WO2016077685A1 - A method for the manufacture of an efficient steel deoxidizer aluminum matrix composite material - Google Patents

A method for the manufacture of an efficient steel deoxidizer aluminum matrix composite material Download PDF

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Publication number
WO2016077685A1
WO2016077685A1 PCT/US2015/060560 US2015060560W WO2016077685A1 WO 2016077685 A1 WO2016077685 A1 WO 2016077685A1 US 2015060560 W US2015060560 W US 2015060560W WO 2016077685 A1 WO2016077685 A1 WO 2016077685A1
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composite material
aluminum
manufacture
free
steel
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PCT/US2015/060560
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French (fr)
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Maxim Seleznev
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Maxim Seleznev
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Application filed by Maxim Seleznev filed Critical Maxim Seleznev
Priority to RU2017120546A priority Critical patent/RU2673252C1/en
Priority to US15/526,394 priority patent/US20170321291A1/en
Priority to CN201580060332.1A priority patent/CN107075597A/en
Publication of WO2016077685A1 publication Critical patent/WO2016077685A1/en

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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • C21C7/06Deoxidising, e.g. killing
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006Adding metallic additives
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • C21C7/076Use of slags or fluxes as treating agents
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22BPRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00Preliminary treatment of ores or scrap
    • C22B1/14Agglomerating; Briquetting; Binding; Granulating
    • C22B1/24Binding; Briquetting ; Granulating
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/20Recycling

Definitions

  • the invention relates generally to the manufacture of composite materials, and more particularly to a method of manufacturing an aluminum matrix composite material for use as a deoxidizer in steel making.
  • Aluminum is one of the most potent deoxidizing (deox) agents and is used for practically all quality flat-rolled steels which comprise about 60% of all steels produced. Aluminum is usually charged into molten steel at two stages of steel making process. First charge, where the bulk of deox aluminum is used, happens at tapping of electric arc furnace (EAF) or basic oxygen furnace (BOF) into a ladle in a form of ingot or cones placed at the bottom of an empty ladle and (or) thrown into tapped steel stream vortex.
  • EAF electric arc furnace
  • BOF basic oxygen furnace
  • LMF ladle metallurgical furnace
  • Molten steel surface in the ladle is covered with protective slag, which contains large amounts of iron oxide. Since aluminum has much lower density than molten steel (2.2 vs. 7 g/cm3 at temperature), it floats to the melt surface where it is trapped in slag covering molten steel and the bulk of aluminum (70%>) is exposed to and reacts with oxygen in slag's iron oxide or atmospheric air instead of oxygen dissolved in the steel and therefore is wasted inefficiently.
  • a straight forward engineering solution to the problem of aluminum floating to steel surface during deoxidation is to join aluminum with a heavier component, so that it submerges deeper when charged into molten steel.
  • a logical choice for heavier component is iron or steel, since it can make joined material heavier without contaminating steel melt. Indeed, if one considers prior art solutions to the problem, such material called ferroaluminum alloy produced via high temperature smelting of iron (or steel) and aluminum is offered on the market since approximately 1970's - see [Deely P.D. "Ferroaluminum - Properties and Uses" in Ferroalloys and Other Additives to Liquid Iron and Steel, ASTM STP 739, J.R. Lampman and A.T.
  • ferroaluminum suffers from a few drawbacks that prevented its wide adoption in the industry. Since the alloy is produced using high temperature smelting, it turned out expensive to manufacture due to high energy and furnace maintenance costs, as well as high aluminum losses due to oxidation. Another problem associated with high process temperature is ferroaluminum' s susceptibility to crumbling during its charging into molten steel due to thermal stresses and large brittle complex intermetallic phases present in the microstructure.
  • a method for the manufacturing of an aluminum matrix composite material includes the steps of forming a porous free-standing preform comprised of aluminum and iron-rich component, applying heat to the free-standing preform to raise its temperature above the melting point of aluminum and below the melting point of iron-rich component, and applying pressure to densify the free-standing preform to solidify.
  • the iron-rich component of the aluminum matrix composite material is steel.
  • the aluminum is present in the range of 10-50% of the composite material by weight. Further, in one embodiment of the present method of manufacture, the aluminum is 30% of the composite material by weight.
  • Another embodiment of the present method of manufacture provides for a freestanding preform formed by a process of mechanical pressing, briquetting, a container, an inorganic binder or a combination of any of those processes.
  • One embodiment of the present method of manufacture provides for a certain amount of heat that is applied to the free-standing preform to raise its temperature over 661 degrees Celsius. In one embodiment, heat is applied to the free-standing preform through a process selected from the group including induction heating, electrical resistance furnace heating, and organic fuel burner furnace heating.
