JP3490215B2 - Ion carburizing furnace - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a carburizing furnace (including a nitriding furnace) for carbonizing or nitriding the surface of an object to be treated, and particularly to the surface of the object to be treated with carbon or nitrogen ionized by glow discharge. The present invention relates to an ion carburizing furnace.

[0002]

2. Description of the Related Art In recent years, in order to increase the surface hardness of a metal material such as steel, an object to be treated is placed in a furnace to introduce a hydrocarbon-based gas, and the object to be treated is used as a cathode and between the anode and the anode. An ion carburizing furnace that generates a glow discharge and implants ionized carbon on the surface of an object to be processed is widely used.

When performing the ion carburization, the gas atmosphere pressure in which the object to be treated is placed is 2 to 4 Torr, which is extremely low pressure as compared with gas carburizing of about 760 Torr or vacuum carburizing of 200 to 400 Torr. Is possible. Therefore, the surface treatment by ion carburization is economical in that the amount of gas used is extremely small, and since the excess carbon does not remain in the furnace, the frequency of maintenance is low. But it is said to be economical.

A prior art furnace used for such ion carburization is shown at 102 in FIG. The conventional ion carburizing furnace 102 has a chamber 103, and a heat insulating space 110 formed of a heat insulating material 104 is provided in the chamber 103 at a distance from the chamber 103. When the basket 115 containing the object to be carburized is placed in the heat insulating space 110, the periphery of the basket 115 is covered with a heat insulating material, and the object to be processed is removed by the heater 114 provided around the basket 115. It is configured to be heated.

A gas inlet 106 is provided in the ceiling portion of the heat insulating space 110, and the gas inlet 106 has
One end of a gas introduction pipe 113 introduced from the outside of the chamber 103 is connected. A gas cylinder 112 is connected to the other end of the gas introduction pipe 113.
A process gas composed of a hydrocarbon gas filled in 2 is
It is configured so that it can be introduced from the gas inlet 106 and sprayed from above the basket 115 in the heat insulating space 110.

A vacuum pump 11 is provided on the side wall of the chamber 103.
7 is provided with a vacuum exhaust port 108, and when the surface treatment of the object to be treated in the basket 115 is performed in the ion carburizing furnace 102, first, the vacuum pump 117 is started and the heater 114 heats the object. Chamber 103
The inside is evacuated, and the heat insulating space 110 is brought into a vacuum state through the gas discharge port 107 provided on the bottom surface of the heat insulating space 110. After that, when the processing gas is introduced from the gas introduction port 106, the processing gas is diffused in the heat insulating space 110, the processing gas is decomposed by glow discharge, and carbon ions are injected into the object to be processed housed in the basket 115 to generate ions. Carburization is performed.

At this time, since the vacuum pump 117 is kept operating, carbon ions are generated by glow discharge.
The processing gas having consumed (C ⁺ ) escapes between the heat insulating material 104 and the chamber 103 through the gas exhaust port 107, and is exhausted through the vacuum exhaust port 108.

In this case, since the inside of the heat insulating material 104 is placed in a vacuum state, the processing gas introduced from the gas introduction port 106 immediately diffuses, but since the vacuum pump 117 operates, the gas introduction port 106 operates. Gas flows 121a and 121b flowing from the gas to the gas outlet 107 are generated.

Of the gas streams 121a and 121b, the gas stream 121a flowing linearly from the gas inlet 106 to the gas outlet 107 has a high concentration, is out of the linear position, and bypasses the basket 115. Gas flow 121b
The concentration of is low. Such gas streams 121a, 121b
The difference in concentration causes unevenness in the amount of processing gas supplied to the object to be processed housed in the basket 115.

When glow discharge is performed while the supply amount is uneven, the amount of carburizing increases on the surface of the object to be treated which is arranged in a place where the concentration of the processing gas is high, and on the other hand, in the place where the concentration is low. The amount of carburizing is small in the placed object.

[0011] Actually, when the objects to be treated contained in various places in the basket 115 were subjected to ion carburization, subjected to carbon diffusion treatment, and then rapidly cooled, the surface condition was measured. As shown by the curve 141 ₁ , the carbon concentration on the surface was high and the hardness was also high in the object to be treated arranged at the high concentration of the treatment gas. In that case, since the carbon is diffused deep, the hardness is high deep.

On the other hand, in the object to be treated which is arranged in a place where the concentration of the treatment gas is low, the carbon concentration on the surface is low and the hardness of the inside is rapidly lowered. The tendency is shown in the curve 141 in FIG.
As shown in _{2-141. 4,} and is pronounced as the surface hardness becomes low.

