白點

  　  白點是鍛件在鍛后冷卻歷程中產生的一種里面缺點。其形貌在橫向低倍試片上為細發絲狀銳角裂紋，斷口為銀白色雀斑。照片6-13為Cr－Ni－Mo鋼鍛件縱向斷口上的白點。其形狀不準則，大小懸殊，非常小長軸尺寸僅2mm，非常大的為24mm。白點本色是一種脆性銳邊裂紋，具備極大的風險性，是馬氏體和珠光體鋼中非常兇險的缺點。

    白點成因是鋼中氫在應力用途下向拉應力區富集，使鋼產生所謂氫脆，發生脆性斷裂，以是氫和附加應力團結用途是白點產生的緣故。

　   對策是：

　    1）低落鋼中氫含量，如留意烘烤爐料，冶煉時充分沸騰，真空除氣，爐外精煉脫氣等。

  　  2）接納消除白點的熱處理，要緊使命是分散鋼中氫，消除應力，如擴氫退火熱處理等。詳見鑄造歷程中多見的缺點中的鍛后清算工藝欠妥常產生的缺點。

自由鍛件直銷哪家好，就找唐山盛通鍛造有限公司。

White dot

   The white point is one of the shortcomings that the forging produced during the post-forging cooling process. Its shape is a fine hairline acute angle crack on the lateral low-magnification test piece, and the fracture is silvery white freckles. Photo 6-13 is the white point on the longitudinal fracture of the Cr-Ni-Mo steel forging. Its shape is not standard, the size is very different, very small long axis size is only 2mm, very large is 24mm. The white point is a brittle sharp edge crack with great risk and is a very dangerous shortcoming in martensite and pearlitic steel.

     The cause of white spots is that hydrogen in steel is concentrated in the tensile stress region under stress, which causes so-called hydrogen embrittlement and brittle fracture, so that the joint use of hydrogen and additional stress is caused by white spots.

The countermeasures are:

1) The hydrogen content in the low steel, such as paying attention to the baking charge, fully boiling during smelting, vacuum degassing, refining outside the furnace and so on.

   2) Accepting the heat treatment to eliminate white spots, the important task is to disperse hydrogen in the steel and eliminate stress, such as hydrogen expansion annealing heat treatment. See the shortcomings of the post-forging clearing process in the most common shortcomings in the casting process.