  • another embodiment of the present method of manufacture provides that an amount of external pressure is applied to the free-standing preform sufficient for a molten aluminum component to fill substantially all porosity and gaps between the iron-rich components.
  • Yet another embodiment of the present method of manufacture is to provide an amount of external pressure to the free-standing preform to densify the preform. The pressure to densify is applied by a means of pressing in a closed die.
  • One embodiment of the present method of manufacture provides for the iron-rich component to be selected from a group including ferromanganese, and a mixture of steel and ferromanganese.
  • the free-standing preform is bound and supported by a process selected from a group that includes mechanical pressing, inorganic binder, a steel container, and any combination thereof. Further, the amount of heat applied to the freestanding preform is applied through a process that may include induction heating, electrical resistance furnace heating, and organic fuel burner furnace heating.
  • One embodiment of the present method of manufacture is to provide a method for the manufacture of an aluminum matrix composite material. The steps include forming a porous free-standing preform comprising of a plurality of fines of aluminum and a plurality of fines selected from the group consisting of: steel, ferromanganese, silicocalcium, calcium carbide, rare earth metals, any ferroalloy other than ferromanganese.
  • the new steel deoxidizer material provided in the present method of manufacture may be best described as aluminum matrix composite.
  • Composite materials are usually defined as comprising of discrete reinforcement or filler particles or fibers that are contained in, or surrounded by, continuous matrix material.
  • metal matrix composites are often referred to as engineered materials.
  • Composites reinforcement and matrix are joined together through an engineered manufacturing process and generally speaking do not find themselves in thermodynamic equilibrium, in many cases being chemically inert to each other - for example refractory ceramic particles in aluminum matrix composite.
  • casting is where reinforcement particles are first pre-mixed with molten metal and then the mixture is cast into a mold.
  • powder metallurgy methods occur when solid reinforcement and matrix particles are mixed, pressed into a shape and then sintered in solid state at high temperature.
  • Another well-known widely applied method may be generally described as pressure infiltration technology.
  • a dry preform of reinforcement particles is first made, heated up, placed into a die, and then molten matrix metal is poured over the die and infiltrated into the dry preform under external pressure applied to the matrix metal, usually via hydraulic press punch.
  • New deoxidizer aluminum matrix composite material described herein is manufactured using a pressure infiltration technology that is radically improved compared to a custom one to make the technology economical to implement and minimize losses of valuable aluminum.
  • the new technology aluminum matrix infiltrant does not have to travel from one boundary of a dry preform made of steel particles through a bulk of the preform and all the way to the opposite boundary in order to infiltrate the preform completely.
  • Such long travel of molten aluminum necessitates complex and precisely machined dies to avoid aluminum bursting out under pressure, and also carries risk of premature aluminum cool down and incomplete preform infiltration as a result.
  • liquid aluminum has to travel only a short distance to fill gaps between steel particles in the preform.
  • pre-mixed aluminum is pre-mixed with the steel particles at the stage of preform manufacturing - a step, which also automatically guarantees precise aluminum to steel weight ratio in the new composite deoxidizer.
  • the pre-mixed aluminum transitions to liquid state during preform heat-up and only travels distances comparable to average steel particle size to fill gaps around them when the preform is squeezed in a hydraulic press die.
  • Such technology may be called in-situ pressure infiltration technology, because aluminum infiltrant is in-situ present in the preform that is being infiltrated.
  • a porous free-standing preform shape is formed from crushed turnings, shavings, borings or other substantially small pieces of aluminum mixed with crushed turnings, shavings, borings or other substantially small pieces of steel, wherein the preferred weight fraction of aluminum is close to 30%.
  • Formation of the shape is a manufacturing operation that will be known to those skilled in the art, and preferably achieved by mechanical pressing or briquetting.
  • the preform shape may be formed using a container, inorganic binder (i.e. sodium silicate), or both to make it free-standing.
  • Geometry of the preform shape might vary.
  • the geometry may be a cylinder between 20 and 200 millimeters in diameter and between 20 to 200 millimeters in height, and having diameter to height ratio of 1 to 1 or close to it.
  • the preform shape is heated to a temperature that is over melting temperature of aluminum, but below melting temperature of steel and for a sufficient time for aluminum component to transition to liquid state.
  • Exact heating temperature value might vary. In a preferred embodiment, the temperature range may be between 661 and 800 degrees Celsius. Possible techniques used to heat up the preform shape will be known to those skilled in the art. In a preferred embodiment, the technique may be induction heating, since it is extremely efficient at heating materials that contain ferromagnetic components, specifically carbon steel.
