JPH10176226A - Method for continuously annealing metallic strip and convection type vertical continuous annealing furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a C type warp developed in a metallic strip. SOLUTION: A convection type vertical continuous annealing furnace 11 is provided with a heating zone 15 for heating the metallic strip 12 to a prescribed temp., a soaking zone 16 for keeping the metallic strip 12 heated at the heating zone 15 to a prescribed temp., a slow cooling zone 17 for slowly cooling the metallic strip 12 kept to the prescribed temp. in the soaking zone 16 to a prescribed lower temp. range, and a cooling zone 18 for cooling the metallic strip 12 slowly cooled to the prescribed lower temp. range in the slow cooling zone 17 to the room temp. range in order from the lower part. In such a case, in the slow cooling zone 17, a circulating device 17a for atmosphere in the slab cooling zone and plural injection holes 17b successively arranged in the width direction of the metallic strip 12 are arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous annealing method for a metal strip and a convection vertical continuous annealing furnace.

[0002]

2. Description of the Related Art As is well known, a continuous annealing method involves continuously passing a cold-rolled metal strip through a furnace.
This is an annealing method for providing a predetermined heat history in a short time (usually about 20 minutes at the maximum).

[0003] There are various types of continuous annealing furnaces used in such continuous annealing methods. Concentration heating-radiation heating is used when focusing on the heating method, and vertical-horizontal heating is used when focusing on the passing direction. Each is roughly divided. Further, when attention is paid to the arrangement of the heating furnace, it is roughly classified into an up-heat type and a down-heat type.

As for continuous annealing furnaces classified from such various viewpoints, an up-heat type convective vertical continuous annealing furnace has recently been receiving attention. this is,
Because of the convection type, the annealing treatment capacity (thermal efficiency) is high. Because of the convection type, the heat pattern in the longitudinal direction of the metal strip can be flexibly changed. An up-heat vertical furnace having a cooling zone and a cooling zone in this order, so that the low-temperature and low-pressure side is the open side and high safety, and the vertical arrangement prevents material drooping (catenary) in the furnace. Because it is not necessary to take any measures, it is possible to eliminate the occurrence of flaws and to suppress an increase in equipment costs.

FIG. 3 is an explanatory view showing the flow of hot air on the surface of the metal strip 2 in the heating zone 1 of such a convection type continuous annealing furnace. FIG. 3A is a horizontal sectional view. 3 (b)
Is a vertical sectional view.

[0006] The heating zone 1 is configured so that the periphery thereof is covered with a refractory material 3, and a header 4 to which hot air is supplied is disposed inside a strongly reducing atmosphere (hydrogen atmosphere). A large number of hot air jet nozzles 5 communicating with the header 4 are provided on both sides of the metal band 2 in the metal band traveling direction and the width direction, respectively. Gas G is blown.

[0007] The blown hot air gas G collides with the front and back surfaces of the metal strip 2 to heat the metal strip 2 and, as shown in FIG.
As shown in (b), convection flows along the front and back surfaces of the metal strip 2. FIG. 4 is an explanatory view schematically showing a circulation state of the hot air gas G in the convection vertical continuous annealing furnace 6.

The metal strip 2 is sent to the inside of a convection type vertical continuous annealing furnace 6 through a pair of seal rolls 7.
Then, the high-temperature hot air gas G is sent to the upper slow cooling / cooling zone 6b together with the metal zone 2 near the front and back surfaces of the metal zone 2. The hot-air gas G sent to the slow cooling / cooling zone 6b is rapidly cooled and circulates downward.

In this way, the convection vertical continuous annealing furnace 6
, Hot blast gas G circulates in a convection and circulates, and near the boundary 6c between the heating / uniform tropical zone 6a and the slow cooling / cooling zone 6b, high-temperature hot-air gas and low-temperature cooled gas are mixed, and The atmosphere inside was changing rapidly.

[0010] Therefore, the temperature distribution in the front and back surfaces and the width direction of the metal strip 2 is not constant, and the temperature distribution is non-uniform. In this way, when the metal band 2 in which the temperature distribution in the front and back surfaces and the width direction is non-uniform passes through the convective vertical continuous annealing furnace 6, the metal band 2 is warped in the sheet width direction.

