JPH04116127A - Bright annealing furnace - Google Patents

Abstract

PURPOSE:To shorten the standby time in the start and resumption of operation without decreasing heat efficiency by providing an air pipe having many air ports opened toward the shell in a gap between the lining refractory and shell. CONSTITUTION:A metallic thin strip 1 is continuously traveled in an airtight furnace consisting of a heating zone 2 provided with a heating element 8 and a cooling zone 3, directly heated in a reducing atmosphere and then cooled. In this bright annealing furnace, slit air passage gaps 38 are provided in plural lines in the boundary between the lining refractory 11 of the furnace wall and the shell 14. An air pipe 39 is set in the gap 38. The pipe 39 is detained on the inner wall of the shell 14 by a fixture 47 and pierced with many air ports 39a opened toward the shell 14. The gas in the furnace is sucked from the air port 39a and discharged outside the furnace through the pipe 39, and the gas is freed of impurities outside the furnace, purified and recirculated into the furnace. Consequently, the standby time in the start and resumption of operation is reduced without decreasing heat efficiency.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bright annealing furnace, and in particular significantly shortens the start-up time (seasoning time) at the start of operation of a newly installed furnace and at the time of restarting after repair. This is a vertical and horizontal continuous bright annealing furnace that has been made possible.

[Conventional technology]

When manufacturing iron, nickel, chromium, cobalt, aluminum, titanium, copper, zinc, tin, and their alloy ribbons, so-called bright annealing is used to improve the material quality while maintaining the surface quality after cold rolling. will be applied.

In such bright annealing, it is important to maintain the inside of the furnace in a reducing atmosphere so that oxidation does not occur during the annealing. Whether the inside of the furnace has a completely reducing atmosphere can usually be determined by measuring the dew point of the water vapor in the furnace gas.

By the way, for example, bright annealing of stainless steel is 800~
Since it is necessary to carry out the annealing at a high temperature of about 1200°C, annealing furnaces, such as direct-fired annealing furnaces, are lined with refractories on the inner walls of the furnace, and the outer walls of the furnace are covered with iron skin to protect the inside of the furnace. A furnace with an airtight structure is used. A furnace having such a structure is designed to heat the ribbon introduced into the furnace by radiant heat from a heating element such as an electric heater or a radiant tube and refractory bricks also installed in the furnace.

However, in an annealing furnace with such a structure, when a new furnace is installed, or when the furnace is once opened and exposed to the atmosphere for repairs, moisture, oxygen, carbon dioxide, etc. in the atmosphere can enter the refractory bricks. Infiltrate.

Therefore, after starting or restarting the annealing process, a long time was required to create a reducing atmosphere in the furnace.

That is, if moisture or the like has entered the bricks in the furnace, dehydration and deaeration occur relatively quickly on the inner wall side of the furnace, which immediately becomes hot. However, those located from the middle layer of the furnace wall to the shell side (outer layer) are unstable near the decomposition temperature of crystallized water due to the temperature gradient, and do not reach the boiling point or the decomposition temperature of crystallized water. However, dehydration took a long time, and therefore it was not possible to maintain a reducing atmosphere in the furnace for a long period of time.

Therefore, if the furnace is operated without sufficient dehydration and without creating a sufficiently reducing atmosphere, the residual moisture in the refractory bricks will gradually come out into the furnace, and the dew point will not drop, resulting in, for example, Even if an attempt is made to anneal a ribbon containing highly reactive metals (Cr, Mn, Al, etc.) such as stainless steel, the desired bright annealing cannot be achieved. As a result, conventionally, in order to perform bright annealing at a satisfactory low dew point, a long seasoning period of one to two months was required.

By the way, in order to solve the above problem, conventionally, a cylinder made of heat-resistant steel called Matsufuru 24 as shown in FIG. ) was proposed, and an indirect heating type furnace was proposed in which the radiant heat from the heating element was transmitted to the ribbon through the matsufuru 24.

