DE2448434A1 - DUESE FOR EXTRUDING A METAL MOLTEN TO MANUFACTURE FINE WIRE - Google Patents

Description

DR. BERG DIPL.-ING. STAPF DIPL.-ING. SCHWABE DR. DR. SANDMAIR

8 MUNICH 86, POST BOX 86 02 45

Anualtsakte 25 454 ¹ J Q. OCT. 1974

Monsanto Company,
St. Louis, Missouri / USA

Nozzle for extruding a molten metal to produce fine wires.

The invention is generally directed to improving an apparatus for making thread-like products by continuous Extruding directed towards very low viscosity melts. In particular, the invention relates to the improvement of a nozzle arrangement for extruding Metal melts and melts of metal alloys to form a wire with a fine diameter.

ι 509817/0284 - 2 -

11-52-02 417 GU

l / learn through what fine-diameter wires run through Melt spinning, d. i. by pressing a metal melt through a nozzle as a free, thread-like melt jet, are known and described in U.S. Patents 3,216,076 and 3,658,979, among others. at A melt (e.g. the melt of a metal or a metal alloy) with low viscosity is experienced as a result of this squeezed into a selected atmosphere at a suitable rate. When the hot jet that comes out exits the spray nozzle, comes into contact with this atmosphere, a reaction takes place, which leads to the formation a skin around the beam surface leads. This skin also known as "stabilizing film", acts as a protective cover in such a way that they thread-like jet protects against tearing off due to forces originating from surface tension until a a sufficient amount of heat can be given off to bring about a change of state into the solid state.

The device used in carrying out this procedure consists essentially of a crucible, which in its bottom a nozzle element, either as part of the bottom or preferably has as a nozzle insert. The crucible is further with heating devices for melting the batch and

B09817 / 0284 .- 3 -

for maintaining the melting state. Additionally devices are provided through which a positive head pressure is applied to the melt charge so that it can be sprayed out through a spray nozzle at suitable jet speeds.

From the nature of the procedure it is clear that it is strict Requirements are placed on the materials that form the nozzle. Among other requirements, the materials must be highly resistant to thermal shocks and have a sufficiently high temperature resistance to enable them can absorb the mechanical stresses that occur during extrusion. Also must for a successful In operation, the nozzle material must be chemically compatible with the extruded melt charge. That is, the nozzle material should be corrosion and erosion resistant to chemically reactive melts at high temperatures, so that the nozzle remains dimensionally stable during operations.

In the past few years, materials science has moved into has developed at a rapid pace, information and data are not yet available on a material with such could indicate properties that fully meet the strict requirements

509817/0284

requirements in the above sense could be sufficient. Thus, a considerable amount of time and effort has been devoted to discovering a suitable material. Materials including alumina, sapphire, zirconia, etc. Ceramic materials that have been successfully used in metallurgical processes to contain molten metals, such as steel, have been investigated but have failed to operate as the nozzle opening forming members by which molten metals can be extruded as fine diameter filament jets. The reason for such failure is variously inadequate strength, poor resistance to thermal breakage and chemical incompatibility with the charge under the temperature and pressure conditions required for ejecting molten metal through nozzle openings with diameters below 0.9 mm . Errors occur particularly enhanced when the highly corrosive melts of different iron alloys are processed, where l / ER drive 1SQO temperatures above ⁰ C are often required.

In a relatively short one. Developments in the past, as can be seen from US Pat. No. 3,584,678, Nozzles made of high-density beryl alumina in a device for extruding molten metal to form wire with

509817/0284

fine diameter used. Although this development is a clear advance compared to the rest of the state of the Technique, it has been found that dimensional changes in the nozzle opening exceed some acceptable limits, in the l / elaboration of certain molten metals, such as various steel alloys occur when such nozzles made of beryl alumina can be used.

According to the invention it has now been found that an extrusion device for forming wire of fine diameter from a metal melt advantageously has a nozzle structure made of polycrystalline thorium oxide (ThO2) with a density of 9.5 to 10.0 g / cm and a purity of at least 99.5 % is built up. The gate earth can be in the completely pure form or contain up to 0.5 percent by weight of a sintering agent. However, while not essential, it may be advantageous to select the sintering agent or densification aid used as one of many compounds known to perform such an action. As illustrative examples, calcium oxide, ytter oxide, ammonium chloride, cerium oxide and magnesium oxide, among others, can be given.

509817/0284

In the drawing is a preferred embodiment shown for an extrusion device for retall melts.

