Back | Blog posts overview

Molding plastics with molybdenum


Molybdenum-alloyed mold steels are a key component of plastic-injection molding machines. They must be easy to machine into complex geometries that mirror the finished molding, resist deformation and wear under the stress and abrasion of the process; and be able to maintain a high surface polish for long production runs. Molybdenum is a vital alloying element in meeting these requirements.

Of the many molding processes available, the most widely-used and versatile is injection-molding. As its name implies, this process injects molten plastic into a mold, usually made of steel. Molybdenum-alloyed steels are the mold material of choice because of their strength and durability at elevated temperatures.

Two of the most widely-used steel grades, AISI P20 (UNS T5 1620) and AISI H13 (UNS T20813) have nominal molybdenum contents of 0.42% and 1.3% respectively. These two alloys have spawned a large number of compositional variants to customize them for specific applications, although most retain molybdenum in their composition. One major mold steel supplier offers 14 variants with molybdenum contents up to 3.6%.

Injection molding is a growth industry and the ever-increasing demand for larger components with more sophisticated designs will continue to drive higher performance equipment and tooling. Molybdenum will help to provide the right steel for these new products because of the strength, durability, stability and high surface quality it brings to the process. 

This post is adapted from an original article in MolyReview, in which we showcase some of the most interesting and amazing uses of molybdenum. Jump straight to the full version of this article here.

Back | Blog posts overview