Mechanical testing must be on parts or on coupons ?

[stanislasdz]

In foundry some costumers ask to do the mechanicals tests on coupons however other costumers ask to do theses tests on parts.

What is the best method ?

Because if we do this on coupons it depends on the positions and the size of the feeders. If we do this on parts it's not esay to sacrifie a part only for extracting à piece for mechanical testings

 

[metengr]

stanislasdz;
The method for conducting tests should be based on the applicable material specification. For example, ASTM A 703 or ASME SA 703 provide specific guidance for verifying mechanical properties of castings based on test bars or other coupons.

 

[arunmrao]

Most often the test samples are drawn from standard keel blocks which are cast separately. For purposes of identification a witness pour or stamping is often done. Also at times integral test bars are recommended.

These methods satisfy most of the inspectors.

However, in a few rare cases in the absence of sufficient test bars or if the section thicknes of the casting is too large so that the mechanical properties from keel block sample may not be a true representative, samples are drawn from a section of the casting. normally it is the heaviest section of the casting. But this issue will be discussed right at the beginning.

 

[dbooker630]

When a new cast part is being validated it is good practice to submit both separately cast tensile bars as well as coupons sectioned from an area of the casting agreeable to foundry and end user.

The tensile bar is the lot-to-lot process control; coupons subsequently are not necessarily required in production lots unless there is a problem with the tensile sample. The end user should specify in writing when the job is awarded exactly what is required in production.

 

[kenvlach]

Re "What is the best method ?"

The 'best method' is one that satisfies ASTM, ASME, etc. requirements, plus any additional customer requirements.
The specifications tell whether samples must be cut from cast parts, the required sample geometry and frequently give the sample location for different part geometries.

I suggest buying the Annual Book of ASTM Standards, Volume 01.02, January 2007, Ferrous Castings; Ferroalloys at

http://www.astm.org/cgi-bin/SoftCar...2007/01.02.html?L+mystore+jsgv4065+1169421158

Also buy the Steel Castings Handbook, 6th Edition

http://www.asminternational.org/Tem...=Ecommerce/ProductDisplay.cfm&ProductID=11274

The Steel Founders' Society Of America has free, downloadable supplements to the Steel Castings Handbook, 6th Edition. Go to

http://www.sfsa.org,

click on Publications, then Electronic Publications (Free). All seem useful; 'Test Coupons and Casting Properties' seems most relevant to this thread.

Also, from the LHS menu, click on Casting Design and Purchase. There are described general specifications on which customers & foundries must be in agreement.

 

[stanislasdz]

Thanks a lot for all for these nice answers