In an annealing furnace with such a structure, the dew point can be easily lowered by completely replacing the atmospheric gas in the Matsufuru 24 even at the start and restart of furnace operation; 11)
Matsufuru is easily deformed by heat and has a short lifespan, requiring frequent periodic repairs or replacement; iii) Since it is an indirect heating method, thermal efficiency is poor and the length of the furnace is long for the same capacity. Due to these drawbacks, small reactors struggled and large reactors could not be put to practical use.

[Problem to be solved by the invention]

Therefore, the inventor of the present invention solved the problems of the conventional technology as described above, namely, that it takes too much time to adjust the atmosphere inside the furnace and start up the furnace at the time of new construction and restart, and furthermore, it is difficult to apply it to large furnaces. We conducted intensive research with the aim of developing a continuous bright annealing furnace that would solve these problems.

As a result, it was found that the reason why the inside of the furnace did not quickly become a reducing atmosphere was that the moisture and oxygen that had accumulated in the low-temperature refractory bricks near the steel shell leached into the furnace over a long period of time. Therefore, if such moisture and oxygen can be actively discharged outside the furnace at an early stage and replaced with normal atmospheric gas, the atmosphere inside the furnace (
This allows for the early realization of a reducing atmosphere.

After numerous experiments and studies based on the above viewpoint, the present inventor previously published Japanese Patent Application No. 2-115740.
We have developed a new bright annealing furnace that can meet these demands.

The structure of this annealing furnace is characterized by:
A plurality of rows of ventilation holes are provided, and a suction pipe with a large number of suction ports opened on the circumferential surface is arranged within the ventilation holes,
The reason is that the gas generated inside the furnace (impure gas that remains in the lining) is actively discharged outside the furnace through this suction pipe. After removing impurities from the sucked furnace (atmosphere) gas, the cleaning (reducing) gas is
We have proposed a bright annealing furnace in which the gas is supplied back into the furnace as in-furnace gas through a circulation device.

However, the bright annealing furnace proposed above still has some points to be improved in terms of gas suction capacity in the furnace, and
Although the suction pipe was buried in refractory material, there was also the problem that it lacked protection because it was rather close to the inside of the furnace.

Therefore, in the present invention, a bright annealing furnace as described below was developed for the purpose of further improving the functions of the bright annealing furnace proposed previously.

[Means for Solving the Problems] As a novel bright annealing furnace that meets the above objectives, the present invention has a furnace wall configured by providing a refractory lining inside an outer wall iron skin, It is an airtight furnace whose interior mainly consists of a heating zone and a cooling zone connected downstream of the heating zone, in which the metal ribbon continuously introduced from the heating zone is directly heated in a reducing atmosphere. In an annealing furnace that heats to a temperature and then cools, a plurality of rows of strip-shaped ventilation gaps are provided at the boundary between the refractory lining of the furnace wall and the outer wall steel, and in these ventilation gaps, A bright annealing furnace, characterized in that a ventilation pipe having a large number of vents opening toward the iron skin side of the peripheral surface is disposed, and the ventilation pipe is locked to the inner surface of the iron skin. suggest.

In addition to the above configuration, another bright annealing furnace of the present invention is configured such that the gas inside the furnace is discharged to the outside of the furnace through the ventilation pipe, and the gas in the suctioned and discharged gas is discharged to the outside of the furnace. A furnace gas circulation device is attached to the furnace to remove impurity components and clean it, and then re-supply the gas into the furnace.

[Function] When building a new furnace, mortar is used to join the bricks. Here, in the high-temperature part of the furnace inner wall, the crystallized water in the mortar decomposes at an early stage and is easily released outside the furnace, but in the vicinity of the furnace outer wall it is difficult to reach the decomposition temperature (usually 350 to 600°C). First, it gradually decomposes depending on the operating temperature and time, and as this decomposes gradually enters the furnace during operation, the dew point inside the furnace is difficult to lower.

