There are various methods for detecting the vibration of the long nozzle sleeve. At present, the primary approach is to measure the vibration of the operating arm directly connected to the long nozzle sleeve. Vibration of the long nozzle sleeve will inevitably trigger vibration of the operating arm, which explains why on-site operators often grasp the operating arm to perceive vibration differences and judge slag carry-over. Extracting the characteristics of vibration signals during molten steel pouring, converting manual observation experience into automatic identification by a computer system to accurately determine slag carry-over, constitutes the core key to the successful development of this system.

Technical Parameters

Slag carry-over detection efficiency: Over 96%

Tundish liquid level control precision: ±0.5 tons

System response time: Less than 0.5 seconds

Sensor parameters: Weight: Less than 5 kilograms;

Dimensions: 200×100×80mm

Protection: Multi-layer all-steel protective casing with cooling protection via compressed air;

Applicable ambient temperature up to 150°C;

Service life: Over two years

Control cabinet dimensions: 20000H×600W×600D mm

Vibration-Type Ladle Slag Detection Technology (National Invention Patent, Patent No.: 200510050311.X)

- Vector quantization processing technology is adopted to obtain vibration characteristic parameters of ladle slag tapping. The system can automatically eliminate interferences from nozzle slide gate switching and other external disturbances, achieving a slag tapping alarm accuracy of over 96%.

- The system features easy installation without any modifications to on-site equipment or steel ladles.

- It has a short commissioning cycle that can be completed within one week, and installation and commissioning will not interrupt continuous casting production.

- The equipment boasts simple operation, high reliability and nearly maintenance-free performance.

Vibration Signal Enhancement Device (National Invention Patent, Patent No.: 200910100688.X)

It effectively isolates external interferences, improves signal-to-noise ratio and keeps the equipment away from high-temperature zones.

Tundish Liquid Level Automatic Control Technology (National Invention Patent, Patent No.: 200710067218.9)

It realizes multi-channel vibration signal extraction, improves the effectiveness of ladle slag tapping detection, inhibits slag entrapment from ladles, and achieves a liquid level control precision of 0.5 tons.

Remote Monitoring Technology (National Invention Patent, Patent No.: 200910152594.7)

- It enables convenient remote monitoring and fault diagnosis of the slag tapping detection system.

- It supports remote system commissioning and control functions.

- It allows remote system upgrading and maintenance.

1. It can effectively reduce the slag thickness in the tundish, improve the quality of continuous casting billets and prevent the secondary oxidation of molten steel, especially enhancing the quality of transition billets during ladle exchange. Its application in steel mills including Shougang, Xinggang, Xingcheng and Wuhan Iron and Steel has proven that the tundish slag thickness can be cut by over 25% compared with manual operation.

2. It can raise the yield of molten steel. To avoid slag carry-over from ladles, operators lacking experience have to close the nozzle in advance, which is especially common when casting high-grade special steel. This leads to a larger volume of residual molten steel left in the ladle. By adopting this slag detection technology, the sliding nozzle can be closed promptly once slag flows out, lifting the molten steel yield while guaranteeing the quality of continuous casting billets.

3. It extends the service life of tundishes and increases the number of continuous casting heats. Controlling the amount of slag in the tundish alleviates the erosion of refractory lining materials inside the tundish caused by molten slag, thereby prolonging tundish service life.

4. Controlling the volume of carried slag reduces the bore enlargement of ladle sliding nozzles and extends the service life of slide plates and long nozzles.

5. It enables automatic control of the tundish liquid level, stabilizes the liquid level inside the tundish, cuts down labor intensity for workers and ensures stable continuous casting production.

6. The equipment features a simple structure and easy installation. No modification is required for existing equipment in the continuous casting workshop, resulting in low installation and operation costs.

7. The system requires almost no maintenance during operation, bringing low maintenance expenses.

Tundish Slag Detection Case of Xingcheng Special Steel

The VSD2000 vibrating ladle slag detection system manufactured by Hangzhou Pucheng Teddy Industrial Co., Ltd. has been equipped and installed by major domestic steel mills. Up to now, more than 200 sets have been deployed on continuous casting lines of steel mills at home and abroad. Attaching great importance to steel product quality, Xingcheng Special Steel installed our ladle slag detection systems for its subsidiary enterprises as early as 2006. Thanks to the outstanding performance of the equipment, the company also promoted this product to other steelmaking subsidiaries within the group.

