Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
  • C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/05—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
  • H01B1/023—Alloys based on aluminium

Definitions

• the invention relates to a method for producing an aluminum strip with high strength and high electrical conductivity, and also to an aluminum strip which can be produced using this method, or to an aluminum strip made from such a strip
• the alloy EN AW-6101B is the standard for applications that require high electrical conductivity and strength. These conductor materials are usually extruded, including quenching and outsourcing, or via rolling processes, which are separate
• FIG. 1 shows such a method from the prior art for producing an aluminum strip for electrical aluminum conductor applications.
• the individual process steps are from left to right in FIG. 1, and those in the temperature-time diagram below are qualitative and schematic
• a bar 6 is first cast in a first step 4 in the DC ingot casting, for example from the alloy EN AW-6101B.
• a homogenization step 8 in a homogenization furnace 10 hot rolling 12 then takes place on a hot rolling stand 14 and a subsequent cold rolling 16 on a cold rolling stand 18 to the desired final thickness.
• the homogenization can be preheated
• Hot rolling temperature can be integrated.
• a solution annealing 20 in a continuous furnace 22 is required in this production method after cold rolling, before the material is finally subjected to a heat aging annealing 24 in one
• Heat aging annealing furnace 26 is subjected to increase the strength and the electrical conductivity of the material again.
• FIG. 2 shows a corresponding process flow 30, the individual
• Hot rolling step to produce a hot strip instead of cold rolling, the process 30 is followed first by solution annealing 20 and then by hot aging 32 in a hot aging furnace 34 before the strip is finally cold rolled on the cold rolling stand 18. After the cold rolling, the annealing 24 takes place again in the annealing furnace 26.
• the method described in FIG. 2 can indeed be used to produce aluminum conductor materials with good electrical conductivity, strength and ductility.
• the process is very long and complex with many different process steps.
• the object of the present invention is to provide a faster and more efficient method which can nevertheless be used to achieve good properties with regard to electrical conductivity and strength.
• this object is achieved according to the invention by a method for producing an aluminum strip, in which a melt made of a hardenable aluminum alloy by means of a continuous casting process, in particular double-roll casting
• Aluminum strip is shaped, in which the aluminum strip is rolled to a thickness by cold rolling and in which the aluminum strip is between the
• Combination of good strength and high electrical conductivity can be produced, which are comparable to the strengths and electrical conductivities of an aluminum strip produced according to the method from FIG. 1, but with a significantly shortened, faster and more economical process sequence.
• the process sequence is in particular also shorter, faster and more economical than the process sequence according to FIG. 2.
• Casting process is provided. This also means providing one for the solution annealing of the continuous furnace required can be dispensed with, so that investment costs are reduced.
• the cold rolling after the continuous casting process in the process therefore preferably takes place without intermediate solution annealing. This enables significant cost savings and shortening of the process chain to be achieved.
• a melt made from a hardenable aluminum alloy is shaped into an aluminum strip by a continuous casting process, in particular double-roll casting.
• the melt is continuously formed into a band.
• the melt is placed in the nip of two cooled casting rolls, so that a continuous aluminum strip emerges from the nip on the other side of the casting rolls.
• the thickness of the aluminum strip is determined by the thickness of the nip.
• the aluminum strip is rolled to its final thickness by cold rolling.
• Cold rolling is carried out in particular in several passes on a cold rolling stand.
• the aluminum strip is also hot-aged between the continuous casting process and cold rolling.
• the aluminum strip is preferably wound onto a coil after the continuous casting process and then placed in coil form in a hot aging oven, in which it is at a predetermined hot aging temperature above a predetermined one
• Warm aging period is warmed up.
• the hot aging is preferably the only heat treatment of the aluminum strip between the continuous casting process and the cold rolling.
• the above-mentioned object is further achieved according to the invention by a method for manufacturing an aluminum strip, in which a melt made of a hardenable aluminum alloy is shaped into an aluminum strip by a continuous casting process, in particular by double-roll casting, in which the
• Aluminum strip is rolled to an intermediate thickness in a primary cold rolling process, in which the aluminum strip is rolled to final thickness in a secondary cold rolling process and in which the aluminum strip is heat-aged between the primary cold rolling and the secondary cold rolling.
