KR20160080823A - Iron-based diffusion bonded powders and method for manufacturing the same - Google Patents

Abstract

Disclosed are an iron-based diffusion bonding powder, and a method for manufacturing the same. One embodiment of the present invention provides the method for manufacturing the iron-based diffusion bonding powder, comprising: a step of injecting water to molten steel to manufacture iron-based powder of which a surface is oxidized; a step of mixing the iron-based powder and molybdenum-based powder; and a step of obtaining iron-based diffusion bonding powder by thermally treating the mixed powder in reducing atmosphere. The step of obtaining iron-based diffusion bonding powder by thermally treating the mixed powder in reducing atmosphere reduces the mixed powder and enables the reduced molybdenum-based powder to be diffusion-bonded to a surface of the reduced iron-based powder.

Description

FIELD OF THE INVENTION The present invention relates to iron-based diffusion bonded powders,

One embodiment of the present invention relates to an iron-based diffusion bonded powder and a method of manufacturing the same.

Recently, the demand for automobile parts using powder metallurgy is increasing. This is because the mechanical properties are lower than that of the processed parts, but precise and complex parts can be mass-produced at low cost. Particularly, in order to manufacture sintered parts for automobiles, a sintered body which is light in weight and exhibits properties of high strength and high toughness is required.

In general, iron-based sintered parts manufactured by powder metallurgy are superior in quality and economical to those manufactured by forging or rolling. However, due to the nature of the manufacturing process, sintered products necessarily form pores in the product, and these residual pores degrade the mechanical properties of the sintered product. This is because the pores act as a stress concentration portion and reduce the effective volume to receive stress.

Accordingly, many techniques for producing iron-based alloy powder by adding various metals to iron-based sintered parts have been developed in order to prevent deterioration of properties due to pores. In particular, carbon, copper, and molybdenum are alloying elements that are mainly added to pure iron powder, which affects the mechanical properties, moldability, and sinterability of the sintered body and is mixed at an appropriate ratio.

Examples of the method for producing the alloy include simple mixing using a general mixer, and preliminary alloying by adding an alloy element to the molten steel state.

However, these methods have various problems such as generation of segregation or deterioration of moldability, and a method of producing a diffusion bonded powder in which an additive metal is diffused and bonded to the surface of an iron-based powder is used.

In one embodiment of the present invention, when the additive elements are diffused and bonded on the basis of the iron-based powder, the particle size of the powder, the process temperature, and the atmosphere in the furnace are controlled under optimum bonding process conditions, An iron-based diffusion bonded powder excellent in strength and toughness, and a method for producing the same.

One embodiment of the present invention is a method

Water-spraying molten steel to produce an iron-based powder whose surface is oxidized;

Mixing the iron-based powder and the molybdenum-based powder; And

Heat-treating the mixed powder in a reducing atmosphere to obtain an iron-based diffusion bonded powder;

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Heat-treating the mixed powder in a reducing atmosphere to obtain an iron-based diffusion bonded powder;

Wherein the mixed powder is reduced and the reduced molybdenum powder is diffused and bonded to the surface of the reduced iron-based powder.

A method for producing an iron-base diffusion bonded powder is provided.

The content of carbon (C) in the molten steel may be more than 0 and 3.0 wt% or less.

Water-spraying the molten steel to produce an iron-based powder whose surface is oxidized; And then adding carbon (C) to the water-injected iron-based powder.

The molybdenum-based powder may include molybdenum (Mo) powder, molybdenum oxide (MoO _x ) powder, or a combination thereof.

The content of the molybdenum-based powder to the mixed powder may be 0.2 to 10 wt%.

The reducing atmosphere may be a hydrogen (H ₂ ) gas atmosphere or a mixed gas atmosphere containing hydrogen (H ₂ ).

The mixed gas atmosphere may further include nitrogen (N ₂ ), carbon monoxide (CO), methane (CH ₄ ), argon (Ar), ammonia (NH ₃ ), or a combination thereof.

The heat treatment may be performed in a temperature range of 600 to 1,050 占 폚.

The heat treatment may be performed for 10 to 90 minutes.

Heat-treating the mixed powder in a reducing atmosphere to obtain an iron-based diffusion bonded powder; Thereafter, quenching the obtained iron-based diffusion bonded powder may be further included.

