The metal work pieces prepared in ingot or slab casting processes often have individual faults or surface defects, such as cracks for example, on their surface which do not permit the further processing of the work piece in a rolling mill. These faults may be spaced relatively far apart on the large area of ingots or slabs. In order to remove all these faults in the surfaces, one has turned to the selective flame-scarfing of the surfaces, i.e. flame-scarfing only there where the surface faults are present. It is possible without difficulties to process the entire surface of a work piece, but this becomes uneconomical particularly when such a surface has only a single fault, for example.
The selective flame-scarfing of surfaces is already known (German application No. 1,193,342). In this known selective flame-scarfing process, the flame-scarfing oxygen flow is maintained at a value which is required for flame-scarfing the full length of the fault. At the end of the fault, the flow of oxygen is gradually diminished. The disadvantage in this known flame-scarfing process, however, is that upon completion of the procedure there remains on the work piece surface unburned iron covered with slag, which subsequently must be removed by supplemental flame scarfing. In addition, it is disadvantageous here that because of the reduction of oxygen flow at the end of the flame-scarfing course, there results an angular termination, whose side edges lie deeper than the surface not scarfed. Prior to further processing, these edges must be flame-scarfed again, since these faults cannot be equalized in the rolling of the work piece. Because of this usually manual after-processing of the work piece, the entire selective flame-scarfing procedure thus requires relatively much time.
USPTO Backgrounds
USPTO Backgrounds