Ceramic Fiber Insulation Block | Metallurgical Car Bottom Furnace Lining Solution | CCEWOOL®

A car bottom furnace is a typical intermittent variable-temperature furnace. In the metallurgical industry, it is mainly used for pre-forging heating of steel ingots and heat treatment of workpieces. According to different applications, car bottom furnaces are generally divided into two types:
Car bottom heating furnace: operating temperature is generally 1250–1300°C
Car bottom heat treatment furnace: operating temperature is generally 650–1150°C
A car bottom furnace usually consists of three main parts: a movable car bottom mechanism, the furnace chamber, and a lift-up furnace door.

Among them, the car bottom structure is generally composed of heat-resistant steel plates and refractory brick construction; the furnace chamber is the main insulation area; and the furnace door and the area below it must withstand not only insulation demands, but also frequent opening and closing as well as mechanical impact.

For car bottom furnaces, lining design is not only about meeting temperature resistance requirements. More importantly, it must also achieve the following goals at the same time:
Meet insulation requirements in different temperature zones
Reduce furnace heat storage and improve energy-saving performance
Reduce the structural weight of the furnace
Improve installation efficiency and simplify later maintenance

For this reason, car bottom furnaces are increasingly suitable for full fiber or composite fiber lining structures. By configuring ceramic fiber insulation blocks, ceramic fiber blankets, and monolithic spray-applied insulation systems in different sections, a more reasonable furnace lining design can be achieved.

Furnace Temperature and Structural Features Determine the Need for Zoned Material Selection

Although both types of car bottom furnaces are intermittent variable-temperature furnaces, their operating temperatures and heat loads differ significantly depending on their use.

For a car bottom heating furnace, the operating temperature is higher, and the furnace walls and roof are exposed to high heat loads for long periods. Therefore, the hot-face materials must have better high-temperature stability.

For a car bottom heat treatment furnace, the overall temperature is lower than that of a heating furnace, but good insulation performance, lightweight furnace structure, and installation efficiency are still required.

Therefore, the lining design of a car bottom furnace does not mean using one single product throughout the whole furnace. Instead, it requires zoned configuration according to the actual working conditions of different sections. Generally speaking:
Furnace walls and roof: main insulation areas
Furnace door and the area below it: frequently opened and closed, and easily subject to impact
Car bottom load-bearing area: carries the weight of workpieces and provides basic refractory support

This determines that different areas require refractory and insulation products in different forms and temperature grades.

Lining Solution for Car Bottom Heating Furnaces Under 1250–1300°C Conditions

For car bottom heating furnaces, the focus of lining design is to withstand long-term operation under higher temperatures while minimizing heat storage and heat loss through the outer shell.

Furnace Wall Section

The furnace wall can adopt the following composite structure:
Two flat-laid layers of CCEWOOL® 1260HPS ceramic fiber blanket or 1400LZ ceramic fiber blanket
Then stacked with CCEWOOL® 1430HZ ceramic fiber insulation block

Among them, the hot-face layer should use zirconia-containing ceramic fiber modules, while the backup layer can use HPS or LZ ceramic fiber blankets. This configuration mainly serves to:
Allow the hot-face layer to withstand the main high-temperature load
Further reduce heat loss through the backup layer
Make the overall structure lighter and more favorable for furnace lightweighting
Improve overall sealing and insulation performance of the furnace wall

Furnace Roof Section

The furnace roof can adopt the following structure:
Two flat-laid layers of CCEWOOL® 1260HPS ceramic fiber blanket or 1400LZ ceramic fiber blanket
Then stacked with CCEWOOL® 1430HZ ceramic fiber insulation block in a single-hole suspended anchoring structure

Here again, the hot-face layer is suitable for zirconia-containing ceramic fiber modules, while the backup layer can use HPS or LZ ceramic fiber blankets. This configuration is better suited to the long-term high-temperature conditions at the furnace roof and can simultaneously ensure:
Overall roof insulation performance
Anchor reliability
Lining integrity
Easier later maintenance

Furnace Door and the Area Below It

Because the furnace door and the area below it are subject to frequent lifting and material impact, they are generally better suited to the following structure:
CCEWOOL® monolithic spray-applied insulation system
Internal stainless steel anchors welded as the supporting framework

Compared with ordinary layered blankets or standard modules, this structure is better able to withstand mechanical disturbance and localized impact, making it more suitable for the special operating conditions of the door area.

