NL2025183B1

NL2025183B1 - A method for processing scrap metal

Info

Publication number: NL2025183B1
Application number: NL2025183A
Authority: NL
Inventors: Jacob Roelof Jonkman Pim
Original assignee: Pianima B V
Priority date: 2020-03-20
Filing date: 2020-03-20
Publication date: 2021-10-20

Abstract

The invention concerns a method for processing scrap into an at least partially ﬁnished product. Metal grit, obtained from said scrap, is processed into said product. A quantity of said metal grit is introduced in a first mould cavity and squeezed to a volume body. One or more of such volume bodies are brought into a second mould cavity that defines said product. These one or more volume bodies are heated and squeezed in said second mould cavity at an elevated temperature to form the product.

Description

A method for processing scrap metal The present invention relates to a method for processing scrap into an at least partially finished product, wherein metal grit is obtained from said scrap and processed into said product.

Conventional methods of processing scrap metal generally involve separating ferro- and non- ferro metal parts from the scrap into material specific fractions. These fractions are separated and/or molten into renewed metal. Such re-use of metal evidently is efficient form a perspective of use of natural resources, but consumes a considerable amount of energy due to the relatively high melting point of many metals, like 1400-1500 °C for iron. An important non-ferro metal that is being recovered on large scale from scrap material is aluminium. Apart from construction engineering, aluminium is also an important raw material for packaging. Waste aluminium may be recovered relatively easily and its relative low melting point of 600 °C makes it relatively easy and cost effective for re-use. But besides aluminium and ferro-metals, especially traces of other non-ferro metals may be comprised in scrap material. So far, the prior art fails to provide a cost-effective technique for gaining these non-ferro out of scrap material such that they may be recovered on an industrial scale. itis inter alia an object of the present invention to provide a new and cost-effective method for gaining specifically non-ferro metals from scrap material that meets the latter. In order to achieve said object, a method of the type described in the opening paragraph is according to the invention characterized in that a quantity of said metal grit is introduced in a first mould cavity and squeezed to a volume body at a relatively low first temperature, in that one or more of such volume bodies brought into a second mould cavity, defining said product, and are heated and squeezed in said second mould cavity at an elevated, second temperature, that is higher than said first temperature, to form the product. More particularly, a specific embodiment of the method of the invention is thereby characterized in that said metal grit is cold-pressed at first temperature that is at least substantially equal to ambient temperature and that said one or more volume body are hot-pressed at a second temperature that is maintained below a melting point of said one or more volume body, particularly, near an annealing temperature of said one or more volume body.

2- According to the invention, the separated metal grit fraction, hence, is not being melted and cast directly into a workpiece, but instead a quantity of microscopic grit is cold-pressed at a moderate temperature, particularly substantially at room temperature, to create one or more macroscopic volume bodies as an intermediate stage and workpiece. The at least partially finished product is hot-pressed out of one or more of these intermediate volume bodies at elevated temperature. Particularly good results are obtained in a specific embodiments of the method according to the invention, characterized in that said second temperature is between 350 °C and 450 °C for aluminium, between 200 °C and 300 °C for zinc, between 500 °C and 750 °C for copper, brass or bronze, and between 800 °C and 1000 °C for steel and stainless steel.

It turns out that, although annealing of the original relatively fine metal grit appears not really feasible in practice, these larger volume bodies, that were cold-formed out of the metal grit, may indeed be {pre)annealed at a sufficiently elevated second temperature to be able to press them into a united newly created metal body. This metal body might be a finished product or can be used as a part to be put into a larger assembly. The second temperature is thereby kept particularly below the metal point of the volume bodies to save considerably on energy and maintain the process practical.

A specific embodiment of the method according to the invention is characterized in that said metal grit is squeezed into a volume body at a first pressure, below a yield point of said metal, and that said product is squeezed from said one or more volume bodies at a second pressure that is higher than said first pressure and beyond said yield point.

