Title: Newly Developed Casting Alloys Of Low Thermal Expansion With High Yield Strength For CFRP Molding Dies

Authors: Kotaro Ona1, Haruyasu Ohno1, Naoki Sakaguchi1, Shin Utsunomiya2 Shinhokoku Steel Corporation15-13-1 Shinjuku-chou,Kawagoe, Saitama, Japan National Astronomical Observatory of Japan2 2-21-1 OsawaMitaka, Tokyo, Japan

DOI: 10.33599/nasampe/c.19.0857

Abstract: New low thermal expansion (LTE) casting alloys with high yield strength have been developed as molding die materials for carbon fiber reinforced plastic (CFRP). Molding dies of CFRP in aerospace industries are often made of LTE alloys either rolled or cast. Fe-36%Ni LTE alloy is used for autoclave process and Fe-29%Ni-17%Co LTE alloy for hot press process [1]. Casting alloys are cost-effective, but have problems of low yield strength and Young’s modulus because their grain sizes are coarse in comparison with rolled or forged alloys [2]. The new alloys have been developed by using an advanced process of cryogenic treatment for martensitic transformation combined with after-annealing for recrystallization and reversible transformation. 36%Ni alloy do not transform to martensite at liquid nitrogen temperature of 77 K. The composition was modulated to 34%Ni in order that martensitic transformation occurred at 77K. 29%Ni-17%Co LTE Alloy has larger coefficient of thermal expansion (CTE) than CFRP, and then the content of Ni and Co was adjusted to 30%Ni-15%Co to have equivalent CTE to CFRP. The recrystallization and reversible transformation after martensitic transformation refined grains of the alloys. Their yield strength increased by 70 to 180% from the original casting alloys. The alloy was adopted for volume-production of guide vanes and the benefits were confirmed.

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Conference: CAMX 2019

Publication Date: 2019/09/23

SKU: TP19-0857

Pages: 9

Price: $18.00