JPH01127618A - Heat-treatment of metal - Google Patents

Abstract

PURPOSE: To prevent the intrusion of the air in a surface by suitably introducing reducing gas and non-reacting gas into a heat-treatment zone and a cooling zone, respectively and forming the different atmosphere in each zone, at the time of executing the heat treatment to metals as non-continuous state in a continuous furnace.

CONSTITUTION: A mesh belt 11 is driven and the metal to be treated is passed through an inlet 4, heat treatment zone 8, cooling zone 10 and outlet 6 in order, to execute the heat treatment. At this time, in the cooling zone 10, nitrogen is introduced from injectors 30, 32 to reject the air from the furnace, and the heat treatment zone 8 is heated to a necessary treating temp. Successively, into the heat treatment zone 8, the nitrogen and methanol are introduced from injectors 18, 20 and also, the nitrogen is introduced from supplying holes 14, 16. Then, the gas in the heat treatment zone 8 is almost flowed in the inlet 4 direction and further, into a flue 38 through a sliding plate 40 and thereat, flame generating component is burnt. By this method, the intrusion of the air from the inlet 4 is prevented to control the oxidation of the metal to be treated.

COPYRIGHT: (C)1989,JPO

Description

[Detailed description of the invention] The present invention relates to a method for heat treating metals.

Heat treatments of metals, such as annealing, spheroidizing, sintering, brazing, malleable, and hardening, are usually preferably carried out in a reducing or non-oxidizing atmosphere in the furnace. Heat treatment can be carried out batchwise or continuously. Continuous heat treatment furnaces usually have open ends.

These furnaces include an inlet for the metal or workpiece to be heat treated, a heat treatment zone, a cooling zone, and a workpiece outlet. The workpiece is fed through the furnace at a certain speed and is subjected to the required treatment in the heat treatment area! ! It is heated to a temperature and then cooled in a cooling section to a temperature at which it will not oxidize when exposed to ambient air. The required atmosphere is usually created, for example, by an exothermic or endothermic gas generator or an ammonia cracker.

The atmosphere is supplied to the heat treatment zone and expands, filling the gas space within the furnace. Since the atmosphere is particularly flammable, combustion must normally occur at both the inlet and the outlet of the furnace. There are therefore two directions of flow inside the furnace, and gas emanates from the heat treatment area in both directions.

The gas must be supplied at a flow rate sufficient to maintain a positive pressure within the furnace. Otherwise, there is a risk that air will enter the furnace from the furnace inlet or outlet and create oxidizing conditions within the furnace. Hence the heat! l! L L! l! It is practical to feed at a flow rate in excess of what is theoretically necessary to create the required reducing or non-oxidizing conditions within the zone.

An object of the present invention is to provide a heat treatment method that improves the drawbacks of such conventional methods.

According to the invention, a method for heat treating metal in a continuous furnace having sequentially provided inlets, heat treatment zones, cooling zones and outlets, in which air enters the furnace through the inlets and outlets is provided. introducing non-reacting gases and reducing gases at predetermined locations within the furnace; subjecting substantially the entire furnace to non-oxidizing or reducing conditions; A method is provided comprising the steps of creating a gas flow within the furnace to create an atmosphere of different composition in different zones and passing the metal through the furnace from the inlet to the outlet.

The term "non-reactive gas" as used herein refers to a gas that does not react with other components of the atmosphere and with the workpiece or metal being heat treated. Nitrogen is generally used as the non-reactive gas, but in some cases, argon may be used if nitrogen has any deleterious effect on the metal being heat treated.

Furthermore, the term "heat treatment of metal" as used herein includes annealing (including spheroidization), sintering (for example, of powders including non-metallic powders), brazing, hardening, and malleable. The method of the invention is particularly suitable for annealing and sintering.

The method of the invention is suitable both for horizontal continuous furnaces (furnaces in which the workpiece is fed entirely horizontally) and for vertical furnaces (furnaces in which the workpiece is fed in a vertical direction).

Examples of horizontal continuous furnaces include continuous strip wire furnaces,
There are Metschbelt furnaces, roller bed furnaces, and Butsha furnaces.

Typically, non-reacting gases and reducing gases are introduced directly into the heat treatment zone of the horizontal furnace. Alternatively, the gases are directed to one or more cooling zones close to the heat treatment zone;
Alternatively, it may be introduced at a location further away from the heat treatment zone, or both, where a substantial portion of the reducing gas flows into the heat treatment zone. Normally, non-reacting gases and reducing gases are introduced into the furnace at ambient temperature, but since the heat treatment zone can reach temperatures as high as 1100°C, depending on the type of heat treatment being performed, there is a substantial Expansion occurs. Gas thus flows from the heat treatment zone both in the direction of the furnace inlet and in the direction of the cooling zone.

In the case of a horizontal furnace, it is preferred that the amount of gas exiting the heat treatment zone is substantially greater at one end of the zone than at the other end. It is also desirable that the gas leaving both ends of the furnace be non-flaming, but the flaming gas is only burned out near one end of the furnace. Typically, the end where the gas is burnt out is the inlet of the furnace, and the flow of gas from the heat treatment zone to the cooling zone is blocked. Devices may be provided in the cooling zone of the furnace to physically obstruct the flow of gas from the cooling zone through the furnace outlet. Preferably, the non-reacting gas has a horizontal velocity component in the direction of the heat treatment zone at one or more points in the cooling zone to direct the flow of gas from the heat treatment zone to the cold zone. is supplied to

This makes it possible to considerably reduce the amount of gas flowing from the heat treatment zone into the part of the cooling zone opposite this zone, and thus to reduce the total amount of non-reactive gas supplied to the heat treatment zone.

These devices make it possible to substantially reduce the amount of reducing gas reaching the furnace outlet, thereby eliminating the need to combust the gas at the furnace outlet into the shell. Therefore, in order to prevent air from flowing into the furnace, it is desirable to seal the flue, etc. at or near the outlet.

To create a positive flow of gas through the outlet of a horizontal furnace that prevents or substantially limits air from entering the furnace through the outlet, the non-reacting gases have a velocity component in the direction of the outlet. It is therefore desirable to introduce the material into the horizontal furnace from one or more points at or near the outlet. Typically, such non-reactive gas also serves the function described above to reduce the proportion of non-reactive gas in the atmosphere exiting the furnace outlet. Preferably, to help prevent the ingress of air from the outlet of the furnace, a flow [11+] device is provided which prevents the entry of gas into the furnace without preventing the metal being processed from exiting the furnace. . Typically, the device that physically obstructs the exit of gas from the cooling zone also serves to prevent gas from entering the furnace through the outlet. flow m
A suitable υ1 device is one comprised of one or more curtains comprising a plurality of generally vertically depending fibers or filaments. When the fibers or filaments are not moved, they close off substantially the entire cross-sectional area of the furnace at or near the outlet, but their lower ends are moved laterally to the metal passing through the furnace. pass. The combination of such a flow restriction device and a device for introducing non-reactive gas into the furnace at or near the device generally substantially prevents air from entering the furnace through the outlet. It is particularly effective.

In a preferred embodiment of the method of the invention, spaced partitions and/or curtains or the like define at least one chamber into which nitrogen or other non-reacting gases are introduced in the part of the cooling zone close to the furnace outlet. will be provided. The partitions are configured to allow the metal to be processed to pass through the chamber.

Such techniques would be commonly applied in heat treatment furnaces to reduce the overall consumption of gas.

