Reheating Furnaces serve the purpose of heating steel blooms, billets or slabs in steel rolling mills. Reheating furnaces takes this steel stock up to approximately 1200 degree Celsius. The steel begins to deform at this temperature, and the steel rolling process can begin. In a reheating furnace, the heat provided to the steel stock is constant. The stock is charged at the entrance, heated up to the assigned temperature in the furnace and discharged at the reheating furnace exit. During the process, the heat gets transferred to the stock in the furnace with the help of radiation and convection. This takes place due to the placement of the burner gasses and furnace walls.
How Does the Heat Transfer Mechanism Operate in a Reheat Furnace?
A steel stock charging temperature can vary drastically, ranging from ambient to the high temperature of 1200-degree celsius. Depending on the dimensions of the steel stock, speed of rolling, and overall steel composition, the exit temperature of a steel stock might differ. The factor of steel quality also plays a huge role when it comes to temperature as it puts limitations on the surface and gradient temperature. It is to be noted that both gaseous and liquid fuels are used in these reheating furnaces.
What Are the Main Characteristics of a Reheating Furnace?
A Reheating furnace’ size depends on its ability to produce hot steel from the cold steel stock and is calculated in tons per hour. The increased heat content determines a reheating furnace and its energy efficiency. When the steel stock is heated from 10 degrees celsius to approximately 1200-degree celsius and is then divided by fuel energy used, efficiency can then be calculated accurately. The energy efficiency of a furnace also relies upon the design aspects of various reheating furnaces.
Design Features That Play a Role in the Energy Efficiency of a Reheating Furnace
- Different styles of burners
- Dimensions of a Reheating Furnace.
- The total number of furnace zones
- Different kinds of roof and wall insulation
- Design of skid
- Combustion air and preheating fuel in recuperators
An energy-efficient reheating furnace is developed in a particular method to allow the steel stock to heat up at a uniform temperature without consuming too much labour and fuel.
Here are some of the important parameters that a reheating furnace must include:
- The amount of heat that must be imparted to the charge
- Creation of necessary heat inside the reheating furnace required to heat the stock and curb steel losses
- The transfer of heat created onto the surface of the stock that needs to be heated
- Temperature equalisation within the stock
- A decrease in heat losses from the reheating furnace to a minimum
Several operational approaches also play a crucial role in the energy efficiency of a reheating furnace. The ideal case of a reheating furnace is when the furnace is operated at the rated capacity with one kind of steel stock, which has the same dimension and composition. But often, this practice is not followed, which hampers the efficiency of the reheating furnace.
Factors That Affect Efficiency of a Reheating Furnace
- Differences in the dimension and composition of steel stock
- Delays in rolling can delay or halt the movement of steel stock in the furnace
- The composition of the fuel and its availability may differ
- The conditions of the burners and the internal state of the reheating furnace might deteriorate
How Are Reheating Furnaces Classified?
Several types of reheating furnaces are available in an average steel rolling mill, but how are they classified into different categories? Reheating furnaces are usually placed in four categories based on:
- Heating Method
- Charging the reheating furnace method
- Steel stock movement inside the reheating furnace
- Recovery of the heat method
If the reheating furnace is classified based on the heating method, there will be two types of heating.
- Electrical Heating
- Combustion Heating
Combustion heating reheating furnaces are able to use solid, gaseous and liquid fuels.
When the classification is based upon the steel stock’s movement in the furnace, a continuous furnace can be categorized further.
- Pusher Furnace
- Walking Beam Furnace
- Roller Hearth Furnace
- Walking Hearth Furnace
- Rotary Hearth Furnace
When the classification depends on heat recovery, there are only two types of reheating furnaces.
- Regenerative Type
- Recuperative Type
The regenerative type of reheating furnace operates on regenerative burners. On the other hand, the recuperative variety of reheating furnaces functions with recuperators.
FAQs
What is a reheating furnace?
