Production of steel pipe by laser welding

FIELD: process engineering.

SUBSTANCE: invention relates to production of pipes by laser welding. Laser welding comprises emitting of two laser beams along edges at open pipe upper surface. Said laser beams are transmitted via different optical fibre glass and have focused spots of diameters making over 0.3 mm. Said laser beams are emitted so that front laser beam and rear laser beam are inclined to welding direction. Note here that incidence angles are defined relative to direction perpendicular to open pipe top surface. Front laser beam falls on open pipe top surface in welding direction before rear laser beam while the letter falls on open pipe top surface in welding direction after front laser beam. Front laser beam incidence angle is set larger than that of rear laser beam. Gap between front laser beam centre and that of rear laser beam is set at open pipe rear surface equal to 1 mm and more.

EFFECT: higher quality of weld, higher yield.

17 cl, 4 dwg, 3 tbl, 1 ex

 

The technical field to which the invention relates

The present invention relates to a method for manufacturing a steel pipe by welding the longitudinal edges of the open pipe with a laser beam (hereinafter called a laser welded steel pipe), in particular, to a method of manufacturing a laser welded steel pipe suitable for wells and transport oil or natural gas, for example, steel pipes for oil or pipelines.

Prior art

In General, steel pipes, namely, pipe for oil or pipelines are of welded steel pipes, (for example, steel pipe, welded by resistance welding resistance, steel pipes, manufactured by the UOE process, as well as other methods of welded pipe and seamless steel pipe. Among these welded steel pipes are economically profitable steel pipe, welded by resistance welding the resistance of a hot-rolled steel strip (so-called hot-rolled steel coils), which serves as the source material.

However, in standard steel pipe, welded by resistance welding resistance, inevitably there is a butt joint (so-called weld bead formed by welding), �ecause of the pipe, welded by resistance welding resistance, made of steel strips, which through a plurality of rolls configured in open tube of cylindrical shape (open pipes here and hereafter are referred to as steel strip, which by means of a set of rolls the shape of a pipe, with welded edges) and perform a contact resistance welding (also called high-frequency resistance welding) the edges of an open pipe (i.e., both lateral edges of the steel strip cylindrical shape with a simultaneous compression of the edges of the open pipe compressive rollers. The disadvantage of this weld is poor low-temperature impact strength. Thus, there is the problem of the use of oilfield and main pipes, welded by resistance welding resistance, in regions with cold climate. The reason for the deterioration in toughness of the weld at low temperature, is as follows: when welding the longitudinal edges of the hot molten metal reacts with oxygen of air to form an oxide, which likely remains in the seam.

Another disadvantage of steel tubes welded by resistance welding resistance is reduced corrosion resistance of the weld, due to the segregation Les�arousih elements in the molten metal. Thus, oilfield or major pipelines that use steel pipe, welded by resistance welding resistance, difficult to apply in a corrosive environment (e.g., acidic environment).

Meanwhile, the welding laser beam (hereinafter referred to as laser welding) has attracted attention as a method of welding, the application of which is not reduced low-temperature toughness and corrosion resistance of the weld. In laser welding, the dimensions of the heat source can be small, while thermal energy can be concentrated with high density. Thus, the use of laser welding to prevent the formation of oxide in the molten metal or segregation of alloying elements in the molten metal. Consequently, the application of laser welding it is possible to prevent the decrease in low-temperature toughness and corrosion resistance of the weld.

Thus, in the manufacture of welded steel pipes in practice is used the technology of manufacture of steel pipe by using laser beams directed to the edges of the open pipe for welding edges (i.e., laser welded steel pipes).

In the laser welding process welded portion of the pipe is exposed to the laser beam, which is presented�splash zones a light beam with high energy density, the focused element of the optical system, resulting in faster melting of the metal. Thus formed from the bath of molten metal spatter of molten metal. The molten metal adheres to the welding equipment, in this connection, the weld quality is deteriorating. At the same time, the spray adhere to the element of the optical system, as a result, disrupt the stability of the operation of welding. Since laser welding concentrates thermal energy of a high density, a large number of splashes of molten metal, resulting in arise weld defects such as undercut or failure to complete the weld (or weakening). When there is a failure to complete the weld, the weld area is reduced.

In view of these problems have been studied various ways to prevent adhesion of the spray, as well as ways to prevent splashing of the molten metal in the laser welding process. In practice, for example, was implemented way to prevent splashing of the molten metal by reducing the laser output power, either through a significant change of the location of the focus (i.e., through defocus). However, as a result�the reducing power of the laser radiation, either defocus is reduced welding speed (i.e., a reduction in the efficiency of welding), and there is the risk of problems associated with lack of fusion.

In patent literature 1 is disclosed a method of preventing the occurrence of splashing of the molten metal by separating a laser beam into multiple laser beams. However, the technology of laser welding using multiple laser beams obtained by splitting a laser beam, similar to laser welding technology with low power laser radiation. Thus, when laser welding according to this technology not only reduces the efficiency of welding, but also increases the likelihood of problems associated with lack of fusion. In addition, dearness prisms used to split the laser beam, expenses for carrying out the welding operation will inevitably increase.

