JP2000256754A - Continuous heat treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous heat treatment method, with which the responsiveness to temp. control and the stability of temp. are excellent and the equipment space is small and also, a metallic material excellent in mechanical strength can be obtd. after the heat treatment. SOLUTION: A heater part 3 disposed with plural heaters generating near infrared radiation in the width direction of a base material S, is disposed with the interval passable to the base material S in the facing condition and in the case of using [WE] for the output of the heater disposed at the edge part in the width direction of the base material S in plural heaters 3 disposed in the heater part 3 and [WC] for the output of the heater disposed at the center part in the width direction of the base material S, a process for passing the base material S through the between the heaters under condition of [WC]<[WE], is contained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously heat-treating a metal material, and more particularly to a method for continuously reducing the temperature such as tempering after quenching aluminum or aluminum alloy material to a relatively low temperature of about 200 ° C. or less. The present invention relates to a continuous heat treatment method capable of accurately heating and keeping the temperature.

[0002]

2. Description of the Related Art Conventionally, in continuous heat treatment of aluminum or an aluminum alloy material, a continuous annealing furnace which continuously heats in a plate state is used instead of a batch method in which the coil is annealed in order to improve productivity. Often done.

Various methods have been proposed for continuous heating. There is a method in which a nozzle capable of blowing out a heating gas is provided in a chamber, and a high-temperature gas is blown onto an aluminum or aluminum alloy plate to heat the aluminum or aluminum alloy plate as in a hot blast stove (JP-A-56-102566).

A method of providing an induction heating furnace and a holding furnace in a heat treatment furnace and heating an aluminum or aluminum alloy plate by induction heating in the induction heating furnace (Japanese Patent Laid-Open No. 10-2)
No. 98668).

Further, a hot-air heating means is disposed in a heating zone corresponding to a temperature rising region in a far-infrared furnace, and a high-temperature gas is blown onto an aluminum or aluminum alloy plate to rapidly raise the temperature and heat it with far-infrared rays. Method (Japanese Unexamined Patent Publication
-40490).

[0006]

However, in the case of an aluminum alloy material which is a heat treatment type alloy of the 6000 series, tempering may be performed after quenching in order to improve the strength characteristics.

A method in which a high-temperature gas is blown onto the tempered gas to heat it as in the above-mentioned hot blast stove (JP-A-56-1025)
No. 66), there is little variation in the temperature distribution of the plate, but it takes time to start up to a predetermined temperature, the length of the furnace required for heat treatment becomes long, and it is difficult to set a fine temperature. There is a problem that is. In particular, when tempering is performed immediately after quenching, in order to stabilize the properties and quality of the aluminum alloy sheet after the heat treatment, it is necessary to control the heat treatment conditions according to the state of the aluminum alloy sheet immediately after quenching. In a furnace, there is a problem that it is extremely difficult to finely correct the temperature. Further, if the predetermined length cannot be obtained due to the space of the equipment, there is a possibility that sufficient heating cannot be performed.

Further, when the above-described method of heating by induction heating (Japanese Patent Application Laid-Open No. Hei 10-298668) is used for tempering, while fine temperature control is possible, depending on the location of the aluminum alloy plate, the temperature may be reduced. There is a problem that variation occurs and temperature stability is lacking.

Further, in the case of using the above-mentioned method of heating with far infrared rays and blowing a high temperature gas for tempering (Japanese Patent Laid-Open No. 2-40490), the temperature control is not performed in the case of heating with far infrared rays having a long wavelength. Although it is good, the rising time is shortened by blowing high-temperature gas. In addition, there is a problem that the line speed has to be greatly reduced in order to perform a predetermined heat treatment. Further, if the predetermined length cannot be obtained due to the space of the equipment, there is a possibility that sufficient heating cannot be performed.

The present invention has been made in view of the above problems, and is a metal material which is excellent in response to temperature control and temperature stability, has a small equipment space, and has excellent mechanical strength after heat treatment. It is an object of the present invention to provide a continuous heat treatment method capable of obtaining the following.

[0011]

According to the present invention, there is provided a continuous processing method according to the present invention, wherein a heater unit provided with a plurality of heaters for generating near-infrared rays in the width direction of a substrate is opposed to each other so that an interval at which the substrate can pass therethrough. The heater output of the heater installed at an end in the width direction of the base material is defined as [WE] among a plurality of the heaters arranged at intervals and installed in the heater unit, and the heater output in the width direction of the base material is defined as [WE]. When the heater output of the heater installed at the center is [WC], [WC] <[WE]
A step of allowing the base material to pass between the heater sections under the following conditions. Here, near-infrared rays are infrared rays having a short wavelength of 720 nm to 2.5 μm.

