WO2014054527A1

WO2014054527A1 - Plate forming method and plate forming device

Info

Publication number: WO2014054527A1
Application number: PCT/JP2013/076252
Authority: WO
Inventors: 佐藤　広明; 邦彦阿部
Original assignee: 三菱重工業株式会社
Priority date: 2012-10-02
Filing date: 2013-09-27
Publication date: 2014-04-10
Also published as: JP2014073500A

Abstract

Provided is a plate forming method and plate forming device capable of processing a plate with high precision when forming a plate by local heating. This plate forming method is characterized by comprising: a compression step (S3) of bending a titanium material plate by pressing the same against a mold in a situation where a tensile load is applied so that a prescribed tensile stress is generated on the plate; a preforming step (S5) of locally stretching the portions of the plate that are contacting the mold so that portions floating from the mold contact the mold; a contact inspection/determination step (S6, S7) of inspecting and determining whether the plate is contacting the mold; and a primary forming step (S9) of forming the entire plate by heating the same to a temperature where plastic deformation thereof starts and stretching to an extent where the shape is deformed does not occur.

Description

Sheet material forming method and sheet material forming apparatus

The present invention relates to a plate material forming method and a plate material forming apparatus for locally heating and forming a plate material.

If a plate of titanium or titanium alloy (hereinafter referred to as titanium-based material) is cold worked, springback and cracking are likely to occur. Further, in cold working, it is essential to remove residual stress generated after molding. For this reason, in the plate processing of a titanium-based material, it is not necessary to remove residual stress, and hot processing with good formability is performed. However, hot processing requires dedicated equipment for heating and processing, and the cost of equipment and jigs such as a mold having strength against high temperatures is expensive. Moreover, in hot processing, heating time and holding time are required, and there is a problem that processing time is long.

On the other hand, the local thermoforming technique is different from the conventional hot working in which the whole plate material is thermoformed, and the plate material is locally heated to form a target shape. For the local heating, for example, a heating source that is movable and can heat the plate material in a dot shape or a relatively small circular shape is used. This technology is cheaper in equipment cost and jig cost than conventional hot working, and can be processed in a short time.

Patent Document 1 describes basic specifications regarding a local heat forming apparatus.

US Pat. No. 6,601,426

By the way, as shown in FIG. 1, components such as an aircraft fuselage outer plate, a wing leading edge, and a metal cover of a helicopter blade are made of a titanium material plate 10 having a mountain shape or a substantially U-shaped cross section, and a tapered shape. In many cases, it is manufactured by pressing against a mold 2 having a composite curved surface whose cross-sectional area changes in a curved shape.

In this case, as shown in FIG. 2, the opposite edge portions of the plate material 10 are pulled by a clamping device or the like and applied with a uniform tensile load in the width direction to be pressed against the mold 2 to be bent. . The taper rate of the mold 2 is, for example, about 5%. Here, if the plate material 10 is an aluminum-based material that is excellent in progress, it is easy to stretch the plate material 10 as a whole by stretch molding and make it adhere along the surface of the mold 2.

However, if the plate material 10 is a titanium-based material, in addition to being inferior in developability compared to an aluminum-based material, there are also the problems of the spring back described above, and the plate material 10 is brought into close contact with the surface of the mold 2. Becomes difficult. That is, the mold 2 having a tapered compound curved surface has different surface lengths in the direction crossing the mountain in each longitudinal section, whereas the plate 10 has a width in the width direction. This is due to being uniform. In short, the plate material 10 is in close contact with the surface of the mold 2 on the large cross section side of the mold 2, but tends to be lifted from the surface of the mold 2 on the small cross section side, which causes a reduction in the shape accuracy of the molded part. It was.

On the other hand, the local heating technique using the local heating molding apparatus such as Patent Document 1 does not describe specific molding conditions, and there is a cause for the reduction in shape accuracy as described above, and the molding conditions must be adjusted. It is not pointed out that high-precision molding cannot be performed. Therefore, in the molding method using the local heat molding apparatus according to the prior art, it is difficult to accurately mold the plate material while pressing the plate material 10 against the mold 2 having the composite curved surface as described above.

The present invention has been made in view of such circumstances, and with a simple equipment configuration and a short processing time when pressing a titanium material plate into a mold having a composite curved surface, It is an object of the present invention to provide a plate material forming method and a plate material forming apparatus which can form a curved plate with high shape accuracy by bringing a titanium material plate material into close contact with a mold.

The plate material forming method according to the present invention is a plate material forming method in which a formed portion of the plate material is pressed against a mold having a compound curved surface having a curvature of a forming target in a state where a tensile load is applied to the plate material of the titanium material. A pressing step of bending the pressed portion against the mold in a state in which a tensile load is applied so that a predetermined tensile stress is generated on the plate, and the mold of the molded portion A preforming step for locally extending the part in close contact with the mold so that the part floating from the mold is in close contact with the mold, and inspecting / determining whether the plate material is in close contact with the mold A contact inspection / determination step, and a main forming step of heating and forming the whole plate material at a temperature at which plastic deformation of the material starts to occur and does not cause elongation to deform the shape. Features.

