DE2103614B2 - Process for the production of semi-finished products from AIMgSIZr alloys with high notched impact strength - Google Patents

Description

Hot-formed AlMgSi alloys are suitable for a wide variety of purposes and are, for. B. in shape can be used for extruded profiles, forgings or rolled sheet metal. In many forms of application, e.g. B. in extruded semi-finished products keen interest in hot worked alloys that have both high strength and high impact strength own. So z. B. Railings of road bridges or road crash barriers Extruded aluminum or corresponding aluminum alloys have significant impact resistance exhibit.

It is the object of the invention. Semi-finished products made from AlMgSi alloys with both high strength and high notched impact strength in the hot-worked condition to provide. This object is achieved by the invention.

It was known per se from US-PS 32 34 054, consisting of aluminum-magnesium-silicon alloys from 0.6 to 0.9% aluminum-silicon, 0.4 to 0.6% magnesium and R · Muminium, which are used as optional components up to 0.3> ο iron, 0.1% copper, up to up to 0.1% manganese, up to 0.1% chromium, up to / u 0.1% Zinc and up to 0.1% titanium, hot-worked at a temperature above 510 C by extrusion. to a maximum temperature of 177 C and finally 15 minutes to 24 hours to be stored at a temperature of 93 to 210 C for a long time. Homogenization gluing can also be carried out before hot forming inserted at temperatures of at least 521 C.

However, zirconium-free alloy systems treated in this way do not have sufficient notched impact strength on.

Furthermore, alloy systems from IIS-PS 31 13 052 are known which _{contain the compound Mg 2} Si as a structural component and consist of 0.43 to 1.40% magnesium, 0.24 to 0.8 () 70 silicon, with the proviso that magnesium and silicon are in such a ratio to one another that 0.74 to 2% Mg ₂ Si are formed, 0.01 to 0.3% titanium, chromium, manganese, molybdenum each. Tungsten and / or zirconium and / or

21 03

0.001 to 0.1% boron, the latter elements total Do not exceed 0.75% and the remainder is aluminum. In order to develop high strength properties, these alloys must be deformed Condition must be subjected to solution treatment, and also must be subjected to homogenization treatment Followed by a 3-stage delayed cooling treatment, which also includes a holding time of at least 2 hours. Although this known alloy system also has zirconium as a mandatory component contains no reports of an improvement in the notched impact strength.

Surprisingly, it has now been found that it succeeds by means of a very simple sequence of process steps. Semi-finished product with good strength shafts and, above all, a satisfactory notched impact strength if you have a certain Sequence of process steps which are inherent in the application to alloys of different compositions is known, applies to a per se known alloy of the Al-Mg-Si-Zr type.

Accordingly, the invention consists in the use of a method for producing semifinished products AlMgSi alloys, in which the cast body is thermoformed at temperatures above 454 ° C, on temperatures Quenched to a maximum of 177 ° C and finally heated to 93 to 210 C for 15 to 24 hours be outsourced to a known one. Alloy composed of 0.3 to 1.3% silicon, 0.3 "to 1.5% magnesium, 0.03 to 0.4% chromium. 0.03 to 0.2% zirconium and optionally up to 0.4% manganese and optionally up to 0.1% titanium, optionally up to 0.15% vanadium and up to 0.6% iron, up to 0.3% copper, up to 0.5% zinc, up to 0.008% boron and up to 0.1% each of other conventional impurities, the total amount of which does not exceed 0.5%. Remainder aluminum.

The procedure used here differs, among other things, from the working method the US-PS 31 13 052 that no solution heat treatment is required after hot forming and that the Hot deformation takes place at a higher temperature.

As the tests with the comparative alloy D of Example 2 confirm, the application of the Process stages on zirconia-free alloy systems do not lead to a corresponding improvement in the Impact strength.

It is believed that in the zirconium-containing alloys contemplated herein a special structure forms, which fibrous structure grains with a high ratio of length too thick, between which a large number of sub-grains are embedded.

According to a preferred embodiment, the sequence of the above method is applied to an alloy applied, the 0.4 to 0.9% silicon, 0.4 to 1% magnesium. 0.05 to 0.15% zirconium and 0.05 contains up to 0.35% chromium.

Furthermore, very good results are obtained when applying the method to an alloy of the type described Type obtained which additionally contains 0.03 to 0.4%, preferably 0.05 to 0.3%, manganese.

With regard to the other electoral components mentioned, they have chosen to apply the process sequence Alloys proved to be beneficial, which additionally contain up to 0.1% titanium and up to 0.15% vanadium contain.

