Powder Metallurgy FAQ

Frequently asked questions


What is gas-atomization?
Gas-atomization is a process to manufacture metal powders in which molten steel is atomized through the use of inert gas jets into fine metal droplets which cool down during their fall in the atomizing tower. Metal powders obtained by gas-atomization offer a perfectly spherical shape and high cleanliness level, unlike water-atomization.
The gas-atomization process is used for the production of a wide range of steels with high alloy content, such as tool steels, high speed steels, stainless steels. It is also used for low-alloyed steels and nickel-base or cobalt-base alloys.
Gas atomized powders are suitable in many processes such as:

  • Hot Isostatic Pressing
  • Thermal Spraying
  • Plasma Transferred Arc (PTA)
  • Metal Injection Moulding
  • Laser prototyping
  • Etc.


 

What is hot isostatic pressing?
Hot Isostatic Pressing is a process to densify gas-atomized metal powders, placed in a metal container, through the combination of high gas pressure (100 to 200 MPa) and high temperatures (from 900°C to 1250°C). The HIP operation takes place in a HIP furnace where the gas pressure act uniformly in all directions, hence providing isostatic properties and 100% densification.
Hot Isostatic Pressing is used both for the manufacturing:

  • of semi-finished products such as capsules which are further forged and rolled into round or flat bars
  • of Near Net Shape components.


 

What is Dvalin™?
Dvalin™ is the name of an exclusive process used by Erasteel since 2005 in Soderfors, Sweden for the manufacturing of gas-atomized metal powders. The Dvalin™ process includes an Electro-Slag Heating (ESH) tundish metallurgy and gas-atomizing process to refine the molten steel, resulting in the removal of most of the melt-related oxide inclusions. After atomizing, powder is protected during handling to prevent the powder oxidation or the introduction of extraneous sources of foreign material into the process. Thanks to the Dvalin™ process, the number of large non-metallic inclusions has been reduced by 90% compared with the previous process and the steel offers a cleanliness level approaching the levels of traditional remelted steels.
This cleanliness provides improved fatigue properties, as well as toughness, polishability, and EDM consistency, compared to other process routes for PM steels.


 

What is the importance of the cleanliness for ASP® steel grades?
The Dvalin™ process used by Erasteel to produce the ASP® products the result of two decades of process improvement in melting and powder handling. This process removes nearly all of the inclusions normally present in less advanced powder production processes. Because of the very low inclusion content, ASP® grades can offer improved fatigue properties, EDM consistency, and polishability compared with other PM grades. ASP® grades are particularly recommended where these properties are important for the performance of a tool or mechanical component.

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