JPH0658839B2 - Induction plasma device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an induction plasma apparatus which is capable of efficiently heating and melting powders of ceramics, metals, etc. in an inductively coupled plasma for injection, and is mainly used for thermal spraying.

<Conventional technology> Conventional technology of this kind is the Society Publication Center
An inductively coupled plasma apparatus is disclosed as a light source unit in inductively coupled plasma optical emission spectrometry in a book “Atomic emission spectrometry of liquid samples” of the Spectroscopical Society of Japan method 5 published on October 10, 1983. As shown in FIG. 2, its schematic configuration is such that a water-cooling induction coil 4 is provided on a torch having a triple structure composed of an outer tube 1, an intermediate tube 2 and a carrier gas introducing tube 3, which is made of transparent quartz. Has become. Outer tube 1
Has an upper end opened and a lower end joined by being joined to the outer periphery of the lower portion of the intermediate tube 2, and an outer gas supply unit 5 is opened tangentially in the lower end thereof. The upper end of the intermediate pipe 2 is located below the upper end of the outer pipe 1, the outer diameter of the upper end is enlarged, and an annular small gap 6 is formed between the inner pipe and the inner peripheral surface of the outer pipe 1. The lower end is closed by being joined to the outer periphery of the lower part of the carrier gas introducing pipe 3, and the intermediate gas supply passage 7 is provided in the lower end.
Are tangentially opened along the same circumferential direction as the outer gas supply passage 5. The carrier gas introducing pipe 3 has an upper end formed to have a small diameter and opens near the upper end in the intermediate pipe 2, and the lower end serves as a carrier gas supply passage 8. In the figure, 9 is a plasma flame, and 10 is a spectroscope, which is the optical axis.

This plasma device supplies argon or nitrogen as an outer gas from the outer gas supply passage 5, supplies argon as an intermediate gas from an intermediate gas supply passage 7, and supplies a carrier gas (argon) and a sample mist from a carrier gas supply passage 8. It is supplied and the induction coil 4 is operated and used. The outer gas is supplied mainly for cooling the outer pipe 1, and the outer pipe 1 has an outer diameter of about 20 mm, and the outer gas flows at 10 to 15 min / min. This outer gas is introduced into the outer tube 1 in the tangential direction, and therefore flows out while rotating spirally. The small gap 6 is about 1 mm,
As a result, the linear velocity of the gas is increased and the cooling efficiency is increased. The intermediate gas usually flows at 1 to 2 minutes per minute, and has an auxiliary effect of floating the plasma slightly upward. The carrier gas is for making the sample into an aerosol and introducing it into the plasma, and the inner diameter of the tip of the carrier gas introducing pipe 3 is 1.5 to 2 mm, and 0.5 to 1.5 per minute is passed.

When plasma is ignited without carrier gas flowing,
The plasma has a frame shape with a uniform inside and a slightly flat bottom. When the carrier gas is flown here and the flow rate is gradually increased, a low brightness part appears in the center of the plasma when it reaches about 0.5 per minute, and there is a donut-shaped hole 11 when viewed from above. Can be confirmed with the naked eye. This hole at the center is due to the supply of carrier gas, and this hole is used in plasma emission spectroscopy, so that sample particles are efficiently introduced into the plasma, and complete atomization occurs while passing through the tunnel at high temperature. Excitation light emission occurs. If the sample is supplied in a state where there are no holes in the plasma, the sample cannot enter the center of the plasma and passes through the relatively low temperature part in the peripheral part, causing the hardly dissociable compound to completely atomize and emit light. Is difficult.

<Problems to be Solved by the Invention> Since the plasma device in the emission spectroscopic analysis is designed so that a very small amount of sample is introduced into a high-temperature tunnel of plasma, the sample is heated to a high temperature to generate atomic emission. The purpose is achieved by making it. However, this invention uses an induction plasma device to supply a significantly larger amount of material such as ceramic or metal than the sample in the emission spectroscopic analysis, and inject it in a molten state,
The purpose is to perform thermal spraying to form a coating on the surface of the material. Therefore, when trying to apply the plasma device in the conventional optical emission spectroscopy to thermal spraying, the thermal spraying material will pass through the hole of the plasma described above, and this hole is a relatively low temperature portion from the whole plasma flame, The heating efficiency of the thermal spray material is not always good. When the thermal spray material is supplied to the plasma having no holes, the plasma passes through the peripheral portion of the plasma having a temperature lower than that of the holes as described above, and the heating efficiency further deteriorates.