  • the heated preform shape is squeezed in an adequately tight volume at a pressure sufficient for in-situ molten aluminum component in the shape to fill practically all porosity and gaps between steel particles, so that the composite becomes near fully dense with a density at least higher than 90 percent of theoretical and preferably higher than 95 percent of theoretical.
  • Pressure on the preform should be maintained until the moment where the molten aluminum solidifies.
  • Squeezing operation may be performed using wide variety of techniques known to those skilled in the art. In a preferred embodiment, the technique may be pressing in a closed die mounted on a hydraulic press. The die suitable for squeezing operation may be much less complex compared to dies used in custom pressure infiltration technology.
  • weight fractions of aluminum in the free-standing porous shape may vary between 10% and 50%.
  • the porous freestanding preform shape is formed from crushed turnings, shavings, borings or other substantially small pieces of aluminum mixed with substantially small pieces of ferromanganese, wherein the weight fraction of aluminum is close to 25%.
  • the rest of the process steps, including shape heating and heated shape squeezing are substantially the same.
  • a rational for substituting steel with ferromanganese is that on one hand, it is known to those skilled in the art that combined effect of aluminum and manganese as deoxidizers is stronger than of either element separately.
  • ferromanganese may serve the same functions as steel as far as making aluminum- containing deoxidizer heavier and providing efficient induction coupling during induction heating of the porous free-standing preform shape.
  • some of the steel and aluminum in the free-standing porous preform shape may be replaced by additions useful in the steelmaking process, such as silicocalcium, calcium carbide, rare earth metals and other useful additions.
  • Such additions may help deoxidize steel even better than aluminum alone, or modify shape and size of oxides and other non-metallic particles suspended in molten steel, making them smaller and more compact, thus improving appearance and mechanical properties of a final flat rolled steel product.
  • the new steel deoxidizer aluminum matrix composite material manufactured as described in the preferred embodiment above is used to deoxidize steel at the stage of EAF or BOF tapping into a ladle as direct replacement of aluminum ingot or cone.
  • weight ratio of the deoxidizer composite material to weight of aluminum ingot or cone it replaces may be estimated as 1.66 to 1 based on the following considerations. It is known from past industrial practice that non-crumbled ferroaluminum containing close to 30% aluminum by weight saves about 50% of aluminum compared to deoxidation using ingot or cone. Therefore, each kilogram of aluminum ingot or cone may be replaced by 0.5 kilogram of aluminum contained in ferroaluminum, or in case of the present method of manufacture in deoxidizer aluminum matrix composite. For a preferred weight ratio of aluminum to steel of 30 to 70, one may calculate the total weight of new deoxidizer replacing one kilogram of aluminum ingot or cone as 0.5 kilogram multiplied by 100 and divided by 30, which equals 1.66 kilogram.

Abstract

A method of manufacture to provide an efficient and economical steel deoxidizer aluminum matrix composite material that is near fully dense, free of brittle intermetallic compounds and allows for deep penetration of aluminum into molten steel thus cutting unnecessary losses of this valuable metal to parasitic oxidation reactions with slag and atmosphere.

Description

A METHOD FOR THE MANUFACTURE OF AN EFFICIENT STEEL
DEOXIDIZER ALUMINUM MATRIX COMPOSITE MATERIAL
CROSS REFERERNCE TO RELATED APPLICATION
This application claims priority to and takes the benefit of United States Provisional Application Serial No. 62/079,558 filed on November 14, 2014, the contents of which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates generally to the manufacture of composite materials, and more particularly to a method of manufacturing an aluminum matrix composite material for use as a deoxidizer in steel making.
Description of the Related Art
Steel deoxidation (i.e. oxygen removal from molten steel before casting) is a necessary technological step in modern steelmaking. During casting operations, as molten steel cools down and solidifies, dissolved oxygen reacts with carbon and forms carbon monoxide (CO) gas bubbles which become trapped in steel slabs or ingots resulting in porosity. Porosity is a serious defect in the manufacturing process causing a reduction in the mechanical properties of steel and of flat-rolled steel products in particular; therefore it is imperative that oxygen be removed from steel prior to casting. To deoxidize molten steel, metallurgists normally introduce strong oxide-forming elements like Mn, Si and Al into the steel melt. These elements react with dissolved oxygen and form solid oxide particles that are lighter than molten steel and float to the melt surface joining slag that protects molten steel surface. Aluminum is one of the most potent deoxidizing (deox) agents and is used for practically all quality flat-rolled steels which comprise about 60% of all steels produced. Aluminum is usually charged into molten steel at two stages of steel making process. First charge, where the bulk of deox aluminum is used, happens at tapping of electric arc furnace (EAF) or basic oxygen furnace (BOF) into a ladle in a form of ingot or cones placed at the bottom of an empty ladle and (or) thrown into tapped steel stream vortex. Aluminum charge carried out at tapping, in addition to its primary deox purpose, also increases throughput because deoxidation with aluminum is quick and runs to completion while the ladle is transferred to the next operation. The second charge, where smaller amount of aluminum is usually used, is delivered into the ladle itself at a ladle metallurgical furnace (LMF) - a special half-way facility between melting furnace and caster dedicated to improving molten steel quality and bringing its composition to specification. On average 2 kilograms of aluminum per ton of steel is used in the industry.