The content of molybdenum (Mo) with respect to the iron-base diffusion bonded powder may be 0.001 to 10 wt%.

The molybdenum (Mo) content of the iron-based diffusion bonded powder may be 0.2 to 10 wt%.

In the iron-based diffusion bonded powder, the diffusion bonding thickness of the reduced iron-based powder and the reduced molybdenum-based powder may be 1 to 6.5 탆.

Another embodiment of the present invention provides an iron-based diffusion bonded powder produced by the above-described method for producing an iron-based diffusion bonded powder, wherein molybdenum (Mo) powder is diffusion bonded to the surface of iron (Fe) powder.

The content of molybdenum (Mo) with respect to the iron-base diffusion bonded powder may be 0.001 to 10 wt%.

The molybdenum (Mo) content of the iron-based diffusion bonded powder may be 0.2 to 10 wt%.

In the iron-based diffusion bonded powder, the diffusion bonding thickness of the reduced iron-based powder and the reduced molybdenum-based powder may be 1 to 6.5 탆.

According to one embodiment of the present invention, when joining the additive elements based on the iron-based powder, the grain size of the powder, the process temperature, and the atmosphere in the furnace are controlled under the optimum joining process conditions, Based diffusion bonded powder excellent in strength and toughness, and a method for producing the same.

According to one embodiment of the present invention, it is possible to provide an iron-based diffusion bonded powder and a method of manufacturing the same that can reduce the oxidation layer of the iron-based powder and can perform the diffusion bonding and increase the production amount per unit time.

Also, according to one embodiment of the present invention, there can be provided an iron-based diffusion bonded powder capable of producing a bonded powder having excellent bonding conditions and a low concentration of impurities, and a method for producing the same.

1 is a block diagram of a belt-type reduction furnace according to an embodiment of the present invention.
FIG. 2 is a graph showing the relationship between Fe-Mo diffusion bonding powder prepared according to an embodiment of the present invention and DAB (1.5 wt% Cu-1.75 wt% Ni-0.5 wt% (wt%) with respect to the total amount (wt% Cu-4.0 wt% Ni-0.5 wt% Mo).
FIG. 3 is a graph illustrating the relationship between Fe-Mo diffusion bonding powder prepared according to an embodiment of the present invention and DAB (1.5 wt% Cu-1.75 wt% Ni-0.5 wt% (wt%) with respect to the carbon content (wt% Cu-4.0 wt% Ni-0.5 wt% Mo).
FIG. 4 is a view showing a diffusion bonding site of Fe-Mo diffusion bonded powder prepared by using Mo powder and heat treatment at 900 ° C. for 1 hour according to an embodiment of the present invention.
FIG. 5 is a view showing a diffusion bonding region of Fe-Mo diffusion bonded powder prepared by using the Mo powder and annealing at 1,000 ° C. for 1 hour according to an embodiment of the present invention.
FIG. 6 is a view showing a diffusion bonding site of Fe-Mo diffusion bonded powder prepared by using MoO ₃ at 900 ° C. for 1 hour according to an embodiment of the present invention.
FIG. 7 is a view showing a diffusion bonding region of Fe-Mo diffusion bonded powder prepared by using a Mo powder and heat-treating at 900 ° C. for 2 hours according to an embodiment of the present invention.
FIG. 8 is a view showing a diffusion bonding site of the Fe-Mo diffusion bonded powder prepared by using the Mo powder and heat-treating at 1,000 ° C. for 2 hours according to an embodiment of the present invention.
9 is a view showing a diffusion bonding site of Fe-Mo diffusion bonded powder prepared by using MoO ₃ at 900 ° C for 2 hours according to an embodiment of the present invention.
10 is a view showing a diffusion bonding site of Fe-Mo diffusion bonded powder produced by using MoO ₃ according to an embodiment of the present invention and annealing at 1,000 ° C for 2 hours.

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.

The present invention relates to a method and apparatus for controlling the grain size, process temperature and in-furnace atmosphere of a powder by diffusion bonding of an additive element based on an iron-based powder under optimum bonding conditions, And to provide a method for producing a superior diffusion bonded powder.

