JP2004183013A - Heat treatment method and heat treatment furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an economical heat treatment method of high production efficiency and heat efficiency by solving problems with in-furnace rail type and hearth-roller type batch furnaces. <P>SOLUTION: A heat treatment furnace has a pre-heating chamber 3, a heat treatment chamber 4 and a soaking chamber 5 via partition doors 1 and 2 inside a straight furnace body, and independently-driven hearth rollers 6, 7 and 8 are provided in the chambers 3, 4 and 5. When a work W is heat-treated, the hearth roller 7 in the heat treatment chamber 4 is stopped, and preferably, the hearth rollers 6 and 8 in the pre-heating chamber 3 and the soaking chamber 4 are rotated in the forward direction and the reverse direction to oscillate the work W. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a metal heat treatment method and a heat treatment furnace, and more particularly, to a roller hearth type heat treatment furnace and a heat treatment method therefor.
[0002]
[Prior art]
Conventionally, a furnace having a configuration shown in FIG. 5 has been provided as an in-furnace rail type heat treatment furnace. In the figure, reference numeral 10 denotes a charging table, 11 denotes a heat treatment chamber, 12 denotes an oil tank, 13 denotes an outlet conveyor, and W denotes a work (for example, see Patent Document 1).
[0003]
For example, in the case of the above-mentioned batch furnace of the in-furnace rail type, in the case of carburizing treatment, carburizing (930 to 1050 ° C.) and cooling and soaking (830 to 850 ° C.) are repeated in the same chamber. And there is a problem that production efficiency and heat efficiency are poor. Further, the furnace rail receiver is made of brick, brittle, and has a large heat storage amount, so that there is still a problem that the seasoning time is long.
[0004]
In addition, a furnace having a configuration shown in FIG. 6 is provided as a hearth roller type batch furnace. In the figure, the same parts as those in FIG. 4 are denoted by the same reference numerals. In the figure, reference numeral 14 denotes a hearth roller (for example, see Patent Document 2).
[0005]
For example, in the case of the carburizing process, the hearth roller type batch furnace repeats carburizing (930 to 1050 ° C.) and cooling and soaking (830 to 850 ° C.) in the same chamber in the same manner as the rail furnace batch furnace. In addition, there is a problem that it takes time to raise and lower the temperature and equalize the temperature, resulting in poor production efficiency and thermal efficiency. Further, in order to prevent the deformation of the hearth roller 14 in the high-temperature heat treatment chamber, a space for constantly rotating the hearth roller 14 forward and backward while the work W is supplied is required. The problem that heat radiation is large due to penetrating the wall remains (for example, see Patent Document 2).
[0006]
[Patent Document 1]
Japanese Patent No. 3103905 [0007]
[Patent Document 2]
JP-A-63-33552
[Problems to be solved by the invention]
The present invention solves the problems of the in-furnace-type and hearth-roller-type batch furnaces having the above-described configuration, and provides an economical heat treatment method with improved production efficiency and thermal efficiency, and a compact and economical heat treatment furnace for implementing the heat treatment method. The purpose is to provide.
[0009]
[Means for Solving the Problems]
The heat treatment method according to claim 1, wherein a preheating chamber, a heat treatment chamber, and a soaking chamber are provided inside a linear furnace body via a partition door, and each of the chambers is provided with a independently driven hearth roller. Wherein the hearth roller in the heat treatment chamber is stopped during the heat treatment of the work.
[0010]
According to the first aspect of the invention, since the inside of the furnace main body is partitioned by the partition door into the preheating and nitriding, heat treatment chamber, and the soaking chamber, the atmosphere and temperature control in various heat treatments can be accurately performed.
[0011]
Further, in the conventional roller hearth furnace, in order to prevent deformation of the hearth roller due to high-temperature heating, the hearth roller is rotated forward and reverse in the heat treatment chamber. However, in the present invention, the hearth roller is inverted in the heat treatment chamber. Do not rotate. That is, only forward rotation or inching is performed.
[0012]
As a result of the above, a space for reciprocating the work is not required, and the heat treatment chamber and the entire furnace body can be made compact. At the same time, the effect of stirring the atmosphere gas by the stirring fan, that is, the flow rate distribution of the atmosphere gas became more uniform, and it was confirmed that the uniform heat in the heat treatment chamber was improved. For example, it was confirmed that the temperature was ± 7.5 ° C. in the furnace in which the conventional hearth roller was rotated forward and backward, while the temperature was within ± 6.0 ° C. in the compact furnace according to the present invention. Thus, the quality of the processed product can be improved as compared with the conventional furnace.
[0013]
Further, the compactness of the heat treatment chamber is particularly effective because the heat treatment chamber is at a high temperature. In other words, the heater and burner required for heating, the power and gas consumption thereof and the cost thereof are reduced, and the cost of the heat insulating material and the like is greatly reduced.