A major problem with aluminum use for steel deoxidation is that this valuable metal lost irreversibly. Once aluminum reacts with oxygen to form alumina or aluminum- containing oxides that float to the molten steel surface and mix with cover slag, there are no practical ways to recover aluminum back to metallic form. Consequently, up to 4% of primary (reduced from bauxite ore) aluminum produced in the world is lost in a non- recoverable way to steel deoxidation. However, only about 30% of these losses are technologically necessary and are due to reaction of oxygen dissolved in molten steel with aluminum, the other 70% are waste. To understand why, consider that in a course of steel deoxidation, aluminum in a form of ingot or small cones is charged into a ladle containing molten steel. Molten steel surface in the ladle is covered with protective slag, which contains large amounts of iron oxide. Since aluminum has much lower density than molten steel (2.2 vs. 7 g/cm3 at temperature), it floats to the melt surface where it is trapped in slag covering molten steel and the bulk of aluminum (70%>) is exposed to and reacts with oxygen in slag's iron oxide or atmospheric air instead of oxygen dissolved in the steel and therefore is wasted inefficiently.
It should be noted, that aluminum is an extremely energy-intensive metal to make, requiring 174 GJ of electrical energy per one ton of primary aluminum produced from bauxite ore. Luckily aluminum strongly resists atmospheric corrosion and is easily recycled via secondary scrap smelting - an operation that uses about 10 times less energy than primary aluminum production from ore. Therefore, in light of global climate change caused by carbon dioxide emissions produced to a large extent in a process of electric energy generation, unrecoverable loss of aluminum in general and unnecessary unrecoverable loss in particular is a very serious environmental problem.
A straight forward engineering solution to the problem of aluminum floating to steel surface during deoxidation is to join aluminum with a heavier component, so that it submerges deeper when charged into molten steel. A logical choice for heavier component is iron or steel, since it can make joined material heavier without contaminating steel melt. Indeed, if one considers prior art solutions to the problem, such material called ferroaluminum alloy produced via high temperature smelting of iron (or steel) and aluminum is offered on the market since approximately 1970's - see [Deely P.D. "Ferroaluminum - Properties and Uses" in Ferroalloys and Other Additives to Liquid Iron and Steel, ASTM STP 739, J.R. Lampman and A.T. Peters, Eds, American Society for Testing of Materials, 1981, pp. 157-169]. Its practical usage in steelmaking industry demonstrated that aluminum consumption for steel deoxidation can be cut in half. However, though technologically a success, ferroaluminum suffers from a few drawbacks that prevented its wide adoption in the industry. Since the alloy is produced using high temperature smelting, it turned out expensive to manufacture due to high energy and furnace maintenance costs, as well as high aluminum losses due to oxidation. Another problem associated with high process temperature is ferroaluminum' s susceptibility to crumbling during its charging into molten steel due to thermal stresses and large brittle complex intermetallic phases present in the microstructure. Some of these intermetallic phases also react with water vapor in atmosphere, so ferroaluminum alloy often crumbles to dust even during storage. Crumbled deoxidizer is much less efficient since light crumbs are easily trapped in a slag on molten steel surface as deoxidizer is charged into molten steel.
It is claimed that above mentioned drawbacks of ferroaluminum can be overcome by mechanically briquetting aluminum-steel particles mixture per US Pat. No. 6350295. Another approach to joining aluminum with a heavier component that is taught in the prior art is to melt aluminum and cast it into or around prefabricated steel shapes - see for example US Pat. 4,801,328 or China patent CN21102974Y. A technique of feeding aluminum wire for deoxidation purposes is described for example in US Pat. No. 3,331,680. An innovative technology for manufacturing of aluminum deoxidizer material is disclosed in the Russian Federation patent N° 2269586.
