Ductile-iron castings commonly have problems with porosity or micro porosity caused by shrinkage taking place during the solidification process. To counter this problem, foundries frequently increase the capacity of the casting riser, wasting iron and increasing casting costs.
Elkem’s Lamet® magnesium-ferrosilicon – which will be featured in Elkem’s CastExpo booth this April – takes a more reliable and cost-effective approach. Containing lanthanum, this nodularising alloy often eliminates shrinkage entirely while the magnesium converts graphite into small, randomly-distributed nodules. This structure is needed to obtain the higher ductility and improved mechanical properties typical of ductile-iron castings.
Optimum magnesium recoveries and costs from nodularising additions of Lamet® magnesium-ferrosilicon can be obtained when the alloy is used in an Elkem computer-designed pocket in the ladle -- together with Elkem’s specialty cover alloys, such as Topseed® conditioner. The pocket and conditioner delay the molten iron from reaching the magnesium until the ladle is almost full of iron. As a result, the magnesium has greater exposure to iron as it travels up through the ladle, increasing magnesium recoveries significantly.
In addition, Elkem’s Lamet® magnesium-ferrosilicon helps produce a structure without the iron carbides or “chill” that can reduce machinability. For greater assurance that castings will not have any hard carbides, Elkem offers several specialty inoculants designed for ductile iron. One of the most effective is Ultraseed® inoculant – an alloy that is available in four grades designed to improve nodularity and reduce micro shrinkage in addition to strong chill reduction.
Elkem will display automotive SiMo ductile-iron exhaust manifolds at its CastExpo booth #1707 in Atlanta, Georgia from April 27-30, 2019. These castings were nodularised with Lamet® magnesium-ferrosilicon and inoculated with Ultraseed® Ce and Alinoc® inoculants. In addition, casting producers and users can meet Elkem’s technical team to discuss which of Elkem’s complete line of specialty inoculants, nodularisers, cover alloys, preconditioners, and ferrosilicon best fits their foundry practices. They can also contact Elkem at www.elkem.com for further information.