DE1433756B2 - Process for the production of wound strip cores from silicon steels - Google Patents

Description

The invention relates to a method for the production of wound strip cores made of silicon steels, wherein the wound core is used to improve the magnetic properties of a heat treatment is subjected.

It is known that the magnetic cores as used in transformers and the like are electrical Apparatus are used, so-called winding cores can be, usually by winding a strip or tape of magnetic material around a suitably shaped winding mandrel, then Shaping the core, if necessary, and subsequent heat treatment of the core for Stabilize its shape and develop its magnetic properties.

Although all magnetic materials are appropriately used to make such cores crystal-oriented, magnetic materials are advantageously used. at Crystal-oriented, magnetic materials can be the strip or tape from which the core is made should be treated in such a way that when the resulting core is magnetized becomes, the predominant direction of orientation with regard to the magnetic properties essentially lies parallel to the direction of magnetization and thus ensures that after a suitable The core losses of the core are lowest and the permeability depending on the heat treatment the applied, oriented, magnetic material has the highest value.

So far, the production of tape-wound cores has been based on the following general guidelines performed: A tape or strip of magnetic material was placed cold on a winding mandrel wound up. After winding, the core was wound into it by means of appropriate holders Form held. After that, the core and the jig were heat-treated brought to the appropriate annealing temperature and then core and holder to room temperature cooled down. . '■ "■' ■ '■'

In some cases the core can be made by cutting open the tape or strip of magnetic Material into a plurality of strips of suitable lengths, assembling the strips a stack and deforming this stack into a complete core or a core segment will.

Typical examples of such cores are shown in the drawings, where ....; ....

Fig. 1 is a perspective view of a C-core and

Fig. 2 shows a perspective view of a toroidal core. ■ :: ': ₅ g

It should be noted that Fig. 1 shows two U- or C-shaped parts 1 and 2, each consisting of a A plurality of correspondingly shaped metal sheets 10 exist (a smaller number is for simpler description represented by thicker sheets than are actually used in practice). The whole core is produced by placing the surfaces 17 of the two sections 1 and 2 against one another; because Because of the shape of each section, such cores are known as C-cores.

According to a known method for producing C-cores, the following steps are carried out:

a) A strip or tape of magnetic material is wound around a winding mandrel until the desired thickness in the core is achieved; then the free end of the strip will go through Fixed point soldering;

b) this core formed in this way is simultaneously removed from the winding mandrel and onto a so-called Forming mandrel placed on which a subsequent shaping is carried out in order to obtain the shape;

c) the core is removed from the mandrel at the same time and a so-called glow mandrel is inserted, while the core is clamped to maintain its shape;

d) the core, the filament and the clamps are subjected to a heat treatment in order to obtain the to stabilize the formed shape and to fully increase the magnetic properties of the core material to develop;

e) the individual layers in the core are bonded with glue;

f) the core is cut apart to form the two C-shaped sections.

In Fig. 2, a toroidal core 31 is shown, consisting of a plurality of turns 35 of a tape made of magnetic material. Such cores are commonly referred to as toroids.

According to a known manufacturing method, toroids can be formed by the following process steps:

a) A strip or tape of magnetic material is wound around a cylindrical mandrel until a core of the desired thickness is reached; then the free end of the strip is attached by point soldering;

b) the winding mandrel is removed;

c) the core thus formed is subjected to a heat treatment in order to stabilize its shape and develop the magnetic properties of the magnetic material.

The above description only explains the typical manufacturing processes that have been used up to now for the formation of winding mandrels. Many variations of such procedures will of course be apparent to those skilled in the art common.

These methods have certain disadvantages. Cold-wound magnetic material is elastic (in the sense that it is hard and stiff and, when deformed, tends to revert to its original shape). It is therefore necessary to maintain the coiled shape, until it is through the heat treatment is stabilized. That makes the use of clamps and domes which are costly to manufacture and too are necessary. The heating and cooling used heretofore are time consuming and expensive, since a large part of the amount of heat applied is required for the clamps and To heat thorns. These also reduce the amount of time needed to heat the cores in the heating device available space.

The object of the invention is to provide a simplified method in which the core in a single or continuous operation molded and heat treated to create.

