JP2002030478A - Molten salt electrodepositing device and molten salt electrodepositing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molten salt electrodepositing device and a molten salt electrodepositing method by which a coating layer can easily be formed by using a molten salt electrolytic bath shallower than the length of the bar-shaped or tubular member to be treated. SOLUTION: This device contains a cylindrical body 3 to be stored with a salt, a molten salt melting means 5 for heating and melting the salt excepting the vicinity of the bottom part of the cylindrical body 3, an electrode 7 arranged on the inside of the cylindrical body 3 and a power source part 15 electrically connected to the electrode 7 and the bar-shaped or tubular member 23 to be treated, the cylindrical body 3 has a bottom board 17 clogging the bottom part, and the bottom board 17 is formed with a through-hole 19 through which the member 23 to be treated can be inserted and passed. In this way, the cylindrical body 3, i.e., the molten salt electrolytic bath 25 is relatively moved to the member 23 to be treated, by which the surface of the member 23 to be treated can be successively be formed with a coating layer, so that the coating layer can easily be formed by using the molten salt electrolytic bath 25 shallower than the length of the bar-shaped or tubular member to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten salt electrodeposition technique for forming a coating layer on a member surface, and more particularly to a molten salt electrodeposition technique for forming a coating layer on a rod-shaped or tubular member surface. About.

[0002]

2. Description of the Related Art In a process of forming a coating layer on a member surface by molten salt electrodeposition, in a conventional molten salt electrodeposition technique, a member to be processed is immersed in a molten salt electrolytic bath housed in a bath. A coating layer is formed on the member surface by performing molten salt electrodeposition.

[0003]

When a coating layer is formed on a rod-shaped or tubular member to be processed by a conventional molten salt electrodeposition technique, the molten salt has a depth corresponding to the length of the rod-shaped or tubular member. An electrolytic bath, that is, a tank containing a molten salt is required. However, the size of the tank is limited because the amount of the molten salt to be used increases and the size of the apparatus increases. For this reason, when forming a coating layer on a rod-shaped or tubular member to be processed by a conventional molten salt electrodeposition technique without increasing the size of the tank, a part of the rod-shaped or tubular member to be processed is partially melted in the molten salt electrolytic bath. To form a coating layer partially, and further immersing the remaining portion in a molten salt electrolytic bath in a tank to form a coating layer on the entire surface of the member to be processed. Is complicated. Furthermore, depending on the length of the member to be treated, molten salt electrodeposition may not be performed without increasing the size of the tank.

An object of the present invention is to make it possible to easily form a coating layer using a molten salt electrolytic bath that is shallower than the length of a rod-shaped or tubular member to be processed.

[0005]

SUMMARY OF THE INVENTION A molten salt electrodeposition apparatus of the present invention comprises: a cylindrical body for accommodating salt; salt melting means for heating and melting the salt except for the vicinity of the bottom of the cylindrical body; The tubular body includes an electrode disposed inside and a power supply unit electrically connected to the electrode and a rod-shaped or tubular member to be processed, and the cylinder has a bottom plate that closes a bottom portion. The above object is achieved by forming a through-hole through which a processing member can be inserted. Further, the salt melting means is configured to heat and melt the salt except for the vicinity of both ends of the cylindrical body.

Further, the molten salt electrodeposition method of the present invention comprises an electrodeposition step of forming a coating layer on the surface of a rod-shaped or tubular member to be treated in a molten salt electrolytic bath by molten salt electrodeposition. The above problem is solved by repeatedly performing a moving step of moving the molten salt electrolytic bath relative to the processing member in the axial direction of the member to be processed.

According to such a molten salt electrodeposition apparatus and a molten salt electrodeposition method, after a coating layer is formed on the surface of a portion of a member to be treated in a molten salt electrolytic bath melted by salt melting means, By moving the cylindrical body, that is, the molten salt electrolytic bath relative to the member to be processed, a coating layer can be formed on the surface of a different portion of the member to be processed. Forming a coating layer sequentially on a rod-shaped or tubular surface of the member to be processed by repeating the electrodeposition step of forming such a coating layer and the moving step of moving the molten salt electrolytic bath relative to the member to be processed. Can be. That is, the coating layer can be easily formed by using a molten salt electrolytic bath that is shallower than the length of the rod-shaped or tubular member to be processed.