For example, in sintering, it is known to provide a preheating zone between the sintering (or heat treatment) zone and the furnace inlet. ! I
The lubricant is oxidized in the preheating zone. Accordingly, a limited amount of air is allowed to enter through the inlet to create an oxidizing atmosphere.The invention therefore also comprises an inlet, a heat treatment zone, a cooling zone, and an outlet provided sequentially, and at least metal in a continuous furnace comprising, at or near one end, spaced partitions and/or curtains (or the like) defining at least one chamber through which the metal to be processed passes; a method of heat treating, introducing a suitable gas or gases into the heat treatment zone to create a suitable atmosphere for the heat treatment;
supplying a non-reactive gas to the chamber to substantially prevent air from outside the furnace from entering through the IL chamber into the furnace section between the WA exchanger and the heat treatment zone, and the inlet; A method comprising the steps of passing metal through the furnace from to the outlet is provided.

Non-reactive gases are preferably introduced directly into the chamber.

The rate of introduction of non-reactive gas into the chamber and the physical obstruction of the partition to the gas flow are preferably such that the following conditions hold.

Pc>Pu and Pu>Pa where Pc is R9! Pu is the pressure of the furnace atmosphere in the vicinity of the chamber and the area between the chamber and the heat treatment area; Pa is the atmospheric pressure.

More preferably, the horizontal furnace is equipped with at least two chambers and as follows.

Pc>Pu>Pt>Pa Here, Pc is the pressure in the room closest to the heat treatment area, Pu and Pa are the same as before, and Pt is the pressure in the heat treatment zone; It is.

If a chamber is located within the cooling zone near the outlet end of the furnace, and the pressure within the chamber is greater than ambient pressure, less air will enter the cooling zone of the furnace from the furnace outlet. If the pressure is greater than that in the rest of the zone and in the heat treatment zone, the formation of the required flow in the furnace by the non-flaming gas mixture leaving the furnace outlet is facilitated, while at the same time the non-reacting and reducing gas The total demand l!m can be reduced.

If two or more such chambers are used, they will typically be interconnected at substantially the same pressure.

Preferably at least two, and usually three or more, chambers are provided, each of which is directly supplied with non-reactive gas. In particular, in such chamber configurations, if necessary, a relatively high hydrogen (or other reactant gas) concentration (e.g.
0% or higher), and the concentration can be decreased sequentially from the inner chamber to the outer chamber (the hydrogen concentration in the outermost chamber is such that the atmosphere there is non-flammable). become something). Since the specific heat of hydrogen is relatively high, increasing the degree of hydrogen in the cooling zone helps cool the metal.

Such high water # concentrations are desirable if the furnace processes particularly large amounts of metal per hour. However, in other cases it is unnecessary and the hydrogen concentration in the heat treatment zone can instead be reduced by introducing most of the hydrogen directly into the heat treatment zone or into a portion of the cooling zone close to the heat treatment zone. It is desirable to maximize.

The partition is usually hinged or pivoted to a suitable support at or near the ceiling of the furnace. If the metal to be processed is a well-shaped strip, each partition will be in the form of a flap that seals or engages the metal to be processed and the sides of the furnace in a substantially fluid-tight manner. . If the metal to be processed is a bulkier item (e.g. a gear), each partition may be pivoted or hinged to the top of the furnace with a row of "finger" members that overlap adjacent ones and allow the furnace to process. It would probably consist of something that hangs down to the object conveyance surface.

Such a configuration allows the metal being processed to pass through, but creates a physical barrier to gas flow. Various materials may be used for the partitions. For example, it can be a steel or ceramic material, or a suitable composite or laminate.

The reducing gas can be hydrogen, typically supplied from a high pressure vessel of commercially pure hydrogen, an ammonia cracker, or a hydrocarbon such as methane or propane. The reducing gas can also be a mixture of hydrogen and carbon monoxide created in situ by thermal decomposition of volatile organic compounds such as methanol. At temperatures above 700°C, 1 mole of methanol decomposes to form 1 mole of carbon monoxide and 2 moles of hydrogen. Methanol is a suitable source of hydrogen if oil is present in the heat treated workpiece.

If there is grease on the workpiece, it may be beneficial to introduce water into the processing or preheating zone to remove the soot on the workpiece. This is due to the fact that a non-reactive gas is passed through a humidifier.
This may be done by placing the workpiece into a processing area. The metal itself is not oxidized and it is therefore important that non-oxidizing and reducing conditions are maintained substantially throughout the furnace as far as the metal is concerned.

If necessary, a non-reacting gas, preferably with a horizontal velocity component in the direction of the inlet, is passed between the heat treatment zone and the inlet to prevent or restrict air from entering the furnace through the inlet. It may be introduced into the furnace at one or more points. The inlet end of the furnace could be provided with one or more baffles or a chamber supplied with a non-reactive gas such as that used in the cooling zone. The reducing gas in the gas mixture passing through the inlet is burned off as in normal operation of a continuous heat treatment furnace.

The composition of the atmosphere in the heat treatment area of the furnace depends, among other things, on the type of treatment being carried out, the composition of the metal being treated, the dew point of the fluid forming the atmosphere, and the presence of oil on the surface of the metal being treated entering the furnace. are selected according to their efficiency in regulating or excluding air from the furnace.

By substantially restricting the entry of air into the furnace,
If necessary, the average concentration of reducing agent in the furnace atmosphere for the process involved is lower than in conventional furnace operation, without substantially lowering the concentration of reducing gas available in the heat treatment zone. It can be performed. Furthermore, by using commercially pure hydrogen and nitrogen rather than, for example, cracked ammonia, the dew point of the furnace atmosphere can be lowered, and therefore at lower reducing gas levels than when using cracked ammonia as the reducing gas source. Able to perform work. By blocking the flow of gas from the heat treatment zone to the cooling zone, the amount of reducing gas that must be supplied to the heat treatment zone can be reduced. That is, in many cases,
The gas supply rate to a normal horizontal treatment ready furnace can be significantly reduced.
This makes it possible to reduce their operating costs.

Typical atmospheres that can be created in the heat treatment area for various heat treatments of different materials are shown in Tables 1 and 2 below (higher hydrogen concentrations may be used in some cases).

In the method of the invention, the atmosphere in the heat treatment and cooling zones of the furnace is not homogeneous. Typically, the proportion of reducing gases such as hydrogen contained in the atmosphere in the cooling zone is substantially lower than in the heat treatment zone. However, in some cases, a relatively high reducing gas concentration is required in a large portion of the cooling zone for efficient cooling or to increase the efficiency of the operation, and the reducing gas concentration is even higher than in the heat treatment zone. It's okay to be. In such a case, the hydrogen concentration will be high. Therefore, non-homogeneous atmospheres in the heat treatment and cooling zones apply.

Table 1 Alloy steel 2-4 - - -
− Remainder mild steel −−2-4−−
Remaining part mild steel ---3-7-Remaining part mild steel/carbon steel 2-4 - - -
− Remainder mild steel/carbon steel −0,5−
1--Remainder mild steel/carbon steel ---1-15-50
Remainder The method of the invention is also applicable to the heat treatment of ferrous and non-ferrous metals in continuous vertical heat treatment furnaces. An example of such a furnace includes a generally vertical ascending leg having an inlet at the bottom and a generally vertical descending leg having an outlet at the bottom;
There are vertical strip annealing furnaces in which the tops of the legs are interconnected.

