JPS61257461A - Bluing method - Google Patents

Abstract

PURPOSE:To form an oxide film of a uniform thickness by evacuating a chamber contg. an article to be treated to degas the ambience around the article and the void in the article, introducing an oxidizing atmospheric gas into the chamber and carrying out bluing. CONSTITUTION:An article to be treated is placed in a bluing furnace 4 after oil is removed from the article in a burn-off furnace 1. The furnace 4 is evacuated by working a vacuum pump 8 to degas the ambience around the article and the void in the article. An oxidizing atmospheric gas mixed optionally with steam is then introduced in the bluing furnace 4 to carry out bluing. The evacuation degassing and the introduction of the oxidizing atmospheric gas are repeated plural times as required.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a bluing treatment method for depositing an oxide film on the surface of a steel material such as a steel plate.

(Prior Art) Conventionally, a motor core, which is a laminated product of thin steel plates, has been subjected to a bluing treatment to form a thin oxide film on the surface of the steel plate for the purpose of preventing rust and improving insulation properties.

Fig. 3 shows an example of this processing arrangement, in which the product to be processed (motor core) is first charged into the burn-off type 1 and placed in the air for 30 minutes.
After being heated to 0 to 400°C to remove oil, it is charged into a bluing furnace 2, and heated to 400 to 500°C in an oxidizing atmosphere gas G such as exothermic gas to undergo a bluing treatment. At this time, moisture (steam) is generally fed into the furnace along with the atmospheric gas, so that the dew point is maintained at 10 to 65° C., and the furnace internal pressure is maintained at about 10 sAQ. After being held in the class 2 for a predetermined period of time (for example, 1 hour), the products to be processed are sequentially sent out of the furnace through an annealing chamber 3. If necessary, the workpiece sent out from the burn-off type 1 is first charged into an annealing furnace (not shown) for strain relief annealing, and then transferred to the bluing furnace 2 for re-brewing treatment. Sometimes it is done.

(Problem to be solved by the invention) However, in the above method, the workpiece is Basquera 1.
Because they are transported through each furnace in a state where they are stacked in multiple stages, the oxidizing atmosphere gases mentioned above do not penetrate sufficiently into the thin laminated gaps between the stacks and each thin steel sheet that forms the motor core, resulting in an oxide film. There was a problem that the thickness was insufficient and the oxide film thickness varied widely.

The present invention is intended to solve the above-mentioned conventional problems, and to provide a bluing treatment method that can produce treated products with less variation in oxide film thickness.

(Means for Solving the Problems) However, in the bluing treatment method of the present invention, after depressurizing the interior of the storage chamber containing the article to be treated and deaerating the voids around and within the article, Oxidation f in the above containment chamber! This is a bluing treatment method characterized by performing the bluing treatment by introducing an I-atmosphere gas.

(Function) In the method of the present invention, by reducing the pressure in the storage chamber in which the items to be processed are housed, the voids around the items to be processed, that is, the places where the items are stacked (between the items and between the items to be processed) Narrow gaps such as those in contact with Basquera 1~ and narrow gaps between internal laminated plates when the product to be processed is a laminate of plates, etc., are deaerated, so the 1 The oxidizing atmospheric gas at normal pressure or pressurized state for the ruing process sufficiently penetrates into the deaerated voids to form an oxide film of approximately uniform thickness in each part.

(Example) An embodiment of the present invention will be explained below with reference to FIG.

In the figure, the bluing furnace 4 uses airtight doors at each part of the charging inlet and the outlet leading to the slow cooling chamber 3, and each part has a pressure-resistant structure to withstand reduced pressure.

Further, 5 is a cooler, and 6 is a vacuum pump.

