CA1328925C - Process of continuous casting with detection of possibility of break out - Google Patents
Process of continuous casting with detection of possibility of break outInfo
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- CA1328925C CA1328925C CA000584465A CA584465A CA1328925C CA 1328925 C CA1328925 C CA 1328925C CA 000584465 A CA000584465 A CA 000584465A CA 584465 A CA584465 A CA 584465A CA 1328925 C CA1328925 C CA 1328925C
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- temperature
- temperature measuring
- measuring points
- continuous casting
- variation speed
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Abstract
ABSTRACT OF THE DISCLOSURE
A continuous casting process introduces factor of temperature variation speed for detecting break out in a cast metal. Introduction of temperature variation speed as parameter representative of the cast metal condition is successful for avoiding the influence of variation of the casting condition, fluctuation of the powder to be introduced between the casting mold wall and the cast metal, casting speed and so forth. For achieving accurate detection of break out of the cast metal by introducing the temperature variation factor, casting mold wall temperatures are measured at various measuring points which are circumferentially aligned. Temperature variation speed at each measuring point and average temperature variation speed of all measuring points are derived and compared for making judgement of possible break out when the difference of the temperature variation speed at each measuring points and average temperature variation speed becomes greater than a predetermined value.
A continuous casting process introduces factor of temperature variation speed for detecting break out in a cast metal. Introduction of temperature variation speed as parameter representative of the cast metal condition is successful for avoiding the influence of variation of the casting condition, fluctuation of the powder to be introduced between the casting mold wall and the cast metal, casting speed and so forth. For achieving accurate detection of break out of the cast metal by introducing the temperature variation factor, casting mold wall temperatures are measured at various measuring points which are circumferentially aligned. Temperature variation speed at each measuring point and average temperature variation speed of all measuring points are derived and compared for making judgement of possible break out when the difference of the temperature variation speed at each measuring points and average temperature variation speed becomes greater than a predetermined value.
Description
1 32~925 ~ 1- 72199-14 BACKGROUND OF TH~ INV~NTION
Field of the Invention The present invention relates generally to a pro~ess of continuous casting of a mol~en metal. More specifically, the invention relates to a technique for detecting of possible breaking out of cast metal ln continuous casting and prevention thereof. The invention also relates to a device for precisely measuring temperature of casting mold, which is applicable for detection of possible breakout of the cast metal.
Descri~tlon of the Backqround Art Conventionally, various approaches have been taken for detecting possibility of breakout of cast metal in continuous casting process. In general, conventionally proposed method of detection of breakout of the cast metal takes temperature variation of the casting mold as parameter for detection of breakout. For example, Japanese Patent First (unexamined) Publication (Tokkai) Showa 57-115961 discloses a method, in which temperature of a continuous casting mold at temperature measuring points which are mutually different from each other in drawing direction. The measured temperatures are compared to each other for detecting temperature variation' thereby detecting possibility of breakout in a cast metal. On the other hand, Japanese Patent second (examined) Publication (Tokko) Showa 56-7783 discloses a method of detection of possible breakout by detecting temperature difference in copper walls of casting mold.
Furthermore, Japanese Patent First Publication (Tokkai) Showa 57-152356 discloses employment of thermometric couple disposed in the wall of the casting mold. In the method of Tokkai Showa 57-152356, possible breakout is detected when the measured temperature once rises above an average temperature and sub-sequently drops below th~ average temperature.
Such conventlonal methods of detection of breakout were not complete and not satisfactory due to the following defe~ts.
Namely, the temperature of the casting mold is variable depending upon the casting speed. It rises as the casting speed increases and lowers as the casting speed decreases. Therefore, there is a possibility of mis-detection of the hreakdown of the cast metal when casting speed fluctuat~s.
In addition, the detection of breakout of the cast metal can be inaccurate when powder introduced between the casting mold wall and the cast metal is uneven or formation of air gap occurs.
In order to avoid the defects in the aforementioned prior art, there are some proposals for improvement in detection of the possible breakout of cast metal. For example, Japanese Patent First Publication (Tokkai) Showa 60-44163 discloses a method of detection of the breakout, in which casting mold wall temperatures are measured at least at two measuring points.
Judgement of possibility of breakout is made when the measured temperature at two measuring points are inclined to higher temperature side in relation to a normal tempera~ure level for a given period of time. On the other hand, Japanese Patent First Publication (Tokkai) Showa 61-2B9954 utilizes a plurality of set reference temperatures to be compared with the measured temperature data for detecting the breakout. Japanese Patent First Publication (Tokkai) Showa 61-226154 utilizes present data showing relationship of the wall temperature of the casting mold " ., -1 32~q25 versus the casting speed. Utllizing the present data, a data component in the temperature data influenced by variation of the casting speed can be successfully avoided. Then, the temperature data at selected one measuring polnt are compared with those obtained from remaining measuring points. In this Tokkai Showa 61-226154, judgement of possible breakdown is made when the relative temperature between the selected measure point and the remainders becomes greater than an upper limit or smaller than a lower limit.
In case of the technique shown in Tokkai Showa 60-44163, breakout cannot be detected when the casting speed is continuously varying or meniscus fluctuating. On the other hand, in case of Tokkai Showa 61-2289954, the possibility of mis-detection increases unless the set reference temperatures are adapted to the casting conditions. Therefore, in such case, set reference temperatures have to be adjusted depending upon the casting condi~ions. In case of Tokkai Showa 61-226154, since it requires precise measurement of parameters adapted to positions of the temperature measurement and casting condition, setting has to be adjusted every time the temperature measuring points are differentiated or casting condition i~ changed.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a process of continuous casting including detection of a possible breakout of a cast me~al, which can avoid influence of variation of meniscus position and/or casting condition.
Another object of the present invention is to provide a casting mold wall temperature measuring device which is useful for 1 32~925 -g- 72199-14 implementing the breakout detection according to the present invention.
In a continuous casting process according to the present invention, the factor of temperature variation speed is introduced for detecting breakout in a cast metal. The introduction of temperature variation speed as a parameter representative o~ the cast metal condition is successful for avoiding the influence of variation of the casting condition, fluctuation of the powder introduced between the casting mold wall and the cast metal, lo casting speed and so forth. For achieving an accurate detection of breakout of the cast metal by introducing the temperature variation factor, casting mold wall temperatures are measured at various measuring points which are circumferentially aligned. The temperature variation speed at each measuring point and the average variation speed of all measuring points are collected and compared for making judgement of po~sible breakout when the difference of the temperature variation speed at each measuring points and an average temperature variation speed becomes greater than a predetermined value.
According to one aspect of the invention, there is provided a method for detecting a breakout in continuous casting comprises the steps of:
arranging a plurality of temperature measuring devices at temperature measuring points oriented in circumferential alignment with a given interval on a wall of a continuous casting mold for measuring temperature of the wall at respective temperature measuring points;
deriving variation speed of temperature at respective -~a- 72l9g-l4 temperature measuring points;
deriving an average temperature variation speed based on temperature variation speed of respective temperatur~ measuring points;
deriving a difference between the temperature variation speed at each temperature measuring point and the average temperature variation speed;
comparing the derlved difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point; and observing sequential distribution and propagation of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagation of the abnormal temperature measuring points is detected.
According to another aspect of the invention, there is provided a process of continuous casting comprises the steps of:
casting a molten metal to one end of a continuous casting mold at a given controlled casting speed;
drawing solidifying cast block from the other end of the continuous casting mold at a given casting speed;
measurlng temperature of a wall of the continuous casting mold at a plurality of temperature measuring points oriented in circumferential alignment with a given interval;
deriving variation speed of temperature at respective temperature measuring points;
1 328q2'.-) -4b- 72199-14 deriving an average temperature variation speed based on temperature variation speed of respective temperature measurlng po ints;
deriving a difference between the temperature variation 1 ~28925 speed at each temperature measuring point an~ the average temperature variation speed;
comparing the derived difEerence with a predetermined threshol~ for detecting abnormal temperature variation of each temperature measuring point;
observing sequential distribution and propagration of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagration of the abnormal temperature measuring points is 0 detected; and controlling at least one of pouring speed and drawing speed for preventing the cast block from causing breakout The predetermined sequential distribution and propagration pattern of the abnormality includes transferring of abnormality to adjacent temperature measuring points at both sides. The temperature measurinq points are arranged in alignment on a plane perpendicular to the longitudinal axis of the continuous casting mold. The temperature measuring points are oriented downstream of meniscus.
A further aspect of the invention provides asystem for detecting breakout in continuous casting comprises:
a plurality of temperature measuring devices arranged in circumferential alignment with a given interval on a wall of a continuous casting mold for measuring temperature of the wall at respective temperature measuring points and producing casting wall temperature indicative signals representative of the measured temperature at respective temperature measuring points;
first means for deriving variation speed of temperature at respective temperature measuring points;
means for deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring points;
second means for deriving a difference between the temperature variation speed at each temperature measuring point and the average temperature variation speed; and third means for comparing the derived difference with a 3 ~ ~ 9 2r~ 72199-14 ~ 6 ~
predetermined threshold ~or detecting abnormal temperature variation of each temperature measuring point, and observing sequential distribution and propagration oE abnormal temperature measuring points for detecting possibility of breakoUt when predetermined pattern of sequential distributi~n and propagration of the abnormal temperature measuring points is detected.