A guiding device is usually provided in the furnace to guide the strip parts from the inlet to the outlet. A heat treatment area is provided near the top of the descending leg, and below this is a cooling area. In the operation of such a furnace according to the invention, a non-reactive gas such as nitrogen is supplied to a plurality of spaced locations on the ascending leg, and one or both of the cold section and the heat treatment section of the descending leg are supplied with a non-reactive gas such as nitrogen. Preferably, a reducing gas containing hydrogen is introduced.

To prevent air from entering the furnace, it is preferable to
One stream is introduced near the inlet of the furnace and the other stream is introduced near the outlet. If desired, a chamber as described above may be provided at the outlet end, and a similar arrangement may be provided at the inlet end. In a vertical strip annealing furnace as described above, the partition would consist of a horizontal plate with holes to guide the strip. By substantially preventing air from entering the furnace, less hydrogen can be used in the atmosphere within the heat treatment zone.

However, proper cooling must be provided in the cooling area. Therefore, in many such furnaces there is a relatively high concentration of hydrogen in the cooling zone due to hydrogen's relatively high thermal conductivity (compared to nitrogen).
It is preferable to maintain

Therefore, hydrogen or cracked ammonia may be introduced only in the cooling zone to create an atmosphere containing more hydrogen than is required in the heat treatment zone. Since hydrogen tends to rise from the cooling zone to the heat treatment zone due to its low density compared to nitrogen or argon, the necessary atmosphere may be created therein.

The flow of hydrogen from the descending leg of the furnace to the ascending leg is essentially υ1.
Nitrogen or other non-reactive gas is preferably supplied to the riser leg of the furnace to limit or prevent the reaction. This reduces the amount of hydrogen that must be supplied to the furnace compared to conventional methods.

The method of the invention will become clearer from the illustrative description with reference to the accompanying drawings, in which: FIG.

This example uses a standard Birlec 18
“The Metschwerd furnace is concerned with the annealing of ferrous metal parts in...

As shown in FIG. 1, the meshbelt furnace, designated by the reference numeral 2, has an inlet 4 and an outlet 6 for the workpiece to be annealed. The furnace 2 has a heat treatment section 1i provided near the inlet 4.
18 and a cooling zone 10 provided between the outlet 6 and the heat treatment zone 8.

The heat treatment zone 8 includes [Glover 1 heating elements (not shown)]
heated by.

The workpiece to be annealed is fed onto an endless mesh belt 11. This belt 11 is driven around an endless path extending within the series 2 from the inlet 4 to the outlet 6.

Belt 11 is mounted on rollers 12, and at least one of these rollers is driven by a motor (not shown). In operation, the workpiece to be annealed is placed on the belt 11 just before the inlet 4, fed through the furnace at a predetermined speed, and lifted off the belt 10 to the outlet 6.

On the underside of the belt 11 in the heat treatment zone 8 there are two inlets 14 and 16 through which gas can be supplied to the heat treatment zone 8 . These inlets 14 and 16 form part of the furnace before it is configured to carry out the method according to the invention.

Two coaxial nitrogen/methanol injections WA 18 and 20 extend from the top of the furnace downward to the heat treatment area. Injector 1
Reference numeral 8 includes an outer pipe 22 for nitrogen and an inner pipe 26 for methanol coaxial therewith. The tip of the pipe 26 is connected to the pipe 2
It is placed slightly above and inside the exit of No. 2. The injection 320 is substantially the same as the injection fi 18 and includes an outer pipe 24 for nitrogen and an inner pipe 28 for methanol. Injector 18 and 2
In case 0, droplets of methanol are entrained in nitrogen, vaporized, and then collided with the workpiece to be annealed.

A directional nitrogen injector 3o extends from the ceiling of the furnace 2 into the cooling zone 10, comprising a pipe with a buff ray or hole oriented at an angle of 45° to the vertical in the direction of the outlet 6. The position of the injector 30 within the cooling zone is relatively close to the furnace outlet 6. Between the injector 30 and the outlet 6, four rows of curtains 34 hang from the ceiling of the furnace 2, the lower ends of which extend to a distance sufficient to pass the workpiece above the mesh belt 11. Each of these curtains typically consists of a plurality of interconnected, generally vertically depending glass fibers that substantially block the furnace outlet when the curtain is "closed." ,
As the metal passes through the furnace, it is forced open to allow the metal to exit the furnace.

A directional nitrogen injector 32 with a puff ray or hole oriented at an angle of 45° to the perpendicular to the direction of the heat treatment zone 8 extends downward into the upper part of the cooling zone 1'C. Injector 32 is located between injector 30 and heat treatment zone 8 .

In operation of furnace 2, nitrogen is typically supplied to injectors 30 and 3.
2 into the cooling zone 10 to expel air from the furnace. The device for heating the heat treatment zone 8 is then activated to bring the temperature therein to the desired location 111! Bring to temperature. Nitrogen and methanol are then introduced into the heat treatment zone 8,
Create the necessary atmosphere in it. The methanol enters the treatment zone 8 in liquid form, where it is vaporized by extensive expansion. Similarly, nitrogen introduced into processing zone 8 through injectors 18 and 20 and inlets 14 and 16 is heated from ambient temperature to processing temperature and also expands. The nitrogen introduced into the cold zone 10 from the injector 32 has a velocity component in the direction of the heat treatment zone 8 , and the flow expands within the heat treatment zone 8 and exits the cooling zone 10 .
be sufficient to substantially prevent the flow of gas into the

Therefore, most of these gases flow in the direction of the inlet 4.

The gases enter the flue 38 where the flammable components are burned off. A sliding plate 40 is woven to regulate the gas flowing into the flue 38.

- Inside the shell, the gas flow passing under the plate 40 is sufficient to prevent a significant amount of air from entering the furnace through the inlet 4. However, if necessary, nitrogen is introduced into the furnace between the processing zone 8 and the inlet 4 by a nozzle or injector (not shown) having one or more outlets directed towards the inlet 4. You may also do so. This additional nitrogen flow helps prevent air from entering through inlet 4.

The structure of the injector 30 and curtain 34 substantially restricts air from entering the furnace through the outlet 6.

If any flue, such as flue 38, is provided at the outlet 6 to burn off the non-flaming gases, it must be sealed to prevent air from entering the furnace through it. Must.

A nitrogen methanol supply SUM suitable for use with the furnace of FIG. 1 is shown in FIG. The apparatus includes a nitrogen supply pipeline 50 connected to a commercial purity nitrogen source (not shown). The nitrogen source is typically a vacuum-insulated tank containing liquid nitrogen, and a vaporizer is attached to the top of the tank to vaporize the liquid nitrogen. Supply vii also
A pipeline 52 is provided that connects to a tank (not shown) containing liquid methanol. The supply of methanol to this pipeline 52 may be effected by a pump or by the pressure of nitrogen supplied to the drawdown space of the methanol tank.

An isolation or shutoff valve 54 is provided in the nitrogen pipeline 50, connecting the inlets 14 and 16, the injectors 18, 20, 30, 32
Operate so as to cut off the nitrogen source from the nitrogen source. pipeline 5
A pressure regulator 56 is provided downstream of the valve 54, and a pipe 58.6 is connected to the pipeline 50 downstream of the pressure regulator 56.
Adjust the pressure of nitrogen supplied to the 0.62.64. The pipe 58 leads to two branch pipes 72 and 74, which branch pipes 172 and 74 respectively connect the injectors 30 and 3.
Supply to 2. Vibro 0 connects to inlets 14 and 16. Vibro 2 is connected to nitrogen pipe 22 of injector 18 and Vibro 4 is connected to nitrogen pipe 24 of injector 20. Each Vibro 0°62.64 is equipped with a flow control well 66. A flow meter 68 is provided downstream of these valves 66 . Also, 5m1t for pipe 58
ea is provided. A pressure regulator 70 is provided downstream of each flow meter 68 of the Vibro 0.62.64.

