JPS63165021A - Manufacture of electric welded steel pipe - Google Patents

Abstract

PURPOSE:To enlarge the range of a roll serving both and to reduce a rolling cost by adjusting a roll gap until the forming completion stage by a fin pass roll and specifying the major and minor diameter ratio of the pipe to be welded under the constraint by a squeezing roll. CONSTITUTION:In the case of the maximum diameter pipe the interval 3 of an upper roll 1 and lower roll 2 is made maximum and engaged with a 1st stand. Both end edge parts are then formed with narrowing them gradually according to going to a 3rd stand from a 2nd stand, and the gap 3 is made smaller so as to reach a specified value at a 4th stand to form the major and minor bore ratio less. And in a squeezing roll 7, a welding is performed with constraining just as the elliptical shape so as to regulate the major and minor diameter ratio to <=1.05. At the next stage a round electric welded pipe is obtd. with forming in the specified dimension by plural sizing rolls.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention aims at the dual use of pipe manufacturing equipment for ERW steel pipes having different outer diameters, and in particular, the ratio of the applicable maximum diameter to the applicable minimum diameter of the dual use equipment. This relates to a method for manufacturing ERW steel pipes that can increase the roundness of the final finished steel pipes by forming them into a nearly perfect circle at the end of forming with the fin pass rolls, thereby increasing the roundness of the final finished steel pipes at the subsequent sizing rolls. The present invention provides a method for manufacturing ERW steel pipes with excellent accuracy.

In general, ERW steel pipes are made by passing a steel strip through hole-shaped rolls to gradually form it into a cylindrical open pipe, then pressing both ends of the steel pipe against each other with a squeeze roll and welding them using high-frequency current, and then using sizing rolls to shape the steel pipe into a predetermined shape. It goes through a manufacturing process to finish it.

(Prior art) The rolls used in the above-mentioned series of manufacturing processes must be replaced every time the outer diameter of the ERW steel pipe to be manufactured differs, and the work stoppage caused by changing the rolls significantly slows down production. The problem is that not only is the roll damaged, but the number of rolls that must be prepared increases, and the effort and cost of managing them also increases.

(Problems to be Solved by the Invention) Attempts are being made to use the forming roll in common even under different pipe diameters, and the applicant filed a patent application in
The gist of the electric resistance welded steel pipe manufacturing method disclosed in the specification of No. 172651 is as follows.

In the first stage of front and rear breakdown, both end side edges of the steel strip are curved to an appropriate radius R.

In the latter stage breakdown of the second stage, the central part of the steel strip is curved in the same direction as the side edges.

Then, in the third stage of fin passing, the curved side edges are rolled through a plurality of fin passes to gradually narrow the fin width and bring the both side edges closer together.

Furthermore, in the fourth step, welding is performed on the butt side edges while restraining with squeeze rolls.

Thereafter, in the fifth step, the product is finished to a predetermined size using a sizing roll.

In this case, by making the radius of curvature at the breakdown stage correspond to the applicable minimum diameter, it becomes possible to use the roll for both the breakdown equipment and the fin pass stage until the maximum applicable diameter is reached within a certain tolerance range.

In other words, in the first bending process of the side edges in the breakdown stage, the upper and lower horizontal rolls are divided into two in the axial direction, and the interval in the axial direction of the divided rolls is adjusted to match the sheet width (therefore, this first bending process The bending process is a process in which rolls can also be used when making pipes with different diameters.

Next, in the bending process of the center part, since an unprocessed part may be left between the center part and the side edge parts, there is no particular restriction on the board width, and therefore, rolls can also be used for this process.

Furthermore, forming with a Fipas roll involves bending the central part and bringing together the side edges that are close together in a weldable state, and does not specifically form into a circular cross section, so the rolls used are , it is not necessary to have an outer circumferential surface that matches the curvature of the tube to be manufactured, and therefore the fin pass roll can be used for manufacturing tubes of various diameters also in this process.

The shape of the cylindrical body obtained in the above steps has an oval cross section except for the tube with the minimum outer diameter that can be manufactured, but this is finished into the desired circular cross section in the sizing process after welding.