A still further aspect of the invention provides an apparatus of continuous casting for casting molten metal to one end of a continuous casting mold at a given controlled casting speed, and drawing solidifying cast block from the other end of the continuous casting mold at a given drawing speed, comprises:
a plurality of temperature measuring device, arranged in circumferential alignment on the wall of the casting mold, for measuring temperature of the wall of the continuous casting mold at a plurality of temperature measuring points oriented in circumferential alignment with a given interval, each of the ~emperature measuring device producing a temperature indicative signal indicative of the measured temperature at associated temperature measuring point;
first means for receiving the temperature indicative signals from the temperature measuring devices and deriving variation speed of temperature at respective temperature measuring points to produce a temperature variation speed data;
second means for receiving the temperature variation data from the first means and for deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring polnts, the second means producing an average temperature variation speed data;
third means for comparing the temperature variation data of respective temperature measuring points with the average temperature variation speed for deriving a difference between the temperature variation speed data at each temperature measuring point and the average temperature variation speed;
fourth means for comparing the derived difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point;
1 328q~j fifth means for observing sequential distribution and propagration of abnormal temperature measuring points for detecting possibility of breakout~ when predetermined pattern of sequential distribution and propagration of the abnormal temperature measuring points is detected; and sixth means for controlling at least one of casting speed and drawing speed for preventing the cast block from causing break out.
In a~ preferred construction, the temperature measuring means may comprise:
a hollow cylindrical mounting bolt which is threaded to the wall of the continuous casting mold, the mounting bolt defining an axially extending opening;
a hollow housing disposed within the axially extending opening, the hollow housing including first and second mutually separated cylindrical components, which first cylindrical component is arranged close to the wall of the casting mold and the second cylindrical component is arranged remote from the wall;
a resilient member disposed between the first and second components of the cylindrical housing and designed to push the first component toward the wall;
a seal member carried by the end of the first cylindrical component and mating with the wall surface for establishing liquid tight seal; and a temperature sensing element disposed within the housing and contacting with the wall surface for monitoring the temperature of the wall of the casting mold. The temperature measuring device may further comprises a pushing means for resiliently pushing the temperature sensing element toward the wall surface.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiment of the invention, which, however, should not be taken to limit the invention to the specific embodiment but are for explanation and understanding 1 32~q2''~
only .
In the drawings:
Fig. 1 is an explanatory section of a continuous casting mold with cast metal in the Casting mold~ showing layout of a plurality of temperature measuring device in circumEerential alignment Figs. 2(A~, 2(B) and 2(C) are chart respectively showing variation of molten metal surface level ML, casting speed vc, casting mold wall temperature and relative temperature variation speed and Pig. 3 is a section of the preferred embodiment of a temperature measuring device which is applicable for measuring the temperature of the casting mold wall in the continuous casting DES~RIPTION OF ~HE PREFERRED EMBODIMENT
.. .. . .
Referring not to the drawings, particularly to Fig. 1, the preferred embodiment of continuous casting process, according to the present invention, introduces a feature of measurement of temperatures of a casting mold wall 10 at a plurality of temperature measuring points i, i~l, i+2, i+3, i-l and i-2. The temperature measuring points i, i+l, i+2, i+3, i-l and i-2 are oriented at positions downstream of a meniscas line M and arranged in circumferential alignment. The temperature measuring points i, i~l, i+2, i+3, i-l and i-2 are thus circumferentially arranged with a given interval.
It should be appreciated that though the shown embodiment includes one group of temperature measuring points i, i+l, i~2, i+3, i-l and i-2 circumferentially aligned, two or more groups of temperature measuring points may be used if desired.
For each temperature measuring points i, i+l, i+2, i+3, i-l and i-2, a temperature measuring device 20 of Fig. 3. The temperature measuring device 20 is inserted into the casting mold wall of the casting mold 10 for measuring the temperature. The temperature measuring device is designed to monitor the temperature of the wall of the casting mold at the associated temperature measuring point and produces a temperature indicative signal. The detailed construction of the temperature measuring 1 32~q25 device 20 will be discussed later.
The temperature measuring dev~ce 20 is connected to an arithmetic circuit 40 whlch includes a temperature variation speed derivation stage 41, an average temperature variation speed derivation stage 42 and a discriminator stage 43. The temperature indicative signals from respectlve temperature measuring devices 20 are at first processed by the temperature variation speed derivation stage 41 to derive the temperature variation speed at respective temperature measuring polnts. An average temperature variation speed is then derived on the basis of the temperature variation speeds at all of the temperature measuring points in the average temperature variation speed derivation stage 42. Then, the temperature variation speed of each temperature measuring point is compared with the average temperature variation speed to derive a difference in the discriminator stage 43. In the discriminator stage, it is lurther performed to compare the difference with a predetermined abnormal temperature variation representative criterion to make judgement whether the temperature variation speed of the temperature measuring point is within the normal range or abnormal range. In the discrlminating stage 43, pattern of propagratlon or transferring of the temperature measuring polnts where abnormal temperature variatlon is checked and compared wlth a preset pattern which is experimentally set in view of the past experienced breakout The discri~inator stage 43 outputs a discriminator signal to a speed controller 50 for controlling casting speed and/or casting speed for preventing the cast block from causing breakout.
The process performed by the aforementioned arithmetic circuit will be discussed in detail herebelow. Based on the measured temperature, temperature variation speed ~i is derived with respect to each temperature measuring point i~ i+l, i+2, i+3, i-l and i-2. The temperature variation speed ~i can be derived from the following equation:
1 32~ 5 72199-14 where ~i is instantaneous temperature e'i is the temperature at ~t be~ore and ~t is a period of time.
On the other hand, average temperature variation speed av of all of the measuring points (i = 1 to N) can be derived according to the following equation:
N
~av l/N x ~ Bi .......... t2) where N 19 number of temperature measuring points.
From the temperature variation speed ~i at each temperature measuring polnt i, i~l, 1+2, i~3, i-l and i-2, ànd the àverage temperature variation speed 0 , relative temperàture variation speed i can be calculated by the following equation:
~ av ---- ~3) When the temperature variation at respective temperature measuring points i5 caused by factor other than breakout gradient of tempesature variation speed points becomes substantially equal at respective temperature measuring points. Therefote, in such case, the tempeeature vaeiation speed can be illustrated by: 5 i D 9 ~ i = C/s As long as the condition set focth above is satisfied, judgement can be made that temperature variation is caused by a factor other than break out of the cast metal.
Hereafter will be discussed the practical process of detection of breahout utilizing the temperature variation speed ~i at respective temperature measuring points and the average temperature variation speed ~ . Here, it is assumed that break-1 32~925 72199-14 out occurs at the point A on the meniscas M between the temperature measuring points i and i+l or, in the alternative, adjacent the temperature measuring point i. By continuing casting, the relative temperature variation speeds ~ri and ~ir~l at the temperature measuring points i and i+l are simultaneously increased. Or, in the alternative, the relative temperature variation speed ~i at the temperature measuring point i is at first increased and subsequently, the relative temperature ~i+l is increased. By further continuing casting, the relative temperature variation speeds 0i_l-and ~i+2 at the temperature measuring points i-l and i+2 are simultaneously increased. Or, in the alterna~ive, the relative temperature variation speed ~i 1 at the temperature measuring point i-l is increased and subsequently, the relative temperature i+2 is increased.
As will be appreciated herefrom, when breakout occurs in the cast block, the relative temperature variation speed increases in order. It may also be appreciated from the above discussion that, when breakout occurs, variation of the relative temperature variation speed occurs simultaneously or alternatively at both sides of the point at which the breakout occurs, in order. To the contrary, when thermometric couple in one temperature measuring point is damaged, variation of the relative temperature variation speed occurs at respective temperature measuring points in order in one direction. For instance, assuming thermometric couple at the temperature measuring point i-l being damaged, variation of the relative temperature variation speed occurs in order of i - (i+l) - (i+2) ... Therefore, this type of variation of the relative temperature variation speed can be distinguished from that occurring upon breakout, The variation of the temperature variation speed occurring as set forth above was found as typical phenomena occurring immediately before occurrence of actual breakout whish is caused by sticking from the analysis of temperature variation data of several tens examples.
As will be appreciated herefrom, accurate detection of possible breakout becomes possible, according to the present "
.~ . . .
invention, by detecting abnormal temperature variation at each temperature meaSuring point and propagration characteristics of abnormality to adjacent temperature measuring points. Since the manner of detection of possible occurrence o~ bcea~ut in cast metal is made based on qualitative analysis of temperature variation occurring at respective temperature measuring points, the method of detection of possible breakout is applicable without requiring substantial change of setting of the parameters.
