The production of excavators in our country started late. Since the reform and opening up, advanced foreign technologies have been actively introduced, digested and absorbed to promote the development of my country's excavator industry. Since 2010, the excavator market in my country has been increasing at an average rate of 30%.
It is one of the largest shopping malls in the world. Over 70% of domestic excavators are occupied by foreign brands. Domestic brands are still dominated by small and medium excavators, but the proportion of domestic excavators is gradually increasing. With the continuous expansion of the market, the slewing bearing damage problem, which is an important transmission part of the excavator, often occurs. The first manifestation is that the broken teeth and the raceway gap become larger in the process of use. Below, our company combines the planning and application of various OEMs and excavator accessories slewing bearing agents through many experiments and practices to draw the following conclusions:
1. The original factory planning is unreasonable.
The gear modulus of a 30-ton excavator produced by a certain excavator factory is 10m. After 2 years of response information from the main engine of the market, the slewing ring of its excavator will frequently show teeth broken regardless of whether it uses a joint venture or a domestically-made slewing ring.
2. The original material is not tempered or tempered
The original material of the slewing bearing of the normal production excavator is 50Mn, and its function is satisfiedExcavator Slewing BearingApplication requirements. Because domestic manufacturers of original materials often fail to normalize and temper in order to save electrical costs, and often many companies have relatively vague and simple arrangements for the arrangement and arrangement of original materials. Our company has obtained through metallography that the arrangement of 50Mn normalized is ferrite + pearlite, the crystals are coarse, most of the crystals are ferrite surrounded by pearlite, and the arrangement is brittle. Through years of practice, it has been proved that normalizing or incomplete normalizing material simply deforms. After the slewing ring with a diameter of 1100~1410mm is quenched through the intermediate frequency raceway and the teeth, the deformation of the slewing ring is detected to be more than 1mm. When the slewing bearing leaves the factory, the tooth jump of the slewing bearing is detected by an average of 6 points scattered on the circumference, and the tooth jump of the non-full tooth is checked. Therefore, the detected maximum point of tooth jump is not one-it is determined as the maximum point of slewing ring tooth jump, most of which are close to the maximum point of tooth jump, and the device process type reducer pinion and slewing ring are matched against the slewing ring The teeth are sprayed with green paint parts. If the side clearance of the device is too small during the installation process, it is very easy to knead with the real maximum point of the slewing bearing. During the operation process, the noise is loud, and the teeth are worn out seriously, and the gears will seize and break the teeth. The original materials of quenching and tempering have been metallographically inspected for damage to the slewing bearing produced by our company. The arrangement is sorbite + tempered sorbite + lath martensite, which has good strength and plasticity And toughness, and fine crystals. The slewing bearing is processed through the quenched and tempered material, and the amount of tooth jump is mostly 0.2~0.5mm, which is not easy to deform. The maximum value of the industry standard tooth jump in our country is 0.75mm, and the accuracy is higher than the industry standard. It is not easy to cause the gear meshing backlash to be too large or too small to form a slewing ring tooth.
3. Unqualified slewing bearing production caused the slewing bearing to break teeth, and the raceway was worn because my country's heat treatment process was relatively backward compared with Japan, Germany and the United States, and most of the slewing bearings of excavators above 20 tons were single-tooth quenched. During production, due to factors such as equipment, quenching fluid, temperature, water pressure, etc., a certain tooth hardness and hardened layer are unqualified, but it is difficult to find in the inspection process, and this type of slewing bearing is also a relatively common phenomenon. If the hardness is too hard, a tooth will be broken during the application process, which is the so-called tooth loss phenomenon; if the lack of hardness or the lack of hardened layer will simply cause local gear wear during the application process, the slewing bearing will be flattened in severe cases. Regional gear.
It is difficult for the slewing ring to wear out under normal circumstances in the use of the excavator, but it often appears that a new slewing ring is in use, and the gap is getting bigger and bigger. Most of these situations are caused by the slewing bearing manufacturer's improper production or planning of the contact angle of the slewing bearing. At the same time, it does not rule out that the gap after the wear caused by the lack of grease on the slewing bearing in the application process becomes larger.
Fourth, the slewing bearing is improperly installed in the process of use, and the damage caused by lack of maintenance
