Effect of pouring speed on black spot defect of diesel engine cast iron cylinder liner

In the solidification process of liquid metal in centrifugal casting, too slow pouring speed will promote the formation of layered structure in the cooling solidification process of liquid iron, which is more obvious when the liquid metal temperature is low. With the increase of pouring temperature and pouring speed, this problem can be weakened or eliminated. In order to verify the influence of pouring speed on casting black spot defects, the test is carried out by applying No. 1 inoculant at low temperature in combination with the speed of pouring speed. The test results are shown in the table.

Note: ① fast pouring: the pouring speed is about 8 s, reaching the upper limit of normal pouring speed (8 ~ 10 s).
② Slow pouring: the pouring speed is more than 30 s, far exceeding the normal pouring speed requirements
The slowest value allowed.

It can be seen from the table that casting black spot defects appear in both modes, in which the proportion of casting defects in fast pouring is higher. Contrary to the theoretical assumption, it is proved that the speed of pouring has no direct impact on the black spot.