Thermal processing furnace for workpieces

A thermal processing furnace for workpieces has a blowing hood in which a nozzle is installed, the nozzle blowing a gas flow to thermally process a workpiece, including a driving mechanism that adjusts a distance between the nozzle and a portion of the workpiece facing the nozzle so that the gas flow blown from the nozzle impinges on workpieces of various dimensions at a desired flow velocity, wherein a plurality of nozzles are arranged as the nozzle along a conveying direction of the workpiece in a zone where the thermal processing is performed, and the driving mechanism adjusts a distance between each of the nozzles and a portion of the workpiece facing the nozzle individually in each of the plurality of nozzles.

TECHNICAL FIELD

This disclosure relates to a thermal processing furnace for workpieces having a blowing hood in which a nozzle is installed, the nozzle blowing a gas flow to perform thermal processing such as heating, soaking, and cooling on the workpieces, and relates to a thermal processing furnace for workpieces capable of efficiently performing thermal processing by causing a gas flow having a high flow velocity to impinge on the workpieces regardless of the dimensions of the workpieces, thereby contributing to space saving and energy conservation.

BACKGROUND

Some thermal processing furnaces for workpieces such as steel materials, having thermal conductivity by heating, soaking, or cooling the workpieces include a blowing hood, and are configured to blow hot air or cold air as a gas flow from a nozzle provided in the blowing hood.

For example, a “continuous heating furnace” in Japanese Patent Laid-Open No. 2009-57621 is a heating furnace which heats and soaks a steel material by continuously conveying the steel material, the continuous heating furnace including a combustion burner, a fan that circulates a flue gas within the furnace, a partition plate that covers a steel material conveyance path and guides the flue gas from a furnace bottom to its top, and a slit plate that regulates the flow of the flue gas above the steel material conveyance path and below the partition plate, wherein a slit width of the slit plate changes in a steel material conveying direction. Thus, the continuous heating furnace has excellent temperature rising and furnace temperature distribution characteristics. The slit corresponds to the nozzle, and the steel material is conveyed by a walking beam.

In the past, a steel material conveying surface of the walking beam and the slit plate where the slit blowing a gas flow is formed have a constant distance relationship. Therefore, roughly speaking, a distance between the steel material and the slit varies depending on the magnitude of the dimensions of the steel material on the steel material conveying surface. To be more specific, there is such a distance relationship that a steel material having a large height dimension is located close to the slit, and a steel material having a small height dimension is located far from the slit.

The gas flow of the flue gas blown from the slit has a high flow velocity immediately after being blown out, while the gas flow is diffused and the flow velocity is decreased with distance from the slit. When the steel material is thermally processed by causing the gas flow to impinge on the steel material, heat is more efficiently transferred from the gas flow to the steel material as the flow velocity is higher, that is, as the distance between the steel material and the slit is smaller.

Based on the above description, a steel material having a smaller height dimension is located farther from the slit so that the flow velocity of the gas flow impinging on the steel material is decreased, and it is difficult to ensure sufficient heat transfer. Therefore, it takes a long time until the steel material is heated to a desired temperature.

When a thermal processing furnace that handles steel materials of various dimensions is designed, it is necessary to determine a height dimension from a steel material conveying surface to a slit plate located above the surface based on the dimensions of a tallest steel material. Meanwhile, it is also necessary to determine a heating time required to heat the steel material to a desired temperature based on the dimensions of a shortest steel material with poor heat transfer. Thus, to ensure the heating time, a facility having large heating capacity is required, and a large facility space is required since the furnace is extended in a conveying direction.

It could therefore be helpful to provide a thermal processing furnace for workpieces having a blowing hood in which a nozzle is installed, the nozzle blowing a gas flow to perform thermal processing such as heating, soaking, and cooling on the workpieces, and to provide a thermal processing furnace for workpieces capable of efficiently performing thermal processing by causing a gas flow having a high flow velocity to impinge on the workpieces regardless of the dimensions of the workpieces, thereby contributing to space saving and energy conservation.

