DE2011677A1 - Method of making an oriented silicon iron sheet material - Google Patents

Description

Process for making an oriented silicon sheet material

The invention relates to a method for producing a grain-oriented silicon steel raw material by melting a batch, tapping the melt into a pan, keeping slagging to a minimum, adding substantially all of the silicon required, Vacuum degassing with stirring, continuous pouring with minimal cooling of the slab if it is out of shape emerges, and processing to a final product in the usual way, with at least one cold-rolling, and finally Annealing to cause secondary recrystallization.

The method is suitable for using an oriented silicon steel sheet material with either a Goss texture or a cube texture. Under the terms Both "oriented" and "grain-oriented" are intended to be Goss textures as well as cube textures. Materials with eoss-Xextur have a large number of crystals, which in the vicinity of the (11O) [OOI] -orientation according to the

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Müller's see

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Müller's see indices are oriented. Cube texture materials but consist mainly of crystals »with the (10O) - or ffUrfelflächeplanes running parallel to the sheet metal surface. Under this general term "throw texture" are "doubly oriented" or (100) [001] -3? texture materials as well To understand materials with an almost arbitrary distribution of the [001] directions in the plane of the sheet.

According to the invention, a molten metal charge is tapped into a pan using a method when they are carried out, the volume of slag entering the ladle is kept to a minimum. You silicon addition preferably takes place in the pan, to a silicon content from 2.5 - 4.0 weight ^. Then it is in a vacuum degassed under conditions which ensure thorough mixing occurs. It then becomes continuous potted with cooling, cooling at the minimum speed required for this, sufficient Achieve skin strength to maintain the molten interior of the slab within the limits of controllable warpage to keep. The slab is then processed to its final diameter, using the usual methods. These ketenen in one hot rolling, at a distance of scale, in one Cold rolling, in a decarburization as well as in dinem primary and secondary recrystallization annealing. The term "slab" should be understood to mean the product that is produced by the continuously operating casting machine is produced.

In U.S. Patent 3,226,224 the manufacture of a Silcium steel described from a non-killed steel, and ' by vacuum degassing, adding silicon after degassing and continuous casting from the vacuum chamber.

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U.S. Patent 3,253,909 describes the preparation of grain-oriented silicon steels by vacuum decarburization and removing hydrogen and then adjusting of the oxygen content to a value between 0.07 and 0.12 56 before the addition of the silicon and afterwards Cast in the form of iron usual blocks. The US patent 3 125 440 asked for a vacuum degassing saun content, whereby the oxygen content is reduced to less than 100 ppm, While the hydrogen content is around 1 ppm and the Nitrogen content is reduced to 20 ppm or below. It is stated that a steel containing approximately 1 ppm hydrogen * is insensitive to peeling. The vacuum degassing is followed by a continuous casting process at. U.S. Patent No. 2,253,421 relates to vacuum degassing of molten steel, with a slight bleeding Impurity parts and causes a flotation of the same will. In addition, the trapped gases, such as hydrogen * nitrogen and carbon monoxide, are removed. U.S. Patent 2,144,200 relates to the manufacture of silicon iron alloys by a vacuum melting process, which consists in introducing the total iron an oxidizing agent su decarbonize, remaining oxygen and nitrogen by adding a vaporizable reducing agent Remove mi and then the required amount Sususetsen of silicon and distribute the silicon in the bath. The aisle is then preferably in a vacuum shed. She U.S. Patent 3,069,299 teaches the importance of rapidly cooling a casting in order to optimally magnetic properties in an oriented silicon steel reach.

Albeit the production of a silicon-containing steel

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according to a method is known that a vacuum release and continuous pouring, so it was so far not possible to get a material bu that is too a high quality oriented silicon steel can be processed. None of the patents described above suggests the special procedures that are required for this the corresponding structure was omitted. The mere admixture of silicon is not enough to produce a high quality oriented silicon steel by continuous casting.

