Selection of casting method for bridge bearing steel casting

According to the position of molten metal introduced into the mold, the pouring methods can be divided into top pouring, bottom pouring, side pouring (including step pouring), or the comprehensive use of several pouring methods. The advantages and disadvantages of several pouring methods are as follows.

1.Top casting

Advantages: rapid filling speed, small temperature drop, which is conducive to prevent defects such as insufficient pouring and cold shut.

Disadvantages: it is difficult to control the soft movement of molten metal, so that the pyrolysis products of foam pattern can be involved in the cavity and produce carbon slag defects.

2.Bottom casting

Advantages: slow and smooth filling, rising metal layer by layer, which is conducive to the discharge of foam pyrolysis products.

Disadvantages: the casting top surface filling time is the latest, which is easy to produce carburization, slag inclusion, porosity and other defects, especially for thick and large parts.

3.Side casting

Advantages: injection from the middle of the pattern, moderate filling speed and low probability of carbon defects on the casting surface.

Disadvantages: liquid metal is greatly affected by wall attachment effect, and carbon defects are easily involved in the casting.

It can be seen from the above that several pouring methods have their own advantages and disadvantages. For the steel damping bearing products studied in this study, because they belong to medium-sized thick parts, simple top pouring or bottom pouring are not suitable. In order to make comprehensive use of the advantages of various pouring methods, the pouring method of “side bottom pouring” is selected, that is, the location of the inner gate is set at one side of the model and close to the bottom, so that the liquid metal can be soft After casting, mold filling is carried out along the diagonal main direction of the model, and the pyrolytic product of the foam pattern is concentrated as far as possible to the riser, thereby reducing the carbon defect of the casting itself.

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