As such, a first particular embodiment of the method according to the invention, wherein said one or more volume parts comprise at least predominantly one or metals from a group comprising of copper and zinc, is characterized in that said first pressure is of the order of between 0.3 and 0.5 MPa (30-50 Ton/m?), in particular approximately around between 0.35 and 0.4 MPa (35-40 Ton/m?) to create said one or more volume bodies, and in that said one or more volume bodies are subjected in said second mould to a second pressure of the order of between 1 and 2 MPa {100-200 Ton/m?), in particular of around between about 1.6 and 1, 8 MPa (160-180 Ton/m?) to form said product.

A second particular embodiment of the method according to the invention, wherein said one or more volume parts comprise at least predominantly one or metals from a group comprising of aluminium, brass and bronze, is characterized in that said first pressure is of the order of between 0.6 and 1.2 MPa (60-120 Ton/m?), in particular approximately around between 0.8 and 1.0 MPa (80-100 Ton/m’) to create said one or more volume bodies, and in that said one or more volume bodies are subjected in said second mould to a second pressure of the order of between 3 and 4 MPa (300-400 Ton/m?), in particular of around 3.5MPa (350 Ton/m}?) to form said product.

A third particular embodiment of the method according to the invention, wherein said one or more volume parts comprise at least predominantly steel, is characterized in that said first pressure is of the order of between 1 and 2 MPa {100-200 Ton/m?), in particular approximately around between 1.4 and 1.6 MPa (140-160 Ton/m’} to create said one or more volume bodies, and in that said one or more volume bodies are subjected in said second mould to a second pressure of the order of between 6 and 7 MPa (600-700 Ton/m?), in particular of around between about 6.3 and 6.6 MPa {630-660 Ton/m?) to form said product.

The process according to the invention not only appears to render the resulting product mechanically sufficiently stable and strong, but also delivers a very attractive superficial finish on the product, still resembling the metal grains out of which it was formed. In that respect a further specific embodiment of the method according to the invention is characterized in that said metal grit comprises metal particles having a particle volume around an average grain size, said volume bodies have a body volume and said product has a product volume, wherein said average grain size and said body volume meet a ratio of at least the order of 1:100-1.000.000 and said body volume and said product volume meet a ratio of at least the order of 1:1-100. More particularly, the method according to the invention is carried out with metal grit having an average grain volume that is of the order of between a few tenth of a cubic millimetre and 100 cubic millimetre.

Although many non-ferro metals may be recovered from scrap material using the inventive method, a further specific embodiment of the method according to the invention is characterized in that said metal fraction comprises at least predominantly, in particular almost exclusively, one or more non-ferrous metals or alloys from a group comprising brass, bronze,

-A- tin, copper, silver and gold. Particularly copper, bronze and brass are often found among scrap materials and may be gained this manner from scrap metal in an economically feasible fashion. Silver and gold may be recovered especially from electronic equipment, notably printed circuit boards.

The product that is obtained by the method of the invention may be a final end product or it may serve as an intermediate product, still to be assembled into a larger entity. The metal grit may be used as a starting point of the method according to the invention. A specific embodiment of the method is thereby characterized in that said metal fraction is formed almost exclusively by a single metal or single alloy. Alternatively, a special embodiment of the method according to the invention is characterized in that said metal grit is being obtained by milling of at least a portion of said scrap, particularly a selected fraction thereof. The invention will now be described in further detail along the lines of a specific explanatory embodiment and with reference to a drawing. In the drawing: Figures 1-6 show consecutive stages of an embodiment of the method according to the invention. It should be noticed that the figures are represented purely schematically and not drawn to scale. Particularly, certain dimension may be exaggerated to a lesser or greater extent in order to clarify certain aspects of the embodiment. Same parts and members are designated by a same reference numeral throughout the drawing. Starting material for the method according to the invention may be regular metal scrap. The metal scrap is formed into pieces, see figure 1. These pieces are still relatively coarse and may still contain several materials, ranging from basic metals to coatings, glass and plastics. The metal parts are collected and milled into relatively fine grit, see figure 2. This grit is sorted into different fractions using conventional separations techniques. Ferro-metal grit, notably iron grit, may be for instance be drawn out relatively easily using permanent magnetism. Other metals, like aluminium and copper, may for instance be separated with the aid of eddy currents that render these metals also temporarily magnetic, while metals may be mutually separated based on a difference in specific weight. This will deliver a fraction of metal grit 20 that predominantly or exclusively consists of a single metal or metal alloy, see figure 2.

