JP2000334588A - Production pof austenitic stainless steel welded tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stabilized welding quality while suppressing a lap in high productivity by roll-forming an austenitic stainless steel strip to be a tubular and then welding it with laser beam while pushing up edge parts between a final fin pass roll and a squeeze roll after preheating. SOLUTION: An austenitic stainless steel strip is continuously formed to a tubular by plural roll forming stands, both edge parts of butting parts of the tube stock obtained between a final fin pass roll 3a and a squeeze size roll 6 are desirably preheated to >=500 deg.C by an electrical resistance heating method or an induction heating method using a contact tip, is welded by laser beam to be joined, so that a steel tube 12' is formed. At this time, preheated edges are subjected to butt welding while pushing up from below by a pushing up roll arranged between the final fin pass roll 3a and a squeeze size roll 6. The pushing up quantity is preferably adjusted according to the result by measuring the gap in the height direction of both edges.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an austenitic stainless steel welded steel pipe, and more particularly to an austenitic stainless steel welded steel pipe suitable for use in chemical engineering machines, nuclear power piping, etc., with high productivity. The present invention relates to a method of manufacturing a stainless steel welded steel pipe.

[0002]

2. Description of the Related Art Austenitic stainless steel pipes are widely used in chemical engineering machines, nuclear power piping materials and the like because of their excellent pitting corrosion resistance and good mechanical properties and weldability.

Conventionally, an austenitic stainless steel welded steel pipe has been manufactured by forming a raw steel strip into an open pipe shape and performing TIG welding on the butted portions of the opposite ends of the raw pipe prepared in this manner.

In the case of the TIG welding method, since welding is performed in an inert gas atmosphere, there is an advantage that a flux is not required and a high quality weld metal can be secured, but there is a disadvantage that a welding speed cannot be increased. For this reason, a TIG hot wire welding method and the like have been developed in which a filler wire to be appropriately supplied at the time of welding is heated by resistance heating the filler wire to increase the supply speed of the filler wire to improve the welding speed.

According to the TIG hot wire welding method,
Although high-speed welding about twice as high as that of a normal TIG welding method is possible, the welding speed is about several tens cm / min, and it is obvious that productivity is inferior. For this reason, from the viewpoint of improving productivity, the development of a laser welding method having a very high welding speed compared to the TIG welding method has recently been promoted. As a laser welding method, for example, JP-A-8-28
No. 1458.

The laser welding method is a method in which a laser beam is focused by a lens or a mirror to locally melt an object, and at the same time, an inert gas is jetted to weld while sealing a welded portion. The laser welding method has the following advantages. Similar to the TIG welding method, defects such as slag entrapment do not occur because no flux is used, and since the welding is performed in an inert gas atmosphere, the oxygen concentration in the welded portion is suppressed to the same level as the base metal. Therefore, a high quality weld metal can be obtained. Before laser welding, both edges are ERW (hereinafter E
The welding speed can be increased by preheating by an electric resistance heating method or an induction heating method using a contact tip used in the RW method). Therefore, the productivity is very superior to other welding methods.

[0007]

However, when the edge of the steel sheet is preheated by the electric resistance heating method or the like, as described later, the heat conductivity of a high alloy steel such as austenitic stainless steel is smaller than that of carbon steel. Therefore, the temperature distribution becomes high only in the vicinity of the edge of the steel sheet as compared with carbon steel. Accordingly, only the outermost edge of the steel sheet is softened, and both edges are pressed against each other with a squeeze side roll to abut each other (hereinafter, referred to as a squeeze side roll)
The outermost softened portion is displaced (slid) due to slight vertical external force acting on
Deform. Therefore, so-called wraps shown in FIGS. 1A and 1B are very likely to occur as compared with carbon steel.

For these reasons, when manufacturing austenitic stainless steel welded steel pipes by the laser welding method,
In order to suppress the occurrence of the lap, the preheating temperature of both edges of the steel sheet is lowered or the steel sheet is manufactured without preheating. However, this causes an increase in manufacturing cost due to a reduction in manufacturing speed.

The present invention has been made in view of the above situation, and is a method capable of producing austenitic stainless steel welded steel pipe suitable for piping of a processing machine with high productivity by a laser welding method. Is provided.

