JPS61195273A - Melting handy furnace for low melting-point metal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a handheld melting furnace for metals that melt at relatively low temperatures, such as low melting point metals, such as aluminum and aluminum alloys, zinc and zinc alloys.

Conventionally, various proposals have been made as melting hand furnaces for low-melting point metals. For example, in a melting hand furnace with melting, holding and unloading chambers, gas fuel is used as the heat source for melting, and gas fuel is used as the heat source for holding in the holding chamber. Alternatively, many methods using electricity have been proposed. Because this type of melting furnace uses gas fuel for melting, the production of oxides due to metal oxidation during melting is unavoidable no matter how much gas combustion is controlled, and because the gas fuel is a carbohydrate. It is impossible to avoid hydrogen contamination with the molten metal. Therefore, similar problems occur when the surface of the molten metal is heated using gas fuel as the heat source in the holding chamber, and there is also the disadvantage that the temperature distribution of the molten metal within the holding chamber becomes wide, which hinders casting. A furnace that uses an electric resistance heating element as a heat source has also been proposed as a crucible-type furnace for melting and holding, but since this type is an indirect heating type, there is a limit to thermal efficiency, and it takes a long time to melt and requires a large amount of electricity. There is a drawback.

A method has also been proposed in which gas fuel is used for melting and top heating type electric heating is used for holding, but as mentioned above, there are drawbacks such as generation of oxides, absorption of hydrogen gas, and nonuniform hot water temperature.
Recently, it has been proposed to use gas fuel for melting and immersion-type electric heating in the holding chamber, which has somewhat compensated for the above-mentioned drawbacks, but problems such as oxidation of the molten metal during melting and mixing of hydrogen into the molten metal have been proposed. Points not resolved. In addition, various types of induction heating type electric furnaces outside the hearth have been proposed as mentioned above, but because of the stirring action of the molten metal during melting and heating by the secondary electric flux, impurities are likely to be mixed into the molten metal, and the molten metal is Oxidation also has drawbacks that cannot be ignored, and the furnace equipment is complicated and expensive, which is said to be a drawback in terms of molten metal cost.

Furnaces have also been proposed in which a large number of electrical resistance heating elements are placed on the ceiling of the melting and holding chamber to melt and control the temperature of the molten metal to be held, but the furnace equipment is quite expensive. Moreover, since it is a heating method similar to the above-mentioned surface heating method that heats the area below the ceiling, it has drawbacks such as the formation of oxides due to overheating of the surface of the molten metal and non-uniformity of the temperature of the molten metal.

The present invention was invented in order to solve the above-mentioned drawbacks of the conventionally proposed melting furnaces for various low-melting point metals.

The present invention will be explained in detail below with reference to the accompanying drawings, in which a burner cylinder 7 with a number of holes is installed inside an annular melting cylinder 4, the upper part of which is connected to a preheating duct 8.
, which forms a chimney-shaped melting chamber. The bottom of this melting chamber is a dry hearth that slopes above the surface of the molten metal in the molten metal holding chamber 2. This dry hearth is heated by a plate-shaped electric heater 5 on the outside. The above is the general structure of the melting chamber. To explain the details, the annular melting cylinder 4 has an electric resistance heating element on its inner surface, and the heating element is held by an annular refractory ceramic. . A burner cylinder made of refractory ceramics is placed at a constant distance from this melting cylinder.The burner cylinder is perforated with many holes and is enriched with preheated air or inert gas through a preheating duct at the top. The air is heated to a high temperature through the mI gap between the melting seal redder and the burner cylinder, and is injected into the burner cylinder from multiple holes in the burner cylinder to melt the metal pieces to be melted charged into the burner cylinder. A preheating duct made of heat-resistant metal or highly thermally conductive ceramics is guided to the top and preheated from inside, and the heat-resistant blower 9 is passed through a conduit that is kept warm from the top of the preheating duct.
, and then blown into the preheating duct 8 again. At this time, blow into the conduit.