Pipe 58 connects to pipes 72 and 74, and each of these pipes 72 and 74 is provided with a flow it II III valve 76 and 78, respectively. The apparatus shown in FIG. 2 includes a device for heating the nitrogen supplied to the injector 20. The heating device comprises a drum 82 containing water with an inlet 80 submerged under the water. Inlet 8o connects to pipeline 64 downstream of valve 70. The drum 82 has an outlet that connects with a pipe 86 that leads to the nitrogen pipe 24 of the injector 20. This and the inlet 80 of the pipeline 64
If the nitrogen flowing downstream of the connection point with is dry, valve 84 is opened and all nitrogen in pipeline 64 flows through valve 84 to pipe 86. When valve 84 is closed, all nitrogen in pipeline 64 passes through drum 82. The purpose of this heater will be explained later.

The methanol pipeline 52 is connected to a first insulating or shutoff valve 8
8. This valve 88 has a filter 90 downstream thereof to remove solids suspended in the methanol. Pipeline 96 connects to pipeline 52 on the F flow side of filter 90
Connect to. Pipeline 96 connects to methanol pipe 26 of injector 18 . A flow control valve 9 is installed in the pipe 96.
8 is provided, and a flow meter 100 is installed downstream of this valve 98. A m flk Ill Ill valve 92 is provided downstream of the connection point of the pipeline 52 with the pipeline 96, and a flow meter 94 is provided downstream of this valve. Downstream of the flow meter 94, the pipeline 52 connects to the methanol pipe 28 of the injector 20.

Make modifications to install injectors 18, 20, 30, 32 and h-T'
ltA)), the furnace 2 is operated at 2
．． It was operated by directing 1,000 standard cubic feet (54 cubic meters) of concentrated exothermic gas into heat treatment zone 148 through inlets 14 and 16. The resulting flaming gas mixture was burnt out at both ends of the furnace. It has been found that when the furnace is modified as shown in FIGS. 1 and 2, bright workpieces are obtained by carrying out the method of the invention. In one exemplary example, a universal joint forging is annealed at 900° C. in heat treatment zone 8 and then cooled in cold zone 10 to about ambient temperature! He was ranked J1. The supply of nitrogen and methanol to each fluid inlet and injector was performed as follows.

Inlets 14 and 16: 220el subcubic feet (5,
94 m3) of nitrogen.

Injectors 18 and 20: 400 standard cubic feet per hour (11
, 88 m3) of nitrogen and 2 liters of methanol per hour.

Injector 30: every ii oo standard cubic feet (2,7 m
3) Nitrogen.

Injector 32: 100 standard cubic feet per hour (2.7Tr
L3) (7) u element.

The flow was split equally between injectors 18 and 20. One liter of methanol per hour decomposes at the processing temperature to produce 20 standard cubic feet (0.54 m3) of carbon oxide per hour and 40 standard cubic feet (1.08 m3) of hydrogen per hour. Therefore, the total flow rate of gas into the furnace is 1°000 per hour.
It can be seen that this results in a standard cubic foot (27TrL3), which is half the exothermic gas flow rate.

Various parts, from large castings to small presses, are processed in a furnace supplied with nitrogen and methanol at the above rates and with a maximum temperature in the heat treatment area in the range of 720 to 1060°C. I was disappointed.

FIG. 3 shows the changes in the composition of the furnace atmosphere at various points in the furnace when the processing zone 8 is operated at 970°C. As can be seen in this figure, the concentration of hydrogen in the atmosphere in the treatment zone 18 is approximately 7%, and from there it gradually decreases along the cooling zone 10 in the direction of the outlet 6 and reaches the outlet 6. Before that, it had fallen to less than 1%. Similarly, carbon monoxide levels range from values between 3,5% and 4% in heat treatment zone 8 to heat treatment zone 1it! 8 and down to a value of less than 1% at the end of the cooling zone 1o opposite to 8. Similarly, the carbon dioxide concentration decreases from about 0.4% in the heat treatment zone 118 to less than 0.1% at the end of the cooling zone 1o opposite to the heat treatment zone 8 (all percentages are by volume). be). The gas immediately leaving the furnace outlet 6 is substantially free of flammable reducing gas.

In this example, methanol was chosen as the reducing gas source since the workpiece being treated was oily. This provides a relatively high dew point of the atmosphere within the heat treatment zone and eliminates entrained oil buildup on the heating element when a nitrogen methane or nitrogen hydrogen atmosphere is used.

However, since the cooling zone 10 is supplied with nitrogen, a predominantly non-reactive atmosphere is created there, so that workpieces with a bright finish can be obtained.

Injectors 18 and 20 were designed such that their pipes 22 and 24 were open at the bottom but provided with orifices on their sides. Therefore, the methanol coming out of pipes 26 and 28 is the l! of pipes 22 and 24. It hits the end of the I chain and breaks, forming a drop. These droplets are carried by nitrogen through the orifices of pipes 22 and 24 and enter the treatment zone 8. This prevented the relatively fast moving methanol jet from striking heating elements in other parts of the furnace before it vaporized. If such a blow were to occur, it would result in carbon deposits on the workpiece.

Also, at the level of hydrogen and carbon oxide used in heat treatment zone 8, the air into the furnace is sufficient to reduce the dew point of the atmosphere in cooling zone 10 to such a level that inferior quality workpieces are produced. It has been found that it is generally desirable to direct the nitrogen from the injector 30 toward the curtain 34 to avoid large ingress.

A hot water drum 82 was used to prevent soot build-up on the workpiece and furnace structure by adding water vapor to the atmosphere, especially if the workpiece was contaminated with oil or grease.

When processing large presses, a flame saw was constructed under the mesh belt 11 at the inlet end of the furnace. The purpose of this is to consume the oxygen in the air trapped on the underside of the press.

EXAMPLE 2 This example concerns the sintering of bronze onto a steel backing in a suitable continuous sintering furnace as shown in FIG.

In FIG. 4, a continuous furnace 200 includes an inlet 202 for the workpiece to be sintered, a heat treatment zone 204 having a device (not shown) for heating the workpiece to a processing temperature, an inlet 202 and a heat treatment zone 202.
4, a workpiece outlet 208, and a cooling zone 210 between the heat treatment zone 204 and the outlet 208. ? ? Adjacent to the heat treatment zone 204 of the 7w zone 210 is an inlet vibrator 212 that supplies a gas mixture into the zone 204 suitable to create the required atmosphere within the heat treatment zone 204 . Inlet 212 is part of the normal fittings of the furnace. In addition to the inlet 212, eight injectors 214 are connected to the cooling section 14.
210. Each injector 214 is connected to a respective nitrogen supply pipeline 216, and into these pipelines 216 is a flow ffi ill III valve 2.
18 and a calibrated orifice 220 downstream thereof.

All pipes 216 are a common pipeline 222 for nitrogen supply.
Connect to.

A nitrogen distribution pipe 224 extends into the furnace near outlet 208. The orientation of this distribution pipe 224 can be adjusted to change the direction of gas emitted therefrom.

