What’s up guys? This is Michael with Michlin Metals back at ya with another video and today we’re going to close out the year w/our last video of 2020. Come on back in 2021 – Jan 7th will be our next video. Please consider subscribing as most of you who watch are not clicking that little button to subscribe. Help me out and just click it already! Let’s jump in!
So here we are with the last video of 2020 so we thought we would close with some quick explanations of some terms used in the production of modern specialty metals. Our series this fall was about stainless steels, nickel alloys, and cobalt based alloys. Chemical analysis defines the alloy and what it can do in applications. Production of stainless and the nickel and cobalt alloys can include multiple melting and refining steps to make the alloy.
Often production starts with the melting of scrap and master alloys in an electric arc furnace. EAF for short. Very efficient at melting, striking an arc from graphite electrodes into the scrap “charge”.
A separate specialized unit used when needed to further refine the melt is an AOD vessel. AOD stands for Argon Oxygen Decarburization. Used for removing carbon and making chemistry adjustments to the melt. Molten metal is “charged” into this vessel and oxygen is blown through the melt to adjust the carbon content. Alloying elements or additional scrap components are added to adjust the chemistry and temperature to target values. An inert gas is used to remove oxygen remaining in the melt prior to casting.
A “Heat” is the term that identifies a single chemical batch of the alloy melted. A “Heat Lot” is the entire amount produced of that specific alloy. For instance, sometimes a mill (the manufacturer of metal) will require a very large quantity to produce a specific grade or shape. Thus they require you to purchase the entire amount made thus you have to purchase the entire “lot” of that “heat”.
A Heat number is the assigned identifier of that melt batch and it is typically an alphanumeric sequence assigned by the producing mill.
The heat is then cast either into individual ingot molds or continuously cast through water cooled molds. In either case, sequence within the “pour” is maintained, as testing is often required at specific intervals within the cast to assure quality.
Special molds are used to cast electrodes when a further second melt is to be employed.
For critical applications, secondary or melting in a vacuum is used to further eliminate undesirable non-metallic components that can exist in the air melted and cast metal.
VIM is Vacuum Induction Melted. Induction coils provide the energy to melt the alloy within a vacuum chamber.
Multiple types of secondary melting are included in the term CEM which stands for Consumable Electrode Melted. All melt an electrode of the alloy chemistry under conditions that eliminate dissolved gases and undesirable inclusions and then resolidify in a mold at the bottom of the unit. CEM is the most generic term. All of the following are included in the term CEM
CEVM stands for Consumable Electrode Vacuum Melted.
VAR stands for Vacuum Arc Remelted is a specific type of CEVM
ESR stands for Electro Slag Remelted. Here an Electrode is melted under a protective slag rather than through a vacuum.
Specifications may require specific melting requirements for the alloy. As you probably guessed, multiple melting or vacuum processing adds a lot of cost to already expensive materials. So check the specs.
We hope you have enjoyed this year’s series and join us for more in the coming year. So see ya later 2020 you bag of trash. We’ll all be happy to see this year end. There will be no video next week but come on back and join us in the first week of 2021 for the 7th video! As always, if you have made it this far, you must really love metal. If that’s the case, SUBSCRIBE!!! Just click it! If you have missed any previous videos, click here. Thanks again for watching, this is Michael with Michlin Metals, OUT!