In addition, even in a furnace that has been completely dried through long-term processing, volatile metal components such as manganese and boron can become vapor and diffuse in the atmospheric gas, albeit in trace amounts, from the material to be treated during operation. This crystallizes and adheres to the furnace walls near the condensation temperature (mainly at the joints and back sides of refractory bricks). Therefore, when the furnace is opened for maintenance, these metal components react with water and oxygen in the atmosphere to form metal oxides with water of crystallization, and the locations where these metal oxides adhere are at relatively low temperatures. Because of this, it took a long time to decompose the crystal water when restarting operations.

As a solution to the above problem, an indirect heating type annealing furnace has been proposed in which a heat-resistant steel Matsufuru 24 is disposed between the workpiece 1 and the heat generating part, as shown in Fig. 5. However, as mentioned above, such annealing furnaces still have various problems.

Therefore, in the present invention, in order to solve the problem of the above-mentioned direct-fire annealing furnace, as shown in FIG. We decided to install a gas exhaust structure in the furnace body, especially in the heating zone, consisting of a ventilation gap for suctioning gas from the furnace atmosphere, a suction pipe with a suction port disposed within the gap, and a discharge port. . In such a gas suction and discharge structure, in particular, if the furnace atmosphere gas that has flowed into the ventilation gap or suction pipe is quickly sucked and discharged outside the furnace through the exhaust port, even if the gas inside the refractory near the steel shell is Even if the crystal water decomposes in the low vortex section of the furnace, the generated water can be discharged to the outside of the furnace along with the atmospheric gas through the gas suction and discharge structure, so it will not enter the furnace and adversely affect the furnace operation. .

With such a configuration, the present invention can efficiently suck and discharge the gas generated in the furnace with a small suction load, and therefore can advantageously solve the above-mentioned drawbacks of the prior art. This also creates the ripple effect of uniformly distributing the temperature inside the furnace.

[Example] Preferred embodiments of the present invention will be described in detail below.

FIG. 1 schematically shows a preferred example of the continuous bright annealing furnace of the present invention. In the figure, reference numeral 1 is a metal ribbon which is the material to be processed, 2 is a heating zone, and 3 is a cooling zone, which constitute a continuous bright annealing furnace. is introduced into the furnace which is kept airtight through the
After being subjected to a predetermined heat treatment while being conveyed through the heating zone 2 and the cooling zone 3, it is led out of the furnace from the furnace outlet seal portion 5. In addition, 6 is a gas cooler 7 is a blower.

FIG. 3(a) is an enlarged view of the furnace wall in the heating zone, and FIG. 3(b) is a view taken along line B--B in the figure. What is indicated by reference numeral 8 in the figure is a heating element consisting of an electric heater, which is energized from the power supply member 9, and depending on the input power amount,
This is to adjust the temperature inside the furnace. 10 is a support metal fitting for the electric heater. The lining that makes up the furnace wall is made of fireproof and insulating bricks shown as 11 and 12 in the diagram.
It consists of a heat insulating material 3 preferably made of castable material, and the outer wall is made of an iron skin 14.

In the present invention, as shown in FIGS. 3(a) and 3(d), a heat insulating material 13 is provided between the steel shell 14 and the lining, particularly between the steel shell 14 and the refractory insulation bricks 12, that is, in contact with the steel shell 14. In particular, in the case of a horizontal type, the ventilation gaps 38 in the form of strips obtained by cutting holes are provided in multiple rows so as to surround the furnace chamber with the upper part of the furnace shell as the center. A metal ventilation pipe 39 is loosely inserted into the ventilation gap 38 adjacent to the ventilation gap 38, which is used for suction of gas in the furnace or for discharging reflux gas into the furnace.

As a method for fixing the ventilation pipe 39 along the inner surface of the steel shell 14 within the ventilation gap 38, as shown in FIG. etc. are suitable. This is because the ventilation pipe 39 must be installed in a state that can absorb expansion and contraction due to temperature differences.

