JP2003021467A - Continuous heat treatment furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous heat treatment furnace comprising a fluidized bed in which the temperature of a workpiece can be raised more quickly by preventing temperature drop in the fluidized bed at the inlet of the furnace when a workpiece is thrown in and temperature distribution in the fluidized bed can be made more uniform. SOLUTION: The continuous heat treatment furnace 10 comprising a fluidized bed 20 where powder and granular material 24 is heated by blowing hot air and fluidized heat treats a metallic workpiece 26 while moving it through the fluidized bed 20 from the inlet 12 to the outlet 16. Heaters 18a and 18b exist in the fluidized bed 20 at the inlet 12 of the continuous heat treatment furnace 10.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an Al alloy, Mg
TECHNICAL FIELD The present invention relates to a continuous heat treatment furnace for continuously heat treating a metal such as an alloy, and more specifically, a continuous heat treatment suitably used for heat treatment for improving mechanical strength of a metal product, for example, an automobile wheel made of an Al alloy. Regarding the furnace.

[0002]

2. Description of the Related Art Aluminum alloys, magnesium alloys, ceramics, metal composite materials, resin materials such as FRP, etc. have been conventionally known as lightweight materials for automobiles and the like. Of these, for example, aluminum alloy is
With a density of 3, already engine cylinder heads of cars,
High-speed injection molding, that is, casting products manufactured by a so-called die casting method are often used for engine cylinder blocks and the like.

Further, for underbody parts of automobiles and the like that are required to be lighter, for example, for light alloys such as aluminum alloys and magnesium alloys, high-speed injection die casting manufacturing method, squeeze casting method, semi-melt processing method, etc. Has been applied. The light alloy cast products obtained by these die casting method and squeeze casting method, if the mechanical properties such as tensile strength, proof stress and elongation can be further improved by improving the manufacturing method, the thickness and dimension of the member In addition, it is possible to make the weight thin, small and light, which in turn improves the fuel efficiency of automobiles and is also environmentally long-awaited.

From the above viewpoints, light alloy castings have conventionally been subjected to further heat treatment in order to improve their mechanical properties. For example, in the case of an aluminum alloy obtained by adding Mg to an Al-Si-based alloy, Mg ₂
Precipitation hardening occurs due to the intermediate phase of Si, and the strength and the like are improved.

As described above, for example, the strengthening of an Al alloy is obtained by adding another element and thereby aging precipitation of an intermediate phase. The heat treatment for aging precipitation includes solution treatment and aging. Consists of processing.

The solution treatment is a heat treatment for solidifying the non-equilibrium phase crystallized during solidification at high temperature and then water cooling to obtain a solid solution having a uniform composition at room temperature. The aging treatment subsequent to the solution treatment causes precipitation hardening due to an intermediate precipitation phase by holding at a relatively low temperature, and these heat treatments aim to improve mechanical properties of a metal, for example, an Al alloy. You can

Conventionally, an atmosphere furnace such as a tunnel furnace using air as a heat medium has been used for such solution heat treatment and aging treatment. However, the temperature rising rate up to the solution heat treatment temperature is slow and it takes time to raise the temperature. In addition, the temperature fluctuation is about ± 5 ℃
Therefore, there is a problem that the solution treatment and the aging treatment cannot be performed at a higher temperature.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to increase the temperature rising rate and reduce the temperature fluctuation, and An object of the present invention is to provide a continuous heat treatment furnace capable of continuously performing solution treatment and aging treatment at a higher temperature. Further, another object of the present invention, in a continuous heat treatment furnace consisting of a fluidized bed, it is possible to prevent a temperature drop in the furnace inlet part fluidized bed at the time of loading the workpiece, and to raise the temperature of the workpiece faster, Another object of the present invention is to provide a continuous heat treatment furnace which can make the temperature distribution in the fluidized bed more uniform.

[0009]

That is, according to the present invention, a fluidized bed that is used for heat treatment of a workpiece made of metal and has a fluidized bed in which powder particles are heated by the blowing of hot air and is flowing is provided. A continuous heat treatment furnace for performing heat treatment while moving the workpiece from the inlet to the outlet in the fluidized bed, wherein a heater is present in the fluidized bed at the inlet of the heat treatment furnace. A continuous heat treatment furnace is provided.

In the present invention, it is preferable that the temperature rise time to the heat treatment temperature of the workpiece be shortened to a predetermined value or less by forming the fluidized bed at the inlet portion of the heat treatment furnace larger than a predetermined value. Further, the continuous heat treatment furnace of the present invention is preferably used when performing solution treatment on a workpiece made of a light alloy such as an Al alloy or a Mg alloy.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. The present invention is a continuous heat treatment furnace for continuously heat treating a metal such as an aluminum alloy and a magnesium alloy,
The furnace has a fluidized bed in which powder particles are heated by the blowing of hot air and is flowing, and heat treatment is performed while moving the workpiece from the inlet to the outlet in the fluidized bed.