The figure of the drawing represents a schematic longitudinal section of a typical extrusion apparatus with which Melting metal in the form of thread-like rays for training v / on fine diameter wire extruded. The molten metal charge is accommodated in the crucible 2 which has a base plate 3, the crucible and the base plate are supported by a stand 4. An insulating cylinder 5 and a susceptor 6 surround the crucible 2 and its base plate 3. The heat required to carry out the process is generated by induction heating coils 7. Head pressure for extrusion is created by a pressurized inert gas (gas source not shown), which is supplied via the gas line 8, which communicates with the interior of the unit via the unit head 9 stands. Sealing rings 10 are used to maintain the pressure within the envelope and prevent leakage through the Avoid base plate 3. The molten metal 1 is applied through the nozzle 11 in the nozzle plate 12 by the Head pressure to form a thread-like melt jet pressed. When emerging from the nozzle 11, the resulting jet passes through a skin-forming atmosphere, which is inside

509817/0284 " ⁷ "

of the cavity 14 of the stand 4 is included. The one through the Skin-stabilized melt stream then passes through a cooling column (not shown) in which it is converted into the solid state sufficient heat is removed.

As indicated above, nozzle structures are in accordance with the invention made of a polycrystalline thoroxide material, uel-

ty rj

ches has a density of 9.5 g / cm to 10.9 g / cm and a purity of at least 99.5 % . A number of methods are presently known by which pore earth can be compacted to the values necessary for the practice of the invention. One such process, commonly referred to as "hot pressing", is fully described on pages 183-230 of the book "High Temperature Oxides" written by Allen M. Alper and published by the Academic Press of New York and London. Briefly said, powder-like particles of the ceramic are compressed and compacted at high pressures and temperatures, the pressures normally used being of the order of 71 to 704 kg / cm ² at temperatures generally in the range of 1500 to 2000 ° C. A Another suitable method is described in U.S. Patent 3,574,645, Similarly, an amount of fine grain thoroxide having a particle size of about 0.05 to 2.0 microns is first die pressed at about 704 kg / cm

509817/0284 " ⁸ '

a compacted "green" molded article to obtain a density of about 40 to 50% of the theoretically possible density, The preform is then sintered Uasserdampf atmosphere Uasserstoff-substantially to the theoretical density at a temperature of at least etua 2000 ⁰ C in a, which has a dew point between etua -25 ⁰ C to +25 ⁰ C. The sintering process is carried out over a period of about 7 hours.

As stated, the Thorerded nozzle can be made of 10G / S pure Thorerde or a composition consisting of torch earth and up to 0.5 percent by weight of a sintering agent, for example calcium oxide (CaO). Uenn the compression aid optionally used, it can be mixed with the Thorerde particles prior to the densification process be o

Plates or disks made of high-density polycrystalline Torde earth can easily be cut to the desired shape and size processed using known methods'. Fine diameter nozzle orifices are commonly made by working out a countersink in the feed surface of the nozzle plate with subsequent drilling and Polishing a nozzle opening of the desired diameter and

509817/0284

concentric with the countersink. The nozzle opening may, if desired, be ausgerundat _o In a given plate or disc may be present as a nozzle opening more.

As indicated above, the members forming the nozzle can also serve as a base plate for the crucible. In principle, however, it is preferred to have nozzle plate inserts in the base plate of the crucible, as shown in the figure. The nozzle plate insert is generally circular in shape and can pass through the base plate if desired Use a clamp or a hold-down ring. Multiple nozzle insert disks can be used in the Base plate of the crucible can also be used. The nozzle opening should have an aspect ratio between 1 and 2G, preferably less than 10, from the countersink.

The following examples illustrate the considerable superiority of nozzle elements according to the invention for use in an apparatus for extruding molten metal under difficult environmental conditions.

- 10 -

509817/0284

- ίο -

Example I.

An extrusion apparatus of the type shown in the figure was equipped with a nozzle insert disc which has a composition of polycrystalline tharoxide and 0.125 percent by weight Had calcium oxide as a compaction aid. The capillary nozzle inlet was conical with an apex angle from about 30.

To find out the operating characteristics of the above described nozzle structure, a series of tests was carried out under difficult environmental conditions resulted from the manufacture of fine diameter wire from a highly corrosive steel-silicon alloy batch. Additionally to the steel and 1 to 2 percent by weight silicon, the batch used still contained from about 0.25 to 0.75 Weight percent manganese.

To initiate the experimental procedure, a solid block of the steel alloy was first placed in the crucible of the device before heating was initiated. The crucible of the apparatus was then heated to a temperature in the range of about 1510 to 155o C ^0. At this point, a second steel alloy ingot was slowly fed into the heated crucible through a Q-ring seal in the head

5098 17/0284

placed in the pressure chamber (i.e., the block melted at the bottom and the drops were directed into the crucible).

After the crucible was filled with the molten metal charge ~, the chamber was pressurized to about 2.4 kg / cm. This resulted in a pressure gradient across the Thorerde nozzle insert through which the steel alloy melted the capillary nozzle opening was pressed through. In ^ which this pressure difference, as well as a continuous replenishment the batch was maintained by dropping molten metal into the crucible from the rod supplied Device in operation for 91 hours. This provides an exceptionally long spray life without it being possible to detect nozzle errors under such difficult conditions.