The gas heated to a high temperature as described above in the melting chamber heats the metal to be melted as a heat flux, and at the same time the burner cylinder is heated by the outer melting cylinder and radiates heat rays inward to heat the metal to be melted. . In order to improve the radiation efficiency, it is preferable to use silicon carbide, zircon, or zirconia as the material for the ceramic melting cylinder. As mentioned above, the high-temperature gas that melted the charged metal to be melted heats the unmolten metal at the top of the melting chamber, preheats the preheating duct, returns to the blower with residual heat, and returns to the preheating duct again. Blowing is an important aspect of the present invention. The metal to be melted is melted with high efficiency by the heat flow rate of the high-temperature gas and the radiation inside the melting cylinder, and the energy required for melting can be reduced by preheating and recirculating the gas with residual heat. At the same time, by using a gas enriched with inert gas, oxidation of the metal to be melted can be minimized, and since hydrocarbon fuel is not used, it is possible to prevent hydrogen from entering the melted metal. The inventor of the present invention has found that.

The metal to be melted thus melted drops onto the tilted tri-bars heated by the plate-shaped electric heater 5, and flows down into the holding chamber 2 along the tilt.

In this case, the heater 5 does not necessarily have to be a plate heater as shown in the figure, but a type known as an immersion heater.
A heater in which a resistance heating element is inserted into an outer tube made of silicon carbide or silicon nitride may be used.

The relatively low-temperature molten metal melted inside the burner cylinder 7 in the melting chamber is dropped onto the inclined dry nose λ-, and is heated and heated by the plate heater 5 described above.

The molten metal that has flowed into the holding chamber 2 in this manner is heated and maintained at an appropriate temperature by an immersion heater 6 (for example, Aldiaper). Naturally, the number of immersion heaters varies depending on conditions such as the amount of molten metal and the temperature. The molten metal prepared in the holding chamber is sent to the next process from the pumping chamber 3.

By using the melting and holding system as described above, it has been possible to overcome the drawbacks of the conventionally proposed low melting point melting furnace for osmanthus.

Next, the effects of the present invention will be described using examples.

Example Melting heater cylinder 4, tubular heater 17, and plate heater 5 each have a rated power of 18 KW H, l K
Equipped with a heater of W H, 5K W H, using a silicon carbide cylinder heater, and two immersion heaters (trade name Aldaiper) (rated output 5KWH) in the holding chamber.IQ
Using a KWH, an aluminum alloy melting furnace capable of melting 50 kg of aluminum alloy pieces per hour and holding 380 kg of molten metal was fabricated, and experiments on melting, holding, and pumping were conducted.

In this case, the melting temperature of the pumping chamber was set at 700°C±5°C. The temperature of each heater was controlled by a thyristor control method, that is, the temperature of the gas ejected from the burner cylinder was kept at 950 to 1,000 degrees Celsius, the ambient temperature of the plate heater was kept at 950 to 1,000 degrees Celsius, and the temperature of the tubular heater was kept at 950 to 1,000 degrees Celsius. The temperature was kept at 350-400°C, and the temperature inside the holding chamber was kept at 700-750°C.

Melting work was started while controlling each heater in this manner, and a total of 205.2 KW of power was consumed in order to obtain 50 molten metal per hour and turn it into 380 molten metal after 7.6 hours. The average was 27KWH.