After oil content is removed from the workpiece in a burn-off furnace 1, the workpiece is subjected to strain relief annealing in an annealing furnace (not shown) if necessary, and then charged into a bluing furnace 4, and the inside of the bluing 4 is heated by operating a vacuum pump 6, for example. The pressure is reduced to a degree of vacuum of 100 to 200 Torr. Next, an oxidizing atmospheric gas G is fed into the chamber 4 along with steam as necessary to carry out a bluing process. The depressurization and feeding of the atmospheric gas G described in -F are repeated once to several times depending on the size of the void within the product to be processed. Further, when filling with the atmospheric gas G, the pressure inside the furnace is set to a positive pressure of, for example, about 10 sAQ, as in a normal bluing process, and excess atmospheric gas is discharged to the outside of the furnace from an exhaust port (not shown). After the bluing process, the products to be treated are sequentially sent to an annealing chamber 3 to be cooled, and then taken out of the furnace.

Using the above-mentioned apparatus, the above-mentioned treatment was carried out by stacking motor stator cores of 130# outer diameter and 40 mm inner diameter, which were laminated thin steel plates with a thickness of 0.5 m, in three stages in a basket. However, as the oxidizing atmosphere gas G, a mixture of exothermic gas and steam is used, and the ultimate vacuum degree of the furnace 4 is 100.
The time required to reduce the pressure at Torr is 5 minutes, and the subsequent atmospheric gas supply time is 3 minutes.
This was repeated several times, and then the bluing process was carried out by holding at 460°C for 36 minutes in a state filled with atmospheric gas G. jq
The thickness of the oxide film on the treated product was 2 to 4 μm on the outer surface of the stator core, and 1 to 2.5 μ on the inner laminate surface. On the other hand, as a comparative example, the same workpiece as above was placed in atmospheric gas G for 46 hours without performing the above depressurization.
When bluing treatment was carried out by holding the sample at 0° C. for 60 minutes, the thickness of the oxide film on the treated product varied widely, ranging from 1 to 4 μ on the outer surface and 0.2 to 2 μ on the inside.

In the above embodiment, the pressure is reduced and the oxidizing atmosphere gas G is introduced into the bluing furnace 4, where the products to be processed remain for a long time, so that the pressure can be reduced multiple times without particularly slowing down the conveyance speed of the products to be processed. Although it is easy to degas and form a sufficiently thick oxide film inside the product to be processed,
If the oxide film can be relatively thin, the pressure may be reduced in the front chamber 7 of the bluing furnace 2, as shown in FIG. Since the structure can be changed, equipment costs can be kept low. In this case, the degassed voids of the workpiece are filled with oxidizing atmosphere gas in the front chamber 7, and then transferred to the bluing unit 2 where the bluing process is performed in a heated state. If the conveyance speed of the product is slow, a heating facility may also be provided in the front chamber 7 so that part of the bluing process can be performed within the front chamber 7 as well.

Although the bluing process for motor cores has been described above, the present invention can also be applied to bluing processes for other workpieces other than motor cores.

(Effects of the Invention) According to the above-described invention, the oxidizing atmospheric gas sufficiently penetrates into the voids that have been degassed by reduced pressure, so there is little variation in the thickness of the oxide film formed in each part. Processed products can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an equipment system diagram showing an example of the equipment used in the method of this invention, FIG. 2 is an equipment system diagram showing another example, and FIG.
The figure is an equipment system diagram of an example of a conventional brewing device. 2...Brewing type, 4...Brewing type, 6
... Vacuum pump, 7... Front chamber, G... Oxidizing atmosphere gas.

Claims (1)

[Scope of Claims] 1. After depressurizing the storage chamber in which the product to be processed is stored and deaerating the voids around and within the product, oxidizing atmospheric gas is introduced into the storage chamber to A bluing treatment method characterized by performing a bluing treatment. 2. The bluing treatment method according to claim 1, wherein degassing under reduced pressure of the product to be treated and feeding the oxidizing atmosphere gas are repeated multiple times. 3. The bluing treatment method according to claim 1 or 2, wherein the storage chamber is a furnace chamber of a bluing furnace. 4. The bluing treatment method according to claim 1 or 2, wherein the storage chamber is a front chamber of a brewing furnace.