JPH0677773B2 - Method for manufacturing thin metal tube - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

In the present invention, the ratio of the plate thickness t to the pipe outer diameter D (t / D)
Is a small thin metal tube, so that
The present invention relates to a method for continuously manufacturing by effectively utilizing pre-deformation due to plastic bending given to a metal plate.

[Prior art]

Conventionally, in order to manufacture a metal tube, a metal sheet is sequentially bent in the width direction by using a roll forming machine including a forming roll or a cage roll having calibers arranged in a large number of tandems to form a tubular shape. A manufacturing method by a continuous line in which both side edges of the formed metal plate are joined by butt welding is generally adopted.

[Problems to be Solved by the Invention]

However, when an attempt is made to manufacture a thin-walled metal pipe by such a conventional method, since the thickness t of the metal plate is much smaller than the outer diameter D of the pipe, it is bent to the curvature radius (R = D / 2) of the product. Since the metal plate cannot undergo sufficient plastic deformation until it is pressed, the elastic deformation of the metal plate during the bending process is large, so that a large springback occurs while leaving one roll and being bitten by the next roll. In addition, there was a problem that the plate side edge was not bent enough, and the edge stretch was large and edge waves were likely to occur. In order to solve such a problem, a method of increasing the number of rolls to suppress the springback as much as possible is adopted, but this method requires a long time to change or adjust the rolls because the combined size range is narrow. At the same time, there is a problem in that the metal sheet is strongly contacted with the roll for a long time before being formed into a tubular shape, and surface defects are likely to occur.

[Means for solving problems]

