For most of the copper rotor casting trials, the shot sleeves were fabricated from H-13 tools steel. The shot sleeves are pre-heated using either electric cartridge heaters inserted into holes drilled into the sleeve, or by external electrical or gas heaters. The life of the shot sleeves was surprisingly good. Only limited heat checking was observed at the biscuit end of the sleeve. Typically the life of the sleeve was limited by erosion occurring directly beneath the pour hole. A replaceable insert at the point of pour into the shot sleeve would allow for convenient replacement of this high wear area, and designs for replaceable sleeve inserts are shown in Figure 1.

Figure 1: Designs for shot sleeves with replaceable inserts (designs provided by Dietec AG)

Plunger Tip

When die casting copper rotors, typically the plunger tip is fabricated from H-13 tool steel hardened to 44-48 Rc. Experimental work demonstrated that plunger tips fabricated from beryllium-copper have extremely short lives.

The clearance between the inside diameter of the shot sleeve and the outside diameter of the plunger tip should be about 0.08 mm.

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