According to this plate material forming method, a formed portion of a titanium-based material plate that is loaded with a tensile load so as to generate a predetermined tensile stress is pressed in a pressing step onto a mold having a compound curved surface with a curvature to be formed. Curved when applied. At this time, due to the composite curved surface of the mold, the plate material is in close contact with the mold on the large cross section side of the mold, but the plate material tends to be lifted from the mold on the small cross section side of the mold.

In the preforming step, the portion that is in close contact with the large cross section side of the mold is locally stretched until the lifted portion is in close contact with the small cross section side of the mold. For example, the yield stress (yield strength) of the material is lowered by locally heating only the portion in close contact with the large cross-section side, and the plate material on the large cross-section side is stretched by a pre-loaded tensile load. Thereby, a board | plate material can be closely stuck to a metal mold | die.

In the adhesion inspection / judgment step, it is determined whether or not the plate is in close contact with the mold by, for example, analyzing the sound by striking the plate or analyzing the rate of temperature rise by heating the surface of the plate. Inspected and judged. As a result, when the plate is not in close contact with the mold, the pre-forming step is repeated, and when it is determined that the plate is in close contact with the mold, the pre-forming step is terminated. Since the preforming step and the contact inspection / determination step are performed locally, they can be completed in a short time.

In the main forming step, the whole plate is heated and formed at a temperature at which plastic deformation of the raw material starts to occur and the elongation is not enough to deform the shape. As a result, the plate material that is in close contact with the mold is heated again at a low temperature condition so as to become familiar with the mold, and is stable in a state of being molded according to the shape of the mold without causing a springback or cracking. The heating and holding time may be short.

Therefore, according to this plate material forming method, with a simple equipment configuration and a short processing time, a titanium material plate material can be completely formed in close contact with a mold and curved with high shape accuracy. Further, whether or not the plate material is in close contact with the mold can be easily determined by a method of hitting the plate material and listening to the sound.

As described above, in the preforming step, the molded portion of the plate material is heated and stretched at a temperature at which the stress caused by the tensile load exceeds the proof stress of the material of the plate material and less than the tensile strength. You may do it. In other words, the yield stress of the material is reduced by locally heating only the portion closely contacting the large cross-section side of the plate material to a high temperature, and the plate material on the large cross-section side is stretched by a preloaded tensile load.

According to this plate material forming method, since the heated portion is local, existing equipment such as a lamp, laser, burner, etc. can be used as the heating means. For this reason, unlike the case where the whole plate material is hot-worked together with the mold, no dedicated equipment or equipment such as a mold having strength against high temperatures is required, and the cost for the equipment can be reduced. Further, since the heated portion is local, the heating time and holding time are short, and the processing time can be shortened.

In the preforming step, it is preferable that the plate material is preferentially extended from an area pressed against a portion having a large curvature radius of the mold among the molded portion of the plate material.

When the mold is a compound curved surface, the plate material tends to adhere at a portion where the radius of curvature of the mold is large (large cross section side), and floats at a portion where the radius of curvature is small (small cross section side). For this reason, the whole board | plate material can be closely_contact | adhered to a metal mold | die by extending a board | plate material preferentially from a part with a large curvature radius.

In the preliminary forming step, the formed portion of the plate material may be locally rolled and stretched by shot peening or burnishing.

In this case, only a necessary portion of the plate material can be easily stretched by locally performing shot peening or burnishing in a state where a tensile stress is applied to the plate material by a preloaded tensile load. For this reason, a preforming step can be completed within a short time. Since shot peening and burnishing are techniques that have been used in the past, it is not necessary to add new equipment and can be performed at low cost.

In the pre-forming step, at least one slit may be formed in a portion of the plate material to which the tensile load is applied, and the tensile load may be varied with the slit as a boundary.

In this way, when the mold has a complex curved surface, the tensile load can be individually set to an optimum strength in accordance with each curved surface, thereby making it possible to easily perform the preforming step.

In the adhesion inspection / determination step, it is possible to inspect / determine whether or not the plate is in close contact with the mold by striking the surface of the plate and analyzing the sound.

In this case, when the plate is not in close contact with the mold, there is a reverberant sound, and when it is in close contact, there is a non-resonant sound. Can be determined.

In the adhesion inspection / determination step, it is possible to inspect / determine whether or not the plate material is in close contact with the mold by heating the surface of the plate material and analyzing the temperature increase rate. .

In this case, when the plate is not in close contact with the mold, the heated plate immediately heats up, and when it is in close contact, the heat applied to the plate escapes to the mold and the plate is difficult to increase in temperature. By measuring the time until the temperature of the plate material rises, it is possible to easily determine the adhesion state of the plate material.

In the main forming step, it is preferable that at least the forming portion of the plate material is continuously or intermittently heated on a plurality of parallel heating lines to be adapted to the mold.

The titanium-based material has a lower thermal conductivity than the aluminum-based material, and the temperature gradient increases at the boundary between the heated region heated by the heating unit and the non-heated region that is not heated. Therefore, the thermal expansion of the heating region is constrained by the non-heating region, and the heating region is deformed out of plane by the thermal expansion. In this plate material forming method, the plate material is continuously or intermittently heated on one heating line and heated on a plurality of heating lines parallel to each other. Therefore, the plate material is not heated entirely or only in one line, but the heated part is at least two lines, and the heating area is controlled, Compared to the case where the entire surface is heated or the case where the plate material is heated only by one line, it is easy to form the plate material to the curvature of the forming target.

