Metal Powder Blending and How It Affects Sintered Components

April 17, 2018

To obtain the finest possible compacted and sintered parts, the powder metallurgy sector requires access to a source of properly blended raw material. These are the mixed powders that mingle with alloying additives and lubricants. It’s here that the industrial machinery breaks from its normal linear processing configuration. Back at square one in the production run, the operation uses a dual-action sequence to really shake up the freshly atomized metal.

Powder Metallurgical Processing 

Streaming in from the powder pulverizing station, the fine-grained mountain of metal enters a mixing chamber. To one side, the feed line is open. Another feed channel is located on the other side of the chamber. From here, the homogenized mass receives a second ingredient, which is usually where a waxy, powdered lubricant enters the mix. Mechanically spun and rotated at speed, the blended load distributes that oily discharge. The lubricant and metal merge as a thoroughly intermingled mass of powder. This, as we all know, is a basic description, one that perhaps does this processing stage a disservice. Let’s dive deeper.

An In-Depth Process Review 

Look closer, this isn’t a plain mixing chamber. It has multiaxis turn points, plus internally mounted baffles. The drum is rotating on one axis, then it’s spinning on a second axis. Meanwhile, inside the hollow drum, blades are maximizing the blending action. And are we still talking about a fundamental mix? Not in the least, there are compaction binders and secondary lubricants in that carefully blended mass. They expedite the mixing operation and stop in-process die friction. Meanwhile, what if other alloying metals enter the drum? This is the place for that metal mix to form. In fact, metal-to-metal amalgamates form here that don’t normally occur in traditional alloy manufacturing science.

A Whole-Picture View 

Tiny quantities of zinc stearate overcome die friction. Mixed with this process lubricant, binding agents assure a solid product takes form during the compaction and sintering stage. There’s even a de-flocculant in the blended material load, an ingredient that’s there to inhibit the clumping effect that can plague some powder metal mixes. Finally, one or more alloys combines with a primary lubricant inside the mixing drum. That churning mix combines with the additives, and the pulverized mixture speeds on towards the compaction stage.

Ruling the blending stage, that all-important sealed drum guarantees a homogenized compound. Powder metallurgy science absolutely relies on a high degree of mixing excellence. Like a precisely controlled recipe, the ingredients must be portioned correctly and mixed wholly if the product is to pass through the sintering stage the right way.

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