A research group led by Choe Kyong Chol, a lecturer at the Faculty of Materials Science and Technology, has established a casting process of a backing roller for a cement kiln on the basis of an effect analysis of factors on the quality of large steel castings.
For its design, two things should be taken into consideration ― it is a large and massive steel casting (tens of tonnes) and its thick walls could cause mass effect.
Therefore, what is important for the establishment of casting processes is proper design of casting plans, design of inner chill, selection of molding material and inoculation of molten metal.
They considered the contraction amount as 1.8% according to the chemical composition of a backing roller to calculate the gating system and they used ProCAST2016 to simulate the flow and solidification of molten metal to design a proper casting plan.
Both riser and chill were used at the same time to ensure directional solidification due to the great height of castings.
The weight of inner chill was set to be 2% of pouring weight of casting and its dimensionφ20mm in diameter.
Rahung silica sand was used as molding material (about 5mm in diameter). The coating was made by magnesia clinker (about 2mm in thickness).
Boron, titanium and rare earths were added to the molten metal to raise the quality of a backing roller and to reduce mass effect.
The backing roller has a tensile strength of over 550 MPa, an elongation of 12% and a hardness of about HB180.
This casting process can be used for manufacturing massive large steel castings.
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