In addition, when the plate material is heated intermittently on one line, the amount of elongation can be reduced or the lifting can be suppressed compared to the case where the plate material is heated continuously on one line. Accuracy can be improved. The heating temperature may be adjusted by the set temperature of the heating unit, or may be adjusted by heating the same scanning line a plurality of times.

The heating of the plate material is such that the heating unit can move relative to the plate material, and the heating unit heats the plate material continuously or intermittently in one direction, and then moves onto the adjacent heating line. Also good. Alternatively, a black body paint may be applied to the surface of the plate material and the heating unit may be heated uniformly with respect to the plate material. The portion to which the black body paint is applied has a higher absorption capacity than the metallic luster portion and is easily heated. In addition, the portion where the black body paint is applied does not change the emissivity due to oxidation due to heating, and can be heated to a stable temperature. Furthermore, the heating unit may be configured to have a shape in which a heating pattern is formed, and the plate material may be heated in a heating pattern shape by a single heating.

In addition, the plate material forming apparatus according to the present invention includes a load portion for applying a tensile load to a plate material made of titanium material, and a formed portion of the plate material to which the tensile load is applied, and a gold plate having a compound curved surface with a curvature to be formed. A pressing portion that presses against a mold, a preforming portion that extends a portion that is in close contact with the mold so that a portion of the forming portion that is floating from the mold is in close contact with the mold, and Of these, at least the molded part is provided with a main molded part that is molded by heating at a temperature at which plastic deformation of the material starts to occur and elongation does not occur so as to deform the shape.

According to this plate material forming apparatus, a mold part of a titanium material plate material that is loaded with a tensile load so that a predetermined tensile stress is generated by the load portion has a compound curved surface having a curvature of a forming target by the pressing portion. Pressed against. If the tensile load is not enough to stretch the titanium-based material at room temperature, the plate material will be in close contact with the mold on the large cross section side of the mold due to the compound curved surface of the mold. On the cross-sectional side, the plate material is lifted from the mold.

And the part that is in close contact with the large cross section side of the mold until the material is heated to a temperature at which plastic deformation is likely to occur locally by the preforming part, and the raised part is in close contact with the small cross section side of the mold Is stretched locally. For this reason, a board | plate material can be closely stuck to a metal mold | die.

Then, in the main forming portion, the forming portion of the plate material is formed by heating at a temperature at which plastic deformation of the material starts to occur and does not generate elongation enough to deform the shape. As a result, the plate material that is in close contact with the mold is heated again at a low temperature condition so as to become familiar with the mold, and is stable in a state of being molded according to the shape of the mold without causing a springback or cracking.

Therefore, according to this plate material forming apparatus, with a simple equipment configuration and a short processing time, a titanium material plate material can be intimately adhered to a mold and curved with high shape accuracy.

The preforming part may be a first heating part that heats and extends the molded part of the plate material at a temperature at which the proof stress of the material is lower than the stress applied by the tensile load applied to the material. .

According to this plate material forming apparatus, the first heating section reduces the yield stress of the material by locally heating only the portion that is in close contact with the large cross-section side of the plate material, and the load portion loads in advance. The plate material on the large cross section side can be stretched by the tensile load being applied.

According to this plate material forming apparatus, since the heating part is local, existing equipment such as a lamp, laser, and burner can be used as the heating means, reducing the cost of the equipment and processing time. Can be shortened.

The preforming part may be a shot peening device or a burnishing device. If it carries out like this, only the required part of a board | plate material can be easily extended by performing shot peening and burnishing locally in the state in which the tensile stress is added to the board | plate material with the tensile load previously loaded by the load part. For this reason, preforming can be completed within a short time. Since shot peening and burnishing are techniques that have been used in the past, it is not necessary to add new equipment and can be performed at low cost.

The main molding unit may be a second heating unit that causes at least the molding part of the plate material to be continuously or intermittently heated on a plurality of parallel heating lines so as to conform to the mold.

This plate material forming device uses the characteristics of a titanium-based material that has a lower thermal conductivity than an aluminum-based material and has a large temperature gradient at the boundary between a heated area heated by a heating unit and an unheated area that is not heated. Thus, the plate material can be easily formed to the curvature of the forming target. Moreover, since the amount of elongation of the plate material can be reduced or the lifting can be suppressed, the molding accuracy can be improved.

According to the plate material forming method and the plate material forming apparatus according to the present invention, when a titanium material plate material is pressed against a metal mold having a complex curved surface to form a curve, the titanium material can be formed with a simple equipment configuration and a short processing time. The plate material can be curved and formed with high shape accuracy by bringing the plate material into close contact with the mold.

