JPH0730413B2 - Aluminum strip heat treatment method and continuous heat treatment furnace - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heat-treating aluminum strip while floating it, and a continuous heat-treatment furnace.

[0002]

2. Description of the Related Art Conventionally, a method and a furnace for carrying out heat treatment while continuously transporting an aluminum strip in a floating state from a heating zone to a cooling zone have been known.

[0003]

However, in the above heat treatment method and furnace, the aluminum strip expands in the plate width direction when heated in the heating zone, and when the aluminum strip is conveyed from the heating zone to the cooling zone and cooled. In addition, there is a problem that the aluminum strip contracts in the width direction, and wrinkles in the transport direction, that is, seagull wings occur on the aluminum strip due to the expansion or contraction.

Therefore, as a result of various investigations by the inventors on the conditions under which the seagull wing is generated, the buckling strength of the metal material suddenly drops at the recrystallization temperature, and the recrystallization temperature varies depending on the type of alloy. In the case of batch annealing, it is estimated to be about 250 ° C, and in the case of rapid heating,
For example, when heated at a rate of 100 ° C./sec, recrystallization starts at about 440 ° C. and ends at about 520 ° C.
Recrystallization is completed at about 440 ° C when heated at a rate of c, and the seagull wing does not occur below the material temperature of about 350 ° C on the test line, below which,
Since the seagull wing was generated above that, it was found that the critical temperature for generation of the seagull wing is considered to be about 350 ° C.

The seagull wing is generated by the strip buckling in the plate width direction. To prevent this, the strip may be conveyed in a waving state, for example, along a sinusoidal curve. As shown, it is known that the minimum buckling stress of the material increases as the amount of waving increases.

[0006]

The present invention has been made on the basis of the above findings, and the first invention is a method for heat-treating aluminum strips while floating and transporting them.
The aluminum strip is conveyed in a waving state at least in a zone where the material temperature is about 350 ° C. or higher,
In the other zones, they are transported in a catenary state.

A second aspect of the present invention is a furnace for heat-treating aluminum strips while floating and transporting the strips. In the first half of the heating zone, floater nozzles composed of a pair of upper and lower pressure pads are arranged at predetermined intervals. A plurality of round nozzles are placed between the caterpillars and a catenary zone that conveys the aluminum strip in a catenary state while supporting the aluminum strip at the position of the floater nozzle, and the latter half of the heating zone is a floater nozzle composed of a pair of upper and lower pressure pads. And a cooling zone having at least the latter half of the cooling zone having the same configuration as the above-mentioned catenary zone.

[0008]

According to the first invention, the material temperature is about 350.
Since the aluminum strip is conveyed in a waving state at a temperature of not less than ° C, buckling resistance of the aluminum strip in the zone is strengthened in the plate width direction and the occurrence of seagull wings is prevented.

According to the second aspect of the invention, the strip is efficiently levitated and heated in the catenary zone, so that a heat-treated state with good energy efficiency can be obtained.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a continuous heat treatment furnace 1 (hereinafter referred to as “furnace 1” in the description of the embodiments) of an aluminum strip S (hereinafter referred to as “strip S” in the description of the embodiments). The heating zone A, the slow cooling zone B, and the cooling zone C are provided, and the catenary zones Z _C1 and Z _C2 are provided on the strip entrance side (to area) of the heating zone A and the strip exit side (to area) of the cooling zone C. Placed respectively,
The area surrounded by these catenary zones Z _C1 and Z _C2 (~
The seagull zone Z _S is located in the area). The catenary zone means a region where the strip is conveyed in a suspended state, and the seagull zone means a region where the strip is conveyed in a waving state, for example, along a sinusoidal curve.

