KR100583017B1 - Method for manufacturing hot rolled strip steel - Google Patents

Abstract

The present invention relates to a method for producing hot rolled strip steel through at least two deformation stages, each having at least one rolling stage, from a continuous cast bloom, the bloom being at a drawing rate from the continuous casting plant in a first deformation stage. The unfinished strip is thus rolled up and wound up from the first deformation step at the drawing speed into a coil before the second deformation step. When the desired coil weight is reached, the unfinished strip is not wound, fed to the second deformation stage at an initial drawing speed for finishing rolling and then wound to a finished coil of the desired size. In the first deformation stage, at least 40 tons of continuous casting of the continuous casting plant is rolled into an unfinished strip by continuous rolling and wound without cutting to become an unfinished coil. The unfinished strips of the unfinished coils are finish rolled almost continuously, and after the second deformation step they are each cut to correspond to the desired coil weights and wound as finished strips.

Description

Method for manufacturing hot rolled strip steel

FIELD OF THE INVENTION The present invention relates to a method for producing hot rolled strip steel through at least two deformation stages each having at least one rolling stand from a continuous cast bloom, the bloom being from a continuous casting plant in a first deformation stage. Rolled at a drawing speed, the resulting unfinished strip is coiled from the first deformation step at the drawing speed before the second deformation step, becomes a coil, does not wind when the desired coil weight is reached, and is drawn at the initial drawing speed for finish rolling. After being fed in two deformation stages, it is wound up to a finished coil of the desired size.

Similar methods are described, for example, in German patent specification 38 40 812 C2, which is disclosed as an ISP-method. An essential feature of the method is a two-step rolling process, the first deformation step of which is carried out directly at the casting machine at a casting speed, the second deformation step of which is carried out at a much faster rolling speed. The two steps of the rolling process are connected by a semi bobbin in the form of a reel box, in which the continuous cast slab is rolled and wound into a coil, and the weight of the coil is desirable. It corresponds to the weight of the finished coil. Therefore, the strip continuously produced at the beginning is cut when the coil weight is rolled in the second deformation step and then equals the finished coil weight after the first deformation step.

In the hot rolling of the strip by the above procedure, the insertion of the strip head into the reel box implies a rolling speed limit, since there is a risk that the strip head will rise up on the drawing roller table when the speed is very fast. If the strip head is fitted in the reel box, the rolling speed may actually increase arbitrarily within the range of equipment capacity and technical requirements.

To overcome the rolling speed limitations described above, a continuous rolling method was developed based on the principle of joining the blooms together before entering the furnace. For example, it is proposed to weld a number of blooms side by side in order to shorten the fitting process and to be able to roll almost continuously. However, welding the blooms as described above requires very expensive equipment and also limits the possible rolling speed.

In the method of the present invention, as already carried out, the bloom is produced and wound by a continuous casting method to form a coil, the weight of which corresponds to the weight of the finished coil. To this end, the bloom is cut when it reaches a corresponding coil weight in a semi bobbin, and the connection with the casting equipment is cut off so that the strip develops into the furnace at a relatively high speed. However, when the strip head is inserted into the reel box due to the risk described above, the rolling speed is limited, and thus, a large problem occurs when hot rolling the thin strip having a size of 1.5 mm or less. Therefore, conventional production does not allow mass production of thin hot rolled strips.

In addition to these problems and drawbacks of the prior art, the present invention aims to provide a method for producing hot rolled strip steel in which a very thin strip can be rolled safely even at a relatively fast finish rolling speed.

In order to achieve the object of the present invention, in the first deformation step, at least 40 tons of continuous castings in the continuous casting equipment is an unfinished strip by continuous rolling, wound without cutting to become an unfinished coil, the unfinished strip of the unfinished coil Suggests that after finishing rolling almost continuously, after the second deformation step, the respective desired coil weights are cut and wound as finished strips.

The bloom to be finished in the furnace is produced in a continuous rolling process following the casting plant followed by the deformation. Unlike the general operation method in which the bloom is cut to the weight of the post coil, the bloom for continuous rolling is not cut after the deformation step and is wound continuously to be an unfinished coil including a plurality of finished coils. In the continuous rolling process from the unfinished coil to the completion furnace, a plurality of coil lengths are finish rolled. The size of the unfinished coil is limited only by the rolling time during which the mechanical design of the bobbin device and the completion furnace can be operated without replacing the rolling mill. It is conceivable to continuously roll large tons of continuous castings that are minimal in substantial bobbin arrangements but substantially more than is possible in conventional installations.

The steps in the method according to the invention are based on the buffer capacity of the semi bobbin. Increase significantly. When the bobbin capacity is approximately 100 tonnes, for example, the buffer capacity is increased to 60 minutes per unfinished coil. Due to the relatively fast finishing rolling speed possible in this way, hot rolled strips smaller than 1.2 mm in thickness can be produced without problems. The production capacity of the plant is improved because a typical roll tongue is deployed only for the front of the first coil and the back of the next last coil to completion. In addition, the quality of the rolled product can be improved, because the unstable state of the initial pass impact only appears in the first coil.

The unfinished strip can be wound up without a spike to become an unfinished coil, as well as wound onto a spike to be an unfinished coil. In addition, according to another feature of the present invention, there may be a change in material within the length of the unfinished coil due to the temperature change and the variable speed before the unfinished coil and / or before the second deformation step.

In another aspect of the invention, the apparent quality of the finished coil made from the unfinished coil is changed by appropriately adjusting the rolling parameters while the unfinished strip is deformed within the second deformation step.

It is desirable to prevent cooling of at least the unfinished strip edges while the unfinished strip is wound to become an unfinished coil.

Summarizing the advantages of the above method, continuous rolling is possible without welding the bloom, continuous rolling with the same bloom quality in temperature and appearance is possible, the process of sandwiching the reel box and the large distance between the casting strip and the finishing furnace. Due to the relatively fast rolling speed, which is no longer limited by the buffer capacity, the plant productivity can be improved.

The method can be applied in installations with one or two strands, and the bloom can be wound not only on spikes in the reel box, but also without spikes in the so-called coil box.

Claims (5)

A method for producing hot rolled strip steel through a plurality of deformation stages each having at least one rolling stage from a continuously cast bloom, The bloom becomes an unfinished strip by continuous rolling at a bloom drawing speed from the continuous casting plant in the first deformation step, and the unfinished strip is wound continuously from the first deformation step at the drawing speed before the second deformation step. After being rolled up to become a coil, it is unloaded and continuously supplied to a finish rolling part, cut to correspond to a coil weight of a predetermined size, and wound up as a finished strip, At least 40 tons of continuous castings in the continuous casting plant are cast into bloom, rolled in the first deformation stage to an unfinished strip, and the material of the unfinished strip is a temperature change and a variable speed before the unfinished coil or before the second deformation stage. A method for producing hot rolled strip steel from continuous cast bloom, characterized in that there is a change. 2. The hot rolled strip from continuous cast bloom according to claim 1, wherein the appearance quality of the finished coil made from the unfinished coil is changed by suitably adjusting the rolling parameters during deformation of the unfinished strip in the second deformation step. Method for manufacturing steel. The method of claim 1 or 2, wherein the unfinished strip is wound on a spike to form an unfinished coil. 3. A method according to claim 1 or 2, wherein the unfinished strip is wound without spikes to become an unfinished coil. 3. A method according to claim 1 or 2, wherein cooling of at least the unfinished strip edges is prevented while the unfinished strip is wound to become an unfinished coil.