JPH06262253A - Production of square tube with excellent shape characteristic - Google Patents

Abstract

PURPOSE:To obtain a square tube having a shape characteristic being respectively suitable for a structural square tube and a decorative square tube by changing a 1st stage set push-in ratio corresponding to the structural square tube and the decorative square tube to the produced. CONSTITUTION:When a square tube is produced from a cylindrical stock tube with a roll forming machine with forming rolls arranged in two or four stages, supposing the outer diameter of the stock tube is D, a wall thickness of the raw tube is t, and max. caliber height is H, a set push-in ratio Q of a 1st stage forming process which is defined as Q=(D-H)/(D-t)X100 is maintained in a range 12-23% at the time of producing a structural square tube and maintained in a range 20-24% at the time of producing a decorative square tube. Then, the square tube is formed in a target shape in a forming following a 2nd stage. Therefore, by regulating the set push-in amount, the structural square tube with the excellent flatness on a plane part and the decorative square tube having a sharp corner part can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rectangular tube having a shape characteristic according to demand by a roll forming machine, particularly a roll forming machine incorporating a small number of forming rolls.

[0002]

2. Description of the Related Art Square tubes are manufactured by press molding or roll molding. For example, in the press molding method, two cutting plates are formed in a concave shape, and the upper and lower portions are welded, and then sizing and straightening are performed. There is also a method of forming a round pipe manufactured from a steel plate into a deformed pipe by a large press. Both press moldings have low productivity because square tubes are manufactured in a batch system. In this respect, the roll forming method is a method suitable for continuous production and capable of producing a square tube with high productivity. The roll forming method includes a method in which a running strip is bent into an irregular cross-sectional shape while welding both ends in the width direction that are butted to each other, and a round tube manufactured by electric resistance welding or the like is used as a raw tube. It is roughly classified into a method of forming a tube into a square tube by a sizing mill or the like. The method of performing molding together at the time of manufacturing a steel pipe is advantageous in that the number of manufacturing steps is small,
Dedicated square tube manufacturing equipment is required. On the other hand, the method of forming a round tube into a square tube requires a relatively small production facility and is a method with high operation flexibility according to demand.

In the roll forming method for forming a cylindrical raw tube into a rectangular tube, the forming is performed while pulling the raw tube between the forming rolls. For this reason, it is difficult to pull out the blank tube in an accurate positional relationship, defects such as bending occur, and the accuracy of the obtained rectangular tube is likely to be low. A method is also known in which a blank tube is pushed between molding rolls. In the push-in method, since the pushing force is applied from the rear end of the raw pipe, the stroke of the push-in mechanism such as the hydraulic cylinder becomes large, making the equipment larger and
Increasing complexity is unavoidable. As an improvement of the pushing method, a locking mechanism that locks the rear end of the raw pipe at an appropriate position is placed between the hydraulic cylinder and the raw pipe, and the raw pipe is molded while moving the locking mechanism together with the raw pipe. What to do is Sho 62-545
No. 64 is introduced. Although the stroke of the hydraulic cylinder is reduced to some extent by incorporating the locking mechanism, the equipment configuration becomes complicated. Further, since the pushing force is applied to the base pipe from the rear end side, there is a drawback that the base pipe is apt to be deformed such as bending and buckling.

Therefore, the present inventors have arranged a plurality of push-in tools capable of advancing and retracting on both sides in the running direction of the raw pipe in order to apply a propulsive force while clamping the raw pipe fed to the forming roll from both sides. We developed a device for running these pushers along an endless track, and filed a patent application separately. When pressing force is applied by pressing tools that clamp the tube from both sides,
Deformation such as bending and buckling is suppressed. Further, there is no limitation on the length of the raw pipe that can be formed, and it is possible to continuously roll-form a plurality of raw pipes.

[0005]

In the profiled pipe manufacturing apparatus proposed in the prior application, the forming rolls are arranged in three stages, the first stand is used for preforming the raw pipe, and the second stand is used for forming a predetermined shape. , 3rd stand is used for finish molding. As described above, when forming a raw pipe with a roll forming machine having a small number of stands, the influence of the processing conditions in each stand on the final shape becomes large. If the processing conditions are not set properly, the flat surface of the obtained square tube may be warped or dented,
Defects such as large corners are generated. Therefore, in Japanese Unexamined Patent Publication No. 4-224022, the warp of the flat portion of the obtained rectangular tube is reduced by reducing the final stage reduction amount as the ratio of the wall thickness to the outer diameter of the raw tube increases. It's suppressed. Further, in Japanese Patent Laid-Open No. 4-224023, the roll caliber at the final stage is made small to suppress the warp of the flat surface portion.

