Patent Grant
10927425
Cored wire has found wide application in the treating of molten ferrous metals. In one application, cored wire is used to introduce a core material (e.g., calcium) into the molten ferrous metal after the molten ferrous metal has been tapped from a furnace, in order to reduce unwanted elements (e.g., sulfur and oxygen) in the bath of molten ferrous metal. A detailed discussion of this overall process is provided in U.S. Pat. No. 4,481,032, which is expressly incorporated herein by reference. Further methods of treating molten metals using a clad reactive cored metal composite in the form of an elongated wire are disclosed in U.S. Pat. Nos. 4,512,800; 4,705,261; 4,094,666; 4,698,095; 4,035,892; 4,097,268; and 4,671,820, all expressly incorporated in their respective entirety herein.
Cored wire has found commercial use in the steel, aluminum, copper and foundry industries. In general, cored wire is a continuous metal tube filled with a solid or granule element or alloy used as a core material to control the chemistry of the molten metal to which it is added. The manufacture of cored wire generally involves the use of roll forming equipment, which takes a flat steel strip, bends it in a general U-shape, adds a core material (e.g., calcium), and then folds and crimps the radial edges of the steel strip over on themselves (or welds the radial edges together) and coils the product into a spool for later use in connection with treating molten metals.
The encapsulated core material, calcium metal, has higher recovered yield when the final encapsulated core material is in a solid rod form rather than particulate/granular form. U.S. Pat. No. 6,280,497 to Mineral Technologies, which is expressly incorporated herein by reference, shows a two-step process for producing a calcium rod product where the rod is first produced by extrusion and afterward, in a separate manufacturing operation, encased in a steel jacket. Benefits directly attributable to calcium treatment of steel include greater fluidity, simplified continuous casting and improved cleanliness (incl. reduced nozzle blockage), machinability, ductility and impact strength in the final product.
However, calcium metal and other core materials may display a high affinity to oxygen, a low melting and/or vapor point, a high vapor pressure, a low solubility in the molten metal, low density compared to the molten metal, or a combination of these factors. As such, the calcium may sublime when the core material is exposed to the molten metal and then quickly react with dissolved oxygen in the steel. This sublimation of the calcium from solid directly to gas may cause splashing at the surface of the melt creating problems during refining, and may result in a lower recovered yield (i.e. the amount of core material remaining in the molten metal divided by the amount of core material injected into the molten metal). Calcium has such a high vapor pressure (its boiling point is several hundred degrees below steelmaking temperatures) and reactivity that special techniques have been devised to introduce and properly retain even a few parts per million in the melt.
Because calcium exists as a gas in molten steel, and because it is scarcely soluble in steel, any reaction between calcium and the oxygen and sulfur in the melt can only take place at the calcium vapor/liquid steel interface. However, this interface forms only temporarily as the calcium vapor quickly rises to the top of the melt. Therefore, lance and cored wire injection techniques have been developed to introduce the calcium as close the bottom of the melt as possible, to thereby increase the amount of time the calcium gas is in contact with the liquid steel.
According to one aspect, an elongated cored wire for treating molten steel includes a solid elongated rod including calcium metal, a particulate material, and an exterior metal jacket. A length of the rod extends along a length of the cored wire. The particulate material is continuously arranged along the length of the cored wire. The exterior metal jacket radially surrounding the rod and the particulate material along the length of the cored wire. When the cored wire is introduced into the molten steel, the particulate material undergoes thermal decomposition to release carbon dioxide, hydrocarbons, or combinations thereof.
According to another aspect, a method of making a cored wire for treating molten steel includes providing a metal strip defining a trench extending along a length of the metal strip. A providing a solid rod including calcium metal is arranged in the trench such that a length of the rod extends along the length of the metal strip. A particulate material is introduced into the trench such that the particulate material is continuous along the length of the metal strip. The rod and the particulate material are radially surrounded with the metal strip along the length of the metal strip. When the cored wire is introduced into the molten steel, the particulate material undergoes thermal decomposition to release carbon dioxide, hydrocarbons, or combinations thereof.
According to yet another aspect, a method of treating molten steel includes providing a cored wire including a solid rod including calcium metal and extending along a length of the cored wire, a particulate material arranged along the length of the cored wire, and an exterior metal jacket radially surrounding the rod and the particulate material along the length of the cored wire. The cored wire is introduced into the molten steel such that the particulate material undergoes thermal decomposition to release carbon dioxide, hydrocarbons, or combinations thereof as a shroud around a leading end of the rod to thereby allow the calcium at the leading end of the rod to melt.
