Common precision casting machining defects

The common defect of precision casting is bubble, which refers to the smooth hole defect of precision casting. Bubbles are usually found after machining. Dongguan precision casting technicians have been separated from the workshop consumption experience for many years, and the causes and preventive measures of bubbles in precision casting are summarized as follows:

I. reasons:

1. In most cases, the first reason for the appearance of bubbles is that the precision cast outer shell is not fully roasted, and a lot of gas can't be discharged smoothly during the pouring of steel, and then it intrudes into the liquid metal to form bubbles;

2. Due to the reason of shell making process or shell type data, the permeability of the shell is too poor, and the gas in the cavity is difficult to be discharged and enters into the metal liquid to form bubbles;

3. Air trapped in the molten steel during pouring fails to drain out and forms casting bubbles.

Ii. Preventive measures

1. Where conditions for precision casting permit, exhaust bubbles shall be placed at the top of the disordered casting.

2. When planning the casting system, fully consider the demand for shell exhaust.

3. The roasting temperature and time of the shell should be reasonable, and the holding time should be enough.

4. Thoroughly clean the wax when dewaxing.

5. Properly drop the distance from the ladle nozzle to the sprue cup, and the pouring speed should be even to ensure the steel degree is stable and full of the cavity, and as little as possible involve the air in the molten steel, so that the air in the cavity and the molten steel can be discharged smoothly.