The object of the invention is to create a high-quality, grain-oriented silicon steel, in the production of which the gate parts are used in sum ereten IbI, which offers continuous casting. In the case of materials with an ÖOBB texture, the term "high quality ^{11" means} an average permeability of approximately 1820 or above with a magnetization force of 10 oersted in the direction bu. The invention provides an intact continuous slab with a chemical composition and structure created that are sufficient to achieve the desired oriented grain structure after subsequent customary processing to the final thickness. In particular, after renewed heating and hot rolling, the hot strip has that distribution of inclusions which favors secondary recrystallization during final annealing.

In practicing the invention, these advantages are achieved by a vacuum degassing with stirring to homogenize the melt bu and to reduce the impurities by continuously pouring the metal against oxidation protected between the acetabular cup and the IOrm

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becomes »and by cooling the slab emerging from the mold, at the minimum speed required to achieve sufficient skin firmness, 'the sufficient to do this, the molten interior without a non-controllable one To support warping, scored. According to a preferred Ausfahrungeform the invention is the manganese content on a Value between 0.04 and 0.08 wt- ^ held to the solubility the sulfides in the slab during the renewed Sr-. hi teens before hot rolling to improve.

The vacuum degassing is used to achieve a stirring effect, through which the alloy constituents © are distributed, whereby a temperature change is also prevented. Further hydrogen and nitrogen are generated by the vacuum degassing as well as impurities removed, especially oxides, namely by agglomeration and flotation.

It was found that the hydrogen content of the metal, that goes into the continuously operating casting machine, should be kept below 1 ppm to avoid the formation of To avoid pinholes and surface defects during continuous casting, in those cases in which Hydrogen may be available in the form, for example due to an organic mold release agent.

This continuous pouring takes place under protection of the metal carried out against oxidation at least between the tundish and the mold, the protection against an oxidation preferably between the pan and the intermediate pan takes place.

It was found that slow cooling of the slab,

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which emerges from the continuously operating mold, a Structure with better magnetic properties after a Ena work out as a result. ·

Gate parts are also obtained when higher carbon contents (approximately 0.027-0.040 #) and low slope grades (approximately 0.04 - 0.08 #), in contrast to the typical properties of a grain-oriented silicon steel produced in a conventional manner.

The invention is explained in more detail with reference to the accompanying drawing. This drawing represents a flow sheet, which alternative embodiments of the method according to the invention are shown.

The flow diagram shows an alternative arrangement of a Siemens Martin oven, which can be tapped into a first pan, to which aluminum has been added as a deoxidizer is used to partially calm the steel. You batch will then tapped at the bottom in a second pan by a method by which the bulk of the slag in the first pan remains. In the second pan all the silicon or a rope of silicon is added to it is necessary to manufacture the respective steel grade. In The silicon is usually placed on the bottom of the pan, before the melt is added

Optionally, according to the preferred embodiment of the invention a batch in an! arc furnace or in a> Oxygen is melted in a blow-up furnace and tapped into a pan, from which the whole or a rope of the required

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High silicon sugesetst has been made. The amount of slag which gets into this pan »is based on known methods kept to a minimum.

You need to remove the slag at this point about the manganura conversion through the reaction

2 "iO + Si- ^
keep bu to a minimum.

Sohmelse is aneohlieeeend transferred into a vacuum degassing unit, which is a "preferably in portions ¹¹ working unit, and" was either a BH Elnheit or RE unit (see * Metal Progress ¹¹ September 1964, page 74-80). If the type If there is no limitation on the degassing system, care must be taken with regard to this system that circulation and thorough mixing are necessary in order to prevent temperature reduction and metallurgical stratification. Smaller additions can be made in the degassing device may be necessary in order to give the steel its desired composition. The required silicon can be sugesetst in the annealing device, but due to thermal considerations the addition in the ladle, as mentioned above, appears advisable an agglomeration of impurities, mainly of Oxides, which then rise to the surface of the bath. Furthermore, hydrogen is removed in a known manner during the vacuum degassing.

