JP2803569B2 - Laser welding tube manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the manufacturing technique of laser welded pipes, particularly welded pipes made of non-austenitic steel.

[0002]

2. Description of the Related Art Compared with other welding methods, laser welding has a high energy density of a heat source, so that it can be deeply penetrated and can be welded at high speed, and since the total heat input can be reduced, the performance of the welded portion is good. For this reason, it is attracting attention as a welding method for steel pipes, and its application is being promoted. Further, a technique for further increasing the speed by adding high-frequency preheating to the laser welding method has been proposed (Japanese Patent Application Laid-Open No. 56-168981, etc.).

[0003] Incidentally, since high-speed welding has become possible by the above-mentioned laser welding method, generation of roll flaws in high-speed rolling has become a problem. Roll flaws are flaws formed when a metal band is formed by a roll, and are generated when a flat metal band is bent into a tube due to a difference in roll peripheral speed and metal band speed in the width direction of the metal band. It is. That is, since the molding speed increases with high-speed welding, roll flaws are easily generated. Roll flaws are also significant when the thickness of the metal strip is increased and the forming load is increased.

On the other hand, the conventional pipe making method having a low forming speed and the laser welding method for a thin metal band having a thickness of up to about 3 mm do not cause roll flaws. It is not necessary to use rolling oil at this time.

[0005]

However, in recent years, by increasing the capacity of a laser welding machine and using high-frequency preheating together, it has become possible to weld a thick metal band at a high speed, and to suppress the occurrence of roll flaws. However, lubricants (rolling oil and cooling water) have to be used. As a technique for performing roll rolling without a lubricant, a split roll method, a method using a high hardness roll or a low hardness roll, and the like are known. However, the split roll method has a problem that the generation of roll flaws cannot be suppressed so much, the generation of roll flaws cannot be suppressed so much even with a high-hardness roll, and the roll wear is remarkable with a low-hardness roll.

Therefore, a lubricant is used to cope with a large rolling load and a high forming speed. The lubricant is a water-soluble lubricant containing an emulsifier (surfactant) based on a mineral oil or an animal or vegetable resin, and a phosphorus-based, sulfur-based or molybdenum disulfide for improving lubrication performance. A water-soluble lubricant containing an extreme pressure additive or a poorly water-soluble lubricant containing a large amount of an extreme pressure additive in a mineral oil or animal or vegetable resin is preferred. However, when the above-mentioned lubricant was used, it was found that a part of the lubricant penetrated into the welded portion, and bubbles and hydrogen were interposed in the weld metal. Hydrogen is not preferred because it causes hydrogen cracking of the weld metal, and air bubbles cause a decrease in strength.

[0007] Cooling of the molding heat is generally carried out using a lubricant in which oil is used in combination with water. However, since water also generates hydrogen by thermal decomposition, hydrogen cracking may occur. Therefore, an object of the present invention is to provide a laser welding method that does not have a fear of hydrogen cracking or the like on the assumption that a lubricant is used.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors first examine in detail the effect of a lubricant on welding, and consider the case where the lubricant remains on the welded end before welding. It has been found that hydrogen cracks are easily generated in the weld metal, and that bubbles are generated in the weld metal even when the vaporized vapor of the lubricant is just mixed into the welded portion. In addition, it was confirmed that even if a lubricant was present in a portion other than the welded end portion, the above-described hydrogen cracking and bubble generation hardly caused a problem.

In other words, in order to render the lubricant harmless, it is sufficient to remove the lubricant present at the weld end face and in the vicinity thereof before welding, and a vaporization method by "heating" is suitable as a removing method. I came to know. The specific method is as follows.

[0010] A roll-type tube forming apparatus for bending a flat metal band into a tubular shape, a high-frequency heating means for heating opposite ends of the bent metal band, and an upstream of vaporized vapor with compressed air or an inert gas. And a laser welding machine are arranged in series in this order, and a lubricant such as a lubricating oil or cooling water used in a roll-type tube forming apparatus is evaporated by the high-frequency heating means. Blowing is performed by a blow means in a direction away from the welding torch, and laser-welding is performed on the opposite end portions with the lubricant removed.