Here, maximum abnormality propagration period (T) can be arithmetically obtained from the following equation:
T = (w x tan B)/( x V ) ........ (5) where w is a distance between adjacent temperature measuring points Vc is a casting speed B is breaking angle of solidifying shell and Q is constant (0.5 to 1.0) On the other hand, number of abnormality detecting temperature measuring points to make judgement of possible break-out can be determined in relation to the distance Lp from the leading end of the break line to the outlet of the casting mold, casting speed Vc' after detection of possible breakOUt and period of time td required for deceleration, to satisfy the following relationship:
ks/(Lp - aVc x td)/Vc'> dB O ---- (6) Lp = L - ~m - (n x w)/2 tan ~ ... (7) where ks is solidifying speed constant (mm.min ) of molten metal in casting mold Vc is casting speed (m/min) L is a length of casting mold (m) dB O is experimentally obtained minimum thickness :. .
. .
1 32~92'~ 72199-14 (mm) of solidifying sh~ll which does not cause breakout by bulging immediately below the casting mold ~m is a distance (m) from the entrance of the casting mold to the temperature measuring points and S n is number of abnormality detecting temperature measuring points for detection of break~Ut of cast metal.
The number of the abnormality detecting temperature measuring points is preferably a maximum number which can satisfy the relationship of formula (6) set forth above. By utilizing the greater number of temperature measuring points for making judgement that breakout possibly occurs, occurrence of mis-detection can be reduced.
As will be appreciated herefrom, for detecting possible breakout the following parameters are to be set:
9cr which is upper limit value of the temperature variation speed t which is a minimum period of time in which is 0 maintained 9. > 9 l = cr B, a, and n.
In practice, t is set for avoiding mis-detection lead by temporary fluctuation of the molten metal temperature which causes ~i 2 9 . Therefore, by providing t influence of molten metal temperature fluctuation can be successfully avoided. B and a can be obtained from temperature data upon occurrence of break-out. Normally, B is set in a range of 20 to 45 and a is set in a range of 0.5 to lØ On the other hand, n can be derived from the aforementioned formula (6) and equation (7). Therefore, it is practically required to two parameters, i.e. ~ and t , to be set. These two parameters may be set based on temperature variation pattern in experienced break out.
EXAMPLE
In order to confirm performance of detection of break-out according to the invention, experimental casting was performed , 1 3 2 ~ q 2 ~ 72199-14 according to the casting and temperature measuring conditions set in the following table I.
T~BLE I
rype of Caster (Bending Type~ (Vertical Mold (Vertical Mold ~ending Bending Type) Type) Kind of Steel Stainless Steel teel Plate ow Carbon illed Steel High Carbon igh Tension Carbon Steel Steel Killed Steel Size of ~lock rhickness rhickness hickness 200 - 260 mm 200 - 260mm 230 - 260 mm Width Width idth 850 - 1250 mm900 - 1900 mm800 - 1900 mm Casting Speed Vc (m/min)0.6 - 1.0 0.9 - 1.4 0.9 - 2.0 Temperature variation Speed _ 0.5 0.6 0.7 Detection Range (m/min) 0.5 or more0.5 or more 0.8 or more ~inimum Period _ trC (sec) 6.0 4'.0 4.0 remp. Measure-ent Depth22 - 10 mm 28 - 10 mm 33 - 10 mm w 196 mm 150 mm 152 mm ~m 250 mm 330 mm 272 mm L 700 mm 800 mm 900 mm _ 20 _ 45u 20 _ 45v 20 - 45 0.5 - 0.9 0.5 - 0.9 0.5 - 0.9 n 2 3 3 During experimental casting, accuracy of detection of breah~ut was checked. In order to compare with the result in the inventive method, comparative experiments for detecting breakout wa~
performed in a method according to that disclosed in Tokkai Showa 61-226154, set forth above. The results are shown in the following table II.
1 3~925 72199-14 TA~LE II
caster_TYe- = 1 2 3 Invention A0.003470.001310.00202 B 40% 100~ 100 C 10% 0% 0%
Comparative A0.05560.00409 0.00673 B 25~ 32~ 30%
C 18~ 18~ 16%
In table II above, A indicates occurrence of alarm per one heat, s is a rate of occurrence of breakoUt mark on the surface of cast block in the casting mold upon occurrence of the alarm ((brea~ut mark occurrence 2b)/A(total occurence number of alarm, a) x 100), C is occurrence of overlooking of breakOUt ((overlooking occurrence 2c)/(B + overlooking occurrence) x 100).
Figs. 2(A), 2(B) and 2(C) are chart showing variation of molten metal surface level ML, casting speed Vc, casting mold wall temperature and relative temperature variation speed during experiment, in which possibility of breakOUt is detected. As will be appreciated herefrom, temperature variation speed is maintained essentially unchanged even when the casting speed Vc and the molten metal surface level ML fluctuate at significant level.
In the process shown in Figs. 2(A), 2(B) and 2(C), casting speed was decelerated at the timing shown by arrow in response to alarm for possibility of breakOUt In observation of the corresponding portion of the cast block, marking showing 30 growth of sticking type break out appeared. From this, it is clearly proven that method of detection of the breakOUt according to the present invention works very effectively.
Pig. 3 shows the preferred construction o~ the temperature measuring device which is useful for implementing the preferred process of detection of possible breakOUt. In the shown construction, the casting mold copper wall 10 is formed with a plurality of groove 11 defining a cooling water path. A cooling water box 12 has a planer section mating with the back surface of the copper wall 10 of the casting mold to stationally support the 1 32~q25 - 16 ~
copper wall. The cooling water box 12 and the copper wall 10 are rigidly connected to each other by means of a fixing bolt 13. The fixing bolt 13 is formed with an axially extending through opening 13a.
The temperature measuring device 20 has an inner cylindrical housing 24 extending through the opening 13a. The inner cylindrical housing 24 is slidably disposed within the opening 13a and has an end section carrying water seals 24a and 24b. The rear end of the inner cylindrical housing 24 contacts with one end of coil spring 25 which pushes the cylindrical housing 24 toward the copper wall 10 to establish liguid tight seal by depressing the water seal 24a. To the other end of the coil spring 25, an outer cylindrical housing 26 contact at the inner end. The outer cylindrical housing 26 has a threaded section 26a which engages with a female thread formed on the inner periphery of the opening 13a. Therefore, the outer cylindrical housing 26 is thus threaded to the opening 13a.
The inner end of the inner cylindrical housing 24 carries a holder 27 via the water seal 24b. The holder 27 is axially pushes by a coil spring 28. Through axially extending openings of the cylindrical housings 24 and 26, a thermometric couple introducing tube 29 extends. The thermometric couple introducing tube 29 contacts with the coil spring 28 at the inner end thereof. The thermometric couple introducing tube 29 is formed with a threaded portion 29a. The threaded portion 29a engages with the female thread formed on the inner periphery of the outer cylindrical housing 26. Therefore, the thermometric couple introducing tube 29 is fixed to the outer cylindrical housing 26.
Through the center opening of the thermometric couple introducing tube 29, a termometric couple 30 extends to contact the inner end to the copper wall 10. The front end portion of the thermometric couple 30 is gripped by the holder 27. Since the holder 27 is pushed toward the copper wall 10, by means of the coil spring 28. The inner end of the thermometric couple 30 resiliently pushed onto the copper wall 10 to assure contact therebetween. The pushing force of the coil spring 28 is regulated by a stopper member 31 which is fixed onto the outer end portion of the outer cylindrical housing 26 and restrict axial movement of the thermometric couple introducing tube 29 toward the copper wall.
Sealing packing 14 is disposed between the outer end portion of the fixing bolt 13 and the inner periphery of the cooling water box 12 for establishing tight seal and fixing the fixing bolt.
With the construction set forth above, the cooling water leaked from the grooye 11 of the copper wall 10 through paths 32 and 33 can be blocked to flow into the inside of the fixing bolt 13 by the water seal 24a. On the other hand, the leaked water flowing through paths 32, 33, 34 and 35 can be blocked by the water seal 24b. Therefore, the thermometric couple becomes free from influence of the leaked water. Water tight seal established by the water seals 24a and 24b can be maintained even upon occurrence of thermal distortion of the copper wall 10 because the inner cylindrical housing 24 is resiliently pushed by means of the coil spring 25 to constantly establish water tight seal by the water seals 24a and 24b. On the other hand, as the inner end of the thermometric couple 30 held by the holder 27 is constantly pushed toward the copper wall 10 by the coil spring 28, contact between the thermometric couple 30 and the copper wall 10 can be constantly maintained for assure measurement of the temperature of the copper wall.
In the preferred construction, the water seals 24a and 24b may be formed into O-ring and made of fluorine, fluon, metal, such as copper, alminium, or so forth.
