CN110382136A - The crystal grain refinement of the ingot casting of shear-induced - Google Patents

Abstract

Molten metal can be during direct chill (DC) casting (DC of such as aluminium be cast) by having the feed pipe of the nozzle with opening to be introduced into liquid storage vessel.The opening of the nozzle is capable of being shaped to and/or is dimensioned to generate molten metal jet stream in the liquid storage vessel.The molten metal jet stream can be presented in or higher than threshold quantity Reynolds number.Compared with standard casting techniques, this kind of jet stream can be realized improved metallurgy characteristic, such as improved crystal grain refinement.It can be realized sufficiently high Reynolds number by supplying the molten metal with sufficiently high speed.When with constant volume flow rate molten metal feed (for example, to avoid fluctuation of casting speed), the nozzle can be elaborated with the opening less than normal diameter, to generate the jet stream for being higher than standard speed.

Description

Shear-induced grain refinement of cast ingots

Cross References to Related Applications

This application claims the benefit of U.S. Provisional Application No. 62/465,014, filed February 28, 2017, and entitled "SHEARINDUCED GRAIN REFINEMENT OF A CAST INGOT," which reads It is incorporated herein by reference in its entirety.

technical field

The present disclosure relates generally to metal casting, and more particularly to controlling the delivery of molten metal to a mold cavity.

Contents of the invention

Wide variations in grain size can be found through cross-sections of direct chilled (DC) ingots due to the inherent position-dependent solidification rate of the process. The use of turbulent jets as a metal entry method has the potential to significantly reduce grain size as well as its variability in location. Experiments have been carried out to investigate the effect of spray power on grain size and distribution in Al4.5Cu DC ingots. The findings indicate that significantly increasing jetting power may not significantly reduce the grain size. In contrast, a threshold injection power required for grain refinement has been determined, beyond which only minor improvements are expected.

Description of drawings

The specification refers to the following drawings, in which the use of like reference numbers in different drawings is intended to illustrate like or analogous components. Elements included in the description herein may not be drawn to scale.

FIG. 1 is a schematic top view depicting locations for taking samples from an ingot for metallographic analysis, according to certain aspects of the present disclosure.

Figure 2 is a surface diagram depicting the grain size distribution in one quadrant of a standard cast (SD cast) Al4.5Cu alloy.

3 is a surface diagram depicting the grain size distribution in one quadrant of a jet cast (JT cast) Al4.5Cu alloy with a jet having a Reynolds number of 64,000.

4 is a surface diagram depicting the grain size distribution in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 69,000.

5 is a surface diagram depicting the grain size distribution in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 81,000.

6 is a surface diagram depicting the grain size distribution in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 97,000.

7 is a surface diagram depicting the grain size distribution in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 121,000.

Figure 8 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a standard cast (SD cast) Al4.5Cu alloy.

9 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a jet cast (JT cast) Al4.5Cu alloy with a jet having a Reynolds number of 64,000.

10 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 69,000.

11 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 81,000.

12 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 97,000.

13 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 121,000.

Figure 14 is a graph depicting average grain size and dendrite arm spacing as a function of jet Reynolds number ( _Rej ).

15 is a graph depicting the divergence (eg, range) of grain size and dendrite arm spacing as a function of jet Reynolds number (Re _j ).

Figure 16 is a series of photomicrographs depicting samples taken from ingots cast using injection casting techniques and standard casting techniques.

17 is a partial cross-sectional view of a metal casting system with a single nozzle, according to certain aspects of the present disclosure.

18 is a partial cross-sectional view of a metal casting system with multiple nozzles in accordance with certain aspects of the present disclosure.

Detailed ways

Certain aspects and features of the present disclosure relate to the application of turbulent mixing jets as a method of homogenizing and refining the grain structure found in direct chilled (DC) cast aluminum ingots. By exploiting the understanding of convective solidification, the effect of spray (eg shear) power on grain refinement and homogeneity in cast aluminum products such as Al4.5Cu rolled slab ingots can be examined. Through experiments described herein, it has been found that by supplying liquid metal to molds and liquid sumps using nozzles designed to provide high velocity flow, surprisingly desirable metallurgical properties can be achieved in direct chill (DC) cast products. Such nozzles may have reduced diameter openings to provide higher velocity flow at a constant volumetric flow rate than nozzles with standard diameter openings.

A fine and uniform grain structure is desirable for optimum formability and uniform mechanical properties of wrought aluminum products. Grain structure (size, distribution and morphology) is an important parameter affecting defects such as thermal cracking. In direct chilled (DC) castings, the grain structure depends on many factors including alloy composition, introduction of heterogeneous nucleation sites (e.g. grain refiners), growth conditions, and cooling rate. Due to the shape of the solidification interface (eg, sump) formed during DC casting, the solidification rate of individual grains is extremely position dependent. This variation in solidification rate can lead to large variations in grain size and structure through large rolled slab ingots.

Typically, the grain morphology in commercial grain-refined castings is equiaxed and dendritic. However, non-dendritic grains have been reported in DC cast aluminum alloys upon grain refinement. It has been reported that within the central portion of the grain-refined AA2024 alloy, the isothermal dendrites ("floating grains") appear non-dendritic compared to the rest of the dendritic structure.

