JPH09184769A - Thermocouple for measuring molten metal temperature - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a molten metal temperature measuring thermocouple capable of quickly and accurately measuring the molten metal temperature injected into a cavity. A thermocouple C includes a heat-resistant electric insulator 2 made of a ceramic sintered body having one end surface 10 in contact with a molten metal M, and
The heat resistant electrical insulator 2 has a pair of strands 3 and 4 made of alumel and chromel, one end of which is exposed at the one end face 10 by penetrating the heat resistant electrical insulator 2 independently of each other. , 4 is used as the high temperature joint between the ends.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermocouple for measuring the temperature of a molten metal, and more particularly to an improvement of the thermocouple for measuring the temperature of the molten metal injected into a mold.

[0002]

2. Description of the Related Art Conventionally, as this type of thermocouple, a heat-resistant protective cylinder in which the outer surface of an end wall is in contact with a molten metal, and a pair of wires accommodated in the protective cylinder with a high-temperature joint positioned near the inner surface of the end wall. When,
In order to fix these strands in a protective cylinder, there is known one provided with an electric insulating material filled in the protective cylinder (see JP-A-5-209794).

[0003]

However, in the conventional thermocouple, since the high-temperature junction is covered by the protective case, first, when measuring the temperature, the end wall of the protective case is heated by the molten metal. Next, since the temperature of the end wall is 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, when the maximum measurement temperature is significantly lower than the solidus temperature of the molten metal, it is impossible to detect a temperature change during the solidification process 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, an object of the present invention is to provide a thermocouple which has a fast response speed and therefore can measure the temperature of the molten metal quickly and accurately.

[0006]

According to a first aspect of the present invention, there is provided a thermocouple for measuring the temperature of a molten metal injected into a mold, which comprises a ceramic sintered body having one end surface in contact with the molten metal. A heat-resistant electrical insulator; and a pair of strands made of alumel and chromel with one end exposed at the one end face by penetrating the heat-resistant electrical insulator independently of each other. The molten metal is used as a high temperature joining portion between the one ends of the above, and the invention of claim 2 is characterized in that, in addition to the above features, the molten metal is embedded in a mold of a pressure casting apparatus and is placed in a cavity of the mold. It is characterized in that it is used to measure the temperature of a pressure-filled molten metal in a semi-molten state.

[0007]

[Operation] In the above structure, when the molten metal reaches one end of both strands, the molten metal forms a high temperature joint,
The temperature of the molten metal can be measured quickly and accurately.

[0008] The thermocouple measures the maximum temperature of the molten metal within the measurement range with the lapse of time. However, since the response speed is fast, the maximum measured temperature is not much lower than the solidus temperature of the molten metal. Therefore, it is possible to accurately detect a temperature change during the solidification process of the molten metal.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below based on embodiments of the present invention illustrated in the accompanying drawings.

The thermocouple C according to the embodiment shown in FIGS.
A holder cylinder 1, a rod-shaped heat-resistant electric insulator 2 connected to the holder cylinder 1, and an electric insulator 2 which are used for measuring the temperature of a molten metal having an Al alloy composition injected into a mold (mold). It has a pair of strands 3 and 4 penetrating each other independently.

The holder cylinder 1 is made of stainless steel and has a cylindrical part 5 and a flange part 6 formed on one side of an outer peripheral surface thereof, and a female screw hole opened in one end surface in the cylindrical part 5. 7
a and a circular concave portion 7b 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 electric insulator 2, while BN contributes to improving the separability of the electric insulator 2 from the casting and the machinability. After sintering, electrical insulator 2
, Two narrow through holes 8 and 9 along the longitudinal direction are formed independently of each other, and the two wires 3 and 4 are inserted into the 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 strands 3, 4
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 wires 3 and 4 slightly protrude from the one end face 10 of the electric insulator 2. The material of each of the strands 3 and 4 is determined according to the measurement temperature.

A male screw 1 is provided on the outer peripheral surface of the other end of the electric 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 strands 3 and 4 extend outside from the concave portion 7b of the holder tube 1, and the concave portion 7b is filled with an alumina-based adhesive 14 and hardened. 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.
Are formed. The stepped hole 19 has a large-diameter portion 20, a medium-diameter portion 21, and a small-diameter portion 22 sequentially arranged from the concave portion 17 side.
Consists of The electric insulator 2 is fitted to the small diameter part 22, the cylindrical part 5 is fitted to the middle diameter part 21, and the flange part 6 is fitted to the large diameter part 20, respectively.
Is held. In this holding state, the one end face 10 of the electric insulator 2 and the inner face 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 wires 3 and 4.

The terminal member 23 has an annular mounting frame 24 made of stainless steel. The mounting frame 24 is loosely fitted in the concave portion 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 a on the outer peripheral surface with the step b on the inner peripheral surface of the mounting frame 24. The retaining of the electrical insulating plate 26 inward 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 terminals 29 and 30 projecting from the electric insulating plate 26 so as to sandwich the through hole 28. One terminal 29 is made of alumel, and around the terminal 29 is wound an alumel strand 3 drawn out from the through hole 28 and an alumel conducting wire 31 on the measuring instrument main body side.
Is pressed and fixed to the outer surface of the electric insulating plate 26 by the electric insulating nut member 32 screwed into the nut. The other terminal 30 is made of chromel, and the terminal 30 has a chromel wire 4 drawn out from the through hole 28 and a chromel lead 3 on the measuring instrument main body side.
3 are wound, and both wires 4 and 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 casting material in a solid state 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 cooled at a temperature of 575 ° C. The cavity 18 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 ) corresponds to the thermocouple with a protection cylinder 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 casting material M in a semi-molten state reaches one end 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. Is done. The measurement start temperature Ts at this time is as shown in FIG.
538 ° C. as shown in FIG.

