Tube-type atmosphere resistance furnace This specialized equipment is primarily used in industries such as metallurgy, glass manufacturing, heat treatment, lithium-ion battery cathode and anode materials, new energy, and abrasive tools to determine material properties under specified atmospheric conditions.
Modern tubular furnaces typically employ three types of furnace lining: brick lining, refractory fiber spray coating, and castable refractory lining.

Brick structure
Brick-lined furnace linings are constructed using refractory bricks, including standard and shaped refractory bricks. Their advantages lie in the ability to select different types, properties, and grades of refractory bricks and refractory mortars based on the varying operating temperatures, service conditions, and thermal loads of different sections of the heating furnace. However, their disadvantages include poor structural integrity and sealing performance, as well as low construction efficiency.
Refractory Fiber Spraying Structure
Refractory fiber spraying involves using a specialized fiber-spraying machine to deliver pre-treated, loose fiber wool at high pressure through the spray gun, while simultaneously injecting an inorganic binder—delivered uniformly via several dedicated fluid-delivery systems—into the fiber wool through the outer annular nozzle of the spray gun. The two components mix externally at the nozzle and are then sprayed as a unified mixture onto the furnace lining. The advantages of this refractory fiber-spraying construction technique include rapid installation, a seamless lining, and excellent air tightness, making it particularly suitable for constructing complex, irregular furnace wall sections. Its disadvantages are:
(1) The furnace lining has low strength and is easily damaged by mechanical forces during operation;
(2) Poor resistance to airflow erosion;
(3) The construction environment is harsh, and quality is subject to human factors, resulting in instability and making it difficult to ensure the equipment’s performance during operation.
Castable Structure
The lining of the furnace is primarily constructed from refractory materials such as heat-resistant concrete and castable refractories. Its main advantages include excellent structural integrity and gas tightness, long service life, ease of mechanized installation, and high construction efficiency. However, it also has certain drawbacks: the refractory materials must be used within their specified shelf life, and repairing the lining is less flexible than with brick-lined furnaces.
Usage Steps
Add water and stir.
The castable material is supplied in pre-packaged bags, each containing the main ingredient and a small sachet of admixture. The main ingredient and admixture should be poured into a mixer. Before using a forced-action mixer, the castable material must be dry-mixed for about 1–2 minutes, after which clean tap water is added and the mixture is stirred. For every 100 kg of castable material, add 77% ± 1 kg of tap water, gradually adding water while mixing until the material is uniformly wet; only then may it be discharged. The freshly mixed wet material should be promptly transported to the construction site for placement. (If the wet material is stored for too long, resulting in degraded workability, it must be discarded; under no circumstances should such material be returned to the mixer, re-wetted, and reused.)
Formwork and concrete pouring
The formwork shall be erected tightly and securely (large-scale slurry leakage is strictly prohibited), and then coated with oil or a release agent in a thin, even layer. After the formwork is properly set, concrete shall be placed evenly along the formwork; when the placement thickness reaches 200–400 mm, the vibrator shall be started promptly. The vibrator should be advanced quickly and withdrawn slowly, with uniform vibration, and prolonged vibration at any single location must be avoided to prevent particle segregation. When slurry begins to appear on the concrete surface and the number of air bubbles decreases, it indicates that the concrete placement has been completed. For sections with a thickness greater than 400 mm, layered construction is required, and such layered construction must be carried out continuously.
Demolding and Curing
Formwork for the castable should be removed only after the material has developed sufficient strength (typically 12–24 hours at ambient temperature). Until the strength is adequate to withstand substantial loads, steps on or impacts against the castable must be avoided, as such actions can lead to cracking and damage to edges and corners. When ambient temperatures are low, curing time should be extended accordingly, or thermal insulation measures should be implemented; ideally, the curing temperature should be maintained above 10°C. If the construction schedule is tight, the ambient temperature may be raised appropriately to accelerate the hardening of the castable. After formwork removal, the castable must continue to cure in a warm, humid environment for at least 12–24 hours before baking can commence.
Lining baking
The furnace lining shall be baked in accordance with the established baking plan and baking curve [1].
Precautions
(1) Water addition must be strictly in accordance with the specified ratio; excessive water will significantly reduce the strength and high-temperature performance of the castable, and water should be minimized as much as possible while still ensuring adequate workability.
(2) The temperature of construction water shall not be lower than 5°C, and the curing temperature shall also be maintained at or above 5°C. When ambient temperatures are low, the curing period should be appropriately extended, or measures should be taken to raise the ambient temperature. It is strictly prohibited to expose uncured, wet-poured concrete to environments with temperatures below 0°C.
(3) The mixed castable material shall be used up within 25–30 minutes; otherwise, the mortar will lose its thixotropic flowability. Castable material that has lost its thixotropic flowability must not be diluted with water and reused.

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