How To Make Stainless Steel Powder

In the industrial field, the core technology of producing stainless steel powder has only one key word: atomization.

Simply put, the molten steel is sprayed out, using high-pressure gas (gas atomization, used to produce spherical powder) or high-pressure water (water atomization, used to produce irregular powder) as a medium, the metal flow is crushed into fine droplets, and then cooled and solidified into powder. Of course, there are also more specific processes like the plasma rotating electrode (PREP), which are specifically used to make ultra-pure spherical powders. When we design these processes, the goal is very clear: to provide raw materials for 3D printing (additive manufacturing) or sintering processes.

Key Industrial Atomization Methods

To really understand how to make stainless steel powder, we must distinguish between specific atomization technology. The choice of process directly determines the morphology and purity of the powder, which determines whether it is ultimately suitable for additive manufacturing or traditional sintering.

Gas Atomization

This is the current mainstream method of producing high-quality powder, and it is also the process that I have the most daily contact.

Process: Stainless steel raw materials are first melted in an induction furnace. As the molten metal flows through the special nozzle, it encounters a high-velocity flow of inert gas (usually nitrogen or argon). The kinetic energy of the gas slams into the metal stream, shredding it into fine droplets.

Key point: Why is it so important? Because the droplets are cooled in an inert atmosphere, they have enough time to shrink into a perfect spherical shape before solidifying. Moreover, the protection of inert gas effectively prevents oxidation, which is essential to control the low oxygen content.

Application: The spherical powder has excellent fluidity, which makes it the industry standard for additive manufacturing (AM) and metal injection molding (MIM).

Water Atomization

The logic of water atomization is similar to that of gas atomization, but the change of medium leads to very different results.

Process: We use high-pressure water gun instead of gas to bombard the stainless steel flow. The specific heat capacity of water is much greater than that of gas, which causes the molten droplet to “quench” instantaneously once it contacts water.

The result: this extreme cooling makes it too late for the droplets to shrink into balls and eventually form irregularly shaped particles. Although water contact may introduce a slightly higher oxygen content, the production efficiency of this method is very high and suitable for walking volume.

Application: Irregular powder has good interlocking properties when pressed, so it is the first choice in traditional “press-sintering” processes that are sensitive to cost.

Plasma Rotating Electrode Method (PREP)

If the customer has extreme requirements for cleanliness, ordinary atomization is not enough. At this time, it depends on PREP.

Process: Unlike standard atomized poured molten steel, PREP uses solid stainless steel rods as electrodes. The plasma gun melts the end of the rotating bar, and as the bar rotates at high speed, centrifugal force throws the molten droplets off the surface.

Results: During the whole process, the metal did not contact the ceramic crucible or the guide nozzle, which completely eliminated the risk of ceramic inclusions. The result is an ultra-pure, highly spherical powder.

Application: This high-end powder is usually reserved for critical high-performance components that absolutely do not allow material failure.

Step-By-Step Workflow

Whether it is gas or water, the underlying logic of industrial production of stainless steel powder is the same. From alloy raw materials to finished products, the following sequence must be strictly followed:

Step 1: Melting

It all starts in a furnace, usually an induction furnace. The stainless steel alloy is heated to a molten state. Temperature control is extremely critical, it directly affects the stability of the subsequent metal flow in the atomization stage.

Step 2: Atomization

This is the core transformation phase. The metal stream is poured into the atomizing chamber and encounters the atomizing medium. If it is high-pressure gas, the fluid is broken into balls; if it is high-speed water flow, the fluid is shatter into irregular shapes.

Step 3: Solidification

The metal stream must solidify after breaking up into droplets. In aerosolization, the droplets are solidified as they fall in a huge atomizing tower; in water atomization, cooling is accomplished almost instantaneously on contact with water.

Step 4: Collection And Post-Processing

The final step is to harvest the powder.

Dehydration and drying: For water-atomized powders, this step must be rapid to remove moisture to prevent rust.

Sieving: The powder is passed through a sieve and classified by particle size. If this step is not done well, it will directly affect whether the product meets the specific specifications of 3D printing or sintering.

Author： David Chen

I am a senior materials engineer specializing in powder metallurgy. With a focus on industrial atomization, I share insights on how to make stainless steel powder using Gas, Water, and PREP technologies to ensure high purity for Additive Manufacturing applications.