DE1920666A1 - Silicon steel sheet prodn - with fixed maximum magnetisation direction - Google Patents

Abstract

Silicon steel (2-4% Si) contg one or more alloying elements, In particular 0.01-0.07% Al, 0.01-1.0% Ti, 0.01-0.3% Zr, 0.05-0.5% Ta, and opt. 0.001-0.1% V (not more than 0.5% in total), is hot and cold rolled subjected to refining, and then to nitroding in a N2 contg atmosphere at 450-750 degrees C (to convert the alloying elements into nitrides), and finally subjected to a secondary recrystallization. The presence of nitrides promotes the secondary crystallization. The crystals are predominantly oriented in the (110) (100) direction, whereby high magnetic flux in the (100) direction can be obtained. The products are suitable for use in transformer cores, or the like.

Description

Method of manufacturing silicon steel sheet with a fixed direction of magnetization The invention relates to a method for manufacturing silicon steel sheet with solid Direction of magnetization and excellent electromagnetic properties. Under the term "plate" used in the context of the description also includes stripes to understand.

The silicon steel sheet used as a transformer core, etc., for example with a fixed direction of magnetization is polycrystalline; when each crystal grain of the Silicon steel sheet, which represents a structural component and any Assumes direction, is oriented in the direction of (110) <100>, where the direction <100> corresponds to the direction of easy magnetizability, thus a soft electromagnetic material with little iron loss is obtained and a large magnetic flux density> if one considers the magnetic flux in the Direction of <100> sends through. Something like that electromagnetic Material was produced on an industrial scale. In technical production however, this material is the technique for achieving a stable secondary recrystallization structure significant; Many attempts have been made in this regard, wherein however, no satisfactory process could be found.

Most of the conventional methods of manufacturing a silicon steel sheet with a fixed direction of magnetization, a dispersed fine precipitate is used, to prevent normal grain growth during primary recrystallization. While the industrial production must be the state of precipitation of this dispersed precipitate be regulated throughout the process, i.e. at the original chemical Assembling, heating the ingot, hot rolling, cooling with water after the hot rolling, the coiling temperature of the steel strip and the subsequent one Cold rolling, tempering, etc. For this reason, an extremely precise regulation is at the Manufacture of a (mono-directional) silicon steel sheet with a fixed direction of magnetization required to achieve good reproducibility and a large yield.

The invention therefore provides a method of making an extremely stable silicon steel sheet with a fixed direction of magnetization and good reproducibility, in which a silicon steel containing 2 to 4% Si, Regt iron and unavoidable Impurities9 to which a small amount of one of the elements Al, Ti, Zr or Ta or two or more of the elements Al, Ti, Zr9 Ta or V as nitride-forming element was added, hot-rolled in a known manner, Cold-rolled to the desired thickness, fresh, etc., the nitride-forming elements converted into nitrides in a nitriding process and finally tempered, to orient the crystals in the direction (110) <100> after annealing.

In Figs. 1 to 3 are photographs of the macrostructures from below silicon steel sheet obtained in various conditions according to the invention fixed direction of magnetization.

According to the invention, the Al, Ti, During the nitriding process, Zr, Ta and V are converted into nitrides to form a secondary To achieve recrystallization before the final annealing. These nitrides are very effective good as a dispersed precipitate and prevent normal grain growth in the primary recrystallization; furthermore, they favor the production of the final silicon steel sheet with a fixed direction of magnetization and secondary recrystallization structure. That Adding the nitride-forming elements to the silicon steel and transferring them Elements in the nitrides immediately before the final tempering to achieve the above The effects described can be extremely simple and reproducible in technical terms Execute scale.

A feature of the invention resides in the addition of the nitride-forming Elements related to the silicon steel used.

If you only add one of the elements mentioned, the salary should be for Al 0.01 to 0.07 wt.%, for Ti 0.01 to 0.2 wt.% for Zr 0.01 to 0.3 total% and at Ta 0.05 to 0.5 wt.%. If you give two or more of these elements, including V to, then Ti, Zr, Ta and Al should be in the above specified proportions and V in an amount of 0.01 to 0.1 wt.% was added will. However, the total amount should not exceed 0.5%.

