Engineers at Mitsubishi Corporation Technos—a branch of the Japanese industrial giant dedicated to providing advanced solutions for industrial parts manufacturing—have developed a new alloy, called MTS Additive Mold Steel, or MAMS, that has properties equivalent to SKD61 tool steel. This makes it superior to other AM maraging steels currently used in AM in terms of thermal conductivity, opening up many new possibilities in the use of AM for aluminum die-casting molds.
SKD61 is a high chromium alloy tool steel with high hardness and wear resistance after heat treatment and hardenability. It has good dimensional stability and hot hardness. Common AM maraging steels have low thermal conductivity and hybrid molding of maraging steels and SKD61 is too complex.
Mitsubishi Corporation Technos developed the new MAMS material in collaboration with a major material manufacturer and, for the first time, in the world, they have established modeling conditions that enable modeling with a density of 99.996 ~ 8. This has made it possible to put it to practical use in die-casting of dies for mass production.
Traditional maraging steel requires thin wall designs, which can lead to water leakage due to cracks.
Because of MAMS’ higher thermal conductivity, mold walls can be made thicker, without a reduction in the cooling effect, which increases the degree of freedom in die (and model) design. MAMS has been developed as a high thermal conductivity material that is ideal for aluminum die-cast parts. By achieving high thermal conductivity it can shorten cycle times by improving cooling efficiency and lead to crack prevention by enabling thicker wall designs, reducing total costs by extending mold life.
MAMS hardness can be adjusted by tempering after molding (tempering at 550 ° C or higher is recommended to release residual stress). The materials’ tensile strength is 0.2%, which is equivalent to SKD61 series steel with the same mold hardness. Its Impact value is higher than SKD61 series steel with the same hardness due to the effect of low carbonization.
Rather than fully modeling the entire shape by AM, it can be manufactured by hybrid modeling in which only the free water pipe-shaped part at the tip is added to the base processed by conventional methods. Conventionally, there is only a combination of SKD61 steel for the base and maraging steel for the molding part, and due to the difference in the coefficient of thermal expansion, cracks occur from the interface between the base and the molding part during mass production. The combination of MAMS and SKD61 can reduce the occurrence of cracks at the base and interface.
This hybrid process is a particularly good fit for Japanese manufacturing capabilities. While Japan is seen as somewhat lagging behind in AM adoption (but that has been changing lately) it also has a history of automated manufacturing capabilities which are ideal to address issues such as post-processing and for combining AM with other elemental technologies. Japan leads the use of technologies such as surface treatment, complex, precise cutting, and grinding processes. In particular, mold technology, which is a Japanese specialty, has overwhelming technological capabilities, and Mitsubishi engineers now believe that by combining it with the use of metal 3D printing technology, they can create added value that is second to none in the world.