JPH01252723A - Method for preventing oxidation of atmosphere - Google Patents

Abstract

PURPOSE:To prevent the flowing of an oxidizing atmosphere into a heating chamber and further to prevent the turbulence of the atmosphere in the heating chamber by sucking raw gas and air into the heating chamber when evacuated, and thermally decomposing the gaseous mixture to form a reducing gas in the heating chamber. CONSTITUTION:Solenoid valves 14 and 15 are opened along with the movement of a high-temp. work to introduce a mixture contg. an appropriate ratio of the raw gas such as propane and air (oxygen) into ring burners 11 and 13 when the heating chamber H is evacuated. In this case, the opening degree of the valves 14 and 15 is controlled so that a small amt. of air is left after the combustion in the burner 11. The gas is ignited in the burner 13, but incompletely burned due air deficiency at the combustion port 12. Concretely, the combustion is adjusted based on the flame lengths of the burners 11 and 13. A solenoid 7 is then energized, and a stop valve 2 is opened to introduce the external air freed of oxygen into the heating chamber H. Since the chamber H is held at high temp., the sucked raw gas and air are thermally decomposed to form a reducing gas, and the oxidation is prevented. The vacuum in a furnace is simultaneously turned off, and hence the turbulence of the atmosphere in the chamber H can be prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for preventing oxidation of the atmosphere during heat treatment, and is particularly effective for heat treatment methods in which a carrier gas is not supplied to the heating chamber or the flow rate of the carrier gas is reduced. The present invention relates to a method for preventing oxidation in a harsh atmosphere.

[Conventional technology]

In conventional heat treatment methods, the hardened layer is generally not constrained due to the difference in the insertion position of the product into the furnace, and negative pressure is created to prevent disturbance of the atmosphere inside the heating chamber due to outside air or atmosphere flowing into the furnace from the cooling chamber side. Therefore, the atmosphere inside the furnace is 5 to 5 times per hour.
A large amount of carrier gas such as endothermic gas was supplied so as to be replaced 10 times, and a predetermined amount was flowed out from the exhaust stack and burned to maintain the pressure inside the furnace. Therefore, in the conventional general heat treatment method, recovery of the negative pressure in the furnace was also quick. However, since then, methods have been proposed in which a raw material gas such as hydrocarbon gas is directly supplied into an atmosphere furnace without using a shift furnace (carrier gas), or a heat treatment method in which the flow rate of the carrier gas is reduced (Japanese Patent Application Laid-Open No. 59-22
No. 2571, JP-A-61-159567, etc.).

This method does not require a converter furnace, and the amount of gas supplied to the furnace is, for example, 51 kg per minute! Although it is very small and economical, the inside of the furnace becomes negative and positive due to the charging of room-temperature workpieces and the movement of high-temperature workpieces after heat treatment. The atmosphere was disturbed by breathing in outside air (oxygen), and in some cases there was a risk of explosion.

For this reason, the present applicant has developed a furnace pressure regulating device (1) that opens an on-off valve to allow the introduction of outside air when negative pressure inside the furnace is assumed, and that when introducing the outside air, oxygen in the outside air is combusted by a ring burner. Utility Model Application No. 62-28868).

[Problem to be solved by the invention]

The above furnace pressure adjustment device provided by the applicant is a conventional quenching vestibule, cooling chamber, etc. (hereinafter simply referred to as "cooling chamber").
It was installed in the lower temperature part of the room.

That is, it is not appropriate to install it in a heating chamber where disturbances in the atmosphere are averse, and furthermore, it has been installed in a place where there is a drastic change from high temperature to low temperature (expansion to contraction (negative pressure)), such as in a quenched bestible.

However, when a high-temperature workpiece is moved from the heating chamber to the cooling chamber via an intermediate door, the heating chamber becomes negative pressure, and there is a possibility that outside air may flow in. Furthermore, the cooling chamber temporarily becomes high pressure, and cooling The atmosphere in the heating chamber was sometimes disturbed by the flow of atmosphere from the heating chamber.

The present invention aims to eliminate the above-mentioned drawbacks.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a heat treatment method that has a heating chamber and a cooling chamber, and does not supply a carrier gas to the heating chamber or reduces the flow rate of the carrier gas. is inhaled, and a reducing gas is generated in the heating chamber through thermal decomposition.

[For production]

In the present invention, when a negative pressure in the heating chamber is assumed, that is, the solenoid valve (141 (151) is opened in accordance with the movement of the high-temperature workpiece to the heating chamber after heat treatment, and the pilot burner (161) is activated by the ring burner (Ill ( 13+ is ignited, and then the solenoid (7) is energized and the on-off valve (2) is opened.

