JP2556072B2 - Ion carbonitriding furnace - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ion carbonitriding furnace for performing ion carburization and ion nitriding of an object to be treated independently or simultaneously.

[Conventional technology]

Recently, as a method of hardening the surface of an object to be processed such as steel, a processing gas consisting of a mixed gas of a carrier gas such as argon and a CH-based gas or nitrogen gas is introduced into the vacuum container containing the object to be processed. Ion carburizing (also called plasma carburizing) or ion nitriding (also called plasma nitriding) in which glow discharge is generated between the anode and the anode and ionized carbon or nitrogen is implanted on the surface of the object to be treated has been put into practical use. FIG. 5 shows an example of an apparatus for this treatment method, 1 is a furnace shell made of steel, 2 is an anode also serving as a heat insulating material made of graphite, 3 is a cathode made of stainless steel, and its base is an insulator 4 It is fixed to the furnace shell 1 via. Reference numeral 5 denotes an object to be processed attached to a mounting jig, and 6 denotes a graphite hearth on which the object to be processed 5 is placed, which is fitted to the upper end of the cathode 3. Reference numeral 7 is a graphite rod-shaped heater that generates heat by resistance heating and heats the workpiece 5 mainly by radiant heat, and 8 is a tubular gas manifold made of graphite for supplying a processing gas. , Multiple pieces are arranged side by side around the object to be processed 5,
It has a plurality of outlets for blowing the processing gas toward the object to be treated 5. Reference numeral 9 is an exhaust port provided in the furnace shell 1, and 10 is a vacuum pump connected to the exhaust port 9.

[Problems to be solved by the invention]

However, in the ion carburizing furnace 11 having the above-mentioned configuration, the exhaust port 9 connected to the vacuum pump 10 is provided only at one location in the furnace shell 1, so that the process gas flowing out from the outlet of the gas manifold 8 is in the furnace. When the gas is circulated through the exhaust port 9 and exhausted from the exhaust port 9, the flow state of the processing gas around the object to be processed 5 is constant. Therefore, for example, a large number of stacked objects to be processed are different depending on their respective positions. There is a problem in that there is a difference in the concentration of the processing gas around it and there is a large variation in the carburizing depth or nitriding depth of the object to be treated.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an ion carbonitriding furnace capable of performing uniform treatment with little variation in carburizing depth and nitriding depth.

[Means for solving problems]

However, the ion carbonitriding furnace of the present invention, in the furnace shell,
In an ion carbonitriding furnace equipped with an anode and a cathode having a container shape surrounding an object to be processed, a gas manifold for supplying a processing gas, and a heater for heating the object to be processed, the furnace shell is provided with a plurality of exhaust ports. An ion carbonitriding furnace characterized in that each of the exhaust ports is connected to a vacuum pump through an on-off valve.

[Action]

In the ion carbonitriding furnace of the present invention, by operating each on-off valve provided at a plurality of exhaust ports, the exhaust port exhausted from the furnace during the ion carburizing or ion nitriding can be switched. By this, the flow state of the process gas flowing in the furnace is switched, the process gas flow state around each object to be processed can be made uniform, and the process gas concentration can be made uniform, and the carburizing depth or Variation in nitriding depth is suppressed. Further, this exhaust does not necessarily have to be performed by only one exhaust port. For example, when the object to be processed is composed of one large component such as a mold, all exhaust ports are opened for simultaneous exhaust. The uniform distribution of the processing gas distribution around the entire circumference of the object to be processed, etc., and the optimum number of exhaust openings and the order of opening the exhaust ports can be freely selected according to the shape and number of objects to be processed. Can be processed with.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

5, those parts which are the same as those corresponding parts in FIG. 5 are designated by the same reference numerals, and a description thereof will be omitted. The furnace shell 1 has 4
Four exhaust ports 12a to 12d (collectively referred to as exhaust ports 12) are provided at equally divided positions, and four electromagnetically operated on-off valves 13a to 13d are connected to each exhaust port. The exhaust side of these on-off valves 13 is connected to one vacuum pump 10. The anode 2 is provided with an opening 14 on the side and has a box-like container shape surrounding the object 5 to be treated, and is formed by assembling a carbon fiber plate-shaped molded body having heat insulation and air permeability. In FIG. 1, reference numeral 15 is a manually openable / closable lid whose side is supported by the furnace shell 1 by a hinge (not shown), and 16 is an O-ring for sealing. Reference numeral 17 denotes an inner lid attached to the lid 15, which is made of carbon fiber like the anode 2 and has an opening 14
It opens and closes. Reference numeral 18 denotes a processing chamber surrounded by the inner lid 17 in a closed state and the anode 2. 19 is the anode 2
A DC power supply connected between the cathode 3 and the cathode 3, 20 an AC power supply for energizing the heater 7, and 21 a processing gas supply source connected to the gas manifold 8.

In the ion carburizing furnace 22 having the above-mentioned configuration, the object 5 to be treated is placed on the hearth 6 by a transport fork (not shown) or the like, and the lid is closed.
Close 15 and operate the vacuum pump 10 to move the inside of the furnace at 0.5-10 Torr.
Use a vacuum of a certain degree. At this time, any one of the on-off valves 31 may be opened. After exhausting the gas from the furnace, the heater 7 is energized to heat the workpiece 5 to a predetermined temperature (for example, 900 ° C.), and argon and hydrogen gas are supplied into the furnace from the gas manifold 8 so that the anodes 2 and the cathodes 3 are covered. The surface of the object to be processed is cleaned by collision of hydrogen ions by glow discharge with the object to be processed 5.

