DE2019699A1 - Process for the production of sheet metal - Google Patents

Description

Patent attorney
Dipl.-Phys. Rudolf Peorboom "

Wupportal- Βε.πιοη Ρ 1441/70

Friedrich- Engels -Allee 349/351 Tel. 55 6147

United Austrian Iron 20 ι 9b 9 U and Stahlwerke Aktiengesellschaft in Linz

Process for the production of sheet metal

The invention relates to a method of manufacture of sheet metal from continuously cast slabs that have not been cast, the slabs being heated to rolling temperature and be deformed in several stitches «,

Various problems arise in the production of sheet metal from continuously cast slabs that have not been cast on. First, a steel must be made, its oxygen content and temperature on the chemical Composition are precisely coordinated. Furthermore, the cross-section of the strand, in particular the strand thickness, as well as the grain speed and the cooling conditions in the continuous caster are important, i.e. the quality factors influencing the product.

When continuously cast slabs made from unkilled steel are processed into sheet metal on a rolling mill are to be subjected to a pre-treatment. The surface must be checked and surface defects must be eliminated. After cooling down completely, the slabs are heated to rolling temperature in pusher furnaces before they are rolled out into sheets in several passes. When heated to the rolling temperature, the in the Continuously cast slabs existing bladder ring, which is characteristic of unskilled steel, great difficulties, because the bladder rim allows heat to be transferred from the surface of the slab to the core of the slab when it is heated obstructed in gas or oil-fired ovens. As a consequence of this the surface becomes overheated and a strong one occurs Scaling without the core being sufficiently penetrated

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is warmed · This again results in qualitative and technical rolling disadvantages when rolling the slabs. the strong scaling and overheating of the surface can lead to the fact that the bladder ring with the outside atmosphere, which has an oxidizing effect, comes into contact, causing a welding of the gas bubble cavities during the rolling is made difficult or completely prevented; Sheets made from such a starting material are rejects.

In order to avoid the difficulties involved in heating continuously cast slabs of unskilled steel in As a result of the presence of the bladder rim, it has already been proposed that heating to the rolling temperature be used in electric induction furnaces instead of gas or oil fired furnaces. The heating through electrical induction runs more evenly over the cross-section of the slab, i.e. the insulating effect of the With this type of heating, the bladder ring does not appear as disadvantageous and there are qualitative deficiencies that occur in gas or oil-fired ovens - that are unavoidable from the surface, appear less. Induction furnaces however, they are extremely expensive to purchase and operate. It is therefore with a general Use of induction heating for slabs is not expected for economic reasons.

The thickness of continuously cast slabs made of unkilled steel is usually 250 to 300 mm; the width the slab is around 1250 mm and the length of the individual slabs can be up to 12 m. It surrender thus considerable cross-sections and unit weights. The professional world endeavors to find a solution that is economical and to find qualitative problems when rolling continuously cast slabs from unkilled steel, but so far the warming problem resulting from the presence of the bladder rim is still unsolved.

The invention aims to avoid the disadvantages and difficulties described and consists in a Process for the production of sheet metal from continuously cast slabs which have not been cast, with the slabs at rolling temperature heated and deformed in several passes,

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in that the cast strand after complete solidification deformed in one stage before cutting into cast slabs as soon as the solidified strand has a temperature that is as uniform as possible over the entire cross section in the range of 900 to 1200 ° C, preferably 1000 to 1100 ° C.

It is expedient to make the temperature uniform over the entire cross section of the strand in carried out in a known manner in that an uncooled or heated compensation zone behind the secondary cooling zone is provided through which the strand is guided before the single-stage deformation.

The deformation according to the invention is dimensioned so that it approximately corresponds to the volume of the bladder cavities in the Strand corresponds and thus causes a compaction of the material. The reduction in cross section in the inventive single-stage deformation is about 10 - 20 $>, without any noticeable stretching deformation occurring. It's more of a transformation.

In the accompanying drawing is the cross-section of a strand of unkilled steel prior to that of the invention Deformation shown. The macrostructure of a slab is shown schematically. One distinguishes clearly three zones, u.zw. the bubble-free zone 1, which is also known as the "layer of fat", is the real one Marginal bubble zone 2 and the core zone 3 of the strand cross-section. The thickness of the bubble-free surface layer 1 in the slab of unskilled steel depends on the lowering speed and the intensity of the boiling of the metal in the mold and is generally not less than 10 mm.

When heating to the rolling temperature, care must be taken that the sealed zone 1 is preserved as possible remains so that no oxidizing gases penetrate into the marginal blisters. If this condition is met, then weld the edge blisters when rolling completely.

As mentioned, according to the invention, the marginal bubbles are already formed by a slight subsequent deformation

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compressed to the solidification of the strand, so that they weld and the strand a compression in the area der Randblas en ζ one 2 learn, whereby the heat-insulating Bladder wreath is eliminated. A strand of non-killed steel compacted according to this process can without difficulty in an economical way just like a strand of killed steel in gas or oil-fired ones Furnaces are heated to rolling temperature «

The effort for a roll stand in connection with a continuous casting plant is low. For single-stage forming the intrinsic heat of the strand is used j the rolling pressure is relatively small because of the compression the bladder cavities does not require large amounts of energy. The fact that the bladder is relatively light is to be eliminated is also the reason that the remaining zones of the strand cross-section are practically hardly deformed will. Before carrying out the process, only the bubble volume has to be determined, which depends on the steel quality and depends on the strand cross-section, but otherwise remains within narrow limits. So you become this Only have to carry out the investigation once and then the decrease in cross-section during the compression according to the invention of the material.

The aim of the invention to improve the quality of continuously cast slabs in terms of thermal engineering ^ so that a significantly improved heat transfer is created is achieved even if not all bubbles are complete weld. Individual bubbles still present after the deformation impair the heating process barely. Thus, the method according to the invention does not provide a particularly high level of accuracy for the detection of the bladder cavity, thereby simplifying its use in operation.

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Claims (3)

Patent claims! 1.! Method of making sheet metal from unquieted - cast continuously cast slabs, the slabs being heated to rolling temperature and deformed in several passes are, characterized in that the cast strand after complete solidification before cutting to length is deformed in one stage in cast slabs, as soon as the solidified strand, one over the whole Cross-section as uniform as possible temperature in the range from 900 to 1200 ° C, preferably 1000 to Has reached 1100 ° C. 2. The method according to claim 1, characterized in that that an equalization of the temperature over the entire cross-section of the strand is known per se Way is carried out by arranging uncooled or heated compensation zones. 3. The method according to claim 1 or 2, characterized in that the cross section of the cast strand in the single-stage Deformation is reduced by about 10 to 20 $, without any noticeable stretching deformation occurring. 009847/1111 Blank page