KR101657464B1 - Method for manufacturing iron-based powders - Google Patents
Method for manufacturing iron-based powders Download PDFInfo
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- KR101657464B1 KR101657464B1 KR1020140100527A KR20140100527A KR101657464B1 KR 101657464 B1 KR101657464 B1 KR 101657464B1 KR 1020140100527 A KR1020140100527 A KR 1020140100527A KR 20140100527 A KR20140100527 A KR 20140100527A KR 101657464 B1 KR101657464 B1 KR 101657464B1
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Abstract
A method for producing an iron-based powder is disclosed. An embodiment of the present invention is a method of manufacturing a steel plate, comprising: preparing a steel-based powder having an oxide layer formed on its surface by spraying molten steel having a predetermined carbon content; Adding and mixing carbon into the iron-based powder; And reducing the oxidized layer by charging the carbon-mixed iron-based powder into a reducing furnace reducing furnace, wherein the reducing is performed by self-reduction by carbon in the iron-based powder, reduction by hydrogen in the reducing furnace Based powder is produced at the same time.
Description
One embodiment of the present invention relates to a method for producing an iron-based powder.
The parts manufacturing technology using the iron-based powder has advantages of increasing the dimensional accuracy of the final parts, facilitating mass production, and reducing machining and material loss.
In addition, since the component can be easily adjusted, the product performance can be maximized. Therefore, the importance of the component is increasing as a key technology in the precision parts and materials manufacturing industry.
Especially, by applying powder metallurgy process to automobile and electromechanical parts manufacturing, it can be produced at a cost of 40% or less compared with the conventional machining process.
Recently, with the development of the automobile and household appliances industries, the demand for iron powder sintered parts has increased, and the use of iron-based powders has been rapidly increasing. In order to manufacture sintered parts for automobiles, the powder itself must have high quality so as to produce high-density sintered bodies such as proper particle size, flowability, apparent density, molding density, and high cleanliness.
The manufacturing process of the iron-based powder is a water-spraying process of pulverizing molten metal by spraying high-pressure water onto the molten metal while falling molten metal through a tundish and a molten metal nozzle using a converter or an electric furnace, separating the powder and water A dehydration and drying process for removing water, a reduction process for removing an oxide layer on the surface of the powder produced during the water injection process, and a crushing and mixing process.
At this time, an important process that determines the composition and characteristics of the powder is a reduction process, which is a process that requires a large expense in the entire process. It has the limitation that it can not improve the final productivity because it acts as a bottleneck process because the processing speed of the reducing process is the slowest in the whole manufacturing process.
Therefore, in order to improve the economical efficiency in the production of the iron-based powder, it is necessary to more efficiently constitute the reducing process which occupies a large portion of the manufacturing cost.
An embodiment of the present invention is to provide a method of manufacturing an iron-based powder capable of shortening a reduction time by improving the rate at which an oxide layer is reduced in a reduction furnace.
Further, one embodiment of the present invention is to provide a method for producing an iron-based powder having excellent quality such as high cleanliness and high molding density.
An embodiment of the present invention is a method of manufacturing a steel plate, comprising: preparing a steel-based powder having an oxide layer formed on its surface by spraying molten steel having a predetermined carbon content; Adding and mixing carbon into the iron-based powder; And reducing the oxidized layer by charging the carbon-mixed iron-based powder into a reducing furnace reducing furnace, wherein the reducing is performed by self-reduction by carbon in the iron-based powder, reduction by hydrogen in the reducing furnace Based powder is produced at the same time.
The content of carbon in the molten steel may be more than 0 and not more than 3.0 wt%.
The molten steel is an alloy of iron (Fe) and molybdenum (Mo), and the content of molybdenum in the molten steel may be 0.001 to 10 wt%.
The amount of carbon added to the iron-based powder may be 0 to 3.0 wt% or less.
The inside of the reducing furnace may be maintained at a temperature of 800 to 1150 캜.
The hydrogen content in the hydrous atmosphere may be 20 to 100% by volume.
The submerged atmosphere may further comprise CO, N 2 , CH 4 , Ar, NH 3 , or a combination thereof.
The step of reducing the oxide layer may be performed for 10 to 90 minutes.
Charging the carbon-mixed iron-based powder into a reducing furnace in a reducing atmosphere to reduce the oxidized layer; Thereafter, the iron-based powder may be quenched.
According to the method of producing an iron-based powder according to an embodiment of the present invention, the reduction time can be shortened by improving the rate at which the oxide layer is reduced in the reduction furnace, and thus the production amount per unit time can be increased in the same facility.