SUMMARY

We thus provide:Our thermal processing furnace for workpieces is a thermal processing furnace for workpieces having a blowing hood in which a nozzle is installed, the nozzle blowing a gas flow to thermally process a work piece, the thermal processing furnace including a driving mechanism that adjusts a distance between the nozzle and a portion of the work piece facing the nozzle so that the gas flow blown from the nozzle impinges on workpieces of various dimensions at a desired flow velocity.

The driving mechanism adjusts the distance between the nozzle and the portion of the work piece facing the nozzle so that the gas flow blown from the nozzle impinges on the workpieces of various dimensions at a constant flow velocity.

The driving mechanism drives the blowing hood or the nozzle to adjust the distance between the nozzle and the portion of the work piece.

A plurality of nozzles are arranged as the nozzle along a conveying direction of the workpiece in a zone where the thermal processing is performed, and the driving mechanism adjusts a distance between each of the nozzles and a portion of the workpiece facing the nozzle individually in each of the plurality of nozzles.

The workpiece is conveyed by a conveyor while moving up and down, and the driving mechanism adjusts the distance between the nozzle and the portion of the workpiece facing the nozzle in synchronization with a timing of the up-and-down motions of the workpiece so that an up-and-down speed and an up-and-down stroke of the adjustment are equivalent to an up-and-down speed and an up-and-down stroke of the workpiece, respectively.

The furnace further includes a controller to which information on a dimension of the workpiece is input, the controller connected to the driving mechanism, and outputting information on the dimension of the workpiece to control the driving mechanism.

The furnace further includes a sensor that automatically detects the dimension of the workpiece in advance, and inputs the dimension to the controller.

Our thermal processing furnace for workpieces is thus directed to a thermal processing furnace for workpieces having a blowing hood in which a nozzle is installed, the nozzle blowing a gas flow to perform thermal processing such as heating, soaking, and cooling on the workpieces, the furnace capable of efficiently performing thermal processing by causing a gas flow having a high flow velocity to impinge on the workpieces regardless of the dimensions of the workpieces, thereby contributing to space saving and energy conservation.

REFERENCE SIGNS LIST

DETAILED DESCRIPTION

In the following, one preferable example of a thermal processing furnace for workpieces is described in detail by reference to the accompanying drawings. A thermal processing furnace1is basically a thermal processing furnace1having a blowing hood12in which a nozzle12bis installed, the nozzle12bblowing a gas flow F to thermally process workpieces w1and w2, the furnace1including a driving mechanism13that adjusts a distance H between the nozzle12band a portion X of the work piece facing the nozzle12bso that the gas flow F blown from the nozzle12bimpinges on the workpieces w1and w2of various dimensions at a desired flow velocity as shown inFIGS. 1, 2, and 4(a) and (b). The thermal processing includes surface processing such as quenching in addition to heating and cooling processes.

The driving mechanism13adjusts the distance H between the nozzle12band the portion X of the work piece facing the nozzle12bso that the gas flow F blown from the nozzle12bimpinges on the workpieces w (w1and w2) of various dimensions at a constant flow velocity. The driving mechanism13drives the blowing hood12to adjust the distance H between the nozzle12band the portion X of the workpiece.

A controller14to which information on the dimensions of the workpieces w is input is provided. The controller14connects to the driving mechanism13, and outputs information on the dimensions of the workpieces w to control the driving mechanism13. A sensor15that automatically detects the dimensions of the workpieces w in advance and inputs the dimensions to the controller14is provided.

FIG. 1shows a schematic sectional side view of the thermal processing furnace1. The thermal processing furnace1includes a heating zone4, a soaking zone5, and a cooling zone6from a charging port2to an ejection port3for the workpieces w (w1; a workpiece having a large height dimension, w2; a workpiece having a small height dimension).