However, though several attempts were made to develop an efficient aluminum deoxidizer material that can be economically manufactured, a practical solution acceptable to steelmaking industry is still lacking as evidenced by current industry deoxidizing practice of charging aluminum cone and ingot into molten steel - an inefficient process that leads to huge irreversible losses of aluminum and of energy used for its production. So, there is a real practical need for a new aluminum deoxidizer material that provides for more efficient use of aluminum in steel deoxidation compared to current practice, as well as technologically and economically viable process for its manufacture.
SUMMARY OF THE INVENTION
The instant composite material and method of manufacture, as illustrated herein, are clearly not anticipated, rendered obvious, or even present in any of the prior art mechanisms, either alone or in any combination thereof. Thus the several embodiments of the instant method of manufacture are illustrated herein.
It is an object of this method of manufacture to provide an efficient and economical deoxidizer aluminum matrix composite material that is near fully dense, free of brittle intermetallic compounds and allows for deep penetration of aluminum into molten steel thus cutting unnecessary losses of this valuable metal to parasitic oxidation reactions with slag and atmosphere.
It is another object of this method of manufacture to provide an innovative and cost efficient technology for deoxidizer aluminum matrix composite manufacture based on in-situ pressure infiltration technology, meaning infiltration of a steel-aluminum or other ferrous filler-aluminum preform porous shape by aluminum component that is in- situ present in the preform.
It is another object of this method of manufacture to provide for near fully dense, free of brittle intermetallics and therefore non-crumbling deoxidizer aluminum matrix composite that is safe and easy to use in steelmaking process without any equipment change or disruption to existing manual or automated deoxidizing practices employed in the industry.
It is still another object of this method of manufacture to provide for deoxidizer- modifier aluminum matrix composite that contains one or more deoxidizing and inclusion-modifying agents in addition to aluminum thus rendering the new material even more potent in deoxidizing and improving steel properties.
In one embodiment of the present method of manufacture, there is provided a method for the manufacturing of an aluminum matrix composite material. The method includes the steps of forming a porous free-standing preform comprised of aluminum and iron-rich component, applying heat to the free-standing preform to raise its temperature above the melting point of aluminum and below the melting point of iron-rich component, and applying pressure to densify the free-standing preform to solidify.
In yet another embodiment of the present method of manufacture, the iron-rich component of the aluminum matrix composite material is steel. The aluminum is present in the range of 10-50% of the composite material by weight. Further, in one embodiment of the present method of manufacture, the aluminum is 30% of the composite material by weight. Another embodiment of the present method of manufacture provides for a freestanding preform formed by a process of mechanical pressing, briquetting, a container, an inorganic binder or a combination of any of those processes. One embodiment of the present method of manufacture provides for a certain amount of heat that is applied to the free-standing preform to raise its temperature over 661 degrees Celsius. In one embodiment, heat is applied to the free-standing preform through a process selected from the group including induction heating, electrical resistance furnace heating, and organic fuel burner furnace heating. Further, another embodiment of the present method of manufacture provides that an amount of external pressure is applied to the free-standing preform sufficient for a molten aluminum component to fill substantially all porosity and gaps between the iron-rich components. Yet another embodiment of the present method of manufacture is to provide an amount of external pressure to the free-standing preform to densify the preform. The pressure to densify is applied by a means of pressing in a closed die.
One embodiment of the present method of manufacture provides for the iron-rich component to be selected from a group including ferromanganese, and a mixture of steel and ferromanganese.
In yet another embodiment the free-standing preform is bound and supported by a process selected from a group that includes mechanical pressing, inorganic binder, a steel container, and any combination thereof. Further, the amount of heat applied to the freestanding preform is applied through a process that may include induction heating, electrical resistance furnace heating, and organic fuel burner furnace heating. One embodiment of the present method of manufacture is to provide a method for the manufacture of an aluminum matrix composite material. The steps include forming a porous free-standing preform comprising of a plurality of fines of aluminum and a plurality of fines selected from the group consisting of: steel, ferromanganese, silicocalcium, calcium carbide, rare earth metals, any ferroalloy other than ferromanganese. Next, applying an amount of heat to the free-standing preform sufficient to raise its temperature above the melting point of aluminum and below the melting point of the other components of the preform and applying an amount of pressure to densify the free-standing preform to a near full density to allow for the aluminum in the free-standing preform to solidify.
There has thus been outlined, rather broadly, the more important features of a method of manufacturing an aluminum matrix composite in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the composite material and method of manufacture that will be described hereinafter and which will form the subject matter of the claims appended hereto.
To the accomplishment of the foregoing and related ends, certain illustrative aspects are described herein in connection with the following description. These aspects are indicative of the various ways in which the principles disclosed herein may be practiced and all aspects and equivalents thereof are intended to be within the scope of the claimed subject matter. Other advantages and novel features will become apparent from the following detailed description.
