Application of Surface Layer Inoculation Processes to Solid Solution-Strengthened Ductile Cast Iron
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opyright 2020 The Author(s) https://doi.org/10.1007/s40962-020-00406-5
Abstract Within the present investigations, an in-mould inoculation method for ductile cast iron with elevated silicon contents was developed. The inoculation process takes place at the interface between the mould’s surface and the melt. The application of a mould wall inoculation process allows inoculation at the latest possible point in time, which means high efficiency due to reduced fading effects. For this purpose, various inoculant suspensions are produced, containing inoculants in different amounts and grain fractions. The inoculant is applied to the surface of a PEP SETTM-bonded moulding material by means of an airpressurized spraying pistol. The specimen geometry used in the tests is a 5-stepped wedge, which represents wall
thicknesses in the range of 5–40 mm. For a total of 8 castings, inoculant fractions in the spectrum of 0–25 and 0–45 lm are used to produce the solid solution-strengthened grade EN-GJS-500-14 that is specified in the European standard EN 1563. Metallographic investigations show that a complete solidification according to the stable system can be adjusted in the investigated wall thicknesses by inoculation with grain fractions of 0–25 lm.
Introduction
silicon contents from 3.2 to 4.3 wt.%, significantly higher elongations can be achieved at the same tensile strength. In particular, Bjo¨rkegren et al.3 showed that by alloying with 3.74 wt.% Si elongations at fracture of 14% can be achieved at a set tensile strength of 500 MPa. Compared to conventionally ferritic–pearlitic cast iron grades, this means an increase in elongation at fracture of 100% without loss of strength. The specifications for the material grade EN-GJS-500-14 according to the European Standard EN 1563 are given in Table 1.4 Weiß et al.5 point out that due to alloying with alternative solid solution strengthening elements such as aluminium and nickel, the mechanical properties of these alloys can be further increased. Grades of high-silicon ductile cast iron are therefore particularly qualified for the use in higher loaded components and lightweight applications. Consequently, high-silicon
Modern cast iron grades of solid solution-strengthened ductile cast iron were incorporated into the European Standard EN 1563 in 2012. These are primarily characterized by their elevated silicon content, ranging from 3.2 to 4.3wt.% Si. Bjo¨rkegren et al.1 showed that an increased silicon content leads to a fully ferritic matrix, which results in both improved machinability and very good static mechanical properties. According to Lo¨blich,2 this is due to a more homogenous hardness distribution within the matrix. Furthermore, this alloy concept results in a widening of the interval between metastable and stable eutectic temperature. For this reason, the tendency to metastable eutectic solidification and the formation of cementite is significantly reduced. By alloying elevated
International Journal of Metalcasting
Keywords: cast iron, ductile cast iron, solid sol
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