In patent literature 2 is disclosed a method of preventing left blank weld the molten metal by means of welding wire used to carry out laser welding. However, this method may lead to changes in the composition of the weld metal from the components of welding wire. Therefore, there is a need in the selection of components, welding wires� respectively the composition of the material exposed piping, therefore, increasing indirect costs associated with the inventory of welding wire and with the production control of the laser welding.

In patent literature 3 discloses the method for preventing weld defects by combining laser welding and arc welding. However, this method complicates the design of welding equipment, which places increased indirect costs associated not only with maintenance, but with the control of the welding operation.

In patent literature 4 discloses a welding method using two beams, forming circular spots. However, this method does not reduce weld defects in laser welding performed in the conditions that lead to occurrence of voltage on Shrivenham the site (for example, in the conditions, and the resulting voltage in the bath of molten metal resulting from precipitation that runs on Shrivenham site steel pipe). In particular, increasing the number of splashes of molten metal with the rear surface of the steel strip.

For a list of reference literature

Patent literature

Patent literature 1: Japanese patent No. 2902550.

Patent literature 2: Published unexamined Japanese patent application No. 2004-330299.

Patent literature 3: Japanese patent No. 4120408

Patent�th literature 4: Publication of unexamined Japanese patent application No. 2009-178768.

Disclosure of the invention

Technical problem

The object of the present invention is to provide a method of manufacturing a laser welded steel pipe, which will ensure stable production with high yield and excellent quality of the weld without reducing the effectiveness of the weld, preventing the occurrence of spatter, reducing the likelihood of on welded area of the undercut or left blank. The method includes the maintenance of certain angles of incidence of the two laser beams aimed at the product, keeping diameter of the focused on the product of spots of laser beams corresponding to the location of the laser beams and the adjustment of the laser welding parameters.

The solution to the problem

To steel pipes by laser welding to form at the edges of the open pipe welded area without welding defects, the inventors have researched and studied the technology of laser welding.

Fig.2 shows a perspective view, which schematically shows an example of applying the traditional method of laser welding the joined edges 2 of the open pipe 1 by means of a vertically emitted laser beam for the purpose of manufacturing a laser welded steel pipe. The arrow on Fig.2 indicates the direction in which welding is performed. The drawing is made�len perspective view of a deep cavity 4 (hereinafter called through penetration), formed by emitting a laser beam 3, and the molten metal 5 formed around the through-penetration 4.

As shown in Fig.2, when emitting a laser beam 3 edges 2 of the open pipe are melted under the action of concentrated heat energy of high density and in the molten metal 5 is formed by through-penetration 4 as a result of evaporating pressure and under the action of the reactive force of the vapors that are created during evaporation of the molten metal 5. In the inner part of the through-penetration 4 penetrates the laser beam 3, and the specified internal parts are believed high-temperature plasma occurs as a result of ionization of metal vapor under the influence of the energy of the laser beam 3.

Through-penetration 4 is a plot in which there is the greatest concentration of thermal energy of the laser beam 3. For stable manufacturing a laser welded steel pipe it is necessary to ensure precise alignment of the contact points of the edges 2 of the open pipe with a through-penetration 4. However, if emitted by a single laser beam, the necessary high-precision technology to ensure precise alignment of the contact points of the edges 2 of the open pipe with through penetration. The instability of the mode of processing of the edges 2 of the open pipe or unstable position Grand�ö edges 2 causes an unstable condition of the molten metal 5. Accordingly, there is often a spatter of molten metal and in the weld, the probability of occurrence of defects, such as undercut or underflow.

If the molten weld pool, there is a voltage induced draught performed on Shrivenham site, it is necessary to further increase the energy of the emitted laser beam for the purpose of maintaining complete penetration. The increase in energy can strengthen the spatter of molten metal, to ensure complete dissolution of the metal in the cavity arise and welding defects such as undercut or underflow.

In connection with the foregoing, the inventors focused their attention on technology involving the emission of two laser beams directed to the welded region 2 exposed pipes. The inventors found that it is possible to prevent splashing of molten metal, if emitting two laser beam by determining the direction and location of each laser beam by adjusting the parameters of the emitted laser beams, such as the angles of incidence or the diameters of the spots, to avoid intersection of the laser beams in the steel strip is configured into an open pipe. Based on these data it was proved that the above method allows to obtain sworn�precinct of excellent quality preventing the occurrence of undercut or left blank, and enables stable manufacture of laser welded steel pipes with high yield ratio.

Although details of the mechanism for preventing the occurrence of spatter is unknown, the inventors have suggested the reasons set out below. Scattering the spray is prevented by the distribution of energy between the two laser beams emitted from the workpiece at a certain angle of incidence, with one of the laser beams provides preheating of the steel strip, suppressing the occurrence of splashing and the second laser beam is emitted after the first laser beam in the direction of welding and melts the edges of the steel strip. In the description of the invention the angle of incidence of each laser beam is defined as the angle formed between the direction perpendicular to the workpiece, and the direction of emission of the laser beam.

