JPS6235007Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an improvement of a gas-heated forced circulation annealing furnace.

For example, an annealing furnace for elongated bodies such as conductors for various cables includes a gas-fired furnace body equipped with an introduction part for the elongated body, that is, an object to be annealed, a drawer part, and a gas combustion burner, and a combustion furnace in the furnace body. A gas heat forced circulation annealing furnace whose main component is a gas heat forced circulation device is generally used.

Such a gas thermal forced circulation annealing furnace uses a forced circulation device to circulate high-temperature combustion gas (CO ₂ , CO, H ₂ O, N _2, etc.) generated by gas combustion of fuel gas injected into the furnace. This is a device that performs annealing by circulating the air and spraying it onto the object to be annealed. In this case, the amount of fuel gas and air are brought close to the theoretical combustion ratio to achieve almost complete combustion, thereby keeping the residual oxygen in the furnace as low as possible. For example, it has the advantage of enabling bright annealing that avoids oxidative discoloration of the object to be annealed without introducing other gases such as water vapor and N ₂ .

However, in general, there is no mixer, burner, or the like that can perform annealing while keeping the mixture ratio of fuel gas and air constant at all times, with the amount of fuel gas supplied ranging from a small amount close to zero to an unlimited amount. Therefore, in practice, the amount of heat required to raise the temperature of the furnace at the start of work is set as the maximum flow rate, and the above-mentioned fuel gas flow rate between that and the minimum flow rate reaching the lower limit (this minimum/maximum ratio is generally referred to as town-down) Generally, the annealing operation is performed while appropriately controlling the fuel gas/air ratio within a so-called control range, which is a portion where the fuel gas/air ratio is within an allowable range.

In the gas heat forced circulation type annealing furnace, introduction of excessive air hinders bright annealing of the object to be annealed, so the town-down is restricted to be narrower than that of general gas combustion equipment, and is approximately 1/3 the size. Naturally, the amount of combustion gas generated increases depending on the amount of fuel gas burned in the annealing furnace, and some of it is discharged outside the furnace, which creates a pressure difference between the inside and outside of the furnace, and as described above. This effectively suppresses the inflow of outside air into the furnace. In particular, the above-mentioned oxidation discoloration tends to progress in the annealing furnace draw-out section where the temperature of the object to be annealed reaches a certain temperature or higher, so water seals are especially applied in this section to prevent the above-mentioned outside air from flowing into the furnace. I have to.

On the other hand, in view of the recent rise in the price of thermal energy, there has been a remarkable increase in thermal efficiency due to improvements in insulation and exhaust efficiency for this type of annealing furnace. The amount of fuel gas burned during continuous annealing in an annealing furnace is now sufficient, which lowers the pressure inside the furnace, resulting in the above-mentioned outside air flowing in from outside the furnace, which can lead to oxidative discoloration of the object to be annealed. It was something that caused it to occur.

As a result of intensive studies to solve this problem, the inventors installed a heat exchanger in the annealing furnace to take out a part of the heat inside the furnace during continuous annealing, and determined the temperature inside the furnace based on this. They discovered that it was possible to prevent the occurrence of oxidative discoloration of the object to be annealed by increasing the amount of fuel gas supplied to correspond to the drop and raising the pressure inside the furnace, and completed this idea.

That is, this idea divides the inside of the furnace into two upper and lower air ducts through a partition wall, communicates both air ducts with a circulation passage, and installs a gas combustion burner and a forced circulation device for combustion gas in the upper air duct. In the gas heat forced circulation annealing furnace, the lower air passage is provided with an introduction part and a drawer part for the material to be annealed, and the drawer part is provided with a water sealing device for preventing outside air from flowing into the furnace. A heat exchanger is installed in the upper air duct, and a part of the heat inside the furnace is taken out of the furnace through the heat exchanger as a heating source for auxiliary equipment such as a water sealing device, and is supplied to the inside of the furnace by lowering the furnace temperature. This is a gas thermal forced circulation type annealing furnace characterized by increasing the amount of fuel gas and increasing the furnace internal pressure.

An embodiment of this invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a furnace body divided into two upper and lower air passages 1A and 1B by a partition wall 1a.
Circulation communication portions 1b and 1c are provided to communicate with each other.

The upper air passage 1A is provided with a gas combustion burner 2 and a combustion gas circulation fan 3, and the lower air passage 1B is provided with a gas combustion burner 2 and a combustion gas circulation fan 3.
has both ends serving as an inlet 5 and an outlet 6 for the object to be annealed 4, and circulates the combustion gas from the burner 2 between the air passages 1A and 1B via the partition wall communication parts 1b and 1c. The structure is configured to perform continuous annealing.

A water seal device 7 is connected to the outlet 6.
is installed. This water seal device 7 is a seal having a passage hole 10a on the pass line of the object to be annealed 4 in a chain 9 having a water reservoir portion 8 at the bottom and opening only into the furnace through the outlet 6 of the furnace main body. It is constructed by constructing a water holding tank 10.

