The Challenge of Foundry Defects:
At the heart of every foundry lies a crucial challenge: producing components free from defects. From porosity to inclusions, the quest for perfection is an ongoing battle. Foundry are always targeting to achieve defect-free castings and eliminating impurities formed during melt treatment and casting process. In case of Spheroidal Graphite (SG) iron production, during magnesium (Mg) treatment, a lot of slag and unwanted impurities are produced (Namely Slag and Dross).As term slag is commonly known in foundry, dross is defined as endogenous Magnesium silicate (namely Mg and Si) formed by oxidizable elements with oxygen, due to lower densities than molten iron both dross and slag are found near top region or near gating area. .If they are not removed properly, the cast component will fail in service as these defects initiate fatigue crack propagation.. Foundries are extremely keen to adopt a green and commercially viable technology to control such defects. But what if the process took care of the foundry defects….? Process selection is very important for getting defect free components based on the critical applications. For example the components for critical application contain these foundry defects namely slag and dross which for was not detected, the casting will fail in service as slag will compromise the component integrity and will also lead to more maintenance as the mechanical property of the material is reduced due to dross. So It is always better to choose an apt process for critical applications and minimise your risk by reducing your downtime and critical failure. Now let us see how the centrifugal process ensures your components are defect free…
Fig 1: SG iron with slag and Dross Fig 2: SG iron at 100x Etched
The Science Unveiled:
Vertical centrifugal casting of nodular graphite iron (SG Iron) is not your regular casting method; it's a conjunction of physics and precision engineering. Picture this: After setting the composition and stringent pouring temperature, the melt is poured into a pre-heated mould in vertical axis above the critical speed which is pre determined based on the mould size and composition of the melt, thus creating a enough centrifugal force ,guided by this force the slag, blow holes which arises near mould wall and other impurities are segregated from mould wall towards the spinning vertical axis based on the specific density.
Along with this, melt is also reflected from the mould wall which causes turbulent inflow, as solidification progresses, the tip of dendrite gets fragmented which moves towards the center region where if the conditions are favorable results in crystal multiplications, ultimately resulting in grain size refinement. As the mould is also preheated, it promotes slower or controlled solidification based on critical thickness which also promotes secondary columnar grains to become more broader and prominent along with equiaxed grains to become finer. This ensures the components cast through centrifugal casting process are defect free and boasts a higher mechanical strength.
It's precision engineering at its finest, and the results speak for themselves. (Our Technical team, did a SPC study on EN-GJS-500-7C, we got a 20%-60% higher mechanical property)
Most Recently, Vijay Spheroidals presented a Technical paper at the Transactions of IIF’s 72nd Indian Foundry Congress, which was held at IFEX 2024 at Bangalore. So this paper delves into the effectiveness of centrifugal force on the casting process in removing slag and other impurities in Spheroidal Graphite (SG) iron castings (IS 1865:1991) of size 120 x 120 x 500 mm. It also reports the changes in (a) optical microstructures and (b) mechanical properties of Spheroidal Graphite (SG) iron castings (IS 1865:1991) of size 120 x 120 x 500 mm.
Ready to Embrace defect free components?
By now you're probably itching to dive headfirst into the world of vertical centrifugal casting. But where do you begin? Fear not, for we're here to guide you every step of the way. With decades of experience in the field of metallurgy, we're not just a company – we're your metal expertise in your critical applications. Schedule a consultation with us today, and let's explore the possibilities together. From design to delivery, we're committed to delivering casting solutions that exceed your expectations. The future of foundry excellence awaits – are you ready to seize it?
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