One embodiment of the present invention is a method of manufacturing a steel sheet, comprising the steps of: water jetting molten steel to produce an iron-based powder whose surface is oxidized; Mixing the iron-based powder and the molybdenum-based powder; And heat-treating the mixed powder in a reducing atmosphere to obtain an iron-based diffusion bonded powder, wherein the step of heat-treating the mixed powder in a reducing atmosphere to obtain an iron-based diffusion bonded powder comprises: reducing the mixed powder, And the reduced molybdenum powder is diffused and bonded to the surface of the reduced iron-based powder. The present invention also provides a method for producing the iron-based diffusion bonded powder.

Another embodiment of the present invention provides an iron-based diffusion bonded powder produced by the above-described method for producing an iron-based diffusion bonded powder, wherein molybdenum (Mo) powder is diffusion bonded to the surface of iron (Fe) powder.

In this case, the content of molybdenum in the iron-base diffusion bonded powder may be 0.001 to 10 wt%, more specifically 0.2 to 10 wt%. When the content of molybdenum in the iron-base diffusion bonded powder is within the above range, the improved strength change of the powder itself is acceptable at the time of molding and the sintering strength can be greatly improved.

The diffusion bonding thickness of the reduced iron-based powder and the reduced molybdenum-based powder in the iron-based diffusion bonded powder may be 1 to 6.5 탆. When the diffusion bonding thickness is within the above range, there is an advantage that the molding strength at the time of molding is excellent at a later stage, and that it is stable from the risk of falling off of the bonded components.

Hereinafter, a method of manufacturing the iron-based diffusion bonded powder according to one embodiment of the present invention will be described in detail.

The method of manufacturing an iron-based diffusion bonded powder according to an embodiment of the present invention includes mixing an iron-based powder having an oxide layer formed on its surface with a molybdenum-based powder and then heat-treating the powder in a reducing atmosphere to simultaneously perform reduction and bonding of the powder. .

First, the process of forming the oxide layer on the surface of the iron-based powder will be described.

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.

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 exceeds 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.

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).

Alternatively, in an embodiment of the present invention, after forming an oxide layer on the surface of the iron-based powder, carbon (C) may be added to the water-added iron-based powder.

More specifically, a recarburizer may be added to the water-sprayed iron-based powder to have a target carbon content. For example, both the spherical and irregular forms of carbon may be used, and the particle size of the carbon 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 . When carbon is added in the CO atmosphere, it is necessary to selectively control the process time during the reduction process because the alloy can be made into the product by reducing the carbon in the CO atmosphere containing carbon.

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.

At this time, the amount of carbon to be added to the iron-based powder is preferably 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.

Meanwhile, the recarburizer described above may be introduced into the molten steel.

Thereafter, the iron-based powder having the oxide layer formed on its surface is mixed with the molybdenum-based powder.

The molybdenum-based powder may include molybdenum (Mo) powder, molybdenum oxide (MoO _x ) powder, or a combination thereof. Since molybdenum oxide such as molybdenum dioxide (MoO ₂ ) or molybdenum trioxide (MoO ₃ ) can easily be reduced to molybdenum, it can be used as an effective bonded powder considering the bonding energy and diffusion coefficient of each atom.

At this time, the content of the molybdenum-based powder relative to the mixed powder may be 0.2 to 10 wt%. When the content of the molybdenum-based powder in the mixed powder is within the above range, an improved strength change of the powder itself is acceptable at the time of molding and there is an advantage that the sintering strength can be greatly improved.

Thereafter, the iron-based powder, the molybdenum-based powder and the mixed powder are heat-treated in a reducing atmosphere to reduce the iron-based powder and the molybdenum-based powder, and simultaneously the reduced molybdenum-based powder, that is, the molybdenum powder, Diffusion bonding to the surface of the iron powder.

The oxidation reaction of the iron-based powder and the molybdenum-based powder can be removed through the reduction reaction and the bonding reaction between the powders. Thus, when the final powder is obtained, oxygen is removed from the surface, or an iron-based diffusion containing only a trace amount of oxygen A bonded powder can be produced.

For example, the heat treatment in the reducing atmosphere may be performed using a conveyor belt furnace.