The present invention is made on the basis of the obtained data. Thus, according to the present invention provides a method of manufacturing a laser welded steel pipe by forming the steel strip into a cylindrical open pipe by means of forming rolls and performing laser welding on the edges of the open pipe by the emission of the laser beam on the edges of an open pipe while staticdev compressive rollers, moreover, laser welding includes: emitting two laser beams along the edges of the upper surface of the open pipe, these laser beams are transmitted through different optical fibers and have focused spot diameters are greater than 0.3 mm; the emission of the laser beams so that the front laser beam of two laser beams and a rear laser beam of two laser beams were inclined to the direction of welding, and the incidence angles are defined relative to the direction perpendicular to the upper surface of the open pipe, moreover, the front laser beam impinges on the upper surface of the open pipe at the weld in front of the rear laser beam, and the rear laser beam impinges on the upper surface of the open pipe at the weld after the front of the laser beam; adjusting the front angle of the laser beam so that it was more of the angle of incidence of the laser beam rear; and the installation of the gap between the center of the front of the laser beam and the center of the back of the laser beam on the rear surface of the open pipe so that it was 1 mm or more.

In accordance with the method of manufacturing a laser welded steel pipe according to the present invention, preferably, the anterior angles of incidence of the laser beam and laser beam rear are �the thinning of a range from 5 to 50°. Either or both of the laser beam, namely, a forward laser beam and the rear laser beam can be separated by the optical element into two rays, and can be emitted on both sides of the edges of the open pipe. During the welding process performed on Shrivenham plot precipitate preferably is from 0.2 to 1.0 mm. When performing laser welding, preferably, a sum of power of laser radiation of a forward laser beam and the rear of the laser beam exceeds 16 kW and the welding speed is more than 7 m/min, Preferably, before carrying out laser welding steel strip is heated and post-weld roller weld process by cutting or grinding.

The beneficial effects of the invention

In the manufacture of laser welded steel pipe according to the present invention is provided a welded section of excellent quality without reducing the effectiveness of welding because it prevents splashing and the occurrence of undercut or left blank. Therefore, it is possible to ensure stable production of laser welded steel pipes with high yield. Weld laser welded steel pipe according to the invention has excellent low-temperature toughness and excellent corrosion resistance and, thus,�asana pipe for oil or pipelines, used in cold regions or aggressive environment.

Brief description of the drawings

Fig.1 is a perspective view, which schematically shows an example of applying the present invention using two laser beams for welding a seam between the edges of the open pipe. Fig.1 shows in perspective a complete penetration, surrounded by molten metal.

Fig.2 is a perspective view, which schematically shows an example of the use of traditional welding method using a single laser beam for welding a seam between the edges of the open pipe. Fig.2 shows in perspective a through penetration, surrounded by molten metal.

Fig.3 is a side view, where as an example, schematically shows the arrangement of a forward laser beam and the rear of the laser beam shown in Fig.1, regarding the lines, directed perpendicular to the top surface of the open pipe.

Fig.4 is a plan view, which as an example, schematically shows the location of the area or areas of the upper surface of exposed pipes, exposed front of the laser beam, the area or areas of the upper surface of the open pipe that is subjected to a rear of the laser beam, and shows the edges of an open pipe.

Description of the embodiments and�gaining

Fig.1 shows a perspective view, which schematically shows an example of applying the present invention using two laser beams for welding a seam between the edges of the open pipe. By the arrow A in Fig.1 shows the direction of welding. Fig.1 shows in perspective through-penetration 4 arising under the action of the emitted laser beams 3A and 3b and is surrounded by molten metal.

According to the present invention two laser beams 3A and 3b are emitted from the upper surface of the open pipe 1 along the edges 2 of the open pipe 1. If transmitted through the optical fiber the laser beam is split using an optical element (for example, by means of a prism) into two rays, then the angles of incidence or the diameters of the spots of the two beams, which will be described later, are not individually controlled. In this regard, the emitted laser beams 3a and 3b must be transmitted through different optical fiber.

You can use one or two of the laser generator. If you are using only one laser generator and is required to obtain two laser beam, oscillating the laser beam is divided in two beam generator, after which the two laser beam can be transmitted through different optical fiber.

As shown in Fig.1, the laser beams 3A and b are emitted along the edges 2 of the open pipe, this is one of the laser beams is positioned in front of and the other of the laser beams is behind. The laser beam is incident on the upper surface of the open pipe 1 before the other laser beam in the direction of the welding operation, identified as a forward laser beam 3a, and the laser beam is incident on the upper surface of the open pipe after the front of the laser beam, is defined as a rear laser beam 3b.

