JPH05161956A - Atomized forming method - Google Patents

Abstract

PURPOSE:To prevent the development of cavity and to improve the yield of sound part by heating a preform body and executing atomizing deposition while uniforming temp. distribution of the preform body surface. CONSTITUTION:Jet flow of high pressure gas is jetted to dropped stream 6 of molten metal 2 to atomize the molten metal and the atomized metal particles are deposited on a base plate 8 to obtain the preform body 9. By heating the preform body 9 from the surface side, the temp. difference between the center part and the peripheral part at the highest apex surface of the preform body 9 is eliminated and the metal particles are locally and quickly solidified and the development of the cavity is prevented. By this method, the necessity of a checking process of the porosity before forging and a peeling process can be eliminated and crack at the time of forging can be prevented. Further, since the temp. difference between the center part and the peripheral part in the horizontal direction of the preform body 9 is eliminated, the development of variation of the material characteristic in the inner part of the preform body 9 can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spray molding method known as an Osprey method or a spray casting method, and more particularly to a spray molding method which does not cause voids in a deposited preform. Is.

[0002]

2. Description of the Related Art The spray molding method can obtain a uniform fine structure at a high density and can simplify the molding process as compared with the conventional powder metallurgy method, so that it can be expected to greatly improve the productivity. Attention has been paid. An example of this spray molding method is JP-B-54-29985.

FIG. 3 is an explanatory view showing an example of an apparatus for producing a block preform by using a spray forming method. A metal melt 2 is put in the tundish 1, and the metal melt 2 is allowed to naturally flow through a tundish nozzle 13 into a chamber 3 having a non-oxidizing atmosphere. A gas atomizer 4 is arranged below the tundish 1, and a high-pressure inert gas ejected from the gas atomizer 4 becomes a jet stream 5 and is sprayed onto a molten metal stream 6 to atomize it. .. The atomized metal particles are deposited in a semi-solidified state on the substrate 8 set on the lower collector 7 and gradually solidified. The collector 7 can be moved up and down and rotated by using a stepping motor 10 or the like as a drive source. If the collector 7 is gradually lowered according to the amount of metal particles deposited, the collector 7 is placed between the tundish nozzle 13 and the topmost surface of the deposition. The distance can be kept constant, and it is possible to obtain a lump-shaped preform 9 having an increased deposition height.

[0004]

The peripheral side portion of the deposit deposited on the collector 7 tends to be lowered in temperature due to the cooling action by the atmospheric gas and the like, so that it is located between the side surface portion and the central portion of the preform 9. Causes a large temperature difference. Therefore, in the vicinity of the side surface portion, the metal particles rapidly solidify while maintaining the particle shape in the vicinity of the topmost surface of the deposition to form a gap between the particles,
Voids are easily formed (see reference numeral 19 in FIG. 4), and the vacancies have been a factor of reducing the yield of the deposited compact.
Further, in order to prevent forging cracks due to the holes, there is a problem that an extra step of checking the holes and peeling the side portion of the preform (cutting of the side surface) is required.
Therefore, attempts have been made to improve the vertical movement and horizontal movement of the collector 7 in order to prevent the generation of voids, but there is a physical limit to the range in which the above-mentioned movement can be adjusted, and this is greatly effective in reducing the occurrence of voids. It did not reach the effect. In view of the above circumstances, the present invention can prevent the generation of holes,
The purpose of the present invention is to submit a spray molding method that improves the yield of sound parts of preforms.

[0005]

According to the present invention, which has achieved the above object, a jet stream of high-pressure gas is sprayed onto a falling stream of molten metal to atomize it, and atomized metal particles are deposited on a substrate. In the spray molding method to obtain a preform,
The gist is to perform spray deposition while heating the surface of the preform.

