JPS62166282A - Continuous heat treatment furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a continuous heat treatment furnace, and more specifically, to improving the temperature controller 1 to roll functions in the slow cooling zone.

[Prior art and its problems] The processed material is conveyed in series from a heating and soaking machine (F) to an annealing zone, and the processed material is heated according to a required temperature curve.

A conventional continuous heat treatment furnace for cooling is shown in FIG. In the figure, 1 is a conveyor that conveys the processed material a in the direction of the arrow;
2 is a heating/soaking zone, and 3 is a gradual cooling zone. 4,4...
indicates a heat source such as a radiant tube burner. The heating/soaking zone 2 and the slow cooling zone 3 are divided into a number of temperature zones by partition walls 5, 5, . . . , and each zone is equipped with a heat source 4, 4, . Then, the temperature of the furnace gas in each zone is detected by thermocouples 6, 6, etc., and a temperature controller 7 is used to maintain each temperature zone at the required set temperature.
, 7... controls the amount of heat generated by the heat sources 4, 4.... Figure 5 shows the set temperature of each zone of this heat treatment furnace and the temperature curve of the processed material.
By dividing the temperature into a large number of temperature zones in this way, the temperature of the processed material is gradually lowered.

That is, if the number of divisions is small, the temperature difference between each zone will be large, and the processed material will be rapidly cooled each time it moves from one zone to another, resulting in abnormal quality. In particular, when the processed material is a glass product such as a Bralan tube, there is a risk of cracking due to rapid cooling. For this reason, it was essential to subdivide the temperature zones, making the construction cost of the furnace high. In addition, a heat source is installed in slow cooling zone 3 to avoid rapid cooling of the material to be treated when the temperature in each temperature zone is low, such as when the furnace starts operating, but due to continuous operation, the heat released from the material is When heat is stored in the walls, the heat source is cut off, and when the heat released from the processed material is greater than the heat released from the furnace walls, cold air is passed through the radiant tubes to remove the heat.

Therefore, the furnace must have a complicated temperature control function, making the cost of the furnace even higher.

[Means for Solving the Problems] The continuous heat treatment furnace of the present invention is intended to solve the above problems, and the heat insulation of the furnace wall of the slow cooling zone following the heating/soaking zone improves from the heating/soaking zone. It is characterized in that it gradually becomes smaller as it gets farther away. Further, the present invention provides the continuous heat treatment furnace as described above, in which a circulation fan is provided to circulate the gas sucked from the vicinity of the outlet of the slow cooling zone into the heating/soaking zone, and the hot air in the heating/soaking zone is made to flow into the slow cooling zone.
Detects the temperature of the gas in the furnace near the outlet of the slow cooling zone,
A second feature is that the amount of gas circulated by the circulation fan is controlled.

[Operation: By gradually reducing the heat insulation of the furnace wall of the slow cooling zone, the heat dissipated per unit length of the furnace is made to be the same over the entire length of the slow cooling zone.

Since the hot air from the heating/soaking zone is passed through the slow cooling zone, the temperature gradient in the slow cooling zone becomes linear, making it possible to literally slowly cool the processed product and making it easy to control the temperature.

[Example 1] Fig. 1 shows a longitudinal cross-sectional view of a continuous heat treatment furnace according to the present invention,
FIG. 2 shows a horizontal sectional view of the slow cooling zone. In the figure, a represents the processed material, and 1 represents the conveyor.

