US3921700A

US3921700A - Composite metal article containing additive agents and method of adding same to molten metal

Info

Publication number: US3921700A
Application number: US488755A
Authority: US
Inventors: Sr John G Frantzreb; John R Nieman
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1974-07-15
Filing date: 1974-07-15
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25
Also published as: CA1046285A; FR2278772A1; GB1504979A; FR2278772B1; JPS5132413A; IT1040888B; DE2531573C2; SE7508035L; DE2531573A1

Abstract

A composite wire-like structure for adding relatively volatile metallic agents such as magnesium to molten ferrous metal comprising an inner core of said metallic agent, an outer sheath of ferrous metal, and an insulating material disposed between said sheath and said core in surrounding relation to the core. A method is also provided for adding said agent to molten ferrous metal comprising the steps of continuously feeding the composite wire-like structure containing said agent at a controlled rate sufficient to provide a desired amount of said agent in the molten metal.

Description

' United States Patent Frantzreb, Sr. et al.

[ 1 Nov. 25, 1975 COMPOSITE METAL ARTICLE CONTAINING ADDITIVE AGENTS AND METHOD OF ADDING SAME TO MOLTEN METAL Inventors: John G. Frantzreb, Sr., Peoria; John R. Nieman, Pekin, both of I11.

Assignee: Caterpillar Tractor (30., Peoria, 111.

Filed: July 15, 1974 Appl. No.: 488,755

US. Cl 164/57; 29/1916; 75/130 B Int. Cl. B221) 27/20 Field of Search 164/55, 56, 57, 270;

75/130 B, 130 R, l29',29/l91.2, 191.6

References Cited UNITED STATES PATENTS 6/l956 Went et a1. 29/1916 X 2/1959 75/130 B UX 6/1961 l-lurum 75/130 B UX 10/1962 Chisholm et a1. 75/130 B UX 10/1973 Ohkubo et a1. 75/129 X FOREIGN PATENTS OR APPLICATIONS 1.912.134 9/1970 Germany 75/130 B 374,602 6/1962 Japan 17,620 9/1972 Japan 164/57 Primary Examiner-Robert D. Baldwin Assistant Examiner-John E. Roethel Attorney, Agent, or FirmPhillips, Moore, Weissenberger Lempio 8L Strabala [57] ABSTRACT A composite wire-like structure for adding relatively volatile metallic agents such as magnesium to molten ferrous metal comprising an inner core of said metallic agent, an outer sheath of ferrous metal, and an insulating material disposed between said sheath and said core in surrounding relation to the core. A method is also provided for adding said agent to molten ferrous metal comprising the steps of continuously feeding the composite wire-like structure containing said agent at a controlled rate sufficient to provide a desired amount of said agent in the molten metal.

12 Claims, 2 Drawing Figures US. Patent Nov. 25, 1975 COMPOSITE METAL ARTICLE CONTAINING ADDITIVE AGENTS AND METHOD OF ADDING SAME TO MOLTEN METAL BACKGROUND OF THE INVENTION The present invention relates to a composite metal article containing additive agents and method of adding same to molten metal. More particularly, the invention relates to a composite metal article for adding relatively volatile metallic agents to molten ferrous material as it is being cast.

The addition of alloying and treating agents into molten metal, such as steel, is well known in the art. The addition of such agents in wire-like form is also known and has been described in U.S. Pat, No. 3,634,075 and in the Oct. 28, 1971 issue of Iron Age. In addition, the use of wire-like agents for adding material to molten steel is also disclosed in theco-pending patent applications of John R. Nieman, et al, entitled Method and Apparatus for the Introduction of Additives Into a Casting Mold," Ser. No. 488,758, of John R. Nieman entitled Improved Method and Apparatus for Introducing Additives Into a Casting Mold," Ser. No. 488,756, both filed concurrently herewith on July 15. 1974, and of Maurice L. Caudill, et al, entitled Method and Apparatus for Adding Treating Agents to Molten Metal," Ser. No. 487,934, filed vJuly [2, 1974, all owned by Assignee of the presentapplication. Thus,

7 the use of wire-like structures for adding alloying and treating agents to molten metal provides an advantageous means of providing a final desired casting under excellent controlled conditions.

However, certain problems have been encountered where the agent to be added is relatively volatile because of the tendency of the material to be discharged or released prematurely when fed into a ferrous melt. For example, where such treating agents are carried in a sheathed wire, materials such as magnesium melt at a temperature below the melting point of a ferrous melt, and thus become discharged or released before the wire is melted and absorbed into the molten bath.

