JPH07294339A - Thermocouple for measuring molten metal temperature - Google Patents

Abstract

PURPOSE:To provide a thermocouple for measuring molten metal temperature with faster response. CONSTITUTION:A thermocouple C is manufactured in order to measure the temperature of molten metal injected into a mold 15. The thermocouple C is provided with a heat resistant electrical resistor 2 whose one end face 10 is in contact with a molten metal M and a pair of wires 3 and 4 whose one end parts are exposed at the one end face 10 by penetrating them in the insulator 2 respectively. The molten metal M is used for a high-temperature joint part between the one end parts in the wires 3 and 4. Thus, when the molten metal M reaches the one end parts of the wires 3 and 4 of the thermocouple C, the temperature of the molten metal M can be measured quickly and accurately by the thermocouple C.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermocouple for measuring a molten metal temperature,
In particular, it relates to improvements in thermocouples for measuring the temperature of molten metal injected into a mold.

[0002]

2. Description of the Related Art Conventionally, as this type of thermocouple, a heat-resistant protective cylinder whose outer surface contacts the molten metal, and a pair of wires which are housed in the protective cylinder with a high temperature joint located near the inner surface of the end wall. When,
It is known that the wires are provided with an electric insulating material filled in the protective cylinder in order to fix them in the protective cylinder (see Japanese Patent Laid-Open No. 5-209794).

[0003]

However, in the conventional thermocouple, since the high temperature joint portion is covered by the protective case, in measuring the temperature, first, the end wall of the protective case is heated by the molten metal. Then, since the temperature of the end wall is to be measured, there is a problem that the response speed is slow and therefore the temperature of the molten metal reaching the thermocouple cannot be measured quickly and accurately. In this case, it is impossible to detect the temperature change in the solidification process of the molten metal when the measured maximum temperature is much lower than the solidus temperature of the molten metal.

Further, when the response speed is slow as described above, it becomes impossible to accurately detect the order of arrival of the molten metal in the cavity.

In view of the above, the present invention has the above-mentioned thermocouple, which has a fast response speed, and therefore can measure the temperature of the molten metal quickly and accurately, and can accurately detect the arrival sequence of the molten metal in the cavity. The purpose is to provide.

[0006]

SUMMARY OF THE INVENTION The present invention is a thermocouple for measuring the temperature of molten metal injected into a mold, wherein a heat-resistant electric insulator having one end surface in contact with the molten metal, and a heat-resistant electric insulator thereof. A pair of strands of which one end is exposed at the one end face by penetrating each other independently in a conductive electrical insulator,
It is characterized in that the molten metal is used as a high temperature joint between the one ends of the two wires.

[0007]

In the above structure, when the molten metal reaches one end of each of the wires, the molten metal forms a high temperature joint, so that the temperature of the molten metal can be measured quickly and accurately.

Then, with the passage of time, the thermocouple measures the maximum temperature of the molten metal present in the measurement range. However, since the response speed is fast, the measured maximum temperature does not fall far below the solidus temperature of the molten metal. Therefore, it is possible to accurately detect the temperature change in the solidification process of the molten metal.

Further, since the response speed is high as described above, it is possible to accurately detect the arrival order of the molten metal in the cavity, with the arrival of the molten metal at the start of temperature measurement of the molten metal.

[0010]

EXAMPLE A thermocouple C according to the example shown in FIGS. 1 and 2 is used to measure the temperature of a molten metal having an Al alloy composition injected into a mold (mold). A rod-shaped heat-resistant electric insulator 2 connected to 1 and an electric insulator 2
It has a pair of strands 3 and 4 penetrating each other independently.

The holder cylinder 1 is made of stainless steel, has a cylindrical portion 5 and a flange portion 6 formed on one side of the outer peripheral surface thereof, and has a female screw hole formed in the cylindrical portion 5 at one end surface thereof. 7
a and a circular recess 7b having an opening on the other end surface are formed coaxially.

The electric insulator 2 is a ceramic sintered body and has a composition such as Si ₃ N ₄ : BN = 1: 1.
In this case, Si ₃ N ₄ contributes to improving the strength of the electrical insulator 2, while BN contributes to improving the separability of the electrical insulator 2 from the casting and the machinability. After sintering, electrical insulator 2
Two thin through holes 8 and 9 along the longitudinal direction are formed independently of each other, and both strands 3 and 4 are inserted into these through holes 8 and 9.

