| 摘要 |
The surface of a metal casting is modified by applying a material (1) to the surface of a mould or core, or inserting (1) in a recess in the surface of the mould or core. A vacuum is then applied from behind (1) while it is in contact with the molten metal being cast; and the vacuum is pref. maintained until solidification is complete. (1) is pref. a preformed agglomerate of powder and a binder but, alternatively to binder is used and the powder is held in place by the vacuum. (1) can be applied by brushing or spraying; and the material is pref. covered by a plastic foil used to seal porous mould or core surfaces so the vacuum can be applied. A vacuum chamber is pref. formed in the mould or core behind (1). The mould or core may consist of a conventional bonded foundry sand; or a binder-free sand may be used and held in place by a vacuum esp. by using a plastic foil round the sand. Used for example, during the mfr. of steel castings, where (1) is used locally in the mould to provide a wear-resistant surface. The vacuum permits the reaction or mixing of the molten metal and (1) in the absence of air so oxidn. is avoided. |
