JPS62218513A - Circulation method for atmospheric gas in heat treatment - Google Patents

Abstract

PURPOSE:To advantageously utilize atmospheric gas formed by a gas generator, by utilizing atmospheric gas exhausted from one heat treating chamber and supplying to the other heat treating chamber requiring atmospheric gas of lower unburnt component ratio than this. CONSTITUTION:Gaseous C3H7 is burnt by a gas generator 1 under insufficient air state to supply heat generating gas having high unburnt component ratio of reducing gas such as CO, H2 as shown in a table, to the heat treating chamber 2. A substance 5 to be heated is heated in the atmospheric gas in the furnace 2 until required combustion temp. is attained to prevent oxidation thereat. The substance 5 is sent to a slowly cooling chamber 15, the temp. is slowly lowered in the atmospheric gas to maintain tempering state. On the other hand, atmospheric gas exhausted from the chamber 2 is supplied 24 to a conversion apparatus 3, unburnt component such as CO, H2 is oxidized in atmospheric gas contg. O2 to be added 25, the ratios of these unburnt components are decreased as shown in the tale, this is converted to heat generating gas oxidizable weakly and supplied to the second heat treating chamber 4.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to [1] of the atmospheric gas in an atmospheric gas heat treatment furnace.
11 methods.

[Conventional technology and problems] Generally, the atmospheric gas in a heat treatment furnace is used for reduction treatment, for example.

Non-oxidation treatment 9 Atmospheric gases of various compositions suitable for the processing purpose of the metal, such as weak oxidation treatment, are used.

As is well known, among the components contained in the atmospheric gas, GO2
, H20,02 is an oxidizing gas, and H2tCOz is a reducing gas. Therefore, whether the atmospheric gas is oxidizing, reducing, or neutral is determined by its partial pressure ratio (CO/
CO2 or H2/H20), and the higher the ratio of unburned components such as Hz and COz, the stronger the reducing property (for example, in the heat treatment process of electrical steel sheets for motor cores).

In order to eliminate processing strain during press punching and improve electromagnetic properties, the material is placed in a heat treatment chamber and annealed in a neutral or reducing atmosphere to prevent oxidation. Next, this electrical steel sheet is placed in another heat treatment chamber filled with a weakly oxidizing atmospheric gas, and in this heat treatment chamber, the surface is coated with iron tetroxide (Fe304) through so-called bluing.
This is done to improve rust prevention and electrical properties.

However, when there is a difference in composition between the two heat treatment chambers (that is, there is a difference in the ratio of unburned components such as H2, GO, etc.), conventionally the two heat treatment chambers A are used as shown in Figure 3. , B were supplied with atmospheric gas generated by controlling the composition by gas generators a and b, respectively. For this purpose, two gas generators were required, and heat treatment chamber A.

Since the atmospheric gas supplied to B was discarded as it was, there were problems such as a large amount of harmful gas being generated and easily becoming a source of pollution, as well as high gas consumption and high running costs.

[Means for solving problems] The present invention aims to solve the above problems.

At least two heat treatment chambers are provided depending on the purpose of processing the object to be heated, and when there is a difference in the proportion of unburned components in the composition of the atmospheric gas to be maintained in both heat treatment chambers, first, the proportion of unburned components is determined relative to each other. A gas generator generates an atmospheric gas with a relatively high temperature, supplies this atmospheric gas to a heat treatment chamber where the ratio of unburned components is to be kept high, and adds oxygen to the atmospheric gas discharged from this heat treatment chamber. This method of circulating atmospheric gas in heat treatment is characterized in that this atmospheric gas is supplied to the other heat treatment chamber in which the proportion of unburned components is to be kept relatively low. To explain this according to FIG. 2, 1 is a gas generator that generates an atmospheric gas with a relatively high proportion of unburned components, which is supplied to the heat treatment chamber 2;
is a conversion device that adds oxygen to the atmospheric gas discharged from the heat treatment chamber 2 to lower the unburned component ratio of the atmospheric gas, and the unburned component ratio that is adapted from the conversion device to the other heat treatment chamber 4 is relative. A low atmospheric gas is supplied to the

[Function] The atmosphere gas discharged from one of the heat treatment chambers is used to supply the atmosphere gas to the heat treatment furnace, which requires atmosphere gas with a lower proportion of unburned components, so the atmosphere gas generated by the gas generator can be used effectively, contributing to energy savings and equipment savings.

[Example] FIG. 1 shows the entire continuous annealing furnace for an electromagnetic steel sheet for a motor core 2 and the temperature curve of the object to be heated in each heat treatment process as an example. In the figure, ■ is a generator, 2 is a first heat treatment chamber, 3 is a converter, 4 is a second heat treatment chamber, 5 is an electromagnetic steel plate as an object to be heated, and the object to be heated is a conveyor roller 6. ... is transferred to the right in the figure. 7
8 is a burn-off chamber for incinerating and removing press punching oil adhering to the object to be heated 5; 8 is its entrance door; the burn-off chamber 7 is maintained in an air atmosphere and is equipped with a burner (not shown) for ignition.
is installed on its side wall. 9 is a ceiling fan.