However, the final shape is affected not only by the roll forming of the final stage but also by the processing conditions of the roll forming on the upper stage side. For example, when manufacturing a square tube with two stands, the shape accuracy of the final shape changes depending on the processing conditions of the first stand. Therefore, it has been difficult to stably manufacture a square tube having a shape that meets the demand. The present invention has been devised to solve such a problem.
By adjusting the set indentation rate of the step, it is possible to stably manufacture a square tube having a shape according to the application such as structural material and decoration.

[0007]

In the present invention, in order to achieve the object, when forming a cylindrical raw pipe by a first stage forming roll, the outer diameter and the wall thickness of the raw pipe are D and t. , When the maximum caliber height is H, Q = (D−H) / (D−
t) The set indentation rate Q defined by 100 is used properly according to the required shape of the obtained rectangular tube. In the case of a structural rectangular tube that requires flatness of the flat surface, the set indentation rate Q is 12 to 2
Keep in the range of 3%. For a decorative rectangular tube that requires a sharp corner, the set indentation rate Q is maintained within the range of 20 to 24%. The formed pipe is finished into a predetermined cross-sectional shape by the subsequent forming rolls of the second stage and further the third stage and thereafter. The total number of stands is not particularly limited to the present invention, but at least two stands are required, and the third stand and the fourth stand are arranged as necessary.

The present invention will be described in detail below with reference to the drawings. For example, when a square tube is manufactured by a two-stand roll forming machine, a cylindrical raw pipe P ₀ is fed to the first stand 20 by the idler roll 10 as shown in FIG. As shown in FIG. 2, the first stand 20 includes a right roll 21, a left roll 22, and an upper roll 2.
3 and the lower roll 24 are arranged. Each roll 21-2
4 has a concave crown peripheral surface shape, and roll 21
The inside surrounded by -24 is a molding space for the raw pipe P ₀ . The tube P _{0 that} has passed through the first stand 20 is rolled by the roll 2
Corresponding to the molding space divided by the peripheral surface of 1 to 24, FIG.
The pipe body P ₁ has an intermediate shape shown in FIG. Intermediate-shaped tube P ₁
The height of the hole diameter is the maximum caliber height H. Tube P ₁
Are then fed to the second stand 30. As the forming roll of the second stand 30, a roll having a small crown or a flat roll is assembled from four sides as in FIG. The rectangular tube P _{2 that} has passed through the second stand 30 is in a state of being chamfered as shown in FIG.

The square tube P ₂ thus obtained becomes a product having a good flatness or a product having sharp corners, depending on the processing conditions. It is used as a structural square tube, a decorative square tube, etc., depending on the respective shape characteristics. As shown in FIG. 4 (a), the structural rectangular tube is most required to have a flat plane portion in order to reduce the grinding cost. On the other hand, the corners are not required to have a very small radius depending on the application, but it is preferable to make the radius small for the purpose of product differentiation. On the other hand, in the decorative square tube, in order to harmonize with surrounding equipment and building materials,
It is required to have a corner with a small radius as shown in. In this case, the flat surface is required to be flat for the purpose of being mirror-polished, but in other decorative applications, the surface skin is often an HL-polished product,
Flatness is not required as much as a structural rectangular tube.

The flatness and the corner radius are influenced by the pushing amount in the first stand 20. Specifically, as shown in FIG. 5, from the profile of the raw pipe P ₀ to the product square pipe P
_{With 2} profiles, each degree of indentation is first
The base pipe P ₀ was roll-formed on the stand 20, and changes in flatness and corner radius depending on the degree of indentation were observed. In addition, in the present specification, the following values are adopted as indexes indicating the flatness and the corner radius. As shown in FIG. 6, the flatness is represented by f / W, where W is the width of the flat surface of the obtained rectangular tube and f is the height from the deepest portion to the highest portion of the flat portion. As shown in FIG. 7, the corner radius is represented by R _s / t where R _s is the length of the radius stop at which the gauge radius R _g is measured and t is the wall thickness of the rectangular tube.

The flatness was excellent in both the structural square tube and the decorative square tube as shown in FIG. 8 when the first-stage and second-stage roll forming was performed with the same indentation degree. Then, the flatness deteriorated as the pushing amount of the first step or the second step was reduced and the predetermined cross-sectional shape was obtained with the other pushing amount. In particular, in the degree of indentation for forming the product into a substantially product shape in the first stage, a flat surface portion having a recessed central portion was formed as in the case of forming with a single stand forming roll. The structural square tube was an annealed material, and the decorative square tube was a rolled material. Degree of each push ~ is expressed by push amount,
FIG. 9 is a graph showing the relationship between the pushing amount and the flatness. As is clear from FIG. 9, the square tube P with excellent flatness
_In order to obtain ₂ , it is necessary to maintain the indentation amount by the first stage roll forming within a predetermined range.