In the shown construction, since the thermometric couple 30 extends from the inner end of the holder 27 for a length of 1 mm to 3 mm. There may not occur buckling even when substantially small diameter thermometric couple, such as that has 1 mm to 2 mm diameter, is used. As is well known, smaller diameter of thermometric couple has higher sensitivity of the temperature.
Therefore, the shown construction allows the temperature measuring device 20 satisfactorily sensible of the copper wall temperature.
1 32~q2~
In addition, by the shown construction, since the inner cylindrical housing 24 carrying the water seals 24a and 24b will not rotate when fastening the outer cylindrical housing 26 because it is separated from the outer cylindrical housing via the coil spring 25. Furthermore, presence of the coil spring 28 absorbs the rotational torque to be exerted on the termometric couple introducing tube 29 when the later is fixed to the outer cylindrical housing 26. 8y this construction, the water seals 24a and 24b will never be damaged upon assembling.
EXAMPLE
Experimentally, the temperature measuring device is assembled in the following specification:
Eixing bolt 13 outer diameter: 18 mm length : 470 mm nominal diameter: W18 opening (inner diameter): 10 mm material : SUS 630 Inner cYlindrical housing 24 external diameter: 9.0 mm inner diameter: 5.5 mm length: 400 mm material: SUS 304 Coil spring 25 external diameter: 9.0 mm inner diameter: 5.5 mm spring constant: 4 kgf/mm material: SUS 304 section: square Outer cylindrical housing 26 external diameter: 9.0mm inner diameter: 5.5 mm length : 27 mm material: SUS 304 Holder 27 material: copper - 19 1 3 2 ~ q 2 5 Thermometric couple 30 external diameter 1.0 mm being silver brased and extended therefrom for the length of 3 mm Coil spring 28 external diameter: 5.0 mm inner diameter: 3.5 mm spring coefficient: 1 kgf/mm material: SUS 304 Thermometric couple introducing tube 29 external diameter: 5.0 mm inner diameter: 3.5 mm length: 440 mm material: SuS 304 ~tilizing the above-specified temperature measuring device, experimental measurement of the copper wall temperature was performed. In the experiment, fluorine O-rings are used as the water seals 24a and 24b, which O-rings are provided a resistantive temperatures of 260 C and 200 C respectively. The coil springs 25 and 28 are pre-loaded at 11 kg and 5 kg, respectively. The pressure of the cooling water passing through the cooling water path 11 is set at 8 kgf/cm2.
- During experimental measurement, leak of the cooling water in the thermometric couple introducing tube 29 was observed.
Despite cooling water leakage, the measured temperature was stably maintained within a range of 150 C to 350 C.
After experimental casting for 500 heats, the temperature measuring device 20 was removed from the fixing bolt 13. In observation of the temperature measuring device 20, the carbonized portion was found on the water seal 24a at the portion mating with the copper wall 10. However, no leakage of the cooling water through the water seal was observed.
The shown type of temperature measuring device is advantageously introduced in imprementation of the preferred method of detection of possible break out since it does not require disassembling of the casting mold upon installation.
1 ~2~925 secause disassembling of copper wall upon installation of the temperature measuring device results in releasing of the copper wall from stress which is caused due to distortion, difficulty of re-assembling of the casting mold may occur otherwise.
Furthermore, since the shown embodiment oÇ the temperature measuring device can establish complete water seal, stable measurement oE the copper wall temperature can be performed. In addition, since the thin thermometric couple can be employed in the temperature measuring device, satisfactorily high sensibility is facilitated. Furthermore, since the shown temperature measuring device is substantially compact and thus allowed to be housed within the fixing bolt, flexibility of installation can be conveniently established.
While the present invention has been disclosed in terms of the prefereed embodiment in order to facilitate better understanding of the invention, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention. Therefore, the invention should be understood to include all possible embodiments and modifications to the shown embodiments which can be embodied without departing from the principle of the invention set out in the appended claims.
Field of the Invention The present invention relates generally to a pro~ess of continuous casting of a mol~en metal. More specifically, the invention relates to a technique for detecting of possible breaking out of cast metal ln continuous casting and prevention thereof. The invention also relates to a device for precisely measuring temperature of casting mold, which is applicable for detection of possible breakout of the cast metal.
Descri~tlon of the Backqround Art Conventionally, various approaches have been taken for detecting possibility of breakout of cast metal in continuous casting process. In general, conventionally proposed method of detection of breakout of the cast metal takes temperature variation of the casting mold as parameter for detection of breakout. For example, Japanese Patent First (unexamined) Publication (Tokkai) Showa 57-115961 discloses a method, in which temperature of a continuous casting mold at temperature measuring points which are mutually different from each other in drawing direction. The measured temperatures are compared to each other for detecting temperature variation' thereby detecting possibility of breakout in a cast metal. On the other hand, Japanese Patent second (examined) Publication (Tokko) Showa 56-7783 discloses a method of detection of possible breakout by detecting temperature difference in copper walls of casting mold.
Furthermore, Japanese Patent First Publication (Tokkai) Showa 57-152356 discloses employment of thermometric couple disposed in the wall of the casting mold. In the method of Tokkai Showa 57-152356, possible breakout is detected when the measured temperature once rises above an average temperature and sub-sequently drops below th~ average temperature.
Such conventlonal methods of detection of breakout were not complete and not satisfactory due to the following defe~ts.
Namely, the temperature of the casting mold is variable depending upon the casting speed. It rises as the casting speed increases and lowers as the casting speed decreases. Therefore, there is a possibility of mis-detection of the hreakdown of the cast metal when casting speed fluctuat~s.
In addition, the detection of breakout of the cast metal can be inaccurate when powder introduced between the casting mold wall and the cast metal is uneven or formation of air gap occurs.
In order to avoid the defects in the aforementioned prior art, there are some proposals for improvement in detection of the possible breakout of cast metal. For example, Japanese Patent First Publication (Tokkai) Showa 60-44163 discloses a method of detection of the breakout, in which casting mold wall temperatures are measured at least at two measuring points.
Judgement of possibility of breakout is made when the measured temperature at two measuring points are inclined to higher temperature side in relation to a normal tempera~ure level for a given period of time. On the other hand, Japanese Patent First Publication (Tokkai) Showa 61-2B9954 utilizes a plurality of set reference temperatures to be compared with the measured temperature data for detecting the breakout. Japanese Patent First Publication (Tokkai) Showa 61-226154 utilizes present data showing relationship of the wall temperature of the casting mold " ., -1 32~q25 versus the casting speed. Utllizing the present data, a data component in the temperature data influenced by variation of the casting speed can be successfully avoided. Then, the temperature data at selected one measuring polnt are compared with those obtained from remaining measuring points. In this Tokkai Showa 61-226154, judgement of possible breakdown is made when the relative temperature between the selected measure point and the remainders becomes greater than an upper limit or smaller than a lower limit.
In case of the technique shown in Tokkai Showa 60-44163, breakout cannot be detected when the casting speed is continuously varying or meniscus fluctuating. On the other hand, in case of Tokkai Showa 61-2289954, the possibility of mis-detection increases unless the set reference temperatures are adapted to the casting conditions. Therefore, in such case, set reference temperatures have to be adjusted depending upon the casting condi~ions. In case of Tokkai Showa 61-226154, since it requires precise measurement of parameters adapted to positions of the temperature measurement and casting condition, setting has to be adjusted every time the temperature measuring points are differentiated or casting condition i~ changed.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a process of continuous casting including detection of a possible breakout of a cast me~al, which can avoid influence of variation of meniscus position and/or casting condition.
Another object of the present invention is to provide a casting mold wall temperature measuring device which is useful for 1 32~925 -g- 72199-14 implementing the breakout detection according to the present invention.
In a continuous casting process according to the present invention, the factor of temperature variation speed is introduced for detecting breakout in a cast metal. The introduction of temperature variation speed as a parameter representative o~ the cast metal condition is successful for avoiding the influence of variation of the casting condition, fluctuation of the powder introduced between the casting mold wall and the cast metal, lo casting speed and so forth. For achieving an accurate detection of breakout of the cast metal by introducing the temperature variation factor, casting mold wall temperatures are measured at various measuring points which are circumferentially aligned. The temperature variation speed at each measuring point and the average variation speed of all measuring points are collected and compared for making judgement of po~sible breakout when the difference of the temperature variation speed at each measuring points and an average temperature variation speed becomes greater than a predetermined value.
According to one aspect of the invention, there is provided a method for detecting a breakout in continuous casting comprises the steps of:
arranging a plurality of temperature measuring devices at temperature measuring points oriented in circumferential alignment with a given interval on a wall of a continuous casting mold for measuring temperature of the wall at respective temperature measuring points;
deriving variation speed of temperature at respective -~a- 72l9g-l4 temperature measuring points;
deriving an average temperature variation speed based on temperature variation speed of respective temperatur~ measuring points;
deriving a difference between the temperature variation speed at each temperature measuring point and the average temperature variation speed;
comparing the derlved difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point; and observing sequential distribution and propagation of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagation of the abnormal temperature measuring points is detected.
