NO136323B - - Google Patents

Description

Method of manufacturing a remanent magnetic reed element.

The invention relates to a method for producing the element arranged for remagnetization for a self-retaining switch affected by remagnetization, in which an alloy consisting of 40 to 75 parts by weight cobalt and 60 to 25 parts by weight iron, in such a ratio that the sum of the iron and cobalt contents gives 100 parts by weight, and 1 to 5 parts by weight of vanadium is hot-worked, soft-annealed at at least 750°C, cold-worked after quenching and separation

cured for 1/2 to 6 hours at 550 to 670°C.

In Bell System Technical Journal for January

1960, on page 1, etc., a class of switching arrangements is described which is designated as "ferreeds". These devices are characterized by tightly enclosed or sealed metallic contacts which form part of a magnetic switching circuit which also contains at least one remanent magnetic part. The remanent part or parts which are switched, usually by means of an enclosing wire coil, have sufficient remanent magnetism so that the contacts can be held in either open or closed position without continuous consumption of energy.

Ferreed structures are currently in use all over the world. These are of particular importance in modern telephony, and millions of these devices are in use in electronic telephone switching systems.

The common ferreed construction currently in use comprises two magnetically soft tongue or reed elements which carry contact areas, these reed elements being magnetic elements which are usually located outside the switch itself. Construction designs that were proposed around the time of the development of the prototype device include a simplified construction where the reed elements themselves contain or are constructed of a remanent magnetic material (see Bell System Technical Journal as above, and US-PS 3,059,075).

The inherent advantages of the remanent magnetic reed construction are several. It is in the nature of the matter that elimination of external remanent magnetic elements leads to both cheaper manufacturing and a reduction in size. Under many conditions, the internal remanent magnetic reed construction can also be operated with a certain energy saving.

Despite the apparent inherent advantages of the internal remanent magnetic reed construction, this has not found widespread commercial use. In general, the continued production of the somewhat more expensive, larger construction that uses the externally located remanent switching device can be attributed to certain manufacturing difficulties associated with the remanent magnetic reed device. The main difficulty is connected with the actual design of the reed element. This operation is preferably carried out by simple punching or pressing (extensive rolling out of a round thread). It has been found that this operation, when performed on a material with suitable magnetic properties, often results in a brittleness that causes breakage.

For the above-mentioned embodiments, the use of a known alloy composition which is generally known as "Remendur" and which is a 50:50 cobalt-iron alloy with a small addition of vanadium is assumed. The production of the appropriate remanence (of the order of magnitude at least 10,000 gauss) comprises one or more hardening operations.

From DT-AS 1 458 521 it is for manufacturing

of the elements arranged for remagnetization in switches which are affected by remagnetization, known to use a permanent magnet alloy consisting of 40 to 75 percent by weight cobalt,

25 to 60 weight percent iron and 1 to 5% vanadium, and which is subjected to a final treatment consisting of cold rolling with at least 60% and tempering for a period of from 0.25 to 25 hours at 400 to 6 75°C, where the shorter times correspond to the higher temperatures. This magnetic material is to be used in the sleeve in self-retaining switches and, with high remanence and a good square ratio, exhibit a stable coercive force over a large temperature range.

The purpose of the invention is to provide

a method which allows the tongue or reed elements in a switch of the type indicated at the outset to be produced from such a magnetic material.

This purpose is achieved according to the invention by using a method of the type indicated at the outset, which is characterized by the fact that when producing an element arranged for remagnetization in the form of a flat coupling tongue with a round shaft that serves to fuse a glass capsule, the cold working is carried out in two stages, and in such a way that in the first stage of the cold working a round wire is produced with a diameter equal to the shaft diameter, and the round wire is then again, and continuously, soft annealed for at least 5 seconds at 850 to 1,050°C, and that the tongue part in the second stage of the cold working is rolled out by at least 40% (final thickness divided by the diameter of the round wire times 100). In this method, curing is then carried out at 550 to 670°C, i.e. in the upper part of the known temperature range.