It has since been found that the length-to-width ratio of the cross section of the elliptical open pipe formed by the fin pass rolls needs to be about 1.05 at most. If this is exceeded, it will be difficult to finish the tube into a perfect round tube using a standard number of sizing roll stands, and there is also the risk of material deterioration due to work hardening.

The roll profile of the fin pass roll is designed as a roll flower based on the applicable minimum diameter. Therefore, the product with the minimum applicable diameter in the squeeze roll pass is circular, that is, the ratio of major and minor axis is 1, but the product with the applicable maximum diameter is 1. The diameter of the product has the maximum length/minor diameter ratio, and when this ratio is 1.05, the diameter of the maximum diameter pipe/the diameter of the minimum diameter pipe is 1.1.

In other words, according to the specification of Japanese Patent Application No. 60-172651, the roll flower is designed based on the minimum diameter to which Finpass rolls can be applied, so the diameter of the maximum diameter pipe is limited to 1.1 times the diameter of the minimum diameter pipe. be done. In other words, since the range of dual-purpose rolls is narrow, many hand-held rolls are still required.

This invention was made in view of the above circumstances, and by making the radius of curvature from the flange part to the fin part smaller from the front stage stand to the rear stage stand in the roll flower design of the fin pass roll, it is possible to expand the range of the dual-purpose roll. The purpose is to

(Means for Solving the Problems) This invention involves a preforming process in which both side edges and the center in the width direction of the steel strip are sequentially bent in advance, and then the steel strip can be used for multiple purposes for steel pipes with various outside diameters. In a manufacturing method of an ERW steel pipe including a step of pressure forming into an open pipe in a forming process using two-roll type fin pass rolls, the roll gap is adjusted by the end of forming using the fin pass rolls, This is a method for manufacturing an electric resistance welded steel pipe, characterized in that the length-to-width ratio of the welded pipe is regulated to 1.05 or less while being restrained by squeeze rolls.

In the roll flower design of Sunawachi and FinPass rolls, by increasing the radius of curvature from the flange to the fins from the front stage stand to the rear stage stand, for example, in the case of a 4-tier stand FinPass roll, in the case of the smallest diameter pipe, The third stand is circular, and the fourth stand is used only as a butt guide for both ends of the steel strip.On the other hand, in the case of the largest diameter pipe, the diameter ratio in the fourth stand is 1.05. do.

According to this invention, the diameter of the maximum diameter pipe/the diameter of the minimum diameter pipe is 1.
3, and the range of dual-purpose roles can be greatly expanded.

(Function) As shown in the specification of Japanese Patent Application No. 172,651/1980, the open pipe formed in the front stage of the fin pass roll has both edges of the steel strip having a radius with the applicable minimum diameter as standard.
have.

In the fin pass roll forming step, the open pipe is formed into a predetermined shape while guiding both end edges through a four-tier stand, and then welded while being restrained with a squeeze roll in the next step, and then welded with a sizing roll. A perfectly round electric tube is obtained by molding and finishing to a predetermined size.

On the other hand, the forming method at the fin pass roll forming stage in the present invention will be explained in detail with reference to FIG.

First, in the case of a minimum diameter pipe, as shown in Fig. 1(a), the open pipe 4 is designed so that the distance (gap) 3 between the upper roll 1 and the lower roll 2 is minimized, and the radius of curvature near the fins is the maximum applicable. Upper roll 1 with small diameter 5, radius of curvature of caliber bottom 6
is bitten into the first stand F consisting of the lower roll 2 having the minimum applicable diameter, is further narrowed and formed at both end edges in the second stand F2, is made into an almost circular shape in the third stand F3, and is formed in the fourth stand. At F4, only both end edges are narrowed, and then welded while being restrained in a circular shape by squeeze rolls 7.

On the other hand, in the case of the maximum diameter pipe, as shown in Fig. 1(b),
The distance (gap) 3 between the upper roll 1 and the lower roll 2 is maximized, and the upper roll 1 and the lower roll 2 are bitten by the first stand F1.

Next, shaping is performed while gradually narrowing both end edges from the second stand F2 to the third stand F3, and the fourth stand F3 is formed.
In step 4, the gap 3 is reduced to a predetermined value, and the length ratio is reduced. In this way, the squeeze roll 7 welds while restraining the elliptical shape such that the length ratio is 1.05 or less.

