Patent Application
20090277304
The present invention relates to a process for production of an Fe-based amorphous alloy at a low cost.
Amorphous alloy ribbons whose base component system is Fe—B—Si have excellent properties as electromagnetic materials. When used as an iron core material in an electric power transformer, such an amorphous alloy ribbon can lower core loss to about ⅓ that when using conventional grain-oriented Si-steel sheet. However, the implementation of the mass production of Fe—B—Si amorphous alloy ribbons has been slow.
One of the main reasons for this may be that the cost of the amorphous alloy ribbons is much higher than that of Si-steel sheet. Most of the cost is accounted for by the Fe—B or other main raw material.
A method for inexpensive production of amorphous alloy is described in Japanese Patent Publication (A) No. S58-77509 which provides a process for smelting reduction of boron oxide or boric acid and iron oxide using a carbon-based solid reducing agent such as coke. However, owing to the use of a carbon reducing agent, this method has a problem in that when it is attempted to directly produce the amorphous alloy to optimum B and Si contents for obtaining a steel with good electromagnetic properties, the C content comes to exceed the optimum range.
For overcoming this problem, Japanese Patent Publication (A) No. S59-38353 describes a method of once producing a matrix alloy with high B and Si contents so that a C content in the optimum range can be obtained and thereafter diluting the B and Si with a separately produced molten steel. However, since the product is obtained via the matrix alloy with a high B content, this method shortens the service life of the melting furnace refractory and increases raw material consumption per unit product because B reduction yield is lowered. Japanese Patent Publication (A) No. S62-287040 further describes a method for overcoming these problems by adjusting the composition of the matrix alloy to a somewhat low B content and high Si content.
However, the above-described methods all reduce B, Si and Fe oxides with carbon. Such methods can thus be flawed in the point of requiring great reductive energy and also in the point that they increase refractory cost tremendously because the reductive energy is obtained by using a hot air blast to burn the carbon, thus producing a high temperature that forms a molten slag made of B, Si and Fe oxides that readily causes fusion damage of the refractory.
Other general methods for producing Fe—B as a B raw material can include methods that perform refining by the aluminum thermite reaction or the electric furnace method. However, the electric furnace method consumes significant amount of electric power, likely resulting in high power costs and increasing the cost of amorphous alloy production. Although the aluminum thermite method is low in production cost, the resulting Fe—B includes Al and Ti, and an amorphous alloy produced using the Fe—B is therefore increased in Ti concentration and Al concentration. As increased Ti and Al concentration is known to degrade magnetic properties, Fe—B produced by the aluminum thermite reaction cannot be used to produce amorphous alloys until cheap removal of Ti and Al becomes possible.
Although it is also possible to lower production cost by using scrap Si-steel sheet or the like as the starting material containing Fe and Si, such scrap is difficult to use for amorphous alloy because the Al contamination of the scrap similarly increases the Al concentration of the amorphous alloy.
Accordingly, there may be a need to address and/or overcome at least some of the deficiencies described herein above.
In view of the previously-described problems, [0013] Exemplary embodiments of the present invention can be provided with an exemplary process for production of an Fe-based amorphous alloy ribbon at low cost by efficiently removing magnetic-property-degrading Al and Ti when using inexpensive Fe—B or scrap as an amorphous alloy raw material.
An exemplary embodiment of the present invention for overcoming such problems can provide a process for production of an Fe-based amorphous alloy comprising, by mass, about 2 to 4% of B, about 1 to 6% of Si, and a balance of Fe and unavoidable materials. Using such exemplary process, it is possible to determine whether a molten alloy obtained by melting a main raw material has a Ti concentration or Al concentration of about 0.005 mass % or greater. When it does, it is possible to add thereto an iron oxide source having an iron content of about 55 mass % or greater to reduce both Ti and Al to less than about 0.005 mass % by oxidative removal.