(1) the diameters of the focused spots of a forward laser beam and laser beam rear

When the diameters of the focused spots of the front of the laser beam 3a and the rear of the laser beam 3b is 0.3 mm or less, the roller of the weld during the welding process has a small width in the cavity and remains partially unmelted metal. Therefore, it is necessary to make adjustment of the diameters of the focused spots so that they accounted for more than 0.3 mm. on the other hand, if the diameters of the spots are more than 1 mm, the laser beams have low energy density and the likelihood is low that the through penetration will be stable. Thus, it is preferable that the diameters of the focused spots of the front of the laser beam 3A and the rear laser beam 3b was 1 mm or less.

Preferably, the front spot of the laser beam 3A and the rear laser beam 3b are circular in shape but may have elliptical�th form. If the spots are elliptical, the minor axis, the focused spot of each beam should have a length of more than 0.3 mm. in addition, the length of the minor axis of the focused elliptical spot should be 1 mm or less, for the same reason, which is limited by the diameter of the circular spot.

(2) the Distance from the upper surface of the open pipe to focus the Distance from the upper surface of the open pipe until the focus is denoted by t (mm), and the thickness of the steel strip of exposed pipes denoted by T (mm). If the distance t from the upper surface of the open pipe to focus greater than 3 x T (i.e., the focus is distant from the upper surface by more than the value of 3T), the focus is set too high, as a result, it is difficult to maintain the stability of complete penetration. On the other hand, if the distance t exceeds -3 x T (i.e., the focus is on 3T below the top surface), the focus is set too low, resulting in increases the likelihood of splashing from the back surface of the steel strip (i.e., the inner surface of the open pipe). Thus, the distance t from the upper surface of the open pipe until the focus is preferably installed so that it was within the range of -3 x T to 3 T.

(3) the Angle of incidence of a forward laser beam and the angle of incidence of the laser beam rear

Fig.3.�shows a side view, where as an example, schematically shows the arrangement of a forward laser beam 3A and the rear laser beam 3b shown in Fig.1, regarding the lines, directed perpendicular to the top surface of the open pipe. As shown in Fig.3, the front laser beam 3A and the rear laser beam 3b are emitted to the upper surface of the open pipe 1 at an angle relative to the direction of welding, indicated in the drawing by the arrow A. it Should be noted that the angle 6A formed by the forward laser beam and a line perpendicular to the top surface of the open pipe 1, is defined as the angle of incidence of the front of the laser beam 3A, and the angle Θb formed by the rear laser beam 3b and the line perpendicular to the top surface of the open pipe 1, is defined as the angle of incidence of the laser beam rear 3b, the angles of incidence is adjusted to satisfy the ratio Θ>Θb.

In addition, it is determined that the location of the front of the laser beam 3A and the rear laser beam 3b in which their intersection is excluded in the steel strip of the open pipe 1. If the distance from the upper surface of the steel strip 1 to the point of intersection of the front laser beam 3A and the rear of the laser beam 3b is denoted by X (mm) and thickness of the steel strip 1 are denoted by T (mm), preferably, the value of X was in �the thinning of 0≤X≤2 x T (i.e., to the point of intersection of the rays was not lower than the upper surface of the steel strip 1 and no further from the upper surface of the steel strip 1 than 2T). The reason specified adjustments described below. When the value of X<0, the front laser beam 3A and the rear laser beam 3b intersect in the steel strip 1. Thus, the through-penetration 4 front laser beam 3A and the rear laser beam 3b are combined with each other and form large through-penetration, resulting in, of course, a large amount of spatter. On the other hand, when the value X>2 x T, there is a separation of the molten metal 5 and the molten state of the coupled phase becomes unstable, resulting in, of course, a large amount of spatter.

When the angle Θ falling front of the laser beam 3A and the angle of incidence Θb of the rear of the laser beam 3b is set so as to satisfy the ratio Θ<Θb increases the moving distance of the rear of the laser beam from the upper surface to the rear surface of the open pipe 1. Thus, the energy of the rear of the laser beam 3b is weakened and the effectiveness of the heating is reduced. Accordingly, the melting of the edges through the rear of the laser beam 3b is unstable, while there has been the effect of pre-heating the edges of the 2 front laserna� beam 3A.

On the other hand, if the angles 6A and 9b of incidence is set so as to satisfy the ratio Θ=Θb, complete penetration and caused a forward laser beam At a rear laser beam 3b, in all probability, are combined with each other and form large through-penetration. Thus, there may be a large amount of spray.

In this regard, the anterior angles of incidence of the laser beam 3A ishinaga laser beam 3b must be set to satisfy the ratio Θ>Θb. In particular, a large angle Θ falling front of the laser beam 3A, to prevent splashing preheating of the edges 2 of the open pipe. With a small angle of incidence Θb of the rear of the laser beam 3b to improve the efficiency of heating by melting the edges 2.

