JPS5825860A - Method and device for heating of casting - Google Patents

Abstract

PURPOSE:To remove molding sand from castings with a simple device and stages by supplying the castings stuck with the molding sand into a hardning furnace, and circulating hot wind therein thereby allowing the binder solidifying the sand to evaporate. CONSTITUTION:Castings of Al or the like in a high temp. state are contained in baskets 1 and are supplied into a hardening furnace 3. Hot wind is forcibly circulated from a circulating fan 9 provided with heating elements such as radiant tubes 8 provided in the furnace 3. Further, the concn. of O2 in the furnace 3 is maintained at about 17-21%. The castings are heated uniformly by the circulating hot wind, and the binder solidifying the molding sand evaporates quickly, and loses the adhesive power. Thus the molding sand and core sand drop easily from the castings and are carried out by means of a hopper 10 and a screw feeder 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a casting process in which a casting is supplied to a quenching furnace, and the casting is not only heated to its quenching temperature, but also removes mold sand adhering to the casting. The present invention relates to a method of heating a product and a heating device for performing the method.

Generally, after the cast product is removed from the mold, it is supplied to a quenching furnace where it is heated to the heating temperature, then it is supplied to a quenching tank where it is quenched, and then it is supplied to a tempering furnace where it is heated to the tempering temperature. It is used as a product after going through a series of heat treatment steps.

Aluminum cast products, such as cylinder heads, require heat treatment of quenching and tempering, just like cast steel products, and are used as products after undergoing such heat treatment. Conventionally, molding sand adheres to the cast product just taken out from the casting machine, so as shown in FIG. 4, conventionally there was a step of removing molding sand before the heat treatment step. Conventionally, there are various methods for removing molding sand, but when cast products are mass produced, molding sand is often removed using a sand kiln. When sand is removed from the mold using a sand kiln, the binder that solidifies the mold sand in advance is thermally decomposed by the heat and the presence of 0□! A binder is used that is vaporized and loses its ability to solidify the molding sand, making it easier for the molding sand attached to the cast product to fall off.

To remove sand using a sand kiln, the cast product is placed on a conveyor and transported from the inlet to the outlet of the sand kiln. In this method, the sand is applied to the castings being transported to remove the adhering sand, but it is necessary to supply excessive air to each burner so that the 02 concentration in the blown flame is about 15%. This is promoted by quaternization of the binder. However, 0. It is very difficult to make 15% exist, and if 02# degree k 10 ! If the concentration is about That is, the cast product must remain in the sand kiln for a long time, which requires a large sand kiln and consumes a large amount of fuel. Also, the amount of exhaust gas emitted from the sand kiln is large.

Not only is a large amount of thermal energy discarded together with the exhaust gas, but since the exhaust gas contains sand, it cannot be discharged as it is, and the exhaust gas cannot be discharged after passing through a device for removing sand from the exhaust gas. Therefore, large equipment is required to remove sand from the exhaust gas.

The present invention applies to cast products immediately after being removed from the mold.

As shown in FIG. 5, it is immediately supplied to a quenching furnace and subjected to a heat treatment process. If the cast product has not yet cooled down and is still at a high temperature immediately after being taken out of the mold, thermal energy will be saved accordingly. The quenching furnace of the present invention not only heats the cast product to its quenching temperature, but also simultaneously removes molding sand adhering to the cast product within the quenching furnace.
The sand kiln process shown in FIG. 4 can be omitted, and the process can be shortened, the equipment can be simplified, and fuel and labor can be saved to a large extent at the same time.

The heating method of the quenching furnace used in the present invention is different from the conventional direct heating method in which combustion gas is blown into the furnace using a burner. A heating element is provided, and a circulation blower is provided to forcefully circulate the hot air inside the furnace. Since a heating element is installed in the hot air circulation path, the hot air receives the heat of the heating element and imparts heat to the cast product. This heating method makes it possible to maintain the 0□ concentration in the furnace at a high level of 17% to 21%. Therefore, the castings fed into the quenching furnace are heated to the specified quenching temperature mainly by the hot air inside the furnace. Due to the high temperature and extremely high concentration of hot air that circulates at the same time as it is uniformly heated, the binder that hardens the molding sand is made into paper much more quickly than in the case of the sand kiln mentioned above, and its adhesive strength is improved. This is a heating method and heating device that removes molding sand from the cast product. The cast product leaving the quenching furnace can be immediately supplied to a quenching tank and subjected to heat treatment.

Experiments on the quenching furnace according to the present invention were conducted mainly on cylinder heads that were cast aluminum. For aluminum cylinder heads, the quenching temperature is 480℃ to 530℃.
The test results were that not only the sand on the surface of the aluminum cylinder head but also the sand in the core could be removed, and the cylinder head was uniformly heated to the quenching temperature in one hour. However, if the 0□ concentration is lowered to 15% or less, it will take a long time to remove the molding sand, which can be matched with the heating time to the quenching temperature. It turned out to be uneconomical.

The present invention will be explained in more detail with reference to FIG. 1, FIG. 2, and FIG. 3, which show examples of aluminum cylinder hardening.

In Fig. 1, the aluminum cylinder heads are housed in baskets 1.1', 1'', one or several pieces each, and first the supply tape /l/'l is placed in front of the entrance of the quenching furnace.
The ajvz'/inner head supplied above has just been taken out from the casting machine, has not cooled down at all, and is in a high temperature state. The higher the temperature, the more thermal energy is saved. In this case, the cylinder head is supplied with molding sand and core sand attached to it.

