JPS6250060A - Method for attaching thermocouple to continuous casting mold - Google Patents

Abstract

PURPOSE:To stabilize temp. measurement and to eliminate the influence of noise by preliminarily subjecting the crossing point at the top ends of the different metals of a twisted thermocouple to insert casting then inserting the thermocouple into the hole bored on the opposite side of a casting mold wall, bringing the same into press contact with the inside of the mold wall and securely fixing the crossing point by stud welding thereto. CONSTITUTION:The crossing point at the top ends of the different metals 5, 6 for the thermocouple which are insulated and twisted is embedded with a brazing filler metal or solder, etc. by casting and is inserted into the hole bored to the mold surface on the opposite side of the casting mold. The point is then brought into thorough press contact with the hole bottom on the inside of the mold wall. The crossing point is thereafter securely adhered thereto by stud welding. The temp. measurement by the thermocouple is stabilized by such secure adhesion. The influence of noise is eliminated by the twisted and braided wires and the measured value is made exact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for attaching a temperature measuring thermocouple for scene level detection or breakout prediction to a mold for a continuous casting machine.

[Conventional technology]

Conventionally, this type of thermocouple has been manufactured using the so-called pressure contact method (Japanese Unexamined Patent Publication No. 47-10545, Japanese Unexamined Patent Publication No. 10545/1989), in which the tip of a tungsten rod inserted into a hole in the side wall of the mold is pressed into contact with the copper base material of the mold. 48-89130, etc.), or a method in which the copper of the mold is used as one metal, and another metal that produces thermoelectric power is inserted and stud welded to form a thermocouple (see JP-A-56-141955). ) is embedded in the continuous casting mold.

(Problems to be Solved by the Invention) However, with thermocouples attached using the pressure welding method, the contact between the thermocouple and the mold often deteriorates due to mold vibration, making it difficult to maintain reliability. In addition, although thermocouples made by stud welding are highly reliable during normal use, if the thermocouple is repeatedly removed and reattached for mold replacement, etc., the inside of the thermocouple insertion hole may become damaged. The copper plate is scraped.As a result, the temperature measurement level fluctuates and may cause false detection.

In addition, detection of leakage on the surface of the molten metal, breakout prediction, etc. are performed even when the molten metal in the mold is electromagnetically stirred;

- Since induced noise is applied to the wire of the thermocouple, accurate temperature measurement becomes impossible due to the influence of the induced noise. In order to eliminate false detections caused by this induced noise, it is necessary to attach the wires of different metals having thermoelectric power to the mold in a twisted state.

However, when installing dissimilar metal wires into narrow holes in a mold, it is difficult to insert the wires into the holes and weld the ends.

One possible method to facilitate this work is to bifurcate the tip of one of the strands by machining such as sawing, sandwich the other strand between them, and perform stand welding. However, when using this method, it is required to accurately divide the tip into two parts. Otherwise, the amount of heat generated is I
``Since it is proportional to H, the heat generation of the larger ■, that is, the thicker side, will be larger, so an appropriate weld will not be formed.
Furthermore, the obtained thermocouple also has poor strength.

In view of these problems in the prior art, the present invention
The purpose of this invention is to reliably attach a thermocouple in a continuous casting mold with sufficient bonding strength and with good reproducibility.

[Means for solving problems]

In order to achieve the object, the present invention embeds a thermocouple in the wall of the continuous casting mold to detect the temperature of the molten metal or slab in the continuous casting mold. After forming a thermocouple by forming a hole in advance at the intersection of the tips of dissimilar metals having thermoelectric power, the thermocouple is inserted into the hole provided on the non-casting side of the mold, and the tips are pressed together at a predetermined pressure. The stand is welded.

[Effect]

In the present invention, for example, a steel material is used as one end of a thermocouple, and the intersection point of this and a dissimilar metal such as a constanton having thermoelectric power is cast-in with brazing material or solder, and then the end of a thermocouple insertion hole provided in a mold is formed. Weld the stand against the inner wall. That is, since the thermocouple is cast-in in advance and then stand-welded, the thermocouple is firmly attached to the mold by re-melting and re-solidifying the cast-in material. This joining was done in Japanese Unexamined Patent Publication No. 5
Unlike the method disclosed in Japanese Patent No. 6-141955, there is no possibility that a completely unrelated bonding material is interposed between dissimilar metals having thermoelectric power to change the thermoelectric power.

〔Example〕

Next, features of the present invention will be explained in more detail with reference to embodiments shown in the drawings.

FIG. 1 is a step-by-step explanation of the preparation process for attaching a thermocouple in this embodiment.

