I just started my experiment about casting Duplex Stainless Steel by induction furnace. AOD and VOD aren’t available for us due to lack of budget and experts. So I need all of your advice to help me.
Detail about experiment:
- Raw material : stainless steel grade 316L (<0.03% C, 16-18.5% Cr, 10-14% Ni, 2-3% Mo, <2% Mn, <1% Si, <0.045% P, <0.03% S)
- Casting : stainless steel grade 2205 Duplex (UNS S32205)( <0.03% C, 21-23% Cr, 4.5-6.5% Ni, 2.5-3.5% Mo, 0.8-2.0% N, <2% Mn, <1% Si, <0.03% P, <0.02% S )
- Equipment : induction furnace (open atmosphere) ( 1 Ton )
- Should I choose Purging N-Ar or Adding nitrogen bearing ferrochrome into liquid metal in furnace?
- If I purge N into liquid metal, how much Bar I choose apply and how long?
- How to measure N in casting?
- What is suitable media for quenching (Water or Oil)?
- Should I concern myself with anything else?
The cast version of 2205 is either ASTM A890 Grade 4A CD3MN or ASTM A995 Grade 4A CD3MN. It will have your chemistry requirements and heat treating requirements. Quenching after solution anneal should be done in water.
If you are starting off melting duplex, I would suggest you buy AOD refined ingot. In a 1 ton you should be able to melt and go with little to no alloying additions.
If you need to use 316L, be sure it is all L grade. If you get some 316 in your melt with a .04-.08 carbon, your going to have a hard time. Also you will need to add a bit of Cr. Again, be sure you have good .025 ferrochrome or electrolytic would be better. As long as you have good low carbon 316L, you should be good alloying the Mo up with ferroMo. Your Ni addition should help with the carbon.
I always added Nitrogen with nitrogen bearing chrome. You will need to get the melt up to 2900 to 3000 degrees and have the power on after adding the N-Cr. Also, there will be quite a bit of nasty gummy slag when you add the N-Cr. You will need a nitrogen analyzer to get a good nitrogen content. I have never found the nitrogen from a spectrometer to be reliable. It can be close depending on your sample prep and gas cleanliness but, to be sure of what you have you will need a stand alone combustion analyzer.
If you do not have a nitrogen analyzer, you need to buy certified AOD/VOD ingot. Remelt, deox and pour. You should not lose any nitrogen.
Remember, Nitrogen is an alloying element. You do not want to use any deoxidizers that also tie up nitrogen such as Zr or Ti.
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