A furnace may include a furnace muffle that can accommodate relatively larger workpieces than other furnaces. The furnace muffle may include a cover that includes one or more sets of plates. The plates may be configured to prevent sag during extended runtimes while still enabling the furnace to reach a temperature (e.g., a temperature between 1590° C. and 1650° C.) for sintering a workpiece. In some examples, the cover may include a first set of plates of a first material (e.g., a first alumina refractory material) and a second set of plates of a second material (e.g., a second alumina refractory material). The second material may have greater thermal conductivity than the first material. Accordingly, plates of the second set may be located in higher temperature zones of the furnace to enable efficient heat transfer from heater elements through the furnace muffle to a contact plate where a workpiece is heated.

A double insulating wall structure heating furnace capable of preventing its inner pipe whose strength has decreased due to high-temperature heating from being damaged. A double insulating wall structure heating furnace 1 includes an outer pipe 2 and an inner pipe 3 disposed inside the outer pipe 2, in which a sealed space 8 formed between the outer and inner pipes 2 and 3 is depressurized and a heating space 13 formed inside the inner pipe 3 is heated, and in which a tubular reinforcing member 6 is disposed so as to cover an outer circumference of the inner pipe 3, the tubular reinforcing member being formed of a material having a higher heat resistance and a higher strength than those of the material of the inner pipe 3.

A heat resistant structure includes: a core formed of a plurality of C/C composite members; and a shell material covering at least a portion of a surface of the core and made of metal.

A double insulating wall structure heating furnace capable of preventing its inner pipe whose strength has decreased due to high-temperature heating from being damaged. A double insulating wall structure heating furnace 1 includes an outer pipe 2 and an inner pipe 3 disposed inside the outer pipe 2, in which a sealed space 8 formed between the outer and inner pipes 2 and 3 is depressurized and a heating space 13 formed inside the inner pipe 3 is heated, and in which a tubular reinforcing member 6 is disposed so as to cover an outer circumference of the inner pipe 3, the tubular reinforcing member being formed of a material having a higher heat resistance and a higher strength than those of the material of the inner pipe 3.

A furnace may include a furnace muffle that can accommodate relatively larger workpieces than other furnaces. The furnace muffle may include a cover that includes one or more sets of plates. The plates may be configured to prevent sag during extended runtimes while still enabling the furnace to reach a temperature (e.g., a temperature between 1590 C. and 1650 C.) for sintering a workpiece. In some examples, the cover may include a first set of plates of a first material (e.g., a first alumina refractory material) and a second set of plates of a second material (e.g., a second alumina refractory material). The second material may have greater thermal conductivity than the first material. Accordingly, plates of the second set may be located in higher temperature zones of the furnace to enable efficient heat transfer from heater elements through the furnace muffle to a contact plate where a workpiece is heated.