JPS5881925A - Heat-treatment of metal by fluidized-bed furnace - Google Patents

Abstract

PURPOSE:To enable to perform the safe, sanitary and economic heat-treatment of a metal over a broad temperature range, by supplying atmospheric gas during raising or lowering a temperature to preset values for the heat-treatment to fluidize the heat resistant powdery body on a fluidized bed, and unfluidizing the powdery body during holding the temperature at said preset value. CONSTITUTION:By opening a valve 10, atmospheric gas heated at a predetermined temperature by a preheater 11 is supplied to a pressure chamber 2 and let flow through a gas-diffusing plate 3 into furnace bed to fluidize heat resistant powdery body 4. Thereafter, the air cylinder 13 of a means 12 for opening or closing an oven covr is driven to detach the oven cover 7, a metal 19 to be treated, directly or as received in a bascket or the like, is submerged in the fluidized bed, and the cover 7 is reattached to a retort 6. When the temperature of the metal 19 detected by a temperature controller 16 and the furnace temperature detected by a temperature-indicating and controlling means 17 come in a preset range for heat-treatment during heat-treatment, applying an electric current to a heater 5 is stopped through a controller 18, and the atmospheric gas is intercepted or reduced by controlling the valve 10. Consequently, the powdery body is unfluidized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal heat treatment method using a fluidized bed furnace.

Heat treatment of metals is a combination of various operations such as heating and cooling that is performed for the purpose of imparting special structures and properties to solid metals, and is an operation that utilizes metal recrystallization, atomic diffusion, or phase transformation. It is.

This includes quenching, tempering, annealing, normalizing, isothermal transformation heat treatment 1, and surface hardening.

In these treatments, the metal to be treated is heated or cooled from a certain temperature to a predetermined temperature, or held at that temperature for an appropriate period of time, and then proceed to the necessary next stage of operation.

That is, a transient state of temperature in which a metal to be treated at a certain temperature is heated or cooled to a predetermined temperature, and the metal is held at the heat treatment temperature for a predetermined period of time, that is, recrystallization of the metal, diffusion of atoms, and spheroidization.

It consists of a constant temperature holding state that is maintained for the time necessary to perform constant temperature transformation.

The heating or cooling rate and holding time are carefully set according to the purpose of the treatment, the material and size of the metal to be treated, etc., as well as the temperature setting.

Conventionally, these operations have involved placing the metal to be processed in a container that can be heated with electricity, gas, or liquid fuel by keeping air or a predetermined gas atmosphere in the container, or keeping the metal at a predetermined temperature. This was done by using a method such as immersion in molten salt or molten metal as a heat medium.

However, in the former method, it is difficult to rapidly heat or cool the material to be treated, resulting in uneven temperature of the metal to be treated, and the operating conditions that can be applied are only within a very limited range.

The latter allows for rapid heating or rapid cooling, which widens the range of applicable operating conditions; however, there are risks such as corrosion of the metal to be processed, the risk of explosion due to foreign matter such as moisture entering the heating medium, and deterioration of the working environment due to steam. Another disadvantage is that the melting point is relatively high, which limits the applicable temperature range.

The present invention aims to improve the drawbacks of the above-mentioned conventional methods and provide a metal heat treatment method that is safe, hygienic, and economical and allows treatment in a wide temperature range.

The method according to the invention that achieves this objective is to fluidize the heat-resistant powder in the hearth by supplying atmospheric gas while the temperature is being raised or lowered to the set heat treatment temperature, and while the temperature is being maintained at the set heat treatment temperature. is a metal heat treatment method using a fluidized bed furnace, characterized in that the supply of the gas is stopped or reduced to make the heat-resistant powder in the hearth non-fluidized.

In the wood invention, "atmosphere gas" refers to an inert gas such as N2 gas used in quenching, tempering, annealing, etc., or a mixture of various components such as carburizing gas or carbonitriding gas. This term refers to gas other than air, such as gas.

Next, to explain the invention in detail based on an example, in the furnace temperature raising step, in FIG. 1, compressed air is supplied from the air supply pipe (1) to the pressure chamber (2), 3) Heat-resistant powder (4) such as alumina filled above is fluidized by the air passing through the diffuser plate (3), forming a so-called fluidized bed.

Further, after a predetermined operation, the heater (5) is energized to heat the fluidized bed. The retort (6) is closed by a furnace lid (7), and heated air gas is discharged from an exhaust pipe (8) attached to the furnace lid (7).

In this way, the temperature is gradually increased, and when the temperature inside the furnace approaches the heat treatment temperature, the atmospheric gas replacement step begins.

That is, the pulp (not shown) provided in the air supply pipe (1) is closed and the supply of compressed air is stopped, and at the same time, the pulp (not shown) provided in the atmospheric gas supply pipe (9) is closed.
is opened, and atmospheric gas heated to a predetermined temperature by the preheater (111) is supplied to the pressure chamber (2).

The atmospheric gas passes through the diffuser plate (3) and flows into the hearth, and the heat-resistant powder (4) is fluidized by the atmospheric gas, forming a fluidized bed with an atmosphere suitable for heat treatment. . At this time, as the air gas previously supplied to the hearth is heated to a high temperature, it gradually flows upward and is discharged from the exhaust pipe (8).

In this manner, after a predetermined period of time has elapsed and the air gas is replaced with atmospheric gas, the next step is to charge the object to be processed.

