When selecting graphite materials, two popular types are extruded graphite и molded graphite. While both are synthetic graphites, they differ significantly in terms of manufacturing process, grain size, механические свойства, and common applications.
Both are types of synthetic graphite made from petroleum coke and coal tar pitch binder, but their manufacturing processes lead to significant differences in structure, properties, и приложения.
Difference between extruded graphite and molded graphite
1. Manufacturing Process:
Extruded Graphite:
Процесс: A mixture of calcined petroleum coke (filler) and coal tar pitch (связующее вещество) is heated to make it plastic. This hot, semi-solid mix is then forced (extruded) through a die with a specific cross-sectional shape (например, round, square, rectangular). Think of it like squeezing toothpaste from a tube or extruding aluminum profiles.
Result: Produces long, continuous shapes like rods, blocks, or tubes.
Molded Graphite:
Процесс: The coke and pitch mixture (often using finer coke particles than extrusion) is placed into a mold cavity. High pressure is then applied to compact the material into the desired shape. This pressure can be:
Uniaxial/Biaxial: Applied from one or two directions (like pressing powder in a die).
Isostatic (Isotropic): Applied uniformly from all directions, typically using hydrostatic pressure (fluid pressure in a chamber). This is often referred to as “iso-molded” или “isostatically pressed” graphite.
Result: Produces discrete parts or blocks within the confines of the mold. Isostatic molding creates billets that are then machined.
2. Grain Structure and Isotropy:
Extruded Graphite:
Состав: The extrusion process tends to align the graphite particles (coke grains) parallel to the direction of extrusion.
Isotropy: This alignment makes the graphite anisotropic. Its properties (like strength, thermal conductivity, electrical resistivity) are different when measured parallel versus perpendicular to the extrusion direction (Представление преимуществ производительности машины для изготовления клапанных пакетов).
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