As a result, outside air that does not contain oxygen is allowed to flow into the furnace, but in the present invention, raw gas and air (oxygen) with an appropriate mixing ratio are intentionally introduced into the furnace.

In other words, by adjusting the opening degree of the solenoid valve (14109), a little air (oxygen) is left in the ring burner (+31) due to combustion, and although the ring burner (+31) is ignited, the air (oxygen) in the combustion port 021 remains. It is set so that insufficient combustion results in incomplete combustion.

Specifically, the above setting is possible by adjusting the length of the flame of ring burner 1 (+31).

In other words, if the flame of the ring burner (like a ring burner) is set to a length that does not reach the center of the ring burner, an appropriate amount of air (oxygen) will not be provided for combustion, and the flame will not reach the center of the ring burner (like a ring burner).
It is attracted to the 1st side. Since there is not enough air (oxygen) in the ring burner (131 part), it is difficult to completely burn the raw gas, and therefore the flame is short and does not reach the center of the ring burner (131 part). Air (oxygen) is sucked into the heating chamber without being completely heated and combusted without being subjected to combustion.

-1 The heating chamber is at a high temperature, and the raw gas and air (oxygen) sucked into it are thermally decomposed and become a reducing gas, so-called exothermic gas (DX gas), which exhibits an antioxidant effect, and at the same time inside the furnace. Since the negative pressure is quickly eliminated, it is possible to prevent outside air or the atmosphere from the cooling chamber side from flowing in, and it is possible to prevent the atmosphere in the heating chamber from being disturbed. Note that the raw gas and air suction portion in the present invention is not limited to the above-mentioned heating chamber, but may be provided in any high-temperature portion capable of thermal decomposition.

〔Example〕

An embodiment of the present invention will be described in detail below.

Figures 1 and 2 show an example of an apparatus suitable for carrying out the method of the invention.

In the figure, (1) is an exhaust pipe, which is provided on the ceiling of the heating chamber fH1, and is provided with an on-off valve (2) whose upper end is gently curved outward and raised.

Further, a suspension rod (3) is provided at the center of the on-off valve (2).

The on-off valve (2) can slide upward without being held down by the hanging rod (3), and when the inside of the furnace becomes pressurized more than necessary, it floats up and automatically drains the gas inside the furnace. It is configured in 5 ways to discharge.

Next, one end of the suspension rod (3) is fixed to the shaft (6) at one end of the support rod (5) whose approximately center is supported (4) on the exhaust pipe (11 side).
and the exhaust pipe (solenoid (7) installed on the +1 side) at the other end.
The plunger (8) is connected by a shaft stop (9).

Furthermore, a ring burner (II) with a large number of combustion ports (+01 provided inside) is provided above the large diameter portion (1a), and a large number of combustion ports A21 are provided inside. A ring burner 03+ is provided, so that raw gas such as methane, propane, etc. can be supplied in a timely manner through the ring burners (ill (131 each have a solenoid valve α4) α9).

Furthermore, the on-off valve (
2), the solenoid valve (141(1,
51 is opened, and the ring burner (ill (131) is ignited by the pilot burner a61.

1 q By using the device with the above configuration, as mentioned above, raw gas and air can be sucked into the heating chamber at an appropriate mixing ratio, and as a result, the negative pressure in the heating chamber is quickly resolved and the inside of the heating chamber is It is capable of generating reducing gas.

〔Effect of the invention〕

According to the present invention, an oxidizing atmosphere is prevented from flowing into the heating chamber, and disturbance of the atmosphere can be prevented, which is particularly effective in a heat treatment method in which raw material gas is directly supplied to the heating chamber.

[Brief explanation of the drawing]

The drawing shows an example of the apparatus used to carry out the invention, and shows a tooth 1
The figure is a partially cutaway front view when not in use, and Figure 2 is a partially cutaway front view showing the used state. (1)...Exhaust pipe, (2)...Opening/closing valve, (3)...
・Hanging rod, (111 (131-war ring burner, α41
(151... Solenoid valve. 匈-＾-4't Figure

Claims (1)

[Claims] In a heat treatment method that has a heating chamber and a cooling chamber and does not supply carrier gas to the heating chamber or reduces the carrier gas flow rate, raw gas and air are sucked in when the heating chamber is assumed to be under negative pressure, and the heating chamber is heated by pyrolysis. A method for preventing oxidation of an atmosphere characterized by generating a reducing gas.