JPH0328272B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial field of application) Laser welding allows welding with low heat input, so welds may deteriorate when the heat input increases, or materials that are more susceptible to weld cracking, such as stainless steel or heat-resistant superalloys. Effective for welding nonferrous materials such as , Ti, and Zr. The present invention relates to a pipe manufacturing welding method that uses these materials and prevents welding defects that occur during pipe manufacturing using a laser. (Prior Art) Small-diameter, thin-walled welded pipes made of stainless steel, heat-resistant superalloys, and non-ferrous metals such as Ti and Zr have conventionally been made by TIG welding (tungsten inert gas welding). This is because TIG welding can provide high quality welds for this type of application, and the manufacturing method involves forming a band-shaped hoop of a predetermined width into a tube shape using an upset roll, and then TIG welding the end faces. Welding is performed by I-type butt welding, with the end faces being upset with rolls and the gap (root gap) being zero. On the other hand, as mentioned above, laser welding allows for low heat input welding and is suitable for welding stainless steel, heat-resistant superalloys, and non-ferrous metals such as Ti and Zr, which are susceptible to weld cracking, and because laser is a heat source with high energy density. When applied to welding, high-efficiency welding can be performed and it is considered to be suitable for pipe-making welding of this type of metal. However, according to experience, laser welding has a drawback in that undercut welding, such as pipe-making welding, tends to produce undercuts 5 on the surface as shown in FIG. This is because while laser-based uranami welding (penetration welding) forms a narrow weld metal, there is no difference in width between the front and back surfaces, and the weld metal tends to burn through, resulting in a bead on the front surface. Furthermore, in welding methods such as laser welding that produce a bead with deep penetration, gas, metal vapor, etc. are likely to be trapped, and blowholes are likely to occur. Furthermore, although hot cracking is less likely to occur in laser welding due to rapid solidification, hot cracking may become a problem depending on the material. As described above, in tube manufacturing welding using laser, it is necessary to prevent welding defects such as undercuts, blowholes, and hot cracks. (Object of the invention) The present invention aims to provide a welding method that prevents welding defects such as undercuts, blowholes, and hot cracks when applying laser welding to pipe manufacturing welding. Heat-resistant superalloy, Ti,
Targets thin-walled small-diameter pipes made of non-ferrous metals such as Zr. (Structure and operation of the invention) The present invention provides a method for manufacturing a welded pipe by forming a hoop into a tubular shape between opposing upset rolls and irradiating the abutting portion with a laser beam. The position should be 5 to 50 mm forward of the weld line from the intersection of the line connecting the shaft center and the weld line, and the gap d of the hoop abutment should be x = 5 above.
Laser welding characterized by welding at 0.01 to 0.30 mm in the range of ~50 mm, and further setting the upset amount u, that is (hoop width - welded pipe circumference) / (hoop width) x 100 (%), to 0.05 to 1%. The main topic is pipe manufacturing and welding methods. That is, in the method of the present invention, the laser irradiation position x is shown in FIG. The intersection point of the welding line 2 and the line connecting the centers of the axes of the upset rolls 1, which are arranged opposite each other, is defined as the origin O, and is located 5 to 50 mm above the welding line in front of the entrance side of the upsetting rolls. The gap d between the abutting parts of the hoop is set in the range of x = 5 to 50 mm, that is, x ₁ to x ₂ = 5 to 50 mm in Fig. 3.
If so, it should be 0.01 to 0.30 mm within that range. The upset amount u is set to 0.05 to 1%. The above conditions are satisfied. Next, the reason for limiting the configuration requirements as described above will be described. Prevention of undercut Using stainless steel SUS304 material, wall thickness 2.0mm, diameter
A 50.8 mm welded pipe was manufactured by laser welding.
In this case, the relationship with the undercut depth was investigated when the laser irradiation position x was changed on the weld line on the entry side of the upset rolls 1,1. Note that the butt gap d is 0.01 to 0.30 mm when x = 5 to 50 mm,
The upset amount u=0.4%. The result is the fourth
As shown in the figure. The welding conditions other than those mentioned above are as follows. Laser: _CO2 laser, laser power:
4kW, welding speed: 3m/min, lens focal length:
190.5mm, focal position: sample surface. Figure 4 shows that undercut occurs when the laser irradiation position x is less than 5 mm, whereas
= 5 to 50 mm, it can be seen that the molten weld metal is pushed in the plate thickness direction by the upset, thereby preventing the occurrence of undercuts. If x exceeds 50 mm, the gap between the butts will become too wide and burn-through will occur. In addition, Figure 5 shows the same conditions as in Figure 4 above.
The relationship between the depth of the undercut when the laser irradiation position x is 15 mm and the foreset amount u is changed is shown. If the upset amount u is less than 0.05%, the effect of preventing undercut is small, and in the range of 0.05 to 1%, the effect of preventing undercut by extrusion of the molten weld metal is observed. In addition, if it exceeds 1%, the deformation of the pipe will be large and it will be difficult to manufacture the pipe. Prevention of blowholes Blowholes can be prevented by determining the laser irradiation position x and applying a predetermined upset u as described above. This is thought to be because the blowhole is crushed when the molten weld metal is pushed out by the upset. Prevention of hot cracking Hot cracking is caused by tensile force during solidification of molten weld metal, so hot cracking is prevented under the above conditions of applying compressive force to the weld metal. Improvement in Welding Efficiency Since the method of the present invention involves butt welding with a gap d, the limit speed v at which Uranami welding can be performed is improved compared to the conventional welding method with zero gap. Figure 6 shows the relationship between the critical welding speed at which a back wave is formed and the laser irradiation position under the same welding conditions as in Figure 4. However, if the irradiation position x is 5 mm or more, a gap is created (see Figure 4). ), when the critical speed increases and x exceeds 50 mm, the gap becomes too large and the weld metal melts down. (Example) Under the common welding conditions shown in the table below, SUS304 material, 2.0 thickness 50.8 mmφ, was welded by the method of the present invention, that is, laser welding that satisfies the three conditions described above, and laser welding by a method of the present invention that does not satisfy the above conditions. Several examples of each tube were manufactured and the presence or absence of welding defects such as undercuts and blowholes was investigated.

