JPS631368B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat treatment apparatus for sand mold castings, and particularly to a heat treatment apparatus of a direct heating type that uses combustion in a burner or the like for heating.

Sand mold cast products taken out of casting equipment are generally subjected to heat treatment such as heating and cooling in order to modify the casting structure, etc., and are washed after removing core sand and casting sand adhering to the surface of the cast product. sent to the process.

For example, in the case of aluminum die casting, which is suitable for casting products with complex shapes, the cast product is heated to a temperature of approximately 500°C, and then subjected to a heat treatment that rapidly cools it in water or oil. Allowing the sand to disintegrate and fall out of the casting.

However, in the case of a cast product with a complex internal structure, core sand, etc. is not completely removed during this heating and is delayed until the cooling process, so it is necessary to provide additional removal means. There is.

In the case of a direct-fire heating method that uses a combustion flame such as a burner for heat treatment, the inside of the heating furnace is tightly shielded in order to maintain an appropriate heating atmosphere and use thermal energy as effectively as possible. Also, the amount of air taken in from the outside can be reduced to the minimum necessary for combustion in the burner.

Therefore, the oxygen concentration in the atmosphere inside the heating furnace gradually decreases from the normal state of about 21% to about 5 to 10% due to combustion in the burner.

In addition to the original heat treatment effect, high-temperature air also plays the role of oxidizing and decomposing the polymeric binder that binds the sand, causing the sand to disintegrate and fall off.
If the oxygen concentration in the atmosphere in the furnace is reduced in this way, the casting sand will be prevented from falling down, and the casting will proceed to the next cooling step with a large amount of casting sand attached. For this reason, for example, it is necessary to provide a stirring device, a sand pump, etc. in the cooling tank to remove and discharge the casting sand by the stirring action of the water flow.

However, since the removed casting sand is usually recovered and used again, additional labor and time are required for separating and removing moisture or oil, drying, etc.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the drawbacks of the prior art and to effectively promote the disintegration of casting sand from a cast product, especially when a direct heating method is used for heat treatment inside a heating furnace. The object of the present invention is to provide a heat treatment device for sand mold castings that can perform the following steps.

In order to achieve this object, the present invention provides a heating furnace configured to heat-treat sand mold castings brought in from a casting facility by combustion in an atmosphere substantially shielded from the outside air, and In a heat treatment equipment for sand mold castings, which is equipped with a cooling device that rapidly cools the product being carried out in water or in an oil solution, fresh outside air is heated and introduced between the heating furnace and the cooling device. The heating furnace is characterized by being provided with a casting sand collapse promotion zone that provides a high-temperature combustion atmosphere with a higher oxygen concentration than in the heating furnace.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a plan view showing an outline of a continuous heat treatment apparatus for aluminum die-cast products as an example of the apparatus of the present invention. The cast iron is sequentially conveyed through a preheating furnace 1, a heating furnace 2, a casting sand collapse promoting device 3, and a cooling device 4, and is subjected to continuous heat treatment during this period.

In order to increase the heating efficiency of the product P in the heating furnace 2 and to save energy, the preheating furnace 1 effectively utilizes high-temperature exhaust gas discharged from the heating furnace 2 or the casting sand collapse promoting device 3 to remove the product from the casting equipment. This is a zone for uniformly preheating each part of the product P prior to heat treatment, and includes an endless chain (not shown) for transporting the product P along the direction of arrow A during preheating.

The heating furnace 2 is provided perpendicularly to the discharge side end of the preheating furnace 1, and is a zone in which the preheated product P is heated to a predetermined heating temperature and heated at that temperature for a predetermined period of time. It is equipped with a large number of pass rollers for conveying the product P along the direction of the lost mark B during the heat treatment.

Further, as shown in the cross-sectional view of FIG. 2, the heating furnace 2 is
It is sealed by a double-walled casing 5 with a heat insulating material interposed therebetween, and a burner 6 and a turbo fan 7 are disposed facing each other at predetermined intervals along the conveying direction B on the upper part of the casing 5. The atmosphere in the furnace is heated to the heating temperature using a direct heating method, and high-temperature exhaust gas is discharged to the outside of the furnace through the duct 9 and around the product P by a turbo fan 7 rotationally driven by a fan motor 8. The discharged exhaust gas is introduced into the preheating furnace 1 and the product P in the preheating furnace 1 is
It is designed to be used as a preheating source.

A screw conveyor 10 is disposed below the casing 5 for discharging casting sand falling from the product P being conveyed in the furnace, and a recovery bucket 11 is attached to the discharge end of the conveyor.