The orientation is preferably such that a substantial velocity component is created in the direction of the exit. Normally, distribution pipe 22
4 has an exit orifice whose axis extends at an angle of 45° to the vertical.

A curtain 226 between the injection pipe 224 and the outlet 208
will be installed. The construction of this curtain is the same as that described in FIG.

The distribution pipe 224 has its own nitrogen supply pipe 228 which is equipped with a flow control valve 230 and a calibrated orifice 232 downstream thereof. Pipe 228 is connected to pipeline 222.

Cooling zone 210 is typically cooled by a water jacket 234 .

By means of a distribution pipe 238 similar to distribution pipe 224,
Section 206 of furnace 200 is also supplied with nitrogen. Bye 12
38 is installed so that a substantial velocity component of the gas to be injected from it is in the direction of the inlet 202. Typically, the pipe 238 is constructed so that the gas exiting from it is at a 45° angle to the vertical. pipe 238
is connected to pipe 240. This pipe 240 has a certified orifice 242 and a flow control valve 24 upstream thereof.
4.

Gas population 212 is connected to a gas mixing panel 246, which in turn is connected to a nitrogen source (not shown) and a source of cracked ammonia. A nozzle entry lobe 250 is provided as a standard fitting at the inlet and outlet ends of the furnace. These pipes are sealed. Flues 252 are also provided at the inlet and outlet ends of the furnace. The flue at the outlet end of the furnace is sealed.

The operation of the furnace of FIG. 4 is substantially the same as that of FIG. The workpiece to be sintered is conveyed through furnace 200 by suitable equipment (not shown). A selected mixture of nitrogen and decomposed ammonia is supplied to the inlet 21 located within the cooling zone 210.
2 into the heat treatment zone 204 of the furnace. Injector 2
Nitrogen is introduced by 14 into a plurality of spaced locations within the cooling zone 210 to help prevent free flow of gas from the inlet 212 and the heat treatment zone 204 toward the outlet 208 . is created within the cooling zone 210. Further, curtain 226 prevents gas from exiting furnace 200 through outlet 208. curtain 22
6 also prevents air from entering the furnace through the outlet 208 along with the nitrogen injected from the distribution pipe 224 towards the curtain. Similarly, nitrogen directed from the distribution pipe 238 toward the inlet 202 helps prevent air from entering the furnace through the population 202.

The nitrogen and cracked ammonia entering the heat treatment zone 204 expand, and the heat WIL'l! is generated because nitrogen is introduced into the cooling zone 210 from the injector 214. It exits section 204 through section 206 and enters flue 252 . The flaming gas (hydrogen) contained therein is burnt out in this flue. Injector 214 and distribution pipe 224 to cooling zone 2
By introducing nitrogen into 10, the outlet 2 is removed from the furnace.
The amount of flaming gas contained in the gas exiting through 08 will be negligible.

Typically, when sintering powdered bronze onto a steel backing, an atmosphere containing 20 to 30% by volume hydrogen and the balance nitrogen is preferably used. This atmosphere is supplied into the furnace through inlet 212 and sealed inlet 250. The amount of hydrogen required can be substantially reduced, and each injector 214 and distribution pipe 2
Nitrogen flow to 24 and 400 to 50% per hour is typically
0 standard cubic feet (10,8 to 13,5 m3) k:
Become. This nitrogen flow is split evenly between the eight injectors and distribution pipes.

The gas mixture supplied to pipe 212 and thus to heat treatment zone 204 is typically 50 standard cubic feet per hour (50 standard cubic feet per hour).
1,357 FL3) of cracked ammonia (25% nitrogen and 75% hydrogen) and 300 standard cubic feet per hour (8,
17FL3). Nitrogen is preferably supplied at a rate of 150 to 200 standard cubic feet per hour.
05 to 5.47 FL3) to the distribution pipe 238.

Example 3 This example concerns bright annealing of stainless steel strip performed in a vertical annealing furnace.

In FIG. 5, a vertical stainless steel bright annealing furnace 300 includes an ascending leg 302 and a descending leg 304 connected at the top by a connecting section 306.

There is a strip inlet 308 at the bottom of the lift leg 302;
At the bottom of the descending leg 304 is a strip outlet 310.

The inlet 308 and outlet 310 are narrowed compared to the overall cross-sectional area of the leg. Baffle 312 near entrance 308
An inlet 30 is provided from above the baffle.
Regulates the flow of gas toward 8. A similar baffle is provided near the outlet 310 to restrict the flow of gas from above to the outlet 310. A guide roll 314 is provided at the inlet 30 for continuously feeding the strip through the furnace.
8, outlet 310 and section 306.

A heat treatment zone 320 is set in the upper section of the descending leg 304. This heat treatment area is surrounded by radiant heating elements 322 from the outside of the lower leg 304. A cooling zone 318 is provided and provided below the heat treatment zone 320 in the descending leg 304 . The cooling zone 318 includes a fan (not shown) to circulate gas therein.

Gas inlets to the ascending leg 302 and descending leg 304 of the furnace 300 are provided at multiple spaced locations on the legs. The first nitrogen population 324 is located in the area near the inlet 308 of the ascending leg (inlet 3
08 and its baffle 312) to prevent air from entering the furnace 300.

A plurality of inlets 326, all connected to the rising legs of the furnace, also create an atmosphere in the W leg meat that is substantially composed of nitrogen. A third population 328 supplies nitrogen to the portion of the descending leg 304 near the exit 0310 between this exit and its baffle 312 . The nitrogen thus directed to the outlet 310 substantially completely prevents air from entering the furnace through the outlet 310. A plurality of inlets 330 supply hydrogen or cracked ammonia (3 parts hydrogen and 1 part nitrogen) to cooling zone 318 . The relative feed rates of nitrogen and hydrogen (or cracked ammonia) to the furnace are selected to create favorable conditions in the cooling and heat treatment zones for bright annealing the stainless steel. By completely or nearly eliminating air from the furnace, much less hydrogen or cracked ammonia can be used than would otherwise be possible. Additionally, by delivering enough nitrogen to the riser leg 302 to prevent the flow of hydrogen from the faller leg 304 to the riser leg 302, the rate of hydrogen supply to the furnace is adjusted to the desired rate within the cooling and heat treatment zones. You can limit it to only what is necessary to create the atmosphere. Therefore,
Much less hydrogen can be present in the atmosphere than in conventional processes using cracked ammonia.

Nitrogen also flows from the ascending leg 302 to the descending leg 304. The atmosphere within cooling zone 318 and heat treatment zone 320 therefore includes both nitrogen and hydrogen. However, the proportion of hydrogen in the cooling area is higher.

Negatively, in conventional bright annealing of stainless steel in a furnace using decomposed ammonia, 2.600 cubic feet per hour (70,21 FL3) (1) decomposed ammonia was used; can reduce the total gas flow rate to the order of 1,700 to 1.800 cubic feet (45.9 to 48.6 m3) per hour.

In order to perform proper cooling within the cooling zone 1i11318, heat treatment area Fl! It is customary to use an atmosphere containing higher concentrations of hydrogen in the tg range. This is because hydrogen has higher thermal conductivity than nitrogen.

If the hydrogen source is cracked ammonia, the hydrogen concentration in the cooling zone will be 60 to 62% (50°C dew point).