2 is a heating/soaking zone, 3 is a slow cooling zone, and 4, 4, . . . are radiant tube burners provided in the heating/soaking zone 2. Is the side wall of the slow cooling zone 3 heated and soaked as shown in Figure 2? It is formed so that it becomes gradually thinner as it moves away from IF2, so that its heat insulating properties gradually decrease. As a result, the heat dissipated per unit length of the furnace Q (K
cal/hm) is made to be the same over the entire length of the slow cooling zone. Further, an inlet 8 is provided near the outlet of the annealing zone 3, and a circulation fan 7 sucks the gas in the annealing zone 3 through the inlet 8 and circulates the sucked gas to the heating/soaking zone 2. 10 is a thermocouple provided near the outlet of the slow cooling zone 3; 11 is an electromagnetic flow rate control valve provided in the dust connecting the circulation fan 7 and the intake port 8 to control the flow rate of the suction gas; 12 is a controller that receives a temperature detection signal from the thermocouple 10 and issues a feedback command to the electromagnetic flow control valve 11. However, no heat source is provided in the slow cooling zone 3; the required temperature is maintained by flowing hot air from the heating/soaking zone 2 into the slow cooling zone 3. That is, the hot air in the heating/soaking zone 2 is transferred to the slow cooling zone 3 by the circulation of gas by the circulation fan 7.
The temperature of the slow cooling zone is raised to the set furnace temperature. In the slow cooling zone 3, the furnace wall gradually becomes thinner, so the temperature of the hot air gradually decreases as it moves away from the heating/soaking zone.

In FIG. 1, the temperature of the gas in the furnace is represented by a broken line, and the temperature of the processed material a is represented by a solid line. In this way, heating
By introducing hot air from the soaking zone, the temperature of the slow cooling zone 3 changes linearly. Since the amount of circulation by the circulation fan 7 is controlled by the flow rate control valve 11, the opening degree of the flow rate control valve 11 is controlled by the controller 12 using the thermocouple lO so that the temperature near the outlet of the slow cooling zone 3 reaches the desired set temperature. Let it be controlled. That is, when the temperature near the outlet of the slow cooling zone 3 becomes lower than the required set temperature, the opening degree of the flow rate control valve 11 is increased to increase the ring metering amount of gas and flow from the heating/soaking zone 2 to the slow cooling zone 3. Control the flow of hot air to increase so that the temperature near the outlet of the hot air becomes high, and conversely slow cooling;
j When the temperature near the F3 outlet becomes higher than the required set temperature, the opening degree of the flow control valve 11 is lowered and the heating/soaking zone 2
By suppressing the amount of hot air flowing from the cooling zone 3 to the slow cooling zone 3 and lowering the temperature in the vicinity of the outlet, feedback control is performed so that the temperature in the vicinity of the outlet is always maintained at the required set temperature. As a result, the temperature of the slow cooling zone 3 decreases rapidly from that of the heating/soaking zone 2,
The temperature of the processed material a can be lowered gently.

FIG. 3 shows an annealing zone in which the furnace wall is gradually thinned as in FIG. 2 (in this case, the inside width of the furnace remains unchanged and the outside surface of the furnace is tapered). In addition, FIG. 4 shows a slow cooling zone in which the wall of the furnace q is gradually thinned from the inner surface of the furnace q. In addition to this embodiment, various other methods can be considered.

[Effects of the Invention] As described in the embodiments above, the continuous heat treatment furnace of the present invention can linearly change the set furnace temperature without providing a large number of temperature zones in the slow cooling zone9, and Does not cause problems such as quality abnormalities or cracks. In addition, the slow cooling zone does not require a heat source and the temperature control system is simple, so the construction cost of the furnace is reduced, which has significant effects.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of a continuous heat treatment furnace showing an embodiment of the present invention and its temperature diagram, Fig. 2 is a horizontal cross-sectional view of its lehr-cooling zone, and Figs. 3 and 4 are its lehr-cooling zone. FIG. 3 is a horizontal cross-sectional view showing another embodiment of No. 3; FIG. 5 is a longitudinal cross-sectional view of a conventional continuous heat treatment furnace and its temperature diagram. a... Processed material, 2... Heating/soaking zone, 3...
・Slow cooling zone, 7...Circulation fan, 8...Intake port,
IO...Thermocouple, 11...Flow control valve. Diagram 2

Claims (1)

[Scope of Claims] 1. A continuous heat treatment furnace characterized in that the heat insulation property of the furnace wall of the slow cooling zone following the heating/soaking zone gradually decreases as the distance from the heating/soaking zone increases. 2. A circulation fan is installed to circulate the gas sucked in from near the exit of the slow cooling zone to the heating/soaking zone, and the hot air from the heating/soaking zone flows into the slow cooling zone. 2. The continuous heat treatment furnace according to claim 1, wherein the temperature of the internal gas is detected and the amount of gas circulated by the circulation fan is controlled.