Efforts have been made to provide a solution to the problem, and U.S. Pat. No. 3,056,190 discloses a method of combining magnesium withsilicon to form magnesium silicide and carry the same within a ferrous metal envelope. However, even in this form, the magnesium tends to become discharged or released prematurely. In U.S. Pat. No. 3,741,753, amethod is taught for adding manganese to molten steel under vacuum conditions where the manganese is relatively volatile and presents a problem. In accordance with that patent, the manganese is first alloyed so as to reduce its volatility before being used. Thus, it is seen that both of these patents require an additional alloying step in preparing the material for use as an additive to molten metal.

SUMMARY OF THE INVENTION In accordance with the invention, a composite wirelike structure is provided for adding relatively volatile metallic agents to molten metal prepared for casting. The structure comprises an inner core of relatively vol atile metallic agents, an outer sheath of relatively nonvolatile metal, and an insulating material disposed be tween said sheath and said core in surrounding relation to the core.

As used herein, the tcrm relatively volatile" is intended to embrace substances that exert a substantial vapor pressure at the temperature of the molten metal to which the agent is to be added. The outer sheath will generally be of a metal similar in melting point to the molten metal being treated, and advantageously will be of a similar composition. In other words. the outer sheath will generally not materially affect the composition of the molten metal, but it will be understood that non-volatile alloying agents or other additives could be included in the outer sheath, if desired. The insulating material may be any material capable of retaining the core material below its boiling point or the point at which the vapor pressure becomes excessive prior to the melting of the sheath material. Preferably, the core material is also kept below its melting point. In this way, delivery of the core material will occur simultaneously with the melting of the sheath material.

The insulating material should also be a substance which is compatible with the molten melt desired, i.e., it should not add any unwanted materials. Thus, a preferred form of insulating material is a particulate substance of either an agent desired to be added, or of a composition substantially similar to the melt. or a combination of both.

In its method form, the invention provides a method of adding an agent to molten metal comprising the steps of continuously feeding a composite wire-like structure containing said agent at a controlled rate sufficient to provide a desired amount of the agent in the melt, said composite wire-like structure comprising an inner core of relatively volatile metal agent, an outer sheath of non-volatile metal, and an insulating material disposed between said sheath and said core. The invention has been particularly valuable in adding alloying or treating agents to molten ferrous metal, where the temperature of the melt will be of the order of around 2600F. or higher. and where a number of the desired additives are volatile.

For example, it is well known to add magnesium to cast iron or steel in order to provide nodular treatment thereof. However, magnesium has a boiling point of about 2025fF. Accordingly, additions of magnesium have been somewhat troublesome in the area now under discussion; Similarly, zinc has a rather low boiling point and where it is desired to add zinc to a molten metal, volatility'problems are likely to occur. In addition,- certain casting processes are carried out in a vacuum, and in such a case metals such as aluminum and manganese are also sufficiently volatile to cause problems. Thus, these and any other materials, which may be sufficiently volatile to cause a problem, may be advantageously added by using the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred form of the invention is illustrated in the accompanying drawings forming a part of this description, in which:

FIG. I is an isometric view partly in section o'fa composite wire-like structure fabricated in accordance with the invention; and

FIG. 2 is a sectional view of the structure shown in FIG. 1 taken substantially in the plane of line 2-2 of FIG. 1.

While only the preferred form of the invention is shown. it should be understood that various changes or modifications may be made within the scope of the claims attached hereto without departing from the spirit of the invention.

DETAILED DESCRIPTION OF THE PREFERRED 4 due to its high specific heat (0.11 btu/lb. degree F) and relatively slow thermal conductivity.

The following parameters setting forth the composition more clearly is given in Table I below:

Table I VOLUME/100 Ft. t /(l DENSITY WEIGHT ('4) Sheath 408.89 cc (18.8) X 7.82 3,197.5 gms. (33.3) Fe Powder 1.521.67 cc (70.1) X 3.92 5,964.9 gms. (62.2) Mg. Core 241.32 cc (11.1) X 1.80 434.4 gms. (4.5)

Total 2.1 7 l .88 cc 100.0) X 4.42 9596.8 gms. 100.0)

EMBODIMENT EXAMPLE 2 Referring now more particularly to the drawings, there is shown in FIG. 1 a composite wire-like structure 11 comprising an inner core 12 of relatively volatile agent, an outer sheath 13 of relatively non-volatile metal, and an insulating material 14 disposed between said sheath and said core in surrounding relation to the core.

