The way to obtain a steel strip or sheet

 

The invention relates to the production of steel strip or sheet for deep drawing in the manufacture of cans. The liquid steel is poured into the continuous casting for forming thin slab and using foundry heat slab served in the heating means, compresses in a reduction mill to an intermediate thickness, and continue rolling in the finishing rolling stands with obtaining a steel strip or sheet of the desired final thickness. To obtain a steel strip, laminated in the ferritic condition, the slab or part thereof served continuously at least from the heating means at a speed, which essentially correspond to the speed input in the crimp crate, and after reducing the thickness of the serves of the reduction mill to the processing device that is located after the finishing rolling stands, and the band comes out of the reduction mill, cooled to ferritic region, in which the steel is essentially ferritic structure, and the strip laminated in the ferritic condition, after reaching the desired final thickness cut into pieces of the required length, which is wound into a roll, where the steel strip is made of low carbon steel with a carbon content of from 0.1 to 0.01 steel, in the continuous casting, on the one hand, and steel, rolled in a reduction mill, on the other hand. In the second embodiment, the steel strip is cooled at an intermediate thickness of less than 1.8 mm from the austenitic region to ferritic region, where the total compression after rolling in the ferritic region is less than 90%. The invention allows to obtain a steel strip or sheet with greater efficiency. 2 S. and 3 C.p. f-crystals, 3 ill.

The invention relates to a method for obtaining a steel strip or sheet for deep drawing by making deep drawn cans.

When in the following text mention steel strip, it should be understood that this term includes steel sheet. The term "thin slab" means a strip of a thickness of less than 150 mm, mostly less than 100 mm

According to the known from the prior art method the molten steel poured into the continuous casting to form a thin slab and using foundry heat it passed through the heating means, compresses in a reduction mill to an intermediate thickness, and continue rolling in the finishing rolling stands with obtaining a steel strip or sheet of the desired end touchoromo thin continuous-cast steel slab after homogenization tunnel heating means (furnace) rolled over several stages of hot rolling, namely, in the austenitic region, receiving strip having a thickness less than 2 mm

To achieve the final thickness using a rolling devices and lines rolling, which can be implemented in practice, the heated steel strip, mainly in the induction furnace, at least after the first stand of the rolling mill.

Between continuous casting and tunnel heating means (oven) is a separating device, which is used for cutting thin continuous-cast slab into parts of approximately equal length, which are subjected to a homogenization tunnel heating means at a temperature of from about 1050 to 1150oC. After exiting the tunnel heating means part of the slab can, if necessary, again cut in half, the weight of which corresponds to the weight of the wound roll, which wound steel strip after rolling means.

The present invention is a method similar to the method known type, which provides more options and, in addition, using which it is possible to obtain a steel strip or steel sheet with greater efficiency. For resi strip, laminated in the ferritic condition, the slab or part transferred continuously at least from the heating means at a speed, which essentially correspond to the speed input in the crimp crate, and after reducing the thickness of the tube stand to the processing device that is located after the finishing rolling stands, and the band comes out of the crimp rolling stands, cooled to a temperature at which the steel is essentially ferritic structure; (b) to obtain a steel strip, rolled in the austenitic state, the strip leaving the rolls reduction mill, is brought to a temperature in the austenitic range or maintain at this temperature and rolled her into the finishing rolling stands up to the final thickness essentially in the austenitic region, and then after rolling is cooled to a temperature of ferritic region.

In this context, the concept of the bar denotes the reduced slab thickness.

In the way of conventional type to obtain ferritic or cold-rolled strip of the original position is the hot rolling of steel, as is the carry out when using the known method of EP 0666112. Roll hot-rolled steel of this grade typically has a weight of from 16 to 30 so In this case voznikala/thickness, i.e., the thickness profile across the width of the strip and along the length of the strip. Due to the discontinuity in the material flow behavior in the rolling device of the initial and the terminal part of the hot rolled strip is different from the Central part. Controlling the login process to the finishing rolling mill and exiting the hot rolled strip during rolling in the ferritic condition or cold rolling and represents the above-mentioned problem. In practice, the use of modern or self-regulatory systems and numerical modeling in an attempt to make the front and rear ends that are inaccurate dimensions were as short as possible. However, each roll has front and rear ends, which are subject to rejection and may have a length up to several tens of meters.

