Preparation method of gh4738 alloy fine-grain billet for steam turbine blade of supercritical power station

Abstract

The invention discloses a GH4738 alloy fine-grain blank manufacturing method for a supercritical power station steam turbine blade and aims at existing technical states that a temperature field and the deformation rate are difficult to meet high requirements of alloy deformation parameter sensitivity degree, and microstructures are low in homogenization degree in a process of blank manufacturing by hammer forging a GH4738 alloy ingot. According to the method, an extrusion method for blank manufacturing is used for replacing an original hammer forging manner for blank breakdown. The GH4738 alloy ingot is heated to the recrystallization temperature or more so as to be subjected to extrusion deformation; the moulding of the alloy ingot can be improved by using a three-direction pressure state in the extrusion deformation, so that the moulding deformation can be played to the greatest extent; the fine grain is improved by adopting the deformation with a large extrusion ratio; a coating and sleeving technology is used for reducing the temperature drop during transfer and extrusion deformation of the alloy, so that the extrusion ratio is controlled accurately; a temperature rising effect is adopted for enabling the alloy to be subjected to heat deformation in the appropriate temperature field all the time, so that alloy bars having the fine grain and the high microstructure homogenization degree are manufactured.

Description

technical field [0001] The invention relates to a hot-working blanking method for a nickel-based deformed superalloy in the metallurgical industry, in particular to a method for preparing a GH4738 alloy fine-grain billet for a supercritical power station steam turbine blade using a forging blanking method for a difficult-to-deform superalloy. Background technique [0002] The rapid development of China's economy and the continuous improvement of people's living standards require the continuous growth of power supply to meet its needs. To improve thermal efficiency and reduce CO 2 , SO X and NO X The country is vigorously developing ultra-supercritical units to achieve the goal of "high efficiency and low consumption". 12%Cr heat-resistant steel is often used as rotors and moving blades of steam turbines at all levels. Considering the long-term service of ultra-supercritical power plants, 12%Cr steel can no longer meet this strict requirement. In view of the good resistanc...

AI Technical Summary

Problems solved by technology

Research is being carried out on the production of ultra-supercritical steam turbine blade materials in China. Technically, the ingot is used in the same way as the free forging on the fast forging machine to prepare the bar. Although the billet produced by this process has a relatively uniform grain size, However, in the subsequent forging process, it is easy to cause problems such as cracking of the forging, uneven distribution of grains, and substandard mechanical properties. This is due to the high degree of alloying of the GH4738 alloy, which makes it sensitive to deformation temperature and deformation rate. Uneven temperature field, inconsistent forging rate, etc., resulting in a large number of uneven microstructures in the prepared billet, and a substantial increase in development costs

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