Referring now to the drawings, which are for illustrating exemplary embodiments and not for purposes of limiting the same,
A length of the cored wire 10 extends perpendicular to the plane of the cross-section shown in
The jacket 16 defines the exterior surface of the cored wire 10, and is included to temporarily isolate the core material 12 from the molten metal. After the cored wire 10 is inserted into the molten metal, the jacket 16 will eventually melt or otherwise be consumed by the molten metal, to thereby expose the particulate material 14 and core material 12 to the molten metal. This temporary isolation of the core material 12 provided by the jacket 16, allows the core material 12 to be inserted deeper into the mass of the molten metal before being exposed to the molten metal.
The jacket 16 also isolates the core material 12 and particulate material 14 from the environment during transport and storage of the cored wire 10. The jacket 16 also acts as a package to contain the core material 12 and particulate material 14 and to keep the core material 12 and particulate material 14 together and in contact with one another. In this regard, the length of the cored wire 10 is defined by the length of the jacket 16.
The jacket 16 can be formed from a continuous sheet metal stock such as a continuous metal sheet or strip. The jacket may be made of any suitable metal(s) or alloy(s). In one embodiment, the jacket 16 is a steel jacket, such as formed from a low carbon 1006/1008 grade of steel, for example. The jacket 16 may have an outside diameter of about 5 mm to about 25 mm, and a thickness of the wall of the jacket 16 may range from 0.1-2 mm. In an exemplary embodiment, the jacket 16, and thus the cored wire 10, has an outside diameter of 5-15 mm, preferably 9-13 mm.
The exterior metal jacket 16 may be continuous along the length of the cored wire 10, and may be formed from a continuous strip of metal sheeting. The edges 18 of the jacket 16 may be joined together by a lock seam 20, which is made by overlapping and folding the edges 18 together as shown, a double lock seam, or may be welded together by a lap joint or a butt joint, or other type of welded joint. Since the edges 18 of the jacket 16 are joined together, the jacket 16 thus surrounds the core material 12 and the particulate material 14 in a radial direction. If desired, two longitudinal ends (in the length direction) of the cored wire 10 may be sealed such as by crimping, folding, welding, brazing, or otherwise. To encapsulate the core material 12 and the particulate material 14.
The core material 12 is included for refining (i.e. treating) the molten metal. The core material 12 may include any suitable material for treating the molten metal, including but not limited to pure metals of calcium, aluminum, nickel, or combinations thereof; and alloys of calcium-silicon alloy (CaSi), a ferro-titanium alloy (FeTi), a ferro-boron alloy (FeB), calcium-aluminum, magnesium-calcium, magnesium-aluminum, calcium-silicon, etc., or any combination thereof. These metals and alloys of the core material 12 may be substantially free of impurities, which means that the core material 12 contains less than 1% w/w impurities, such as less than 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2% w/w impurities, e.g. less than 0.1% w/w impurities. The core material 12 can be any material having a melt point below a temperature required to mechanically lock radial ends of the sheet metal stock after further roll forming (e.g., by welding, soldering, etc.).
The core material 12 may be a continuous and elongated solid structure, as opposed to being in particulate form. In an exemplary embodiment, the core material 12 is a solid core material 12 in the form of an elongated solid wire/rod. Along the length of the cored wire 10, the solid rod of core material 12 may be continuous (i.e. a single piece of core material 12 extending the length of the cored wire 10) or discontinuous (more than one piece of core material 12 abutted against each other and collectively extending the length of the cored wire 10). In an exemplary embodiment, the core material 12 is a single elongated piece of core material 12 that is continuous along the length of the cored wire 10. The rod of core material 12 may be formed by extrusion, drawing, casting, roll forming, or other processes to make a solid rod of core material 12. In an exemplary embodiment, the core material 12 may be an extruded rod, e.g. an extruded rod of calcium metal.
In an exemplary embodiment, the core material 12 includes or consists of calcium. Alternatively, the reactive component can be sulfur, magnesium, tin, antimony, lead, sodium, or any other material as desired for a particular application. When included in the core material 12, the calcium may be substantially free of impurities. The calcium is in the form of a solid rod that is solid and may be continuous along the length of the cored wire 10. Being in the form of a solid rod, only the outer surface of the calcium rod may be exposed the atmosphere and thus possibly subjecting the outer surface to oxidation. However, the inner mass of the calcium rod is not exposed to the atmosphere and thus may not oxidize. This characteristic can be beneficial as compared to calcium in particulate form being used as the core material 12, since calcium in particulate form has a greater surface area per mass than a solid rod. This provides an increased surface area per mass that can be exposed to the atmosphere, and possibly subjected to oxidation.