According to another exemplary embodiment of the present invention, a process can be provided for a production of an Fe-based amorphous alloy comprising, by mass, about 2 to 4% of B, about 1 to 6% of Si, and a balance of Fe and unavoidable materials. This exemplary process can determine whether a main raw material has a composition whose Ti concentration or Al concentration is 0.005 mass % or greater. When such result is obtained, it is possible to precharge an iron oxide source having an iron content of about 55 mass % or greater into a melting vessel together with the main raw material.
According to yet another exemplary embodiment of the present invention, the Fe-based amorphous alloy can further include, by mass, one or both of about 0.001 to 3% of C and/or about 0.008 to 0.15% of P. Further, Fe can be partially replaced by at least one of Co plus Ni of at most about 20% of Fe content and Cr of not greater than about 6% of Fe content.
These and other objects, features and advantages of the present invention will become apparent upon reading the following detailed description of embodiments of the invention, when taken in conjunction with the appended claims.
Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying figure showing illustrative embodiment(s), result(s) and/or feature(s) of the exemplary embodiment(s) of the present invention, in which:
Throughout the figures, the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components or portions of the illustrated embodiments. Moreover, while the present invention will now be described in detail with reference to the figures, it is done so in connection with the illustrative embodiments.
According to an exemplary embodiment of the present invention, using a small melting furnace, it can be determined that addition of iron oxide to an Fe-based amorphous alloy raw material during melting provide an efficient oxidative removal of Ti and Al. Ti and Al are oxidized preferentially relative to B or Si constituting the main components of the amorphous alloy and can therefore be oxidatively removed without significantly reducing B or Si yield.
In one exemplary embodiment of the present invention, a main raw material mixed with the required B and Si components can be melted in a melting furnace. When a molten alloy has been formed, Ti and Al can be oxidatively removed by adding an iron oxide source containing at least 55 mass % of iron.
In a small-scale experiment, an amorphous alloy raw material containing B: about 3.2 mass % and Si: about 1.8 mass % was produced in a melting furnace, the temperature of the molten alloy was raised to about 1,500° C., and an iron oxide source was added at the rate of, by mass, about 50 kg per ton of molten alloy. The experiment was conducted using various iron oxide sources. A graph of certain results of the time-course changes in the concentrations of Ti and Al in the molten alloy is provided in
However, the speed of Ti and Al oxidative removal decreased in proportion as the iron oxide source was lower in iron content and higher in content of gangue constituents other than iron oxide. On the other hand, when steelmaking dust of an iron concentration of less than about 55% was used as the iron oxide source, the Ti and Al oxidative removal speed was slow and Ti was not reduced to less than about 0.005 mass %. A production cost analysis was carried out taking into account the amount of added iron oxide source required, refining time, slag treatment expense owing to increase in generated slag volume from gangue and the like, and other factors. The results showed that the effect can be small unless the iron concentration is about 55% or greater.
The holding time after iron oxide source refining can depends on the amount of iron oxide source used, and may be preferably about 15 min or longer.
In another exemplary embodiment of the present invention, an iron oxide source containing at least about 55 mass % of iron can be precharged into a melting furnace together with a main raw material prepared to include the required B and Si contents. Thereafter, melting may be conducted to produce an amorphous alloy raw material. When the dust collection capability of the melting furnace is low, this exemplary embodiment can be preferably adopted because the prior-described exemplary embodiment in which the iron oxide source can be added after producing the molten alloy may generate dust at the time of the addition.
Table 1 shows exemplary Ti and Al concentrations of the molten alloy when, in the small-scale experiment discussed earlier, the various iron oxide sources were precharged into the melting furnace at the rate of, by mass, about 50 kg per ton of molten alloy and melted together with the main raw material. The temperature at 10 min after meltdown was about 1,370 to 1,380° C. If Ti and Al had not been removed, their concentrations would have stayed the same as the initial values in
With respect to exemplary embodiments of the present invention, the Fe-based amorphous alloy and its content ranges are explained below. Unless specifically indicated, all content ranges are expressed in mass %.
