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锻件折迭与裂纹的控制 Forging fold and crack control

2021-09-15


  坯料横截面尺寸大,制坯形状不合理,局部压入式成形,模具模膛过渡处圆角半径较小,操作时一次压下量太大。  
 
  消除折迭的方法  
 
  将模具模膛的模锻斜度由5°增大到7°;将模膛φ23mm与锻件过渡处的圆角半径由R3mm增大到R8mm;将锻件易折迭部分模膛处的制造抛光方向顺着金属流动方向进行;将模膛表面粗糙度值Ra=1.6μm减小到Ra=0.4μm;将坯料制坯尺寸变为38mm×58mm×74mm,在锻件终锻成形时按先轻后重的方式进行操作,并适当地润滑上模模膛。  
 
  轴承盖裂纹的分析  
 
  492Q汽油机轴承盖锻件,材料为LY11的挤压棒料,下料尺寸为φ70mm×120mm,重1.3kg。当沿坯料轴向镦粗制坯后再终锻,在锻件坯料轴线45°方向产生宏观斜裂,裂纹开口角度为30°~50°。  
 
  裂纹产生的原因  
 
  挤压铝棒料具有明显的各向异性,其中纵向机械性能明显高于横向机械性能(纵向韧性最大,而横向韧性最小)。在终锻开始时在三向应力不等的情况下或非三向压应力的作用下,存在最大剪应力,易造成坯料晶粒间联系破坏,不利于滑移变形的发展,变形能力差而产生斜裂。同时因变形不均而引起的附加应力和温度不均产生的热应力较大,变形大的部分和变形小的部分相互作用,拉应力超出该部分强度时便产生开裂。  
 
  消除裂纹的方法  
 
  严格控制始、终锻温度,减少坯料装炉数量,缩短坯料出炉到锻造的时间,当坯料在加热一定的时间后进行翻动;利用挤压坯料沿轴向韧性好、塑性好的特点,沿坯料径向即垂直于纤维方向锻造压扁制坯,然后终锻。  
 
  油堵折迭与裂纹的分析  
 
  油堵锻件,材料为LY11或LY12的挤压棒料,下料尺寸为φ35mm×45mm,重0.08kg。在RFX-45箱式电炉中加热,每次出炉量15件,但在锻造10件以后,采用轴向或径向镦粗制坯,然后终锻时,出现与沿分模面方向的飞边成15°~35°的裂纹,并沿伸到锻件。当采用φ30mm×60mm的坯料沿轴向镦粗制坯时,在锻件环R10mm处四周产生较大的折迭。  
 
  折迭与裂纹产生的原因  
 
  每次坯料出炉量过多,始锻温度低,制坯终锻时变形程度过大或锻造比过大,锻模预热或润滑不当。  
 
  消除折迭与裂纹的方法  
 
  选择坯料规格的最小直径为φ35mm,坯料加热到480℃保温2h,每次坯料出炉量在10件以下,终锻按先轻后重的方式进行,提高锻模的预热温度,并每隔2件润滑上模一次。
 
 
  The cross-sectional size of the blank is large, the shape of the billet is unreasonable, the local press-fit is formed, and the radius of the fillet is smaller.
 
  Eliminate the folding method
 
  The die forging angle of the mold cavity is increased from 5 ° to 7 °; the radius of the fillet φ23mm and the transition angle of the forging is increased from R3mm to R8mm; the polishing direction of the part is easy to be folded According to the direction of metal flow; the mold surface roughness value Ra = 1.6μm reduced to Ra = 0.4μm; the blank blank size into 38mm × 58mm × 74mm, forging the final forging when the first light weight To operate and to properly lubricate the upper mold cavity.
 
  Analysis of Cracks in Bearing
 
  492Q gasoline engine bearing cover forging material LY11 extrusion bar material, cutting the size of φ70mm × 120mm, weight 1.3kg. When the blanks are upsetted along the billet and then forged, the macroscopical fissures are generated in the direction of the 45 ° of the forging billet, and the opening angle is 30 ° ~ 50 °.
 
  The cause of the crack
 
  Extruded aluminum bar has obvious anisotropy, in which the longitudinal mechanical properties are significantly higher than the transverse mechanical properties (longitudinal toughness is the largest, and transverse toughness is the smallest). In the case of the final forging in the case of three-dimensional stress or non-three-way compressive stress under the action of the existence of the maximum shear stress, easy to cause the relationship between the billet crystal damage is not conducive to the development of slippage deformation, Produce an oblique crack. At the same time due to uneven deformation caused by the additional stress and temperature unevenness of the thermal stress generated by large deformation of the large part of the small part of the interaction, tensile stress exceeds the strength of the part of the crack.
 
  Eliminate the crack method
 
  Strict control of the beginning and end forging temperature, reduce the number of billet furnace, shorten the billet baked to forging time, when the blank after a certain period of time to turn the blank; the use of extruded billet along the axial toughness, good plasticity, Radial, that is, perpendicular to the direction of the fiber forging flattened blanks, and then the final forging.
 
  Analysis of Oil Closure and Crack
 
  Oil forging forgings, materials for the LY11 or LY12 squeeze bar, cutting the size of φ35mm × 45mm, weight 0.08kg. Heating in the RFX-45 box electric furnace, the amount of each time the amount of 15, but after 10 forging, the use of axial or radial upsetting blank, and then the final forging, and along the direction of the sub-surface with the flash Into a crack of 15 ° to 35 ° and extend to the forging. When the use of φ30mm × 60mm blank along the axial upsetting the blank, in the forging ring around the R10mm to produce a large fold.
 
  The reason of folding and cracking
 
  Each time the billet is too large, the initial forging temperature is low, the deformation degree of the blank forging is too large or the forging ratio is too large, the forging die is preheated or lubricated improperly.
 
  Eliminate the method of folding and cracking
 
  Select the blank size of the minimum diameter of φ35mm, blank heating to 480 ℃ insulation 2h, each billet out of the amount of 10 or less, the final forging the first light and heavy way to improve the forging die preheating temperature, and every 2 Lubrication on the mold once.