The thermal processing furnace1applies thermal processing such as heating, soaking and cooling to the workpieces w sequentially and continuously passing through the zones4to6. The furnace1performs the thermal processing on the workpieces w such as steel materials having thermal conductivity. The furnace1is provided with a conveyor7including a conveying surface7ato convey the workpieces w from the side of the charging port2to the side of the ejection port3through the respective zones4to6. Any means such as walking beam-type, pressure-type, belt-type and roller-type means may be employed as the conveyor7.

The workpieces w conveyed by the conveyor7are charged into the heating zone4from the charging port2and heated therein, subsequently soaked in the soaking zone5, subsequently cooled in the cooling zone6, and thereafter ejected outside of the furnace1from the ejection port3. The configuration of the furnace1in the drawing is merely one example, and the furnace1may include at least one of the zones4to6such as the soaking zone, or may include an additional zone.

FIG. 2shows an enlarged schematic sectional side view of the soaking zone5out of the heating zone4, the soaking zone5, and the cooling zone6. The heating zone4and the cooling zone6have substantially the same configuration as the soaking zone5.

The soaking zone5includes a furnace body10having an inlet opening8and an outlet opening9that communicate with the heating zone4and the cooling zone6on the both sides. The above conveyor7arranged on a bottom portion of the furnace body10, a circulating fan device11arranged on a top portion of the furnace body10, the blowing hood12provided above the conveying surface7aof the conveyor7, and a heating device (not shown) that heats a furnace atmosphere to maintain the furnace atmosphere in a given high-temperature state are provided in an internal space of the furnace body10.

The circulating fan device11is composed of a hollow duct11awhose upper end and lower end are open, and a fan11bthat is provided at the upper end of the hollow duct11a, and circulates the furnace atmosphere heated by the heating device within the furnace body10. Particularly, the fan11bgenerates a downward gas flow from the top portion side toward the conveying surface7aby the blowing hood12.

The blowing hood12is formed to be downwardly enlarged toward the end. A sliding tube section12ais provided at a narrowed upper end of the blowing hood12. The sliding tube section12aconnects to the hollow duct11ato be slidable in a vertical direction without letting the gas flow from the fan11bescape to the outside. The nozzle12bhaving a planar shape is provided facing the conveying surface7ainside an enlarged lower end of the blowing hood12.

The planar nozzle12bis composed of a mesh-like plate member where a plurality of holes is formed, or a mountain-shaped plate member provided with slits. The plurality of holes or slits face the conveying surface7a. The downward gas flow generated by the fan11bis blown from the holes of the nozzle12btoward the conveying surface7athrough an internal space of the blowing hood12. The workpieces w are thermally processed by the blown gas flow.

The blowing hood12is provided with the driving mechanism13that drives the blowing hood12. The driving mechanism13is composed of a driving section13ainstalled on the top portion of the furnace body10, and a rod13bthat penetrates the furnace body10, with one end coupled to the driving section13aand the other end coupled to the blowing hood12in the example shown in the drawings. When the driving section13ais driven, the rod13bmoves up and down so that the blowing hood12is driven up and down in the vertical direction with respect to the conveying surface7awith the sliding tube section12asliding with respect to the hollow duct11a.

By moving the blowing hood12close to and away from the conveying surface7aof the conveyor7that conveys the workpieces w, a distance between the workpieces w on the conveying surface7aand the nozzle12bof the blowing hood12is adjusted. Any mechanism such as cylinder-type and rack-and-pinion-type mechanisms may be employed as the driving mechanism13as long as the mechanism can drive the blowing hood12to move close to and away from the conveying surface7a.

The downward gas flow blown from the nozzle12bimpinges on the workpieces w. When the nozzle12band the workpieces w are in a vertical relationship as in this example, the gas flow tends to impinge on the portion X of the workpiece facing the nozzle12b, i.e., a top portion in a height direction of the workpiece w on the conveying surface7a.

