دورات هندسية

 

 

WELD CRACKS, DEFINITIONS, CAUSES, PREVENTION & REPAIR

النتائج 1 إلى 3 من 3
  1. [1]
    الصورة الرمزية سيد صلاح الصاوى
    سيد صلاح الصاوى
    سيد صلاح الصاوى غير متواجد حالياً

    مشرف متميز

      وسام مشرف متميز


    تاريخ التسجيل: Aug 2008
    المشاركات: 826
    Thumbs Up
    Received: 62
    Given: 43

    WELD CRACKS, DEFINITIONS, CAUSES, PREVENTION & REPAIR

    WELD CRACKS, DEFINITIONS, CAUSES, PREVENTION & REPAIR

    ARC CRACKS

    Definition: A depression left at the termination of the weld where the weld pool is left unfilled.

    Cause: Improper weld termination techniques

    Repair: If no cracks exist, simply fill in the crater. Generally welding from beyond the crater back into the crater.

    Longitudinal Crack

    Definition: A crack running in the direction of the weld axis. May be found in the weld or base metal.

    Cause: Preheat or fast cooling problem. Also caused by shrinkage stresses in high constraint areas.

    Prevention: Weld toward areas of less constraint. Also preheat to even out the cooling rates.

    Repair: Remove and reweld

    Transverse Crack

    Definition: A crack running into or inside a weld, transverse to the weld axis direction.

    Cause: Weld metal hardness problem

    Crater Crack

    Definition: A crack, generally in the shape of an “X” which is found in a crater. Crater cracks are hot cracks.

    Cause: The center of the weld pool becomes solid before the outside of the weld pool, pulling the center apart during cooling

    Prevention: Use crater fill, fill the crater at weld termination and/or preheat to even out the cooling of the puddle

    Throat Crack

    Definition: A longitudinal crack located in the weld throat area.

    Cause: Transverse Stresses, probably from shrinkage. Indicates inadequate filler metal selection or welding procedure. May be due to crater crack propagation.

    Prevention: Correct initial cause. Increasing preheat may prevent it. be sure not to leave a crater. Use a more ductile filler material.

    Repair: Remove and reweld using appropriate procedure. Be sure to correct initial problem first.


    Toe Crack

    Definition: A crack in the base metal beginning at the toe of the weld

    Cause: Transverse shrinkage stresses. Indicates a HAZ brittleness problem.

    Prevention: Increase preheat if possible, or use a more ductile filler material.


    Root Crack

    Definition: A crack in the weld at the weld root.
    Cause: Transverse shrinkage stresses. Same as a throat crack.

    Prevention: Same as a throat crack

    Underbead Crack

    Definition: A crack in the unmelted parent metal of the HAZ.

    Cause: Hydrogen embrittlement

    Prevention: Use LOW HYDROGEN electrodes and/or preheat

    Repair: (only found using NDT). Remove and reweld.

    Hot Crack

    Definition: A crack in the weld that occurs during solidification.

    Cause: Micro stresses from weld metal shrinkage pulling apart weld metal as it cools from liquid to solid temp.

    Prevention: Preheat or use a low tensile filler material.

    Repair: Remove and reweld, correct problem first, preheat may be necessary, increase weld size.

    Cold Crack

    Definition: A crack that occurs after the metal has completely solidified

    Cause: Shrinkage, Highly restrained welds, Discontinuities

    Prevention: Preheat, weld toward areas of less constraint, use a more ductile weld metal

    Repair: Remove and reweld, correct problem first, preheat may be necessary.


    Repairs to Cracks

    Determine the cause
    Correct the problem
    Take precautions to prevent reoccurrence
    Generally required to repair using a smaller electrode


    Here is a link to a powerpoint presenation.
    http://pntbeldyk.wirefire.com




    -------------------------------------------------------------------

    Go to
    http://www.eng-tips.com/faqs.cfm?fid=85 to view this FAQ.

    Go to
    http://www.eng-tips.com/threadminder.cfm?pid=330 to view the Metal and Metallurgy engineering forum.

    Go to
    http://www.eng-tips.com/ to join Eng-Tips forums (membership is free).

    Eng-Tips Forums is the hot web community where engineering professionals meet and talk.

    P.S. Eng-Tips Forums is member supported. Click the link below to help keep it free.
    http://www.eng-tips.com/supportus.cfm

    ============================================
    Copyright ©2009 Tecumseh Group, Inc. All rights reserved.
    Reproduction in whole or in part without written permission is prohibited.
    (Yea, but feel free to forward it to your friends :-)


  2. [2]
    سدير عدنان
    سدير عدنان غير متواجد حالياً
    عضو فعال جداً
    الصورة الرمزية سدير عدنان


    تاريخ التسجيل: Jul 2006
    المشاركات: 282
    Thumbs Up
    Received: 3
    Given: 0
    الاستاذ سيد صلاح الصاوي لاندري كيف نشكرك وكيف نقدر هذه المساعدات والكتب العلمية العملاقة .....مع التقدير للك ولكل المهندسين

    0 Not allowed!



  3. [3]
    walid 2009
    walid 2009 غير متواجد حالياً
    عضو


    تاريخ التسجيل: Apr 2009
    المشاركات: 15
    Thumbs Up
    Received: 0
    Given: 0
    Brother, the link you provided for the powerpoint presentation requires a domian user name and password. I couldn't view the presentation

    0 Not allowed!



  
الكلمات الدلالية لهذا الموضوع

عرض سحابة الكلمة الدلالية

RSS RSS 2.0 XML MAP HTML