According to another aspect of the invention, there is provided a process of continuous casting comprises the steps of:
casting a molten metal to one end of a continuous casting mold at a given controlled casting speed;
drawing solidifying cast block from the other end of the continuous casting mold at a given casting speed;
measurlng temperature of a wall of the continuous casting mold at a plurality of temperature measuring points oriented in circumferential alignment with a given interval;
deriving variation speed of temperature at respective temperature measuring points;
1 328q2'.-) -4b- 72199-14 deriving an average temperature variation speed based on temperature variation speed of respective temperature measurlng po ints;
deriving a difference between the temperature variation 1 ~28925 speed at each temperature measuring point an~ the average temperature variation speed;
comparing the derived difEerence with a predetermined threshol~ for detecting abnormal temperature variation of each temperature measuring point;
observing sequential distribution and propagration of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagration of the abnormal temperature measuring points is 0 detected; and controlling at least one of pouring speed and drawing speed for preventing the cast block from causing breakout The predetermined sequential distribution and propagration pattern of the abnormality includes transferring of abnormality to adjacent temperature measuring points at both sides. The temperature measurinq points are arranged in alignment on a plane perpendicular to the longitudinal axis of the continuous casting mold. The temperature measuring points are oriented downstream of meniscus.
A further aspect of the invention provides asystem for detecting breakout in continuous casting comprises:
a plurality of temperature measuring devices arranged in circumferential alignment with a given interval on a wall of a continuous casting mold for measuring temperature of the wall at respective temperature measuring points and producing casting wall temperature indicative signals representative of the measured temperature at respective temperature measuring points;
first means for deriving variation speed of temperature at respective temperature measuring points;
means for deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring points;
second means for deriving a difference between the temperature variation speed at each temperature measuring point and the average temperature variation speed; and third means for comparing the derived difference with a 3 ~ ~ 9 2r~ 72199-14 ~ 6 ~
predetermined threshold ~or detecting abnormal temperature variation of each temperature measuring point, and observing sequential distribution and propagration oE abnormal temperature measuring points for detecting possibility of breakoUt when predetermined pattern of sequential distributi~n and propagration of the abnormal temperature measuring points is detected.
A still further aspect of the invention provides an apparatus of continuous casting for casting molten metal to one end of a continuous casting mold at a given controlled casting speed, and drawing solidifying cast block from the other end of the continuous casting mold at a given drawing speed, comprises:
a plurality of temperature measuring device, arranged in circumferential alignment on the wall of the casting mold, for measuring temperature of the wall of the continuous casting mold at a plurality of temperature measuring points oriented in circumferential alignment with a given interval, each of the ~emperature measuring device producing a temperature indicative signal indicative of the measured temperature at associated temperature measuring point;
first means for receiving the temperature indicative signals from the temperature measuring devices and deriving variation speed of temperature at respective temperature measuring points to produce a temperature variation speed data;
second means for receiving the temperature variation data from the first means and for deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring polnts, the second means producing an average temperature variation speed data;
third means for comparing the temperature variation data of respective temperature measuring points with the average temperature variation speed for deriving a difference between the temperature variation speed data at each temperature measuring point and the average temperature variation speed;
fourth means for comparing the derived difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point;
1 328q~j fifth means for observing sequential distribution and propagration of abnormal temperature measuring points for detecting possibility of breakout~ when predetermined pattern of sequential distribution and propagration of the abnormal temperature measuring points is detected; and sixth means for controlling at least one of casting speed and drawing speed for preventing the cast block from causing break out.
In a~ preferred construction, the temperature measuring means may comprise:
a hollow cylindrical mounting bolt which is threaded to the wall of the continuous casting mold, the mounting bolt defining an axially extending opening;
a hollow housing disposed within the axially extending opening, the hollow housing including first and second mutually separated cylindrical components, which first cylindrical component is arranged close to the wall of the casting mold and the second cylindrical component is arranged remote from the wall;
a resilient member disposed between the first and second components of the cylindrical housing and designed to push the first component toward the wall;
a seal member carried by the end of the first cylindrical component and mating with the wall surface for establishing liquid tight seal; and a temperature sensing element disposed within the housing and contacting with the wall surface for monitoring the temperature of the wall of the casting mold. The temperature measuring device may further comprises a pushing means for resiliently pushing the temperature sensing element toward the wall surface.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiment of the invention, which, however, should not be taken to limit the invention to the specific embodiment but are for explanation and understanding 1 32~q2''~
only .
In the drawings:
Fig. 1 is an explanatory section of a continuous casting mold with cast metal in the Casting mold~ showing layout of a plurality of temperature measuring device in circumEerential alignment Figs. 2(A~, 2(B) and 2(C) are chart respectively showing variation of molten metal surface level ML, casting speed vc, casting mold wall temperature and relative temperature variation speed and Pig. 3 is a section of the preferred embodiment of a temperature measuring device which is applicable for measuring the temperature of the casting mold wall in the continuous casting DES~RIPTION OF ~HE PREFERRED EMBODIMENT
.. .. . .
Referring not to the drawings, particularly to Fig. 1, the preferred embodiment of continuous casting process, according to the present invention, introduces a feature of measurement of temperatures of a casting mold wall 10 at a plurality of temperature measuring points i, i~l, i+2, i+3, i-l and i-2. The temperature measuring points i, i+l, i+2, i+3, i-l and i-2 are oriented at positions downstream of a meniscas line M and arranged in circumferential alignment. The temperature measuring points i, i~l, i+2, i+3, i-l and i-2 are thus circumferentially arranged with a given interval.
It should be appreciated that though the shown embodiment includes one group of temperature measuring points i, i+l, i~2, i+3, i-l and i-2 circumferentially aligned, two or more groups of temperature measuring points may be used if desired.
For each temperature measuring points i, i+l, i+2, i+3, i-l and i-2, a temperature measuring device 20 of Fig. 3. The temperature measuring device 20 is inserted into the casting mold wall of the casting mold 10 for measuring the temperature. The temperature measuring device is designed to monitor the temperature of the wall of the casting mold at the associated temperature measuring point and produces a temperature indicative signal. The detailed construction of the temperature measuring 1 32~q25 device 20 will be discussed later.
The temperature measuring dev~ce 20 is connected to an arithmetic circuit 40 whlch includes a temperature variation speed derivation stage 41, an average temperature variation speed derivation stage 42 and a discriminator stage 43. The temperature indicative signals from respectlve temperature measuring devices 20 are at first processed by the temperature variation speed derivation stage 41 to derive the temperature variation speed at respective temperature measuring polnts. An average temperature variation speed is then derived on the basis of the temperature variation speeds at all of the temperature measuring points in the average temperature variation speed derivation stage 42. Then, the temperature variation speed of each temperature measuring point is compared with the average temperature variation speed to derive a difference in the discriminator stage 43. In the discriminator stage, it is lurther performed to compare the difference with a predetermined abnormal temperature variation representative criterion to make judgement whether the temperature variation speed of the temperature measuring point is within the normal range or abnormal range. In the discrlminating stage 43, pattern of propagratlon or transferring of the temperature measuring polnts where abnormal temperature variatlon is checked and compared wlth a preset pattern which is experimentally set in view of the past experienced breakout The discri~inator stage 43 outputs a discriminator signal to a speed controller 50 for controlling casting speed and/or casting speed for preventing the cast block from causing breakout.
The process performed by the aforementioned arithmetic circuit will be discussed in detail herebelow. Based on the measured temperature, temperature variation speed ~i is derived with respect to each temperature measuring point i~ i+l, i+2, i+3, i-l and i-2. The temperature variation speed ~i can be derived from the following equation:
1 32~ 5 72199-14 where ~i is instantaneous temperature e'i is the temperature at ~t be~ore and ~t is a period of time.
On the other hand, average temperature variation speed av of all of the measuring points (i = 1 to N) can be derived according to the following equation:
N
~av l/N x ~ Bi .......... t2) where N 19 number of temperature measuring points.
From the temperature variation speed ~i at each temperature measuring polnt i, i~l, 1+2, i~3, i-l and i-2, ànd the àverage temperature variation speed 0 , relative temperàture variation speed i can be calculated by the following equation:
~ av ---- ~3) When the temperature variation at respective temperature measuring points i5 caused by factor other than breakout gradient of tempesature variation speed points becomes substantially equal at respective temperature measuring points. Therefote, in such case, the tempeeature vaeiation speed can be illustrated by: 5 i D 9 ~ i = C/s As long as the condition set focth above is satisfied, judgement can be made that temperature variation is caused by a factor other than break out of the cast metal.
