hot rolled steel
Hot rolling and cold rolling are the two main methods of steel processing, each with its own unique advantages and disadvantages.
Fast forming speed and high output: The hot rolling process adopts a continuous and automated production method, which can quickly complete the forming of steel and has high production efficiency.
No damage to the coating: During the hot rolling process, the surface coating of the steel is not easily damaged and maintains good surface quality.
Can be made into various cross-section forms: hot rolling can adapt to different cross-section requirements and produce steel products of various shapes to meet diverse usage conditions.
Significantly reduce energy consumption and reduce costs: During hot rolling, the metal has high plasticity and low deformation resistance, which can significantly reduce the energy consumption of metal deformation.
Improve the processing performance of metals and alloys: Hot rolling can break the coarse grains in the casting state, reduce or eliminate casting defects, and improve the processing performance of alloys.
Residual stress in the cross section: During the hot rolling process, residual stress may exist inside the steel, which affects the overall and local buckling characteristics of the steel.
Poor torsion resistance: Hot-rolled steel is generally an open section with low free torsion stiffness, easy to twist when bent, and poor torsion resistance.
Weak ability to bear local concentrated loads: The wall thickness of hot-rolled steel is small, and it is not thickened at the corners where the plates are connected, so the ability to bear local concentrated loads is weak.
The thickness of the product is difficult to control: The control accuracy of the thickness of the hot-rolled product is relatively poor, and the surface is rougher than that of the cold-rolled product.
Uneven organization and performance: Hot rolling cannot control the mechanical properties required by the product very accurately, and the organization and performance of the hot-rolled product cannot be uniform.
Fast forming speed and high output: Cold rolling also has a faster forming speed and higher output.
No damage to the coating: During the cold rolling process, the coating on the surface of the steel is also not easily damaged.
Various cross-sectional forms: Cold rolling can also produce steel with a variety of cross-sectional forms.
Increasing the yield point of steel: Cold rolling can cause greater plastic deformation of steel, thereby increasing the yield point of steel.
Good surface quality: The surface quality, appearance, and dimensional accuracy of cold-rolled steel plates are better than those of hot-rolled plates.
Residual stress: During the cold rolling process, residual stress may also exist inside the steel.
Poor torsional performance: The cold-rolled steel section is generally an open section, the free torsional stiffness of the section is low, and the torsional performance is poor.
Weak ability to withstand local concentrated loads: The wall thickness of cold-rolled steel is small, and the ability to withstand local concentrated loads is weak.
To sum up, hot rolling and cold rolling each have their own advantages and disadvantages. The choice of processing method mainly depends on the specific usage requirements and conditions.
Hot-rolled steel: slabs are used as raw materials, and after heating, they are made into strip steel by rough rolling units and finishing rolling units.
Cold-rolled steel: hot-rolled steel coils are used as raw materials, and after pickling to remove the oxide scale, cold rolling is carried out, and the finished product is hard rolled coils.
Strength: Although not very high, it is enough to meet general use needs.
Plasticity and weldability: Good, so hot-rolled steel is more commonly used.
Appearance color: Not bright, the surface may have an oxide layer or a black layer of ferroferric oxide.
Strength: High.
Toughness and weldability: Relatively poor, the material is hard and brittle.
Surface quality: Since surface finishing is performed during the cold rolling process, the surface quality of cold-rolled steel is usually better than that of hot-rolled steel, and the surface is bright.
Hot-rolled steel: ironmaking → steelmaking → continuous casting (or die casting) → hot rolling (hot-rolled products). During the hot rolling process, the material needs to be heated to a high temperature, and generally it needs to be heated above the recrystallization temperature before rolling to allow the steel to recrystallize inside and have better material properties.
Cold-rolled steel: On the basis of hot-rolled steel, further cold rolling is performed, that is, ironmaking → steelmaking → continuous casting (or die casting) → hot rolling (hot-rolled products) → cold rolling (cold-rolled products). The cold rolling process requires a large rolling mill power, and the rolling efficiency is low. Intermediate annealing is usually required to eliminate work hardening.
Hot-rolled steel: The appearance color is usually black or dark gray, and the surface may have an oxide layer or an iron oxide layer.
Cold rolled steel: The surface quality is better, usually metallic in color, smooth and bright.
To sum up, there are significant differences between hot-rolled steel and cold-rolled steel in terms of formation, performance, process, appearance and surface quality. Hot-rolled steel has good plasticity and weldability, but its surface quality is relatively poor; while cold-rolled steel has higher strength and better surface quality, but its toughness and weldability are relatively poor. Therefore, in practical applications, the appropriate steel type needs to be selected according to specific needs.
The cross section is H-shaped, mainly used to manufacture large building structures, engineering machinery, large containers, etc.
Common specifications include H100, H200, H300, etc.
I-shaped steel
The cross section is I-shaped, similar to H-shaped steel, and is often used in large building structures, such as bridges, squares, reinforced concrete columns, steel structure buildings, etc.
Common specifications include I100, I200, I300, etc.
Angle steel
It has an L-shaped cross section and is mainly used to manufacture components of various mechanical equipment, induction facilities, power equipment structures, light building components, etc.
Common specifications include 50×50, 75×75, 100×100, etc.
Channel steel
The cross section is channel-shaped, commonly used to manufacture various structural parts, storage racks, etc.
Round steel)
Steel with uniform diameter, commonly used in machinery manufacturing, light buildings and bridge components, etc.
Square steel
It has a square cross section and is commonly used in building structures, machinery manufacturing, electrical equipment, etc.
It is a steel plate processed by cold rolling, with a thickness of generally more than 0.5mm and a width of generally between 500-2500mm.
It is widely used in automobiles, home appliances, electronics, construction and other fields, such as car doors, housings, refrigerators and air-conditioning compressors.
Cold-rolled strip steel is a steel strip processed by cold rolling, with a width of generally between 100-800mm and a thickness of generally between 0.1-4.0mm.
It is widely used in construction, electronics, electrical appliances, automobiles and other fields, such as wires, cables, metal hoses, refrigerator door panels, etc.
Cold-rolled bar is a steel bar processed by cold rolling, with a diameter of generally 5-50mm and a length of generally between 2-6 meters.
It is widely used in mechanical processing, automotive parts, construction and electrical appliances and other fields.
Hot-rolled steel is mainly known for its high production efficiency and large cross-sectional size, and is widely used in fields such as large building structures and heavy machinery.
Cold-rolled steel is favored for its high dimensional accuracy, surface quality and specific mechanical properties. It is often used in fields with high precision requirements such as automobiles, home appliances, and electronics.
Hot-rolled steel and cold-rolled steel each have their own characteristics and application areas, and choosing the right steel type is critical to meeting engineering needs and ensuring product quality.
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