[0011] The steam blow means may be replaced by a shielding gas of a welding torch.

[0012]

Before welding, the lubricant is vaporized and evaporated, and the vapor is blown away from the welding point to prevent the vaporized vapor from reaching the weld.

[0013] If the blowing is carried out with a shielding gas for welding, the equipment can be simplified.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a schematic diagram of a roll-type tube forming apparatus provided with a laser welding machine according to the present invention. The roll-type tube forming apparatus 1 is an apparatus that gradually forms a flat metal band W into a tubular shape. A lubricant is used for high-speed molding. On the outlet side of the roll-type tube forming apparatus 1, a high-frequency heating means 2, a steam blow means 3, and a laser welding machine 4 are arranged in this order.

FIG. 2 is a plan view (first embodiment) of a laser welding machine and ancillary equipment according to the present invention. The gas purge nozzles 3a, 3a of the steam blow means 3 are provided upstream of a welding torch 5 of the laser welding machine. And the contact tips 2a of the high frequency heating means 2 are arranged upstream of the gas purge nozzles 3a. Reference numeral 2b denotes a high-frequency oscillator, and the contact chips 2a, 2a supplied from the high-frequency oscillator 2b have ends W1, W1 of the metal band W before laser welding.
This is a contact for energizing W1. Note that the contact tip 2a is an example, and may be, for example, an annular coil for induction heating.

FIG. 3 is a side sectional view (second embodiment) showing an arrangement example of the gas purge nozzle according to the present invention.
Is closely aligned with the upstream side of the welding torch 5 because the width is shifted by the drum-shaped squeeze roll 6 (for convenience, the close portion is //
/, The welding bead portion is hatched with XXX. )
The upper purge nozzle 3b and the lower purge nozzle 3c are arranged so as to blow a portion upstream from the close contact portion. The gas ejected from the purge nozzles 3b and 3c is preferably compressed air, nitrogen gas, argon gas, and helium gas. However, use the compressed gas that has been cleaned and dried.

The operation of the laser welding machine and the auxiliary device described above will be described based on test results. Table 1 shows test conditions common to the comparative example and the example.

[0018]

[Table 1]

That is, the test material was API X-65 outer diameter 1
It is a metal band for making a carbon steel pipe having a thickness of 01.6 mm and a thickness of 6.0 mm. As the lubricant, an emulsion prepared by dissolving a water-soluble fat in water so that the effects of both oil and water can be examined (for example, a multi-cut made by Kyodo Yushi) was used. The preheating device (high frequency heating means) sets the oscillation frequency to 4
The frequency was set to 50 kHz. Gas purge nozzle is 10mm × 5
The nozzle was a 0 mm rectangular cross-section nozzle, and a total of 300 l / min of compressed air was flowed from this nozzle. The welding machine is 2
5kW carbon dioxide gas laser machine, 2 from welding torch
Helium gas was allowed to flow at a rate of 0 m / sec.
Table 2 shows the contents and results of the comparison test performed under the above common conditions.

[0020]

[Table 2]

In the table, roll flaws were determined by visual inspection of three pipes having a length of 6 m, and if any one was defective, it was rejected. The welding quality was determined by using three samples having a welding length of 200 mm. A transmission X-ray inspection was performed.

In Comparative Examples 1 to 11, experiments were conducted without gas purging. In Comparative Examples 1 and 3, since the welding speed was as low as 2 or 5 m / min, rolling was possible without using a lubricant, the roll flaw was good, and the welding quality was good. However, since the productivity is low, the overall evaluation is “x”. In Comparative Examples 2 and 4, welding speed = 2 or 5
The sample was rolled at a rate of m / min using a lubricant, and the roll flaw was good, but the hydrogen cracking occurred and the welding quality was poor, so the evaluation was "x".

In Comparative Example 5, although the welding speed was as high as 10 m / min, a roll flaw was generated because no lubricant was used, and the evaluation was "x". Comparative Example 6
Since the welding speed was as high as 10 m / min, rolling was performed using a lubricant. Although no roll flaw was generated, the evaluation was "x" because hydrogen cracking was generated.