One side 1 of a combination of different metals having thermoelectric power, such as copper and constantan, is insulated and wound around the other strand 2 as shown in FIG. 1(a). As shown in FIG. 1(b), the wound tip is cast with silver solder or solder 3, which is a W4-based alloy that has good weldability to copper, which is the mold material. Next, the cast-wrapped tip is shown in Figure 1 (
By shaping as shown in c), the workability of stand welding is improved. It is desirable that this tip shape is finished with a tip angle of about 120" or less to correspond to the tip shape of the thermocouple insertion hole provided in the mold. In this way, when welding the stud, the brazing part will be placed at the tip of the part. is melted, and this molten brazing material fills the gap between the thermocouple and the mold to join them.According to experiments and studies by the present inventors, joining is easiest when the brazing temperature is in the range of 80 to 90@, and It was found that sufficient bonding strength could be obtained.

When a thermocouple is constructed by such a manufacturing method, the hot junction of dissimilar metals is the location indicated by the reference numeral A in FIG. Therefore, if the length of B shown in Fig. 1 (c) is increased, there will be a delay in the temperature received by the thermocouple embedded in the mold, and the temperature will be indicated slightly slower than the temperature of the mold copper plate. .For this reason, when a quick grasp of the absolute value is required,
It is necessary to keep portion B short as long as bonding strength is not impaired. On the other hand, when quick grasping of absolute values is not an issue and it is used for trend management based on relative values over time, it is preferable to make the length of part B slightly longer so as to obtain uniformity. In this way, the bonding strength of the hot junction portion is also improved.

In addition, the preparation process for twisting the wires together and attaching the thermocouple is shown in FIG. 2 step by step. As shown in FIG. Either wrap the copper wire 6 around it and then cover the whole thing with a Teflon tube 7, or wrap the coated copper wire 8 around the constant wire 5 and cover the whole thing with a Teflon tube 7 as in the previous example, as shown in Figure 2(b). Cover. This covering with Teflon tube 7 is for penetrating the mold cooling water box and attaching the tip of the thermocouple. After inserting the thermocouple thus made into the thermocouple insertion hole provided in the mold,
Weld studs.

The thermocouple for mold temperature measurement installed using this method is
Even when 12 pieces were buried in the mold surface and used for continuous casting of 20 or more wheels, not a single piece came off, and it was in a condition that it could be used continuously.

On the other hand, with a method that does not involve brazing, in which the tip of the constant wire is split and the copper wire is sandwiched, installation itself is difficult, and even if it is installed, it takes only 2 to 3 charges, and 30 to 40% of the charge is due to mold vibration. It came off.

Also, predicting a breakout becomes impossible even if one thermocouple comes off. However, in the thermocouple obtained in this example, there is no loss of one as described above, so there is no deterioration in the predictive ability. FIG. 3 shows an example S of the effect of removing noise N caused by electromagnetic stirring in a thermocouple obtained by twisting the strands, in comparison with a thermocouple obtained without twisting.

The thermocouples of this example and comparative example were stud-welded under the welding conditions shown in Table 1, and the comparative example had the highest strength, while the inventive example had the average strength. .

Table 1 [Effects of the Invention] As described above, in the present invention, contacts made of dissimilar metals having thermoelectric power are cast in advance, and then stand welded by contacting the inner wall at the tip of the buried hole, resulting in high joint strength. Not only is this possible, but the thermocouple is assembled and then attached to the mold.
The wires can be easily twisted, and as a result, temperature can be measured without being affected by noise induced by electromagnetic stirring.

Therefore, great effects are brought about, such as increasing the stability of operations such as measuring the level of molten steel in the mold and predicting breakouts using thermocouples, and significantly improving the operability and productivity of continuous casting.

[Brief explanation of drawings]

Figures 1 (a), (b) and (c) explain the method of creating a thermocouple tip according to an embodiment of the present invention in order, and Figures 2 (a) and (b) are This is to explain the insulation structure in the embodiment of the invention, and FIG. 3 is to explain the effect that the twisting of the thermocouple inserted using this method has on the inductive noise removal effect.

Claims (1)

[Claims] 1. When embedding a thermocouple in the wall of the mold to detect the temperature of the molten metal or slab in the continuous casting mold, a hole is provided on the side of the mold wall opposite to casting, and a dissimilar metal having thermoelectric power is installed. After forming a cast-in thermocouple in advance at the intersection of the tips, the thermocouple is inserted into a hole provided on the non-casting surface side of the mold, and the tips are pressed together at a predetermined pressure and stud welded. How to attach a thermocouple to a continuous casting mold.