JPS6333552A - Batch operated carburizing furnace - Google Patents

Abstract

PURPOSE:To shorten the time for heating up and cooling down and to improve a carburizing treatment capacity by constituting a furnace body of ceramic fibers, supporting both ends of conveying rollers povitally on the furnace wall, providing cooling tubes to the inside of the furnace body and passing a refrigerant in the tubes. CONSTITUTION:The entire part of this batch operated carburizing furnace 1 is constituted of the ceramic fibers. Steel materials 21 are moved through a purging chamber 12 into the furnace body 1 by the conveying rollers 3 which are pivotally supported at both ends to the outside wall of the furnace wall 1b. The steel materials are subjected to radiation heating by the radiant tubes 7 in a carburizing gaseous atmosphere and are thus subjected to the carburizing treatment. A cold gas is then passed into the cooling tubes 8 to decrease the temp. in the furnace 1 forcibly so that the steel materials 21 are forcibly cooled. The amt. of the carburization diffusion is thereby quantitatively recognized. The treated steel materials 21 are passed through the purging chamber 12 and is immersed into a hardening tank 11, by which the materials are quickly cooled. Heat energy is economized by the above-mentioned mechanism, by which the treatment capacity of the carburizing furnace is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a batch type carburizing furnace for surface treating steel materials by gas carburizing method.

[Problems with the conventional technology] Carbon is applied to the surface of the steel material by heating and soaking the steel material to the required carburizing temperature (850°C to 950°C) in a carburizing gas atmosphere such as CO-based gas or hydrocarbon-based gas. A patch treatment type carburizing furnace for hardening the surface of a steel material by infiltration is conventionally known as a set of tray pushers as shown in FIGS. 4 and 5. That is, this furnace body a has a finger-shaped hearth with bricks, on which three roller conveyors C9C are arranged in two rows, radiant tubes d, d, etc. are installed on the inner surface of the side walls, and fans are installed on the ceiling. e was provided, and the load of the steel g on the tray f was applied to the brick hearth via the columveyors C and e. However, although bricks generally have excellent load-bearing capacity, they have a large heat capacity, so they have the disadvantage that it takes a very long time to raise the temperature, for example, when the furnace is stopped for one to two days and then used for the first time in the morning. Ta.

Moreover, FIG. 6 shows a temperature curve of steel material carburized by this carburizing furnace. As shown in the figure, in this case, generally after heating the steel material to a carburizing temperature of 850 to 950°C,
By lowering and maintaining the temperature at 50 to 850°C, deformation and crystal grain enlargement are prevented. However, since the conventional carburizing furnace shown in FIG. 1 uses natural cooling, it takes more than one hour to lower the temperature to the target temperature. As a result, not only does the required processing time become longer as a whole, resulting in poor processing efficiency, but because the temperature is lowered slowly over time, it is difficult to quantitatively grasp the amount of carburizing diffusion, making it difficult to achieve the desired target accuracy of carburizing processing. The problem was that it was difficult to do.

[Means for Solving the Problems] The present invention aims to provide a batch type carburizing furnace that can solve the above problems. The furnace is characterized in that a conveyor roller which is pivotally supported on the outside of the side wall is arranged in a row, and a cooling tube through which a cooling medium can flow is arranged inside the furnace body.

[Function] By configuring the entire furnace body with ceramic fibers having a small heat capacity, the amount of heat stored in the furnace body is reduced, and the time for heating up during use, etc. can be shortened, and the time for cooling down can also be shortened to some extent. Furthermore, by using a cooling tube to further shorten the temperature drop time, processing capacity can be improved and quality can be stabilized.

[Example] FIG. 1 and FIG. 2 show a batch type carburizing furnace according to the present invention.

In the figure, l represents a ceiling wall 1a and a side wall 1b.

