RD&D-Programme 2004 - SKB

Figure 5-3. Graphite shapes in cast iron according to EN-ISO 945. The dominant graphite shape
in nodular cast iron is no VI (nodular graphite).
cast iron in the finished product. The best agreement is obtained in the casting of small pieces.
The advantage of cast-on test bodies is that they can be sawn of off the component without
damaging it.
During the development work, SKB studied the material properties obtained in both cast-on
test bars and discs cut from the insert itself. The inserts were cast with extra length so that a cut
disc could be evaluated from the top of the insert. The extra length has made it possible to make
inserts of the specified lengths despite removal of the disc. However, some inserts were cut
up so that additional discs along the legnth of the inserts could be used for extensive material
testing.
A number of nodular irons are internationally standardized in SS-EN 1563. The standard
makes no requirements on chemical composition. But it does state that the graphite shape
shall essentially correspond to shapes V and VI. Specified requirements are made on the
mechanical properties of castings of different sizes. SKB’s canister inserts represent a much
thicker-walled casting than has been stipulated in this standard. However, the standard leaves
open the possibility that specific material requirements can be agreed on with the supplier in
each individual case. Precise material requirements that ensure that the inserts meet the design
requirements can be established when relevant strength calculations and verified compression
tests have been carried out in accordance with the following programme.
Conclusions in RD&D 2001 and its review
In RD&D 2001, SKB concluded that the mechanical properties of the nodular iron are highly
dependent on the dimensions of the cast body. Material testing must therefore be performed on
the finished inserts.
50 RD&D-Programme 2004