JPS6099467A - Detection of shell rupture in continuous casting - Google Patents

Abstract

PURPOSE:To detect efficiently the shell rupture in a mold for continuous casting by embedding a thermocouple in the copper plate of the mold and measuring the heat flux. CONSTITUTION:An overall coefft. K(t) of heat transmission is preliminarily determined with the thickness of the side wall of a casting mold as a parameter. A heat flux Q is calculated by the equation from the actually detected temp. value of a thermocouple. The calculated value is compared with a reference value for deciding shell rupture and when the difference exceeds a permissible value, the shell rupture is decided. The equation is Q=(TQ-TW).K(t) where Q: the heat flux (Kcal/m<2>Hr), K(t): the overall coefft. of heat transmission (Kcal/ m<2>Hr deg.C), TQ: the value indicated by the thermocouple ( deg.C), TW: the temp. of the cooling water in the mold ( deg.C), t: the thickness of the side wall of the mold (m).

Description

[Detailed description of the invention] (Industrial application field) The present invention (lSl: 91r1 piece made by continuous steel casting method)
Regarding J1 construction, this is a method for accurately detecting shell fractures in casting) (!).

(Prior Art) In continuous steel casting 1c, a major factor that hinders production is a phenomenon called break-a-wat, where the solidified shell breaks just below the mold and the bath water flows out.

Once a breakout occurs, it takes a long time to repair it, resulting in a significant drop in productivity. Therefore, in order to avoid breakouts, we installed dozens of thermocouples on a VJ-type copper plate, and by comparing the temperature values, we were able to grasp all the preliminary phenomena of breakouts. mosquito,
For example, it is proposed in Kariko No. 56-7783.

However, with such conventional temperature detection means, heat fli due to repair cutting of the J-type copper plate;
7. %'7 Since the temperature detection value changes more than the pressure due to temperature fluctuations, there is a period j・-set point which is said to have low reliability.
It is difficult to completely prevent breakout. (Objective of the Invention) The present invention provides an effective means for preventing the occurrence of breakout as described above. Is it possible to effectively detect shell breakage and thereby eliminate the breakout/occurrence? This is the purpose.

(Invention" tl * Sei 3 Sakugawa) The invention involves embedding one or more thermocouples in a hook molded copper plate (piece type piece), and emitting heat v1 from the bundle by 6111 times. By doing so, shell 1t1. is used to detect sound interruption.

Now, the inventors t9
”, it was determined that the breakout occurs as follows.

That is, during casting, the openings 91 of the slab are restrained by the mold copper plate for some reason, and the position of the slab does not change.If the slab stops moving, that part and the mold are pulled downward. kaT
A break occurs at the boundary with the normal fishing piece, and as the work continues, the broken part of the shell moves downward, and when the broken part reaches the lower end of the +4 mold. Molten steel flows out, resulting in a so-called breakout.

Therefore, breakout can be effectively prevented by quickly detecting the shell breakage and taking appropriate operational measures such as temporarily stopping casting or reducing the slab withdrawal speed.

As a result of our research focusing on heat flux, the inventors of the present invention succeeded in detecting shell rupture with the utmost precision.

Heat flux is the amount of heat that passes per unit time and per unit area, and the inventors of the present invention determined the heat flux to be expressed by the following equation (1).

Q = (TQ-1'w), K(t) ・= ・−・・
・・・・・・−・(1) Q...Heat flux (Kad/*+'
, Ll r )K(t)--Overall heat transfer coefficient (#
32B'J-'iii board) (Kcnf7m'tlr'
CITQ ... Thermocouple indication value ('C) '1゛W ... Cold water temperature in the mold (℃) t ... Mold steel plate thickness (m) Overall heat transfer of the mold copper plate according to the above formula (1) The coefficient K(t) is
The distance between the thermoelectric lamp and the surface of the mold copper plate (the surface in contact with the bath water) (
4, the shape of the cooling grooves in the mold, etc., and is determined by calculation, and is a function of the mold steel plate thickness t.

The heat flux Q is calculated as a candy that eliminates "mere fluctuations in the thermocouple indicated value" due to changes in the distance between the thermocouple and the surface of the mold copper plate, and changes in the temperature of the cooling water inside the mold. Significantly increases reliability.

Figure 1 is a graph showing time changes in the surface of the mold copper plate and the indicated value of the thermocouple, with time (sec) on the horizontal axis and temperature (C) on the vertical axis. Self-red giant AT is 3
In the case of the throat, 13 indicates the case of 15 gates.As is clear from FIG. 1, when the distance l changes, the indicated value of the thermocouple changes greatly n1υ. Therefore, if t changes due to factors such as υj-type cutting, relying on the indicated value of heat 1b and pair will result in a large error in judgment.

2nd and 1st is fever? Using the indicated value of L+', as a reference, calculate the heat flow east Q according to equation (1) above, and show the change between li and 7 in a graph, with time (8 (a)) on the horizontal axis and vertically. 0 heat on shaft
11 bundles (Kad/n?II r ) are taken, curve 22 shows the case where the distance t is 3 degrees, and curve 23 shows the case where the distance t is 15 degrees.