The catenary zones Z _C1 and Z _C2 are shown in FIG.
As shown in FIG. 3, floater nozzles 10 each consisting of a pair of upper and lower pressure pads 11 whose main purpose is to float the strips are arranged at predetermined intervals, and the main purpose is to transfer heat between the floater nozzles 10. Round nozzle 1 which is a heat transfer nozzle
A plurality of 3 are arranged. A well-known one having a slit nozzle in the strip width direction is used as the pressure pad 11 of the floater nozzle 10, and a chevron pad having an excellent strip floating property is used as the lower pressure pad 12, for example, as described later. ing.
In the following description, the pressure pad 12 will be referred to as "chevron pad 12".

On the other hand, in the seagull zone Z _S , as shown in FIG.
As shown in FIG. 3, the floater nozzles 10 are arranged at predetermined intervals by alternating the vertical relationship of the pressure pad 11 and the chevron pad 12, and the floater nozzle 10 (1
0 ') can be moved up and down.

As shown in FIGS. 5 to 8, the chevron pad 12 has an upper surface, that is, an opposed surface 20 of the strip S conveyed in the arrow X direction (hereinafter referred to as "pad face 2").
"0". ) Has slit nozzles 21 and 21 extending in the strip width direction (arrow Y direction), and a plurality of rectifying members 22 are provided between the slit nozzles 21 and 21. The rectifying member 22 is formed in a V shape and is composed of an inner rectifying plate 23 and an outer rectifying plate 24 which are arranged in parallel with each other. A plurality of long holes 27 and 28 extending in the plate width direction are formed, respectively, which are provided with the straightening walls 25 and 26. Then, the rectifying member 22 has a rectifying plate central portion (bending portion) 2
A plurality of sets of 9 and 30 are arranged symmetrically so as to project toward the ends, and bolts 31 and 32 are inserted into the long holes 27 and 28, respectively, and fixed to the pad face 20.
On the pad face 20, round nozzles 33, which are air ejection holes, are arranged between the inner straightening vane 23 and the outer straightening vane 24 at predetermined intervals along the straightening vanes 23 and 24 in a V shape. Has been done.

The strip levitation characteristics of the chevron pad 12 will be described below.
Causes the fluid, eg, gas, supplied to the internal space to be ejected from the slit nozzles 21 and the round nozzles 33 and sprayed on the strip S. The fluid ejected from the round nozzle 33 hits the lower surface of the strip S and forms a kind of air curtain. To adjust the gas ejection amount of the round nozzle 33, move the straightening vanes 23 or 24 in the width direction and adjust the amount of overlap between the round nozzles 33 and the straightening vanes 23 or 24, that is, the opening area of the round nozzle 33. Done by. On the other hand, the fluid ejected from the slit nozzles 21 and 21 in the opposite direction moves in the strip width direction after joining. However, the fluid that moves to the side is rectified by the rectifying member 22.
And is regulated by the air curtain. Moreover, the current plate 2
3 and 24 are arranged with their central portions (bent portions) 29 and 30 facing outward, and have a strong ability to regulate the fluid that escapes toward the ends, and the regulated fluid to the left and right rectifying members 22. Has a strong holding power in the enclosed area. Therefore,
As shown in FIG. 9, a static pressure region P is formed in a wide area between the strip S and the strip S, and the levitation force of the strip S is significantly stronger than that of the pressure pad 11 having only the slit nozzles 21 and 21.

In the furnace 1 having the above construction, the strip S is carried into the furnace 1 in the direction of the arrow X, and first heated in the catenary zone Z _C1 of the heating zone A. This catenary zone Z
_{At C1} , hot fluid is sprayed onto the strip S from above and below by the pressure pad 11 and the chevron pad 12 at the facing portion of the floater nozzle 10. Further, the lower chevron pad 12 is superior to the upper pressure pad 11 in the floatability of the strip S,
The support pressure of the high temperature fluid ejected from the chevron pad 12 stably supports the strip S in a suspended state. Further, the high temperature fluid is sprayed from the round nozzle 13 to be efficiently heated.

