Optimum time for Chek-Out in Steel Casting 2

[stanislasdz]

From a simulation software, we compute the evolution of the temperature during cooling of a steel casting part in 18CrNiMo grade.

I have some questions, if any one can help

1- What is the optimal temperature for cheking out the part from the mold during cooling ?

2- What is the metallurigical effects if we chek out à 500°C, 300°C or 200 °C ?

 

[arunmrao]

Normally 24 hours is the recommended time of shake out for most castings. The only concerns then are ability to handle the sand + casting mass, the ease with which sand separates out from the castings,any thin parts or projections that might crack or break.

Since all the castings undergo homogenizing heat treatment, time of shake out will not be a predominantly controlling factor. Floor space and ability to turn around the casting in a short time will be important.

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

 

[stanislasdz]

thanks arunmrao !

But is there any relationship bettwen time of shake out and some foundry defects like :

- hot teraing
- Rock candy
- crack under riser

ps: sorry my english is so poor !!!!!

 

[arunmrao]

time of shake out does not have any influence on rock candy fracture or under riser cracks.

hot tear can occur due to hot shake out as the metal may not have sufficient strength to withstand the thermal and mechanical stresses.

but on the contrary there have been instances when a deliberate hot shake out has been done to avoid the hot tears. This is when you have very thin sections and large sand mass surrounding this section and it is a constraint for it to shrink during cooling.

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

 

[stanislasdz]

But Rock Candy fracture depend on the colling rate and if we shake out the part early we can increase the colling rate and then decrease the risk of the rock candy fracture

 

[arunmrao]

Understanding 'rock candy' fracture in steel castings.
By Dutcher, Daniel E.
Publication: Modern Casting
Date: Monday, February 1 1999

Avoiding Aluminum Nitride Embrittlement in
Steel Castings for Valve Components

http://www.flowserve.com/vgnfiles/F...tLiterature/FlowControl/Edward/V-REP 84-1.pdf

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

 

[stanislasdz]

Arunmmrao : thanks a lot ! this is wonderfull paper !
thanks again !