On the contrary, the corner radius R, as shown in FIG. 10, is small when the indentation is such that it is formed close to the final shape at once, or large when the indentation is equal when the indentation amounts of the first and second steps are equal. became. Corner radius R
11 is a graph showing the relationship between the design indentation amount. As is clear from the comparison between FIG. 9 and FIG. 11, the indentation degree of the first stage is changed between the manufacturing conditions of the rectangular tube requiring flatness and the manufacturing conditions of the rectangular tube requiring sharp corners. There is a need. As a result of investigating and experimenting the influence of the degree of indentation on the shape of the square tube, it was clarified that it can be quantified by the set indentation rate Q (%) defined by the following equation. Q = (D−H) / (D−t) × 100 (where D: outer diameter of the raw pipe, t: wall thickness of the raw pipe, H:
Maximum caliber height)

When the set indentation rate Q is maintained in the range of 20 to 24% and the first-stage roll forming is performed on the mother tube whose raw tube is a rolled material, the corner radius R = R _s / t is 1.
It becomes 0% or less, and a square tube having sharp corners suitable for decoration is obtained. On the other hand, when the set indentation rate Q is less than 20%, the corner radius becomes large, and conversely, when it exceeds 24%, the flatness exceeds the SAS standard of 0.5%. As a result, in any case, the shape required for the decorative rectangular tube cannot be satisfied. Further, when the set indentation rate Q is maintained in the range of 12 to 23% and the first-stage roll forming is performed on the mother tube in which the raw tube is an annealed material, the flatness f / W becomes 0.15% or less. A square tube can be obtained in which the grinding of the flat surface portion can be omitted or reduced after molding. On the other hand, when the first-stage roll forming is performed at a set indentation rate Q of less than 12%, the flat portion after forming tends to have a concavely curved shape. On the contrary, when the set indentation rate Q exceeds 23%, the convexly curved flat surface portion is likely to be formed.

By adjusting the set indentation rate Q in this manner, it is possible to reproducibly manufacture a structural square tube having excellent flatness of a flat surface portion and a decorative square tube having a sharp corner portion on the same roll forming line. . In addition to the two-stage roll forming machine shown in FIG. 1, the set indentation rate Q in the first stage roll forming is
A roll forming machine in which forming rolls are incorporated in three to four stages also exhibits the same operation. However, as the number of steps increases, the influence of the set push-in rate Q decreases. Also, from the viewpoint of equipment, the roll forming machine to which the present invention is applied is practically a two-stage or three-stage roll forming machine. The set indentation rate Q can be adjusted by changing the rolls having different crowns as the first-stage forming rolls.

[0015]

【Example】

Example 1: (Production of structural rectangular tube) SUS having an outer diameter D = 50.8 mm and a wall thickness t = 1.4 mm
Using a 304 stainless steel pipe (annealed material) as a raw pipe, a square pipe having a flat portion width W = 39.6 mm was manufactured by a two-stand roll forming machine. Since the distance from the topmost peripheral surface of the raw tube to the flat surface of the rectangular tube is 5.6 mm, the pushing amount in the first stand is set as shown in FIG. 5, and the remaining distance is the pushing amount in the second stand. And Table 1 shows the push amount and the set push rate Q corresponding to the push degrees set in this way.

[Table 1]

The shape of the square tube obtained by roll forming in the first and second stands was investigated. Then, when the flatness f / W and the corner radius R _s / t are arranged by the set indentation rate Q, the relationships shown by the solid lines in FIGS. 9 and 11 are obtained. 9 and 11, n = 3
The average value of is shown. As is clear from FIG. 9, in the case where the first-stage roll forming is performed while maintaining the set indentation rate Q in the range of 12 to 23%, the flatness required for the structural rectangular tube is 0.14 or less. Is pleased. Corner radius R _s
/ T is also well below the target value of 1.8 as shown in FIG. On the other hand, when the set indentation rate Q is too small, the flat surface of the obtained rectangular tube is concavely curved, resulting in poor flatness.

Example 2 (Manufacture of Square Decorative Tube) SUS with outer diameter D = 50.8 mm and wall thickness t = 1.4 mm
Using a 304 stainless steel pipe (rolled material) as a raw pipe, a square pipe having a flat portion width W = 39.6 mm was manufactured by a two-stand roll forming machine. Since the distance from the topmost peripheral surface of the raw tube to the flat surface of the rectangular tube is 5.6 mm, the pushing amount in the first stand is set as shown in FIG. 5, and the remaining distance is the pushing amount in the second stand. And Table 1 shows the push amount and the set push rate Q corresponding to the push degrees set in this way.

