JPS639566B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous annealing furnace for heat treating metal strip.

Generally, in a continuous annealing furnace, the ends of metal strips of different materials and sizes are connected by welding and annealed continuously, depending on the type of product required. In this case, precise heat treatment must be performed that matches the material and dimensions of the metal strip.

Therefore, in the past, furnace temperature settings for each zone were calculated using a computer based on conditions such as line speed, soaking temperature conditions, plate thickness, and heat balance equations, and the furnace was operated based on the set furnace temperatures.

However, in this conventional method, in actual operations, it is common to consider various possible cases, provide each data, perform offline calculations, and convert the results into approximate formulas and input them into a process computer for processing. However, it is difficult to perform precise heat treatment control in all cases, and there is a drawback that accuracy is poor.

The present invention was proposed in order to solve the above-mentioned drawbacks, and it is possible to precisely control the soaking temperature of a metal strip with a simple controller and low equipment cost without requiring complicated calculations, thereby improving product quality. The purpose is to provide an improved continuous annealing furnace.

The gist of the present invention is to provide a monitoring zone at the entrance of the soaking zone that compensates for only the amount of heat dissipated in order to maintain the target soaking furnace temperature of the metal strip. This is a continuous annealing furnace in which the furnace temperature in each zone of the heating zone is feedback-controlled based on the change in furnace temperature in the monitoring zone.

First, the premise of the establishment of the present invention will be explained using an electric heater type horizontal continuous annealing furnace.

When soaking a metal strip at a target temperature in a continuous annealing furnace, ideally an infinitely long furnace would be provided and all zones would be brought to a furnace temperature equal to the target temperature. However, since it is practically difficult to provide such a furnace, a method is used to uniformly heat the product by lowering the line speed as much as possible. However, due to the recent trend toward energy conservation and higher line speeds, higher head furnace temperatures are being promoted. The goal is to get an A. In the present invention, a monitoring zone 5 is provided between the heating zone 6 and the soaking zone 7 in which the amount of heat radiated is compensated for, and the furnace temperature in this monitoring zone 5 is always maintained at the target soaking temperature Aa of the metal strip. . When the metal strip is heated according to the ideal temperature increase pattern A, the metal strip enters the monitoring zone 5 at a temperature Ai, which is approximately the same as the target soaking temperature Aa, and exits at a temperature Ao.
If the metal strip adopts temperature rise pattern B for some reason, the material temperature at the entrance of monitoring zone 5 will be Bi,
The material temperature at the outlet is Bo, and the furnace temperature Ba in the monitoring zone 5 at that time satisfies the following relationship: Bi=Ba−ΔB1≦Ba−ΔB2=Bo≦Ba (1).

Conversely, if the metal strip follows temperature increase pattern C, the material temperature at the entrance of the monitoring zone 5 is Ci, the material temperature at the exit is Co, and the furnace temperature Ca of the monitoring zone 5 at that time is Ci=Ca+ΔC1≧Ca+ΔC2 ＝Co≧Ca ……(2) Satisfies the relationship.

Here, ΔB1, ΔB2, ΔC1, and ΔC2 are the temperature deviation amounts between the furnace temperature and the material temperature.

Therefore, when the furnace temperature in monitoring zone 5 reaches Ba,
By increasing the furnace temperature of the heating zone 7 sequentially in the 6th, 5th, 4th zones, etc., the furnace temperature of the monitoring zone 5 is raised from Ba to
If Aa is set, the temperature increase pattern changes from B to A, and the optimum temperature increase pattern, that is, the optimum soaking condition is established.

Conversely, when the furnace temperature in the monitoring zone reaches Ca, the heating zone
By lowering the furnace temperature in monitoring zone 5,
If Ca is changed to Aa, the temperature increase pattern changes from C to A, and the optimum temperature increase pattern, that is, the optimum soaking conditions are established.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments with reference to the drawings.

