Powder Metal Services

Powder metal services use pressure and heat to form precision parts and shapes from ferrous and nonferrous metals. The powder metal (P/M) process begins by filling a die with powder and then compacting it at room temperature to form an engineered shape such as a gear. Next, this compacted shape is ejected from the press and fed through a high-temperature furnace. This process, called sintering, metallurgically fuses the particles without melting them.  After sintering, there are a variety of secondary operations that powder metal services can perform. These operations include sizing, plating, coining, CNC machining, CNC turning, ID/OD grinding, surface grinding, tumbling, drilling, tapping, heat treating, steam treating, and impregnation.

Powder metal services begin with powder in either elemental or pre-alloyed stages. Elemental powder is the derivative of a single element, such as lead, iron, or gold, which can either be used alone, or mixed with other powders to form alloys. Pre-alloyed powders are mixtures of elemental powders or other pre-alloys. They are composed of more than one type of metal. Once the choice of elemental or pre-alloy powder has been made, additives such as die lubricants or graphite can be mixed into the composition before the compacting begins.

In the compacting process, powder metal services place a specific amount of mixed powder (from two to three times the finish volume) into the compacting die. Compaction is achieved through pressure from above and below on the die. Many factors dictate the amount of pressure that will be used to compact the powder, including the powder distribution in the die cavity, the lateral flow of the powder mixture, and the specific tolerance needs of the finished part. Once powder metal services complete the compaction portion of the process, the component (referred to as a "green compact”) is ejected from the die and prepared for the next step, sintering.

In the sintering process, powder metal services place the green compact on a moving belt that is pulled through a furnace. The part is heated to a temperature just below the melting point of the primary elements in the compact. This allows the elemental particles to fuse together into a solid mass. Sintering changes the mechanical bonds in the compact into metallurgical bonds, leading to a finished product with similar physical properties to wrought or cast items with the same chemical composition.

Powder metal services may also perform optional finishing stages to complete the raw component. In most cases, the compacting process leaves the component with a somewhat pockmarked exterior. Infiltration, a process that involves filling these voids with another metal or alloy, can be performed during sintering. Infiltration improves the overall strength of the component, as well as sealing edges and improving machinability.

Coining is another common finishing process for powder metal services. Coining improves overall sizing and repairs aspects of the component that experienced heat distortion during sintering. At this stage of powder metal (P/M) process, the component is ready for plating if nearly complete, or a variety of machining procedures if still believed to be in the raw state.

• Sheet-Metal Fabricator Grows at 40% Per Year for 3 Years
  MNdustries, Inc. is a 40,000 square-foot full-service sheet-metal fabricator. The shop's main application was originally custom powder coatings, but soon the company began investing in sheet metal...
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