Preferably. the structure is used for adding an agent to molten ferrous metal comprising the step of continuously feeding the wire-like structure at a controlled rate sufficient to provide a desired amount of agent in the molten ferrous metal. In the preferred form, the tubular sheath 13 is also generally composed of ferrous metal In this example, the protective blanket consists of a blend of iron powder and graphite, while the sheath is steel and the core is magnesium. It is well known that carbon suppresses the reaction of magnesium vapor, and is therefore included to control the degree of the reaction. It will also be appreciated that the addition of carbon can be tolerated in certain desired ferrous alloys by starting with a melt capable of utilizing such addition. Moreover, the amount of carbon added by this example is rather small. The physical parameters given in Table II below have been established for the article of this example:

Table 11 VOLUME/100 Ft. (7)) DENSITY WEIGHT (V1) Sheath 408.89 cc (18.8) X 7.82 3,197.5 gms. (37.9) Fc Powder 1,141.25 cc (52.5) X 3.92 4,473.7 gms. (53.0) Graphite (C) 380.42 cc (17.6) X 0.89 338.6 gms. (4.0) Mg. Core 241.32 cc (11.1) X 1.80 434.4 gms. (5.1)

Total 2.171.88 cc (100.0) X 3.89 8,444.2 gms. (100.0)

with or without an allo in a em, and the insulatin y g g g EXAMPLE 3 material 14 is preferably composed of particulate ferrous material such as iron or steel.

The wire-like treating agent is used to add alloying agents for treating materials or both by any of the available processes for adding wire-like treating agents to molten metal. For a more detailed description of such process, the citations given above may be consulted.

In order to better illustrate the invention, the following examples of composite articles are given, and it should be understood that these examples are given for illustrative purposes and are not to be construed as lim- Table III VOLUME/100 Ft. (7:) DENSITY WEIGHT ("/1) Sheath 408.89 cc (18.8) X 7.82 3,197.5 gms. (65.5) Mag-Coke Powder 1,521.67 cc (70.1) X 0.82 1.2478 gms. (25.6) Mg Core 241.32 cc (11.1) X 1.80 434.4 gms. (8.9)

Total 2.171.88 cc (100.0) X 2.25 4,879.7 gms. (100.0)

The thermal protection afforded by the blanket 14 is iting the invention. In the examples. the wire core 12 determined by the thermal conductivity and particle has a diameter of 0.125 inch and the tubular sheath 13 has a nominal diameter of 0.375 inch and a wall thickness of 0.15 inch.

EXAMPLE 1 size of the blanket material.

Thus, it is seen that the preferred insulating material is a particulate form of one or more of the substances to be added and has a melting or subliming point (temperature) at least about equal to the melting point of the outer metallic sheath. Thus, as illustrated in the preceding examples, iron has a melting point substantially equal to the melting point of the steel sheath while graphite and coke sublime well above the melting point of the sheath. These particles may vary from small powder form to large granular form. Since corespondingly smaller particles present a greater number of nonhomogeneous heat transfer surfaces. and therefore reduced thermal conductivity, the protection provided by any of the above blanket compositions may be varied by an appropriate change in the size of the particles incorporated in the blanket. lt has been determined that a wire having the aforementioned dimensions in a composition as described in Example 1 will melt in a 2500F bath at a rate of approximately 6 to 7 inches per second. For these conditions, the iron powder protective blanket of Example 1 comprising particles between 40 and 140 mesh provide adequate thermal protection to prevent premature melting and vaporization of the magnesiusm core. In the event that it is found desirable to increase the thermal protection provided by the 40 to 140 mesh particles, smaller particles could be used. In this way, a slower feed rate could be used.

For large castings that may require wire feed rates above 6 to 7 inch per second melting rate provided the instant wire, two or more wires may be fed simultaneously into the molten metal bath. Alternatively, the wire may be heated to increase the melting rate. In general, any suitable heating method may be used such as passing the wire through a heated zone or utilizing resistance heating of the sheath.

lf resistance heating of the sheath is desired, the blanket and/or the core should be electrically isolated to prevent resistant heating of these components. For this purpose, electrically non-conductive materials may be selected for the blanket or electrically conductive materials may be processed such as by coating to render them non-conductive. Also a non-conductive coating could be provided on the inner surface of the sheath or on the outer surface of the core.

From the above examples, it is seen that the wire-like structure made according to the invention is suitable for use in any of the methods cited above, and may be utilized either with or without additional heating. it is also seen that the composite wire-like structure is capable of protecting the inner core of volatile material from premature release in a reliable manner.

A further benefit is provided by the present invention by virtue of the fact that as the wire is melted, the granular or particulate blanket material is absorbed into the molten stream. This absorbtion reduces the temperature of the stream at a small zone contiguous to the end of the wire where the inner core is being delivered. This reduced temperature zone permits cores such as magnesium to be absorbed into the stream in a less volatile manner since the severity of the magnesium reaction is temperature dependent.

