JP2006137964A - Continuous vacuum carburizing furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous carburizing furnace for a few varieties of workpieces which are to be mass-produced and are required to be comparatively deeply carburized in a short cycle time, at the low initial cost, maintenance cost and running cost of a facility. <P>SOLUTION: This continuous carburizing furnace has a heating chamber 2, a carburizing chamber 3, a diffusion chamber 4 and a cooling chamber 5 placed in series, wherein each of the heating chamber 2, the carburizing chamber 3, the diffusion chamber 4 is composed so as to accommodate a plurality of trays or baskets 10 (hereafter called tray 10) each of which accommodates the workpiece of ferro-alloy parts. The continuous carburizing method includes sequentially carrying one tray 10 which accommodates the workpiece out in a predetermined cycle time, while carrying the same number of the trays 10 in. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a continuous vacuum carburizing method for an iron alloy part in which a heating chamber, a carburizing chamber, a diffusion chamber, and a descending chamber are arranged in series, and an improvement of the continuous vacuum carburizing furnace.

The conventional continuous vacuum carburizing furnace for batch-feeding iron alloy parts is, for example, the continuous vacuum carburizing furnace as shown in Fig. 5 of AD Update in VACUUM-BASED CARBURIZINNG issued in June 1998 by ADVANNCED METALS & PROCESSES magazine F Preisser et al. Are known. This continuous vacuum carburizing furnace is an independent diffusion chamber separated by a vacuum seal door having a plurality of stations after vacuum carburizing in an independent carburizing chamber partitioned by a plurality of vacuum seal doors, following the temperature raising chamber. It was diffused with.
FIG. 2 of Patent Document 1 describes a continuous vacuum carburizing furnace that can accommodate a plurality of trays or baskets in each of a temperature raising chamber, a carburizing / diffusion chamber, and a descending greenhouse arranged in series. Describes a continuous vacuum carburizing furnace having a plurality of carburizing and diffusion chambers arranged in series and having a temperature raising function. Patent Document 3 discloses a temperature raising, carburizing, diffusion, and temperature lowering function arranged in series, respectively. A continuous vacuum carburizing furnace is described having a plurality of heating chambers with:
Japanese Patent No. 3302967 Japanese Patent No. 3547700 Japanese Patent Laid-Open No. 2003-155552

  However, the vacuum carburizing treatment method, as is well known, must strictly control the carburizing time (Tc) and diffusion time (Td) and change each time ratio (Td / Tc) according to the carburizing temperature. It is. For example, when the processing temperature is changed from 930 ° C. to 1040 ° C., the ratio (Td / Tc) must be changed greatly from 1.5 to 3.5. In particular, when the required carburization depth is deep, the processing time required for diffusion accounts for most of the total carburizing time. In the continuous carburizing furnace in Fig. 5 of "UPDATE ON VACUUM-BASED CARBURIZINNG" above, an example is shown in which three baskets or trays are placed in the heating chamber and one in each subsequent chamber. When Td / Tc) is 1.5, it is necessary to adjust the cycle time of the carburizing chamber and diffusion chamber to 0.25 in the carburizing chamber and 1.25 in the diffusion chamber. The cycle time for each of the carburizing chamber and the diffusion chamber is very long. If the production time is large due to deep carburization, that is, if the cycle time is short, multiple lines of continuous carburizing furnaces are required, which requires a lot of space and cost. Need.

  As a solution to this problem, in Patent Document 1, a plurality of trays or baskets can be accommodated in each of the heating chamber, the carburizing / diffusion chamber, and the descending chamber arranged in series, and the ratio (Td / Tc) can be flexibly accommodated. A carburizing furnace is disclosed, and in Patent Document 2 and Patent Document 3, each has a plurality of heating chambers having a temperature raising, carburizing and diffusing function so that each step of temperature raising, carburizing and diffusing can be performed. The proposal discloses a continuous carburizing furnace in which each chamber is leveled so as to enter a predetermined cycle time as a furnace body, but the carburizing chamber has a carburizing pressure control device, a carburizing gas nozzle and a flow rate adjusting device. Of course, many devices such as a burnout device in a carburizing chamber are required as compared with a temperature raising chamber and a diffusion chamber, the initial cost is high, and there are many complicated devices, so that maintenance costs are also high. In Patent Document 1, a large carburizing / diffusion chamber capable of accommodating a plurality of trays or baskets is used, which increases the cost of the carburizing chamber. In Patent Document 2 and Patent Document 3, a plurality of carburizing chambers are provided. Having it increases the amount of carburizing gas and increases the initial cost and running cost. Furthermore, since the metal in the carburizing chamber is made of an iron-based material and is expected to shorten its life, it is necessary to use a material that is not easily carburized, such as ceramics. Therefore, continuous carburizing furnaces with large carburizing / diffusion chambers and multiple heating chambers with multiple functions are flexible and advantageous for various workpieces, but deep carburizing is particularly required, and continuous carburizing furnaces for mass production workpieces. However, there was a problem that the cost was high in view of the initial cost, maintenance cost, and running cost of the equipment.