[0014]
The heat treatment method according to claim 2, wherein a preheating chamber, a heat treatment chamber, and a soaking chamber are provided through a partition door inside the linear furnace body, and each of the chambers is provided with a independently driven hearth roller. In the preheating and soaking of the work, the hearth rollers of the preheating chamber and the soaking chamber are rotated forward and backward to swing the work, and the hearth roller of the heat treatment chamber is stopped during the heat treatment of the work. Is a heat treatment method.
[0015]
According to the second aspect of the present invention, in the heat treatment method in which the hearth roller of the heat treatment chamber is stopped during the heat treatment of the work, a uniformly preheated work can be supplied to the heat treatment chamber, and an accurate equalization of the heat-treated work can be achieved. Thermalization is possible.
[0016]
The heat treatment furnace according to claim 3, wherein a preheating chamber, a heat treatment chamber, and a soaking chamber are provided through a partition door inside the linear furnace body, and each of the chambers is provided with an independently driven hearth roller, The hearth rollers of the preheating chamber and the soaking chamber are rotatable forward and backward, and the hearth roller of the heating chamber is rotated only forward. Therefore, only normal rotation or inching is performed in the heat treatment chamber.
[0017]
According to the third aspect of the invention, the heat treatment method according to the first and second aspects can be easily performed, and at the same time, the work does not reciprocate in the heat treatment chamber. The whole furnace body can be made compact. This downsizing of the heat treatment chamber enables a significant cost reduction as described in connection with claim 1 above.
[0018]
In one embodiment of the heat treatment furnace according to claim 4, the hearth roller is a material in which a very small amount of tungsten, cobalt, or titanium is added to super heat-resistant steel to improve creep characteristics. Heat treatment furnace. According to the embodiment of the present invention, it is not necessary to rotate the hearth roller forward and reverse to prevent the deformation thereof in the heat treatment chamber as in the related art, and the heat treatment of the work is performed while the hearth roller is stopped. Therefore, no space is required for reciprocating the work, and the entire furnace body can be made compact. Further, since the diameter of the hearth roller can be reduced, the amount of heat radiation from both ends penetrating the furnace wall can be reduced.
[0019]
An embodiment of the heat treatment furnace according to claim 5 is characterized in that the furnace wall of the furnace main body is formed from a compression molding of a brick layer, a silica layer, titanium oxide and inorganic fibers from inside the furnace. Item 6. A heat treatment furnace according to item 3 or 4. According to the fifth embodiment of the present invention, the heat dissipation from the furnace surface is reduced along with the improvement of the heat insulating effect of the furnace wall, and an economic effect is obtained by saving heating energy. Further, the furnace wall thickness can be reduced, and at the same time, the shortening of the hearth roller and the effect of preventing the deformation of the hearth roller due to the shortening can be improved.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view of a heat treatment furnace according to the present invention and an embodiment of carburizing treatment, FIG. 2 is a schematic side view of a heat treatment furnace according to the present invention and an embodiment of nitrocarburizing treatment, and FIG. FIG. 4 is a schematic side view of a furnace and an example of a refining process, FIG. 4 is a sectional view of a furnace wall and an adiabatic temperature curve of the heat treatment furnace according to the present invention, FIG. 5 is a schematic side view of a conventional rail type batch furnace, and FIG. 1 is a schematic side view of a conventional hearth roller type batch furnace.
[0021]
In the heat treatment furnace 1 according to the present invention, as shown in FIGS. 1 to 3, a preheating chamber 3, a heat treatment chamber 4, and a soaking chamber 5 are provided via partition doors 1 and 2 inside a linear furnace body. Provided. In the figure, 10 is a charging table, 12 is an oil tank, and 13 is an outlet conveyor. Further, as a preferred example, in the embodiment shown in the drawings, the preheating chamber 3: the heat treatment chamber 4 and the soaking chamber 5: the heat treatment chamber 4 each have a size of 1: 3, and the entire length is almost the same as that of the conventional furnace. About three times the production volume.
[0022]
In the present invention, the preheating chamber 3, the heat treatment chamber 4, and the soaking chamber 5 are provided with independently driven hearth rollers 6, 7, and 8, respectively. Further, the hearth rollers 6 and 8 in the preheating chamber 3 and the soaking chamber 5 are configured to be freely rotatable in the normal and reverse directions, and the hearth roller 7 in the heat treatment chamber 4 is configured to be capable of only the normal rotation or inching.