Then, as time passes, the thermocouple C measures the maximum temperature of the casting material M within the measurement range, and since the response speed is fast, the maximum measurement temperature Tm is:
As shown in FIG. 4, it is 557 degreeC. As described above, the maximum measured 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. Can be accurately detected.

Further, since the response speed is high as described above, the arrival order of the casting material M in the cavity 18 can be accurately detected with the start of temperature measurement of the casting material M as the arrival of the casting material M. is there.

In the thermocouple according to the conventional example, due to its low response speed, the time at the start of measurement is approximately Δt = about as compared with the thermocouple according to the embodiment as shown by the line (C ₁ ) in FIG. In the case of the thermocouple C according to the embodiment, the time from the start of measurement to the measurement of the maximum temperature is about 0.04 seconds, 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 measurement temperature Tm is 488 ° C. as the temperature of the casting material decreases. The measured maximum temperature Tm is lower than the solidus temperature by about 100 ° C., so that it is impossible to detect a temperature change in the solidification process of the casting material M.

In FIG. 5, the mold (mold) in the pressure casting apparatus 35 is composed of a horizontal fixed mold 36 and a movable mold 37 which moves in the vertical direction 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
Then, a short columnar casting material M in which a solid phase and a liquid phase coexist as described above is erected.

A gate 40 is opened on the inner surface of the bottom of the chamber 39 by the cooperation of the fixed and movable molds 36 and 37.
And the cavity 4 for casting molding which communicates with the gate 40.
1 is formed. A plunger 42 is slidably fitted in the sleeve 38, and the cavity 41 is filled into the cavity 41 through the gate 40 at high speed while pressurizing the casting material M in the chamber 39 by the plunger 42.

A cavity 41 is provided in the fixed mold 36.
Four thermocouples U1, U2, U3, and U4 according to the embodiment shown in FIGS. 1 and 2 are embedded at predetermined intervals from the entrance side to the back side. One end face 10 of the electric insulator 2 of each thermocouple U1 to U4 is located on the same plane as the upper surface of the cavity 41. Therefore, the one end faces 11 and 12 of the two wires 3 and 4 of each thermocouple U1 to U4 are 41 is exposed on the upper surface. The other ends of the wires 3 and 4 of each of the thermocouples U1 to U4 are 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 therefore, the two wires 3 of each thermocouple G, L1 to L4.
4 are exposed on 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 the two wires 3 and 4 are connected to the measuring instrument body.

A semi-molten casting material M having the same Al alloy composition as described above and having 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 up. 42, 0.07 m / sec, mold temperature 250 ° C., casting material M gate passing speed 3 m / sec.
Under the condition of sec, the casting material M at 575 ° C. is passed through the gate 40 while being pressurized to fill the cavity 41 with high-speed laminar flow, and the temperature of the casting material M is measured by the thermocouples G, U1 to U4, and L1 to L4. went.

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

Table 2 shows 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.

[0033]

[Table 2]

The arrival time depends on the thermocouple G on the gate 40 side.
When the casting material M reaches the temperature of the casting material M, that is, when the thermocouple G starts measuring the temperature of the casting material M, it is assumed that the casting material M is zero.
4, L1 to L4, that is, the time until each thermocouple U1 to U4, L1 to L4 starts measuring the temperature of the casting material M. 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 <46.
0 ° C.

FIG. 8 shows each thermocouple G, U1 to U4, L1 to L4.
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 embodiment, since the response speed is fast, each thermocouple G, U1 to U4 is used.
4. It is possible to accurately detect the arrival of the casting material M to L1 to L4 and to clearly know the filling state of the casting material M in the cavity 41.

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 semi-molten casting material described above, and naturally includes a material composed only of a liquid phase.

[0039]

EFFECTS OF THE INVENTION According to the present invention, with the above-mentioned structure, it is possible to provide a thermocouple capable of quickly and accurately measuring the temperature of a molten metal.

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.

According to the second aspect of the invention, since the temperature of the semi-molten molten metal filled in the cavity under pressure can be measured quickly and accurately, the semi-molten casting material can be measured. It is possible to accurately detect a temperature change in the solidification process of (molten metal).

[Brief description of the drawings]

FIG. 1 is a perspective view of a thermocouple.

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

FIG. 3 is a longitudinal sectional view showing a relationship between a mold and a thermocouple.

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

FIG. 5 is a vertical sectional view of a pressure casting apparatus.

FIG. 6 is a graph showing a relationship between elapsed time and a temperature measured by a thermocouple located 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 in which a casting material reaches 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), wherein one end face (10) of the ceramic is in contact with the molten metal (M). A heat-resistant electrical insulator (2) made of a sintered body, and an alumel having one end exposed at the one end face (10) by penetrating the heat-resistant electrical insulator (2) independently of each other; Molten metal temperature, characterized by having a pair of chromel strands (3, 4) and using the molten metal (M) as a high temperature joint between the ends of both strands (3, 4). Thermocouple for measurement. 2. A mold (15, 3) of a pressure casting device (35).
6,37) embedded in the mold (15,36,3)
The thermocouple for measuring a molten metal temperature according to claim 1, which is used for measuring a temperature of a semi-molten molten metal which is pressurized and filled in the cavity (41) of 7).