Now, in the present invention, the furnace wall structure of the heating zone 2 of the furnace is as follows:
As mentioned above, by arranging a large number of ventilation gaps 38 and ventilation pipes 39 in a row in the part that contacts the iron skin 14, firstly,
The reaction gas generated in the furnace atmosphere of the heating zone 2 can be sucked and discharged, and secondly, the reflux gas can be discharged into the furnace again. Moreover, by adopting such a structure, the inside of the furnace can be kept airtight, and heat will not be wasted out of the furnace.

The vent holes 39a provided in the vent pipe 39 are desirably opened on the circumferential surface of the pipe, particularly facing the iron shell 14 side, and these are desirably opened in two rows. According to such a configuration, the furnace gas flowing along the inside of the furnace wall shell can be effectively sucked.

FIG. 3(c) shows that the inside of the furnace is 12 in the above furnace wall structure.
It shows the temperature distribution in the thickness direction of the furnace wall when heated to 00'C. As is clear from the figure, the temperature of the furnace wall becomes lower as it approaches the steel shell 14, and for this reason, the ventilation pipe 39 is arranged at the boundary between the steel shell 14 and the lining refractory 13. I understand the significance of what I do.

Next, in the case where the present invention is applied to a vertical bright annealing furnace, the flow of atmospheric gas in the vertical bright annealing furnace will be explained based on FIG.

The fresh atmospheric gas supply system (■) connects the gas supply port 16 provided in the cooling zone 3 to each seal section 4, 5 on the inlet and outlet sides of the furnace.
It is supplied to replenish the leakage from the furnace and maintain the pressure inside the furnace higher than atmospheric pressure at all times. In addition, cooling zone 3
In this case, the gas in the furnace is sucked and cooled by a blower via the gas cooler 6, and after being pressurized, the gas is blown back into the furnace as cold air through a nozzle. This is the only atmospheric gas supply system in a conventional annealing furnace.

In this regard, in the bright annealing furnace of the present invention, in addition to the above-mentioned new gas supply system
9, the atmospheric gas inside the heating furnace and the atmospheric gas at the inlet and outlet sides of the furnace are collected and sucked through a large number of vent holes 39a provided on the circumferential surface thereof.

A circulating gas system consisting of system (2) is added.

First, the circulating gas system (①) includes a blower 17, a dew point meter 18 that measures the dew point of the atmospheric gas, and a system that reacts free oxygen that has adhered to the ribbon 1 and entered the furnace with hydrogen in the atmosphere. It is composed of deoxo 19, which converts it into water, and a dehydrator 20, which adsorbs and removes moisture and carbon dioxide in the atmospheric gas. Alternatively, the gas may be blown into the cooling zone 3 inside the furnace from the gas supply port 16.

In addition, in the circulating gas system (2), atmospheric gas is sucked in from near the seals on the inlet and outlet sides of the furnace, and after measuring the dew point with a dew point meter 21, the gas is passed through the blower 22 and connected to the circulating gas system (2) and deoxo. This is a circulating gas system that merges just before No. 19.

Although there are some differences between vertical and horizontal furnaces, the above-mentioned gas exhaust structure has a long ventilation pipe 39 that runs the entire length of the heating zone 3 along the furnace wall, as shown in Figure 1. In addition to the case where short ventilation pipes 39 are arranged in parallel, for example, as shown in FIG.
may be connected. In any case, the ventilation gaps 38 and the ventilation pipes 39 are arranged so as to surround the furnace body.

Furthermore, such a gas exhaust structure may be provided not only in the heating zone but also in the inlet side portion.