In the devices used at the present time, the ratio of width/thickness of approximately 1200-1400, consider the maximum that can be tolerated in practice: increasing the ratio of width/thickness leads to overly long front and rear ends before reaching the steady state and hence the excess trimmings.

On the other hand, from the point of view of efficiency of the use of the width with the same or reduced thickness. In the consumer market requires relationships width/thickness of 2000 or more, but in practice, when using the known method it is impossible to achieve for the above reasons.

The method in accordance with the present invention allows to perform the crimping of the steel strip at any speed output from the heating means in intermittent or continuous operation mode, in the austenitic region, with cooling it to a temperature of ferritic region and rolling in the ferritic region to obtain the final thickness.

Proven suitability for use of a much more simple method of regulation with feedback to control the dimensions of the strip.

The present invention also allows you to understand that you can use a technique in which in accordance with the preceding technical solution in this way produce only hot-rolled strip, while using essentially the same tools that can also be used in this way to obtain, in addition to the steel strip, rolled in the austenitic state, and also the steel strip, laminated in the ferritic condition that has the properties of cold rolled strip.

This gives the opportunity for the bands, and more specifically, to obtain a steel strip, which have a much higher added value for the consumer market. In addition, the method provides a particular advantage when rolling ferritic strip in accordance with the stage and, as will be explained in the following text.

The invention also provides several other important advantages, as will be presented in the following text.

When performing the method according to the present invention it is preferable that the crimp was made in the austenitic region, as soon as possible after the heating means, which produce homogenization of the slab at a given temperature. In addition, it is preferable to choose a high rolling speed and high compression. In order to obtain steel with stable properties, it is necessary to avoid the rolling of the slab, or at least a significant part in the two-phase region, in which the austenitic and ferritic structures are adjacent to each other. After leaving the heating means homogenized and placed in the austenitic state, the slab is cooled faster than the side edges. It was found that cooling occurs primarily around the part of kremasti chilled side edges limit by rolling immediately after its exit from the furnace and preferably with high compression. This allows you to get in the lane exact shape and with a stable, predefined properties virtually over the entire width.

In fact, a homogeneous distribution of temperature homogenization in width, and the thickness of the slab provides an additional advantage over a wide operating range, which can be used in the present invention. Since it is undesirable to perform rolling in the two-phase region, the operating range in terms of the temperature limit on the sides of the temperature of the portion of the slab, which first enters the two-phase region, i.e., the plot edges. In the way of conventional type, the temperature of the Central part is much higher than the phase transition temperature, at which begins the transformation of austenite into ferrite. However, in order to be able to use a higher temperature of the Central part, in the preceding technical solution proposed to heat the edges. When using the present invention in this measure is not necessary, or necessary at least to a much lesser extent, as a result of the rolling process in the austenitic state, you can continue up until the Yes.

A more uniform temperature distribution prevents the situation where a relatively small part of the slab has transformed into a two-phase region, thereby making further rolling junk, while the greater part of it is still in the austenitic state and thus could still be rolling. It should also be noted that during cooling from the austenite region over a relatively small temperature interval in the temperature range within which the phase transformation, most of the material is turning. This means that even a slight drop in temperature below the phase transition temperature results in the fact that in most parts of the steel is turning. For this reason, in practice a significant concern in the temperature falls below the highest temperature in this temperature range.

A more detailed description of the variants of the present invention and the device for its implementation, as well as preferred options given in the patent application NL-1003293, which is believed to be thereby attached in its entirety to the present invention.

The present invention particularly Procol hoods, steel quality must meet several requirements, some of which are important requirements are discussed below.