In Comparative Examples 7 and 8, 100 ° C.
Alternatively, the test material was preheated to 200 ° C., but the evaluation was “×” because it did not suppress the occurrence of hydrogen cracking. In Comparative Examples 9, 10, and 11, the test material was heated at a higher temperature of 30%.
Since it was preheated to 0 ° C., 600 ° C. or 100 ° C., and only generated bubbles, the welding quality was slightly improved and the evaluation was “△”.

In Examples 1, 2, and 3 in which gas purging was performed, the preheating temperature was set to 300 ° C., 600 ° C., or 1 ° C. under the conditions of a welding speed of 10 m / min and a lubricant.
Although the experimental examples were changed to 000 ° C., the roll flaws and welding quality were all good, and the evaluation was “○”.

FIG. 4 is a correlation diagram between the purge gas flow rate and the number of detected bubbles.
Although it was set to 0 l / min, it was examined to what extent this gas flow rate could be reduced practically. That is, 1
It can be squeezed down to about 20 l / min, and below that, it is considered that purging is insufficient and bubbles are generated. In addition, the tendency was similar at the preheating temperatures of 300 ° C. and 1000 ° C.
It was found that preheating at 300 ° C. was sufficient, as it evaporates well at 00-300 ° C. Conversely, it can be said that preheating to 1000 ° C. is not very desirable because evaporation becomes active and the generation of bubbles increases. Therefore, it has been found that the preheating temperature should be determined according to the characteristics of the lubricant used.

Next, another embodiment of the apparatus suitable for carrying out the method of the present invention will be described. FIG. 5 is a sectional view of another embodiment of FIG. 3 (third embodiment), and FIG. 6 is a sectional view of a double seal type welding torch.
The upper purge nozzle 3b is abolished.
As shown in FIG. 6, a double-sealing welding torch 10 is provided with a first gas nozzle 11 directly surrounding a laser beam, and is disposed radially outward from the first gas nozzle 11 and shielded radially downward toward a metal band W. A second gas nozzle for blowing gas. The gas flow from the second gas nozzle 12 pushes the vaporized lubricant back to the upstream side. That is, the lubricant is evaporated by the contact tip 2a in FIG. 5, and the vaporized steam is pushed back to the upstream side by the welding torch 10 and the lower gas purge nozzle 3c. 6 is preferable because the flow rate of the first gas nozzle 11 and the flow rate of the second gas nozzle 12 can be freely selected.

FIG. 7 is a view showing still another embodiment (fourth embodiment) of FIG. 3, in which an upper purge nozzle 3b is provided outside the pipe, and a shield member 1 having substantially the same shape as the second gas nozzle 10 shown in FIG.
4 are arranged. As shown in FIGS. 2, 3, 5, and 7, the gas purge nozzles 3a, 3
b, 3c, the welding torch 10 and the shield member 14 may be arbitrarily combined and arranged outside and / or inside the tubular metal strip W.

FIG. 8 is a plan view of a lubricant supply mechanism for a squeeze roll suitable for carrying out the method of the present invention. FIG. 9 is an explanatory view of a main part of FIG. 8, and as shown in FIG. 6, bracket 21, plate 22, rubber plate 23
And a sweeper mechanism 20 comprising: The rubber plate 23 is disposed on the downstream side of the lubricant spray pipe 24 and on the upstream side of the metal strip W along the rotation direction of the squeeze roll 6, and further, touches the outer peripheral surface of the squeeze roll 6 or closes a predetermined gap. Placed and placed. Therefore, of the lubricant sprayed from the lubricant spray pipe 24, the excess lubricant 25 is dropped down, adheres to the squeeze roll 6 in a required amount in the form of a film, and is used for lubrication between the metal band and the roll. You.