As described above, by allowing the workpiece to exist in the fluidized bed in which the granular material is heated and fluidized, and heat-treating the workpiece, the temperature of the workpiece can be raised more quickly and the temperature in the fluidized bed can be increased. The distribution becomes more uniform (temperature fluctuation becomes smaller), and solution treatment and aging treatment can be performed continuously at higher temperature.
In particular, the present invention is characterized in that a heater is provided in the fluidized bed at the inlet of the heat treatment furnace. In this way, by providing a heater in the fluidized bed at the inlet of the heat treatment furnace,
It is possible to prevent or minimize the temperature drop in the fluidized bed at the inlet when a non-heated (low temperature) workpiece is thrown into the fluidized bed at the inlet, resulting in a faster rise of the workpiece. Further homogenization of temperature and temperature distribution in the fluidized bed can be achieved.

Hereinafter, the continuous heat treatment furnace of the present invention will be described in more detail with reference to the drawings. 1 (a) (b) (c)
Is an example of a continuous heat treatment furnace according to the present invention,
1A is a plan view, and FIG. 1B is XX of FIG.
A sectional view and FIG. 1C are sectional views taken along the line YY of FIG. 1 (a), (b) and (c), 10 indicates a continuous heat treatment furnace according to the present invention.
Is an inlet portion 12, a heat treatment strip portion 14 following the inlet portion 12,
And a take-out portion (outlet portion) 16 following the heat treatment strip portion 14. These inlet portion 12, heat treatment belt portion 14
Inside of each of the extraction units 16 forms a fluidized bed 20 in which hot air is blown from the dispersion pipe 30 to heat and fluidize the granular material 24.

As can be seen from the plan view of FIG. 1A, the inlet portion 12 has a larger cross-sectional area with respect to the moving direction and a larger volume than the other heat treatment strip portions 14 and the take-out portion 16. In addition, heaters 18a, 18 are provided on both sides of the inlet portion 12 at the protruding portions 12a, 12b, respectively.
b is arranged. From the inlet portion 12 to the heat treatment strip portion 14,
A conveyor 22 is arranged in the fluidized bed 20 reaching the take-out section 16, a work piece 26 is placed on the conveyer 22, and the work piece 26 flows from the inlet section 12 of the heat treatment furnace to the take-out section 16 in the fluidized bed 20. It is designed to be heat-treated while moving inside.

The work piece 26 is loaded into the fluidized bed 20 of the entrance portion 12 by the work piece carry-in device 28 at the entrance portion 12 and placed on the conveyor 22. Here, as described above, the inlet portion 12 is formed to be larger in volume than the heat treatment belt portion 14 and the take-out portion 16, and the heaters 18a, 18b is arranged and the granular material 2 in the fluidized bed 20
4 and hot air are further heated and kept warm. in this way,
Since the volume of the fluidized bed 20 of the inlet portion 12 is large and the amount of the granular material 24 is large and the heat retention amount of the inlet portion 12 is large, the low temperature workpiece 26 is thrown into the fluidized bed 20 of the inlet portion 12. Also, the temperature drop of the fluidized bed 20 is prevented, and a faster temperature rise of the workpiece 26 is achieved.

Next, the workpiece 26 introduced into the inlet section 12 passes through the heat treatment strip section 14 from the inlet section 12 as the conveyor 22 moves, and reaches the take-out section 16 in the fluidized bed 20.
Although moving inside, the workpiece 26 is subjected to a desired heat treatment from the inlet portion 12 through the heat treatment strip portion 14 to the take-out portion 16. Therefore, the length and size of the heat treatment furnace from the inlet portion 12 to the extraction portion 16 via the heat treatment zone portion 14 and the treatment time are determined by the type of heat treatment to be treated,
It is determined depending on the type and size of the metal that is the work piece.

The workpiece 26, which has been subjected to a predetermined heat treatment and has reached the take-out portion (exit portion) 16, is carried out of the furnace by the work piece carry-out device 32 to be a product,
Alternatively, it will be subjected to the next processing step. In this way, according to the continuous heat treatment furnace 10 of the present invention, the workpiece 26 in the non-heated state (low temperature) is the fluidized bed 2 of the inlet portion 12.
The temperature drop of the fluidized bed 20 when being charged into 0 is effectively prevented or minimized, and the workpiece 26 is heated more quickly, and the inlet portion 12 reaches the heat treatment zone 14 and the take-out portion 16. Further homogenization of the temperature distribution in the fluidized bed 20 can be achieved.

The metal to be used in the present invention is not particularly limited, and it can be applied to all metals requiring heat treatment, but light alloys such as Al alloy and Mg alloy are preferable.

