Silicon carbide plates play an important role in heating, supporting, and protecting within kilns and furnaces across high-temperature industries. Influenced by various factors, silicon carbide plates may experience issues like cracking, shedding, oxidation, and deformation, shortening the service life and contaminating products, leading to adverse effects on production.
This article will provide a detailed overview of common problems encountered during the use of silicon carbide plates in kilns. Combining practical application cases from daily-use ceramic kilns, it will conduct an in-depth analysis of the primary causes of these issues to serve as a reference for kiln production practitioners.
Silicon Carbide Plates Used in Daily-Use Ceramic Kilns5 Common Problems with Silicon Carbide Plates in Kiln Applications
Although silicon carbide plates have excellent high-temperature performance, they are more likely to be damaged by external factors in high-temperature cycles and complex kiln atmospheres. The following are 5 common types of damage to silicon carbide plates.
Cracking & Fracturing
It is the most common issue for silicon carbide plates in kiln applications. It is represented as micro-cracks, irregular fissures, or complete structural failure.
Cracking is mainly caused by thermal and mechanical stress. The sudden change in temperature in the kiln causes uneven expansion and contraction of the plates. When it exceeds their tensile strength, cracks are bound to occur. Incorrect assembly can also cause uneven stress distribution, leading to cracks.
Shedding
Shedding directly damages tableware, cups, and plates, increasing the scrap rate. If silicon carbide plates exhibit shedding, the fallen particles land on the products being fired in the kiln, resulting in surface defects.
Moreover, carbon particles generated by incomplete combustion can also fall through flame gaps, forming black spots on the products.
Oxidation & Deformation
Silicon carbide reacts with oxygen at high temperatures and forms silica. At temperatures of 180-270℃ and 570-600℃, silica experiences rapid and violent volume expansion and then destroys the plates.
Meanwhile, excessive loading of the silicon carbide plates or misaligned installation of the kiln pillars can cause the plates to warp or deform at high temperatures, further compromising the uniform heating effect within the kiln.
Gas Permeation & Heat Loss
High-temperature gases in the kiln can easily permeate silicon carbide plates and create internal pores. It will degrade the mechanical performance and shorten the service life.
The sintering will occur when the silicon carbide plates are used for a long period at a high temperature. It will reduce the efficiency of the plates in heating, which will affect the efficiency of the kiln.
Corrosion & Aging
Silicon carbide plates are also expected to react with ceramic materials, glazes that are fired in the kiln, as well as corrosive gases that are produced. This reaction will lead to corrosion.
The sintering process at high temperatures causes changes in the size of the plates, resulting in aging. The performance of plates will gradually decline, until they finally fail to meet the requirements of kiln operations.
Case Analysis of Silicon Carbide Plates in Kiln Applications
Taking the RBSiC plates used in a daily-use ceramics kiln as an example, this case provides a detailed analysis of the causes behind the cracking, deformation, and dross shedding. We will provide measures for your reference when using SiC plates in similar kilns.
Background
An enterprise producing daily-use ceramics experienced cracking, deformation, and dross shedding with their silicon carbide plates. The falling particles contaminated the products, and carbon particles within the kiln resulted in black spots on the ceramics. These problems directly led to an increase in the reject rate and a significant rise in kiln furniture replacement costs.
Problems Encountered by The Enterprise’s Silicon Carbide PlatesAnalysis
Testing shows that the silicon carbide plates have no inherent defects. All issues were from external factors.
There was no standardized heating and cooling protocol. The heating rate within critical temperature intervals was too rapid, resulting in thermal stress that caused cracking.
The assembly processes were also not adequately standardized. Mechanical impact resulted in hidden damage to the plates, an uneven pressure distribution increased the tendency for cracking.
Strong oxidizing atmosphere and high humidity inside the kiln accelerated the oxidation of the silicon carbide. And insufficient combustion air resulted in incomplete combustion, causing contamination with carbon particles. It intensified the dross shedding.
Rectification Measures
When using new silicon carbide plates for the first time, they are uniformly placed in the central area of the kiln to minimize the impact of temperature fluctuations.
The factory has standardized operating procedures to slow down the heating and cooling rates within critical temperature intervals. It took protective measures during the handling and assembly of the plates to avoid mechanical damage. Moreover, they inspected regularly to ensure the plates are repaired or replaced on time.
The kiln has been optimized to avoid humidity and excessive moisture. The factory also improved the combustion system and kiln sealing to reduce the generation of carbon particles.
Results
Following the measures, the issue of silicon carbide plate damage has been improved, and contamination from dross and carbon particles has been eliminated. The service life of the plates has been extended, and the replacement frequency of kiln furniture has decreased by 60%+. The product rejection rate returned to normal levels.
If you are facing similar issues, the analytical approach of this case can serve as a reference.
Proper Usage of Silicon Carbide Plates in Kilns
Most damage to silicon carbide plates in kilns stems from non-standard practices in usage, operation, and installation. You can manage the process by the following 5 dimensions.
Proper Selection and Compatibility
Choose silicon carbide plates with specifications that match your working conditions. Also pay attention to material compatibility. Ensure silicon carbide plates will not undergo a chemical reaction with the firing ceramic bodies or glazes.
Adhere to Installation Specifications
Plate handling should reduce mechanical impact or vibrations, which may result in damage to the plates. Plates should be kept level. Their support should utilize the three-point support method. The supports need to align vertically with each other.
Proper expansion spaces should be reserved between the plates and between the plates and the kiln walls.
Strengthen Operational Control
Place products gently to prevent mechanical damage caused by products striking the silicon carbide plates. Slowing down heating and cooling will reduce thermal shock.
Undried product must not be placed in the kiln. For electric kilns, avoid empty firing or dry firing.
Optimize Kiln Environment
In humid conditions, please take moisture-proof and dehumidification measures and regularly inspect the sealing of the kiln. Repair any problems in the kiln body promptly. Proper air circulation in the kiln should be achieved to create a stable and suitable environment for kiln operations.
Timely Maintenance
Develop an inspection and maintenance process. During each maintenance, inspect the plate surfaces carefully for cracking, shedding, deformation, or corrosion. Clean residues from the surface of the silicon carbide plates and replace severely damaged plates.
Silicon carbide plates should be stored in a dry and ventilated place to avoid moisture.
FAQs
Why does uneven heating cause plate failure?
Rapid temperature changes will cause uneven expansion and create internal stress. When stress exceeds tensile strength, the plates crack.
How do kiln pillars affect plate life?
Misaligned pillars will create uneven pressure distribution. This leads to warping or fracturing at high temperatures. Always use vertical three-point support for stability.
What causes black spots on finished ceramics?
Incomplete combustion generates loose carbon particles. These particles fall through gaps onto the products.
Can moisture damage silicon carbide plates?
Yes. High humidity can accelerate oxidation. It degrades mechanical performance over time. So you need to store plates in dry, ventilated places and ensure products are dry before firing.
When should I replace kiln plates?
Inspect surfaces during every maintenance cycle. Look for deep cracks, shedding, or severe warping. If there are, or they no longer meet operational requirements, replace them.
Conclusion
The operational status of silicon carbide plates is directly related to kiln efficiency and product quality. Mastering scientific usage methods and implementing full-process control can effectively prevent various types of damage. This significantly extends the service life of silicon carbide plates, reduces replacement costs and production losses, and enhances production efficiency and comprehensive benefits.
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Thanks for your reading. Hope this article will be helpful.