It is a perspective view in the case of carrying out curve shaping | molding by pressing the board | plate material of a titanium-type raw material to the metal mold | die which has the compound curved surface which changes a taper-shaped cross-sectional area. It is a top view in the case of pressing a plate material made of a titanium-based material against a mold having a composite curved surface whose cross-sectional area changes in a taper shape and curve-molding. It is a side view which shows the board | plate material shaping | molding apparatus which concerns on one Embodiment of this invention, a metal mold | die lowered | hung and the board | plate material was restrained by the clamp. It is a side view of the board | plate material shaping | molding apparatus which shows the state which a metal mold | die went up and the board | plate material curved. It is an enlarged side view which shows the state which the board | plate material has floated from the metal mold | die. It is a side view of the board | plate material shaping | molding apparatus which shows the state at the time of preforming. It is a side view of the board | plate material shaping | molding apparatus which shows the state of this shaping | molding step. It is a side view of the board | plate material shaping | molding apparatus which shows the state from which the board | plate material which completed shaping | molding was removed. It is a side view which shows the state by which the unnecessary part of the molded component was cut. It is a flowchart which shows the board | plate material shaping | molding method by the board | plate material shaping | molding apparatus which concerns on one Embodiment of this invention. It is a perspective view of a board | plate material, (A) is a case where a part with a large curvature radius exists in one end of a metal mold | die, (B) is a case where a part with a large curvature radius exists in the both ends of a metal mold | die, (C) is a curvature radius. It is a figure which respectively shows the case where a large part exists in the center part of a metal mold | die. It is a top view which shows the heating condition of the board | plate material in a preforming step. It is a top view which shows the heating condition of the board | plate material in this formation step. (A), (B), (C) is a top view which shows the procedure which extends a board | plate material in preforming. It is a graph which shows the relationship between the stress of a titanium-type raw material, and temperature. (A), (B), (C) is a top view of a metal mold | die and a board | plate material which shows the example of the heating pattern in this shaping | molding step. It is a top view of a metal mold | die and a board | plate material which shows the heating area | region and component part in a main forming step. It is a longitudinal cross-sectional view which shows the condition which heats several places in the state in which the board | plate material was pressed by the metal mold | die, and investigates the relationship between the temperature and the amount of material elongation at the time of local heat forming. It is the top view which expand | deployed the board | plate material in FIG. It is a diagram which shows the relationship between the measurement position in several temperature conditions, and distortion amount. It is a longitudinal cross-sectional view which shows the concept of burnishing. It is a longitudinal cross-sectional view which shows the burnishing apparatus by a spherical body. It is a longitudinal cross-sectional view which shows the burnishing apparatus by a roller. It is a top view which shows the state in which the equal tensile load was loaded along the edge part of a board | plate material. It is a top view which shows the state in which different tensile load was loaded on the boundary formed on the slit formed in the edge part of a board | plate material.

An embodiment of the present invention will be described below with reference to the drawings.
The plate material forming method and plate material forming apparatus according to the present invention form a plate material of titanium material such as pure titanium or a titanium alloy containing titanium as a main component (including aluminum, iron, tin, molybdenum, vanadium, etc. as additive elements). For example, it is intended to manufacture aircraft fuselage skin, wing leading edges, helicopter blade metal covers, and the like.

Specifically, as shown in FIG. 1, a plate material 10 made of titanium material is pressed against a mold 2 having a chevron-shaped cross section to be bent. The surface of the mold 2 has a curved surface that has a curvature that is a molding target and has a taper-shaped cross-sectional area that changes in taper. The taper ratio is, for example, about 5%. As shown in FIG. 2, the opposite edge portions of the plate material 10 are pulled by a clamp 5 of the plate material forming apparatus 1 described below, and pressed against the mold 2 in a state where a uniform tensile load is applied in the width direction, thereby bending the plate. To do.

As shown in FIGS. 3 to 8, the plate material forming apparatus 1 according to the present embodiment includes a mold 2, a hydraulic cylinder 3 (pressing section) for moving the mold 2 up and down, and a first heating section. 4A (preliminary molding part), 2nd heating part 4B (main molding part), a pair of clamps 5 arranged opposite to each other with the mold 2 in between, and each clamp 5 are rotated up and down respectively. And a hydraulic cylinder 7 (loading portion) for applying a tensile load to the plate 10 by moving the clamps 5 in the horizontal direction. Note that an electrically driven cylinder, a pneumatic cylinder, or the like may be used instead of the hydraulic cylinder 7 as long as the length of expansion and contraction and the load can be adjusted.

The hydraulic cylinder 3 can move the mold 2 closer to or away from the plate material 10, and operates to raise the mold 2 and press it against the molded portion of the plate material 10. The first heating unit 4A and the second heating unit 4B are lamps using light energy such as a condensing halogen lamp, light sources such as various lasers, or heat sources such as a burner. The first and

second heating units

4A and 4B are freely movable with respect to the plate material 10 so that the entire surface of the plate material 10 can be heated.

The clamp 5 can firmly hold and release the edge of the plate 10. The clamp 5 grips the edge of the plate 10 by, for example, screwing or a hydraulic mechanism. The hinge 6 has one end connected to the clamp 5 and the other end connected to the hydraulic cylinder 7. The clamp 5 can be rotated with respect to the hydraulic cylinder 7 to change the direction of the clamp 5. Although not shown in the figure, the hinge 6 preferably has a function of adjusting the angle with respect to the hydraulic cylinder 7.

