JPS642645B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for partially heating a metal workpiece using a fluidized bed furnace.

Conventionally, it has been common practice to immerse a metal workpiece into a fluidized bed to heat the entire workpiece, but it is rarely practiced to immerse only a portion of the workpiece into a fluidized bed to perform partial heating. Not yet.

This is because even if heated in this way, the portion exposed to the outside of the fluidized bed is heated to a temperature close to the heating temperature of the portion immersed in the fluidized bed. Because it cannot be done.

As is well known, when performing partial hardening, for example, the part to be hardened must be heated to a predetermined high temperature while the part not to be hardened must be kept at a predetermined low temperature. The temperature of the part to be quenched (T ₁ °C) and the temperature of the part not to be quenched (T ₂ °C)
It is necessary to maintain a temperature difference of 200°C or more, but as mentioned above, it is not possible to heat to such a state in a fluidized bed.

This has hindered the general use of fluidized bed furnaces.

The present invention focused on these problems, and as a result of intensive study from various aspects in order to solve them, it was discovered that partial heating can be achieved in a fluidized bed furnace by heating using an air-cooled box jig. .

That is, the method of partially heating a metal workpiece using a fluidized bed furnace according to the present invention is characterized in that the lower end portion of the metal workpiece, which is exposed by penetrating the bottom of an air-cooled box jig, is immersed in a fluidized bed and heated. It is something.

Hereinafter, to describe more specifically based on the drawings, in FIG. 1, 1 is a retort, 2 is a gas dispersion device fixed in the retort 1, and 3 is a fluidizing gas supply pipe opened at the bottom of the retort 1. 4 is an electric heater, 5 is a heat insulating material, and the pressure chamber 6 is connected from the pipe 3 to the pressure chamber 6.
The pressurized gas supplied to the furnace is uniformly dispersed by the dispersion device 2 and flows to the hearth, where it fluidizes the heat-resistant powder such as alumina granules or zirco sand, forming a so-called fluidized bed. form 7,
The fluidized bed 7 is then heated to a predetermined temperature by the electric heater 4.

In the present invention, when partially heating a metal workpiece using such a fluidized bed heating furnace, as shown in the figure, the lower end portion of the metal workpiece 9 is heated in the fluidized bed 7 via an air-cooled box jig 8. Dip it inside and process.

That is, as shown in FIGS. 2 and 3, the box jig 8 includes a box 10 made of a heat-resistant material and a tube body with both ends closed, in which a plurality of air jet holes 11 are bored. a pair of short tubular nozzles 12a, 12b, an air supply pipe 13a piped to the nozzle 12a, and the nozzle 12.
The air supply pipe 13b is connected to the nozzles 12a, 12b and the supply pipe 1.
3a and 13b are fixed within the box 10 by suitable means (not shown).

On the other hand, the metal work 9 is inserted into an opening provided at the bottom of the box 10 and set in the air-cooled box jig 8 so that its lower end portion is exposed outside the box 10. Specifically, wire ropes 15a, 15b, one end of which is fixed to the bar 14 extending over the upper end of the opening of the box 10, are secured to hooks 16a, 16b screwed onto the upper end surface of the metal workpiece 9. is set to a predetermined value. In addition, a hanging device 17 is fixed to the upper end of the box 10 by appropriate means, and the box 1 is fixed to the upper end of the box 10 by a ceiling hoist or the like via this hanging device 17.
0 is hanging.

The bottom of the box 10 is connected to the top surface 18 of the fluidized bed 7.
If the lower end portion of the metal workpiece 9 is placed in a portion, the lower end portion of the metal workpiece 9 can be immersed into the fluidized bed 7 and heated to a predetermined temperature.

During the heat treatment, pressurized air at room temperature is supplied to the nozzles 12a, 12b via air supply pipes 13a, 13b connected to a supply source. This prevents the upper end portion of the metal work 9 from being excessively heated by the air flow jetted toward the metal work 9 from the group of air jet holes 11, that is, an upward flow is forcibly generated within the box 10. Therefore, the hot air from fluidized bed 7 is transferred to box 1.
Box 10 does not flow from the upper end of the opening.
The hot air inside can be exhausted from the upper end of the opening, thus keeping the temperature of the upper end portion of the metal workpiece 9 much lower than the temperature of the lower end portion of the metal workpiece 9 which is immersed in the fluidized bed 7 and heated. be able to.

