· Moldes y machos ·
Alexander Brown
James Durrans and Sons Limited, UK
67th World Foundry Congress
The need for control of raw materials is critical to the success of iron
casting production from greensand systems. The base silica sand is often
overlooked with the main focus on bentonite additions. Carbonaceous
additives can be considered a “necessary evil” to ensure a good surface
finish and reduction in sand related surface defects. Other additives are
used when systems get out of balance and these in turn add further to the
complex nature of greensand systems.
For castings requiring cores this becomes a
bigger issue, as many differing resin systems
are employed for core production and these
must be taken into consideration when
controlling both the carbonaceous levels and
the overall grading of the sand system.
Possible changes on the loss on ignition
properties and the effect on the carbon level
needs careful understanding and control.
Various test methods are discussed including volatile and loss on ignition
(LoI), and control methods such as total carbon are reviewed.
The quality of additives and their role and more
importantly their interaction is highlighted, as
this is an area often neglected as foundrymen
battle for success to produce consistent quality
castings. The use of automatic mill control has
simplified the production of usable moulding
sand but this cannot replace the correct
balance of additives and having sand at the
mill, prior to additions, in the optimum condition
Also reviewed is the interpretation of results and the action required to
ensure control for consistent quality castings from greensand systems,
with the focus on the use and understanding of carbonaceous additive on
casting performance.
