UNWORKED CONTINUOUSLY CAST HEAT-TREATABLE ALUMINUM ALLOY PLATES

Abstract

The present disclosure relates to methods of producing heat-treatable as-cast plate, and products based on the same. Generally, the new methods comprise continuously delivering a molten aluminum alloy having at least one of zinc (Zn), magnesium (Mg), silicon (Si), and copper (Cu) to a molten belt caster, continuously solidifying the molten aluminum alloy into an aluminum alloy plate via the horizontal belt caster, then continuously discharging the aluminum alloy plate at an exit of the horizontal belt caster, and then quenching the discharged aluminum alloy plate via a quenching apparatus located proximal the exit of the horizontal belt caster.

Claims

1. A method comprising: (a) continuously delivering a molten aluminum alloy to a horizontal belt caster; (i) wherein the molten aluminum alloy comprises a sufficient amount of at least one of zinc (Zn), magnesium (Mg), silicon (Si), and copper (Cu) to promote formation of strengthening precipitates; (b) continuously solidifying the molten aluminum alloy into an aluminum alloy plate via the horizontal belt caster; (c) continuously discharging the aluminum alloy plate from an exit of the horizontal belt caster at a rate of from 1 inch to 20 inches per minute; (i) wherein the discharged aluminum alloy plate has a gauge of from 0.25 inch to 5.0 inches; (d) quenching the discharged aluminum alloy plate via a quenching apparatus located proximal the exit of the horizontal belt caster, thereby producing an as-cast heat-treatable aluminum alloy plate; (i) wherein the quenching comprises contacting outer surfaces of the discharged aluminum alloy plate with a quenching media.

2. The method of claim 1, further comprising: artificially aging the as-cast heat-treatable aluminum alloy plate, thereby developing strengthening precipitates within the as-cast heat-treatable aluminum alloy plate.

3. The method of claim 2, wherein the strengthening precipitates are coherent phases comprising silicon, copper, magnesium and/or zinc.

4. The method of claim 3, wherein the as-cast heat-treatable aluminum alloy plate comprises a sufficient amount of the strengthening precipitates to realize a peak strength (T6) that is at least 5 ksi higher than the naturally aged strength (T3).

5. The method of claim 2, wherein the as-cast heat-treatable aluminum alloy plate comprises an as-cast grain structure, the method comprising maintaining the as-cast grain structure of the heat-treatable aluminum alloy plate; wherein, after the artificially aging step, the heat-treatable aluminum alloy plate comprises the as-cast grain structure with the strengthening precipitates.

6. The method of claim 5, comprising: providing the as-cast heat-treatable aluminum alloy plate to a customer, wherein the as-cast heat-treatable aluminum alloy plate comprises the as-cast grain structure and the strengthening precipitates.

7. The method of claim 5, wherein the maintaining step comprises forgoing hot or cold working of the as-cast heat-treatable aluminum alloy plate after the continuously casting step.

8. The method of claim 1, comprising: melting an aluminum alloy scrap feedstock, thereby producing the molten aluminum alloy; wherein the aluminum alloy scrap feedstock comprises a combination of scrap of at least two different aluminum alloys.

9. The method of claim 8, wherein the at least two different aluminum alloys are at least two different classes of aluminum alloys.

10. The method of claim 9, wherein the at least two different classes of aluminum alloys are selected from the following aluminum alloy series: 1xxx, 2xxx, 3xxx, 4xxx, 5xxx, 6xxx, 7xxx, and 8xxx aluminum alloys.

11. The method of claim 9, wherein the at least two different classes of aluminum alloys are selected from the following aluminum alloy series: 3xxx, 4xxx, 5xxx, 6xxx, and 7xxx aluminum alloys.

12. The method of claim 9, wherein the at least two different aluminum alloys are selected from the group consisting of 3xxx, 4xxx, 5xxx, and 6xxx aluminum alloy scrap.

13. The method of claim 8, wherein the at least two different aluminum alloys are from the same class of aluminum alloys.

14. The method of claim 13, wherein at least two different aluminum alloys are both 6xxx aluminum alloys.

15. The method of claim 13, wherein the two different aluminum alloys are both 7xxx aluminum alloys.

16. The method of claim 13, wherein the at least two different aluminum alloys are both 2xxx aluminum alloys.

17. The method of claim 1, wherein the discharged aluminum alloy plate is one of a 2xxx, 6xxx, 7xxx, and 8xxx(HT) aluminum alloy plate.

