The nodular cast iron accessories of wind power mainly include the wheel hub, main shaft seat, gearbox, torque arm and pitch adjusting frame of the fan, and the material grades mainly include QT400-18L and QT350-22L. In terms of mechanical properties, in addition to meeting the requirements of tensile strength, hardness and elongation, it is also necessary to have low-temperature impact toughness of not less than 12j impact absorption energy at – 20 ℃ or – 40 ℃. As the whole wind turbine is usually placed in the harsh environment with high wind speed and low temperature, such as desert, mountain and sea, and the equipment maintenance is difficult, the quality requirements of wind turbine nodular iron accessories are extremely strict, no casting defects are allowed inside, and the service life is at least 20 years. These high requirements for performance and quality have increased the difficulty in the production of wind power ductile iron accessories.
In the past, the research on nodular cast iron mostly focused on the pursuit of high strength, but ignored the impact toughness of nodular cast iron, especially at low temperature. When the wind power fittings produced by ordinary nodular cast iron are used in cold environment, due to its great brittleness at low temperature, it is very easy to produce brittle fracture when bearing the impact load caused by high-speed wind, resulting in the failure of the whole fan. Therefore, nodular cast iron with high low temperature impact toughness must be selected for the production of wind power nodular cast iron accessories.
At present, the research on the low-temperature impact toughness of nodular cast iron has attracted more and more attention. Because the impact toughness of nodular cast iron decreases significantly with the decrease of temperature, how to strengthen the low-temperature impact toughness of nodular cast iron has become the key to the development of nodular cast iron for wind power fittings. As we all know, the mechanical properties of materials are determined by the structure of materials. In nodular cast iron, the structure is composed of graphite ball and metal matrix, and its mechanical properties are also determined by both. In order to make nodular cast iron have high low temperature impact toughness, they need to be effectively optimized.
Through the study of nodular cast iron for wind power fittings, this paper not only summarizes the influencing factors and variation law of nodular cast iron low-temperature impact toughness in theory, but also develops the production technology of nodular cast iron for wind power fittings in practice, and puts forward the production method that can effectively improve the low-temperature impact toughness of nodular cast iron, which has certain guiding significance for the production of nodular cast iron for wind power fittings.