In an attempt to modify the macrosegregation pattern, a turbulent jet equipped with a specific mixing nozzle was used to move the grains that had settled to the bottom of the tank. Turbulent agitation resulted in the discovery of non-dendritic grains, and an increase in grain refinement and homogeneity of the solidified structure was observed. Similar to these results, in electromagnetic casting (EMC), unlike conventional DC casting, the grain size is more uniformly distributed across the entire cross-section of the ingot, which is the result of forced convection, lower thermal gradients, and more intense transport of the slurry The result is a solid phase within the region (eg, the "mushy region").

The formation of a non-dendritic structure favors the structural homogeneity of DC cast products, thereby improving their mechanical properties near the solid-phase curve, reducing macrosegregation, and reducing crack susceptibility. On the other hand, the formation of very fine spherical grains is believed to increase hot tear susceptibility due to the limited permeability of the semi-solid region (ie, the "mushy region"). An important feature of the non-dendritic grains formed during solidification is the unique dependence of the non-dendritic grain size on the cooling rate. The size of the non-dendritic grains at a certain cooling rate is the same as the dendrite arm spacing of the dendritic grains formed at the same cooling rate.

These observations may not be unique to DC casting. The viscosity of partially solidified melts was studied using a Couette viscometer. Inadvertently, the dendritic structure was sheared and broken, and the partially solidified material was found to exhibit thixotropic behavior. This discovery led to rheocasting, an extrusion and die-casting technique that exploits the properties and unique microstructure of sheared and broken dendritic structures. This discovery stimulated people's research interest in forced convective solidification. In an attempt to put the disclosure into perspective, a highlight of this study is presented.

Solidification behavior under forced convection.

Almost all alloys of commercial importance solidify dendriticly, in columnar or equiaxed dendritic structures. During dendritic solidification of castings and ingots, a number of processes occur simultaneously within the semi-solid region (eg, the "mushy region"). These processes include crystallization, solute redistribution, maturation, interdendritic fluid flow, and solid motion. The dendritic structure is greatly influenced by interdendritic flow and solid motion, which in conventional solidification is caused by intrinsic factors such as density difference and uneven distribution of temperature.

In studying conventional solidification, transparent organic alloys have been widely used to study the solidification behavior at the microstructural level by direct observation. However, this was not possible to solidify under forced convection, even with organic analogues, due to the blurry images caused by vigorous agitation. For this reason, the current understanding of solidification behavior under forced conventions is obtained indirectly by examining the final solidified microstructure.

It has been established from experimental observations that solidification under agitation of the melt produces non-dendritic structures. Work on Sn-Pb systems using a rotational rheometer confirmed that the semi-solid solid phase has a degenerate dendritic structure or rosette morphology. With prolonged stirring time, such particles become more or less spherical in shape with entrapped liquid through the ripening process. Increasing the shear rate accelerates this morphological transition and reduces the amount of entrapped liquid inside the solid particles. Rosette morphology of solid particles has also been observed in many stirred alloys by other investigators using rod and impeller type stirrers. Subsequent work on solidification under magnetohydrodynamic (MHD) stirring confirmed the formation of fine and degenerated dendritic structures.

grain density.

It has been observed that under forced convection there is a greater grain density than under conventional solidification techniques. The grain refinement is attributed to the fact that the convection associated with mold filling was still strong at the onset of solidification. Experiments that have been performed have shown that if there is convection at the onset of solidification, structures with many smaller grains can form. The superheated liquid Al4.5Cu alloy is drawn into a thin sheet copper mold. The dendritic structure on the surface of the cast plate is visible to the naked eye. If the metal is drawn into the mold with a lot of superheat, large dendrites are observed on the surface of the cast plate. If the metal is drawn with significantly less superheat, a greater number of smaller dendrites is observed. It is believed that during the experiment, the metal tip in the channel would freeze first, stopping the flow. For metals cast at higher superheats, the metal behind the tip of the frozen flow will be at rest as it begins to solidify. Due to the absence of convection during solidification, the final grain size is large. In the case of metals cast with significantly less superheat, the metal behind the flow tip will likely have started to solidify before the flow tip freezes, which results in a finer grain size throughout the casting.

A theory to explain the effect of convection on grain refinement was tested using carbon tetrabromide with phenyl salicylate, a transparent simulated casting system, and video equipment to show that when convection is present during solidification, many solid particles Will suddenly be released from the "mushy zone" and will move into the bulk melt. The "big bang" theory explains this observation by assuming convection-induced thermal fluctuations, which in turn lead to fluctuations in growth rates and remelting of dendrite arms. The separated arms are then thought to be transported into the bulk melt by convective flow or buoyancy, resulting in a structure with many smaller grains.

To explain the observed grain refinement by melt stirring, a dendrite arm fragmentation mechanism is proposed to explain the grain multiplication. It is proposed that the dendrite arms bend plastically under the shear forces generated by the stirring of the melt. Plastic bending introduces large orientation errors into the dendrite arms in the form of "geometrically necessary dislocations". At high temperatures, such dislocations rearrange themselves through recrystallization to form high-angle grain boundaries. Any grain boundaries with energy greater than twice the solid/liquid interfacial energy are then wetted by the liquid metal, resulting in the separation of dendrite arms.

Following these earlier proposals, it was proposed that secondary dendrite arms could detach at their roots as a result of their remelting due to solute enrichment and thermosolute convection. To explain crystal doubling in semisolid processing, it is proposed that temperature fluctuations during MHD rheocasting play an important role in the structure evolution. Continuous nucleation can occur without appreciable reglow, with each volume element of the liquid periodically passing through different temperature regions.