The strip S that has passed through the catenary zone Z _C1 is then conveyed to the seagull zone Z _S of the heating zone A. In the seagull zone Z _S , the vertical relationship between the chevron pad 12 and the pressure pad 11 is alternately switched, and as shown in FIG. 3, the strip S is conveyed in a waving state along a sinusoidal curve. Further, as shown in FIG. 4, the strip S gradually rises in temperature in the process of being conveyed through the heating zone A, and the inlet 1a of the furnace 1
At room temperature (about 20 ° C), the material temperature is about 33 at the boundary between the catenary zone Z _C1 and the seagull zone Z _S.
0 ° C., reaching approximately 520 ° C. at the exit of heating zone A.

The strip S that has passed through the heating zone A is then conveyed to the slow cooling zone B, where it is cooled by spraying a low temperature fluid from the floater nozzle 10. The slow cooling zone B belongs to the seagull zone Z _S , and the strip S is continuously conveyed in the waving state. The slow cooling zone B is intended to prevent a sharp temperature decrease of the strip S to which the low temperature fluid is sprayed and a rapid contraction due to the temperature decrease, and is particularly effective for the strip S of a thin plate material or a wide material. is there.

The strip S which has passed through the Johiyatai B is conveyed Seagull zone Z _S of the cooling zone C in waving state, is cooled by cryogenic fluid ejected from floater nozzle 10. When passing through the Seagull zone Z _S, the strip S enters the Katenarizon Z _C2, where while being sprayed cryogen from floater nozzle 10 and round the nozzle 13 is transported in a catenary state, fed from the outlet 1b of the furnace 1 Be done. In addition, as shown in FIG. 4, the strip at the temperature of about 520 ° C. at the outlet of the heating zone is
It is cooled to about 260 ° C. at the boundary between the seagull zone Z _S and the catenary zone Z _C2 and about 80 ° C. at the outlet of the cooling body.

As described above, in the furnace 1, the strip S is conveyed in the waving state and has a buckling resistance under the temperature condition where the seagull wing is likely to occur in the strip S, that is, the material temperature of 350 ° C. or higher. Since it is reinforced, the strip S is expanded by expansion during heating and contraction during cooling.
There is no seagull wing.

In the above embodiment, the slow cooling zone B is provided between the heating zone A and the cooling zone C, but the strip S
However, if it is possible to sufficiently prevent the seagull wing from being generated by transporting a thick plate material in a waving state, it is not necessary to provide an annealing zone. Further, when the strip S for rapid water quenching is provided by providing a spray nozzle for cooling water, a quench head, or the like on the outlet side of the slow cooling zone B, by adjusting the temperature of the fluid ejected from the floater nozzle 10 here, The temperature of the strip S passing through the slow cooling zone B may be maintained at the outlet temperature of the heating zone A (about 520 ° C. in the above embodiment) to ensure hardenability. In this case, the slow cooling zone B is used as a soaking zone.

A nozzle array in which a round nozzle 13 is arranged between the floater nozzles 10 (hereinafter referred to as "catenary type")
Say. ) (See FIG. 2) and a nozzle array (hereinafter referred to as “floater type”) in which floater nozzles and round nozzles are alternately arranged and the same kind of nozzles face each other vertically (hereinafter referred to as “floater type”). In the model type, a lot of energy is consumed to levitate the strip, whereas in the catenary type, the strip can be supported only by the chevron pad, so that a large number of round nozzles with high heat transfer efficiency can be arranged, resulting in convection. The heat transfer coefficient hc is improved by 8% compared to the floater model.

Next, comparing the nozzle pressures, from the relational expression of hc∝α · P ^0.345 P: nozzle pressure, (P1 / P2) ^0.345 = 1 / 1.08 P1: catenary type nozzle pressure P2: floater type nozzle Pressure ∴P1 = (0.8) ・ P2, and for the same furnace length, the catenary type nozzle pressure P1
Is 20% less than the floater type nozzle pressure P2.