More specifically, the reducing atmosphere may be a hydrogen atmosphere (H ₂ ) gas atmosphere or a mixed gas atmosphere containing hydrogen (H ₂ ). The mixed gas atmosphere may further include nitrogen (N ₂ ), carbon monoxide (CO), methane (CH ₄ ), argon (Ar), ammonia (NH ₃ ), or a combination thereof in addition to hydrogen.

For example, the mixed gas atmosphere may be a mixed gas atmosphere of H ₂ -N ₂ . In this case, H ₂ -N ₂ When the content of H _{2 in} the mixed gas is increased, the reduction rate is high and the reduction time is shortened. However, when the content of H ₂ is included, the effect of the reduction efficiency is insignificant, so that it can be appropriately adjusted within 1 to 100 vol%.

The heat treatment may be performed in a temperature range of 600 to 1,050 DEG C for 10 to 90 minutes. The iron-based powder and the molybdenum-based powder can be easily reduced in the temperature range described above. 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 mixed powders of iron powder (95 wt%) and nickel powder (5 wt%) each having an oxide layer formed on its surface were controlled at molar ratios of about 70 to 80 mu m at 830 DEG C, 900 DEG C, , And the oxygen concentration and carbon concentration of the bonding site and final powder were analyzed after joining the iron powder and the molybdenum powder. At this time, the molybdenum powder mixed with the iron powder was simultaneously subjected to reduction and bonding under a hydrogen fluoride atmosphere (H ₂ -N ₂ mixture). The reduction time in the reduction process was controlled to be 1 hour and 2 hours, respectively, and the reaction was quenched after the completion of the reduction process to prevent further reaction.

The experiment was carried out in a conveyor belt type furnace (an example of an experimental apparatus is shown in FIG. 1).

The chemical reactions occurring during the reduction of water-injected iron-based powders and molybdenum-based powders are as follows. These reactions occur simultaneously. A small amount of carbon is contained in the water-sprayed iron powder, and these carbons accelerate the reduction.

FeO + C = Fe + CO

FeO + CO = Fe + CO ₂

FeO + H ₂ = Fe + H ₂ O

MoO ₂ + 2H ₂ = Mo + 2H ₂ O

MoO ₂ + 2CO = Mo + 2CO ₂

MoO ₃ + 3H ₂ = Mo + 3H ₂ O

MoO ₃ + 3CO = Mo + 3CO ₂

evaluation

After the experiment, the concentration of oxygen and carbon in the powder was measured to evaluate the degree of reduction of the powder.

FIG. 2 and FIG. 3 are graphs showing the relationship between Fe-Mo diffusion bonding powder prepared according to an embodiment of the present invention and DAB (1.5 wt% Cu-1.75 wt% Ni-0.5 wt% Mo), which is a conventional commercialized Hoganas powder, (Wt%) and carbon concentration (wt%) with respect to DAE (1.5 wt% Cu-4.0 wt% Ni-0.5 wt% Mo).

2 and 3, the Fe-Mo diffusion bonded powder prepared according to an embodiment of the present invention is mixed with DAB (1.5 wt% Cu-1.75 wt% Ni-0.5 wt% Mo ) And DAE (1.5wt% Cu-4.0wt% Ni-0.5wt% Mo), except that the heat treatment was performed for one hour using MoO ₃ . It can be confirmed that the oxygen concentration and carbon concentration of the Mo diffusion bonding powder correspond to DAB and DAE.

FIG. 4 is a view showing a diffusion bonding site of Fe-Mo diffusion bonded powder prepared by using Mo powder and heat treatment at 900 ° C. for 1 hour according to an embodiment of the present invention. FIG. 5 is a view showing a diffusion bonding region of Fe-Mo diffusion bonded powder prepared by using the Mo powder and annealing at 1,000 ° C. for 1 hour according to an embodiment of the present invention. FIG. 6 is a view showing a diffusion bonding site of Fe-Mo diffusion bonded powder prepared by using MoO ₃ at 900 ° C. for 1 hour according to an embodiment of the present invention.

