WeldGk
From my perspective, it sounds like the grated test coupon you mention is really a separate multiple (bend bar) keel block test coupon, and the integral cast test coupon is what it is, test coupons which are cast integrally with the castings.
Source of the above - none other than ASTM A 703 "Steel Castings, General Requirements, for Pressure-containing Parts"
I'm not sure if I understand the question correctly. Do you mean integrally vs separately casted test coupons? The way I understand, gated test coupon is integraly-cast test coupon. Test bars usually are cast outside the mould, (Y-block or Keel block) as per ASTM specifications, and I don't think there's much difference other than convenience. Sometimes, (customer requirements or other reasons) test bars may be cast in the mould and attached to the casting, so the bars see the same thermal history as the casting.
The location of test coupons needs to be discussed in advance with the buyer and any 3rd party inspector. From a foundry point of view,it is simple to attach the coupon to the gating system,which can then be separated easily. also this arrangement does not impair the quality of the casting. But,this might involve,prior approval from the inspector. Also,since the casting and test coupon are separated,it may be possible that there could be differences in heat treatment.
Attaching a test coupon on to a casting,demands proper location of the test block in the mould. This may need larger mould boxes,also if it is not suitably attached,to the casting,casting zone near the test bar can indicate signs of porosity due to improper feeding( This is more due to poor foundry practice). From an inspector's point of view the test coupon remains attached to the casting,through it's complete process cycle and can only be separated at the stage of final inspection.
Hope, I have not complicated a simple issue.
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"The richer we have become materially, the poorer we have become morally and spiritually." Martin Luther King Jr
I agree with arunmrao. An integrally cast test coupon needs to be physically continuous with the casting. A gated test coupon would be separated from the casting by the gating system. Both methods would ensure that the casting and the coupon were poured using the same metal, which you don't get with separately cast test coupons.
In addition to foundry process flaws, such as porosity, mentioned above, coupons cast from a separate gating system might show metallurgical differences vs coupons cut from the bulk material (destructive test). There are non-equilibrium factors at work during solidification. For example if coupons freeze more quickly, there may be grain size, directionality, and chemical segregation differences.
