JP4315005B2 - ERW steel pipe manufacturing equipment - Google Patents

Description

  The present invention relates to an apparatus for manufacturing an electric resistance steel pipe, and more particularly to a technique effective for cutting and removing inner surface beads when manufacturing a high-strength, thin-walled electric resistance steel pipe.

  An electric resistance welded steel pipe is generally manufactured by unwinding a coiled steel strip as a raw material and continuously forming it into a cylindrical shape with a group of forming rolls, and then welding both ends in the width direction of the steel strip. (See Patent Document 1). For example, in the production, a steel slab obtained by continuously casting molten steel as a raw material is heated to a predetermined temperature (usually 1200 to 1300 ° C.) in a heating furnace, and then rolled up to a constant width by hot rolling. Coiled steel strip is used. Then, after unwinding the coiled steel strip 1 with an uncoiler, the steel strip surface is fed horizontally at a constant speed onto a group of forming rolls in which various types of rolls having various shapes are arranged in multiple stages. The tube body 2 processed by the forming roll and formed into a cylindrical shape (referred to as an open tube because the end portion in the width direction that is abutted is unjoined) 2 continues to the width direction that is abutted as shown in FIG. Both ends 3 are heated by an induction coil 4, pressed by a squeeze roll 5, crimped and welded, and an integrated steel pipe 6 is obtained. Since the protrusions called beads 7 are formed on the inner and outer surfaces of the joint portion extending substantially linearly continuously in the longitudinal direction of the steel pipe 6, the beads 7 are aesthetic or workable on the inner and outer surfaces. From this point of view, it is removed by using bead cutting means (bite or the like) 8. Here, the trace which cut | disconnected such an inner surface bead is called the inner surface bead cutting trace. Further, the steel pipe 6 from which the beads 7 have been removed is reheated in a heating furnace (not shown), and the dimensions are adjusted by a multi-stage drawing rolling machine such as a hot stretch reducer or a sizer to obtain a desired size and characteristics. After checking whether it has, it becomes an ERW steel pipe as a primary product. The inner surface bead cutting means 8 is constituted by a bite supported by a support bar 9 inserted from one end into the raw steel pipe 6, and the radius of curvature of the bite is equal to the inner radius of curvature of the raw steel pipe 6. It sets so that it may correspond, and it contacts the inner surface bead 7 of the raw steel pipe 6, and cuts it.

By the way, in the case where an ERW steel pipe is manufactured with a high-strength thin-walled material (for example, an outer diameter of 88 to 146 mmΦ, a wall thickness of 2 to 3 mm, and a material strength of 500 MPa or more), in the manufacturing process described above, pressing with a squeeze roll 5 As shown in FIG. 2 (a), the spring steel tube 6 has a cross-sectional shape that does not take a perfect circle and tends to be a vertically long ellipse (so-called pilken shape). Therefore, not only the curvature radius of the inner surface of the steel pipe becomes various sizes but also does not coincide with the curvature radius of the cutting tool. In this case, cutting defects (such as streak residue) occur in the traces of the inner bead of the raw steel pipe 6, and the problem that productivity is impaired due to a decrease in product yield or the like frequently occurs.
JP 2002-28718 A

  In view of such circumstances, an object of the present invention is to provide an apparatus for producing an electric resistance welded steel pipe capable of always making the inner surface bead cutting trace into a constant shape even when the material is a high-strength thin-walled material.

  The inventor has intensively studied to achieve the above object, and the results have been embodied in the present invention.

  That is, the present invention relates to an uncoiler for rewinding a coiled steel strip, a group of forming rolls that run the unwound steel strip at a constant speed and abut both ends in the width direction to form a cylindrical shape. Manufacture of electric resistance welded steel pipe comprising induction heater for heating part, squeeze roll for crimping heated part to make steel pipe, and inner surface bead cutting means for cutting bead formed on inner surface of crimped part In the apparatus, at the downstream side of the squeeze roll and the upstream side of the inner surface bead cutting means, the steel pipe is pressed from above, and the deviation of the outer diameter of the steel pipe is maintained at 3.0% or less. An apparatus for producing an ERW steel pipe, characterized by providing a pressing roll. In this case, it is preferable that the holding roll is provided with a hole type that avoids the outer surface bead of the raw steel pipe. More preferably, the coiled steel strip has a thickness of 2.0 to 3.0 mm and a tensile strength of 500 MPa or more.

  According to the present invention, the cross-sectional shape of a so-called pilicene steel pipe released from a squeeze roll can be restored to a perfect circle before cutting the inner surface bead. As a result, the radius of curvature of the inner surface of the steel pipe coincides with the radius of curvature of the cutting tool during inner surface bead cutting, the inner surface bead can be cut smoothly, and the shape of the cutting trace is always constant.

  Hereinafter, the best embodiment of the present invention will be described based on the background of the invention.

