JPH05247543A - Separation of scrap of clad material - Google Patents

Abstract

PURPOSE:To efficiently separate respective metallic layers of scrap of clad material by heating the scrap of clad material obtd. by combining an Al alloy layer with a stainless layer at a high temp. and forming brittle intermetallic compounds on the joined face of the clad material by a specified thickness. CONSTITUTION:The scrap of clad material obtd. by combining a layer constituted of Al or an Al alloy with a layer constituted of stainless or steel is heated at a high temp. (e.g. >= about 580 deg.C for >=1hr holding time) to form brittle aluminum iron intermetallic compounds such as FeAl3 by >=10mu. This clad material is allowed to cool, by which respective metallic layers are naturally peeled off, and efficiently separated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scrap (waste material) of an aluminum alloy-stainless steel clad material in which aluminum or aluminum alloy (hereinafter abbreviated as aluminum alloy) and stainless steel or steel (hereinafter abbreviated as stainless steel) are adhered to each other. Regarding separation method.

[0002]

2. Description of the Related Art A clad material which is a combination of an aluminum alloy and stainless steel is widely used because the characteristics of both metals are utilized to improve the performance as a composite material.
When various products are manufactured using this clad material, scrap of the clad material is generated at each stage of the manufacturing process, the processing process, etc., or in the form of a product that has been scrapped. However, since the clad material is made by joining dissimilar metals, in scrap processing, if processing such as melting is carried out at once in the same way as normal processing of iron scrap, etc., it will be a mixture of both metals, so it will be recycled. However, the scope of use is limited. Therefore, recycling of each metal
From the viewpoint of effective use of resources, it is very necessary to efficiently separate each metal layer in the processing of such a clad material scrap. Conventionally, as a method for separating clad material scraps of aluminum alloy and stainless steel, Utilizing the fact that the melting point of aluminum alloy is lower than that of stainless steel, the scrap temperature is heated above the melting point of the aluminum alloy to preferentially melt and separate the aluminum alloy. Clad material scraps at a temperature of 500 ° C. or higher and a melting point temperature of aluminum alloy or lower for 5 minutes to 1
After heating for a period of time, cooling to room temperature, and then peeling off both metals constituting the cooled scrap by mechanical force such as pliers (JP-A-62-96623). The clad material scrap is separated by heating the clad material scrap at a temperature of 550 ° C. or higher and lower than the melting point temperature of the aluminum alloy for a time of 5 minutes or more and 30 minutes or less, and immediately after completion of the heating, at least one surface of the clad material scrap is forcibly cooled. There is a method (Japanese Patent Application No. 2-259322) and the like.

[0003]

However, each of the above conventional methods has the following problems. That is, 1. In the method of 1, it is necessary to heat the scrap to 700 ° C. or higher on an inclined hearth to preferentially melt only the aluminum alloy and let it flow out of the furnace, and then take out the stainless steel at a high temperature outside the furnace. Yes, there are many problems in terms of workability, safety, and thermal efficiency. Further, since the aluminum alloy adheres to the taken out stainless scrap, it is difficult to sufficiently separate it. 2. In the method (1), since the separation is performed by mechanical force, it is difficult to automate when the shape of the scrap is indefinite. Therefore, a large amount of manpower and man-hours are required, and there is a problem in efficiency. Further, depending on the width, thickness, and shape of the scrap, it may be heavy, difficult to grasp, sharp, and sharp, which may cause a problem in terms of worker safety. 3. Method of 2. Although it is more efficient than the above method, the heating facility and the cooling facility must be provided adjacent to each other because it is necessary to forcibly cool immediately after heating, and the place where the treatment is performed is limited. In addition, the manpower and cost of forced cooling are high. The present invention has been made in view of the above circumstances, and it is possible to reliably and safely separate a clad material scrap made of an aluminum alloy and stainless steel at low cost with simple means. It is intended to provide a method

[0004]

In order to achieve the above object, the inventor of the present invention has made extensive studies on the properties of the joint interface of a clad material composed of an aluminum alloy and stainless steel, and as a result, has reached the present invention. That is, the present invention, as defined in claim 1,

In a scrap of a clad material in which a layer made of aluminum or an aluminum alloy and a layer made of stainless steel or steel are combined, the clad material scrap is heated at a high temperature and a brittle aluminum-iron intermetallic compound ( FeAl ₃ etc.) thickness 10 μm
It is a method for separating a clad material scrap, which is characterized in that the clad material scrap is generated as described above, then allowed to cool, and then naturally peeled.