  The object of the present invention is to solve the problems of the prior art, requiring a relatively deep carburizing, and a continuous carburizing furnace for a small-scale, high-volume production work with a short cycle time, reducing the initial cost, maintenance cost, and running cost of equipment. Each is to be provided at a low cost.

  For this reason, the present invention is a continuous vacuum carburizing furnace for iron alloy parts in which a heating chamber, a carburizing chamber, a diffusion chamber, and a descending chamber are arranged in series, and each of the carburizing chamber and the diffusion chamber can accommodate a plurality of trays or baskets, The continuous vacuum carburizing method and the continuous vacuum carburizing furnace characterized in that a corresponding number of trays or baskets are carried out while sequentially carrying in one tray or basket every predetermined cycle. Settled.

  In the present invention, the carburizing chamber and the diffusion chamber can each accommodate a plurality of trays or baskets, and carry out a corresponding number of trays or baskets while sequentially loading one tray or basket every predetermined cycle. The continuous vacuum carburizing method and the continuous vacuum carburizing furnace are characterized in that the initial vacuum, maintenance cost, and running cost of the equipment are low, especially for high-volume production work that requires deep carburizing. A method and continuous vacuum carburizing furnace were provided.

  The best mode for carrying out the present invention will be described with reference to the drawings. In each drawing, FIG. 1 shows a first embodiment of the present invention, an elevational schematic block cross-sectional view of a continuous vacuum carburizing furnace with a carburization depth of 1.2 mm and a cycle time of 15 minutes (each chamber is below it). FIG. 2 shows a second embodiment of the present invention, and shows a vertical vacuum carburizing furnace elevation of 1.6 mm carburizing depth and a cycle time of 26 minutes, including a processing time chart for one tray or basket. FIG. 3 is a schematic block cross-sectional view, FIG. 3 is a vertical schematic block cross-sectional view of a continuous vacuum carburizing furnace showing a third embodiment of the present invention, a carburization depth of 1.6 mm, and a cycle time of 15 minutes, and FIG. Fig. 2 shows an elevational schematic block cross-sectional view of a continuous vacuum carburizing furnace having a plurality of (three) carburizing and diffusion chambers having a temperature raising function shown in Patent Document 2 and a carburizing depth of 1.2 mm and a cycle time of 40 minutes. .

  As shown in FIGS. 1 to 3, the continuous vacuum carburizing method and the continuous vacuum carburizing furnace according to the best mode for carrying out the present invention are separated by a vacuum door 9 and are independent of each other, a heating chamber 2 and a carburizing chamber 3. In the continuous vacuum carburizing furnace of iron alloy parts in which the diffusion chamber 4 and the descending chamber 5 are arranged in series, each of the temperature raising chamber 2, the carburizing chamber 3, and the diffusion chamber 4 has a plurality of (for example, four in FIG. 1) iron alloy components. A tray or basket 10 (hereinafter referred to as “tray 10”) containing a workpiece can be accommodated, and the tray 10 containing the workpiece is moved from the left to the right as viewed in the figure with an internal feeding device such as a walking beam (not shown). As described above, one tray 10 is sequentially loaded every predetermined cycle, and a corresponding number of trays 10 are unloaded. In FIG. 1, the descending greenhouse 5 can accommodate three trays, and the quenching chamber 6, the loading chamber 1, and the unloading chamber 7 can each accommodate one tray 10.

  Fig. 1 shows an example of a process for a steel SCM 420 material iron alloy part work with a required carbon concentration of 0.3% at a carburization depth of 1.2 mm from the surface, and the cycle time is 15 minutes / tray. In operation, the entrance door 8 of the carry-in chamber 1 is opened, a single tray 10 is carried into the carry-in chamber 1, the entrance door 8 is closed, and the inside of the carry-in chamber 1 is evacuated to about 0.05 kPa and depressurized. The inlet vacuum door 9 of the heating chamber 2 is opened and one tray 10 is carried into the heating chamber 2 from the carry-in chamber 1, and at the same time, the outlet vacuum door 9 of the heating chamber 2 is opened and the top 4 of the four rising One tray 10 is carried into the carburizing chamber 3 in the right direction by one pitch at a cycle time of 15 minutes. At the same time, the outlet vacuum door 9 of the carburizing chamber 3 is opened, and one tray 10 of the leading four of the four is loaded into the diffusion chamber 4 in the right direction by one pitch every 15 minutes of cycle time. Are sequentially carried into and out of the descending greenhouse 5, the quenching chamber 6 and the unloading chamber 7. The temperature rising chamber 2 is heated and maintained at about 1000 ° C., and the iron alloy part work on the tray 10 carried in from the loading chamber 1 is 13 minutes after soaking for 2 minutes, including the transfer time, and then 15 minutes each. The temperature is raised for 15 minutes for a total of 60 minutes.