• the primary and secondary cold rolling take place after the continuous
• the total rolling degree is preferably less than 30%, preferably less than 20%.
• the primary cold rolling is preferably carried out in only one cold rolling pass. In this way, the procedure is simplified.
• the above-mentioned object is further achieved according to the invention by an aluminum strip which can be produced with the previously described method according to the first aspect of the present disclosure or with the previously described method according to the second aspect of the present disclosure, or by an aluminum alloy product, for example one, produced from such an aluminum strip Aluminum sheet or an aluminum cable.
• Aluminum strip or aluminum alloy product is accordingly a product produced in a continuous casting process, in particular in double roll casting, with a combination of good strength and high electrical conductivity.
• Aluminum alloy strips or products are manufactured with which or with which a limit drawing ratio of at least 1.9, determined in the cell drawing test according to DIN EN 1669 with a gradual increase in the round diameter until failure in the drawing test, can be achieved. So that's one
• Aluminum alloy strip particularly suitable for the production of products by cold forming, in particular deep drawing.
• a product produced by a continuous casting process and cold rolling can be distinguished from a product produced by ingot casting, hot rolling and cold rolling by the mid-segregations that only occur in a continuous casting process, which can also be found in the finished product after cold rolling. This applies to both those with the
• the aluminum strip or a product made from it is particularly suitable for electrical applications.
• the above task is corresponding
• an aluminum alloy is used
• Type 6xxx aluminum alloy used. Such alloys have proven to be particularly suitable for the desired combination
• the aluminum alloy has the following:
• Impurities in each case up to a maximum of 0.05% by weight, in total up to a maximum
• Si and magnesium cause the precipitation hardening of the aluminum strip and thereby increase its strength.
• a minimum Si and Mg content of 0.2% by weight is therefore provided for the alloy.
• the levels of Si and Mg are each limited to 1.0% by weight.
• the Si content is preferably in the range from 0.3-0.6% by weight and / or the Mg content is preferably in the range from 0.35-0.6% by weight.
• the ratio of the Si content to the Mg content is preferably in the range between 1.3 and 1.5.
• Iron reduces the electrical conductivity and should therefore not exceed a content of 0.5% by weight, preferably 0.3% by weight. However, Fe can be contained in small amounts, since otherwise the requirements for the starting materials for the melt become too high, which increases the production costs.
• the Fe content is preferably in the range 0.1-0.3% by weight.
• Melting interval which has a negative impact on the castability of double-roll casting, and is therefore limited to max. 0.5% by weight, preferably max. 0.4% by weight, more preferably max. 0.3% by weight.
• Small amounts of copper increase the Strength, heat resistance and creep resistance, so that a targeted addition of Cu in this area can be useful.
• Zirconium is poor for conductivity and increases the liquidus temperature and the melting interval of the alloy and is therefore limited to 0.2% by weight.
• the Zr content is preferably even limited to 0.03% by weight in order to achieve better conductivities.
• the impurities also deteriorate the conductivity and are therefore limited to 0.05% by weight individually and 0.15% by weight in total, preferably even to 0.03% by weight individually and 0.10% by weight in Sum to achieve better conductivities.
• the aluminum alloy accordingly has the following composition in% by weight:
• Impurities in each case up to a maximum of 0.03% by weight, in total up to a maximum of 0.10% by weight,
• the aluminum melt which typically has a temperature above 670 ° C, is used in a continuous casting process, in particular
• Double roll casting has already cooled very quickly, so that the strip temperature, measured on the strip surface, already emerges from the casting nip, in particular from the roll nip of the casting rolls used for double roll casting has cooled down very much.
• the aluminum strip temperature, measured on the strip surface is preferably in the range from 300 to 450 ° C. when it emerges from the casting gap or roll gap; this temperature range can be set, for example, by targeted cooling or dimensioning of the casting installation for the continuous casting process, in particular the casting rolls of the double-roll casting installation, and the casting strip thickness and the casting speed.
• Cooling the melt during double-roll casting results in an advantageous structure in the aluminum strip in order to be able to achieve the desired mechanical properties of the aluminum strip to be produced.
• the aluminum strip is cooled to a temperature, measured on the surface of the strip, of less than 200 ° C. immediately after the continuous casting process.
• the cooling can take place, for example, by active cooling, for example by providing suitable cooling elements or by
• Air possibly cooled air, is applied to the aluminum strip.
