DRUŠTVO LIVARJEV SLOVENIJESLOVENIAN FOUNDRYMEN SOCIETY
Član The World Foundry OrganizationMember of World Foundry Organization

Recent advances in understanding the metal-casting processes into green sand moulds have indicated that reoxidation plays a key role in the quality control of castings. As the liquid metal enters the mould cavity, thermal degradation of binders, water, and additives produces large quantities of gases and vapours. Air oxygen, mould atmosphere or oxides in the moulding sand can reoxidize the metal fl ow. Imperfect filling of castings induces agitation of the metal fl ow with oxygen present in gases and vapours, which results in secondary oxidation or the so-called metal reoxidation. Reoxidation processes in liquid metal can cause a number of defects in iron and steel castings.

The production of vermicular cast iron [compacted graphite cast iron] by the method of restricted or exact addition of magnesium treatment alloy is diffi cult due to the very narrow range of residual Mg, which is often less than  ± 0,001%. The microstructure of vermicular cast iron is highly sensitive to the solidifi cation conditions of the casting (section thickness, i.e. cooling intensity), chemical composition and inoculation, which requests process optimization and strict control of production parameters with the purpose of obtaining the requested properties of vermicular iron castings.
In this paper the infl uence of chemical composition of treated melts, fading of Mg during pouring, section thickness (cooling intensity) and inoculation on obtained microstructure properties and hardness of the vermicular cast iron samples (castings) have been analyzed.
Key words: vermicular [compacted graphite] cast iron, microstructure properties, production parameters

With MAXXALLOY ®, a family of premium diecasting alloys is introduced. The latest family member MAXXALLOY ®-ultra enables the production of diecasting parts with the mechanical properties of 6082 alloy forgings. This goal can be achieved without the necessity of a thermal treatment.
A further possibility for saving the heat treatment is the use of self-hardening alloys. These alloys of the type AlZnSiMg are known under the name “UNIFONT ®”. Castings made from UNIFONT ® reach in the hardened condition high values of tensile strength and yield strength, the poor ductility, however, limits the application of the alloy. With a reduced Zinc content elongation is improved, which is connected, however, with a loss of tensile strength and proof stress. UNIFONT ® can be used in diecasting as well as in permanent mould casting.
Without a heat treatment, for many applications the mechanical properties of AlSiMg type alloys are not satisfactory. Now with the newly developed SST heat treatment process, it is possible to reach a drastic increase of the elongation with only slightly lowered strength and a clear reduction of costs at the same time. Firstly developed for diecastings and thixoformed parts, it was found that also the mechanical properties of permanent mould castings and counterpressure castings will be signifi cantly improved. This process can be used also for parts cast from the natural ageing alloy UNIFONT ® to improve ductility.
Key Words: Diecasting alloys, aluminium magnesium alloys, self ageing alloys