Around the world, stainless steel production is a 24/7, 365-day-a-year process. Factors such as industry consolidation and increasing energy costs are prompting manufacturers to improve energy efficiency ratios en route to meeting the global net zero carbon emissions quest by 2050.
Stainless steel is 100% recyclable, and these days, orders contain as much as 60% recycled steel. This is a double whammy for stainless steel production companies, who, from start to finish, work to reduce costs as well as environmental impact.
101 Fun Fact: The allusion 101 references college code for an introductory course on a subject, usually without prerequisites.
- The primary process is the conversion of liquid iron into steel via a BOF (basic oxygen furnace) or DRI (direct reduced iron) using an electric arc furnace.
- The secondary step is all about refining’ removing impurities and adding various alloys.
Sounds simple enough, but like any good dance, there are many steps that constitute the whole. So, let’s review the whole process in slow-motion.
Understanding that liquid iron, being the start of it all, necessitates huge furnaces, it is commendable that continuous emissions monitoring begins right here too. We’re talking acronyms from here on out, so bear with…
From the furnace, manufacturers regulate carbon content. It’s a typical Three Bears Tale of not too much, not too little, but a ‘just right’ scenario to reduce and remove carbon content. Most foundries use one of two options:
- AOD (Argon Oxygen Decarburization) – whereby an argon gas mixture is injected into the molten steel to reduce carbon content.
- VOD (Vacuum Oxygen Decarburization) – where oxygen is injected into steel while it is heated. Further reduction of carbon content is achieved through a vacuum removal of vented gases from the chamber.
In both methods, carbon content is precisely controlled to ensure a proper mixture and precise characteristics at the end of the process.
A triune of raw material analytics will take place about now:
- XRD (X-ray Diffraction) determines the presence and amounts of minerals species, and it is also used to identify phases.
- XRF (X-ray fluorescence) supplies details regarding chemical composition without phases.
- OES (Optical Emission Spectroscopy) analysis is a rapid method for determining the elemental composition of a variety of metals and alloys.
Carbon reduction is followed closely by balancing and homogenization of temperature and chemistry. Under the big umbrella of the grade of metal intended, batch consistency has to be precise. Hats off to the lever dudes with fancy equipment who get that right every time.
Now the shaping and forming of the stainless steel must take place as the metal cools. In alphabetical order, those shapes start out as:
Then billets and blooms become wires and bars, slabs become plates, sheets and strips and rods largely remain rods. In many repeated steps, of hot rolling cold rolling, and annealing in controlled heating and cooling cycles, the steel is softened and internal stress relieved.
Often after the next stage of pickling or descaling to impart steel’s corrosion and stain resistance, repeated annealing creates the final desired results for each specific grade of stainless steel.
If you’re keen to learn how stainless steel might work for your project, consult Steelmor – we are happy to share our 40 -years of experience in the industry.