What is the difference and connection between hot and cold steel?

Cold rolling is a cold working process for steel bars that has emerged in recent years. It is to roll the surface of the round steel bar out of the pattern at room temperature. This can improve the hardness and surface grip of the rebar.

This kind of steel is limited in the use of parts, but it can significantly save steel in terms of tensile strength. Regarding the production and acceptance of the steel, the state has mature standards. Hot rolling and cold rolling are subject to different standards.

If there is a connection, it is that the material used for cold-rolled steel bars is hot-rolled steel bars.

Cold working of rebar includes:

1.Cold drawing: It can improve the yield degree and save materials, and the hot-rolled steel bar is tensioned with cold drawing equipment to make it elongated. After cold drawing, the yield strength can be increased by 20%-30%, and the steel can be saved by 10%-20%.Cold drawing: high tensile strength, low plasticity, high brittleness. At room temperature, the &6-8FR HPB235 steel bar is strongly pulled through the wire drawing die.

3.Cold twisting: HPB235 disc rod is formed by cold drawing, straightening and cold twisting of the steel bar cold rolling torsioner, and the continuous spiral reinforced steel bar with a certain pitch is formed. There is no obvious yield, and the plasticity is reduced.

4.Cold-Tied Rebar: I don't know.

Hot-rolled steel bar: a pressure processing method that makes the processed steel billet pass through the gap (various shapes) of a pair of rotating rolls at high temperature, and the material cross-section is reduced and the length is increased due to the compression of the rolls.

Hot-drawn steel is rolled when it is hot, and cold-drawn steel is rolled when it is cold, and the toughness of cold-drawn steel is better.

Cold-rolled steel vs hot-drawn steel

Cold-rolled steel is steel that has been produced by cold rolling. Cold rolling is the process of further thinning the steel plate to the target thickness at room temperature. Compared to hot-rolled steel plates, cold-rolled steel plates have a more precise thickness, a smooth and beautiful surface, and a variety of superior mechanical properties, especially in terms of processing properties.

Hot rolled steel is made of continuous casting slab or initial rolling slab as raw material, heated by a step-by-step heating furnace, high-pressure water descaling into the rough sail such as the rolling mill, the rough rolling car stops the material through the cutting head, tail, and then enters the finishing mill, the implementation of computer control rolling, after the final rolling, it will go through laminar flow cooling (computer controlled cooling rate) and coiler coiling, become a straight hair roll.

Difference Between Cold Rolled Steel and Hot Rolled Steel

1. Appearance and surface quality

Because the cold-drawn steel is obtained by the hot-rolled steel after the cold-rolled process, and the cold-rolled steel will also carry out some surface finishing, so the cold-rolled steel is better than the hot-rolled steel in terms of surface quality (such as surface roughness, etc.), so if there are higher requirements for the coating quality of the product such as post-painting, the cold-rolled steel will generally be selected, and the hot-rolled steel can be divided into pickled plate and unpickled plate, and the surface of the pickled plate is normal metallic color due to pickling, but the surface is not cold-rolled so the surface is still not as high as the cold-rolled steel. Unpickled plates usually have an oxide layer on the surface, a black layer, or an iron oxide black layer. Generally speaking, it is as if it has been roasted by fire, and if the storage environment is not good, it will usually have a little rust.

2. Performance: Under normal circumstances, there is no difference between the mechanical properties of hot-rolled steel and cold-rolled steel in the project, although there is a certain work hardening of cold-rolled steel in the process of cold rolling, (but it is not excluded that the mechanical properties are strict, then it needs to be treated differently), cold-rolled steel will usually be slightly higher than the hardness and strength of hot-rolled steel, and the hardness of the surface is also higher. But in any case, the strength of annealed cold-drawn steel is higher than that of hot-drawn steel.

3. Forming performance: because the performance of cold and hot steel is basically not too much, the influencing factors of forming performance depend on the quality of its surface, because the quality of the surface is better than that of cold steel, so generally speaking, the steel plate of the same material, the cold steel is better than the forming effect of the steel plate.

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Both HW and HM are hot-rolled.

HW is called wide flange H-beam, and hot-rolled H-beam refers to the cross-sectional strip steel produced by continuous casting billet and hot-rolled billet as raw materials, through heating and universal rolling machine.

HM middle flange H-beam submerged arc welding H-beam adopts Wuzhu process: steel plate, automatic slitting assembly, automatic submerged arc welding, flaw detection, flange correction, web correction, end face processing, sandblasting and rust removal, painting.