[0010]

Means for Solving the Problems The present inventors have continuously formed a steel strip made of austenitic stainless steel into a cylindrical shape by a plurality of roll forming stands, In the method of manufacturing a welded pipe using a laser beam for joining seams, both edges before laser welding are preheated by electric resistance heating method or induction heating method, and the gap in the height direction of both edges is measured. However, if butt welding is performed while adjusting the amount of push-up using a push-up roll device arranged between the final fin pass roll and the squeeze roll, the production speed can be increased and the lap can be sufficiently suppressed. In addition, it was found that a welded steel pipe having no welding defect and having stable welded portion quality can be manufactured.

The present invention has been made based on the above findings.

According to the first aspect of the present invention, the austenitic stainless steel strip is continuously formed into a tubular shape by using a plurality of roll forming stands, and both edge portions, which are the butted portions of the thus-prepared tube, are subjected to electric resistance. In a method for producing an austenitic stainless steel welded pipe which is preheated by an induction heating method or laser-welded, a push-up roll device is disposed between a final fin pass roll and a squeeze roll, and both edges are moved by the push-up roll device. The butt welding is performed while pushing up the part from below.

The invention according to claim 2 is characterized in that the preheating temperature of the both edge portions before laser welding is set to 500 ° C. or more.

The invention according to claim 3 is characterized in that the gap in the height direction of the two edges is measured, and the butt welding is performed while adjusting the amount of pushing up by the pushing up roll device according to the result. Things.

According to a fourth aspect of the present invention, a height direction gap G of both edges is measured at an arbitrary position within an edge convergence area L represented by the following equation (1), and is measured by the following equation (2). It is characterized in that the push-up amount by the push-up roll device is adjusted so as to satisfy the following conditions.

L ≦ √ [(D / 2−B) · (Df + BD / 2)] --- (1) where, in the above formula (1), L is the distance from the center of the squeeze side roll to the upstream of the forming. Edge convergence area, D: outer diameter of welded pipe, Df: outer diameter of flange of squeeze side roll, B: distance obtained by subtracting outer diameter of flange of side roll from center distance of squeeze side roll and dividing by 2.

[(A × G) ^1/2 × R ^1/2 ] /t≦0.25 (2) where, in the above equation (2), G: the gap amount in the height direction of both edges ( mm), R: Upset amount of squeeze side roll (mm), t: Plate thickness of steel strip (mm), a: Distance from edge squeeze side roll center to measurement position in edge convergence area L in correction term depending on measurement position Divided by.

[0018]

Next, an embodiment of a method for manufacturing an austenitic stainless steel welded steel pipe according to the present invention will be described in detail together with experimental results obtained. 1. Material steel strip The material steel strip may be any material steel strip made of austenitic stainless steel with excellent corrosion resistance and ductility.
Although not particularly limited, for example, SUS304, SUS304L, SUS316, and SUS specified in the JIS standard
316L or other standard material with an austenite ratio of 90
%, It is preferable to use a material steel strip that has been subjected to a solution treatment adjustment so as to be%. 2. Preheating temperature As a method of preheating both edges before laser welding, an electric resistance heating device using a contact tip used in the ERW method or an annular induction heating device is arranged in front of the squeeze roll, The desired temperature is heated by controlling the input power to these.

In order to determine the effect of increasing the welding speed by preheating the edge portion of the steel sheet before laser welding, welding is performed by changing the preheating temperature from room temperature to around the melting point under a constant laser output of 20 kW, and performing penetration welding. The possible limit speed was investigated.

A carbon steel strip having an outer diameter of 273 mm and a plate thickness of 6.5 mm was heated at a desired temperature by direct energization of both edges of the carbon steel strip before laser welding by a pipe mill shown in FIG. FIG. 3 shows the result of welding with the laser beam device 5 after preheating to the maximum.

In FIG. 2, 1 indicates a breakdown roll group, 2 indicates a cage roll or cluster roll group, and 3 indicates a fin pass roll group.

As is apparent from FIG. 3, there is a tendency that the penetration limit welding speed increases as the preheating temperature increases. However, when the preheating temperature is less than 500 ° C., the increase rate of the welding speed, which is determined by the ratio with the penetration limit welding speed when the laser is used alone (without preheating), is as low as 1.5 times or less, resulting in poor productivity.
For this reason, in order to obtain high productivity, it is necessary to set the preheating temperature before the laser to 500 ° C. or higher.

