Technology Progress and Industrialization Analysis of Titanium Alloy Dieless Rolling

The dieless rolling technology has unique advantages in the forming of dual-performance turbine disks for engines, and is widely used in the processing and forming of large and complex disks such as high-temperature alloys, titanium alloys, light alloys, and steels.

The technology and equipment for disc-less rolling compaction was first invented by the Ufa Institute of Superplasticity of the Russian Academy of Sciences in the 1990s. The highlight of the technology was to replace large-scale presses and save mold costs. At that time, φ 800 mm titanium alloy turbine discs could be formed. And has been used in gas turbines; later related research funded by the United States GE company proved that the equipment can form complex shapes, microstructure distribution and good mechanical properties of titanium alloy turbine disks. However, due to the confidentiality of its technology, no research report on their technology and equipment has been found so far, and no relevant research results have been seen on the formation of superalloy turbine disks.

The National Academy of Mechanical Sciences began tracking this technology in 2003, and related personnel did a lot of basic research work. The Jin Quanlin team finally developed a small-scale rolling test equipment prototype in 2006, but it could only be formed at room temperature at that time. Lead discs with a diameter not greater than φ 280 mm. In 2009, the team carried out a numerical control transformation on the original equipment and added a heating system to realize the numerical control roll forming of alloy discs, and achieved some process design results on how to control the microstructure distribution.

In 2010, Jin Quanlin and others used temperature-controlled high-frequency induction heating equipment to solve the problem of insufficient high temperature. In order to avoid interference with the rolling head, the induction coil can only be sleeved at both ends of the disk, thus forming the core low temperature zone and the disk edge. The uneven temperature field in the high temperature zone. For the titanium alloy, the formation of the dual-phase zone has formed (the core α+β phase is fine, and the disk edge β phase is coarse), which coincides with the specifications of the dual-performance turbine disk. Therefore, the designer gave up the initial rolling The proposal of process isothermal superplastic forming turned to the process characteristics of non-uniform temperature field + dual performance forming, and through anatomical analysis of the TC4 test sample, the effect of different tissue distribution was obtained.

But when trying to roll superalloy materials, the equipment showed insufficient capacity. In addition, the method of repeated rolling forming above the allowable forging temperature lacks research value, and it is impossible to carry out in-depth research on the mechanism and process of superalloy rolling forming. Therefore, the current domestic moldless rolling technology and equipment are still in the basic research stage.

As my country’s 400 MN, 800 MN die forging presses, 360 MN vertical extrusion presses, 200 MN isothermal forging presses and other large-scale equipment have been put into service one after another, the tonnage bottleneck caused by the integral forging of titanium alloys and high-temperature alloys has been solved, such as the diameter of 2 in 2014 The superalloy turbine disc with a weight of 6 tons has been successfully developed on the 800 MN die forging press of China Second Heavy Machinery Group Corporation.

In terms of reducing equipment load and moldless forming, Baosteel adopted the zone forging method on a 40 MN fast forging machine in 2005 to forge a GH2674 gas turbine disc with a diameter of 2 m;

In 2008, Guizhou Anda University used non-rectangular section tapered rollers to form a stainless steel gas turbine disk with a diameter of 2 m on a 5 MN ring rolling machine, and rolled symmetrical and asymmetric hollow or solid disks;

In recent years, Northwestern Polytechnical University has applied ACDR swing rolling technology to explore and research the forming of large disk parts. The above new equipment and processes have had a great impact on the moldless rolling technology. Rolling technology is based on the continuous forming of “points”. The speed and feed rate of the rolling head can be adjusted and the temperature control system can be used to achieve flexible control of the microstructure of all areas of the workpiece, so as to achieve the goal of “dual performance”; Forging, zone forging, rolling and other processes are “surface and line” forming, which cannot achieve small local structure control. Therefore, a medium-sized equipment prototype with large rigidity and large load was trial-produced, and a prototype turbine disk product with dual performance or better performance was formed to prove the feasibility and advancement of the technology, thereby realizing its industrialization path, which is important for improving our country. The manufacturing level of high-performance turbine discs and the resolution of technological bottlenecks are of great significance.

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