So, in cranks of crankshafts from 20G steel of powerful ship diesels quality of the ESC metal of the cheeks and crankpins in the melting together zone after annealing and subsequent normalization with tempering significantly exceeds that of the metal of cranks, manufactured by conventional casting, not just in regard to strength, ductility, and toughness , but also in regard to fatigue strength , whereby properties of the metal in the melting together zone don't differ at all from those of the electroslag cast metal of the cheeks, which was not subjected to overheating.
Mass of electroslag casting billet of the crank is about 5 t, and diameter of the crankpin is about 0.
First billet of the cheek with a crankpin in the form of a boss is melted (Figure 1, a).
Crankpin grinding using an indexing-type cylindrical grinder involves rotating the crankshaft in a fixture in which the shaft's main bearings are offset by one-half the distance of the stroke while the crankpin sidewalls, radii, and diameter are plunge-ground using a wheel dressed to full width.
Indexing crankpin grinders inherently lack flexibility due to their mechanical nature.
Because a conventional wheel typically begins breaking down at the corners midway through the sidewall plunging operation, frequently the grinding cycle must be interrupted to complete a dressing operation prior to grinding the radii and the crankpin OD.
Extensive testing and actual production experience have shown this approach to be significantly better than conventional processes in holding crankpin geometric tolerances, as well as shaft index and throw, which are critical to controlling diesel emissions.
Rejected parts are unloaded through a chute, and good parts transported to the crankpin grinding operation via elevator.
For example, a new single-crankhead and crankpin holding fixture (one per unit) with hydrostatic spindle bearings eliminates the need for dual crankheads and eliminates alignments necessary with dual crankheads.
Crankpin rough grinding is performed at 120 rpm, and finish grinding at 84 rpm.
etj] = frictional force between the piston and crankpin