On 2018-08-08 14:48:54
temperature requirements for properties and casting superalloy castings
The casting temperature of superalloy castings is lower, and the helix length is 700 ~ 800mm at 680 ° C. Aluminum alloy is easy to be aspirated and oxidized at high temperature, which affects its mechanical properties. Therefore, attention should be paid to isolate the contact between the alloy liquid and furnace gas, and some purification measures should be taken.
Properties of superalloy castings for metal heat treatment equipment
During the production of superalloy castings, the technological performance presented is called casting performance, which is an important factor to ensure the casting quality to a certain extent. The casting performance of the alloy mainly includes fluidity, shrinkage and segregation tendency.
The fluidity of a molten metal is called fluidity. It is easy to obtain the casting with complete shape, accurate size, clear outline or thin and complex wall.
There are many factors affecting metal fluidity, such as high casting temperature, which can keep the metal in liquid for a long time, but too high casting temperature will lead to the increase of the total shrinkage of the metal and excessive absorption of gas, resulting in defects such as shrinkage cavity and porosity. In short, the casting temperature should not be too high and too low. The alloy composition also has great influence on the fluidity, for example, eutectic alloy has low melting point and good fluidity.
The shrinkage of a contracting metal during cooling is called its shrinkage. The shrinkage of metal can be divided into liquid shrinkage, solidification shrinkage and solid shrinkage. Liquid shrinkage occurs at high temperature, which only causes the metal liquid level of the casting riser to decrease. Solidification shrinkage may cause shrinkage porosity and porosity. When solid shrinkage is hindered, internal stress of casting occurs. In order to prevent shrinkage cavity and porosity, the inner runner should be enlarged, and the runner should be used for direct shrinkage, or the riser should be set at the wall thickness, and the solidification and shrinkage at the wall thickness should be supplemented by the metal liquid in the riser.
3. Segregation tendency Metal or alloy during the solidification of the formation of non-uniform chemical composition phenomenon known as segregation. Heat resistant steel castings suggest that it is related to the temperature interval between liquidus and solidus of the alloy. In addition, segregation occurs easily when sulfur, phosphorus and carbon are high in gray cast iron. Segregation can also be caused by high casting temperature and slow cooling speed. When the segregation of casting is not serious, the segregation can be eliminated by annealing.