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Reduce steelmaking costs! Summary of the thermal insulation vacuum tundish test! Compared with ordinary bags, the temperature drop of medium bags can be reduced by about 4.5℃!

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The vacuum tundish is a cooperation project among industry, academia and research between a company and Wuhan University of Science and Technology. It aims to use the principle of vacuum insulation to reduce the heat dissipation of the tundish shell during the pouring process, increase the thermal insulation effect of the tundish, and further reduce the tapping temperature. Save energy and material consumption in the steelmaking process and achieve the goal of low superheat and constant temperature pouring, thereby achieving the goals of environmental protection, energy saving, and stable production. After full research and industrial testing in the laboratory, the insulation vacuum tundish technology was industrially verified and promoted for use in a special steel company from October to December 2023.

1.Production of vacuum tundish

The external dimensions (length, width, height, etc.) of the vacuum tundish are basically the same as those of the original ordinary tundish, that is, the vacuum chamber is set up to meet the needs of heat insulation while ensuring the capacity of the tundish.

 Make appropriate fine-tuning of the installation and construction plans for the quick-change mechanism, permanent tundish layer tire mold, working layer, and flow stabilizer to meet the needs of vacuum tundish construction.

The permanent layer of the vacuum bag adopts a permanent layer with low thermal conductivity to further reduce the heat dissipation of the tundish.

2. Test situation

2.1 Operating conditions

Model: R9m 5 machine 5 strand continuous casting machine

Cast billet section: 150mm×150mm

Working speed: 3.0-4.0m/min

Tundish capacity: 25 tons

Steel type: HRB400(E)

2.2 Test Plan

The tundish planning time is planned according to 48 hours, 72 hours, and 96 hours, so as to track and analyze the insulation effect of the thermal insulation vacuum tundish for different durations.

2.3 The vacuum tundish has been produced and used 6 times. The relevant production information is as follows

serial numberPlanned durationWatering start datetimeWatering stop datetimedurationReason for offline
148 hoursOctober 298:58October 319:1236 hours and 13 minutesOffline as planned(Power trip, secondary pouring)
272 hoursOctober 510:58October 89:0570 hours and 7 minutesOffline as planned
372 hoursNovember 1111:21November 148:4869 hours and 27 minutesOffline as planned
472 hoursNovember 1711:21November 209:4970 hours and 28 minutesOffline as planned
572 hoursNovember 2311:34November 269:0069 hours and 26 minutesOffline as planned
696 hoursNovember 2911:41December 38:1692 hours and 35 minutesOffline as planned

2.4.1Statistical comparison table between vacuum tundish and ordinary tundish

projectInsulated vacuum tundishXitong tundish (machine #1)   Compared
Winning numberWangxin0197149average
Test date10.29-
Total number of furnaces (furnace)101162166187241163182170188196
Number of valid data furnaces (furnaces)87146152169238157179193
Average temperature after argon (℃)1558.471557.941559.201557.021559.441558.411558.701559.101559.761560.351558.941559.37  -0.96
Average temperature of middle bag (℃)1526.581526.511526.911526.401527.031526.691522.311522.401522.861522.811524.541522.98   3.70
Pouring time (minutes)42074167422855554539418642154175409641724169
Output of medium contract (tons)10127.349745.5310857.0013826.3311139.0510159.8310563.409828.8710306.2810642.0910300.09
Average pouring cycle (minutes)24.9025.9725.1022.6123.0524.3325.6823.1624.5621.7921.2923.29   1.03
Average furnace output (tons)62.5158.7158.0657.3759.1662.3358.0457.8254.8254.3057.46   1.70
Amount of copper excess (tons/minute)2.412.342.572.492.452.432.512.352.522.552.47  -0.02
Waiting time for pouring (minutes)3.384.764.473.824.344.155.794.
Average temperature drop (℃)31.8931.4332.2830.6132.431.7235.4036.6436.937.5634.3936.18  -4.46

2.4.2 Basis for data collection

The number of valid data furnaces removes abnormal data such as temperature measurement and new ladles; it mainly collects and analyzes data such as the average temperature after argon blowing, the average temperature of the tundish, the average pouring cycle, waiting time for pouring, and the amount of steel passed per minute. In order to avoid the influence of weather, the data collection time period of the ordinary tundish package basically coincides with the time period of the experimental vacuum package; the data of 5 tundish packages were taken for comparison.

2.4.3 Data analysis results

Since the two parameters of the amount of steel and the waiting time for pouring have a direct and obvious impact on the cooling of the middle ladle, a key statistical analysis was made on these two data:

(1) The pouring time of the ordinary package and the insulated vacuum tundish in this period are similar, the ordinary package is 4.39 minutes, and the insulated vacuum package is 4.15 minutes;

(2) The steel passing capacity per minute of the ordinary package and the insulated vacuum package during this period is similar, the ordinary package is 2.47t/minute, and the insulated vacuum package is 2.45t/minute. The two important parameters are similar, indicating that the temperature drop in the middle package is comparable.

Compared with ordinary bags, the temperature drop of the insulated vacuum tundish can be reduced by about 4.5°C.

3. Data of vacuum tundish refractory materials:

1. Dry material: The residual thickness of the intermediate slag line is above 30mm, and the residual thickness of the molten pool and the bottom of the ladle is above 90mm. The overall situation is equivalent to that of ordinary ladles off the line;

2. The flow stabilizer, the side wall is equivalent to the ordinary bag (residual thickness 50-60mm, erosion 40-50mm);

3. The residual thickness of the impact point is 90-100mm; the residual thickness of the rear wall is 140-170mm (erosion 30mm), which is equivalent to ordinary bags.

4. Conclusion

1. The thermal insulation vacuum tundish has no impact on the construction and baking of the permanent layer and working layer of the tundish, and the results after use are equivalent to ordinary tundish;

2. The insulated vacuum tundish structure fully considers and reserves the discharge channel of water vapor of the refractory material of the tundish, which is equivalent to that of ordinary tundish.

3. Thermal insulation vacuum tundish adopts vacuum chamber design to achieve the effect of heat insulation without affecting the capacity and flow field of the original tundish.

4. Surface temperature of the tundish: the main temperature measurement points such as the large surface, impact zone, corners of the impact zone, and bottom of the tundish are all <200°C. It clearly reflects the thermal insulation effect of the middle package and greatly improves the working environment in the pouring operation area, making it truly environmentally friendly.

5. The insulated vacuum tundish used in this industrial trial is supplemented by a low thermal conductivity permanent layer. The temperature drop of the tundish after use can be reduced by about 4.5°C compared with ordinary tundishes. According to the algorithm recognized in the industry: every time the molten steel decreases by 1°C, the cost can be reduced by 1 yuan, that is, if the temperature is reduced by 4.5°C, the steelmaking cost can be saved by 4.5 yuan/ton of steel.

LMM YOTAI established in 2007. Our production technology comes from Japanese Yotai. As an experienced and international player in the refractories industry. We have succeeded in expanding both the breadth of its product range and the depth of its services. From raw material selection, refractory portofio & optimization, installation & services & recycle of used refractories on site to further reduce client’s Opex & Capex in refractory consumption per ton steel output, meanwhile improve product quality of client.

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