The present invention relates to steel foam and, more particularly, to steel foam and methods of producing steel foam.
Metal is considered a foam if pores are distributed within the metal to take up a certain minimum percentage of the total volume of the metal. The introduction of pores or voids into a metal component typically decreases the density and weight of the metal component compared to a solid metal component. Metal foam components also frequently display a higher plate bending stiffness than solid metal components. Currently, commercial metal foam components are generally limited to aluminum, despite the fact that steel foam components would exhibit many superior properties if they could be produced in volume at reasonable cost.
Embodiments of the present invention provide the ability to produce steel foam components having consistent densities. In addition, embodiments of the present invention provide the ability to produce steel foam components having predictable mechanical properties. Furthermore, embodiments of the present invention provide the ability to produce steel foam components on an industrial scale.
The present invention provides engineers working with steel a new degree of freedom: density. The design space potentially covered by steel applications can grow significantly with density as a variable. Among other things, the present invention opens new opportunities for designers to find suitable military and naval applications for not only energy absorption, but also blast resistant and ballistic applications to resist the impact of sharp objects due to their high strength and hardness.
Some embodiments of the present invention provide a method of producing a steel foam component, wherein the method comprises providing a mold defining a cavity, positioning an insert within the cavity of the mold, wherein the insert is configured to form a generally uniform pattern of pores within the steel foam component and occupies at least 20 percent of the cavity, pouring molten steel into the cavity, cooling the molten steel into the steel foam component, and removing the steel foam component and the insert from the mold.
In some embodiments, the present invention provides a steel foam component comprising a body having a plurality of pores, the plurality of pores forming a generally uniform pattern throughout the body and occupying at least 20 percent of a volume of the body.
Some embodiments of the present invention provide an insert for use with a mold for creating a steel foam component, wherein the insert comprises a 3D-printed body including a plurality of interconnected cores, the 3D-printed body being configured to be positioned within the mold to form the steel foam component having a desired density that is less than a solid steel component.
Other aspects of the present invention will become apparent by consideration of the detailed description and accompanying drawings.
Before embodiments of the present invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
Positioned within the pour opening 38 is a filter 62. In some embodiments, the filter 62 may be composed of alumina. In other embodiments, the filter 62 may be composed of other materials suitable for use with molten steel. In the illustrated embodiment, the filter 62 is coupled to the top half 22 of the mold 14. The filter 62 is secured within the pour opening 38 and substantially fills a length of the pour opening 38.
The system 10 also includes at least one chaplet 66 positioned within the cavity 34 of the mold 14. Each chaplet 66 is a relatively thin shim made of metal. The chaplets 66 support an insert 78 above the lower inner surface 46 of the mold so that the insert 78 is spaced apart from (i.e., does not directly contact) the lower surface 46.
In addition, the illustrated inserts 78a-c are composed of sand bonded with a chemical binder (e.g., resin), but may alternatively be composed of other suitable materials. As used herein, “sand” refers to any flowable material or media, such as small breads, grains, or granules. For example, the sand may be conventional sand, foundry sand, kinetic sand, sand-fiber mixtures, sand-clay mixtures, ceramics, silica alumina, combinations of materials, and the like. The sand is a media that can withstand high temperatures for steel casting, but is held together by a binder that burns off slowly when exposed to the high temperatures.
Although the inserts 78a-c are described below with reference to specific embodiments, it should be readily apparent that other shapes and sizes of inserts may also or alternatively be employed. For example, by creating the inserts 78a-c with a 3D printer, the geometric configuration of the inserts 78a-c may be selected and designed to create any desired pattern of pores within a steel component. Furthermore, the dimensions of the inserts 78a-c may be scaled as desired to match the dimensions of any steel component. Multiple inserts may also be positioned within a single mold cavity to achieve desired geometries and sizes.
As shown in
Each of the interconnected cores 82a includes a central portion 86a and protrusions 90a extending from the central portion 86a. The illustrated central portions 86a are spheres. In the illustrated embodiment, four protrusions 90a extend from each of the central portions 86a in directions parallel to either the horizontal axis H or the vertical axis V. As shown, two of the protrusions 90a extend parallel to the horizontal axis H and in opposite directions. Further, two of the protrusions 90a extend parallel to the vertical axis V and in opposite directions. The protrusions 90a adjacent edges of the insert 78a further define ends that are flat surfaces 94a. Each core 82a additionally includes two secondary protrusions 98a extending in opposite directions from the central portions 86a along a third axis T. The third axis T is perpendicular to the horizontal axis H and the vertical axis V. The illustrated secondary protrusions 98a are generally smaller than the protrusions 90a. The protrusions 98a further define ends with flat surfaces 102a. The insert 78a further defines a periphery 120a, which includes the endmost rows 84a (i.e., highest and lowest along the vertical axis V) and the endmost columns 88a (i.e., leftmost and rightmost along the horizontal axis H.).
Although the illustrated central portions 86a are spherical, in other embodiments, the central portions 86a may be non-spherical. For example, the central portions 86a may be square, hexagonal, octagonal, rotund, bulbous, oblong, footballs, and the like. Alternatively, the central portions 86a may essentially be omitted such that the protrusions 90a, 98a are directly connected together as a series of pipes. In some embodiments, the shapes of the central portions 86a may vary throughout the insert 78a.