-5- In this exemplary embodiment of the invention, a quantity of copper grit 20 is taken and introduced into a cavity of a first mould 30, see figure 3. This metal grit typically is micro-sized at an average grain size of the order of not more than a few cubic millimetre.

Using a hydraulic excentre press or a screw impact press, a pressure of the order of 40 Ton/m’ is applied to the movable head 35 that closes mould 30. This is handled at room temperature such that the metal grit 20 is cold-squeezed into a volume body 25, hereinafter referred to as billet, as depicted in figure 4. In this case, these billets 25 are small discs have a diameter of the order of 30 millimetre and a height of the order of 20 millimetre.

Alternatively these billets 25 may have a different shape and may also be smaller or larger, up to severat litre, depending on the final product to be formed.

In a next step one or more of these billets 25 are used to form the final product.

To that end a sufficient volume of billets is introduced in a cavity of a second mould 40, see figure 5, after having been annealed to an elevated temperature of around 670 °C, i.e. of the order of 500- 750 °C.

This renders the metal already ductile and soft but is still considerably below the melting point of copper, which lies around 1100 °C.

The billets 25 are carried through an oven to attain said operating temperature before they are released into the cavity of the second mould 40 that defines the final product.

By means of a high force press, a pressure of around 160 Ton/m? is applied to the closure 45 of the mould 40 while the billets 25 are still at elevated temperature.

The billets are thereby hot-squeezed in the second mould cavity 20,25 and pressure forced into the finished product that may be released from the mould instantaneously thereafter.

This product is depicted in figure 6 and may be a final product or an intermediate work piece to be assembled in a larger setup.

The following table provides some figures of a number of exemplary embodiments of a same or a similar process for selected metals within the framework of the present invention: Metal: 1 Yield Point 2 2m 2 Melting Pressure Pressure Temperature Temperature Point: [Mpa] [Mpa] [MPa] [°C] Range [°C] [°C] Copper 40 70 160 670 550-750 1100 Zinc 40 70 160 256 200-300 420 Aluminium 86 150 343 402 350-450 660

-6- Brass/Bronze 91 160 366 548 500-700 900 steel 157 275 629 850 800-1000 1450 Stainless Steel 314 550 1257 850 800-1000 1400 Although the invention has been described in further detail hereinbefore with reference to merely a single example, it wil! be clear that the invention is by no means limited to that example. On the contrary, many more embodiments and variation are feasible to a skilled person without departing from the scope and spirit of the present invention.

For instance, depending on the size and material of the billets, the final formation step of the product may be carried out at a different temperature and pressure. Specifically also metals like brass and bronze are processed at a temperature of between 500 and 750 °C, like copper at 670 °C in the preceding example, but aluminium and zinc are preferably hot-pressed at a temperature of between 350 and 450 °C respectively between 200 and 300 °C, while steel and stainless steel are for instance preferably hot pressed at a temperature between 800 and 1000 °C, Generally a temperature is applied that renders the billets already ductile to a certain extent, but below a melting point of the billets such that the material does not become fluid and will flow out of the mould.

Claims

-7- Embodiments:

1. A method for processing scrap into an at least partially finished product, wherein metal grit, obtained from said scrap, is processed into said product, characterized in that a quantity of said metal grit is introduced in a first mold cavity and squeezed to a volume body, in that one or more of such volume bodies are brought into a second mold cavity, defining said product, and are heated and squeezed in said second mold cavity at an elevated temperature to form the product.