[0006]

By heating the surface of the preform formed by depositing the metal particles from the surface side, the temperature difference between the central portion and the peripheral portion on the top surface of the preform is eliminated, and the metal particles are localized. And prevent the above-mentioned voids from being rapidly solidified. As a result, it is possible to eliminate the need to perform the step of checking the holes and the step of peeling before forging, and to prevent cracks during forging. Further, since there is no difference in temperature between the central portion and the peripheral portion in the horizontal direction of the preform, it is possible to prevent the change of material characteristics inside the preform.

[0007]

1 is an explanatory view showing an embodiment of a spray forming apparatus used in the present invention, and the structure for atomizing molten metal and the moving structure of the collector 7 are the same as those of the apparatus shown in FIG. is there. A dust-proof cover 24 having a plasma passage hole is provided on the side of the collector 7, and a plasma torch 20 is provided inside the dust-proof cover 24. The plasma torch 20 is connected to a plasma power supply device 21 and an arm for movement. 22a, 22b
It can be moved horizontally and vertically. Reference numeral 23 indicates a cooling gas supply device, in which the side portion of the preform is overheated, the cooling rate on the surface of the preform becomes unstable, and the material properties change between the side portion and the inside of the preform. Is to prevent.

(Experimental Example) Comparative Example 1 A preform having a height of 200 mm and a diameter of 200 mm was manufactured by the apparatus shown in FIG. The rotation speed of the collector 7 is 150 rpm.
In addition, the descent speed was set to 8 × 10 ^-4 m / s. As a result of observing the cross section of the preform manufactured by the above method with an optical microscope, as shown in FIG. 4, a large number of holes 19 were formed from the side surface 9A of the preform toward the center side within about 10 mm. Admitted. Example 1 Using the apparatus shown in FIG. 1, a preform was manufactured under the same conditions as in Comparative Example 1. The conditions of the plasma device and the cooling gas supply device are as shown in Table 1.

[0009]

[Table 1]

As a result, it was found that the generation of voids was greatly reduced as shown in FIG. Example 2 Under the conditions shown in Example 1, the torch distance was changed by moving the position of the plasma torch closer to or farther from the side surface of the preformed body to change the depth at which holes are reduced (hereinafter referred to as the hole reduction depth). It investigated and obtained the result of Table 2.

[0011]

[Table 2]

As is apparent from Table 2, in order to reduce the occurrence of voids, the torch should be placed as close as possible to the side of the preform, and the torch distance is preferably 30 mm or less. The shape of the deposited molded body to which the present invention is applied is not limited to the billet-shaped one described above, and may be roll-shaped or plate-shaped. Further, the heating means of the pre-molded body is not limited to plasma heating but only the surface. Electron beam and laser are preferable when directing the heating. Microwave,
An arc, a flame (oxygen-acetylene, etc.) may be used, and it is recommended to perform induction heating or electromagnetic heating for a material such as an aluminum-based metal that may cause a dust explosion.

[0013]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to prevent the generation of voids in the preform, improve the yield of sound parts, and omit the subsequent void check and peeling process. It became like. Further, since the generation of voids is eliminated, it is possible to prevent the occurrence of cracks during the forging process.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a spray molding apparatus used in the present invention.

FIG. 2 is an explanatory view showing a cross section of a preformed body manufactured according to the present invention.

FIG. 3 is an explanatory diagram showing an example of a conventional spray molding apparatus.

FIG. 4 is an explanatory view showing a cross section of a preformed body manufactured by the apparatus of FIG.

[Explanation of symbols]

 5 Jet Flow 6 Metal Melt Flow 7 Collector 9 Preform 19 Hole 20 Plasma Torch 23 Cooling Gas Supply Device

Claims (3)

[Claims] 1. A spray forming method for obtaining a preformed body by spraying a jet stream of high-pressure gas onto a falling stream of molten metal to atomize the jet stream and depositing atomized metal particles on a substrate. A spray molding method characterized by performing spray deposition while heating the body and making the surface temperature distribution of the preform uniform. 2. The spray molding method according to claim 1, wherein the metal particles are spray-deposited while heating the side surface near the surface of the preform. 3. The spray molding method according to claim 1, wherein the preform is plasma-heated while the metal particles are spray-deposited.