Mechanism for Development of Faults Originating from Compound Inclusions in the Forging Process of 30Cr2Ni4MoV Heavy Ingots

  • Zhao Wen Long
    Department of Mechanical Engineering, Tsinghua University Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University
  • Ma Qing Xian
    Department of Mechanical Engineering, Tsinghua University Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University
  • Zha Shi Li
    Angang Heavy Machinery Limited Liability Company

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Abstract

Non-metallic inclusions are considered undesired, yet unavoidable components of all steels and are prone to act as sources of stress that play a predominant role in crack initiation. Experiments conducted during the forging process of 30Cr2Ni4MoV steel revealed that cracks mainly originate from compound inclusions, especially intensive plastic inclusions or sliced brittle inclusions containing particles in their interior. The deformation behavior of these two types of compound inclusions was then simulated. It has been shown that the intensive plastic inclusions parallel to the applied stress result in two effects that cause additional stress and produce strain concentration, which are key factors of the union of inclusions and the origins of cracks. Tensile stress that can also lead to cracking certainly exists among intensive plastic inclusions distributed perpendicular to the applied stress. In a compound brittle inclusion, as the amount of deformation increases, areas of strain concentration first develop and then conical cracks are initiated on both sides of the interior particle. When multiple particles are distributed within a small distance, the adjacent conical cracks tend to be connected under the maximum shear stress and finally sever the sliced brittle inclusion at an angle of 45°.

Journal

  • MATERIALS TRANSACTIONS

    MATERIALS TRANSACTIONS 55 (8), 1324-1331, 2014

    The Japan Institute of Metals and Materials

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