# Brief Introduction of Jiangyin Xingcheng Special Steel Co., Ltd.

Affiliated to Citic Special Steel Group, Jiangyin Xingcheng Special Steel Co., Ltd. was founded in 1993 with investment from Hong Kong CITIC Pacific Limited. It is now a national key high-tech enterprise under the National Torch Program, the chairmanship unit of the China Special Steel Enterprises Association, China’s first Class 4A enterprise with good standardized national operation, and one of Jiangsu Province’s Top Ten Energy Conservation and Emission Reduction Demonstration Enterprises.

The core production equipment of Jiangyin Xingcheng Special Steel, including steelmaking, steel rolling and inspection facilities, are all imported from overseas, and internationally advanced processes are adopted throughout production. The company has developed into a major domestic base for premium special steel production, covering high-standard bearing steel, high-grade gear steel, alloy spring steel, alloy tube bloom steel, high-grade mooring chain steel, free-cutting non-quenched and tempered steel, electroslag remelting steel and other varieties. All core products have obtained international quality certifications, and the output and sales volume of multiple high-end products have ranked first nationwide for years. Notably, its continuously cast round bloom with a diameter of ∮1000mm has filled the global market gap. The enterprise boasts 11 national key new products, 12 products winning the Golden Cup Award for Physical Quality of Metallurgical Products, and 43 products designated as Jiangsu Provincial Key High-tech Products. It holds 54 national patents, takes the lead and participates in drafting and revising multiple national and metallurgical product technical standards, and undertakes two national key metallurgical research projects.

Corporate Strategic Goal: To build the world’s most competitive special steel enterprise.

# Introduction to the Ladle Slag Detection Project

At the final stage of molten steel pouring from a ladle, steel slag floating on the molten steel surface gradually flows into the tundish. Excessive slag entering the tundish will reduce the cleanliness of molten steel, accelerate erosion of the tundish lining, lower the number of consecutive casting heats, impair cast bloom quality and disrupt continuous casting production. In severe cases, breakout accidents may occur. Therefore, real-time monitoring and control of slag outflow during the late pouring stage are mandatory.

The VSD2000 continuous casting ladle slag detection system identifies slag outflow during continuous casting by capturing vibrations of the mechanical manipulator arm. During molten steel pouring, molten steel flows through the long nozzle into the tundish, and the impact of molten steel against the long nozzle wall generates vibrations on the mechanical manipulator arm that supports the long nozzle. The specific gravity of steel slag is less than half that of molten steel, so slag floats on top of molten steel and only appears when a ladle is nearly empty. Steel slag features low density, high viscosity and poor fluidity. The impact force exerted by the mixed flow of molten steel and slag on the long nozzle wall differs significantly from that of pure molten steel. Accordingly, this system monitors slag outflow from continuous casting ladles by measuring and analyzing vibration discrepancies of the mechanical manipulator arm.

Details of ladle slag detection systems installed at Xingcheng Special Steel are listed as follows:

1. November 2006: No.3 continuous casting line of the Third Steelmaking Plant, Huashan Branch of Xingcheng Special Steel; 50-ton ladles, four-strand square blooms. (1 set)

2. May 2007: No.1 and No.2 continuous casting lines of the Third Steelmaking Plant, Huashan Branch of Xingcheng Special Steel; 50-ton ladles, four-strand square blooms. (2 sets)

3. October 2007: No.1 and No.2 continuous casting lines of the Second Steelmaking Plant, Binjiang Branch of Xingcheng Special Steel; 100-ton ladles, four-strand and three-strand large round blooms respectively. (2 sets)

4. August 2008: No.1 and No.2 continuous casters in Phase III Project of Binjiang Branch of Xingcheng Special Steel; 150-ton ladles, five-strand square blooms and three-strand large square blooms respectively. (2 sets)

5. September 2008: No.3 continuous caster in Phase II Project of Binjiang Branch of Xingcheng Special Steel; 100-ton ladles, three-strand large round blooms. (1 set)

6. April 2010: No.3 continuous caster of Xingcheng Special Steel Phase III Project put into operation; 150-ton ladles, three-strand large round blooms. (1 set)

Below are on-site photos of partial installations at Jiangyin Xingcheng Special Steel.

（Click to view the detailed case videos）