Gas Wiping Nozzle Temperature Control for Steel Strip Coating
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Solution Overview
Problem
In hot-dip metal coated steel strip production, existing techniques for improving wiping ability to reduce splashing fail to accurately predict and maintain gas temperature at the stagnation point, leading to varying splashing and top dross quantities due to changing operation conditions.
Innovation Solution
A baffle plate with temperature sensors is used to predict and maintain the gas temperature at the stagnation point within a predetermined range by feedback-controlling the gas temperature supplied to the gas wiping nozzles, ensuring consistent coating quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If gas pressure is increased to reduce coating weight, then coating weight is reduced, but splashing increases significantly
Solution Approach 1:
The patent changes the temperature parameter of the gas from conventional temperatures to a specific range (200°C to 500°C). This temperature optimization allows the gas to effectively reduce coating weight through controlled thermal effects on the molten metal, while the optimized temperature range prevents excessive gas kinetic energy that would cause splashing. The temperature parameter is precisely controlled to balance coating reduction effectiveness with splashing prevention.
2Ease of operation
If gas temperature at nozzle outlet is increased to improve wiping ability, then wiping ability is improved, but gas temperature at stagnation point becomes unpredictable due to distance and operation condition variations
Solution Approach 1:
The patent implements a feedback control system where the gas temperature at the nozzle outlet is adjusted based on the measured temperature at the stagnation point. The controller continuously monitors the stagnation point temperature and modifies the gas temperature setting to maintain it within the optimal range (200°C to 500°C), compensating for variations in distance and operation conditions. This closed-loop feedback ensures consistent wiping ability and predictable stagnation point temperature.
3Productivity
If line speed is increased to increase production volume, then productivity is increased, but initial coating weight increases due to molten metal viscosity, requiring higher gas pressure
Solution Approach 1:
The patent optimizes the gas temperature parameter to compensate for the increased coating weight resulting from higher line speeds. By maintaining gas temperature within the optimized range (200°C to 500°C), the system achieves effective coating weight adjustment through enhanced thermal effects, avoiding the need to increase gas pressure which would cause splashing. This allows high productivity operation with controlled coating weight.
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 approach stabilizes the production of high-quality hot-dip metal coated steel strips by preventing coated surface defects caused by splashing and top dross, even under varying operation conditions.
Implementation Method 1
a temperature sensor is provided on the baffle plate, wherein the temperature sensor predicts a temperature of the sprayed gas based on a temperature measured by the temperature sensor
Implementation Method 2
the temperature of the sprayed gas is feedback-controlled, based on the measured temperature, to maintain the temperature of the sprayed gas within a predetermined temperature range
Data Source
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AI summary
An apparatus for producing a hot-dip metal coated steel strip by which a hot-dip metal coated steel strip of high quality can be stably produced by preventing coated surface defects caused by splashing or top dross even in the case where operation conditions vary is provided. An apparatus 100 for producing a hot-dip metal coated steel strip includes: a pair of gas wiping nozzles 20A and 20B that adjust a coating weight on both surfaces of a steel strip P; a gas supply mechanism 22; a gas temperature adjusting mechanism 24; a baffle plate 26 located near a transverse edge of the steel strip P and in a plane extended from the steel strip; a temperature sensor 28 located on at least one surface of the baffle plate 26; and a controller 30 that controls the gas temperature adjusting mechanism 24 based on an output of the temperature sensor 28.