7 to 10 as a comparative example by using Mo, MoO ₃ each shows the result after the two-hours' heat treatment at 900 ℃, 1,000 ℃. More specifically, FIG. 7 shows the profile of the diffusion bonding region of the Fe-Mo diffusion bonded powder produced by using the Mo powder and heat-treating at 900 ° C for 2 hours. FIG. 8 is a view showing a diffusion bonding site of the Fe-Mo diffusion bonded powder prepared by using the Mo powder and heat-treating at 1,000 ° C. for 2 hours according to an embodiment of the present invention. 9 is a view showing a diffusion bonding site of Fe-Mo diffusion bonded powder prepared by using MoO ₃ at 900 ° C for 2 hours according to an embodiment of the present invention. 10 is a view showing a diffusion bonding site of Fe-Mo diffusion bonded powder produced by using MoO ₃ according to an embodiment of the present invention and annealing at 1,000 ° C for 2 hours.

Referring to FIGS. 4 to 6, it can be seen that the Fe-Ni diffusion bonded powder according to an embodiment of the present invention has a thickness of the diffusion bonding region of about 1 to 6.5 μm. When the diffusion bonding thickness is within the above range, there is an advantage that the molding strength at the time of molding is excellent at a later stage, and that it is stable from the risk of falling off of the bonded components.

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 (17)

Water-spraying molten steel to produce an iron-based powder whose surface is oxidized;
Mixing the iron-based powder and the molybdenum-based powder; And
Heat-treating the mixed powder in a reducing atmosphere to obtain an iron-based diffusion bonded powder;
Lt; / RTI >
Heat-treating the mixed powder in a reducing atmosphere to obtain an iron-based diffusion bonded powder;
Wherein the mixed powder is reduced and the reduced molybdenum powder is diffused and bonded to the surface of the reduced iron-based powder.
A method for producing an iron-base diffusion bonded powder.
The method according to claim 1,
Wherein the content of carbon (C) in the molten steel is more than 0 and 3.0 wt% or less.
3. The method of claim 2,
Water-spraying the molten steel to produce an iron-based powder whose surface is oxidized; Since the,
Adding carbon (C) to the water-injected iron-based powder;
Based diffusion bonded powder.
The method according to claim 1,
The molybdenum-
Molybdenum (Mo) powder, molybdenum oxide (MoO _x ) powder, or a combination thereof.
The method according to claim 1,
Wherein the content of the molybdenum-based powder relative to the mixed powder is 0.2 to 10 wt%.
The method according to claim 1,
In the reducing atmosphere,
Wherein a mixed gas atmosphere containing hydrogen (H ₂ ) gas atmosphere or hydrogen (H ₂ ) is used.
The method according to claim 6,
The atmosphere of the mixed gas is,
Wherein the gas mixture further contains nitrogen (N ₂ ), carbon monoxide (CO), methane (CH ₄ ), argon (Ar), ammonia (NH ₃ ) or a combination thereof.
The method according to claim 1,
The heat-
Is carried out in a temperature range of 600 to 1,050 占 폚.
9. The method of claim 8,
The heat-
Is carried out for 10 to 90 minutes.
The method according to claim 1,
Heat-treating the mixed powder in a reducing atmosphere to obtain an iron-based diffusion bonded powder; Since the,
Quenching the obtained iron-base diffusion bonded powder;
Based diffusion bonded powder.
The method according to claim 1,
Wherein a content of molybdenum (Mo) with respect to the iron-base diffusion bonded powder is 0.001 to 10 wt%.
12. The method of claim 11,
Wherein the content of molybdenum (Mo) in the iron-base diffusion bonded powder is 0.2 to 10 wt%.
The method according to claim 1,
Wherein the diffusion bonding portion has a thickness of 1 to 6.5 占 퐉.
14. A process for the preparation of a compound according to any one of claims 1 to 13,
An iron-based diffusion bonded powder in which molybdenum (Mo) powder is diffusion bonded to the surface of iron (Fe) powder.
15. The method of claim 14,
Based diffusion bonded powder having a molybdenum (Mo) content of 0.001 to 10 wt% with respect to the iron-base diffusion bonded powder.
16. The method of claim 15,
Based diffusion bonded powder having a molybdenum (Mo) content of 0.2 to 10 wt% with respect to the iron-base diffusion bonded powder.
15. The method of claim 14,
Wherein the diffusion bonding portion has a thickness of 1 to 6.5 占 퐉.

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