Cracked Slitting Saw Blades
Two slitting saw blades were delivered for the purpose of determining the cause of damage. One had cracked while the other one came from a prior sheet delivery, that had less tendency to crack formation according to the manufacturer. The blades were supposed to have been stamped out of a sheet made from a 55 kp/sq mm strength steel. The saw blades were used for separating steel profiles at high rotational speeds. The cracks in question were located at the base of the teeth, i.e. at the point of highest operating stress. Metallographic examination showed that all cracks were non-decarburized and were free of chromium deposits. Therefore they could not have existed before heat treatment and chrome plating. It was concluded that the damage was due neither to poor quality of the sheet nor to defective stamping or heat treatment, but had occurred later either during surface treatment or during operation.