In an embodiment, the core material 12 (e.g., calcium) is present in the cored wire 10 at about 0.02 pounds per linear foot of the cored wire 10, up to about 0.10 pounds per linear foot of the cored wire 10. In a more specific embodiment, the reactive component is about 0.045 pounds per linear foot of the cored wire 10.
The particulate material 14 is included in the cored wire 10 for further isolating the core material 12 from the molten metal over and above the isolation provided by the jacket 16, and may be generally non-reactive or have a low reactivity with the molten metal such that the chemistry of the molten metal is not significantly changed by the particulate material 14.
While not being bound by theory, it is believed that the particulate material 14 isolates the core material 12 from the molten metal in a number of ways. First, the particulate material 14 may be arranged in the cored wire 10 so as to radially surround the core material 12 as depicted in
The particulate material 14 is included inside the jacket 16 in a continuous manner along the entire length of the cored wire 10. In other words, the particulate material 14 is included in the cored wire 10 so that there is a continuous line of particulate material 14 along the entire length of the cored wire 10. In this configuration, if the cored wire 10 were cut at any point along its length, the portion of the cored wire that is cut would necessarily include particulate material 14. This embodiment including a continuous line of particulate material 14 may be contrasted to a comparative cored wire having islands of particulate material 14 along its length, which islands would have gaps between them separating one from another. In this contrasting configuration, if the cored wire were cut at a point along its length, the cut portion may or may not include particulate material 14.
The particulate material 14 is also included in a substantially uniform amount along the length of the cored wire 10. That is, the amount of particulate material at any point along the length of the cored wire 10 is at or above a minimum predetermined threshold. In this configuration, if the cored wire 10 were cut at any point along its length, the portion of the cored wire that is cut would necessarily include at least a minimum amount of the particulate material 14 that is at or above the predetermined threshold.
The particulate material 14 may be radially interposed between core material 12 and the jacket 16 (
In
In one embodiment, the particulate material 14 is about 1 to about 30 percent of the total linear weight of the cored wire 10. In a specific embodiment, the particulate material 14 comprises wood, e.g. wood particles or wood sawdust. FLOWS and thus fills up empty space within the jacket 16 not occupied by the core material 12. For example, the particulate material 14 may include one or more species of wood such as Maple, Oak, and other non-resinous or low-resinous species. The wood may exclude high-resinous species such as cedar, fir, juniper, pine, redwood, spruce, yew, larch.
The particulate material 14 may have a mesh size of about 10-100, or an average particle size of 0.149 mm to 2 mm. In one embodiment, the particulate material 14 is not soaked or loaded with any liquid. The particulate material 14 may be dried or otherwise may have a moisture content of less than 10 wt %, less than 8 wt %, or less than 5 wt %.
When the particulate material 14 is of a size and moisture content as described herein, individual particles of the particulate material 14 may freely flow past one another, for example when arranged on an inclined surface and subject to gravity. This feature may be useful in preparing the cored wire 10 as described in more detail herein. When the particulate material 14 has a size or moisture content outside those specified herein, the particulate material 14 may not readily flow, and instead individual particles may agglomerate or stick to various surfaces of production equipment.
The particulate material 14 may include other non-reactive components used with, or in substitution for the wood. These include, but are not limited to, dry polyurethanes, Bauxite, cellulose fibers, bentonite clays, lime products (e.g., calcium oxide), hemp, cotton, burlap, jute (natural or synthetic), flax, rayon, felt or silk, or other materials, such as cellulosic materials, that may undergo thermal decomposition in the molten metal and release carbon dioxide, hydrocarbons, or combinations thereof as a gas shroud around the core material 12.
Advantageously, it is believed that the particulate material 14 forms a shrouding gas when the cored wire 10 is added to molten steel, which has the beneficial effect of creating a protective shielding volume for the reactive core material 12 (e.g., calcium). In other embodiments, the particulate material 14 may be replaced or supplemented by the use of the above-referenced non-reactive components in the form of string, twine, ribbon, cloth or strips arranged radially around or next to the core material 12.