Further, as in the present invention, by using a fluidized bed furnace as a heat treatment furnace, it is possible to perform heat treatment at a higher temperature by homogenizing the temperature inside the fluidized bed (about ± 2 to 3 ° C.), For example, it is possible to perform solution treatment of Al alloy at a higher temperature, and since heat transfer efficiency is good,
It is possible to shorten the temperature rising time to the solution heat treatment temperature.

Further, the fluidized bed system is generally an indirect heating system such as a container heating system in which the fluidized bed container is heated from the outside or a radiant tube system in which a radiant tube is built in the fluidized bed, or a direct blowing of hot air. Although a direct heating method is known, in the present invention, the direct heating method by direct blowing of hot air is adopted because the temperature distribution in the fluidized bed becomes good. In the present invention, the above-mentioned other method may be used in combination with the direct heating method.

[0021]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples. (Example) Using the continuous heat treatment furnace shown in FIG. 1, solution treatment and aging treatment of an Al alloy were performed. The heat treatment furnace used has the plane dimensions shown in FIG. 2, the width of the inlet portion 12 is 3 m, and the length is 1.5 m.
4. The total length up to the take-out portion (exit portion) 16 was 7.5 m, and the lateral width of the heat treatment strip portion 14 and the take-out portion (exit portion) 16 was 1 m. The height of the heat treatment furnace was 1.5 m. Inside the furnace, sand (granular material) having an average particle size of 50 to 500 μm is fluidized by the hot air blown from the dispersion pipe 30 to form the fluidized bed 20. Radiant tube type heaters 18a and 18b are arranged on both sides of the inlet portion 12a and 12b, respectively.
The workpiece 26 is placed on the conveyor 22 which is disposed in the fluidized bed 20 from 2 to the heat treatment zone 14 and the takeout section 16 so that the fluidized bed 20 extends from the inlet section 12 to the takeout section 16 of the heat treatment furnace. Heat treated while moving. In addition, 500m
Operate the conveyor 22 with m pitch feed, and work piece 2
6 was processed at a rate of 15 per hour. Further, the temperature distribution in the inlet portion 12 of the heat treatment furnace was measured, and it was confirmed that it was within a range of ± 2 ° C during the solution treatment.

A cast aluminum wheel for a vehicle (14 kg) was used as a workpiece to be heat-treated, and a test piece was sampled at an outer rim flange. The composition of the aluminum wheel is 7.0 for Si.
%, Mg was 0.34% by mass, Sr was 50 ppm, and the balance was Al. As the heat treatment conditions, as shown in the schedule of FIG.
C., the aging treatment temperature was 170.degree. C., the solution treatment temperature was kept for 60 minutes, and the aging treatment was kept for 60 minutes.

A test piece was taken from the vehicle aluminum wheel heat-treated as described above and subjected to a tensile test (tensile strength, 0.2% proof stress, elongation). As a result, the tensile strength was 270 MPa or more and 0. The 2% proof stress was 170 MPa or more and the elongation was 7% or more.

[0024]

As described above, according to the continuous heat treatment furnace of the present invention, since the heating heater is present in the fluidized bed of the inlet portion, the workpiece in the unheated state is the fluidized bed of the inlet portion. It is possible to effectively prevent or minimize the temperature drop of the fluidized bed at the inlet when it is charged into
As a result, it is possible to achieve a faster temperature rise of the workpiece and a more uniform temperature distribution in the fluidized bed.

[Brief description of drawings]

FIG. 1 shows an example of a continuous heat treatment furnace according to the present invention, in which (a) is a plan view, (b) is a sectional view taken along line XX of (a), and (c) is taken along line Y- of (b). It is a Y sectional view.

FIG. 2 is an explanatory diagram showing plane dimensions of a continuous heat treatment furnace used in Examples.

FIG. 3 is a graph showing a heat schedule of an example.

[Explanation of symbols]

10 ... Continuous heat treatment furnace, 12 ... Inlet, 12a, 12b
... both-side overhanging part, 14 ... heat treatment zone part, 16 ... take-out part (outlet part), 18a, 18b ... heater, 20 ... fluidized bed,
22 ... conveyor, 24 ... powder, 26 ... workpiece,
28 ... Workpiece loading machine, 30 ... Dispersion pipe, 32 ...
Workpiece unloader.

Claims (3)

[Claims] 1. A heat treatment for a workpiece made of metal, wherein the furnace has a fluidized bed in which powder particles are heated by blowing hot air and is flowing, and the workpiece is provided from an inlet portion to an outlet portion. A continuous heat treatment furnace for performing heat treatment while moving in the fluidized bed, wherein a heater is present in the fluidized bed at the inlet of the heat treatment furnace. 2. The temperature rising time to the heat treatment temperature of the workpiece is shortened to a predetermined value or less by forming the fluidized bed at the inlet portion of the continuous heat treatment furnace larger than a predetermined value. Continuous heat treatment furnace. 3. The continuous heat treatment furnace according to claim 1, wherein the workpiece made of a light alloy is subjected to solution treatment.