Method and apparatus for controlling the strip temperature of the rapid cooling section of a continuous annealing line

Patent metadata

Field	Value
Publication number	US-9783867-B2
Application number	US-201214364944-A
Country	US
Kind code	B2
Filing date	Dec 12, 2012
Priority date	Dec 15, 2011
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

Provided are a method and apparatus for uniformly controlling the strip temperature of the rapid cooling section of a continuous annealing line. A plurality of sets of cooling nozzle blocks for controlling the strip temperature is installed at the front and back sides of the strip, and is divided into lengthwise flow control nozzle blocks and widthwise flow control nozzle blocks. Strip center temperature meters and widthwise direction temperature meters are installed at the intake and discharge sides of the rapid cooling section. Temperatures obtained using the strip center temperature meters and the width direction temperature meters are used to respectively control the spraying of mist for the lengthwise flow control nozzle blocks and the widthwise flow control nozzle blocks in order to uniformly control the strip temperature and minimize changes in the flatness of the strip. The widthwise temperature meters at the intake and discharge ends of the rapid cooling section of the continuous annealing line are used to detect the temperature. Feedback/feedforward control technique can be used to uniformly control the widthwise temperature of the strip through flow rate control over mist sprayed in the widthwise direction of the rapid cooling section.

First claim

The invention claimed is:

1. A method of uniformly controlling a strip temperature in a rapid cooling section of a continuous annealing line, the method comprising steps of:
determining valve open ratios of lengthwise flow control nozzle blocks and widthwise flow control nozzle blocks, the nozzle blocks spraying mist to front and rear sides of a strip, based on strip temperature measurement values and strip information;
determining opening compensation values of the lengthwise flow control nozzle blocks such that the flow rates of the spray mist are adjusted by deducing an actual discharge-side temperature of the strip at every period from a target discharge-side temperature of the strip with respect to the determined valve open ratios; and
determining opening values of a plurality of servo valves of the widthwise flow control nozzle blocks such that the flow rates of the spray mist are adjusted in a plurality of areas in a widthwise direction of the strip with respect to the determined valve open ratios,
whereby the strip temperature is uniformly controlled through flow rate control over the mist sprayed to the strip, and changes in flatness of the strip are minimized,
wherein the step of determining the valve open ratios of the lengthwise flow control nozzle blocks and the widthwise flow control nozzle blocks comprises steps of:
calculating a compensation cooling capacity from a present intake-side temperature, a discharge-side temperature and a target temperature of the strip using information on a thickness, a width and a steel type of the strip inputted from a next coil information input module;
calculating a flow rate value of the mist;
dividing the flow rate value of the mist with a number of blocks which is predetermined by a spray nozzle block determination module and calculating a valve flow rate coefficient C v using the divided flow rate value as an input value of a valve open ratios calculation module; and
finally determining valve open ratios of the blocks using the valve flow rate coefficient C v .

2. The method according to claim 1 , wherein, at the step of calculating the compensation cooling capacity, the compensation cooling capacity is calculated using an equation presented by Formula 3=Formula 1−Formula 2:
{dot over (Q)} s _ act =ρ s C ps ( T o _ act −T i _ act ) {dot over (V)} s   Formula 1,

where {dot over (Q)} s _ act is the present cooling capacity (W/m 3 ·K) of the strip, ρ s is the density (Kg/m 3 ) of the strip, C ps is the specific heat (J/Kg·K) of the strip, T o _ act is the actual absolute temperature (K) of an RCS discharge-side plate, and {dot over (V)} s is the volume ratio (m 3 /sec) of the strip,
{dot over (Q)} s _ target =ρ s C ps ( T o _ target −T i _ act ) {dot over (V)} s   Formula 2,

where {dot over (Q)} s _ target is the target cooling capacity (W/m 3 ·K) of the strip, ρ s is the density (Kg/m 3 ) of the strip, C ps is the specific heat (J/Kg·K) of the strip, T o _ target is the target absolute temperature (K) of a discharge-side plate, T i _ act is the actual absolute temperature (K) of an RCS intake-side plate, and {dot over (V)} S is the volume ratio (m 3 /sec) of the strip, and
Δ {dot over (Q)} s =ρ s C ps ( T o _ target −T o _ act ) {dot over (V)} s   Formula 3,

where Δ{dot over (Q)} s is the compensation cooling capacity (W/m 3 ·K) of the strip.

3. The method according to claim 1 , wherein the step of calculating the flow rate value of the mist comprises:
calculating the flow rate value of the mist using Formula 5 obtained from Formula 4 below:

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Assignees

• Posco

Inventors

• Lee Gyoo Taek
• Park Jung Hun

Classifications

• G05D23/19

  characterised by the use of electric means {(G05D23/1393 takes precedence)} · CPC title

• C21D9/5735

  Details · CPC title

• C21D1/667

  for spray quenching · CPC title

• C21D9/52

  for wires; for strips {; for rods of unlimited length} · CPC title

• C21D11/005 Primary

  for cooling · CPC title