As shown in FIG. 2, a monitoring zone 5 is provided between the heating zone 6 and the soaking zone 7 by arranging and partitioning the zones with partition walls 4, 4, . Such a partition wall 4,
4..., the furnace temperature in the monitoring zone 5 is not affected by the furnace temperatures in the heating zone 6 and the soaking zone 7, and the accuracy of control is improved. Furthermore, within this monitoring zone 5, a heater 10, which is a first heating means, is arranged to compensate for the amount of heat that is radiated. This heater 10 is connected to a control device 13. This control device 13 further includes a thermocouple 8 which is a furnace temperature detection means disposed in the monitoring zone 5 and a heater 1 disposed in the heating zone 6.
Connected to 2.

Next, the operation of this embodiment will be explained.

A metal strip 2 is passed through a furnace 1 by means of hearth rolls 3. First, the control device 13 calculates the relationship between the predetermined heat retention furnace temperature and the input heat amount as shown in FIG. 3 when the monitoring zone 5 is heated in an empty furnace state.
The target soaking furnace temperature is also set. When operating the continuous annealing furnace prepared in this manner, first the soaking zone 7 and monitoring zone 5 are set to the target soaking temperature of the metal strip 2, and the heating zone 6 is set to a set temperature commensurate with the throughput. At this time, the control device 13
Heater 1 which is the first heating means controlled by
0, the amount of heat determined based on the relationship shown in FIG. 3 is injected into the monitoring zone 5, and the amount of heat dissipated is compensated. When the metal strip 2 is passed through the metal strip 2 in this state and the temperature of the metal strip 2 is raised according to the optimum temperature increase pattern A, the temperature of the monitoring zone 5 does not change and remains at the target soaking temperature, but the thermocouple 8 The temperature measured by
An amount of heat commensurate with the amount of deviation is applied to the heater 12 which is the second heating means which is the furnace temperature control system of the heating zone 6. When using materials with different soaking times or changing line speeds, it is recommended to configure the partition walls 4, 4, etc. to be removably installed at desired positions so that the position of the guard zone 5 can be selected each time. , enabling more flexible operations. In addition, it can be realized simply without a partition wall.

As explained above, the present invention uses a simple temperature control system, does not require direct temperature measurement of the metal strip, does not require complicated calculations, and can precisely control the soaking temperature of the metal strip with low equipment costs. This has the effect of improving product quality.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the relationship between the temperature rise pattern of the metal strip and the furnace temperature of the monitoring zone, Fig. 2 is a configuration diagram of an embodiment of the present invention, and Fig. 3 is an illustration of the relationship between the heating pattern of the metal strip and the furnace temperature of the monitoring zone. It is an explanatory diagram of the relationship between the heat retention furnace temperature and the input heat amount, which are determined in advance in the furnace state. 1... Furnace, 2... Metal strip, 3... Hearth roll, 4... Partition wall, 5... Monitoring strip, 6...
...Heating zone, 7...Soaking zone, 8...Thermocouple, 10,
12... Heater, 13... Control device.

Claims (1)

[Claims] 1. In a continuous annealing furnace in which the temperature of the metal strip in the furnace is controlled by adjusting the atmospheric temperature in the furnace, a partition wall is provided between a heating zone and a soaking zone. a monitoring zone; a first heating means for compensating only for a predetermined amount of heat dissipated in the monitoring zone to maintain a target soaking temperature of the metal strip; and a metal strip passing through the monitoring zone. Furnace temperature detection means for detecting the furnace temperature within the monitoring zone that changes depending on the temperature of the heating zone; second heating means for controlling the furnace temperature of the heating zone; and the target soaking temperature is set, and the furnace temperature detection means According to a signal from the means, the second temperature is controlled so that the furnace temperature in the monitoring zone becomes the target soaking temperature according to the deviation between the furnace temperature in the monitoring zone and the target soaking temperature.
A continuous annealing furnace characterized by comprising: control means for feedback controlling the heating means of the furnace.