Here, the intermetallic compound is formed to a thickness of 10 μm.
The heating conditions to be generated above are not particularly limited because the amount of the intermetallic compound of aluminum and iron increases as the heating temperature is high and the time is long, but the heating ultimate temperature is 580 ° C. or more and the holding time is Is preferably 1 hour or more. However, at 625 ° C or higher, the formation of intermetallic compounds is 2
Since it is almost saturated at 0 μm, even if the heating temperature is 625 ° C. or higher, its effect is not affected and the cost is rather increased, which is not preferable.

[0007]

The reason why the clad material composed of the aluminum alloy and stainless steel according to the present invention is separated into both metal layers is as follows. By heating and holding the clad material composed of the aluminum alloy and stainless steel at a high temperature for a long time, a hard intermetallic compound having poor ductility is generated on the entire bonding interface between the aluminum alloy and the stainless steel. When the thickness of the intermetallic compound layer is 10 μm or more, the joining force between the aluminum alloy and stainless is almost lost.
When the clad material is cooled in such a state that the bonding force at the bonding interface is almost lost, the amount of thermal contraction during cooling is reduced due to the difference in the thermal conductivity and the thermal expansion coefficient between the aluminum alloy and stainless steel even during slow cooling. Difference occurs and residual stress occurs at the bonding interface. This residual stress acts as a shearing force on the intermetallic compound layer having almost no bonding force and causes delamination at the interface, so that the clad material can be separated into the aluminum alloy layer and the stainless steel layer. Since the amount of intermetallic compounds formed on the joint surface increases, there may be a concern that the scrap value will decrease. However, when the joint interface of an aluminum alloy and stainless after separation was subjected to X-ray diffraction, the aluminum alloy side interface peaks of FeAl ₃ only at the peak of Al was not observed, the peak of FeAl ₃ from the bonding interface of the stainless steel side Admitted.
That is, it was found that the intermetallic compound adhered to the stainless steel side during the separation, and the iron component from the stainless steel was hardly mixed in the aluminum alloy. Therefore, the scrap value of the aluminum alloy is hardly reduced, and the aluminum alloy scrap having high purity can be obtained. In addition, the intermetallic compound that is generated and attached to the stainless steel side does not reduce the scrap value as iron-based scrap. This is because the aluminum content in the intermetallic compound is FeAl ₃ and Fe ₂ Al as intermetallic compounds.
Assuming that ₅ occupies 50%, the amount of Al contained in this is FeAl ₃ In the case of Fe ₂ Al ₅ Therefore, the weight% of the elements is about 43% on average. When the ratio with an aluminum plate with a thickness of 2.0 mm is calculated (20 μ
m / 2.0 mm) * 43% = 0.43% This is the amount of reduction in aluminum recovery and the amount of impurities on the stainless steel side, but it is a trace amount of less than 1% and can be ignored as a loss amount. is there. The separation method according to the present invention does not require special equipment even for the clad material processing in which dissimilar metals are joined, the heating furnace of the rolling mill / scrap processing factory, the shredder of the scrap processing factory, the magnetic separator, the heavy liquid sorting Existing equipment such as machines can be used, no special equipment is required for cooling, and natural cooling by leaving it indoors or outdoors is sufficient. Therefore, when performing the scrap processing according to the present invention, there is no need for new capital investment and it is cost effective. Since the scrap collection and distribution mechanism currently established can be used as it is, recycling is efficient. It is economical ・ Since scrap processing can be performed in the manufacturing factory by the present invention even in the clad material manufacturing factory, transportation to a scrap processing company can be omitted, cost can be reduced accordingly, and scrap value can be increased. Since it can be recycled and reused, there is an effect that scrap is eliminated. Comparing the above-mentioned conventional technique with the separation method according to the present invention, the conventional technique 1. Compared with (a method of melting and separating only aluminum), the separation method according to the present invention requires less heat energy because it is not at a temperature high enough to melt aluminum. Further, mixing of stainless steel into aluminum alloy and aluminum alloy into stainless steel Since the amount of adhesion is very small, there are advantages such as high scrap purity of aluminum alloy and stainless steel.
In addition, the prior art 2. Compared with (the method of mechanically peeling after cooling by heating), the amount of the intermetallic compound produced is large in the method according to the present invention, but most of the intermetallic compound adheres to the stainless steel side. Although the values are almost the same, the labor cost is much cheaper and safer because it is not necessary to apply mechanical force to the scrap scrap. In addition, the prior art 2. Since the condition is to hold for 5 minutes to 1 hour, it is necessary to provide a gap in each scrap mass in order to uniformly heat the whole scrap to a predetermined temperature in a short time when processing a large amount of scrap. However, there is a problem that the efficiency of insertion into the heating furnace becomes poor and the separation becomes impossible if the heating is insufficient. However, in the method according to the present invention, there is no problem even if the heating temperature is raised and the holding time is lengthened to increase the amount of intermetallic compounds to some extent. Then, the whole can be completely separated by heating sufficiently. Therefore, the insertion efficiency into the heating furnace is increased, the insertion work is facilitated, the thermal efficiency is improved, and the on-site work is also facilitated in temperature control and the like. Prior art 3. Compared with (a method of forcibly cooling at least one side after heating), the conventional technique 2. As in the above, the disadvantage of the present invention is that there are many intermetallic compounds, but the present invention is advantageous in that the efficiency of insertion into a heating furnace, the point of thermal efficiency, and the need for forced cooling, and that the treatment is simple. There is an advantage in this method.