One strand 3 is made of alumel and the other strand 4 is made of chromel. One end of both wires 3, 4 is
It is exposed at one end face 10 of the electric insulator 2 which comes into contact with the molten metal, and the one end face 10 and one end faces 11, 12 of the two strands 3, 4 are exposed.
Are located on the same plane, or the one end faces 11 and 12 of the two strands 3 and 4 slightly project from the one end face 10 of the electrical insulator 2. The material of each of the strands 3 and 4 is determined according to the measurement temperature, and is not limited to alumel-chromel, for example, F
It may be e-constantan.

A male screw 1 is provided on the outer peripheral surface of the other end of the electrical insulator 2.
3 is formed, and its male screw 13 is screwed into the female screw hole 7a of the holder cylinder 1. The other ends of the two wires 3, 4 extend outward from the recess 7b of the holder cylinder 1, and the recess 7b is filled with an alumina-based adhesive agent 14 and cured, whereby the holder cylinder 1 and the electric insulator 2 are formed. Are joined together, and both strands 3, 4
The holder cylinder 1 and the electrical insulator 2 are joined together.

In FIG. 3, the wall member 16 of the mold 15 has a substantially elliptical recess 1 for opening the outer surface of the wall member 16.
7 and a stepped hole 19 for mounting a thermocouple whose both ends are opened to the bottom of the recess 17 and the inner surface of the cavity 18 for casting molding, respectively.
And are formed. The stepped hole 19 has a large-diameter portion 20, a medium-diameter portion 21, and a small-diameter portion 22 which are sequentially arranged from the concave portion 17 side.
Consists of. The small-diameter portion 22 is fitted with the electrical insulator 2, the medium-diameter portion 21 is fitted with the tubular portion 5, and the large-diameter portion 20 is fitted with the flange portion 6, whereby the thermocouple C is fitted to the mold 15.
Held in. In this holding state, the one end surface 10 of the electrical insulator 2 and the inner surface of the cavity 18 are located on the same plane, so that the molten metal is used as a high temperature joint between the one ends of the two strands 3, 4.

The terminal member 23 has an annular mounting frame 24 made of stainless steel, and the mounting frame 24 is loosely fitted in the recess 17 and fixed to the mold 15 via a plurality of setscrews 25.
An electric insulating plate 26 made of ceramic is fitted inside the mounting frame 24, and the electric insulating plate 2 is used to prevent the ceramic electric insulating plate 26 from coming out of the die 15.
6 This is achieved by engaging the step portion a on the outer peripheral surface with the step portion b on the inner peripheral surface of the mounting frame 24. The retaining of the electric insulating plate 26 from the inside of the mold 15 is performed by a stainless steel holding frame 27 welded to the mounting frame 24. The holding frame 27 is in contact with the outer surface of the flange portion 6 of the thermocouple C, whereby the thermocouple C is prevented from coming off.

The electrical insulating plate 26 has a through hole 28 in its central portion.
And a pair of screw-shaped terminals 29, 30 are projected on the electric insulating plate 26 so as to sandwich the through hole 28. One terminal 29 is made of alumel, and the alumel elemental wire 3 drawn out from the through hole 28 and an alumel conducting wire 31 on the measuring instrument body side are wound around the terminal 29, and both wires 3 and 31 are connected to the terminal 29.
It is pressed and fixed to the outer surface of the electric insulating plate 26 by the electric insulating nut member 32 screwed onto the electric insulating plate 26. The other terminal 30 is made of chromel, and the chromel wire 4 drawn from the through hole 28 to the terminal 30 and the chromel wire 3 on the measuring instrument body side.
3 is wound around, and both wires 4, 33 are fixed to the outer surface of the electric insulating plate 26 by an electric insulating nut member 34 screwed to the terminal 30.

In measuring the temperature of the molten metal, a solid-state casting material having an Al alloy composition shown in Table 1 was selected. The liquidus temperature of this casting material is 629 ° C., and the solidus temperature is 557 ° C.

[0019]

[Table 1] The solid casting material is heated to prepare a semi-molten casting material (molten metal) in which a liquid phase and a solid phase coexist, and the casting material is heated at the temperature of 575 ° C. to form the cavity 18 of the mold 15.
Was filled under pressure and the temperature of the casting material was measured.