Next, comparing the air volumes, the opening area per zone (length: 3.5 m) in the catenary type is 0.6
If the air volume is 624 m ² , the air volume Q1 is as follows. Q1 = 0.6624 / 4√ (P1) On the other hand, if the opening area per zone (length: 3.5 m) in the floater model is 0.7004 m ² , the air volume Q2
Is as follows. Q2 = 0.7704 / 4√ (P2)

From the above, when comparing the fan power of the catenary type for supplying the fluid to the nozzle: KW1 and the fan power of the floater type: KW2, (KW1 / KW2) = (Q1 · P1) / (Q2 · P2) = 0.8 · [0.6624 · √ (0.8)] / [0.7004 · √ (1.0)] = 0.68, which means that the catenary model saves 32% less power than the floater model.

Specifically, seven zones are provided in the cooling zone,
If all of these zones are catenary type and the output of the fan that supplies fluid to them is 132 kW, the power saving is 132 (KW) .7 (units). (1-0.68) = 296 (KW). Further, if the heat transfer nozzles in the above seven zones are divided into three in the width direction and headers are provided to supply fluid to each of them, and both ends are closed at the time of narrow material processing, further power saving is achieved.

In the above description, the floater nozzle 1
0 is composed of the conventionally known pressure pad 11 and chevron pad 12, but the floater nozzle 10 may be composed of two pressure pads 11. However, since the chevron pad 12 is superior to the pressure pad 11 in the floating stability of the strip, it is preferable to use the chevron pad 12.

[0027]

As is apparent from the above description, according to the heat treatment method for a strip according to the first aspect of the invention, the strip is conveyed in the waving state in the zone where the material temperature is about 350 ° C. or higher, so that the width is increased. Since the buckling resistance in the direction is strengthened, a seagull wing does not occur and a high-quality product without wrinkles can be obtained. Moreover, the continuous heat treatment apparatus according to the second aspect of the present invention can achieve energy-efficient treatment in the catenary zone.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an aluminum strip continuous processing furnace.

FIG. 2 is a side view of the catenary zone.

FIG. 3 is a side view of a seagull zone.

FIG. 4 is a diagram showing a temperature change of a strip.

FIG. 5 is a plan view of a chevron pad.

FIG. 6 is a sectional view of the chevron pad taken along the line VI-VI.

FIG. 7 is a plan view of a flow regulating member.

FIG. 8 is a sectional view taken along line VIII-VIII of the flow regulating member.

FIG. 9 is a diagram showing a static pressure region of a chevron pad.

FIG. 10 is a diagram showing the relationship between the amount of waving and the buckling stress in the strip width direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Continuous processing furnace, 10 ... Floater nozzle, 11 ... Pressure pad, 12 ... Chevron pad, 13 ... Round nozzle, A ... Heating zone, B ... Slow cooling zone, C ... Cooling zone, Z _C1 ,
Z _C2 … catenary zone, Z _S … seagull zone.

Claims (2)

[Claims] 1. A method of heat-treating an aluminum strip while levitating and transporting the aluminum strip, wherein the aluminum strip is transported in a waving state in a zone having a material temperature of about 350 ° C. or higher, and in a catenary state in other zones. A method for continuously heat treating an aluminum strip. 2. In a furnace for heat-treating aluminum strips while being floated and conveyed, the first half of the heating zone is provided with floater nozzles composed of a pair of upper and lower pressure pads at predetermined intervals, and a plurality of round nozzles are provided between the floater nozzles. The nozzle is arranged, and is constituted by a catenary zone that conveys in a catenary state while supporting the aluminum strip at the position of the floater nozzle, the latter half of the heating zone is arranged with a large number of floater nozzles consisting of a pair of upper and lower pressure pads, A continuous heat treatment furnace for aluminum strips, characterized by comprising a seagull zone for transporting the aluminum strip in a waving state by these floater nozzles, and having a cooling zone having at least the latter half of the same configuration as the above-mentioned catenary zone.