B can effectively improve amorphous phase forming ability and thermal stability. It may be added in an amount suitable in light of the property requirements. When B content is less than about 2%, amorphous phase cannot be obtained stably, and when it exceeds about 4%, the melting point rises to make amorphous phase formation difficult.
Si can also effectively improve amorphous phase forming ability and thermal stability. It may be added in an amount suitable in light of the property requirements. When Si content is less than about 1%, amorphous phase cannot be obtained stably, and when it exceeds about 6%, its effect of improving thermal stability saturates.
C can effectively enhances the magnetic flux density of amorphous alloy ribbon and improves amorphous phase forming ability (improves castability). Its content is decided as a suitable amount in light of the property requirements. The wettability between the molten alloy and the cooling substrate can be improved to form a good amorphous alloy ribbon by making the C content 0.001% or greater and preferably 0.003% or greater. In addition, C content is preferably made 0.01% or greater, because an effect of improving amorphous phase forming ability is obtained. When C content exceeds 3%, the effect of enhancing magnetic flux density declines.
P can effectively improves core loss property and amorphous phase forming ability. P may be included in an amount suitable in light of the property requirements. Although presence of P can improve core loss property and amorphous phase forming ability, and may increase the allowable content of impurity elements, the effects of amorphous phase forming ability improvement and core loss property improvement may not be observed at a P content of less than about 0.008%. In addition, the effect of increasing the allowable content of the impurity elements Mn and S may not be exhibited. With increasing amount of P addition, cracks more readily propagate in the amorphous alloy ribbon, thereby degrading workability. Therefore, to avoid such problem, P content may be preferably about 0.15% or less.
Moreover, the effect of the exemplary embodiment of the present invention is not particularly impaired when for the purpose of improving magnetic flux density, corrosion resistance property, annealing conditions and the like, the Fe of the composition of the exemplary embodiment of the present invention Fe-based amorphous alloy can be partially replaced by at least one of Co plus Ni of at most about 20% of the Fe content and Cr of not greater than about 6% of the Fe content. Although Co and Ni can effectively improve magnetic flux density, they are expensive, so that from the viewpoint of raw material cost, the replacement of Fe thereby may be preferably held to about 10% or less and also preferably to about 5% or less of the Fe content.
Moreover, the effect of the exemplary embodiment of the present invention is in no way impaired by including in the composition of the invention Fe-based amorphous alloy as constituent elements not only Fe, B, Si, C, P, Ni, Co and Cr and also known constituents such as N, Ti, Zr, V, Nb, Mo, and Cu.
Ti and Al can decline to less than about 0.005 mass % insofar as the temperature is equal to or higher than the matrix melting point but that the higher the temperature, the better is the Ti and Al oxidation efficiency, the lower is the final Ti and Al concentration, and the better are the B and Si yields. However, the higher the temperature, the greater is the amount of electric power needed for melting and the greater is the melting furnace refractory cost. The molten alloy temperature may therefore be preferably lowered to the level at which the required amount of Ti and Al oxidative removal can be achieved.
The exemplary embodiments of the present invention can be explained based on the following examples.
Amorphous alloy raw material produced using a 3-ton class high-frequency melting furnace were subjected to Ti and Al oxidative refining. As main raw material was used low-cost magnetic steel scrap and Fe—B of the compositions shown in Table 2. Certain amount of Fe—Si was used for Si concentration adjustment. The amounts of the raw materials per unit mass are also shown in Table 2.
