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To plate rolling process, for example, introduced in the rolling process.

First, the medium-sized steel plate is an indispensable national modernization of steel varieties, (is widely used in large diameter pipes, pressure vessels, boilers, bridges, offshore platforms, all types of ships, armor, vehicles, building components, machines Structure and other fields) Plate rolling mill level in a country is also one of the signs of a country's steel industry and equipment level, and thus to a certain extent, a reflection of a country's industrial level. // With the development of our country's industry, for medium and thick steel products, higher requirements have been put forward both in quantity and quality. // Therefore, the study of plate rolling process is necessary and promising. What is the plate? In accordance with the custom, according to the thickness of the plate is divided into the plate, plate, especially thick plate, the customary plate, plate, plate are collectively referred to as plate. At present, most of the plate specifications produced by plate rolling mills in China are 4-250mm thick. Width of 1200-3900mm, the length is generally not more than 12m.

Second, the introduction of rolling process

(A) plate production of raw materials

Plate production of raw materials through the ingot - initial bloom - continuous casting billet evolution. Continuous casting billet: continuous casting of molten steel into its mold by slab caster, a certain thickness and width of the slab is continuously drawn and cut into a certain length.

Advantages: 1. Simplify and shorten the production process, reduce equipment and capital. 2. Energy conservation, improve metal yield. 3. Physical and chemical properties of uniform.

Therefore, the use of continuous casting billet for improving product quality and reduce production costs is of great significance.

(B) slab heating

Slab heating using continuous heating furnace, the heating process is divided into preheating section, heating section and soaking section.

Preheat section: First, the heating is slow, so as not to heat up too fast, resulting in thick slab temperature difference is too large, resulting in thermal stress caused by internal cracks; second is the use of waste heat heating segment slab preheating, you can save energy. Heating section: increase the heating rate.

The soaking section: the interior of the slab is heated evenly.

Continuous heating furnace based on slab in the furnace forward in different ways are divided into push-type furnace and stepping furnace two. As the push-type heating furnace slab heating uneven; slab lower surface scratches and other shortcomings are gradually being replaced by step-type furnace.

Stepping furnace advantages: 1. Uniform heating 2. Slab surface without scratching 3. Slab does not produce arching phenomenon.

(Three) phosphorus removal

Slab in the rolling process prior to rolling and must be removed during the heat of the furnace oxide scale and the regeneration process generated during the regeneration of the scale, a process called phosphorus removal. Phosphorus removal is very important for ensuring the surface quality of the Hong Kong version. Phosphorus removal equipment is divided into: Here we use "high-pressure water phosphorus removal", the use of high-pressure water impact crushing and removal of the surface of the slab oxide scale has been widely used.

(D) rough rolling

The slags after phosphorus removal are sent to the roughing mill. The main task of the roughing stage is to widen the slab to the required width and to extend it to a large extent.

By slab into the rolling mill in different ways can be divided into full cross-rolling method, full-rolling method, cross-rolling - vertical rolling method. When the slab length greater than or equal to the width of the plate, you can directly use the full cross-rolling method.

When the slab width slightly greater than or equal to the width of the finished steel, you can use the full-length rolling method.

Cross-rolling - vertical rolling method: including vertical rolling, rolling and rolling vertical rolling three processes. Spread rolls are used to rotate the slab 90 ° during roll broadening.

Rotating roller table: Roller roller is a ladder-type or conical shape, the adjacent two rollers are alternately arranged and turn the opposite rotation of the slab torque generated rotation, when no need to rotate all of the roller slab roll steering the same as General roller roller use.

(E) insulation device, cut and tail and phosphorus removal

The insulation on the roller table between roughing mill and finishing mill helps to improve product quality and save energy. Cut the tail: the bad shape of the head and tail cut off, so that the smooth slab into the finishing unit. In order to remove the secondary iron oxide produced in the rolling process, a phosphorus removal device is installed on the rolling mill.

