Method of Making a Filled Tubular Article and Article Made Thereby

Technical Field The present invention relates to a method of making a filled tubular article for controlled inser¬ tion into a molten metal as it is being cast, and to the article made thereby.

^" Background Art The addition of alloying and treating agents into a molten metal such as iron, by insertion of an elongated rod-like article into a casting mold's down- sprue is becoming more well known in the art. More sophisticated methods and apparatuses have recently been developed to controllably insert filled tubular- articles into the casting molds during metal pouring at exactly the rate and point required to obtain the desired castings. These elongated articles usually have a core of powdered ingredients or particulate material carried in a protecting tube. As far as is known, such articles are manufactured by depositing the powdered ingredients onto a strip of metal that may be partly formed into a trough. The strip is thereafter formed into a tube by conventional methods with the edges either abutting or overlapping. Unfor¬ tunately, a major problem is experienced at this point because the ingredients of the core are not sufficiently densified within the tube which results in the powder tending to separate and move within the tube. Conse- quently, it has been fo nd necessary to pass the tube axially through a forming die which reduces its exter¬ nal diameter and compacts the powdered ingredients. Even with this extra step it is a frequent practice to

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crimp or pinch the ends of the tubes to keep the par- ticulate material from falling out. Such crimping practice is also used for retaining powder in an alternate construction embodying short stiff tubes which are filled with powder after the tubes are made. Not only are the aforementioned manufactur¬ ing procedures for making the filled tubes complica¬ ted, but also it has been found that the thickness of the tubes is often excessive or irregular, and therefore the volumetric ratio or proportion of the core material to the entire article is dispropor¬ tionately low. For example, if attempts are. made to make the radial thickness of the metal tubes below approximately 0.25 mm with current technology then the edges of the tubes generally fail to remain in abutment and this allows powder to fall out. On the other hand, if the tube edges are overlapped, when the rod is inserted into a molten bath the melting rate around its periphery is unequal. Because of the relatively poor dissolution or melting rate of the relatively thick prior art tubes, the rate of feeding them into the molten bath has necessarily been reduced in order to prevent the unmelted and excessively stiff remaining portions of the tubes from penetrating the sides of the casting mold's downsprue.

In view of the above, it would be advan¬ tageous to replace the relatively thick and non- uniform prior art tubes with a thinner casing, and yet retain a relatively high degree of uniformly dense fill material within the core.

Disclosure of Invention.

The present invention is directed to over¬ coming one or more of the problems as set forth above.

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In accordance with one aspect of the pre¬ sent invention, this is accomplished by extruding a treating material to form an elongated core element and by helically wrapping the extruded core element in a protective casing to form a filled tubular article. Advantageously, the core element is of uniformly consolidated density and the casing is thin so that the article is flexible and the casing will experience ^' a relatively rapid rate of dissolu- tion in the molten bath. Furthermore, the instant invention will provide increased core volume per - unit length.

In accordance with another aspect of the invention the filled tubular article for altering molten metal includes an elongated core element having a particulate mixture of a treating agent and a binding agent consolidated in a range of about 85 to 95% theoretical density-, the treating agent comprising about 90 wt.% or more of the core element and the binding agent about 1 to nor more than 10 wt.% of the core element, and a casing helic¬ ally wrapped about the core element and substantially covering the entire exterior surface thereof.

Brief Description of the Drawings FIG. 1 is a diagrammatic side elevational view of a manufacturing facility illustrative of the method of making the filled tubular article in accor¬ dance with one embodiment of the present invention. FIG. 2 is a diagrammatic and enlarged fragmentary view of one embodiment of the filled tubular article of the present invention made by the manufacturing facility of FIG..1

FIG. 3 is a view similar- to FIG. 2, ^" only showing a second embodiment filled tubular article with an overlapped form of exterior casing.

FIG. 4 is an enlarged and fragmentary dia¬ grammatic side elevational view of a third embodi¬ ment filled tubular article showing two layers of exterior casing.

Best Mode For Carrying Out The Invention

Referring to FIG. 1, a manufacturing facil¬ ity 10 is shown for making an improved filled tubular article 12 in accordance with the present invention. In its simplest form, the manufacturing facility con- templates use of an extruding apparatus or press 14 - for making an elongated core element 16, and use of a rotatable wrapping device 18 for applying a helic¬ ally wrapped casing 20 encirclingly about the core element. The exemplary tubular article thus produced is shown in FIG. 2.