However, in the case of using austenitic stainless steel, if the preheating temperature of the steel plate edge portion before laser welding is increased, lapping is very likely to occur during upsetting. Therefore, the present inventors calculated the temperature distribution at the steel sheet edge when preheating by an electric resistance heating method or the like from numerical calculation, in order to pursue a correlation between the lap phenomenon and the preheating temperature in the austenitic stainless steel, The behavior of the steel sheet edge due to preheating was considered.

(Temperature Analysis) First, the following 3 is assumed.
The condition of the point was satisfied. (1) One-dimensional heat conduction. (2) Physical properties are constant regardless of temperature. (3) The current distribution is constant regardless of the temperature.

Next, the temperature distribution at the edge of the steel sheet was determined based on the basic equations shown in the following equations (3) and (4).

Heat balance: ΔT / Δt = α (∂ ² T / Δt ² ) + j ² / Cp · ρ · σ (3) Current distribution: j = j ₀ · exp (−x / δ --- (4) where, in the above equations (3) and (4), T: temperature (° C.), t: time (s), α: thermal diffusivity (m ² / s), Cp: specific heat ( J / kg · ° C.), ρ: density (kg / m ³ ), α: specific electrical conductivity (Ω · m), j, j ₀ : electric density (A / m ² ), δ: penetration depth (m ).

[0027] The initial conditions: at t = 0, T = 0 boundary conditions: at x = 0, in ∂T / ∂x = 0 _{(adiabatic) x = x E, ∂T /} ∂x = 0 ( adiabatic) x _E = analysis region width (sufficiently large) above (3) and (4) ∂T from the equation ^{/ ∂t = α (∂ 2 T} / ∂t 2) + (j 0 2 / Cp · ρ · σ) · exp (−x / δ) --- (5)

The following equation is modified and substituted into the above equation (5).

Λ = Cp · ρ · α where λ: thermal conductivity (w / m · ° C.) Therefore, ΔT / ∂ (α · t / δ ² ) = α∂ ² T / ∂ (x / δ) ^Two + Become _{^{(j 0 2 · δ 2 /}} σ · λ) · exp (-2x / δ) --- (6).

Here, in the above equation (6), the dimensionless temperature: θ = σ · λ · T / j₀ ^Two・ Δ^Two  Dimensionless length: x = x / δ Dimensionless time: τ = α / δ^Two Then, ∂θ / ∂τ = ∂^Twoθ / ∂x^Two+ Exp (-2x) --- (7)

By solving the equation (7) under the initial condition and the boundary condition, the temperature distribution at the steel sheet edge is obtained. In addition,
Here, it was solved by the forward difference method.

FIG. 4 shows that the temperature at the edge of the steel sheet is 750 ° C.
4 shows the temperature distribution from the steel sheet edge at the center of the sheet thickness in carbon steel and austenitic stainless steel in the case of. The physical properties of the steel used here are as shown in Table 1.

[0033]

[Table 1]

As shown in Table 1, in a high alloy steel such as austenitic stainless steel, the thermal conductivity is smaller than that of carbon steel, and therefore, as shown in FIG. A temperature distribution resulting in a high temperature occurs.

FIG. 5 is a graph showing the ratio of the steel sheet strength at that temperature to the steel sheet strength at room temperature (hereinafter, referred to as a steel sheet strength ratio) based on each temperature calculated by the above calculation. As shown in FIG. 5, in austenitic stainless steel, compared to carbon steel, a sharp decrease (softening) occurs only in the vicinity of the steel sheet's edge. FIG. 6 shows the distribution of the strength ratio of the steel sheet in the austenitic stainless steel when the temperature at the edge of the steel sheet is set to 500 ° C. by the same method. As is clear from FIG. 6, if the preheating temperature drops to about 500 ° C., the local softening of the outermost edge portion shown in FIG. 5 is not recognized.

