# An Experimental Investigation to Facilitate an Improvement in the Design of an Electromagnetic Continuous Casting Mould

^{1}

^{2}

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## Abstract

**:**

## 1. Introduction

_{3}O

_{4}-Ethylene glycol) past a channel with a sinusoidal upper wall, the thermal behaviour of an external electric field was discussed [10]. The results showed that the fluid deformation appeared and the heat transfer performance was enhanced, at a different Reynolds number, due to the external electric field. For a flow past a porous diamond shape obstacle, the results showed that the average Nusselt number decreased with increasing Stuart number (ratio of electromagnetic to inertial forces).

^{−3}to 1.5 × 10

^{−4}m [18,19]. However, one of the issues for the EMCC technique in being utilized by industry is its slit-segment structure. Slit-segment structure allows the high frequency magnetic field to permeate the mould and act on the molten alloy. However, this feature destroys the stiffness of the mould and increases the potential risks of accidents during the industrial production. Subsequently, the simplification of the EMCC mould’s configuration, whilst maintaining the same metallurgy effect, is the problem investigated in this paper.

## 2. Basic Principles and the Experimental Facilities

#### 2.1. Basic Principles

**J**. With Faraday-Maxwell equation:

**E**and

**B**are electric field intensity and the magnetic flux density, respectively. The alternating magnetic field

**B**, with the same frequency of

**J**, is then generated. Simultaneously, the induced current

**J**

_{i}is present in the molten alloy due to Ampere–Maxwell equation:

_{0},

**J**

_{i}and μ

_{0}are the permittivity of free space, the induced current density and the permeability of the free space, respectively. The displacement current, ${\u03f5}_{0}{\mu}_{0}\frac{\partial \mathbf{E}}{\partial t}$, can be neglected in conducting media (liquid metal, eutectic alloy, etc.) [20]. Equation (2) can be rewritten as:

**F**, which is caused by the interaction of

**B**and

**J**

_{i}:

**F**can improve the lubricating conditions between the strands and the mould, which allows allowing a higher casting speed resulting in the improvement of the surface quality of the strands and the production rate.

#### 2.2. The Experimental Facilities

_{1}to S

_{19}, as labelled in the figure. Mica slides were placed between the segments in the assembling process with the aim of preventing the large scale loop of induced current along the outer surface of the mould [22]. The height of the slit has the same value as that of the mould. The width of the slit is 0.0005 m, which is acquired from the previous research [12]. The length of segment S

_{1}to S

_{18}is a, where a = 0.0245 m, and the length of S

_{19}is 2a. Large segment (S

_{19}) structure design allows us to compare the magnetic feature in the vicinity of S

_{19}to that near the small segment (S

_{9}to S

_{10}). Once the relative uniform magnetic field is achieved, the small segments can be replaced by large segments. The number of segments will be reduced, and the stiffness of the mould will increase accordingly. The mould is surrounded by a five-turn hollow copper coil and it is cooled by cooling water. The distance between induction coil top and mould top was 0.053 m. The ISP-200 kW (Hunan Yueci Gaoxin Technology CO., Ltd., Yueyang, China.) supersonic frequency power supply (frequency range: 10–50 kHz) was adopted. The power supply was connected to the induction coil to provide the AC. The generated magnetic field has the same frequency of the applied AC.

**B**can be expressed as:

**E**

_{c}is the induced voltage. E

_{cmax}is obtained whist θ = 0

^{o}and the effective part of E

_{eff}(${E}_{cmax}/\sqrt{2}$) can be displayed by a voltage meter. Therefore, the maximum magnetic flux density can be calculated by [23]:

^{−4}m

^{2}.

_{19}. ${\text{TC}}_{j}^{i}$ denotes different thermal couples, where i ∈ (1–5) and j ∈ (1–2) denote the row and column number, respectively. The location of i = 1 is 0.053 m to the mould top and j = 1 is 0.003 m to the edge of the S

_{19}. The distance between the thermal couple tip to the hot surface of the mould is 0.003 m. The distance between different i and j are 0.02 and 0.021 m, respectively. Another thermal couple was placed in the molten metal pool with an intention to capture the variations of the liquid alloy’s temperature. All the temperatures were recorded by the MW100 temperature recording system. All experiments are carried out at a constant electric frequency input (f = 25 kHz).

