JPH02197792A - How to operate a sintering furnace - Google Patents

Abstract

PURPOSE:To eliminate the affection of the convection of pressure gas in a heating chamber effectively and permit the holding of temperatures at the upper and lower parts in the heating chamber uniformly at all times by a method wherein the outputs of respective heating sources are unified when a pressure in a furnace is vacuum or normal pressure while the output of the heat source at the side of the lower part is increased to obtain a specified output rate when the pressure in the furnace is high. CONSTITUTION:When a pressure in a furnace is vacuum or normal pressure, the outputs of respective heaters 5, 6 are equalized substantially so that the ratio of respective outputs becomes 50% of the whole output respectively. According to this method, a work zone 4 is heated uniformly from the surroundings thereof and a work in the work zone 4 may be heated uniformly from the upper and lower sides thereof. On the other hand, when the pressure in the furnace is increased, the output of the lower heater 6 is increased. When the pressure in the furnace is increased to a degree higher than 100kg/cm<2>, the output of the lower heater 6 is increased to the degree of 85% of the whole of outputs while the output of the upper heater 5 is decreased to the degree of 15% of the whole of outputs. According to this method, the affection of the convection of pressure gas, which is generated when the pressure in the furnace has become high, may be eliminated and a temperature difference between the upper part and the lower part of a heating chamber 3 may be reduced sufficiently.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method of operating a sintering furnace.

[Conventional technology]

When manufacturing sintered bodies of metals, ceramics, etc., the powder of the metal, etc. is compression-molded in advance to form a green compact, which is then heated and sintered in a sintering furnace. In order to improve the material properties of the sintered body, an increasing number of cases are being adopted where the operating method is to pressurize the sintered body to the required pressure.

In such cases, conventionally, the powder compact is placed in a work zone, and heating sources are provided to surround the work zone, and while the work zone is uniformly heated by these heat sources, Evacuation and pressurization inside the furnace are controlled.

[Invention or problem to be solved]

However, in such a case, when the furnace is in a vacuum state, the work zone can be heated evenly from its surroundings, but when the furnace is in a high pressure state, convection occurs in the pressurized gas in the furnace, causing an increase in the temperature. There is a problem in that the flow particularly heats the upper part of the work zone, resulting in a large temperature difference between the upper and lower parts of the work zone, which tends to cause unevenness in the degree of sintering of the green compact.

The present invention has been made in view of the above circumstances, and is a sintering method that maintains a uniform temperature distribution in the work zone regardless of the pressure in the furnace and can obtain a high-quality sintered body with little unevenness. The purpose is to provide a method for operating a furnace.

[Means to solve the problem]

In the present invention, a heating chamber is provided in a horizontal cylindrical furnace vessel using a heat insulating material, and a plurality of heating sources are arranged inside the heating chamber so as to surround a work zone. In a method of operating a sintering furnace in which a workpiece stored in the work zone is heated and sintered by the heating source so that the internal pressure can be controlled from vacuum to high pressure, the output of each of the heating sources can be controlled independently. When the pressure inside the furnace is vacuum or normal pressure, the output of each heating source is approximately equal to uniformly heat the workpiece from the surroundings,
When the pressure inside the furnace is set to high pressure, each heating source is adjusted so that the output of the heating source located below the central horizontal line in the cross section of the heating chamber is within the range of 55 to 95% of the output of the entire heating source. It is characterized by controlling the output of.

[Effect]

In the operating method of the present invention, when the pressure inside the furnace is a vacuum or normal pressure and the effect of convection occurring inside the heating chamber is small, the output of each heating source is equalized to uniformly heat the work zone from its surroundings. When the pressure is made high with pressure gas, the output of the heating source located at the lower side of the work zone is increased so that the output is 55 to 55% of the output of the entire heating source.
By setting it within the range of 95%, the influence of convection of pressure gas is eliminated and the upper and lower temperatures in the work zone are made equal.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a groove sectional view showing a schematic configuration of a sintering furnace to which the operating method of the present embodiment is applied, in which reference numeral l denotes a furnace vessel, 2 a heat insulating material for forming a heating chamber 3, 4 is a work zone provided within the heating chamber 3, and a work (not shown) is housed inside this work zone 4.

