Split Tilting Smelting Furnace

Split tilting smelting furnace working sequence — nine stages from the two-part layout and the separation that fixes the lead length, through the pivot axis that sets the moment and the drive that carries it, to the interlocked rotation, the pour geometry and a closed heat record.

Steps 1 — Separation Distance and Two-Part Layout. Nothing is fixed before the distance between the power cabinet and the vessel is decided, because that distance is an electrical quantity before it is a layout quantity. The conductor from the inverter to the coil carries the highest current in the station, so every metre added to it contributes inductance and voltage drop to the circuit that delivers power to the metal. The separation is set by three things at once: the room a crucible or shell change needs between the two units, the bending radius the flexible connection requires at the extreme of the sweep, and the shortest lead the electrical design will accept. Input: connected load and highest-current circuit, change-out clearance, sweep envelope, conductor bending radius, spill zone. Output: a fixed separation with the lead length, cable route and change-out clearance recorded.

Steps 2 — Pivot Axis and Centre-of-Gravity Setting. This is the decision that cannot be corrected later without rebuilding the frame. The moment the drive must hold is the mass of the loaded vessel multiplied by the gravitational constant and by the horizontal distance from the axis to the centre of gravity of that vessel, so moving the axis towards the centre of gravity reduces the drive duty at the start of the pour. The same movement increases the angle through which the vessel must rotate before its lip comes over the mould and before a retained heel reaches the lip, which delays the pour and lowers the pour rate at any given tilt rate. The centre of gravity is established for the loaded vessel rather than the empty one. Input: loaded vessel mass, crucible and refractory geometry, metal depth and its movement through the sweep, mould line and lip height, retained heel. Output: an axis position with its distance from the centre of gravity, the worst-point moment and the total sweep angle recorded.

Steps 3 — Tilt Moment Rating and Drive Selection. With the moment known, the drive is placed on the ladder rather than chosen by habit. Published practice puts a manual lever or handwheel at or below about one hundred kilograms of charge, a motorised or reducer drive from about one hundred to about five hundred kilograms, and hydraulic cylinders from about five hundred kilograms upward to several tonnes. The drive is rated on the worst moment of the cycle, the attitude at which the lever arm from the axis to the centre of gravity is longest, with a margin for pivot friction and for a stiffened charge. A hydraulic drive adds proportional valving, a main pump with a backup and inlet throttle or check valves so a loss of pressure does not let a full vessel fall; a manual or motorised drive adds a self-locking or brake arrangement. Input: worst-case moment, pivot and trunnion friction, charge and vessel mass, intended pour precision, availability of hydraulic power. Output: a drive type and rating with its hold-with-power-off behaviour, control arrangement and published capacity band recorded.

Steps 4 — Flexible Power, Water and Signal Routing. The separated machine has one point that moves and one that does not, and everything crossing between them has to survive the movement. The power connection at the vessel is a flexible, water-cooled conductor with a strain relief at each end, sized on the current the coil actually draws rather than the cycle average, and arranged in a loop whose radius stays above its minimum bend radius at every point of the sweep. The cooling circuit crosses the same hinge, so the hose routing and the leak detection are laid out so a failure cannot discharge water into the metal or onto the electrical cabinet. Input: coil current and conductor size, minimum bend radius, cooling flow, pressure and return temperature, strain relief and loop geometry, leak detection at the hinge. Output: a routed flexible connection with its bend radius, strain reliefs, conductor lengths and protection against catching recorded.

Steps 5 — Tilt Limit, Interlock and Control Setting. The rotation has to be stopped by something that does not depend on the operator’s judgement, and it has to be stopped twice. A limit switch removes the drive at the set angle; a mechanical stop behind it carries the load if the switch is missed, so the two protections do not share a failure. The command is hold-to-run rather than latched, and the set angle comes from the pour geometry rather than the drive’s capability. The interlock schedule is written against the failure modes of a tilting vessel: no tilting with the cover, guard or spout out of position, no tilting into a mould that is not in place, no charging while tilted, and a defined state for a command that sticks on a full vessel. Input: set angle and a second mechanical limit angle, limit switch type and redundancy, hold-to-run arrangement, lid, guard and spout interlocks, emergency tilting sequence. Output: a documented interlock schedule with set angles, proven trip tests and emergency procedure recorded.

Steps 6 — Spout Geometry and Pour Stream Setting. The pour is a rotation, so the stream is a geometry problem rather than a valve problem. Pour rate is the tilt rate in degrees per second multiplied by the sweep of metal surface passing the lip in that rotation, so the rate is set by how fast the vessel turns and how much surface faces the lip at the angle from which the pour starts. The lip is positioned so the stream leaves on the same line as the angle changes, the drop height from lip to mould is kept low and constant, and the spout can be replaced or dressed because a worn lip scatters the stream. The start angle is chosen with the retained heel in mind. Input: crucible bore and metal surface geometry, intended tilt rate and range, retained heel, mould position and preheat, lip height above the mould, spout material. Output: a pour recipe per alloy and per mould with the start angle, tilt rate, lip-to-mould height and release temperature recorded.

Steps 7 — Crucible Seating and Split Change-Out Fit. The reason to separate the power section from the vessel is that the crucible and the refractory shell have to be reachable, so the seating is designed around the change rather than the melt. The crucible sits in a shell or support whose sections can be released without dismantling the coil, the electrical assembly or the tilt mechanism, and the axis alignment is maintained by the frame rather than the crucible, so a change does not require the axis to be re-set. The change is rehearsed at commissioning and timed, and the boundary between a wear part and a warranty item is drawn before the order. Input: crucible grade and seating, shell sections and fixings, lining and cement, axis alignment arrangement, tilt mechanism clearance, lifting provision for a loaded vessel. Output: a rehearsed change-out procedure with its measured duration, a consumables schedule with expected lives and an axis alignment record.

Steps 8 — Melt-Down, Rocked Skimming and Hold. Melting runs on the same physics as any induction crucible, but the tilting vessel adds an operation a fixed furnace does not have. Because the vessel can be rocked to a shallow angle, the dross and slag floating on the metal can be walked to the lip and skimmed off deliberately rather than chased around a level surface, so the metal left behind is cleaner at the moment it is poured. The power programme is written per alloy with its soak points, the charge is fed so it does not bridge above the pool, and because a split machine keeps its power section at floor level, the coolant temperature, the flexible conductor and the cabinet interior are watched during the melt as part of the same routine. Input: power programme per alloy, charge form and feeding sequence, flux, cover or gas blanket, rocked-skimming angle, superheat ceiling, a sample for composition verification. Output: a molten, homogenised, skimmed pool at a verified temperature and composition, with the cycle time and energy used recorded.

Steps 9 — Pour, Return and Turnaround Closure. The pour is executed as a recipe rather than a movement: the mould is preheated to its setting, the vessel is brought to the start angle, the tilt rate is run at its recorded value, and the rotation is stopped when the mould is full or the pour target reached. Because pour rate is the tilt rate times the surface sweep at the lip, a slow pour is produced by rotating slowly and not by interrupting the stream, and a pour stopped and restarted leaves a mark on the cast surface the next operation has to remove. The vessel is returned to level under control, the skull and the skimmed dross are recovered, weighed and assayed, the pour angle and tilt rate actually used are written into the heat record, and the station is reset with the tilting mechanism inspected on its own schedule. Input: pour recipe per alloy and per mould, mould preheat, tilt rate and start angle, return sequence, crucible wear inspection, tilting mechanism inspection, consumables schedule. Output: cast bars or ingots released against the heat record, a closed charge-to-product balance with the skull and dross ascribed, and a furnace reset for the next heat.