It is particularly useful to apply the relevant process sequence to alloys, which each contain 0.03 to 0.2% chromium, zirconium and manganese with the proviso that the total content of these three elements is 0.2 to 035%

The aluminum alloys treated by the aforementioned process generally have a tensile strength of at least 26.6 kgf / mm ^2, a 0.2 limit of at least 24.5 kg / mm 2 and an elongation at break of at least 8%. The minimum notched impact strength (according to C har ρ y) of the aluminum alloys in question is at least 2.1 mkp for a test specimen approximately 3.2 mm thick. In the case of a 1 cm thick test specimen, a notched impact strength of at least Z8 mkp, for example from 4.1 to 5.5 mkp, is achieved. The numerous other excellent properties of the aluminum alloys processed by the aforementioned method include their good suitability for extrusion and their high corrosion resistance.

The melting and casting methods are not critical, and conventional corresponding methods can be used be applied. However, it is advisable to homogenize the castings prior to hot forming / u, to evenly distribute the silicon and magnesium in the alloy matrix. Before or During the hot forming process, a certain amount should develop due to the chromium, zirconium and manganese content Form an amount of high temperature precipitate as this inhibits recrystallization will. The same goal can, however, also be achieved both by reheating for hot deformation and by homogenization can be achieved.

In the method used, the hot forming is preferably carried out at a final temperature above about 482 "C. The" final temperature "here is to be understood as the last temperature at which a significant degree of deformation is achieved by means of hot deformation. The hot deformation can, for. B. consist of forging, rolling or extrusion, with rolling and extrusion being preferred. The aforementioned minimum final temperature corresponds to extrusion (about 454'C) the mold outlet temperature. To achieve maximum strength in practice it is preferred to operate at a temperature so high that essentially the total amount of magnesium and silicon is brought into solution. After the hot forming will be the aluminum alloys expediently with a cooling rate of 555 to 5550 C / min. Quenched to at least 177 C. For this purpose the alloys are usually immersed in water submerged or passed through a water spray quenching device. Then the aluminum alloys preferably cold worked to a thickness reduction of 5%, e.g. B. by rolling or Warriors.

The aluminum alloys contemplated here are generally sensitive to quenching. It is therefore particularly surprising that this quench sensitivity is particularly preferred in the case of one embodiment of the invention can be reduced. In this embodiment the aluminum alloys each contain 0.03 to 0.2% chromium or zirconium or manganese, and the The total proportion of chromium, zirconium and manganese is 0.2 to 0.35%. It was found that aluminum alloys this composition with a

Cooling speed from 55 to 555 ° C / min. can be air-cooled. For air cooling are generally useful arranged fans used in the processing of the aforementioned particularly preferred aluminum alloys to 5, the heat distortion at a finish temperature above 482 ° C, preferably above 510 ⁰ C is performed.

The examples explain the experience.

IO

example 1

Aluminum alloys (alloy A or B) are obtained by fusing those listed in Table I. Components made in a gas-fired open-hearth furnace and in a conventional manner processed into cast ingots using the continuous casting process (water casting). After the alloy is formed the melt is degassed by passing chlorine gas through it for 20 minutes. When pouring becomes a temperature of 743 ° C applied. The casting speed is also 11.4 cm / min., While the metal casting head is maintained at dimensions of 6.4 to 7.6 cm.

Table I. Components Components

Alloy A
Silicon
magnesium
iron
titanium
chrome
zirconium
manganese
copper
zinc
aluminum

Alloy B
Silicon
magnesium
iron
titanium
chrome
zirconium
manganese

Table II

Shares

0.73

0.47

0.14

0.01

0.05

0.056

0.054

0.04

rest

0.81

0.53

0.14

0.01

0.107

0.108

0.108

35

40

45

50 alloy B

copper

zinc

aluminum

Shares

0.03

rest

The cast ingot vergenannten herding 10 hours at 550 ⁰ C is homogenized and then cooled in air. Thereafter, the billets sawn to length are reheated for extrusion at a controlled temperature of 538 ° C in a billet furnace with gas firing. Surface temperatures of 524 to 552 ° C are measured on the bars before they are introduced into the press. Three different extrusion dies are used to produce extruded profiles with thicknesses of 0.317 cm, 0.635 cm and 1.27 cm. The outlet temperatures are 527 to 538 ° C. An extruded profile of each of the aforementioned thicknesses is then in each case after exiting the press by means of a fan with a cooling rate of 55 to 555 ° C / min. cooled down. Another extrusion of each thickness is quenched with water by passing it through an open-ended trough which is fed with water at both ends in an upward flow. The quenching is carried out using a quenching speed of 555 to 5550 ° C./min. performed. All extruded profiles are then aged for 24 hours at room temperature and then aged for 5 hours at 177 ° C. Test specimens for determining tensile strength and notched impact strength according to Charpy are then produced from the extruded profiles. The approximately 0.317 cm and approximately 0.635 cm thick extruded profiles are tested with a reduced width, based on the standard width of 1 cm, and the value for the notched impact strength is corrected with regard to the reduced cross-sectional area.