FIG. 5 shows a metal strip 2 generated in this way.
FIG. 4 is an explanatory diagram schematically showing a state of occurrence of a so-called C warp (a phenomenon in which a metal band 2 warps in a C-shaped cross section), which is an example of the warp phenomenon. The C warpage amount is as shown in FIG.
It is defined by the distance between both ends 2a (2b) and the center 2c of the metal strip 2.

FIG. 6 is an explanatory view showing two aspects of the C-warping. FIG.
FIG. 6 (b) shows a case where it is formed in a convex shape with respect to the rotation surface of FIG.
Indicates a case where the C warpage is formed in a concave shape with respect to the turn roll 8.

When the C warpage occurs as shown in FIG. 6B, the metal band 2 is given a predetermined amount of tension. The contact extends and deforms both ends so as to be in close contact with the turn roll 8. For this reason, the C warpage generated in the metal strip 2 is naturally eliminated.

However, when the C warpage occurs as shown in FIG. 6A, the metal strip 2 is fixed at both ends by contact with the turn roll 8, and bends at a part (central part) in the width direction. It may cause flaws. Since the occurrence of such flaws in the metal band 2 extremely reduces the yield of the metal band 2, improvement thereof is desired.

The warpage generated in the metal strip 2 is as follows.
In addition to the C warp, there is also a W warp (a phenomenon in which the metal strip 2 warps in a W-shaped cross section). FIG. 7 is an explanatory diagram showing the state of occurrence of such a W warp. As with the C warp, there are two forms of the W warp formed so as to be convex or concave with respect to the rotation surface of the turn roll 8.

Various proposals have conventionally been made in order to eliminate the warping phenomenon caused by the non-uniform temperature distribution in the front and back surfaces and the width direction of the metal strip 2. For example, Japanese Patent Application Laid-Open No. 3-68720 discloses that a shielding air nozzle and a buffering air nozzle are provided in a slow cooling zone of a vertical continuous annealing furnace so as to achieve a uniform temperature distribution in the width direction of the metal strip. A technique for suppressing the occurrence of C warp and W warp due to rapid cooling is disclosed in Japanese Patent Application Laid-Open No. 62-116724.
Techniques have been proposed in which cooling gas is blown from a number of nozzles across a metal band in a cooling zone of a vertical continuous annealing furnace to thereby cool the metal band and make the temperature distribution uniform in the width direction. .

[0017]

However, even with these conventional techniques, it is not possible to eliminate the warping phenomenon that occurs in the metal strip passing through the convection vertical continuous annealing furnace.

That is, in the convection type vertical continuous annealing furnace, the air heated in the soaking zone rises and reaches the slow cooling zone and the cooling zone, and returns to the soaking zone through the cooling zone and the slow cooling zone again. Convection will occur. For this reason, in the slow cooling zone, the atmosphere in the furnace near the boundary between the heating and the solitary zone becomes extremely unstable. For this reason, the temperature distribution has been uneven in the front and back surfaces and the width direction of the metal band.

As described above, in the conventional convection type vertical continuous annealing furnace, it is difficult to eliminate the unevenness of the temperature distribution of the metal strip, particularly the unevenness of the temperature distribution in the front and back surfaces and the width direction.
The occurrence of C warpage or the like could not be eliminated.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art,
A hot air circulating fan is installed in the slow cooling zone of the convection vertical continuous annealing furnace to force convection of the atmosphere in the slow cooling zone. By spraying in the plate width direction, the nonuniformity of the temperature distribution in the front and back surfaces and the width direction of the metal strip is intended to be eliminated.

According to the first aspect of the present invention, a metal zone heated and maintained at a predetermined temperature by passing through a heating zone and a soaking zone in a convection vertical continuous annealing furnace is gradually cooled in a slow cooling zone. By spraying the cooling gas circulating inside the band from a plurality of injection ports arranged in the width direction on both sides of the metal band, the distribution of the surface temperature in the front and back surfaces and the width direction of the metal band is made uniform. This is a continuous annealing method for metal strips.