Lining Solution for Car Bottom Heat Treatment Furnaces Under 650–1150°C Conditions

Although the overall temperature of a car bottom heat treatment furnace is lower than that of a heating furnace, the general lining design logic remains the same, still centered on lightweighting, energy saving, and convenient installation.

Furnace Wall Section

The furnace wall can adopt:
Two flat-laid layers of CCEWOOL® 1260°C ceramic fiber blanket
Then stacked with CCEWOOL® 1260°C ceramic fiber insulation block using a herringbone or angle-iron anchoring structure
In heat treatment furnaces, this structure can effectively reduce the heat storage of the furnace wall, improve insulation performance, and better suit intermittent operating conditions.

Furnace Roof Section

The furnace roof can adopt:
Two flat-laid layers of CCEWOOL® 1260°C ceramic fiber blanket
Then stacked with CCEWOOL® 1260°C ceramic fiber insulation block in a single-hole suspended anchoring structure
This structure is basically the same as that used in the roof of a heating furnace, with the specific temperature grade selected according to the actual conditions of the heat treatment furnace.

Furnace Door and the Area Below It

This section is likewise better suited to:
CCEWOOL® monolithic spray-applied insulation system
Internal stainless steel anchor framework
The main reason is that this area is frequently opened and closed and easily subjected to impact, so it requires stronger structural stability and better resistance to mechanical disturbance.

Installation Method of the Fiber Lining in Car Bottom Furnaces

According to the structural characteristics of car bottom furnaces, the fiber lining installation mainly falls into two categories: layered ceramic fiber blanket lining and ceramic fiber module installation.

Layered Fiber Lining

Layered ceramic fiber blankets generally adopt a 2–3 layer flat-laid structure, with installation requirements including:
A staggered joint distance of about 100 mm between layers
No through-joints
Fixing with stainless steel bolts and speed clips
This method is more suitable as a backup layer, with the main purpose of improving overall sealing and reducing heat loss.

Ceramic Fiber Module Installation

When installing ceramic fiber modules, they should be arranged reasonably according to the anchoring structure. The main principles include:
Modules arranged in the same direction along the folding direction
A U-shaped folded blanket of the same material placed between adjacent rows for shrinkage compensation
Herringbone or angle-iron anchors may be used for wall sections
A single-hole suspended anchoring structure is used for roof sections
Main Advantages of Full Fiber or Composite Fiber Lining in Car Bottom Furnaces

When a car bottom furnace adopts this type of full fiber or composite fiber lining, the advantages mainly include:
Lighter furnace body: helps reduce the load on the steel structure and lowers equipment investment pressure
Lower heat storage: more suitable for intermittent operation and reduces non-productive heat loss
Faster installation: layered blanket + module structures offer higher installation efficiency
Easier maintenance: modules and layered structures are relatively convenient to remove and replace
Better insulation performance: helps reduce external shell heat loss and system energy consumption
More responsive temperature control: lightweight fiber linings reduce thermal mass and improve heating and cooling control efficiency

For metallurgical car bottom furnaces, a truly effective lining solution is not simply one that meets the temperature requirements of different furnace types. More importantly, it must be based on the structural characteristics of the furnace and provide zoned design for the furnace walls, roof, furnace door, and the area below the door, using corresponding temperature grades and structural forms of CCEWOOL® ceramic fiber insulation block, ceramic fiber blankets, and monolithic spray-applied insulation systems. In this way, the furnace can better achieve lightweight construction, easier installation, more convenient maintenance, and improved system energy efficiency, thereby more effectively meeting the comprehensive requirements of metallurgical heat treatment and pre-forging heating equipment for lining efficiency and structural performance.