When the workpieces w having different height dimensions are conveyed and thermally processed, the driving mechanism13drives the blowing hood12up and down with respect to the workpieces w so that a distance between the workpiece portion (the workpiece top portion) X facing the nozzle12bof each of these workpieces w and the nozzle12bbecomes constant. Since the distance is adjusted to be constant, the gas flow blown from the nozzle12bimpinges on the workpieces w having different height dimensions at a constant flow velocity.

Naturally, the flow velocity of the gas flow impinging on the workpieces w can be controlled by adjusting the distance between the nozzle12band the workpiece portion X, and the gas flow can be caused to impinge on the workpieces w at a desired flow velocity. Also, the driving mechanism13is not limited to driving the blowing hood12up and down. As in a modification shown inFIG. 5, the blowing hood12may be fixed to the furnace body10, the rod13bof the driving mechanism13may penetrate through the blowing hood12and coupled to a support plate20with a blow hole provided on the nozzle12b, and the nozzle12bmay be made slidable with respect to the blowing hood12by a sliding section21so that the nozzle12bitself that is made vertically movable with respect to the blowing hood12may be driven up and down by moving the rod13bup and down. In this case, the hollow duct11aand the sliding tube section12aare omitted, and the blowing hood12is configured in series and integrally with the circulating fan device11.

Although the soaking zone5where the furnace atmosphere is circulated by the fan11bis described in the above description, the heating zone4and the cooling zone6are configured similarly to the soaking zone5except that heating air or cooling air is supplied into the furnace from outside of the furnace, and the temperature-decreased or temperature-increased furnace atmosphere is discharged outside of the furnace.

An apparatus configuration that controls the drive of the driving mechanism13is shown inFIG. 1. The controller14that controls the driving section13aof the driving mechanism13connects to the driving section13a. The dimensions of the workpieces w, in this example, the height dimensions are input to the controller14by manual operation by an operator or the like.

The controller14outputs the input height dimensions of the workpieces w to the driving section13a, and the driving section13avertically drives up and down the blowing hood12(or the nozzle12b) according to the height dimensions of the workpieces w input from the controller14to adjust the distance between the nozzle12band the workpiece portion X facing the nozzle12bto be constant even when the workpieces w have different height dimensions.

The furnace1may include the sensor15that automatically detects the height dimensions of the workpieces w in advance before the workpieces w are charged from the charging port2. The sensor15connects to the controller14, and automatically inputs the detected height dimensions of the workpieces w to the controller14. When the sensor15is provided as described above, the blowing hood12(or the nozzle12b) is also controlled by the automatic control.

Next, operation of the thermal processing furnace1is described. In the furnace1, the thermal processing of the workpieces w is performed by continuously conveying the workpieces w (w1and w2) brought together according to the height dimensions. When the height dimensions of the workpieces w are changed, all of the previous workpieces w having the same height are temporarily ejected, and the driving mechanism13then drives the blowing hood12(or the nozzle12b) to change a height position in all of the zones4to6in response to the change in the height.

Also, the blowing hood12(or the nozzle12b) is driven to be changed in the height position sequentially from the zones4to6where ejection of the workpieces w having the same height has been completed, and the new workpieces w having a different height dimension are charged therein. Accordingly, the length of time not contributing to production can be reduced.

To be more specific, when the height dimensions of the workpieces w are changed, the dimensions of the workpieces w are input to the controller14by manual operation. Alternatively, the sensor15automatically detects the height dimensions of the workpieces w in advance, and the automatically-detected height dimensions are input to the controller14.

The controller14to which the height dimensions have been input drives the driving mechanism13according to the height dimensions of the workpieces w to be subsequently processed, thereby moving up and down the blowing hood12(or the nozzle12b) and adjusting the distance between the nozzle12band the workpiece portion X facing the nozzle12b. That is, the driving mechanism13drives the blowing hood12(or the nozzle12b) so that the distance between the nozzle12band the workpiece portion X facing the nozzle12balways becomes constant even when the height dimensions of the workpieces w are changed.

