JPH04285134A - Structure of cooling furnace for continuous strip heat treatment equipment and its control method - Google Patents

Abstract

PURPOSE:To provide the subject structure and control method, in which plural kinds of strips having mutually different qualities can be continuously cooled with a temp. pattern according to the quality in each strip. CONSTITUTION:By controlling the strip passing through each cooling unit arranged along advancing direction of the strip in a cooling furnace according to the quality of each strip, the desired heat treatment can be executed to the plural kinds of strips having mutually different qualities with one set of the heat treatment equipment.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to continuous strip heat treatment equipment for continuously applying heat treatment such as annealing to multiple types of strips such as steel strips made of different materials.
The present invention relates to the structure of a cooling furnace provided downstream of a heating furnace and its control method.

0002

2. Description of the Related Art There is a continuous heat treatment facility for strips in which strips are continuously passed through heat treatment furnaces such as heating furnaces and cooling furnaces in order to heat treat the strips.

[0003] As an example of such heat treatment equipment, a continuous annealing treatment equipment for steel strips has a heating furnace, a soaking furnace, a primary cooling furnace, an overaging furnace, and a secondary cooling furnace as heat treatment furnaces. , the steel strip is passed through each furnace continuously.

0004

[Problems to be Solved by the Invention] The optimum cooling pattern in the above-mentioned cooling furnace differs depending on the material of the steel strip to be threaded. For example, a steel strip made of general steel is preferably cooled after slow cooling, and a steel strip made of high tensile strength steel is α/γ
From the γ phase, which is rapidly cooled and concentrated from the two-phase region, martensite,
1 because it is necessary to generate retained austenite.
It is necessary to rapidly cool the material in the next cooling furnace. Therefore, in the past, high-strength steel could not be annealed using the same continuous annealing equipment as general steel, and separate continuous annealing equipment had to be installed for each type of steel, which not only increased the size of the equipment, but also However, there was a problem of rising costs when producing in small quantities.

In view of the problems of the prior art as described above, the main object of the present invention is to provide a continuous strip system capable of cooling a plurality of types of strips of different materials with a temperature pattern depending on the material of each strip. An object of the present invention is to provide a cooling furnace structure for heat treatment equipment and a control method thereof.

[0006]

[Means for Solving the Problem] According to the present invention, the above-mentioned object has a heating furnace and a cooling furnace provided after the heating furnace, and a plurality of continuous strips of different materials are produced. A structure of a cooling furnace in a continuous strip heat treatment facility in which the strip is continuously passed through each furnace in order to heat-treat the strip, the cooling furnace having settings changed individually along the traveling direction of the strip. A cooling furnace structure for strip continuous heat treatment equipment characterized by having a plurality of strip cooling units, and a cooling furnace having a heating furnace and a cooling furnace provided after the heating furnace, and having multiple types of different materials. A method for controlling a cooling furnace in a continuous strip heat treatment facility in which the strip is continuously passed through each of the furnaces in order to heat-treat successive strips, the method comprising: A method for controlling a cooling furnace of a continuous strip heat treatment facility, characterized in that the strip is cooled in a temperature pattern according to the material of each strip by controlling a plurality of cooling units provided in the strip, the settings of which can be changed individually. This is achieved by providing In particular, it is preferable that the interior of the cooling furnace is divided into a plurality of chambers along the traveling direction of the strip, and each chamber is provided with the strip cooling unit whose settings can be changed individually.

[0007]

[Operation] In this way, by controlling each cooling unit installed in the cooling furnace along the traveling direction of the strip according to the material of the strip to be passed through, one heat treatment equipment can handle multiple types of different materials. The desired heat treatment can be applied to the strip.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below based on specific embodiments shown in the accompanying drawings.

FIG. 1 shows a schematic configuration of continuous steel strip annealing equipment to which the present invention is applied. A steel strip 2 is continuously supplied from a payoff reel 1 installed at the line entrance of this equipment, and the tip of the next steel strip is welded to the end of the previous steel strip to the connection device 3.
The cleaning device 4
It is cleaned by the inlet looper device 5, the supply amount is adjusted by the inlet looper device 5, and then sent into the furnace for heat treatment. And heating furnace 6, soaking furnace 7, primary cooling furnace 8, overaging furnace 9,
The steel strip 2 which has been heat-treated according to a predetermined heat cycle after passing through the secondary cooling furnace 10 is fed into the skin pass mill 12 after the feed amount is adjusted by the exit looper device 11 . After being temper rolled in this skin pass mill 12, it is divided or defective parts are removed in an inspection and finishing device 13, and the treated steel strip 2 is wound onto a tension reel 14. A large number of hearth rolls 15 are provided in each furnace for applying appropriate tension to the steel strip 2 and causing it to run continuously.