• additional active cooling which cools the aluminum strip to a temperature below 200 ° C immediately after the continuous casting process, coarse structure precipitations can be prevented, so that overall a more homogeneous supersaturated mixed crystal is formed, which has a positive effect on the hardenability in the subsequent one Warm aging affects.
• the aluminum strip is between the continuous casting process and the cold rolling at an aging temperature in the range of 100 ° C to 210 ° C, preferably 170 ° C to 190 ° C, and an aging period the aging temperature in the range of 30 minutes to 10 hours
• the aluminum strip is between the primary and the secondary cold rolling in one
• Aging temperature in the range of 100 ° C to 210 ° C, preferably 170 ° C to 190 ° C, and a aging time at the aging temperature in the range of Aged for 30 minutes to 10 hours. In experiments, this has
• Casting process and cold rolling turned out to be advantageous in order to achieve the desired combination of good electrical conductivity and high strength.
• a short aging period at a relatively low temperature results in an aged aluminum strip.
• the maximum strength (state T6) can be increased by extending the
• Aging time to at least 2 hours or an increase in temperature can be achieved.
• high strength was achieved in tests after hot aging at 185 ° C for 8 hours.
• condition T7 Due to a high temperature above 200 ° C and a long aging time of at least two hours, coarse precipitations occur in the aluminum strip, so that the aluminum strip reaches the outdated area (condition T7). In experiments, this state was achieved, for example, at an aging temperature of 205 ° C for 8 hours.
• the aged condition can also be caused by
• Annealing can be generated at higher temperatures up to 300 ° C.
• the aluminum strip is annealed after cold rolling.
• the annealing leads to a lowering of the strength
• the annealing temperature is and the longer the annealing time is.
• the desired ratio of electrical conductivity and strength of the aluminum strip can thus be set by back-heating. In the case of the method according to the second aspect of the present disclosure, the back-heating takes place at one
• a particularly good compromise between electrical conductivity and strength can be achieved at a heat treatment temperature in the range from 160 ° C to 210 ° C, preferably 180 ° C to 190 ° C and a heat treatment time at heat treatment temperature of at least 2 hours, preferably in the range of 2 to 5 hours.
• the aluminum strip is rolled to a final thickness in the range from 0.2 to 3 mm during cold rolling. These end thicknesses have been found to be suitable for applications in electrical conductor technology.
• the total degree of deformation during cold rolling (total degree of rolling during cold rolling) is over 50%. Accordingly, the material is preferably reduced in thickness by more than half during cold rolling. This high degree of deformation enables the aluminum strip to be manufactured to be stronger.
• the total degree of forming in primary and secondary cold rolling is together, i.e. the total degree of forming from the first pass of primary cold rolling to the last pass of secondary cold rolling, over 50%. The total degree of deformation is preferably at
• the primary and the secondary cold rolling are preferably carried out without intermediate annealing. Accordingly, there is no between the individual passes of primary and secondary cold rolling
• the primary cold rolling preferably comprising only one pass anyway.
• Warm aging is basically to be distinguished from intermediate annealing.
• the intermediate annealing serves for soft annealing of the aluminum strip and therefore requires high temperatures, in particular of more than 300 ° C
• the hot aging takes place at lower temperatures of at most 300 ° C, preferably at most 250 ° C.
• the degree of rolling after the intermediate annealing is preferably over 50% in order to achieve good strength.
• the aluminum strip is preformed with a strip thickness in the range from 3 to 12 mm.
• strip thicknesses have been found to be suitable, on the one hand, for rapid cooling of the aluminum strip in the continuous casting process and, if appropriate, immediately following active cooling, and for being able to achieve the desired rolling degrees with the desired final thicknesses during cold rolling.
• R p0.2 , R m and Asomm reference is made to the tensile test according to DIN EN ISO 6892-1: 2017-02.
• Vickers hardness reference is made to DIN EN 1SO 6507-1: 2006-03 and for the determination of Brinell hardness HBW 2.5 / 31.25 to EN ISO 6506-1 2015-2.
• Fig. 1 shows a first method for producing an aluminum strip from the
• Fig. 2 shows a second method for producing an aluminum strip from the
• Fig. 3 shows an embodiment of the method described here for
• FIGS 1 and 2 show the previously described methods from the prior art.
