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Stainless Steels
Martensitic stainless steels (AISI 420, 420F) are widely used for producing plastic molds, especially,
for cavities of small to medium sizes with complicated shapes and substantial differences in cross-
sections. They are supplied as annealed to HB 200, and their heat treatment after machining is
simple.

Alloy Steels and Plain Carbon Steels
Alloy and even plain carbon steels are used for various general parts such as holders, pillars, pins,
rings, etc. Moreover, in many cases (low-run production dies, some kinds of molds) AISI/SAE
4130, 4140 and 4150 steels are main materials for forming parts. These three steels are usually
Die and Mold Materials
supplied in an annealed state or pre-hardened to HRC 32-35 and can be hardened to HRC 44-52.
The die and mold industry handles practically all types of engineering materials, but the most typical
for the branch are tool steels.

Cast Iron
Cast iron (especially grey) is also considered as a die and mold material for manufacturing large-
sized parts, plates, spacers, bushings and other components where wear is not expected. In
addition, nodular cast iron sometimes is used for dies, punches, jigs and pads and even for molds.

Nonferrous Metals
Aluminum is not the most popular material in the die and mold industry, but it often used for
prototype dies and molds, for multiplied identical molds, short life molds and various extrusion
molds because it is easy to machine and low cost. Today aluminum starts to penetrate into resin
mold manufacturing due to its much better thermal conductivity, machinability and polishability
compared to mold steels. The following aluminum alloys: 2024, 6061 and 7075 (in accordance
with the Aluminum Association Alloy and Temper Designation System) are more and more
common in mold making practice.

Beryllium-copper alloys and zinc alloy are materials for blow molds, injection mold components
and cavity inserts. Modern metal producers offer beryllium-copper alloys that have enough strength
and good wear and corrosion resistance properties. In machining, they are cut 2-3 times faster
than tool steels. The alloys’ hardness is HRC 30-42, depending on the hardness grade. For this
reason the beryllium-copper alloys can replace traditional tool steels and stainless steels as a mold
material in some cases.

Electrical discharge machining (EDM) is another important field of nonferrous metals application
in die and mold making. Electrodes for EDM are produced from brass, copper, copper tungsten
(60-70% of tungsten) and graphite.

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