Introduction to low-alloy H-beams

Low-alloy H-beam is a kind of high-efficiency section with more optimized cross-sectional area allocation and more reasonable strength-to-weight ratio, which is named because its cross-section is the same as the English letter "H".

Because all parts of the low-alloy H-beam are arranged at right angles, the low-alloy H-beam has the advantages of strong bending resistance, simple construction, cost saving and light structural weight in all directions, and has been widely used.

Hot-rolled coil: It is made of slab (mainly continuous casting billet) as raw material, and is made into steel strip by roughing mill and finishing mill after heating. The hot steel strip from the last rolling mill is cooled to the set temperature by laminar flow, and then rolled into a steel strip coil by the coiler, and the cooled steel strip coil is processed into steel plate, flat coil and slitting steel strip products according to the different needs of users through different finishing lines (leveling, straightening, cross-cutting or slitting, inspection, weighing, packaging and marking, etc.).

To put it simply, a billet is heated (that is, the kind of red and hot steel in TV) after several rolls, and then cut the edge and corrected into a steel plate, which is called hot rolling.

The thickness of hot-rolled coil (in the form of flat plate or coil) is generally between, of which the hot-rolled coil ** gradually decreases from thin to thick; Most of the steel mills are basically the same, some manufacturers, markets and hot plate coils may be higher than the plate, the hot plate coil represents the specification of thick products, and under normal circumstances, the plate is slightly higher than the coil.

Cold-rolled coil: using hot-rolled steel coil as raw material, cold continuous rolling after pickling to remove the oxide scale, the finished product is rolled hard coil, due to the cold work hardening caused by continuous cold deformation, the strength and hardness of the rolled hard coil rise, and the toughness index decreases, so the stamping performance will deteriorate, and it can only be used for simple deformation parts. Rolled hard coils can be used as raw materials for hot-dip galvanizing plants, because hot-dip galvanizing units are provided with annealing lines.

The weight of the rolled hard coil is generally 6 tons, and the steel coil is continuously rolled at room temperature for hot rolling pickled coil, with an inner diameter of 610mm. Cold rolling is processed and rolled on the basis of hot-rolled coils, generally speaking, it is hot-rolled--- pickled --- cold-rolled. Cold rolling is processed from hot-rolled plate at room temperature, although it will also heat up the steel plate during the processing process, but it is still called cold rolling.

Cold-rolled coil (in the form of a flat plate or coil) is generally in between, which does not include the product ** gradually decreases from thin to thick, the product ** is basically the same, greater than less than or equal to the cold coil ** slightly higher than the group distance cold coil **, the representative specification of the cold-rolled coil is that under normal circumstances, the ** of the flat plate is slightly higher than the ** of the coil.

Go to Wangyao ** to understand, steel knowledge, steel ** are available.

One. Cold-rolled ribbed steel bar is a kind of steel bar with a two-sided or three-sided crescent shape formed by using hot-rolled wire rod to reduce the diameter of multiple cold-rolled ribs, pressing ribs and eliminating internal stress. Cold rolling is processed from hot-rolled plate at room temperature, cold-rolled is cold working, including cold drawing, cold drawing, rust removal, straightening, and the most important thing is through cold drawing strengthening and steel aging, so that the performance of steel has changed!

The cold-rolled hardness is high, and the processing is relatively difficult, but it is not easy to deform and the strength is high. Due to a certain degree of work hardening, cold rolling has low toughness, but can achieve a good yield ratio, and because the yield point is close to the tensile strength, there is no foresight of danger in the use process, and accidents are prone to occur when the load exceeds the allowable load. Cold-rolled ribbed steel bar in the prestressed concrete member, is the replacement product of cold-drawn low-carbon steel wire, in the cast-in-place concrete structure, then can replace the grade steel bar, to save steel, is a better one of the same kind of cold-worked steel.

Now it is commonly used in various construction sites, and there are many sizes. In the cast-in-place concrete structure of the house and various public buildings, the cold-rolled ribbed steel bar can be used for the following purposes:

1. The main reinforcement and distribution reinforcement of cast-in-place floor slabs and roof panels.

2. Horizontal and vertical distribution of ribs in the shear wall.

3. When the stirrups in the beam and column are calculated according to the stressed stirrups, the design value of their tensile strength is 310N mm [2].

4. Reinforcement of ring beams and structural columns.

Two. Hot rolling is hot working, so that the inside of the steel is recrystallized, so that its material properties are better, and the blacksmith's treasure knife is the process of hot rolling (I have always seen it in the movie). The hot-rolled hardness is low, the processing is easy, and the ductility is good.