[0023]
The hearth rollers 6, 7, and 8 have a creep characteristic enhanced by adding a small amount of tungsten, cobalt, and titanium to super heat resistant steel. It is not necessary to prevent the deformation by repeating the rotation. Therefore, a space for reciprocating the work W in the heat treatment chamber 4 is not required, and the heat treatment chamber and the entire furnace body can be made compact. In addition, since the diameter of the hearth roller can be reduced from, for example, 104 mm to 90 mm, the amount of heat radiation from both ends penetrating the furnace wall can be reduced.
[0024]
The deformation, specifically, the bending of the hearth roller has a great effect on the strength of the hearth roller and the temperature difference between the temperature of the work W and the furnace temperature. In this regard, the temperature difference between the temperature of the workpiece W and the furnace temperature is large in the preheating chamber 3. Therefore, in the preheating chamber 3, the hearth roller 6 is rotated forward and reverse to reduce the temperature difference. The deformation of the hearth roller 7 in the heat treatment chamber 4 can be minimized by supplying the heat treatment to the heat treatment chamber 4.
[0025]
In the heat treatment chamber of the carburizing furnace, the conventional product and the hearth roller according to the embodiment of the present invention were tried. In the case of the conventional product, the bending was less than 2 mm at the time of receiving, but after using for 3 months, the bending was 5 mm. While the above bend resulted in the necessity of replacement, the hearth roller according to the embodiment of the present invention was 0.3 mm at the time of receipt, but was kept at 1 mm or less even after eight months of use. Yes, there was no need for replacement.
[0026]
The above numerical values are measured by a dial gauge between a point 75 mm inward from the flanges at both ends of the hearth roller and a center point, and the conventional hearth roller is a case where normal rotation and reverse rotation are repeated. In this case, the hearth roller in the embodiment of the present application is a case where only the inching (stop and forward rotation) is performed.
[0027]
FIG. 4 shows a furnace wall structure and an adiabatic temperature curve diagram of the heat treatment furnace according to the present invention. That is, the furnace wall is composed of a 115 mm brick layer 15, a 85 mm silica layer 16, a 50 mm titanium and a compression molded layer 17 of inorganic fiber from the furnace. Looking at the adiabatic temperature curve, the surface temperature of the furnace body, which was maintained at 950 ° C. in the furnace, was 50.2 ° C. (atmospheric temperature: 20 ° C.). Became possible.
[0028]
The heat treatment furnace of the present invention is used for various heat treatments of metals. FIG. 1 shows one embodiment of the carburizing process. That is, the work W supplied to the charging table 10 is supplied to the preheating chamber 3 through a charging door (not shown), and the hearth roller 6 in the preheating chamber 3 is rotated forward and reverse to perform uniform preheating. Is
[0029]
Thereafter, the partitioning door 1 between the preheating chamber 3 and the heat treatment chamber 4 is opened, the hearth rollers 6 and 7 are driven, and the work W is transported to the heat treatment chamber 4 and, for example, the carbon potential 1. Carburizing treatment is performed at 0% and a predetermined temperature of 940 ° C. for a predetermined time of 540 minutes.
[0030]
In the heat treatment furnace shown in FIGS. 1 to 3, the carburization treatment in the heat treatment chamber 4 is performed without stopping the hearth roller 7 in the reverse direction. That is, the workpiece W is sequentially moved to a predetermined position in the heat treatment chamber 4 by rotating or inching the hearth roller 7 provided in the heat treatment chamber 4, and carburizing is performed without rotating the hearth roller 7 in the reverse direction.
[0031]
Specifically, in the case of the above-described carburizing treatment conditions, three blocks of the work W that can be transported and accommodated in the heat treatment chamber 4 are allowed to stay in the heat treatment chamber 4 for 540 minutes, respectively, so that the carburizing treatment is performed. As it is performed, the hearth roller 7 in the heat treatment 4 is rotated forward or inching and stopped, and the carburizing process is performed. At the same time, the work W that has been carburized is transported to the soaking chamber 5, and the next work W to be carburized is carried in from the preheating chamber 3.
[0032]
The work W which has been carburized in the heat treatment chamber 4 is conveyed to the heat equalization chamber 5 by opening the partitioning door 2 between the heat treatment chamber 4 and the heat equalization chamber 5 and driving the hearth rollers 7 and 8. The hearth roller 8 in the soaking chamber 5 is rotated forward and backward to lower the temperature to a predetermined soaking temperature, for example, 850 ° C., and maintain the soaking temperature.
[0033]
Thereafter, an opening / closing door between the soaking chamber 5 and the oil tank 12 (not shown) is opened to quench the soaking work W. When the quenching is completed, an exit door (not shown) is opened, and the work W is removed from the outlet conveyor 13. It is carried out to.
[0034]
As described above, in the heat treatment furnace shown in FIGS. 1 to 3, the work W is charged into the preheating chamber 3, the work W is transferred from the preheating chamber 3 to the heat treatment chamber 4, The transfer of the work W to the heat chamber 5, the transfer of the work W from the soaking chamber 5 to the oil tank 12, and the transfer of the work W from the oil tank 12 to the outlet conveyor 13 are efficiently and continuously performed. , The production efficiency is increased.