By the way, since the salt in the cylindrical body is not heated by the salt melting means near the bottom or both ends of the cylindrical body, the partially melted salt is partially melted toward the bottom or both ends of the cylindrical body. It is a solid salt. The partially molten or solid salt provides a seal, such as to prevent the molten salt from flowing out of the bottom or to prevent the molten salt from contacting the atmosphere. But,
If the space between the bottom or both ends of the cylindrical body and the member to be processed is closed with solid salt, the solid salt fixes the space between the bottom of the cylindrical body and the member to be processed, and The relative movement of the cylinder may not be possible.

In view of the above, a structure including a member heating means for heating the member to be processed is adopted. Further, an electrodeposition step of forming a coating layer by molten salt electrodeposition on the surface of a portion of the rod-shaped or tubular member to be treated in the molten salt electrolytic bath by the molten salt electrolytic bath sealed with a solid salt; A method of repeatedly performing a solid salt melting step of melting the solid salt in contact with the member and a moving step of moving the molten salt electrolytic bath relative to the member to be processed in the axial direction of the member to be processed. If you do this,
When the member to be processed is heated by the member heating means, a portion of the solid salt in contact with the member to be processed is melted, so that the cylindrical body can be relatively moved with respect to the member to be processed, which is preferable.

Further, the member heating means comprises a first member heating means provided at one end of the cylindrical body and a second member heating means provided at the other end of the cylindrical body. And a molten salt electrodeposition apparatus having the following configuration. On the other hand, at the same time as the electrodeposition step, a preheating step of previously heating a portion of the member to be formed on which the coating layer is to be formed, and an interface between the coating layer and the member at the portion where the coating layer of the member to be processed is formed. And a diffusion process step of forming a diffusion layer on a different portion of the member to be processed.

According to the molten salt electrodeposition apparatus and the molten salt electrodeposition method, the first member heating means and the second member heating means each bring the member to be treated to a temperature required for the electrodeposition step. A preheating step of heating in advance and a diffusion processing step of forming a diffusion layer on the portion of the member to be processed on which the coating layer has been formed in the electrodeposition step can be performed at the same time, which is preferable. Furthermore, the first member heating means and the second member heating means can also perform a solid salt melting step. Further, it is preferable that the member heating means is a high-frequency heater because only the member to be processed made of a conductive material can be efficiently heated.

Further, if a seal member is provided in the through hole formed in the bottom plate of the cylindrical body, powdery salt at the bottom of the cylindrical body can be prevented from leaking out of the cylindrical body. preferable.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a molten salt electrodeposition apparatus to which the present invention is applied will be described below with reference to FIGS. FIG. 1 is a perspective view showing a schematic configuration of a molten salt electrodeposition apparatus to which the present invention is applied. FIG. 2 is a flowchart showing a procedure for forming the coating layer and the diffusion layer. FIG. 3 is a sectional view showing the operation of the molten salt electrodeposition apparatus. FIG. 4 is a flowchart showing steps of a molten salt electrodeposition method according to the present invention.

As shown in FIG. 1, a molten salt electrodeposition apparatus 1 according to the present embodiment is a cylindrical body 3 for accommodating salt, and an electric power serving as a salt melting means provided so as to surround a central portion outside the cylindrical body 3. The furnace 5, a cylindrical electrode 7 serving as an anode provided inside the central portion of the cylindrical body 3, high-frequency heaters 9 and 11 provided near both ends of the cylindrical body 3, and the electrode 7 are shown. The power supply 15 is electrically connected to the unprocessed member by the wiring 13. The cylindrical body 3 is formed of a refractory material, for example, ceramics, and is installed with its axis directed vertically. The bottom of the cylinder 3 has a bottom plate 17,
At the center of the bottom plate 17, a through hole 19 having substantially the same shape as the cross-sectional shape of the member to be processed is formed. A ring-shaped seal member 21 is attached to the through hole 19 and the inner peripheral surface portion. The high-frequency heater 9 is provided above the cylinder 3, and the high-frequency heater 11 is provided below the cylinder 3. Power supply 15
The positive electrode is connected to the electrode 7 serving as the anode, and the negative electrode of the power supply 15 is connected to the member to be processed (not shown) serving as the cathode via the wiring 13.