The next stage involves multiple stages of sizing rolls (not shown)
A perfectly circular electric resistance welded tube is obtained by forming the tube into a predetermined size.

(Example) Using a fin pass roll with a minimum diameter of 48.6φ (the corresponding minimum applicable radius of 5.6 is 27.0mmR), according to the present invention, a roll with a diameter of 60.5mmφ×6. Ommt
x! (length) is shown in FIGS. 2(a) and 2(b) together with a comparative example using a dual-purpose roll as shown in Japanese Patent Application No. 1972-1'72651.
The roll flour length/breadth axis ratios are compared in Table 1.

Table 1 Open pipes formed by breakdown of steel strips with a predetermined length/width ratio of each flower are the first stand, the second stand, and the second stand of the fin pass roll.
The third stand is gradually formed into an oval shape with both end edges narrowed as shown by the solid line in FIG. 2(a). Up to this stage, the steps are common to both Examples and Comparative Examples.

At the fourth stand, there is a gap t as shown by the broken line in the same figure.
15.0 mm (example), 19°6 mm (comparative example)
In this invention, in particular, the radius of curvature from the flange part to the fin part is set to 32.0 mm (example)47.
8 mm (comparative example), and the major/minor axis ratio was 1.01 (example) and 1.14 (comparative example). ), 1.
No. 18 (comparative example) was welded while being restrained, and finished with a 4-function sizing roll to produce a product.

The roundness of the product was measured and as shown in Figure 3, the roundness was 0.93% for the comparative example, while it was 0 for the example.
．． This has improved to 18%.

Generally, the tolerance value for roundness is set to be 0.30% (more preferably 0.2%) or less, so while the comparative example exceeds this tolerance value, the method of the present invention allows It is within the range. That is, in the comparative example, 60.5φ
The outer diameter of the dual-purpose roll exceeds the range of the dual-purpose roll, and therefore, the usage range of the dual-purpose roll was narrow.However, according to the present invention, the usage range of the dual-purpose roll has been changed to the diameter of the maximum diameter pipe/minimum diameter. diameter = 1.1, but according to the present invention, it has been reduced to 1.1.
It was expanded to 3.

As mentioned above, in the roll flower design of a 4-stage fin pass roll, in the case of the minimum diameter, the third stand becomes circular, and in the case of the maximum diameter, the steps up to the third stand are the same as the conventional technology. The range of application of dual-purpose rolls is greatly expanded by the method of manufacturing ERW steel pipes of the present invention, in which the fourth stand is formed into a nearly circular shape while reducing the gap so that the diameter ratio in the squib roll is 1.05. .

Effects of the invention (1) Reduction in roll costs by reducing the number of hand-held rolls (
2) It is possible to improve the line operating rate by reducing the frequency of roll changes.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the forming procedure for the minimum and maximum diameters of the fin pass roll and squeeze roll of the present invention. FIG. FIG. 3 is a comparison diagram of the roll flower according to one embodiment, and FIG. 3 is a comparison diagram of the roundness of the pipe in the prior art and one embodiment of the present invention after pipe production. It is an explanatory view of tube forming of a prior art. 1...Top roll 2...Bottom roll 3...
Gap 4...Open pipe 5.6...
・Applicable minimum radius of curvature patent applicant Kawasaki Steel Co., Ltd. Same applicant Sanyo Seiso Kosai Co., Ltd. Figure 2 Comparative example Tip example
r゛′-) d, 2
75. Knee 1 (-\-) - Issui ρ eight (

Claims (1)

[Claims] 1. Two rolls that can be used for steel pipes with various outside diameters after undergoing a preforming process in which both side edges and the widthwise center part of the steel strip are sequentially bent in advance. In the manufacturing method of ERW steel pipe, which includes the step of pressure forming into an open pipe in the forming process using fin-pass rolls, the roll gap is adjusted by the end of the forming process using the fin-pass rolls, and the pipe is restrained by squeeze rolls. A method for manufacturing an electric resistance welded steel pipe, which comprises regulating the length-to-width ratio of the welded pipe to 1.05 or less.