They remove hydrogen to a level below 1 ppm

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results in optimal results with continuous casting of silicon steel. Even if hydrogen in one Amount in excess of 1 ppm easily in common steels with low carbon content can be tolerated, it has nevertheless been found that hydrogen above 1 ppm can be tolerated sufficient, small holes created by inflation and related surface defects in the case of continuous Casting produced silicon steel slabs under some gritting conditions, so that the mechanical Properties of the product are deteriorated. Even if it was previously known that hydrogen was one Peeling of Schmiedestttoken ssur follows, it still stands the appearance of peeling is in no way related to the formation of holes on the surface of continuously cast slabs.

Am peeling caused by hydrogen Is a phenomenon which occurs at room temperature on heavy steel rods. As the steel cools, its solubility decreases Fttr hydrogen, the gas diffuses and settles at grain interfaces or other discontinuities in the steel collects. Druok can develop, causing microscopic hoisting or peeling. These act as sharp notches in the steel and result in premature failure under stress.

The surface porosity observed in continuously cast silicon steel slabs is apparently one another phenomenon, which, however, has not yet been explained is.

After the end of the degassing, the melt is in a Slip station

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Casting station transferred, with which a tundish in connection stands. The melt then becomes continuous potted and slit opposite an oxidation, namely • at least between the intermediate pan and the mold, wherein a protective submerged inlet pipe and a powder coating on the metal in the mold. In as is known, melting this powder favors its Acts as a flux and as a lubricant between the Slab in their formation and the walls of the mold. According to one The preferred embodiment of the invention is used as a flux mainly an inorganic silicate used as this the absorption of hydrogen from the mold release agent is reduced to a minimum. .

It was previously known that silicon steel slabs should be cooled very quickly when they leave the mold in order to develop a fine dispersion of sulfides in the slab. U.S. Patent 3,069,299, referenced above, teaches such a teaching. It is described in this patent a process for the production of silicon steel having a Goss Iextur, wherein in performing this method, the casting quickly (preferably 130 ⁰ C per minute) from a liquid state or from a SuIfidlösungstemperatur (1300-1400 ⁰ C) is cooled to 800 ⁰ G, According to this patent specification is thereby obtained a fine dispersion of sulfides which inhibit normal grain growth during final annealing-. While such cooling rates cannot be achieved during the solidification of a slab approximately 152 mm (6 inches) thick, it was obvious to those skilled in the art that the cooling rate should be as fast as possible. If one follows this well-known doctrine, one poses a completely opposite one

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Relationship firm. Contrary to expectations, it was found that slow cooling rates during the casting of the slab have better magnetic properties have consequence. Although slab structures are in cast condition (with the slabs at low cooling speeds have cooled down) have been examined microscopically » yet no explanation has yet been found for this positive phenomenon.

It has proven impossible to control the cooling rate to be measured in degrees of temperature per unit of time in the slab itself, since there are no means which exactly Able to record absolute cooling rates. The best Hess method is the flow rate of spray water, which is applied between the mold and the point of complete solidification. The flow velocity range fluctuates from one casting machine to the other, and depending on the number and geometry of the spray nozzle, the slab thickness, the slab width, the casting speed and the machine structure. In a typical machine with a curved shape, the spraying speed of 757 - 1514 per lonne steel, leading to slabs with a bead of 152 mm (6 inches) and a width of 864 mm (34 inches) will vary. You desired cooling rate can best be defined as the speed that produces cooling at the minimum speed, which is necessary to maintain a sufficient skin strength of the slab, namely a strength that sufficient to do this, the melted interior without an uncontrollable one To maintain warping. In other words, 'this means that the cooling is at a speed should take place, which is sufficient to prevent physical destruction of the slab.

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The relatively slow cooling rate generates relative the size and distribution of suIfide insole nuts in the inside of the casting is a problem. Fm this difficulty JBU »the manganese content of the melt should be kept relatively low» preferably between 0.04 and 0.08% by weight, around the sulphides in the subsequent renewal Heating the slab before hot rolling to make it more soluble. These low slope contents can be reduced by suitable Achieve sole melting methods and sole token production methods, the latter keeping manganese conversion to a minimum keep.

There is another auxiliary hall to solve this problem in it »to roll the cast slab under the best heat» around the Grain structure by breaking up columnar grains refine »uad to the size of the suIfidelnschluss before the to modify the usual renewed heating and hot rolling.

