Introduction

Hello. I'm Azami, a sensor solution creator.
Macnica offers a thermal measurement system that uses infrared cameras.
We will share an example of how we worked to visualize slag in order to automate the slag removal process in the casting and melting process, resulting in work style reform.

Eliminate industrial accidents! Safely work in front of the furnace

The melting process for casting involves "furnace front work," which is done in front of the melting furnace.
Working in front of the furnace is extremely dangerous work, with dust that can be harmful to the body flying around, andtasks such as measuring the temperature, adjusting the composition, taking samples, and removing slag being carried out in close proximity to molten metal that is over 1000°C.
Among these, "slag removal" is hard work that involves manually removing tens of kilograms of slag.
If the slag is not removed, it can have a significant impact on the quality of the castings, and in some cases can result in damages of several million to several tens of millions of yen. In terms of safety, there have been accidents that lead to health problems and industrial accidents due to inhalation of dust, and in the worst case, fatal accidents have occurred in which workers have fallen into the melting furnace.

Are you worried about how to perform this slag removal work safely and steadily?

In order to carry out slag removal work safely, it is possible to use slag removal equipment to remove it automatically or remotely, but in order to remove slag steadily, it is important to use sensors to determine the amount and location of the slag.

Look for the sensor

What kind of sensor should I use to determine the amount and location of norovirus?
A common approach is to use a visible light camera, which is readily available and relatively inexpensive.
We actually tried to see if we could see the slag in the melting furnace with a visible light camera.
The results are shown in Figure 1.

Figure 1: Results obtained with the visible light camera

The left and right pictures are comparisons of photos taken in the same furnace, taken a few seconds apart. The slag is visible on the left, but not on the right. In other words, depending on the timing, the slag may or may not be visible.

Why does this happen? It is because fumes are coming out of the melting furnace.
With a visible light camera, the fumes coming from the melting furnace can block the view of the slag on the molten metal.
It's like looking at something with your eyes and not being able to see through the steam.

This is how Noro looks!

Unfortunately, it seems that it is not possible to reliably visualize norovirus using visible cameras.
So Macnica used an infrared camera.
The results are shown in Figure 2. To make it easier to understand, we've displayed the visible and infrared images side by side.

Figure 2: Comparison images of visible light camera and infrared camera (noroast detection camera)

The image was obtained by using a visible camera and an infrared camera at the same time, and it can be seen that the infrared camera can see the slag that cannot be seen with the visible camera.

Why are infrared cameras immune to fumes?

An infrared camera is a sensor that senses the infrared radiant energy of an object.
Infrared radiant energy passes through the fumes and can be sensed, making the noro visible.
However, there may be people who say, "I tried an infrared camera before, but it didn't work."

This is due to the specs of the infrared camera.

We have an infrared camera to measure the temperature of hot iron, but it is affected by fumes.
Infrared cameras have specifications for measurement wavelengths, and it is necessary to select an infrared camera with a wavelength band that is not affected by fumes.
An infrared camera is a camera that senses the temperature (infrared radiant energy) even if you can see inside the melting furnace without being affected by fumes.

Isn't "molten metal" and "noro" almost the same temperature? I think some people think.

Actually, the temperature is almost the same.
However, objects have a measure of how much infrared energy they emit called emissivity.
Molten metal has low emissivity, while slag has a solid, dark, rusty metal-like surface with high emissivity.
(Even solid metals, such as polished aluminum, have low emissivity. Darkened or rusty metals have high emissivity.)

That's why you can see the difference in temperature.
An infrared image with temperature bars is shown in Figure 3.

Figure 3: Infrared image

You can see that the white part is slag and the temperature is higher than the molten metal.
Note that this solution is not intended to measure the exact temperature of the melt, so the displayed temperature is different from the actual melt temperature.
The actual temperature is assumed to be around 1400°C. If you want to accurately measure the temperature of the molten metal, you will also use a radiation thermometer.

Once the slag is visualized, the amount of slag needs to be quantified and a decision made as to whether or not slag removal can be completed.
We plan to cover how to do this in a future article, so please look forward to the sequel.

What we found in this article

• Visualizing the slag is the key to automating the pre-furnace work in the melting process.

• With a visible camera, the slag may not be visible due to the fume emitted from the melting furnace.

• Infrared camera can visualize noro without being affected by fumes