• FIG 3 now shows an embodiment of the method described here for producing an aluminum strip with high strength and high electrical Conductivity according to the first aspect of the present disclosure.
• the individual process steps are shown schematically from left to right.
• the temperature-time diagram below illustrates qualitatively and
• a continuous casting process preferably a double-roll casting 52, takes place in the first method step 52.
• a melt 54 made of an aluminum alloy is introduced into the nip 56 of two rotating casting rolls 58, 60, so that the aluminum melt 54 solidifies and a continuous aluminum strip 62 forms.
• the nip 56 is
• the thickness of the aluminum strip 62 is in the range 3 to 12 mm.
• the melt 54 consists of a hardenable aluminum alloy and preferably has the following compositions in% by weight:
• Impurities in each case up to a maximum of 0.03% by weight, in total up to a maximum of 0.10% by weight,
• the two casting rolls 58, 60 are preferably cooled so that the
• the temperature of the aluminum strip 62 measured at the strip surface, has a temperature in the range 64 to 300 ° C. at the point 64 of the exit from the nip 56. Furthermore, the aluminum strip 62 is preferably immediately after the Exit from the nip 56 further cooled to a temperature, measured on the belt surface, of below 200 ° C.
• a cooling device 66 can be arranged behind the nip, through which the aluminum strip 62
• a cooling air flow can be applied. Due to the sufficiently rapid cooling of the aluminum strip 62, a supersaturated mixed crystal structure is achieved. After cooling, the aluminum strip 62 is wound up into a coil 68.
• the coils 68 are heat-aged in a hot aging oven 76, preferably at a hot age temperature in the range from 100 ° C to 210 ° C, preferably 170 ° C to 190 ° C, and for a hot aging period (at the hot aging temperature) in the Range from 30 minutes to 10 hours.
• the hot aging leads to a
• Method step 80 cold rolled to final thickness on a cold rolling stand 82.
• Cold rolling takes place in several passes without intermediate annealing and with one
• the final thickness of the aluminum strip 62 is preferably in the range of 0.5 to 3 mm.
• the aluminum strip wound up again to form a coil 88 is back-heated in a back-heating furnace 90.
• a back-heating furnace 90 different furnaces or one and the same furnace can be used for the outsourcing in method step 74 and for the back-heating in method step 86.
• the back-heating is preferably carried out at a back-heating temperature in the range from 160 ° C. to 210 ° C., in particular 180 ° C. to 190 ° C., and at a
• Flashback time (at the flashback temperature) of at least 2 hours
• the method 50 in FIG. 3 can be used to produce an aluminum strip which combines good strength with high electrical conductivity.
• the process 50 in FIG. 3 not only manages with significantly fewer process steps, but in particular also without the energy-intensive and - due to the continuous furnace required for this - investment-intensive solution annealing (process step 20 in FIGS. 1 and 2), so that the method 50 can be carried out faster and more economically.
• Hot aging with different hot aging temperatures and durations The exact hot aging parameters are listed in Table 2 below.
• the strip sections in question were cold-rolled in several passes without intermediate annealing to a final thickness of 1 mm.
• the total degree of deformation during cold rolling was therefore 80%.
• the decrease in thickness per stitch was 10% in each case.
• Sample sections divided. Some of these sample sections were then subjected to back-heating - with different back-heating temperatures and different back-heating times.
• test series B1-4 correspond to the aged condition
• experimental series C1-4 correspond to the state T6
• these comparison strip sections [analogous to the method from FIG. 1) at 530 ° C. and a holding time of 15 minutes in a sand bath furnace which simulates a continuous furnace at the laboratory level, solution annealed and then quenched with water.
• the products produced in this way were each divided into several comparative sample sections, some of which were subsequently at 205 ° C. with a holding time of 45 minutes (state T6) and others at 205 ° C. with one
• the (Vickers) hardness of a material is correlated with its strength. By determining the Vickers hardness, the strength can also be deduced in a simple manner. Basically, it can be assumed here that a higher Vickers hardness also goes hand in hand with a higher strength (R m or R p0, 2) and vice versa.
• Figure 4 shows the measurement results of the electrical conductivity measurement and the Vickers hardness measurement for the test series Cl-4.
