Nodular cast iron plunger pump block

In the hydraulic system, the most important function similar to the “heart” is the high-pressure plunger pump, which is also a core component used to form high-end hydraulic equipment. By 2017, the scale of China’s hydraulic industry has ranked second in the world, with large output, but the technology is still in a low-level state. In terms of the selection of plunger pump, China still chooses the imported 35 MPa high-pressure plunger pump. At present, some high-performance products of axial piston pump are mainly manufactured by Rexroth, Linde, Parker, Eaton, density and other foreign enterprises. In addition to these enterprises, some manufacturers mainly engaged in construction machinery in Japan also develop piston pump products independently, such as Mitsubishi, Kawasaki, Toshiba and Komatsu. Therefore, compared with foreign countries, the piston pump produced in China has a great gap in terms of reliability, advanced technology and service life.

As shown in the figure is the structure of friction pair of swash plate axial piston pump. There are three friction pairs in the figure, which are slipper swash plate, port plate cylinder body and cylinder block plunger. The end face of the cylinder block and the port plate is called the oil distribution surface. The plug hole and the surface of the plunger constitute a moving sealing surface. When the piston pump is working, the two parts move at a relatively high speed under high hydraulic pressure. The gap size and material between the two affect the performance and life of the piston pump. In the traditional process, the two pairs of friction pairs are made of materials with different soft and hard degrees. Therefore, hard materials are generally used to make plunger and oil distribution plate, while soft materials are used to make corresponding surface of cylinder block.

Through the research of Xu Tianyi and Qian Xiaohao, it is shown that the nodular cast iron is a good material for plunger pump cylinder block. After the traditional friction pair structure is changed, the manufacturing process is simplified and casting defects are reduced on the basis of improving the performance of cylinder block and oil distribution plate, cylinder block and plunger friction pair. Therefore, in this experiment, lzqt600-3 ductile iron was selected as the experimental material.