Influencing Factors on Premature Fracture of Cast Iron Support of Electric Motor in Aluminium Rolling Line

• Published in: IOP conference series. Materials Science and Engineering 2020-06, Vol.877 (1), p.12023
• Main Authors: Preda, F, Riposan, I, Stan, S
• Format: Article
• Language: English
• Subjects: Aluminum; Cast iron; Casting defects; Damping capacity; Electric motors; Fracture toughness; Graphite; Inclusions; Inoculation; Low level; Morphology; Pinhole defects; Pinholes; Vibration damping
• ISSN: 1757-8981; 1757-899X
• DOI: 10.1088/1757-899X/877/1/012023

There is a limited increase in the temperature of the cast iron supports during rolling (up to 30...50°C), but there is a wide range of vibration level (2.6 - 4.4 mm/s) representing 58-98% (75-80% as medium values) from the maximum admitted level (4.5 mm/s, ISO 10816). The maximum level of vibration is identified in the area where a fan is installed to cool the electric motor. In all electric motor types it appears a difference between several measurements, which highlights the appearance of various conditions in the rolling process, or in the quality of the cast iron support. The fracture of the support takes place predominantly in the area of fixing it with a screw. The cracks connect firstly the areas with casting defects (inclusions, pinholes, shrinkage and micro-shrinkages), but also coarse graphite particles (Kish or Type C-ASTM, spiky graphite) or undercooled graphite morphologies (Type-D ASTM). Lamellar graphite cast irons (traditionally used in this domain) are characterized by a low level of fracture resistance but high vibration damping capacity due to which it is necessary to make parts without casting defects and with a controlled graphite phase (high amount of graphite, graphite Type-A ASTM, without undercooled graphite), usually obtained through high performance inoculation [1,2].