From these results, when the preheating temperature is set to 500 ° C. or higher using austenitic stainless steel, the stress generated at the end face of the steel sheet during upset is increased in the vertical direction in addition to the direction perpendicular to the end face. Also, it is considered that the softened portion at the outermost edge portion easily shifts due to the stress in the vertical direction and deforms, and the abutting surface shifts. That is, it is considered that wrapping occurs. This speculation is in good agreement with the phenomenon experienced in actual operation in which the generation of lap can be suppressed by lowering the preheating temperature before laser welding in the production of austenitic stainless steel tubes.

However, as described above, when the preheating temperature before laser welding is less than 500 ° C., the increase rate of the welding speed obtained by the ratio with the penetration limit welding speed when using the laser alone (no preheating) is 1.5 times. Therefore, the present inventors have studied a pipe forming method that can prevent lapping even in a state where a softened portion at the outermost edge at a preheating temperature of 500 ° C. or higher exists. Hereinafter, this method will be described. 3. Forming Conditions Observation of Behavior of Both Edges Generally, the first cause of the lap is that if the edge wave 11 shown in FIG. Although the edge wave 11 is slightly smaller than the thickness of the steel sheet, the state of insertion of both edges of the steel sheet into the squeeze side roll 6 shown in FIG. Due to the edge wave 11 or the like, stress generated on the end face of the steel plate at the time of upsetting is generated not only in the component perpendicular to the end face but also in the vertical direction, and the butt surface is shifted due to the vertical stress.

FIG. 8 shows the results of measuring the fluctuation in the height direction of both edges of the open pipe with a non-contact laser displacement meter when a welded pipe was manufactured under the following pipe forming conditions. FIG. 4 shows a correlation diagram between the measurement results. In addition, the measurement of the height direction gap amount G of both edge portions was calculated as a difference amount between the measurement values of both edge portions measured by the laser displacement meter. (Pipes) Welded pipe outer diameter x thickness: 73.0mm x 1.2mm, Material: Cold rolled steel plate (equivalent to SPCC), Forming machine configuration: Breakdown roll (3 steps), Cage roll stand, Fin pass Roll stand (3 steps),
Squeeze roll stand (1 stage), squeeze roll stand required dimensions: squeeze side roll flange outer diameter Df: Df = 160
mm, the distance obtained by subtracting the outer diameter of the squeeze side roll flange from the distance between the centers of the squeeze side rolls and dividing by 2 B: B = 3 mm The squeeze side roll 6 is used as a squeeze mechanism and mainly has a large diameter. Is used together with two rolls of the squeeze side rolls 6, two rolls of the squeeze top roll and one roll of the squeeze bottom roll. Uses only two squeeze side rolls 6. The restraint by the squeeze side roll is much larger than the restraint by the squeezed soprole.

As is apparent from FIG. 8, the influence of the position in the tube axis direction (longitudinal direction) on the edge fluctuation is almost equal to the area within the edge convergence area L of FIG. 9 represented by the following equation (1). Shows a tendency to be constant. As a result, the gap G in the height direction at both edges shows a monotonous decrease within the edge convergence area L. The reason why the edge change is constant within the edge convergence area L is that the open pipe is hardly deformed by being sufficiently constrained by the forming roll, and the pipe originates from the material of the raw material and the camber of the raw material. It is considered that disturbance such as self-excited vibration of the entire non-uniform open pipe can be eliminated.

Therefore, the gap G in the height direction at both edges
Is suitable as a position for measuring the edge convergence region L where the edge fluctuation is constant and the gap G monotonically decreases as described above. Since the gap G shows a monotonous decrease within the edge convergence area L, a proper evaluation can be performed by multiplying the gap G by a value obtained by dividing the edge convergence area L by the measurement position. Although the number of measurement points of the gap G may be plural, one point is sufficient since the gap G monotonously decreases.

L ≦ √ [(D / 2−B) · (Df + BD / 2)] --- (1) where, in the above formula (1), L is the distance from the center of the squeeze side roll to the upstream of the forming. Edge convergence area, D: outer diameter of welded pipe, Df: outer diameter of flange of squeeze side roll, B: distance obtained by subtracting outer diameter of flange of side roll from center distance of squeeze side roll and dividing by 2.