To get tight, so-called two-part banks, the first of which consists of the base and the housing, and the second part is a lid, and the basis for the first part is the flat blank made of steel for deep drawing, which is first subjected to deep drawing to form a Cup having a diameter of, for example, 90 mm and a height of, for example, 30 mm, the walls of which are then subjected to the hood for the formation of banks having a diameter of, for example, 115 mm Typical thickness of the steel material at different stages of production are: the initial blank thickness of 0.26 mm, the thickness of the base and walls of the Cup of 0.26 mm, substrate thickness banks of 0.26 mm, a wall thickness of banks partly to 0.09 mm, the thickness of the upper edge of the banks of 0.15 mm

Steel for deep drawing must be extremely flexible and to remain so for an extended period of time, i.e., should not grow old. Aging leads to high effort deformation, cracking during deformation and surface defects caused by the slip lines. One of the ways protivodeistvia when using the possibility of producing much more light cans also affects in turn the need for high plasticity, starting with a given initial thickness of the workpiece, which is to achieve the lowest possible finite thickness of the walls of banks, as well as the top edge of the banks. The edge of the banks has specific requirements for steel for deep drawing. After the formation of the banks by drawing walls, the diameter of the upper edge decreases due to the process known as the formation of a neck, to be able to use the lid of a smaller size, thereby saving material for the cover. After necking along the top of the top edge to form a flange, to be able to attach the cover. The formation of a neck and a flange, in particular, are processes that demand high availability of additional ductility of steel for deep drawing, which has already been pre-predeterminada in the education corps.

In addition to the plasticity of the importance of cleanliness of the steel. The concept of purity in this case, means an amount which is limited by the presence of inclusions, mainly oxides or gaseous inclusions. The inclusion of such formed during the production of steel in devices for the production of steel with oxygen blowing and casting powder additives, the deep drawing. In the process of formation of a neck or flange inclusion can lead to the formation of cracks, which in turn cause subsequent leakage of banks, which was filled with content, and then sealed. In the process of storage and transportation of the content arising from the jar, may cause pollution, in particular, to cause damage to other cans and things around her, the number of which is many times more expensive than just deriving banks with its contents. Since the thickness of the edges can be reduced, the risk of cracks arising from inclusions increases. Therefore, the steel for deep drawing must not contain inclusions. Because of the inevitable inclusion in the existing method of production of steel, their sizes should be maintained as small as possible, and they must be present in very small quantities.

Another requirement relates to the level of anisotropy of the steel for deep drawing. When made in two installments to the Bank with a deep hood/hood walls or with fine walls, the upper edge of the banks does not fit into a flat surface, and actually has a wavy appearance on the peripheral surface of the banks. Among specialists wavy ridges p is Aiki. Ears be cropped to the smallest level in order to get a top edge which fits into a flat surface and can be deformed to form the flange, and this process leads to loss of metal. The size of the ears depends on the total reduction during cold rolling and of the carbon concentration.

Typically, the development process starts from the hot-rolled sheet or strip, having a thickness of 1.8 mm or more. When the compression approximately 85% of this leads to a final thickness of approximately 0,27 mm Based on the need to minimize the consumption of material for each of the banks, it is desirable to have a smaller thickness, preferably less than 0,21 mm Already discussed trends to obtain thicknesses of approximately 0,17 mm At a given initial thickness of approximately 1.8 mm this requires a reduction of over 90%. Under normal concentrations of carbon this leads to the formation of the ears of considerable size, and as a result trimming these ears leads to additional waste material, thereby partially negating the benefits gained from a smaller thickness. The solution was found in using ultra-low - or ultramicroporous steel (ULC-steel). The steel of this grade, which is generally concentric molten steel at the plant for production of steel with oxygen-blown so to a large part of the carbon burned. If you followed these can be made vacuum in the mold to further reduce the carbon content. As a result of the introduction of molten steel more oxygen it also leads to the appearance in the molten steel undesirable metal oxides that remain in the form of inclusions in a cast steel slab, and subsequently cold-rolled strip. The influence of inclusions increases with less thickness cold rolled steel. As shown, the inclusion of bear damage, as they can lead to the formation of cracks. As a result, the lower end of the thickness of this damaging impact, the more inherent ULC steel. The result is a low yield in varieties ULC steel, designed for packaging purposes because of the high number trimmings.

