DE1433782A1 - Process for the production of sheet steel with magnetic properties comparable to those of low-carbon steels or mild steel - Google Patents

Description

Society Anonymous Cockerill-Qugr $ e, Seraing (Belgium)

"Process for producing steel sheet with magnetic properties comparable to those of low-carbon Steels or mild steels "

The invention relates to a method for the production of steel sheet, which has magnetic properties similar to those exhibited by low carbon steels (mild steels), in particular a process for the production of steel sheets with low coercive force and with permeability and induction values, that reach to saturation.

^ s is known in the manufacture of steel sheets with lower Coercive force and / or high magnetic permeability of pure üisen to go out. The manufacture of such sheets using using pure iron as the starting material is very difficult and very expensive «

Steel sheets, with low coercive force and / or high magnetic However, according to the invention, permeability can also be produced,

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if. a "commercial low-carbon, unsettled Mild steel is used as the starting material, which has the following composition, for example with regard to the usual components * ','

o, o5 - C ^ o,
S ^ o,

Such a low carbon steel is now before going to the following described method according to the invention is subjected, by j.'arm rolling to a sheet or strip of 1 - 5 mm thickness formed, which then in a known manner, for example under Use of sulfuric acid, is pickled in order to then be cold-rolled in such a way that the sheet or strip thickness is a Reduction of up to $ 40-80, (i.e. $ 40-80 cold rolling or Deformation), with the highest possible uniformity of the sheet or strip thickness.

The material pre-processed in this way is then processed further in the method according to the invention. The process according to the invention is essentially characterized in that the sheet metal pretreated in the manner described is subjected to decarburization and pre-hardening in the critical area in such a way that a grain structure or grain structure (lexture) is obtained by subsequent annealing in which large grains in preferred direction (fibers, rows or columns) are arranged. . '" ^: -' ■ ^; '' ■■■■■■■■ ■■■ ''■""'BAD" ORIGINAL

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To make a sheet or strip with improved and more homogeneous (more uniform distributed) magnetic properties, it has proven to be advantageous to work hardening according to the invention to be carried out in such a way that the cold-rolled strip or sheet passes through a re-rolling or skin-pass pass} the The best results were achieved with a re-rolling pass with 1.69ε up to 2 $ degree of deformation (percentage reduction in thickness during rolling) achieved. It was found that this result is further improved It can be ensured that this percentage reduction in thickness is made in total in a single pass.

The combination of a decarburization annealing with a reduction in thickness From 1.6 $ to 2 $ degree of deformation through a re-rolling or skin pass pass offers the advantage of a considerable grain growth bi3 to the core in the course of a subsequent annealing treatment enable. This grain growth progresses from the sheet metal surface towards the inside, as a result of the strain hardening in the sheet caused by the re-rolling pass, which results in a Grain structure is obtained in which the grains stand out from the sheet metal surface starting out in preferred directions to form fibers or columns. This particular fine structure results together with the low carbon content due to decarburization annealing excellent magnetic properties and a coercive force between 0.4 and 0.8 öerstedt.

In principle, decarburization can be carried out according to any of the known methods Procedures are made. However, it is particularly advantageous to carry out this decarburization by annealing, e.g. in a hood furnace, for loosely rolled (open-coil ") sheet metal or tape wraps or bundles

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or in a continuous furnace in a furnace atmosphere with hydrogen (more than 65ε) _f nitrogen and water vapor, which has a reducing effect on the steel. Experience has shown that this treatment according to the invention, depending on the type of furnace atmosphere, the annealing time and the annealing temperatures, which are between 650 ° C. and 850 ° C., can easily produce sheets or strips with a final carbon content of between o, oo5 # and o, ooo5 $ receives.

In the case described above, the decarburization process takes place re-rolling or skin-passing, and this is followed by

"around after cutting" a second annealing, namely a grain annealing between 700 ° and 900 ° C, the duration of which between a few minutes and .50 hours can be. "

The annealing that follows the re-rolling or skin-pass treatment can be reduced to ■ different ways are carried out, be it that laminated stacks are arranged in an annealing furnace suitable for this purpose, be it that sheet metal coils - or bundles annealed in a hood annealing furnace or a furnace suitable for annealing loosely wound ("open-coil") bundles (coils) be, or finally in the form that stretched wrap or Bundles are annealed.

If sheet metal coils are annealed, straightening (leveling) of the strip or sheet is necessary before further processing eliminate the bend or curvature that sheet metal retained in the coil or coil during annealing.

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If it is the shape of the blank the cut to their final sizes Sheet metal is allowed, the annealing following the re-rolling (skin pass) can be carried out in a pull-through furnace or in a stack heating furnace be made. This is advantageous when it comes to decarburized steel because of the changes in shape caused by the annealing are negligible

In another embodiment of the method according to the invention the decarburization annealing preceding the re-rolling or skin-passage is used by a recrystallization annealing of the known type at a temperature of preferably between 680 and 720 C above replaced a few hours of duration. In this case, the decarburization annealing is used after re-rolling or skin-passing, for example in the case of loosely wound ("open-ccil") bundles or winding at an annealing temperature carried out between 700 ° C to 850 ° C until Ausa? eichencle decarburization has occurred

After cutting, the sheets or strips are advantageously a ·, stress relief annealing between 300 ° G and 600 ° C over a period of time subjected to between half an hour and a few hours.