As a result of various studies to solve the above problems, the present inventors arranged a bending roll having a small diameter in the width direction of the metal plate,
Free deformation in the longitudinal direction (bending due to stress inside the metal plate)
When the metal plate is curved in the width direction with the inner surface of the pipe being constrained as the inner side, the plastic plate is continuously plastically bent with the inner surface of the pipe being the inner side by the bending roll, The present invention has been completed by clarifying that it is possible to easily manufacture a thin-walled metal pipe by making the metal plate into a tubular shape having a manufacturing curvature by using the bending in the width direction of the metal plate and joining the abutting portions of the metal plate. Of. The principle of deformation of the metal plate in the method of the present invention will be described below with reference to FIG. First, as shown in the left part of FIG. 1, a metal plate is continuously bent by being bent along a small-diameter bending roll having a radius of curvature R ₁ arranged in the width direction (Y direction). A minute portion of the metal plate that has undergone this plastic bending will be taken out and considered next. First, if the free deformation in the longitudinal direction (X direction) and the width direction (Y direction) of this minute portion is restrained as shown in the central portion of FIG. 1, that is, if the metal plate is kept flat, the small diameter The part that was bent by the bending roll of No. 1 stretched in the longitudinal direction and the part that was bent outside contracted in the longitudinal direction to generate stresses σ _x and σ _y in the X and Y directions,
A bending moment Mx is generated in the longitudinal direction (X direction) and a bending moment My is generated in the width direction (Y direction). In this way, the minute portion of the metal plate continuously plastically bent by the small-diameter bending rolls arranged in the width direction is straightened only in the longitudinal direction as shown in the lower right part of FIG. When a bending moment is applied only in the longitudinal direction so as to restrain the free deformation in the longitudinal direction, the bending moments Mx and My cause arc-shaped deformation to have a curvature (1 / R ₂ ) in the width direction. This curvature (1 / R ₂ ) is long enough to cause so-called saddle-shaped warpage as shown in the upper right part of Fig. 1 for a metal plate continuously plastically bent by a small-diameter bending roll arranged in the width direction. When the metal piece whose width or width or length and width is sufficiently small does not restrain the free deformation of the metal piece in the longitudinal direction or the width direction, the curvature in the longitudinal direction and the curvature in the width direction are 1 respectively. / Rx and 1 / Ry
And the Poisson's ratio is ν, the following equation is given. 1 / R ₂ = (1 / Rx) + ν (1 / Ry) In addition, a small portion of a metal plate continuously plastically bent with a small-diameter bending roll arranged in the width direction with the inner surface of the tube as the inner surface , As shown in the right middle part of FIG. 1, when a bending moment is applied only in the width direction so as to be in a straight state only in the width direction, that is, to restrain free deformation in the width direction, the bending moments Mx and My By and, it deforms into an arc shape with a curvature (1 / R'x) in the longitudinal direction. Bending moments Mx and My caused by such plastic bending
Curvature of bending in the width direction and the longitudinal direction caused by and (1 /
The values of R ₂ ) and (1 / R′x) vary depending on the material properties of the metal plate, the plate thickness, the plastic bending conditions (especially the diameter of the small diameter bending roll and the pressing force of the small diameter bending roll), When these conditions are determined, they are uniquely determined. These values are calculated using the equations shown in FIG. 1 and, for example, “Plasticity and Machining” Vol.
Although it can be obtained by the theoretical analysis method shown in pages 988 to 994 of the issue (1976-12), it is easy to restrain the free deformation of the metal plate after plastic bending in the longitudinal direction or the width direction. It is easy to obtain by measuring the curvatures in the width direction and the longitudinal direction at that time. In the formula shown in FIG. 1, EI is bending rigidity. Here, E is Young's modulus, I is a bt ^3/12 a geometrical moment of inertia, where b is the plate width, t is the plate thickness. A metal plate continuously plastically bent by a small-diameter bending roll arranged in the width direction with the inner surface of the pipe as the inner side is restrained from free deformation in the longitudinal direction as shown in the lower right part of FIG. When a bending moment is applied only in the longitudinal direction, the metal plate is deformed into an arc shape with a curvature (1 / R ₂ ) due to the bending in the width direction caused by the bending moment generated by plastic bending. A thin metal tube can be manufactured by bending a deformable metal plate to a product curvature and joining the abutting portions of the metal plates. At this time, the curvature of the bending in the width direction (1 / R ₂ ) caused by the bending moment generated in the metal plate continuously plastically bent by the small-diameter bending roll arranged in the width direction is, for example, the diameter of the small-diameter bending roll. It can be made larger by making it smaller, but there is a limit to the size of the diameter, so if plastic bending can only be performed so that the curvature of the bending in the width direction due to plastic bending becomes smaller than the product curvature, As the bending roll of B, the radius of curvature R ₁ should be selected as small as possible, and the squeeze roll should be used to bend to the product curvature at the position where the abutting parts of the metal plates are joined. If the curvature of the bend in the width direction caused by the moment (1 / R ₂₎ is selected smaller diameter bending rolls radius of curvature R ₁ that exceeds the product curvature, small-diameter bending low When the metal plate is continuously bent in the width direction and the free deformation in the longitudinal direction is constrained by using the bending in the width direction generated by the bending moment generated in the metal plate continuously plastically bent at When welding the contact parts of the metal plates by welding, both sides of the