Using a Powder Production Line to Produce Metal Powder Batteries
A Powder Production Line is a complex machine with many parts that must be made correctly to ensure the finished product meets the exacting dimensional requirements. Using powder metallurgy is one way to do that.
Powder metallurgy involves mixing and sintering iron-based alloy structural components. These components are pressed in a die that determines the basic part shape.
Raw Materials
Metal powders are used in the production of batteries. The powders are mixed with liquid mixer electrolytes, oxidized metals and additives to produce batteries with more reliable and consistent performance. These powders are also used in energy storage systems as a means of increasing the power capacity and lifetime of rechargeable batteries.
In the powder metallurgy process, liquid metal is broken into fine particles using atomization or other processes and then pulverized and sieved to form the raw material powder. The powder is shaped into the desired part by die compaction with a hydraulic, mechanical or servo-controlled press. The pressure compacting the powder increases density and reduces potential voids within the finished AM part.
Unlike casting, which can result in gaps and voids, powdered metal manufacturing produces parts with high quality and consistency. Stainless steel is often used in powder metallurgy due to its corrosion resistance and tensile strength. Other metals and alloys are suitable for powder metallurgy as well.
The raw powder lot is then blended to obtain a specific chemistry and particle size distribution (PSD). Blending allows for higher productivity by reducing the number of times the powder is tested. This is especially useful for critical applications such as aerospace and medical. In these cases, combining heats with varying chemistry can bring the powder lot into specification and avoid surprises when the PM part is built.
Mixing & Blending
When dealing with powdered ingredients, proper mixing is essential to ensure consistent product consistency. Achieving a perfectly blended mix takes the right process equipment and experience. Our design engineers can help you determine the correct equipment configuration based on your unique specifications. This includes mixing & blending line design, hopper & bin size selection, spray nozzle placement and blending speed control. Our team of experts can also guide you through a number of lab-scale trials to test the best equipment for your specific materials.
Mixing is especially important in powder metallurgy (PM) processes. PM processes are common manufacturing techniques that involve spherical metal powders mixed with plastic or wax as binding agents, then injected into a mold to form a green part. The green part is then heated to fuse the particles together in a hot isostatic press (HIP) to create a near solid, high-density part with as-wrought mechanical properties.
Achieving a perfect powder blending operation is challenging, especially in continuous direct tableting lines. The continuous setup requires continuous injection of APIs and tableting excipients into the mixer, which puts a premium on ensuring adequate blend homogeneity and product content uniformity. A key challenge is selecting feasible feeder setups. DoE experiments conducted using a single-screw volumetric and gravimetric feeder demonstrated the impact of various mass flow and screw rotation speeds on blending efficiency. Using these experimental data, we created a predictive model that integrated the digital twin models of the feeders and the RTD model of the powder blender to evaluate the system’s output contents uniformity.
Sintering
A sintering process takes pure powdered materials and transforms them into integral, net-shape parts by fusing and melting them. This is a popular manufacturing Packaging Machinery Supplier technique for metals, ceramics and some polymers. It is used in powder metallurgy and powder bed fusion (PBF), as well as in direct laser sintering, which is an advanced form of additive manufacturing, or 3D printing.
To prepare for sintering, the powder is mixed with a binder or plastic. The mixture is then pressed under controlled conditions into a part shape, known as a green part. This is often a complex geometry that would be difficult or impossible to machine. The green part is then heated in an atmospherically controlled sintering process. This removes the binders and causes the particles of the powder to fuse together and coalesce into a sintered part with higher strength.
Sintering processes can be divided into two broad categories; solid-phase sintering, where the densification is driven by atomic diffusion between adjacent powder grains, and liquid phase sintering where the densification is driven by a change in the bulk composition. For long length products it is important to manage the shrinkage of the sintering process, in order to achieve good geometrical control of the product and avoid geometrical deformation. To accomplish this, a number of different strategies can be employed, such as changing the green density, particle size optimization and/or the addition of pore formers. Linseis push rod dilatometers are utilized to measure the rate of sintering in various atmospheres, to ensure that a consistent sintering environment is maintained to prevent excessive shrinkage and micro-structural variation.
Finishing
Metal powders are injected into a pre-designed mold. It is possible to create an unlimited range of shapes and sizes using this method, with excellent dimensional tolerances. This eliminates the need for complex machining operations, which reduces production costs and lead time. The process is very similar to plastic injection molding or high pressure die casting. The main difference is that the final product does not require any additional finishing, which makes it a competitive alternative to traditional manufacturing techniques.
After a pre-powder treatment, sintering is the next step. This is done in a hot isostatic press (HIP). In this type of process, the metal powders are gas atomized and spherical in shape, and the entire spherical mass is placed into a metal can that serves as a mold. The spherical mass is then heated and subjected to a high amount of internal pressure, which compresses the powder particles into the desired shape. This is a very efficient process, and it yields parts that have the same microstructure and density as those produced by traditional forming methods like forging.
In addition, it allows workpieces to be made from materials that are not easily formed by other methods. For example, it is possible to make metal glasses for microwave use and high-temperature applications, as well as a variety of other special products.