2. The method according to claim 1, characterized in that said metal grit is cold-pressed at first temperature that is at least substantially equal to ambient temperature and that said one or more volume bodies are hot-pressed at an elevated second temperature that is maintained below a melting point of said one or more volume body, particularly, near an annealing temperature of said one or more volume body.

3. The method according to claim 2, characterized in that said one or more volume body comprise at least mainly aluminum and said second temperature is between 350 °C and 450 °C.

4. The method according to claim 2, characterized in that said one or more volume body comprise at least mainly on or more metals from a group comprising copper, brass and bronze, and said second temperature is between 500 °C and 750 °C.

5. The method according to claim 2, characterized in that said one or more volume body comprise at least mainly zinc and said second temperature is between 200 °C and 300 °C.

6. The method according to claim 2, characterized in that said one or more volume body comprise at least mainly steel and/or stainless steel and said second temperature is between 800 °C and 1000 °C.

7. The method according to anyone of the preceding claims, characterized in that said metal grit is squeezed into a volume body at a first pressure, below a yield point of said metal,

and that said product is squeezed from said one or more volume bodies at a second pressure that is higher than said first pressure and beyond said yield point.

8. The method according to claim 7, wherein said one or more volume parts comprise at least mainly one or metals from a group comprising of copper and zinc, characterized in that said first pressure is of the order of between 0.3 and 0.5 MPa {30 -50 Ton/m?), in particular approximately around between 0.35 and 0.4 MPa (35-40 Ton/m?) to create said one or more volume bodies, and in that said one or more volume bodies are subjected in said second mold to a second pressure of the order of between 1 and 2 MPa (100-200 Ton/m?), in particular of around between about 1.6 and 1, 8 MPa (160-180 Ton/m?) to form said product.

9. The method according to claim 7, wherein said one or more volume parts comprise at least mainly one or metals from a group comprising of aluminum, brass and bronze, characterized in that said first pressure is of the order of between 0.6 and 1.2 MPa {60-120 Ton/m?), in particular approximately around between 0.8 and 1.0 MPa (80-100 Ton/m"} to create said one or more volume bodies, and in that said one or more volume bodies are subjected in said second mold to a second pressure of the order of between 3 and 4 MPa (300-400 Ton/m?), in particular of around 3.5MPa (350 Ton/m?} to form said product.

10. The method according to claim 7, wherein said one or more volume parts comprise at least mainly steel, characterized in that said first pressure is of the order of between 1 and 2 MPa (100-200 Ton/m?), in particular approximately around between 1.4 and 1.6 MPa (140-160 Ton/m?) to create said one or more volume bodies, and in that said one or more volume bodies are subjected in said second mold to a second pressure of the order of between 6 and 7 MPa (600-700 Ton/m?), in particular of around between about 6.3 and 6.6 MPa (630-660 Ton/m?) to form said product.

11. The method according to one or more of the preceding claims, characterized in that said metal grit comprises metal particles having a particle volume around an average grain size, said volume bodies have a body volume and said product has a product volume, wherein said average grain size and said body volume meet a ratio of at least the order of 1:100-1,000,000 and said body volume and said product volume meet a ratio of at least the order of 1:1-100.

9-

12. The method according to claim 11, characterized in that said average grain size is of the order of between a few tenth of a cubic millimetre and 100 cubic millimetre.

13. The method according to one or more of the preceding claims, characterized in that said quantity of metal grit comprises at least mainly, in particular almost exclusively, one or more non-ferrous metals or alloys from a group comprising brass, bronze, tin , copper, aluminum and zinc.

14. The method according to claim 13, characterized in that said metal fraction is formed almost exclusively by a single metal or single alloy, particularly steel and/or stainless steel.

15. The method according to one or more of the preceding claims, characterized in that said finished product is formed from a single volume body.

16. The method according to one or more of the preceding claims, characterized in that said metal grit is being obtained by milling of at least portion of said scrap, particularly a selected fraction thereof.