#### 2.3. The Experimental Procedures

_{m}) was studied by investigating the magnetic flux density distribution along the casting direction and the variations of the effective acting region (R

_{ef}) for different electric power inputs. R

_{ef}is first defined. The h

_{m}variation was achieved by changing the locations of the stainless steel self-cooling cube. The probe was placed between the simulator and the mould, moving from the top of the mould along a casting direction with an increment 0.01 m or 0.005 m. The magnetic flux density data was obtained. The metal simulator is placed at three locations, relative to the mould top, h

_{m}= 0.04, 0.076 and 0.11 m, respectively. Once the optimum h

_{m}was selected, the second step was progressed to study the magnetic field uniformity, particularly in the vicinity of the meniscus.

_{m}= 0.076 m. After this step, two trials of experiments (trials A and B) were conducted (Figure 2).

_{m}= 0.076 m, the slide, as shown in Figure 1b, located at the bottom of the mould, was opened to a certain point. The mass of the alloy poured into the mould equalled the mass out so that h

_{m}maintained the same value.

## 3. Magnetic Performance

#### 3.1. Selection of h_{m}

_{m}.

_{m}affects the location where the maximum value of B

_{z}appears: as h

_{m}increases (departing from the mould top), the location of the maximum B

_{z}appears to also depart from the mould top. This is due to the maximum value of B

_{z}usually appearing in the vicinity of the meniscus. Furthermore, as h

_{m}increases, the maximum value of B

_{z}decreases: e.g., for P = 64.6 kW, as h

_{m}increases from 0.04 m to 0.11 m, the maximum value of B

_{z}decreases by 15.8%. This can be understood as follows, the maximum magnetic flux density usually consists of two main factors: one, the magnetic flux enters from the top of the mould; two, the magnetic flux density permeates from the slits of the mould. As h

_{m}increases, the magnetic flux density, which enters from the mould top decreases, and this causes a decrease of the total value of the magnetic flux density.

_{c}and the effective acting region R

_{ef}in the mould at different h

_{m}and p values. Here, B

_{c}is defined as the critical or expected magnetic flux density in the production and R

_{ef}is defined as the range along the casting direction where the magnitude of B

_{z}is over B

_{c}, as shown in the figure. The results show that R

_{ef}decreases as h

_{m}is departing from the mould top for a given B

_{c}at a lower value of P, e.g., 11.2 kW. Interestingly, as P increases, e.g., P = 37.8 and 64.6 kW, this trend is found for the higher value of B

_{c}: B

_{c}≥ 0.4 and 0.5, respectively. This is due to at the higher value of P with lower B

_{c}, the R

_{ef}covering most of the region of the mould.

_{m}= 0.04 m. However, a small value of h

_{m}(free level approaching the mould top) can increase the potential risk of accident during the industrial production process, due to fluctuations of the meniscus, etc. In the present research, h

_{m}= 0.076 m is selected.

#### 3.2. Overview of the Magnetic Field

_{m}= 0.076 m.

_{z}appears in the vicinity of the mould top (h = 0 m), and the second peak appears below the meniscus (h

_{m}) region. The first peak value is attributed to the part of the magnetic field that comes into the mould through the open top of the mould. The second peak value will influence the initial solidification process of the strands. The steel simulator causes the compression of the magnetic field, which permeates into the mould through the slits, to the inner surface of the mould. The influence of the peak value occurs below the meniscus level. Considering the testing locations 1# and 5#, the two curves in red and blue in the figure, are very close at different h values along the casting direction at different p values considered.

_{a}is the defined as the average value of B

_{z}at 1# to 8# at a certain value of h:

## 4. Thermal Performance

#### 4.1. Alloy Pool Temperature Variation with P

**J**

_{i}at different P for trial A and trial B, respectively, as shown in Figure 6.

_{p}at a constant value. As P increases, T

_{p}increases as well: the magnitudes of T

_{p}are 370, 376 and 405 K for the electric power inputs of 9, 16.8 and 48 kW, respectively. Similar results were obtained for trial B. However, the magnitudes of T

_{p}were found to be higher than those for trial A. The is because trial B uses the high temperature molten alloy, and this alloy enhances the overall temperature of the pool.

