Construction machinery hydraulic transmission system in the main components such as gearbox torque converter (referred to as double change) and the work unit hydraulic system in the multi-way reversing valve with O-ring and other seals, most of them have been used fluorine rubber (FKM) for sealing the material has a good oil resistance, abrasion resistance and resistance to high temperatures and so on, in order to prevent leakage of the system, improve the system durability has achieved a certain effect. However, due to the existence of such seals, high price, poor resistance to rancidity deterioration of oil, cold resistance and other negative factors, making the cost of the product increases, and affects the sales of the product, so it is necessary to find an economical and durable sealing material instead of the existing sealing material.
HNBR and Its Properties
HNBR is a new type of oil-resistant elastomer introduced by Nippon Zeon in 1984, which was developed to meet the urgent need for rubber fittings under harsh conditions in the automobile industry. It is the excellent oil resistance of nitrile rubber (code name NBR) molecular structure of the carbon-carbon double bond selectively hydrogenated (saturated) processing of the molecular structure of the change, change the NBR heat-resistant, maroon chemical stability of the weakness of the poor, with excellent strength and resistance to high and low temperatures, resistance to oil and chemical media such as resistance to outstanding, unique and very balanced performance. At the same time maintains the excellent wear resistance and processability of NBR. Compared with FKM and NBR
HNBR's main performance characteristics are as follows:
(1) Temperature adaptability: HNBR can be used for a long time at l50 ℃, short-term use of temperature up to l75 ℃.
HNBR, can be used for a long time at 230 ℃, the short-term use of temperature up to 300 ℃. HNBR heat resistance between NBR and FKM, but in terms of low temperature resistance, FKM's cold resistance is poor (-15 ℃ that is easy to brittle fracture); and HNBR has excellent low-temperature performance, with a good balance between oil resistance
(2) Physical and mechanical properties: most oil-resistant rubber due to low tensile strength, so it limits the scope of its application, such as FKM tensile strength of 19.6-21.6MPa, HNBR strength than NBR, ACMXNBR, EPDM and FKM and other types of rubber are higher, such as Zeon ZSC hydrogenated nitrile butadiene rubber tensile strength up to 6OMPa more importantly, the HNBR at high temperatures ( More importantly, HNBR at high temperature ( 15O ℃ ) under the strength ( 14.7-29.4MPa ) and room temperature NBR to maintain the same level at high temperatures in a variety of complex oils and chemical media can still maintain excellent mechanical properties, high temperature physical and mechanical properties are better than most of the other elastic ah body, good abrasion resistance. Through appropriate matching
Combination of technology, you can get excellent high-temperature compression permanent deformation performance, and this performance of FKM is not as good.
(3) chemical media resistance: HNBR has excellent oil resistance at high temperatures, resistance to a variety of lubricants hydraulic oil, fuel oil containing a variety of additives, strong corrosive oxidizing oils and metal slag performance, and has excellent ozone resistance, high-temperature radiation resistance and hot water resistance.
From the above characteristics of HNBR, compared with FKM, the former better overall performance, FKM, although in the heat resistance, oil resistance, resistance to combustion oil is better than HNBR, but HNBR in the working temperature of the mechanical properties of the steam resistance, resistance to oil additives, resistance to oxidation and rancidity degradation of the oil and other chemical properties, such as superior to the FKM. In addition, the FKM in the manufacturing and molding process due to the poor fluidity of the material, raw materials and product performance is not stable, so its cost. In addition, FKM is more expensive in the process of manufacturing and molding due to poor material flow, unstable raw materials and product performance, while HNBR is less expensive than FKM due to good material molding and processing, stable performance and lower price.
Application status of HNBR and analysis of its application in construction machinery
Due to the excellent comprehensive performance of HNBR, it has been widely used in many aspects to replace FKM in foreign countries: it has been used in the automobile industry to manufacture automobile crankshaft front and rear and gearbox oil seals, H-type shaft seals, seals for fuel injection system, piston cylinder vibration damping seals, carburetor O-rings, etc.; and in the metallurgical industry, it is used in the manufacture of metallurgy high-line rolling mill axle diameter double-sided seals, and the seals for fan-shaped cylinders in domestic continuous casting machine; and in the oilfield industry, it is used in the manufacture of drilling rigs, and the seals for drilling rigs. In the oilfield industry, they are used to make the seal of drill bit protector for drilling wellhead sealing, oil plug pump sealing, and so on.
For loaders and other construction machinery, its hydraulic transmission components such as gearboxes, torque converter internal normal operating temperature theoretically 8O-90 ℃, the highest does not exceed 120 ℃, but such as long hours of overloaded work. Up to or even more than 130 ℃ internal cycle of high-temperature fluid deterioration and deterioration over time, while the parts of the metal slag (meshing movement of metal components and the time of the work process of the metal shavings falling in the working medium) in the high-temperature hot oil driven by the seals caused by the impact of the seals, thereby affecting the service life of the seals.
Therefore, HNBR can be used in the high temperature strength, low temperature resistance, high temperature compression permanent deformation, oxidation and acid degradation of oil and metal sludge performance and other aspects of the price of the advantages shown, with its replacement of the current FKM seal, both to improve the service life of the seals, but also reduce the frequency of replacement of the working medium; and high temperature resistance of the FKM is significantly too small. For construction machinery working device hydraulic system, the system working pressure is generally 16MPa (is a high-pressure system), the working medium (HM46 or HM32 hydraulic oil) of the normal operating temperature of 45-55 ℃, due to the working conditions of the device is poor, coupled with improper operation of the user as well as for the pursuit of economic benefits of overloading, are prone to make the hydraulic system flow oil temperature More than this limit, thus causing the deterioration of hydraulic oil.
In addition, the composition of the hydraulic system components of high-speed rotary movement (hydraulic pump) and frequent reciprocating sliding (hydraulic cylinder piston rod and multi-way reversing valve valve stem) also produces metal slag and oil deterioration, the seals also caused by the impact of friction, the system other failures caused by the pressure reduction and even sudden loss of pressure, are the seals have a negative impact on the current NBR class seals, due to its tensile strength and resistance to degradation of the oil properties For the existing NBR seals, due to its tensile strength and resistance to degradation of oil and very easy to fail, due to the strength of HNBR, good recovery, in part of the sudden loss of pressure on the performance of the seals have little impact, so in the hydraulic system of cylinders, pumps, valves, and other hydraulic components on the use of HNBR seals can greatly improve sealing effect and service life.