First, the air cylinder 03 of the furnace cover opening/closing device 0z is operated to make the rod protrude. Then, the arm αΦ is moved upward and the furnace lid (7) is removed from the retort (6). When the arm α is further raised, this arm circle itself is rotated at a predetermined angle, and the furnace lid (7) is moved to the retort (6).
) is moved from above to another location.

That is, the protrusion provided on the inner diameter side of the shaft support (151) is fitted into the guide groove provided on the outer diameter side of the arm circle, and the protrusion is located in the straight part (al) of this guide groove. In this state, the arm 04 moves only upward,
When the protrusion is located at the spiral portion (bl) connected to the straight portion (a), it rotates and moves upward.

After the furnace lid (7) is removed from the retort (6) in this manner, the metal to be treated is then placed directly or in a basket or the like and immersed in the fluidized bed. For example, the metal to be treated or the basket containing the same may be suspended from the furnace lid (7), or the metal to be treated or the basket containing the same may be immersed with support means provided in the retort (6). It can also be immersed in various other ways.

Once immersed in the specified amount, operate the air cylinder OJ of the furnace lid opening/closing device α2, sink the rod, and attach the furnace lid (7) to the retort (6) as before to begin the heat treatment process. .

During processing, the heater (5) is controlled by a temperature controller αe and a temperature indicator controller (+71) to keep the temperature inside the furnace constant.
, is controlled ON-OFF via the control device 0 section, and the supply amount of the atmospheric gas is controlled in synchronization or almost synchronization with this ON-OFF control.

That is, when the temperature of the metal to be treated u detected by the temperature controller Oe and the furnace temperature detected by the temperature indicating controller 09 fall within the set heat treatment temperature range, the temperature is transferred to the heater (5) via the controller 0 seconds. At the same time, the pulp 10) is controlled at the same time or almost simultaneously, and the supply of atmospheric gas is completely cut off or the supply amount is reduced. Therefore, the heat-resistant powder (4) that had been fluidized becomes stationary or almost stationary, that is, a non-fluidized state.

Then, the heating by the heater (5) is stopped, and when the atmosphere has passed for a predetermined period of time and the temperature inside the furnace and the temperature of the metal to be treated α9 gradually decrease and reach the lower limit of the set heat treatment temperature range, the temperature controller α mark A predetermined detection signal is sent from the temperature indicating controller 09 to the control device at 0 seconds, energization to the heater (6) is started via the control device α mark, and at the same time or almost simultaneously the valve (10) is fully opened. The same amount of atmospheric gas as before is supplied to the hearth. Thus, the heat-resistant powder in the hearth, which is stationary or almost stationary, becomes fluidized again.

Note that if the temperature inside the furnace and the temperature of the metal to be treated 00 reach the upper limit of the set heat treatment temperature range or higher, the control is such that the atmospheric gas is supplied to the hearth while the power to the heater (6) is stopped. Ru.

Thereafter, heat treatment is performed by controlling the furnace temperature and the supply of atmospheric gas in the same manner.

The product is then heat-treated in this way for a predetermined period of time and then taken out from the furnace. This product removal step is performed by operating the furnace lid opening/closing device (2) in the same manner as when charging the metal to be processed into the furnace.

As can be understood from the above, in the great invention, the treatment is performed in a non-fluidizing atmosphere without supplying atmospheric gas while the temperature is maintained within the set heat treatment temperature range, and when the heat treatment temperature is outside the set heat treatment temperature range. When the temperature is increased or decreased by controlling the temperature, an atmosphere gas is supplied and the process is carried out in a fluidized atmosphere.This allows the amount of expensive atmosphere gas to be reduced. It is possible to speed up the temperature control to bring the temperature within the range, and it is also possible to perform processing in a wide temperature range.

In other words, it is possible to reduce the amount of atmospheric gas used while maintaining the characteristics of a fluidized bed, which is excellent in temperature rise, heat retention, uniformity of temperature distribution, and ease of temperature control. Compared to the conventional method that always supplies a constant amount of atmospheric gas, the amount of gas used can be reduced by approximately 20%, and the amount of electricity used can also be reduced by approximately 20%.
In this way, processing costs can be significantly reduced.

In the present invention, when N: gas is used as the atmospheric gas, it is preferable to preheat it (generally to 400°C to 500°C) before supplying it to the hearth, which causes the N2 gas to thermally expand and increase its volume. Therefore, its usage can be further reduced.

Furthermore, the fluidized bed can be heated not only by the electric heater described above, but also by various methods such as heating by supplying fuel into the furnace.

In Fig. 1, the shank indicates a pressure regulating valve, and (2) indicates a furnace body having an adiabatic structure, and the pressure regulating valve (2) prevents outside air from entering.

As described in detail above, according to the great invention, processing can be carried out in a wide range of areas and is safe and hygienic.

Moreover, an economical metal heat treatment method can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a fluidized bed furnace. (2): Pressure chamber, +31: Diffusion plate, +41: Heat-resistant powder (5): Heater, +61: Retort,
(91: Atmospheric gas supply pipe

Claims (1)

[Claims] (1) While the temperature is rising or falling to the set heat treatment temperature, an atmospheric gas is supplied to fluidize the heat-resistant powder in the hearth, and while the set heat treatment temperature is maintained, the supply of the gas is stopped or reduced. A metal heat treatment method using a fluidized bed furnace, characterized in that at least the heat-resistant powder in the hearth is rendered non-fluidized.