In the refractory industry, “pre-firing” typically refers to the heat treatment of raw materials during manufacturing, whereas the step required before bricks enter the furnace is “preheating” or “baking,” aimed at removing moisture and preventing thermal shock. For your clients, confusing the two concepts can lead to serious safety incidents or shortened furnace lining life.
As a ferroalloy factory, Beifang Alloy understands that the operating conditions of submerged arc furnaces and refining furnaces are extremely harsh. Below is an analysis expanded from four dimensions: procurement requirements, industry research, procurement guide, and supplier comparison, intended for publication on your website.
When clients inquire about “whether pre-firing is needed,” the first step is to clarify their actual procurement scenario. For standard shaped refractory bricks (such as high alumina bricks, clay bricks, silica bricks), the “pre-firing” step should have been completed by the refractory manufacturer during the production process (clinker sintering). The bricks procured by clients are already finished products.
However, from a procurement requirement perspective, the following mandatory preheating conditions must be clearly communicated in the technical agreement or procurement specifications:
Newly built or majorly repaired furnace linings: The entire furnace lining contains a large amount of moisture from masonry mortar and bricks themselves, which must be baked according to a defined heating curve. Rapid heating will cause the moisture to vaporize rapidly, leading to surface spalling or even explosion of the bricks.
Bricks stored in humid environments or subjected to moisture: Clay bricks and high alumina bricks have certain porosity. If stored improperly and moisture is absorbed, they must be dried before use; otherwise, cracking will occur upon heating.
Specific material limitations: Certain low-cement castables or phosphate-bonded prefabricated blocks, although not exactly “bricks,” as refractory materials, require strict drying and baking curves during first use to exclude free water and crystalline water.
In the current refractory industry, technological development is actually moving toward reducing client-side baking time. Industry research indicates that:
Conventional brick linings: Require slow temperature rise according to the manufacturer’s curve. Taking clay bricks as an example, some sources recommend preheating not lower than 30°C, with sufficient heat preservation and slow temperature rise to avoid thermal shock cracking. For large industrial furnaces, the baking period can last several days.
New monolithic refractories: Companies like Krosaki Harima have introduced products like Dry-Free™, whose core selling point is eliminating the long drying process and reducing furnace idle time by improving material permeability to prevent explosive spalling. This is an important trend worth noting in procurement decisions: if production continuity is extremely high and baking time cannot be afforded, prioritizing suppliers with “rapid drying” or “dry-free” technology can significantly improve furnace utilization.
When purchasing refractory bricks, Beifang Alloy recommends that clients use the following questions to clarify technical specifications and avoid disputes:
Ask the supplier: “Is this batch of bricks ready for direct use upon arrival, or is a specific baking curve required?” If baking is needed, request the curve from the supplier as a delivery document attachment.
Review masonry design: Does the design include expansion joints? Do the bricks require pre-assembly? In low-temperature environments (below 0°C), bricks must be preheated above 0°C before masonry, and the temperature of refractory mortar should not be lower than 10°C.
Distinguish between material types: If procurement targets are unshaped refractories (castables, ramming masses) rather than bricks, default to “must bake” and strictly follow the three-stage system of “free water removal → crystalline water removal → homogenization”.
When comparing suppliers, the following dimensions should be examined regarding “baking/preheating” support:
| Comparison Dimension | Inferior Suppliers | High-Quality Suppliers (Such as Beifang Alloy Standards) |
|---|---|---|
| Technical Data | Only provide brick physical and chemical indicators | Provide complete baking curve and masonry precautions |
| Material Adaptability | Uniformly claim “no baking needed,” regardless of material | Clearly inform which materials must be baked and which can be rapidly heated based on material properties (such as phosphate-bonded, cement-bonded) |
| Storage Guidance | No guidance on moisture protection | Clearly require moisture-proof and rain-proof storage, with pre-use inspection of brick condition |
| After-sales Support | No follow-up after delivery | Provide guidance on initial furnace commissioning heating specifications |
Beifang Alloy’s Recommendation: For ferroalloy furnace applications, do not risk skipping the baking step to save a few hours of furnace time. The cost of a single furnace lining explosion far exceeds the fuel cost of several days of baking. If you have questions about the preheating requirements for specific refractory materials (such as high alumina bricks, magnesia-carbon bricks, or castables), please feel free to contact us at info@hnxyie.com or visit www.beifangalloy.com for technical consultation.
