JPS62134162A - Production of casting - Google Patents

Abstract

PURPOSE:To enable sound production of a casting which is thin-walled and has particularly intricate shape by melting an active metal such as titanium or the alloy thereof by a plasma arc in an inert gaseous atmosphere and pouring such molten metal into a casting mold the inside of which is sucked to a reduced pressure. CONSTITUTION:The inert gaseous atmosphere of Ar, etc., is maintained in a melting chamber 1. A plasma torch 2 and a water-cooled crucible 8 made of copper, etc. is connected to a power source to generate the plasma arc 20 to melt the raw material of the active metal or alloy in the crucible 8. Such molten metal is poured through a runner 18 to a product part 19 in a casting device. A negative pressure is applied to the casting mold 12 by a vacuum pump so that the molten metal is degassed and is spread to all the corners of the product part 19 prior to casting. The contamination with impurities during melting is eliminated by such constitution by which the production of even thin-walled and intricate casting at a high yield is possible and the casting mold is easily executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing castings of active metals or alloys, such as titanium.

(Prior Art and Problems) Active metals or alloys such as titanium, zirconium, niobium, or their alloys have very strong chemical reactivity and high melting points, so it is necessary to use a special melting furnace. is arc melted in an inert gas such as Ar or in vacuum,
Obtaining ingots. The type of arc melting furnace differs depending on the purpose of the ingot (processing or casting), but when casting a casting, the raw material is melted by a consumable electrode arc or a non-consumable electrode arc, and a skull is melted along the inner wall of a water-cooled crucible. A layer is formed, the raw material is further arc-melted on this skull layer, and the resulting molten metal is poured into a mold to obtain a casting.6 Graphite or the like is used as the mold material.

However, since the raw materials such as titanium to be melted are very active, they are melted in a water-cooled crucible, but sufficient superheat cannot be obtained with consumable electrode arcs, etc. It was difficult to obtain castings in good condition without defects such as blowholes.

(Objective of the Invention) The present invention solves the drawbacks of the prior art, and is capable of melting active metals such as titanium or alloys with less contamination from impurities, and is capable of melting thin-walled castings with particularly complex shapes. The purpose of this invention is to provide a method that allows for the production of

(Structure of the Invention) In order to achieve the above object, the present inventors conducted various studies on melting methods and casting methods, and as a result, improved crucibles and molds in a plasma arc melting furnace that uses a plasma arc as a heat source. We discovered that this is possible by adding .

In other words, the method for producing active full-flex alloy castings according to the present invention involves melting raw materials for active full-flex alloy castings or alloys charged into a water-cooled crucible using a plasma arc in an inert gas atmosphere, and melting the resulting molten metal. This method is characterized by pouring the metal into the mold using vacuum suction from behind.

The present invention will be explained in detail below based on examples.

(Example) FIGS. 1 and 2 are diagrams showing an example of a plasma melting furnace and a mold used for carrying out the present invention.

A melting chamber 1 of a plasma melting furnace is provided with a plasma torch 2, a raw material tank 3, and a feeder 4 at its upper part. The plasma torch 2 is provided with an inert gas inlet 5 for creating an inert gas atmosphere such as Ar in the furnace, and the melting chamber 1 is provided with a gas outlet 6 for replacing the gas in the furnace. ing. Note that 7 is a valve. The feeder 4 is disposed at the lower part of the raw material tank 3, and is capable of cutting out the raw material in predetermined Gt portions and charging it into a crucible 8 placed in the melting chamber 1.

The crucible 8 is made of copper and water-cooled, and can be tilted for casting.

A mold device 9 is placed near and below the crucible 8 .

As shown in FIG. 2, the molding device 9 includes a box 11 made of a refractory 10 made of an appropriate material.
A mold 12 is placed or held inside the mold 1 . Mold 1
2 and the box 11 is open only with a bottom opening 14, which is connected to the hose 15.
is connected to the bottom opening 16 of the lysis chamber 1 via a vacuum pump (not shown). Further, an appropriate number of mold heaters 17 are embedded in the refractory 10 to preheat the mold 12.

The mold 12 is made of a mold material such as Ti that has little reaction with molten metal and is appropriately porous.

However, when the molten metal poured from the crucible 8 passes through the runner 18 and fills the product part 19 (a plurality of branches are formed on the left and right in FIG. 2), the space 13 behind the mold 12 It is necessary to mold the product in such a way that it can maintain its shape even when a moderate amount of negative pressure is applied using a vacuum pump. Prior to casting, negative pressure is applied to the mold using a vacuum pump, and molten metal is poured into the mold. At the same time as the molten metal fills the mold, it spreads to every corner of the product section 19 due to the vacuum effect, and furthermore, a degassing effect of the molten metal can be expected. Therefore, even if the shape of the casting is particularly thin and complicated, a sound casting can be obtained. The negative pressure may be about 10-1 to 10-'' Pa, and it is possible to vacuum the back of the !8 mold for melting in an inert atmosphere of 1 atm in the melting chamber.

During melting, the inside of the melting chamber 1 is made into an inert gas atmosphere such as Ar, the plasma torch 1 and the crucible 8 are connected to a power source as shown in the figure, and the plasma arc 20 is generated to release the active total bending and alloy raw materials in the crucible 8. dissolve.

Using the plasma melting furnace with the above configuration, melting was performed using titanium sponge as a raw material, and the negative pressure behind the mold was set to 10""Pa.
When we visited the turbine blade mold, we found that there was no impurity contamination in the casting, and a sound product was obtained.

Further, although the mold 12 in the above embodiment is entirely made of a mold material, the same effect can be obtained even if the portion constituting the product portion 19 is made of a porous mold material.

(Effects of the Invention) As detailed above, according to the present invention, active metals or alloys such as titanium can be melted without impurity contamination, and moreover, the casting can be performed by drawing a vacuum from behind the heated mold. Therefore, even thin castings or castings of various complicated shapes can be manufactured at a high yield. Further, since there is no need to vent gas from the mold again, manufacturing of the mold is easy.

It is particularly suitable for producing castings of pure titanium and titanium alloys (eg, those containing An).

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the configuration of a plasma melting furnace used for carrying out the present invention, and FIG. 2 is a sectional view showing a mold device disposed in the plasma melting furnace. 1... Melting chamber, 2... Plasma torch, 3... Raw material tank, 4... Feeder,
5...Inert gas inlet, 8...Water-cooled crucible. 9... Mold device, 10... Refractory, 11.
...Box, 12...Mold, 13...
Space behind the mold, 15... hose, 17... heater for heating the mold, 18 - runner, 19... product department,
22... Molten metal. Patent applicant: Daido Steel Co., Ltd. Patent attorney Hisashi Nakamura Figure 1 Figure 2

Claims (1)

[Claims] An active metal or alloy raw material charged in a water-cooled crucible is melted by a plasma arc in an inert gas atmosphere, and the resulting molten metal is poured into a mold that is vacuum-suctioned from behind. Manufacturing method for metal/alloy castings.