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Gry cast iron GG25 welding repair

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  • Gry cast iron GG25 welding repair

    Helo every body,can any one help to solve the following :
    A repair of pump casing of grey cast iron ( GG25 , FC250, ISO 250) material with arc welding electrode EutecTrode XHD-2230 with 3.2mm diam.The rubber lined casing was big,no possibility to preheat,so the welding processess was conducted very slow with cooling to ambiant temperature.
    However, the next day during dye penetrant test it was detected craks around the weld.
    Whenever we tried to correct and re-weld the same phenomenon reappears.

    Please advise

  • #2
    I think it needed preheat. Just my thought...Bob
    Bob Wright

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    • #3
      Gray cast iron is the most brittle of all cast irons. Cast irons contain large amounts of carbon, this keeps the molten iron fluid for easy casting, mold fill-out and the like. When cast iron solidifies, the excess carbon (above 1%) comes out of solution. In gray cast iron, this carbon precipitates as graphite flakes. These are fracture initiation points.

      When you weld/braze cast iron, the heat affected zone expands. When the weld solidifies, the weld is frozen with all that expansion. When it cools, something has to give. Since gray iron is brittle, it cracks in the HAZ.

      Preheating is the only way. Since you mentioned rubber coating, this is something that has to be dealt with.

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      • #4
        Gry cast iron GG25 welding repair

        Thank you Keith_J ,since during the solidification the problem occures ,so the post heating and the cooling down is important .
        In fact , the circulation pump pump casing has aprox, 2m diameter and 30 cm thick and rubber lined (it is for gyspsium slurry).
        We tryed a local pre-heating for the area that we partialy removed the rubber , but as you said , I sould try the post heating and monitor the cooling down.
        I 'll try and come back.

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        • #5
          Gry cast iron GG25 welding repair

          Hi Kenth-J,
          I have a good news,westerday we started a local preheating ( with torch) and then started to weld and between each pass heating again with torch end at the end we covered the welded area with blanket.the next day dye penetrant test showed no crack .

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