metal plate in the width direction are abutted against each other to form a tube and the inside of the tube has the same curvature as the product. A curvature mandrel should be placed. Further, in the case where the width of the metal plate continuously plastically bent by a small-diameter bending roll is wider than the product curvature radius by 4π or more, a double winding tube or a multiple winding tube can be used. As described above, in the present invention, the metal plate continuously plastically bent by the small-diameter bending rolls arranged in the width direction with the inner surface of the pipe as the inner side is the plastic bending when the free deformation in the longitudinal direction is restrained. Using the bending in the width direction generated by the bending moment generated by the above, the abutting portions of both side edges are joined in a state of being bent in a tubular shape having a product curvature, to manufacture a thin metal tube. At this time, the joining of the abutting portions of the metal plate formed into a tubular shape may be performed by brazing or bonding, instead of welding as in the conventional method of manufacturing a metal tube. Next, a method for manufacturing a thin metal tube according to the present invention will be described based on the perspective view shown in FIG. 2 and the side view shown in FIG. First, a small-diameter bending roll 1a installed immediately after the uncoiler 5 on the inlet side of the continuous forming line and the small-diameter bending roll 1a.
With a pre-deformation device 1 consisting of a polyurethane lining roll 1b against which a 1a is pressed, a small diameter is arranged on a metal plate 2, preferably a stainless steel plate, a high-tensile steel plate or a titanium plate, with the inner surface of the pipe being the inner surface in the width direction. Bending roll
When the free deformation in the longitudinal direction is restricted by 1a, the plastic plate is continuously plastically bent so that the inner surface of the pipe is the inner surface and the metal plate is curved in the width direction. Bending roll with small diameter when restraining free deformation in the longitudinal direction
If the bending curvature (1 / R ₂ ) in the width direction with the inner surface of the pipe as the inner side is almost equal to the product curvature due to the bending moment generated by the plastic bending in 1a, the pre-deformation device 1 outputs the line. A roll or cage roll having one or more sets of calibers installed at positions separated by about 30 times or more of the product diameter such that the longitudinal extension of the side edge portion of the metal plate 2 in the lateral direction is substantially within the elastic range. At the positions of the side rolls 3 and the feed rolls 4, the metal plate 2 has a product shape, that is, a tubular shape, and while moving from the pre-deformation device 1 to the side rolls 3, the width direction generated by the bending moment generated by plastic bending as described above. Curvature of curvature (1 /
Deformation is continuously performed until R ₂ ). That is, when the free deformation in the longitudinal direction is constrained, the metal plate has the above-mentioned curvature up to the curvature of the width direction (1 / R ₂ ) caused by the bending moment generated by the plastic bending that is plastically bent continuously with the small-diameter bending roll. Since it is naturally bent by the bending moment, springback does not occur until the radius of curvature of the metal plate reaches R ₂ by sufficiently setting the deformation zone length. However, due to the relationship between the diameter of the small-diameter bending roll and the material properties of the metal plate, the plate thickness, etc., when the free deformation in the longitudinal direction is constrained, the bending caused by the plastic bending continuously plastically bent by the small-diameter bending roll. If the bending curvature in the width direction caused by the moment is smaller than the product curvature, from the bending curvature (1 / R ₂ ) in the width direction due to plastic bending to the product curvature, use a roll such as a forming roll or cage roll having a caliber. Although it is necessary to form it into a tubular shape, even in this case, the degree of bending of the additional metal plate by a forming roll is very small compared to the case of passing a virgin material that does not give any pre-deformation. The back can be reduced. In addition, when the curvature of the bending in the width direction (1 / R ₂ ) generated by the bending moment generated by plastic bending when free deformation in the longitudinal direction is constrained is sufficient, that is, the radius R _{2 in the} tubular shape is the radius of the product. If the width of the metal plate 2 becomes smaller and both side edges of the metal plate 2 overlap with each other, the bending roll has a small diameter.
The metal plate 2 between the side roll 3 and the side roll 3 in which the free deformation in the longitudinal direction is restrained in a state in which the width direction is straightly restrained by 1a and is bent in a tubular shape having a product curvature. A mandrel (not shown) may be installed so that the metal plate 2 is wound from the position where the both side edges of the width direction are butted to each other to form a tubular shape to the joining position. A small-diameter bending roll 1a is arranged in the width direction with the inner surface of the pipe being the inner side when the free deformation in the longitudinal direction is restrained.
If the curvature of the bending in the width direction generated by the bending moment generated by the plastic bending that is continuously plastic-bent is insufficient, the forming is insufficient near the downstream side of the continuous line between the pre-deformation device 1 and the side rolls 3. A caliber roll or a cage roll can be arranged according to the amount to form a tube, and a thin-walled metal tube can be formed even with a conventional device having a large number of forming rolls and a pre-deformation device 1 only. Becomes Thus, when the metal plate 2 is formed into a tubular shape having the same curvature as the product curvature, both side edges of the metal plate 2 in the width direction are butted and butt-welded with the welding torch 6 or the like, or lapped and lap-welded or brazed. If the metal plate 2 remains on the outside when the joint is a superposed structure, that is, one side edge in the width direction of the metal plate 2 protrudes from the joint and the outside of the pipe. If it is located at, the protruding portion may be cut off to form a thin metal tube.