Hereafter will be discussed the practical process of detection of breahout utilizing the temperature variation speed ~i at respective temperature measuring points and the average temperature variation speed ~ . Here, it is assumed that break-1 32~925 72199-14 out occurs at the point A on the meniscas M between the temperature measuring points i and i+l or, in the alternative, adjacent the temperature measuring point i. By continuing casting, the relative temperature variation speeds ~ri and ~ir~l at the temperature measuring points i and i+l are simultaneously increased. Or, in the alternative, the relative temperature variation speed ~i at the temperature measuring point i is at first increased and subsequently, the relative temperature ~i+l is increased. By further continuing casting, the relative temperature variation speeds 0i_l-and ~i+2 at the temperature measuring points i-l and i+2 are simultaneously increased. Or, in the alterna~ive, the relative temperature variation speed ~i 1 at the temperature measuring point i-l is increased and subsequently, the relative temperature i+2 is increased.
As will be appreciated herefrom, when breakout occurs in the cast block, the relative temperature variation speed increases in order. It may also be appreciated from the above discussion that, when breakout occurs, variation of the relative temperature variation speed occurs simultaneously or alternatively at both sides of the point at which the breakout occurs, in order. To the contrary, when thermometric couple in one temperature measuring point is damaged, variation of the relative temperature variation speed occurs at respective temperature measuring points in order in one direction. For instance, assuming thermometric couple at the temperature measuring point i-l being damaged, variation of the relative temperature variation speed occurs in order of i - (i+l) - (i+2) ... Therefore, this type of variation of the relative temperature variation speed can be distinguished from that occurring upon breakout, The variation of the temperature variation speed occurring as set forth above was found as typical phenomena occurring immediately before occurrence of actual breakout whish is caused by sticking from the analysis of temperature variation data of several tens examples.
As will be appreciated herefrom, accurate detection of possible breakout becomes possible, according to the present "
.~ . . .
invention, by detecting abnormal temperature variation at each temperature meaSuring point and propagration characteristics of abnormality to adjacent temperature measuring points. Since the manner of detection of possible occurrence o~ bcea~ut in cast metal is made based on qualitative analysis of temperature variation occurring at respective temperature measuring points, the method of detection of possible breakout is applicable without requiring substantial change of setting of the parameters.
Here, maximum abnormality propagration period (T) can be arithmetically obtained from the following equation:
T = (w x tan B)/( x V ) ........ (5) where w is a distance between adjacent temperature measuring points Vc is a casting speed B is breaking angle of solidifying shell and Q is constant (0.5 to 1.0) On the other hand, number of abnormality detecting temperature measuring points to make judgement of possible break-out can be determined in relation to the distance Lp from the leading end of the break line to the outlet of the casting mold, casting speed Vc' after detection of possible breakOUt and period of time td required for deceleration, to satisfy the following relationship:
ks/(Lp - aVc x td)/Vc'> dB O ---- (6) Lp = L - ~m - (n x w)/2 tan ~ ... (7) where ks is solidifying speed constant (mm.min ) of molten metal in casting mold Vc is casting speed (m/min) L is a length of casting mold (m) dB O is experimentally obtained minimum thickness :. .
. .
1 32~92'~ 72199-14 (mm) of solidifying sh~ll which does not cause breakout by bulging immediately below the casting mold ~m is a distance (m) from the entrance of the casting mold to the temperature measuring points and S n is number of abnormality detecting temperature measuring points for detection of break~Ut of cast metal.
The number of the abnormality detecting temperature measuring points is preferably a maximum number which can satisfy the relationship of formula (6) set forth above. By utilizing the greater number of temperature measuring points for making judgement that breakout possibly occurs, occurrence of mis-detection can be reduced.
As will be appreciated herefrom, for detecting possible breakout the following parameters are to be set:
9cr which is upper limit value of the temperature variation speed t which is a minimum period of time in which is 0 maintained 9. > 9 l = cr B, a, and n.
In practice, t is set for avoiding mis-detection lead by temporary fluctuation of the molten metal temperature which causes ~i 2 9 . Therefore, by providing t influence of molten metal temperature fluctuation can be successfully avoided. B and a can be obtained from temperature data upon occurrence of break-out. Normally, B is set in a range of 20 to 45 and a is set in a range of 0.5 to lØ On the other hand, n can be derived from the aforementioned formula (6) and equation (7). Therefore, it is practically required to two parameters, i.e. ~ and t , to be set. These two parameters may be set based on temperature variation pattern in experienced break out.
EXAMPLE
In order to confirm performance of detection of break-out according to the invention, experimental casting was performed , 1 3 2 ~ q 2 ~ 72199-14 according to the casting and temperature measuring conditions set in the following table I.
T~BLE I
rype of Caster (Bending Type~ (Vertical Mold (Vertical Mold ~ending Bending Type) Type) Kind of Steel Stainless Steel teel Plate ow Carbon illed Steel High Carbon igh Tension Carbon Steel Steel Killed Steel Size of ~lock rhickness rhickness hickness 200 - 260 mm 200 - 260mm 230 - 260 mm Width Width idth 850 - 1250 mm900 - 1900 mm800 - 1900 mm Casting Speed Vc (m/min)0.6 - 1.0 0.9 - 1.4 0.9 - 2.0 Temperature variation Speed _ 0.5 0.6 0.7 Detection Range (m/min) 0.5 or more0.5 or more 0.8 or more ~inimum Period _ trC (sec) 6.0 4'.0 4.0 remp. Measure-ent Depth22 - 10 mm 28 - 10 mm 33 - 10 mm w 196 mm 150 mm 152 mm ~m 250 mm 330 mm 272 mm L 700 mm 800 mm 900 mm _ 20 _ 45u 20 _ 45v 20 - 45 0.5 - 0.9 0.5 - 0.9 0.5 - 0.9 n 2 3 3 During experimental casting, accuracy of detection of breah~ut was checked. In order to compare with the result in the inventive method, comparative experiments for detecting breakout wa~
performed in a method according to that disclosed in Tokkai Showa 61-226154, set forth above. The results are shown in the following table II.
1 3~925 72199-14 TA~LE II
caster_TYe- = 1 2 3 Invention A0.003470.001310.00202 B 40% 100~ 100 C 10% 0% 0%
Comparative A0.05560.00409 0.00673 B 25~ 32~ 30%
C 18~ 18~ 16%
In table II above, A indicates occurrence of alarm per one heat, s is a rate of occurrence of breakoUt mark on the surface of cast block in the casting mold upon occurrence of the alarm ((brea~ut mark occurrence 2b)/A(total occurence number of alarm, a) x 100), C is occurrence of overlooking of breakOUt ((overlooking occurrence 2c)/(B + overlooking occurrence) x 100).
Figs. 2(A), 2(B) and 2(C) are chart showing variation of molten metal surface level ML, casting speed Vc, casting mold wall temperature and relative temperature variation speed during experiment, in which possibility of breakOUt is detected. As will be appreciated herefrom, temperature variation speed is maintained essentially unchanged even when the casting speed Vc and the molten metal surface level ML fluctuate at significant level.
In the process shown in Figs. 2(A), 2(B) and 2(C), casting speed was decelerated at the timing shown by arrow in response to alarm for possibility of breakOUt In observation of the corresponding portion of the cast block, marking showing 30 growth of sticking type break out appeared. From this, it is clearly proven that method of detection of the breakOUt according to the present invention works very effectively.
Pig. 3 shows the preferred construction o~ the temperature measuring device which is useful for implementing the preferred process of detection of possible breakOUt. In the shown construction, the casting mold copper wall 10 is formed with a plurality of groove 11 defining a cooling water path. A cooling water box 12 has a planer section mating with the back surface of the copper wall 10 of the casting mold to stationally support the 1 32~q25 - 16 ~
copper wall. The cooling water box 12 and the copper wall 10 are rigidly connected to each other by means of a fixing bolt 13. The fixing bolt 13 is formed with an axially extending through opening 13a.
The temperature measuring device 20 has an inner cylindrical housing 24 extending through the opening 13a. The inner cylindrical housing 24 is slidably disposed within the opening 13a and has an end section carrying water seals 24a and 24b. The rear end of the inner cylindrical housing 24 contacts with one end of coil spring 25 which pushes the cylindrical housing 24 toward the copper wall 10 to establish liguid tight seal by depressing the water seal 24a. To the other end of the coil spring 25, an outer cylindrical housing 26 contact at the inner end. The outer cylindrical housing 26 has a threaded section 26a which engages with a female thread formed on the inner periphery of the opening 13a. Therefore, the outer cylindrical housing 26 is thus threaded to the opening 13a.
The inner end of the inner cylindrical housing 24 carries a holder 27 via the water seal 24b. The holder 27 is axially pushes by a coil spring 28. Through axially extending openings of the cylindrical housings 24 and 26, a thermometric couple introducing tube 29 extends. The thermometric couple introducing tube 29 contacts with the coil spring 28 at the inner end thereof. The thermometric couple introducing tube 29 is formed with a threaded portion 29a. The threaded portion 29a engages with the female thread formed on the inner periphery of the outer cylindrical housing 26. Therefore, the thermometric couple introducing tube 29 is fixed to the outer cylindrical housing 26.