The casing 5 to screw conveyor 10 and the like are similarly provided in the preheating furnace 1 described above and the casting sand collapse promoting device 3 described later.

As shown in FIG. 1, the casting sand collapse promoting device 3 is disposed between the end of the product passage of the heating furnace 2 and a cooling device 4, which will be described later. atmosphere (e.g., oxygen concentration 21%)
This is to promote the oxidative decomposition of the foundry sand binder by applying the normal outside air composition to the product.

That is, the casting sand collapse accelerating device 3 has the features shown in FIGS.
As shown in the figure, a heat exchanger 12 is provided to heat and introduce fresh outside air.

The heat exchanger 12 has fresh outside air with an oxygen concentration of 21% taken directly into the heat exchanger 12 and an exhaust duct 13 opened into the duct 9 in the casting sand collapse promoting device 3.
A total heat exchanger is used that forcibly exchanges heat with the high temperature exhaust gas that is delivered and taken in through the duct 13. The heated outside air is introduced by a fan 14 through an air supply duct 15 whose outlet is opened into the casting sand collapse promoting device 3 .

Note that 16 is an exhaust duct that discharges the exhaust gas after heat exchange to the outside.

The cooling device 4 is a zone provided adjacently for rapidly cooling the product from the casting sand collapse promoting device 3,
A cylinder-driven product shelf 18 and water tank 17 for making the product P appear and appear in the water tank 17 in the pit.
It is equipped with a pump 19 that stirs the water inside, and a sand pump 20 that discharges the cast sand that has fallen from the product P together with the water.

Incidentally, cylinders 21 are installed between the heating furnace 1, the heating furnace 2, and the casting sand collapse promoting device 3 so that the atmosphere in the processing zone is appropriately maintained in a desired state.
They are separated from each other by a partition door 22 that can be opened and closed by. Furthermore, such partition doors 22 are also provided at the entrance of the preheating furnace 1 and the exit of the casting sand collapse promoting device 3, respectively.

In the apparatus of the present invention having the above configuration, the aluminum die-cast product P to be heat-treated is first carried into the preheating furnace 1 and transported in the direction of arrow A by the endless chain, where the heat generated by the exhaust from the heating furnace 2 is absorbed. It is uniformly preheated at a relatively low predetermined temperature (for example, about 100°C) using the

Next, the product P that has been preheated is transferred to the cylinder 2.
1 is driven to open the partition door 22, the material is carried into the heating furnace 2, and while being conveyed in the direction of arrow B on pass rollers (not shown), it is heated by the burner 6 to a predetermined heat treatment temperature (for example, about 510℃). ℃), and heat-treated at this temperature for a predetermined period of time (for example, about 240 minutes).

The heating air is effectively uniformly distributed by the turbo fan 7 installed in the furnace, and the product P is heated.
is heated and then discharged outside the furnace, and the discharged high-temperature exhaust gas is then introduced into the preheating furnace 1 and used as a preheating source.

Here, the core sand bound inside the product P and the casting sand attached to the surface disintegrate as the binder that binds them decomposes due to oxidation and heating during the heat treatment, and is separated from the product P. Falling off, casing 5
It is discharged by the lower screw conveyor 10 and collected into a bucket 11.

However, in order to improve thermal efficiency in the heating furnace 2, the introduction of outside air is suppressed to the extent necessary for combustion in the burner 6, so the oxygen concentration gradually decreases during the heat treatment and reaches a state of about 21% of the normal level. Approximately 5-10% from
decrease to a certain extent. In such a state, the binder is not sufficiently oxidized and decomposed, making it difficult for the casting sand to fall off the surface of the product.

For this reason, in the apparatus of the present invention, fresh outside air at a high temperature and with a high oxygen concentration is introduced into the casting sand collapse promoting device 3 in the next step.

That is, in the casting sand collapse promoting device 3 into which the heat-treated product P is transported, fresh outside air is heated in the heat exchanger 12 by heat exchange with high-temperature exhaust air sent through the duct 13. After that, air is introduced from the supply duct 15 by the fan 14, and the oxygen concentration of the atmosphere inside the device 3 is increased to about 15 to 20%. This promotes oxidative decomposition of the casting sand binder, causing the casting sand to collapse and fall off easily from the product P. The fallen casting sand is then discharged and recovered by a screw conveyor 10 similar to that of the heating furnace 2.