In this respect, before explaining at least one embodiment of the method of manufacture of the composite material in detail, it is to be understood that the methodology is not limited in its application to the details of composite material and to the arrangements of the steps of the manufacturing process set forth in the following description. The method of manufacture is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
These together with other objects of the composite material and method of manufacture, along with the various features of novelty, which characterize the system, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the methodology, its operating advantages and the specific objects attained by its uses, reference should be made to the descriptive matter in which there are illustrated preferred embodiments of the method of manufacture.
DETAILED DESCRIPTION OF THE SEVERAL EMBODIMENTS
The new steel deoxidizer material provided in the present method of manufacture may be best described as aluminum matrix composite. Composite materials are usually defined as comprising of discrete reinforcement or filler particles or fibers that are contained in, or surrounded by, continuous matrix material. Unlike conventional metallic alloys comprised of different metallic phases whose interactions are governed by thermodynamic equilibrium laws, metal matrix composites are often referred to as engineered materials. Composites reinforcement and matrix are joined together through an engineered manufacturing process and generally speaking do not find themselves in thermodynamic equilibrium, in many cases being chemically inert to each other - for example refractory ceramic particles in aluminum matrix composite.
From an engineering point of view, there is a compelling reason for adding composite materials to an already wide arsenal of previously available metals and alloys. This is because composites allow to engineer materials, with microstructures and properties not achievable using established methods of melting, casting, heat treating, cold and hot-working that rely on physicochemical processes and reactions in metallic systems. For example, to make a deoxidizer material heavier than aluminum, one could use smelting of aluminum with iron at a high temperature resulting in metallurgical ferroaluminum alloy described earlier in the text. Ferroaluminum is heavier than aluminum, but contains large amounts of brittle and corrosion-prone intermetallic phases that make it crumble in storage or when it is charged into molten steel. However, if steel particles could be joined with aluminum matrix into engineered near fully dense composite material using manufacturing method other than high temperature smelting, the resulting material will be much denser than aluminum, but at the same time, free of brittle intermetallic phases that reduce ferroaluminum deoxidizer efficiency due to crumbling.
There are many technological methods for the manufacturing of metal matrix composite materials well known to those skilled in the art. For example, casting is where reinforcement particles are first pre-mixed with molten metal and then the mixture is cast into a mold. Another example, powder metallurgy methods occur when solid reinforcement and matrix particles are mixed, pressed into a shape and then sintered in solid state at high temperature. Another well-known widely applied method may be generally described as pressure infiltration technology. In its custom implementation, a dry preform of reinforcement particles is first made, heated up, placed into a die, and then molten matrix metal is poured over the die and infiltrated into the dry preform under external pressure applied to the matrix metal, usually via hydraulic press punch. Drawbacks of custom pressure infiltration technology are that it requires a complex tooling, precise control over manufacturing parameters of each individual briquette. Also, the most critical shortcoming is the necessity to melt and hold large batches of matrix metal, which in the case of aluminum, leads to high losses of aluminum to dross.
New deoxidizer aluminum matrix composite material described herein is manufactured using a pressure infiltration technology that is radically improved compared to a custom one to make the technology economical to implement and minimize losses of valuable aluminum. Unlike custom technology, the new technology aluminum matrix infiltrant does not have to travel from one boundary of a dry preform made of steel particles through a bulk of the preform and all the way to the opposite boundary in order to infiltrate the preform completely. Such long travel of molten aluminum necessitates complex and precisely machined dies to avoid aluminum bursting out under pressure, and also carries risk of premature aluminum cool down and incomplete preform infiltration as a result. Instead, in the new technology, liquid aluminum has to travel only a short distance to fill gaps between steel particles in the preform. This is because aluminum is pre-mixed with the steel particles at the stage of preform manufacturing - a step, which also automatically guarantees precise aluminum to steel weight ratio in the new composite deoxidizer. The pre-mixed aluminum transitions to liquid state during preform heat-up and only travels distances comparable to average steel particle size to fill gaps around them when the preform is squeezed in a hydraulic press die. Such technology may be called in-situ pressure infiltration technology, because aluminum infiltrant is in-situ present in the preform that is being infiltrated.
