CD4MCuN cast stainless steel

[Phils49]

We are casting a small but rather complex and thin sectioned casting in CD4MCu stainless steel, and have experience problems with misruns and with cracking or hot tears. It has been suggested that we should increase our level of Silicon to improve flowability, at present we aim for .5%. max is 1%, can anyone suggest what level we should aim for. It has also been suggested that we add Nitrogen to assist with the cracking/hot tears we are getting, any comments appreciated,
thanks.

 

[metengr]

I am not an expert on foundry problems but before you start introducing changes to multiple variables associated with chemical composition you need to determine if the casting defects are being introduced from your mold design and hot metal feed system. Pouring temperature is critical because duplex stainless steel castings should initially solidify as ferrite and as the temperature decreases austenite forms, as islands.

Have you had a lab analysis performed on one or more scrap castings to confirm the cracks are hot tears, did you confirm mechanical properties and the appearance of the as-cast microstructure? If not, the above needs to be done before changes in chemical composition is required.

 

[EdStainless]

Nitrogen may help, but it is an austenite stabilizer and it may change the phase balance in the alloy and prevent you from ending up with the correct structure.

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Plymouth Tube

 

[arunmrao]

Are you trying to pour closed impeller castings? I presume they are sand castings and not investment castings.

Look at the core gases being generated by the binder ,provide more vents and possibly keep the mold hot to reduce . Can you consider using smaller pouring ladles, so that you can pour them fast into the molds.