• FIG. 5 shows the measurement results of the electrical conductivity measurement and the Vickers hardness measurement for the test series Dl-4. The respective ones are on the horizontal axis of abscissa
• FIG. 6 shows the results of the tensile tests, from left to right first of all of the samples from tests B1, CI and Dl (ie in the as rolled state without back-heating) and to the right of the samples from comparative tests A1 and A2.
• the bars show the tensile strength R m on the right bar) and the yield strength R p0 , 2 on the left bar) with the associated axis on the left side (in MPa) and the elongation at break Aso mm as points connected by lines with the associated one Axis on the right side (in%)
• the associated results of the electrical conductivity measurement are also shown in bars.
• Figure 7 also shows results of tensile tests, namely of samples of the
• Test series B3, C3, D3 and B4, C4, D4. The diagram shows from left to right the results of the samples of B3, C3 and D3 with a 5-hour glow period at 185 ° C, then the results of the B3, C3 and D3 samples with a 8-hour glow period at 185 ° C and finally the results of the samples of B4, C4 and C4 with a back-heating time of 8 h at 205 ° C.
• the results for R m , R p o, 2 and Aso mm are plotted as in FIG. 6. For the samples of B3, C3 and D3 at one
• the glow time of 8 h is also the results of the electrical conductivity measurement.
• the desired ratios between electrical conductivity and hardness or strength can thus be set by suitably setting the annealing temperature and the annealing duration.
• the results of the comparative tests A1 and A2 likewise entered in FIGS. 4 and 5 show that the combination of the continuous casting process with the hot aging prior to cold rolling in accordance with the method described here results in better electrical properties
• DIN 40501-2 defines the following minimum values for strength and electrical conductivity for aluminum products in electrical applications of the alloy EN AW-6101B:
• the conductivity can be further improved by back-heating with still high strength.
• the method described here thus enables the production of aluminum strips or products made therefrom with high electrical conductivity and high strength. This is also achieved in a manufacturing process that is significantly shortened compared to the previous methods (cf. FIGS. 1 and 2) and which, in particular, does not require complex solution annealing. This means that aluminum strips suitable for electrical applications can be produced more quickly and more economically.
• Mitigerations occur during rapid cooling of the aluminum strip cast in a continuous casting process from the outside in and are also retained in the subsequent processing (aging, cold rolling, etc.). In discontinuous casting processes (esp. Ingot casting) such occur
• FIG. 8 shows an example of a thickness micrograph of a sample section from the test series B1.
• a piece of sheet metal was cut out of the sample section and ground on one side edge. The sanded side edge was then photographed; 8 shows a section of this photograph.
• the position of this cutout on the side edge of the piece of sheet metal used for the micrograph is indicated schematically in FIG. 8.
• the cutout shown does not cover the entire thickness of the side edge, but shows a central cutout in which the central increases occur.
• a dark stripe can be seen in the middle of the thick micrograph. These are the mid-segregations that occurred in the continuous casting process in the middle of the sheet (in relation to the sheet thickness).
• the areas above and below ie the areas closer to the top and bottom
• Table 6 The two aluminum strips W1 and W2 were then each subjected to hot aging with an 8-hour hold time, in the case of strip W1 at 185 ° C. and in the case of strip W2 at 205 ° C. After the hot aging, the two aluminum strips were cooled to room temperature over several hours and then subjected to a first cold rolling in several passes without intermediate annealing to a thickness of 1.0 mm. The total rolling degree during the first cold rolling was therefore 80%. The decrease in thickness per stitch was 33% in each case.
• sample sections in 1 mm, 0.5 mm and 0.3 mm thickness were subjected to back-heating with a 5-hour hold time at a temperature of 185 ° C. and 205 ° C., respectively
• the cooling after the back annealing took place with a cooling rate of 30 ° C / h.
• a section of the tape W3 was aged for 8 h at 185 ° C and cooled to room temperature over several hours. Another section of the band W3 was not aged. Neither cold rolling nor back-heating was carried out on the strip sections of strip W3.
• FIG. 9 shows the results of these measurements for the test series W2.5 (without back-heating);
• Figure 10 shows the results of these measurements for the test series W2.ll (after re-annealing at 205 ° C).