In a preferred embodiment, first, a porous free-standing preform shape is formed from crushed turnings, shavings, borings or other substantially small pieces of aluminum mixed with crushed turnings, shavings, borings or other substantially small pieces of steel, wherein the preferred weight fraction of aluminum is close to 30%. Formation of the shape is a manufacturing operation that will be known to those skilled in the art, and preferably achieved by mechanical pressing or briquetting. Alternatively, the preform shape may be formed using a container, inorganic binder (i.e. sodium silicate), or both to make it free-standing. Geometry of the preform shape might vary. In a preferred embodiment, the geometry may be a cylinder between 20 and 200 millimeters in diameter and between 20 to 200 millimeters in height, and having diameter to height ratio of 1 to 1 or close to it.
Next, the preform shape is heated to a temperature that is over melting temperature of aluminum, but below melting temperature of steel and for a sufficient time for aluminum component to transition to liquid state. Exact heating temperature value might vary. In a preferred embodiment, the temperature range may be between 661 and 800 degrees Celsius. Possible techniques used to heat up the preform shape will be known to those skilled in the art. In a preferred embodiment, the technique may be induction heating, since it is extremely efficient at heating materials that contain ferromagnetic components, specifically carbon steel.
It should be noted, that though some oxidation of aluminum during heating of the preform will take place, it will be drastically minimized compared to melting and holding of large aluminum batches in open air furnaces because of brevity of the process and restricted air paths in the preform.
Then, the heated preform shape is squeezed in an adequately tight volume at a pressure sufficient for in-situ molten aluminum component in the shape to fill practically all porosity and gaps between steel particles, so that the composite becomes near fully dense with a density at least higher than 90 percent of theoretical and preferably higher than 95 percent of theoretical. Pressure on the preform should be maintained until the moment where the molten aluminum solidifies. Squeezing operation may be performed using wide variety of techniques known to those skilled in the art. In a preferred embodiment, the technique may be pressing in a closed die mounted on a hydraulic press. The die suitable for squeezing operation may be much less complex compared to dies used in custom pressure infiltration technology. This is because in custom pressure infiltration hydraulic press punch has to drive a relatively large volume of liquid metal under high pressure for a considerable distance until it fully infiltrates dry preform. Hot liquid metal under pressure may burst out of a die if it finds even a tiny gap between the punch and die wall. To avoid bursting, precise machining of the die and punch to minimize the gap is necessary, which in turn, makes it difficult to extract the punch from the die once infiltration is complete. Difficulties with punch extraction often lead to further complexities in die design.
For example, use of a split die may be necessary for extraction, instead of unitary cylindrical die. In the case of in-situ pressure infiltration, the punch has to travel only a short distance to densify the preform, and material being pressed by the punch is semisolid, not fully liquid like aluminum in the case of custom pressure infiltration technology. This allows for much less tighter gaps between the punch and die walls and relieves punch extraction problem, so that a simple cylindrical unitary die may be used. In alternative embodiments of the method of manufacture, weight fractions of aluminum in the free-standing porous shape may vary between 10% and 50%.
In another alternative embodiment of the method of manufacture, the porous freestanding preform shape is formed from crushed turnings, shavings, borings or other substantially small pieces of aluminum mixed with substantially small pieces of ferromanganese, wherein the weight fraction of aluminum is close to 25%. The rest of the process steps, including shape heating and heated shape squeezing are substantially the same. A rational for substituting steel with ferromanganese, is that on one hand, it is known to those skilled in the art that combined effect of aluminum and manganese as deoxidizers is stronger than of either element separately. On the other hand, ferromanganese may serve the same functions as steel as far as making aluminum- containing deoxidizer heavier and providing efficient induction coupling during induction heating of the porous free-standing preform shape. In other alternative embodiments of the method of manufacture, some of the steel and aluminum in the free-standing porous preform shape may be replaced by additions useful in the steelmaking process, such as silicocalcium, calcium carbide, rare earth metals and other useful additions. Such additions may help deoxidize steel even better than aluminum alone, or modify shape and size of oxides and other non-metallic particles suspended in molten steel, making them smaller and more compact, thus improving appearance and mechanical properties of a final flat rolled steel product. In a preferred embodiment, the new steel deoxidizer aluminum matrix composite material manufactured as described in the preferred embodiment above is used to deoxidize steel at the stage of EAF or BOF tapping into a ladle as direct replacement of aluminum ingot or cone. Not to be held to a particular theory, weight ratio of the deoxidizer composite material to weight of aluminum ingot or cone it replaces may be estimated as 1.66 to 1 based on the following considerations. It is known from past industrial practice that non-crumbled ferroaluminum containing close to 30% aluminum by weight saves about 50% of aluminum compared to deoxidation using ingot or cone. Therefore, each kilogram of aluminum ingot or cone may be replaced by 0.5 kilogram of aluminum contained in ferroaluminum, or in case of the present method of manufacture in deoxidizer aluminum matrix composite. For a preferred weight ratio of aluminum to steel of 30 to 70, one may calculate the total weight of new deoxidizer replacing one kilogram of aluminum ingot or cone as 0.5 kilogram multiplied by 100 and divided by 30, which equals 1.66 kilogram. While the above description contains many specificities, these should not be construed as limitations on the scope of the method of manufacture, but rather as an exemplification of preferred embodiments thereof. Many other variations are possible. Accordingly, the scope of the method of manufacture should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.