[0008]

EXAMPLES Examples of the present invention will be described below. In this example, the following existing equipment was used as the processing equipment. Scrap cutting Shredder heating and cooling in the scrap factory Heating furnace in the aluminum rolling factory Natural cooling by leaving the cooling outside the building Magnetic separation, heavy liquid sorting Magnetic separation machine and heavy liquid sorting machine in scrap factory [Example 1 ] Aluminum alloy (1100) plate thickness 2mm
And a two-layer clad material made of stainless steel (SUS430) with a plate thickness of 0.4 mm, thickness 2.4 mm x width 320 mm x
A 300 mmφ disc was blanked from a plate having a length of 960 mm, and this was cut into about 50 mm square by a cutting machine to obtain a clad material scrap. The scrap having a depth of 300 mm was placed in a 500 mm square container, the container was placed in a heating furnace, heated at 610 ° C. for 60 minutes, and allowed to cool outside the furnace. After cooling to room temperature, when looking at each fragment, the aluminum alloy and stainless steel were separated at the joint interface, and the apparent bulk increased to a depth of 350 mm. When this scrap was magnetically separated and the aluminum alloy and stainless steel were separated, it was possible to separate almost 100% aluminum alloy scrap and stainless steel scrap, respectively. Incidentally, in the present embodiment, the scrap is cut into a size that can be inserted into a container and has a small apparent bulk, facilitates separation after heating, and makes it difficult to separate the scrap pieces after the separation because they are entangled. This is to prevent this. Therefore, in carrying out the separation method according to the present invention, it is desirable to cut the scrap as a pretreatment of the heat treatment. [Example 2] The same clad material as in Example 1 having a thickness of 2.4 m.
A 300φ disc was blanked from a plate of m × width 320 mm × length 960 mm, was drawn to form an article, and the edge cut portion generated at that time and the formed article were treated as scrap. When cutting, heating, cooling and magnetic separation were performed in the same manner as in Example 1, almost 100% aluminum alloy scrap was obtained on the aluminum alloy side, but the aluminum alloy and stainless steel were folded and overlapped on the stainless steel side. Was mixed by 12%. This was caused by the fact that the original scrap was a curved instrument, and although it was peeled off at the interface, it could not be separated because the aluminum alloy was sandwiched by curved and folded stainless steel. is there. This stainless steel scrap was further cut into 10 mm square pieces, and when magnetically selected, the amount of aluminum alloy and stainless steel folded and folded was reduced to 1% (0.65% in the amount of aluminum). In order to prevent this overlapping, it is sufficient to perform a work such as selecting the bent scrap, extending it, and cutting it before the first cutting. However, since it is labor-intensive and the scrap value of stainless steel does not decrease even if a small amount of aluminum is mixed into stainless steel, re-cutting and magnetic separation after heating separation is sufficient only once. Example 3 Magnetic stainless steel (SUS430) plate thickness 0.3 mm and aluminum alloy (1100) plate thickness 1.5 mm and non-magnetic stainless steel (SUS30)
4) Based on a coil of a three-layer clad material having a plate thickness of 0.2 mm, scrap (20 mm width) at the widthwise end generated when slitting the coil is cut into 50 mm length, and a 500 mm square container It was inserted into the reactor, heated at 590 ° C. for 2 hours, and allowed to cool outside the furnace. After cooling to room temperature, when looking at each fragment, the aluminum alloy and each stainless steel were separated at the interface and separated into three layers. This scrap was magnetically separated and separated into a magnetic SUS430 and a non-magnetic aluminum alloy and SUS304, and then an aluminum alloy and SUS304 were separated by a heavy liquid sorting method (specific gravity 3.0). As a result, aluminum alloy, SUS430, SU