• the axis of abscissa shows the measurement position over the bandwidth, i.e. the measuring position on the strip transverse to the rolling direction.
• the left ordinate axis shows the Brinell hardness HBW 2.5 / 31.25 and the right ordinate axis shows the conductivity in MS / m.
• the respective measuring points for the Brinell hardness are connected with solid lines; the respective measuring points for the electrical conductivity are connected with dashed lines.
• the respective measuring position in the rolling direction strip start, strip center, strip end) is indicated by a
• FIG. 11 shows the results of the measurements for the test series W2.3 and W2.5 - W2.13.
• the left ordinate axis gives the tensile strength R m and the yield strength R p0.2 in MPa and the right ordinate axis the elongation at break Aso in%.
• FIG. 11 show that comparable mechanical properties are achieved after the re-annealing over a large thickness range (0.3-2.3 mm). This is advantageous for the further processing of aluminum strips or sheets into products, in particular if aluminum sheets of different thicknesses are used or thickness-changing forming steps are carried out, in particular cold forming steps.
• FIG. 12 also shows the results of the yield strength measurements R p o, 2 , the Brinell hardness HBW2.5 / 31.25, the elongation at break Aso and the conductivity in MS / m as well as in% IACS for the test series Wl.l - W1.7 (without back-heating).
• the thickness of the respective sample sections is plotted on the abscissa axis; on the left axis of ordinate is the proof stress R p0 2 in MPa and on the right
• the Brinell hardness HBW2.5 / 31.25, the elongation at break Aso in% and the conductivity in MS / m or% IACS are plotted on the ordinate axis.
• Round diameter divided by punch diameter determined in the cell pulling test according to DIN EN 1669 with a gradual increase in the round diameter until failure in the pulling test.
• a limit drawing ratio of 2.1 could be achieved without crack formation.
• hot tensile tests were carried out at 80 ° C and 115 ° C on the corresponding sample sections of the test series W1.5, W1.8 and Wl.ll.
• some tensile samples of these sample sections were heated to 80 ° C or 115 ° C in an oven and tensile tests were carried out in the oven at these temperatures in accordance with DIN EN ISO 6892-1: 2017-02, the yield strength R p0, 2, tensile strength R m and elongation at break Asom m were measured.
• the results of the hot tensile tests are shown in FIG.
• the hot tensile tests at 80 ° C yield strengths R p o, 2 of more than 160 MPa and the hot tensile tests at 115 ° C yield strengths R p0 , 2 of more than 140 MPa were achieved Products made from it are also suitable for use at elevated temperatures.
• Aluminum strips even at high temperatures, ensure that an aluminum conductor made from such an aluminum strip also fulfills the required mechanical properties even at such temperatures.
• Solution annealing through the use of a continuous casting process becomes unnecessary, since a suitable heat-aging structure of the aluminum strip is already achieved through the continuous casting. An elaborate and cost-intensive solution annealing before hot aging can therefore be dispensed with.
• FIG. 15 now shows an exemplary embodiment of the method described here for producing an aluminum strip with high strength and high electrical conductivity according to the second aspect of the present disclosure.
• the individual process steps are shown schematically from left to right.
• the temperature-time diagram below illustrates qualitatively and schematically the respective material temperatures for the individual
• a continuous casting process preferably a double-roll casting 102, takes place in the first method step 102
• Double-roll casting places a melt 104 made of an aluminum alloy in the nip 106 of two rotating casting rolls 108, 110, so that the aluminum melt 104 solidifies and forms a continuous aluminum strip 112.
• the nip 106 is preferably set so that the thickness of the
• Aluminum strip 112 is in the range 3 to 12 mm.
• the melt 104 consists of a hardenable aluminum alloy and preferably has the following compositions in% by weight:
• Impurities in each case up to a maximum of 0.03% by weight, in total up to a maximum of 0.10% by weight,
• the two casting rolls 108, 110 are preferably cooled so that the
• the temperature of the aluminum strip 112, measured at the strip surface, at the point 114 of the exit from the nip 106 has a temperature in the range from 450 to 300 ° C.
• the aluminum strip 112 is preferably further cooled immediately after emerging from the nip 106 to a temperature, measured on the strip surface, of below 200 ° C.
