JP2003013142A - Heat treatment method for cast-iron pipe and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable even a socket part with a thick wall of a tube to be heat treated almost simultaneously with a straight part of the tube, when annealing the cast-iron tube having the socket part with the thick wall. SOLUTION: This heat treatment method for heating the tube 3 provided with the socket in a heat treatment furnace 1 after casting, is performed by heating the socket part 3a of the cast-iron tube 3 in a fluidized bed furnace 6 arranged in the heat treatment furnace 1, at the same time when heating the tube 3 in the heat treatment furnace 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method for cast iron pipes and an apparatus therefor.

[0002]

2. Description of the Related Art Pipes such as cast iron pipes and ductile cast iron pipes are preferably cast out of a metal frame as soon as possible after casting to improve production efficiency.

For this reason, conventionally, a cast water metal mold of a cast iron pipe is installed in a cooling sleeve, and cooling water is supplied between the metal frame and the cooling sleeve to cool the rotary water jacket system. Often cast in a casting machine.

[0004]

However, since the casting apparatus of this system cools the metal frame with cooling water, the cooling rate of the cast pipe is high, which makes it easy for crystallization of cementite in the product structure. There was a problem that the material was hard and brittle.

Therefore, when a pipe is cast by such a casting apparatus, a heat treatment step of annealing is required to decompose the cementite crystallized in the dough structure to form ferrite. In the heat treatment furnace for performing this annealing, generally, the inside of the furnace is heated by a heating device such as a kerosene burner, and the heat contained therein heats the cast iron pipe carried into the furnace. As shown in FIG. In the pipe 3, since the wall thickness T1 of the receiving portion 3a is generally thicker than the wall thickness T2 of the straight pipe portion 3b, even if the thin straight pipe portion 3b is transformed into the target dough structure, the receiving portion 3a
The heat treatment in the thick core portion, that is, in the vicinity of the central portion of the thickness, may remain insufficient.

In this case, the material of the straight pipe portion and the material of the receiving portion are different even though the heat treatment is performed, which is a quality problem. In order to solve such a problem, it is conceivable to lengthen the heat treatment time so that sufficient heat treatment is performed up to the central portion of the wall thickness of the receiving portion, but such a treatment is not suitable for product quality control. Even if it is preferable, since the straight pipe portion is subjected to unnecessary heat treatment, the heat treatment wastes time and cost, which is not a good measure in terms of manufacturing efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and to make it possible to heat-treat a receiving portion of a pipe having a thick wall at almost the same time as a straight pipe portion. It is a thing.

[0008]

In order to solve the above problems, the heat treatment method for a cast iron pipe according to the first aspect is such that when the pipe with a socket is heat treated in a heat treatment furnace after casting, the pipe is kept in the heat treatment furnace. The heat treatment is performed simultaneously on the inlet portion of the cast iron pipe in the fluidized bed furnace provided in the heat treatment furnace during the treatment.

Therefore, according to this method, the thin-walled tube portion of the tube with the receiving port is the heat in the heat treatment furnace, and the thicker receiving portion is in the fluidized bed furnace provided in the heat treatment furnace. Since the flowing heat transfer medium is processed with high heat conduction efficiency, the time required for heat treatment of the receiving part can be shortened, and as a result, the pipe receiving part can be operated only by the time required for the heat treatment of the straight pipe part. The heat treatment of the entire tube including it becomes possible within a short time.

According to a second aspect of the present invention, there is provided a heat treatment apparatus for a cast iron pipe, which is an apparatus for performing the method according to the first aspect, wherein the heat treatment furnace is equipped with a heating device necessary for heat treating the cast iron pipe after casting. A fluidized bed furnace having a volume capable of receiving the receiving portion of the cast iron pipe is provided, and the receiving portion of the cast iron pipe carried into the heat treatment furnace can be inserted into the fluidized bed furnace.

According to this apparatus, it is possible to perform efficient heat treatment simply by providing a fluidized bed furnace in the conventional heat treatment furnace, and it is possible to perform efficient heat treatment with a small amount of equipment.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described. FIG. 1 is a sectional view of a heat treatment furnace for carrying out the method of the present invention.

The heat treatment furnace 1 for carrying out the method of the present invention is
A heating device such as a kerosene burner (not shown) is provided in a furnace chamber formed of a heat insulating material 1a such as refractory brick. A guide rail 4 is provided along the ceiling 1a of the heat treatment furnace 1, and a suspension device 5 for the cast iron pipe 3 to be heat treated such as annealing is provided.
Are movably supported along the guide rails 4.

