Continuous Casting Nozzle Sealing with Tundish Powder
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Solution Overview
Problem
The use of argon gas as a seal gas in continuous casting methods leads to bubble defects on the surface of cast slabs due to gas bubbles trapped in the molten steel, necessitating costly grinding to achieve quality standards and increasing nitrogen content, which affects the properties of the stainless steel.
Innovation Solution
A continuous casting method employing a long nozzle to immerse the spout into the tundish, initially using argon gas as a seal, then switching to nitrogen gas, and applying a tundish powder to cover the molten metal surface, reducing gas interaction and preventing nitrogen absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If argon gas is used as seal gas around the molten steel in the tundish, then the molten steel surface is shielded from atmospheric oxidation, but argon gas bubbles are trapped in the molten steel causing surface defects on the cast slab
Solution Approach 1:
The patent extracts the harmful function of using inert gas (argon) as seal gas by completely eliminating it from the system. Instead of using argon gas to shield the molten steel surface, the invention uses a combination of tundish powder coating and nitrogen gas sealing, thereby removing the source of bubble defects while maintaining protection against oxidation
Solution Approach 2:
The patent changes the physical state of the seal medium from gaseous (argon) to particulate (tundish powder) for surface protection, and uses nitrogen gas only for atmospheric displacement without direct contact with molten steel. This parameter change from gas-phase sealing to powder-coating sealing eliminates bubble formation while maintaining oxidation protection
2Stability of the object's composition
If argon gas is supplied to seal the molten steel, then nitrogen content increase is prevented, but bubble defects appear due to argon gas remaining in the molten steel
Solution Approach 1:
The patent uses tundish powder as a disposable protective layer that is consumed during the casting process. The powder coating serves its protective function and then is discarded with the slag, eliminating the need for expensive inert gas sealing while preventing surface defects
Solution Approach 2:
The patent introduces tundish powder as an intermediary substance between the molten steel and the atmosphere. This powder layer acts as a barrier that prevents both oxidation and nitrogen pickup without introducing gas bubbles into the molten steel, unlike direct gas sealing methods
3Object-affected harmful factors
If the spout of the long nozzle is immersed into the molten metal in the tundish, then gas interaction is minimized, but the pouring process becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-coating the tundish interior and molten steel surface with protective powder before the pouring process begins. This preliminary protective layer is in place before molten steel contact, eliminating the need for complex gas sealing systems during pouring
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively suppresses nitrogen content increase and surface defects by minimizing gas interaction with the molten steel, resulting in higher quality stainless steel slabs with reduced bubble formation and lower nitrogen pickup.
Implementation Method 1
a spraying step for spraying a tundish powder so as to cover a surface of the molten metal in the tundish between the pouring step and the casting step
Data Source
Figure 1
Figure 2A~2D
Figure 3A~3D
AI summary
In a continuous casting device 100 for casting a stainless steel billet 3c, a long nozzle 2 extending into a tundish 101 is provided at a ladle 1. A molten stainless steel 3 is poured through the long nozzle 2 into the tundish 101, and a spout 2a of the long nozzle 2 is immersed into the poured molten stainless steel 3. During pouring, an argon gas 4a is supplied around the molten stainless steel 3 in the tundish 101. Further, continuous casting is performed, in which, while immersing the spout 2a of the long nozzle 2 into the molten stainless steel 3 in the tundish 101, the molten stainless steel 3 is poured from the ladle 1 into the tundish 101 and poured from the tundish 101 into a casting mold 105. During casting, a nitrogen gas 4b is supplied instead of the argon gas 4a around the molten stainless steel 3 inside the tundish 101.