Sterling Sintered's Powdered Metallurgy Process

Sterling Sintered Technologies - Powdered Metallurgy Experts

The P/M Process:
How P/M Parts Are Made

There are three basic steps for producing conventional density parts by the powdered metallurgy process: Mixing, Compacting, Sintering.

	STEP ONE: MIXING
	Elemental or pre-alloyed metal powders are first mixed with lubricants or other alloy additions to produce a homogeneous mixture of ingredients. The initial mixing may be done by either the metal powder producer or the P/M parts manufacturer.

STEP TWO: COMPACTING

A controlled amount of mixed powder is automatically gravity-fed into a precision die and is compacted at pressures usually between 30 and 50 tons per square inch depending on the density requirements of the part.
Compacting the loose powder produces a "green compact", which in conventional pressing techniques, has the size and shape of the finished part when ejected from the die, and sufficient strength for in-process handling and transport to a sintering furnace. Typical compacting uses rigid dies set into special mechanical or hydraulic presses.
Tool sets are made of either hardened steel and/or carbides, and consist of at least a die body or mold, and upper and lower punch, and in some cases one or more core rods.

Compacting: Step Two in the Powder Metallurgy Process

STEP THREE: SINTERING

In the typical sintering step, the "green compact", placed on a wide-mesh belt, slowly moves through a controlled-atmosphere furnace. Parts are heated to below the melting point of the base metal, held at the sintering temperature, and then cooled. Basically a solid state process, sintering is transforms compacted mechanical bonds between the powder particles into metallurgical bonds. This process provides the P/M part's primary functional properties. P/M parts generally are

ready for use after sintering. However, some secondary processes may be necessary to finish the part and bring it to within the customer's specifications.

SECONDARY OPERATIONS P/M parts maybe repressed, impregnated, machined, tumbled, plated, or heat treated following sintering is special properties are required.
Repressing - coining or sizing, effects the densification and dimensional control.
	Oil Impregnation makes bearings self-lubricating. Resin Impregnation may be used to improve machinability., seal parts gas or liquid tight, or prepare the surface for plating. Ferrous Infiltration improves strength and seals parts gas or liquid tight.
Structural Infiltration prepares the surface for plating with other metals and improves the ductility and machinability. Heat Treating improves the strength and hardness and makes the surface hard and wear resistant.
Machining can be done to install set or assembly screws, form undercuts or slots, or to remove stock to make faces parallel and improve surface finishes. Finishing includes, deburring, burnishing, coating oil dip, plating, welding, and mechanical surface treatments

Sterling Sintered Technologies, Inc.
249 Rockwell Street
Winsted, CT 06098
Phone: (860)379-2753
Fax: (860)738-0664
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