Carburizing Low-carbon Sleeves

: The Working Of Steel

Low-carbon sleeves are carburized

and pushed on malleable-iron differential-case hubs. Formerly,

these sleeves were given two treatments after carburization in

order to refine the case and the core, and then sent to the grinding

department, where they were ground to a push fit for the hubs. After

this they were pushed on the hubs. By the method now employed,

the first treatment refines the core, and on the second treat

the sleeves are pushed on the hub and at the same time hardened.

This method cuts out the internal grinding time, pressing on hubs,

and haulage from one department to another. Also, less work is

lost through splitting of the sleeves.

The machine for pushing the sleeves on is shown in Fig. 64. At

A is the stem on which the hot sleeve B is to be pushed. The

carburized sleeves are heated in an automatic furnace, which takes

them cold at the back and feeds them through to the front, by which

time they are at the correct temperature. The loose mandrel C

is provided with a spigot on the lower end, which fits the hole

in the differential-case hub. The upper end is tapered as shown

and acts as a pilot for the ram D. The action of pushing on and

quenching is similar to the action of the Gleason tempering machine,

with the exception that water instead of oil is used as a quenching

medium. The speed of operation depends on a number of variables,

but from 350 to 500 can be heated and pressed on in 11 hr.