The hydraulic cylinder 7 can move the clamp 5 and can move the clamp 5 closer to the mold 2 side or away from the mold 2. The hydraulic cylinder 7 can apply a tensile load to the plate 10 by moving the clamp 5 in a direction away from the die 2 when the mold 2 is pressing the plate 10.

Next, a plate material forming method by the plate material forming apparatus 1 of the present embodiment will be described with reference to FIGS.

First, as shown in FIG. 3, the plate 10 is restrained by the clamp 5 in a state where the hydraulic cylinder 3 is contracted and the mold 2 is lowered (step S1 in FIG. 10). Next, as shown in FIG. 4, the position of the clamp 5 is adjusted while raising the mold 2 (step S2). That is, as the mold 2 moves up, the hydraulic cylinder 7 operates so that the clamp 5 is brought closer to the mold 2 side. At this time, the plate 10 is brought into close contact with the surface of the mold 2 by the rotation of the hinge 6.

Then, while the position of the mold 2 is fixed by the hydraulic cylinder 3, the hydraulic cylinder 7 is contracted to apply a tensile load to the plate material 10 (step S3: pressing step). With a relatively soft plate material such as an aluminum material instead of a titanium material, molding is completed in the state up to here (step S3). However, a titanium-based material has a high yield stress, and a springback occurs after molding at room temperature, so that the shape cannot be sufficiently imparted as it is.

That is, when the mold 2 has a complex curved surface, the plate material 10 partially lifts from the mold 2 as shown in an enlarged view in FIG. The reason why the plate material 10 floats from the mold 2 in this way is that the titanium-based material has a higher yield stress than the aluminum-based material and is inferior in progress, and in addition to the occurrence of springback after molding at room temperature, In each longitudinal section of the mold 2, the length on the surface of the mold 2 is different, whereas the width of the plate 10 is uniform.

In this embodiment, in order to form the plate material 10 of the titanium-based material that is inferior to the aluminum-based material, the first heating unit 4A is reserved as shown in FIG. 6 while maintaining the state of step S3. It arrange | positions at the heating position of shaping | molding (step S4), and pre-forms the board | plate material 10 locally by this 1st heating part 4A (step S5: pre-formation step).

The heating position of the pre-molding is a portion of the plate 10 that is receiving a tensile load that is in close contact with the mold 2, and the close contact portion is locally heated and stretched. As will be described later, the heating temperature at this time is set to a temperature at which the stress generated by the tensile load applied in step S3 exceeds the proof stress of the material of the plate member 10 and less than the tensile strength. As a result, the portion of the plate material 10 that is in close contact with the mold 2 can be extended without breaking, and the portion of the plate material 10 that is floating from the mold 2 can be brought into close contact with the mold 2.

When the plate material 10 is formed by the mold 2 having the compound curved surface whose sectional area changes in a taper shape with a constant gradient from one end to the other end, there is a portion having a large curvature radius at one end of the mold 2. The plate member 10 is most strongly pressed against this portion. Therefore, the vicinity of the end portion on the large cross section side of the plate member 10 tends to be in close contact with the mold 2, and the vicinity of the end portion on the small cross section side tends to rise from the mold 2. Therefore, in this case, as shown in FIGS. 11A and 12, the first heating is preferentially performed with the region on the large cross section side of the plate member 10 (the portion with a large radius of curvature) as the pre-forming range PF (molded portion). It is heated and stretched by the part 4A.

For example, when the shape of the mold 2 is a bowl shape, there are portions with large curvature radii at both ends, and the plate material 10 is most strongly pressed against these portions. Therefore, the vicinity of both end portions of the plate material 10 is in close contact with the mold 2, and the vicinity of the center portion tends to be lifted from the mold 2. Therefore, in this case, as shown in FIG. 11 (B), the area near both ends of the plate member 10 is preferentially extended as a preforming range PF.

Furthermore, for example, when the mold 2 is a chevron and there is a portion with a large radius of curvature at the center in the longitudinal direction, the portion with a large radius of curvature is at the center, and the plate 10 is most strongly pressed against this portion. . For this reason, the vicinity of the center portion of the plate material 10 is in close contact with the mold 2, and the vicinity of both end portions tends to be lifted from the mold 2. Therefore, in this case, as shown in FIG. 11C, a region near the center of the plate member 10 is preferentially extended as a preforming range PF.

Thus, by extending the plate material 10 preferentially from a portion having a large curvature radius, the entire plate material 10 can be brought into close contact with the mold. In any of the above cases, it is necessary to perform pre-molding with care so that the portion of the mold 2 that is in close contact with the large cross-section side does not extend too much and floats up from the mold 2.

In the pre-forming step S5, as a procedure for extending the plate material 10, as shown in FIGS. 14 (A) to (C), pre-heating is performed a plurality of times, and the plate material 10 is positioned on the large end portion side of the mold 2. The part to be extended is extended in the width direction. Since a tensile load is applied to the plate material 10 in the width direction, the plate material 10 is stretched each time it is heated, and approaches the developed shape 2 a of the mold 2.

