JPS6362561B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing low oxygen-containing iron powder by atomizing a molten iron alloy with a hydrocarbon liquid. relates to a method that enables the production of iron powder with low oxygen content to be carried out reliably and safely. Iron powder with low oxygen content is important as sinter forging and welding rod material.

[Conventional technology]

It is known in the art to atomize molten metal with atomizing agents such as compressed air, nitrogen, argon, steam or pressurized water, hydrocarbons. Molten metal is supplied from a casting vessel having a pouring hole in the bottom and placed above one or more nozzles. The pouring stream flows through the pouring hole and encounters the atomizing agent which is injected at high velocity, so that the pouring stream is broken into fine droplets. It is known that metal powders produced in this way absorb oxygen from the atomizing agent during their production, primarily as surface oxygen, and that this oxygen reacts with easily oxidized alloying elements.

In order to reduce the oxygen content to acceptable levels in alloy steels, for example, atomization with nitrogen or argon rather than the usual atomization with water or steam was practiced early on. This means that atomizing media (gases) have been used which are quite expensive and have significantly poorer grinding and cooling properties. However, for certain purposes, for example to produce powders with spherical particles, atomization with gas is preferred since it has the opportunity to shrink the powder particles into a spherical shape.

There have been problems in producing special alloy powders with low oxygen content when a finely divided product is desired. This requires a large amount of gas,
A significant proportion of oxygen from the oxygen remaining in the inert gas will therefore come into contact with the pouring stream of molten metal, resulting in a high oxygen content in the powder formed. The use of an oxidizing atomizing agent, such as water, has the opposite effect, ie, the increased amount of water reduces the oxygen content of the powder through a faster cooling process. However, it is not possible to obtain such low oxygen contents by atomization with nitrogen gas or argon.

[Problem to be solved by the invention]

Therefore, the use of hydrocarbons as an atomizing agent has come into practical use, but unlike inert gases such as argon, nitrogen, or water, this method itself lacks stability against high heat, so This poses a problem: when in contact with molten hot metal, it generates other low hydrocarbons, hydrogen and its own vaporized gases, which fluctuates the granulation chamber pressure and makes the granulation operation extremely difficult. Particularly, at the start of operation, the pressure in the granulation chamber fluctuates greatly due to the inflow of the cooling atomizing agent, the inflow of high-temperature molten metal, the generation of cracked gas, etc. If the operation becomes steady, the pressure fluctuations will be constant, but if the balance between the supply amounts of the atomizing agent and molten metal is lost, the pressure inside the granulation chamber will fluctuate rapidly. A complex control system is required to reliably and safely prevent air from entering during such rough operations, but the granulation chamber is often filled with droplets and powder, which can clog the pipes. The reality is that even complex control systems are prone to failure, and a reliable and safe control system is expected. Moreover, even with such a control system, it is difficult to produce iron powder with a low oxygen content.

An object of the present invention is to provide a method that allows iron powder with low oxygen content to be reliably, safely and stably obtained using simple equipment and an atomization method using hydrocarbons as an atomizing agent. be.

[Means to solve the problem]

The method for producing iron powder according to the present invention includes the steps of: providing a closed granulation chamber filled with a protective gas atmosphere containing a hydrocarbon liquid in the lower part; generating a stream and subjecting the stream to a controlled amount of pressurized hydrocarbon liquid atomizing agent in the form of a continuous stream to atomize the molten metal stream; and atomizing the molten metal stream; A method for producing iron powder comprising the steps of cooling the obtained iron metal particles in an atmosphere and collecting the resulting powder of iron metal particles in the hydrocarbon liquid, wherein the molten metal contains Cr and The closed granulation chamber is made of Mn-containing molten metal, and the closed granulation chamber has an inlet for a protective gas, but not an outlet thereof, and the protective gas atmosphere is maintained at a constant pressure during the atomization step. By providing a liquid locking means having a channel for supplying said protective gas inlet through an inlet and communicating with said closed granulation chamber, said liquid locking means is provided with said protective gas inlet via an inlet, said liquid locking means having said channel in communication with said closed granulation chamber, said liquid locking means being provided with said protective gas inlet through said inlet and said liquid locking means having said channel in communication with said closed granulation chamber. It is characterized in that the granulation chamber is isolated from the atmosphere during the atomization stage.

