JPS6021180A - Welding method with high quality and high efficiency in production of spiral steel pipe - Google Patents

Abstract

PURPOSE:To produce a steel pipe having high quality with high efficiency by welding the butt part thereof by an electric resistance welding method and subjecting said part to outside surface welding and inside surface welding by an arc welding method. CONSTITUTION:A belt-like steel plate 1 which is preliminarily formed with a projecting part is spirally wound and the side edges thereof are melted or half melted by high frequency induction heating just before 7 in which the one side edge meets the other side edges with a minus gap. The side edges are pressed at 8 from above and below by pressing rolls and at the same time the squeezed out molten metal is shaped by pressing rolls having a projecting shape. The edges are then subjected to arc welding on the outside surface at 9 after going half around and to arc welding on the inside surface at 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an extremely effective welding method for producing high-quality, highly efficient steel pipes in the production of spiral steel pipes made by spirally winding and welding hot-rolled coils or strip-shaped thick plate materials. .

Conventional welding methods for spiral steel pipes (submerged arc welding) are mainly used for internal and external surface welding, and in some cases submerged arc welding is performed in a separate process after preliminary welding by CO2 arc welding, or electric resistance welding is used. Improving the productivity of spiral steel pipes means improving pipe manufacturing efficiency, that is, welding speed, and in conventional submerged arc welding, multi-electrode welding and the development of high-speed welding loops have been carried out. However, the current situation is that dramatic improvements cannot be expected.

Electric resistance welding allows for high-speed welding compared to submerged arc welding, but it has rarely been applied to spiral steel pipes, and has only been applied to thin plates with a thickness of 68 mm or less and small diameters. On the other hand, as an electric resistance welding method for relatively thick plates of spiral steel pipes,
There is No. 9% Kai No. 52-72353. In particular, in the latter case, in order to continuously apply uniform pressure to the electric resistance weld, straight seam steel pipe a uses a different crimping process to guide the root gap in a negative state (see Figure 1 (a)), and by high-frequency heating. Although the concept of automatically pressing the opposite surfaces of semi-molten or molten steel plates in the thickness direction and welding them together has been proposed, there is no example of this being implemented.

The main reason for this is that it is difficult to obtain sufficient squeezing force when pressing with a negative gap, so the molten metal is not squeezed out sufficiently at the joint, especially on the thick side, and the welded metal is not completely cut due to the plate thickness. This is because it is difficult to obtain a throat thickness of 100% or more, making it difficult to use as a final product.

Therefore, electric resistance welding is only effective for temporary attachment, and conventional arc welding must be performed within the same process or in another process, so no improvement in pipe manufacturing efficiency could be expected.

The present invention solves the above-mentioned problems related to the manufacture of spiral steel pipes, and makes it possible to manufacture spiral steel pipes with ultra-high efficiency and high quality. In this method, the protrusions are pressed with a negative gap to automatically pressure-weld them, and then arc welding is performed on the inner and outer surfaces.The throat thickness of the electric resistance welding part is made large, and the inner and outer surfaces are not fully fused by forming a bead. The amount of welding deposited by arc welding is achieved by performing makeup welding by arc welding after shaping the chisel.

The amount of penetration can be reduced, the internal arc welding point is not performed at the seam butt part, so off-center (welding position eccentrically from the center of the pipe) can be freely selected as an advantageous position, and electric resistance welding By combining the high speed of electric resistance welding with the decorative welding of arc welding, the heating acts as preheating for subsequent arc welding, making it possible to produce pipes at more than twice the speed of conventional arc welding. It becomes possible to manufacture high-speed, high-quality composite welded steel pipes. Furthermore, depending on the required qualities such as strength and toughness, the degree of bonding can be changed by changing the ratio of the electric resistance welded part and the arc welded part to the plate thickness. In addition, even if the throat thickness of the electric resistance welded part is 10'0% of the plate thickness, it is necessary to compensate for the disadvantages such as poor bendability of the electric resistance welded part by arc welding, and if this is not necessary, After electric resistance welding, the inner and outer welds are shaped and the final product is unique.

How to shape the internal and external welds after electric resistance welding.