Dendrite fragmentation mechanisms attempt to rationalize the final microstructural features observed in solids, but the important question remaining is how likely it is that shear can exert such high bending moments on small dendrite arms that they fragment. Under some theories, the microscale of turbulent flow must be on the order of the particle size for viscous forces to act in bending dendrite arms, which is only possible at very high shear rates. Furthermore, fragmented dendrite arms are expected to grow dendriticly in the melt at least during the initial phase of growth until collision of the diffusion field occurs. This understanding is incompatible with some experimental observations in which primary particles can be seen in small numbers but exhibit degenerate dendritic or spherical microstructures.

Given some difficulties with existing theories of dendrite fragmentation, the experimentally observed grain refinement under highly convective turbulence can be explained by a number of nucleation mechanisms. Under the intense mixing action, the temperature and composition field inside the liquid alloy are extremely uniform. During continuous cooling under forced convection, heterogeneous nucleation occurs simultaneously throughout the liquid phase. The actual nucleation rate may not increase compared to conventional solidification, but due to the uniform temperature field, all nuclei formed will survive, resulting in an increase in the effective nucleation rate. In addition, the strong mixing action will disperse potential nucleating agent clusters, resulting in a greater number of potential nucleating sites.

Experimental setup and procedures

For each experiment, the charge was loaded into a commercial gas fired furnace. The melt was degassed and filtered to commercial standard. The charge was inoculated with approximately 25 ppm TiB grain refiner in order to maintain consistency with previous studies. A typical "coffin type" bottom block was used with a 600 x 1750mm WAGSTAFF LHC ^™ open top mould. The steady state casting speed was about 65 mm/min. Casting speed and metal levels varied during approximately the first 500 mm of casting before reaching steady state values. The alloy used was an Al4.5Cu alloy, although similar or corresponding results could be achieved with other alloys.

To vary the degree of jet power used to refine the grain structure, a series of fused silica downspouts, each with a unique diameter, were prepared. The unique diameter along with the flow rate and physical properties of the Al4.5Cu alloy produces a unique turbulent Reynolds number for each test. The Reynolds numbers studied during this series of experiments were: 64,000, 69,000, 81,000, 97,000 and 121,000. In contrast, Reynolds numbers associated with standard nozzles may be at or below 15,000. In order to maintain the strength of the mixed jet, no combination bag was used during these trials. In some cases, the use of generally standard combination bags can reduce the efficacy of any jets produced by the nozzles.

After casting, the chilled ingots were each traversed at a casting length of approximately 1800 mm. Each cross section was divided into quadrants by symmetry, and a series of 45 samples were removed for metallographic analysis using a 1 inch core drill, as depicted in FIG. 1 .

1 is a schematic top view depicting the location of a sample 102 from an ingot 100 for metallographic analysis in accordance with certain aspects of the present disclosure. Symbols A, C and E correspond to the photomicrograph images depicted in FIG. 16 . Ingot 100 may be considered to have four quadrants, including Quadrant 1 (not labeled), Quadrant 2, Quadrant 3, and Quadrant 4.

Metallographic samples were etched with dilute hydrofluoric acid solution and analyzed for grain size and dendrite arm spacing using optical microscopy according to the established intercept method.

2-7 are surfaces depicting the grain size distribution in one quadrant of an ingot produced using standard casting techniques or various jet stirring techniques (e.g., high velocity jet technology or jet ingot casting) according to certain aspects of the present disclosure picture. Surface maps can be taken along the cast length of the ingot at a length of approximately 1800 mm. Surface plots depict the grain size distribution using color bars of the same scale, ranging from about 50 microns (eg, dark blue) to up to or greater than 250 microns (eg, dark red). Typically, the grain size can vary from about 50 μm at the short face where solidification is fastest (eg, the far left of the figure) to over 250 μm near the center of the sump where the steepest and slowest solidification rate.

Figure 2 is a surface diagram depicting the grain size distribution in one quadrant of a standard cast (SD cast) Al4.5Cu alloy. Standard cast alloys can be performed without high velocity jets (eg, jets with Reynolds numbers at or below 15,000, or with combination bags). Grain sizes seen in standard ingots range from about 50 microns to at or above about 250 microns. A region of about −500 to 0 mm from the center along the x-axis and about 50 to 150 mm from the center along the y-axis shows a large grain size distribution (eg, a distribution of large grains). The area near the lower left corner of the surface plot shows a small grain size distribution (eg, a distribution of smaller grains). For reference, the area at the lower left corner of the surface plot represents the area near the middle of the short face of the ingot.

3 is a surface diagram depicting the grain size distribution in one quadrant of a jet cast (JT cast) Al4.5Cu alloy with a jet having a Reynolds number of 64,000. The area near the edge of the plot shows a smaller grain size distribution (eg, a distribution of smaller grains) than the area near the middle of the plot.

4 is a surface diagram depicting the grain size distribution in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 69,000. The area near the edge of the graph shows a smaller grain size distribution (eg, a distribution of smaller grains) than the area near the middle right of the graph.

5 is a surface diagram depicting the grain size distribution in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 81,000. The area near the edge of the graph shows a smaller grain size distribution (eg, a distribution of smaller grains) than the area near the middle right of the graph.