According to a second aspect of the present invention, in the method for continuously annealing a metal strip according to the first aspect, the convective vertical continuous annealing furnace includes a heating zone for heating the metal zone to a predetermined temperature, and a heating zone for heating the metal zone to a predetermined temperature. , A metal zone heated at a predetermined temperature by the soaking zone, a slow cooling zone for gradually cooling the metal zone held at a certain temperature by the soaking zone to a predetermined temperature range, and a predetermined cooling zone by the slow cooling zone. And a cooling zone for cooling the metal zone gradually cooled to the temperature range to the normal temperature zone in order from the bottom.

According to a third aspect of the present invention, there is provided a heating zone for heating a metal strip to a predetermined temperature, a solitary zone for maintaining the metal zone heated by the heating zone at a certain temperature, and a predetermined temperature for the soaking zone. A cooling zone that gradually cools the metal strip held at the predetermined temperature range to a predetermined temperature range and a cooling zone that cools the metal strip slowly cooled to the predetermined temperature range to the normal temperature range by the cooling zone. A vertical continuous annealing furnace with convection provided with an atmosphere circulating device in the annealing zone and a plurality of injection ports connected in the width direction of the front and back sides of the metal strip in the annealing zone. It is characterized by that.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view showing the entire convective vertical continuous annealing furnace 11 of the first embodiment. The metal strip 12 in the present embodiment is a base material of a lead frame material forming an IC frame structure.

The metal strip (strip) 12 unwound from the coil is guided through a first turn roll 13 into a convection vertical continuous annealing furnace 11 formed above. At the entrance of the convection vertical continuous annealing furnace 11, a pair of entrance-side seal rolls 14 are arranged to maintain airtightness in the furnace.
The convection type vertical continuous annealing furnace 11 includes heating zones 1 in order from the bottom.
5, a tropical zone 16, a slow cooling zone 17 and a cooling zone 18 are arranged.

Above the cooling zone 18, a second turn roll 19 and a third turn roll 20 are sequentially arranged. The metal strip 12 is guided by these, and is conveyed by a convection type via an outlet seal roll 21. It passes through a vertical continuous annealing furnace 11.

A fourth turn roll 22 is disposed below the exit side seal roll 21, and the metal strip 12 is transported rightward in the drawing by the fourth turn roll 22, and is wound by a winding machine (not shown). It is wound up.

Here, a heater 15a for generating hot air and a fan 15b for circulating the hot air heated by the heater 15a are installed in the heating zone 15. Further, the heating zone 15 has fans 15 on both sides of the metal zone 12.
b, to which the hot air from b is supplied;
A plurality of hot air jet nozzles 15d arranged in a row in the direction of conveyance of the metal band are arranged at the position c.

In the heating zone 15, by operating the heater 15a and the fan 15b, hot air is jetted from the hot air jet nozzle 15d toward both sides of the metal strip 12, and
2 is heated and heated to a predetermined temperature. The temperature of the hot air circulating in the heating zone 15 is usually about 600 ° C. to 900 ° C.

Similarly to the heating zone 15, the soaking zone 16 is also provided with a heater 16a, a fan 16b, a header 16c, and a hot-air jet nozzle 16d to keep the metal zone 12 at a predetermined temperature. The temperature of the hot air circulating in the solitary tropics 16 ranges from 600 ° C. to 90
It is about 0 ° C.

The convection type vertical continuous annealing furnace 11 of the present embodiment is characterized in that an annealing atmosphere circulation fan 17 a for circulating the internal atmosphere in a slow cooling zone 17 and a number of The hot air jet nozzle 17b is newly provided. Hereinafter, the structure of the slow cooling zone 17 will be described in detail with reference to FIG.

FIG. 2 is an explanatory view showing the structure of the annealing zone 17 in the convection type vertical continuous annealing furnace 11 of the present embodiment. FIG. 2 (a) is a horizontal sectional view, and FIG. FIG. 2C is a vertical sectional view as viewed from the front, and FIG. 2C is a vertical sectional view as viewed from the side.

As shown in FIGS. 2 (a) to 2 (c), the inner atmosphere of the annealing zone 17 on both sides and both sides of the metal strip 12 to be conveyed has a furnace atmosphere circulation. The fan 17a is installed.

The wall of the annealing zone 17 includes a furnace inner wall 23a, an inner heat insulating material 23b formed on the inner peripheral side thereof, and a furnace inner wall 23a.
a and a gas purge zone 23c formed between the inner heat insulating material 23b.

