Advantages and disadvantages of cold and hot rolled cold and hot rolling

Advantages and disadvantages of hot rolling:

Advantages: It can destroy the casting structure of the steel ingot, refine the grain of the steel, and eliminate the defects of the microstructure, so that the steel structure is dense and the mechanical properties are realized.

Be improved. This improvement is mainly reflected in the rolling along the rolling.

direction, so that the steel is to a certain extent no longer isotropic; Bubbles, cracks and porosity formed during pouring can also be welded under high temperature and pressure.

Cons: 1After hot rolling, non-metallic inclusions (mainly sulfides) inside the steel are formed.

and oxides, but also silicates.

It is pressed into thin sheets, and delamination (interlayering) occurs. Delamination greatly deteriorates the tensile properties of the steel along the thickness direction, and interlaminar tearing is possible when the weld shrinks. The local strain induced by weld shrinkage often reaches several times of the yield point strain, which is much larger than the strain caused by the load.

2.Residual stresses due to uneven cooling.

Residual stress is the stress of internal self-equilibrium without external force, and hot-rolled sections of various cross-sections.

There are such residual stresses, and the larger the cross-sectional size of the general section steel, the greater the residual stress. Although the residual stress is self-equilibrizing, it still has a certain influence on the performance of the steel member under the action of external force. For example, it may have adverse effects on deformation, stability, fatigue resistance, etc.

Advantages and disadvantages of cold rolling:

Advantages: fast forming speed, high output, and no damage to the coating, can be made into a variety of cross-sectional forms to meet the needs of the use conditions; Cold rolling can cause large plastic deformation of the steel, which improves the yield point of the steel.

Cons: 1Although there is no thermoplastic compression during the forming process, there are still residual stresses in the cross-section, which will inevitably affect the overall and local buckling characteristics of the steel.

2.The cold-rolled steel section style is generally an open cross-section, which makes the free torsional stiffness of the cross-section low. It is easy to torsion when bending, and bending-torsional buckling is easy to occur when compression, and the torsional performance is poor;

3.The wall thickness of cold-rolled forming steel is small, and there is no thickening at the corner of the plate connection, so the ability to bear local concentrated load is weak.

Cold Rolling and Hot Rolling: Two methods of rolling just to make it form.

Cold and hot rolledThe differences are as follows:

1. Hot rolling is mainly used for the production of steel structures, bridges, ships, vehicles and various mechanical parts, and cold rolling is mainly used for household appliances such as automobiles, refrigerators, washing machines, as well as industrial equipment and various building materials.

2. Hot-rolled section steel.

and residual stresses in cold-rolled sections.

There are different reasons and therefore the distribution in the cross-section is also very different. The residual stress distribution on the cross-section of cold-formed thin-walled steel is curved, while the residual stress distribution on the cross-section of hot-rolled or welded steel is film-like.

3. The free torsional stiffness of hot-rolled steel is higher than that of cold-rolled steel, so the torsional performance of hot-rolled steel is better than that of cold-rolled steel. The cold-rolled section allows local buckling of the cross-section, thus making full use of the post-buckling capacity of the rebar. However, local buckling of hot-rolled sections is not allowed.

The differences are as follows.

Conceptual differences.

Cold-rolled steel coil is used as raw material, and cold continuous rolling is carried out after pickling to remove the oxide scale, which is relative to cold rolling, which is rolled below the recrystallization temperature, and hot rolling is the rolling above the recrystallization temperature.

Differences in characteristics.

1.Cold-rolled formed steels allow local buckling of the cross-section, whereas hot-rolled sections do not allow local buckling of the cross-section.

2. The residual stress distribution on the cross-section of cold-formed thin-walled steel is bending, while the residual stress distribution on the cross-section of hot-rolled steel or welded steel is thin-film type.

3. The free torsional stiffness of hot-rolled steel is higher than that of cold-rolled steel, so the torsional resistance of hot-rolled steel is better than that of cold-rolled steel.

Different uses.

The use of hot-rolled products is suitable for general structural steel and hot-rolled steel plates and steel strips for engineering, which can be used for welded pipes, cold-rolled materials, bicycle parts, as well as important welding, riveting, bolting components, automobile beams, beams, etc.

Cold rolling mainly produces some high-precision products that cannot be produced by hot rolling. They have excellent performance in terms of surface quality, dimensional accuracy, and mechanical properties. For example, cold-rolled steel plate (automobile panels, home appliance plates, silicon steel sheets, etc.), cold-rolled steel bars (fine iron wires, steel strands for automobile tires, etc.), cold-rolled steel pipes.