The main raw materials were melted and the molten alloy was then heated to 1,500° C. In the Invention Examples, as shown in Table 3, the same iron oxide sources as used in the small-scale experiment, namely, iron ore (Mount Newman: iron content of 65 mass %), steelmaking dust (dust occurring during decarburization treatment: iron content of 64 mass %), and sintered ore (iron content of 58 mass %), were each added in an amount of 150 kg (50 kg/t) and the melt was tapped 20 min thereafter. In certain Examples, C, P, Co, Ni and Cr were added to the main raw material for property improvement. Specifically, the molten composition after melting was made to contain one or both of C: about 0.001 to 3% and P: about 0.008 to 0.15%, and/or the Fe thereof was partially replaced by one or more among Co plus Ni of not greater than about 20% of the Fe content and Cr of not greater than about 6% of the Fe content. A refining operation was also similarly conducted. In the Comparative Examples, the same or similar method was used except that the refining treatment was conducted with addition of iron oxide sources having an iron content of less than 55 mass %, e.g., about 150 kg of steelmaking dust (e.g., dust occurring during hot metal pretreatment: iron content of about 53 mass %) or mixed steelmaking dust and slag.
Table 3 shows the compositions of the molten alloys sampled just before iron oxide source addition and Table 4 shows the compositions of the molten alloys just before tapping. The Exemplary Embodiment, which used iron oxide sources having iron content of 55 mass % or greater, had their concentrations of both Ti and Al lowered to less than 0.005 mass %, a level at which no effect on magnetic properties is observed. They were also found to be low in B and Si oxidative loss and have yields of 95% or greater relative to the initial mixing proportions. Moreover, in cases where the composition contained one or both of C: 0.001 to 3% and P: 0.008 to 0.15%, and the case where the Fe thereof was partially replaced by at least one of Co plus Ni of at most 20% of the Fe content and Cr of not greater than 6% of the Fe content, these effects were not impaired. In contrast, in the Comparative Embodiment, which used iron oxide sources having iron content of less than 55 mass %, the B and Si yields were on the same level but Ti concentration or Al concentration was 0.005 mass % or greater.
Raw material of the same kind in the same amount as used in Example 1 was charged into a 3-ton class high-frequency melting furnace together with an iron oxide source that, as shown in
Table 5 shows the compositions of the molten alloys after meltdown and Table 6 shows their compositions just before tapping. The Exemplary Embodiments, which used iron oxide sources having iron content of 55 mass % or greater, had their concentrations of both Ti and Al lowered to less than 0.005 mass %, a level at which no effect on magnetic properties is observed, from the stage in which the material melted down, and the Ti and Al concentrations decreased still further at the tapping stage after temperature increase. They were also found to be low in B and Si oxidative loss and have yields of 92% or greater relative to the mixing proportions before tapping. Moreover, in case where the composition contained one or both of C: 0.001 to 3% and P: 0.008 to 0.15%, and the case where the Fe thereof was partially replaced by one or more among Co plus Ni of not greater than 20% of the Fe content and Cr of not greater than 6% of the Fe content, these effects were not impaired. In contrast, in the Comparative Embodiments, which used iron oxide sources having iron content of less than 55 mass %, the B and Si yields were on the same level but Ti concentration or Al concentration was 0.005 mass % or greater.
The exemplary embodiments of the present invention provides a process for production of an amorphous alloy at low cost by efficiently removing magnetic-property-degrading Al and Ti when using inexpensive Fe—B or scrap as an amorphous alloy raw material.
The foregoing merely illustrates the exemplary principles of the present invention. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous modification to the exemplary embodiments of the present invention which, although not explicitly shown or described herein, embody the principles of the invention and are thus within the spirit and scope of the invention. All publications, applications and patents cited above are incorporated herein by reference in their entireties.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-108422 | Apr 2006 | JP | national |
This application is a national stage application of PCT Application No. PCT/JP2007/058121 which was filed on Apr. 6, 2007, and published on Oct. 25, 2007 as International Publication No. WO 2007/119806 (the “International Application”). This application claims priority from the International Application pursuant to 35 U.S.C. § 365, and from Japanese Patent Application No. 2006-108422 filed Apr. 11, 2006, under 35 U.S.C. § 119. The disclosures of the above-referenced applications are incorporated herein by reference in their entities.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/058121 | 4/6/2007 | WO | 00 | 10/10/2008 |
