Measurement of molten metal

Temperature is one of the most critical process parameters affecting the resulting quality, strength and working properties of a metal casting. Molten metal which is too hot will damage the sand moulds. A temperature which is too low will result in low fluidity. Especially complex and thin-walled cast metal parts demand precisely controlled casting temperatures. A molten mass which is not hot enough will exhibit poor metal flow within the complex passages of the mould and may result in bubbles or cavities. Strict compliance with process parameters is therefore of utmost importance – and this requires precise temperature monitoring and control.

The temperature of molten metal is most commonly measured using immersion probes. The probe is dipped into the liquid metal after the ladle is filled, that is before pouring even begins. Data accuracy is subject to the precision with which the foundry operator performs the measurement. Depending on the immersion depth and the position of the probe, temperature readings can deviate.

The CellaCast pyrometer is an optical non-contact temperature measurement device. It is a wear and maintenance-free measurement system to measure the temperature in melting, holding, cupola and blast furnaces, and in automatic casting machines.

Liquid metal presents a unique characteristic due to the composition of its surface which is particularly susceptible to slag and oxides. To obtain accurate temperature data, it is essential that the pyrometer only detects and processes the infrared radiation emitted from the clean metal surface. CellaCast is equipped with a special CSD function (Clean Surface Detection) which filters out the signal obtained from the metal surface which is free of slag and oxides.

The two-colour measurement technique provides reliable data in harsh industrial environments, even when dust or steam is in the field of view.

The pyrometer requires virtually no maintenance and does not contain parts subject to wear. Foundries eliminate the need for expendable thermocouple and thus reduce their operating costs.




Measuring point melting furnace (1)

The pyrometer continuously measures the temperature in a runner of the blast furnace, the cupola furnace or the automatic casting machine. It is therefore easy to react to temperature changes immediately and to reach a constant material temperature.


Solution


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The CellaCast PA 80 is used to measure the temperature of liquid metal in runners. It has a very high-resolution optical system and therefore safely detects slag and oxide-free spots within the running melt even from a great distance. The temperature is measured and displayed periodically.The measurement readings can be displayed online, recorded and archived either with a data logger available on site or with the PC software CellaView that comes with the CellaCast system.For optical alignment and control of the target area the devices are equipped with through-the-lens sighting, a laser or a video camera to check the measuring spot from the control centre at any time.The portable pyrometer CellaPort PT 180 can be used for mobile temperature checks.



Measuring point decanting the melt (2)

Temperature is of crucial importance as the molten metal passes from the melting furnace or forehearth to the transport ladle or pouring ladle. The liquid metal must be poured into the mold within a limited time to minimize heat loss. When cooling exceeds 10 °C per minute, the minimum permissible pouring temperature might be violated.


Measuring point casting machine (3)

With optical temperature detection at metal casting operations, a pyrometer is focused on the free falling liquid metal stream. The pyrometer detects the temperature of the molten metal of each cast directly when the moulds are filled. In this process, the position of the pouring stream may vary depending on the pouring nozzle size and shape or the tilting angle of the ladle.


Solution

CellaCast PA 83 was specially designed to measure the temperature of liquid metal poured from a foundry ladle or discharged from a bottom-pour ladle.The unique feature of the CellaCast PA 83 is a rectangular measurement area. As long as the moving stream remains some-where within this rectangular area, CellaCast PA 83 captures the pour and produces an accurate temperature reading.CellaCast features an intelligent ATD function (automatic temperature detection) which automatically produces a temperature reading for each mould. Thanks to ATD, the pyrometer starts measuring just as the ladle starts pouring. Interferences such as flames or molten metal drip (as opposed to a pour stream) will not impact the measurement. The temperature reading will remain very accurate despite such disturbances. When the measurement process is finished, CellaCast displays the temperature reading for each poured mould. Data is transmitted via analogue output and serial interface. This value can also be viewed at a large external digital display so that the foundry operator can instantly see the temperature reading. As an option, a visual alarm signal can be connected so that temperature limit violations can be seen. The temperature data can be saved in a PC or recorded via a data acquisition system. This system ensures full control and documentation of the temperature of all cast workpieces.



Sighting options of the measuring system

Through-the-lens
The CellaCast can be supplied with through-the-lens, parallax-free sighting. The wide field of view makes it easy to focus on the target object. The ocular features a widened interpupillary distance, making it suitable for users who wear glasses or a helmet. The target marker in the viewfinder indicates the exact position and size of the measured target spot.

Laser spot light
Another sighting option available for CellaCast PA 80 is an integrated laser spot light. The laser dot marks the center of the target spot and is well visible even from a distance of up to 10 m. The laser is activated either directly by push-button or remote by means of an external switch or via interface.

Video camera
As an option, the pyrometer can be equipped with a built-in colour video camera to view the target. Based on the latest HDR (High Dynamic Range) technology, the camera provides a higher dynamic range from the imaging process and automatic exposure control. The video image appears without over-exposure and glare.

Another special feature is TBC (target brightness control). The light sensitivity adapts dynamically to the target object captured within the measurement spot to produce a high-contrast image of the target, regardless of whether the object focused on is cooler or hotter than the background. The video signal also transmits the measurement data. The temperature reading is superimposed onto the screen. A separate PC is not required.



Components of the measuring system CellaCast




Technical data of the stationary systems PA 80 and PA 83:

In- and outputs 2 switching inputs / outputs
2 analogue Outputs 0(4) - 20 mA
analogue Input 0 - 10 V
Digital Interface USB and RS 485
Adjustable parameters Scaling of the analogue in- and outputs, Smoothing filter, min/max memory, Alarm contacts (mode and limits), Sensitivity of the dirty window monitoring, TBC Target Brightness Control, White balance of the camera, Simulation of current and temperature, Emissivity, ATD function parameters, Function of LEDs
Power supply 24 V DC
LED display 4-digit (digit height 8 mm)
Protection IP 65 according to DIN 40050
Housing Stainless steel


Technical data of the portable systems PT 180 and PT 183

Digital Interface USB
Adjustable parameters Table for up to 10 emissivity ratio values, Emissivity, ATD function parameters, Function of LEDs
Power supply Built-in battery, Mains adapter for continuous operation
LED display 4-digit (digit height 8 mm)
Protection IP 40 according to DIN 40050
Housing Housing: aluminium
Handhold: polyamide
CellaCast PACellaCast PTCellaCast GießrinneCellaCast Messung

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Measuring System CellaCast

for non-contact temperature measurement of molten metal

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