DE3008358B2 - - Google Patents

Description

The invention relates to the use of mixed old scrap for the production of aluminum rolled products by continuous or strip casting of rolled ingots or plates and by subsequent hot and Cold rolling.

Aluminum scrap comes from used consumer goods or machines that are either entirely from Aluminum alloys consist or substantial components of aluminum and its alloys contain. These consumer goods or machines made of aluminum or their aluminum parts can be made from wrought aluminum materials by cold or hot forming or from cast aluminum materials be made by molding. Because of the requirements of the various manufacturing processes the compositions of wrought aluminum alloys and cast aluminum materials differ in fundamentally. Aluminum wrought materials have high alloy contents of Mg, Mn and Zn, while aluminum casting materials are characterized by high Si and often higher Fe and Cu contents.

If such used aluminum materials are reused, the scrap parts are therefore removed kept separated according to their division into wrought and cast materials to be used in the new production processes to avoid disruptions in forming or casting processes after remelting. A sort of All scrap by type of material must be done before melting.

However, since especially aluminum castings are often poured in or adhering Kremclmetalle such as /. B. iron, / ink and copper, there is often an accumulation of disruptive metals for the further production process, even with scrap melted collars from sorted old scrap, which can only be compensated by blending with pure primary aluminum. Another source of interference are cast parts made of zinc or magnesium alloys, which are difficult to separate out during sorting processes and which lead to inadmissibly high Mg or Zn contents in the scrap melt batches for further use as aluminum remelting cast alloys. In addition to blending with primary aluminum, the environmentally unfriendly chlorination treatment or an energy-intensive vacuum treatment at elevated temperature are used to reduce such excessive Mg or Zn contents.
Another source of increasing Mg and Zn contents in scrap smelting batches is the frequent assembly of consumer goods and machines from wrought aluminum and cast aluminum materials.

For example, engine blocks and cylinder heads as well as transmission housings are often made of a cast aluminum alloy from * type AISiCu, attached auxiliary unit housing Made of Zn-DruekguB, chassis parts, paneling in the body area exist made of wrought aluminum alloys of the types AlMgSi or AlMg5. The same applies to large household appliances where cast aluminum parts and paneling, facings and decorations made of wrought aluminum alloys are processed together.

To achieve an economical shredding of scrap and to have built-in iron parts made of cast aluminum All aluminum scrap can be removed using a shredding process with subsequent magnetic separation are subjected to iron removal. The product of such grinding processes is small-scale shredded scrap in which the original wrought aluminum and cast aluminum materials are mixed and are no longer distinguishable. After melting down such scrap, the above The mentioned process of blending with valuable primary aluminum or chlorination is used to produce reusable cast alloys.

The object of the present invention was to find a way of using mixed old scrap from used cast and wrought materials while avoiding the disadvantages mentioned above.

As can be seen from DIN 1725 Part 1, aluminum wrought semi-finished products and thus also rolled semi-finished products are made made of special alloys with a very narrow and defined composition, with their Properties depend on the type and amount of the alloy constituent contained therein. Surprisingly it has now been shown that an alloy completely melted from uncut scrap Sheets manufactured with an unconventional composition have excellent properties in terms of strength and above all formability during roll forming or deep drawing.

This makes a sensible and economical M) use of those made of cast and wrought materials mixed scrap for the production of sheet metal and strips.

The manufacture of the sheets. Plates or strips are made by melting old scrap together From aluminum cast alloys to wrought aluminum alloys without the addition of primary aluminum zi · an alloy with contents of 1 to 6% Si. 1 to 3% Mg. 0.5 to 3% Zn. 0.5 to 3% Fe, 0.3 to 2% Cu and up to

1% Mn, up to 0.2% Ti, up to 0.5% Cr and up to 0.5% Pb, Bi, Sn. According to the invention, the alloy melt is ^{kept at at least 730 °} C. for 1 to 2 hours before casting and poured off with an inlet temperature of at least 710 ^{° C.} The rolling ingots 12 are annealed to 24 hours at 490 ⁰ C and subsequently rolled down in a conventional manner hot and cold to the desired final gauge. It is advantageous that cast alloy scrap of the type AlSi, AlSiCu, AISiMg is melted together with wrought alloy scrap of the type AlMn, AlMg, AlMgMn, AlZnMg, AlZnMgCu, AIMgSi and / or AlCuMg in a mass ratio of 1: 1 to 2: 1.

A preferred application of the method according to the invention is characterized in that the Old scrap is processed in a shredding process with downstream magnetic separation.

The use according to the invention enables such melts from mixed scrap to be converted into advantageously without the costly or environmentally friendly measures of blending Primary aluminum or chlorination can be used for the production of plates and sheets or tapes with good performance properties.

By keeping such melts from mixed scrap at a temperature of at least 730 ^° C. for a period of 1-2 hours and by continuous casting to form rolling ingots or plates with inlet ^{temperatures in the casting device of at least 710 °} C., the continuous cast structure is given a structure for subsequent rolling Sheet metal particularly suitable structure. The formability necessary for w: 'itere production processes for the production of sheet metal parts by cold forming z. B. in roll forming or deep drawing is also influenced favorably by this treatment of the old red alloy melts

Sheets from rolling billets produced in this way show unusual properties for wrought materials Composition increased sensitivity to corrosion The corrosion protection can be used in the usual Way to be created by painting or coating. It is more advantageous according to the invention however, if a roll plating occurs during the rolling out of the billets from such scrap alloy melts of 5 to 10% on both sides with AlZn 1.5 based on Al 99.8 or more pure.