In addition, the use of an outer core of a material having a melting point similar to that of the molten metal being treated causes the delivery and reactions such as the magnesium reaction to occur while below the surface of the molten material. This further reduces the severity of the reaction.

From the foregoing description, it is seen that an improved composite metal article containing additive agents are provided for use in a method of adding alloying or treating agents to molten metal. It is also seen that an article is provided which is particularly advantageous for adding volatile additives such as magnesium to molten ferrous metal and the like.

What is claimed is:

l. A method of adding a relatively volatile metallic agent to molten ferrous metal comprising the steps of continuously feeding a composite wire-like structure containing said agent at a controlled rate sufficient to provide a desired amount of said agent within the molten ferrous metal, said composite wire-like structure comprising an inner core containing said relatively volatile metallic agent, an outer sheath of ferrous metal substantially concentrically disposed to said core, and a particulate insulating material having a melting or subliming point generally at least about equal to the melting point of said outer sheath disposed between said core and said sheath, said insulating material providing a heat barrier sufficient to protect said inner core from delivery prior to the melting of said outer sheath of ferrous metal.

2. A method of adding an agent to ferrous metal as defined in claim 1, in which the composite wire-like structure is preheated prior to feeding same into the molten ferrous metal.

3. A method as in claim 1, wherein said relatively volatile metallic agent is delivered below the surface of the molten ferrous metal.

4. A composite wire-like structure for adding relatively volatile metallic agents to a molten metal, comprising an inner core of relatively volatile metallic agent, an outer sheath of non-volatile metal having a melting capability at the temperature of said molten metal, and a particulate insulating material with a melting or subliming point generally at least about equal to the melting point of said outer sheath disposed between said sheath and said core in surrounding relation to said core, said insulating material providing a heat barrier sufficient to protect said core from delivery prior to the melting of said outer sheath.

5. A composite wire-like structure as defined in claim 4, in which the insulating material also comprises additional additive agents.

6. A composite wire-like structure as defined in claim 4, in which the sheath is of a metal having a chemistry substantially similar to the chemistry of the molten metal.

7. A composite wire-like structure for adding relatively volatile metallic agents to a molten ferrous metal, comprising an inner core of relatively volatile metallic material, an outer sheath of ferrous metal having a melting capability at the temperature of said molten ferrous metal to which the structure is to be added substantially concentrically disposed to said core, and a particulate insulating material having a melting or subliming point generally at least about equal to the melting point of said outer sheath disposed between said core and said sheath providing a heat barrier sufficient to protect said core from delivery prior to the melting of said outer sheath.

8. A composite wire-like structure as defined in claim 7, in which the inner core comprises a nodularizing agent.

9. A composite wire-like structure as defined in claim 8, in which the nodularizing agent is magnesium.

10. A composite wire-like structure as defined in claim 7, in which the particulate material is iron.

11. A composite wire-like structure as defined in claim 7, in which the particulate insulating material is an alloy of iron. 7

12. A composite wire-like structure as defined in claim 7, wherein the particulate material is magnesium coke.

Claims

1. A METHOD OF ADDING A RELATIVELY VOLATILE METALLIC AGENT TO MOLTEN FERROUS METAL COMPRISING THE STEPS OF CONTINUOUSLY FEEDING A COMPOSITE WIRE-LIKE STRUCTURE CONTAINING SAID AGENT AT A CONTROLLED RATE SUFFICIENT TO PROVIDE A DESIRED AMOUNT OF SAID AGENT WITHIN THE MOLTEN FERROUS METAL, SAID COMPOSITE WIRE-LIKE STRUCTURE COMPRISING AN INNER CORE CONTAINING SAID RELATIVELY VOLATILE METALLIC AGENT, AN OUTER SHEATH OF FERROUS METAL SUBSTANTIALLY CONCENTRICALLY DISPOSED TO SAID CORE, AND A PARTICULATE INSULATING MATERIAL HAVING A MELTING OR SUBLIMING POINT GENERALLY AT LEAST ABOUT EQUAL TO THE MELTING POINT OF SAID OUTER SHEATH DISPOSED BETWEEN SAID CORE AND SAID SHEATH, SAID INSULATING MATERIAL PROVIDING A HEAT BARRIER SUFFICIENT TO PROTECT SAID INNER CORE FROM DELIVERY PRIOR TO THE MELTING OF SAID OUTER SHEATH OF FERROUS METAL.

11. A composite wire-like structure as defined in claim 7, in which the particulate insulating material is an alloy of iron.