As described above, the heating temperature in the pre-forming step S5 is the stress caused by the tensile load applied in step S3 is the yield strength of the material of the plate 10 (the yield stress of a metal having no yield point such as a titanium-based material). The temperature is set to a value that exceeds the corresponding stress) and less than the tensile strength. That is, as shown in FIG. 15, for example, when the stress generated by the tensile load is 200 MPa, the preheating temperature is set in the range of 620 ° C. to 670 ° C. This heating temperature is appropriately set according to the material, thickness, shape and the like of the plate material.

Since the heating part at the time of preforming is local, existing equipment such as a lamp, a laser, and a burner can be used as the first heating unit 4A. For this reason, unlike the case where the whole plate material 10 is hot-worked together with the mold 2, no special equipment for hot-working or equipment such as a mold having strength against high temperatures is required, and the cost of the equipment is reduced. It can be made cheap. Further, since the heated portion is local, the heating time and holding time are short, and the processing time can be shortened.

As described above, in a state where the plate material 10 loaded with a tensile load is pressed against the mold 2, only the portion that is in close contact with the large cross section side of the plate material 10 is heated by the first heating unit 4 </ b> A. By locally heating to a high temperature, the yield stress of this portion can be reduced, and the region on the large cross-section side can be extended by a tensile load preloaded by the load portion. Then, if the portion of the plate material 10 that is in close contact with the mold 2 can be extended without breaking, the portion of the plate material 10 that is relatively lifted from the mold 2 is in close contact with the mold 2 and finally The entire plate material 10 can be completely adhered to the mold 2.

After the pre-forming step S5, it is inspected and determined whether or not the plate 10 is in close contact with the mold 2 (steps S6 and S7: contact inspection / determination step). Here, it is inspected and determined whether or not the plate 10 is in close contact with the mold 2 by hitting the surface of the plate 10 and analyzing the sound. In this case, when the plate material 10 is not in close contact with the mold 2, there is a sound with reverberation, and when it is in close contact with it, there is a sound with no reverberation. The situation can be easily determined.

Alternatively, the surface of the plate material 10 is lightly heated, and the temperature rise rate is analyzed to inspect / determine whether the plate material 10 is in close contact with the mold 2. In this case, when the plate 10 is not in close contact with the mold 2, the heated plate 10 is immediately heated, but when it is in close contact, the heat applied to the plate 10 escapes to the mold 2 and the plate Since the temperature of the plate 10 is difficult to increase, the contact state of the plate 10 can be easily determined by measuring the time until the plate 10 is heated.

In the adhesion inspection / determination steps S6 and S7, when it is determined that the plate 10 is not in close contact with the mold 2 (step S7 → NO), the process returns to step S5 again, and steps S5 to S7 are repeated. Moreover, when it determines with the board | plate material 10 having closely_contact | adhered to the metal mold | die 2 (step S7-> Yes), preforming step S5 is complete | finished. Since the adhesion inspection / determination steps S6 and S7 are locally performed as in the preforming step S5, the adhesion inspection / determination steps S6 and S7 can be completed in a short time.

When the preforming step S5 is completed, as shown in FIG. 7, the second heating unit 4B is arranged at the heating position of the main molding (step S8), and the second heating unit 4B causes the second heating unit 4B as shown in FIG. The whole plate material 10 is heated again and molded (step S9: main molding step).

The heating temperature in the main molding step S9 is set lower than the heating temperature at the time of preliminary molding. Preferably, the plate material using the second heating unit 4B is used until the plastic material of the plate material 10 to which a tensile load is applied begins to be plastically deformed and the temperature is in a temperature range in which the shape is not deformed enough to be deformed. 10 is fully heated. The temperature range where plastic deformation is applied is the temperature range when the strength is increased to about half of the strength at normal temperature, that is, 500 ° C. to 600 ° C. for titanium-based materials.

At a temperature of 500 ° C. or higher, the material strength of the titanium-based material starts to rapidly decrease, so that it becomes easier to give plastic deformation to the plate material 10 than at normal temperature, and elastic deformation is caused by a decrease in the yield stress of the plate material 10. Since the amount is reduced, the amount of springback after molding is also minimized. As a result, it is possible to stably maintain the shape in which the plate material 10 is made to conform to the mold 2 and is brought into close contact with the mold 2 by the preliminary molding. The heating and holding time in the main forming step S9 may be a short time.

As described above, when the temperature of the plate 10 is increased to the predetermined temperature by the second heating unit 4B, the second heating unit 4B is moved in the longitudinal direction or the longitudinal direction of the plate 10. 16A, 16B, and 16C show examples of patterns for moving the second heating unit 4B in the main forming step S9. As shown here, the 2nd heating part 4B heats the board | plate material 10 continuously or intermittently on the several heating line 12 mutually parallel. The pitch of the heating line 12 is narrowed or widened, and is appropriately determined according to the processing conditions.

Then, when the predetermined heating area is covered by the movement of the second heating unit 4B, the main molding step S9 is terminated. In addition, when the phenomenon which the board | plate material 10 floats from the metal mold | die 2 arises by the deformation | transformation accompanying heating, a tensile load is increased by driving the hydraulic cylinder 3 and the hydraulic cylinder 7, and the board | plate material 10 and the metal mold | die 2 are increased. Adhere. Then, in a state where no gap is generated between the plate material 10 and the mold 2, the plate material 10 is heated and molded to obtain a more accurate component.