In this case, it is preferable that the distance between the heater and the surface of the substrate is 30 to 80 mm.

In the present invention, a heater section having a plurality of near-infrared heaters is disposed so as to face each other, and the output of the heater at the end section is determined between the end and the center in the width direction of the base material passing therethrough. By making the output higher than the central portion, the heating state of the base material can be made uniform. Also,
Since a plurality of heaters are provided and these heater outputs are merely changed depending on the location, the size of the equipment can be reduced.
Furthermore, since a uniform heat treatment can be performed, a metal material having excellent mechanical strength can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a continuous heat treatment method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1A is a schematic diagram illustrating a continuous heat treatment apparatus according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA in FIG.

In the continuous heat treatment apparatus 1 of this embodiment,
A heater unit 3 to which a near-infrared heater 2 capable of generating a plurality of near-infrared rays is installed is opposed to each other. The base material S is provided between the heater units 3 installed facing each other.
Are separated by a distance W that can pass through. A thermometer 5 that measures the temperature of the substrate S that has exited from the continuous heat treatment apparatus 1 as the substrate S advances in the traveling direction D, and a near-infrared heater 2 that controls output of the near-infrared heater 2 based on the temperature measured by the thermometer 5 Infrared heater 2
And the SCR 4 provided in.

The near-infrared heater 2 is a heat source having a high energy density. In order to enhance the heat collection effect of the near-infrared heater 2, a reflector 6 is provided on the heater section 3 side of the near-infrared heater 2. Due to the combined action of near infrared rays directly emitted from the near infrared heater 2 by the reflector 6 and infrared rays reflected by the reflector 6, the substrate S can be heated even more efficiently.

Hereinafter, the reasons for limiting the continuous processing method of the present invention will be described in detail.

The reason why a plurality of heaters are arranged is that fine-grained heating control can be performed in accordance with the temperature condition of the metal material in accordance with the size and shape of the metal material. In particular, in the case of aluminum or an aluminum alloy material, the temperature at the end portion in the width direction tends to be lower than that at the center portion due to its heat dissipation. It is preferable that the interval between the near-infrared heaters be set closer to the end of the substrate than to the center in the width direction of the substrate.

The heater installed at the widthwise end of the substrate
The heater output [WE] is set at the center of the substrate in the width direction.
Heater output [WC] of the placed heater: [WC] <[W
E] Particularly in the case of aluminum or an aluminum alloy material, the temperature at the end portion in the width direction tends to be lower than that at the center portion due to its heat dissipation. Therefore, the heater output [WE] of the heater installed at the end in the width direction of the substrate needs to be higher than the heater output [WC] of the heater installed at the center in the width direction of the substrate. That is, [WC] <[WE]. The output of the heater is controlled by a thyristor regulator (S
CR) or the like. It is preferable to control the near-infrared heaters at the end and the center in the width direction of the base material separately.

Distance between heater and substrate surface: 30 to
If the distance between the 80 mm heater and the surface of the substrate is shorter than 30 mm, the substrate may come into contact with the heater and break when passing through the substrate to be heat-treated. In addition, air cooling is performed to cool the electrodes of the heater during heating, and the cooling air may be affected. On the other hand, when the distance between the heater and the surface of the base material exceeds 80 mm, there is a problem that thermal efficiency is reduced and good heating becomes difficult. Therefore, the distance between the heater and the substrate surface is set to 30 to 80 mm.

The moving speed of the aluminum alloy substrate is preferably 10 m / s. This is because, for example, in order to obtain strength characteristics in the heat treatment of a 6000 series aluminum alloy material, it is necessary to heat it at a low temperature of around 100 ° C. and then immediately wind it around a coil. This is because the heat dissipation is high, and if the flat state is long, the cooling is quick, so that the effect of the predetermined heat treatment hardly occurs.

The continuous heat treatment apparatus 1 of the present embodiment can be applied to a continuous quenching apparatus. FIG. 2 is a schematic diagram showing a configuration in which the continuous heat treatment apparatus according to the embodiment of the present invention is applied to a continuous quenching apparatus.

In the continuous quenching apparatus, as shown in FIG. 2, the coil 7 around which the substrate S is wound, a continuous heating furnace (heating zone) 8 for heat-treating the substrate S, and the substrate S are cooled. It has a cooling zone 9, a continuous heat treatment apparatus 1, and a coil 10 for winding the heat-treated base material S.

As shown in FIG. 2, the substrate S is guided by a plurality of guide rolls from a coil 7 around which the substrate S is wound, passes through a continuous heating furnace 8, then passes through a cooling zone 9, and Continuous heat treatment device 1 via guide roll
, Heat treatment is performed, and then the heat-treated base material S is wound around the coil 10.