Also, if the hydrogen source is a cylinder of commercially pure hydrogen, the hydrogen concentration should be 54-60% by volume (55°C dew point). However, the hydrogen trace in the atmosphere in the heat treatment zone is typically 36 to 43% by volume when the hydrogen source is cracked ammonia, and 28 to 41% by volume when the hydrogen source is a cylinder of compressed commercially pure hydrogen. Let's be Such an atmosphere can generate between 800 and i,ooo cubic feet per hour (21,6
Inlets 324 and 32 at a flow rate within the enclosure of 277FL3)
6 into the rising leg 302, m hours 300 to 400
cubic feet (8,1 to 10,8 m3) 17) flow rate of nitrogen from inlet 328 into descending leg 304 and inlet 3
30 into the cooling zone 318 at a flow rate of 400 to 450 cubic feet (10,8 to 12,15 m3) per hour (or at a flow rate of 200 to 300 cubic feet (5,4 to 8,17 FL3) per hour). It can be made by introducing (hydrogen). The less dense hydrogen moves upward, and the nitrogen in the ascending leg 302 moves to the descending leg 3.
04, the gas analysis results are as shown in Table 3.

The results of this analysis are based on a quantitative stainless steel strip (30
0 series) was annealed at a temperature of 1050°C. The exact amount of hydrogen required in the cooling zone will depend on the thickness of the strip. - The thicker the strip in the shell, the greater the amount of hydrogen required in the cold zone. If necessary, the furnace can be shut down periodically, for example every weekend, but still by supplying a gas mixture of 96% nitrogen and 4% hydrogen by volume to section 306. Conditions are maintained that create such an atmosphere throughout the furnace.

Example 4 This example relates to bright annealing of ferrous or non-ferrous metal strip in a FHD mesh belt furnace.

In FIG. 6, a mesh belt (not shown) passes the strip or other metal to be processed into the furnace through an inlet 6o2 and out of the furnace through an outlet 604. The furnace is
Sequentially from inlet 602 to outlet 604 are an inlet zone 606, a heat treatment zone 608, and a cooling zone 610. At the end of the cooling zone 610 opposite the heat treatment zone 608 are chambers 612, 614, 616 defined by a generally vertical partition 618 and the furnace wall. A doubling plate 619 is provided at the outlet 604.

This I! ! ! The moving plate is the closest partition 618
Together with this, another chamber 621 is defined.

A flare-off device 620 is coupled to the top or ceiling 11 of the inlet area 606 at a location between the chamber 622 and the heat treatment area 608 within the inlet area 606 . The chamber 622 is defined by the furnace wall, a first sliding plate 626 provided at an angle to the vertical, and a hinged plate 624.Hinged plate 62
4 can be moved up and down to change the size of the gap between its lower edge and a mesh belt (not shown).

Chambers 612, 614, and 616 are each filled with an upper nitrogen supply.
! communicates with S chamber 628 and lower nitrogen supply filling v630;
The chamber 622 also has similar nitrogen supply sources vA' above and below.
i! Connects with 632.634.

The furnace also has a variable angular number '! It is equipped with an Ii elementary injector 636. In addition, the heat treatment section [60
A nitrogen inlet 640 is provided adjacent to 8. Furthermore, a variable angle hydrogen injection illumination 638 is provided in the cooling zone 610 adjacent to the chamber 612.

The configuration of chambers 612, 614, 616 is shown schematically in FIG.

As can be seen, the partition 618 is constructed by a steel plate or flap hinged to a support 642 depending from the ceiling 644 of the furnace.

A plurality of spaced apart slots 648 are provided in the ceiling 644 and floor 646 of the furnace through which nitrogen flows into the chamber 6.
28 and 630 to chambers 612, 614, and 616. Chambers 628, 630 have nitrogen inlets 650 and 652 that connect to a nitrogen source. Baffle plates 654 and 656 are provided within chambers 628 and 630 to
0.652 and slot 648 to prevent a direct path. Therefore, during operation, nitrogen is supplied to the baffle 654°6.
56 and enters the furnace through slot 648, typically creating a laminar flow of gas. In order to deflect the nitrogen in the direction of the outlet and create a horizontal velocity component in that direction, the partition 618 is oriented at an angle of approximately 10° to the vertical such that its lower edge is closer to the outlet 604 than its upper edge. It is hung with.

The lower edge of each partition 618 contacts the metal strip being processed as it passes through the furnace. If desired, sealing means (not shown) may be provided at the edges of each partition 618 to substantially eliminate gas flow between the partition and the oven wall. However, between the rooms,
Communication remains between what passes over the top edge of the partition and what passes through the mesh belt 658 of the furnace. However, it is easy to provide a seal at such an upper edge if necessary. - The less communication between the chambers 612, 614, 616 in the thigh, the better the flow of hydrogen and other gases exiting the furnace through the outlet end 604 and the flow of air entering the furnace through the outlet end 604. The amount can be reduced, therefore, chamber 61
2,614.616 and the heat treatment zone 608 to create a high hydrogen concentration in the cooling zone 610 while creating a non-flaming atmosphere in the chamber 621 next to the outlet 604. This also substantially prevents air from entering the furnace through outlet 604.

The operation of the furnace shown in FIGS. 6 and 7 is as follows.

nitrogen is supplied to chambers 628, 630, 632, 634;
Expel the air from the furnace. The heat treatment zone 11608 is heated to the heat treatment temperature by a heating device (not shown) provided in the furnace. Hydrogen is then supplied to the furnace from variable angle injector 638. The angle of the injector 638 is typically such that it directs the gas downwardly at a 20° angle to the vertical and has a horizontal velocity component in the direction of the inlet end of the furnace. The hydrogen reacts with residual air in the heat treatment zone, and once substantially all residual air is removed, the strip is continuously passed into a furnace to be annealed. When this process is performed, the furnace is set so that inlets 636 and 640 are closed and plates 624, 626, 619 are in their lowest positions.

Nitrogen is supplied to chambers 612 and 61 from upper and lower supply chambers 628 and 630.
4. Sent to 616. These '3612°614.6
A pressure higher than the outside air pressure is applied to the interior of the chamber 16. A portion of the nitrogen therefore flows from chamber 616 to chamber 621 and exits 604.
and exit the furnace.

Hydrogen is introduced into cooling zone 14610 from injector 638 and into cooling zone 610 from chambers 616, 614, 612.
As the nitrogen flows inside, a gas mixture of nitrogen and hydrogen flows into the heat treatment section 1fi608. This directional flow is caused in part by partition 618 and chamber 612.61.
4.616 and in part by the combustion of the flaming gases exiting the heat treatment zone 608 in the 7 rare-off device a620 (such combustion Furnace inlet 602
(to help guide people in the direction of) As the gas flows or diffuses toward the heat treatment zone ki 1608, it is gradually heated by convection from the heat treatment zone. Such heating causes the gas to expand and create a back pressure within the cooling zone 610. Therefore, as long as nitrogen is supplied to chambers 628 and 630 at a suitable flow rate, cooling section 1610
adjacent to and connected to chamber 612 within heat treatment area 608
The pressure located between is higher than the ambient pressure and also higher than the pressure within the heat treatment zone 608 itself.

A portion of the hydrogen flows into chamber 6 in a direction opposite to the overall direction of flow.
12,614,616 should be refined to diffuse through. The introduction rates of nitrogen and hydrogen are selected such that the hydrogen concentration in the cooling zone 610 and heat treatment zone 608 of the furnace is relatively high (e.g., greater than 50% by volume);
Exit 604 generally through chambers 612, 614, 616
The hydrogen diffusing in the direction is gradually diluted by the nitrogen so that the gas mixture as it exits the furnace outlet 604 is non-flaming.

