Application of high temperature camera thermometer in steel industry

Remote imaging and non-contact temperature can be well combined steel used in some processes, for example, a heating furnace and rolling mill. The high temperature camera thermometer provides an excellent tool for optimizing monitoring and temperature measurement functions because of its flexible combination of unique video imaging and infrared temperature measurement. This combination opens up new avenues for steel mills that have not used cameras before, especially making it easier to repair the furnace. The following highlights the potential applications of high temperature camera thermometers in steel plants, and introduces the temperature measurement of solid and liquid steel.
Steel Industry & Temperature Measurement In general, because steel has the property of low radiation rate, it is difficult to measure the temperature of steel with an infrared thermometer. The radiation rate is a property of matter that indicates how much infrared radiation is emitted from the same black object (which is an object with an emissivity of 1, which represents an excellent radiation). The higher the radiation value, the higher the energy reaching the detector. Basically, the higher the emissivity, the easier it is to measure the temperature of an object.
For steel products, the emissivity varies with temperature, surface conditions, and the chemical composition of the steel. One variable that has a large effect on emissivity is the surface condition. For example, an oxidized stainless steel (as when processed at a factory) has an emissivity of about 0.4. For highly oxidized (more "black") surfaces, this value rises to 0.8. For surfaces that are planed (very "bright"), the emissivity is reduced to 0.2. Since the high-temperature camera thermometer provides a flexible method of changing the emissivity for each of the cursor-selectable areas on the screen of the terminal, as long as we know the parameters and specifications of the raw materials to be processed, reliable measurement temperatures can be obtained.
Another problem to be understood is the thermal reflection of the steel surface by the hot furnace wall, which is more important for the application of steel in solid state, such as steel in heating furnaces and annealing furnaces. There is a large temperature difference between the steel surface and the furnace wall, combined with the high reflectivity properties of steel (like a mirror), making it difficult to measure absolute temperatures in these applications. However, it is possible to periodically observe the product or changes in its processing with relevant measurements. In the application of steel melting, this issue is not important. Especially for electric furnaces, it is not affected by this problem because the furnace wall is not the hottest part of the process. The following sections detail the potential applications and potential difficulties of high temperature camera thermometers in the steel industry.
The blast furnace blast furnace is where the steel production process begins and where continuous operation is required. It is a container in which iron ore and limestone , coke (solid matter obtained from the residue of coal , bitumen , petroleum ) are mixed. These mixtures are heat treated in a blast furnace to produce molten iron which then falls to the bottom of the furnace. These molten mixtures are moved by the fish-shaped ladle to the next step in the process. This is an extremely dusty environment with very poor visibility. Installing a camera in the blast furnace area is of little value.
A surveillance camera with temperature measurement is very useful in order to control the combustion in the "cavity" (burning zone) of the furnace, unless it is used as a fuel at the tuyere or at the steel mill. The camera installed in this position is not used to observe the product, nor to watch the fireball. Since the flame is full of particles, it is possible to measure their temperature. Knowing the temperature and size of the furnace "cavity" is valuable and a very important control tool. Due to the potential low fuel cost, and the use of pulverized coal as a fuel in combination with blowing oxygen to promote its combustion has become very popular in European society.
There are two (container) parts in the blast furnace that make it easy to repair by using a high temperature camera thermometer, one for the furnace and one for the fish-shaped ladle. The furnace body is a container for generating the hot air required by the furnace. It is a high-cylindrical structure made of heat-resistant brick. The heat generated by a large burner is stored before it is sent to the air used as a blast. Each blower unit has 3-4 furnace bodies. The refractory life is critical. Some factories use infrared imaging for very small hot spots and then use black and white photographs to locate the actual location in the furnace. High-temperature camera thermometers are useful in this application by identifying the location of the hotspot (using the magenta-yellow palette) and then setting the cursor area to the maximum temperature mode to identify the temperature at that point. Fish ladle is used to heat the metal product to the furnace from the blast furnace steel production. Generally, it is a large cylindrical object made of refractory material and mounted on wheels. No combustion occurs at this stage. If it has not been empty for a long time, the appearance of hot metal is enough to provide enough brightness for using the camera. Continuous monitoring of refractory bricks is normal, but it is difficult to observe all of the contents. However, a high temperature camera thermometer with a 78" vertical lens can successfully see every corner of it. The temperature measurement function of the high temperature camera thermometer with visible image can help you decide which brick needs to be replaced. The stability and integrity are critical. Failure during transportation can cause serious damage, for example, complete damage to containers, rails, work areas, etc., resulting in expensive downtime – any of these rolling mills are paid Can't afford it.
There are three steel production processes commonly used in the steel production process: oxidation, open hearth furnaces and electric furnaces. At this stage, iron from the blast furnace is converted into low grade steel and then ingots or billets are formed.