6 is a surface diagram depicting the grain size distribution in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 97,000. The area near the edge of the graph shows a smaller grain size distribution (eg, a distribution of smaller grains) than the area near the middle right of the graph.

7 is a surface diagram depicting the grain size distribution in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 121,000. The area near the edge of the graph shows a smaller grain size distribution (eg, a distribution of smaller grains) than the area near the middle right of the graph.

With respect to Figures 2-7, it is evident that the grain size patterns from each of the spray ingot tests look very similar in their variation from the standard results. Regardless of the magnitude of the injection power (eg Reynolds number), the observed trend towards slower cooling - and thus larger grain size - towards the center of the ingot is similar to that observed in standard casting tests. However, the observed grain size range is greatly reduced. While standard ingots have grain sizes up to and above about 250 microns, spray cast ingots have much smaller grain sizes, with most grains at about 100 microns and the largest grains having a diameter at, about, or below at 150 microns.

8-13 are diagrams depicting spatial secondary dendrite arms in one quadrant of ingots produced using standard casting techniques or various jet stirring techniques (e.g., high velocity jet technology or jet ingot casting) according to certain aspects of the present disclosure Surface plot of the spacing (DAS) profile. Surface maps can be taken along the cast length of the ingot at a length of approximately 1800mm. Surface maps depict dendrite arm spacing using the same scale colored bars, ranging from about 20 microns (eg, dark blue) to up to or greater than 70 microns (eg, dark red). The ingots used for the surface maps of Figures 8-13 may be the same ingots as the corresponding surface maps of Figures 2-7.

Figure 8 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a standard cast (SD cast) Al4.5Cu alloy. Standard cast alloys can be performed without high velocity jets (eg, jets with Reynolds numbers at or below 15,000, or with combination bags). Grain sizes seen in standard ingots range from about 50 microns to at or above about 250 microns. A region of about −500 to 0 mm from the center along the x-axis and about 50 to 150 mm from the center along the y-axis shows a large grain size distribution (eg, a distribution of large grains). The area near the lower left corner of the surface plot shows a small grain size distribution (eg, a distribution of smaller grains). For reference, the area at the lower left corner of the surface plot represents the area near the middle of the short face of the ingot.

9 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a jet cast (JT cast) Al4.5Cu alloy with a jet having a Reynolds number of 64,000. The area near the edge of the plot shows a smaller grain size distribution (eg, a distribution of smaller grains) than the area near the middle of the plot.

10 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 69,000. The area near the edge of the graph shows a smaller grain size distribution (eg, a distribution of smaller grains) than the area near the middle right of the graph.

11 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 81,000. The area near the edge of the graph shows a smaller grain size distribution (eg, a distribution of smaller grains) than the area near the middle right of the graph.

12 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 97,000. The area near the edge of the graph shows a smaller grain size distribution (eg, a distribution of smaller grains) than the area near the middle right of the graph.

13 is a surface diagram depicting the spatial secondary dendrite arm spacing in one quadrant of a spray cast Al4.5Cu alloy with a jet having a Reynolds number of 121,000. The area near the edge of the graph shows a smaller grain size distribution (eg, a distribution of smaller grains) than the area near the middle right of the graph.

With respect to Figures 8-13, it is evident that the maximum spatial secondary dendrite arm spacing from each of the spray-cast ingot tests appears to be substantially lower than that of the standard ingot. Furthermore, for jets with the lowest Reynolds numbers (e.g., 64,000; 69,000; and 81,000, Figures 9-11, respectively), the extent of the DAS is much smaller, with around 35-40 microns at the periphery and growing to approximately 50 microns. For these castings, DAS is also more uniform than standard or higher Reynolds number jets. For these jets at higher Reynolds numbers (eg, 97,000 and 121,000 for Figures 12 and 13, respectively), the periphery of the ingot exemplifies a DAS of only about 25 microns and grows to perhaps 50 microns at the center. Although in some respects the profile may be similar to the standard case, the average DAS of these castings is less than the other samples.

Figure 14 is a graph depicting average grain size and dendrite arm spacing as a function of jet Reynolds number ( _Rej ). To better quantify the effect of turbulent jet agitation, standard distribution bag sizes and velocities were specified to yield an effective Reynolds number of 15,000 for the standard case.

The power of the jet appears to have little effect on the corresponding dimensions. The simple addition of the mixing jets achieved about a 25% reduction in the grain size of all mixing jets. The DAS is somewhat less responsive, showing only about a 10% reduction for the strongest jets (eg, 97,000 and 121,000), while the other mixed jets show smaller deviations.

Certain aspects and features of the present disclosure may result in a cast product having a cast product having a thickness at or below about 150 μm, 149 μm, 148 μm, 147 μm, 146 μm, 145 μm, 144 μm, 143 μm, 142 μm, 141 μm, 140 μm, 139 μm, 138 μm, 137 μm, 136 μm, 135 μm, 134μm、133μm、132μm、131μm、130μm、129μm、128μm、127μm、126μm、125μm、124μm、123μm、122μm、121μm、120μm、119μm、118μm、117μm、116μm、115μm、114μm、113μm、112μm、111μm、110μm、 Average grain size of 109 μm, 108 μm, 107 μm, 106 μm, 105 μm, 104 μm, 103 μm, 102 μm, 101 μm or 100 μm.