-10- Conclusions:

A method for processing scrap into an at least partly finished product, wherein metal grit obtained from the scrap is processed into the product, characterized in that a quantity of metal grit is introduced into a first mold cavity and pressed therein to a volume part in that one or more such volume parts are introduced into a second mold cavity defining the product and heated to be pressed into the product at an elevated temperature in the second mold cavity.

A method according to claim 1, characterized in that the metal grit is cold pressed at a first temperature which is at least substantially equal to an ambient temperature and that the one or more parts by volume is hot pressed at an elevated second temperature which is below a melting point of the or more parts by volume is maintained, especially near an annealing temperature of the one or more parts by volume.

Method according to claim 2, characterized in that the one or more parts by volume comprise at least predominantly aluminum and the second temperature is between 350°C and 450°C.

Method according to claim 2, characterized in that the one or more parts by volume comprise at least predominantly one or more metals from a group comprising copper, brass and bronze, and said second temperature is between 500°C and 750°C.

Method according to claim 2, characterized in that the one or more parts by volume comprise at least predominantly zinc and the second temperature is between 200°C and 300°C.

Method according to claim 2, characterized in that the one or more parts by volume comprise at least predominantly steel and/or stainless steel and the second temperature is between 800°C and 1000°C.

-11-

Method according to one or more of the preceding claims, characterized in that the metal grit is pressed to a volume part at a first pressure, below a yield point of the metal, and that the product is pressed at a second pressure, higher than the first pressure, and higher than the yield point, is formed from the one or more parts by volume.

Method according to claim 7, wherein the one or more parts by volume comprise at least predominantly one or more metals from a group of copper and zinc, characterized in that a first pressure of the order of between 0.3 and 0.5 MPa ( 30-50 Ton/m*) is installed, in particular approximately around between 0.35 and 0.4 MPa (35-40 Ton/m?) and that the one or more parts by volume at a second pressure of approximately between 1 and 2 MPa (100-200 Ton/m²), in particular of around between about 1.6 and 1.8 MPa (160-180 Ton/m²), are pressed into the product.

Method according to claim 7, wherein the one or more parts by volume comprise at least predominantly one or more metals from a group of aluminium, brass and bronze, characterized in that a first pressure of the order of between 0.6 and 1.2 MPa (60-120 Ton/m?) is applied, in particular approximately around between 0.8 and 1.0 MPa (80-100 Ton/m?) and that the one or more parts by volume at a second pressure of approximately between 3 and 4 MPa (300-400 Ton/m²), in particular of about 3.5 MPa (350 Ton/m²), are pressed into the product.

Method according to claim 7, wherein the one or more parts by volume comprise at least predominantly steel, characterized in that a first pressure of the order of between 1 and 2 MPa (100-200 Ton/m²) is applied, in particular approximately around between 1.4 and 1.6 MPa (140-160 Ton/m?) and that the one or more parts by volume at a second pressure of approximately between 6 and 7 MPa (600-700 Ton/m?), in the especially from around 6.3 to 6.6 MPa (630-660 Ton/m?) are pressed into the product.

Method according to one or more of the preceding claims, characterized in that said metal grit comprises metal particles having a particle volume around a mean grain size, said volume bodies have a body volume and said product has a product volume, said mean grain size and said body volume being sufficient. to a ratio of at least the order of at least 1:

-12-100-1,000,000 and said body volume and said product volume meet a ratio of the order of at least 1:1-100.

Method according to claim 11, characterized in that the mean grain size is in the order of a few tenths of a cubic millimeter to 100 cubic millimeters.

Method according to one or more of the preceding claims, characterized in that the amount of metal grit comprises at least predominantly, in particular almost exclusively, one or more non-ferrous metals or alloys from a group comprising brass, bronze, tin, copper, aluminum and zinc.

Method according to claim 13, characterized in that the metal fraction is formed almost exclusively by a single metal or single alloy, in particular steel and/or stainless steel.

Method according to one or more of the preceding claims, characterized in that the finished product is formed from a single volume part.

Method according to one or more of the preceding claims, characterized in that the metal grit is obtained by grinding at least part of the scrap, in particular a selected fraction thereof.