An advantageous embodiment of the method according to the invention consists in that the round wire between the continuous soft annealing at 850 to 1,050°C and the second stage of the cold working is additionally cold worked with a degree of working referred to the cross section of from 20 to 50%.

The invention shall be described in more detail in

the following with reference to the drawing which shows a

side view of a ferreed construction made in accordance with the invention.

I. The drawing

The figure shows a prototype of a remanent reed construction which is illustrative of the constructions intended for production according to the invention. A detailed description of this device and of a number of variations thereof is given in the aforementioned US-PS

3 059 075. The figure shows a glass capsule 1 which contains two reed elements or tongues 2 and 3 which are each provided with

with contact areas 4 or 5. The majority of each of the reed elements 3 and 4 is rolled out of a round wire with the cross-sectional shape retained by the unrolled, projecting parts 6 and 7. The parts 6 and 7 ef introduced into the cap

len 1 through glass sealing areas 8 and 9. Although many different circuit arrangements are possible and various variations are in use, the device shown is provided with two separate windings 10 and 11, one winding, when suitably energized by means of a device not shown, results in polarization of the reed element 2 in one of the two permitted directions, while the other winding 11 results in polarization of the reed element 3 when energized in a suitable manner. This particular arrangement, which in more advanced designs may include overlapping coils, allows separate control of each of the reed elements and can therefore be adapted for use in a crossover point grouping.

The operation of the device is simple. Polarizing reed elements 2 and 3 in the same direction (ie north-south from left to right) provides closure, while magnetizing reed elements 2 and 3 in opposite directions (ie north-south for reed element 2 and south -north of the reed element 3, for both of them from left to right) results in an open circuit. As described above, the properties of the remanent material, of which at least part of at least one of the reed elements 2 dg 3 is made, are of such a nature that either a closed or open circuit can be maintained without energy consumption, i.e. the remanent magnetization is sufficient to overcome the natural restoring forces in the structure and to maintain the closed state.

Variations of the construction include the possible use of permanent biasing of one reed element, for example by constructing it from a permanent magnetic material that does not switch during operation, or by using a separate magnetic biasing element, incorporating any number of additional reeds -elements and/or contacts, and many different circuit arrangements.

2. The composition of the remanent reed element

It has been stated above that the remanent magnetic material used is part of the class of materials sometimes referred to as "Remendur". It is further indicated above that the entire range of this composition class comprises 40 to 75 parts by weight of cobalt, 25 to 60 parts by weight of iron and 1 to 5 parts by weight of vanadium. Compositional variations and preferred ranges are set forth in US-PS 3,364,449 (DT-AS 1,458,521). As indicated therein, the nominal (and preferred) compound contains approximately equal amounts of cobalt and iron, a preferred range for the main constituents being stated to be from 45 to 65 parts cobalt and the balance iron. The preferred range of vanadium included to control coercivity is from 2 to 4 parts by weight based on 100 parts by weight of the three components cobalt, iron and vanadium. Additional ingredients may include manganese added to reduce the harmful effects of any sulfur deposits (usually up to about 1 part by weight on the above basis), and possibly smaller amounts of silicon and aluminum (both in an amount less than 1 part by weight on the above basis). These last two components serve to bind oxygen, which can also be harmful, during the treatment. In addition to the specified intended components, there are acceptable amounts of commonly occurring contaminants. Such contaminants, the total amount of which does not exceed 1 part by weight on the above basis, may include

nickel, carbon, copper and sulphur.

3. Processing

A. The remanent magnetic material.

The specified compound is known as "Remendur" only when it has such a medium hardness that it results in a remanent magnetization of the order of at least 10,000 gauss. In the soft magnetic state the compound is sometimes known as "Permendur", while in the hardened state it is sometimes known as "Vicalloy". Development of the required degree of magnetic hardness necessarily entails both cold working and phase separation hardening. The invention is largely based on the special way in which these process steps are carried out. Although the most important processing steps from the point of view of the invention are the final three steps (numbered below as 5 or 5 plus 5a, 6 and 7), the following description indicates suitable initial steps, starting from the formation of the alloy compound itself.