[Table 2]

The shape of the square tube obtained by roll forming in the first and second stands was investigated. Then, when the flatness f / W and the corner radius R _s / t were sorted by the set indentation rate Q, the relationships shown by the dotted lines in FIGS. 9 and 11 were obtained, respectively. 9 and 11 show the average value of n = 3 as in the first embodiment. As is clear from FIG. 11, in the case where the first-stage roll forming is performed while maintaining the set indentation amount Q within the range of 20 to 24%, the corner of the target value 1.0 or less required as the decorative steel pipe is obtained. R degree R
_s / t. Further, as shown in FIG. 9, the flatness f / W is also well below the target value of 0.5, and it can be seen that a decorative steel pipe having good shape characteristics is obtained. On the other hand, if the set indentation rate Q is outside the range of 20 to 24%,
Although the flatness of the flat surface of the square tube was good, a square tube having a large radius corner and a square tube with flatness outside the SAS standard value were produced, and were not suitable for decoration.

In the above examples, a SUS304 stainless steel pipe was used as a raw pipe to manufacture a square pipe by a two-stand roll forming machine. However, the present invention is not restricted to this, and exhibits the same action and effect on other stainless steels and ordinary steels, and satisfies the shape characteristics required for structural steel pipes and decorative steel pipes. Square tubes are manufactured. Further, even when the three-stage and four-stage roll forming machines were used, the square tube having a shape according to the application was manufactured by adjusting the set indentation rate Q in the same manner.

[0020]

As described above, according to the present invention, when a square tube is manufactured from a cylindrical raw tube with a roll forming machine equipped with a small number of forming rolls, the setting in the first stage roll forming is performed. By specifying the indentation rate, square tubes with flatness and corners suitable for structural steel tubes and decorative steel tubes are manufactured. For example, in a structural square tube,
Since the flatness of the flat surface is excellent, it is used as a structure capable of omitting or reducing the grinding process. On the other hand, in the decorative steel pipe, since sharp corners are formed,
It is used as a highly discriminating product in harmony with the surrounding equipment and furnishings.

[Brief description of drawings]

FIG. 1 A roll forming machine in which forming rolls are arranged in two stages.

FIG. 2 First stage forming roll

[Fig. 3] Process of forming a square pipe by a two-stage molding

FIG. 4 is a structural square tube (a) and a decorative square tube (b).

[Fig. 5] First-stage indentation degree when processing into a square tube ~
Figure explaining

FIG. 6 is a diagram for explaining the flatness of the formed rectangular tube.

FIG. 7 is a diagram for explaining the corner radius of a formed rectangular tube.

FIG. 8: Change in flatness corresponding to indentation degree

[Fig. 9] Relationship between set indentation amount Q and flatness

FIG. 10: Change in corner radius corresponding to indentation degree

[Fig. 11] Relationship between set push amount Q and corner radius

[Explanation of symbols]

P ₀ : Cylindrical _element pipe P ₁ : Intermediate tube P ₂ : Rectangular tube with rectangular cross section D: Outer diameter of element tube t: Wall thickness of element tube W: Width of rectangular tube flat portion R _g : Gauge radius R _s : Earl stop length 10: Idler roll 20: First stand 3
0: Second stand

Claims (2)

[Claims] 1. When roll-forming a cylindrical raw pipe into a rectangular pipe, when the outer diameter of the raw pipe is D, the wall thickness of the raw pipe is t, and the maximum caliber height is H, Q = ( D−H) / (D−t) ×
A first stage molding step of molding the raw pipe into a rectangular sectional shape while maintaining the set indentation rate Q defined by 100 within a range of 12 to 23%, and the raw pipe molded into a rectangular sectional shape is targeted. 1. A method for manufacturing a structural rectangular tube having excellent flatness, which comprises a second and subsequent forming steps of forming into a shape. 2. When roll-forming a cylindrical tube into a rectangular tube, when the outer diameter of the tube is D, the wall thickness of the tube is t, and the maximum caliber height is H, Q = ( D−H) / (D−t) ×
A first stage molding step of molding the raw pipe into a rectangular cross-sectional shape while maintaining the set indentation rate Q defined by 100 within the range of 20 to 24%, and the raw pipe shaped into the rectangular cross-sectional shape is targeted. A method for manufacturing a decorative rectangular tube having sharp corners, characterized by undergoing a second and subsequent molding steps for molding into a shape.