FAQ

How to Properly Install MoSi2 Heating Elements?

1. Vertical Suspension MoSi₂ heating elements exhibit high brittleness at room temperature but become ductile at elevated temperatures. Therefore, the optimal installation method for U-shaped MoSi₂ heating elements is vertical suspension. The silicon molybdenum rod is suspended vertically from the furnace ceiling using clamps and straps. This installation approach prevents mechanical stress from being applied to the heating end of the MoSi₂ element, which could otherwise cause fracture. Translated with DeepL.com (free version) 2. Clamp (Accessories) The entire weight of the MoSi2 heating element is borne by the clamp, which also determines its position. Therefore, it must be installed carefully to ensure the element hangs vertically. To prevent localized overheating, the conical lower end of the MoSi2 heating element must extend into the furnace chamber. 3.Connection Straps The connecting wires in contact with the MoSi₂ heating elements use aluminum straps or multi-layer aluminum foil. The outer clamps serve only to secure the connection and do not conduct electricity. The wire ends connect to the busbar. To prevent mechanical stress from being transmitted to the MoSi₂ heating elements, the wire length should be slightly greater than the straight-line distance between the MoSi₂ heating elements and the busbar.

Precautions for Using MoSi2 Heating Elements:

1.Temperature Range Restrictions: MoSi₂ heating elements should not be used within the temperature range of 400°C to 700°C, as low-temperature oxidation occurs in this range, leading to element damage. 2.Atmosphere Suitability: MoSi₂ heating elements are suitable for use in air or neutral atmospheres. Reducing atmospheres will destroy the protective layer, while chlorine and sulfur vapors cause direct damage to the elements. 3.Continuous Operation: During heating, MoSi₂ heating elements form a protective silica layer on their surface to prevent further oxidation. Therefore, continuous operation is recommended to maintain their service life. 4.Hot-End Clearance: Maintain a specified distance between the hot end of MoSi₂ heating elements and furnace walls to prevent wall damage or element fracture. 5. Low-voltage startup: During initial operation, the resistance of MoSi2 heating elements increases sharply with rising temperature. Therefore, a low-voltage startup is recommended, with a startup current of 25%-30% of the normal operating voltage, not exceeding 300A. After 15 minutes, switch to the normal operating voltage. 6. Avoid frequent operation below 800°C: Repeated heating and cooling cycles in electric furnaces cause frequent expansion and contraction of MoSi2 heating elements, leading to partial loss of the silica protective coating. Therefore, frequent operation below 800°C should be avoided. 7. Regeneration of the silica protective layer: After use in a hydrogen atmosphere, the silica protective layer on the surface of the molybdenum disilicide rod should be regenerated by heating it to 1500°C for one hour in an air atmosphere. Adhering to these precautions ensures the effective and safe operation of MoSi₂ heating elements.

How to use accessories?

1.Terminal clamp: The terminal clamp of the MoSi2 heating element should be clamped as tightly as possible to ensure full contact with the cold-end aluminum-sprayed section and prevent sparking. 2. Inspect clamp and strap: Regularly check whether the clamp is securely fastened and whether the strap is loose to prevent component damage or other safety hazards.

Installation method for SiC:

1. Due to the brittle nature of silicon carbide elements, handle with care during installation and maintenance to prevent damage. 2.To ensure uniform furnace temperature and load distribution across each element, perform resistance matching before installation. The resistance deviation between each element group should be controlled within ±5%. 3.When initially energizing the furnace, gradually increase the voltage slowly. Do not apply full load at once, as excessive inrush current may cause element damage. 4.The elements usage must be equipped with adjustable transformer or SCR voltage regulator,voltage meter,current meter and auto-control temperature meter etc. During the operation,the voltage should be raised to kee pthe normal furnace temperature because the resistance value will increase gradually caused by the oxidation of element. When the voltage israised to the top limit of the transformer but still fails to meet the requirements, the furnace should be stopped, changing the way of wire connection and then continue to work. 5.During the long term operation of the furnace,if any individual heating element is damaged for some reasons and need to be replaced, proper one with appropriate resistance value should be selected based on the growth of resistance values, never use a new heating element random.If many heating elements are damaged or resistance value increases too much and cannot reach the furnace temperature,it is better to replace all heating elements with new ones. Test and mark the resistance value of the old elements having been replaced(with voltmeter and ammeter), adjust the resistors and distribute them in low temperature area. 6.New furnace or the furnace that has not been used for a long time must be dried before use. When drying them,it is better to use old elements or other heat source.

What are Molybdenum disilicide heating elements?

