5 Key Factors Behind Ladle Shroud Cracking

ADAM

Operators often see cracks and damage in ladle shrouds, long nozzles, and refractory parts. This happens because of a few main reasons:

Fast temperature changes can cause thermal shock and peeling.
Mechanical stress comes from handling, hitting, or working forces.
Hot slag and molten steel can wear down and get into the parts.
Material problems like tiny holes or mistakes made during making.
Issues with design, how things line up, or how they fit together.

Knowing these reasons helps teams stop corrosion, breaks across the part, and chemical damage. This helps ladle shrouds last longer.

Key Takeaways

Quick temperature changes can cause thermal shock. This can crack ladle shrouds. Heating slowly and checking the temperature can stop this damage.
Mechanical stress from moving and using parts can cause cracks. Storing parts carefully and handling them right helps lower this risk. Installing them the correct way also helps.
Hot slag can wear down and get into refractory materials. This makes them weaker. Using strong materials and checking slag conditions can protect the parts.
The quality of materials is important. Good raw materials and careful making of parts help stop cracks. Having the right amount of porosity makes parts stronger and better at handling shock.
Good design and alignment lower stress and stop leaks. Smooth shapes and tight fits help keep ladle shrouds and nozzles strong. Checking them often also helps.

1. Thermal Shock

Temperature Changes

When the temperature changes quickly, it puts stress inside refractory materials. During ladle preheating, the working layer gets hot on one side and stays cool on the other. This big difference in temperature causes strong pulling stress at the top of the working layer. Sometimes, this stress can get as high as 39.06 MPa. Damage often starts at the top and near the sidewall burner nozzles. If the ladle heats up too fast, alumina-magnesia castables get stiffer but weaker. The material turns more brittle and can break more easily. When steel is poured, the ladle shroud faces sudden heat, which also builds up stress.

Tip: Teams should watch temperature changes during preheating and pouring. Using thermal imaging cameras can help find hot spots and uneven heating. These signs show where cracks might happen.

Crack Formation

Thermal shock cracks show up a lot in high-temperature furnace linings and steel ladles. These parts go through fast heating and cooling many times. When the temperature changes too quickly, the refractory grows or shrinks more than it can handle. If the material is brittle, especially under 1100°C, cracks form easily. Big parts, uneven heating, and outside forces make cracking worse. Changes in the material’s structure can also raise the risk.

Common scenarios for thermal shock cracking:Ladle preheating with fast temperature rise.
Steel pouring with sudden molten metal exposure.
Quenching or cooling steps in steelmaking.
High-temperature furnace linings in steel, cement, glass, and ceramics.

Thermal shock can cause early failure with small and large cracks. Operators often see pieces breaking off, falling apart, and cracks along the ladle shroud and nozzle. Checking often and tracking temperature changes helps teams stop damage before it gets worse. Using materials that handle thermal shock better and heating slowly can help lower the chance of cracks.

2. Mechanical Stress

Handling Damage

Mechanical stress often starts when workers do not handle parts carefully. Sometimes, workers drop or hit the ladle shroud by mistake. This can chip, crack, or even break it before use. Teams may forget how important good storage is. If the storage area is wet or rough, the refractory gets weaker. This makes it easier to crack later.

Operators should do these things to stop handling damage:

Keep ladle shrouds in dry, clean places.
Teach workers to lift and move parts the right way.
Check each part for chips or cracks before using it.
Heat the ladle shroud slowly so it does not crack.

Tip: Handle parts with care and heat them slowly. This helps stop early cracks and makes the ladle shroud last longer.

Operational Impact

Mechanical stress keeps happening when the equipment is used. Taking off coatings or moving the ladle shroud can hurt the refractory. Forces between the upper nozzle and ladle bottom can cause stress. These forces come from heat changes, steel shell growth, and heavy loads.

These types of mechanical stress often cause cracks or bending:

Pulling forces from blocked thermal expansion.
Pushing forces that make the part bend for good.
The steel shell grows wider and faces thermal shock.

The table below shows how these forces can hurt the structure:

Operators who know about these stresses can pick better materials. They can also install parts better and lower the chance of cracks. Checking often and lining up parts right helps keep steelmaking equipment strong.

3. Slag Erosion

Slag Penetration

Hot slag attacks the outside of ladle shrouds and nozzles. The molten slag moves over the refractory and brings heat and chemicals. These things break down the material. Slag penetration happens when liquid slag gets into small pores and cracks. This changes the inside of the refractory and makes a weak layer. That weak layer can break apart easily.

