Implementation of Metal Casting Best Practices - EERE - U.S. ...

Furthermore, the facility enlisted the assistance of NADCA and Case Western Reserve
University to engage in rapid tooling activities and selection of proper die steels for its
production needs. The utilization of Case Western die material studies led to significant
improvement in die life at this facility. Case Western research showed that electro-slag re-melted
H-13 steel with a modified chemistry exhibited a superior thermal fatigue resistance as compared
to premium H-13 steel that has been the standard for casting dies. Die life is important because
the more predictable the life of the steel, the more accurately the plant can estimate the costs of
dies. Repairing and replacing dies is very costly in the die casting operation, involving not only
the cost of the repair itself but also the additional loss in productivity while repairs are being
performed. By working with NADCA and Case Western, the plant was able to select the
appropriate die steel for the number of runs needed. The application of NADCA/Case Western
research results also enabled this plant to use machine pre-hardened die materials to shorten its
lead time and allow quick turnarounds on orders.
In-plant trials on a specific casting showed that extended die life was five to six times. Thus, the
facility was able to keep up with increased demand and tight delivery schedules. Another trial on
a different part increased die life from 200,000 shots to a new 300,000-shot level with reduced
heat checking on critical surfaces. This improved die material could also be machined in the ashardened
condition, which, although it reduced the die life, also enabled the die caster to shorten
delivery time and die costs on short orders where die life did not need to be optimized.
2. Areas of Improvement
Even with all of the proactive quality assurance measures the facility had implemented, this plant
still has areas where it could implement further improvements to achieve benefits, in many cases
with very little investment. Many of these recommendations involve simple ways to save
resources that plant personnel often overlook in the greater interest of timely delivery on orders.
Furnace Coverings
The assessment team identified substantial energy losses in both the primary gas reverberatory
melting furnaces and the electric holding furnaces, since none of them had covers. Operating
uncovered furnaces appeared to be a routine, around the clock practice. An exposed square foot
of furnace will loose approximately 6,600 Btu/hour at 1,300 ºF. At this facility, there were
approximately 60 square feet of uncovered molten metal baths at temperatures ranging from 650
ºF (for zinc) and 1,300 ºF (for aluminum). The open furnaces will also lead to wide swings in
pouring temperatures because of the lost energy and the plant operator’s tendency to allow metal
baths to get excessively low before recharging. These large swings in pouring temperatures also
cause more scrap to develop in die casting operations.
The assessment team recommended that the plant conduct and present to management a detailed
analysis quantifying the costs associated with the energy losses resulting from the uncovered
furnaces. It further suggested that the study include costs associated with purchasing insulated
covers and calculate the payback on that investment.
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