A reheating furnace is an industrial furnace used to raise the temperature of semi-finished steel products like billets, blooms, and slabs before further hot working in processes such as rolling, forging, or extrusion. It ensures that the material reaches a uniform and optimal temperature, typically above 1,100°C, so it can be shaped without cracking or losing strength.
What is the purpose of a reheating furnace in a rolling mill?
In a rolling mill, the reheating furnace plays a critical role by preparing metal for deformation. It heats steel billets or ingots to the appropriate temperature to make them malleable before passing them through rollers. This ensures efficient material flow, better mechanical properties, and improved surface finish in the final rolled product.
What are the main types of reheating furnaces used in steel plants?
The most common types of reheating furnaces include pusher type furnaces, walking beam furnaces, rotary hearth furnaces, and shaft furnaces. Each type is selected based on production volume, fuel efficiency, heating uniformity, and the type of material being processed. Walking beam furnaces are popular in modern rolling mills due to their ability to prevent billet skid marks and ensure uniform heating.
How does the reheating furnace process work?
The reheating furnace process involves feeding metal billets into a furnace chamber, gradually increasing their temperature through zones (preheating, heating, and soaking), and maintaining this temperature for uniformity. Once the billets reach the desired temperature, they are discharged to the rolling mill for further processing. Proper combustion control and temperature monitoring are essential for energy efficiency and metallurgical quality.
What fuels are commonly used in reheating furnaces?
Reheating furnaces can be powered by various fuels including natural gas, furnace oil, diesel, LPG, and even electricity in some advanced setups. Natural gas is considered the most efficient and environmentally friendly option, offering clean combustion and easy temperature regulation. The choice of fuel significantly affects operating costs and emissions.
Why is uniform heating important in reheating furnaces?
Uniform heating in a reheating furnace is crucial to prevent thermal stresses and material defects. If parts of the billet are heated unevenly, it can lead to cracking, poor surface finish, or dimensional inaccuracies during rolling. Consistent temperature distribution also improves metallurgical properties and helps maintain the structural integrity of the final product.
What are the key components of a reheating furnace?
Key components of a reheating furnace include the combustion system (burners, fuel lines), the furnace chamber (lining, insulation), charging and discharging systems, temperature sensors, control panels, and flue gas exhaust systems. In walking beam or pusher type furnaces, billet movement mechanisms are also integral parts of the operation.
What are the advantages of modern reheating furnaces?
Modern reheating furnaces offer several advantages such as improved fuel efficiency, lower emissions, precise temperature control, and higher productivity. Advanced automation systems help optimize combustion and billet movement, reducing energy consumption and minimizing human error. This leads to better process consistency and overall cost savings.
How can reheating furnaces be made more energy efficient?
To increase energy efficiency in reheating furnaces, manufacturers often use regenerative burners, waste heat recovery systems, and advanced insulation materials. Automating the process with temperature control and fuel monitoring systems also helps minimize losses. Regular maintenance and calibration of equipment play a key role in ensuring optimal performance.
What safety measures should be taken during the reheating furnace operation?
Operating a reheating furnace requires strict safety measures including temperature and pressure monitoring, proper ventilation for flue gases, emergency shutdown systems, and the use of personal protective equipment (PPE) by operators. Preventing over-heating, leak detection, and adhering to fire safety protocols are also critical to safe furnace operation.
Why Choose Reheating Furnaces From the Best Rolling Mill Manufacturers
When you select reheating furnaces from The Steefo group, you are guaranteed superior quality. Get your hands on the most innovative and futuristic products that will help you change the face of your business.
Our projects and products also experience strict testing and quality checks to deliver best-in-class products. Our emphasis on technology and innovation also delivers up-to-date products for your rolling mill.
To learn more about the Steefo Group and our reheating furnace and how they can improve your productivity and profits, contact +91 98240 76873 or drop a mail at marketing@thesteefogroup.com.