Here, a procedure for forming a coating layer on the surface of the member to be processed by molten salt electrodeposition and a diffusion layer at the interface between the member to be processed and the coating layer by diffusion treatment will be described. That is, as shown in FIG. 2, the coating layer and the diffusion layer are subjected to a pre-treatment step 101 in which acid cleaning is performed to remove stains, oxide films, and the like on the surface of the member to be processed on which the coating layer is formed. Preheating step 103 for raising the temperature to near the temperature at which molten salt electrodeposition is to be performed in advance, an electrodeposition step 105 for forming a coating layer on the surface of the member to be treated by molten salt electrodeposition, Diffusion treatment step 107 of forming a diffusion layer by heat treatment at the interface with the coating layer formed in the step, and after blowing off unnecessary molten salts on the surface of the member to be treated, washing the surface of the member to be treated after the melting. It is formed by a salt removal and washing step 109.

The operation of the molten salt electrodeposition apparatus of this embodiment and the features of the present invention will be described. In the present embodiment, a case will be described as an example in which a stainless steel tube is used as a member to be processed, and a silicon layer is formed as a coating layer and a silicide layer is formed as a diffusion layer on the surface of the tube. Further, the molten salt electrodeposition apparatus 1 of the present embodiment includes a preheating step 103, an electrodeposition step 1 in the coating layer and the diffusion layer forming steps shown in FIG.
05, and a device for performing the diffusion process step 107. Therefore, the pretreatment step 101 and the molten salt removing and washing step 109 are performed by a different device or equipment from the molten salt electrodeposition apparatus 1.

As shown in FIG. 3, a through hole 1 is formed in the cylindrical body 3.
From 9, a stainless steel tube 23 as a member to be processed is inserted coaxially. In a state where the member 23 to be processed is inserted into the cylindrical body 3, a powdery metal salt, for example, NaCl-KC
1 and a mixture of a powdery silicon compound. At this time, a gap between the through hole 19 formed in the bottom plate 17 of the cylindrical body 3 and the pipe 23 is sealed by the seal member 21, so that a powdery metal salt or the like leaks out of the cylindrical body 3. I'm preventing.

Among the powdered metal salts contained, the metal salt heated by the electric furnace 5, that is, the metal salt located at the center of the cylindrical body 3 is melted to become a molten salt, and the molten salt layer 25 is formed.
To form The powdered silicon compound is melted in the molten salt layer 25, and the molten salt layer 25 becomes a molten salt electrolytic bath in molten salt electrodeposition. The temperature of the metal salt contained in the cylindrical body 3 gradually decreases from the portion of the molten salt layer 25 heated by the electric furnace 5 toward the bottom and upper ends of the cylindrical body 3, that is, both ends. For this reason, as the metal salt moves from the molten salt layer 25 to both ends of the cylindrical body 3, the metal salt becomes a partially molten salt layer 27 in which the metal salt is partially melted, and the metal salt becomes a non-melted state, that is, a solid state. A certain solid salt layer 29 is formed. The solid salt layer 29 includes a powdery portion and a massive solid salt such as a salt that has once melted and solidified. In the molten salt electrodeposition apparatus 1 according to the present embodiment, the partial molten salt layer 27 and the solid salt layer 29 are connected to the molten salt leaking out of the molten salt layer 25 or the molten salt layer 25 is connected to the atmosphere outside the cylinder 3. It serves as a seal to prevent contact.

In this state, the molten salt electrodeposition apparatus 1 of this embodiment simultaneously performs the preheating step 103, the electrodeposition step 105, and the diffusion processing step 107 on different portions of the tube 23. As described above, the preheating step 103 includes the high-frequency heater 9
Is a step of heating the tube 23 to a temperature near the temperature at which molten salt electrodeposition is performed. The electrodeposition step 105 is a step of forming a silicon layer as a coating layer in the molten salt layer 25, that is, on the surface of the tube 23 in the molten salt electrolytic bath by molten salt electrodeposition.
The diffusion process 107 is performed by the high-frequency heater 11 for the pipe 2.
3 is a step of forming a silicide layer as a diffusion layer at the interface between the silicon layer formed in the electrodeposition step 105 and the pipe 23 by heating.

