In recent years, with the continuous improvement of manufacturing technologies such as aero-engines, high-performance superalloy rings have been widely used. These annular parts are mainly used to manufacture various annular parts with different diameters and heights such as compressor locks, turbine locks, combustion chamber locks, mounting edges, sealing rings, baffles, casings, etc. of gas engines. Different conditions have different requirements for materials, and with the increase of engine thrust and thrust-to-weight ratio, ring parts made of traditional heat-resistant steel are gradually being replaced by deformed superalloys.
Analysis of production process and heat preservation method
At present, the production of superalloy rings mainly adopts the rolling process. The advantages of using the rolling process to produce the rings are high dimensional accuracy, low material consumption, less machining, high efficiency and low cost; Dense organization; high equipment utilization rate, long mold life; easy automation and low labor intensity.
Another production method is free forging, which is characterized by fast production and no weight limitation, but low material utilization rate and poor metal flow line. production.
Analysis of thermal insulation methods
Due to the particularity of the superalloy material itself, the hot working process has poor plasticity and strong process sensitivity, and in the rolling process of the ring, if the rolling temperature is increased blindly, although the plasticity of the superalloy can be improved, it will cause crystal grains. Too coarse, and in terms of the degree of rolling deformation, it is not enough to break the grown grains to re-nucleate and grow, and it is easy to form an uneven internal structure.
When reducing the rolling temperature, due to the long rolling time, the billet will continue to cool down during rolling, resulting in a low final rolling temperature, resulting in insufficient driving force for recrystallization, resulting in insufficient recrystallization of the alloy. Part of the elongated grains are easily formed in the structure. At the same time, the excessive temperature drop increases the deformation resistance of the superalloy, and it is easy to generate cracks on the surface of the billet (especially at the corners of the surface). Therefore, relatively low rolling temperature and good heat preservation measures are a more suitable method for ring rolling.
At present, most of the blanks are kept warm by wrapping, and the high temperature resistant fiber mat is wrapped on the outer surface of the blank at room temperature, tied with fine iron wires, and then the blank is heated in the furnace to ensure that the fiber mat is not easy to fall off during the transfer process of the blank. During rolling, due to the increased brittleness of the fiber mat after being heated at high temperature, it will gradually fall off with the rolling deformation of the ring. However, there are also some disadvantages in using the soft wrapping process: the process of wrapping and bundling the iron wire of the fiber mat is more complicated and time-consuming, which will reduce the production efficiency of the ring; fiber mats with better quality generally have higher costs; It will affect the workshop environment. After the fiber monofilament is broken, it will produce tiny filaments, which are easily inhaled by the human body and deposited in the lungs, causing damage to the respiratory system.
In response to the above problems, our company has successfully developed a water-based thermal insulation coating for superalloy rolling at different temperatures and holding times. It is coated on the surface of the superalloy before it is heated in the furnace. After drying, it can be heated with the billet in the furnace. The representative paint models are GZH-3-1 and GZH-5.
