Crankshaft Manufacturing Technology
|The crankshaft is one of the key components of an automobile engine, and its performance directly affects the life of the vehicle. The crankshaft is subjected to large loads and changing bending moments and torques. The common failure modes are bending fatigue fracture and journal wear. Therefore, the crankshaft material is required to have high rigidity and fatigue strength as well as good wear resistance.|
For the melting of high-grade cast iron, a large-capacity intermediate frequency furnace will be used for smelting or variable-frequency intermediate frequency furnace smelting, and a direct reading spectrometer will be used to detect the molten iron composition. The spheroidal cast iron treatment adopts subcontracting to develop a new variety of spheroidizing agent, and adopts advanced gestation methods such as gestation, intra-inoculation and compound gestation. The parameters of the melting process enable microcomputer control and screen display.
Lost foam casting will be developed and promoted. In sand casting, boxless injection molding and extrusion molding will be valued and will continue to be promoted in new or rebuilt plants. The original high-pressure molding line will continue to be used, and some of the key components will be improved to achieve automatic core and lower core.
The automatic line with hot forging press and electro-hydraulic hammer as the main engine is the development direction of forged crankshaft production. These production lines will generally adopt precision shearing, roll forging (cross wedge rolling), medium frequency induction heating and so on.
Crankshaft roughing will use CNC lathes, CNC internal milling machines, CNC broaching machines and other advanced equipment to perform CNC turning, internal milling and car-broaching on the main journal and connecting rod journals to effectively reduce the deformation of crankshaft machining. Crankshaft finishing will be extensively ground with a CNC-controlled crankshaft grinding machine.
The grinding machine will be equipped with the automatic dynamic balancing device of the grinding wheel, automatic tracking device of the center frame, automatic measurement, automatic compensation device, automatic dressing of the grinding wheel, constant line speed and other functional requirements to ensure the stability of the grinding quality. High-precision equipment relies on the status quo of imports and is not expected to change in the short term.
Heat treatment technology and surface strengthening technology
(1) Crankshaft medium frequency induction hardening
The medium frequency induction hardening of the crankshaft will adopt the microcomputer monitoring closed-loop medium frequency induction heating device, which has the characteristics of high efficiency, stable quality and controllable operation.
(2) Crankshaft soft nitriding
For high-volume production of crankshafts, in order to improve product quality, a microcomputer-controlled nitrogen-based atmosphere gas soft nitriding line will be used in the future. The nitrogen-based atmosphere gas soft nitriding production line consists of a front washing machine (cleaning and drying), a preheating furnace, a soft nitriding furnace, a cooling oil tank, a post-cleaning machine (cleaning and drying), a control system, and a gas-making gas distribution system.
(3) Crankshaft surface strengthening technology
Ductile iron crankshaft fillet rolling strengthening will be widely used in crankshaft machining. In addition, the composite strengthening process such as round roll rolling strengthening and journal surface quenching will also be widely used in crankshaft machining. Forging steel crankshaft reinforcement will be more The ground is rounded and quenched.
The main reason for crankshaft fracture:
- (1) Long-term use of engine oil deteriorates; severe overload and over-hanging cause long-term overload operation of the engine and burnt tile accidents. The crankshaft is severely worn due to the burning of the engine.
- (2) After the engine is repaired, the loading has not passed the running-in period, that is, the overload is overloaded, and the engine is overloaded for a long time, so that the crankshaft load exceeds the allowable limit.
- (3) Surfacing welding is used in the repair of the crankshaft, which destroys the dynamic balance of the crankshaft, and does not perform balance check. The unbalanced amount exceeds the standard, causing large vibration of the engine and causing the crankshaft to break.
- (4) Due to poor road conditions, the vehicle is seriously overloaded and over-suspended. The engine is often in the critical speed of torsional vibration, and the damper fails, which will also cause the crankshaft torsional vibration fatigue damage and break.
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