A portion of the gas in the heat treatment zone 1i 1608 is transferred to the cooling zone 61.
0, but because of the pressure differential in the direction of the net flow of gas through the furnace, the majority of the gas in the heat treatment zone 608 flows in the direction of the furnace inlet 602.

As mentioned above, the flaming gas mixture is transferred to the flare-off device 620.
burned inside. Nitrogen supplied to chamber 622 from supply chambers 632 and 634 helps prevent hydrogen from flowing beyond the combustion zone and prevents air from entering the furnace through inlet 602.

By keeping the rate of air ingress into the furnace low in this manner, the amount of reducing gas needed to create a non-oxidizing atmosphere can be much reduced. Furthermore, by providing flow to only one flare-off or combustion outlet, the total amount of gas used in the furnace per unit time can be reduced. These advantages of the present invention are achieved without compromising the quality of the metal or workpiece treatment.

Table 4 summarizes the experimental results obtained when the heat treatment zone was operated with warm melon at 600°C. The hydrogen concentration was measured by taking samples at various locations in the furnace, and the samples were used to measure the oxygen potential of the atmosphere at locations.

The steps from location to 1 are as follows.

8 - In the chamber 622, B-7 In the entrance area 606 near the rare-off device 620, C - In the heat treatment area 608, D - Heat treatment area 608 closer to the cold W area 610 than location C.
E-cooling zone 61 between heat treatment zone 608 and chamber 612;
0 inside, F-chamber 612, G-chamber 614, 1-1-chamber 616, 1-chamber 621.

Experiments 1 and 2 demonstrate that the hydrogen concentration in the cooling and heat treatment zones can be relatively high while the gas exiting the furnace through outlet 604 is non-flaming. ing. In experiment number 3, additional nitrogen was supplied to the furnace through inlet 640. As a result, the proportion of hydrogen in the heat treatment zone was substantially lower than in the first and second experiments, although the proportion of hydrogen in the cooling zone was still relatively high. This indicates a generally unidirectional flow from the cooling zone to the heat treatment zone.

Experiments 4 and 5 show that all of the nitrogen supplied to chambers 612, 614, 616 can be introduced from upper fill chamber 628, and the nitrogen supplied to chamber 622 can be introduced from lower fill chamber 634.

A chamber near the outlet end of the furnace can be created by attaching a custom unit to the outlet end, thereby extending the length of the furnace.

The method of the invention can be carried out in a continuous sintering furnace having a zone in which oil and lubricants deposited on the workpiece to be sintered are oxidized. Such a zone is located between the furnace inlet and the heat treatment zone. Typically the sintering temperature in the heat treatment zone is 1
100°C, and 500 to 700°C in the lubricant removal zone
The temperature is maintained within the range of . The furnace may be provided with chambers such as those shown in FIGS. 6 and 7 at its inlet and outlet ends. In such a furnace, gas is supplied at the following rate and a suitable gas flow is created by burning off the gas only near the inlet end. Nitrogen is supplied to the chamber at the end of the cooling zone opposite the heat treatment zone at a rate of 150 to 200 cubic feet (4,05 to 5.'1 L3) per hour, and to the chamber at the inlet end of the furnace at a similar rate. Supplied by Gas generated from an endothermic generator (containing approximately 40% hydrogen by volume in the Litt type) at a rate of 100 cubic feet (2.7 m") per hour is outside the chamber within the cooling zone. At a point nearby, it flows into the cooling area.

Such an endothermic gas can also be used at a rate of 250 cubic feet per hour (
6,75 m3) into the cooling zone at a point close to the heat treatment zone, and nitrogen is introduced at a rate of 350 to 400 m3).
cubic feet (9.45 to 10.8 m3) are introduced into the same area. This creates a general flow of nitrogen and water in the direction of the heat treatment zone, maintaining a reduced S condition in both the cooling zone and the heat treatment zone. 200 cubic feet (5.4 m3) of heated nitrogen per hour is pumped into the area between the heat treatment zone and the oxidation zone of the furnace to create conditions for oxidation of oils, lubricants, etc. in the oxidation zone. .

This addition of nitrogen is carried out in such a way as to oxidize the lubricant etc. on the compound without decarburizing the workpiece itself to be sintered. The flaming gas mixture exiting the oxidation zone is burnt out. This step helps create a gas flow generally in the direction of the furnace inlet. The gas demand is substantially less than in conventional furnace operation where the flaming gas mixture is burnt out at both the inlet and outlet ends.

Embodiments of the invention are as follows.

(1) Sequentially provided inlet, heat treatment area, cold 7
A method of heat treating metal in a continuous furnace having a JI section and an outlet, the method comprising: substantially preventing air from entering the furnace through the inlet and the outlet; introducing a gas flow into the furnace to bring substantially the entire furnace to non-oxidizing or reducing conditions and creating an atmosphere of different composition in the heat treatment zone and the cooling zone; A method comprising the steps of passing the metal through the furnace from to the outlet.

(2) In the method of item 1 above, the continuous furnace is a horizontal furnace, and the gas flowing out from the heat treatment area is substantially
(3) In the method of paragraphs 1 or 2 above, the non-reacted gas flows from the heat treatment zone in the direction of the cold FJI zone. is supplied to one or more locations of the cooling zone.

(4) The method of paragraph 3 above, wherein the non-reacting gas and reducing gas are introduced into the cooling zone and a flow is created such that a substantial portion of the reducing gas flows into the heat treatment zone. .

(5) In the method of any one of paragraphs 2 through 4 above, a direct flow of gas through the outlet so as to prevent or substantially restrict air from entering the furnace through the outlet. 1 in the cooling zone or in the vicinity of the outlet to make
A method in which the non-reacting gas is introduced into the furnace from one or more points.

(6) In the method of any one of paragraphs 2 through 5 above, the outlet includes a flow restriction device that prevents gas flow into the furnace without preventing the metal being treated from exiting the furnace. A method provided for.

(7) The method of any one of paragraphs 2 through 6 above, wherein the portion of the cooling zone proximate to the furnace outlet defines at least one chamber through which the metal to be processed can pass. (8) a method comprising a partition and/or curtain (or the like) in which the non-reacting gas is introduced directly into at least one of the chambers;
partitions and curtains (or the like) having an outlet and defining, at or near at least one end, at least one chamber through which the metal to be processed can pass; A method of heat treating metal in a continuous furnace comprising one or both of the following:
introducing one or more gases into the chamber to substantially prevent air from outside the furnace from entering through the chamber and into the furnace section between the chamber and the heat treatment area; and passing metal through the furnace from the inlet to the outlet.

(9) In the method set forth in paragraph 7 or paragraph 8 above, P.
c>Pu and Pu>l) a With Te, Kokote,
A method in which Pc is the pressure in the chamber or one of the chambers, Pu is the pressure in the cooling zone near the chamber and between the chamber and the heat treatment zone, and Pa is the ambient pressure.

(10) In the method of item 9 above, at least two chambers are provided, and Pc>Pu>Pt>PaFM, where pc is the pressure in the chamber closest to the heat treatment area, and Pu and Pa are the patent A method as in claim 10, wherein Pt is the pressure within the heat treatment zone.