Further, according to the method for producing an iron-based powder according to an embodiment of the present invention, it is possible to provide an iron-based powder having high quality such as high cleanliness and high molding density.
1 is a configuration diagram of a belt-type reduction furnace according to an embodiment.
2 is a graph showing oxygen concentrations according to the concentration of Fe-Mo alloy powder, pure Fe powder, and conventional commercialized Hoganas powder (Astaloy Mo: 1.5%) manufactured according to an embodiment of the present invention .
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.
In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.
In addition, since the sizes and thicknesses of the respective components shown in the drawings are arbitrarily shown for convenience of explanation, the present invention is not necessarily limited to those shown in the drawings.
Also, throughout the specification, when an element is referred to as "including" an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.
One embodiment of the present invention includes the steps of: (a) preparing an iron-based powder having an oxide layer formed on its surface by spraying molten steel having a predetermined carbon content; (B) charging carbon into the iron-based powder and mixing them; And (c) charging the iron-based powder mixed with carbon into a reducing furnace under a humid atmosphere to reduce the oxidized layer, wherein the reduction is performed by self-reduction by carbon in the iron-based powder, Wherein the reduction of the iron powder is performed simultaneously with the reduction of the iron powder.
First, step (a) is performed in which molten steel having a predetermined carbon content is injected to prepare an iron-based powder having an oxide layer formed on its surface.
The molten steel having undergone the component adjustment through the steelmaking process in the converter is introduced into the ladle, and the molten steel is spouted in the tandem tile under the ladle.
Then, the molten steel is dropped into the lower water jetting process chamber through a circular ceramic orifice (nozzle) having an inner diameter of 8 to 40 mm located at the bottom of the tundish.
At this time, the carbon content in the molten steel is preferably more than 0 and 3.0 wt% or less. If the carbon content in the molten steel is more than 3.0 wt%, the carbon content in the iron-based powder after the reduction is excessive, and the quality of the iron-based powder may be deteriorated due to the carbon remaining in the iron-based powder after the reduction. In addition, if the final iron-based powder has a high carbon content, the strength may increase and subsequent molding processes may be difficult.
In addition, the molten steel may be alloyed by adding molybdenum (Mo) to the pure steel molten steel, and molybdenum may be dissolved in the iron powder to improve strength and hardness.
Here, the molybdenum content to be added may be 0.001 to 10 wt%. When the content of molybdenum is less than 0.001 wt%, the hardenability and the corrosion resistance are not advantageous as compared with the pure iron powder. When the content exceeds 10 wt%, it is difficult to manufacture parts due to problems such as strength during molding. Preferably, molybdenum may be added in an amount of 0.5 to 1.5 wt%.
The surface of the iron-based powder produced by the water jetting process reacts with air and oxygen contained in moisture to form an oxide layer of iron oxide (FeO).
(b) of injecting and mixing carbon into the iron-based powder prepared in the step (a).
In step (b), a recarburizer may be added to the iron-based powder to have a target carbon content. For example, both spherical and irregular types of carbon may be used, and their particle size is preferably smaller than that of the iron-based powder. Alternatively, carbon may be introduced through a reducing gas atmosphere such as CO or CH 4 . C, it is possible to make an alloy such as Molycarbide when the carbon is added. Therefore, if the carbon is introduced in the CO atmosphere, the process time should be selectively controlled during the reduction process . In addition, since there is a problem that carbon is deposited when a reducing gas such as CO or CH 4 is injected at a low temperature (about 950 ° C or less), a reducing gas must be injected by selectively controlling the temperature condition when the reducing gas is injected.
The recarburizer may be introduced into the molten steel in the step (a).
At this time, it is preferable that the amount of carbon to be added to the iron-based powder is more than 0 and 3.0 wt% or less. When the amount of carbon is more than 3.0 wt%, it is difficult to mold due to high strength, which may result in downgrading of parts density.
(c) charging the iron-based powder mixed with carbon in a reducing furnace atmosphere in step (b) to reduce the oxide layer.
Here, in the step (c), the reducing process may be a conveyor belt type.
At this time, the content of hydrogen in the submerged atmosphere is preferably 20 to 100% by volume. The submerged atmosphere may further include CO, N 2 , CH 4 , Ar, NH 3 , or a combination thereof in addition to hydrogen.
For example, the submerged atmosphere may be an H 2 -N 2 mixed gas atmosphere. In this case, as the content of H 2 in the H 2 -N 2 mixed gas increases, the reduction rate is high and the reduction time is shortened. However, when the content exceeds 50 vol%, the effect of the reduction efficiency on the increase in H 2 is insignificant, 2 is preferably 20 to 50% by volume.