The above-mentioned nitride-forming elements are said to be composed of the following Reasons are added in the specified proportions: 1. If the added Quantities are less than the minimum quantities given above, the quantity of the is sufficient formed nitride does not lead to the normal grain growth of the primary recrystallization grains and there is no stable secondary recrystallization growth.

2. If the maximum quantities specified above are exceeded, Excess nitride is precipitated, causing the growth of secondary recrystallization is prevented.

Silicon is used first in an amount of 2 to 4% for improvement added to the magnetic properties in technical production. Silicon steel also contains 0.01 to 0.10% carbon, its presence for the following reasons The advantage is: Since carbon has a negative influence on the magnetic Has properties, its amount should be as small as possible. If, however, the carbon content is below 0.01% in the production of the steel ingot, the deoxidation of the Insufficient steel. As with a steel with a high oxygen content one If the magnetic properties deteriorate, the lower limit should be set of the carbon content are 0.01%. If the carbon content is above 0.1% it becomes difficult to refine during machining, | so that unnecessarily long Fresh times become necessary; The aggregate structure of the sheet metal is distant Rolling and tempe n also adversely affected. For these reasons, the Carbon content between 0.01 and 0.10f.

Another feature of the invention is that the nitride-forming Silicon steel sheet containing elements immediately before the final annealing of a Is subjected to nitriding. This nitriding can be achieved by simply heating of the silicon steel sheet in a pure nitrogen atmosphere, a nitridable water-siff-nitrogen mixture or an ammonia decomposition gas obtained from liquid ammonia will. The heating temperature in nitriding is preferably 450 to 750 ° C. The silicon steel sheet is preferably kept at the lowest possible temperature heated to soften and harden the sheet metal coils due to the high temperature to avoid. However, the softening and hardening of the coils is determined by both strength and width of the sheet as well as influenced by the nitriding temperature. Since the Nitriding after the completion of the refining carried out in a continuous furnace primary recrystallization takes place, the nitriding temperature must be taken into account the coil hardening can be selected based on the softening of the coil; at a suitable However, the device can use the most economical temperature within this range can be chosen at will.

The heating during nitriding depends on the temperature and the nitrogen partial pressure and the content of nitride-forming elements in the steel; it will be so long heated until the secondary recrystallization is complete, which is about 2 to 20 Lasts hours, Other conditions besides the above, which are not a feature of the invention can be appropriately selected and applied. For rolling the silicon steel to a certain thickness, the steel is e.g.

hot rolled, then descaled, tempered and then cold rolled, cold rolling can be carried out twice or once. According to the one-time A steel sheet with a thickness of 1 1.5 to 2.5 mm is used in the cold rolling process to a decrease in thickness from 70 to 90% cold rolled to a desired thickness and then after freshening nitrided. In the two-time cold rolling process, a steel sheet from 2 to 3 mm thickness first rolled with a thickness reduction of 50 to 80%, then Refined at 700 to 9000C, then at a strength reduction of 40 to 60% Cold rolled a second time, refined and then nitrided.

The invention will now be explained further with the aid of the following example.

Steels with the composition listed in the following table were obtained made in the form of bars of 100 kg. Each ingot was set to 1000 to 12000C heated.

and then forged into a plate 10 mm thick, 100 mm wide and 150 mm long. This plate was then hot rolled to a thickness of 2.3 mm. The hot-rolled steel was descaled in each case, then annealed (heated to 8000C for 20 minutes, (20 minutes at 800C), cold-rolled a second time (to 0.35 mm thickness), refined (20 minutes at 7800C), then at the rate given below Nitrided atmosphere and then tempered one last time. The tempering between the second cold rolling is necessary; however, refining is not always necessary for steels with a low carbon content. Table Chemical composition in% by weight Descriptive voltage C Si Mn PS Cu Ni Cr Al Ti Ta Zr V C 0.05 3.03 0.11 0.011 0.004 0.082 0.06 0.04 0.019 - - - - 126 0.08 3.16 0.10 0.002 0.005 <0.01 <0.01 <0.01 - 0.025 - - - 128 0.072 3.38 0.11 0.002 0.004 <0.01 <0.01 <0.01 - - - 0.022 - 133 0.08 3.13 0.18 0.004 0.006 0.02 0.01 <0.01 0.006 - 0.21 - - 136 0.08 3.15 0.20 0.006 0.008 <0.01 0.009 0.007 0.016 - - 0.029 - 139 0.08 3.15 0.10 0.005 0.007 0.01 0.01 0.008 0.005 - - 0.034 0.044 Example 1 A steel sheet 0.35 mm thick after the second rolling was nitrided after refining for 10 hours at 500 ° C. in an ammonia decomposition gas prepared from liquid ammonia; it was then heated to 11Q00C for 4 hours in a hydrogen atmosphere.