(11) In the method of paragraph 1 above, the furnace is a vertical furnace having two generally vertical legs connected at the top, and the workpiece to be heat treated has one waist leg (rising leg). and downwardly through the other leg (the descending leg), a heat treatment zone being provided at or near the top of the leg meat, and a cooling zone being provided at the bottom of the leg meat in the descending vagina. A method provided on the underside of the heat treatment area.

(12) In the method of paragraph 11 above, reducing gas is introduced into the cooling zone and/or heat treatment zone, and substantially preventing the reducing gas from flowing into the ascending leg. Non-reacting gas is introduced into a plurality of locations in the decamate leg, and non-reacting gas is introduced into the outlet of both the upper Schiff leg and the lower arm to substantially prevent air from entering the furnace. the reducing gas is hydrogen and is introduced into the cold W zone, the cooling zone and the heat treatment zone containing an atmosphere comprising nitrogen and hydrogen, and the cooling zone tii
A method in which the proportion of hydrogen in the atmosphere is greater than in the heat treatment zone atmosphere.

[Brief explanation of the drawing]

1 is a schematic diagram of a mesh belt for carrying out the method of the invention; FIG. 2 is a schematic diagram showing a flow circuit for supplying nitrogen and methanol to the furnace of FIG. 1; FIG. , a graph showing typical examples of the composition of the atmosphere at various points along the length of the furnace; Figure 4 is a schematic diagram of a continuous sintering furnace; Figure 5 is a diagram showing a typical example of the composition of the atmosphere at various points along the length of the furnace; FIG. 6 is a schematic diagram of another Metschbelt furnace for carrying out the method of the invention; FIG. 7 is a schematic diagram of a chamber forming part of the cooling zone of the furnace of FIG. This is a schematic diagram showing the structure of . 2...Mesh belt heat treatment furnace, 4...Workpiece inlet, 6...Same outlet, 8...Heat treatment zone, 10...Cooling zone, 11...Mesh belt, 12...Belt feed roller , 14.16... gas supply inlet, 18.2
0...Nitrogen/methanol injector, 30.32...Nitrogen injector, 34...Curtain, 38...1! F! road, 4o... sliding plate, 50... nitrogen supply pipeline, 52... methanol supply pipeline, 82... warmer, 200...
Continuous sintering furnace, 202--Workpiece entry, 204--Heat treatment zone, 206--Inlet zone, 208--Workpiece outlet, 210--Cooling zone, 212--Gas mixture inlet Vibrator, 214...Nitrogen supply injector, 216.228...Nitrogen supply pipeline, 222.
...Nitrogen supply common pipeline, 224.238...
Nitrogen distribution pipe, 226...Curtain, 234...
Water jacket, 246... Gas mixing panel, 252...
...Flue, 300...Vertical annealing furnace, 302...Rising shaft, 304...Untimely landing gear, 306...Joining section, 308...Workpiece inlet, 310...Same outlet, 31
2... Baffle, 314... Workpiece guide roll, 3
18... Cooling zone, 320... Heat treatment zone, 322
...Heating element, 324.326,328...Nitrogen inlet, 330...
Hydrogen or ammonia inlet, 602...F HD mesh belt heat treatment furnace processed product inlet, 604... same outlet,
606...Enter [1 zone, 608...Heat treatment zone, 6
10... Cooling area, 612, 614, 616, 621
．． 622...Room, 618...Partition, 619.624.626...Plate, 620...
Flare-off device, 628.630, 632.634... Nitrogen supply filling chamber, 636... Nitrogen injector, 638... Hydrogen injector,
640... Nitrogen inlet, 642... Partition support, 64
4... Furnace ceiling, 646... Same method, 648... Slot, 650.652... Nitrogen inlet, 654.656
...Baffle, 658...Metschwert.

Claims (12)

[Claims] (1) A method of heat treating discontinuous metal parts in a continuous furnace having a successive inlet, heat treatment zone, cooling zone, and outlet, wherein air enters the furnace through the inlet and outlet. introducing non-reacting gases and reducing gases into predetermined locations within the furnace; bringing substantially the entire furnace under non-oxidizing or reducing conditions and having different heat treatment zones and cooling zones; A method comprising the steps of creating a gas flow in the furnace to create a compositional atmosphere and passing the metal parts through the furnace from the inlet to the outlet. (2) The method of claim 1, wherein the continuous furnace is a horizontal furnace, and the gas exiting the heat treatment zone flows substantially from the outlet toward the inlet. (3) In the method of claim 1 or 2, the non-reacting gas is contained in one or more of the cooling zones to prevent gases from the heat treatment zone from escaping through the cooling zone. The method by which the parts are supplied. (4) In the method of claim 3, the non-reacting gas and reducing gas are introduced into the cooling zone, and a flow is created such that a substantial portion of the reducing gas flows into the heat treatment zone. How to do it. (5) In the method of any one of claims 2 to 4, the gas passing through the outlet prevents or substantially restricts air from entering the furnace through the outlet. The non-reacting gas is introduced into the furnace from one or more points within the cooling zone or near the outlet to create a positive flow of. (6) In the method of any one of claims 2 to 5, a flow restriction device for preventing gas flow into the furnace without blocking the metal being treated from exiting the furnace. is provided at the outlet. (7) In the method according to any one of claims 2 to 6, the portion of the cooling zone near the furnace outlet
spaced partitions and/or curtains (or the like) defining at least one chamber through which the metal to be treated is passed, the non-reacting gas being introduced directly into at least one of the chambers; method. (8) at least one inlet, a heat treatment zone, a cooling zone, and an outlet provided sequentially and capable of passing the discontinuous metal part to be treated at or near at least one end thereof; A method of heat treating metals in a continuous furnace with spaced partitions and/or curtains (or the like) defining a chamber, in which a suitable heat treatment area is provided to create a suitable atmosphere for the heat treatment. introducing one or more gases into the chamber to substantially prevent air from outside the furnace from entering through the chamber and into the furnace section between the chamber and the heat treatment area; and passing the metal part through the furnace from the inlet to the outlet. (9) The method of claim 7 or 8, wherein Pc>Pu and Pu>Pa, where Pc is the pressure in the chamber or one of the chambers, Pu is the pressure in the vicinity of the chamber and A method, wherein the pressure in the cooling zone between the chamber and the heat treatment zone, Pa is ambient pressure. (10) The method of claim 9, wherein at least two chambers are provided, and Pc>Pu>Pt>Pa, where Pc is the pressure in the chamber closest to the heat treatment area; A method in which Pu and Pa are the same as in claim 10, and Pt is the pressure within the heat treatment zone. (11) The method of claim 1, wherein the furnace is a vertical furnace having two generally vertical legs connected at the top, the workpiece to be heat treated being a heat treatment zone is provided in or near the top of the descending leg, and a cooling zone is provided in the descending arm. A method provided on the underside of the heat treatment area. (12) The method of claim 11, wherein a reducing gas is introduced into the cooling zone and/or the heat treatment zone, and the reducing gas is substantially prevented from flowing into the ascending leg. A non-reactive gas is introduced into a plurality of locations on the ascending leg to prevent air from entering the furnace, and a non-reactive gas is introduced into the exits of both the ascending leg and the descending arm to substantially prevent air from entering the furnace. or into the vicinity thereof, the reducing gas is hydrogen, and the cooling zone and the heat treatment zone contain an atmosphere comprising nitrogen and hydrogen; A method in which the proportion of hydrogen is greater in the heat treatment zone atmosphere.