FIG. 10 shows an outer diameter of 323.8 mm × a plate thickness of 6.
When a 2mm carbon steel pipe is molded by the molding machine shown in Fig. 2, lead is inserted into both edges of the cold joint, and the roll of the edge is transferred to the lead by rolling the lead on the steel sheet edge. It is an observation result of the behavior of both edges of the steel sheet immediately before the center of the squeeze side roll 6 from the cross-sectional microscopic result of the transfer surface.

As is apparent from FIG. 10, the edges of the steel sheet immediately before the center of the squeeze side roll 6, that is, immediately before the upset, are separated by a gap G in the height direction. It can be seen that one side is strongly pushed from the side, and both edges behave completely differently.

From these results, it can be seen that the stress generated on the end face of the steel plate at the time of the upset acts not only in the direction perpendicular to the end face but also in the vertical direction, and since the stress directions are different at both edges. It can be guessed that slip deformation occurs on the butted surfaces and leads to wrap. In particular, when the outermost edge is extremely softened at a preheating temperature of 500 ° C. or higher, such as austenitic stainless steel, the softened portion easily shifts and deforms. It is thought that it is likely to occur.

Therefore, as a measure for preventing lapping during high-temperature preheating of austenitic stainless steel, the present inventors set the distance between the final fin pass roll 3a of the fin pass roll group and the squeeze side roll 6 as shown in FIG. A push-up roll device 7 was arranged to push up both edges from below, thereby applying tension to both edges to improve the butt condition and performing welding.

The structure of the lifting roll device 7 may be as described in JP-A-5-208213 and JP-A-9-1232. For example, as shown in FIG.
A pair of right and left push-up rolls 8, push-up rolls 8 for pushing up the 2 'seam portion 12a from inside the pipe.
And a push-up height detector (not shown) for detecting a height position of the push-up roll 8 and a wheel 10 for supporting the push-up roll device 7 on the inner surface of the steel pipe. I have.

FIG. 13 shows an outer diameter of 323.8 mm and a thickness of 6.
It is the result of observing the work of both edges of the steel plate within the both-edge convergence region L represented by the above-mentioned formula (1) when a 2 mm carbon steel pipe is formed using the push-up roll device 7. FIG.
As is clear from the above, the behavior of both edges of the steel sheet immediately before the center of the squeeze side roll 6, that is, immediately before the upset is corrected by using the push-up roll device 7, and the gap G in the height direction of both edges is also reduced. It turns out to be slight, and it can be seen that the behavior is almost the same.

As described above, the push-up roll device 7 is arranged between the final fin pass roll 3a and the squeeze side roll 6, and both edges are pushed up from below by the push-up roll device 7, and tension is applied to the edges. While performing butt welding, the work of the both edges of the steel plate immediately before the upset is corrected to be almost the same, and the stress components other than the direction perpendicular to the end surface generated at the edges of the both edges of the steel plate at the time of the upper set are extremely reduced. Can be reduced.

FIG. 14 shows that the preheating temperature of both edges before laser welding when the austenitic stainless steel sheet was used was set to 500 ° C. or more and the amount of push-up was changed variously according to the embodiment described later. When the pipe is piped, the height direction gap G between both edges of the steel sheet within the edge convergence area L expressed by the above equation (1), the upset amount R obtained by the pipe circumference difference before and after passing through the squeeze side roll 6, FIG. 7 is a graph showing the effect of the steel strip thickness t on the occurrence of lapping, in which the horizontal axis represents the value obtained on the left side of the following equation (2), and the vertical axis represents the occurrence of lapping. is there.

L ≦ √ [(D / 2−B) · (Df + BD / 2)] --- (1) where, in the above formula (1), L is the distance from the center of the squeeze side roll to the upstream of the forming. Edge convergence area, D: outer diameter of welded pipe, Df: outer diameter of flange of squeeze side roll, B: distance obtained by subtracting outer diameter of flange of side roll from center distance of squeeze side roll and dividing by 2.

[(A × G) ^1/2 × R ^1/2 ] /t≦0.25 (2) where, in the above equation (2), G: the gap amount in the height direction of both edges ( mm), R: Upset amount of squeeze side roll (mm), t: Plate thickness of steel strip (mm), a: Distance from edge squeeze side roll center to measurement position in edge convergence area L in correction term depending on measurement position Divided by.

