DE1433809A1 - Process for reducing the sulfur loss in iron-silicon alloy sheets during final annealing - Google Patents

Description

E ELECTRIC Hanau, March 13, 1962

/ ΛΊΟΗ Bk / Dr-Schz / Bt

East Pittsburgh, PA ./ USA 61/9218 1 4 3 3 809 ^,

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Process for reducing the Schv / efelv§ <iiu, j IL ¹ L 'lii iron-silicon bearing plates during the final annealing

j'ierje J-.rfindung inspects to an annealing process for producing magnetic iron-silicon sheets with Würfeltexturc sub-cube texture is understood to mean _s that a cube face of the unit cube of the crystal lattice lies parallel to the rolling plane and in the rolling direction as well as perpendicular thereto, one each Cube edge,. Ä

According to the method according to the invention. Alloys as described in patent application V / 31 552 VIa / i8c, which does not belong to the state of the art ", in a special way the critical characteristic of the procedure of the patent application V / 31 552 exists in that a certain minimum of the sulfur content must be present in the alloy sheets, if at the The final annealing is the transformation into grains with a cube texture start of secondary recrystallization}. This critical one The sulfur content in iron-silicon alloy sheets during the final annealing is 0.0005 percent by weight, and this is a minimum the bed content must be present for so long bi3 the secondary recrystallization is completely over * It has been found that seeds with cube texture in the Iron-silicon sheets only grow preferentially over other germs during the final annealing when sulfur present in a certain amount iot “Such germs with Cube texture have crystal lattice surfaces that are substantially parallel to the surface of the sheet.

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After the process of the above-mentioned patent application * Vf 31 552, an atmosphere of visually / dry hydrogen must be used in the final annealing treatment of the Jisen-silicon alloys in order to prevent the formation of or Any oxide films present on the surface 4eä Blechet side. Such oxide films can annoy the desired TJe-JI conversion to a cube texture or ittCtt ^? completely prevent «. . ν - ^: \ »

When annealing in dry hydrogen, the sulfur content of the iron-silicon alloy sheets to be treated decreases very quickly. Am certain sulfur content but is in the alloy sheets for formation a cube texture is necessary, so that the conversion occurs when the sulfur content falls below this value to the cube texture is ended prematurely.

• The present invention is intended to provide a method by which the undesired loss of sulfur in the iron silicon layers during the final annealing can be reduced or even eliminated.

On an economic scale, the Sehlußglühüng is called ". Mass annealing either in the form of stacked metal sheets or carried out by rolled-up baiscl®ra «you individual During annealing, sheets are stacked or rolled up Hung toeh a powdery agent, usually pure aluminum oxide, isolated from one another to produce a Prevent the individual sheet metal layers from welding together. According to the invention, the sulfur is lost reduced during the final annealing treatment of the stacked or wound iron-silicon sheets, that the flow rate of hydrogen im Furnace is kept within a critical range.

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sheets to be subjected to the final cooling according to the method according to the invention, which are thus prepared Have-been that cube-oriented germs are present, a dry Vasoeratoffatmosphäre

'' exposed to a dew point of -40 ° C or below,

The shrinkage of sulfur in the alloy sheets is controlled by keeping the flow velocity of the dry water at 0 to 1 * 50 cm per minute is limited, and, the annealing in one Temperature range from 1100 ° C to 1350 ° C takes place for a long enough time to complete To effect secondary recrystallization .. The preferred one The flow rate of the hydrogen is in the range from 10 to 50 cm per kinute. I.

You flow rate is usually by one Volume expressed per unit of time. However, such units have little meaning if Ufen are very different Cross-section silts are used. For the present considerations, the flow velocity therefore indicated by de3 Yoluaen that per unit of time goes through the unit of the average cross section, in which the stack annealing takes place. You * ao expressed Flow rate is independent of the cross-section of the furnace used and can therefore be adjusted according to The teaching of this invention furnace with several different Size to be applied. "

The influence of the flow rate of hydrogen during the final annealing treatment on formation of Y / iirfeltexturromaterial was in various test series investigated, Some examples of these investigations are given below:

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Example I.

An iron-silicon sheet of 0.305 mm thickness and the _following: composition was treated according to the invention: 4

Alloy composition (analysis of the hot rolled / rolled strip) in %

Sample C Mn S 0 _? Si Pe. . BD-4 0.0097 0.002 0.0006 0.0010 3 * V. remainder '\

It should be pointed out that the alloy referred to above has a sulfur content which is so low that even a small loss of sulfur reduces the sulfur content of the sheet below the critical value of 0.0005 #. This alloy is in terms of composition and a emfindliches difficult material for conversion to cubic texture is Dao alloy sheet was characterized by a single Kaltwalzechritt with a deformation of 76 $. | a 1.27 on thick plate. The single sheet ι

a key anneal was achieved in one made of aluminum oxide

standing furnace tube (tube width 44.3 mm) in the presence of a hydrogen atmosphere with a dew point of -42 ° 0 at a temperature of 1200 ° C. The flow rate of hydrogen was nearly 31 cm per Hinute that ölühzeit "17 hours was found to be 80 i» the sheet surface had experienced secondary recrystallization by conversion to cubic texture ·

Example II

A 0.305 mm thick sheet containing the alloy composition according to Example I, the same final annealing as ι

exposed in Example I, but the flow rate was dec hydrogen 200 cm per hour. Also, in this sheet metal, approximately 80 ^ of its sheet metal upper- ■ ' surface secondary recrystallization, but no · « of the secondary recrystallized grains formed had a cubic texture.