FIG. 2 is a diagram showing the structure of the primary cooling furnace 8, and FIG. 3 is an enlarged view of a part of FIG. 2 and a diagram showing the pipe configuration. As shown in FIG. 2, the primary cooling furnace 8 is divided into three chambers 16 to 18 along the traveling direction of the steel strip 2, that is, from top to bottom. Each of the rooms 16 to 18 has a plurality of water injection nozzles each equipped with a large number of water injection nozzles for injecting water along the width direction of the steel strip 2 toward the front and back surfaces thereof, as part of the cooling units 20 to 22, respectively. A header 23 is provided.

[0011] Further, at the upper end of the chamber 16, in order to prevent water from entering the soaking furnace 7 side from the chamber 16 and to cool the steel strip 2 as the case requires, there are holes on the front and back surfaces of the steel strip 2. A reverse injection nozzle 24 is provided that injects air obliquely downward and convergently. Water knives 25 and 26 are provided between each chamber 16 to 18 to spray water diagonally upward and convergently on the front and back surfaces of the steel strip 2,
Each room 16 to 18 is isolated. Two water knives 27 and 28 similar to those described above are provided at the lower end of the chamber 18, as well as an air knife 29 for draining water that injects gas obliquely upward and convergently onto the front and back surfaces of the steel strip 2.
is provided.

Plate thermometers 30 and 31 are provided at the inlet end and the outlet end of the primary cooling furnace 8, and are connected to a control unit 38, which will be described later.

Since each of the cooling units 20 to 22 has a similar configuration, FIG.
Explain with reference to. Each header 23 of the cooling unit 20
is connected to one port of a three-way valve 33 via a supply line 32. The other port of this three-way valve is connected to a water supply source 41 via a pipe line 34, a flow meter 35, and a flow rate adjustment valve 36, and water is supplied from the supply source at a predetermined pressure. There is. The remaining one port of the three-way valve 33 is connected to a return line 37 to the water supply source.

Furthermore, the three-way valve 33 is connected to a control unit 38 consisting of a programmable controller via a setting switching controller 39, and the pipe line 34 is selected as the supply pipe line 32 or the return pipe line 37 according to a command from the control unit 38. The water flow path can be switched by communicating with the water. The control unit 38 is also connected to a flow meter 35 and a flow rate adjustment valve 36 via a setting switching controller 39, a flow rate regulator 40, and is capable of monitoring and adjusting the flow rate of water supplied to each header 23. There is.

In reality, each header 23 is connected to a gas supply line mainly consisting of nitrogen, and a mixture of this gas and water in a desired ratio is applied to the front and back surfaces of the steel strip 2. It will be sprayed towards the target and cooled down.

In such cooling units 20 to 22, when water and gas are actually being supplied to the header 23, the temperature is normally adjusted according to data from the plate temperature gauges 30, 31, flow meter 35, etc. The sheet passing speed, the number of headers 23 used, and the flow rates of water and gas are controlled. At this time, the three-way valve 33 connected to the header 23 that is not currently in use is connected to the pipe line 34.
and the return pipe 32 are communicated with each other, and the flow rate adjustment valve 36 is closed.

When this unused header 23 is used for the next steel strip, conventionally the number of headers 23 used was changed by opening and closing the flow rate regulating valve 36, resulting in poor response (20 seconds to 30 seconds). seconds), this header 2 during the passage of the current steel strip.
The flow rate adjustment valve 3 of this header 23 may be affected by supercooling caused by an increase in the amount of water injected from the header 23, or by
Insufficient cooling caused by opening 6 has been a problem.

However, in this embodiment, when the next steel strip is in the previous stage, the flow rate regulating valve 36 is opened in advance with the pipe line 34 communicating with the return pipe line 37, and after adjusting the flow rate to the required value,
A three-way valve 33 connects the conduit 34 to the supply conduit 32. Therefore, responsiveness is improved (approximately 5 seconds), and it is possible to prevent plate temperature deviations such as those caused by overcooling or insufficient cooling as described above. In addition, if the header 23 used for the current steel strip is to be discontinued when the next steel strip starts passing, a normal on-off valve can be used since the three-way valve 33 is only used to switch the water flow path. There is no need to worry about so-called water hammer, and there is no need to reinforce the valve body or pipe more than necessary.

When passing the steel strip 2 made of general steel through the steel strip continuous annealing equipment having the above-described configuration, as shown in FIG.
In the cooling unit 20 in the primary cooling furnace 8, all headers 23 are not used, in the cooling unit 21, some headers 23 are used from the downstream side, and in the cooling unit 22, all headers 23 are used. header 23 is used. In addition, by making the flow rate of water relatively small and adjusting the strip passing speed, as shown by the solid line in Figure 6, which shows the strip temperature change of the steel strip 2, the first half is slowly cooled and then the final 300 to
I try to keep it around ℃. Thereby, overcooling due to water dripping can be prevented.