The illustrated interconnected cores 82a in
As shown in
The interconnected cores 82b form a plurality of rows 84b parallel to the horizontal axis H. The interconnected cores 82b also form a plurality of columns 88b arranged parallel to the vertical axis V. In the illustrated embodiment, the insert 78b includes sixteen rows 84b and sixteen columns 88b of cores 82b. Further, the interconnected cores 82b form a plurality of layers 92b, each formed of sixteen rows and sixteen columns of interconnected cores 82b. The layers 92b are arranged along the third axis T, which is perpendicular to the vertical axis V and the horizontal axis H. In the illustrated embodiment, the insert 78b includes two layers 92b of cores 82b, but may alternatively include three or more layers 92b of cores 82b.
The interconnected cores 82b in
As shown in
The pores 174a in
As illustrated in
In other embodiments, the plurality of pores 174a may not communicate with the peripheral edge 156a and/or may communicate with the first and second faces 148a, 152a. For example, the embodiment shown in
Further, the embodiment shown in
As discussed above in reference to
At Step 200, the mold 14 (
Next, at Step 204, the insert 78 is positioned within the bottom half 18 of the mold 14. The insert 78 can be one of the 3D-printed inserts 78a-c illustrated in
In some embodiments, the insert 78 is positioned in the cavity 34 such that the insert 78 is spaced apart from the lower inner surface 46 of the mold 14 and/or from the upper inner surface 42 of the mold 14. The one or more chaplets 66, as shown in
Positioning the insert 78 so it is spaced from the lower inner surface 46 of the mold 14 provides the steel foam component 140, after casting, with a continuous first face (i.e., a solid surface without any openings 178 within the first face 148). Positioning the insert 78 so it is spaced from the upper inner surface 42 of the mold 14 provides the steel foam component 140, after casting, with a continuous second face (i.e., a solid surface without any openings 178 within the second face 152). Positioning the insert 78 so that it abuts the inner peripheral surface 50 of the mold 14 creates the openings 178 in the peripheral edges 156 of the steel foam component 140. In some embodiments, the insert 78 may also or alternatively be spaced apart from the inner peripheral surface 50 of the mold 14 so that one or more of the peripheral edges 156 of the steel foam component 140 are continuous.
At Step 208, the alumina filter 62 is positioned within the pour opening 38 of the mold 14. The filter 62 can be positioned within the opening 38 when the mold 14 is first created, or when the mold 14 is assembled after the insert 78 is in position. In some embodiments, this step may be omitted if a filter is not needed.
At Step 212, molten steel is poured into the cavity 34 of the mold 14 through the pour opening 38. As the molten steel is poured into the cavity 34, the molten steel fills the cavity 34 between the insert 78 and the lower inner surface 46, the upper inner surface 42, and the inner peripheral surface 50. The alumina filter 62 (if present) helps control the velocity of the molten steel being poured into the cavity 34, and inhibits the molten steel from deforming or crushing the insert 78 before the steel has cooled.
At Step 216, the molten steel can be cooled using known techniques (e.g., waiting a period of time).
After the steel has cooled, the steel foam component 140 can then be removed from the mold 14, at Step 220. At this stage, the insert 78, which may be a 3D-printed sand insert 78, has broken down into a powder or other flowable form. The powder still remains within the steel foam component 140. As such, the insert 78 is removed from the mold 14 with the steel foam component 140.
At Step 224, the powder remains of the insert 78 are decored (i.e., removed) from the steel foam component 140. In some embodiments, the powder remains may exit the steel foam component 140 through the openings 178 by, for example, shaking the component 140. In other embodiments, a new hole may be drilled or cut into the steel foam component 140 to facilitate removal of the powder from the component 140, such as when the steel foam component is provided with no exterior holes through which the powder can exit, or whether an insufficient number of such holes exist. Once the insert 78 is removed from the component 140, the plurality of pores 174 are exposed (i.e., left as empty voids within the steel foam component 140). Further, the steel foam component 140 may be processed to remove excess parts from the steel foam component 140 that are byproducts of the casting process. For example, the pour opening 38 may have retained cooled steel that remains attached to the desired component. This excess cooled steel can be cut off of the component 140 using known techniques.
At Step 228, the steel foam component 140 may be treated to achieve desired physical properties. For example, the component 140 may be heated treated to a desired hardness (e.g., between 100 BHN and 400 BHN). Additionally, the component may be welded by conventional welding techniques to other steel foam components 140 to form a desired structure. The steel foam components 140 are also machinable by common metalworking techniques. The resulting steel foam components 140 can comprise plain carbon and low alloy steels of matrix strengths varying, for example, from 50 ksi to 150 ksi.
Although the steel foam components shown in
The above techniques allow for the creation of steel foam components with ballistic resistant applications for both military structures (e.g., ballistic plates), civilian structures (e.g., buildings and bridges), naval applications, and the like. The steel foam components also have applications in energy absorption and blast resistance. The steel foam components also have controllable and uniform densities. Steel foam components manufactured according to the processes described herein can be produced relatively inexpensively and on an industrial scale. Compared to aluminum foams, steel foams have higher specific stiffness, higher hardness, and higher strength. Structural advantages of steel foam compared to solid steel include minimization of weight, maximization of flexural strength, increased energy dissipation, and increased mechanical damping. Further applications for steel foam components include, among other things, pistons and propellers. In particular, in a vehicle equipped with a steel foam component for crash protection, the steel foam component decelerates over a longer distance and a longer period of time, thereby limiting changes in speed experienced by vehicle occupants. Further, non-structural benefits of the steel foam components include lower thermal conductivities, improved acoustic performances, allowance of air and fluid transport within the steel foam component, and better electromagnetic and radiation shielding properties.
Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention.
Various features and advantages of the invention are set forth in the following claims.