Electrochemical investigations of the corrosion potentials on the alloy sheets according to the invention from mixed scrap and on cladding materials and on short-circuit elements made of these Alloy sheets and various cladding materials have shown that AlZn 1.5 is based on Al 99.8 or purely an optimal corrosion protection both by covering the sheet metal surface and by

Table 1

electrochemical effects due to the potential difference between the core material and the cladding layer guaranteed

example 1

Rolling ingots were cast from a melt of mixed scrap in the continuous casting process after the alloy melt had been ^{kept at a temperature of 730 °} C. for two hours. The inlet temperature into the rolling ingot molds was set to 710 ^° C. during the continuous casting. The rolling ingots had the following composition in percent by mass:

Fe

Cu

Mn

Mg Cr Zn

4.90 0.94 0.92 0.31 I, 0 _; 0.15 0.50 0.035

The rolling billets were subjected to an annealing treatment at 490 ° C. for 12 hours. The hot rolling Made with an initial temperature of 46CC. During hot rolling, a cladding layer of Al 99.8 Zn 1.5 with 10% of the sheet thickness was applied on both sides The clad hot strip was then cold rolled to its final thickness. The strength values and some Forming parameters in different states are given in Table 1 together with others from Example 2.

Example 2

Rolling ingots were cast from a second melt of mixed scrap in the continuous casting process after the alloy melt had been kept ^{at a temperature of 730 ° C. for two hours.} The inlet temperature into the rolling ingot molds was set to 710 ° C. during continuous casting. These rolling ingots had the following composition in percent by weight:

Fe

Cu

Mn Mg Cr

Zn

1.07 1.10 1.08 0.25 2.8 0.16 2.63 0.03

v> The rolling bars were subjected to an annealing treatment at 490 ^° C. for 24 hours. Hot rolling took place at an initial temperature of 460 ^° C. During hot rolling, a cladding layer of Al 99.8 Zn!, 5 of 10% of the sheet thickness was applied on both sides. The clad hot strip was then cold rolled to its final thickness.

The strength values and some deformation parameters in different conditions are summarized in Table 1 with those of Example 1 indicated.

Strength «- and forming parameters of sheets with a thickness of 1.2 mm from the scrap alloy melts of the Examples 1 and 2

State examples Examples Examples Examples Examples I 2 I 2 I 2 1 2 I 2 ft _{/ M} i ₂ (N / mm ² ) Ä _m (N / mnr> .-MI '.) /; η Krichsen pitch (mm)

Walzhart
1114. semi-hard

260
215

290

248

280
235

310 268

continuation 5 30 08 358 1 6th Ί
Il Examples
I 2
hrichsen-
lielung (m..i) Status Examples
I 2
«,." ,, (N / mnr) Examples
I 2
Ä "(N / miir'i Examples
1
. ■ Ifi ¹ : ..) 24
25th
17th Examples
1
/; 0.22
0.30
0.13 10 10
8 10
6 7 Soft
Annealed 530 C
deterred
Artificially hardened,
24 h 170 C 85 80
108 102
345 310 170 200
262 259
390 400 27
22nd
12th 0.18
0.28
0.07

The sheets from both examples exhibited good formability in the soft as well as in the solution-annealed and quenched state, as can be seen from the hardening exponent π and the Erichsen depression, and achieved high strength values after artificial hardening.

The corrosion behavior of such clad sheets from scrap alloy melts turned out to be very good.

The sheets were well suited for anodic oxidation, to create decorative sheet metal surfaces.

The semi-finished rolled products produced in this way can, due to their good properties, be used for numerous Areas of application, for example in construction (facades), vehicle construction (Bepianluiigen, body parts) or used for other purposes ν earth.

Claims (4)

Patent claims: t. Use of cast aluminum alloys of type A! Si, AISiCu and / or AISiMg and Wrought aluminum alloys of the type AIMn, AIMg, AIMgMn, AIZnMg, AlZnMgCu, AIMgSi and / or AlCuMg in a ratio of 1: 1 to 2: 1 without the addition of primary aluminum for mixed scrap Manufacture of rolled semi-finished products with a composition from 1 to 6% Si, 1 to 3% Mg, 0.5 to 3% Zn, 0.5 to 3% Fe, 03 to 2% Cu and up to 1% Mn, up to 0.2% Ti, up to 0.5% Cr and up to 0.5% Pb, Bi, Sn, the remainder aluminum. 2. Use of old scrap for the production of rolled semi-finished products according to claim 1, which in one Shredding process with downstream magnetic separation have been processed. 3. Manufacture of semi-finished rolled products from old scrap according to claim 1 or 2, characterized in that the alloy melt is initially held for 1 to 2 hours at at least 730 "C, with an inlet temperature of at least 710 ° C in the continuous casting process to form rolling ingots or strips and these 12 are annealed to 24 hours at 490 ⁰ C and then hot rolled and cold in üb'icher manner. 4. Rolled semi-finished products produced from old scrap according to claim i or 2, characterized in that that they are made on both sides with 5 to 10% by volume AIZnIA on the basis of Al 99.8 or more pure, are roll clad.