Step 1. A melt is made from starting ingredients. Suitable constituents are electrolytic cobalt, electrolytic iron, ferrovanadium (an alloy of vanadium and iron) and electrolytic manganese. The components are melted (melting temperature approx. 1550°C). The temperature is maintained for 1 minute or 2 to ensure thorough mixing and an ingot is formed on cooling.

Step 2. The ingot is heat worked at a temperature

of between 900 and 1250°C. The processing can be in the form of rolling, drop forging or extrusion. The water treatment continues to a suitable dimension, i.e. to a diameter of approx. 6.5 cm. This step usually involves several phases.

Step 3. The heat-treated body is softened by heating to a temperature of at least 750°C, and quenching at a rate sufficient to avoid significant phase separation. This is usually achieved by rapid immersion in ice water. Room temperature is maintained for a period of substantially less than 1 min.

Step 4. The quenched bar is cold worked to the desired final dimension (cold drawn to a round wire diameter of from 0.025 to 0.125 cm).

Step 5. The first of the special procedure steps

which is considered responsible for appropriate device manufacturing in accordance with the invention, includes a wire annealing.

In accordance with this step, the thread is softened by water treatment

to result in a tensile strength of a maximum of approx. 14,000 kg/cm and an extension of at least approx. 10%. An illustrative treatment comprises maintaining a temperature over a range of from approx. 850 to 1050°C. This temperature should be maintained for a minimum time of at least approx. 5 sec.,-.'where the upper time limit is uncritical and determined on the basis of what is appropriate. In accordance with a method which has been found satisfactory, the wire is passed through a hot zone of 1 meter at a speed of approx. 2 meters per minute, whereby maintenance of a temperature approaching the temperature of the zone is achieved for a period of approx. 15 sec. Immediately after this heating, the wire is passed through a cooled chamber to quench the wire at a rate sufficient to prevent phase separation and associated hardening.

For several reasons, this step is carried out in a reducing atmosphere, such as hydrogen or pressure-distilled ammonia. Although a neutral atmosphere is in principle permissible from

from a practical point of view, it is more appropriate to work with a reducing atmosphere than to use the degree of care necessary to exclude minor amounts of oxidizing constituents from commercial "neutral" gases. The purpose of the reducing atmosphere, or more generally Late non-oxidizing atmosphere, is to avoid the formation of surface oxide, especially vanadium dioxide, which, due to its abrasive properties, results in rapid punch wear during step 6. The use of such a non-oxidizing atmosphere is also desirable to provide a relatively clean surface for later plating for the contact formation according to section B below.

Step 5a. Although, as far as the properties of the device are concerned, as described above, a wire annealing is sufficient to prepare the material for the cold working according to step 6, certain practical considerations may dictate a variation.

It has been found, for example, that the final reed element exhibits different magnetic properties between the rolled-out part which carries the contact and the still round part which is preferably retained for sealing purposes. When it comes to appropriate manufacturing, it may be desirable to treat the reed element in such a way that these properties are made more similar to each other. Although this will not have any significant impact on the operating characteristics of the device, it may for example be appropriate due to such practical considerations as the specification of the properties of the thread for the intermediate product to undergo the treatment indicated in step 6. A possible method in this connection is to use a weakly hardened wire in this step. This can be achieved, for example, by cold working after the wire annealing already specified in step 5. This cold working,

which will be sufficiently weak to allow the thread to remain within the maximum allowable tensile strength values, may be in the form of an area reduction of as little as 20%

or possibly as much as 50%. This method is considered optional.