The inside of the reducing furnace is preferably maintained at a temperature of 800 to 1150 캜. When the temperature inside the reducing furnace is lower than 800 ° C, reduction is difficult. When the temperature is higher than 1150 ° C, there is a problem that Mo content control is difficult due to the volatilization problem of Mo.
The step (c) is preferably performed for 10 to 90 minutes. When the reduction time is less than 10 minutes, there is a problem in that the reduction is in the initial stage and therefore it is not reached at the completion of the reduction. When the reduction time is more than 90 minutes, the reduction is already completed.
Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are only illustrative of the present invention and are not intended to limit the scope of the present invention.
Experimental Example
The carbon contents in the aqueous Fe-Mo alloy powders (Mo: 1.52 wt%, O: 2.28 wt%, and C: 0.023 wt%) were further mixed at 0.05, 0.1, 0.2 and 0.5 wt% And to confirm the influence of methane. Thereafter, in order to prevent loss of MoO 3 in the reduction furnace, the reduction furnace was controlled at a temperature of 1100 ° C., and reduction with carbon mixed with the Fe-Mo alloy powder and reduction with hydrogen in the furnace were simultaneously performed A mixed gas atmosphere of H 2 -N 2 (50% by volume of H 2 and 50% by volume of N 2 ) was formed. The reduction time was 60 minutes. After the reduction, the reaction was quenched to prevent the reaction from progressing. The experiment was carried out in a belt type furnace, and an example of an experimental apparatus is shown in Fig.
The in-furnace chemical reactions occurring during the reduction of Fe-Mo alloy powders are as follows.
FeO + C = Fe + CO
FeO + CO = Fe + CO 2
FeO + H 2 = Fe + H 2 O
MoO 3 + 3C = Mo + 3CO
MoO 3 + 3CO = Mo + 3CO 2
MoO 3 + 3H 2 = Mo + 3H 2 O
Fe 2 MoO 4 (s) + 4H 2 (g) = Fe 2 Mo (s) + 4H 2 O (g)
After the experiment, the concentration of oxygen and carbon in the powder was measured to evaluate the degree of reduction of the powder.
2 is a graph showing the oxygen concentration (wt%) of Fe-Mo alloy powder, pure Fe powder and conventional commercial Hoganas powder (Astaloy Mo: 1.5%) according to the present invention, Fig.
Referring to FIG. 2, the Fe-Mo alloy powder prepared according to an embodiment of the present invention under the same conditions has a better reduction ratio than that of pure Fe powder, and the Hoganas powder (Astaloy Mo: 1.5 wt% ), It can be seen that the oxygen concentration is small. Oxygen concentration was the lowest at 0.2 wt%.
Table 1 shows the oxygen and carbon concentrations of Fe-Mo alloy powder prepared according to one embodiment of the present invention and conventional commercialized Hoganas powder (Astaloy Mo: 1.5 wt%).
Referring to Table 1, it can be seen that the carbon concentration in the Fe-Mo alloy powder produced according to one embodiment of the present invention is also smaller than that of the conventional Hoganas powder (Astaloy Mo: 1.5 wt%).
Therefore, according to the present invention, it can be understood that Fe-Mo alloy powder of high purity can be manufactured compared to Hoganas powder which is commercially available.
It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.
Claims (9)
Adding and mixing carbon into the iron-based powder; And
And charging the carbon-mixed iron-based powder into a belt-type reduction furnace in a hydrous atmosphere to reduce the oxide layer,
Wherein the molten steel is an alloy of iron (Fe) and molybdenum (Mo), the content of molybdenum in the molten steel is 0.001 to 10 wt%
The amount of carbon to be added to the iron-based powder is more than 0 and not more than 3.0 wt%
Wherein said reduction causes self-reduction by carbon in the iron-based powder and reduction by hydrogen in said belt-type reduction furnace simultaneously.
Wherein the content of carbon in the molten steel is 0 to 3.0 wt%.
Wherein the inside of the belt type reduction furnace is maintained at a temperature of 800 to 1150 占 폚.
Wherein the content of hydrogen in the hydrous atmosphere is 20 to 100% by volume.
Wherein the submerged atmosphere further comprises CO, N 2 , CH 4 , Ar, NH 3 , or a combination thereof.
Reducing the oxide layer,
Based powder for 10 to 90 minutes.
Charging the carbon-mixed iron-based powder into a belt-type reduction furnace in a reducing atmosphere to reduce the oxide layer; Since the,
And rapidly cooling the iron-based powder.
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