Thus, the front laser beam 3A provides preheating of the edges 2 of the open pipe. In addition, since the front laser light 3A emitted at an inclination to the direction of welding, prevents splashing. Accordingly, the rear laser beam ensures the melting of the edges 2 of the open pipe. Since region 2 open tubes were preheated, the spatter of molten metal occurs. Accordingly, p is prevented�Dresen or underflow, because it reduces the likelihood of splashing.

If the angle Θ falling front of the laser beam 3A is less than 5°, the angle Θ drop is too low and in this case, the action front of the laser beam 3A is similar to the action of a forward laser light 3A emitted vertically. Thus, the front laser beam 3A cannot create a useful effect to prevent the occurrence of spatter. On the other hand, if the angle Θ drop exceeds 50°, the distance is increased, which passes the front of the laser beam 3A from the upper surface to the rear surface of the open pipe 1, whereby the energy of a forward laser beam 3A is weakened. Accordingly, the front laser beam 3A can not provide a large enough pre-heating effect. Consequently, it is preferable that the angle Θ falling front of the laser beam 3A were within the range of from 5 to 50°.

If the angle of incidence Θb of the rear of the laser beam 3b is less than 5°, the angle of incidence Θb is too low and in this case, the action of the rear laser beam 3b is analogous to the rear of the laser beam 3b is emitted vertically. Thus, the rear laser beam 3b can't create a useful effect to prevent the occurrence of spatter. On the other hand, if the angle of incidence Θb exceeds 50°, uvelichivayuschaya, which passes back the laser beam 3b from the upper surface to the rear surface of the open pipe 1, whereby the energy of the rear of the laser beam 3b is weakened. Thus, the rear laser beam 3b can not penetrate into the molten metal in sufficient depth. Consequently, it is preferable that the angle of incidence Θb of the rear of the laser beam 3b were within the range of from 5 to 50°.

(4) the Interval between the centers of the front of the laser beam and the rear of the laser beam on the rear surface of the open pipe

Between the centers of the front of the laser beam 3A and the rear laser beam 3b on the back surface of the open pipe 1 is installed in the gap L, which should be 1 mm or more. When the interval L is 1 mm or more, a bath of molten metal on the rear surface of the pipe continues in the direction in which welding is performed, and the amount of splashing that occurs on the back surface decreases. Thus, can be obtained platen weld without cutting or left blank. However, if the gap L between the center points of the laser beams exceeds 10 mm, the molten pool is at the rear of the pipe will split up and, in all likelihood, there will be splashing. Therefore, preferably, the interval L between the centers of the front of the laser beam 3A and the rear l�Zernova beam 3b were within the range of from 1 to 10 mm.

(5) Allowance for draught

When performing laser welding, preferably, the welded area had the allowance for sediment from 0.2 to 1.0 mm. If the allowance for draught is less than 0.2 mm cannot be repaired fistula formed during laser welding. On the other hand, if the allowance for a draught of more than 1.0 mm, laser welding is unstable, as a result, a large amount of spatter.

(6) the Weld between the edges of the open pipe

The weld between the edges 2 of the open pipe 1 can be performed by compressing the edges of the clamping rollers to the position at which the average distance G between the edges 2 of the open pipe in the direction of the strip thickness will be 0.5 mm or less.

In addition, the laser beams transmitted from one or two laser generators using different optical fibres, namely, a front laser beam 3A and the rear laser beam 3b can be divided into two beams by an optical element (for example, by means of a prism) and emit on the edge 2 of the open pipe on both sides. Fig.4 (b) as an example shows a rear laser beam 3b is divided into two beams and emitted from both sides of the edges 2 of the open pipe (the irradiated region 3-2 and 3-3). Fig.4 (C) as an example of a forward laser beam 3A, is divided into two beams and emitted from both sides of the edges 2 of the open pipe� (irradiated region 3-1 and 3-2). Alternatively, as shown in Fig.4 (d), the front laser beam 3A and the rear laser beam 3b can be emitted from both sides of the edges 2, and the front laser beam 3A is divided into two rays (the irradiated region 3-1 and 3-2) and rear laser beam 3b is divided into two rays (the irradiated region 3-3 and 3-4). At the specified emission front of the laser beam 3A and the rear laser beam 3b of the edge 2 of the open pipe are constantly within the irradiated areas.

(7) the Power of the laser beam and the welding speed

In General, at lower power laser radiation and reducing the welding speed decreases the amount of spatter generated during laser welding. However, the decrease of laser power and welding speed to prevent splattering leads to lower productivity in the manufacture of laser welded steel pipes. In view of this, according to the present invention it is preferable that a sum of power of laser radiation of a forward laser beam 3A and the rear of the laser beam 3b is larger than 16 kW and laser welding was performed at a speed higher than 7 m/min. If the amount of capacity of the laser radiation does not exceed 16 kW and laser welding is performed at a maximum speed of 7 m/min, the productivity in the manufacture of laser welded steel pipes is reduced.