[0013] Hardness of the workpiece carburization is carried out over it when viewed in a depth that decreases to the base material hardness in the order of the surface hardness is low curve 141 _{1-141 4,} shallow as D ₁ to D ₄ You can see that

Therefore, when a large number of objects to be processed are accommodated in one basket 115 and ion carburization is performed at the same time, the positions of the objects to be processed and the positions of the gas inlet 106 and the gas outlet 107 are the same. Due to the difference in the relationship, there is a problem that the hardness of the objects to be processed varies and the quality is different even in the same lot.

In order to solve such a problem, in the prior art, the process gas is introduced while moving the gas manifold in the furnace so as to make the concentration of the process gas around the object to be treated uniform (Japanese Patent Laid-Open No. 147052), various attempts have been made such as providing uniform gas concentration by providing a plurality of gas inlets around the object to be treated (Japanese Patent Laid-Open No. 1-159365), but sufficient effects have been obtained. No, and the solution was desired.

[0016]

SUMMARY OF THE INVENTION The present invention was created in order to solve the above-mentioned disadvantages of the prior art, and an object thereof is to provide an ion carburizing furnace capable of uniformly surface-treating an object to be treated. .

[0017]

In order to solve the above-mentioned problems, the present invention according to claim 1 is such that a chamber configured to be capable of being evacuated and a chamber provided inside the chamber for storing an object to be processed therein. An ion carburizing furnace having a heat insulating space formed by a heat insulating material, a gas inlet for introducing a processing gas into the heat insulating space, and a gas outlet for discharging a processing gas existing in the heat insulating space, A plurality of the gas outlets are provided, the gas inlet is arranged above the object to be processed, and the plurality of gas outlets are arranged below the object to be treated, and the gas inlet is provided between the gas inlet and the plurality of gas outlets. When placing the processed material,
The processing gas introduced from the gas introduction port and used for the ion carburization is uniformly discharged from each of the gas discharge ports.

In that case, as in the invention described in claim 2,
A strut may be inserted through each of the gas discharge ports, and the strut may support the object to be processed.

Further, as in the invention described in claim 3, when a plurality of the gas inlets are provided in the ion carburizing furnace according to any one of claims 1 or 2, the plurality of gas inlets are provided near the ceiling of the heat insulating space. The processing gas spraying pipes should be arranged horizontally, and the plurality of gas inlets should be composed of holes arranged in line on the bottom surface of the processing gas spraying pipe, and each of the gas inlets should be arranged in the heat insulating space. It may be located above the center of the object to be processed.

According to the ion carburizing furnace having the above-described structure, the chamber of the ion carburizing furnace is configured to be evacuated,
In the chamber, a heat insulating space formed of a heat insulating material is provided so as to accommodate the object to be processed, and a gas inlet for introducing the process gas and a gas outlet for discharging the process gas are provided in the heat insulating space. By evacuating while introducing the processing gas and generating glow discharge with the object to be treated as a cathode, it becomes possible to perform surface treatment of the object to be treated by ion carburization.

Among such conventional ion carburizing furnaces, there is a conventional one in which a plurality of gas inlets are arranged around a basket accommodating an object to be processed so as to uniformly supply the processing gas. However, when the glow discharge is generated and the ion carburization is performed, the processing gas is decomposed and carbon is consumed. Therefore, the uniform supply of the processing gas cannot make the carbon ion supply amount to the object to be processed uniform. . Rather,
It is important to properly flush the processing gas after it is decomposed by the glow discharge and the carbon ions are consumed, from around the object to be processed.

In general, in a carburizing furnace, the processing gas whose carbon has been consumed by glow discharge is usually configured to flow out from a gas outlet provided in the heat insulating material.
The positional relationship between the gas exhaust port and the gas supply port as well as the disposition state of the gas exhaust port and the disposition state of the gas supply port are major factors that determine the gas flow direction of the processing gas in the heat insulating space.

Focusing on this point, in the ion carburizing furnace of the present invention, the gas inlet is located near the ceiling of the heat insulating space, the processing gas is supplied to the object to be processed by downflow, and the bottom surface of the heat insulating space is provided. Since a plurality of gas outlets are provided in the unit and the used processing gas is evenly discharged from each of the gas outlets, the gas flow of the processing gas flows evenly over the entire object to be processed. It became possible to carry out ion carburization without variation.

In this case, it is preferable to provide a plurality of gas introduction ports of such an ion carburizing furnace because the gas concentration around the object to be treated becomes more uniform and the carbon supply amount can be made uniform.
Only by arranging a large number of gas inlets, the cost is increased and the effect is small. Rather, since the inside of the heat insulating space is depressurized, 1.0 kg from the gas inlet is used from the viewpoint of uniformly dispersing the processing gas into the heat insulating space.
If a processing gas having a pressure of about / cm ^{2 to} 0.5 kg / cm ² G is blown out, it is sufficient without providing a gas inlet on the side surface of the heat insulating space.