For subsequent melting work, melting-related heaters are controlled by a hot water level sensor that emits signals depending on the rise and fall of the hot water level in the drawing chamber.
The immersion heater in the holding chamber is a system whose output is controlled by the signal from the temperature sensor in the drawing chamber, and the setting conditions at that time are that when there is sufficient molten metal in the drawing chamber, the melting operation is stopped, and the molten metal is ejected from the burner cylinder at that time. The output of the melting-related heater was reduced so that the gas temperature was 450°C to 500°C, and the atmospheric temperature of the plate heater was 8°C.
The output is lowered to 50 to 950°C, and the immersion heater in the holding chamber is separately controlled to keep the molten metal temperature in the pumping chamber at 700°C ± 5°C.
The melting in the melting chamber was stopped and the temperature inside the melting chamber was maintained at 450 to 500°C. When 30 kg of molten metal is pumped out from the pumping chamber and the level of the molten metal in the pumping chamber drops, a signal is sent by the level sensor and melting starts again in the melting chamber, and the melting heater is turned on to the above-mentioned temperature to restore the level. For this purpose, the gas ejected from the burner cylinder was raised to 950-1.000°C, and the atmosphere of the plate heater (7) was raised to 950-1.000°C. In this example, the amount of electricity required to obtain 30 kg of molten metal and maintain the temperature at the outlet at 700°C ± 5°C is as follows: 31 minutes were required to pump out the 30 kg mentioned above.
Immediately after that, the heater for melting was activated by the signal from the hot water level sensor, and 30μ of molten metal was replenished in 18 minutes. This 4
The power requirement for 9 minutes is 2.0 for the first 31 minutes. OKW
12, IKW during the next 18 minutes, totaling 14.7KW.

Calculating from this data, including the temperature rise of the furnace body, the thermal efficiency of making 380 kg of molten metal and bringing it to 700℃ is 54%, and the thermal efficiency of molten metal replenishment and temperature maintenance thereafter is 70% and 76%, respectively. %.

This value was sufficient for industrial use as a handheld furnace for melting aluminum alloys.

On the other hand, the hydrogen gas content of the pumped and cast specimen was measured and the result was 0.12 C, C in 100 gr (number of samples: 17
The arithmetic mean of

Also, during the melting and holding work, visual inspection showed that there were very few oxides on the surface of the melt in the lower part of the melting chamber, and the oxide film on the surface of the melt in the drawing chamber was very thin, indicating good fluidity during casting. From these results, it was found that oxidation products were also greatly reduced.

This example proves that the melting furnace system of the present invention is extremely superior to various furnaces that have been proposed industrially.

[Brief explanation of drawings]

FIG. 1 shows a sectional side view of a melting furnace according to the present invention, and FIG. 2 shows a plan view. 1 is a dissolution chamber, 2 is a holding chamber, 3 is a pumping chamber,
4 is a melting heater cylinder, 5 is a plate heater,
6 is an immersion heater, 7 is a burner cylinder, 8 is a preheating duct, 9 is a heat-resistant blower, 10 is a filter damper,
11 is a cleaning lid, 12 is a tap hole, 13 is a slide damper, 14 is a spout, 15 is a hot water level sensor, 16 is a conduit, 17 is a tubular heater, 18 is an inert gas blower, 19 indicates a 7-shaped tube.

Claims (4)

[Claims] (1) An electric resistance heating element is used as the heat source in the melting chamber of a hand furnace for melting low-melting point metals, and the heating element is protected from mechanical shock when the input metal is charged, and the heat generated by the input metal or the metal that is melted after inputting. In order to prevent short circuits in the body, a protective device made of ceramics is provided, and air heated by the heating element is blown into the melting chamber through a part of the ceramic, and the heat flux of the heated high-temperature gas and the heating element The metal is melted by heat radiation from the ceramics that protect the melting chamber, and the gas with residual heat is recirculated. This is a handheld melting furnace for low melting point metals, which is characterized by adjusting molten metal to a predetermined temperature using an immersion type heating heater. (2) A device for preheating the air blown into the melting chamber using an electric resistance heating element in an air circuit before heating it in a heat generating section provided in the melting chamber. A handheld furnace for melting low-melting point metals. (3) For low melting point metals according to claim 1, characterized in that the air blown into the melting chamber is enriched with an inert gas to inert the atmosphere in the melting chamber to reduce oxidation of the metal during melting. Melting furnace. (4) The portable furnace for melting low-melting point metals according to claim 1, characterized in that the melting metal is heated by installing an electric resistance heating element at the bottom of the melting chamber.