JPH09279324A - Method for repairing plating of hot dip coated electric resistance welded tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an online repair method which eliminates unequal repair, provides beautiful appearance, does not degrade the productivity of a production line and eliminates the restriction on a repair material. SOLUTION: A bead cutter 5, a bead cut part heater 6, a repair bar material heater 8 and a repair bar material presser 7 one disposed on the production line of the hot dip coated electric resistance welded tube. After a weld bead cutting part 3 is subjected to bead cutting by the bead cutter 5, the bead cut part is heated by the bead cut part heater 6 or the repair bar material 9 heated by the repair bar material heater 8 is pressed to the bead cut part by the repair bar material presser 7 in a non-oxidizing atmosphere. The front end of the repair bar material 9 is heated by weld preheating to the temp. above its m.p. and is welded to the bead cut part under movement, by which plating repaired.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for on-line plating repair of a bead cutting portion of a hot-dip galvanized electric resistance welded pipe.

[0002]

2. Description of the Related Art A thermal spraying method has hitherto been adopted as an on-line plating repair method for a bead cutting portion of an electric resistance welded steel pipe manufactured from a hot-dip galvanized steel sheet. In this thermal spraying method, a metal jet such as a zinc wire is melted by a heat source such as a gas and an arc, and a gas jet such as compressed air is supplied to the molten metal to atomize the molten metal. This is a method of spraying and adhering at high speed.

However, the adhesion between the sprayed metal and the bead cutting surface (base material) by the spraying method is such that the metal fine particles are sequentially deposited on the base material.
Since the layers form a close contact with each other, many pores are mixed between the fine metal particles in the coating layer. Therefore, the adhesion between the sprayed coating layer and the bead cutting surface is poor, and when the electric resistance welded steel pipe is bent, the plating repair layer is peeled off.

In order to solve the above problem, Japanese Patent Laid-Open No. 62-1
3561 (Prior Document 1), JP-A-3-28176.
JP-A-58-737 discloses a method in which a molten metal pool for repair is formed on a bead cutting portion and is directly supplied to the bead cutting portion to perform plating repair in JP-A-58-737.
Japanese Patent Laid-Open No. 72 (Publication 3) proposes a method in which a metal wire having a plating composition close to that of the bead cutting portion is supplied in direct contact with the bead cutting portion, and the metal wire is melted and attached.

[0005]

However, in the method according to the prior art document 1 or the prior art document 2, the molten metal flows out from the gap between the bead cutting portion and the molten metal supply nozzle which are moving at high speed, or the supply nozzle is Block it. For this reason, the appearance of the plating repair layer is more dirty than the surrounding plating film, and uneven welding (uneven repair) occurs, so that a highly reliable repair layer cannot be formed. In addition, in order to secure a highly reliable repair layer, it is necessary to stop the production line and replace the closed nozzle, and it takes a long time, which reduces the productivity of the electric resistance welded pipe production line. .

In the method according to the prior art 3, since the plating repair material is a wire, it is smaller than the width of the bead cutting portion, and the plating repair layer after welding is not smooth. Therefore, it is necessary to install special equipment for smoothing the repair layer such as an ultrasonic iron. Further, if the plating repair material has an alloy composition with poor workability, for example, a Zn-Al alloy containing 30 wt% or more of Al, a wire with high workability cannot be manufactured. Therefore, it is not possible to repair the plating of Al-containing hot-dip Zn-plated electric resistance welded pipe having the same plating composition as the repair material.

The present invention has been proposed in order to solve the above-mentioned problems of the prior art. It does not cause repair unevenness, the appearance of the plating repair layer is beautiful, and the productivity of the electric resistance welded pipe manufacturing line is high. Of the hot-dip galvanized welded steel pipe that can be repaired online without any special equipment for smoothing the plating repair layer and without any restrictions when manufacturing the plating repair material. The purpose is to provide.

[0008]

The present invention comprises a bead cutting device, a bead cutting part heating device, a repair bar material heating device, and a repair bar material pressing device on a production line after electric resistance welding, In a non-oxidizing atmosphere, the bead cutting device bead-cuts the welding bead part and then the bead cutting part heating device heats the bead cutting part, or the repair bar material heated by the repair bar material heating device is repaired. A hot-dip galvanizing method characterized by pressing the bead cutting part with a bar pressing device, heating the tip of the repair bar to a temperature above its melting point with residual heat from welding, and welding it to the moving bead cutting part for plating repair. This is a plating repair method for sewing steel pipes.