[Effect]

The structure is designed to minimize the chance of atmospheric contamination, and is equipped with an inlet pipe for a protective gas consisting of an inert gas such as argon or nitrogen or a reducing gas, but there is no exhaust pipe, so particles are The granulation chamber is completely isolated from the outside, and the reaction is maintained in the granulation chamber filled with smoke and steam, thereby avoiding any danger of explosion. In addition, since the granulation chamber is configured as a closed body as much as possible, the operation start state can be easily and quickly configured by introducing and filling the granulation chamber with a hydrocarbon liquid, and then replacing the reducing liquid with a protective gas. can. However, even if the atomization operation is carried out with such a granulation chamber configuration, it is difficult to produce iron powder with low oxygen content, and it is difficult to overcome this difficulty.
It has been found effective to use certain Cr- and Mn-containing iron alloys to reduce the oxygen content to a level of 100 ppm.

〔Effect of the invention〕

By using the iron alloy of the present invention containing as much predetermined amount of Cr and Mn as possible and producing iron powder by the atomization method using specific equipment, violent and rough operations can be carried out reliably and safely. This makes it possible to completely isolate the granulation chamber from the outside air regardless of pressure changes in the granulation chamber during operation, making it possible to produce iron powder with low oxygen content, which was previously difficult. .

〔Example〕

In order that the invention may be more easily understood, the following description is given, by way of example only, with reference to the accompanying drawings, in which: FIG.

In the drawing, the granulation chamber 1 is filled with oil, preferably 86.8% carbon, 12.5% hydrogen, 0.58% sulfur,
The remainder is partially filled with a fuel oil hydrocarbon liquid containing 0.12% ash. In the granulation chamber 1, a pouring hole 12 is provided at the bottom of a casting container 11 containing molten metal 10. An inlet pipe 3 for a protective gas is provided in the upper part of the granulation chamber 1, but no outlet pipe is provided. A nozzle 14 projects into the chamber for supplying an atomizing agent 15 of hydrocarbon liquid. In the embodiment of the apparatus for carrying out the method of the invention shown in FIGS. 1 and 2, a liquid lock reservoir 9 in the form of a channel is provided. The liquid lock tank 9 is preferably provided as close as possible to the granulation chamber 1, and preferably connected to the granulation chamber 1 as shown in FIGS. 1 and 2. The liquid lock tank 9 cooperates with a thick tube 6 which communicates with the granulation chamber 1 via a valve 7, the open end of which is below the level of the liquid 8 in the liquid lock tank 9. . The liquid lock tank 9 has a capacity such that the open end of the tube 6 is always below the liquid level during the metal powdering operation.

Before the atomization begins, the valve 7 and the bottom valve 5 are closed, after which the granulation chamber 1 is completely filled with hydrocarbon liquid up to the pouring hole 12, when the liquid level is as desired for the atomization process. Protective gas is supplied through the inlet pipe 3 at the same time as the pressure is lowered to a low level. next,
The valve 7 is opened, so that the reducing gas 4 in the upper part of the granulation chamber 1 is brought to a pressure above atmospheric pressure by an amount corresponding to the length of the tube 6 immersed in the liquid 8 in the liquid lock tank 9. maintain. The capacity of the liquid 8 is such that it can sufficiently absorb changes in capacity due to expansion and contraction of the granulation chamber 1. The actual atomization process is now carried out. The molten metal 10 from the casting vessel 11 flows down through the pouring hole 12 in the form of a metal stream 13 and is made to collide with a hydrocarbon liquid atomizing agent 15 injected from a nozzle 14 .

FIG. 3 shows another embodiment of an apparatus for carrying out the process of the invention, in which the function of the liquid lock is constituted by a hydrocarbons reservoir 2 below the granulation chamber 1, i.e. The chemical chamber 1 is divided into upper and lower parts of the protective gas chamber 4 and the hydrocarbon liquid reservoir 2, and one of the protective gas chamber 4 and the hydrocarbon liquid reservoir 2 can be moved vertically. The opening diameter is smaller than the upper opening diameter of the hydrocarbon liquid reservoir 2, and the hydrocarbon liquid reservoir 2 is configured to also serve as the hydrocarbon liquid reservoir 9 of the liquid lock, and the hydrocarbon liquid reservoir 2 and the protective gas chamber are configured. 4 is moved up and down to immerse the lower opening of the protective gas chamber 4 into the hydrocarbon liquid in the hydrocarbon liquid reservoir 2 for a predetermined length, thereby connecting the space in the upper protective gas chamber 4 with outside air. It is characterized by forming a liquid lock by blocking the space between the two. If the granulation chamber 1 is filled with liquid before it is filled with gas, the hydrocarbons sump 2 is raised or the protective gas chamber 4 is lowered, and the hydrocarbons sump 2 It serves as the hydrocarbons reservoir 9 of the liquid lock according to the embodiment of FIG. The advantage of the embodiment shown in FIG. 3 is that its function is more reliable, since the liquid lock is of larger size and can safely and reliably absorb and cope with any volume changes due to pressure fluctuations in the granulation chamber 1.