Another objective of the present invention is to provide a method of producing steel for deep drawing of grades low carbon grade steel, which in the usual sense means that the content of carbon is from 0.1 to 0.01%, allowing a small finite thickness at high yield material, as well as ensuring the achievement of other pre is no a low carbon steel, having a carbon content of from 0.1 to 0.01%, and it is subjected to cooling from the austenite region to ferritic region at an intermediate thickness of less than 1.8 mm, and the total compression during rolling in the ferritic region is less than 90%. The degree of anisotropy depends on the concentration of carbon and the total compression during rolling, which is a steel for deep drawing is subjected during rolling in the ferritic region.

The invention is based on the further understanding that the total compression in the ferritic region after the phase transition from the austenitic region is important from the point of view of education and ears that the formation of the ears can prevent or limit, if rolling to perform in the ferritic region while maintaining compression within certain limits, for a given carbon content, by entering in the ferritic region sufficiently thin strips.

A preferred variant of the method in accordance with the present invention is characterized by the fact that the total compression during rolling in the ferritic region is approximately less than 87%. The degree of compression during rolling, which provides the minimum anisotropy depends on the concentration of carbon increases with decreasing concentraciones anisotropy and, therefore, education minimum ears, is in the range of less than 87%, and more preferably less than 85%. In connection with high capacity for deformation, it is preferable that the total compression was more than 75%, and more preferably more than 80%.

Compression, which should be performed in the ferritic region, can be maintained at a low level, with a small finite thickness, in another embodiment of the present invention, which is characterized in that an intermediate thickness is less than 1.5 mm

In the described method proposed steel for deep drawing, which can be obtained in a known manner by using a well-known device and which allows you to get thinner steel for deep drawing, than hitherto possible. For rolling and further processing in the ferritic region can be used known techniques.

