Metallography Part I - Macroscopic Techniques

00:08:33
https://www.youtube.com/watch?v=fc8zrgYJCJw

概要

TLDREl vídeo explora les tècniques macroscòpiques de la metal·lografia per examinar materials metàl·lics, començant amb la secció d'un ingot d'aliatge d'alumini. Es descriuen els passos de tall, molinat i període d'etiquetatge per descobrir l'estructura interna del material, enfocant-se en com els grans cristal·lines es tornen visibles després del procés d'etiquetatge. També s'analitzen altres materials com un pistó d'un motor i mostres d'acer, destacant la importància de la tècnica de tall i com el tractament amb àcids ajuda a identificar zones enduretes, defectes i l'estructura del material. Finalment, es menciona l'observació de cristalls en entorns quotidians com làmpades galvanitzades i llaunes d'acer, mostrant la seva rellevància en l'aplicació pràctica de la metal·lografia.

収穫

  • 🔍 Introducció a la metal·lografia i la seva importància.
  • ⚙️ Examen de components metàl·lics com aliatges d'alumini i acer.
  • 🪚 Tall i molinat humit per a l'examen del material.
  • 🧼 Etiquetatge amb àcids per revelar l'estructura interna.
  • 🌈 Contrastos de gra visibles després de l'etiquetatge.
  • 🔬 La importància de la refrigeració durant el tall.
  • 🍃 Exemplificació amb materials d'ús quotidià com làmpades galvanitzades.
  • 💎 Observació de defectes cristal·lins en grans.
  • 📏 Tècniques de preparació de mostres per a anàlisi detallada.
  • 📊 Identificació de zones enduretes en materials a través de diferències de color.

タイムライン

  • 00:00:00 - 00:08:33

    En aquest video, s'introdueixen les tècniques macroscòpiques de la metal·lografia per analitzar materials metàl·lics. Es comença amb la secció d'un ingot d'aliatge d'alumini, que es talla amb una serra de cinta, seguint un procés de mòlta humida per eliminar les marques de tall. Un procés d'atac amb àcids després revela l'estructura del material, mostrant cristalls anomenats gra, que es fan visibles gràcies al contrast de gra. També s'examina un pistó d'un motor de gasolina amb un procés similar de secció, mòlta i atac, revelant cristalls imperfectes. A més, es presenten mostres de diversos materials d'acer, amb atacs àcids que mostren zones dures i suaus, així com la metal·lografia de soldadures i efectes de la galvanització en objectes quotidians.

マインドマップ

ビデオQ&A

  • Què és la metal·lografia?

    La metal·lografia és l'estudi de les estructures dels materials metàl·lics, incloent la seva composició i grans cristalls.

  • Quins passos implica la preparació d'una mostra metal·logràfica?

    La preparació implica talls, molinat humit i un procés d'etiquetatge per visualitzar les estructures internes.

  • Per què és important refrigerar el material durant el tall?

    La refrigeració és important per evitar canvis en l'estructura del material durant el tall.

  • Quin tipus de cristalls es poden trobar en materials metàl·lics?

    Es poden trobar grans cristalls anomenats grans i també defectes cristal·lins.

  • Què revela el procés d'etiquetatge?

    L'etiquetatge revela contras de gra basades en l'orientació cristal·lina del material.

  • Es poden estudiar tots els materials mitjançant metal·lografia?

    Sí, quasi tots els materials del món poden ser examinats metal·logràficament.

  • Quins materials adicional s'analitzen en el vídeo?

    S'analitzen components d'acer, un pistó d'un motor i una roda dentada.

  • Com es detecten les zones enduretes en els materials metàl·lics?

    Les zones enduretes es detecten a través de diferències de color a la superfície després de l'etiqetat.

  • Quina és la importància de la tècnica de tall en la metal·lografia?

    El tall és essencial per obtenir seccions del material per a una anàlisi detallada.

  • Com influeixen les reaccions amb l'àcid en el procés d'estudi?

    Les reaccions amb àcids ajuden a revelar la microestructura dels materials examinats.