  The temperature of the carburizing chamber 3 is raised and maintained at about 1000 ° C., and the pressure is reduced to about 0.05 kPa. The tray 10 of the carburized 1 carried into the carburizing chamber 3 from the temperature rising chamber 2 has an inlet / outlet vacuum door. After 9 is closed and soaked for 2 minutes including the transfer time, the carburizing gas is supplied for 4 minutes while controlling the ethylene gas as the carburizing gas to the indoor pressure of 2 kPa, then the carburizing gas is stopped and the indoor pressure is reduced to about 0.05 kPa. And then diffuse for 9 minutes (2 minutes soaking time including transport time is diffused when moving from the heating chamber 2 of the immersion 10 tray 10 to the carburizing chamber 3 because it passes through a low temperature area. Not added to time). Since the tray 10 for immersion 2 to immersion 4 is moved while being heated and maintained at about 1000 ° C. in the carburizing chamber 3, diffusion is performed for 2 minutes, so diffusion is performed for 9 minutes. However, it is added to the diffusion time of 11 minutes in total including the transfer time of 2 minutes. The iron alloy part work of each tray 10 in the carburizing chamber 3 has a total carburizing time of 16 minutes and a total diffusion time of 42 minutes in 4 cycles.

  The inside of the diffusion chamber 4 is heated and maintained at about 1000 ° C. and depressurized to about 0.05 kPa. The expanded tray 10 carried into the diffusion chamber 4 is transported with the inlet / outlet vacuum door 9 closed. After soaking for 2 minutes including the time, it is diffused for 13 minutes. (When the tray 10 in the immersion 1 is moved from the carburizing chamber 3 into the diffusion chamber 4, it passes through a low temperature area, so the 2 minutes soaking including the transport time is taken. (The heat time is not added to the diffusion time.) The trays 10 to 2 are expanded while being heated and maintained at about 1000 ° C. in the diffusion chamber 4, so that the transfer time is 2 minutes. Since it is diffused, even if diffusion is performed for 13 minutes, it is added to the diffusion time of 15 minutes in total including the conveyance time of 2 minutes. Each tray 10 in the diffusion chamber 4 has a total diffusion time of 58 minutes in 4 cycles. The diffusion time is 100 minutes in total in the carburizing chamber 3 and in the diffusion chamber 4, and the total carburizing time (Tc) 16 Minutes, the total diffusion time (Td) is 100 minutes, and the time ratio (Td / Tc) is 6.25.

Three trays 10 are placed in the descending greenhouse 5 and one tray 10 is placed in the quenching chamber 6 and the unloading chamber 7, respectively. Then, after being quenched in the quenching chamber 6, it is unloaded from the unloading chamber 7. As a result of the above treatment, the iron alloy part workpiece obtained a carbon concentration of 0.3% and a surface carbon concentration of 0.8% at a carburization depth of 1.2 mm from the surface. In the embodiment shown in FIGS. 1 to 3, the temperature drop chamber 5 is a vacuum temperature drop method, but may be a convection temperature drop method using N ₂ gas.

  4 has three carburizing / diffusion chambers 13 having a temperature raising function shown in Patent Document 2 for comparison, carburizing temperature, diffusion temperature of about 1000 ° C, carburizing depth of 1.2 mm, cycle time of 40 An elevational schematic block cross-sectional view of a continuous vacuum carburizing furnace implemented in minutes and a processing time chart for each tray or basket in each chamber are shown below, and processing was performed under the same processing conditions as in FIG. In FIG. 4, in carburizing and diffusion chambers 13 of the carburizing and diffusing chamber 13, 5 minutes of carburizing and 14 minutes of diffusion and 2 minutes of carburizing and 17 minutes of diffusion after a transfer time of 2 minutes, respectively. In Carrying 3, Carrying Time 2 minutes, Carrying 2 minutes and 36 minutes diffusion, Total carburizing time 16 minutes, Total diffusion time 98 minutes, Time ratio (Td / Tc) is 6.125. Thus, carburization with a carburization depth of 1.2 mm and a carbon concentration of 0.3% was obtained from almost the same surface as the embodiment of FIG. 1, but the cycle time was 40 minutes, and the cycle time of the embodiment of FIG. If necessary, two or three continuous vacuum carburizing furnaces as shown in FIG. 4 are required, which increases the cost in terms of the initial cost, maintenance cost, and running cost of the equipment.