15 is a graph depicting the divergence (eg, range) of grain size and dendrite arm spacing as a function of jet Reynolds number (Re _j ). Likewise, the Reynolds number for a standard ingot is identified as 15,000. The introduction of turbulent jet has little effect on the divergence of DAS. However, the grain size exhibits drastic changes. A standard ingot has a grain size distribution of about 200 microns (e.g., about 100 microns to about 300 microns), while the introduction of a turbulent jet reduces this range to only about 75 microns (e.g., about 100 microns to about 175 microns) . Jet power seems to have little effect on this range, the simple presence of the jet immediately reduces the grain size distribution.

Certain aspects and features of the present disclosure may result in a cast product having a cast product having a thickness at or below about 290 μm, 285 μm, 280 μm, 275 μm, 270 μm, 265 μm, 260 μm, 255 μm, 250 μm, 245 μm, 240 μm, 235 μm, 230 μm, 225 μm, 220 μm, 215 μm, Maximum grain size of 210 μm, 205 μm, 200 μm, 195 μm, 190 μm, 185 μm, 180 μm, 175 μm, 170 μm, 165 μm, 160 μm, 155 μm, 150 μm, 145 μm, 140 μm, 135 μm or 130 μm.

Certain aspects and features of the present disclosure can result in a cast product having a thickness at or less than about 200 μm, 195 μm, 190 μm, 185 μm, 180 μm, 175 μm, 170 μm, 165 μm, 160 μm, 155 μm, 150 μm, 145 μm, 140 μm, 135 μm, 130 μm, 125 μm, 120 μm , 115 μm, 110 μm, 105 μm, 100 μm, 95 μm, 90 μm, 85 μm, 80 μm, 75 μm, 70 μm, 65 μm, 60 μm, or 55 μm grain size spread (eg, the range between the smallest and largest grain size). In other words, a cast product with a smaller grain size spread can be considered to have a more uniform grain size distribution, while a cast product with a larger grain size spread can be considered to have a less uniform grain size distributed.

Figure 16 is a series of photomicrographs depicting samples taken from ingots cast using injection casting techniques and standard casting techniques. The injection casting technique is performed using a jet having a Reynolds number of approximately 97,000. Samples were taken at positions A, C and E of the ingot in FIG. 1 . Position A corresponds to the central region of the ingot, C corresponds to the mid-thickness region, and E corresponds to the edge region.

While quantifiable data have been presented herein, other qualitative observations can be seen in FIG. 16 . For the standard case, positions E and C exhibit a dendritic structure, with the structure of E being finer than that of C. For the standard case, sample A appears to be non-dendritic in structure. In contrast, samples A and C in the case of injection casting are characterized by fine non-dendritic microstructures, while sample E appears to be a mixture of non-dendritic and dendritic microstructures, which is also very fine.

After experiments and trials, it became apparent that the power of the turbulent jet seemed to have little effect on increasing the degree of grain refinement. This is similar to other observations that increasing agitation speed does not significantly affect particle density or size. In contrast, the simple presence of stirring promotes grain refinement and non-dendritic structure. It is worth noting that increasing the shear rate can lead to an increase in particle density while reducing the average particle size. Mixing by turbulent jets appears to be sufficient to homogenize the temperature isotherms to promote a multitude of nucleation mechanisms. Increased survival of the nuclei limits grain growth and results in a smaller overall grain size.

Notably, the most turbulent jets (eg, 97,000 and 121,000) produced the most uniform grain profiles with the smallest uniform dendrite arm spacing profiles. While lower Reynolds number jets that stratify the melt pool are sufficient to produce uniform solidification rates (eg, as evident by similar microstructures), the most turbulent jets isolate microstructures while producing uniform grain sizes. Additionally, the most turbulent jets in macrosegregation studies are designed to suspend grains from the center and suppress preferential settling by redistributing "excess" floating grains. Although this trend seems to be observed with uniform grain size, there seems to be a disconnect with DAS. One possible explanation is that there is crosstalk between grain size data and DAS data, since DAS is difficult to isolate in non-dendritic structures. This can artificially distort the distribution of DAS in these jets, since they are most likely to give rise to spherical structures (ie DAS = grain size).

17 is a partial cross-sectional view of a metal casting 1700 with a single nozzle 1708 in accordance with certain aspects of the present disclosure. The metal casting system 1700 may be used to cast metal products as described herein, such as using a nozzle shaped to produce a jet 1734 of molten metal 1726 having a sufficiently high Reynolds number, as with reference to FIGS. 3-7 and 9-13 those described. However, in some cases other casting systems may be used.

Metal source 1702 , such as a sprue cup, may supply molten metal 1726 down feed tube 1736 . Bottom block 1722 may be lifted by hydraulic cylinder 1724 to interface with the walls of mold cavity 1716 . The bottom block 1722 may be lowered steadily as the molten metal begins to solidify within the mold. Cast metal 1712 may include solidified sides 1720 , and molten metal 1726 added to the cast may be used to continuously elongate cast metal 1712 . In some cases, the walls of mold cavity 1716 define a hollow space and may contain a coolant 1718, such as water. Coolant 1718 may exit the hollow space as a jet and flow down side 1720 of cast metal 1712 to help solidify cast metal 1712 . The ingot being cast may include solidified metal 1730 , transition metal 1728 and molten metal 1726 .

