page_title: Hot pressing
section_title: Indirect resistance heating
hierarchical_section_title: Hot pressing / Indirect resistance heating
caption_attribution_description: English: scheme indirect resistance heating
context_page_description: Hot pressing is a high-pressure, low-strain-rate powder metallurgy process for forming of a powder or powder compact at a temperature high enough to induce sintering and creep processes. This is achieved by the simultaneous application of heat and pressure.
  Hot pressing is mainly used to fabricate hard and brittle materials. One large use is in the consolidation of diamond-metal composite cutting tools and technical ceramics. The densification works through particle rearrangement and plastic flow at the particle contacts. The loose powder or the pre-compacted part is in most of the cases filled to a graphite mould that allows induction or resistance heating up to temperatures of typically 2,400 °C. Pressures of up to 50 MPa can be applied. Other great use is in the pressing of different types of polymers.
  Within hot pressing technology, three distinctly different types of heating can be found in use: induction heating, indirect resistance heating and field assisted sintering technique / direct hot pressing.
context_section_description: With indirect resistance heating technology, the mold is placed in a heating chamber. The chamber is heated by graphite heating elements. These elements are heated by electric current. The heat is then transferred into the mold by convection. As the electrical energy heats the heating elements that then heat the mold in a secondary manner, the process is called indirect resistance heating.
  Advantages are high achievable temperatures, independent from the conductivity of the mold and independent from heat and pressure. Main disadvantage is the time that it takes to heat up the mold. It takes relatively long for heat transfer to take place from the furnace atmosphere to the mold surface and subsequently throughout the cross-section of the mold.
caption: Figure II: Indirect resistance heating
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