(8) the Gap between� the welding line and the irradiated area on the upper surface of the open pipe, exposed to a laser beam

Front laser beam 3A and the rear laser beam 3b is preferably positioned so that the centers of the irradiated areas 3-1 and 3-2 on the upper surface of the open pipe 1 coincide with the edges 2, as shown in Fig.4 (a). However, when welding is hard enough to support the above arrangement of the beams 3A and his favorite roles thus, the centers of the irradiated areas 3-1 and 3-2 on the upper surface of the open pipe 1 does not always coincide with the edges 2. If you increase the gap between the edges 2 and the center of each irradiated region 3-1 or 3-2 front laser beam 3A or the rear laser beam 3b may deviate from the butt of the cavity, resulting in increases the probability of occurrence of welding defects, for example, partial melting of the metal in the cavity.

If in the process of welding the edges 2 of the open pipe are within the irradiated regions 3-1 and 3-2, welding defects, despite the fact that the centers of the irradiated areas 3-1 and 3-2 do not coincide with the edges 2. Thus, the gap between the edges of the open pipe and the center of each irradiated region 3-1 or 3-2 must be within the radius of the irradiated area 3-1 or 3-2.

According to the present invention laser welding can be performed even on thick-walled open-tube (e.g., having a thickness of 4 mm or more) without �rewritelog heating the edges with the use of high frequency induction heating or other means. However, the preliminary heating of the edges of an open pipe with the use of high frequency induction heating or other heating type contributes to the achievement of beneficial effects, for example, in the manufacture of laser welded steel pipes improves the performance. When pre-heating high frequency induction heating is applied on the welded portion of the pipe bulge formed. The resulting bulge after the laser welding can be removed by cutting or grinding, to give the brewed pipe section required properties.

(9) a laser beam Generator

Any of various types of generators can be used as a laser beam generator used in the present invention. Preferred examples of generators include gas laser in which the medium is a gas (e.g., gaseous carbon dioxide, neon, helium, argon, nitrogen, and iodine); a solid-state laser in which the medium is a solid body (for example, yttrium aluminum garnet doped with a rare earth element); fiber laser, in which instead of the bulk medium is a fiber; and a disk laser. Alternative may be used a semiconductor laser.

(10) Auxiliary heat source

Auxiliary�flax heat source can be used to heat the open pipe 1 from the outer side of the open pipe 1. Configuration auxiliary heat source is not specifically limited provided that the heat source can heat and melt the outer surface of the open pipe 1. For example, as an auxiliary heat source suitable heating means, which implement the method of melting using burners, e-beam and other methods of fusion.

Preferably, the auxiliary heat source is combined with the laser beam generator. This is because when combining the auxiliary heat source to the generator of the laser beam is achieved the desired beneficial effect and need less heat to prevent the occurrence of weld defects such as undercut or left blank). It is preferable that the electric arc generator was located in front of the laser beam generator. This is because at the specified location can be removed moisture or oil from the edges of the open pipe.

Preferable as the auxiliary heat source to use the electric arc. The electric arc generator may be the device that provides the application of electromagnetic forces (i.e., electromagnetic forces created by the magnetic field of the welding current) to molten metal in the direction in which the excluded ol�Zhog metal. For example, it is possible to apply the known techniques such as welding tungsten electrode in inert gas or plasma-arc welding. Preferably, the electric arc generator is combined with the laser beam generator. The reason for this arrangement is as described above, achieve a beneficial effect from the influence of the magnetic field generated around the welding current, which creates an arc on the metal melted by the laser beam. It is preferable that the electric arc generator was located in front of the laser beam generator. This is because at the specified location can be removed moisture or oil from the edges of the open pipe.

Method according to the present invention provides the desired effect even in combination with the known technology, such as welding shielding gas or welding metal. Such joint welding technology can be applied not only in the manufacture of welded steel pipes, but also for the welding of thick steel plates.

As described above, according to the present invention laser welded steel pipe is made, respectively, supporting the diameters of the spots of the two laser beams, ensuring appropriate allocation of two laser beams and by adjusting the parameters of laser welding, �key angles of incidence of the laser beams. This prevents the occurrence of spatter, reduces the probability of formation of undercut or left blank on the welded portion of the pipe and can be obtained welded area of excellent quality without compromising performance welding, which enables stable manufacture laser welded steel pipe with high yield. Through the use of the advantages of laser welding weld laser welded steel pipe has excellent low-temperature toughness and corrosion resistance, resulting in the specified pipe for oil or pipelines used in cold regions or aggressive environment.

Example

Laser welded steel pipe produced by forming a steel strip into a cylindrical open pipe using forming rolls, subsequent compression of the edges of the open pipe compressive rolls and emitting two laser beams to the outer surface of the open pipe, as shown in Fig.1. Chemical composition of steel, which produced bands, are presented in table 1.

Laser welding was performed using two fiber laser generators with a maximum power output of 10 kW, the operating parameters of which are presented in table 2. �length of the leg t (mm) from the upper surface of each open pipe until the focus was set equal to 1/2T, where T is the thickness of the strip. The corners 9a and 9b of incidence of the laser beams, are presented in table 2, correspond to the angles shown in Fig.3. The negative value of the angle of incidence indicates that the emitted laser beam is tilted in the opposite direction to A welding operation.

