Method for measuring temperature of castings in cooling and directional-solidification process of liquid metal

Abstract

The invention provides a method for measuring the temperature of castings in the cooling and directional-solidification process of liquid metal, which belongs to the field of temperature measurement of the castings, and is characterized in that a superfine thermocouple wire is adopted; a couple head is coated by using ceramic size, so as to reduce measurement lags and errors; the thermocouple wire is buried in a shell, so as to avoid interference of an outgoing line in radiation outside the shell while the thermocouple wire is prevented from being contacted with cooled metal to the greatest extent; when the rigid outgoing line can be used under the circumstance that a geometric condition is permissive, the thermocouple wire is sealed by using an integral nonarticulate ceramic insulating tube so as to prevent the thermocouple wire from being contacted with the cooled metal; and a stainless steel corrugated tube is adopted in the liquid cooled metal beyond a hotspot, or an exposed part of the thermocouple wire can be directly coated by using the size, so as to seal the thermocouple wire. The invention correspondingly provides a method for leading the thermocouple wire from a temperature measuring point to the upper end surface or the lower end surface of the shell. By adopting the method for measuring the temperature of the castings in the cooling and directional-solidification process of the liquid metal, the temperature of the castings at an appointed point can be accurately acquired, and meanwhile, the liquid cooled metal can be guaranteed not to intrude into a thermocouple wire protecting layer, so as to prevent the thermocouple wire from being short-circuited.

Description

technical field [0001] The invention relates to the temperature measurement of a casting in a special technological process, and belongs to the field of experimental temperature measurement. Background technique [0002] In the production of directional solidification and single crystal blades, the "high-speed solidification (HRS) method" is widely used at present. However, the temperature gradient often fails to meet the requirements, especially for the production of large-size gas turbine blades, the above-mentioned shortcomings of the HRS method are very prominent. The liquid metal cooling (LMC) directional solidification technology used to prepare blades began in the 1970s, using low melting point liquid metals (Sn, Al, etc.) Stable, high temperature gradient and solidification rate, the obtained castings have fine structure and less miscellaneous crystal defects, so it has become a research hotspot in recent years. However, due to the complexity of the influencing fac...

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Problems solved by technology

Therefore, the problem of temperature measurement has always been a major technical difficulty for LMC process researchers.

In 2007, Yu Jing used a thermocouple temperature measurement method in his doctoral dissertation (Numerical simulation of the microstructure during directional solidification of superalloy blades. Beijing: Department of Mechanical Engineering, Tsinghua University, 2007: 79), which can basically adapt to the extraction of mold shells. Pulling movement, but it cannot avoid the contact of the metal liquid with the pair wire, and it can only be used in the process of no liquid metal cooling; in 1976, A.F.Giamei inserted the protective tube from the top of the crucible, and used the common pole pair wire to reduce the number of pair wires, and realized the LMC experiment. However, this method requires the shape of the casting to be simple, and the temperature measurement points must be on the same vertical line, which greatly interferes with the internal temperature field of the sample, and it depends on special experimental equipment to achieve it, which is not suitable for production. Furnace pulling movement

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