The> macrostructure of the silicone steel sheet obtained in this way is shown in Fig. 1 reproduced.

Example 2 a. Sheet steel 0.35 mm thick after the second cold rolling was refined and then nitrided for 18 hours at 650 ° C in a pure nitrogen atmosphere; the mixture was then heated to 11500 ° C. for 4 hours in a hydrogen atmosphere. The macrostructure of the steel sheet thus obtained is shown in FIG.

Example 3 A steel sheet 0.35 mm thick after the second rolling was freshened and then heated in a pure. Stickstcffatmosphäre at 750 ° C for 4 hours; the mixture was then heated to 11500 ° C. for 4 hours. The macrostructure of the thus obtained Steel sheet is shown in Fig. 3.

The nitriding atomosphere in Examples 2 and 3 can be selected from hydrogen-containing nitrogen (a gas mixture with a content of less than 15% hydrogen, the remainder nitrogen), which the treated steel sheet to capable of nitriding. In such a mixed atmosphere, a sufficient Nitridation observed; for this reason, the taking of photographs was taken the macrostructure obtained in this way is dispensed with.

In the case of a zirconium-containing steel (designation no. 128), except the sheets with the thickness described above a hot-rolled sheet of 1.5 mm Thickness and made into a sheet of 0.35 mm thickness by one-time cold rolling rolled. The same result was obtained.

All percentages relate to weight.

Claims (7)

P a t e n t a n s p r ü c h e: 1. Method of manufacturing a silicon steel sheet with solid Direction of magnetization by hot rolling a silicon steel containing 2 to 4f Si and unavoidable impurities, subsequent cold rolling and Annealing, characterized in that this silicon steel, which in addition Contains 0.01 to 0.07f Al, 0.01 to 0.2% Ti, 0.01 to 0.3% Zr or 0.05 to 0.5% Ta, nitrided in a nitriding atmosphere at 450 to 750 ° C before the last tempering and the element is converted into the nitride and the nitride-containing sheet is secondary recrystallized. 2. The method according to claim 1, characterized in that the Silicon steel, which additionally contains at least two of the elements Al, Ti, Zr, Ta and / or V contains, in a nitriding atmosphere at 450 to 750 0C before the last Tempering nitrided and these elements converted into the nitrides, and the sheet with secondary recrystallized the nitrides, the content of Al 0.01 to 0.07% Ti 0.01 to 0.2%, for Zr 0.01 to 0.3%, for Ta 0.05 to 0.5% and for V 0.001 to 0.1% and the total amount of these elements is not more than 0.5%. 3. The method according to claims 1 or 2, characterized in that that the silicon steel contains 0.01 to 0.10% carbon. 4. The method according to claims 1 or 2, characterized in that that the nitriding atmosphere is pure nitrogen, a mixture of hydrogen and nitrogen, or an ammonia decomposition gas made from liquid ammonia used. 5. The method according to claims 1 or 2, characterized in that that heating is carried out for 2 to 20 hours during the nitriding. 6. The method according to claims 1 or 2, characterized in that that the silicon steel is hot-rolled, cold-rolled, freshened and nitrided. 7. The method according to claims 1 or 2, characterized in that that the silicon steel is hot-rolled, cold-rolled a first time, refreshed, a second time Sometimes cold-rolled, freshened and nitrided. L e r s e i t e