In order to reduce costs and reduce the quality of structural parts, high-strength materials have been used as the material of choice for the mainframe structure, with a yield strength of more than 500 MPa. Its structural size is significantly reduced. Take the LR1750-750 t product as an example. The thickness of the main carrier plate is less than 35 mm except for the special plate (the track and the frame connection) of the turntable, frame and track frame structure. The structure requires more than 40 mm, and the commonly used plate is 50 to 70 mm). The use of a wide-limb thin-wall structure greatly improves the overall stability and load-carrying capacity of the structure. The proportion of the self-weight of the mainframe structure to the self-weight of the whole machine is also reduced from the usual 60% to 40%. There are two main types of turntable structure, one is the closed turntable structure represented by Europe and the United States, and the other is represented by Japan. Small box type turntable structure. The closed structure consists of two large I-shaped or box-shaped sections with good rigidity and is widely used in large products. The small box structure is provided with a support connection mechanism on the small box section, and the engine shed is placed on the two sides to place components such as an engine, a fuel tank and a swing mechanism. For the convenience of maintenance, Japan has introduced a semi-open turntable structure, with components placed on one side and a running plate on the other side, which is completely open, and the maintainer can easily access the mechanism and power components, replace the wearing parts or check the operating conditions.
There are two combinations of turntables. One is that the turntable, the slewing ring and the frame are integrated into one part, and the other parts of the turntable can be transported independently or disassembled, such as Manitowoc's M21000 type product. The other is to transport the upper and lower cars separately. The separate part and the slewing ring are connected by a quick connection, such as the quick pin connection of the CC5800 model of Terex-Demag.
Considering the increase of the walking traction ability and the improvement of the working speed, the traveling mechanism can be selected from the four-wheel drive type. The structure of the track frame is also improved, and the tensioning is achieved by the tensioning beam being sleeved in the track frame structure. In order to reduce the driving torque, the drive wheel adopts a sprocket type to reduce the diameter. This type is adopted by the Terex-Demag CC2500. The number of track assemblies is not only the traditional two left and right track assemblies, but the use of multiple sets of assemblies, such as Manitowoc's 21000 models, the lower car consists of 8 tracks, each two tracks are one group. Each track is more evenly loaded and requires less foundation and can be formed in a wide mode and a narrow mode to suit different workplace requirements. The structure of the frame has also been significantly improved. Considering the convenience of transportation, the frame of an ultra-large crane is generally composed of three or more parts.
Low creep clay refractory bricks are made of selected high alumina clinker, mullite, combined with clay as the main raw materials, high pressure molding, high temperature sintering and become. The product has excellent high temperature physical properties and chemical corrosion resistance. According to the creep rate (0.2MPa, 1280 ℃, 25h) can be divided into ≤ 0.4%, 0.6%, 0.8% of the three series of low creep clay brick.
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