FIG. 4 shows the measurement results. In the figure, the line (C) corresponds to the case where the thermocouple C according to the embodiment is used, and the line (C ₁ ) shows the thermocouple with a protective tube according to the conventional example. Applicable when used.

As shown in FIG. 3, a thermocouple C according to the embodiment.
In the above, when the semi-molten casting material M reaches one end of each of the strands 3 and 4, a high temperature joint is formed by the casting material M, so that the temperature of the casting material M can be measured quickly and accurately. To be done. The measurement start temperature Ts at this time is as shown in FIG.
Is 538 ° C.

Then, with the passage of time, the thermocouple C measures the maximum temperature of the casting material M existing in the measurement range, but since the response speed is fast, the measured maximum temperature Tm is
As shown in FIG. 4, it is 557 degreeC. Thus, the measured maximum temperature Tm is equal to or close to the solidus temperature of the casting material M and does not fall significantly below the solidus temperature, and therefore the temperature change in the solidification process of the casting material M. Can be accurately detected.

Since the response speed is high as described above, it is possible to accurately detect the order of arrival of the casting material M in the cavity 18 with the arrival of the casting material M at the start of temperature measurement of the casting material M. is there.

In the thermocouple according to the conventional example, due to the slow response speed, as shown in FIG. 4, line (C ₁ ), the measurement start time is Δt = approximately as compared with the thermocouple according to the embodiment. 0.5 seconds later, the time from the start of measurement to the measurement of the maximum temperature is about 0.04 seconds in the case of the thermocouple C according to the example, and the maximum measurement temperature Tm is 557 ° C. as described above. In the case of the conventional example, the time is about 1.2 seconds, and the maximum measured temperature Tm is 488 ° C. as the temperature of the casting material decreases. This measured maximum temperature Tm is about 100 ° C. below the solidus temperature, and it is impossible to detect the temperature change in the solidification process of the casting material M.

In FIG. 5, the mold (mold) in the pressure casting device 35 is composed of a horizontal fixed mold 36 and a movable mold 37 that moves vertically in opposition to the fixed mold 36. A sleeve 38 is erected on the upper surface of the. A chamber 39 is formed in the fixed mold 36, and the chamber 39
In the same manner as above, a short columnar casting material M in which a solid phase and a liquid phase coexist is erected.

A gate 40 opened on the inner surface of the bottom of the chamber 39 by the cooperation of the fixed and movable dies 36 and 37.
And the cavity 4 for casting molding which communicates with the gate 40.
1 and 1 are formed. A plunger 42 is slidably fitted to the sleeve 38, and the plunger 42 pressurizes the casting material M in the chamber 39 while filling the cavity 41 with a high-speed laminar flow through the gate 40.

A cavity 41 is provided in the fixed mold 36.
Four thermocouples U1, U2, U3, U4 according to the embodiment shown in FIGS. 1 and 2 are embedded at a predetermined interval from the inlet side to the inner side. One end surface 10 of the electrical insulator 2 of each thermocouple U1 to U4 is located on the same plane as the upper surface of the cavity 41, and therefore, one end surface 11 and 12 of each of the strands 3 and 4 of each thermocouple U1 to U4 is a cavity. It is exposed on the upper surface of 41. The other end side of both strands 3 and 4 of each thermocouple U1 to U4 is connected to the measuring instrument body.

On the other hand, in the movable mold 37, the gate 4
Five thermocouples G, L1, L2, L according to the embodiment shown in FIGS. 1 and 2 from the 0 side toward the inner side of the cavity 41.
3, L4 are embedded at a predetermined interval. Each thermocouple G,
One end surface 10 of the electrical insulator 2 of L1 to L4 is located on the same plane as the bottom surface of the gate G or the bottom surface of the cavity 41, and accordingly, each of the strands 3 of each thermocouple G, L1 to L4.
The one end surfaces 11 and 12 in 4 are exposed at the bottom surface of the gate G or the bottom surface of the cavity 41. Each thermocouple G, L1 to L
The other ends of both strands 3 and 4 of 4 are connected to the measuring device main body.

A semi-molten casting material M having the same Al alloy composition as described above, in which a solid phase and a liquid phase coexist, is prepared, and then the casting material M is erected in the chamber 39, and then the plunger is set. 42 moving speed 0.07 m / sec, mold temperature 250 ° C., casting material M gate passing speed 3 m /
Under the condition of sec, while pressing the casting material M at 575 ° C., it passes through the gate 40 to fill the cavity 41 with a high-speed laminar flow, and the temperature of the casting material M is measured by each thermocouple G, U1 to U4, and L1 to L4. went.