Molten metal 1726 may exit feed tube 1736 at nozzle 1708 submerged in molten metal 1726 . Nozzle 1708 may be part of feed tube 1736 or may be a detachable part. Nozzle 1708 may have parameters designed to provide flow of molten metal 1726 (eg, jet 1734 of molten metal 1726 ) at or about a desired Reynolds number.

In some cases, the Reynolds number can be obtained using the equation to approximate where Re is the Reynolds number, Ldie is the length of the _die at the rolling face of the resulting ingot (e.g., the "rolling face" of ingot 100 depicted in Figure 1), Djet is the diameter of the _jet , And C is a constant. The constant C can be alloy dependent and can be determined experimentally. The constant C can vary with mold width (e.g., the length of the mold at the short side of the resulting ingot, such as the "short side" of ingot 100 as depicted in FIG. 1), casting speed, kinematic viscosity, and other cross-sectional shapes to account for the jet. varies with the numerical constant. This example for the Reynolds number approximation is given when casting a rectangular ingot in a rectangular mold. However, one of ordinary skill in the art can calculate the Reynolds number of the jet for casting using other shaped molds, such as round billets or non-standard shapes. In some cases, the Reynolds number may vary with jet diameter and effective hydraulic circumference, or may be approximated in other ways.

The diameter of the jet may be at or about the diameter of the opening of the nozzle (eg, nozzle 1708). Accordingly, the Reynolds number for a particular metal casting system (e.g., metal casting system 1700) will increase as the opening diameter of the nozzle (e.g., nozzle 1708) increases and/or as the die length decreases (e.g., to a size comparable to round billets with the same jet diameter) and reduced. The constants defining the Reynolds number for a particular casting system and alloy can be determined by one of ordinary skill in the art.

Molten metal 1726 exiting nozzle 1708 may produce jet 1734 of molten metal 1726 having a particular Reynolds number. Desirable properties of the jet 1734 as described herein (e.g., to improve metallurgical properties such as grain refinement) can be achieved using nozzles 1708 designed or shaped to produce jets with a desired Reynolds number (e.g., jets at or above the threshold number).

18 is a partial cross-sectional view of a metal casting system 1800 having multiple nozzles 1807, 1808, 1809 in accordance with certain aspects of the present disclosure. Metal casting system 1800 may be similar to metal casting system 1700 except that there are multiple nozzles 1807, 1808, 1809 instead of a single nozzle. Metal casting system 1800 is depicted with three nozzles, although any number of nozzles may be used. In some cases, multiple nozzles 1807 , 1808 , 1809 may each be supplied from metal source 1802 by respective separate feed tubes 1835 , 1836 , 1837 . However, in some cases, multiple nozzles may be fed from a single feed tube (eg, a branch feed tube). The flow of molten metal 1826 through the plurality of nozzles 1807 , 1808 , 1809 may generate respective jets 1833 , 1834 , 1835 .

When casting metal using nozzles designed to produce jets with a Reynolds number at or above a certain threshold Reynolds number (e.g., as described with reference to FIG. An implementation wherein the sum of the Reynolds numbers of the plurality of jets produced by the plurality of nozzles is at or above a certain threshold Reynolds number. In such cases, each of the plurality of nozzles may produce a jet having a Reynolds number below a threshold Reynolds number, but if the sum of the Reynolds numbers of the plurality of jets from the plurality of nozzles is above the threshold, then the desired desired metallurgical effect. In particular, the sum of the Reynolds numbers of the jets produced by the plurality of nozzles at a certain point in time may be above a threshold Reynolds number. In some cases, a casting system with multiple nozzles may have less than all of the nozzles operating simultaneously, such as during different phases of casting (eg, start-up, steady state, and end). Thus, as long as the sum of the Reynolds numbers of those jets generated is at or above the threshold Reynolds number, the desired result is achieved.

in conclusion

The effect of turbulent jets on the microstructural properties and distribution of Al4.5Cu rolled slab ingots has been examined. It has been found that the introduction of a turbulent jet promotes grain refinement while having very little effect on the DAS. Even the grain refinement of the most turbulent jet did not show a significant increase relative to the least turbulent jet. This seems to indicate the existence of a threshold Reynolds number for turbulent jets that destabilizes the isotherm and promotes grain refinement below the lowest value evaluated during this study. Although the effect of turbulent jets is obvious, it is probably best suited for numerical studies because the effect is very robust and independent of fine hydrodynamic parameters. A system contemplated for increasing shear in a DC casting system should increase grain refinement when a simple increase in speed does not.