In Fig.1 schematically presents a side view of the device, which can be carried out a method in accordance with the present invention; Fig.2 presents a graph illustrating a curve of the change of the steel temperature as a function of position in the device of Fig. 3 presents a graph illustrating the thickness profile steel kakenya thin slabs. In this description of the installation for continuous casting, you should understand the installation, suitable for casting of thin steel slabs having a thickness of less than 150 mm, preferably less than 100 mm Position 2 indicated ladle, from which the molten steel to be poured, goes in gear bucket 3, which in this construction has the form of a vacuum transfer ladle. Lower gear bucket 3 is the mold 4, in which liquid steel is cleaned and where it solidifies at least partially. If necessary, the mold 4 can be equipped with an electromagnetic stirrer. Vacuum gear bucket and electromagnetic stirrer are optional, and each can be used for their own, providing the possibility of achieving a higher casting speed and the best internal quality steel castings. In the continuous casting of conventional type casting speed of approximately 6 m/min; additional measures, such as the use of a vacuum transfer ladle and/or electromagnetic stirrers, provide casting speed 8 m/min and more. Hardened thin slab enters the tunnel kiln 7, having a length of, for example, 200 the EU each part of the steel slab is much steel, the corresponding five to six regular rolls. In the furnace includes a chamber which accommodates several parts slab of this kind, for example, containing three parts of the slab. As a result, those parts of the installation that are below the furnace during the process stream, can operate continuously, while the ladle continuous casting must be replaced and start casting a new slab. Besides being in the furnace increases the time it parts of the slab, thereby providing improved homogenization of the parts of the slab at a given temperature. The speed at which the slab is supplied into the furnace corresponds to the speed of casting and is thus approximately 0.1 m/sec downstream from the furnace 7 is the tool 9 removal of scale, which in this case is a set snoring away spraying water under high pressure in order to bring down the oxides formed on the surface of the slab. The speed at which the slab passes through the means for descaling and enters the heating means 7, is approximately 0.15 m/S. Rolling tool 10, which performs the function of crimp tools, consists of two four-roll mill. EIG. 2 one can see that the temperature of the steel slab, which, when the output from the transfer ladle is at the level of 1450oWith falls with the passage of the roller conveyor approximately to the level of 1150oWith, and homogenization is performed in the heating medium at this temperature. As a result of intensive spraying water in the means 9 for descaling the temperature of the slab falls from approximately 1150 to 1050oAs during the process of austenization are determined, and in the process of ferritization, marked respectively a and f. In the rolling stands of the rolling tool 10, the temperature falls further 50oWith each pass through the rolls, so that the slab, which originally had a thickness of approximately 70 mm, was deformed in two stages, with an intermediate thickness of 42 mm, steel strip with a thickness of approximately 16,8 mm at a temperature of approximately 950oC. the thickness Profile as a function of the location shown in Fig. 3. The numbers indicate the thickness in mm of the cooling Means 11 and a set of 12 boxes for the rolls and, if necessary, additional heating means (not shown) located downstream from the mill means 10. In the manufacture of strip rolled in the austenitic sostoyaniya rolls, and if, in addition, it is required to increase the temperature, the strip is heated in additional heating means (not shown), which is located downstream from the straw bale. Specialist in the art should understand that the boxes for 12 rolls and additional heating means (not shown) can have a different position one relative to another to those that are higher. By reducing the thickness of the laminated strip comes in a box for rolls with a speed of approximately 0.6 m/s Second unit 13 for descaling is located downstream from the cooling means 11, 12 boxes for rolls or additional heating means (not shown), again to remove the layer of oxides that may be formed on the surface of the laminated strip. If necessary, can be used other means to cut, to trim the front and rear end of the strip. Then the strip is introduced into a line of rolling, which can be configured shestiletnego continuous rolling mill with four-roll stands. If rolled austenitising strip, it is possible to obtain the desired final thickness, for example 1.0 mm, when using the number of digits in Fig.3 for the case of slab thickness 70 mm After leaving the line of rolling strip 14, which has a final temperature of approximately 900oWith a thickness of 1.0 mm, intensively cooled using cooling means 15 and wound in a coil winder 16. The speed with which it enters into the winder, is approximately 13 m/C. If you get a steel strip, rolled in the ferrite region, the steel strip emerging from the rolling means 10, intensively cooled by using the cooling 11. The band then through bypass ducts 12 for the rolls and, if necessary, additional heating means (not shown), and then remove the oxides in the installation of 13 for descaling. The band, which soon reaches the ferritic region, has a temperature of approximately 750oC. As stated above, the material may still remain in the austenitic state, however, it is acceptable depending on the carbon content and the desired final quality. In order to achieve the ferritic strip of the desired final thickness of approximately 0.7 to 0.8 mm, use all six stands of the mill lines 14. How and when do the rolling austenitising strip during rolling of the strip in the ferritic condition, it is rolling stand. This is illustrated in the temperature curve shown in Fig.2, and the thickness profile shown near the bottom of the figures in Fig.3, for rolling steel strip of the ferritic condition as a function of position. The temperature curve shows that the band has an outlet temperature that is considerably higher than the recrystallization temperature. Thus, to prevent the formation of oxides may be desirable to cool the strip through the cooling means 15 to the required temperature cooling, which could still happen recrystallization. If the temperature at the outlet of mill lines 14 is too low, it can be used by the heating means 18, which is located downstream from mill lines, to bring laminated in the ferritic condition of the steel strip, up to the required temperature cooling. The cooling means 15 and the heating means 18 can be arranged in parallel or successively. You can also replace one tool to the other, depending, shall be made of ferritic or austenitic strip. As mentioned above, if the manufacturer is subject ferritic band, the rolling is performed in a continuous mode. the and the heating means 18, has a greater length than is necessary to obtain a single roll, and that part of the slab constituting a full length of the oven or over, rolled continuously. In order to cut the strip to the desired length corresponding to the normal size of the roll, provided by the mechanical shear 17. By appropriate selection of the various components of the device and the process in which they are used to perform such steps as mixing, rolling, cooling and temporary storage, confirmed the possibility to work using this device if you have one continuous casting, while in the preceding technical solution, use two continuous casting in order to reconcile the limited speed of the casting with a significantly higher speed rolling, are commonly used. If need be, immediately behind the line of the rolling mill 14 can be added the so-called hermetic winder in order to facilitate the regulation and temperature strip. This device is suitable for strips having a width in the range from 1000 to 1500 mm, when the thickness of the strip, laminated in Aust is but from 0.7 to 0.8 mm. The time of homogenization in the heating means 7 is about 10 min when placed in the oven three slabs of the same length as an oven. The basket of rolls suitable for storing two full rolls during rolling in the austenitic region.

