression in the forming process, there are still residual stresses in the section, which will inevitably affect the overall and local buckling characteristics of the steel; the cold-rolled steel is generally open-section, making the section free. The torsional stiffness is low. It is easy to twist when bent, and it is prone to bending and torsion buckling when pressed, and the torsion resistance is poor. The wall thickness of cold-rolled steel is small, and there is no thickening at the corners where the plates are joined. The ability to concentrate loads is weak.
Cold rolling uses hot-rolled steel coil as raw material and is subjected to pickling to remove scale and then cold-rolling. The finished product is rolled hard roll. The cold work hardening caused by continuous cold deformation makes the strength and hardness of the rolled hard roll rise and tough. The plastic index is reduced, so the stamping performance will deteriorate and can only be used for parts that are simply deformed.
The high quality rolled hard roll steel coil can be used as raw materials for hot-dip galvanizing plants because the hot-dip galvanizing units are equipped with an annealing line. The rolled hard coil weight is generally 6 to 13.5 tons, and the coil is continuously rolled at a normal temperature. The inner diameter is 610mm.
The difference between cold and hot China high quality rolled hard roll steel coil. cold rolling means that the steel is not heated before rolling, and rolling is carried out at a normal temperature, and these steels are turned into cold-processed by raw drawing, bending, and drawing. A wide range of steels.
The advantage of cold rolling is that it is extremely easy to form and form, and the output is also very high, and the coating can be damaged in a small amount so that it can be easily formed into a variety of cross-section forms to meet the needs of various uses. Moreover, cold rolling can also make the steel produce a large deformation and plastic effect, which enhances its yielding ability.
Similarly, it also has certain shortcomings. Although it does not undergo high-temperature compression and plasticity in the process of shaping it, it still retains its own small temper in the cross-section, and there will be residual stress, which will be a certain steel Part of the degree of bending has a slight effect.
When it accepts bending, it will have some small resistance and its resistance to distortion will be poor. And cold-rolled steel is not shaped like hot-rolled steel in its own soft condition. The hardness of cold-rolled steel is too large. Therefore, the power requirement of the rolling mill is very high during the production process, so the efficiency of making cold-rolled steel is low. Come down. From the processing point of view: cold rolling is cold working, and cold rolling is rolling below the recrystallization temperature.
The surface of the high quality rolled hard roll steel coil has a certain degree of gloss. The hand feels smoother, similar to the very common steel cup used to drink water. The performance advantages of the cold-rolled sheet and hot rolled sheet are as follows:
1. The precision is higher, and the difference in thickness of the cold-rolled strip is not more than 0.01~0.03mm.
2. The size is thinner, the cold-rolled thinnest can be rolled with a steel strip of 0.001 mm; the hot rolling is now as thin as 0.78 mm.
3. The surface quality is superior, and the cold-rolled steel plate can even produce a mirror surface; while the surface of the hot-rolled plate has defects such as iron oxide scale and pitting.
4. Cold-rolled sheets can be adjusted according to user requirements such as tensile strength and process properties such as stamping properties.
Cold rolling, as the name implies, is made in steel at normal temperature. The hardness of this steel is large. The hardness of the cold-rolled sheet is high, and the processing is relatively difficult, but it is not easy to deform and has high strength.
The high quality rolled hard roll steel coil has a certain degree of work hardening, low toughness, but can achieve a good yield ratio, used for cold-bending spring pieces and other parts, and because the yield point is closer to the tensile strength, there is no danger during use. Predictability, an accident is likely to occur when the load exceeds the allowable load.
Most of the China high quality rolled hard roll steel coil is rolled by hot rolling, but because the surface of the steel is prone to iron oxide scale at high temperature, the surface of the hot rolled steel is rough and the size fluctuates greatly. Therefore, steel with a smooth surface, precise dimensions, and good mechanical properties are required. The hot-rolled semi-finished product or the finished product is used as raw material and then produced by a cold rolling method. Rolling at normal temperature is generally understood to be cold rolling. From a metallographic point of view, the limits of cold rolling and hot rolling should be distinguished by recrystallization temperature. That is, the rolling lower than the recrystallization temperature is cold rolling, and the rolling higher than the recrystallization temperature is hot rolling.
The steel has a recrystallization temperature of 450 to 600 C. Cold rolling, generally there is no heating process before rolling. However, due to the small thickness of the strip, the shape of the plate is prone to occur. Moreover, after cold rolling, it is a finished product, and therefore, in order to control the dimensional accuracy and surface quality of the strip, many complicated processes are employed. The cold rolling production line is long, the equipment is numerous, and the process is complicated. As the user’s requirements for dimensional accuracy, shape and surface quality of the strip are improved, the control model, L1, and L2 systems, and the shape control means of the cold rolling mill are relatively hot. Moreover, the temperature of the rolls and strip is one of the more important control indicators.
The cold-rolled product and the hot-rolled product sheet are different from the previous process and the next process. The cold-rolled hot-rolled high quality rolled hard roll steel coil on the hot-rolled steel roll is rolled and rolled, and all are cold-formed. The main method is to roll a thick-form hot-rolled sheet into a thin-sized cold-rolled sheet. Usually, a hot-rolled sheet rolling of 3.0 mm can produce a cold-rolled coil of 0.3-0.7 mm. The main principle is to use extrusion. The principle is forcibly deformed. Uses of cold rolling: used in home appliances such as automobiles, refrigerators, washing machines, industrial equipment, and various building materials.
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