By performing this main forming step S9, the thermal conductivity is lower than that of the aluminum-based material, and the temperature gradient is increased at the boundary between the heated region heated by the second heating unit 4B and the non-heated region that is not heated. By utilizing the characteristics of the system material, the plate material 10 can be easily formed to have a desired curvature. Moreover, since the elongation amount of the board | plate material 10 can be reduced or a lift can be suppressed, a shaping | molding precision can be improved.

In particular, it is possible to suppress warpage occurring in the width direction of the plate material 10 by heating the plate material 10 at intervals without heating the plate material 10 entirely. Further, when the heating temperature is set to a relatively low temperature and the heating pitch is wide, the radius of curvature of the cross section of the molded product by the obtained plate member 10 becomes large. Furthermore, the warp in the width direction of the plate 10 becomes larger when the heating temperature is set to a relatively high temperature and the heating pitch (the interval between the heating lines 12) is narrowed. Furthermore, as the heating temperature is set to a relatively high temperature and the tensile load is increased, the warpage in the width direction of the plate 10 is increased.

In addition, as shown in FIG. 17, a part 14 is obtained by forming a boundary 14 between a heating region in which irradiation is performed by the second heating unit 4 </ b> B and becoming a high temperature and a portion in which irradiation is not performed and the temperature remains low. Heating is performed so as to be outside the portion (outside the range of the mold 2). This makes it possible to prevent residual stress generated at the boundary between the high temperature portion and the low temperature portion from remaining in the molded part. After molding, the part portion can be improved in shape accuracy and the residual stress can be reduced by cutting on the irradiated portion (heating region, high temperature portion) side from the boundary 14.

After the completion of the main forming step S9, as shown in FIG. 8, the tensile load generated by the

hydraulic cylinders

3 and 7 is released, and the clamp 5 holding the molded product 10A formed by the plate material 10 is held. The mold 2 and the molded product 10A are removed (step S11). Thereafter, as shown in FIG. 9, an unnecessary portion of the molded product 10A is cut (step S12), and the molded product 10A is completed. As described above, the residual stress generated at the boundary 14 between the heating region and the non-heating region is eliminated by setting the boundary 14 between the heating region and the non-heating region in FIG. It is possible to increase the molding accuracy.

According to the plate material forming method and the plate material forming apparatus 1 including the steps S1 to S12 described above, a simple equipment configuration is provided when the titanium material plate material 10 is pressed against the metal mold 2 having a composite curved surface to perform curve forming. With a short processing time, the plate material 10 made of titanium can be in close contact with the mold 2 and can be curved with high shape accuracy. Further, it can be easily determined whether or not the plate material is in close contact with the mold.

In carrying out the preforming step S5, which is the greatest feature of the above steps S1 to S12, the inventors previously examined the processing conditions for extending the material as shown in FIGS. In this molding method, as described above, the plate 10 pressed against the mold 2 is locally heated while a tensile load is applied, and the stress caused by the tensile load exceeds the proof stress of the material of the plate 10 (600 In order to heat and stretch at a temperature lower than the tensile strength), the temperature dependence of the amount of elongation of the material during local heat molding was examined.

That is, as shown in FIG. 18, in the plate material 10 pressed against the mold 2, a plurality of measurement points A to I symmetrical with respect to the center line of the mountain shape of the mold 2 are set at 600 ° C., respectively. Heating was performed at temperatures of 650 ° C., 700 ° C., and 750 ° C., and the strain (elongation) at each measurement position (1) to (6) of the plate 10 was measured. The material is Ti-64, and the tensile load is 200 MPa.

As a result, the strain amount increases at the measurement positions (3) and (4) close to the top of the mold 2, and the total strain amount increases as the heating temperature increases, so that the mold 2 and the plate material 10 can be entirely removed. It was found that the material can be stretched under high stress and high temperature conditions as compared with the case of hot forming. That is, it has been found that molding by local heating can increase the degree of freedom of molding and improve molding accuracy than hot molding.

By the way, in the case of performing preliminary molding, in addition to heating the plate 10 pressed against the mold 2 under a tensile load, a shot of hitting a large number of fine steel balls against the molded portion of the plate 10 at high speed with high-pressure air. Rolling and stretching may be performed by peening, or rolling and stretching may be performed by burnishing that rolls while pressing the steel ball 21 or the steel roller 22 at a high pressure as shown in FIGS. In such a case, a shot peening apparatus or a burnishing apparatus is provided in the plate material forming apparatus 1 as a preforming part instead of the first heating part 4A described above.

In this way, by applying shot peening and burnishing locally to the plate material 10 in a state in which a tensile stress is applied to the plate material by a preloaded tensile load, only necessary portions of the plate material 10 are easily stretched and preformed. Step S5 can be completed in a short time. Since shot peening and burnishing are techniques that have been used in the past, it is not necessary to add new equipment and can be performed at low cost. Note that in any of the heating, shot peening, and burnishing methods, it is possible to easily prevent an unintended portion from being stretched by masking a region where the plate 10 is not desired to be stretched.