[Action]

In order to carry out the method for manufacturing a thin-walled metal pipe according to the present invention as described above, plastic bending is performed by continuous plastic bending with the inner surface of the pipe being the inner side by a bending roll having a small diameter arranged in the width direction of the metal plate. When the bending curvature in the width direction caused by the bending moment caused by the product is almost equal to the product curvature, the elongation strain of the side edge of the metal plate is set within the elastic range by setting the deformation zone length to about 30 times the product diameter as described above. It can be accommodated inside and the generation of edge waves can be prevented, and the number of rolls required for molding becomes almost unnecessary. Further, even when the curvature of the bending in the width direction generated by the bending moment generated by the plastic bending processed by plastic bending is not sufficient, the number of rolls required for forming can be significantly reduced as compared with the conventional roll forming, as well as the usual roll forming. Even when the same number of rolls as the conventional roll forming is used without omitting the forming rolls, since the bending in the width direction caused by the bending moment generated by the plastic bending continuously plastically bending the metal plate is used, it is completely unpredictable. Compared to the case of passing the virgin material without deformation, the spring back is reduced, and by extending the forming zone length, edge stretch can be suppressed and edge formability can be improved. . Further, if the thin metal plate to be manufactured is likely to generate a wave (buckling) at its side edge during forming or when the metal plate is formed into a tubular shape, it is continuously applied with a small-diameter bending roll. As shown in the side view of FIG. 3, the plastic bending position is located at the center of the thin-walled metal pipe from the extension line in the moving direction of the bottom of the thin-walled metal pipe (the lower line in FIG. 3 of the pipe passing through the side roll 3). The metal plate side reduces the difference between the length of the metal plate center line and the length of the metal plate side edge from the state of being straightly restrained in the width direction to the position where it can be bent into a tubular shape of the product curvature. It is desirable to prevent the side edge of the metal plate from buckling by reducing the elongation strain of the edge. In this way, a good thin-walled metal pipe can be manufactured by positioning the plastic bending position continuously applied with a small-diameter bending roll toward the center of the thin-walled metal pipe from the extension line of the moving direction of the bottom of the thin-walled metal pipe. Not only that, the length of the continuous line can be shortened to reduce the size of the device. Further, when manufacturing a thin metal pipe by such a continuous line, the elastic limit in the longitudinal direction is applied to the metal plate continuously plastically bent by a small-diameter bending roll arranged in the width direction with the inner surface of the pipe being the inner side. When a tension of less than is applied, the metal plate is bent from the state of being straightly constrained in the width direction by using the bending in the width direction caused by the bending moment due to the plastic bending, and the metal plate is bent into the tubular shape of the product curvature. Since it is possible to suppress the occurrence of Talumi on the side edge of the metal plate until it is brought into a closed state, it is difficult to produce a difference in length in the longitudinal direction of the metal plate, so it is possible to manufacture thin-walled metal tubes in a good shape. However, when this tension exceeds the elastic limit, the bending in the width direction caused by continuous plastic bending with a bending roll with a small diameter disappeared and the metal plate was bent into a tubular shape with the product curvature. Undesirably it becomes difficult to mold the state.

【Example】

Example 1 SU having a thickness of 0.1 mm and a width of 89.5 mm and a 0.2% proof stress of 160 kgf / mm ² .
A metal plate of S 304 is placed in the width direction with the inner surface of the tube as the inner surface, and a bending roll with a small diameter of 3 mm has a diameter of 100
It is pressed by a pressing force of 300 kgf against a polyurethane lining roll with a roll width of 100 mm and a roll width of 100 mm, and plastic bending is performed so that the bending curvature in the width direction caused by the bending moment generated by the plastic bending is 68% of the product curvature. Then, apply a slight tension to the metal plate so that the metal plate does not sag, and use the bending in the width direction generated by the bending moment generated by the plastic bending of the metal plate to restrain the width direction straight at the bending roll position with a small diameter. Bending continuously from the bent state and pressing with a squeeze roll at a position of 950 mm from the position of the small-diameter bending roll, product radius of curvature (28.6 mm)
After being made into a state in which the free deformation in the longitudinal direction was restrained in the state of being bent into a tubular shape, the contact portions of the side edges of the metal plate were joined by microplasma welding to manufacture a thin metal tube. This thin-walled metal tube was a thin-walled metal tube with good roundness and no edge waves. Example 2 JIS of 0.2% yield strength of 55 mmf / mm ² with 0.2 mm thickness and 89.2 mm width
A metal plate consisting of a titanium plate of the 3rd type specified in H4600 is arranged in the width direction with the inner surface of the tube being the inner side. It is a bending roll with a small diameter of 3 mm and a diameter of 100 mm and a roll width of 100 mm. 400 kg with polyurethane lining roll
Plastic bending is performed so that the bending curvature in the width direction caused by the bending moment generated by the plastic bending caused by the pressing force of f is 72% of the product curvature, and then a slight tension is applied to the metal plate so that it does not loosen. Using the bending in the width direction that is generated by the bending moment generated by plastic bending when applied to a metal plate, continuously bend from the state of being straightly constrained in the width direction at the bending roll position of the small diameter and from the bending roll position of the small diameter. When pressing with a squeeze roll at a position of 950 mm and restraining the free deformation in the longitudinal direction while being bent into a tubular shape with a product curvature radius (28.6 mm), the squeeze position is the plastic bending position with a bending roll with a small diameter. Position this squeeze roll so that it is located in the center of the metal pipe by 30 mm from the extension line of the bottom of the metal pipe that is moved out of the roll. Allowed to, to produce a thin metal tube abutting portion of the side edge between the metal plate and joined by microplasma welding. This thin-walled metal tube was a thin-walled metal tube with good roundness and no edge waves. In these examples, a small tension was applied between the small-diameter bending roll and the squeeze roll to prevent loosening of the metal plate, but the bending occurs between the small-diameter bending roll and the squeeze roll due to plastic bending. Since the bending in the width direction caused by the bending moment is used, it is naturally bent in the width direction and buckling does not easily occur in the longitudinal direction. Therefore, tension may not be applied depending on the material properties and thickness of the metal plate. May be.