Welded steel pipe No. 1-4 and 7-10 are presented in table 2 are examples of the pipes during welding which laser beams were arranged as shown in Fig.4 (a), welded steel pipe No. 5 and 11, are presented in table 2 are examples of the pipes during welding which laser beams were arranged as shown in Fig.4 (b), and welded steel pipe No. 6, presented in table 2 is an example of the pipes during welding which laser beams were arranged as shown in Fig.4 (C).

In the manufacture of welded pipes according to the present invention, examples of which are presented in table 2 (welded steel pipe Nos. 1 - 6), was upheld by the diameter of the focused spot of each laser beam, and there is a distance between centers of the front of the laser beam and the rear of the laser beam on the rear surface of the open pipe in accordance with the ranges set according to the present invention. In addition, welded pipes, examples of which are presented in table 2-1 were obtained when emitting front La� - cluster beam and rear laser, the front is a laser beam and laser beam rear was opuscules inclined relative to the direction of welding, the magnitude of the angle of incidence Θa front of the laser beam was more than the value of the angle of incidence Θb rear laser.

Among the comparative examples of welded pipe are presented in table 2-2, welded steel pipe No. 7 is an example of a pipe, the manufacture of which the angle of incidence Θb of the rear of the laser beam was set to 0° (i.e., the rear laser beam is emitted vertically), welded steel pipe No. 8 is an example of a pipe, the manufacture of which the interval between the centers of the front of the laser beam and the rear of the laser beam on the back surface was outside the range established according to the present invention, the welded steel pipe No. 9 is an example of a pipe, the manufacture of which the diameter of the focused spot laser beam rear was out of range, installed according to the present invention, the welded steel pipe No. 10 is an example of a pipe, the manufacture of which front emitted laser beam is tilted opposite to the direction A, in which welding is performed, and welded steel pipe No. 11 is an example of a pipe, the manufacture of which the angle Θ falling front of the laser beam is less than the angle of incidence Θb rear laser�about beam 3b.

After performing laser welding as described above was carried out visual inspection of the upper surface of each welded tubes for the detection on the surface of the presence or absence of the adhered spatter. Besides, the cushion of the weld on the top surface or the rear surface of each of the welded steel pipe was visually monitored to detect the presence or absence of undercut or left blank. The results presented in table 3.

As seen from table 3, in examples, the pipes manufactured according to the invention, was not detected in any of the adhered spatter and no undercut/left blank.

In comparative examples 7-9 was discovered undercut, failure to complete or incomplete fusion of the metal in the cavity, although it was not discovered adhering spray. In comparative examples 10 and 11 was found a large quantity of the adhered spatter and underflow.

Industrial applicability

From the point of view of industrial applicability the present invention is highly effective because it provides a stable production of laser welded steel pipes with high yield ratio.

The list of reference positions

1 open pipe

2 edge

3 laser beam

3A of the front laser beam

3b is a rear laser beam

4 through-penetration (cavity)

5 molten metal

6 St�world seam

Table 1
The type of steelChemical composition (wt.%)Note
SiMnPSCrNiSiAlTiNElse
And0,010,150,350,020,00212,54,50,020,0450,0110,006Fe and inevitable impuritiesStainless steel
In0,060,211,110,010,0010,10,1 0,050,0320,0230,006Fe and inevitable impuritiesCarbon steel

Table 2-1
Welded steel pipe No.Sheet steelWelding conditionsNote
The type of steelSheet thickness (mm)Laser beamThe diameter of the focused spot (mm)The space between the center points of the laser beams on the rear surface (mm)The laser power (kW)The angle of incidence of the laser beam (°)Welding speed (m/min)The allowance for subsidence (mm)
1And6front0,322,010 θ307,50,5High frequency induction preheating and machiningExample according to the invention
rear0,5210θb15
2In5front0,522,510θ40100,8High frequency induction preheating and machiningExample according to the invention
rear0,5210θb20
3In5front0,483,110θ5010 0,6High frequency induction preheating and machiningExample according to the invention
rear0,5210θb30
4And4front0,484,510θ20120,4High frequency induction preheating and machiningExample according to the invention
rear0,4810θb5
5And4front0,521,68θ30100,2High-frequency preliminary�flax heating, without machiningExample according to the invention
rear0,64*10θb10
6And6front0,64*2,08θ307,51High frequency induction preheating, without machiningExample according to the invention
rear0,328θb15
* The laser beam is divided into two beams by the optical system (prism)