The method in accordance with the present invention are suitable mainly for the production of thin austenitic strip having, for example, the final thickness less than 1.2 mm Band this class is suitable given the propensity for the formation of the ears as a result of the anisotropy in the subsequent rolling in the ferritic region for use as steel for packaging, for example, in industry, producing drinks.

Claims

1. The way to obtain a steel strip or sheet suitable for use as packaging steel, in which liquid steel is poured into the continuous casting for the formation of a thin slab, and using foundry heat slab served in the heating means, compresses in a reduction mill to an intermediate thickness, and continue rolling in the finishing rolling stands with obtaining a steel strip or sheet of the desired final thickness, characterized in that to obtain a steel strip, rolled the speeds, which essentially correspond to the speed input in the crimp crate, and after reducing the thickness of the serves of the reduction mill to the processing device that is located after the finishing rolling stands, and the band comes out of the reduction mill, cooled to ferritic region, in which the steel is essentially ferritic structure, and the strip laminated in the ferritic condition, after reaching the desired final thickness cut into pieces of the required length, which is wound into a roll, where the steel strip is made of low carbon steel with a carbon content of from 0.1 to 0.01%, the total compression in the ferritic region is less than 87%, and where there is no connection material between the steel in the continuous casting, on the one hand, and steel, rolled in a reduction mill, on the other hand.

2. The method according to p. 1, characterized in that the total compression in the ferritic region is more than 75%.

3. The method according to p. 1 or 2, characterized in that the intermediate thickness is less than 20 mm

4. The method according to any of paragraphs.1 to 3, characterized in that the ratio of width/thickness of the steel strip or sheet is more than 1500, preferably more than 2000.

5. The way to get began is liveout in the continuous casting for the formation of a thin slab, and using foundry heat slab served in the heating means, compresses in a reduction mill to an intermediate thickness, and continue rolling in the finishing rolling stands with obtaining a steel strip or sheet of the desired final thickness, characterized in that to obtain a steel strip, laminated in the ferritic condition, the slab or part thereof served continuously at least from the heating means at a speed, which essentially correspond to the speed input in the crimp crate, and after reducing the thickness of the serves of the reduction mill to the processing device that is located after the finishing rolling stands, the band comes out of the reduction mill, cooled to ferritic region, in which the steel is essentially ferritic structure, and the strip laminated in the ferritic condition, after reaching the desired final thickness cut into pieces of the required length, which is wound into a roll, where the steel strip is made of low carbon steel with a carbon content of from 0.1 to 0.01%, is cooled at an intermediate thickness of less than 1.8 mm from the austenitic region to ferritic region, where the total compression after rolling in the ferritic region is less than 90%, and where otstaly, rolled in a reduction mill, on the other hand.

 

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FIELD: rolled stock production, possibly rolling merchant bars and rods of continuously cast carbon (standard and high-quality) steel, low alloy, alloy, roll-bearing and spring steels.

SUBSTANCE: method comprises steps of heating steel continuously cast billet until austenite temperature; further multi-pass hot rolling while providing normalized temperature of rolling termination period; performing multi-pass rolling at temperature 860-1000 C of rolling termination period and at total elongation value γ selected according to kinds of steel. Invention provides complete treatment of axial zone of billet, lowered liquation of chemical elements along cross section and length of bar, regular contour of bar cross section.

EFFECT: enhanced quality, less loss of yield.

4 ex, 1 tbl

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