The in-furnace atmosphere circulation fan 17a is started by a drive source (not shown) installed on the outside, and draws gas in front of the fan and blows it to the side. A heater 24 is provided on the inner wall of the slow cooling zone 17 to raise the temperature of the gas sent by the furnace atmosphere circulation fan 17a to a predetermined temperature.

The gas heated by passing through the heater 24 is sent to the header 25. In this embodiment, the header 25 has seven rows in the width direction of the metal strip 12 to be conveyed.
The hot air jet nozzle 17b is installed in a state where the hot air jet nozzles 17b communicate with each other in six stages in the transport direction. Each hot air jet nozzle 17b is
It is installed facing.

A baffle plate 26 is provided in front of the furnace atmosphere circulation fan 17a so as to cover the fan 17a, and the gas constituting the furnace atmosphere is passed through the baffle plate 26 through the baffle plate 26. Atmospheric circulation fan 17a
Inhaled efficiently.

2 (a) to 2 (c), when the heater 24 and the furnace atmosphere circulation fan 17a are operated, the atmosphere gas present in front of the furnace atmosphere circulation fan 17a becomes the furnace atmosphere circulation fan 17a. And is sent to the heater 24. The atmosphere gas is heated to a predetermined temperature by passing through the heater 24 and sent to the header 25.

The atmosphere gas (hot air) heated to a predetermined temperature in this way is jetted from the hot air jet nozzle 17b toward the front and back surfaces and the width direction of the metal strip 12.
By this injection, the metal strip 12 is set to a uniform temperature in the front and back surfaces and the width direction. Atmosphere gas injected into the metal strip 12 is reflected from the metal strip 12 and baffle plate 26
Is sent to the space in front of the in-furnace atmosphere circulation fan 17a, which is covered by the above.

Hereinafter, in order to repeat the flow of the atmosphere gas, the atmosphere in the annealing zone 17 is forcedly convected. The temperature of the hot air circulating in the slow cooling zone 17 is usually 300
About 550 ° C.

Therefore, the atmosphere of the annealing zone 17 is stable,
The metal band 12 has a uniform temperature distribution in the front and back surfaces and the width direction, and is cooled slowly. The temperature of the atmosphere gas can be controlled by adjusting the heating capacity of the heater 24, so that the atmosphere temperature of the annealing zone 17 is controlled to a desired value. The temperature of the atmosphere gas is 300 ° C. or more and 55
It is desirable that the temperature be 0 ° C. or lower.

Further, in FIG. 1, the metal strip 12 having passed through the slow cooling zone 17 is rapidly cooled to a normal temperature by the cooling zone 18. Since the fan 27a and the cooler 27b are installed in the cooling zone 18, the atmosphere gas cooled by the cooler 27b is supplied to the metal zone 12 by the fan 27a.
Can be sprayed toward the front and back surfaces and the width direction, and the temperature of the metal strip 12 can be reduced to a desired value. The temperature of the cold air circulating through the cooling zone 18 is usually 100
It is below ° C.

As described above, according to the present embodiment, the temperature distribution in the front and back surfaces and the width direction of the metal band 12 in the annealing zone 17 is made uniform, so that the passage through the cooling zone 18 and the second
Even by the contact with the turn roll 19, the metal strip 12 is uniformly cooled in the front and back surfaces and the width direction. for that reason,
The uniformity of the temperature distribution of the metal strip 12 with respect to the front and back surfaces and the width direction achieved in the slow cooling zone 17 is continuously maintained. Therefore, the metal strip 12 includes the second turn roll 19
, No shape defects such as C warpage occur.

As described above, according to the present embodiment, shape defects such as C warpage of the metal strip 12 are eliminated. In the continuous annealing furnace 11 according to the present embodiment, in order to remove an oxide film on the surface of the metal strip 12, it is desirable to use a strongly reducing atmosphere (for example, a hydrogen atmosphere: 75% by volume of hydrogen and 25% by volume of nitrogen). The furnace atmosphere characteristics are as follows:
It is desirable to set the temperature to −40 ° C. or lower from the viewpoint of preventing the oxidation of the metal strip 12.