1. The surface of the cold-rolled plate has a certain gloss, and it is relatively smooth to the touch, similar to the very common molten steel cup used for drinking water.

2. If the hot-rolled plate is not pickled, it is similar to the surface of many ordinary steel plates on the market, the rusted surface is red, and the non-rusted surface is purple-black (iron oxide scale).

The performance advantages of cold-rolled plate and hot-rolled plate are:

1) The accuracy is higher, and the difference in the thickness of the cold-rolled strip does not exceed.

2) Thinner size, cold-rolled thinnest rollable steel strip; Hot rolled is now the thinnest achievable.

3) The surface quality is superior, and the cold-rolled steel plate can even produce a mirror surface; The surface of the hot-rolled plate has defects such as iron oxide scale and pitting.

4) The cold-rolled plate can adjust its performance according to user requirements, such as tensile strength and process performance, such as stamping performance, etc.

Cold rolling and hot rolling are two different steel rolling technologies, as the name suggests, cold rolling is the steel is rolled at room temperature, this kind of steel has a high hardness. Hot rolling is the steel being rolled at high temperatures.

Detailed: The hot-rolled plate has low hardness, easy processing and good ductility.

The cold-rolled plate has high hardness and is relatively difficult to process, but it is not easy to deform and has high strength.

The strength of the hot-rolled plate is relatively low, the surface quality is almost (there is oxidation, low finish), but the plasticity is good, generally medium and heavy plate, cold-rolled plate: high strength, high hardness, high surface finish, generally thin plate, can be used as a stamping plate.

The mechanical properties of hot-rolled steel plate are far inferior to cold working, and are also inferior to forging processing, but they have better toughness and ductility.

Due to a certain degree of work hardening, the toughness of cold-rolled steel plate is low, but it can achieve a good yield ratio, which is used for cold-formed spring sheets and other parts, and because the yield point is close to the tensile strength, there is no foresight of the danger in the process of use, and accidents are prone to occur when the load exceeds the allowable load.

By definition, steel ingots or billets are difficult to deform at room temperature, not easy to process, and are generally heated to 1100 1250 for rolling, this rolling process is called hot rolling. Most of the steel is rolled using the hot rolling method. However, because the surface of the steel is easy to generate iron oxide scale at high temperature, the surface of the hot-rolled steel is rough and the size fluctuates greatly, so the steel with smooth surface, accurate size and good mechanical properties is required to be produced by the cold-rolled method with hot-rolled semi-finished products or finished products as raw materials.

Rolling at room temperature is generally understood as cold rolling, and from the point of view of metallurgy, the boundary between cold rolling and hot rolling should be distinguished by the recrystallization temperature. That is, the rolling below the recrystallization temperature is cold rolling, and the rolling above the recrystallization temperature is hot rolling. The recrystallization temperature of steel is 450 600.

Hot rolling, as the name suggests, has a high temperature of the rolled piece, so the deformation resistance is small, and a large amount of deformation can be achieved. Take the rolling of steel plates as an example, one.

Hot rolling refers to the rolling of metals above the recrystallization temperature. As opposed to hot rolling, it is cold rolling. Cold rolling is the process of rolling below the recrystallization temperature.

Difference Between Hot Rolled and Cold Rolled.

1. Different processing technology: cold rolling is cold working, and the cross-section can be bent; Hot rolling is hot working, and the cross-section must not be bent.

2. Different torsion resistance: Comparatively speaking, the torsion resistance of hot-rolled steel is better than that of cold-rolled steel.

3. Different uses: Generally, cold rolling can be used in automobiles, rice cooker liners, washing machines and other household appliances, as well as industrial equipment and various building materials; Hot rolling can be used in bridges, ships, tractors, construction lifting machinery and other machine width stamping and structural parts, as well as skid plates, stairs, etc.

To put it simply, a billet is corrected into a steel plate after several rolls and then cut the edge after heating, which is called hot rolling. Hot rolling can significantly reduce energy consumption and reduce costs. During hot rolling, the metal has high plasticity and low deformation resistance, which greatly reduces the energy consumption of metal deformation.

Hot rolling can improve the processing performance of metals and alloys, that is, the coarse grains in the casting state are broken, the cracks are healed significantly, the casting defects are reduced or eliminated, the casting structure is transformed into a deformed structure, and the processing performance of the alloy is improved.