18. An as-cast aluminum alloy plate having a thickness of from 0.25 inch to 5.0 inches; wherein the as-cast aluminum alloy plate comprises at least 0.5 wt. % of at least one at least one of zinc (Zn), magnesium (Mg), silicon (Si), and copper (Cu); wherein the as-cast aluminum alloy plate has a dendritic microstructure; wherein the as-cast aluminum alloy plate has a secondary dendritic arm spacing of from 30 to 150 microns in all of the longitudinal (L), the long-transverse (LT) and the short-transverse (ST) directions of the as-cast aluminum alloy plate; wherein the as-cast aluminum alloy plate has equiaxed grains and is free of elongated grains.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a schematic representation of a system for continuously casting heat-treatable aluminum alloy plate via a horizontal belt caster (1) and a quenching apparatus (3) located proximal the exit of the horizontal belt caster (1).

[0029] FIG. 2 is a graph showing testing results of Example 1.

[0030] FIG. 3 is a graph showing testing results of Example 2.

DETAILED DESCRIPTION

Example 1Lab Scale Trials

[0031] A horizontal belt caster was used to produce a 4.4 inch (11.18 cm) 6xxx aluminum alloy as-cast plate from a mixture of scrap. After casting, lab-scale sections of as-cast plate were solutionized at 980 F. for 5 minutes in a lab-scale furnace, and then quenched using three different methods: (a) still air, (b) forced air jets and (c) cold water quenching. The materials were then artificially aged at 365 F. for 18 hours. Material properties of the as-cast and artificially aged plate were then determined in accordance with ASTM B557, the results of which are shown in Table 1, below. As shown, heat-treatable alloys were produced from the mixture of scrap, the artificially aged products being substantially stronger than the naturally aged products. The full artificial aging curves (shown in FIG. 2) show that the scrap-based alloy, when properly solutionized and quenched, exhibits the potential for age hardening.

TABLE-US-00001 TABLE 1 Example 1 Results (ksi and MPa) Elonga- Speci- Yield Tensile Yield Tensile tion 4D men Quench Aging Strength Strength Strength Strength or 4W Number Method Method (ksi) (ksi) (MPa) (MPa) (%) 1 Still Natural 11.9 20.7 82 143 6.5 Air Age 2 Forced- Natural 13.0 22.3 90 154 5.3 Air Age 3 CWQ Natural 19.5 30.2 134 208 6.2 Age 4 Forced- Artif. 15.3 24.4 106 169 5.8 Air Age 5 CWQ Artif. 39.7 40.7 274 281 1.6 Age

Example 2Industrial-Scale Quenching and Aging

[0032] A horizontal belt caster was used to produce a 2.225 inch (5.65 cm) as-cast plate from a mixture of 3xxx, 4xxx, 5xxx and 6xxx aluminum alloys. Upon exiting the horizontal belt caster, the as-cast plate was quenched using air knives, supplied by a high volume blower, which directed a continuous blast of ambient air onto the upper and lower surfaces of the as-cast plate. As the plate moved continuously from the caster to the flying saw (FIG. 1), the surface temperature was measured at fixed positions from the caster exit. Using these temperature readings and the casting speed, the plate surface temperature was plotted against time, the results of which are given in Table 2, below, and shown in FIG. 3. Samples from each condition were subsequently artificially aged at 365 F. for 8 hours. Material properties were then measured, the results of which are given in Table 3, below. As shown, increased yield strength is realized using forced air cooling (imposed immediately upon exiting the continuous caster) and the surface temperature of the plate is reduced.

TABLE-US-00002 TABLE 2 Example 2 Cooling Rate Results Blower Time Time Time Time Specimen Rate (1) (1) (2) (2) Time (3) Temp. (3) Number (RPM) (min) ( F.) (min) ( F.) (min) ( F.) 1 0 1.2 900 6.5 865 8.8 832 2 1125 1.1 818 5.8 613 7.9 613 3 1125 1.2 802 6.7 620 9.1 580 4 1125 1.3 751 7.1 575 9.7 525 5 1700 1.3 762 7.1 510 9.7 446 6 2250 1.3 724 6.9 482 9.4 440

TABLE-US-00003 TABLE 3 Example 2 Results (ksi and MPa) Blower Yield Tensile Yield Tensile Specimen Rate Strength Strength Strength Strength Elongation Number (RPM) (ksi) (ksi) (MPa) (MPa) (%) 1 0 18.1 25.1 125 173 2.6 3 1125 25.5 30.5 176 210 2.0 4 1125 25.8 28.5 178 196 1.3 5 1700 35.3 36.0 243 248 1.0 6 2250 33.1 35.5 228 245 1.5

[0033] While various embodiments of the new technology described herein have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the presently disclosed technology.