Analysis of Causes for Ferroalloy Furnace Body Damage

Analysis of Causes for Ferroalloy Furnace Body Damage

Causes and Analysis of Furnace Lining Failure

1.  Excessive Electrode Working Length: Prolonged operation with an excessively long electrode working end leads to significant consumption of bottom refractories. This results in abnormal temperature rise in the furnace hearth and can ultimately cause burn-through.

2.  Insufficient Electrode Working Length: Conversely, prolonged operation with a short electrode working end shifts the high-temperature zone upward. This causes abnormally high temperatures in the furnace walls near the electrode zone and can lead to burn-through and metal/slag leakage around the tap-hole area.

3.  Unfavorable Slag Characteristics: An unreasonable slag type or failure to meet basicity control requirements can cause severe overheating of the molten metal. This accelerates chemical corrosion of the furnace lining, damaging the refractory materials.

4.  Thermal Cycling from Shutdowns/Startups: Following extended furnace shutdowns, the furnace body is highly susceptible to expansion and cracking. Frequent start-stop operations make thermal cycling damage obvious, often manifested as cracking of the furnace shell steel plates due to temperature fluctuations, requiring timely repair.

5.  Oxygen Blowing and Tap-Hole Opening Operations: The practices of oxygen blowing and mechanical tap-hole opening cause significant localized wear to the tap-hole and surrounding furnace wall. Both carbon bricks and magnesia bricks can undergo oxidation reactions under high-temperature conditions. The resulting weakened, altered structure (a "false lining") fails to provide adequate protection, greatly accelerating the physical deterioration of the furnace.

6.  Water Leakage and High Charge Moisture: Furnace water leaks or charge materials with moisture introduce water into the furnace. While some evaporates, the remainder can dissociate at high temperatures, generating oxygen that corrodes the furnace wall.

7.  Corrosion at Elevated Temperatures (e.g., Taman Temperature): In areas like the working lining of high-carbon ferrochrome furnaces, magnesia bricks in contact with slag are subjected to chemical erosion and mechanical impact from hot metal and slag. When temperatures reach critical levels (e.g., the Taman temperature), changes in the composition and mineralogy of the bricks occur. Even below the melting point, destructive diffusion processes begin.

Summary of Primary Damage Mechanisms

Based on the above, the main damaging factors can be categorized into physical, chemical, and mechanical mechanisms:

1.  Melting/Erosion: Occurs when the operating temperature of the refractory exceeds its refractory limit or resistance to corrosive media. Melting and severe erosion are often observed in the furnace wall near the arc zone and the furnace bottom beneath the electrode tip. Analysis of hearth thermocouple data typically shows the highest temperatures at the bottom directly below the electrode. An excessively long electrode working end significantly exacerbates this bottom temperature rise.

2.  Chemical Attack: Refers to the various chemical reactions between refractory materials and slag, molten metal, furnace atmosphere, dust, and exhaust gases. This includes gas-solid, liquid-solid, liquid-liquid, and gas-liquid reactions. Chemical attack by molten metal becomes particularly severe when the refractory's operating temperature approaches or exceeds its service limit.

3.  Mechanical Action/Abrosion: In the working lining, refractories at temperatures above their load-bearing softening point become highly vulnerable to mechanical wear and loss caused by the movement and impact of molten metal and slag.

4.  Spalling and Cracking: Under conditions of thermal shock or uneven heat load, the internal thermal stress within the refractory can exceed its structural strength, leading to localized damage, cracking, and spalling. This phenomenon is particularly evident in the furnace structure after prolonged shutdowns and subsequent heat-ups and can also be observed in tap-hole runners.

 We are a professional electric furnace manufacturer. For further inquiries, or if you require submerged arc furnaces, electric arc furnaces, ladle refining furnaces, or other melting equipment, please do not hesitate to contact us at  susan@aeaxa.com