[0025]

EXAMPLES Hereinafter, examples of a continuous heat treatment method falling within the scope of the present invention will be specifically described in comparison with characteristics of a comparative example.

Under the conditions shown in Table 1, using a 6000 series aluminum alloy material as a material, a continuous quenching apparatus shown in FIG. 2 was used to form a cold-rolled plate having a thickness of 1 mm and a width of 1800 mm. 8, rapidly heated to the solution temperature, and then rapidly cooled in the cooling zone 9;
After quenching to 0 ° C., it continuously passed between the near-infrared heaters 2 of the continuous heat treatment apparatus 1 at a line speed of 20 m / min.

The length of the near infrared heater 2 is 1100 mm
Were arranged at intervals of about 50 mm in the width direction. On the exit side of the near-infrared heater 2, the temperature of the surface of the aluminum alloy material was measured, and the measured value was fed back to control the output of each near-infrared heater 2 by the SCR 4, set to the target temperature of 80 ° C., and heated. As a comparative example, heating was similarly performed using a far-infrared heat source heater.

The temperature variation in the continuous heat treatment apparatus was measured. The evaluation conditions were as follows. Regarding the temperature variation, when the temperature difference between the central part of the base material and the end part of the base material was within 10 ° C., the evaluation was ○. Those exceeding ° C were marked as x.

After winding the substrate, a test piece was cut out from the coil cooled to room temperature, subjected to a 2% residual strain equivalent to press molding, subjected to a heat treatment at 170 ° C. for 30 minutes, and then subjected to a tensile test. The proof stress was measured. This proof stress was defined as bake hard proof stress (BH proof stress). The evaluation condition, for BH strength, and ○ what BH yield strength exceeds 190 N / mm ^2, BH proof stress and those 180 to 190 N / mm ² △, what BH yield strength of less than 180 N / mm ² X. Table 2 shows the results.

[0030]

[Table 1]

[0031]

[Table 2]

As shown in Table 2 above, in Examples 1 to 5 which fall within the scope of the present invention, good results were obtained in both temperature variation and BH proof stress.

On the other hand, in Comparative Examples 6 and 7 exceeding the range of the present invention, good results could not be obtained in both temperature variation and BH proof stress. Comparative Example 6 was inferior in BH proof strength because the type of heater was far infrared rays.

In Comparative Example 7, since the heater output conditions were the same at the end portion and at the center portion, temperature variation occurred.

[0035]

As described in detail above, in the present invention,
A plurality of heaters for generating near-infrared rays are arranged so as to face each other. At the end and the center in the width direction of the base material passing therethrough, the output of the heater at the end is determined by the output of the center. By increasing the height, the heating state of the substrate can be made uniform. Therefore, the substrate heat-treated by this method can be subjected to uniform heat treatment, and thus has excellent mechanical strength. Further, since a plurality of heaters are provided and these heater outputs are merely changed depending on the location, the equipment can be reduced in size.

[Brief description of the drawings]

FIG. 1A is a schematic diagram showing a continuous heat treatment apparatus according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA of FIG. 1A.

FIG. 2 is a schematic diagram showing a configuration in which a continuous heat treatment apparatus according to an embodiment of the present invention is applied to a continuous quenching apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Continuous heat treatment apparatus 2: Near-infrared heater 3: Heater part 4: SCR 5; Thermometer 6; Reflector 7, 10; Coil 8: Continuous heating furnace 9; Cooling zone D;

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor ▲ Taka ▼ Yasuo Ki 15 Kinuigaoka, Moka-shi, Tochigi Pref. Inside the Kobe Steel Moka Works (72) Inventor Satoshi Shigeno 15 Kinuigaoka, Moka-shi, Tochigi Address Kobe Steel Moka Works F-term (reference) 4K043 AA01 AB01 BB02 CA03 DA01 DA03 EA05 FA04 FA12 GA10

Claims (2)

[Claims] 1. A heater unit in which a plurality of heaters for generating near-infrared rays are installed in the width direction of a base member are arranged facing each other with an interval capable of passing through the base member, and installed in the heater unit. Among the plurality of heaters, the heater output of the heater installed at the end in the width direction of the substrate is [WE].
When the heater output of the heater installed at the center in the width direction of the base material is [WC], [WC]
<A continuous heat treatment method comprising a step of passing the substrate between the heater sections under the condition of [WE]. 2. The apparatus according to claim 1, wherein a distance between the heater and the surface of the substrate is 30 to 80 mm.
3. The continuous heat treatment method according to item 1.