【The invention's effect】

As described in detail above, the method for manufacturing a thin-walled metal pipe according to the present invention utilizing a pre-deformation such as continuous plastic bending by a bending roll having a small diameter and arranged with the inner surface of the pipe as the inner side in the width direction. Not only is it possible to manufacture thin-walled metal pipes from high-strength metal plates, which have been difficult to form by roll forming, as well as materials that have been used for metal pipes in the past, and thin-walled metal pipes can be made from unfired pure material. Can be easily manufactured, cost reduction can be expected in addition to the reduction of the number of rolls, and the curvature distribution is excellent because the bending is performed uniformly in the width direction, and the surface flaw is also reduced due to the small number of rolls. ,
It is an industrially excellent method for manufacturing a thin-walled metal tube having great value.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the method for producing a thin-walled metal pipe according to the present invention, FIG. 2 is a perspective view showing a state where a thin-walled metal pipe is being produced by the method according to the present invention, and FIG. 3 is a side view thereof. Is. In the drawing R ₁ ...... Radius of curvature of small-diameter bending roll orthogonal to the longitudinal direction R ₂ ...... Radius of curvature in width direction caused by bending moment caused by plastic bending 1 ... Pre-deformation device 1a ... Bending roll of small diameter 1b Polyurethane lining roll 2 Metal plate 3 Side roll 4 Feed roll 5 Uncoiler 6 Welding torch

Claims (7)

[Claims] 1. A bending roll having a small diameter is arranged in the width direction of the metal plate, and when the free deformation in the longitudinal direction is restrained, the metal plate bends in the width direction with the inner surface of the pipe being the inside. After the metal plate is continuously plastically bent with the inner surface of the pipe as the inner side by the roll, the metal plate is formed into a tubular shape having a product curvature by using the bending in the width direction of the metal plate, A method for manufacturing a thin-walled metal pipe, which comprises joining the contact portions. 2. A continuous line from a plastic bending process using a small-diameter bending roll of a metal plate to a joining process.
A method for manufacturing a thin-walled metal tube according to item. 3. The curvature of the metal plate in the width direction is defined as the product curvature at a position away from the plastic bending position of the metal plate with a small-diameter bending roll by about 30 times or more the product diameter. The method for manufacturing a thin-walled metal tube according to item 2. 4. A thin metal pipe, which is formed into a tubular shape and is moved by joining abutting portions thereof to move the plastic bending position of a small-diameter bending roll, from the extension line of the moving direction of the pipe bottom toward the center of the thin metal pipe. The method for manufacturing a thin-walled metal tube according to claim 2 or 3, wherein 5. The method for producing a thin-walled metal pipe according to claim 1, wherein the abutting portions of the tubular metal plate are joined by welding. 6. The method for producing a thin metal tube according to claim 1, wherein the abutting portions of the tubular metal plate are joined by brazing. 7. The method for producing a thin metal tube according to claim 1, wherein the abutting portions of the tubular metal plates are joined by adhesion.