JP5114933B2 - Tube heater of heat treatment furnace that can prevent deformation of the tube - Google Patents

Description

  The present invention relates to a tube heater for a heat treatment furnace. For example, when steel materials are carburized or annealed, and when metal powder moldings are dewaxed and sintered, various types of materials such as batch or continuous atmosphere furnaces and vacuum furnaces are used. A heat treatment furnace is used. For example, a processing chamber surrounded by a heat insulating material is formed in the furnace, and in the case of a heat treatment furnace equipped with a tube heater in the processing chamber, the steel material or the molded product as described above is charged in the processing chamber. The work is heated with a tube heater. The present invention relates to a tube heater for such a heat treatment furnace, and more particularly to a tube heater in which a heater for insulatingly supporting a resistance heating element is inserted in a tube.

  Conventionally, as a tube heater of a heat treatment furnace, one fixedly installed in the furnace is generally used. However, the conventional tube heater has a problem that the tube is deformed. When a low-temperature workpiece is inserted into a furnace heated to a predetermined temperature by a tube heater, the tube surface facing the workpiece is temporarily quenched, but the tube surface facing the furnace wall is cooled to such a degree. As a result, the tube is recessed and deformed to the workpiece side due to the difference in thermal shrinkage. When the tube heater is installed in the processing chamber surrounded by the heat insulating material, the tube surface on the side facing the heat insulating material is hardly cooled, so that the deformation of the tube is large. When the tube is deformed, the contact between the resistance heating element and the tube is caused by the contact of the workpiece with the conveying means in the furnace, the wear of the tube due to this contact, the damage of the insulating material supporting the resistance heating element, the damage of the insulating material If the heat treatment furnace is a vacuum heat treatment furnace, if the tube is cracked or perforated, the inside of the furnace Can not even be in a predetermined vacuum atmosphere.

Therefore, conventionally, in order to prevent the deformation of the tube that causes many troubles as described above, a tube heater that is rotatably mounted in a heat treatment furnace has been proposed (for example, see Patent Document 1). This conventional proposal has an advantage that the tube can be prevented from being deformed because the tube rotates and the side facing the workpiece changes. However, in this conventional proposal, it is necessary to equip the heat treatment furnace with a rotating mechanism of the tube heater, so that the structure becomes complicated, and in particular, the furnace shell and furnace body of the heat treatment furnace, and the tube heater that rotates with the heat insulating material, Since it is difficult to seal the gap, there is a problem that a sealing failure is likely to occur. If a sealing failure occurs, atmospheric gas leaks, conversely, the intrusion of the air, resulting in a turbulence in the furnace atmosphere, etc. If the heat treatment furnace is a vacuum heat treatment furnace, the inside of the furnace may even be set to a predetermined vacuum atmosphere. become unable.
JP 11-337270 A

  The problem to be solved by the present invention is to provide a tube heater for a heat treatment furnace having a simple structure and capable of preventing deformation of the tube without causing a seal failure between the heat treatment furnace and the tube heater.

The present invention that solves the above-mentioned problems is a tube heater that serves as a heating source for a workpiece charged in a heat treatment furnace, and an auxiliary heater on the side of the main heater facing the workpiece separately from the main heater in the tube There is inserted, according to the tube heater of the heat treatment furnace capable of preventing the deformation of the tube you characterized in that the current supply to said auxiliary heater made so as to separately control the main heater.

  The heat treatment furnace to which the present invention is applied is a batch type or used for, for example, carburizing or annealing of steel materials, or for dewaxing and sintering metal powder molded products. Is a continuous atmosphere furnace or vacuum furnace. Among them, a processing chamber surrounded by a heat insulating material is formed in the furnace, a tube heater is provided in the processing chamber, and a furnace for heating a workpiece by the tube heater in the processing chamber, particularly a vacuum furnace The effect is significant.

  The tube heater to which the present invention is applied is a tube in which a heater for insulatingly supporting a resistance heating element is inserted. Such a tube heater includes a resistance heating element supported by an insulator and having a space between the resistance heating element and the tube, an outer periphery of the resistance heating element covered with an insulating material, a resistance heating element, There are various types such as those filled with an insulating material between the tube, those having both of these, and those having a protective tube.

  In the tube heater of the heat treatment furnace according to the present invention, an auxiliary heater is inserted into the tube on the side facing the workpiece of the main heater separately from the main heater. These main heaters and auxiliary heaters are both heaters as described above. However, the main heater and auxiliary heater have separate control systems for energizing these resistance heating elements, and the auxiliary heater is connected to the resistance heating element. The energization is controlled separately from the main heater.