10 is a door 11.1 between the burn-off chamber 7 and the heat treatment chamber 2.
In the purge chamber (gas replacement chamber) divided by 2,
By transferring the object to be heated 5 to the heat treatment chamber 2 through the purge chamber, air is prevented from entering the heat treatment chamber 2. The heat treatment chamber 2 is equipped with an electric heater 13. A ceiling fan 14 is provided. Reference numeral 15 denotes a slow cooling chamber following the heat treatment chamber 2, and the slow cooling chamber is provided with cooling tubes 16, 16, . . . through which a cooling medium flows. 17 is cooling chamber 1
5 and the second heat treatment chamber 4, this purge chamber is equipped with doors 18 and 19, and when the object to be heated in the cooling chamber 15 is transferred to the heat treatment chamber 4, it is operated in the same way as the purge chamber 10. By opening the layers 18 and 19 alternately, the atmospheric gas in the cooling chamber 15 and the atmospheric gas in the heat treatment chamber 4 are prevented from interacting as much as possible. The heat treatment chamber 4 is provided with a ceiling fan 20 and a heat source (not shown). 21 is an exit door of the heat treatment chamber 4. Reference numeral 22 denotes an air cooling chamber following the heat treatment chamber 4, in which air is blown onto the object to be heated by a fan 23.

However, the gas generator 1 burns propane gas in an air-deficient condition to produce GO, H2 gas as shown in the following table.
An exothermic gas having a high proportion of unburned components of an equireducing gas is supplied to the heat treatment chamber 2.

Gas Composition Table In the heat treatment furnace 2, the object to be heated 5 is heated in this atmospheric gas until it reaches a required annealing temperature, and oxidation is prevented at that time. Further, upon reaching the slow cooling chamber, the temperature of the heated object 5 is slowly lowered in the atmospheric gas, and the annealed state is maintained. The atmospheric gas discharged from the heat treatment chamber 2 passes through the pipe 24 to the converter i.
! I am guided by 3.

In the converter 3, oxygen (air) is added through the valve 25 to oxidize unburned components such as Go and H2 in the atmospheric gas, lowering the ratio of these unburnt components as shown in the table above and weakly oxidizing them. Converts into a hot exothermic gas. This weakly oxidizing atmospheric gas is then supplied to the second heat treatment chamber 4 through the pipe 26.

27 is a controller that detects the CO concentration in the middle of the piping and controls the valve 25 in a feedback manner to adjust the amount of oxygen added so that the CO concentration is always maintained at the desired value. The second heat treatment chamber 4 is a place where so-called bluing treatment is performed, in which the object to be heated 5 is reheated in a weakly oxidizing atmosphere and the surface of the object to be heated 5 is coated with iron tetroxide (Fe3).
This is done in order to generate 0a) and improve the rust prevention ability and electrical properties of the electrical steel sheet. The object to be heated 5 extracted from the heat treatment chamber 4 is further air-cooled in the air-cooling chamber 22 to a temperature at which it can be handled.

In this example, the co concentration is 7% in the converter 3.
This CO+1/202→CO2
The calorific value Qco from the reaction is.

Qco=2570Kcal/m'N Xo, 05
5X 1 m3N = 141, 35 Kcal, and the calorific value Q H2 associated with the decrease in H2 concentration from 5% to 1.2%, that is, Hz + 1 / 202 → 820, is Q H2 = 3020 Kcal / m' HXo, 038
X 1 m3N=114.76Kcal.

Also, the amount of 02 required for this reaction is 1/2 (0,05
5+0.038) =0.093m'N, so the amount of air required is 0.09310.21=0.443m3N
becomes. Therefore, assuming that the initial temperature of the atmospheric gas led through the pipe 24 is 600°C, the rising temperature is 256.11Kcal 0.345Kcal/l1
13 N″C x 600℃ x 0.443m3 NO, 34
Kcal/m' N X 1 wg3 N=484
It becomes ℃. Since the atmospheric gas temperature rises due to this reaction, a heat source may not be required in the second heat treatment chamber 4 in some cases.

[Effects of the Invention] As described above, in the atmospheric gas circulation method of the present invention, the atmospheric gas generated by the gas generator can be effectively used in the two heat treatment furnaces, so the equipment cost and running cost for generating the atmospheric gas can be reduced. In addition to this, the amount of exhaust gas can also be reduced, which has industrially beneficial effects such as a reduction in pollution sources.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of the entire continuous annealing furnace showing an embodiment of the present invention, Fig. 2 is a diagram for explaining the gist of the atmospheric gas circulation of the present invention, and Fig. 3 is a conventional atmospheric gas supply. FIG. 1... Gas generator, 2... First heat treatment chamber, 3... Conversion device, 4... Second heat treatment chamber,
5... Heated object. *gm O2 ats Procedural amendment September 29, 1985 Commissioner of the Japan Patent Office Kuro 1) Akio Yu Tono 2, Name of the invention Circulation method of atmospheric gas in heat treatment 3, Relationship with the person making the amendment Case Patent applicant name Daido Special Steel Co., Ltd. 4. Agent 5o Date of amendment order Voluntary 6. Subject of amendment ``Detailed description of the invention'' column in the specification. 7. Contents of correction

Claims (1)

[Claims] At least two heat treatment chambers are provided depending on the purpose of processing the object to be heated, and when there is a difference in the proportion of unburned components in the composition of the atmospheric gas to be maintained in both heat treatment chambers, first, the proportion of unburned components is determined relative to each other. A gas generator generates an atmospheric gas with a relatively high temperature, supplies this atmospheric gas to a heat treatment chamber where the ratio of unburned components is to be kept high, and adds oxygen to the atmospheric gas discharged from this heat treatment chamber. A method for circulating atmospheric gas in heat treatment, characterized in that the atmospheric gas is supplied to the other heat treatment chamber in which the proportion of unburned components is to be kept relatively low.