Valorization in Metallurgy: how additive manufacturing benefits from metallurgical «waste»
16 January 2023Article by Omid Emadinia, INEGI researcher in the field of advanced manufacturing processes
The material use, energy use and waste production in the metallurgical industry are aspects that must be rethought and improved, in order to make it sustainable, both economically and environmentally2.
Every day, tons of waste are produced in the metallurgical industries. But applying a circular industry logic, it is possible to add value to metallic waste, using them as «secondary» raw materials for new applications, reducing, once again, both costs and environmental impacts.
It is proven that the production of metal from ores leads to a higher consumption of energy and resources, when compared to the recycling of metallic residues for new applications. Therefore, currently, most of the metal waste from the metallurgical industry is collected and recycled 3.
However, there are only a few recycling solutions for metallic waste. Conventionally, metal shavings are consumed as scrap in foundry industries, however, this solution represents a high energy consumption, cost, and environmental impact. Thus, direct and indirect methodologies have been investigated as possible solutions for the reuse of these materials3.
Shavings resulting from machining gain a 2nd life for metallic additive manufacturing
A solution that has become the subject of research in recent years, due to its wide range of opportunities, is the production of metallic powders from scraps resulting from machining. This indirect process of reuse of waste has already been confirmed as being viable and of wide application, especially for the additive manufacturing industry 1.
In recent years, metallic additive manufacturing has received more attention, being considered an alternative to conventional manufacturing processes. In part, because metallic additive manufacturing has the ability to produce unique pieces of high geometric complexity.
The transformation of chips resulting from machining processes into powders for additive manufacturing can be a value-added application and this sustainable approach can be implemented in the future in metallurgical industries that work with additive manufacturing, creating a closed life cycle for waste.
The production of powder from the shavings is carried out after mechanical grinding processes. The final characteristics (shape, size, size distribution, and structure) and properties (such as bounce and compact density or flowability) of the produced powders are the biggest challenge for the valorization of powders for the purpose of being used in additive manufacturing. As a rule, powders are produced by methods in which it is possible to have strict control over the size and shape of the particles, however, when milling is mechanical, it is not easy to obtain the desired characteristics.
For each additive manufacturing process, different powder characteristics are recommended, and in most of them, these characteristics are impossible to obtain with mechanical processes.
Direct Energy Deposition Technology is at the forefront of the process
As an alternative, Direct Energy Deposition (DED) appears, a metallic additive manufacturing process that deserves attention due to its versatility, high production rates. In addition, it is possible to take advantage of the possibility of repairing damaged components and creating coatings for components 4.
The great advantage of the DED process for applying this type of powder is the fact that this process does not have strict requirements in terms of powder characteristics (usually between 45 µm and 150 µm) 5 and not necessarily spherical, being able to print components using powders with large dimensions. Even so, mechanically produced powders present a challenge for the DED process.
Thus, in order to be able to implement this type of solution in industry, it is necessary to investigate the most suitable powder milling methods, as well as to select the ideal parameters for printing the DED process.
INEGI has been supporting research into sustainable solutions for reducing the ecological footprint in various industries, having at its disposal the first DED laboratory station in the country.
One of these studies focuses on the transformation of stainless steel shavings into powder particles for DED 6. The powder is produced through the disk grinding process, and the resulting particles are subjected to a complete characterization in order to identify their size, size distribution, and its shape. After the production and characterization of the powders, the powder impressions are parameterized on a non-preheated structural steel substrate, considering the laser power, the printing speed, and the powder delivery rate.
The objective is to validate the solution so that, in the near future, it can be implemented at an industrial level. Valuing materials that no longer have any value for the industry means creating a circular economy, where doors are opened to support the consumption of raw materials.
Related Pages
Innovation and Technology Transfer | Additive Manufacturing
References
[1] Batista CD, Fernandes AA, Vieira MT, Emadinia O. From Machining Chips to Raw Material for Powder Metallurgy—A Review. Materials. 2021;14(18).
[2] Broadbent C. Steel’s recyclability: demonstrating the benefits of recycling steel to achieve a circular economy. The International Journal of Life Cycle Assessment. 2016;21(11):1658-65.
[3] Bendikiene R, Ciuplys A, Kavaliauskiene L. Circular economy practice: From industrial metal waste to production of high wear resistant coatings. Journal of Cleaner Production. 2019;229:1225-32
[4] Bourell DL, Frazier W, Kuhn H, Seifi M. 20.3 Components of Directed-Energy Deposition Systems. ASM Handbook®, Volume 24 - Additive Manufacturing Processes: ASM International.
[5] Direct Energy Deposition - Benefit from AP&C's highly spherical powders. AP&C a GE Additive company; 2022 [Available from: https://www.advancedpowders.com/industries/ded]. Acedido a 6 de Setembro de 2022.
[6] Production of Sustainable Powders for Direct Energy Deposition (DED), Master thesis, Faculty of Engineering University of Porto, https://sigarra.up.pt/feup/pt/teses.tese?P_ALUNO_ID=126144&p_processo=27474
Master's thesis by Lara Castanheira, held at INEGI's facilities, supervised by Prof. Dr Ana Reis and Dr. Omid Emadinia.