JPH069001Y2 - Batch type heat treatment furnace - Google Patents

Description

TECHNICAL FIELD The present invention relates to a batch heat treatment furnace, and more particularly to a batch heat treatment furnace for the purpose of soaking heat treatment of an object to be treated.

2. Description of the Related Art It is well known that heat treatments such as annealing, quenching, tempering and normalizing are performed on metals and other materials for the purpose of improving the materials. In these heat treatment operations, a desired temperature and a desired time are determined according to the purpose of the heat treatment on the material to be treated, but when an atmosphere and a uniform heating property are required, an electric heating method is generally adopted. Further, a hot air circulation system is adopted as a means for ensuring the uniform heating of the atmosphere, and at that time, both systems in which a heat source is installed inside or outside the heat treatment furnace are known.

Problems to be Solved by the Invention It is known that there are various inconveniences depending on the installation location of the heating element as described above. That is: (1) When the heating element is provided outside the furnace, the temperature gradient of the hot air is naturally high at the hot air inlet, the hot air temperature at the outlet is lowered, the temperature uniformity of the atmosphere is not maintained, and the entire device is inevitably inevitable. It becomes large.

(2) When a heating element is installed in the furnace, if the surface temperature of the heating element is raised when using in an atmosphere of a low temperature range, the surface temperature cannot be raised because the radiant heat directly affects the product from the heating element, and therefore the heat is generated. The body equipment will be large and construction costs will increase.

Means for Solving the Problems The present inventors have succeeded in developing the batch type heat treatment furnace of the present invention as a result of various studies and experiments to solve the above-mentioned drawbacks of the heat treatment furnace of this type. The technical structure of is as specified in the above-mentioned utility model registration claim,
The present invention will be described in detail with reference to the accompanying drawings showing a specific example.

FIG. 1 is a vertical sectional view of the batch type heat treatment furnace, and FIG. 2 is a horizontal sectional view taken along the line AA in FIG.

In the figure, a large number of resistance heating elements 2 are vertically arranged on both side walls 1 of the heat treatment furnace to form a resistance heating element group, and the heating element groups are arranged in a plurality of rows on the side wall 1. These heating element groups are individually surrounded by a cover 3 having a U-shaped horizontal cross section,
The cover 3 has a structure in which upper and lower end surfaces are open, and a space surrounded by the cover 3 forms a hot air circulation space 4. Reference numeral 6 denotes a plurality of inner fans arranged on the furnace ceiling 5, and it is necessary that the central axis of the inner fans 6 is within an installation position range that satisfies the following relational expression: L +>D> L / 2+ In the above relational expression, when D> L +, all the air volume of the inner fan passes through the circulation space inside the cover and is discharged from the lower part of the cover. For this reason, heat is concentrated in the center of the width direction of the furnace and there is no downward flow immediately before the cover. Therefore, there are drawbacks such that stirring in the furnace cannot be performed and radiant heat from the cover cannot be reduced.

Further, in the case of D <L / 2 +, the hot air passage is too narrow to fully utilize the air volume of the inner fan, and the effect cannot be exhibited.

By providing the heating element with the cover in this manner, it is not necessary to consider the influence of radiant heat given to the product by the heating element, and the heating element can be downsized, which leads to downsizing of the device. .

Further, the capabilities of the resistance heating element 2 and the inner fan installed above it are determined by the volume of the heat treatment furnace, the side wall height, the blade diameter, and the like.

The size of the cover 3 should be designed so that the flow velocity in the cover is 2 m / sec or more based on the inner fan capacity. This flow rate is determined by the internal dimensions of the heat treatment furnace.

The heat treatment furnace in the example shown is a tempering furnace, and the inside dimensions are
It is 400 cm, depth 330 cm, height 270 cm. The resistance heating element arranged on the side wall is a coil made of a metal material, but other shapes may be a commonly used meandering shape, and a heater surface load of 1 to 4 W / cm ² is preferable.

The cover 3 is formed by setting the material according to the heating conditions of the heat treatment furnace, and covering the resistance heating element on the side wall with a commercially available metal plate or those coated with a refractory material at a distance related to the above formula. Hot air in the hot air distribution space 4 (arrow)
However, it descends from above from the flow space and the outside of the cover at about 3 m / sec, generates hot air flow in the central part of the furnace while being stirred by these both down flows, and buoyancy due to the difference in specific gravity of hot air also acts, It circulates in the furnace to uniformize the atmosphere in the furnace.

Therefore, by circulating the hot gas in the furnace inside the cover 3, the temperature of the cover 3 can be lowered and the effect of the radiant heat from the cover 3 on the product can be reduced.

In the figure, 7 is the object to be heated placed on a dolly 8, 9 is a thermocouple for hot air temperature measurement, and the amount of radiated heat is different in the front part (door part), the center part and the rear part of the furnace. Will occur,
In order to prevent this, the capacity of each heater can be determined, and the hot air temperature can be detected to control the load of the resistance heating element 2. Also, by downsizing the fans and dispersively installing them, a large fan is used. Compared with stirring, soaking can be performed, and the weight of furnace frame metal can also be reduced.

Effect of the Invention (1) In a large-scale furnace that requires a higher level of temperature uniformity in the furnace atmosphere, the heating source and hot air circulation mechanism are in the same furnace, and multiple heat sources (or groups) are distributed and distributed. By arranging, it is possible to equalize the temperature of the atmosphere in the furnace and reduce the size of the furnace body.

(2) Since the object to be heated can be uniformly heated regardless of the surface temperature of the heating element, the heating element can be downsized (the infrared radiation from the surface of the heating element need not be considered).

(3) The atmosphere temperature distribution within the furnace is kept within ± 5 ° C by determining the forced stirring air volume corresponding to the furnace volume, optimizing the distribution of the stirring fans, and the distribution of the accompanying heater capacity. Can be managed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a batch type heat treatment furnace showing an example of the present invention, FIG. 2 is a horizontal sectional view taken along the line AA in FIG. 1, and FIGS. 3 and 4 are conventionally known batch type furnaces. It is a longitudinal sectional view and a transverse sectional view of a heat treatment furnace, and the same numerals show the same members as Drawing 1 and Drawing 2. In the figure: 1: furnace side wall, 2: resistance heating element, 3: cover, 4: hot air distribution space, 5: furnace ceiling, 6: inner fan, 7: heated object, 8: carriage, 9: hot air temperature measurement thermocouple.

Claims (1)

[Scope of utility model registration request] 1. A plurality of rows of resistance heating elements on both side walls (1) of a heat treatment furnace.
(2) group is disposed, and the heating element (2) group is surrounded by a cover (3) whose upper and lower sides are open and whose horizontal section is U-shaped to form a hot air circulation space (4), A plurality of inner fans (6) are arranged on the furnace ceiling (5) above the distribution space (4), and the installation position of the center axis of the inner fans (6) is expressed by the following relational expression: L +>D> L / 2+