  The workpiece charged in the furnace is usually heated by energizing the resistance heating element of the main heater. However, when a new low-temperature workpiece is inserted into the furnace and the tube surface facing the workpiece is cooled, the auxiliary heater is energized to heat the tube surface. Thereby, cooling of the tube surface on the side facing the workpiece is prevented, and deformation of the tube is prevented.

  According to the tube heater of the heat treatment furnace according to the present invention, deformation of the tube can be prevented with a simple structure without causing a seal failure between the heat treatment furnace and the tube heater.

  FIG. 1 is a partially omitted longitudinal sectional view illustrating a tube heater of a heat treatment furnace according to the present invention, and FIG. 2 is a partially omitted transverse sectional view showing a tube heater of the same heat treatment furnace as that of FIG. Here, the tube heater equipped in the dewaxing chamber of the roller hearth type continuous vacuum heat treatment furnace is shown. Since the roller hearth type continuous vacuum heat treatment furnace itself is known, the entire illustration is omitted, and the cylindrical furnace shell and a part of the heat insulating material forming the dewaxing chamber in the furnace shell are omitted. However, a total of six tube heaters 21 to 26 are inserted into the dewaxing chamber 11 through the furnace shell and the ceiling wall 12 of the heat insulating material forming the dewaxing chamber 11. A plurality of transfer rollers 13 are laid in the dewaxing chamber 11, and a work 14 is placed on these rollers 13. A total of three tube heaters 21 to 23 are placed on the left side of the work 14. Are arranged in a straight line at substantially equal intervals, and a total of three tube heaters 24 to 26 are also arranged in a straight line at substantially equal intervals on the right side.

  The tube heater 21 includes a cylindrical tube 31 with a distal end sealed and a proximal end opened, a main heater 41 inserted in the axial direction of the tube 31, and a main heater 41 separately from the main heater 41. The auxiliary heater 51 inserted in the axial direction in the tube 31 on the side facing the workpiece 14, the sealing plug 61 fixed to the open base end of the tube 31, and the sealing plug 61 are taken out to the outside. The terminal 71 of the main heater 41 and the terminal 81 of the auxiliary heater 51 are provided. The main heater 41 and the auxiliary heater 51 include resistance heating elements 41 a and 51 a and an insulator 91 that supports them. The resistance heating element 41 a of the main heater 41 is connected to the terminal 71, and the resistance heating of the auxiliary heater 51 is also performed. The body 51a is connected to a terminal 81, the terminal 71 is connected to a control system that controls energization to the main heater 41, and the terminal 81 is connected to a control system that controls energization to the auxiliary heater 51, The energization of the auxiliary heater 51 is controlled separately from the main heater 31.

  The other tube heaters 22 to 26 also have the following relationships: the tubes 32 to 36, the main heaters 42 to 46, the resistance heating elements 44a and 54a, the auxiliary heaters 52 to 56, the sealing plug 64, the terminals 74 and 84, and the insulator 94. Since it is the same as that of the tube heater 21 demonstrated above, description is abbreviate | omitted here.

  The work charged into the dewaxing chamber 11 by the roller 13 is normally performed by energizing the resistance heating elements 41a, 44a,. However, when a new low-temperature work 14 is inserted into the dewaxing chamber 11 and the surfaces of the tubes 31 to 36 facing the work 14 are cooled, the resistance heat of the auxiliary heaters 51 to 56 is generated. Energizing the bodies 51a, 54a,... Heats the surfaces of the tubes 31-36. Thereby, cooling of the surface of the tubes 31-36 on the side facing the workpiece 14 is prevented, and deformation of the tube is prevented.

The longitudinal cross-sectional view of a part omission which illustrates the tube heater of the heat processing furnace which concerns on this invention. FIG. 2 is a partially omitted cross-sectional view showing a tube heater of the same heat treatment furnace as in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Dewaxing chamber 12 Ceiling wall of heat insulating material 13 Roller 14 Work 21-26 Tube heater 31-36 Tube 41-46 Main heater 41a, 44a, 51a, 54a Resistance heating element 51-56 Auxiliary heater 61, 64 Seal plug 71, 74 81, 84 Terminal 91, 94 Insulator

Claims (2)

A tube heater serving as a heating source for a workpiece charged in a heat treatment furnace, and an auxiliary heater is inserted into the tube on the side facing the workpiece of the main heater separately from the main heater. tube heater of the heat treatment furnace capable of preventing the deformation of the tube you characterized by comprising as separately controlled from the main heater energization. Is intended heat treatment furnace processing chamber surrounded by the heat insulating material in the furnace is formed, and the thermal processing furnace tube heater can be prevented deformation of the tube according to claim 1, wherein the one which is equipped with the processing chamber Tube heater.

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