An upper heater 5 arranged to surround the upper side of the work zone 4 and a lower heater 6 arranged to surround the lower side of the work zone 4 are provided outside the work zone 4. The temperatures of these heaters 5 and 6 are detected by a sensor 7.7, and based on the detection results, the output of each heater 5 and 6 can be independently controlled by a control device (not shown).

Further, this sintering furnace is equipped with a vacuum evacuation device and a pressure gas introduction device (not shown), and these devices can increase the pressure inside the furnace from vacuum to high pressure.

When operating the sintering furnace configured as described above, a workpiece is charged into the work zone 4, and the inside of the furnace is first evacuated to create a vacuum. After that, the furnace pressure is controlled to a predetermined pressure by introducing vacuum or pressure gas into the furnace depending on the operating conditions, and the work is heated to a predetermined temperature by each heater 5, 6 to perform sintering. At this time, the output of each heater 5, 6 is adjusted as shown in FIG.

That is, when the pressure inside the furnace is a vacuum or normal pressure, the outputs of the heaters 5 and 6 are set to be approximately equal, so that their output ratios are approximately 50% of the total.

As a result, the work zone 4 is heated evenly from its periphery, and the work inside the zone is also heated evenly from above and below.

On the other hand, as the pressure inside the furnace increases, the output of the lower heater 6 increases. Then, the pressure inside the furnace is l OOK9
7cm" or more, the output of the lower heater 6 should be about 85% of the total, and the output of the upper heater 5 should be about 15% of the total. In this case, the output of the lower heater 6 is generally Although it is necessary to increase the output to about 2 to 20 times the output in a vacuum, the output of the upper heater 5 may be kept unchanged at the output at a vacuum or normal pressure, or it may be increased or decreased. Also good.

In this way, by increasing the output of the lower heater 6 at high pressure and making the output approximately 85% of the total,
It is possible to eliminate the influence of pressure gas convection that occurs when the inside of the furnace becomes high pressure, and it is possible to sufficiently reduce the temperature difference between the upper and lower parts of the heating chamber 3. As a result, the work zone 4
This prevents large temperature fluctuations in the workpiece inside.
You can obtain products of consistent quality.

Note that the output ratio of the lower heater 6 at high pressure is not necessarily limited to 85%, and may be set appropriately in consideration of the relationship with the furnace pressure and furnace temperature, but the output of the lower heater 6 If the ratio exceeds 95% of the total, the lower side of the work zone 4 will be heated excessively, and if the output ratio of the lower heater 6 is less than 55%, the effects of convection cannot be sufficiently eliminated, so when high pressure The output ratio of the lower heater 6 must be within the range of 55 to 95% of the total.

The first embodiment has been described above, and next, the second embodiment will be described with reference to FIGS. 3 and 4.

In the sintering furnace applied in this second embodiment, an upper heater 10 and an intermediate heater 11 are installed outside the work zone 4.
, 11, and lower heaters 12 are provided in three stages, upper and lower, and the output of each of these heaters can be controlled independently.

In the case of this second embodiment, when the inside of the furnace is in a vacuum or normal pressure, as shown in FIG. I! The outputs of the lower heaters 12 are all set to be approximately equal so that their output ratios are approximately 1/3 each, and the work zone 4 is heated evenly from its surroundings, and when the pressure is high, the output ratio of the lower heaters 12 is 80%.
%, intermediate heaters 11, 11 and upper heater 10
The output of each heater is controlled so that the output ratio of each heater is about 10%. As a result, half of the output of the intermediate heater 11°11 located on the side of the work zone 4 will heat the upper side of the work zone 4, and half will heat the lower side, so in the end, As in the case of the first embodiment, 85% of the total heater output contributes to heating the work zone 4 from the lower side, and exactly the same effect as in the first embodiment can be obtained.