From the results given in Table II, the combination of high strength and high is Notched impact strength evident. The particularly strongly increased notched impact strength is on the preservation a non-recrystallized grain structure of the aluminum alloys. On the surfaces The extruded profiles contain thin layers of recrystallized grains. These layers are thinner in alloy B than in alloy A.

SlrangpreB-profilslärkc

Alloy cooling or quenching method Tensile strength wedge 0.2 size / e

(kp / mm ² ) (kp / mm ² )

A.
B.

Fan cooling 30.45 Water deterrent 32.27 Fan cooling 30.45 Water deterrent 31.85

28.70
30.38
23.51
29.68

Elongation at break

10
11
9.5
10

Notched impact wedge according to Γ h a r ρ y

(mkpl

2.83
3.49
3.71
3.71

continuation

Extruded profile thickness

Alloy cooling or quenching method tensile strength

(kp / mm ² ) 0.2 limit (kp / mm ² ) (%)

Elongation at break

Charpy impact strength

(mkp)

A.
B.
A.
B.

Fan cooling 30.10 27.51 8 3.32

Water quenching 32.20 29.17 9.5 3.84

Fan cooling 28.91 25.55 9.5 4.87

Water quench 32.06 30.10 9.5 5.23

Fan cooling 28.98 25.90 10.5 4.19

Water quenching 30.80 28.70 11.5 8.00

Fan cooling 26.95 23.31 12 9.50

Water quenching 33.82 32.20 12.5 6.02

Example 2

There are cast ingots using molten aluminum alloys (alloy C to F) the composition shown in Table III of 2 kg each by a conventional casting process manufactured with a swiveling mold (Durville process).

Table III Components

Shares

Alloy C (comparison alloy)

Silicon 0.71

Magnesium 0.56

Iron 0.16

Copper <0.01

Titanium 0.02

Zirconium 0.16

Aluminum rest

Alloy D (comparison alloy)

Silicon 0.83

Magnesium 0.58

Iron 0.20

Copper <0.01

Titanium 0.01

Chrome 0.31

Aluminum rest

Alloy E.

Silicon 0.71

Magnesium 0.57

Iron 0.16

Copper <0.01

Titanium 0.02

Chromium 0.22

Zirconium 0.10

Aluminum resl

Alloy F

Silicon 0.78

Magnesium 0.58

60

Components

Alloy F
iron
copper
titanium
chrome
manganese
zirconium
aluminum

Shares

0.17

<0.01

0.02

0.10

0.09

0.11

rest

35

40

45 The cast ingots are homogenized for 12 hours at 552 ° C. and then hot-rolled by 80% at 538 ° C. in a single pass. The sheets obtained are quenched by immersion in water at room temperature, a quenching rate of 555 to 5550 ° C./min. is achieved. The sheets are then stored at a temperature of 177 ° C for 5 hours. Finally, the tensile properties and the Charpy notched impact strength are determined on test sheets approximately 0.32 cm thick. It can be seen from the results shown in Table IV that the inventive combination of alloy composition and process sequence unexpectedly improves the properties of the aluminum alloys (Alloys E and F) compared to those of the comparison alloys (Alloys C and D). It should be noted that alloy C has no added chromium and alloy D has no added zirconium.

55

Table IV

Lepe- tensile strength- elongation- fracture- notched impact strength tion wedge limit extensible according to Charpy (mkp)

rank

{kp / mm ² ) (kp / mm ² ) (%) single values mean

30.59 27.02 14
30 £ 7 26.88 13
3031 26.74 II

1.44 1.63 1.54
1.74 1.98 1.87
137 1.48 1.42

SW 533/315

1606

continuation Tensile strength
wedge Stretch
border fracture
deh
tion Notched impact strength
after Charpy (mkp) 2.04 middle
value Legie
tion (kp / mm ² ) (kp / mm ² ! (%) Individual values 3.10 1.99 31.01 27.79 11 1.95 2.39 2.98 D. 30.45 26.88 13.5 2.84 2.46 2.49 E. 31.64 27.51 12.5 2.57 2.62 2.48 31.64 24.63 12.5 2.49 2.65 33.04 29.61 11.5 2.68 F.