  First, the inventor considered a measure to smooth the cutting trace of the inner surface bead with a roller after cutting the inner surface bead. However, this measure is insufficient because the streak-like defects cannot be solved sufficiently. Therefore, if the cross-sectional shape of the raw steel pipe is kept in a perfect circle before cutting the inner surface bead, the curvature radius of the inner surface of the raw steel pipe and the curvature radius of the cutting tool will always match, and the cutting work will be stabilized. Therefore, we decided to adopt a pressing roller as a specific means.

  That is, the present invention relates to the uncoiler for rewinding the coiled steel strip, the group of forming rolls that run the unwound steel strip at a constant speed, and butt both ends in the width direction to form a cylindrical shape. An existing electric resistance welded steel pipe provided with an induction heater that heats the part, a squeeze roll that crimps the heated part to form a steel pipe, and an inner surface bead cutting means that cuts a bead formed on the inner surface of the crimped part This is a modification of the manufacturing apparatus (see FIG. 3).

  As the modification, as shown in FIG. 1 and FIG. 2 (b), the steel pipe 6 is pressed from above at a position downstream of the squeeze roll 5 and upstream of the internal bead cutting means 8. The presser roll 10 which can be moved up and down to keep the outer diameter deviation of the steel pipe to 3.0% or less is provided. In the present invention, the shape and size of the pressing roll 10 are not particularly limited. This is because it is necessary to adjust the shape and size as well as the reduction height position by performing a test operation or the like in advance according to the size of the steel pipe to be manufactured. However, since the raw steel pipe 6 is often pressed in a state where the outer surface bead remains, the holding roll is provided with a hole mold 11 for avoiding the outer bead of the raw steel pipe 6 as shown in FIG. This is preferred. The shape and size of the hole mold 11 are not particularly limited, and the material of the roll 10 may be the same as that of a steel pipe conveying roller that is normally used. The outer diameter deviation of the steel pipe is defined as the following equation.

Outer diameter deviation of base steel pipe = 100 x (maximum outer diameter of base steel pipe-minimum outer diameter of base steel pipe) / (target (or average) outer diameter)
Furthermore, since it is a steel pipe made of the above-mentioned high-strength thin wall material that tends to have a longitudinally long elliptical cross section after the raw steel pipe is released from the squeeze roll, the present invention provides a high-strength thin-walled material. This is particularly effective when Specifically, the coiled steel strip has a thickness of 2.0 to 3.0 mm and a tensile strength of 500 MPa or more. This is because a steel pipe having a wall thickness exceeding 3.0 mm is close to a perfect circle during bead cutting, and therefore does not require pressing by this apparatus.

  The steel type is a steel with a tensile strength of 780 MPa, and a steel strip having a plate width of 460 mm is used as a raw material to manufacture a raw steel pipe. An ERW steel pipe having a wall thickness of 2.9 mm was manufactured. The operation was performed in the case of using the manufacturing apparatus according to the present invention shown in FIG. 1 and in the case of using the conventional manufacturing apparatus not equipped with the pressing roll shown in FIG.

  As a result of this operation, the product yield improved by 0.2%. According to the apparatus according to the present invention, it is clear that a high-quality electric resistance welded steel pipe can be manufactured with high productivity. Here, product yield (%) = (weight of steel pipe passed as product (ton) / weight of coiled steel strip supplied to forming roll (ton) × 100)

It is a schematic diagram explaining the manufacturing apparatus of the ERW steel pipe which concerns on this invention. It is a figure which shows the cross-sectional shape of an electric-resistance-welded steel pipe, and the state of an inner-outer surface bead, (a) is a conventional state, (b) is a state at the time of employ | adopting the press roll which concerns on this invention. It is a schematic diagram explaining the manufacturing apparatus of the conventional ERW steel pipe.

Explanation of symbols

1 Coiled steel strip 2 Tube (open tube)
3 End portions in the width direction 4 Induction coil 5 Squeeze roll 6 Raw steel pipe 7 Bead 8 Bead cutting means 9 Support bar 10 Pressing roll 11 Hole type

Claims (3)

An uncoiler that rewinds the coiled steel strip, a group of forming rolls that run the unrolled steel strip at a constant speed, butts both ends in the width direction to form a cylindrical shape, and an induction that heats the butted portion In an apparatus for producing an electric resistance steel pipe comprising a heater, a squeeze roll that crimps the heated part to form a steel pipe, and an inner surface bead cutting means for cutting a bead formed on the inner surface of the crimped part,
A presser roll that can be moved up and down at a position downstream of the squeeze roll and upstream of the inner surface bead cutting means so as to hold the steel pipe from above and keep the deviation of the outer diameter of the steel pipe to 3.0% or less. An apparatus for producing an electric resistance steel pipe. The apparatus for producing an electric resistance steel pipe according to claim 1, wherein the holding roll is provided with a hole mold for avoiding an outer surface bead of the steel pipe. The thickness of the said coiled steel strip is 2.0-3.0 mm, and the tensile strength is 500 Mpa or more, The manufacturing apparatus of the ERW steel pipe of Claim 1 or 2 characterized by the above-mentioned.

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