The hot-dip galvanized ERW steel pipe according to the present invention is A
Using hot dip plated steel sheet such as l, Zn, Zn-Al alloy as the raw material, the production is the same as the conventional ERW steel pipe manufacturing method. It is manufactured by heating by induction heating etc. and then electric resistance welding.

A bead cutting device is arranged on the production line after the electric resistance welding, whereby the weld bead portion is bead cut to form a bead cutting portion. After this, the repair bar is pressed against the moving bead cutting part by the repair bar pressing device, but the bead cutting part at this position is
Immediately after welding, the residual welding heat remains and is in a high temperature state, and the tip of the repair rod (the portion that contacts the bead cutting portion) is heated to a temperature higher than the melting point of the rod by the residual welding heat.

Therefore, the repair rod is welded to the moving bead cutting portion (in the present application, the fusion and adhesion of the repair rod is referred to as welding) for online plating repair and pressing. Therefore, a plating repair layer (plating film) that is smooth and has no repair unevenness is formed.

At this time, the bead cutting portion is heated by the bead cutting portion heating device, or the repair rod is heated by the repair rod heating device. Therefore, the repair bar can be stably and smoothly welded to the bead cutting portion,
A plating repair layer having excellent adhesion and good corrosion resistance is formed.

In addition, since the process from bead cutting to the formation of the plating repair layer is performed in a non-oxidizing atmosphere, the bead cutting portion whose surface is cut at a high temperature and which is chemically active, and the high temperature plating immediately after welding The repair layer (plating film) is not oxidized and a plating repair layer having a beautiful appearance is formed.

Further, since the plating repair material is formed into a rod shape having a low degree of processing, 30% Al is obtained by casting or hot forging.
The repair material can be manufactured even with a difficult-to-work alloy composition such as a Zn-Al alloy containing at least wt%, and the restriction when manufacturing the plating repair material can be solved.

In addition, since the strength of the plating repair material is ensured by forming the plating repair material into a rod shape, it does not break even if it is pressed against the bead cutting portion with a predetermined pressure. Further, by setting the repair material to have an appropriate size, for example, approximately the same as the width of the bead cutting portion, it is possible to form a plating repair layer having a uniform thickness over the entire width of the bead cutting portion just by pressing. As a result, no special equipment is required for smoothing the repair layer, and the productivity of the manufacturing line is not reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a situation in which a plating repair device is arranged on an electric resistance welded pipe manufacturing line to carry out plating repair of a bead cutting portion online.

Here, 1a is a steel pipe after hot-dip galvanized steel is formed by a squeeze roll, and is not yet welded by electric resistance welding (hereinafter abbreviated as steel pipe before electric resistance welding), 1b is an electric resistance welded steel pipe before plating repair, 1c.
Is an electric resistance welded steel pipe after plating repair, 2 is an induction heating device, 3 is a weld bead, 4a and 4b are support rolls, 5 is a bite,
6 is a bead cutting part heating device, 7 is a pressing pressure control device, 8 is a repair bar material heating device, 9 is a repair bar material, 10 is a plating thickness uniformizing device, 11 is a seal box, and 12 is a non-oxidizing gas. It is an introduction pipe.

As shown in the figure, on the electric resistance welded pipe manufacturing line, the induction heating device 2, the support rolls 4a and 4b, the cutting tool 5, the bead cutting part heating device 6, the pressing pressure control device 7, and the heating rod material for repair are heated. An apparatus 8 and a plating thickness uniformizing apparatus 10 are arranged. In addition, the induction heating device 2 and the support roll 4
The above-mentioned plating repair device except a is arranged in the seal box 11.

First, a forming roll and a squeeze roll (neither of which is shown) are arranged in front of the induction heating device 2, and a hot-dip galvanized steel plate is formed into a tubular shape by these rolls, and an upper portion in the longitudinal direction of the steel pipe 1a before electric resistance welding is formed. The butt portion located at is heated by the induction heating device 2 and the support roll 4
A pressure is applied at a to make a pipe.