6 and 7 show thermocouples G, U1 to U4 and L1.
~ Shows the measurement result by L4, line (G), (U1) ~
(U4) and (L1) to (L4) are thermocouples G and U1 to U
4, L1 to L4 respectively.

Table 2 shows that each of the thermocouples G,
Arrival time and arrival order of the casting material M to U1 to U4 and L1 to L4, and thermocouples G, U1 to U4 and L1 to L
4 shows the measurement start temperature Ts and the measurement maximum temperature Tm according to No. 4.

[0032]

[Table 2] The arrival time is the same as the casting material M for the thermocouple G on the gate 40 side.
Is reached, that is, the time when the thermocouple G starts measuring the temperature of the casting material M is zero, and the casting material M is started from that time.
Are thermocouples U1 to U4 and L1 to L4 on the side of the cavity 41
Time to reach, that is, each thermocouple U1 to U4, L
1 to L4 are represented as the time until the temperature measurement of the casting material M is started. However, in the case of the thermocouple L1, the arrival time of the casting material M exceeds 0.130 sec, and therefore the measurement start temperature Ts is Ts <460 ° C.

FIG. 8 shows thermocouples G, U1 to U4 and L1.
The order of arrival of the casting material M to L4 is shown.

As is apparent from FIGS. 6-8 and Table 2,
According to the thermocouples G, U1 to U4, and L1 to L4 according to the example, the response speed thereof is fast, so that the thermocouples G, U1 to U, respectively.
4, the arrival of the casting material M to L1 to L4 can be accurately detected to clearly know the filling state of the casting material M in the cavity 41.

Further, each thermocouple G, U1 to U4, L1 to L4
The maximum temperature Tm measured by is a temperature close to the solidus temperature 557 ° C. of the casting material M, and therefore the casting material M
It is possible to accurately detect the temperature change in the solidification process of.

The molten metal to be measured is not limited to the above-mentioned semi-molten casting material, and naturally includes a material consisting only of the liquid phase.

[0037]

According to the present invention, with the above construction, the response speed is fast, and therefore the temperature of the molten metal can be measured quickly and accurately, and the arrival sequence of the molten metal in the cavity is improved. It is possible to provide a thermocouple capable of accurately detecting

Moreover, this thermocouple has good separability from the casting since only one end face of the electric insulator and one end part of each wire exposed on the one end face are in contact with the molten metal.
Therefore, it is possible to avoid damage at the time of releasing the casting, so that it has excellent durability.

[Brief description of drawings]

FIG. 1 is a perspective view of a thermocouple.

FIG. 2 is a vertical sectional view of a thermocouple.

FIG. 3 is a vertical cross-sectional view showing the relationship between a mold and a thermocouple.

FIG. 4 is a graph showing a relationship between elapsed time and temperature measured by a thermocouple.

FIG. 5 is a vertical cross-sectional view of a pressure casting device.

FIG. 6 is a graph showing the relationship between the elapsed time and the temperature measured by the thermocouple existing on the upper surface side of the cavity.

FIG. 7 is a graph showing a relationship between an elapsed time and a temperature measured by a thermocouple existing on a lower surface side of a gate and a cavity.

FIG. 8 is an explanatory diagram showing the order of arrival of the casting material to each thermocouple.

[Explanation of symbols]

 2 Heat-resistant electrical insulator 3,4 Elementary wire 10 One end surface 15 Mold (mold) 36,37 Fixed and movable mold (mold) C, G, U1 to U4, L1 to L4 Thermocouple M Casting material (molten metal)

Claims (2)

[Claims] 1. A thermocouple for measuring the temperature of a molten metal (M) injected into a mold (15, 36, 37), comprising:
The heat-resistant electric insulator (2) whose one end face (10) contacts the molten metal (M) and the one end face (10) by independently penetrating the heat-resistant electric insulator (2). And a pair of strands (3, 4) with one end exposed, and the molten metal (M) is used as a high temperature joint between the one ends of both strands (3, 4). Thermocouple for measuring molten metal temperature. 2. An end surface (10) of the heat-resistant electrical insulator (2) is arranged so as to be flush with an inner surface of a casting cavity (18) of the mold (15, 36, 37). The thermocouple for measuring the melt temperature according to claim 1, which is provided.