What is blocking the throat of China's equipment manufacturing industry?

2020-09-11

What's stuck in our necks——

"The scale of China's hydraulic industry has become the second largest in the world in 2017, but the industry is large and not strong, especially the high-pressure plunger pump with rated pressure above 35MPa, and more than 90% of it relies on imports. It can be said that the high-pressure plunger pump is a thorn in the throat of China's equipment manufacturing industry Recently, at Taichung Yuci Hydraulic Industry Co., Ltd., Chen Qunli, deputy general manager and senior engineer of the company, told the reporter of science and Technology Daily that "four foreign leading enterprises, such as high-performance plunger pumps and meideri, occupy more than 70% of China's market share, but they are strict with China in terms of technology."


Small parts, big power


High pressure plunger pump is the core component of high-end hydraulic equipment, which is called the "heart" of hydraulic system. Hydraulic system is one of the key components in the equipment manufacturing industry. It is widely used in agricultural and forestry machinery, chemical industry, light and textile machinery, energy industry machinery, metallurgical industry machinery, building materials industry machinery, machine tool industry, as well as military industry, aerospace, ships and so on. According to the relevant data statistics, 95% of the construction machinery, 90% of the CNC machining centers and more than 95% of the automatic lines in developed countries adopt hydraulic transmission technology. It can be said that all engineering fields, where there are mechanical equipment, are inseparable from the hydraulic system.

A complete hydraulic system consists of five parts, namely power components, executive components, control elements, auxiliary components and hydraulic oil. The function of power component is to convert the mechanical energy of prime mover into the pressure energy of liquid, which provides power to the whole hydraulic system. The structure of hydraulic pump is generally gear pump, vane pump, plunger pump and screw pump.

The high pressure plunger pump belongs to the power component. One of the important contributions to the successful flight test of China's domestic large aircraft C919, the world's largest 80000 ton die forging hydraulic press produced by China Erzhong Heavy Industries Co., Ltd., is a high-pressure plunger pump imported from the United States. Dozens of plunger pumps are driven by electric motors to pressurize the hydraulic oil and then push the oil cylinders to produce 80000 tons of forging pressure. Another example is the crawler walking of tanks, which relies on the internal combustion engine to drive the hydraulic pump, so that the oil is sent out through the oil pipe through the valve control, and the motor is driven into rotary motion, and then the crawler is driven. Most of the military machinery such as tanks and armored vehicles are imported high-pressure plunger pumps. Each of these imported hydraulic pumps costs more than 200000 yuan. The replacement and maintenance of these hydraulic pumps will be constrained by the supply cycle and service provided by foreign companies.


It is easy to be similar in shape but difficult in spirit


"To achieve a technological breakthrough in high-pressure plunger pump products, we must first achieve a breakthrough in high-end castings," Chen Qunli said

He said that all parts of the high-pressure plunger pump are "wrapped" in the casting shell. If the high-pressure plunger pump is the heart of hydraulic equipment, then the piston slipper pair can be regarded as the heart valve in this atrium. The cylinder bore and thrust plate matched with plunger and slipper are equivalent to the dynamic parts of "Atrium" and "ventricle". When they output power, they perform their respective duties. They are subjected to the most frequent impact and alternating stress, the maximum pressure, and the highest speed and acceleration. In addition to the characteristics of high hardness and wear resistance, these parts also rely on the high strength of casting shell Precision support.


"The high-pressure plunger pump will be impacted by high frequency of 10-30 MPa in the working process. Under the high-frequency impact of high-pressure plunger pump, the casting shell will bear huge mechanical force and hydraulic pressure. The unqualified casting shell will deform greatly after being stressed (heated), and the shell will appear" sweating "phenomenon in light, and leakage will occur in heavy case, and even some plunger slipper will be detached The phenomenon. " Chen Qunli. In addition, due to the uneven wall thickness, there are many isolated hot spots, and shrinkage porosity and other defects are easy to appear in the casting of high-pressure piston pump, so the casting of high-pressure piston pump has high requirements on technology, process and follow-up treatment.


Compared with foreign brands, the domestic hydraulic piston pump has a large gap in the advanced technology, reliability, service life, variable mechanism control function and dynamic and static performance index, basically equivalent to the level of foreign countries in the early 90s. The gap is mainly reflected in product variety, performance and reliability. Hydraulic products are only 1 / 3 of foreign products, and the service life is 1 / 2 of foreign products. The gap between China's high-pressure plunger pump and foreign advanced level lies in the following: high failure rate, some of our products fail only in one or two months, while those abroad can last for one or two years; the average time between failures in China is less than 2000 hours, while that in foreign countries can reach more than 8000 hours; the volumetric efficiency of the pump is low, and it is very easy for our piston pump to operate for a long time Excessive fever, internal damage, resulting in rapid decline in efficacy.


At present, the domestic production of large-scale hydraulic piston pump are Taichong Yuye, Zhonghang Liyuan, Beijing Huade and other enterprises.


Due to the weak casting process, most domestic enterprises can only achieve "shape similarity", but not "spirit similarity".


It will take time to speed up localization and application


Shanxi is not only an important base for the production and manufacture of hydraulic basic parts, but also a big province for manufacturing and using heavy equipment. Yuci Hydraulic Industry Co., Ltd. of Taichung group is one of the largest high-end hydraulic products manufacturing enterprises in China. Product users throughout the country, exported to Southeast Asia, the Middle East, Europe and the United States and other countries and regions. In recent years, Taichung Yulin liquid Co., Ltd. has introduced international advanced technology, world top hydraulic casting experts, quality control experts and software design