According to the invention, this is achieved in that the steel strip before being wound onto a temperature

temperature of at least 600 ° C, wound on a mandrel under tension at this temperature, in placed in an oven with a temperature between 600 and 1000 ° C and in 15 until 60 minutes is cooled to 400 ° C.

As an example, a method for producing a C-core according to the invention is described below:

The material from which the core is made can be crystal-oriented silicon steel with a preferred orientation be essentially parallel to the rolling direction, so that when magnetizing of this material in this direction the magnetic properties give an optimum, d. i.e. that the Core loss is lowest and permeability is highest.

The material is made into a strip of the desired width by cutting it parallel to the direction of rolling cut.

The strip is then heated to a working temperature of 800 ° C.

Subsequently, the strip can be reached around a suitably shaped and dimensioned mandrel the desired core shape and dimensions are wound until the desired core thickness is reached is.

The wound strip is then cut from the main length of the strip. Because of the great plasticity of the strip at the working temperature, which is within the range of 600 to 1000 ° C or higher and is preferably around 800 ° C, the core shape is self-sustaining, so that neither additional molding or clamping of the core is required, nor is the free end of the strip must be held.

The mandrel is then removed from the wound core and the core is placed in an 800 ° C oven and then gradually cooled from 800 to 300 ° C according to the following scheme:

5 minutes at 800 ° C,

5 minutes at 700 ° C,

5 minutes at 600 ° C,

5 minutes at 500 ° C,

5 minutes at 400 ° C,

5 minutes at 300 ° C.

After another, uncontrolled cooling to room temperature, the core is ready for the following Steps of gluing the individual winding layers and cutting them to form two C-shaped segments.

Experiments which have led to the present invention have found that the desired Core shape can be obtained at working temperatures as low as 600 ° C (this temperature represents the minimum for a satisfactory softening temperature for those commonly available Materials). In many cases, however, it can fully develop the magnetic properties of the core material cannot be obtained at such low temperatures. Hence it may be necessary the cores formed at this lower temperature to a somewhat higher treatment temperature to be heated prior to controlled cooling. On the other hand, it is possible to suit the molding at a perform high working temperature in order to stabilize the shape of the core as well develop its magnetic properties.

In some cases it may be desirable to have controlled cooling prior to removal of the mandrel perform.

By controlling the rate of cooling of the hot-formed core using heat are the magnetic properties that occur during molding or subsequent heating fully developed, not compromised.

The controlled cooling is most advantageously carried out in a duct furnace, although others Devices for achieving a controlled cooling rate known to those skilled in the art are also satisfactory. The cooling speed depends on the type of magnetic material and the size and volume of the core. For example, kernels in the weight range of 0.5 to 10 kg, according to the invention from commercially available, oriented and non-oriented silicon steels were molded to 400 ° C or less within a period of 15 minutes to one Hour to be cooled.

It is possible to stop the controlled cooling at higher temperatures, but it has been found that when the controlled cooling is stopped above 400 ° C the magnetic properties of the core are impaired.

According to a further embodiment of the invention, a strip of the magnetic material be cut into a plurality of individual pieces of suitable lengths, which after heating be stacked and compression molded to the working temperature at that temperature so that the stack is formed into part of a C-core.

Cores made in accordance with the present invention have equivalent and in many cases better magnetic ones Properties compared to those obtained by cold working and forming according to the prior art subsequent heat treatment were generated.

Usually the finished cores of electrical devices have closed magnetic ones Lines. However, as indicated above in the case of C-cores as an example, the complete core can consist of a plurality of core sections. It goes without saying that the present invention is also suitable for producing such sections and the term "core" as it is in the claim is used, not only includes complete cores, but also individual parts of such cores.

Claims (1)

Claim: Process for the production of wound strip cores from silicon steels, the wound Heat treated core to improve magnetic properties is, characterized in that the steel strip is heated to a temperature of at least 600 ° C prior to winding, at this temperature is wound on a mandrel under tension, in a wound form in a Oven with a temperature between 600 and 1000 ° C and brought on in 15 to 60 minutes 400 ° C is cooled. 1 sheet of drawings