In this way, depending on the heat flux Q, the maximum value of the fluctuation, that is, the maximum value of the temperature of the mold copper plate due to the shell breakage 1oi, can be detected at an appropriate time regardless of the fluctuation of the distance t.

By the way, as shown in FIG. 2, the change in distance n (a detection time delay n has occurred due to the second reason. Therefore, the detection time delay n due to the change in the specific gravity 1t) 1 is expressed as 31〉', Shown in I. In Figure 3, the horizontal axis represents the distance in minutes, and the vertical axis represents the time delay n.
(Milk C), but as shown in straight line 31,
Even if the distance pr1t t is 15 +++ m, compared to the 31-kun twist, IJ,
sec), and in actual operation there is no time at all.

(Example) Casting width 920 wv+, λ'jJ'i thickness 250 t
Drawing speed of nrn low carbon 61・-1Qlth (Q!3
1.6 m 7 minutes - r: *1. Figure 4 shows the change in heat flux for the woman 1511 detected during the construction.

fc1IIi, based on the detected value obtained from a thermocouple embedded in a specific part of the molded copper plate.

The horizontal axis represents time (pass), and the vertical axis represents (・: i heat flux (Kai′/
Door, 1lr).

Curve 41 shows this change, and shell rupture was detected at %)'fi dog value A. Therefore, the shell rupture reference value can be any value of the absolute value or increase of the heat flux. It is easier to judge if a table is prepared in advance for each production speed by analyzing past results, and an electronic calculator can be used to calculate 'IH:211j' according to one's own BIB.

In addition, as the shell value, it is possible to use either the absolute value of the flux or the rate of acceleration.

(Effect of the invention) In the continuous casting of copper according to the present invention, WJ type 1/1/1
・1 anti! Buttons such as flJ Fall and 7 cooling water quality changes
It is possible to accurately detect shell breakage (VC breakage), which is a precursor phenomenon of breakout, with high accuracy due to the influence of factors that reduce the sheath in the detection of thermal breakouts in shaped steel plates. Therefore, it is extremely effective in preventing breakouts.

[Brief explanation of the drawing]

Figure 1 is a graph showing the temperature detection status of the thermocouple embedded in the molded copper plate, Section 2 is a graph showing the shell rupture detection status due to heat flux, Figure 3 is the time delay fL of detection of kJ heat flux. , and FIG. 4 is a graph showing a heat flux change curve when shell fracture 1 ( ) is detected by heat flux in the example. 11.12.13...Temperature detection graph ,22゜23・
...Pear 1 Flux Detection Graph Agent Masabu Masaru Akizawa) 1: 2 others December 21, 1981 28 Name of Invention Continuous Casting 1 (Method for Detecting Shell Breakage 3 in Placing, Case of Person Who Makes Corrections) Relationship with Application Address: 2-6 Otemachi, Chiyoda-ku, Tokyo (No. 13) Name (665) Shin Nippon Seiwa Co., Ltd. (4, Ltd.)
Address: 5 Taiyo Hill, 12-1 Nihonbashi Kabuto-cho, Chuo-ku, Tokyo
, Supplementary Order 11□#(!, Fl!rlyo1.1□ Date Showa
Month, day (shipment) 6, number of inventions increased by amendment L
(111 Correct content 1, scope of claims of the present patent application? Corrected as follows. r (1) Continuous casting - 1j type mold piece / (Shell breakage point? Detected from the temperature detection value of the buried thermal α pair? How to do/C
Place the chest piece in advance! Determine the overall heat transfer coefficient K (t) using l@ as a parameter, and then calculate the heat flux Q based on the actual temperature detection value VC of the thermocouple as shown below (1).
The calculated value is compared with the shell image judgment reference value, and when the difference exceeds the allowable value, it is determined that the shell has broken. Shell breakage detection method in
°°°Heat flux (KCaJ3/m2・Hr)K (t)−
・Overall heat transfer coefficient (Kca-6/m2Hr ”C)1
゛Q...-Thermocouple indication value ("C)'l'7...-
・・Cooling water temperature in the mold # (℃) t・・・・・・・Mold single wall thickness (m)” 2, Next to “11” on page 5, line 10 of the specification v (
[Insert "Mold copper plate surface temperature". 3. On page 5, line 10, “12 is,” followed by “vcr at that time.”
Do 4ζf people. 4, same 1' 5 j'a 11th line [13 is -161) next +1c r same''? No one else.

Claims (1)

[Claims] (1) A method of detecting the shell rupture point from the temperature detection value of a thermocouple embedded in a mold piece of a continuous casting mold. Here, the overall heat transfer coefficient K ( t), and then calculate the heat θ core Q as shown below (1) based on the temperature value υ111 detected value of the thermocouple.
- out from stratification with L, said calculation 111 (all / L broken W 4th
Shell failure analysis in continuous casting is characterized in that when the difference exceeds the JR standard value, it is determined that the shell failure has occurred. Q=: (TQ-'Pw), K(t)...
...(1) Q-=heat flow jlj (Ktn9/+r
? , I-1r )K(t) -tri bracket heat transfer coefficient guc4/ ++/ I-1r ℃)'+Jq・・W
'1℃ Electron reading (C)'J''W... Cold cutting in oil mold] Water temperature (℃) t... Mold piece Qj (Thickness (,)