Slag temperature and thickness decide how fast slag moves in.
Chemical reactions between slag and refractory make new compounds.
Pores and the inside structure let slag get in and spread.
Molten steel and slag flow scrape the surface and cause more erosion.
Chemical, mechanical, and heat attacks together make the damage happen faster.

Operators often see melting at the slag line and deep cracks on the sides. The slag line gets soft and weak, so pieces can fall off. Checking often helps teams find early signs of slag penetration. They can fix problems before big damage happens.

Note: Picking refractory materials with fewer pores and using coatings can slow slag penetration. This helps the parts last longer.

Thermal Peeling

Thermal peeling, or spalling, hurts the sides and slag line of ladle shrouds and nozzles. Fast temperature changes during tapping or when steel flows out make the surface expand and shrink quickly. This stress causes the material to crack and flake off.

High slag temperature and fast reactions make peeling more likely.
Big temperature changes cause thermal shock and lead to spalling.
Mechanical shock from scrap charging and steel flow causes scraping.
Oxidation and rough surfaces make the refractory even weaker.
Damage shows up as cracks, flakes, and rough spots at the slag line.

Chemical attack and slag damage happen when the refractory dissolves or makes new compounds after touching molten steel or slag. These changes make the material weaker and easier to crack. Operators should pick refractories that resist chemical attack. They should also use surface treatments to protect against slag erosion.

The ladle shroud nozzle for continuous casting is also called the protective sleeve. It is an important component connecting the ladle and the tundish. It is connected to the lower shroud of the sliding shroud device at the bottom of the ladle, and the lower end extends into the tundish.

The shroud is an important functional refractory material for maintaining casting and improving steel quality. The length of the shroud is generally 600-1800mm, the pipe diameter is 90-150 mm, and the structure of the ladle shroud nozzle is shown in Figure 2. Its use conditions are harsh and must have the following functions: excellent thermal shock resistance; good mechanical strength; excellent resistance to alternating corrosion of molten steel and slag, high oxidation resistance, and in addition, other suitable properties are required for some special steel grades.more information,please check here

Tundish nozzle

Slide Gate Plate is a critical component in the continuous casting process, used to control the flow of molten steel from the ladle or tundish to the crystallizer. The following is a detailed description:

Role and Function

· Flow Control: The sliding gate plate adjusts the opening size of the nozzle through the sliding mechanism, thereby controlling the flow of molten steel. This is very important for maintaining a constant and controllable casting process.

· Operational Flexibility: The sliding gate plate allows operators to adjust the molten steel flow rate as needed during the casting process to adapt to different production requirements and conditions.

· Emergency Stop: In an emergency, the sliding gate plate can completely close the flow channel and stop the flow of molten steel, thereby preventing accidents and losses.

Slide gate plate for Converter

The slide gate plate is made of sintered corundum, fused corundum, fused zirconium corundum, zirconium mullite and other main raw materials. It is combined with new resin, formed by high pressure and fired at high temperature. It has the advantages of high strength, super hard, high temperature resistance and corrosion resistance, and strong thermal stability.

Stopper

Monoblock Stopper is used mainly for flow control on Molten Steel poured from tundish to mould. Monolithic Stopper is installed in the Tundish above the Sub Entry Nozzle and the gap between stopper head and Nozzle decide the throughput requirement of Molten Steel inside the Mould.

Argon can be blown into the tundish through argon inlet to prevent nozzle from Clogging ( specially designed feature wherever it is required we design and customise accordingly)

SPECIAL FEATURES:

o Facility for gas purging

o Anti oxidant properties

o Design and size as per customer’s requirement

o Clogging free casting for long sequence of casting

o Gas purging facilities to prevent alumina clogging (optional)

o Slag zone immersed part re-inforcement with special material for long life

o Argon sealing purging arrangement can be provided on customer’s request

o Wide range of formulation for withstanding oxidation and long sequence casting

o Different assembly methods for assured security even in long sequence casting

o We manufacture Silica free Oxy-bore ladle shroud for less corrosion and long sequence casting

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adam wang | Archinect

Monoblock Stopper is used mainly for flow control on Molten Steel poured from tundish to mould. Monolithic Stopper is installed in the Tundish above the Sub Entry Nozzle and the gap between stopper head and Nozzle decide the throughput requirement of Molten Steel inside the Mould.