#### 4.2. Mould Wall Temperature with P

_{19}, for both trial A and B, the temperature increases as P is increased. This is mainly due to the Joule heat effect. An induced current is generated in both the molten alloy and the mould wall. At a low value of electric power input P, the mould wall temperature decreases with the experimental time t. This is because of the high temperature gradient between the molten alloy and the cold mould wall, which is cooled by water in the segment. As P increases, for both the molten alloy pool and the segment, the magnitude of the induced current in the molten alloy increases. This results in increasing the Joule heat, exhibited by the increase of mould wall temperature. The enhancement of the mould temperature due to Joule heat can also be found in the numerical simulation work of Na et al. [24,25].

_{19}. This is mainly due to deformation of the molten alloy, which causes discontinuity in the contact between the alloy and the mould hot surface. In the vicinity of the edge of the segment S

_{19}(near slit), the molten alloy is pushed to the centre of the mould and part of the alloy to the centre of the segment by Lorentz force, as shown in Figure 8.

## 5. Conclusions

- the effective acting region R
_{ef}for the critical (expected) magnetic field B_{c}was defined. R_{ef}highly depends on the external magnetic field and the relative location between the induction coil and the meniscus. R_{ef}influence will be dominant whilst the liquid region in the mould is large. - Uniformity of the magnetic field was achieved along the casting direction and in the circumferential direction, in the vicinity of the meniscus.
- The temperatures of the molten alloy pool and mould wall increase with increasing electric power input P. The temperature in the vicinity of the segment centre presents a higher value than that near the edge, especially at a high value of P.
- Along the casting direction, the location where the maximum temperature value appears moves towards the outlet of the mould as P is increased.

## Acknowledgments

## Author Contributions

## Conflicts of Interest

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**Figure 1.**(

**a**): basic principles of electromagnetic continuous casting technique [18]; (

**b**) and (

**c**) are the schematic representations of the experimental facilities from the front view and the top view, respectively.

**Figure 3.**(

**Left**): Variations of the magnetic flux density B

_{z}along the casting direction at testing location 1# for different h

_{m}and P. (

**Right**): the critical magnetic flux density B

_{c}vs. the effective acting region R

_{ef}. The legends are the same as that on the left.

**Figure 4.**Magnetic flux density distribution along the casting direction at different testing locations for P = 64.6 kW (

**left**) and 37.8 kW (

**right**) at h

_{m}= 0.076 m.

**Figure 5.**Magnetic flux density distribution at different level of h for different testing locations for P = 64.6 kW (

**left**) and 37.8 kW (

**right**).

**Figure 6.**Variations of the molten alloy temperature at different P for trial A (

**left**) and trial B (

**right**).

**Figure 7.**Mould wall temperature variations at different P at h = 0.076 m for trial A (

**left**) and trial B (

**right**).

**Figure 9.**Temperature distribution along casting direction of mould wall at t = 22 s for different P for trial A (

**left**) and trial B (

**right**), respectively.

Melting Point | Density | Viscosity | Electric Conductivity | Magnetic Permeability |
---|---|---|---|---|

(K) | (kg/m^{3}) | (S/m) | (m^{2}/s) | (H/m) |

368.15 | 9500 | 1.1 × 10^{6} | 3.4 × 10^{−7} | 4π × 10^{−7} |

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**MDPI and ACS Style**

Zhang, L.; Deng, A.; Wang, E.; Sienz, J.
An Experimental Investigation to Facilitate an Improvement in the Design of an Electromagnetic Continuous Casting Mould. *Processes* **2016**, *4*, 14.
https://doi.org/10.3390/pr4020014

**AMA Style**

Zhang L, Deng A, Wang E, Sienz J.
An Experimental Investigation to Facilitate an Improvement in the Design of an Electromagnetic Continuous Casting Mould. *Processes*. 2016; 4(2):14.
https://doi.org/10.3390/pr4020014

**Chicago/Turabian Style**

Zhang, Lintao, Anyuan Deng, Engang Wang, and Johann Sienz.
2016. "An Experimental Investigation to Facilitate an Improvement in the Design of an Electromagnetic Continuous Casting Mould" *Processes* 4, no. 2: 14.
https://doi.org/10.3390/pr4020014