Step 6. This is the punching or pressing operation. During this step, the round wire obtained in step 5 or steps 5 and 5a is rolled out to produce the enclosed area of the reed element (while maintaining the round cross-sectional shape of the part of the element that is hermetically sealed to the capsule ). This pressing operation can also include cutting the reed element to a desired length. Properties developed during step 6 or treatment benefits achieved during step 6 include only the rolling effect. Properties developed during the press operation include a coercivity of approx. 30 to 60 Ørsted.and remanent magnetization values of 7000 to 10,000 gauss. Further improvement of the properties is achieved by phase separation treatment as described in step 7.

As the thread produced by the series of method steps that ends with step 5 or step 5a usually exhibits a certain curvature, it is usual for the thread to be pulled at this point. The wire leaving step 5 or 5a is usually first straightened, then rolled out, and finally cut to the desired length, in this order. The alignment has little effect on the mechanical or magnetic properties.

A further, less mechanical treatment

which can be carried out at this point includes drum cleaning in liquids containing abrasive particles and/or other means to remove any burrs or other surface irregularities produced by the mechanical pressing operation.

It has generally been found that the degree of cold working during the pressing operation is of relatively little importance with regard to the finally developed properties.

With, for example, a round thread of diameter as a starting point

of 0.<5>3 mm which was rolled out to a test piece of 0.12 mm

on the one hand and 0.2 or 0.23 mm on the other, no significant variation in the final magnetic properties arose. In general, a thickness reduction of at least approx.<4>0% (representing the ratio between the smallest final cross-sectional dimension and the non-rolled wire diameter) is sufficient to result in filling-making properties for the device's function in this step.

Step 7. The final treatment step comprises phase separation which is carried out at such a temperature and for such a duration that the desired values of remanent magnetization and coercivity are achieved. For devices for which the invention is intended, it is generally desirable that the remanent magnetization lies within a range of from 10,000 to 20,000 gauss, and that the coercivity lies within the range of from 10 to 50 Ørsted. These verids are a measure of the properties of both the round and rolled parts of the reed element. It has been found that both magnetic properties are produced by heat treatment of the reed element at temperatures within a range of from 550 to 670°C for a time of from 1/2 to 6 hours. Extensive experimentation has shown that significantly longer periods of time and/or higher temperatures will lead to a lowering of both the remanent magnetization and the coercivity to values below the specified level. Shorter time and/or lower temperature results in the retention of higher values of the coercivity, but does not cause the production of the desired magnetization.

In the foregoing, it has been stated that in a preferred embodiment of the invention, the protruding part of the reed element is hermetically sealed in the capsule. It is also indicated that the use of a non-oxidizing or preferably a reducing atmosphere in step 5, in order to avoid

formation of surface oxide, is beneficial during the reed element's pressing and plating operations. It has also been found that hermetic seals of superior quality are produced by means of other processing steps. ' These steps, which together with steps 1-7 above constitute the preferred embodiment, shall be described in the following.

Step 2a. After the heat treatment, the surface oxide layer is removed either mechanically or chemically. Although ordinary pickling with a strong acid solution is serviceable, it has been found most desirable to use mechanical treatment, such as grinding or milling. Here, one is mainly concerned with the smoothness of the surface, so that one can achieve surface conditions on the rod that allow it to be transformed into a thread that has no surface defects. Such a wire is very important for hermetic sealing, as the wire-to-glass seal turns out to be mainly of the pressure type (essentially non-chemical).

Step 3a. After quenching, it turns out that again

a very dense oxide layer has formed, and this is also removed, for example by sandblasting. An alternative method includes pickling. It may be possible to eliminate step 2a

and perform all surface removal in this step. However, attempts to carry out the entire grinding or milling operation in this step have resulted in some tendency to fracture during the cold working in step 4. It is possible that the entire surface removal can be carried out on smaller diameter bars, whether this is achieved by additional hot rolling as in step 2, or by cold working of quenched bars as in step 4..