Table 2-2
Sheet steelWelding conditions
Welded steel pipe No. The type of steelSheet thickness (mm)Laser beamThe diameter of the focused spot (mm)The space between the center points of the laser beams on the rear surface (mm)The laser power (kW)The angle of incidence of the laser beam (°)Welding speed (m/min)The allowance for subsidence (mm)Note
front0,323,510θ30High frequency induction preheating and machining
7And6rear0,5210θb07,50,5Comparative example
front0,520,010θ45High frequency induction preheating and machiningComparative
8In5rear0,5210θb20100,8example
front0,483,110θ50High frequency induction preheating and machining
9In5rear0,27 10θb30100,6Comparative example
front0,481,010θ-10High frequency induction preheating and machining
10And4rear0,3210θa15120,4Comparative example
front0,528θ10High frequency induction preheating, without machining
11And4rear0,64*1,510θb35100,2Comparative example
- The laser beam is divided into two beams by the optical system (prism)

3
Table 3
Compound No.The presence or absence of spatter adhered to the upper surface of the welded steel pipeThe appearance of the upper surface of the welded steel pipeThe appearance of the back surface of the welded steel pipeNote
1NoGoodGoodExample according to the invention
2NoGoodGoodExample according to the invention
NoGoodGoodExample according to the invention
4NoGoodGoodExample according to the invention
5NoGoodGoodExample according to the invention
6NoGoodGoodExample according to the invention
7NoThe presence of undercutGoodComparative example
8NoGoodThe presence left blankComparative example
9NoThe presence of undercut�the caryopsis in the cavity partially unmelted metal Comparative example
10The presence of a large number of the adhered spatterThe presence of undercutThe presence left blankComparative example
11The presence of a large number of the adhered spatterThe presence of undercutThe presence left blankComparative example

1. A method of manufacturing a laser welded steel pipe, comprising forming the steel strip into a cylindrical open pipe by means of forming rolls and performing laser welding on the edges of the open pipe by the emission of the laser beam on the edges of the open pipe in compression compressive edges of the rollers, wherein laser welding is accomplished by the emission of two laser beams along the edges of the upper surface of the open pipe, and these laser beams pass through different optical fiber with getting focused spots, the diameter of which exceeds 0.3 mm, and emit the laser beams thus to the front of the laser beam of two laser beams and a rear laser beam of two laser beams were inclined to the direction of perform swar�and, moreover, the angle of incidence is determined relative to the direction perpendicular to the upper surface of the open pipe, and the front laser beam is served on the upper surface of the open pipe at the weld in front of the rear laser beam, and the rear laser beam serves on the upper surface of the open pipe at the weld behind the front of the laser beam, set the angle of incidence of the forward laser beam is greater than the angle of incidence of the rear of the laser beam, and the spacing between the center of the front of the laser beam and the center of the back of the laser beam on the rear surface of the open pipe is 1 mm or more.

2. A method according to claim 1, wherein the anterior angles of incidence of the laser beam and laser beam rear set within the range from 5 to 50°.

3. A method according to claim 1 or 2, wherein the front laser beam and/or the rear laser beam is separated into two beams by an optical element and emit from both sides of these edges.

4. A method according to claim 1 or 2, wherein when performing laser welding produces a Deposit on Shrivenham area in the range from 0.2 to 1.0 mm.

5. A method according to claim 1 or 2, wherein when performing laser welding the power sum of the forward laser beam and the rear of the laser beam is greater than 16 kW and the welding speed is more than 7 m/min.

6. A method according to claim 1 or 2, wherein before performing laser with�arches provide pre-heating of the steel strip and, after performing the laser welding roller weld process on the machine or grinding.

7. A method according to claim 3, wherein when performing laser welding produces a Deposit on Shrivenham area in the range from 0.2 to 1.0 mm.

8. A method according to claim 3, wherein when performing laser welding the power sum of the forward laser beam and the rear of the laser beam is greater than 16 kW and the welding speed is more than 7 m/min.

9. A method according to claim 4, wherein when performing laser welding the power sum of the forward laser beam and the rear of the laser beam is greater than 16 kW and the welding speed is more than 7 m/min.

10. A method according to claim 7, in which when performing laser welding the power sum of the forward laser beam and the rear of the laser beam is greater than 16 kW and the welding speed is more than 7 m/min.

11. A method according to claim 3, wherein before performing laser welding provide pre-heating of the steel strip, and after performing the laser welding roller weld process on the machine or grinding.

12. A method according to claim 4, wherein before performing laser welding provide pre-heating of the steel strip, and after performing the laser welding roller weld process on the machine or grinding.

13. A method according to claim 7, in which to perform laser welding provide pre-heating of the steel strip, and after performing the laser welding roller weld process on the machine or brushed�eat.

14. A method according to claim 5, in which to perform laser welding provide pre-heating of the steel strip, and after performing the laser welding roller weld process on the machine or grinding.

15. A method according to claim 8, in which to perform laser welding provide pre-heating of the steel strip, and after performing the laser welding roller weld process on the machine or grinding.

16. A method according to claim 9, in which to perform laser welding provide pre-heating of the steel strip, and after performing the laser welding roller weld process on the machine or grinding.

17. A method according to claim 10, wherein before performing laser welding provide pre-heating of the steel strip, and after performing the laser welding roller weld process on the machine or grinding.



 

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