| 摘要 |
<p>PURPOSE:To manufacture a bent pipe of arbitrary bending angle by executing the hardening and tempering after bending a straight pipe made of cast steel under the prescribed condition. CONSTITUTION:A wear resistant straight pipe made of cast steel is manufactured by the centrifugal casting method. The straight pipe made of cast steel is normalized. The normalizing treatment is executed by cooling the pipe in the atmosphere after the pipe is heated to the temperature higher than the temperature of Ac3 or Acm transformation by 30-50 deg.C. Then, the bending is executed under the conditions of high frequency heating where the temperature of pipe: 800-900 deg.C, the heating speed: 0. 5-1mm/sec., the radius of curvature(R): 2D or over, and the air-cooling condition where the cololing speed: 0.3-2.7 deg.C/sec. The bending is executed, for example, along the axis of the pipe from the position (1) (the starting point of bending) to the position (7) (the ending point of bending). After the bending, the hardening and tempering is executed. This constitution manufactures the elbow, the U-tube or the like.</p> |