More particularly, the extruding apparatus 14 preferably includes a feed hopper 22 in which a substantially homogenous mixture of a treating material 24 has been placed. Through gravity, the treating material travels downwardly to be received within the internal, mechanism of the extruding ap¬ paratus or press. As is well known, however, such presses are constructed so as to extrude the treating material 24 under considerable pressure, and often while simultaneously heating the treating material, through an outlet die 26 having a horizontal axis 27 and a suitable orifice of preselected dimensions con¬ centrically disposed on the axis, not shown. Prefer¬ ably, the core element 16 extends axially from the orifice of the die in the form of a continuously elongating cylindrical rod.

It should be-appreciated that. the core element 16 is normally in a "green" state after passing axially outwardly of the die, or to the right when viewing the drawing, and is generally capable

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of experiencing only a relatively limited amount of flexing without cracking. It is contemplated that the extruded core element includes a relatively com¬ pacted mixture of a particulate treating agent or plurality of inoculating elements 28 and a suitable binding or bonding agent 30 as generally indicated in FIG. 2, and may include other additives as well. The term "treating agent" as used herein includes the element or elements which actually alter the molten metal so that upon cooling and hardening thereof into an article, the articles metallurgical " structure has the desired modified physical proper¬ ties. The type of treating agent 28 utilized is dependent upon the base composition of the molten metal to be treated and upon the desired metallur¬ gical characteristics of the article. For example, for treating iron, the treating agent consists essentially of a plurality of ferrosilicon based particles capable of passing through a fine mesh sieve such as between Standard Test Sieve Nos. 30 to 140 (0.6 mm - 0.1 mm nominal diameter of the openings) . Three examples of such treating agents, for iron are set forth below in percentage by weight: Example 1 Example 2 Example 3 Si 74-79% Si 60-65% Si 44-48% Al 1.00-1.5% Mn 5-7% Mg 8-10%

Ca 0.50-1.00% Zn 5-7% Fe balance Fe balance Ba 2-3%

Ca 1.5-2.5% Al 0.75-1.25%

Fe balance Example 1 above is identified as "Grade 75% ferrosilicon." ,- Example -2- is identified as "SMZ- - Alloy" and Example 3 is identified as "9% magnesium ferrosilicon", all of which are manufactured by Union Carbide Corporation, Ferro-Alloys Division, Buffalo, New York. ^* * ^■

As noted in the above examples, the treating agents 28 normally contain small portions of one or more additional elements in addition to the ferrosilicon constituent such as aluminum, calcium, manganese, zir- conium, barium, magnesium, strontium, cerium, and the rare earth elements.

The term "binding agent" as used herein in¬ cludes the resinous or cement-like material that is used to hold the particles of the treating agent together. Preferably, the binding agent 30 is selected from the group consisting of beeswax, sodium silicate, resin, " casein, and organiz plastic material including poly- urethane. The amount of binding agent is preferably limited to a preselected range of from about 1 to not more than 10% of the weight of the core element 16. Enough binding agent is needed to allow proper ex¬ trusion of the core element and to maintain its shape. Too much binding agent, for example above 10%, will form a slug or will alternately lead to other pro- blems such as producing an excessive amount of flames and- bubbling reaction as the filled tubular article 12 is inserted into molten iron.

In addition to the treating agent 28 and the binding agent 30, it is contemplated that a lubricating or slipping agent 31 may be advantageous in forming the core element 16. Particularly, a relatively low pro¬ portion of a lubricating agent such as graphite or zinc stearate may be helpful during the extrusion of the mixture 24 through the die 26. However, it should be understood that the treating agent preferably makes up about 90% or more of the total weight of the treating material making up the core element, the binding agent makes up about 1 to not /more than 10% of the weight . of the core element, and the lubricating agent makes up about 0.3 to 2% of the weight of the core element.

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It is contemplated that the core element 16 is compacted to a relatively dense state by the ex¬ trusion press 14, and experiences minimal swelling after passing axially outwardly of the die 26. For example, the density of the consolidated core element is preferably in a preselected range of about 85% to 95% theoretical density, which is substantially equi¬ valent to having only about 5% to 15% volume in voids. Despite the substantial consolidation of the extruded core element ^* 16, it is to be appreciated that it is advantageous to continue its rightward movement ' along the axis 27 with but minor angular deviation to avoid abrupt flexing of the core element prior to the encasement thereof. Consequently, one or more sup- port rollers 32 and one or more stationary guiding members 33 are preferably utilized for this purpose. Preferably also, a combined traction and support means . 34 is located downstream of the extrusion press 14 to bias or urge the core element to the right when viewing the drawing. A pair of powered endless belts 36 and 38 disposed immediately above and below the core ele¬ ment may be used for this purpose.

