| 摘要 |
PURPOSE:To inhibit the appearance of a pearlite or martensite structure in spheroidal graphite cast iron by immersing the cast iron at a specified temp. or above in warm water to cool the cast iron to a temp. at which only bainitic modification is caused and by holding the cast iron at the temp. to cause only bainitic modification. CONSTITUTION:The structure of spheroidal graphite cast iron is modified into an austenite structure at the A1 modification temp. or above in a heating furnace 1 and the cast iron is immersed in warm water in a warm water cooler 2 provided with a thermostatic mechanism. After the immersed cast iron is cooled to the Ms modification temp. or above at which only bainitic modification is caused, the cast iron is held at the temp. to allow the modification to proceed. Thus, environmental pollution and the danger of combustion during post-treatment in case of oil quenching or the like are staved off. A thickened warm water contg. a thickener is desirably used as the warm water. The bainitic modification is preferably allowed to proceed by successively using a fluidized bed furnace 3 and a tempering furnace 4.
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