After completion of preparation, the workpieces w having the same height dimension are sequentially charged from the charging port2of the furnace1, thermally processed in the heating zone4, the soaking zone5, and the cooling zone6, and ejected from the ejection port3. After that, when the height dimensions of the workpieces w are changed, the driving mechanism13vertically drives up and down the blowing hood12(or the nozzle12b) again to reset the height position.

In conventional cases shown inFIG. 3, a distance D between the blowing hood12and the conveying surface7ais constant, and distances d1and d2between the nozzle12band the workpieces w1and w2vary depending on the height of the height dimensions of the workpieces w1and w2so that the flow velocity of the impinging gas flow F is changed. In that case, when the thermal processing is performed using the gas blown flow F from the nozzle12b, it becomes necessary for the workpiece w2having a small height dimension to be thermally processed for a long time since thermal conduction is deteriorated due to the flow velocity decreased by diffusion of the gas flow (indicated by dotted lines Y in the drawing).

On the other hand, in this example, the distance H between the nozzle12band the workpiece portion X facing the nozzle12b, for example, the workpiece top portion is maintained constant by vertically driving up and down the blowing hood12(or the nozzle12b) by the driving mechanism13in all of the heating zone4, the soaking zone5, and the cooling zone6so that the gas flow F having a constant flow velocity can be caused to impinge on the workpieces w (w1and w2) as shown inFIGS. 4(a) and (b).

By causing the gas flow F to impinge on the workpieces w at a constant flow velocity, the workpieces w can be thermally processed with almost the same amounts of heat transferred thereto regardless of the height (the magnitude) of the dimensions. Even the workpiece w2having a small height dimension can be thermally processed in substantially the same manner as the workpiece w1having a large height dimension. Therefore, it becomes unnecessary to design the furnace1to have a large length for the workpiece w2having a small height dimension. Thus, space saving is achieved for the facility space of the furnace1, and energy conservation is also achieved.

Also, it becomes possible to cause the gas flow F having a high flow velocity to impinge on the workpieces w by bringing the blowing hood12(or the nozzle12b) closer to the workpieces w so that the heat transfer is improved, the thermal processing can be efficiently performed, and a required thermal processing time can be shortened. Moreover, the space saving can be achieved by decreasing the length of the furnace1. Energy conservation can be also achieved since a throughput per hour can be increased.

The controller14to which the dimensions of the workpieces w are input is provided, and the driving mechanism13connects to the controller14, and drives the blowing hood12(or the nozzle12b) according to the dimensions of the workpieces w output from the controller14. Accordingly, the operability of the furnace1can be improved.

Since the sensor15that automatically detects the dimensions of the workpieces w in advance and inputs the dimensions to the controller14is provided, the furnace1can be automatically operated.

Also, existing furnaces can be easily modified and applied for the configuration of the thermal processing furnace1. Substantially the same throughput can be ensured by stopping any of previously operated zones, and using a fewer zones.

Although a situation in which the blowing hood12(or the nozzle12b) is vertically driven up and down to adjust the height between the nozzle12bblowing the downward gas flow F and the workpiece portion X facing the nozzle12bto be constant is described as an example above, the distance can be similarly adjusted by vertically driving up and down the blowing hood12(or the nozzle12b) when the gas flow F is blown upwardly from the nozzle12btoward a workpiece suspended from an upper portion.

Also, when the gas flow F is caused to impinge on the workpieces w from the nozzle12blaterally in a horizontal direction, the blowing hood12(or the nozzle12b) is driven in the right-left horizontal direction so that a horizontal distance between a portion of the workpiece facing the nozzle12b(particularly, a right-left widthwise projecting portion or the like) and the nozzle12bcan be adjusted. Naturally, the same effects as those of the above example can be produced even in the modifications as described above.