The embodiment of the invention cited above The values of the coercive force achieved by the method are comparable to the values already mentioned above

The stress relief annealing just mentioned can also be advantageous take place after straightening or leveling the sheets after previous winding to stretched coils.

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luck here one obtains the same values for the coercive force as they have already been cited. .

In order to better illustrate the essence of the method according to the invention, Examples are given below, but none of them Limiting significance for the process according to the invention.

I. Example :.

A treatment was carried out in steel of the above composition

sjem according to the method according to the invention subjected. -, ■■ .;

After hot rolling into a 3 mm thick strip, pickling and in cold rolling with a degree of deformation of $ 50, i.e. down to a thickness of -1.5 mm, v the sheet metal coil was decarburized at 760 G until a final level was reached carbon between o, oo2 $ and o, oo4 $ has been reached .; .-; -_ ■ -_

) The sheet metal strip decarburized in this way was rerolled in one pass with an average degree of deformation of 1.ej6, -where the ^ _Γ ίο slight degree of deformation was measured by the extension, root .. Ei ^^ B Laugh-rolled strip was then cut to size and the sheet> aket then placed in an annealing furnace. After an annealing:, ■ ;. At 750 ° C. for 25 hours the steel sheet treated in this way had the following magnetic properties: permeability at 100 Gaussi 750 Gauss / Oerstedt ¹¹ "10000 Gauss" 5000 Gauss / Oerstedt "" 15000 Gauss ; 1450 Gauss / Oerstedt.

) These permeability values were obtained by applying a arm magnetization has been exposed. This alternating magnetization

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was achieved through the progressive application of a magnetizing Field, the maximum amplitude of which was 15,000 Gauss. After switching off of the magnetizing field showed that the remaining magnetization, the remanence, was caused by a magnetic Opposite field, the coercive force, is canceled by 0.55 Oerstedto

The same permeability values were obtained for sheet metal packages that were subjected to annealing at 855 ° C for three hours.

2nd example »

A winding made of sheet steel of the same type as in the example 1 was a mean deformation of $ 1.8, measured by the elongation, subjected to a re-rolling or skin pass pass, and immediately afterwards the sheet metal coil was subjected to 9 hours annealed at 825 °, in a loosely wound furnace Sheet metal coils

After an alternating magnetization using a magnetizing Field of 15,000 Gauss, the following permeability values were obtained »

Permeability at 100 Gauss - 650 Gauss / Oerstedt ¹¹ "10000 Gauss» 3750 Gauss / Oerstedt ¹¹ "15000 Gauss» 1230 Gauss / Oerstedt.

In this second example, the coercive force was 0.65 Oerstedt.

3rd example »

Steel sheet was treated in the manner described, but rolled to a final thickness of 0.5 mm. Besides the good values of the

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Coercive force and permeability "with direct current were watt losses of 2.5 W / kg with a magnetic field of 10,000 Gauss and 50 periods measured.

The measurements given above were measured with the aid of a so-called "Baby-Epstein ^M device, with 6 test specimens taken in the longitudinal direction of the rolling and 6 test specimens taken in the transverse direction of the rolling. This is a measuring device that is described in Form A 34 of the American Society of Testing Material (ASTM) is described

- patent claims -

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Claims (8)

Claims 1. Process for the production of steel sheets or strips with magnetic properties comparable to those of low carbon Steel or mild steel, a commercially available low-carbon steel or mild steel being used as the starting material finds, which is rolled out by hot rolling to sheet metal or strip with a thickness between 1 mm and 5 mm, ai closing in a known manner Pickled and cold rolling at a degree of deformation of $ 40 up to 80 $ is rolled out as evenly as possible, characterized that the sheet or strip obtained in this way is decarburized and work-hardened in the critical area, such that a grain structure or grain texture is obtained by subsequent annealing, in which the grains are arranged in fibers or columns are. 2. The method according to claim 1, characterized in that the work hardening was carried out by re-rolling or skin-passing at a degree of deformation between $ 1.6 and $ 2. 3. Method according to one of Claims 1 and 2, characterized in that that the work hardening in a single re-rolling pass or pulling through. 4. The method according to any one of claims 1 to 3, characterized in that that the decarburization is carried out by annealing in a reducing furnace atmosphere. 8Ü9813 / Ü267 H33782 5. Process according to Claims 1 to 4, characterized in that decarburization annealing at temperatures between 650 ° C and 850 ° C takes place before re-rolling » 6. The method according to claim 4 or 5, characterized in that the re-rolling takes place after the decarburization and then a further annealing at temperatures between 700 C and 900 during a few minutes up to. 50 hours to come » 7. The method according to claim 6, characterized in that the second Annealing is carried out after re-rolling or skin-passing with sheet metal packs or with sheet metal or strip wrapping. 8. The method according to claim 7, characterized in that according to the Second annealing of sheet metal or strip coils or bundles straightening or leveling is carried out. 9ο method according to one of claims 1 bü-s 3 »characterized in that that the decarburization preceding the re-rolling or skin pass is carried out at temperatures between 700 ° C and 850 ° C, while the re-rolling itself is preceded by a known recrystallization annealing at temperatures between 680 ° and 720 ° C for a few hours. 10. Process according to claims 7 to 9, characterized in that after decarburizing, cutting and straightening or leveling the steel sheets or steel strips are subjected to stress relief annealing between 300 ° C and 600 ° C for half an hour to a few hours «, 8098 1 3/0267