The hot-rolled strength is relatively low, the surface quality is almost (oxidation, low finish), but the plasticity is good, hot-rolled, the mechanical properties of Liangshansen are far less than cold working, and also inferior to forging processing, but have good toughness and ductility.

Three. When the cost is not considered, cold rolling is better than hot rolling, but each has its own advantages and disadvantages.

Cold-rolled ribbed steel bar is made of ordinary wire rod by cold rolling extrusion into ribbed steel bar, the diameter of the ribbed is generally 5-11mm, mainly used for various cast-in-place plates, the strength is much higher than that of first-class steel. It is a processing process of wire rod or round steel through quasi-rolling and ribbing, its strength should be increased by nearly double, and the grip and wrapping force of cutting is increased by 4-5 times, and it is used in prestressed components, which can save 50-7okg m3 of cement; Used in non-stress risk components, it can save 20-40% of steel.

The grade of hot-rolled ribbed steel bars consists of HRB and the minimum yield point of the grade. H, R, and B are the first letters of the three words "hotrolled", "ribbed" and "bars", respectively.

Its advantages are:

a, economical: due to the high strength, the use of new grade rebar rebar comparable grade rebar rebar can save 10 15% of steel, so can reduce the construction cost of construction projects.

B. High strength and good toughness: the use of micro-alloying treatment, the yield point is more than 400MPa, and the tensile strength is more than 570MPa, which is 20% higher than that of grade threaded steel bars.

c. Seismic resistance: vanadium-containing steel bars have high bending resistance, aging performance, high low-cycle fatigue performance, and their seismic performance is significantly better than that of grade threaded steel bars.

d. Easy welding: due to the carbon content, the welding performance is good, and it is suitable for various welding methods, and the process is simple and convenient.

E, convenient construction: the use of new grade threaded steel bar increases the construction clearance, provides a guarantee for the convenience of construction and the quality of construction.

Cold-rolled steel: Ordinary hot-rolled steel is over-drawn by strong drawing.

Strain hardening. The material of the stage, the strength of the eggplant.

Very high, tough, poor weldability, brittle and hard, mainly used for steel plates. Cold-drawn steel: all kinds of cold-drawn steel produced by cold-drawn methods.

Steel. The special shelter points of cold-drawn steel are: high precision and surface.

Quality. Good. Cold drawing is mainly used in production.

Steel wire. It is also used to produce diameters up to 50 mm. Bar. And.

Hexagonal steel. and those with a diameter of 76mm or less. Steel tube.

Market research shows that cold rolling is rolling under recrystallization, but it is generally understood to be rolling using materials that are rolled at room temperature. Cold rolling of aluminum is divided into plate rolling and foil rolling. The thickness above is called a plate, and the thickness below is called a foil.

Oumei Duo uses 3 6 continuous rolling mills as cold rolling equipment. Due to the lack of heating in the production process, there are no defects such as pitting and iron oxide scale that often occur in hot rolling, and the surface is excellent and the finish is high. Moreover, the dimensional accuracy of cold-rolled products is high, and the performance and structure of the products can meet some special use requirements, such as electromagnetic properties, deep drawing properties, etc.

Common cold-rolled sheet steels:

Cold-rolled ordinary thin steel plate: It is made of ordinary carbon structural steel or low-alloy structural steel cold-rolled. The surface quality of the cold-rolled plate is better. It has good stamping performance. The requirements should be to ensure that the cold bending and cup tests are qualified, and they are often used in automotive and other industries and raw materials for plated plates.

Cold-rolled high-quality steel plate: mainly including various high-quality steel cold-rolled sheets, the most commonly used is carbon structural steel plates, especially cold-rolled sheets for deep drawing, which are cold-rolled sheets made of low-carbon high-quality steel 08al, and the steel plates are divided into three groups according to surface quality; , respectively represents a particularly high-level, high-grade, higher finishing surface, according to the drawing level is divided into ZF, HF, F grade (on behalf of the most complex, very complex, complex parts used for punching drawing), according to the thickness of the steel plate allowable deviation, and divided into A, B two levels of precision, widely used in the automobile tractor industry.

Cold-rolled steel plate, with smooth surface and excellent processing, is used in automobiles, refrigerators, washing machines and other household appliances, as well as industrial equipment and various building materials. With the development of the economy, cold-rolled steel plate has been known as a necessary material in modern society. Classification of cold-rolled products:

Hot-rolled pickling, rolling hard coil, ordinary cold rolling, galvanizing (electro-galvanizing, fingerprint resistance, hot-dip galvanizing), aluminum-zinc plating, electro-tinning, color coating, electrical steel (silicon steel sheet), etc.