Shot, Pellets, Pieces, Ingots, Powder Form Overview

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ESPI offers Shot, Pellets, Pieces, Chips, Powder and other forms made up of many different element’s and/or alloys as well as in manufactured in numerous purities; up to 6N (99.9999%), including:

Ribbon

Chips

Discs

Custom Fabricated Parts

Wire

Sputtering Targets

Ingots

All forms can be manufactured to custom specifications. Or, for those time critical applications where standard sizes will meet project requirements, take advantage of ESPI’s Ready-To-Ship (RTS) program. ESPI stocks pre-fabricated items in foil and sheet that are available for same day shipment.* To view the Ready to Ship products, click here. For a quotation, call, e-mail or click "Chat Now" to the right for immediate assistance.

* Order must be received by 1:00 pm Pacific

SHOT, PELLETS, PIECES, CHIPS and POWDER FORM OVERVIEWs

In metal fabrication, there are different complexities that determine and influence the outcome of the resulting product. What greatly affects the form includes what type of metal is being initially used and whether the metals are of a high temperature or low temperature variety. Often, to make one form, it might require a process in which you create one form that results in another. For example, pellets, often start off as rods and then are cut into individual smaller pieces. There are numerous type of forms available from ESPI which are elaborated on other pages. Some forms are of similar style and are included below with additional information about how they are produced.

Shot

Shot normally comes in round or tear drop form. Historically shot was made in a “Shot Tower” which was a tall tower designed for the production of shot balls by the freefall of molten lead, which is then caught in a cooling basin. This method of manufacturing shot was used for projectiles in early firearms. The material was heated until molten, then dropped through a copper sieve high in the tower. Through surface tension the liquid forms spherical balls while in freefall and partially solidifies. The semi-cooled balls are caught at the floor of the tower in a water-filled basin and harden rapidly. For “round “ shot this concept is utilized in modern fabs with a bit more science behind the process which is controlled by having the material the right distance from the cooling baths and having the correct amount of material in the crucible. When round isn’t critical, “tear drop” shot is made, more rapidly by pouring the molten material over a screen and permitting it to harden into that familiar shape.

Pellets

Pelletizing is the process of compressing or molding a material into the shape of a pellet. By extruding the material through a screen, the pellets are formed by shaving off the parts in predetermined lengths just before hardening. A wide range of different materials are pelletized including metals and chemicals. Ninety percent of pellets are usually made from rod varying in different diameters depending upon the requirement of the user. Uniformity in shape is an attribute of pellets.

Pieces

Pieces are generally irregular shaped portions of metal fragments where the key to selection is the “available surface area.” Pieces come in a variety of sizes and shapes which can range from being quite large (an inch or two in diameter to fractions of inches). Generally, the smaller the pieces, the more surface area there is of the material being used.

Chips

Chips are often made by “shaving” metals with burring type bits. The size of the chips depends upon different criteria such as, the size and roughness of the bit as well as the hardness of the material being shaved or chipped off. Selection and use of chips, like pieces, are often determined by the amount of surface area available on the material.

Ingots

An ingot is a material, usually metal, that is cast into a shape suitable for further processing. Non-metallic and semiconductor materials prepared in bulk form may also be referred to as ingots, particularly when cast by mold based methods. Metal, either pure or alloy, is heated past its melting point and cast into a bar or block using a mold chill method. Polycrystalline and single crystal ingots are made from semiconductor materials by pulling from a molten melt. Uses include the formation of photovoltaic cells from silicon ingots by cutting the ingot into flats, known as wafers. Ingots require a second procedure of shaping, such as cold/hot working, cutting or milling to produce a useful final product. Additionally ingots (of less common materials) can be used as currency, or as a currency reserve as with gold bars.

Ingots are manufactured by freezing a molten liquid (known as the melt) into a mold. The manufacture of ingots has several aims. Initially the mold is designed to completely solidify and form an applicable grain structure required for later processing. The structure formed by the freezing melt controls the physical properties of the material. Next, the shape and size of the mold is designed to allow for ease of ingot handling and further processing. Last, the mold is designed to minimize melt waste and aid ejection of the ingot, as losing either melt or ingot increases the cost of finished products.

A variety of designs exist for the mold, which may be selected to suit the physical properties of the liquid melt and the solidification process. Molds may exist in top, horizontal or bottom-up pouring and may be fluted or flat walled. The fluted design increases heat transfer owing to a larger contact area. Molds may be either solid "massive" design, sand cast (e.g. for pig iron) or water-cooled shells, depending upon heat transfer requirements. Ingot molds are tapered to prevent the formation of cracks due to uneven cooling. Crack or void formation occurs as the liquid to solid transition has an associated volume change for a constant mass of material. Formation of these ingot defects may render the cast ingot useless, and may need to be re-melted, recycled or discarded.