Because of the isolation from the molten metal that is provided by the particulate material 14 (and the jacket 16), the reactive core material 12 tends to melt more slowly than if the particulate material 14 were not included. This allows the core material 12 to be inserted deeper into the molten metal than would otherwise be feasible, thereby releasing the refining core material 12 under high static pressure, separate from oxygen present in the slag and atmosphere above, and increasing the floatation time of low density core material 12, these all being favorable factors for achieving a high recovery.
The cored wire 10 may be formed in a continuous or semi-continuous manner by contouring (e.g. bending) a strip 24 of sheet metal stock 22 into a desired shape to thereby define the jacket 16 and to radially surround the core material 12 and the particulate material 14.
The sheet metal stock 22 may be in the form of a continuous metal strip 24 that is initially flat (e.g. flat cross section), which can be fed from a first roll 26 and processed, such as by roll forming, to contour the metal strip 24 so as to eventually form a tubular shape about the core material 12 and the particulate material 14 to fully surround both the core material 12 and the particulate material 14.
The flat metal strip 24 may be processed by being fed through a first series of rollers 28 and a second series of rollers 38 that roll form the flat strip 24 into a desired shape. During roll forming, strip 24 may be formed to have a trench 32, in which the core material 12 and the particulate material 14 are arranged. The trench 32 may extend along a length of the strip 24. Edges 18 of the strip 24 are then mechanically locked together to form the lock seam 20, which seals the core material 12 and the particulate material 14 within the jacket 16. Alternatively, the lock seam 20 of the jacket 16 could be replaced with welded seams, for example using HF (high frequency) or laser welding.
The first roll 26 provides a continuous flat strip 24 of sheet metal stock 22, which can be delivered to an entrance 30 of the first series of rollers 28 starting with a first set of rollers 48. The first series of rollers 28 contour the flat strip 24 such that the flat metal strip 24 is formed to have the trench 32. This forming may include bending the strip 24 so that the two edges 18 of the strip 24 are moved upward and closer together as compared to when the strip 24 was flat.
As the strip 24 is being fed through the first series of rollers 28, a solid rod 34 of core material 12 is fed from a second roll 36 and arranged on the strip 24. The solid rod 34 may be introduced at the entrance 30 of the first series of rollers 28 as depicted in
After the trench 32 is formed in the strip 24, the strip 24 may have a general U-shaped (
After the particulate material 14 is arranged in the trench 32, the trench 32 may be closed by bringing the two edges 18 of the strip 24 together and sealing them, e.g. with a lock seam 20, to thereby form the cored wire 10. Sealing of the two edges 18 may be performed by the second series of rollers 38, after which the cored wire 10 may be coiled in a spool 46 for storage, delivery, and/or use.
Although the particulate material 14 may be dropped from the funnel 40 to be on top of the rod 34 of core material 12, this configuration may or may not remain constant through the remainder of the process. If the configuration of the particulate material 14 being on top of the core material 12 does remain constant through the remainder of the process, a cored wire 10 may be produced as depicted in
The production of the cored wire 10 may be initiated by feeding a leading edge of the strip 24 and a leading end of the solid rod 34 into the first series of rollers 28. The production of the cored wire 10 may be continuous until one or both of the first roll 26 and the second roll 36 are used up, at which point another roll of sheet metal stock 22 or another roll of core material 12 may be utilized. A leading end and a trailing end of the cored wire 10 may be sealed.
The cored wire 10 may be used for refining molten metal, e.g. steel. The steel may be refined by introducing the cored wire into the molten metal by first inserting a leading end of the cored wire 10 into the molten metal and then continuously feeding a length of the cored wire 10 into the molten metal. As the cored wire is introduced into the molten steel, the jacket 16 at the leading end of the cored wire 10 melts and the particulate material at the leading end of the cored wire 10 undergoes thermal decomposition to release carbon dioxide, hydrocarbons, or combinations thereof as a shroud around the core material 12 at the leading end. This shroud allows the core material 12 (e.g. calcium) at the leading end to melt and react with the molten metal.
The refining process may be discontinued when a predetermined amount of the core material 12 is inserted into the molten metal.
Depending on the composition of the core material 12, the molten metal being treated may include ferrous metal, e.g. steel, or may include other types of metal such as aluminum, copper, or other metals used in foundry industries. The treatment of the molten metal may include using the core material 12 for refining the molten metal, e.g. by de-sulfurization, de-oxidation, alloy addition, inclusion removal, inclusion chemistry modification, and homogenization.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives or varieties thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claim or claims.
The present application claims priority to U.S. Provisional Patent Application Ser. No. 62/585,572, filed Nov. 14, 2017, which is incorporated herein by reference.
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