Components

Shares

Example 3

There are cast ingots made of alloys of the composition shown in Table V according to Example 1 manufactured:

Table V

Components

Shares

Alloy G silicon magnesium iron copper titanium

boron
Alloy H silicon magnesium iron copper titanium chromium zirconium

boron
Alloy! (commercial alloy AA 6351) silicon magnesium iron alloy! (commercially available alloy AA 6351) copper 0.004

Titanium 0.024

Manganese 0.66

Boron 0.004

Alloy J (commercially available alloy 6061)

Silicon 0.64

Magnesium 1.10

Iron 0.25

Copper 0.25

Titanium 0.017

Chromium 0.18

Manganese 0.053

The cast ingots are processed according to Example 2, except that the hot rolling is only up to Performs to a strength reduction of 50% Alloys I and J are also 8 hours aged at about 177 ° C. From the in table VI, the surprisingly favorable properties of alloy H can be seen The Charpy impact test is on

0.84
0.50 Standard test specimens a
guided. 45 H 50 J Vl Stretch
border
(kp / mm ² ) Thickness of 1 cm through 0.20 train
strength
(kp mm ² ) 27.16 0.003
0.023 35 table 1 30.45 27.51 0.004
0.81
0.58
0.19 Le
yaw
40 30.45 29.19 fracture
strain
(%) Notch impact
toughness
after
Charpy
(mkp) 0.004
0.023 G 32.13 29.40 12.0 1.12 0.25 32.27 32.68 11.4 1.09 0.082 34.65 32.41 15.0 5.15 0.004 34.58 29.54 15.0 4.95 351) 33.11 29.61 12.1 1.64 1.08 33.25 12.0 1.65 0.65 12.8 1.35 0.19 13.0 1.33

»1606

Claims (13)

Patent claims: I using a method for manufacturing semi-finished products of AlMgSi Legierungen- at the casting at temperatures above 454 ° C warmverfbrmt, quenched to temperatures of at most 177 ° C and are outsourced finally for 15 to 24 hours, warm to 93-210 ⁰ C, in an alloy known per se, consisting of 0.3 to 13% silicon, 0.3 to 1.5% magnesium, 0.03 to 0.4% chromium, 0.03 to 0.2% zirconium and optionally up to 0 , 4% manganese, optionally up to 0.1% titanium, optionally up to 0.15% vanadium and up to 0.6% iron, up to 0.3% copper, up to 0.5% zinc, up to 0.008% boron and the remainder aluminum a total of a maximum of 0.5% further impurities, of which each individual element may only contain up to 0.1%. 2. Application of a method with the sequence of claim 1 to an alloy of the composition of claim 1 containing 0.4 to 0.9% silicon, 0.4 to 1% magnesium, 0.05 to 0.15% zirconium and contains 0.05 to 0.35% chromium. _2Y 3. Application of a method having the sequence of claim 1 to an alloy of the composition according to claim 1 or 2, which contains 0.03 to 0.4%, preferably 0.05 to 0.3%, manganese. 4. Application of the method with the sequence of claim 1 to an alloy of the composition according to one of claims 1 to 3. up to 0.1% titanium and up to 0.15% vanadium contains. 5. Application of the method with the sequence of claim 1 to alloys of the composition according to one of claims 1 to 4, but each 0.03 to 0.2% chromium, zirconium and Contains manganese with the proviso that the total content of these three elements is 0.2 to 0.35% amounts to. 6. Application of the method with the sequence according to claim I, in which the hot deformation is carried out above 482 C, on alloys of the composition according to one of the Claims I to 5. 7. Application of the method with the sequence according to claim 1 or 6, in which the worm deformation takes place by rolling and in which the hot-formed sheets by means of water with a cooling rate are quenched from 555 to 5550 C per minute on alloys of the composition according to any one of claims 1 until 5. 8. Application of the method with the sequence according to claim I and 6. in which the thermoformed Trays with a cooling rate of 55 to 555 C 'per minute are air cooled on alloys of the composition according to one of claims 1 to 5. 9. Application of the method with the sequence according to claims, in which the hot deformation is carried out at a final temperature above 510 C, on alloys of the composition according to one of claims 1 to 5. 10. Application of the method with the sequence according to claim 6 to 9. in the case of hot forming the extrusion process is used. the final temperature corresponding to the mold outlet temperature, on alloys of the composition according to any one of claims 1 to 5. 1 1. Application of the method with the sequence according to claim 6 to 9, in which the hot rolling method is used for warrave deformation, on alloys of the composition according to one of claims 1 to 5. 12. Application of the method with the sequence according to claim 6 to 1 1 , in which the cast ingots are subjected to a homogenization annealing before the hot forming, on alloys of the composition according to any one of claims 1 to 5. 13 Application of the method with the sequence according to claim 6 to 12, in which the sheets are cold-worked to a thickness reduction of 5% after cooling or quenching, on alloys of the composition according to one of claims 1 to 5.