Referring now to the wrapping device 18, it includes a support stand 40 and a rotary mechanism 42 which is controllably revolved about a central hori¬ zontal axis 44. Preferably, the axis 44 is in substan¬ tial alignment with the axis 27. At least one cylin¬ drical reel 46 is located on a frame member 48 of the mechanism, which reel is generally revolvable in use in a counterclockwise direction when viewing the drawing about an axis 50. A ribbon-like strip 52 extends substantially axially from its stored position on the reel and to a tension monitoring unit 54; - From there the strip extends through a guide 56 and obliquely onto the elongating core element 16.

Preferably, the ribbon-like strip 52 is rela¬ tively thin; for example, within a range of about 0.025 mm to 0.15 mm and preferably about 0.1 mm thick, and is helically wrapped about the core element 16 with its opposite side edges 58 and 60 disposed in aligned axial abutment with the facing side edges of the ad¬ jacent loop as shown in FIG. 2. It is contemplated that the strip is preferably a metal foil selected from the group consisting of a ferrous metal such as steel, aluminum, titanium, copper, and alloys thereof. However, it is to be appreciated that a strip of organic material such as of plastic or fibrous paper composition may be substituted for such metal foil without departing from the spirit of the present invention. After the strip 52 is helically wound about the core element 16, the filled tubular article 12 is urged rightwardly by a powerably rotated cylindrical take-up reel 62 and an associated drive motor 64. The improved filled tubular article produced in this manner and wound on the reel, which is releasable from the motor and a support stand 66, is subsequently control- lably inserted into molten metal for altering the metallurgical structure of the melt upon cooling and hardening thereof in a .casting mold. Such a procedure is disclosed, for example, in more detail in U.S. Patent No. 3,991,808 issued to John R. Nieman, et al on November 16, 1976.

Referring to FIG. 3, an alternate embodiment is shown wherein the various elements of the filled tubular article 12 are the same and, accordingly, similar reference numerals have been applied thereto. However, in the alternate _* embodiment, the ribbon-like strip 52 has been wound about the core element 16 by the manufacturing facility 10 in such a way that the edges 58 and 60 axially overlap and provide more

positive assurance of retention of any inadvertently loose particles of the core element 16. While this provides the disadvantage of a double thickness of the adjacent loops of the strip at the point of overlap, it is to be recognized that such double thickness is still about 30% or more less than the total thickness of the thinnest practical prior art casing.

A more sophisticated embodiment is shown in FIG. 4, wherein the core element 16 and casing 20 are substantially as described above with reference to FIG. 2. However, in this example a second layer or -casing 68 has been applied over the casing 20. The second casing includes a second, continuous ribbon¬ like strip 70 which is advantageously oriented at a different angle of orientation than the first strip 52 relative to the core element as indicated generally on the drawing by the reference letters A and B. Pre¬ ferably, the first and second strips are sequentially and helically wound about the core element from opposite directions as is clearly shown. The dual layer casing is stronger and has a reduced tendency to unwind. Specifically, a single helically wound strip has a ten¬ dency to exhibit a resistance to coiling and a tendency to open up between adjacent loops if forcibly coiled incorrectly. Another wrapping device 18, not shown, would be required to provide the second layer of casing in any continuous extension of the manufacturing facility 10. Such second wrapping device would be located axially intermediate the first wrapping device and the take-up reel 62.

Industrial Applicability

In view, .of ther .forsg.oing, it_ is readily appar¬ ent that the method of the present invention provides an improved filled tubular article useful for controlled

insertion into a molten metal. Rather than simply filling a tube with loose particulate material as has been done in the past, the manufacturing facility 10 contemplates the following sequential procedure: Step (a) mixing a particulate treating agent and a binding agent to form a treating material.

Step (b) feeding the treating material to an extruding apparatus;

Step (c) extruding the treating material, optionally in the presence of heat, through a die to form an elongated core element;

Step (d) helically wrapping the extruding core element in a protective casing; and

Step (e) rolling up the encased core onto a take-up reel.

Moreover, the above described procedure may be extended to helically wrapping the core element in various ways, including helically wrapping a second layer onto a first layer by an additional wrapping step. Still further, the instant manufacturing facility is easily adapted to overlappingly winding one ribbon-like strip or a plurality of such strips about the core element.

Other aspects, objects and advantages will become apparent from a study of the specification, drawings and appended claims.

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