The support roll 4b supports the electro-welded steel pipe 1b before the plating repair and the electro-welded steel pipe 1c after the plating repair, which are sent out after the pipe is made, and guides them to the seal box 11 so as not to shift vertically and horizontally.

The weld bead portion 3 of the electric resistance welded steel pipe 1b is cut by the cutting tool 5 in the seal box 11 by a width of about 10 mm to form a smooth bead cutting portion.

Next, the pressing pressure control device 7 presses the repairing rod 9 against the bead cutting portion which is moving at high speed. Since the bead cutting portion at this position is still in a high temperature state because the welding residual heat still remains immediately after the welding, the tip portion of the repair rod 9, that is, the contact portion with the bead cutting portion, is pressed. It is heated to a temperature higher than the melting point by the residual heat of welding and is welded to the moving bead cutting portion to form a smooth and uniform repair layer (plating film) for repair.

At this time, by placing the bead cutting portion heating device 6 in front of the pressing pressure control device 7 and heating the bead cutting portion, the temperature of the bead cutting portion in the high temperature state where residual welding heat remains remains By homogenizing, more stable welding can be obtained. As a heating method, an apparatus capable of efficiently heating a bead cutting portion having a width of about 10 mm may be used, and resistance heating, high frequency resistance heating, plasma heating or the like is applied.

In addition, by heating the repairing rod 9 to a predetermined temperature by the repairing rod heating device 8, the welding is performed more stably and smoothly. Therefore, the adhesion between the plating repair layer and the bead cutting portion is increased. Increase. The repairing rod heating device 8 may be a system capable of efficiently heating, and a resistance heating device, an induction heating device, or the like is applied.

A non-oxidizing gas introduction pipe 12 is connected to the seal box 11, and a non-oxidizing gas is blown into the seal box 11 to keep the inside of the seal box 11 in a non-oxidizing gas atmosphere. Therefore, the bead cutting portion and the plating weld metal from the bead cutting to the formation of the plating film are not air-oxidized.

As the non-oxidizing gas, it is preferable to use N ₂ gas, Ar gas, H ₂ -N ₂ mixed gas or the like. The oxygen concentration in the seal box 11 should be as low as possible.
It is 0 ppm or less, preferably 10 ppm or less. Further, in order to secure a more reducing atmosphere, it is desirable that the dew point in the atmosphere is -20 ° C or lower.

The repair bar 9 is designed to have a width substantially equal to the bead cutting width, and the shape thereof is a square bar or a round bar. In order to form a film having the same composition as the plating film of the electric resistance welded pipe on the bead cutting portion, the repair material 9 is selected from a metal or alloy composition close to the plating composition. Since a bar material is used as the manufacturing method, even a difficult-to-work alloy composition can be manufactured by a general casting method or hot forging method.

Next, the arranged plating thickness uniformizing apparatus 10
Is pressed against the repair plating film as needed to smooth and uniformize the film. The plating thickness uniformizing device 10 may be a roll or a plate.

The heating temperature of the bead cutting portion is determined by the bead cutting portion heating device 6 for the bar material for plating repair (metal or alloy).
Above the melting point of the above, and the heating temperature of the repairing rod 9 is heated by the repairing rod heating device 8 to about the melting point of the plating repairing rod minus 30 to 100 ° C. in order to ensure stable and smooth welding. desirable.

The pressing pressure of the repairing rod 9 is selected by the pressing pressure control device 7 so as to always supply a predetermined adhesion amount to the bead cutting portion, and is adjusted to, for example, 5 kg / cm ² or less. The function of pressing the repair bar and the function of heating the repair bar may be configured in one device. In this case,
The device can be made compact.

[0031]

EXAMPLES The results of carrying out the plating repair of the hot-dip Zn-plated electric resistance welded steel pipe using the plating repair apparatus configured as shown in FIG. 1 will be described.

An Al-containing hot-dip galvanized steel sheet having a plate thickness of 4.2 mm (plating thickness of one side of about 20 μm) having an outer diameter of 114.3 mm was manufactured by a pipe-making machine for an electric resistance-welded pipe. After that, bead cutting was performed in the non-oxidizing atmosphere in the seal box behind the plate to repair the plating of the moving bead cutting part. The inside of the seal box was replaced with N ₂ gas to have a dew point of −30 ° C. or lower.