After that, a processing gas consisting of CH-based gas is supplied into the furnace from the gas manifold 8 and carbon ions are implanted into the surface of the object to be processed 5 by glow discharge between the anode 2 and the object to be processed 5 to perform the ion carburizing process. . During this ion carburizing process, each of the on-off valves 13a to 13d is individually operated for a predetermined time (for example, 2
For each minute) and exhaust ports 12a, 12b, 12c, 12d
The switching of the exhaust port is repeated in the order of. As a result, the flow state of the processing gas supplied from the gas manifold 8 and flowing in the processing chamber 18 and passing through the wall surface of the anode 2 to the exhaust port 12 is sequentially switched to four ways. Variations in the concentration of the processing gas flowing through each part are reduced and made uniform, and variations in the carburizing depth are also reduced.

Ion carburizing furnace 22 with the above configuration (however, inner diameter of furnace shell 1 = 16
00mm), SCR420 small parts for automobiles are placed on the mounting jig, 20 pieces per step, and 6 steps are stacked.
And processing gas is C ₃ H ₈ gas 7 / min and N ₂ gas 3 / m
Using a mixed gas of in, carburizing was carried out at a furnace pressure of 5 Torr at 900 ° C. for 35 minutes, followed by diffusion treatment for 90 minutes. During the carburization, the exhaust ports 12a to 12d were sequentially opened one by one for 2 minutes by the timer control of the on-off valves 13a to 13d to exhaust the gas, and the carburized product 5 obtained was carburized. The variation in depth was ± 0.09 mm. On the other hand, 1
In the comparative example in which the carburizing process was performed under the same conditions as those of the above example, the carburizing depth of the object to be treated 5 was ± 0.19 mm. Two
Over twice the variation was measured.

The switching of the exhaust port 12 may be performed in an order other than the above order, and depending on the shape and number of the objects to be processed,
It is also possible to open and close the two exhaust ports as one set, or to open all four of the exhaust ports to perform exhaust to make the concentration of the processing gas uniform. Further, the switching of the exhaust port may be performed not only during the ion carburization but also during the cleaning of the surface of the object to be treated with hydrogen ions in the previous step.

Next, FIG. 3 shows another embodiment of the present invention. A gas tight sheet 23 made of graphite having a large ventilation resistance is attached to the inner wall surface of the anode 2, and a plurality of gas tight sheets 23 (in this embodiment, 4 Individual) circular vent holes 24 are provided, and other configurations have the same structure as the above-mentioned embodiment.

In this embodiment, the processing gas supplied from the gas manifold 8 into the processing chamber 18 passes through the air-permeable wall surface of the anode 2 in the ventilation hole 24 and goes out of the furnace through one of the exhaust ports 12. Exhausted. Therefore, the outflow position of the processing gas from the inside of the processing chamber 18 is regulated, and by keeping the gas circulation state in the processing chamber 18 constant, the switching of the exhaust port 12 causes the processing gas in each part of the object to be processed. The concentration can be made more uniform. The position and the number of the vent holes 24 can be determined according to the position and the number of the exhaust ports 12, the shape and the number of the object to be processed, for example, by an experiment or a simulation by a computer or the like. The gas tight sheet 23 may be attached to the outer wall surface of the anode 2.

FIG. 4 shows still another embodiment of the present invention, in which the gas-tight sheet 23 is omitted, and instead a vent hole 25 is directly bored on the wall surface of the anode 2, and the embodiment of FIG. It has the same action and effect as. In this case, the anode 2 may be composed of a carbon plate having no air permeability.

The present invention is not limited to the above embodiments,
For example, the positions and the number of the exhaust ports 12 may be other than the above, and the anode 2 may have a cylindrical container shape or an inner lid 17.
May have no.

Further, the present invention can be applied to an ion carburizing furnace, and can be applied to a through type furnace as well as an in-out type furnace.

〔The invention's effect〕

As described above, according to the present invention, the plurality of exhaust ports provided in the furnace shell can be individually opened / closed by the on-off valve, so that by switching the flow state of the processing gas in the furnace, the object to be processed is switched. It is possible to reduce variations in carburizing depth and nitrogen depth.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an ion carburizing furnace showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is a second embodiment of the present invention. FIG. 4 is a diagram corresponding to FIG. 2, showing another embodiment of the present invention, and FIG. 5 is a diagram corresponding to FIG. 2 showing an example of a conventional ion carburizing furnace. 1 ... Furnace shell, 2 ... Anode, 3 ... Cathode, 5 ... Object, 7 ... Heater, 8 ... Gas manifold, 10 ... Vacuum pump, 12a-12d ... Exhaust port, 13a ... 13d …… Open / close valve,
17 …… Inner lid, 21 …… Processing gas supply source, 22 …… Ion carburizing furnace, 23 …… Gas tight sheet, 24 …… Vent hole, 25 …… Vent hole.

Claims (4)

(57) [Claims] 1. An ion carbonitriding furnace comprising: a furnace shell, which is provided with a container-shaped anode and a cathode surrounding a material to be processed, a gas manifold for supplying a processing gas, and a heater for heating the material to be processed. An ion carbonitriding furnace characterized in that a furnace shell is provided with a plurality of exhaust ports, and the exhaust ports are each connected to a vacuum pump through an on-off valve. 2. The ion carbonitriding furnace according to claim 1, wherein the anode is made of a gas permeable material. 3. The ion carbonitriding furnace according to claim 1, wherein the anode comprises two layers of a breathable material layer and a non-breathable material layer having a plurality of vent holes. 4. The ion carbonitriding furnace according to claim 1 or 2, wherein a plurality of vent holes are formed in the wall surface of the anode.