Recycling sustainability as it relates to Minor Metals witnessed great strides in the last century in the context of specialty steel and tool steel manufacturing. What likely began as a means to save consumers money (and recyclers to earn a living), is now also driven by ‘Green’ forces and the reality that resources are finite. The success of value added scrap owes its credit to both sides of the supplier and consumer equation. On the one side you have a supplier/processor who sees potential for a scrap stream, and with a little ingenuity, develops a process to render material commercially viable for alloy additions. On the flip side, you have a purchasing agent and a metallurgist with an open mind and ingenuity to match.
A perfect example of this confluence is the state of Tungsten and Molybdenum recycling in the 1980’s. My mentor was one of the early pioneers. With a degree in metallurgy, he spent his post graduate years employed by steel manufacturers in the Pittsburgh, PA. area, and eventually was hired as a sales person by an international W and Mo mining concern. In 1984, he left the mining industry and started a W and Mo recycling company. Because these two refractory metals are derived from powder metallurgy, there are many steps between W/Mo compounds and a pure metal product. Every phase of this process generates various byproducts well suited for Ferro-Tungsten and Ferro-Molybdenum substitutes. He had 1st hand knowledge of the companies producing W/Mo metal products because he had sold them chemical precursors and witnessed the various forms of scrap their plants produced. From his days as a metallurgist in the steel industry, he recognized these scrap streams were superior in purity to traditional ferro-alloys and he knew which steel makers could take advantage of these discounted units. With a little tweaking of the scrap, he connected the dots between scrap generator and steel producer. This marriage was only possible due to receptive and creative individuals in the specialty and tool steel industry who were unwittingly participating in one of the earliest examples of ‘Cradle to Cradle’ manufacturing.
Today, innovations in technology and the explosion of critical applications best suited for Minor Metals represent a challenge. This resource saving phenomenon is specifically relevant in the area of Nickel and Cobalt based air melt and vacuum alloys. While there have been advances in the willingness and acceptance by critical and non-critical alloy producers to incorporate processed revert and not rely exclusively on virgin or primary materials, more room exists to expand their comfort and use of recycled Minor Metals and alloys that contain Minor Metals.
As a rule, scrap material substitute for primary material must provide a cost saving alternative that does not sacrifice the quality of the customer’s final product. This is easily accomplished in many instances of high temperature alloys where there is no deviation from the consumer’s chemical specifications and little deviation from their physical specifications. The missed opportunities for additional use of scrap can often be traced back to the research and development behind the manufacturers alloy product.
After a prolonged period of trial and error, a team of R&D engineers finally assembles the right configuration and proportion of elements. Each elemental additive in this assortment has a specific chemistry and morphology. These details logically become the ‘recipe’ or specification for the alloy in question. Sometimes an excessively rigid and literal adherence to the exactness of those details prevent and stifle the use of cost saving scrap alternatives.
Below is a text book example of this phenomenon. A producer of Nickel and Cobalt based high temperature alloys solicited an RFQ for a quantity of Hafnium metal for use as an alloy additive. All raw material specifications for the production of alloy require guidelines on chemistry, size, and form. What separated the specification in question from the many Hf specs. of its peers, was the specificity of form and one particular elemental restriction. The melt stock was required to adhere to very strict dimensions of length, width, and thickness which is common among discriminating melters. What made this case challenging was a very tight Oxygen tolerance in combination with the aforementioned special sizing requirements.
Any MMTA member who supplies Hafnium metal knows Hafnium has as a strong affinity for Oxygen. This affinity is referred to by metallurgists as a “getter”—a not so sexy way of saying it has a predilection to absorb Oxygen in the consolidation and purification phase, similar to that of Titanium and Zirconium. Many applications outside of alloy production that require pure Hf ‘widgets’ are derived from mill product produced by Vacuum Arc Remelting or Electron Beam melting. These two approaches produce Hf metal which contains a moderate level of Oxygen, a level which has no detrimental effect to its ultimate application. Think shielding or control rods for nuclear power generation.
Returning to the example of the finicky melter, while their Hafnium’s Oxygen requirement was technically achievable by VAR or EB melting, it strained these technologies limits—especially when combined with a special geometry. Ultimately, the alloy producer was dependent on a rare intersection of chemistry and form not practical and repeatable on a commercial scale—virtually ensuring an expensive semi-finished product was needed. The solution began with an explanation of these challenges to Purchasing and a promise that a scrap alternative could provide significant cost savings. The next step involved working with Metallurgy and ensuring the scrap alternative would cooperate with the delivery mechanism to the melt and the material would dissolve at an optimum rate. Lastly, we persuaded Quality Assurance that integrity of chemistry would be met and alleviated concerns over traceability and repeatability. The successful adoption of a scrap alternative often relies on the recycler’s navigation of the customer’s internal ‘culture’. In this instance, each of the consumer’s departments was receptive and the goal was achieved.
The sustainability of recycling Minor Metals in the 21st century has become increasingly important in an environment where closed loops and a circular economy have proven to save time, energy, and resources on a planet where all three are limited. But some consumers have resisted substitution based on voices within their Quality Assurance departments stemming from concerns over traceability, sustainability, and form. These stalwarts are forced to pay a premium for their raw material. On the other hand, many companies are willing to explore cost saving avenues and encourage their purchasing agents to collaborate with their metallurgists and QA departments in search of scrap alternatives offered by the recycling sector. When successful, these consumers can benefit from a cost savings in the range of 5% to 30%, or even greater. The future success of these strategies relies on excellent communication between the recycler and producer and their collective creativity.
Joel Nields, Exotech