The cutting width of the weld bead was about 8 mm, and the repair bar was a square bar of 10 mm × 10 mm. 70m /
From the forming of the plated steel sheet to the repair of the plating at a line speed of minutes. The pressing pressure was adjusted to 3 kg / cm ² .

After the plating repair, the appearance quality of the plating repair layer at the bead cutting portion was visually evaluated, the corrosion resistance was evaluated by a salt spray test, and the adhesion of the plating was evaluated by a bending test (6D bending). Table 1 shows the test conditions and test results.

[0035]

[Table 1]

[Example 1] Zn-0.2 was used as a repair bar.
A wt% Al alloy was used, and the composition was the same as the plating composition of the hot dip plated steel sheet. The heating temperature of the bead cutting portion was 460 ° C, and the heating temperature of the repair bar was 370 ° C. As a result, a sound plating repair layer having a plating thickness of about 20 μm was obtained. It was confirmed that the plating appearance was good, and that the corrosion resistance of the plating repair layer was almost the same as the red rust resistance of the bead cutting peripheral portion, and was good without problems. Even in the bending test (6D bending),
No abnormality was observed, the surface appearance after the bending test was smooth and beautiful, and the adhesion was good. Moreover, the repair operation was always stable, and no troubles occurred on the production line.

[Example 2] Zn-5 wt.
% Al alloy, and has the same composition as the plating layer of the hot dip plated steel sheet. The heating temperature of the bead cutting portion was 460 ° C, and the heating temperature of the repair bar was 350 ° C. As a result, as in Example 1, the plating appearance, corrosion resistance, and adhesion were all good, the repair operation was always stable, and no manufacturing line troubles occurred.

[Examples 3 to 5 and Comparative Example 1] The repair bar was made of Zn-55wt% Al-1.5wt% Si alloy, and had the same composition as the plating layer of the hot dip plated steel sheet. Then, the heating temperature of the bead cutting portion was 630 ° C, and the heating temperature of the repair bar was 500 ° C. As a result, Example 1
Similar to the above, the plating appearance, corrosion resistance, and adhesion were all good, the repair operation was always stable, and no troubles occurred on the production line.

In Example 4 in which only the bead cutting portion was heated to 630 ° C. and in Example 5 in which only the repair rod was heated to 500 ° C., the plating appearance, corrosion resistance and adhesion were all good, and the repair operation was always stable. The production line did not have any trouble.

However, Comparative Example 1 in which neither was heated
No good results were obtained with respect to plating appearance, corrosion resistance, and adhesion. In addition, repair unevenness sometimes occurred, and the production line speed was reduced each time.

[0041]

EFFECTS OF THE INVENTION According to the method of the present invention, it is possible to form a plating repair layer having no repair unevenness, a beautiful appearance, excellent adhesion, and good corrosion resistance. Further, it is possible to provide an online plating repair method that does not reduce the productivity of the electric resistance welded pipe production line and does not require special equipment for smoothing the plating repair layer. Further, even if the plating composition is an alloy composition that is difficult to process, the plating repair material can be manufactured without any restrictions.

[Brief description of drawings]

FIG. 1 is a diagram showing a situation in which a plating repair device is arranged on a manufacturing line and plating repair of a bead cutting portion is performed online.

[Explanation of symbols]

 1 ERW steel pipe 2 Induction heating device 3 Weld bead 4 Support roll 5 Bit 6 Bead cutting part heating device 7 Pressing pressure control device 8 Repair rod heating device 9 Repair rod 11 Seal box 12 Non-oxidizing gas introduction pipe

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masaru Sagiyama 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (1)

[Claims] 1. A manufacturing line after electric resistance welding,
Equipped with a bead cutting device, a bead cutting part heating device, a repair bar heating device, and a repair bar pressing device.Bead cutting part heating device after bead cutting the welding bead part with a bead cutting device in a non-oxidizing atmosphere The bead cutting part is heated by the or the repair bar heated by the repair bar heating device is pressed against the bead cutting part by the repair bar pressing device, and the tip of the repair bar is melted by the residual heat of welding. A method for repairing plating of hot-dip galvanized electric resistance welded steel pipe, which comprises heating to the above and welding to a moving bead cutting portion to repair plating.