Melts were used in the manner described above a wide silicon area of 2.5-4.0 # processed. These Melts can have the following, but not limiting, quantity ranges:

0.027-0.040 36 carbon 0.04-0.08 g of manganese

$ 0.020, - $ 0.026 sulfur

less than 0.004 i> oxygen remainder iron and incidental impurities.

It is known that selenium is used in place of sulfur can be, whereby selenium is a full substitute for sulfur »

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As an example, a melt that contains 0.026 # carbon, 0.058 f> manganese, 0.021 $ sulfur and 3.12 # silicon in the ladle is melted in an electric arc furnace, im. Vacuum degassed to less than 1 ppm hydrogen and continuously cast on slabs with a bead of 152 mm (6 inches) and a width of 864 mm (34 inches). The slab is cooled by spraying it with water as it emerges from the orm and swar at a rate of 1003 l (265 gallons) per sun. The slabs obtained are again ^{heated to 1232 9} C (2550 °?) And 8u coils are wound up. The collars are then made into a Goss texture product and a product that is 0.267 mm (0.0105 inches) thick. A customary two-stage cold forming process with a single smoothing of the strand before each whale stage is used. The sulphides present after the Heisswalsen are in a form which favors the development of grains with a cube texture during the final annealing. As is known, secondary recrystallization occurs during the deep annealing by Xorngrensenenerlge, with the primary grain structure being converted to a well developed Goes structure by the consumption of grains with different orientations. The final properties of this material are such that a permeability of 1827 »measured by HaIO Oersted, and an average core loss of 0.479 watts / 0.45 kg at 15 kilograms and 60 herts are determined»

By making appropriate modifications to the composition as well as the processing stages following the continuous glossing, sheet metal materials with a cube texture can be used produced by the process according to the invention

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will. Since secondary recrystallization occurs through surface energy in the production of a cube texture, the modifications required to achieve optimal magnetic properties in the end product are based on the
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Claims (1)

Patent entitlements 1. Process for the production of an oriented silicon-bleu material by cutting a ferrous charge in a furnace, tapping the soot into a pan with a minimal volume of soot, adding essentially the amount of silicon, which is the division of the usual eaten quality of the steel is required, this amount being between 2.5 and 4.0 f> , vacuum gases with stirring to remove lustful gases and to remove impurities through agglomeration and flotation »continuous glazing, whereby the metal is slit against oxidation, and Deformation of the Gtafist & ckes to the original thickness by orphans and annealing, characterized in that the slab, which is formed during continuous casting, is cooled at the minimum speed required to produce a skin firmness sufficient to maintain the peeled interior of the slab without uncontrollable blending. 2. The method according to claim 1, characterized in that the hydrogen content during the vacuum degassing stage is reduced to a level that is low enough to prevent the formation of surface defects during the continuous Avoid pouring. 3. The method according to claim 1, characterized in that the hydrogen content to less than 1 ppm during the vacuum degassing stage is decreased. ' 4. The method according to claim 1, characterized in that the 009839/1549 dl · molten ferrous charge iron carbon content? os about 0.027 to nsg @ for $ hr O ₉ 040 %> _t a manganese content of about 0.04 Mb about 0.08 ^, a sulfur content of about 0.020 to about 0.026 $ and one Oxygen content νου less than about 0.004 f , the best consisting of Elsen with any impurities present. $ · Method according to claim 2, characterized in that the Braimoe is swallowed under Hests ^ m® of the casting process. 6. Method according to Ajispruoli S ₉ daduroh characterized "that the basin is cooled down," is heated to a temperature which is sufficient for this purpose * sulphide inclusion reading "and the braaaa © on the gowüueclit © £ nddiok @ ^ aoh a method is applied , which includes a Helsswalsen, a Beizen, a Kaltwalien and an ulQhen. 7. Driving to Aaspnisli 1, which means that: el »Flux used during continuous flowering (! lessens which consists essentially of an inorganic silicate consists. BATH ORIGINAL 009839/1549 Blank page