After the completion of the run, the device was cooled down and the thoroxide nozzle insert was used for microscopic examination of its macrostructure and for Examination of the extent of dimensional changes in the nozzle capillary taken out. No cracks or other evidence structural defects due to mechanical stresses were found. It was also found that the passage

- 12 -

509817/0284

2U8434

The diameter of the nozzle capillaries is only 0.0178 mm over this long spinning time increased under extreme environmental conditions. This showed an exceptional resilience against the highly corrosive effects of steel alloy melts, as well as the resistance to erosion resulting from the flow of these materials.

Example II

A number of different torrent nozzle inserts were made in the same apparatus and manner as in Example I. tested. The compositions of these inserts for the trial runs were: (1) pure thoroxide and (2) a composition thoraxide and 0.25 weight percent calcium oxide; and (3) a composition of thoraxide and 0.50 weight percent Calcium oxide. The densities of the test nozzle disks ranged between 9.90 and 9.97 g / cm. The diameter the nozzle capillaries were 0.25 mm in all cases.

A steel alloy melt charge as in Example I was prepared under the conditions given in Example I by the Nozzles pressed for periods ranging between 50 and 70 hours. Measurements were made following the test runs the extent of the change in diameter of the nozzle capillaries

- 13 -

509817/0284

carried out. It was found that the increases in Diameter limited to the range of 0.0127 to 0.0762 mm uaren. On microscopic examination there was no indication of structural defects as a result of mechanical stresses established.

Example III

The purpose of this example is to provide test results obtained with a known nozzle insert to compare the high-density gate earth inserts according to the invention according to Examples I and II with it «

A nozzle insert made of high-density beryllium oxide (BeO) was fitted into the crucible plate of the same extrusion apparatus, which was used in Examples I and II «, A melt charge of a steel alloy with a composition as described in the previous examples, then through the nozzle opening over a period of time pressed for 3 hours under extrusion conditions corresponding to those described in Examples I and II are. Following the test run, the changes in diameter of the nozzle capillaries were measured. It was found that the diameter of the original

509817/0284 " ¹⁴ "

borrowed 0.152 mm to 0.279 mm enlarged uar. This matches with a corrosion rate of the nozzle of 0.0381 mm per operating hour compared to a rate of 0.000254 mm to 0.00254 mm per hour for the high-density Thorerded nozzles, which under the same conditions according to Examples I and II have been tested. Thus it can be seen that between the nozzle structures according to the invention and those of high density Beryllium oxide a difference of 15 to 150 times that Corrosion rate is present.

To the relative chemical compatibility of high density'Thorerde with highly corrosive steel alloy melt compared to a large number of other refractory ceramic materials a series of bench tests was carried out. The method used was incision a small slot of known dimensions in the side of a disc of the test material. The disc became then immersed in a heated bath of molten steel alloy. The bath temperatures were between 1500 and 1600 C. After 6 to 100 hours of contact of the disks with the hot melt steel composition, the disks were removed and the dimensional change of the slot is recorded. The extent to which the ceramic was corroded was indicated by an increase in the slot dimensions.

- 15 -

509817/0284

In addition to the high-density thora, samples of high-density ceramics of the following compositions were exposed to the test conditions outlined above: Al2O3 (single crystal and polycrystalline); BeO; MgO; ZrO ₂ ; 2Al ₂ O ₃ . SiQ ₂ ; ZrO ₂ . SiO ₂ ; Y ₂ O ₃ ; CeS; MoSi ₂ and BN.

The test results demonstrated that the corrosion resistance for earthenware ceramics with densities in the range of 9.5 to 10.0 g / cm ^{3 was} far superior to any other refractory material tested. This is particularly evident when molten steel containing silicon and manganese as alloy additives were used as the corrosive medium. Even single crystal materials such as sapphire (Al ₂ O ₃ ) were seriously attacked by these corrosive melts. The slot widths of the slot cut in the Torch earth disk test samples showed dimensional changes of less than 0.0254 mm under all test conditions and times. All other refractory materials showed dimensional changes in the slots ranging from 0.0508 mm after 6 hours to complete dissolution of the disc material in less than 6 hours.

- Expectations -

509817/0284 - 16 -

Claims (2)

Expectations : 1. Abrasion-resistant nozzle for extruding a melt of metal and metal alloys under pressure and at temperatures above 1500 C, characterized by a composition of polycrystalline thoroxide with a density of 9.5 to 10, Q g / cm, a purity of at least 99.5 % thoroxide and due to dimensional changes of less than 0.025 mm after 100 hours in contact with the molten metal at 1500 C. 2. Against wear-resistant nozzle according to claim 1, characterized by a share of big to 0.5 percent a sintering agent. 5098 17/0284