Through the center opening of the thermometric couple introducing tube 29, a termometric couple 30 extends to contact the inner end to the copper wall 10. The front end portion of the thermometric couple 30 is gripped by the holder 27. Since the holder 27 is pushed toward the copper wall 10, by means of the coil spring 28. The inner end of the thermometric couple 30 resiliently pushed onto the copper wall 10 to assure contact therebetween. The pushing force of the coil spring 28 is regulated by a stopper member 31 which is fixed onto the outer end portion of the outer cylindrical housing 26 and restrict axial movement of the thermometric couple introducing tube 29 toward the copper wall.
Sealing packing 14 is disposed between the outer end portion of the fixing bolt 13 and the inner periphery of the cooling water box 12 for establishing tight seal and fixing the fixing bolt.
With the construction set forth above, the cooling water leaked from the grooye 11 of the copper wall 10 through paths 32 and 33 can be blocked to flow into the inside of the fixing bolt 13 by the water seal 24a. On the other hand, the leaked water flowing through paths 32, 33, 34 and 35 can be blocked by the water seal 24b. Therefore, the thermometric couple becomes free from influence of the leaked water. Water tight seal established by the water seals 24a and 24b can be maintained even upon occurrence of thermal distortion of the copper wall 10 because the inner cylindrical housing 24 is resiliently pushed by means of the coil spring 25 to constantly establish water tight seal by the water seals 24a and 24b. On the other hand, as the inner end of the thermometric couple 30 held by the holder 27 is constantly pushed toward the copper wall 10 by the coil spring 28, contact between the thermometric couple 30 and the copper wall 10 can be constantly maintained for assure measurement of the temperature of the copper wall.
In the preferred construction, the water seals 24a and 24b may be formed into O-ring and made of fluorine, fluon, metal, such as copper, alminium, or so forth.
In the shown construction, since the thermometric couple 30 extends from the inner end of the holder 27 for a length of 1 mm to 3 mm. There may not occur buckling even when substantially small diameter thermometric couple, such as that has 1 mm to 2 mm diameter, is used. As is well known, smaller diameter of thermometric couple has higher sensitivity of the temperature.
Therefore, the shown construction allows the temperature measuring device 20 satisfactorily sensible of the copper wall temperature.
1 32~q2~
In addition, by the shown construction, since the inner cylindrical housing 24 carrying the water seals 24a and 24b will not rotate when fastening the outer cylindrical housing 26 because it is separated from the outer cylindrical housing via the coil spring 25. Furthermore, presence of the coil spring 28 absorbs the rotational torque to be exerted on the termometric couple introducing tube 29 when the later is fixed to the outer cylindrical housing 26. 8y this construction, the water seals 24a and 24b will never be damaged upon assembling.
EXAMPLE
Experimentally, the temperature measuring device is assembled in the following specification:
Eixing bolt 13 outer diameter: 18 mm length : 470 mm nominal diameter: W18 opening (inner diameter): 10 mm material : SUS 630 Inner cYlindrical housing 24 external diameter: 9.0 mm inner diameter: 5.5 mm length: 400 mm material: SUS 304 Coil spring 25 external diameter: 9.0 mm inner diameter: 5.5 mm spring constant: 4 kgf/mm material: SUS 304 section: square Outer cylindrical housing 26 external diameter: 9.0mm inner diameter: 5.5 mm length : 27 mm material: SUS 304 Holder 27 material: copper - 19 1 3 2 ~ q 2 5 Thermometric couple 30 external diameter 1.0 mm being silver brased and extended therefrom for the length of 3 mm Coil spring 28 external diameter: 5.0 mm inner diameter: 3.5 mm spring coefficient: 1 kgf/mm material: SUS 304 Thermometric couple introducing tube 29 external diameter: 5.0 mm inner diameter: 3.5 mm length: 440 mm material: SuS 304 ~tilizing the above-specified temperature measuring device, experimental measurement of the copper wall temperature was performed. In the experiment, fluorine O-rings are used as the water seals 24a and 24b, which O-rings are provided a resistantive temperatures of 260 C and 200 C respectively. The coil springs 25 and 28 are pre-loaded at 11 kg and 5 kg, respectively. The pressure of the cooling water passing through the cooling water path 11 is set at 8 kgf/cm2.
- During experimental measurement, leak of the cooling water in the thermometric couple introducing tube 29 was observed.
Despite cooling water leakage, the measured temperature was stably maintained within a range of 150 C to 350 C.
After experimental casting for 500 heats, the temperature measuring device 20 was removed from the fixing bolt 13. In observation of the temperature measuring device 20, the carbonized portion was found on the water seal 24a at the portion mating with the copper wall 10. However, no leakage of the cooling water through the water seal was observed.
The shown type of temperature measuring device is advantageously introduced in imprementation of the preferred method of detection of possible break out since it does not require disassembling of the casting mold upon installation.
1 ~2~925 secause disassembling of copper wall upon installation of the temperature measuring device results in releasing of the copper wall from stress which is caused due to distortion, difficulty of re-assembling of the casting mold may occur otherwise.
Furthermore, since the shown embodiment oÇ the temperature measuring device can establish complete water seal, stable measurement oE the copper wall temperature can be performed. In addition, since the thin thermometric couple can be employed in the temperature measuring device, satisfactorily high sensibility is facilitated. Furthermore, since the shown temperature measuring device is substantially compact and thus allowed to be housed within the fixing bolt, flexibility of installation can be conveniently established.
While the present invention has been disclosed in terms of the prefereed embodiment in order to facilitate better understanding of the invention, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention. Therefore, the invention should be understood to include all possible embodiments and modifications to the shown embodiments which can be embodied without departing from the principle of the invention set out in the appended claims.
Claims (20)
1. A method foe detecting a breakout in continuous casting comprising the steps of:
arranging a plurality of temperature measuring devices at temperature measuring points oriented in circumferential alignment with a given interval on a wall of a continuous casting mold for measuring temperature of said wall at respective temperature measuring points;
deriving variation speed of temperature at respective temperature measuring points;
deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring points;
deriving a difference between the temperature variation speed at each temperature measuring point and the average temperature variation speed;
comparing the derived difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point; and observing sequential distribution and propagation of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagation of the abnormal temperature measuring points is detected.
arranging a plurality of temperature measuring devices at temperature measuring points oriented in circumferential alignment with a given interval on a wall of a continuous casting mold for measuring temperature of said wall at respective temperature measuring points;
deriving variation speed of temperature at respective temperature measuring points;
deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring points;
deriving a difference between the temperature variation speed at each temperature measuring point and the average temperature variation speed;
comparing the derived difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point; and observing sequential distribution and propagation of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagation of the abnormal temperature measuring points is detected.
2. A method for detecting possibility of breakout as set forth in claim 1, wherein the predetermined sequential distribution and propagation pattern of the abnormality includes transferring of abnormality to adjacent temperature measuring points at both sides.
3. A method for detecting possibility of breakout as set forth in claim 1, wherein the temperature measuring points are arranged in alignment on a plane perpendicular to the longitudinal axis of the continuous casting mold.
4. A method for detecting possibility of breakout as set forth in claim 3, wherein the temperature measuring points are oriented downstream of meniscus.
5. A process of continuous casting comprising the steps of:
casting molten metal to one end of a continuous casting mold at a given controlled casting speed;
drawing solidifying cast block from the other end of the continuous casting mold at a given drawing speed;
measuring temperature of a wall of the continuous casting mold at a plurality of temperature measuring points oriented in circumferential alignment with a given interval;
deriving variation speed of temperature at respective temperature measuring points;
deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring points;
deriving a difference between the temperature variation speed at each temperature measuring point and the average temperature variation speed;
comparing the derived difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point;
observing sequential distribution and propagation of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagation of the abnormal temperature measuring points is detected; and controlling at least one of casting speed and drawing speed for preventing the cast block from causing breakout.
casting molten metal to one end of a continuous casting mold at a given controlled casting speed;
drawing solidifying cast block from the other end of the continuous casting mold at a given drawing speed;
measuring temperature of a wall of the continuous casting mold at a plurality of temperature measuring points oriented in circumferential alignment with a given interval;
deriving variation speed of temperature at respective temperature measuring points;
deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring points;
deriving a difference between the temperature variation speed at each temperature measuring point and the average temperature variation speed;
comparing the derived difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point;
observing sequential distribution and propagation of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagation of the abnormal temperature measuring points is detected; and controlling at least one of casting speed and drawing speed for preventing the cast block from causing breakout.
6. A process of continuous casting as set forth in claim 5, wherein the predetermined sequential distribution and propagation pattern of the abnormality include transferring of abnormality to adjacent temperature measuring points at both sides.
