The project
A crusher mantle blank is a poor fit for closed-die tooling on a low-volume replacement-part order — the part's geometry is a simple wide disc, and dedicated die tooling for a shape this large would have added cost and lead time with no real benefit for a single blank. Open-die upsetting from round billet produced the wide, flat forged disc directly, which the customer then finish-machined in-house to the mantle's final wear profile.
The mining customer specified 4140 over a lower-alloy grade specifically for the combination of hardenability and toughness needed after quench-and-temper heat treatment on a wear component subject to repeated impact loading.