FIG. 6shows another modification of the thermal processing furnace1. In the above example (seeFIG. 1), the single blowing hood12(or the single nozzle12b) is provided in each of the zones4to6. The height position of the blowing hood12(or the nozzle12b) is set according to the height dimensions of the preceding workpieces w to be subsequently conveyed thereto. When the following workpieces w having a different height dimension to be conveyed after the preceding workpieces w are thermally processed, the height position cannot be readjusted according to the following workpieces w before all of the preceding workpieces w pass below the blowing hood12(or the nozzle12b).

That is, after the workpieces w are emptied with no workpiece present directly under the blowing hood12(or the nozzle12b), the height of the blowing hood12(or the nozzle12b) is readjusted.

At this point, if the blowing hood12(or the nozzle12b) has a large length dimension in a conveying direction, a zone where no thermal processing is performed exists over a long distance in the facility of the furnace1so that a large loss is caused in terms of time and energy, and the furnace1has a larger size.

In this modification, a length dimension L of the blowing hood12(or the nozzle12b) in the conveying direction is decreased. For example, a plurality of, for example, three blowing hoods12(or nozzles12b) are arranged along the conveying direction of the workpieces w in each of the zones4to6. In other words, the single blowing hood12(or the single nozzle12b) provided in each of the zones4to6is divided into a plurality of portions. When the length of the zones4to6remains the same, the length dimension L of the blowing hood12(or the nozzle12b) in the conveying direction is decreased.

The driving mechanism13adjusts the distance H between each of the blowing hoods12(or the nozzles12b) and the workpiece portion X facing the nozzle12bindependently and individually in each of the plurality of blowing hoods12(or nozzles12b).

When the height dimensions of the workpieces w are switched, the distance where the workpieces w are not present and are emptied can be reduced since the length dimension L of each of the blowing hoods12(or the nozzles12b) in the conveying direction is small. Thus, the loss in terms of time and energy can be reduced, production efficiency can be improved, and the length of the furnace1can be also decreased.

FIG. 7shows yet another modification of the thermal processing furnace1. For example, when the conveyor7that conveys the workpieces w is of a type such as a walking beam type, that involves vertical movement of the conveying surface7a(see an arrow Q out of arrows indicating a rectangular motion inFIG. 7), the distance H between the workpieces w and the blowing hood12(or the nozzle12b) varies during conveyance, and the gas flow F blown from the nozzle12band impinging on the workpieces w becomes unstable. Especially when the distance H is widened, the air velocity drops to lower thermal efficiency. Therefore, the thermal processing cannot be expected to be properly performed at the stage of conveyance.

In this modification, when the workpieces w are conveyed by the conveyor7while moving up and down, the driving mechanism13adjusts the distance H between the nozzle12band the workpiece portion X facing the nozzle12bto be always constant in synchronization with the timing of the up-and-down motions of the workpiece w so that an up-and-down speed and an up-and-down stroke T of the adjustment are equivalent to an up-and-down speed and an up-and-down stroke S of the workpiece w (the conveying surface7a), respectively.

That is, in the walking beam type, the conveying surface7aperforms a rectangular motion or a circular motion within a vertical plane. The blowing hood12(or the nozzle12b) is vertically moved by the driving mechanism13at the same speed and the same timing as those of a vertical component of the motion so that the distance H is always made constant.

A control value of the up-and-down motions of the conveyor7is input to the controller14in advance, and the driving mechanism13is driven according to the control value, thereby vertically driving the blowing hood12(or the nozzle12b).

Accordingly, the workpieces w can be thermally processed by causing the air flow F from the nozzle12bto precisely impinge on the workpieces w at all times not only at the stage in which the conveyor7stops conveying the workpieces w, but also at the stage of the conveyance. It is thus possible to shorten a required heating time, and decrease the length of the furnace1.

Naturally, any of the blowing hood12and the nozzle12bmay be moved up and down in the modifications shown inFIGS. 6 and 7.