• a cooling device 116 can be arranged behind the nip, through which the aluminum strip 112 can be subjected, for example, to a cooling air flow. Due to the sufficiently rapid cooling of the aluminum strip 112, it becomes supersaturated Mixed crystal structure reached. After cooling, the aluminum strip 112 is wound up into a coil 118.
• the aluminum strip 112 is rolled in a primary cold rolling on a cold rolling stand 122 in a cold rolling pass and with a degree of rolling of less than 20% to an intermediate thickness and rewound to a coil 124.
• the coil 124 is then combined in one in the next method step 126
• Heat aging furnace 128 is heat-aged, preferably at a heat-aging temperature in the range from 100 ° C. to 210 ° C., preferably 170 ° C. to 190 ° C., and for a heat-aging period (at which
• the cold rolling stand 122 and the cold rolling stand 132 can be the same cold rolling stand or different cold rolling stands.
• the total rolling degree is for primary and secondary cold rolling
• the degree of rolling of the secondary cold rolling alone is preferably already more than 50%.
• the final thickness of the aluminum strip 112 is preferably in the range of 0.5 to 3 mm.
• the aluminum strip wound up again into a coil 138 is back-heated in a back-heating furnace 140.
• a back-heating furnace 140 different furnaces or one and the same furnace can be used for the outsourcing in method step 126 and for the re-annealing in method step 136.
• the annealing is preferably carried out at a
• Back-heating temperature in the range from 160 ° C. to 210 ° C., in particular 180 ° C. to 190 ° C., and with a back-heating time (at the back-heating temperature) of at least 2 hours, preferably 2 to 5 hours and ductility while reducing the
• the method 100 in FIG. 15 can be used to produce an aluminum strip that combines good strength with high electrical conductivity.
• the method 100 in FIG. 15 not only manages with significantly fewer method steps, but in particular also without the energy-intensive and - due to the continuous furnace required for this - investment-intensive solution annealing (method step 20 in FIGS. 1 and 2), so that method 100 can be performed faster and more economically.
• An aluminum strip W3a with a thickness of 5.0 mm was cast in double roll casting.
• the composition of the aluminum strip W3a is identical to that
• composition of the composition W3 is given in Table 6 above (all figures in% by weight).
• the aluminum strip W3a was divided into different sections, which were then processed in different ways.
• a first group of tests (W3a.l-6) sections of the band W3a were first subjected to hot aging with an 8-hour hold time in accordance with the method from FIG. 3, specifically at temperatures of 160 ° C., 175 ° C. or 185 ° C.
• the sections were cooled to room temperature over several hours and then subjected to cold rolling in several passes without intermediate annealing to a thickness of 2.0 mm or 1.0 mm.
• the total rolling degree during cold rolling was therefore 60% and 80%. Back-heating was not carried out.
• the degree of rolling in the secondary cold rolling was therefore 55% and 77%, respectively.
• the total rolling degree of primary and secondary cold rolling was 60% and 80%, respectively. Back-heating was not carried out.
• test series W3a.l-6 correspond to the method from FIG. 3;
• Test series W3a.7-15 correspond to the method from FIG. 15. At different sample sections of the individual test series
• FIG. 16 shows the results of these measurements for the test series W3a.l-12. On the abscissa axis is the electrical conductivity in MS / m and on the
• the Brinell hardness HBW2.5 / 31.25 is plotted on the ordinate axis.
• Each data point shows the measurement results that were measured for a strip section processed according to one of the test series W3a.l-12.
• the data points for the strip sections processed according to FIG. 3 are marked with a
• results in FIG. 16 show that even better results with regard to hardness / strength and electrical conductivity were achieved with the method according to FIG. 15 than with the method according to FIG. 3 with a corresponding final thickness.
• the lines belonging to the method according to FIG. 15 (solid, dashed) are compared to the lines belonging to the method according to FIG. 3
• the ratio of conductivity and strength can be finely adjusted by choosing a suitable primary or secondary degree of rolling (lower secondary degree of rolling for higher conductivity, higher secondary degree of rolling for higher strength).

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• 2019
  • 2019-06-25 JP JP2020570862A patent/JP7352583B2/ja active Active
  • 2019-06-25 EP EP19735509.2A patent/EP3814544A1/de active Pending
  • 2019-06-25 WO PCT/EP2019/066817 patent/WO2020002324A1/de active Application Filing

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