## 4 Conclusions  
In this study, a low-cost, high-functionality shearing mold manufacturing method using heterogeneous material AM for the efficient shearing of 1.5 GPa grade hot-stamped automobile body parts were studied, resulting in the following conclusions:  
1. Two functional metal alloy powders that could be used in the functional parts of shear steel were developed based on the main principles of the metal AM process, the alloy components of the commercial forging material, and the hardness values after heat treatment. The developed material was able to achieve a hardness of 58 HRC or higher via AM without the application of heat treatment, unlike for a commercial mold steel forged material. 2. To improve the mechanical properties of the developed metal powder material after AM, the changes in mechanical properties due to the application of heat treatment were evaluated via an impact test after the application of heat treatment. No improvement was observed in the impact test results for the heat-treated AM material relative to those for the non-heat-treated material. It was determined that the mechanical properties of the material did not improve even when additional heat treatment was applied to the laminated material, because of the occurrence of quenching after melting at a high temperature during the manufacturing process. 3. After evaluation of the various mechanical properties of Forging_C, which is known to have the best mechanical properties required for shear steel among laminated and commercial forging materials presently available, a shear lifetime evaluation was conducted to test the durability of the AM materials for 100,000 cycles. The AM_A material was determined to have a durability of 90,000 cycles, similar to that of Forging_C. However, the impact value of AM_A, which is an important mechanical property required for shear steel, was evaluated to be as low as 20% of that of Forging_C when compared at similar hardness values. Therefore, it was concluded that the lifespan of the AM_A shear steel does not appear to be in proportion to the mechanical properties. To investigate this discrepancy, the microstructures of the laminated and forged materials were observed using FESEM. For the forged material, precipitated phases were observed to be irregularly precipitated in the matrix structure, which was dependent on the application of heat treatment. By contrast, for the laminated materials, precipitated phases were either not observed or were observed to be precipitated in a regular pattern along the grain boundaries in the matrix structure. Therefore, it was concluded that the lifespan of the shear steel was affected by the distribution and characteristics of the microstructure, along with the mechanical properties of the material. 4. The shear steel composed of the non-heat-treated AM_A material and that composed of the heat-treated Forging_C material exhibited the highest lifetimes. However, because the Forging_C material is from three to four times more expensive than D2, its commercial application is limited by the high mold manufacturing costs. By contrast, the AM material can be applied using the newly developed method on 1-2% of the functional parts of S45C, which is 70-80% cheaper than D2 and is used for 98-99% of the non-functional parts of all shear steel. Therefore, relative to conventional techniques, the newly developed method reduces the mold manufacturing cost. Additionally, based on both the mold manufacturing period and maintenance convenience, commercialization of the proposed method is possible. This study has been conducted with the support of the Korea Institute of Industrial Technology as \"Development of intelligent root technology with add-on modules\" (kitech Co-21-0009), Korea, MOTIE, (project No. 20009839) and also the Ministry of SMEs and Startups, New Technology Development with Purchase Condition Project (S2860926)[PERSON]  
The authors would like to thank those associated with co-research organizations (Shinyoung Co., Ltd. and Andong National University in South Korea).