Molybdenum disilicide heating elements are high temperature protection tubes made of molybdenum disilicide (MoSi2) with excellent resistance to high temperature, oxidation and corrosion, and are widely used for the protection of temperature measuring elements in high temperature environments. Molybdenum disilicide heating elements and MoSi2 heating element, the same at room temperature, hard and brittle, in the installation and transport summary should avoid collision, impact. When the use temperature is above 1300 degrees, it should be installed vertically to avoid deformation. Molybdenum disilicide heating elements product identification method: MS / D / d / L. D represents the outer diameter of the protection tube, d represents the inner diameter of the protection tube, L represents the length of the unit in mm. this product is an extension of the molybdenum disilicide heating element, the use of materials and the production of the same material MoSi2 with high temperature resistance to oxidation, corrosion resistance, good thermal stability and melting point and other characteristics.

Usage Instructions for Silicon Carbide Heating Elements

1. New furnaces or electric furnaces that have been unused for extended periods must be dried out before use. Whenever possible, use old rods or other heat sources for drying. 2. After silicon carbide heating elements pass through the rod holes on both sides of the furnace wall, they should rotate freely 360°. Avoid forced installation or hammering. Before installation, test-fit using an iron pipe matching the rod end diameter.   3. Silicon carbide heating elements are hard and brittle. Exercise extreme caution during transportation, unpacking, installation, and replacement. Handle with care, avoid mechanical impact, and prevent rod breakage. 4. When energizing a new furnace, gradually increase voltage to prevent rod breakage. Typically, start at half the rated voltage. Only after confirming normal operation should voltage be progressively raised.     5. If moisture is released during the heating process of components or materials, the resistance furnace must be equipped with exhaust vents to remove moisture or other harmful gases from the furnace chamber. This prevents adverse effects on the rod's service life.   6. During storage, protect rods from moisture. If the aluminum-coated ends show deterioration or delamination, reapply aluminum coating after surface treatment. If recoating is unavailable, wrap the coated section with several layers of aluminum foil before reuse.   7. Silicon carbide heating elements must never be operated beyond their rated capacity. If an element breaks or exhibits uneven heating—such as localized white-hot or dark red sections—this indicates uneven aging and significant resistance variations across segments. Immediately shut down the furnace for inspection and element replacement.   8. Silicon carbide heating elements must be equipped with a voltage-regulating transformer or thyristor voltage regulator, along with voltage/current meters and automatic temperature control instruments. During operation, rod oxidation causes gradual resistance increase. To maintain normal furnace temperature, operating voltage must be elevated. If voltage cannot meet requirements even at the transformer's maximum capacity, shut down the furnace, reconfigure the rod wiring, and resume operation.

Characteristics of Silicon Carbide Heating Elements：

Silicon carbide heating elements are primarily composed of silicon carbide, an artificially manufactured abrasive material. Silicon carbide is typically categorized into black silicon carbide and green silicon carbide, with green silicon carbide exhibiting higher purity. Silicon carbide possesses relatively stable properties and does not react with any acids. However, at temperatures around 1300 degrees Celsius, it can undergo chemical reactions with alkalis and basic oxides. Beyond its use in the abrasive industry, silicon carbide leverages its electrical conductivity, thermal conductivity, and extended service life in the electrical sector to produce silicon carbide heating elements. Consequently, the chemical properties of silicon carbide heating elements closely resemble those of silicon carbide itself.

Oxidation Resistance of Silicon Carbide Heating Elements

Silicon carbide heating elements experience a rapid temperature rise when energized. Typically, in air, surface oxidation begins when the elements temperature reaches 800 degrees Celsius.As the temperature continues to rise to 1000–1300 degrees Celsius, the heating section of silicon carbide heating elements reacts with air, producing carbon dioxide and silicon dioxide.Silicon dioxide will condense on the surface of silicon carbide heating elements, thereby forming a dense protective layer.As the elements temperature continues to rise to approximately 1550°C, the protective layer thickens due to the continuous production of silicon dioxide. This thickening effectively isolates the silicon carbide heating elements from the air, providing robust protection for the elements.This begins to reduce the oxidation rate of silicon carbide heating elements.However, the silicon dioxide protective layer also has a certain melting point. If the elements continues to heat up to temperatures above 1600 degrees Celsius, the silicon dioxide protective film will be damaged due to excessive heat, leading to reactions such as peeling off. Subsequently, the oxidation rate of the silicon carbide heating elements will increase again.During operation, such situations should be avoided as much as possible. The structure of resistance furnaces or industrial electric furnaces should be designed appropriately. When installing silicon carbide heating elements, pay attention to the positioning of the elements to prevent excessive local temperatures during use or other electrical faults from causing the silicon carbide heating elements to overheat. This significantly reduces the service life of the elements.