Thereafter, the product P is carried into the cooling device 4, cooled in a water tank 17, and then carried out to a subsequent washing device or the like.

Note that some casting sand adheres to the product P carried into the cooling device 4, but when it is immersed in the water tank 17, it falls off into the water due to water agitation by the pump 19, and the sand is removed. It is discharged together with water by the pump 20 and sent to a casting sand recovery device (not shown).

As described above, in the embodiment of the present invention, fresh outside air is introduced between the heating furnace 2 using the direct heating method using the burner 6 and the cooling device 4 at the subsequent stage to create a high temperature atmosphere with high oxygen concentration. Since the device 3 for promoting casting sand collapse is provided, the casting sand, which has become difficult to collapse from the product P due to the decrease in oxygen concentration during the heat treatment in the heating furnace 2, is transferred to fresh outside air with a high oxygen concentration. This has the effect of accelerating the oxidative decomposition of the binder in the casting sand and promoting its disintegration and falling off.

Therefore, most of the casting sand adhering to the product P collapses when passing through the casting sand collapse promoting device 3, and the casting sand that is collected together with the load of the sand pump 20, etc. and moisture in the cooling device 4 of the next stage is removed. The advantage is that the labor and costs of sand recovery and reclamation are significantly reduced.

In addition, by disposing the casting sand collapse promoting device 3 on the outlet side of the heating furnace 2, the temperature inside the furnace is increased due to direct contact with low-temperature outside air when the partition door 22 on the outlet side of the heating furnace 2 is opened. It is also possible to achieve the effect of significantly reducing atmospheric disturbances such as a decrease in .

Furthermore, an atmosphere with a high oxygen concentration as described above can be obtained simply by introducing fresh outside air;
No special oxygen supply source is required, and the heating of the outside air at this time can be effectively performed by heat exchange with the high-temperature exhaust gas from within the casting sand collapse promoting device 3.

Furthermore, the exhaust gas after heat exchange is fed into the preheating furnace 1 through the exhaust duct 16.
It can also be used as a preheating source for the cooling device 4, or it can be used to dry the casting sand containing moisture recovered by the sand pump 20 of the cooling device 4, making the heat utilization of the entire device extremely efficient. Can be done.

In the above-mentioned embodiment, a partition door 22 is attached to the rear of the heating furnace 2 itself, and the zone between this and the discharge end is used as a casting sand collapse promotion zone, but the casting sand collapse promotion device is not used. Of course, it is also possible to provide 3 as an independent zone between the heating furnace 2 and the cooling device 4.

Moreover, although the heated product P is rapidly cooled with water in the water tank 17, ordinary quenching oil can be used as a refrigerant in addition to water as needed.

In addition, the embodiment has been described as a particularly suitable example of heat treatment of aluminum die casting, which is suitable for casting complex structures, and for which mold release properties from casting sand are often a problem. The heat treatment is not limited to this, but can be applied to a wide range of general castings to obtain excellent effects as long as the heat treatment is for products cast using sand molds.

As described above, the present invention has an excellent effect in that casting sand can be easily disintegrated from the product during heat treatment of the sand casting product.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an outline of an embodiment of the present invention, Fig. 2 is a longitudinal sectional view thereof, Fig. 3 is a plan view showing essential parts of an embodiment of the invention, and Fig. 4 is a longitudinal sectional view thereof. It is. Explanation of symbols, 1...Preheating furnace, 2...Heating furnace, 3
... Casting sand collapse accelerating device, 4... Cooling device, 5...
Casing, 6... Burner, 7... Turbo fan, 8... Fan motor, 10... Screw conveyor, 12... Heat exchanger, 15... Air supply duct, P... Aluminum die-cast product.

Claims (1)

[Scope of Claims] 1. A heating furnace configured to heat-treat sand castings carried in from casting equipment by combustion in an atmosphere substantially shielded from the outside air, and products carried out from the heating furnace. In the heat treatment apparatus for sand mold castings, the heat treatment apparatus is equipped with a cooling device for rapidly cooling the product in water or an oil solution, by heating and introducing fresh outside air between the heating furnace and the cooling device. 1. A heat treatment device for sand mold castings, characterized in that a sand-collapse promotion zone is provided to provide a high-temperature combustion atmosphere with a higher oxygen concentration than in a heating furnace. 2. The sand mold according to claim 1, wherein fresh outside air heated by heat exchange with high-temperature exhaust gas discharged from the casting sand collapse promotion zone is introduced into the casting sand collapse promotion zone. Heat treatment equipment for castings.