A heat exchanger 11 is installed in the upper air passage 1A in the furnace, and a circulation pipe 12 is arranged as shown in the figure so that a part of the temperature inside the furnace is exchanged with the seal water.

In the figure, 13 is a heat exchange circulation pump, 14
15 is a seal water circulation pump, and 15 is a seal water heater.

The annealing furnace as described above circulates high-temperature combustion gas in the furnace by igniting the gas combustion burner 2 and driving the circulation fan 3, raises the temperature to an appropriate temperature, and then inserts hard copper wire, etc. from the inlet 5. The wire is passed through the wire and continuous annealing is performed.

Then, using such an annealing furnace, the gas used is butane gas, 1.0 mmφ copper wire, and the line speed is
Figure 2 shows the interrelationships among the gas flow rate, air mixture ratio, and oxide film thickness on the surface of the copper wire when annealing is performed at 10 m/min.

As shown in the figure, the oxide film thickness increases rapidly in the region where the gas supply amount reaches 0.5 m ³ /H and is less than this. In the present invention, the heat exchanger 11 is operated under a certain continuous operation during the annealing operation, and a portion of the heat inside the furnace is absorbed, thereby increasing the amount of gas supplied, thereby making it possible to avoid the area where discoloration occurs. It is.

On the other hand, when an appropriate amount of steam is supplied to the copper wire to be annealed at the outlet of the annealing furnace, the amount of oxide film generated is reduced.

In the furnace of the present invention, steam is generated in the water seal section through the heat exchange described above, and this steam is sent into the furnace from the furnace outlet, thereby appropriately suppressing the formation of an oxide film.

This invention will be specifically explained below with reference to Examples.

(Example) The annealing furnace of the example described above (furnace length 6 m, furnace width 1
m), circulating combustion gas temperature 500℃, circulation amount 30
It was operated under the condition of m ³ /min, and 20 1.0 mmφ copper wires were
The wire was wired and annealed at a wire speed of 30 m/min.

In this case, the amount of burner combustion gas is 0.5 to 0.6 m ³ /
No particular oxide film was observed on the surface of the copper wire. Next, it became necessary to change the type of paint in the baking machine (not shown) installed in tandem with this annealing furnace, so the linear speed was increased to 10 m/min.
When the combustion gas temperature was lowered to 450° C., the gas amount decreased to 0.4 to 0.5 m ³ /H, and the formation of an oxide film on the surface of the copper wire was clearly observed.

The pressure inside the furnace at this time (above the above introduction part) is 16mmHg
This was a sharp decrease from 21mmHg before the gas amount change. On the other hand, when the seal water of the water seal device 7 was circulated as described above through the illustrated heat exchanger (pipe outer diameter 35 mmφ, length 2 m) and heat exchange was performed, the gas amount returned to approximately 0.5 to 0.6 m ³ /H. The oxide film disappeared, and the temperature of the seal water reached about 80° C., making it unnecessary to use a heater of about 5 K.W. that was required to raise the temperature.

As is clear from the above explanation and the results of the examples, the annealing furnace according to this invention extracts a part of the heat in the furnace through heat exchange and increases the amount of combustion gas by the amount of heat, especially during continuous operation. Since the inflow of outside air is prevented by reducing the pressure inside the furnace, the formation of an oxide film on the object to be annealed can be reduced as much as possible, and the heat extracted from the above heat exchange can be used for heating seal water, etc. It has the effect of improving thermal efficiency compared to those that use a boiler.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an example of the annealing furnace of the present invention, and FIG. 2 is a diagram showing the relationship between the gas flow rate and the amount of oxide film in an example of wire annealing using the same apparatus. 1... Annealing furnace, 1a... Partition wall, 1A, 1B...
...Wind channel, 1b, 1c... Circulation communication part, 2... Gas combustion burner, 3... Circulation fan, 4... Material to be annealed, 5... Introducing part, 6... Drawer part, 7... Water Sealing device, 11... heat exchanger.

Claims (1)

[Scope of utility model registration request] The inside of the furnace is divided into two upper and lower air ducts via a partition wall, and both air ducts are connected through a circulation communication section.The upper air duct is equipped with a gas combustion burner and a forced circulation device for combustion gas, and the lower air duct is equipped with a gas combustion burner and a forced circulation device for combustion gas. In the gas heat forced circulation type annealing furnace, the annealing furnace is provided with an introduction part and a drawer part for the object to be annealed, and the drawer part is provided with a water sealing device for preventing outside air from flowing into the furnace. A heat exchanger is installed, and a part of the heat inside the furnace is taken out of the furnace as a heating source for attached equipment such as a water sealing device through the heat exchanger.By lowering the furnace temperature, the amount of fuel gas supplied inside the furnace can be reduced. A gas heat forced circulation type annealing furnace characterized by increasing the internal pressure of the furnace.