Oxidation Process The oxidation process involves mixing the liquid hot metal of the blast furnace with the flux and then transferring it with a large amount of oxygen into a large insulated cast spoon. In the industry, this is often identified as a basic oxidation furnace (Basic Oxygen Furnace or BOF). Basically, no burning is taking place during this batch process. Despite the lack of flame, the high temperature camera thermometer can effectively measure the temperature of the charge. It is a key parameter and it is used to determine the key parameters of the liquid level in the casting spoon to determine when the molten metal will be released. Currently, it is the most common method to measure the charge temperature by inserting a thermocouple into a pool of bath. We have received inquiries about how to use high temperature camera thermometers in this process. Here, there is potential, but we can't make an experimental demonstration to prove this theory. In addition to maintenance and re-laying, the feedback results corresponding to this process are more difficult to determine.
Open hearth process

Open hearth furnaces are the most efficient steel production process (mainly in the ability to process raw materials for pieces/waste). Basically, this process is responsible for the melting of the iron, the crumb/waste limestone charge together with the different fluxes during the batch process. This process is carried out in a large insulated rectangular furnace with a sloping floor. The flame on the charge is ignited from one end of the furnace to the other, melting all the components. In such a furnace, the charge is a mixture of solid and molten metals having different temperatures, so it is necessary to set different emissivity for accurate temperature measurement.
The high temperature camera thermometer installed under the flame generator during this process will provide the operator with:
The temperature measurement of the furnace wall of the melting process - it is useful for assessing the life of the bricks. The temperature of the batch is measured at the end batch temperature - in terms of controlling and obtaining the desired metallurgical properties and once the steel is ready and It is important to ensure that the long-term cooling process in the furnace is eliminated after pouring.
In this process, the electric current is used to generate an electric arc from the electrode to the charge to generate a strong heat and to melt it quickly. There is no need to use oxygen to burn, but the heat is very strong and can be strictly controlled. This provides the most flexible way to produce most of the iron and steel can only be produced in an electric furnace, for example, (1) high-manganese steel, (2) a large number of stainless steel alloys, (3) a high temperature superalloy steel.
We have successfully installed a S high temperature camera thermometer in an iron-free alloy arc melting furnace - similar to a steel production furnace. This system is used to monitor the melting zone and it can be used to monitor both the size of the melt zone and the wear of the refractory bricks. There is no problem with heat reflection in this application, and there is no change in emissivity due to oxidation. As for the video image, there is a big difference between the full power and the starting power of the electrode under bright conditions. If the aperture of the high temperature camera thermometer is immutable, it is difficult to see the product under certain conditions. In order to solve this problem, we have developed a product with a remote control auto iris. Because a strong magnetic field is generated during this process, it is a good idea to install a video monitor in an environment such as a control room. Because if the monitor is close to the arc, the image is likely to be affected.
The soaking furnace soaking furnace is used to make the temperature of the ingot uniform. As discussed earlier, the ingot is cast at the exit of the furnace. This is necessary to ensure the metallurgical properties of the entire product and the "bulk" nature of the structure before thermal processing and further processing in the breakdown (damage) rolling mill.
This process requires a dozen or so ingots and refractory bricks to be placed in a large pit and then heated as a whole. There is no continuous movement in the furnace, so camera monitoring is less needed. However, if the camera is installed to observe the flame, the high temperature camera thermometer is very helpful for fuel control.
The normal temperature range for heating the ingot is between 1175 ° C and 1345 ° C. The exact temperature depends on the grade of the steel and the characteristics of the rolling mill. In order to preserve the fuel here, it is important to measure the temperature of the ingot to avoid overheating the surface. Currently, temperature measurements are mostly done by thermocouples. The ingots are subjected to "soaking" for about 8-12 hours at a time. This process results in a large amount of oxidation of the surface of the ingot and it is difficult to obtain a good viewing angle due to the nature of the emissivity during the operating time.
The reheating furnace steel sheet is the production result of a rolling mill from breakdown (damage). Typical steel sheets are produced to a length of 25 feet and a thickness of 4". During the process of the steel sheet passing through the breakdown (damage) of the rolling mill, the raw material loses a lot of heat, which becomes brittle and the flexibility is deteriorated. The steel sheet needs to be reheated for further processing. At least a steel plate temperature of 1200 ° C is required and this temperature can be reached in the reheating furnace.
The design of the continuous furnace varies with the steel plate travel mechanism, for example, a simple mechanical thruster, a rotary hearth or a walking conveyor. These mechanisms lift the steel plate through the furnace. The hearth (blow torch) is directed in the opposite direction of the movement of the steel plate. The reheating furnace is located in the path in which the rolling mill material travels. Since the reheating furnace may become a production bottleneck, it is necessary to perform continuous temperature measurement on the steel sheet. The steel sheet always travels inside the furnace (sometimes very slowly) and it is difficult to make contact temperature measurements by thermocouples.