The suspending device 5 is supported by the carriage 5a which is movable along the guide rail 4, a moving mechanism 5b which is vertically movable with respect to the carriage 5a, and a moving mechanism 5b. The open / close arms 5e and 5e,
A hook 5d that engages with a band member 5c attached to one end of the cast iron pipe 3 is provided at each tip.

On the floor 2 in the heat treatment furnace 1, an open upper fluidized bed furnace is formed of a heat-resistant material at a position corresponding to the socket 3a at the lower end of the cast iron pipe 3 supported by the suspension device 5. 6 is provided, and the ceramic powder,
The heating medium 7 such as silica sand is filled, and the heating medium 7 is heated by high-temperature hot air blown from a nozzle 8 provided at the bottom of the fluidized bed furnace 6.
Are to be fluidly circulated.

The heat treatment furnace 1 is provided with inlets and outlets (not shown) of the cast iron pipe 3 on both left and right sides of the treatment furnace 1 shown in FIG. 1 so that the heat treatment of the cast iron pipe 3 can be continuously performed. ,
The cast iron pipe 3 is supplied and carried out into the processing furnace 1 by a suspension device 5 which runs along the guide rails 4.

Next, the heat treatment method for annealing will be described.
The band member 5c is attached to the cast iron pipe 3 to be heat-treated, and the hook 5d is hooked on the band member 5c, and is suspended and supported so that the receiving port 3a is at the lower end. It is carried into the heat treatment furnace 1.

When the receiving port 3a portion of the cast iron pipe 3 crosses the peripheral wall of the fluidized bed furnace 6, the moving mechanism 5b is lowered so that the receiving port 3a is inserted into the heating medium 7 in the fluidized bed furnace 6. To

High-heat air is blown from the nozzle in the fluidized bed furnace 6, and the heating medium 7 is circulated and flowed in the fluidized bed furnace 6. Since the heating medium 7 made of ceramics or silica sand powder has a larger amount of heat contained than air, thermal influences from the outside are less likely to float and the temperature in the fluidized bed furnace 6 can be easily maintained at a constant high temperature.

Moreover, since the thermal conductivity of the heating medium 7 such as ceramics and silica sand is about 10 to 1000 times that of air, a large amount of heat can be conducted to the receiving port 3a in a short time.
A large temperature rise can be achieved in a short time even with a thick-walled inlet.

For example, when silica sand is used as the heating medium, it has been confirmed that the time required for heating to a desired high temperature is 1/50 to 1/100 as compared with the case of using only air. ing.

Therefore, while the thin-walled pipe portion other than the receiving port 3a is being heated by the heated air in the heat treatment furnace 1, the receiving port 3a part has a large heat capacity and a high heat conductivity. Is heated to a high temperature in a short time in the fluidized bed furnace 6 in which the is circulated.

Therefore, even in the thick-walled receiving port 3a, which is difficult to be rapidly heated only by the high-temperature heated air in the heat-treating furnace 1, the heat-treatment ends almost simultaneously with the thin-walled pipe portion,
It is possible to eliminate the time waste of continuing the heat treatment until the heat treatment of the receiving end is completed even though the heat treatment of the thin portion is completed as in the conventional case.

[0024]

As described above, according to the heat treatment method for cast iron pipes of claim 1, since the heat treatment of the thick-walled receiving portion is performed by the fluidized bed furnace further provided in the heat treatment furnace, other wall thicknesses are obtained. The heat treatment of the thick-walled receiving portion can be finished at the same time when the heat treatment of the thin portion is finished, and the heat treatment of the pipe with a receiving opening can be accelerated.

Further, according to the heat treatment apparatus for cast iron pipes of the second aspect, since it is only necessary to install the tank of the fluidized bed furnace in the existing heat treatment furnace, the heat treatment furnace for efficient heat treatment is easy. It has the effect that it can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view of a heat treatment furnace for carrying out a heat treatment method for cast iron pipes according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a cast iron pipe to be lined.

[Explanation of symbols]

1 heat treatment furnace 1b insulation 2 Floor of heat treatment furnace 3 cast iron pipe 4 guide rails 5 Suspension device 6 fluidized bed furnace

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Claims (2)

[Claims] 1. When heat treating a pipe with a socket in a heat treatment furnace after casting, the socket portion of the cast iron pipe is provided in the heat treatment furnace while the pipe is being processed in the heat treatment furnace. A heat treatment method for cast iron pipes, characterized in that heat treatment is performed simultaneously in a fluidized bed furnace. 2. A heat treatment furnace equipped with a heating device required for heat treatment of a cast iron pipe is provided with a fluidized bed furnace having a volume capable of receiving a receiving portion of the cast iron pipe, and is carried into the heat treatment furnace. A heat treatment apparatus for a cast iron pipe, which is constructed so that a receiving portion of the cast iron pipe can be inserted into the fluidized bed furnace.