Claims

CLAIMS What is claimed is:
1. A method for the manufacture of a steel deoxidizer aluminum matrix composite material comprising the steps of:
forming a porous free-standing preform, wherein the free-standing preform is comprised of aluminum and an iron-rich component;
applying a quantity of heat to the free-standing preform to raise the temperature of the free-standing preform above the melting point of aluminum and below the melting point of the iron-rich component; and
applying a quantity of pressure to densify the free-standing preform to a near full density and to allow for the aluminum in the free-standing preform to solidify.
2. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 1, wherein the iron-rich component is steel.
3. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 1 , wherein aluminum is present in the range of ten to fifty percent of the composite material by weight.
4. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 3, wherein aluminum is thirty percent of the composite material by weight.
5. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 1, wherein the free-standing preform is formed by a process selected from the group consisting of: mechanical pressing, briquetting, a container, an inorganic binder, and any combination thereof.
6. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 1, wherein the quantity of heat applied to the free-standing preform is sufficient to raise its temperature over six hundred sixty one degrees Celsius.
7. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 1 , wherein the quantity of heat applied to the free-standing preform is through a process selected from the group consisting of: induction heating, electrical resistance furnace heating, and organic fuel burner furnace heating, and any combination thereof.
8. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 1 , wherein the quantity of external pressure applied to the free-standing preform is sufficient for a molten aluminum component to fill porosity and gaps between the iron-rich components.
9. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 1, wherein the quantity of external pressure to densify the preform is applied by means of pressing in a closed die.
10. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 1, wherein the iron-rich component is selected from the group consisting of: ferromanganese, and a mixture of steel and ferromanganese.
11. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 10, wherein the free-standing preform is bound and supported by a process selected from the group consisting of: mechanical pressing, inorganic binder, a steel container, and any combination thereof.
12. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 11 , wherein the quantity of heat to the free-standing preform applied is through a process selected from the group consisting of: induction heating, electrical resistance furnace heating, and organic fuel burner furnace heating, and any combination thereof.
13. A method for the manufacture of a steel deoxidizer and inclusion modifier aluminum matrix composite material comprising the steps of:
forming a porous free-standing preform, wherein the free-standing preform is comprised of a plurality of fines of aluminum and a plurality of fines selected from the group consisting of: steel, ferromanganese, silicocalcium, calcium carbide, rare earth metals, any ferroalloy other than ferromanganese, and any combination thereof;
applying a quantity of heat to the free-standing preform to raise the temperature of the free-standing preform above the melting point of aluminum and below the melting point of other components of the free-standing preform; and
applying a quantity of pressure to densify the free-standing preform to a near full density and to allow for the aluminum in the free-standing preform to solidify.
14. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 13, wherein aluminum is present in the range of ten to fifty percent of the composite material by weight.
15. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 13, wherein aluminum is thirty percent of the composite material by weight.
16. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 13, wherein the free-standing preform is formed by a process selected from the group consisting of: mechanical pressing, briquetting, a container, an inorganic binder, and any combination thereof.
17. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 13, wherein the quantity of heat applied to the free-standing preform is sufficient to raise its temperature over six hundred sixty one degrees Celsius.
18. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 13, wherein the quantity of heat to the free-standing preform applied is through a process selected from the group consisting of: induction heating, electrical resistance furnace heating, and organic fuel burner furnace heating, and any combination thereof.
19. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 13, wherein the quantity of external pressure applied to the freestanding preform is sufficient for a molten aluminum component to fill porosity and gaps between the iron-rich components.
20. The method for the manufacture of a steel deoxidizer aluminum matrix composite material of claim 13, wherein the quantity of external pressure to densify the preform is applied by means of pressing in a closed die.
PCT/US2015/060560 2014-11-14 2015-11-13 A method for the manufacture of an efficient steel deoxidizer aluminum matrix composite material WO2016077685A1 (en)

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CN201580060332.1A CN107075597A (en) 2014-11-14 2015-11-13 Method for manufacturing effective killer aluminium matrix composite

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RU2269586C1 (en) * 2004-04-30 2006-02-10 Леонид Павлович Селезнев Method of preparation of master alloys and deoxidizers
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