Due to these difficulties, infrared thermometers are often used in these applications. The requirement for an infrared thermometer is compensation from the surface of the steel to the radiation emission of the thermometer (generated by particularly hot surrounding objects). The difference of 100 ° C or less between the furnace wall and the steel plate makes the value of the monochrome thermometer read at 0.8 mm higher than the actual 30 ° C. The temperature difference of 200 ° C between the furnace wall and the steel plate makes the value read by the monochrome thermometer 120 ° C higher than the actual value. The specific data will vary with the furnace. If the relevant temperature of the steel plate or the uniformity of heating is important, since the absolute temperature is not the main parameter of this industry, the high temperature camera thermometer can provide useful information. The travel of the steel plate in the furnace can only be observed by the camera monitor. In some places, up to three cameras are used in each furnace to achieve complete observation of the movement of the steel plate.
The final treatment of the applied steel sheet production in the rolling mill is the rolling process, hot rolling and cold rolling. First, the heated steel sheet passes through a hot rolling mill, where the basic function is to reduce the thickness of the steel sheet by 40%. Secondly, the steel plate advances to the last step in the production of steel sheets - cold rolling treatment - hence the name, because the unheated metal passes through the rolling mill. Through this process, the final thickness required for steel sheet products, such as steel sheets for automobiles, steel sheets for beverage containers, building materials, and the like, can be obtained. Cameras have been widely used in rolling mills (hot and cold rolling) for monitoring between rolling mills.
Temperatures need to be measured at the inlet and outlet of the rolling mill (hot and cold). The temperature of the steel plate at the entrance determines the "gap" (the strength of the insulation), which is useful for the operator during rolling. The temperature at the outlet determines the mechanical properties of the steel's final product. Infrared thermometers have been used in these two places. The high temperature camera thermometer at the entrance completes the auxiliary monitoring function by providing an image of the steel plate into the rolling mill; it is necessary for tracking. When the steel plate stays for almost 30 seconds before entering the first stand, the six temperature measurement areas of the high temperature camera thermometer will measure the temperature difference along the length of the steel plate before it enters the rolling mill. This is a potentially large application for high temperature camera thermometers because observation and temperature measurement are equally important.
Other parts of the industry may require continuous casting – for example in rolling mills in some plants. In these applications, before the steel is poured, there is a large furnace to melt the steel (these stoves may also tilt). The product is poured into a series of tanks and the molten metal is distributed to a movable conveyor belt to directly produce steel sheets. There is a need to see the flow of raw materials along the processing path, and infrared thermometers have been used to monitor the solidification process of steel at the end of the conveyor.
The structural changes imposed on the raw material during the cold rolling process of the annealing (toughening) furnace necessitate "annealing (toughening)" (relaxing) the steel structure before being formed. If there is no annealing step, the steel sheet product is fragile during any forming process. There are two types of furnaces: closed annealing and continuous strip annealing. Closed annealing is a batch process that uses a heated air to heat a set of cold rolling mill coils. There is no critical temperature requirement for moving without raw materials. Applying our products here will not bring much value.
On the other hand, the heating and cooling unit in the continuous strip annealing furnace is built into the tower, so there may be potential applications, as our system will bring real benefits to the operators of the rolling mill. The steel moves on a continuous path and quickly passes through the heating and cooling towers (some are five stories high). Steel travels around the top and bottom of the tower around the rollers to increase the time it takes for the steel itself to be in the furnace. Finally, the steel is "cooled" (the molecular structure of the steel at this time is frozen) to its final temperature.
As for the alloy, the steel needs to reach a temperature between 730 ° C and 1050 ° C. The uniformity of temperature over the width of the steel sheet determines the mechanical properties of the steel and is an important parameter. Because the speed of the raw material is changing (up to 7 m / s), and the temperature information from the high temperature camera thermometer can be set at different points, the high temperature camera thermometer can also view the steel plate on the large annealing line. Currently, there is no way to tell where the edge of the strip is related to the roller. This observation is advantageous for the operator to control the movement of the steel plate as long as there is sufficient light.
However, the lens tubes of some furnaces are under controlled air and use non-automatic gas, so cooling of the camera is necessary in these annealing furnace applications.
Summary The above description talks about the traditional application of many cameras and high temperature camera thermometers in a comprehensive steel mill. There are also a number of ancillary applications such as waste melting furnaces, plating lines, extrusion lines and coating lines where the application of the camera is beneficial to both the operator and the rolling mill. These processes do not exist in every steel plant. They are generally found in factories that produce special products.

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