The main quenching furnace 3 is surrounded by a mild steel plate on the outside and a stainless steel plate on the inside, and a heat insulating material is filled between the steel plates.

The basket 1 enters the quenching furnace 3 from the supply table 2 and is taken out to the discharge table 4. In order to actively convey the basket at a constant speed, for example, conventionally known hearth rollers 5, 5', etc. are used. A conveying means is provided. An entrance door 6 and an exit door 7 are provided at the entrance and exit of the quenching furnace, respectively, so as to be automatically raised and lowered at regular intervals.

Inside the main quenching furnace 3, unlike a conventional quenching furnace in which combustion generated gas from a direct-fired burner is applied to the workpiece to directly heat it, one or several radiant tubes 8, 8',
... is provided. In addition, there is 1 in the main quenching furnace 3.
One or more circulation blowers 9, 9', . . . are provided.

Therefore, the structure is such that hot air is forced to circulate inside the furnace as shown by the arrows in FIG. The circulating hot air comes into contact with the surface of the radiant tube provided in its circulation path and receives heat to become high-temperature hot air.The hot air flows into the basket and comes into contact with the cylinder head and imparts heat, so that the cylinder head absorbs the heat from the circulating hot air. It is heated relatively uniformly and the temperature is raised. In addition, by using such a heating method, it is easy to maintain the concentration in the furnace at 17% to 21%.

If circulating hot air of high temperature and high concentration is applied to the cylinder head, the binder that hardens the molding sand will become a solid in a short time, and its adhesive strength will be lost, making it easy to remove the molding sand from the cylinder head. Be brave by dropping the core sand.

Below the hearth rollers 5, 5'... of the main quenching furnace, one or several hoppers 10.10'... and screw feeders 11.11'...... A means for transporting sand is provided.

When the basket 1'' exits from the exit door T of the quenching furnace 3, it is placed on a discharge table 4, which is a part of the elevator mechanism 12, and the basket 1'' is placed on the discharge table 4. It is immersed in a quenching tank 13 provided at the bottom of the tube and undergoes quenching treatment.

In the quenching furnace 3 shown in Figures 1 to 3, a radiant tube is installed as a heating element in the path of the circulating hot air, but instead of the radiant tube, an electric heater is used to heat the hot air and heat the aluminum cylinder head. can do.

In this case as well, it is easy to maintain the O2 concentration in the furnace at 17% to 21%. Radiant tubes, electric heaters, etc. can be said to be indirect heating methods, as opposed to direct fire heating methods, in which the burner flame is directly applied to the object to be heated.

The quenching furnace 3 according to the present invention uses an indirect heating type heating element such as a radiant tube 8, so that it is easy to maintain the 02 concentration in the furnace at 17% to 21%. Mold sand and core sand can be removed from the casting within the time it takes to heat it up to . The dropped sand is removed from the path of the circulating hot air and accumulates at the bottom of the hopper 10, and this settled sand can be easily taken out by the screw conveyor 11, and the hot air inside the furnace is sealed by the settled sand. It gushes outside and dies.

The quenching furnace according to the present invention can omit the step of removing molding sand from a cast product, such as the sand kiln mentioned above. The cast product can be heated relatively uniformly to the quenching temperature. Go by feeding the casting immediately after it is taken out from the casting machine to the supply table to save the thermal energy for heating the casting in the heating furnace. In other words, it is possible to simultaneously shorten the process, simplify the equipment, save fuel, and save labor to a large extent.

In the above explanation, the embodiment was described for quenching an aluminum cylinder head, but the present invention can also be applied to aluminum cast products other than aluminum cylinder heads, and the present invention can be applied to not only aluminum cast products but also cast steel. It can also be applied to products.

[Brief explanation of drawings]

1, 2, and 3 are a side sectional view, a top view, and a TTI sectional view, respectively, of a quenching furnace for an aluminum cylinder head according to the present invention. Figure 4 is a process diagram of the conventional casting process up to the firing process, and Figure 5
The figure shows a process chart up to the heat treatment step in the heating method and heating device of the present invention. 1 is a basket, 2 is a supply table, 3 is a quenching furnace, 4 is a discharge table, 5 is a hearth roller, 6 is an inlet door, 1 is an outlet door, 8 is a radiant tube, S is a circulation blower, 1
0 is a hopper, 11 is a screw feeder, 12 is an elevator mechanism, and 13 is a quenching tank.

Claims (2)

[Claims] (1) Castings with molding sand attached are placed in the furnace at zero
□ Concentration is 17'% to 21%, hot air is forcibly circulated in the furnace, and the casting is supplied to a quenching furnace equipped with an indirect heating type heating element. At the same time, the presence of circulating high-temperature hot air inside the mold sand causes the binder that solidifies the molding sand to become quaternary, causing it to lose its adhesive strength and release the cast product from the mold. A method of heating a casting in a quenching furnace to remove sand. (2) A conveying means 5 is provided for conveying the cast product from the outlet 2 of the quenching furnace 3 to the outlet 4, and one or several indirect heating type heating elements 8.8', 8'' are provided in the quenching furnace. . . . , and one or more circulation blowers 9, 9' . . . for circulating hot air in the quenching furnace. A heating device for a casting, which is provided with a sand transport means 10.11 for transporting sand that has fallen from the sand to the outside.