Crankshaft manufacturing technology:
1. Casting technology of nodular cast iron crankshaft blank
(1) Smelting
Obtaining pure molten iron with high temperature and low sulfur is the key to producing high-quality ductile iron. Domestic production equipment is mainly cupola, and hot metal is not pre desulfurized; Secondly, there is less high-purity pig iron and poor coke quality. At present, the smelting method of duplex plus pre desulfurization has been adopted. The molten iron is melted in the cupola, desulfurized outside the furnace, and then heated up in the induction furnace and adjusted the composition. At present, the vacuum direct reading spectrometer has been widely used to detect the composition of molten iron in China.
(2) Styling
The air impact molding process is obviously superior to the clay sand mold process, which can obtain high-precision crankshaft castings. The sand mold made by this process has the characteristics of no rebound deformation, which is particularly important for multi crank crankshafts. At present, some domestic crankshaft manufacturers have introduced air impact molding technology from Germany, Italy, Spain and other countries, but only a few manufacturers have introduced the whole production line.
2. Forging technology of steel crankshaft blank
In recent years, China has introduced a number of advanced forging equipment, but due to the small number, coupled with mold manufacturing technology and other facilities can not keep up, some advanced equipment has not played its due role. On the whole, there are many old ordinary forging equipment that need to be transformed and updated. At the same time, backward processes and equipment still occupy a dominant position, and advanced technology has been applied, but it is not common.
3. Machining technology
At present, most domestic crankshaft production lines are composed of ordinary machine tools and special machine tools, with relatively low production efficiency and automation. Rough machining equipment mostly adopts multi tool lathe to turn crankshaft main journal and crank neck. The quality stability of the process is poor, which is easy to produce large internal stress, and it is difficult to achieve a reasonable machining allowance. Generally, crankshaft grinding machines such as mq8260 are used for rough grinding, semi fine grinding, fine grinding and polishing, which are usually operated manually, and the processing quality is unstable.
4. Heat treatment and surface strengthening technology
The key technology of crankshaft heat treatment is surface strengthening. Nodular cast iron crankshafts are generally normalized to prepare for surface treatment. Surface strengthening treatment generally adopts induction quenching or nitriding process. Forged steel crankshaft adopts the quenching process of journal and fillet. The imported equipment includes AEG automatic crankshaft quenching machine tool, EMA quenching machine tool, etc.