When a tensile load is applied to the plate material 10, generally, as shown in FIG. 24, clamp margins 25 are provided at both edges of the plate material 10, which are held by the clamps 5 of the plate material forming apparatus 1, Although it is pulled by a load (see FIG. 3), as shown in FIG. 25, at least one slit 26 may be formed at both edge portions of the plate member 10, and the tensile load may be varied with the slit 26 as a boundary.

In this way, when the mold 2 has a composite curved surface, the tensile load can be individually set to an optimum strength in accordance with each curved surface, and thus the preforming step S5 can be easily performed. In addition, it is preferable that the length of the slit 26 extends from both edges of the plate 10 to the boundary between the component parts.

It should be noted that the present invention is not limited to the configuration of the above embodiment, and can be appropriately modified or improved without departing from the gist of the present invention. The form is also included in the scope of the right of the present invention.
For example, the shapes of the mold 2 and the plate material 10 are not limited to those of the present embodiment.
Further, the hydraulic cylinder 7 as the load portion and the hydraulic cylinder 3 as the pressing portion may have different structures.
In short, it suffices if the curved portion is locally stretched and brought into close contact with the mold 2 while being pressed against the mold 2 in a state where a tensile load is applied to the plate material 10.

1 Sheet material forming device 2 Mold 3 Hydraulic cylinder (pressing part)
4A 1st heating part (preliminary molding part)
4B 2nd heating part (main molding part)
5 Clamp 6 Hinge 7 Hydraulic cylinder (load section)
10 Plate material 10A Molded product 12 Heating line 26 Slit PF Preliminary molding range (molded part)
S3 Pressing step S5 Preliminary molding step S6, S7 Adhesion inspection / determination step S9 Main molding step

Claims

In a state in which a tensile load is applied to a titanium-based material plate material, the plate material molding method is a method of curve-forming by pressing a molded portion of the plate material against a mold having a composite curved surface having a molding target curvature,
In a state where a tensile load is applied so that a predetermined tensile stress is generated in the plate material, a pressing step in which the molded portion is pressed against the mold and curved,
A preforming step of locally extending a portion of the molded portion that is in contact with the mold so that a portion of the molded portion that is floating from the mold is in close contact with the mold;
Contact inspection / determination step for inspecting / determining whether or not the plate material is in close contact with the mold,
A main forming step of heating and forming the entire plate material at a temperature at which the material begins to undergo plastic deformation and does not cause elongation to deform the shape;
The board | plate material shaping | molding method containing this.
The said preforming step WHEREIN: The said molded part of the said board | plate material is heated and extended at the temperature from which the stress which arises by the said tensile load exceeds the yield strength of the said board | plate material, and becomes less than tensile strength. Sheet material forming method.
3. The plate material forming method according to claim 1, wherein in the preliminary forming step, the plate material is preferentially extended from an area pressed against a portion having a large curvature radius of the mold among the formed portions of the plate material.
The plate material forming method according to claim 1, wherein, in the preliminary forming step, the formed portion of the plate material is rolled and stretched by shot peening.
The plate material forming method according to claim 1, wherein, in the preliminary forming step, the formed portion of the plate material is rolled and stretched by burnishing.
6. The preforming step, wherein at least one slit is formed in a portion of the plate member to which the tensile load is applied, and the tensile load is varied with the slit as a boundary. Plate material forming method.
7. In the adhesion inspection / determination step, the surface of the plate material is hit and analyzed to inspect / determine whether or not the plate material is in close contact with the mold. The board | plate material shaping | molding method of description.
The inspecting / determining step inspects / determines whether or not the plate material is in close contact with the mold by heating the surface of the plate material and analyzing the rate of temperature increase. The board | plate material shaping | molding method in any one.
9. In the main forming step, at least the forming portion of the plate material is continuously or intermittently heated on a plurality of heating lines parallel to each other to conform to the mold. Plate material forming method.
A load section for applying a tensile load to the titanium-based material plate;
A pressing portion that presses the molded portion of the plate material loaded with the tensile load against a mold having a composite curved surface with a curvature of a molding target;
A preforming portion for extending a portion of the molded portion that is in close contact with the mold so that a portion of the molded portion that is floating from the mold is in close contact with the mold;
At least the molded part of the plate material, a main molded part that is molded by heating at a temperature at which the material begins to be plastically deformed and does not stretch so as to deform the shape;
A plate material forming apparatus.
The pre-formed part is a first heating part that heats and extends the formed part of the plate material at a temperature at which the yield strength of the material is lower than the stress applied by the tensile load applied to the material. Item 10. A sheet forming apparatus according to Item 10.
The plate material forming apparatus according to claim 10, wherein the preforming unit is a shot peening apparatus.
The plate material forming apparatus according to claim 10, wherein the preforming unit is a burnishing apparatus.
The said main forming part is a 2nd heating part which adapts to the said metal mold | die by heating continuously or intermittently at least the said shaping | molding part among the said board | plate materials on several parallel heating lines. The board | plate material shaping | molding apparatus of description.