Next, the operation and effect of the sweeper mechanism 20 will be described. As described above, the present invention is characterized in that the lubricant is preheated (high-frequency heating) to vaporize and evaporate before laser welding, and that the vaporized vapor is gas-purged. However, the lubricant supplied to the squeeze rolls 6, 6 near the welding point (welding torch 5) may directly reach the welded portion. Therefore, FIG.
By limiting the lubricant with the rubber plates 23, 23 shown in (1), the effect on the welded portion is reduced to a negligible extent.

FIG. 10 is a view of another embodiment of FIG. 9, which is characterized in that the rubber plate 26 is wound not only on the roll surface of the squeeze roll 6 but also on the upper surface. Welding point is tubular metal band W
Since the uppermost portion is located at the uppermost position, the uppermost portion of the lubricant is particularly restricted, so that the invasion of the lubricant is favorably suppressed.

FIG. 11 is a supplementary explanatory view of the gas purge nozzle according to the present invention. The gas purge nozzle 3a injects gas such as compressed air from the welding torch 5 in the opposite direction, that is, upstream from the welding point. If the injection speed is too high, a vortex 28 is generated around the nozzle 3a, and the vortex 28 may disturb the gas shield 5a of the welding torch 5. Here, the jet flow from the gas purge nozzle 3a is suppressed to a certain extent, and preferably the speed is equal to or lower than the speed of the gas shield 5a. Then, good weldability is maintained. In addition, the lubricant vapor or fine particles 29 up to the vicinity of the welding torch 5.
May fly. However, these vapors or fine particles 29 are not a problem because they are blocked by the gas shield 5a.

[0033]

According to the present invention, the following effects are exhibited by the above configuration. Claim 1 vaporizes and evaporates the lubricant before welding, and blows the vapor in a direction away from the welding point,
Since vaporized vapor is prevented from reaching the weld, hydrogen cracking and bubble generation can be prevented, and the quality of the weld can be improved.

In the second aspect, the vaporized steam is blown with the welding shielding gas, so that the gas purge nozzle can be omitted and the equipment can be simplified.

[Brief description of the drawings]

FIG. 1 is a schematic view of a roll-type tube forming apparatus provided with a laser welding machine according to the present invention.

FIG. 2 is a plan view of a laser welding machine and ancillary equipment according to the present invention (first embodiment).

FIG. 3 is a side sectional view showing an example of the arrangement of a gas purge nozzle according to the present invention (second embodiment).

FIG. 4 is a correlation diagram between the purge gas flow rate and the number of detected bubbles according to the present invention.

FIG. 5 is a view showing another embodiment of FIG. 3 (third embodiment);

FIG. 6 is a sectional view of a double seal type welding torch according to the present invention.

FIG. 7 shows still another embodiment of FIG. 3 (fourth embodiment).

FIG. 8 is a plan view of a lubricant supply mechanism for a squeeze roll suitable for carrying out the method of the present invention.

FIG. 9 is an explanatory view of a main part of FIG. 8;

FIG. 10 is a view showing another embodiment of FIG. 9;

FIG. 11 is a supplementary explanatory view of the gas purge nozzle according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Roll type pipe forming apparatus, 2 ... High frequency heating means, 2a ...
Contact chip, 2b ... High frequency oscillator, 3 ... Steam blow means, 3a, 3b, 3c ... Gas purge nozzle, 4 ... Laser welding machine, 5 ... Welding torch, 5a ... Gas shield, 6
... Squeeze roll, 10 ... Double seal type welding torch, W
... metal band, W1 ... end (opposite both ends).

Claims (2)

(57) [Claims] 1. A roll-type tube forming apparatus for bending a flat metal band into a tube, high-frequency heating means for heating opposite ends of the bent metal band, and vaporized steam with compressed air or an inert gas. And a laser welding machine are arranged in series in this order, and a lubricant such as lubricating oil or cooling water used in the roll-type tube forming apparatus is evaporated by the high-frequency heating means. A method for producing a laser welded pipe, characterized in that steam is blown in a direction away from a welding torch by the steam blow means, and laser-welding is performed on opposite opposite end portions in a state where a lubricant is removed. 2. The method according to claim 1, wherein said steam blow means is replaced by a shielding gas of a welding torch.