Mold Binder decomposition and gaz defects in Steel Casting 2

[stanislasdz]

Hi guys !

If any one can give me some informations or links on the relationship betwen the mold binder decomposition and the gaz defects in steel casting.

Thanks in advance !

 

[arunmrao]

This data you can obtain from the manufacturers who supply the resin binders. Please bear in mind that organic binders evolve more gas than inorganic binders.

Gas defect and hot tear are 2 common problems attributed to binders. The other important defect being sand wash from cores/molds.

(As an aside, do you have no senior experienced person in the foundry to gude you .His views will be more relevant than what you might get on the net.)

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

 

[gieter]

SFSA has done an extensive research on the subject some years ago.

Try to get hold of research report 87: "Surface contamination of steel castings from furan and phenolic no-bake binders"

 

[stanislasdz]

Thanks all

Arunmrao :

Tanks for your advice, but our internals expert in our foundry can not found the origin of the gaz porosity.

If i can summarize we use :

Steel casting
Alaphaset sand
Arc furnace melting
Low carbone steel
the porosity defects is not constant and somme times we have very good parts and in other times we find gaz in the end solidification part.

The question we ask, the porosity provied from melting (H,O,N) or from the binder and what are the best practise to avoid the porosity in this case.

I am surprised to read that the porosity problems in casting are obvious !!! the paper taht i read underline that is complex to undersatnd and avoid the gaz porosity.

Here some links i found :

http://www.rastgar.com/rec/papers/Porosity in Castings.pdf

http://www.improve.it/metro/file.php?file=/1/Papers/Cast_Iron/99-206.pdf

 

[arunmrao]

Gas porosity problems are caused by improper process controls in your facilty. You have mentioned that at times there are good castings ant at times not. Please check if it repeatedly happens with one team of workers and supervisors in the plant. Alternately please check if it happens with one type of casting or with all. Does it happen only during end pouring or throughout?

Do you frequently change the suppliers for the binders? How good is the mold coating? Is the mold properly torched before closing?

You mention about porosity at the end of castings? It means that the venting is not sufficient for the mold gases to be released . Provide some flow offs. Low carbon steel pouring is very tricky. Try and add some deoxidisers into the moltem metal while pouring into the molds.

I can go on endlessly without knowing the root cause. It was with this in mind I suggested you seek the assistance of a senior.

It is not an insurmountable problem and can be very easily solved at the shop floor without reading academic papers.

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke