The reason:1. Most of the cases present bubble is mainly due to the fine casting exterior shell roasting is not abundant, when pouring molten steel shell suddenly produce a large number of gas cannot successful eduction, which constitute a bubble in liquid metal into the;2. Because of the cause or shell mold material shell making technology, shell permeability is poor, is difficult to exhaust gas in the cavity, into the metal liquid in a bubble;3. When pouring into fails to discharge the air in the molten steel castings bubbles to form.Preventive measures:1: in the precision casting conditions allow conditions, complex in structure of casting the top set exhaust bubble.2;In the design of gating system, the abundant thought to shell exhaust demand.3: shell roasting temperature, time to is reasonable, the holding time is enough.4: when the dewaxing wax material should be thorough cleaning.5;Appropriate to reduce the ladle mouth to the sprue cup interval, to average casting speed, to ensure that the steel cavity filled with degree of stability, as few involved in molten steel in the air, so that in the cavity and the molten steel gas energy discharge smoothly.
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