As described above, according to the present invention, the furnace atmosphere gas flowing mainly into the ventilation gap 38 and the ventilation pipe 39 provided along the inner surface of the iron shell 14 of the heating zone 2 is transferred to the circulating gas system 0.
In addition to suctioning gas through the inlet and outlet sides of the furnace, the atmosphere gas inside the furnace is also sucked through the circulating gas @, and these suctioned and discharged furnace atmosphere gases are circulated back into the furnace, thereby quickly achieving a normal atmosphere inside the furnace. Therefore, it is possible to significantly shorten the waiting time when starting and restarting the operation of the direct-fired continuous bright annealing furnace.

Next, the operating procedures of each supply system in actual furnace operation of the bright annealing furnace of the present invention will be explained.

First, regarding the new gas supply system (2), the amount of gas necessary to maintain the inside of the furnace at a predetermined pressure will be supplied throughout the entire operation period.

Next, the circulating gas system (■) is operated at full capacity when starting or resuming operation, and while monitoring the dew point meter 18, the suction power is gradually weakened as the drying progresses. For example, the stop valve 23 is closed at the same time as the suction by the blower 17 is stopped. The reason why the system (1) is stopped after drying is completed is to prevent volatile metal vapor in the furnace from unnecessarily depositing on the refractories, as described above.

In addition, as a more advantageous measure to prevent the deposition of volatile metal vapors,
After the drying is completed, the clean gas that has completed the dehydration process is supplied by closing the stop pulp 23, opening the stop pulp 26, and stopping the blower 17.
Conversely, it is also possible to send it into the furnace and reflux it through the discharge port 15 and the ventilation pipe 39 provided in the furnace shell, by utilizing the pressure difference between the inside and outside of the furnace.

Further, the circulating gas system @ is the entrance and exit of the furnace and the point of contact with the outside air. Therefore, since AT air constantly enters, it is necessary to monitor the dew point meter 21 and actively suck the air in order to maintain the desired low dew point at all times.

The above explanations of the circulating gas systems (1) and (0) are mainly for the case where the sucked atmospheric gas is reused. However, the present invention does not necessarily require only a circulation supply system for cleaning and re-blowing the sucked atmospheric gas.

Alternatively, a so-called suction and discharge system may be used, which simply sucks and discharges atmospheric gas from at least the furnace wall. Note that in this case, if the sucked atmospheric gas is not cleaned or reused, the sucked gas is released by opening the gas valve 25;
The stop valve 23 in the circulating gas system (2) may be closed and the gas may be directly released into the atmosphere from the dissipation brigoo.

The second explanation based on Fig. 1 is an example in which the structure of each part of the annealing furnace is a joint type; that is, the arrangement of each zone of the sheet passing path from the heating zone inlet to the cooling zone outlet is vertically arranged. However, in the present invention, it is also possible to arrange the respective bands side by side, and even in this case, the operation and effect of the present invention does not particularly change.

That is, FIG. 4 illustrates the configuration of another embodiment of the present invention. In the figure, the metal ribbon 1 conveyed horizontally passes through a furnace inlet sealing section 41, a heating zone 42, an annealing zone 43, and a cooling zone 44 which are arranged horizontally in order, and then passes through a furnace outlet sealing section 45. However, during this time, the ribbon 1 is conveyed horizontally, unlike in the first illustrated example. For this purpose, a plurality of support rolls 46 for supporting the ribbon are arranged in rows along the furnace conveyance line in each zone 42, 43, 44 to prevent the threaded material from sagging.

In addition, the symbols 6.7.14.15 to 23.25 shown in the figure
26 all have the same construction as that of the annealing furnace shown in FIG. 1, and it is sufficient for them to simply arrange the joint molds to suit the horizontal arrangement.

〔Effect of the invention〕

(According to this invention, the waiting time before starting or resuming operation can be significantly shortened compared to the conventional method without reducing the thermal efficiency, which is an advantage of the direct-fired type. It's a big deal.

Moreover, according to the present invention, the furnace atmosphere gas is sucked.

Since the suction pipe is installed in the ventilation gap along the inner surface of the steel shell, where the temperature is lowest, the suction pipe is protected and the gas in the furnace can be suctioned and discharged smoothly. .

