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Electroslag Melting of Titanium Alloys

#1453


Technology of Magnetically-Controlled Electroslag Melting of High-Alloyed Titanium Alloys to Improve Their Service Life and Reliability in Civil Machine-Building Application

Tech Area / Field

  • MAT-ALL/High Performance Metals and Alloys/Materials

Status
3 Approved without Funding

Registration date
27.01.1999

Leading Institute
Institute of Aviation Materials, Russia, Moscow

Collaborators

  • Boeing Commercial Airplane Group, USA, WA, Seattle\nTechnische Universität Hamburg, Germany, Hamburg\nAIRBUS Industrie, France, Blagnac\nKorea-Russian Scientific & Technological Cooperation Center, KIST, Korea, Seoul

Project summary

The purpose of the project is to increase the reliability and the resource of the high- loaded details of modern machinery including big passenger planes that are being made of the high-alloyed titanium alloys such as VT22, VT23, VT22M, VT35, etc.

The reliability and the resource of such details are mainly defined by the quality of the start metal, which is the minimum consistence of harmful impurities in it. It also depends on the absence of the brittle refractory inclusions, porous intercrystalline inclusions, the homogeneity and the grain smallness of its crystalline structure. The further work on titanium alloys has the big influence on the resource and reliability.

The traditional vacuum arc melting (VAM) does not guarantee the receiving of the metal without defects. At the same time, with the usage of the VAM method, some dangerous kinds of defects, that metal has cannot be detected by the modern methods of unbreakable control. Some of these defects are brittle refractory inclusions with high percentage of components such as nitrogen and oxygen. Especially these elements usually cause the reason of damage during the usage of high-loaded details of the planes that are made of titanium alloys.

The further work on metal consists of plastic deformation, mechanical and heat treatment, it can also have the reasonable influence on the resource and the reliability of titanium products.

Therefore, it is very important to develop the new method of melting titanium alloys alternative to the traditional one, so it would have new mechanisms of the effective increase of quality of the casting metal. The new method of melting titanium alloys offered by the authors of the project called magnetically-controlled electroslag melting (MEM) has such advantages.

VIAM the research on developing the technology of making the pressed consumable alloyed electrodes out of the titanium sponge with the imitators of the sources of developing the refractory inclusions will be carried out. The research on the quality of the titanium melted with the usage of the MEM method will be also carried out. It will include the chemical analysis, mechanical tests, researches of the low cycle fatigue, research of the macro- and microstructure of the metal, the developing of the technology of the heat and thermomechanical treatment of the semi-products carried out of the MEM ingots.

The effect of the character of the structure being formed during the production of the semiproducts with the usage of hot deformation method, the condition of the surface of the metal, of remaining strain and some other factors having an influence on the resource and the reliability of the metal will also be studied. The behavior of the high-strength and heat resistant titanium alloys during the exploitation in different conditions will be researched.

The research of the developing the scheme of the effective electromagnetic influence on the liquid bath of melting metal will be carried out. Also, the chemically active metallurgic slag that decreases the quantity of impurities in the metal will be developed and the base will be constructed. The MEM technology of the high-alloyed titanium alloys will be developed as well.

As a result of this project, the technology MEM will be developed. The usage of this technology will make possible to get high-alloyed titanium alloys with the following advantages over the best analogs worldwide:


- the absence of the metallic and nonmetallic inclusions and gas pores;
- the level of consistence of the harmful impurities is much less (for instance, oxygen, nitrogen, carbon, etc.);
- high chemical homogeneity of the metal;
- homogeneous crystalline structure of the metal with small grains;
- the optimal match of the strength and the plasticity of the metal.

The advantages shown above will provide high reliability and the resource of the work of the highly loaded titanium details and the constructions of big passenger planes made of the metal melted with the usage of the MEM technology.

Besides, changing the method of melting titanium to the new one (MEM) will allow to decrease the price of the basic technological equipment considerably (about 10-20%), and also to decrease the expenses on the melting metal (about 10-15%).

At the same time, the considerable increase of the reliability and the resource of working details that are made out of highly alloyed titanium alloys, and the decrease of its price will provide the conditions for a significant expanding of the usage of titanium in a civil aviation. It will help the developing of the conversion processes in aviation industry of Russia and other countries.

Potential role of foreign collaborators

Potential role of foreign collaborators in the given project will be consisted in:


- E.O.Paton Electric Welding Institute (Ukraine) - the research of the developing the scheme of the effective electromagnetic influence on the liquid bath of melting metal during MEM;
- AIRBUS INDUSTRIE (France), Technische Universitat Hamburg-Harburg (FRG) -the expert estimation of technical effectiveness of the titanium alloys melting method and technology which will be developed as a result of fulfilling the project.


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