Patent Application
20100037730
The present invention relates to a high dimensional cored wire containing de-oxidant material (or oxygen remover). Furthermore the invention relates to a process for manufacturing a high dimensional cored wire.
De-oxidation plays an important role in the process of steel making, for which a number of deoxidants have been conventionally used. The term de-oxidant means a chemical compound, alloy or element which will remove the active oxygen present in the liquid metal (e.g., steel) and form an oxide as its final product, usually as a distinct phase and easily separable from the liquid metal. Oxygen, if present in steel in the active/elemental form, will result in pinholes and blowholes in the cast product as well as obstruct the process of continuously casting the steel in the modern continuous casting machines. Steel makers are in regular search of a better and more economical method for removing the oxygen in steel, which will ultimately reduce the consumption of deoxidants.
Conventionally, de-oxidation of steel was carried out by the addition of ferro alloys or aluminum ingots, bars or solid aluminum wire. For bars and ingots the recovery (i.e., ratio of actual quantity and theoretical amount of aluminum) was poor, resulting in greater aluminum consumption. In the case of aluminum wire, the recovery was better, but feeding time was greater, and often the wire could not reach the depth of the molten steel bath.
For doing the primary de-oxidation or the bulk removal of oxygen (primary killing) in steel from a higher level of, say, 800-2000 ppm and above, to a lower level of around 100-200 ppm, alloys such as “ferro-silicon,” “ferro-manganese,” “silico-manganese,” and “coke” are used, though in bulk, and these materials have served the purpose fairly well. These ferro alloys or compounds have a limitation on the extent to which they can be used in steel making and are limited to the extent of the specification that is allowed in the steel. In almost all grades of steel, silicon and manganese elements are used in various forms for the primary de-oxidation, along with aluminum in various forms such as bars, ingots, cubes or solid wires, etc.
For secondary treatment of steel for the purpose of removing the remnant of oxygen, a number of de-oxidants selected from the group of aluminum, titanium and calcium silicide have been used. However, aluminum has been found to be the most suitable de-oxidant for two reasons, e.g., (i) affinity of aluminum for active oxygen and (ii) the requirement of presence of aluminum in predetermined amounts in some grades of steel in the cast product. Aluminum is capable of removing oxygen present in molten steel at very low levels of around 4 ppm or even less. It is also the most economical de-oxidizer element, alloy or compound known at present.
Previously, primary de-oxidation, apart from the use of ferro alloys, was carried out by the addition of aluminum ingots or bars and solid wires of dimension of 13 mm, and secondary or final de-oxidation by adding ingots, notch bars and sometimes even solid aluminum wire. Addition through solid aluminum wire results in a higher percentage of recovery of aluminum compared to bars and ingots. In this specification, unless otherwise specified, the term ‘recovery’ defines the ratio of the actual quantity of aluminum to be added to remove the active oxygen to the theoretical amount of aluminum required. For bars and ingots, the recovery was very poor and accordingly consumption of aluminum increased. In the case of solid aluminum wire, though the recovery was better than bars and ingots, feeding time was greater. The normal size of the aluminum wire that can be injected into the molten steel is around 3 ,6, 9, 13, or 16 mm.
The other problem encountered with solid aluminum wire is that due to the high temperatures encountered in steel making, aluminum becomes very soft due to the high temperatures and is not able to penetrate deeply into the molten steel bath which consequently results in lower recovery.
To solve a similar problem, it is proposed in Chinese patent application publication CN 1498975 A to feed aluminum cored wire directly into molten steel for deoxidizing.
A further method of adding aluminum to steel in a ladle for the purpose of de-oxidation is known from British patent application publication GB 892375. This method comprises progressively feeding a rod or wire of the material to be added at an appreciable depth below the surface of the steel. The material may be in powder or granular form enclosed in a steel tube.
A process for manufacturing cored wires containing deoxidizing constituents as pulverized material within a metal tube is known from U.S. Pat. No. 3,915,693.
An object of the invention is to overcome the above drawbacks and provide a high dimensional cored wire as well as a process to manufacture a high dimensional cored wire.
The present invention attempts to overcome the above drawbacks and provides high dimensional cored wires containing de-oxidant material/oxygen removers, preferably formed from cold-rolled steel sheet, the de-oxidant material being in finely divided granular or powdery form at least partially coated with a protective coating material, such as herein described, the diameter of the cored wires varying between 13 and 40 mm, preferably between 19 and 34 mm. Preferably, the coated de-oxidant material filled in the core is held in place in compacted form by the seaming locks provided during formation of the cored wires after filling. The wire can also be made by totally welding the sheath so that there is no seam.
This invention also provides a process for producing the above cored wires containing the de-oxidant coated with a protective coat in a compacted form, ensuring better recovery and rapid feeding of the de-oxidant material in predetermined amounts.
In other words, the present invention relates to high dimensional cored wires containing de-oxidant material/oxygen removers and a process for making the same. More particularly, this invention pertains to high dimensional cored wires filled with an oxygen-removing material selected from the group of aluminum, titanium, zirconium and calcium silicide, preferably fine granules of reactive aluminum powder, having a coating of inorganic and/or organic material. The coating can also be a mixture or combination of different materials, or even without a coating and simple granules, and a process for preparing such high dimensional cored wires.