Specifically, the temperature difference between the lower end portion and the upper end portion can be maintained at 200° C. or more.

In the present invention, the box of the air-cooled box jig may be made of not only a metal material but also a heat insulating material, etc., and can be provided in various shapes such as a cylindrical container shape and a box shape. The nozzles arranged can also be provided in various shapes such as annular and rectangular shapes. A preferable air cooling box jig is one in which an air jet jacket plate is fixed to the entire inner peripheral surface of the side wall of a box made of a heat insulating material.For setting a metal workpiece, for example, a stopper pin is fixed to the metal workpiece. Set this pin by touching it to the inner bottom of the box,
Alternatively, it can be set in various ways by hanging it from the hanger 17.

Further, it is preferable that the air jet hole of the nozzle is provided so as to jet the air stream toward the corner portion formed by the inner bottom surface of the box and the upper end portion of the metal workpiece.

Next, examples and comparative examples will be described.

Example Prepare a workpiece 9 made of SS41 with a length of 200 mm, a width of 105 mm, and a thickness of 15.5 mm, and the bottom dimension is 125 mm.
An air-cooled box jig 8 was prepared in which nozzles 12a and 12b made of SUS304 were arranged in a box 10 made of SUS304 having a size of 60 mm and a height of 150 mm.

Next, as shown in FIG. 2, a work piece 9 made of SS41 is set on this jig 8 using a bar 14 or the like, that is, set so that the lower end portion of the work piece 9 made of SS41 is exposed by 100 mm outside the box 10 made of SUS304.
This is then suspended and transported using a ceiling hoist.
The box 10 made of SUS304 was immersed so that the bottom part was placed on the upper surface part 18 of the fluidized bed 7, and air was ejected at 4.5 Nm ³ /hr from the nozzles 12a and 12b. The temperature of the fluidized bed 7 was raised to 1050° C., and after immersion heating for 25 minutes, the temperature of this portion was measured using a thermocouple set at the upper end portion of the workpiece 9 made of SS41. As a result, the temperature at a point 95mm below the top of the SS41 workpiece 9 is
It was 830℃.

Comparative Example (1) Without using an air-cooled box jig, a workpiece identical to the SS41 workpiece 9 in the example was immersed for 100 mm into the fluidized bed 7 heated to 1050°C and heated for 25 minutes. The temperature measured at a point 95 mm below the top of the workpiece was 945°C.

Note that temperature measurement in this case was carried out using a thermocouple as in the case of Examples.

Comparative Example (2) Without using an air-cooled box jig, a SUS304 disc (thickness: 2 mm) with a diameter of 140 mm was placed at the midpoint (100 mm from the top or bottom end) of the SS41 workpiece 9 in the example. 1050 for concentrically fixed workpieces
The disk was immersed in the upper surface 18 of the fluidized bed 7, which had been heated to a temperature of 890°C, at a point 95mm below the top of the workpiece after heating for 25 minutes. It was hot.
Note that temperature measurement in this case was also carried out using a thermocouple as in the case of Examples.

Measured in the above examples and comparative examples
When comparing the temperature of the upper end of the SS41 workpiece, the temperature measured in the example (830℃)
is the lowest, and the difference (1050°C - 830°C) from the heating temperature (1050°C) of the lower end of the workpiece is 220°C. Therefore, according to the present invention, this is necessary when performing partial hardening etc. It is possible to perform partial heat treatment, which is considered to be the same, and the fluidized bed furnace can be used for general purposes.

In addition, in Comparative Example (1), the difference from the heating temperature of the lower end of the workpiece (1050°C) is 105°C, and in Comparative Example (2), it is 160°C, so these are inappropriate. Recognize.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a heating mode using a fluidized bed, Fig. 2 is a longitudinal cross-sectional view of an air-cooled box jig, and Fig.
The figure is a cross-sectional view of FIG. 2. 7: Fluidized bed, 8: Air-cooled box jig, 9: Metal workpiece, 4: Electric heater.

Claims (1)

[Claims] 1. A method for partially heating a metal workpiece using a fluidized bed furnace, characterized in that the lower end portion of the metal workpiece, which is exposed by penetrating the bottom of an air-cooled box jig, is immersed in a fluidized bed and heated.