Therefore, in the present invention, a pipe having a plurality of holes used as gas inlets on the side surface is used as a processing gas diffusion pipe, and each hole is located above the center of the object to be processed to be placed in the heat insulating space. As described above, since the processing gas is arranged horizontally near the ceiling of the heat insulating space and the processing gas is evenly introduced from each hole, the processing gas is uniformly diffused in the heat insulating space with a simple structure, and the processed gas is processed. The amount of carbon ions supplied to the product was made uniform.

If a support is inserted into each of the plurality of gas outlets and the object to be processed is supported by each support, the hole used for the support can also be used for the gas outlet. . Therefore, there is no increase in processing labor and cost when manufacturing the ion carburizing furnace.

[0027]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described with reference to the drawings.
Referring to FIG. 1, reference numeral 2 is an ion carburizing furnace according to an embodiment of the present invention, which has a chamber 3. A heat insulating space 10 formed of a heat insulating material 4 having conductivity is provided in the chamber 3, and circular gas outlets 7 _{1 to} 7 ₂ are opened in the bottom surface of the heat insulating space 10. .

The gas outlets 7 _{1 to} 7 ₄ are formed in a circular shape having the same size, and each of the gas outlets 7 _{1 to} 7 ₄ has a circular shape.
Are respectively inserted post 18 _{1-18 4} erected from the bottom of the chamber 3 to exist a gap, each post 18 ₁ to 1
Hearth 19 is attached horizontally to an upper end portion of the 8 _4.

The reference numeral 15 on the hearth 19 is a basket containing the object to be ion carburized,
A voltage can be applied between the basket 15 and the heat insulating material 4. The basket 15 has an outer shape of a rectangular parallelepiped and is configured to allow a gas flow of a processing gas to pass through inside. The size of the basket 15 indicates a working zone.

When this basket 15 is used, a plurality of small objects to be processed are accommodated in the basket 15 so that a large number of objects can be surface-treated by one processing. For large objects,
The surface treatment is carried out by directly placing it on the hearth 19 without using the basket 15. In this case, reference numeral 15 indicates the object to be treated itself.

The bottom surface of the basket 15 and the gas outlet 7
The positional relationship of _{1 to} 7 ₄ is shown in FIG. Each gas outlet 7 ₁
To 7 ₄ are located evenly on a diagonal line of the rectangular image 30 obtained when projecting the outer shape of the basket 15 to the bottom surface of the insulation space 10, the circular symmetry about the center of the rectangular image 30 Are arranged as follows. That is, the gas outlets 7 _{1 to} 7 ₄ are located immediately below the basket 15 and are arranged so as not to be biased with respect to the basket 15.

A heater 14 is disposed around the basket 15 to generate heat when energized (in FIG. 1, only the portion of the heater 14 above and below the basket 15 is shown, and side portions are omitted). The processing gas spraying pipe 5 is horizontally arranged above the basket 15. The positional relationship between the processing gas spraying pipe 5 and the basket 15 is shown in FIG. 2 (b). The processing gas spraying pipe 5 has a symmetry axis 31 along the longitudinal direction of the basket 15.
Are arranged vertically above and parallel to each other at a height H from the basket 15 of, for example, 150 mm. The length of the processing gas spraying pipe 5 is longer than the length L of the basket 15 in the longitudinal direction, and the protruding length a on one side is, for example, 200 mm.

Both end portions of the processing gas spraying pipe 5 are closed, and a plurality of holes are provided in a row in a portion facing the basket 15, and a plurality of gas introduction ports 6 are formed by each hole. The processing gas spraying pipe 5 is connected to the gas cylinder 12 by a gas introduction pipe 13, and the processing gas filled in the gas cylinder 12 (for example, C ₃
(H ₈ gas) is uniformly introduced into the heat insulating space 10 through each gas inlet 6, and the object to be processed housed in the basket 15 can be placed in the processing gas atmosphere. Several gas inlets 6 are also provided in the portion protruding from the top of the basket 15 (the portion having the length a) so that there is no difference in the processing gas concentration in the four side surfaces of the basket 15. There is.

The gas outlet 7 on the bottom of the chamber 3
_The vacuum exhaust port 8 is located directly below the center of _{1 to} 7 _4.
Is provided, and the vacuum exhaust port 8 is connected to a vacuum pump 17.

The vacuum exhaust port 8 and each gas exhaust port 7 _{1 to} 7 ₄
The positional relationship between and is shown in FIGS. 3 (a) and 3 (b). FIG. 3A is a side view of the basket 15 as seen from the longitudinal direction. The vacuum exhaust port 8 is located on the vertical axis of symmetry 32 of the basket 15, and the gas exhaust ports 7 ₁ and 7 ₂ (and the gas exhaust ports 7 ₃ and 7 ₄ ) have a distance T therebetween. , Axis of symmetry 3
Located at T / 2 from 2 respectively, basket 1
5 is arranged so that there is no bias.