For the high dimensional wires proposed in the present invention, feeding of higher dimension solid aluminum wire, as available now, becomes very difficult with the conventional wire feeders.
The present invention aims at overcoming the foregoing shortcomings of the prior art and at carrying out production of steel more effectively, maintaining an optimum level of aluminum in steel.
This invention has also the advantage of further enhancing the recovery of aluminum, simultaneously reducing the quantum of consumption and time of feeding of aluminum to liquid metal.
A further advantage of the present invention is to provide a technique to use aluminum scraps as de-oxidant after converting them into granules, followed by coating with a protective material like graphite, low density polyethylene, polyamide, low molecular weight vinyl acetate polymer, talc, steatite, calcium silicide, powdered lime, and the like to prevent fusion or adhesion of the granular particles into a single mass while being pressed and drawn into the wire. It is also possible to use the aluminum granules without coating.
A still further advantage of this invention is to provide high dimensional cored wires containing aluminum granules coated with graphite, which while being drawn through the forming machine, the contents become tightly packed, thereby imparting dimensional rigidity and stiffness to the wire.
Another advantage of the present invention is to provide a process for preparing high dimensional cored wires containing de-oxidants in granular form and coated with a protective coating to prevent sticking and fusing into a single mass while being pressed and drawn into wire. Further, during immersion of the wire into molten steel the wire begins to melt and the (organic) coating vaporizes rapidly, thus causing homogeneous and rapid spreading of the de-oxidant material within the molten steel.
The subject invention also relates to a process for preparing high dimensional cored wires containing de-oxidant material / oxygen removers as defined above, comprising especially the steps of:-
As pointed out earlier, de-oxidants may be selected from metallic, aluminum, titanium, zirconium and calcium silicide, but aluminum has been found to give best results, as the oxide formed may be removed easily due to phase separation and its refractoriness. Aluminum is used in granular or powdery form, coated with graphite. Scrap aluminum obtained from discarded used beverage cans, sheets/foils/strips/old electrical cable and the like are smelted or shredded and converted into granular form followed by application of a protective coating material like graphite, talc, limestone dust, calcite, steatite, LDP (low density polyethylene) and the like to prevent fusion or adhesion of granules at the time of being pressed and drawn into the wire. The lacquer coating on the used beverage cans also serves the purpose of protective coating. The size of aluminum granules should optimally be around 40 mesh, but finer or coarser sized granules may just as well be used. However, care should be taken to prevent handling loss. While drawing the aluminum granule-filled wire through the forming machine, the contents become tightly packed, thereby imparting dimensional rigidity and stiffness to the wire, ensuring ease of handling the coil.
De-oxidation with aluminum by changing the form of aluminum addition, which is carried out by injecting high dimensional cored wire filled with highly reactive aluminum in fine granular form and coated with an organic material like graphite for better recovery, and achieving the optimum level of oxygen and aluminum with lesser consumption of aluminum are a unique feature of this invention. The coating is not limited to organic materials but can also include inorganic coating materials like calcium oxide, talc, chalk powder, and the like. De-oxidation in accordance with the present invention can be carried out both in the primary and the secondary levels, as per requirement of the steel maker.
As pointed out earlier, aluminum powder is converted into fine granules and then coated with an inert organic coating material, like graphite flakes or any organic or inorganic coating material, to prevent the aluminum powder from sticking and fusing into a single mass while being pressed and drawn into the wire. While drawing the aluminum powder filled wire, the contents become tightly packed, thereby imparting dimensional rigidity and stiffness to the wire. This also ensures ease of handling the coil.
A notable feature of this invention is to use scrap aluminum of any grade in granular or powdered form as the de-oxidant, suitably coated with organic or inorganic coating material as described hereinbefore. Use of scrap/waste aluminum bodies effectively adds to the economy of the overall process.
As an additional feature of this invention, winding of the powder filled coil is subjected to ‘coreless coiling’ so that the coil can be uncoiled from the inner diameter of the stationary coil, generally called a “flipping coil,” either vertical or horizontal. The coil can also be made into a spool with a core made of either wooden, synthetic, metal or any such materials.
The novel product of this invention, namely, high dimensional cored wire filled with fine granules of aluminum powder coated with graphite and securely held inside, is provided with seaming locks. By ‘high dimensional’ it is implied that dimensions of the cored wire ranges between 13 and 40 mm, optimally between 19 mm and 34 mm, and the internal diameter of the wound wire over the mandrel may vary from 200 mm to 2.5 meters, and the weight of each coil may range from 1 MT to around 20 MT (MT—metric ton, usual abbreviation of which is t), depending on customer requirement.
The present invention will be further illustrated by the experimental data included in the following example, but it is to be understood that the invention is not restricted to the results given therein.
Various advantages of the products of the present invention may be briefly outlined as follows:
As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described experimental data are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and ambit as defined in the claims appended hereinafter, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalences of such metes and bounds, are therefore intended to be embraced by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 725/KOL/2006(P) | Jul 2006 | IN | national |
| 725/KOL/2006 | Mar 2007 | IN | national |
This application is a Section 371 of International Application No. PCT/EP2007/006323, filed Jul. 17, 2007, which was published in the English language on Jan. 24, 2008, under International Publication No. WO 2008/009414 A1 and the disclosure of which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2007/006323 | 7/17/2007 | WO | 00 | 1/20/2009 |