On the other hand, since high-strength steel needs to be rapidly cooled at the initial stage of cooling, when passing the steel strip 2 made of high-strength steel, cooling in the primary cooling furnace 8 is performed as shown in FIG. All the headers 23 are used in the units 20 and 21, and some headers 23 from the upstream side are used in the cooling unit 22. In addition, by increasing the flow rate of water and adjusting the threading speed, as shown by the broken line in Fig. 6, the first half is rapidly cooled and then slowly cooled, and the final
The temperature is kept around 0°C.

In fact, gas may also be supplied to the unused header 23 from a gas pipe line (not shown) to perform slow cooling, etc., and depending on the steel strip 2 being threaded and the threading speed, If mixing even a small amount of water results in supercooling, all headers 23 may be supplied with only gas and cooled by gas cooling.

Here, when the steel strip 2 made of high tensile strength steel is passed continuously from the steel strip 2 made of general steel, when the welding point A reaches the entrance of the primary cooling furnace 8, as shown in FIGS. The steel strip 2 is cooled using a cooling pattern shown in FIG. 7 in which the cooling patterns shown in FIG. and,
When the welding point A reaches the outlet of the primary cooling furnace 8, the cooling pattern shown in FIG. 5 is adopted. In this way, only a portion of the general steel in front of the welding point A becomes slightly overcooled, and most of the other portions can be cooled in a desired pattern. If the same cooling pattern as shown in Fig. 7 is used when passing general steel continuously from high-strength steel, only a part of the general steel after the welding point will become slightly overcooled, and most of the other parts will be overcooled. can be cooled in a desired pattern.

[0023]

Effects of the Invention As is clear from the above explanation, according to the cooling furnace structure and control method for continuous strip heat treatment equipment according to the present invention, a plurality of cooling units are provided in the cooling furnace along the traveling direction of the strip. By controlling according to the material of the strip to be passed through, it is possible to apply the desired heat treatment to multiple types of continuous strips of different materials using one heat treatment equipment, so the entire heat treatment equipment can be downsized. , costs can also be reduced. From the above, the effects of the present invention are significant.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a continuous steel strip annealing facility to which the present invention is applied.

FIG. 2 is a schematic configuration diagram showing the structure of the primary cooling furnace in FIG. 1;

FIG. 3 is an enlarged view of a part of FIG. 2 to show its conduit configuration and control system.

FIG. 4 is a configuration diagram similar to FIG. 2 showing how each header is used when a steel strip made of general steel is passed through the primary cooling furnace of FIG. 1;

FIG. 5 is a configuration diagram similar to FIG. 2 showing how each header is used when passing a steel strip made of high-strength steel to the primary cooling furnace of FIG. 1;

FIG. 6 is a graph showing changes in plate temperature of various steel strips when the steel strips are passed through the primary cooling furnace of FIG. 1;

FIG. 7 is a configuration diagram similar to FIG. 2 showing the state of use of each header when the steel strip passing through the primary cooling furnace in FIG. 1 changes from general steel to high-strength steel.

[Explanation of symbols]

1 Payoff reel 2 Steel strip 3 Welding connection device 4 Cleaning device 5 Input side looper device 6 Heating furnace 7 Soaking furnace 8 Primary cooling furnace 9 Overaging furnace 10 Secondary cooling furnace 11 Output side looper device 12 Skin pass mill 13 Inspection and finishing equipment 14 Tension reel 15 Hearth roll 16-18 rooms 20-22 Cooling unit 23 Header 24 Reverse injection nozzle 25-28 Water knife 29 Air knife 30, 31 Plate thermometer 32 Supply pipeline 33 Three-way valve 34 Pipeline 35 Flowmeter 36 Flow rate adjustment valve 37 Return pipe 38 Control unit 39 Setting switching controller 40 Flow regulator 41 Water supply source

Claims (3)

[Claims] 1. A heating furnace and a cooling furnace provided downstream of the heating furnace, wherein the strips are successively placed in each of the furnaces in order to heat-treat a plurality of consecutive strips of different materials. A structure of a cooling furnace in a continuous strip heat treatment facility for passing strips through the strip, characterized in that the cooling furnace has a plurality of strip cooling units whose settings can be changed individually along the traveling direction of the strip. Cooling furnace structure for continuous heat treatment equipment. 2. The inside of the cooling furnace is divided into a plurality of chambers along the traveling direction of the strip, and each chamber is provided with the strip cooling unit whose settings can be changed individually. Cooling furnace structure for strip continuous heat treatment equipment described in . 3. A method comprising: a heating furnace; and a cooling furnace provided after the heating furnace; and in order to heat-treat a plurality of continuous strips made of different materials, the strips are successively placed in each of the furnaces. A cooling furnace control method in a cooling furnace capable of controlling a plurality of individually changeable cooling units installed along the traveling direction of the strip in a strip continuous heat treatment equipment for passing the strip, the method comprising: A method for controlling a cooling furnace of continuous strip heat treatment equipment, characterized by cooling with a temperature pattern according to the material of the strip.