The gap G in the height direction at both edge portions
Is measured by controlling the position of the contact shoe 4 shown in FIG. 2 within the edge convergence area L determined by the above equation (1), and measuring the vertical movement of the contact shoe 4 on both sides by a contact type displacement meter which has been subjected to insulation treatment. , Calculated from the difference between the measured values.

As is clear from FIG. 14, when the value obtained by the above equation (2) is 0.25 or less, the occurrence of rubbing during pipe making is eliminated. Accordingly, it is understood that it is preferable to adjust the push-up amount so as to satisfy the above expression (2).

The push-up roll attached to the push-up roll device may be a single-stage type as shown in FIG.
A multi-stage type as shown in FIG. By making the push-up roll a multi-stage type, the push-up reaction force acting at the time of push-up can be dispersed in each stage, and the roll mark on the inner surface of the tube and the collapse of the push-up roll by the push-up roll can be prevented. Further, since the apparent push-up roll diameter can be increased, the edge is not locally stretched by the push-up.

[0055]

Next, the present invention will be described in more detail with reference to examples. Here, steels having the component compositions shown in Table 2 were melted, steel strips having various thicknesses and widths were manufactured by hot rolling, and supplied to the welded tube blanks.

[0056]

[Table 2]

After the above steel strip was formed into a tubular shape by the forming machine shown in FIG. 2 in sequence, the butting portions of both edges were heated to a desired temperature by controlling the electric power applied to the contact shoe 4, and the output was further increased. Welding was performed using a 25 kW laser welding machine to produce welded pipes having different wall thicknesses and outer diameters.

Here, as shown in FIG. 11, the push-up roll device 7 was installed between the final fin pass roll 3a of the fin pass roll group and the squeeze side roll 6. As a mechanism for holding the push-up roll device 7 at a fixed position between the final fin pass roll 3a and the squeeze side roll 6, the technology described in Japanese Patent Application Laid-Open No. 5-208213 can be employed. Also, the push-up position is
It can be determined by employing the technology described in Japanese Patent Application Laid-Open No. 9-1232.

The measurement of the gap amount G in the height direction of both edges is performed by measuring the position of the contact shoe 4 in FIG.
The position was controlled within the edge convergence area L determined by the equation, and the vertical movement was measured on both sides by a contact displacement meter having been subjected to insulation treatment, thereby calculating from the difference between the measured values. In addition, the upset amount was determined by measuring the outer peripheral length of the pipe before and after passing through the squeeze side roll 6, and determining the difference.

As an index of the effect, when a lap is generated during pipe forming and welding failure occurs, the mark is x, and when lapping does not occur and good welding is performed, the mark is circled. The results are shown in Table 3.

[0061]

[Table 3]

It should be noted that a lap in which both edges do not completely abut can be visually confirmed, but if the lap is wrapped within the thickness of the steel sheet as shown in FIG. For this reason, arbitrary 50 points in the longitudinal direction were observed by cross-sectional polishing from the tube-formed sample, and as shown in FIG. 16, the case where the step tg of both edges of the inner surface or the outer surface exceeded 10% of the plate thickness t was referred to as wrap. did. In addition, in order to make it easy to confirm the lap, the tube was formed without performing bead cutting on the inner and outer surfaces, which is usually performed.

As a result, as shown in Table 3, it was confirmed that the one manufactured by the method of the present invention did not generate any lap, and it was possible to manufacture a welded pipe having stable welding quality.

[0064]

As described above, according to the present invention,
Useful effect of stabilizing the edge butt condition during the pipe making process, making it possible to manufacture austenitic stainless steel welded steel pipe suitable for piping of processing machines with stable welding quality and high productivity Is brought.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing wrapping of a molding material edge portion by a conventional molding method.

FIG. 2 is an explanatory diagram showing a production line for a welded pipe.

FIG. 3 is a graph showing a relationship between a preheating temperature and a penetration limit welding speed.

FIG. 4 shows that the temperature at the edge of the steel sheet is 75
It is a graph which shows distance temperature distribution from the steel plate edge part which arises when it is set to 0 degreeC.

FIG. 5: Temperature 7 at the edge of the steel sheet obtained from heat conduction analysis
It is a graph which shows the relationship between the ratio of the steel plate strength at 50 degreeC and the steel plate strength ratio at room temperature, and the distance from the steel plate edge.