  FIG. 2 shows a second embodiment of the present invention, an elevational schematic block sectional view of a continuous vacuum carburizing furnace having a carburization depth of 1.6 mm and a cycle time of 26 minutes, and one tray in each chamber below it. Alternatively, in the processing time chart of the basket, processing was performed under the same processing conditions as in FIG. The time ratio (Td / Tc) was 4.66 with a total carburization time of 36 minutes and a total diffusion time of 168 minutes.

  FIG. 3 shows a third embodiment of the present invention, an elevational schematic block sectional view of a continuous vacuum carburizing furnace having a carburization depth of 1.6 mm and a cycle time of 15 minutes, and one tray for each chamber below it. Alternatively, the processing was performed under the same processing conditions as in the basket processing time chart and FIG. With a total carburization time of 36 minutes and a total diffusion time of 170 minutes, the time ratio (Td / Tc) is 4.72, which is almost the same as the example of FIG. Although the cycle time was 15 minutes, the cycle time of the embodiment of FIG. 2 was 26 minutes, and the cycle time was increased by increasing the number of storage trays or baskets in the carburizing chamber 3 and the diffusion chamber 4 by two each. Easily shortened by 38%.

[Effects of the best mode for carrying out the invention]
As described above, in the best mode for carrying out the present invention shown in FIGS. 1 to 3, each of the carburizing chamber and the diffusion chamber can accommodate a plurality of trays or baskets, one for each predetermined cycle. A continuous vacuum carburizing method and a continuous vacuum carburizing furnace characterized in that a corresponding number of trays or baskets are carried out while sequentially feeding trays or baskets, and the carburizing chamber is made up of one furnace body. For example, pressure control devices, flow control devices, burnout devices, etc., such as indoor hardware that requires the use of ceramics, etc., need only be placed in this carburizing chamber. The diffusion chamber has a heat source that maintains a predetermined temperature and a predetermined pressure. It is only necessary to have a holding pressure control device, especially for high-volume production work where deep carburization is required. DOO was running costs respectively become as providing a continuous vacuum carburizing method and continuous vacuum carburizing furnace with low cost.

FIG. 1 is a schematic block cross-sectional view of a vertical vacuum carburizing furnace of a continuous vacuum carburizing furnace having a carburization depth of 1.2 mm and a cycle time of 15 minutes, showing a first embodiment of the present invention, and a tray or basket for each tray or basket below it. Processing time chart. Elevated schematic block cross-sectional view of a continuous vacuum carburizing furnace showing a second embodiment of the present invention with a carburization depth of 1.6 mm and a cycle time of 26 minutes, and a tray or basket for each one of each chamber below it. Processing time chart. Elevated schematic block cross-sectional view of a continuous vacuum carburizing furnace showing a third embodiment of the present invention with a carburization depth of 1.6 mm and a cycle time of 15 minutes and one tray or basket in each chamber below it. Processing time chart. Elevated schematic block cross-sectional view of a continuous vacuum carburizing furnace with a carburizing depth of 1.2 mm and a cycle time of 40 minutes having a plurality of (three) carburizing / diffusion chambers as shown in Patent Document 2 for comparison And a processing time chart of each one tray or basket in each chamber below.

Explanation of symbols

2. Heating room 3. Carburizing room 4. Diffusion room 5. Greenhouse
10. ・ Tray or basket containing workpieces of iron alloy parts

Claims (2)

In a continuous vacuum carburizing furnace for iron alloy parts in which a heating chamber, carburizing chamber, diffusion chamber and descending chamber are arranged in series,
The carburizing chamber and the diffusion chamber can each accommodate a plurality of trays or baskets, and carry out a corresponding number of trays or baskets while sequentially loading one tray or basket every predetermined cycle. Continuous vacuum carburizing method. In a continuous vacuum carburizing furnace for iron alloy parts in which a heating chamber, carburizing chamber, diffusion chamber and descending chamber are arranged in series,
The carburizing chamber and the diffusion chamber can each accommodate a plurality of trays or baskets, and carry out a corresponding number of trays or baskets while sequentially loading one tray or basket every predetermined cycle. Continuous vacuum carburizing furnace.

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