The molding methods of refractory castables include: vibration molding, ramming molding, plastic molding, grouting molding, and hot pressing molding.
Generally speaking, a large proportion of refractories castables are used for vibration molding, while not many are used for slip molding and hot press molding. Vibration molding is between the mold and the castable, using a vibrating rod to vibrate to make the castable particles fluid to fill various parts of the mold. At the same time, small particles can also be filled into the gaps of large particles to make the refractory castable More dense.
The advantages of vibration molding are low labor intensity and low cost. It is suitable for large or plate-shaped parts. The disadvantage is that due to the different stiffnesses of the steel plates and springs of the mold, especially large plate-shaped parts will have uneven density. In addition, after the construction is interrupted, the density will be uneven when the construction is resumed. In order to increase the molding density, pressurized vibration can also be used to pressurize while vibrating.
Tamping molding is a molding method that uses a ram to tamp the ramming refractory castables material to a certain degree of density. The ramming hammer is driven by pneumatic or electric power, or manually. The ramming material is added to the model in layers and tamped in layers. Before each addition of materials, the surface of the last compacted material layer should be loosened to avoid separation or cracks between layers. But this method is too labor-intensive and noisy.
Plastic molding is a molding method in which plastic materials are put into a mold and extruded. The method is to use a mud extruder to extrude mud strips, and then cut the mud strips into blanks at the required size at the outlet. It is then dried and fired. In order to increase the density of the green body, vacuum equipment is used to facilitate the exhaust of the mud.
Slurry injection molding is to inject a suspension of powder into a plaster mold. After the plaster mold absorbs water, the slurry solidifies to obtain a green body. Then pour out the solidified mud that is not dehydrated in the center. Grouting molding also includes pressure grouting, centrifugal grouting, and vacuum grouting. Pressure grouting uses gravity or compressed air to shorten the grout suction time and reduce the moisture in the base slurry after demoulding. Centrifugal grouting is to inject the slurry into the mold while it is rotating. The centrifugal grouting will make the material close to the mold wall. In this method, the thickness of the green body is uniform, not easy to deform, and has less moisture. Vacuum grouting is to evacuate the outside of the model. This method absorbs water quickly and can improve the quality of the green body.
Hot press molding is rarely used in refractory materials castable and is mainly used in the ceramic industry. In short, no matter what the molding method is, it depends on the different products of refractory castables.