Step 3b. Previous experience has shown that "Remendur" treated in accordance with step 3 can be subjected to the necessary cold drawing or other cold reduction without the use of metal plating. Less expensive lubrication methods using oil or dry lubricants have generally been found to be adequate. In accordance with the preferred embodiment of the invention, however, it appears that the use of a usually electromechanically applied coating of copper or another soft metal, such as silver or tin, or alternatively of other chemical coating materials, such as zinc phosphate, borax or inorganic oxa- pretend, not only contributes to the lubricating action, but also provides a protective layer which facilitates the production of a wire with a more perfect surface desirable for hermetic sealing. In accordance with prior practice, any such coating material may be removed, usually by mechanical etching, prior to final drawing using diamond dies (as opposed to carbide dies). This generally corresponds to a diameter of the order of 1.5 mm. An acceptable alternative at this stage is to retain the copper coating or another acceptable soft metal coating (organic coatings as well as tin or other low-melting metals must be removed - the final construction must be able to withstand the hermetic sealing temperature of between 600 and 1400°0.

In order to maintain a high degree

of surface perfection in order to optimize the hermetic seal, to avoid notches in the surface, one or more additional wire annealing can be introduced, starting from a diameter of approx. 1.5 mm. Such a one

annealing can consist of the wire at a speed of 1 meter per minute is passed through a hot zone of 1 meter to achieve temperatures of 850 to 1050°C for a period of approx. 1/2 minute, followed by passage through a water-cooled chamber to reduce rapid cooling.

B. Contact details e

The contact parts of the reed elements are supplied with suitable plating in the usual way. Usually a single layer of hard gold (eg cobalt-hardened gold prepared using a cyanide bath with citrate buffer) is sufficient. The plating thickness (also not unusual here) is not critical and can lie in the range 0.5 to 5 p. However, due to the usually small dimensions, especially the particle dimension of the structure, it is usually desirable to maintain uniform thickness within +50%.

C. Hermetic seal

The second operation that should be mentioned here involves the hermetic sealing of the projecting reed element portion to the casing or capsule material. The conditions are the usual for glass-to-metal seals in other areas. A suitable coefficient of thermal expansion in close agreement with the coefficient of expansion of "Remendur" can be obtained by using lead-based glass compounds or other suitable materials. In the foregoing, it has been stated that under normal circumstances the bond is considered to be mainly of the pressure type. The glass encasing material, which has been softened by heating, therefore flows around the projecting reed element. During cooling, compressive stresses occur in the sealing area due to the very slight mismatch between the expansion coefficients for the glass and for the reed material. The best hermetic seals have been provided in accordance with the preferred embodiment of the invention, i.e. using steps 2a, 3a and 3b.

The temperature-sensitive nature of the desired arrangement properties for the "Remendur" reed elements entails a further requirement for the sealing operation. It has been found that when the reed element is kept at temperatures above approx. 800°C even in the short periods of approx. 6 seconds occurring during the sealing operation, this can result in a reduction of coercivity of as much as 20%.

Claims (2)

i 1. Method for producing the element arranged for remagnetization for a self-retaining break affected by remagnetization, in which an alloy consisting of 40 to 75 parts by weight cobalt and 60 to 25 parts by weight iron, in such a ratio that the sum of iron and the cobalt content gives 100 parts by weight, and 1 to 5 parts by weight of vanadium is heat-worked, soft-annealed at at least 750°C, cold-worked after quenching and precipitation-hardened for 1/2 to 6 hours at 550 to 670°C, characterized in that in the production of a remagnetization device element in the form of a flat coupling tongue with a round shaft which is used for fusing in a glass capsule, the cold working is carried out in two stages, and in such a way that in the first stage of the cold working a round wire is produced with a diameter equal to the shaft diameter, and the round wire then again , and it is continuously soft annealed for at least 5 seconds at 850 to 1,050°C, and that the tongue part in the second stage of cold working is rolled out by at least 40% (slu tt thickness divided by the diameter of the round thread times 100). 2. Method according to claim 1, characterized in that the round wire between the continuous annealing at 850 to 1,050°C and the second stage of the cold working is additionally cold worked with a degree of working referred to the cross section of from 20 to 50%.