7. A process of continuous casting as set forth in claim 5, wherein the temperature measuring points are arranged in alignment on a plane perpendicular to the longitudinal axis of the continuous casting mold.
8. A process of continuous casting as set forth in claim 7, wherein the temperature measuring points are oriented downstream of meniscus.
9. A system for detecting a breakout in continuous casting comprising:
a plurality of temperature measuring devices arranged in circumferential alignment with a given interval on a wall of a continuous casting mold for measuring temperature of the wall at respective temperature measuring points and producing casting wall temperature indicative signals representative of the measured temperature at respective temperature measuring points;
first means for deriving variation speed of temperature at respective temperature measuring points;
means for deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring points;
second means for deriving a difference between the temperature variation speed at each temperature measuring point and the average temperature variation speed; and third means for comparing the derived difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point, and observing sequential distribution and propagation of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagation of the abnormal temperature measuring points is detected.
a plurality of temperature measuring devices arranged in circumferential alignment with a given interval on a wall of a continuous casting mold for measuring temperature of the wall at respective temperature measuring points and producing casting wall temperature indicative signals representative of the measured temperature at respective temperature measuring points;
first means for deriving variation speed of temperature at respective temperature measuring points;
means for deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring points;
second means for deriving a difference between the temperature variation speed at each temperature measuring point and the average temperature variation speed; and third means for comparing the derived difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point, and observing sequential distribution and propagation of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagation of the abnormal temperature measuring points is detected.
10. A system for detecting possibility of breakout as set forth in claim 9, wherein the third means is set the predetermined sequential distribution and propagation pattern of the abnormality includes transferring of abnormality to adjacent temperature measuring points at both sides.
11. A system for detecting possibility of breakout as set forth in claim 9, wherein the temperature measuring points are arranged in alignment on a plane perpendicular to the longitudinal axis of the continuous casting mold.
12. A system for detecting possibility of breakout as set forth in claim 11, wherein the temperature measuring points are oriented downstream of meniscus.
13. An apparatus of continuous casting for casting molten metal to one end of a continuous casting mold at a given controlled casting speed, and drawing solidifying cast block from the other end of the continuous casting mold at a given drawing speed, comprising:
a plurality of temperature measuring device, arranged in circumferential alignment on the wall of the casting mold, for measuring temperature of the wall of the continuous casting mold at a plurality of temperature measuring points oriented in circumferential alignment with a given interval, each of the temperature measuring device producing a temperature indicative signal indicative of the measured temperature at associated temperature measuring point;
first means for receiving the temperature indicative signals from the temperature measuring devices and deriving variation speed of temperature at respective temperature measuring points to produce a temperature variation speed data;
second means for receiving the temperature variation data from the first means and for deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring points, the second means producing an average temperature variation speed data;
third means for comparing the temperature variation data of respective temperature measuring points with the average temperature variation speed for deriving a difference between the temperature variation speed data at each temperature measuring point and the average temperature variation speed;
fourth means for comparing the derived difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point;
fifth means for observing sequential distribution and propagation of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagation of the abnormal temperature measuring points is detected; and sixth means for controlling at least one of casting speed and drawing speed for preventing the cast block from causing break out.
a plurality of temperature measuring device, arranged in circumferential alignment on the wall of the casting mold, for measuring temperature of the wall of the continuous casting mold at a plurality of temperature measuring points oriented in circumferential alignment with a given interval, each of the temperature measuring device producing a temperature indicative signal indicative of the measured temperature at associated temperature measuring point;
first means for receiving the temperature indicative signals from the temperature measuring devices and deriving variation speed of temperature at respective temperature measuring points to produce a temperature variation speed data;
second means for receiving the temperature variation data from the first means and for deriving an average temperature variation speed based on temperature variation speed of respective temperature measuring points, the second means producing an average temperature variation speed data;
third means for comparing the temperature variation data of respective temperature measuring points with the average temperature variation speed for deriving a difference between the temperature variation speed data at each temperature measuring point and the average temperature variation speed;
fourth means for comparing the derived difference with a predetermined threshold for detecting abnormal temperature variation of each temperature measuring point;
fifth means for observing sequential distribution and propagation of abnormal temperature measuring points for detecting possibility of breakout when predetermined pattern of sequential distribution and propagation of the abnormal temperature measuring points is detected; and sixth means for controlling at least one of casting speed and drawing speed for preventing the cast block from causing break out.
14. An apparatus of continuous casting as set forth in claim 13, wherein the predetermined sequential distribution and propagation pattern of the abnormality includes transferring of abnormality to adjacent temperature measuring points at both sides.
15. An apparatus of continuous casting as set forth in claim 13, wherein the temperature measuring points are arranged in alignment on a plane perpendicular to the longitudinal axis of the continuous casting mold.
16. An apparatus of continuous molding as set forth in claim 15, wherein the temperature measuring points are oriented downstream of meniscus.
17. A method for detecting possibility of breakout as set forth in claim 2, wherein the temperature measuring points are arranged in alignment on a plane perpendicular to the longitudinal axis of the continuous casting mold.
18. A method for detecting possibility of breakout as set forth in claim 17, wherein the temperature measuring points are oriented downstream of meniscus.
19. A method as set forth in any one of claims 1 to 4, 17 and 18, wherein the temperature measuring device comprises:
a hollow cylindrical mounting bolt which is threaded to the wall of the continuous casting mold, the mounting bolt defining an axially extending opening;
a hollow housing disposed within the axially extending opening, the hollow housing including first and second mutually separated cylindrical components, which first cylindrical component is arranged close to the wall of the casting mold and the second cylindrical component is arranged remote from the wall;
a resilient member disposed between the first and second components of the cylindrical housing and designed to push the first component toward the wall;
a seal member carried by the end of the first cylindrical component and mating with the wall surface for establishing liquid tight seal; and a temperature sensing element disposed within the housing and contacting with the wall surface for monitoring the temperature of the wall of the casting mold.
a hollow cylindrical mounting bolt which is threaded to the wall of the continuous casting mold, the mounting bolt defining an axially extending opening;
a hollow housing disposed within the axially extending opening, the hollow housing including first and second mutually separated cylindrical components, which first cylindrical component is arranged close to the wall of the casting mold and the second cylindrical component is arranged remote from the wall;
a resilient member disposed between the first and second components of the cylindrical housing and designed to push the first component toward the wall;
a seal member carried by the end of the first cylindrical component and mating with the wall surface for establishing liquid tight seal; and a temperature sensing element disposed within the housing and contacting with the wall surface for monitoring the temperature of the wall of the casting mold.
20. A method as set forth in claim 19, wherein the temperature measuring device further comprises a pushing means for resiliently pushing the temperature sensing means toward the wall surface.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62-299885 | 1987-11-30 | ||
| JP62299885A JPH0771726B2 (en) | 1987-11-30 | 1987-11-30 | Continuous casting method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1328925C true CA1328925C (en) | 1994-04-26 |
Family
ID=17878123
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000584465A Expired - Fee Related CA1328925C (en) | 1987-11-30 | 1988-11-29 | Process of continuous casting with detection of possibility of break out |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH0771726B2 (en) |
| CA (1) | CA1328925C (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03138059A (en) * | 1989-10-24 | 1991-06-12 | Nippon Steel Corp | Method for predicting constrained breakout in continuous casting |
| JPH0724927B2 (en) * | 1990-11-13 | 1995-03-22 | 新日本製鐵株式会社 | Constrained breakout prediction method for continuous casting |
| ATE530884T1 (en) | 2006-10-02 | 2011-11-15 | Alstom Technology Ltd | METHOD FOR PASSIVELY DETERMINING THE OPERATING TEMPERATURE IN A HIGH THERMALLY LOADED DEVICE AND DEVICE FOR IMPLEMENTING THE METHOD |
| JP2013052431A (en) * | 2011-09-06 | 2013-03-21 | Jfe Steel Corp | Method for measuring temperature in mold for continuous casting |
| JP5906814B2 (en) * | 2012-03-01 | 2016-04-20 | Ｊｆｅスチール株式会社 | Method and apparatus for predicting constraining breakout in continuous casting equipment |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57115962A (en) * | 1981-01-08 | 1982-07-19 | Nippon Steel Corp | Detection for abnormality of cast steel in continuous casting mold |
| JPH0229419B2 (en) * | 1985-05-02 | 1990-06-29 | Nippon Steel Corp | RENZOKUCHUZOIGATANIOKERUCHUZOKONOHADANKENSHUTSUHOHO |
| JPH0790343B2 (en) * | 1986-10-31 | 1995-10-04 | 住友金属工業株式会社 | Breakout prediction method in continuous casting |
-
1987
- 1987-11-30 JP JP62299885A patent/JPH0771726B2/en not_active Expired - Lifetime
-
1988
- 1988-11-29 CA CA000584465A patent/CA1328925C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01143748A (en) | 1989-06-06 |
| JPH0771726B2 (en) | 1995-08-02 |
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