Based on experiments performed herein, it is expected that when using a Reynolds number at or above a threshold Reynolds number at or around 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000 , 29000, 30000, 31000, 32000, 33000, 34000, 35000, 36000, 37000, 38000, 39000, 40000, 42000, 43000, 44000, 45000, 47000, 48000, 49000, 51000, 52000, 53000, 53000, 53000 , 54000, 55000, 56000, 57000, 58000, 59000, 60000, 61000, 62000, 63000, 64000, 65000, 66000, 67000, 69000, 70000, 71000, 73000, 74000, 76000, 77000, 78000, 78000, 78000 , 79000, 80000, 81000, 82000, 83000, 84000, 85000, 86000, 87000, 88000, 89000, 90000, 92000, 93000, 94000, 96000, 97000, 98000, 99000, 101000, 102000, 103000, 103000, 103000, 103000, 103000, 103000, 103000, 103000, 103000, 103000, 103000, 103000 , 104000, 105000, 106000, 107000, 108000, 109000, 110000, 111000, 112000, 113000, 114000, 115000, 116000, 117000, 118000, 119000, 119000, 111000, 112000, 113000, 114000, 115000, 116000, 117000, 118000, 119000, 119000 Promoted grain refinement is achieved. More specifically, it is expected that when using a Reynolds number at or above a threshold Reynolds number at or about 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000 , 30000, 31000, 32000, 33000, 34000, 35000, 36000, 37000, 38000, 39000, 40000, 42000, 43000, 44000, 45000, 47000, 49000, 50000, 52000, 53000, 54000, 54000, 54000 Promoted grain refinement can be achieved in direct chill casting when jetting at a Reynolds number of 55000, 56000, 57000, 58000, 59000, 60000, 61000, 62000, 63000 or 64000. Promoted grain can be achieved in a multi-nozzle direct chill casting system when the sum of the Reynolds numbers of the multiple jets from the multiple nozzles is at or above any of the aforementioned threshold Reynolds numbers, as described in additional detail herein. refinement.

The foregoing description of the embodiments, including the illustrated embodiments, have been presented for purposes of illustration and description only, and are not intended to be exhaustive or to be limited to the precise forms disclosed. Many modifications, adaptations, and uses thereof will be apparent to those skilled in the art.

As used below, any reference to a series of examples should be read as a separate reference to each of those examples (eg, "Examples 1 to 4" should be read as "Examples 1, 2, 3, or 4") .

Example 1 is a casting system comprising: a feed tube couplable to a source of molten metal; The molten metal is delivered to the molten storage tank, wherein the nozzle is designed to supply the molten metal at a Reynolds number of at least 14,000.

Example 2 is the casting system of example 1, wherein the nozzle is designed to supply the molten metal at a Reynolds number of at least 64,000,

Example 3 is the casting system of Example 1, wherein the nozzle is designed to operate at least , 30000, 31000, 32000, 33000, 34000, 35000, 36000, 37000, 38000, 39000, 40000, 42000, 43000, 44000, 45000, 47000, 49000, 50000, 52000, 53000, 54000, 54000, 54000 The molten metal is supplied at a Reynolds number of 55000, 56000, 57000, 58000, 59000, 60000, 61000, 62000 or 63000.

Example 4 is the casting system of Examples 1-3, further comprising a mold for receiving the molten metal, wherein the mold comprises one or more mold walls and a bottom block lowerable to support a solidified ingot.

Example 5 is a casting system comprising: at least one feed tube couplable to a source of molten metal; and a nozzle bank comprising one or more nozzles, wherein each of the one or more nozzles is located on the at least one feed tube at a distal end and submersible in a melting sump for delivering the molten metal to the melting sump, wherein each of the one or more nozzles has an opening, the opening is dimensioned to achieve molten metal jets within said molten sump at a Reynolds number, wherein the sum of said Reynolds numbers for each molten metal jet is at least 14,000.

Example 6 is the casting system of example 5, wherein the openings of the one or more nozzles are sized such that the sum of the Reynolds numbers per jet of molten metal is at least 64,000,

Example 7 is the casting system of example 5, wherein said openings of said one or more nozzles are sized such that said sum of said Reynolds numbers per jet of molten metal is at least 15000, 16000, 17000 , 18000, 19000, 2000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, 30000, 31000, 32000, 34000, 35000, 37000, 38000, 40000, 41000, 42000, 42000 .

Example 8 is the casting system of examples 5-7, wherein the set of nozzles includes at least two nozzles.

Example 9 is the casting system of Examples 5-8, further comprising a mold for receiving the molten metal, wherein the mold comprises one or more mold walls and a bottom block lowerable to support a solidified ingot.

Example 10 is a method comprising: conveying molten metal from a metal source to a metal storage tank through a feed tube, wherein the molten metal produces one or more jets of molten metal, wherein each of the one or more jets of molten metal has a Reynolds number, and wherein the sum of the Reynolds numbers of each of the one or more jets of molten metal is at least 14,000.

Example 11 is the method of example 10, wherein the sum of the Reynolds numbers of each of the one or more molten metal jets is at least 64,000,

Example 12 is the method of example 10, wherein the sum of the Reynolds numbers of each of the one or more molten metal jets is at least 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, 30000, 31000, 32000, 34000, 35000, 36000, 37000, 39000, 40000, 41000, 42000, 44000, 45000, 46000, 46000 47000, 48000, 49000, 50000, 51000, 52000, 53000, 54000, 55000, 56000, 57000, 58000, 59000, 60000, 61000, 62000, or 63000.

Example 13 is the method of examples 10-12, further comprising solidifying the molten metal into an ingot using a mold comprising one or more mold walls and a bottom block lowerable to support the solidified ingot.

Example 14 is a metal product cast according to the method described in Examples 10-13.

Example 15 is the metal product of example 14, wherein the metal product has an average grain size at or below about 130 μm.

Example 16 is the metal product of example 14, wherein the metal product has an average grain size at or below about 129 μm, 128 μm, 127 μm, 126 μm, 125 μm, 124 μm, 123 μm, 122 μm, 121 μm, 120 μm, 119 μm, 118 μm .

Example 17 is the metal product of examples 14 to 16, wherein the metal product has a maximum grain size at or below about 250 μm.