[0035]
FIG. 2 shows an embodiment of the soft nitriding treatment. That is, the work W supplied to the charging table 10 is supplied to the preheating chamber 3 through a charging door (not shown), and the hearth roller 6 in the preheating chamber 3 is rotated forward and reverse to perform uniform preheating. Is After that, the partition door 1 between the preheating chamber 3 and the heat treatment chamber 4 is opened, the hearth rollers 6 and 7 are driven, and the work W is transported to the heat treatment chamber 4, where the work W is mixed with the RX gas and the ammonia gas in a predetermined atmosphere. Then, for example, a soft nitriding treatment is performed at a predetermined temperature of 550 ° C. for a predetermined time of 120 minutes.
[0036]
When the soft nitriding treatment for a predetermined time is completed in the heat treatment chamber 4, the partition door 2 between the heat treatment chamber 4 and the heat equalizing chamber 5 is opened, the hearth rollers 7 and 8 are driven, and the work W is The work W is conveyed to the heat chamber 5 and the opening / closing door between the soaking chamber 5 and the oil tank 12 (not shown) is opened to quench the work W without going through the soaking step. When opened, the workpiece W is transported to the exit conveyor 13.
[0037]
FIG. 3 shows an embodiment of the refining process. That is, the work W supplied to the charging table 10 is supplied to the preheating chamber 3 via a charging door (not shown), and the hearth roller 6 in the preheating chamber 3 is rotated forward and reverse to perform uniform preheating. Will be After that, the partition door 1 between the preheating chamber 3 and the heat treatment chamber 4 is opened, the hearth rollers 6 and 7 are driven, and the work W is transported to the heat treatment chamber 4 to have a carbon potential of 0.3 to 3 in a predetermined atmosphere. In 0.5%, for example, a refining process is performed at a predetermined temperature of 880 ° C. for a predetermined time of 30 minutes.
[0038]
Subsequent steps are the same as in the case of the soft nitriding treatment, and quenching is performed without going through the soaking step.
[0039]
【The invention's effect】
According to the present invention, it is possible to provide a heat treatment method with improved production efficiency and heat efficiency, and a compact and economical heat treatment furnace for performing the heat treatment method.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a heat treatment furnace according to the present invention and a diagram showing an embodiment of a carburizing treatment.
FIG. 2 is a schematic side view of a heat treatment furnace according to the present invention and a diagram showing an embodiment of nitrocarburizing treatment.
FIG. 3 is a schematic side view of a heat treatment furnace according to the present invention and a diagram showing an embodiment of a heat treatment process.
FIG. 4 is a sectional view of a furnace wall and a diagram of an adiabatic temperature curve of the heat treatment furnace according to the present invention.
FIG. 5 is a schematic side view of a conventional rail-type batch furnace.
FIG. 6 is a schematic side view of a conventional hearth roller type batch furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Partition door 2 Partition door 3 Preheating room 4 Heat treatment room 5 Heat equalizing room 6 Hearth roller 7 Hearth roller 8 Hearth roller 15 Brick layer 16 Silica layer 17 Compression molding layer of titanium oxide and inorganic fiber

Claims (5)

In a heat treatment furnace in which a preheating chamber, a heat treatment chamber, and a soaking chamber are provided through a partition door inside a linear furnace main body, and each of the chambers is provided with an independently driven hearth roller, the heat treatment A heat treatment method comprising stopping a hearth roller in a chamber. In a linear furnace body, a preheating chamber, a heat treatment chamber, and a soaking chamber are provided through a partition door, and in each of the chambers, an independently driven hearth roller is provided. A heat treatment method, wherein the hearth rollers of the preheating chamber and the soaking chamber are rotated forward and backward to swing the work, and the hearth roller of the heat treatment chamber is stopped during the heat treatment of the work. Inside the straight furnace body, a preheating chamber, a heat treatment chamber, and a soaking chamber are provided via a partition door, and each of the chambers is provided with a independently driven hearth roller, and a hearth roller for the preheating chamber and the soaking chamber is provided. A heat treatment furnace, wherein the hearth roller of the heat treatment chamber is configured to rotate only forward and free to rotate forward and backward. 4. The heat treatment furnace according to claim 3, wherein the hearth roller is a material in which a very small amount of tungsten, cobalt, and titanium are added to super heat-resistant steel to improve creep characteristics. 5. 5. The heat treatment furnace according to claim 3, wherein the furnace wall of the furnace body is formed of a brick layer, a silica layer, a titanium oxide and a compression molded layer of inorganic fibers from inside the furnace.

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