(F) finishing

The main task of the finishing stage is quality control, which is a core part of the rolling production process. At present, due to the increasingly higher requirements on the dimensional accuracy and quality of the slab, the form of finishing rolling mills of two four-high rolling mills is increasingly valued.

(Seven) straightening

Straightening is to ensure that the flatness of steel meets the standard requirements of the product. Plate straightening equipment can be roughly divided into roller straightening machine and pressure straightening machine. (Plate 105) The normal rolling notification uses hot straightening, so we chose a roll-type heat straightener.

(Eight) cooling

The cooling rate of steel plate after rolling has a great influence on its microstructure and mechanical properties. Rapid cooling after rolling, inhibition of ferrite growth, further refinement of ferrite, pearlite uniform distribution, resulting in small bainite, improve strength and impact toughness. When the plate through the hot straightening machine after the use of disc roll cooling bed cooling steel. Third, the flash process explain the selection of slab as rolling raw materials. The billet is placed on the receiving roller conveyor and sent to the loading position. The billet is pushed into the furnace through the loading pusher. The slab is moved in the furnace by the stepping mechanism to realize the heating. The heated slab is produced by tapping Machine out from the furnace on the discharge end of the conveyor roller, sent to the high-pressure water phosphorus removal tank for a dephosphorization, and then into the roughing mill roughing, after two phosphorus removal into the finishing unit for finishing rolling, after The temperature of the finishing slab can reach as high as 1000 °, and the slab can be quickly cooled to 700 ° through the laminar cooling device, hot straightened, and the straightened steel sheet is slowly cooled into the cooling bed.

Cold rolled articles
 
1. Steel and pig iron are all alloys of iron and carbon. The main difference between them is the carbon content. The carbon content of steel is generally lower than 1.7%, while the carbon content of pig iron is generally between 1.7% and 4.3% .

2. Ironmaking into the furnace raw materials are: iron ore, fuel and flux, the fuel is used: coke

3 steelmaking methods are: oxygen furnace steelmaking open hearth steelmaking electric furnace steelmaking, which is the largest production of a steelmaking method is: converter steelmaking.

4. Baosteel ladle dusting treatment is mainly used for edge casting molten steel desulfurization and control of inclusions in steel.

5 at the end of the steel must be a certain degree of deoxy, deoxy specific requirements of the operation is to join the furnace or ladle oxygen binding ability strong deoxidizer, commonly used deoxidizer Mn, Si, Al, based Mn As a weak deoxidizer, Al is a strong deoxidizer Si deoxidation center.

  6. The quality of ingot plays an important role in the deoxidation of steel, according to different ways of deoxidation, ingot can be divided into boiling steel, gland steel, semi-killed steel and killed steel.

7. Billet at room temperature is hard and poor plasticity, not easy processing, generally heated to 1150 --- 1300 ℃ for rolling, this method is called hot-rolled, cold-rolled billet (ingot) is hot-rolled to After a certain size, and then in a cold state of rolling a method.

8. At present, the most widely used method for removing scale in cold tandem rolling is chemical treatment based on pickling.

9. After cold rolling, remove the surface by rolling the oil-rolling process called "degreasing", the specific methods of electrolytic cleaning, brush cleaning, cleaning and burning on the machine and several degreasing.

10. Annealing is the most important heat treatment process in the cold-rolled strip production. The strip is heated to a certain temperature (600-720 ° C) in the furnace according to different types of steel, and then is kept warm and slowly cooled. Annealed steel strips eliminate work hardening and achieve good mechanical properties. Annealing method has a bell furnace annealing and continuous annealing points. Bell furnace annealing cycle generally takes 3-5 days. Side-by-side annealing horizontal and tower two, the speed of the strip through the unit up to 600 m / min, the strip at a very high speed operation, only a few minutes in the furnace time. Finished strip annealing should be carried out after the flat (reduction rate of 0.50 --- 4%)

11. After the cold rolled coil is sent directly to the hot-dip galvanizing machine processing, steel surface degreasing cleaning, continuous annealing, immersion zinc pot (with molten zinc) galvanized, when the molten zinc out When the surface has been coated with zinc, the two sides with an air knife blowing method to control the thickness of the zinc layer and the use of zinc flower controller to control the size of zinc flower crystallization of zinc (zinc can also be used in the lead content as a control zinc flower size The means until the product of zero spangle).