It was possible to separate each of the three types of metal scrap of S304. [Example 4] Aluminum alloy (3003) plate thickness 1.5
mm and stainless steel (SUS304) with a thickness of 0.5 mm, a cut plate of a two-layer clad material (thickness 2.0 mm x width 40
(0 mm x 1200 mm in length) is not cut, but is inserted into a return material container with a depth of 500 mm x width of 800 mm x length of 1500 mm without cutting, and then at 610 ° C.
After heating for 1 hour and allowing to cool to room temperature, the plates separated into two layers were manually separated into a return material container for aluminum and a return material container for stainless steel. In this example, since the scrap was of a size and shape that was easy to handle, separation processing was performed with the original shape without cutting, and the separated pieces were manually sorted without magnetic separation or the like. The method of separating the cut plates can be performed in the same manner as in the first embodiment, but in the working method used in the fourth embodiment, the scraps are transported at a reduced number by processing at the scrap generation place, and the cutting process is omitted. Therefore, the total cost can be reduced. [Example 5] The same clad material scrap as in Example 1 deviates from the recommended temperature of the present invention (1) 500 ° C, (2) 55.
0 ° C., and recommended temperature of the present invention (3) 600 ° C., (4)
After heating for 30 minutes at each temperature of 640 ° C., it was gradually cooled in a furnace. As a result, the recommended temperature of the present invention was deviated (1),
In (2), the aluminum alloy and stainless steel were still bonded. When a line analysis was performed on the diffusion region of the cross section of the junction by EPMA, almost no intermetallic compound generated by diffusion was observed in (1). In (2), an aluminum-iron intermetallic compound (diffusion layer) having an average thickness of about 2 μm was recognized although it varied depending on the location. On the other hand, the treatment was carried out at the recommended temperature of the present invention (3),
In (4), the aluminum alloy and the stainless steel were separated into two layers. When a line analysis was performed on the diffusion region of the cross section of the joint by EPMA, a diffusion layer composed of an aluminum-iron intermetallic compound having a thickness of 15 μm in (3) and a thickness of 21 μm in (4) was recognized. It was

[0009]

As described above in detail, according to the present invention, the clad material scrap made of aluminum alloy and stainless steel can be efficiently and easily separated into aluminum alloy scrap and stainless scrap at low cost. .. Further, since the amount of stainless steel mixed in particularly on the aluminum alloy side is small, the aluminum alloy recovered according to the present invention can be reused as it is without requiring adjustment of the alloy components, and thus exhibits a great effect in aluminum recycling. Is. Moreover, since the existing equipment can be used as it is, new equipment investment is not required, and the scrap processing is performed by the method according to the present invention by the equipment owned by the existing scrap processing companies and clad material manufacturers. be able to. Therefore, a new scrap collection route is not required, and it is an effective and preferable method from the viewpoint of recycling movement.

Claims (1)

[Claims] 1. A scrap of a clad material in which a layer made of aluminum or an aluminum alloy and a layer made of stainless steel or steel are combined, and the scrap of the clad material is heated at a high temperature to form a brittle aluminum-iron metal interface on the joint surface of the clad material. Compound (FeAl ₃ etc.) thickness 10μ
A method for separating a clad material scrap, which comprises: generating m or more, then allowing to cool, and spontaneously peeling.