Shot Sleeves

Typically, a shot sleeve may become 100-150° C (200-300° F) hotter at the bottom under the pour hole, than at the top in front of the hole. If the temperature of the sleeve is much higher at the bottom than at the top, unequal expansion will cause it to become oval instead of round. This will also cause the sleeve to become slightly bowed rather than straight. This results in allowing some of the alloy to enter part of the gap between the plunger and the sleeve, affecting the seal between the plunger and shot sleeve, and leading to premature wear and inconsistent shot velocity.

The temperature of a sleeve surface directly under the pour hole can reach as high as 680° C during pouring for structural alloys, for example Silafont. At such a high temperature the integrity of nitride and steel is destroyed. Castool collaborates with a steel manufacturer to create Tuff Temper (TT), which is modified premium W.Nr. 1.2367 steel. The Tuff Temper steel has higher Molybdenum content. The high Molybdenum content increases the corrosion resistance and soldering resistance. The tempering resistance of TT is 45° C higher than W.Nr. 1.2344(H-13). The Tuff Temper sleeve insert reduces the total crack length by 50% than W. Nr. 1.2344(H-13). The TT permits higher temperature nitride treatment and more thermally stable nitride.

The shot sleeve design should incorporate a wall thickness 1/3 of the bore, and the pour spout of no more than 2/3 of the bore.

H-13 (1.2344), Tuff-Temper, Con-Duct Heat Treated, Nitrided and 3P Coated

Medium diameter shot sleeves may require thermal control depending on the application, and when necessary can often use an external cooling saddle. The pour end of the shot sleeve where the temperature is highest, is obviously where cooling is most necessary. Accordingly, the pour-end cooling saddle effectively and economically puts shot sleeve cooling where it is needed most, directly below the pour spout.

A safe alternative to gun-drilling is using partial or complete M-Loop.
Copper tubes are embedded in the outside diameter of the shot sleeve.

For larger shot sleeves, to avoid too much variation in thermal expansion, a series of gun-drilled holes are located along the length of the shot sleeve under the pour spout, and connected to similar holes around the die end of the shot sleeve.

In most cases where vacuum is being used, it is necessary to use a thermally controlled shot sleeve.
A thermal control unit can be used to manage the temperature and flow of a medium, usually oil, to improve control of the shot sleeve temperature and dimensions during production