12. After cold-rolled electrical steel strip into the special annealing furnace for annealing and coating insulation, medium and low grade electrical steel generally do not need intermediate annealing, the purpose of the first annealing is decarburization, the second is Control magnetic. Non-oriented electrical steel can also be not fully annealed or coated with insulation is not available, known as the semi-process electrical steel.

1. Hot rolling process lubrication mechanism

Hot rolling process lubrication is a dynamic process in the deformation zone under high temperature, high pressure, high-speed changes in the state of the oil is difficult to experimentally simulated, one of the views that the hot-rolled, the seam in the harsh working conditions, the roll surface Easily wear and tear, resulting in the surface pits and pitting; and pits and pitting and aggravate wear and tear, resulting in a vicious cycle, the roll quickly scrapped due to wear and tear. If the roll before entering the gap, the surface of the rolling spray lubrication material to form a lubricating film, although the film may be a small part of the film before entering the roll seam is burned by high heat rolling, but most are bitten Into the roll gap, the work roll and rolling contact surface to form a thin layer of lubricating film. Although the contact time between oil film and roll is only a few hundredths of a second, the oil film can lubricate before it is burnt, which can reduce roll wear and prevent pits and pitting soon.

Due to the characteristics of modern hot rolling process is high temperature, high pressure, high speed, hot work roll surface instantaneous temperature up to 600 ∽ 700,, cooling and cooling stabilized at 50 ∽ 80,, therefore, in order to meet the characteristics of hot-rolled process, hot-rolled Lubricants should have the following characteristics:

(1) With the structure of high polarity molecules, it has excellent wettability on the roll surface, which can form a uniform thin layer lubricating film quickly, reduce friction and reduce wear.

(2) The lubricating film has strong adhesive force and instantaneous anti-high pressure capability. It provides stable and excellent lubrication in the roll gap, preventing or reducing the formation of oxides on the work roll and the supporting rod.

(3) The lubricating film in the roll gap can prevent the direct contact between the roll and the rolled material, and avoid the formation of adhesion between the roll and the rolled material at high temperature.

(4) The residual lubricating oil on the strip at the exit of the rolling mill should be burned in the shortest possible time to prevent residual oil from remaining on the surface of the strip and forming new pollutants.

(5) lubricating oil has a high flash point and thermal decomposition stability.

2. The role of hot-rolled lubrication process Application of hot-rolled rolling lubrication technology has obvious advantages:

(1) to reduce the friction coefficient between the roll and rolling hot-rolled friction coefficient without lubrication is generally 0.35. The coefficient of friction with effective lubrication can be reduced to 0.12.

(2) can reduce the rolling force, easy rolling thin gauge strip generally reduce the rolling force of 10% to 25%, thereby reducing energy consumption.

(3) can reduce the roll consumption and reserves, improve work rate In the hot-rolled conditions, the work roll contact with the strip and the cooling water will generate a very hard oxide such as Fe3O4 and Fe2O3, which stick to the roll surface, the roll generated Dark-colored surface, black skin. Black skin is the main reason for the abnormal wear of the roll. The use of hot-rolled lubrication, the roll and the rolling material is separated by a layer of lubricating film between the surface to prevent the roll to produce black skin, reducing roll wear and prolong the life of the work roll; roll change can reduce the time and improve the rolling operation Rate, reduce the work roll reserve. At the same time, the wear and reserve of the backup roll are also reduced.

(4) can reduce the scale into the pressure to improve the roll surface state After using hot-rolled lubrication, the roll and rolling pieces are separated by a layer of lubricating film to prevent the roll surface black skin, thus improving the surface quality of the product, Also improves pickling efficiency.

(5) Rolling kilometers can be extended to reduce the number of roll change, increase operating time.