Determination of causes related to the low hardness of cavities and cores of an injection mold constructed with steel AISI 420 treated thermally

  • A. de Souza


The technical content of this paper is connected with the identification of the conditions directly related to a
heat treatment process of quenching and tempering that conducted to a low hardness HRC of cores and
cavities of an injection mold produced with martensitic stainless steel AISI 420. For this purpose, three
different analyses of these parts of the mold have been performed by qualitative and quantitative techniques of
material investigation: determination of chemical composition using mass spectrometry, hardness
measurement and metallography. The result of these investigations clearly indicates that a low hardness found
in the material of the cores and cavities (AISI 420 type DIN X39 Cr13) was the immediate result of heat
treatment parameters defined wrongly in the tempering process. The direct consequences of this hardness for
the functional characteristics of the injection mold in dependence on the injection molding technology
normally encountered in the practice are also mentioned in this paper.