A furnace body whose bottom wall 1c is entirely made of ceramic fiber, 2 a support frame that supports the outside of the furnace body, 3゜3...
1 shows a conveying roller whose both ends are supported by bearings 4, 4 fixed to the outside of the side wall 1b, and 5 indicates a sprocket for rotationally driving the roller. 6 is a fan installed in the ceiling, 7
．． 7... are heating radiant tubes provided on the inner wall of the furnace, and 8, 8... are cooling tubes provided at intervals between the radiant tubes. Incidentally, a burner is provided at one end of the radiant tubes 7, 7, . . . to blow out a flame into the tube. Moreover, an on-off valve is provided at one end of the cooling tubes 8.8, . . . so that outside air as a cooling medium can be introduced into the tubes. 9 is an opening/closing door that covers the charging/extracting port established on one end wall of the furnace body 1;
0 indicates the cylinder that opens and closes this.

On the other hand, 11 is a quenching tank storing quenching fluid, 12 is a purge chamber formed on the quenching tank, and 13 is a track truck. The purge chamber 12 has an opening 514 on the wall facing the track truck 13.
Opening/closing and 5% 15 are provided on the wall facing the furnace body 1, respectively.
These are opened and closed by cylinders 16 and 17, respectively. In the purge chamber 12, a hanging frame 18 is suspended from a cylinder 19 provided outside the ceiling and is movable up and down. . . . and rollers 20, 20, . Note that 23 is an outlet connected to a circulation pump that stirs the quenching liquid in the quenching tank 11.

However, in the batch type carburizing furnace configured in this way, the steel material 21 on the tray 22 carried on the track truck 13 is charged into the purge chamber 12, and the purge chamber 12 is filled with a non-oxidized, non-decarburized material. After the steel material is replaced with a reactive gas, the steel material is moved into the furnace body 1. In the furnace body 1, the steel material 21 is radiantly heated by radiant tubes 7, 7, etc. in a carburizing atmosphere gas, heated to 850 to 950°C as shown in Fig. 3, and kept at that temperature for 2 hours. While the steel is left for a while, carbon carburizes and diffuses from the steel surface. Thereafter, the steel material 21 is cooled to 750 to 850° C. in about 20 to 30 minutes by passing cold air through the Guhring tubes 8, 8, . . . to forcefully lower the temperature inside the furnace. In this way, steel material 21 can be cooled in a relatively short time by forced cooling.
By lowering the temperature, half-hearted diffusion can be eliminated and the amount of carburization diffusion can be quantitatively understood. Thereafter, the steel material 21 is again moved into the suspension frame 18 of the purge chamber 12, and by extending the cylinder 19, it is immersed in the quenching bath 11 and rapidly cooled.

[Effects of the Invention] As described above, in the batch type carburizing furnace of the present invention, the conveyor roller of the hearth is pivotally supported on the outside of the side wall so that the load is not directly applied to the hearth, and the entire furnace body is made of ceramic fibers. Since the heat capacity is small and the time and thermal energy required for heating and cooling can be saved, it is useful for improving processing capacity and saving energy.In addition, by installing a cooling tube inside the furnace, the furnace can be heated in a shorter time. Since the temperature of the steel inside can be lowered, the non-uniformity of the amount of diffusion due to the slow temperature drop unlike in the conventional method is eliminated, and quality can be stabilized, which is extremely beneficial.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a patch type carburizing furnace showing an embodiment of the present invention, Fig. 2 is a sectional view taken along the line X-X of Fig. 1, Fig. 3 is a temperature treatment curve diagram thereof, and Fig. 4 5 is a longitudinal cross-sectional view of a conventional batch type carburizing furnace, FIG. 5 is a cross-sectional view taken along the line Y--Y in FIG. 4, and FIG. 6 is a temperature treatment curve diagram thereof. ■... Furnace body, 2... Support frame, 3... Conveyance roller. 4...Bearing, 7...Radiant tube, 8...
...Gooling Tube. Patent applicant Daido Steel Co., Ltd. Ka 27 No. 3 Zuka 6 Figure Time Figure 4 Figure 5 Y tool

Claims (1)

[Claims] The entire furnace body is made of ceramic fibers, and conveyor rollers with both ends pivotally supported outside the side walls are arranged in a row on the hearth, and a cooling tube through which a cooling medium can flow is arranged inside the furnace body. This is a batch type carburizing furnace.