Next, a third embodiment will be described with reference to FIGS. 5 and 6. In the sintering furnace applied in this third example,
Outside the work zone 4, an upper heater 20, intermediate upper heaters 21, 21, intermediate lower heaters 22, 22, and lower heaters 23, 23 are provided in four upper and lower stages so that the output of each of these heaters can be controlled independently. is being used.

In this case, as shown in Fig. 6, when the pressure inside the furnace is vacuum or normal pressure, the output of each heater is approximately equal, and the output ratio of each heater is approximately 25%.
At high pressure, the output ratio of the lower heaters 23, 23 is 65%, and the output ratio of the intermediate lower heaters 22, 22 is 20%.
By controlling the output of each heater so that the output ratio of the intermediate lower heaters 21, 21 and the upper heater 20 is 7.5% each, at high pressure, the lower side of the work zone is lower than the lower heater 23, 23 and the intermediate lower heaters 22, 22, which is 85% of the total output, the same effect as in the first and second embodiments can be obtained.

Note that the heater installed outside the work zone may be further divided into a large number of zones so that the output can be controlled. In any case, when the pressure is high, By controlling the output within the range of 55 to 95% of the total, temperature unevenness within the heating chamber can be effectively eliminated and a good product can be obtained.

Further, in the above embodiment, both the furnace vessel and the heating chamber have a circular cross section, but they are not limited to a circular cross section, and may have a rectangular cross section. Further, in the above embodiment, the heat sources are arranged in a circle, but the same effect can be obtained even if the heat sources are arranged in a square shape.

〔Effect of the invention〕

As explained in detail above, according to the present invention, when the pressure inside the furnace is vacuum or normal pressure, the output of each heating source is equalized, and when the pressure inside the furnace is high, the output of the heating source on the lower side is increased. The output ratio is 55~55% of the total output of the heating source.
Since it is controlled within the range of 95%, it is possible to effectively eliminate the influence of pressure gas convection in the heating chamber, and the temperature at the top and bottom of the heating chamber can always be maintained evenly, resulting in high quality products. This has the effect that it is possible to manufacture

[Brief explanation of the drawing]

1 to 6 are diagrams showing embodiments of the present invention. 1 and 2 show a first embodiment of the present invention, FIG. 1 is a cross-sectional view of a sintering furnace to which the method of the first embodiment is applied, and FIG. 2 shows the pressure inside the furnace. It is a figure which shows the relationship between and the output ratio of each heater. 3 and 4 show a second embodiment of the present invention, FIG. 3 is a cross-sectional view of a sintering furnace to which the method of the second embodiment is applied, and FIG. 4 shows the pressure inside the furnace. It is a figure which shows the relationship between and the output ratio of each heater. 5 and 6 show a third embodiment of the present invention, FIG. 5 is a cross-sectional view of a sintering furnace to which the method of the third embodiment is applied, and FIG. 6 shows the pressure inside the furnace. and the output ratio of each heater. 1...Work zone, 2...Insulation material, 3...
...Heating chamber, 4...Work zone, 5.6...
・Heater (heating source), t o, t 1. l 2-
・・Heater (heating 1), 20, 21° 22.23・
...Heater (heating source). Applicant Ishikawajima Harima Heavy Industries Co., Ltd.

Claims (1)

[Claims] A heating chamber is provided in a horizontal cylindrical furnace vessel using a heat insulating material, a work zone is provided inside the heating chamber, and a plurality of heating sources are arranged outside the work zone so as to surround the work zone. , a method of operating a sintering furnace in which a workpiece stored in the work zone is heated and sintered by the heating source while changing the furnace pressure from vacuum to high pressure, the output of each of the heating sources being independently controlled; When the furnace pressure is vacuum or normal pressure, the output of each heating source is approximately equal to heat the work evenly from the surroundings, and when the furnace pressure is high, the cross section of the heating chamber Operation of a sintering furnace characterized in that the output of each heating source is controlled so that the output of the heating sources located below the central horizontal line is within the range of 55 to 95% of the output of the entire heating source. Method.