Abstract: Operational conditions of the mandrel of the large-sized MPM are analyzed, resulting in determination of the MPM mandrel-purpose steel, the heat treatment process for the mandrel and control measures for quality of the mandrel surface chromium-coating. The main physiochemical targeted values of the H13 Steel as developed for making the said MPM mandrel have been up to the requirements for quality of the hot-work die steel as specified under Specification NADCA 207-2006——Quality Super H13 Steel and Heat Treatment Acceptance. As a result, the structure, properties and service span of the mandrel have also been up to relevant advanced international level, whereas manufacture cost thereof is 28% lower than that of the imported ones.