FIG. 6: Temperature 5 at the edge of steel sheet obtained from heat conduction analysis
It is a graph which shows the relationship between the ratio of the steel plate strength at 00 degreeC and the steel plate strength ratio at room temperature, and the distance from the steel plate edge.

FIG. 7 is an explanatory view showing an edge wave generated in a formed material seam portion.

FIG. 8 is a graph showing the relationship between the distance from the center of the squeeze side roll to the upstream side, edge fluctuation, and the gap between both edges.

FIG. 9 is an explanatory diagram showing a positional relationship when measuring a height direction gap amount of both edges.

FIG. 10 is an explanatory view showing the behavior of both edges of a steel sheet near a squeeze side roll and the height gap between the both edges by a conventional forming method.

FIG. 11 is an explanatory view showing an embodiment of the present invention using a push-up roll device.

FIG. 12 is an explanatory diagram illustrating a configuration example of a push-up roll device used in the present invention.

FIG. 13 is an explanatory diagram showing the behavior of both edges of the steel sheet near the squeeze side roll and the height gap between the both edges by the forming method of the present invention.

FIG. 14 is a graph showing the relationship between the gap in the height direction of both edges, the amount of upset, and the thickness of a steel strip on lap generation.

FIG. 15 is an explanatory view showing a multi-stage push-up roll device used in the present invention.

FIG. 16 is an explanatory diagram illustrating a method of determining the quality of a lap.

[Explanation of symbols]

 1: Breakdown roll group 2: Cage roll or cluster roll group 3: Fin pass roll group 3a: Final fin pass roll 4: Contact shoe 5: Laser beam welding device 6: Squeeze side roll 7: Push-up roll device 8: Push Lifting roll 9: Lifting device 10: Wheel 11: Edge wave 12: Steel strip 12 ': Steel pipe 12a: Seam part

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B23K 31/00 B23K 31/00 H (72) Inventor Takashi Ariizumi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan (72) Inventor Yukio Maho 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan 1-2. In-company (72) Inventor Masahito Suzuki 1-2-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 4E028 CA02 CA13 CA16 CA18 4E068 AA02 AJ03 BE00 BE01 BG01 CA14 CB05 CB06 DA15 DB01

Claims (4)

[Claims] An austenitic stainless steel strip is continuously formed into a tubular shape by a plurality of roll forming stands, and both edges of the raw tube thus prepared are joined by an electric resistance heating method or an induction heating method. In the method for producing an austenitic stainless steel welded pipe to be joined by laser welding, a push-up roll device is arranged between a final fin pass roll and a squeeze roll, and the both edge portions are moved by the push-up roll device. Butt-welding while pushing up from below, a method for producing an austenitic stainless steel welded steel pipe. 2. The method for producing an austenitic stainless steel welded steel pipe according to claim 1, wherein a preheating temperature of the both edge portions of the raw pipe is set to 500 ° C. or more. 3. The butt welding according to claim 1, wherein a gap in a height direction between the two edges is measured, and a butt welding is performed while adjusting a pushing amount by a pushing roll device according to the result. A method for producing the austenitic stainless steel welded steel pipe according to the above. 4. An edge convergence area L represented by the following equation (1):
And measuring the gap G in the height direction of both edges at an arbitrary point within the range, and adjusting the pushing amount by the pushing roll device so as to satisfy the condition represented by the following formula (2). The method for producing an austenitic stainless steel welded pipe according to any one of claims 1 to 3. L ≦ √ [(D / 2−B) · (Df + BD−2)] --- (1) In the above equation (1), L is an edge convergence area on the forming upstream side from the center of the squeeze side roll. D: outside diameter of the welded pipe; Df: outside diameter of the flange of the squeeze side roll; B: distance obtained by subtracting the outside diameter of the side roll flange from the center distance of the squeeze side roll and dividing by 2. [(A × G) ^1/2 × R ^1/2 ] /t≦0.25 (2) In the above equation (2), G: the height direction gap between both edges (mm); R: Upset amount of squeeze side roll (mm), t: Thickness of steel strip (mm), a: Edge convergence area L was divided by the distance from the center of the squeeze side roll to the measurement position by a correction term depending on the measurement position. value.