The physical properties and mechanical properties of alumina and titanium oxide brittle inclusions in the riser area of cylinder forgings are quite different from those of the matrix. During the stress deformation process, the brittle inclusions cannot deform with the metal correspondingly, and stress concentration occurs at their joints. , resulting in micro-cracks. During the plastic deformation of the forging, the brittle alumina and titania inclusions are broken along the main deformation direction, so approximately parallel inclusion crack marks appear on the macroscopic morphology.
The over-standard defects at the riser of the cylinder forgings are large alumina and titania inclusions and cracks caused by the inclusions. The molten steel in the furnace is produced with a larger tundish, while the tonnage of the molten steel in the refining ladle is small, and the molten steel is poured. During the process, the heat loss is large and the molten steel and the refining slag are violently mixed, and the slag reaches the lower limit of the pouring temperature before it floats completely, so that the refining slag is poured into the ingot mold with the molten steel, and finally remains in the position below the ingot riser line, resulting in The forged cylinder has ring-shaped dense over-standard defects.
The improvement measures for crack marks in cylinder forgings generally include three aspects:
1. During vacuum pouring, for the small tonnage ladle, try to use a small type of tundish to avoid excessive temperature loss during the pouring process, resulting in low pouring temperature, affecting the flow of molten steel and the floating of inclusions;
2. Properly raise the tapping temperature of molten steel to ensure that there is a margin of 10T from the upper limit of pouring temperature after molten steel enters the tundish. This will help the inclusions in the steel float to the surface smoothly after pouring;
3. After vacuum pouring to the riser, reduce the pouring speed appropriately to avoid pouring the refining slag into the ingot mold.
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