An object of the present invention is to provide an induction plasma device in which a thermal spray material is passed through a high temperature portion in plasma so as to be efficiently heated.

<Means for Solving the Problem> According to the means of the present invention, in the above-mentioned conventional induction plasma apparatus, at least one of the induction coil and the torch can be moved in the axial direction to change the relative positional relationship between them. It is characterized by doing so.

<Operation> Plasma is ignited in the same manner as in a conventional plasma device for emission spectroscopy, and then a carrier gas is flown to form the hole at a relatively low temperature in the center of the plasma, and then an induction coil is attached to the torch. When the carrier gas is relatively displaced forward in the outflow direction, the hole disappears from the front portion in the outflow direction of the carrier gas, and remains slightly in the front portion. That is, the portion that was present as a through hole having a relatively low temperature is changed to a recess, the center portion of the plasma has a high temperature, and the carrier gas is supplied so as to pass through the high temperature portion. Therefore, when powdery thermal spray material is supplied into the carrier gas in this state, the thermal spray material passes through the high temperature portion at the center of the plasma together with the carrier gas, is efficiently heated, is melted, and is jetted forward.

<Embodiment> A schematic structure of an embodiment of the present invention is shown in FIGS.
Shown in. In the figure, 20 is a quartz torch, which is composed of an outer tube 21, an intermediate tube 22, and a carrier gas introduction tube 23, and 24 is an induction coil. The induction coil 24 is water-cooled, and one side of the end face of the cross section is shown. These have almost the same structure as the conventional apparatus for emission spectroscopy analysis shown in FIG. 2, except that the induction coil 24 can be axially moved and adjusted with respect to the torch 20. is there. The movement is adjusted by separately forming a coil support and a torch support and moving them with a screw. In the figure, 25 is an outer gas supply passage, 26 is a small annular gap, 27 is an intermediate gas supply passage, and 28 is a carrier gas supply passage.

To give an example of the dimensional configuration of each part in mm, the inner diameter of the outer pipe 21 is 24, the annular small gap 26 is 0.5, the inner diameter of the carrier gas introduction pipe 23 is 2, and the dimension a between the outer pipe 21 and the intermediate pipe 22 in the axial direction is a. Is 3
0, the axial dimension b between the tips of the intermediate tube 22 and the carrier gas introduction tube 23 is 5, the total length c of the outer tube 21 is 106, the inner diameter of the induction coil 24 (winding 3) is 32, and the axial length of the coil is d is 20, and the distance e from the tip of the induction coil 24 to the tip of the outer tube 21 during plasma ignition is 15.

This induction plasma device is used as follows. Supplying an outside gas (argon or nitrogen) of about 5 / min and an intermediate gas (argon) of about 3 / min while supplying about 1KW of power to the induction coil 24 and using a Tesler coil discharge or grounded carbon rod. Is used to ignite the plasma as in the conventional case. After ignition, the supply amount of the outer gas and the intermediate gas is gradually increased while maintaining the stable state of the plasma by the matching operation of the power supply unit, and the outer gas is reduced to 15
Approximately 20 / min, the intermediate gas is set to about 5 / min, and the high frequency power supplied to the induction coil 24 is gradually increased to about 3 KW.

Next, start the carrier gas supply from a small amount and
Raise to in to form the holes in the plasma. During this time, a matching operation is performed to stabilize the plasma.

