FORMING OPERATIONS, (CONT.)

Deep Drawing

Deep drawing of annealed niobium can be accomplished without much difficulty. Tool materials such as steel, aluminum bronzes, and beryllium copper can all be used for drawing operations. Single draws can be made if the depth of the draw does not exceed the diameter of the blank, and if multiple draws are made, the depth of the first draw should not exceed 40% of the blank diameter. For multiple draws, it may necessary to perform an intermediate vacuum anneal. Sulfonated tallow can be used as a lubricant.

Punching and Blanking

Normal dies and punches made of steel can be used satisfactorily for niobium and niobium alloys. The recommended clearance between the punch and die is 6% and light oils can be used to prevent scoring the dies.

Form Stamping

There are no special techniques required for stamping niobium. Tools made of steel, aluminum bronzes, and beryllium copper may be used, but they should be polished to prevent galling. A light oil lubricant can also be used to limit the amount of galling.

SAFETY

Niobium is non-toxic and there are no specific safety requirements for working with it. There is, however, one precaution that should be followed. Although coarse metal niobium and niobium alloy powders are difficult to ignite, even at 300¡C, small surface area powder, chips, or filings of less than 5 microns may auto-ignite at room temperature. For this reason, machining chips, filings or powder from grinding should not be allowed to accumulate. If a fire does start, it is best to let it burn itself out. Small fires can be controlled with Type D dry powder extinguishers or with dry salt. Under no circumstances should water be used, as a violent explosion may result.

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