The invention is, of course, not limited to the device shown in the drawings, but can be modified in many ways. For example, the atomizing medium may consist of hydrocarbons, specialty oils, and liquefied petroleum, or benzene, methane, and the like. Even silicone oil can be used. Although silicone oil obviously contains oxygen, field tests have shown that silicone oil has a stable viscosity over a wide temperature range and therefore can be used in the context of the present invention. .

Operation example: When casting approximately 10 kg of molten steel, the molten steel was poured from a ladle into a graphite casting vessel with a pouring hole of 6.5 mm in diameter. The molten pouring stream was atomized into powder by oil (fuel oil) from four opposing nozzles directed downwards. Argon was used as the protective gas chamber, but of course other gases such as nitrogen can also be used. The amount of oil used in this example was approximately 500/min and the pressure was
It was 5.5Kg/ ^cm2 . Fluctuations in the internal pressure of the granulation chamber 1 during operation could be safely and reliably absorbed by the liquid lock. It is clear from this example that the atomization with oil carried out according to the invention, in addition to the effect of making the oxygen content in the powder very low, also produces a certain carburization effect. The powder produced consists of particles of various shapes: cigar-shaped, potato-shaped and spherical, with the result that the fine particles are predominantly spherical and the elongated particles are mainly a particularly coarse particle fraction. It was found that it can be concluded that

Mesh analysis of the produced powder gave the following results.

Mesh width % Powder 3360 microns 0.37 1680 microns 2.03 841 microns 18.36 595 microns 23.80 420 microns 24.85 210 microns 24.66 149 microns 4.26 105 microns 1.30 74 microns 0.23 53 microns 0.12 53 microns or less 0.02 Total oxygen content at various particle sizes is 4th From the figure,
The carbon content at various particle sizes can be seen from FIG. As for the oxygen content, as a comparative example, a conventionally produced coarse-grained iron powder containing 1.2% Mn has an oxygen content of 0.76-1% (i.e. 7600-1%).
It can be said that it has an oxygen content of 10,000 ppm).

In other respects, chemical analysis of the steel showed the following values:

% Si 0.57 Mn 1.30 P 0.017 S 0.021 Cr 0.16 Ni 0.03 Mo 0.03 Cu 0.05 V 0.01 Ti 0.01 Al 0.007 The oxygen content of steel is 86ppm.

The reason why iron powder with low oxygen content, which has been difficult to manufacture, can be manufactured is that a special equipment and a ferroalloy containing 1.30 ± 0.5% Mn and 0.16 ± 0.1% Cr were used as the raw material iron. I found out that it is based on this.

[Brief explanation of drawings]

1 is a schematic diagram showing one embodiment of an apparatus for carrying out the method of the invention, FIG. 2 is a similar schematic diagram showing a second embodiment, and FIG. 3 is a similar diagram showing a third embodiment. The schematic diagrams, Figures 4 and 5 are graphs showing the oxygen content and carbon content, respectively, for various particle sizes. 1... Granulation chamber, 2... Hydrocarbon liquid reservoir, 3...
...Protective gas introduction pipe, 4...Protective gas chamber, 5...Bottom discharge valve, 6...Pipe, 7...Valve, 8...Liquid, 9
... Hydrocarbon liquid reservoir, 10 ... Molten metal, 11
...Casting container, 12...Bottom pouring hole, 13...
Molten metal flow, 14... nozzle, 15... atomizing agent.

Claims (1)

[Claims] 1. Providing a closed granulation chamber filled with a protective gas atmosphere in which a hydrocarbon liquid is contained in the lower part, and generating a flow of molten raw material ferrous metal in the protective gas atmosphere. atomizing the molten metal stream by subjecting the stream to a controlled amount of a pressurized hydrocarbon liquid atomizing agent in the form of a continuous stream; A method for producing iron powder comprising the steps of cooling ferrous metal particles and collecting the resulting powder of ferrous metal particles in the hydrocarbon liquid, wherein the molten metal is a molten metal containing Cr and Mn. made of metal, said closed granulation chamber has an inlet for a protective gas, but not an outlet thereof, and said protective gas atmosphere is maintained at a constant pressure during said atomization step through said protective gas inlet. By providing a liquid locking means for supplying a protective gas and having a channel communicating with the closed granulation chamber, during the atomization step the liquid level in the channel is varied according to the internal pressure of the granulation chamber. A method for producing iron powder, characterized in that a granulation chamber is isolated from the atmosphere. 2. The liquid in the liquid locking means is common to the liquid in the lower part of the closed granulation chamber and is separated by the open lower wall of the closed granulation chamber, and the liquid in the locking means is controlled according to the internal pressure of the granulation chamber. A method for producing iron powder according to claim 1, wherein the liquid level is changed immediately.