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Example III

6 sheets of the alloy composition according to Example I were isolated, stacked with Aluniniuno: cyd powder. This stack was annealed at 1200 ° C for 17 levels in dry hydrogen with a dew point of -70 ° G. The hydrogen flow rate was 668 cm per minute. Almost 50 % of the surface of the sheet was secondary recrystallized. Only a small part of the secondary recrystallized grains of the sheet showed cubic shape.

Example IV

Another batch was treated according to Example III, ' however, the flow rate was set at 31 cm per minute. The sheets in this Stacks exhibited 100 # secondary recrystallization in the cube position.

Example V

6 sheets of the alloy from Example I, insulated with aluminum oxide, were stacked. This staple was annealed at 1200 ° C for 17 hours in hydrogen with a dew point of -20 ° C. The hydrogen flow rate was approximately 31 per minute. * These sheets did not suffer secondary recrystallization.It was observed that continuous oxide films were present on the surfaces of all sheets *

Example VI

Another stack was made as in Example V and the process steps repeated, but that was Hydrogen dew point reduced to -35 ° C been. The sheets of this stack experienced about 40 #

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secondary recrystallization of the sheet metal surface. [ The formed oeJimdaren Kürner "showed cube texture = It was observed that a thin, almost continuous Oxide film had formed on the surface of each sheet metal strip through which the growth ■ of the secondary grains has been delayed or stopped

Example VII - ■

A number of 20 cold-rolled sheets with the dimensions 102 203>: 3.05 mm auo a 3 # iron-silicon alloy with a layer content of 0 »001 > were layered in a stack and the individual sheets through Aluminiumcxyd powder (grain size O _t O74 ^mm) "isolated This stack was weighted down with steel plates 2 in order to avoid warping. The stack was placed in a tube furnace with an inner diameter of 127 mm and a length of 1525 mm. The stovepipe consisted of. a high nickel alloy. 33 furnace, was cleaned with a gas mixture of nitrogen and hydrogen gas (dew point -60 ° C), while furnace and batch were kept at temperature. The gas mixture was obtained by splitting ammonia (3 parts by volume of hydrogen to 1 part by volume of nitrogen). At temperatures of about 600 ° C, the furnace was sealed and the hydrogen was prevented from flowing, so that an absolute pressure of 258 Torr to 1034 Torr was maintained. After 24 hours at 1200 ° C., the sheets were taken out of the oven. These sheets had received a 100% cube texture through secondary crystallization. The example illustrates the case in which no gas flow occurs during the final annealing which takes place at high temperature

Can behanalungen the atmosphere during the annealing mentioned in the examples · _r from pure hydrogen, or may be substantial amounts of one or more inert gases such as nitrogen, argon or helium, contain ".

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The pressure of the furnace atmosphere can be significantly below or be above 1 atmosphere. For example, the pressure about 258 to 1550 Torr abaolut. The term "hydrogen atmosphere" refers to such gases.

From the above examples it can be seen that in the. methods described / OHL the deep dew point as well as low flow velocity / sov are NOTV Endig to the L _e, a cube texture gierungablechen cause. The low dew point is necessary to prevent the formation of oxide films that delay or inhibit the growth of the grains in the frontal layer. The low flow rate dec gas avoids a decrease in Schwefelgehaltec in.den alloy sheets "etc. This sulfur iot for Kornvachstun into cubes location necessary can not begin otherwise, such growth or is interrupted prematurely.

As indicated above, a decreased flow of hydrogen at a flow rate in the B _e reaching 0 to -150 cn per minute to Schvrefelgehalt in the alloy sheets not essential. This range of flow velocity has been used just as successfully in laboratory-scale tubular furnaces lined with Kickel alloys as well as in furnaces of larger dimensions.

As described in detail above, it follows. The method according to the invention provides a relatively simple means of control, with a noticeable loss of sulfur on the surface of the Lieen-Silieiun alloy sheet. * ^. ^{7 <} 'which are subjected to a final annealing treatment to form a cube texture.

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Claims (1)

1. Process for reducing the sulfur loss in iron-silicon alloy sheets during a known final annealing treatment in dry hydrogen, at temperatures of 1100 to 1350 ° C, a sufficient glowing time and a corresponding glowing atmosphere that is capable of removing surface oxide films and so in to ensure the alloy sheets a complete sequence of Selcundärrelcristallisierung in cube texture, characterized by. is that the Schvefelverlust cm by adjusting the flow rate of hydrogen of 0 OiB 150 per c Hinute kept small or very venoieden. ο Method according to Claim 1, characterized in that the flow rate dt · Wasitretoffes ■ 'is preferably set to 10 to 50 cm per minute .we de _r , ·. · · 3 " Process according to ₄ claims 1 and S ₁ dtdur Oh, characterized in that hydrogen with a dew point of -40 ° C or less is used as the furnace atmosphere. 'Λ BATH 109412 / OSSe