After the step having the longest processing time among the preheating step 103, the electrodeposition step 105, and the diffusion processing step 107 is completed, the molten salt electrodeposition apparatus 1 moves along the axial direction of the cylindrical body 3 and the pipe 23. And moves upward, that is, in the direction of arrow 31.
At this time, both ends of the cylindrical body 3 and the pipe 23 are fixed by the solid salt layers 29 formed at both ends of the cylindrical body 3. Therefore, the molten salt electrodeposition device 1 is
In order to move in the direction, it is necessary to release the fixing between the tube 23 and both ends of the cylindrical body 3 by the solid salt layer 29. For this reason, the high-frequency heaters 9 and 11 are operated to heat the portions of the tubes 23 located at both ends of the cylindrical body 3, and the tubes 2 of the solid salt layer 29 are heated.
After the surrounding portion 33 is melted, the molten salt electrodeposition apparatus 1 moves.

Accordingly, as shown in FIG. 4, the molten salt electrodeposition apparatus 1 of the present embodiment comprises
3, electrodeposition step 105, diffusion processing step 107, solid salt layer 2
9 by repeatedly repeating a solid salt melting step 111 for melting only the peripheral portion of the pipe 23 and a moving step 113 in which the molten salt electrodeposition apparatus 1 moves along the pipe 23.
On the surface of No. 3, a silicon layer as a coating layer and a silicide layer as a diffusion layer are successively formed.

As described above, in the molten salt electrodeposition apparatus and the molten salt electrodeposition method of the present embodiment, the electrodeposition step 10 for forming the coating layer is performed.
5 and the moving step 113 for moving the molten salt electrodeposition apparatus 1 are repeated, so that the molten salt layer 25 shallower than the length of the tube 23 moves along the tube 23 while the tube 23 in the molten salt layer 25 is moving. A coating layer can be sequentially formed on the partial surface of. Therefore, the coating layer can be easily formed by using a molten salt electrolytic bath that is shallower than the length of the rod-shaped or tubular member to be processed.

Further, since the coating layer can be easily formed by using a molten salt electrolytic bath which is shallower than the length of the rod-shaped or tubular member to be treated, the molten salt electrodeposition apparatus can be downsized. in addition,
The molten salt electrodeposition apparatus 1 of the present embodiment includes a high-frequency heater 9 for performing the preheating step 103 above the upper end of the cylindrical body 3.
The high-frequency heater 11 for performing the diffusion process 107 is provided below the bottom of the cylindrical body 3. Therefore, the preheating of the tube 23 before the electrodeposition step 105 and the formation of the diffusion layer after the formation of the coating layer after the electrodeposition step 105 can be performed at the same time, so that the working efficiency can be improved. Further, the molten salt electrodeposition apparatus includes an acid washer for performing the pretreatment step 101 above the high-frequency heater 9, and a blower and a cleaner for performing the molten salt removal and cleaning step 109 which are provided in the high-frequency heater 11. It is also possible to adopt a configuration provided below. With such a molten salt electrodeposition apparatus and a molten salt electrodeposition method that perform all the steps from the pretreatment step 101 to the molten salt removal and washing step 109 shown in FIG. 2, the working efficiency can be further improved. it can.

In this embodiment, the high-frequency heaters 9 and 11 are provided above and below both ends of the cylindrical body 3, respectively. However, when forming a diffusion layer or preheating a member to be processed separately, etc. It is not necessary to provide the high-frequency heaters 9 and 11 above and below both ends of the cylindrical body 3, respectively. For example, since the member heating means is used only to melt the portion 33 around the pipe 23 of the solid salt layer 29, the solid heating means is used to melt the portion 33 around the pipe 23 of the solid salt layer 29 efficiently. A high-frequency heater may be provided around the outside of the portion of the cylinder 3 where the salt layer 29 is located.