The physical structure of a crystalline material is largely determined by the method of cooling and precipitation of the molten metal. During the pouring process, metal in contact with the ingot walls rapidly cools and forms either a columnar structure, or possibly a "chill zone" of equiaxed dendrites, depending upon the liquid being cooled and the cooling rate of the mold.

For a top-poured ingot, as the liquid cools within the mold, differential volume effects cause the top of the liquid to recede leaving a curved surface at the mold top which may eventually be required to be machined from the ingot. The mold cooling effect creates an advancing solidification front, which has several associated zones, closer to the wall there is a solid zone which draws heat from the solidifying melt, for alloys there may exist a "mushy" zone, which is the result of solid-liquid equilibrium regions in the alloy's phase diagram, and a liquid region. The rate of front advancement controls the time that dendrites or nuclei have to form in the solidification region. The width of the mushy zone in an alloy may be controlled by tuning the heat transfer properties of the mold, or adjusting the liquid melt alloy compositions.

Continuous casting methods for ingot processing also exist, whereby a stationary front of solidification is formed by the continual take-off of cooled solid material, and the addition of molten liquid to the casting process.

Approximately 70 percent of aluminum ingots in the U.S. are cast using the direct chill casting process, which reduces cracking. A total of 5 percent of ingots must be scrapped because of stress induced cracks and butt deformation

Powder

In making powder several techniques have been developed which permit production of powdered particles, often with considerable control over the size ranges of the final grain population. The most common and cost effective method of making powders are often prepared by grinding, or comminution (reduction of solid materials from one average particle size to a smaller average particle size, by crushing, grinding, and other processes.). Other methods of manufacturing powders include: chemical reactions, atomization, electrolytic deposition or solid state reduction.

Chemical

The most common forms of chemical powder treatment involve oxide reduction, precipitation from solutions, and thermal decomposition. The powders produced yield great variation in properties, however, are close in particle shape and size. Powders that are oxide-reduced are typically characterized as “spongy,” due to pores within the individual particles. Powders produced from a solution-precipitated process provide narrow particle size distributions and high purity. Thermal decomposition is most often used to process carbonyls. These powders, once milled and annealed, exceed 99.5 percent purity.

Atomization

In this process, molten metal is separated into small droplets and frozen rapidly before the drops come into contact with each other or with a solid surface. Typically, a thin stream of molten metal is disintegrated by subjecting it to the impact of high-energy jets of gas or liquid. In principle, the technique is applicable to all metals that can be melted and is used commercially for the production of iron; copper; alloy steels; brass; bronze; low-melting-point metals such as aluminum, tin, lead, zinc, and cadmium; and, in selected instances, tungsten, titanium, rhenium, and other high-melting-point materials.

Electrolysis

By choosing suitable conditions, such as electrolyte composition and concentration, temperature, and current density, many metals can be deposited in a spongy or powdery state. Further processing–washing, drying, reducing, annealing, and crushing–is often required, ultimately yielding high-purity and high-density powders. Copper is the primary metal produced by electrolysis but iron, chromium, and magnesium powders are also produced this way. Due to its associated high energy costs, electrolysis is generally limited to high-value powders such as high-conductivity copper powders.

Solid-state Reduction

 In solid-state reduction, selected ore is crushed, mixed with a reducing species (e.g., carbon), and passed through a continuous furnace. In the furnace, a reaction takes place that leaves a cake of sponge metal which is then crushed, separated from all non-metallic material, and sieved to produce powder. Since no refining operation is involved, the purity of the powder is dependent on the purity of the raw materials. The irregular sponge-like particles are soft, readily compressible, and give compacts of good pre-sinter (“green”) strength.

Workmanship Standards

Where not specified in the purchase order or contract, ESPI shall apply standard workmanship tolerances. Rounds (rod, wire, etc): +/-10% for diameter and length. Profiles (plate, sheet, foil, etc): +/- 10% for thickness, width and length. Other non-machined solids (powder, shot, pieces, etc): +/-10% for weight, +/-25% for size.

Purity

Material purities indicate a minimum allowable purity. Purities may be higher than stated in the material description based on availability.  Rare Earth purities are based upon rare earth contaminants.  Metal purities are reported on a metals basis; zirconium purity excludes Hf.  Purities of fabricated metal products are generally based on ingot chemistry.

Quality Assurance

ESPI's comprehensive line of high-purity metals, alloys, and chemical compounds are distributed to scientists worldwide. Trust has been earned by our customers in maintaining a strong commitment to quality and excellence. All materials listed in the catalog are thoroughly tested by our quality control department. The figures given as typical analyses have been compiled through an average of previous batches.  They are provided as a guide to the nature and extent of the impurities which may be expected and may vary from batch to batch. Actual material analyses will be provided free of charge upon request for those items which have had analysis work conducted in the normal course of production.  For those items for which no analysis has been conducted, an analysis will be provided for a charge.