Manufacturing Technology of Crankshaft
Crankshaft manufacturing technology
crankshaft yes the most important part of the engine. It bears the force transmitted by the connecting rod and converts it into torque to output through the crankshaft and drive other accessories on the engine to work. The crankshaft is subjected to the combined action of the centrifugal force of the rotating mass, the periodically changing gas inertial force and the reciprocating inertial force, which makes the crankshaft bear the action of bending and torsion load. Therefore, the crankshaft is required to have sufficient strength and rigidity, and the surface of the journal must be wear-resistant, work evenly, and have good balance.
In order to reduce the mass of the crankshaft and the centrifugal force generated during movement, the crankshaft journal is often made hollow. Oil holes are opened on the surface of each journal to introduce or export oil to lubricate the journal surface. In order to reduce stress concentration, the joints of the main journal, crank pin and crank arm are all connected by transitional arc.
The function of the crankshaft counterweight (also called counterweight) is to balance the rotating centrifugal force and its moment, and sometimes it can also balance the reciprocating inertial force and its moment. When these forces and moments themselves reach equilibrium, the counterweight can also be used to reduce the load on the main bearing. The number, size and placement position of the counterweight should be considered according to factors such as the number of cylinders of the engine, the arrangement of the cylinders, and the shape of the crankshaft. The counterweight is generally cast or forged with the crankshaft. The counterweight of high-power diesel engine is manufactured separately from the crankshaft and then bolted together.
obtaining high temperature and low sulfur pure molten iron is the key to produce high quality ductile iron. The domestic production equipment is mainly cupola, and the hot metal is not pre-desulfurized; The second is high purity pig iron less, poor coke quality. The hot metal is melted by cupola, desulfurized outside the furnace, and then heated and adjusted in an induction furnace. In China, the detection of molten iron composition has been widely carried out by vacuum direct reading spectrometer.
the airflow impact molding process is obviously better than the clay sand mold process, and high-precision crankshaft castings can be obtained. The sand mold produced by this process has the characteristics of no rebound deformation, which is particularly important for multi-turn crankshafts. Some domestic crankshaft manufacturers have introduced airflow impact modeling technology from Germany, Italy, Spain and other countries. However, only a few manufacturers have introduced the entire production line.
electroslag remelting technology is applied to the production of crankshafts, so that the performance of cast crankshafts may be comparable to forging performance. And it has the characteristics of fast research and development cycle, high metal utilization rate, simple equipment and superior product performance.
the automatic line with hot die forging press and electro-hydraulic hammer as the main engine is the development direction of forging crankshaft production. These production lines will generally use precision shear blanking, roll forging (cross wedge rolling) billet, intermediate frequency induction heating, finishing hydraulic press and other advanced technologies, at the same time equipped with manipulators, conveyor belts, mold change devices with turntable and other auxiliary machines, forming a flexible manufacturing system (FMS). Through FMS, workpieces and molds can be automatically replaced and parameter adjustment can be automatically performed, and continuous measurement during work. Display and record data such as forging thickness and maximum pressure and compare them with fixed values, and select the best deformation to obtain high-quality products. The whole system is monitored by the central control room to realize unmanned operation. The crankshaft forged by this forging method has the full fiber property of internal metal streamline, which can improve the fatigue strength by more than 20%.
crankshaft rough machining will widely use CNC lathes, CNC internal milling machines, CNC broaching machines and other advanced equipment for CNC turning, internal milling, turning-broaching processing of main journals and connecting rod journals, in order to effectively reduce the deformation of crankshaft processing. Crankshaft finishing will widely use CNC-controlled crankshaft grinder to finish grinding its journal. This grinder will be equipped with an automatic dynamic balancing device for grinding wheels, the center frame automatic tracking device, automatic measurement, automatic compensation device, automatic grinding wheel dressing, constant linear speed and other functional requirements to ensure the stability of grinding quality. The status quo of high-precision equipment relying on imports is not expected to change in the short term.
intermediate frequency induction hardening of crankshaft
crankshaft intermediate frequency induction quenching will adopt microcomputer monitoring closed-loop intermediate frequency induction heating device, which has the characteristics of high efficiency, stable quality and controllable operation.
for mass-produced crankshafts, in order to improve product quality, a microcomputer-controlled nitrogen-based atmosphere gas soft nitriding production line will be used in the future. The nitrogen-based atmosphere gas soft nitriding production line consists of a front cleaning machine (cleaning and drying), a preheating furnace, a soft nitriding furnace, a cooling oil tank, a rear cleaning machine (cleaning and drying), a control system, a gas-making and gas distribution system.
Crankshaft Surface Strengthening Technology
ductile iron crankshaft fillet rolling strengthening will be widely used in crankshaft processing. In addition, composite strengthening processes such as fillet rolling strengthening and journal surface quenching will also be widely used in crankshaft processing, forged steel crankshaft strengthening method will be more use of journal plus fillet quenching treatment.
