Welding

Svařování elektronovým svazkem.

What is Electron Beam Welding?

Tavné svařování

The following paper displays a summary of illustrative presentation of electron beam welding. This presentation is a part of Days of Science, taking place regularly in ISI Brno, usually at the beginning of November. The visitors may see in operation an electron beam welding equipment in the laboratory of electron beam welding. The principle and use of the electron beam welder are explained in popular form. The process of welding is practically demonstrated.

Basic features of electron beam welding

Profily typických svarů elektronovým svazkem

The kinetic energy of fast moving electrons can be utilised as a source of heat for welding. The free electrons in vacuum can be accelerated by electric field and formed by magnetic lens into a narrow ray carrying high energy, which is transformed into heat at the spot of impact. Thanks to high power concentration (e.g. 104 mm−2) the velocity of temperature increase in the spot of impact is extremely high, making any material melt very rapidly. Consequently, the electrons penetrate rapidly into the material, so producing a deep but narrow weld. Using high enough power, the depth of electron penetration can be as high as e.g. 10 cm in stainless steel, at the depth to width ratio up to 30:1.

Atmosphere density in the space where electron beam is generated and formed must be as low as possible. Also in working space of electron beam welder high vacuum is preferable. Electron beam generator (electron gun), vacuum working chamber, vacuum pumping system, high voltage power supply and control electronics are inevitable parts of each electron beam welder. That's why electron beam welders are very expensive. The acquisition costs may be compensated by low operation costs by some applications, like in mass production. Electron beam in vacuum may be inevitable in some cases, e.g. if highly reactive metals like Titanium or Zirconium, are to be welded.

The construction and dimensions of the working chamber are to be adjusted individually to the dimensions of welding parts. Their volume may vary between litres and hundreds of cubic meters. The EB welders in our laboratory are small sized – the bigger one has capacity about 150 litres, the smaller ones about 7 litres.

Opened-doors days

Den otevřených dvěří v Ústavu přístrojové techniky v denik.cz

Popularisation of science is unavoidable part of scientific institutes's ac­tivities. Institutes of Czech academy of sciences are organizing every year the so called OPEN-DOOR DAYS. Their visitors can see some interesting physical experiments and ask related questions. Such actions usually take place at the begin of November on Thursday and Friday. The real date can be found at the web page.

Electron Beam Welding

Electron beam welding (EBW) is a fusion welding process in which a beam of high-velocity electrons is applied to the materials being joined. The work-pieces melt as the kinetic energy of the electrons is transformed into heat upon impact. Raising electrons to a high energy by accelerating them to roughly 30 to 70 percent of the speed of light provides the energy to heat the weld. The beam penetrates deeply, making it possible to weld much thicker workpieces than is possible with other welding processes.

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Co je to svařování elektronovým svazkem?

Svařování elektronovým svazkem je jedním z tavných způsobů svařování, který využívá pro ohřev spojovaných materiálů fokusovaný svazek elektronů s vysokou energií. Při dopadu se kinetická energie elektronů přemění v teplo, které je využito k ohřevu svařovaných součástí. Svařování probíhá zpravidla bez přídavného materiálu. Díky tzv. hloubkovému efektu lze, v závislosti na parametrech svářečky, svařovat značné tloušťky materiálu na jeden průchod – přes 10 cm v nerez oceli. Více je možné si o svařování elektronovým svazkem přečíst v tomto článku.

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Electron beam welding machines in ISI: past&present

E-beam welder ES-2 manufactured and installed in ISI, Brno

The Institute of Scientific Instruments (ISI) of the Czechoslovac Academy of Sciences (CSAV) was founded in 1957 as successor of so-called „Scientific Workshop“. In 1960 the founders, together with three Laboratories of CSAV in Brno, moved to a new site on Kralovopolska street.

The very first experiment with thermal effects of electron beam in ISI was made in about 1963 by Eng. Karel Hladil who used an old electron microscope for this experiment.

The real technological applications of electron beam in ISI have been made by Eng. Ladislav Zobač in the years 1964 through 1966, which resulted in the design of electron beam welder ES2 after 1968.

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