【table】 The results are shown in Table 2.

[Table] Table 3 shows laser welding that satisfies the structural conditions of the method of the present invention and laser welding that does not satisfy the above conditions under the common welding conditions of Table 1.
SUS304, SUS310S, Incoloy 825 material 2.0 thickness 50.8
The presence or absence of hot cracking was investigated when three mmφ welded pipes were manufactured.

【table】

[Table] (Effects of the invention) As is clear from Tables 2 and 3, the method of the present invention completely prevents the welding defects caused by laser welding, such as undercuts and blowholes, and also prevents the occurrence of hot cracking. Stainless steel heat-resistant superalloy,
It has a remarkable effect on improving the quality of small-diameter, thin-walled welded pipes made of non-ferrous metals such as Ti and Zr, and increasing production efficiency.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing how undercuts occur during laser welding. FIG. 2 is an explanatory diagram showing the laser irradiation position x in the method of the present invention. FIG. 3 is an explanatory diagram of the gap d provided at the abutting portion of the hoop in the method of the present invention. FIG. 4 is a curve diagram showing the relationship between the laser irradiation position x, the undercut depth, and the butt gap d. FIG. 5 is a curve diagram showing the relationship between the amount of upset and the depth of undercut. FIG. 6 is a curve diagram showing the relationship between the Uranami formation limit speed and the laser irradiation position x. 1: Upset roll, 2: Weld line, 3: Hoop (pipe), 4: Weld metal, 5: Undercut.

Claims (1)

[Claims] 1 In a method of manufacturing a welded pipe by forming a hoop into a tubular shape between opposing upset rolls and irradiating the abutting portion with a laser beam, the laser irradiation position Position 5 to 50 mm forward of the weld line from the intersection point,
In addition, the gap d between the hoop abutting parts is set to the above x = 5 to 50 mm.
0.01 to 0.30mm in the range of
(Hoop width) x 100% is 0.05 to 1%.