FIG. 3B is a view of the basket 15 as viewed from the front. The vacuum exhaust port 8 is located on the axis of symmetry 33, and the gas exhaust ports 7 ₁ and 7 ₄ (and the gas exhaust ports 7 ₂ and 7 ₃ ).
Are located at S / 2 from the axis of symmetry 33, where S is the distance between them, and are arranged so as not to be biased with respect to the basket 15.

Regarding the absolute values of the distances T and S, with respect to the length L and the width W of the basket 15, 0.7 · L ≦ T ≦ 0.9 · L (1) 0.7 · W ≦ It is arranged so that S ≦ 0.9 · W (2).

With such a non-biased arrangement, the vacuum pump 17 is started to evacuate the chamber 3 and the processing gas is introduced from the plurality of gas inlets 6 while the vacuum pump 17 is operated. Since the inside of the processing gas is a vacuum, the processing gas diffuses uniformly in the heat insulating space 10, and the processing gas in which the carbon ions are consumed is discharged from the gas outlets 7 _{1 to} 7 ₄ between the heat insulating material 4 and the chamber 3. Evacuated, vacuum pump 1
The gas is exhausted from the vacuum exhaust port 8 by 7. In that case, the gas flow 21 of the processing gas flows evenly around the object to be processed.

Using this ion carburizing furnace 2, a large number of objects to be treated were housed in the basket 15 and simultaneously subjected to ion carburizing. 3 stored in different positions in basket 15
After quenching the individual objects to be treated, the change in hardness depending on the depth from the surface was measured. The result is shown in the graph of FIG.
Depth D at which carburized hardness decreases to base metal hardness
Is sufficiently large, and it can be seen that carburization is carried out reliably. Further, it can be seen that the variation width σ of the hardness change curves 31 _{1 to} 31 ₃ of each object to be processed is very small, and there is no difference in quality between the objects to be processed.

Although the case where the hydrocarbon gas is used as the processing gas has been described above, the ion carburizing furnace according to the present invention is also applied to a case where a gas containing nitrogen is used to perform a nitriding treatment on the surface of an object to be treated. It

[0041]

EFFECTS OF THE INVENTION Ion carburization can be performed uniformly on the surface of an object to be treated. Further, with respect to a large number of objects to be carburized simultaneously, there is no variation in quality among the objects to be processed.

Since the hole for the column can be used as the gas outlet, the cost does not increase even when manufacturing the ion carburizing furnace.

Further, since uniform carburization can be performed without providing a plurality of gas inlets around the object to be treated, it is possible to manufacture an ion carburizing furnace with good performance at low cost.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an ion carburizing furnace of the present invention.

2A is a diagram for explaining the position of the gas outlet, and FIG. 2B is a diagram for explaining the position of the gas inlet.

3A and 3B are views for explaining the positional relationship between the gas inlet and the vacuum outlet.

FIG. 4 is a graph for explaining the results of ion carburizing using the ion carburizing furnace.

FIG. 5 Conventional ion carburizing furnace

FIG. 6 is a graph for explaining the results of ion carburizing using the ion carburizing furnace.

[Explanation of symbols]

2 ... Ion carburizing furnace 4 ... Insulating material 5 ... Support processing gas spraying pipe 6 ... Gas inlet 7 ₁ , 7 ₂ ...... Gas outlet 8 ...
… Vacuum exhaust port

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Claims (3)

(57) [Claims] 1. A chamber that can be evacuated, a heat insulating space that is provided in the chamber and is formed of a heat insulating material so as to accommodate an object to be processed, and a process gas is introduced into the heat insulating space. An ion carburizing furnace having a gas inlet for discharging a processing gas existing inside the heat insulating space, wherein a plurality of the gas outlets are provided, and the gas inlet is provided above the object to be processed. However, the plurality of gas outlets are arranged below, and when the object to be treated is arranged between the gas inlet and the plurality of gas outlets, it is introduced from the gas inlet and used for ion carburization. An ion carburizing furnace characterized in that the treated gas is uniformly discharged from each of the gas outlets. 2. A column is inserted through each of the gas outlets,
The ion carburizing furnace according to claim 1, wherein the pillar is configured to support the object to be treated. 3. The ion carburizing furnace according to claim 1, wherein the gas carburizing furnace has a plurality of gas inlets, and a processing gas spraying pipe is horizontally arranged near a ceiling of the heat insulating space. The plurality of gas introduction ports are holes formed in a row on the bottom surface of the processing gas spraying pipe, and each of the gas introduction ports is located above the center of the object to be processed to be placed in the heat insulating space. An ion carburizing furnace characterized by being configured as follows.