Then, along with the matching operation, the induction coil 24 is moved along the axial direction toward the distal end side of the outer tube 21 by about 10 mm as shown by the phantom line on the opposite side to the original position in FIG. 1 (a).
The plasma changes from the state shown in FIG. 1 (e) to the state shown in FIG. 1 (f). That is, in FIG. 1 (e), plasma 30a
While the hole 31a formed by the carrier gas penetrated the entire length of the plasma 30a, the induction coil 24
In Fig. 1 (f) after moving the plasma, most of the holes are closed in the plasma 30b and a part of the holes is formed on the carrier gas inlet side.
31b remains. Therefore, the higher temperature heating region is expanded by the amount that the hole in the path through which the carrier gas passes is blocked. In this way, in the state where the carrier gas surely passes through the central part of the plasma, a stable state in which the gas flow velocity distribution in the torch is constant is secured, so that the heating region has expanded in that state. The heating efficiency of the thermal spray material powder supplied by the carrier gas is increased. In the figure, the arrow 32 is the outer gas, the arrow 33 is the intermediate gas, and the arrow is
34 shows the moving direction of each carrier gas.

According to experiments, when a spraying material such as nickel chrome, zirconia, alumina, etc. is supplied into the plasma in a powder state through a carrier gas at a rate of several grams per minute, the spraying material is injected in a molten state and the outside From the tip of tube 21
It was confirmed that a film of thermal spray material was formed on the iron plate placed at a position of 30 to 50 mm.

Further, according to another experiment, when plasma was sprayed for a certain period of time without changing the position on the flat material surface using the plasma in which the holes were extinguished in the above-mentioned example, the thickness was thick in the center part and thin in the peripheral part. In contrast to the formation of a convex coating, the induction coil 24 is not moved forward, at the position at the time of ignition,
It was found that when a plasma with a low temperature hole was used to spray the same material surface in the same manner, a concave coating with a thin central portion and a slightly raised peripheral portion was formed. This is because when a plasma with low temperature holes is used, a large amount of the sprayed material to be supplied is concentrated in the central part, but the thinning of the coating results in a considerable amount of melted state in the central part. Therefore, it means that the powder is scattered as it is, and when plasma with no low temperature holes is used, most of the thermal spray material to be supplied is efficiently heated and more is melted and the surface of the material is melted. It is shown that it has adhered to.

Although the torch 20 was used in the downward direction as shown in the above-mentioned experiment, it is not necessarily limited to this direction.

<Effects of the Invention> According to the present invention, the point that the plasma was formed by the low temperature hole penetrating the central portion in the related art is that the carrier gas is caused to flow in the central portion of the plasma which has blocked most of the tip side of the penetrating hole. Since it can be obtained in the state described above, the effect of efficiently heating the thermal spray material can be obtained when the thermal spray material is supplied via the carrier gas. Therefore, it is possible to manufacture an efficient thermal spraying apparatus using the induction plasma apparatus.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. (A) is a schematic longitudinal side view of the torch and induction coil, (b) is a sectional view taken along line BB of (a), and (c) is C of (a). -C sectional view, (d) is DD of (a)
Sectional view, (e) is a vertical side view showing the state of plasma before the induction coil is moved, (f) is a vertical side view showing the state of plasma after the induction coil is moved, and FIG. 2 is a conventional induction plasma device 1 An example is shown in (a), which is a schematic vertical sectional side view of the torch and the induction coil, and (b) is a sectional view taken along line AA of (a). 20 ... Torch, 21 ... Outer tube, 22 ... Intermediate tube, 23 ... Carrier gas introduction tube, 24 ... Induction coil, 25 ... Outer gas supply passage, 26 ... Small annular gap, 27 ... Intermediate Gas supply channel, 28
...... Carrier gas supply channel.

Claims (1)

[Claims] 1. An outer tube which is introduced tangentially from one end and is discharged from an opening at the other end, and an outer tube which is coaxially provided in the outer tube and introduces intermediate gas from one end in the same tangential direction as the outer tube and the other end. And a torch having a triple structure including an intermediate tube for discharging from the opening of the intermediate tube and a carrier gas introducing tube coaxially provided in the intermediate tube for discharging the carrier gas supplied from one end from the opening at the other end, and the opening side of the torch. In an induction plasma device including an induction coil provided on the outer periphery and a high frequency power supply section of the induction coil, at least one of the induction coil and the torch can be moved in the axial direction to change the relative positional relationship between the two. An induction plasma device characterized by the above.