In this embodiment, the high-frequency heaters 9 and 11 are provided as the member heating means.
3 may be heated. However, it is preferable to use a high-frequency heater because a desired portion of the member to be processed, which is a conductive material, can be efficiently heated.

In this embodiment, the molten salt electrodeposition apparatus 1
Moves along the tube 23, but the molten salt electrodeposition device
What is necessary is just to move relatively with respect to a to-be-processed member. For example, a configuration in which the member to be processed moves along the axis of the cylindrical body of the molten salt electrodeposition apparatus may be employed. Further, in the present embodiment,
Although the case where the silicon layer and the silicide layer are formed on the stainless steel tube 23 is taken as an example, the present invention is not limited to this, and various rod-like or tubular conductive members to be treated are subjected to various kinds of molten salt electrodeposition. The present invention can be applied to a molten salt electrodeposition apparatus and a molten salt electrodeposition method for forming a surface coating layer.

[0027]

According to the present invention, a coating layer can be easily formed using a molten salt electrolytic bath which is shallower than the length of a rod-shaped or tubular member to be processed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of an embodiment of a molten salt electrodeposition apparatus to which the present invention is applied.

FIG. 2 is a flowchart showing a procedure for forming a coating layer and a diffusion layer.

FIG. 3 is a sectional view showing the operation of a molten salt electrodeposition apparatus to which the present invention is applied.

FIG. 4 is a flowchart showing steps of a molten salt electrodeposition method according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 molten salt electrodeposition apparatus 3 cylinder 5 electric furnace 7 electrode 9, 11 high-frequency heater 15 power supply 17 bottom plate 19 through hole 23 member to be processed 25 molten salt layer 27 partially molten salt layer 29 solid salt layer

Claims (8)

[Claims] 1. A cylindrical body in which salt is stored, salt melting means for heating and melting the salt except at least near the bottom of the cylindrical body, an electrode disposed inside the cylindrical body, and the electrode And a power supply unit electrically connected to the rod-shaped or tubular member to be processed, wherein the cylindrical body has a bottom plate that closes the bottom, and the bottom plate has a through hole through which the member to be processed can be inserted. A molten salt electrodeposition device in which holes are formed. 2. The molten salt electrodeposition apparatus according to claim 1, wherein the salt melting means heats and melts the salt except for near both ends of the cylindrical body. 3. The molten salt electrodeposition apparatus according to claim 1, further comprising a member heating means for heating the member to be processed. 4. The member heating means includes a first member heating means provided on one end side of the cylindrical body and a second member heating means provided on the other end side of the cylindrical body. The molten salt electrodeposition apparatus according to any one of claims 1 to 3, comprising a member heating means. 5. The molten salt electrodeposition apparatus according to claim 1, wherein said member heating means is a high-frequency heater. 6. An electrodeposition step of forming a coating layer on a surface of a rod-shaped or tubular member to be processed in a molten salt electrolysis bath by molten salt electrodeposition, and performing the molten salt electrolysis on the member to be processed. A molten salt electrodeposition method wherein a moving step of relatively moving the bath in the axial direction of the member to be treated is repeated to form a coating layer on the surface of the member to be treated sequentially. 7. An electrodeposition step of forming a coating layer by molten salt electrodeposition on the surface of a portion of the rod-shaped or tubular member to be processed in the molten salt electrolytic bath, using a molten salt electrolytic bath sealed with a solid salt. Repeating a solid salt melting step of melting the solid salt in contact with the member to be processed, and a moving step of moving the molten salt electrolytic bath relative to the member to be processed in the axial direction of the member to be processed. A molten salt electrodeposition method for sequentially forming a coating layer on the surface of the member to be treated. 8. A preheating step of preheating a portion of the member to be formed on which the coating layer is to be formed simultaneously with the electrodeposition step, and a step of forming a coating layer on the portion of the member to be processed where the coating layer is formed. The molten salt electrodeposition method according to claim 6, wherein a diffusion treatment step of forming a diffusion layer at an interface with the member to be treated is performed on different portions of the member to be treated.