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  • 00:00:00
    [Music]
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    metallography part one macroscopic
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    techniques metallic materials are widely
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    used in many areas of everyday life how
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    are they built up in their inside are
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    there perhaps crystals to be found and
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    if so how big are they what kinds of
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    crystals are there what is their shape
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    and are there voids or
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    inclusions metallography gives an answer
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    in this video we would like to introduce
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    the macroscopic techniques of
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    metallography macroscopic means to
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    investigate a workpiece over a
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    comparatively large area doing this only
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    little or no magnification is required
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    often the naked eye is sufficient to
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    examine the
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    material as a first sample we are going
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    to investigate an Ingot made from an
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    aluminium alloy to have a look at the
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    inside the material tester has to start
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    with a raw cut through the Ingot she
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    picks up the ingot and carries it from
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    the laboratory to the mechanical
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    Workshop the band saw machine has
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    already been prepared the Ingot is
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    positioned on the saw table so that the
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    red laser marking line indicates the
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    intended cutting plane clamping Jaws fix
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    the Ingot
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    securely then the bandur gently sets
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    onto the block and cuts it slowly under
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    intensive liquid cooling it is important
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    to keep the material as cool as possible
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    to avoid changes in the material
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    structure that's it the Ingot has been
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    sectioned back into the lab not much is
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    to be seen on the cross-section apart
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    from the typical saw
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    marks in The Next Step the material
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    tester removes the saw marks by careful
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    wet grinding with silicon carbide paper
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    on the one hand this serves to produce a
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    flat surface on the other hand the
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    plastic deformations are removed that
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    were generated by
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    sawing after the first grinding
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    operation with Co grained paper the
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    material tester rotates the sample by
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    90° and grinds it once more this time
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    with medium grain silicon carbide
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    paper here again she uses sufficient
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    flushing with water this keeps the
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    sample cool and prevents the abrasive
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    paper from being loaded with material
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    particles now a flat medium ground
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    surface has been created but a apart
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    from the grinding marks nothing special
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    can be seen our sample reveals its
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    structure only by the final etching
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    process after washing and drying the
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    sample the material tester dips the
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    ground surface into a suitable ENT in
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    this case the etchin consists of a
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    mixture of different acids Special Care
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    should be taken here the material tester
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    protects herself with a Lap coat special
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    gloves and safety
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    glasses after half a minute of contact
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    time with the etchant she washes the
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    sample thoroughly with water and gently
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    wipes off the gray coat of particles
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    using cotton
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    wool in the last step she rinses the
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    clean surface with alcohol and lets it
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    dry under a hair
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    dryer now the specimen preparation is
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    finished beautiful bright and dark
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    shimmering crystals can be seen in
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    technical terminology these crystals are
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    called grains in the Central and lower
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    region of the sample the grains are
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    comparatively small they are hardly
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    visible with a naked eye but in the
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    upper part large individual grains may
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    clearly be distinguished but why are the
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    grains only visible after etching the
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    reason for this is that the etch and
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    structures the material grains on the
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    surface according to their Crystal
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    orientation experts call it grain
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    contrast
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    etching at lateral illumination the
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    individually structured grains reflect
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    the light in different directions and
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    the grains become
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    visible as a second sample the material
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    tester examines a piston from a petrol
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    engine of a passenger car the procedure
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    is the same as before careful sectioning
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    under liquid cooling is followed by wet
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    grinding with COA grained paper then wet
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    grinding with Med medium grained paper
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    and finally the decisive step the
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    etching after washing cleaning and
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    drying fantastic crystals are visible
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    again it should not be concealed that
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    these crystals these grains are not
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    perfect and uniformly structured
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    crystals but so-called primary grains
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    within the primary grains many other
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    very small crystals and also Crystal
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    defects may be found but these can only
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    be seen with appropriate microscope
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    virtually all materials of our world can
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    be examined
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    metallographically to show part of that
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    variety we will look at some additional
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    test pieces made from different
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    Steels all of these samples have been
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    sectioned first some of them are so
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    small that they have been mounted in
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    resin for easier handling and all of the
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    samples have been wet ground with medium
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    grade abrasive paper this was done
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    towards the end of the preparation as
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    shown here in the case of the tooth of a
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    gear wheel after grinding not much is
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    visible except from the typical grinding
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    marks as before the internal structure
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    will only be revealed by
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    itching but now the material tester uses
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    a different etchant this time it is
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    nitric acid diluted in
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    ethanol she holds the mounted sample
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    with pliers and immerses it into the
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    etchant after a few seconds she takes
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    the sample out again washes it
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    thoroughly with water
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    water then with alcohol and finally
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    dries it with a hair
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    dryer now the preparation of the flame
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    hardened tooth of a gear wheel is
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    finished in this case the individual
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    grains cannot be seen they are far too
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    small but what may be seen very well is
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    the hardened Zone which appears light
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    and the central soft and tough region
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    which appears
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    dark next in line is the section of an
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    induction hardened cylindrical shaft the
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    comparatively soft core is much more
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    affected by the etchant than the
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    hardened surface
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    layer clearly the induction hardened
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    surface layer can be distinguished by
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    its light color from the darker
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    core this section of a spline shaft is
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    induction hardened as well as a result
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    of the etching process the outline of
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    the hardened surface layer May easily be
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    recognized the dark area represents the
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    core that has not been
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    hardened this is a tooth from a Cas
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    hardened gear wheel the surface region
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    of the gear wheel has first been
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    carburized at high temperature and then
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    quenched the edged sample shows the
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    smooth transition from the carburized
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    and hardened surface region to the
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    softer
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    interior weld joints can also be
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    examined metallographically
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    in our case the etching process takes a
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    little more time and the analysis is
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    more difficult but by and by the
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    structure inside the steel plates the
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    position of the weld passes and the heat
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    affected zones may be identified with a
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    skilled
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    eye even in everyday life one meets
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    metallography at this hot dip galvanized
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    lamp post the rainwater has acted as an
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    ENT over the years the large flat zinc
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    crystals have been structured on the
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    surface and can be re recognized as
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    so-called
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    spangle even inside of a tinplate steel
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    can crystals are visible the fruit acid
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    of pineapples has etched the flat
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    crystals of the tin coating a natural
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    and unintentional grain contrast etching
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    process has taken place on the outside
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    the tin coating is still unchanged and
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    shines like new
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    [Music]
タグ
  • metal·lografia
  • tècniques macroscòpiques
  • materials metàl·lics
  • anàlisi metallogràfica
  • etiquetatge
  • estructures internes
  • grans cristal·lines
  • refrigeració
  • tall
  • molinat