Cold rolling is to use hot-rolled steel coil as raw material, and then cold continuous rolling after pickling to remove the oxide scale. The finished product is rolled hard coil, and the strength and hardness of the rolled hard coil increase and the toughness index decreases due to the cold work hardening caused by continuous cold deformation. As a result, the bright pressure performance of the punch will deteriorate and can only be used for parts that are simply deformed.

Hot rolling and cold rolling are two rolling methods commonly used in the processing of metal materials, and they have some differences in terms of processing temperature, process and product performance.

1.Processing temperature:

Hot rolling: Hot rolling is a rolling process that takes place at high temperatures, usually with the steel being processed at temperatures that exceed the recrystallization temperature (typically 900°C-1300°C).

Cold rolling: Cold rolling is a rolling process carried out at or near room temperature, which directly deforms the cooled steel.

2.Process: Debate.

Hot rolling: Hot rolling includes stages such as heating, rolling and cooling. First, the billet is pre-heated or initially heated to bring it to the appropriate deformation temperature; Then, the billet is continuously rolled into the desired shape through a rolling mill at high temperatures; Finally, air-cooled or rapid cooling is used to control the organization and performance.

Cold rolling: Cold rolling mainly includes process steps such as surface cleaning, drawing, and rolling. First of all, the cold-rolled billet is placed in the pickling solution for cleaning to remove surface impurities such as oxides; The billet is then stretched into thin, slender strips by a drawing mill and rolled through a cold rolling mill to form the desired product.

3.Product Performance:

Hot rolled: Hot rolled products have good plasticity and processability, and are suitable for general engineering applications. However, hot rolling results in the growth of grain growth clusters, so its strength and hardness may be relatively large.

Hot rolling and cold rolling are two commonly used metal material processing processes, and there are the following differences between them:

1.Temperature: Hot rolling occurs at high temperatures, and the billet undergoes plastic deformation after heating to high temperatures; Cold rolling, on the other hand, takes place at room temperature and does not require heating.

2.Processing process: In hot rolling, the billet is heated and then changes its shape and size through continuous rolling, stretching and other operations on the roller table; Cold rolling, on the other hand, is to cold roll the billet at room temperature through a series of cold rolling machinery for several times to gradually obtain the desired shape and size.

3.Material properties: due to the action of high temperature, in the hot rolling process, the grains are rearranged, the structure is homogeneous, and the material has good plasticity and toughness; Whereas, the cold rolling process does not involve high temperature treatment, and the grains are fine and distorted, so cold-rolled materials usually have higher hardness and strength than hot-rolled materials.

4.Surface quality: Due to the action of high temperature, in the hot rolling process, the surface of the billet will form oxide scale, rust and other bad surface conditions, so the surface quality of the hot rolled material is relatively poor; Whereas, the cold rolling process is carried out at room temperature, resulting in a smooth and scale-free surface.

5.Dimensional accuracy: due to the high-temperature plastic deformation of the hot-rolled billet in the trace, the dimensional accuracy is relatively low; Whereas, cold-rolled steel is controlled by multiple cold rolls to control the size and shape, and has high dimensional accuracy.

According to the specific needs and application scenarios, it is important to choose the appropriate processing technology and material type. Hot rolling is often used for a.

Hot rolling and cold rolling are two common metal processing methods, and their differences are mainly reflected in the following aspects:

1.Processing temperature: Hot rolling is carried out at high temperatures, usually above the recrystallization temperature of steel; Whereas, cold rolling is carried out at room temperature, that is, processing is carried out at room temperature.

2.Performance: Due to the high temperature processing in the hot rolling process, the grain refinement of the material, the internal stress is relieved, and it is conducive to improving the plasticity and toughness of the material.

The cold rolling process, on the other hand, deforms the grains of the material, increasing the hardness and strength of the material, but may reduce the plasticity and toughness of the material.

3.Surface quality: Hot rolling will produce a certain oxide scale or flakes on the surface of the steel, which needs to be removed by subsequent treatment, so the surface quality of hot rolling is poor. The cold rolling process, on the other hand, can obtain a better surface quality and usually has a smooth appearance.

4.Product size: Hot rolling is usually used for the production of large-size steel such as thick plates and billets, while cold rolling is suitable for the processing of small-sized steel such as thin plates and thin-walled pipes.

5.Processing complexity: Relatively speaking, the hot rolling process is simpler than the cold rolling process and is more suitable for large-scale production. Cold rolling is more complex, and the process requires more control and precision.

Depending on the specific needs and application scenarios, it is necessary to choose between hot rolling or cold rolling processes for metal processing. In practice, steel manufacturers provide product identification based on different process and performance characteristics.