Further, in this embodiment, the uniformity of the shape (the amount of C warpage and the amount of L warpage) of the annealed metal band 12 was measured. As a result, the C warpage was 10 mm or less, and the L warpage was 30 mm or less. In this way, according to the present embodiment, a metal band suitable as a lead frame material can be manufactured while suppressing shape defects such as C warpage to such an extent that there is no practical problem.

[0047]

As described above in detail, according to the present invention, a hot air circulating fan and a hot air injection nozzle are arranged in a slow cooling zone of a convection type vertical continuous annealing furnace so as to extend in the width direction of the front and back surfaces of the metal strip. By spraying, the temperature distribution in the front and back surfaces and the width direction of the metal strip can be made uniform.

Therefore, even if the metal strip comes into contact with the turn roll after passing through the cooling zone, uneven cooling does not occur in the metal strip, and the occurrence of shape defects such as C warpage can be reliably suppressed. The practical significance of the present invention having such effects is extremely remarkable.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view showing an entire convection vertical continuous annealing furnace according to a first embodiment.

FIG. 2 is an explanatory view showing a structure of an annealing zone in the convection vertical continuous annealing furnace according to the first embodiment, wherein FIG. 2 (a) is a horizontal sectional view, and FIG. 2 (b) is viewed from the front. Vertical sectional view, Fig. 2
(C) is a vertical sectional view seen from the side.

FIG. 3 is an explanatory view showing a flow of hot air on a surface of a metal strip in a heating zone of a convection type continuous annealing furnace, and FIG.
Is a horizontal sectional view, and FIG. 3B is a vertical sectional view.

FIG. 4 is an explanatory view schematically showing a gas circulation state inside a convection vertical continuous annealing furnace.

FIG. 5 is an explanatory diagram showing an occurrence state of so-called C-warpage, which is an example of warpage.

FIG. 6 is an explanatory view showing two aspects of C warpage,
FIG. 6A shows a case formed in a convex shape with respect to the turn roll, and FIG. 6B shows a case formed in a concave shape with respect to the turn roll.

FIG. 7 is an explanatory diagram showing a state of occurrence of W warpage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Convection type vertical continuous annealing furnace 12 Metal strip 13 1st turn roll 14 Entrance side seal roll 15 Heating zone 16 Uniform tropical zone 17 Slow cooling zone 17a Furnace atmosphere circulation fan 17b Hot air injection nozzle 18 Cooling zone 19 Second turn roll 20 Third turn roll 21 Outlet seal roll 22 Fourth turn roll 23a Furnace inner wall 23b Inner heat insulating material 23c Gas purge zone 24 Heater 25 Header 26 Baffle plate

Claims (3)

[Claims] In a convection type vertical continuous annealing furnace, a metal zone heated and maintained at a predetermined temperature by passing through a heating zone and a soaking zone in a convection type vertical annealing furnace is provided. By circulating the cooling gas from a plurality of injection ports arranged in the width direction on both sides of the metal band, the surface temperature distribution in the front and back and the width direction of the metal band is made uniform. Continuous annealing of metal strips. 2. The continuous annealing method for a metal strip according to claim 1, wherein the convective vertical continuous annealing furnace is heated by the heating zone for heating the metal zone to a predetermined temperature. A soaking zone for holding the metal strip at a predetermined temperature, a slow cooling zone for gradually cooling the metal strip held at a certain temperature by the soaking zone to a predetermined temperature range, and a predetermined temperature for the slow cooling zone. And a cooling zone for cooling the metal zone, which has been gradually cooled to the zone, to a normal temperature zone, in order from the bottom. . 3. A heating zone for heating the metal strip to a predetermined temperature, a solitary zone for holding the metal zone heated by the heating zone at a certain temperature, and a soothing zone for holding the metal strip at a predetermined temperature. A convection comprising, in order from the bottom, a slow cooling zone for gradually cooling the metal strip to a predetermined temperature range, and a cooling zone for cooling the metal strip slowly cooled to a predetermined temperature range by the slow cooling zone to a normal temperature range. A vertical continuous annealing furnace, wherein the annealing zone is provided with an atmosphere circulation device in the annealing zone, and a plurality of injection ports connected in the width direction of each of the front and back sides of the metal strip. A vertical continuous annealing furnace of the convection type.