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a preferable example of the continuous light annealing furnace of the present invention, which is a vertical example, and Fig. 2 is a joint type continuous annealing furnace of another embodiment of the present invention when the ventilation pipe is divided. A schematic diagram showing the furnace. Figure 3 (a) is an enlarged sectional view of part A in Figure 1, and Figure 3 (b) shows how the ventilation pipe is fixed. (c) is a temperature distribution diagram in the thickness direction of the furnace wall, (d) is a partial cross-sectional view of the ventilation pipe installed, and (e) is (a). ) A cross-sectional view taken along the line X-X in the figure,
Fig. 4 is a schematic diagram showing a preferred example of a horizontal continuous bright annealing furnace which is another embodiment of the present invention, and Fig. 5 is a schematic diagram of a conventional contracted continuous bright annealing furnace equipped with a matzuru in the heating zone. It is. ■...Metal thin strip, 2...Heating zone, 3...Cooling zone,
4...Furnace inlet seal part, 5...Furnace outlet seal part,
6... Gas cooler 7... Blower end... Heating element, 9... Power supply member, 1o... Supporting metal fitting, 11...
...Inner refractory brick, 12...Insulating brick, 13
...Heat insulation material, 14...Iron shell, 15...Discharge port, 15a...Discharge pipe, 16...Gas supply port,
17, 22... Blower 18, 21... Dew point meter, 1
9... Deoxo, 20... Dehydration device, 23, 25
．． 26...Stop pulp, 24...Matsuful,
3I...Inlet seal part, 32...Heating zone, 33.
... slow cooling zone, 34... cooling zone, 35... outlet seal section, 36, 37... support roll, 38... ventilation gap, 39... ventilation pipe, 39a... ventilation port ,
41...Furnace inlet seal part, 42...Heating zone, 43
...Annealing zone, 44...Cooling zone, 45...Furnace outlet seal portion, 46...Support roll, 47...Fixing metal patent applicant Nippon Yakin Kogyo Co., Ltd. Chugai Roko Kogyo Co., Ltd. Agent Patent Attorney Jun Ogawa Sando Patent Attorney Morio Nakamura Figure 1 Figure 3 Figure 2 Wards (d) (e)

Claims (1)

[Claims] 1. It has a furnace wall constructed by providing a refractory lining inside an outer wall iron skin, and the interior mainly consists of a heating zone and a cooling zone connected downstream of the furnace wall. In an annealing furnace which is an airtight furnace and which directly heats a metal ribbon continuously introduced from the heating zone in a reducing atmosphere and then cools it, the furnace wall lining refractory and Multiple rows of strip-shaped ventilation gaps are provided at the boundary with the outer wall steel skin, and within these ventilation gaps, a large number of ventilation holes are opened toward the steel skin side of the surrounding surface. A bright annealing furnace characterized in that a pipe is provided and the ventilation pipe is locked to the inner surface of the iron shell. 2. It is an airtight furnace with a furnace wall consisting of a refractory lining on the inside of the outer shell, and the interior mainly consists of a heating zone and a cooling zone connected downstream of it. In an annealing furnace of the type in which a metal ribbon continuously introduced from the heating zone is directly heated in a reducing atmosphere and then cooled, the boundary between the refractory lining of the furnace wall and the outer wall steel is A plurality of rows of strip-shaped ventilation gaps are provided in the section, and within these ventilation gaps, ventilation pipes with a large number of ventilation holes opening toward the iron shell side of the circumferential surface are arranged. , the ventilation pipe is fixed to the inner surface of the iron shell, and the gas inside the furnace is discharged to the outside of the furnace through the ventilation pipe, and impurity components in the suctioned and discharged gas are discharged outside the furnace. What is claimed is: 1. A bright annealing furnace characterized in that a bright annealing furnace is additionally provided with a circulation device for re-supplying furnace gas to the inside of the furnace after the gas is removed and cleaned.