| 摘要 |
The present invention has provided a welding forged steel single piece piston and its manufacturing methods. A semi-finished head and a semi-finished skirt are forged respectively; the semi-finished head and semi-finished skirt are heat-treated respectively; rough machining is carried out respectively to the semi-finished head and the semi-finished skirt, and a face of weld between the two adjacent ring grooves is higher than the one under the combustion chamber; the head and the skirt are welded together through friction welding; an annular groove, a combustion chamber, a ring groove, a pinhole, an outer annulus and oil inlet/outlet holes are manufactured respectively; and the surface of the piston is phosphorized and graphitized. Compared with one-piece forged piston, it has better processing technology, because the head and skirt are forged respectively and then welded together. Over-all structural rigidity of the piston has been increased, and distortion of the ring groove in high temperature is slight because the cooling oil recess is sealed through welding. As the annular groove is located on the upper part of skirt, the weight of body of the piston is lowered and this kind of structure can accelerate engine oil returning on, decrease the clearance between the piston and the cylinder and reduce the engine oil consumption.
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