Example 18 is the metal product of Examples 14 to 16, wherein the metal product has a maximum grain size at or below about 245 μm, 240 μm, 235 μm, 230 μm, 225 μm, 220 μm, 215 μm, 210 μm, 205 μm, 200 μm, 195 μm , 190μm, 185μm, 180μm, 175μm, 170μm, 165μm, 160μm, 155μm, 150μm, 145μm, 140μm, 135μm or 130μm.

Example 19 is the metal product of Examples 14 to 18, wherein the metal product has a grain size spread at or below about 130 μm.

Example 20 is the metal product of examples 14 to 18, wherein the metal product has a grain size spread at or below about 125 μm, 120 μm, 115 μm, 110 μm, 105 μm, 100 μm, 95 μm, 90 μm, 85 μm, 80 μm, 75μm, 70μm, 65μm, 60μm or 55μm.

Claims (20)

1. A casting system comprising: a feed tube connectable to a source of molten metal; and a nozzle at the distal end of the feed pipe, the nozzle being submersible in a melting tank for delivering the molten metal to the melting tank, wherein the nozzle is designed to operate at a Reynolds temperature of at least 14,000 Several supply the molten metal. 2. The casting system of claim 1, wherein the nozzle is designed to supply the molten metal at a Reynolds number of at least 64,000. 3. The casting system of claim 1 , wherein the nozzle is designed to have a , 30000, 31000, 32000, 33000, 34000, 35000, 36000, 37000, 38000, 39000, 40000, 42000, 43000, 44000, 45000, 47000, 49000, 50000, 52000, 53000, 54000, 54000, 54000 The molten metal is supplied at a Reynolds number of 55000, 56000, 57000, 58000, 59000, 60000, 61000, 62000 or 63000. 4. The casting system of claim 1, additionally comprising a mold for receiving the molten metal, wherein the mold comprises one or more mold walls and a bottom block lowerable to support a solidified ingot. 5. A casting system comprising: at least one feed tube couplable to a source of molten metal; and a nozzle bank comprising one or more nozzles, wherein each of the one or more nozzles is located at the distal end of the at least one feed pipe and is submersible in a melting sump for conveying the molten metal to the melting sump, wherein each of the one or more nozzles has an opening sized to achieve a jet of molten metal within the melting sump at a certain Reynolds number, wherein each melt The sum of said Reynolds numbers of the metal jets is at least 14,000. 6. The casting system of claim 5, wherein the openings of the one or more nozzles are sized such that the sum of the Reynolds numbers per jet of molten metal is at least 64,000. 7. The casting system of claim 5, wherein said openings of said one or more nozzles are sized such that said sum of said Reynolds numbers per jet of molten metal is at least 15000, 16000, 17000 , 18000, 19000, 2000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, 30000, 31000, 32000, 34000, 35000, 37000, 38000, 40000, 41000, 42000, 42000 . 8. The casting system of claim 5, wherein the set of nozzles includes at least two nozzles. 9. The casting system of claim 5, further comprising a mold for receiving the molten metal, wherein the mold comprises one or more mold walls and a bottom block lowerable to support a solidified ingot. 10. A method comprising: Molten metal is conveyed from a metal source to a metal storage tank through a feed pipe, wherein the molten metal produces one or more jets of molten metal in the metal storage tank as it exits the feed pipe, wherein the one or Each of the plurality of molten metal jets has a Reynolds number, and wherein the sum of the Reynolds numbers of each of the one or more molten metal jets is at least 14,000. 11. The method of claim 10, wherein the sum of the Reynolds numbers of each of the one or more molten metal jets is at least 64,000. 12. The method of claim 10, wherein the sum of the Reynolds numbers of each of the one or more molten metal jets is at least 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, 30000, 31000, 32000, 34000, 35000, 36000, 37000, 39000, 40000, 41000, 42000, 44000, 45000, 46000, 46000 47000, 48000, 49000, 50000, 51000, 52000, 53000, 54000, 55000, 56000, 57000, 58000, 59000, 60000, 61000, 62000, or 63000. 13. The method of claim 10, further comprising solidifying the molten metal into an ingot using a mold comprising one or more mold walls and a bottom block lowerable to support the solidified ingot. 14. A metal product cast according to the method of claim 10. 15. The metal product of claim 14, wherein the metal product has an average grain size at or below about 130 μm. 16. The metal product of claim 14, wherein the metal product has an average grain size at or below about 129 μm, 128 μm, 127 μm, 126 μm, 125 μm, 124 μm, 123 μm, 122 μm, 121 μm, 120 μm, 119 μm, 118 μm . 17. The metal product of claim 14, wherein the metal product has a maximum grain size at or below about 250 μm. 18. The metal product of claim 14, wherein the metal product has a maximum grain size at or below about 245 μm, 240 μm, 235 μm, 230 μm, 225 μm, 220 μm, 215 μm, 210 μm, 205 μm, 200 μm, 195 μm, 190 μm , 185μm, 180μm, 175μm, 170μm, 165μm, 160μm, 155μm, 150μm, 145μm, 140μm, 135μm or 130μm. 19. The metal product of claim 14, wherein the metal product has a grain size spread at or below about 130 μm. 20. The metal product of claim 14, wherein the metal product has a grain size spread at or below about 125 μm, 120 μm, 115 μm, 110 μm, 105 μm, 100 μm, 95 μm, 90 μm, 85 μm, 80 μm, 75 μm, 70μm, 65μm, 60μm or 55μm.