The high-temperature soft excess produced by electric resistance welding may be crushed and shaped using a pressure welding roll, or may be cut and removed using a cutting tool or the like. However, if the excess is formed in a constant shape without defects, there is no need to forcefully shape it, and the next arc welding can be carried out with that dimension. After reed electric resistance welding, if the inner and outer surfaces are welded in another process, the excess buildup from electric resistance welding will have hardened, and if the excess buildup is a bead with a fixed shape without defects, it should be cut and removed. is preferred.

In other words, the present invention overcomes the drawbacks such as difficulty in obtaining a perfect thick wall with suppressed electric resistance welding of spiral steel pipes, and welds normal spirals from the thin wall side to the thick wall side, from the small diameter to the large diameter 1. This technology allows electrical resistance welding of all sizes of steel pipes to be made into final products.

This method is a completely new process that has never been put into practical use, and especially when electric resistance welding and arc welding are performed in the same process, it is unlikely that high-efficiency and high-quality spiral steel pipes can be manufactured in 1 mil. It became a high-productivity mill for a long time.

The present invention solves the problems associated with the conventional manufacturing of spiral steel pipes, and produces extremely innovative high quality products.

This method provides a highly efficient welding method, where one side edge of the 5-strip steel and the other side line meet with a negative root gap, and the butt parts on both sides are continuously welded using an electric resistance welder. Electric resistance welding is performed, and external and internal welding is performed continuously or continuously by arc welding to form a composite welded part and arc welded part. By increasing the throat thickness of the press-welded part by 50% to 100% of the plate thickness, the amount of welding and penetration in the subsequent arc welding of the outer and inner surfaces can be reduced, and the welded part that has been melt-welded can be This is a welding method characterized by welding with one strain so that part or all of the throat thickness remains.

Next, the method of the present invention will be explained in detail with reference to the drawings.

FIG. 1 illustrates a conventional arc welding method. At 3, latent arc welding is performed from the inside of the butted side edges, and after half a turn, latent arc welding is performed at 4 on the outer surface, resulting in a joint in which the inner and outer latent arc welding beads have a sufficient metal touch.

As for the welding positions in the submerged arc welding method, as shown in FIG. 1(b), the inner welding torch is eccentric by a distance t at the 3rd position, and the outer welding torch 6 is eccentric by a distance t2 at the 4th position as well. The reason for this is to solidify the molten steel advantageously while maintaining a good bead shape and welding at higher speeds.
In the case of inclined welding, the amount to prevent molten steel from flowing down, and 1. Currently, it is difficult to expect a significant improvement in welding speed due to the limited length of welding.

In contrast, FIG. 2(a) illustrates the welding process in accordance with the present invention.

As shown in Fig. 2(C), a strip steel plate 1 on which protrusions have been formed in advance is wound spirally, and just before one side edge meets the other side edge with a minus gap 7, the side edge is heated by high frequency heating. The molten metal is made into a molten or semi-molten state and pressurized from above and below with pressure rolls at 8, and at the same time the squeezed out molten metal is shaped using protruding pressure rolls.After half a turn, the outer surface is arc welded at 9. In this method, the inner surface is arc welded in step 10. One type shown in FIG. 2(a) is a case where an electric resistance weld is used as a tack weld, and welding is performed by arc welding in a conventional manner so that the outer surface weld metal and the inner surface weld metal meet. In this case, the quality is significantly improved compared to conventional welding methods, but the line speed is hardly improved.

■ Type is throat thickness SC of electric resistance welding part in 7 and 8.
50 inches to 100% of the plate thickness, and remove incomplete welds on the inner and outer surfaces and beads containing a lot of oxide squeezed out by electric resistance welding.
Arc welding was performed from the outer surface in 1 and from the inner surface in 10, and the electric resistance welded part of the medium-thickness part was left as the main bead in the joint.Compared with type 1. However, the amount of welding and penetration in arc welding only needs to be extremely small, and the role is only to build up.1 This allows high-speed arc welding to be more than double the speed of conventional welding.

■The type is when a throat thickness of 100% of the plate thickness is obtained only by electric resistance welding, and a large negative gap is applied. After applying a sufficient squeeze, the inner and outer surfaces are squeezed out. The final product f is rubbed simply by shaping the bead, and it is possible to perform wider and higher speed welding than type (3).

The following is an example of the method of the present invention.

The photograph in FIG. 2 (1)) shows a cross-sectional macro photograph of the welded joint when the I and If types are actually produced. (3) is a case where the pipe was made with a plate thickness of 12 mm and a welding speed of 6.0 l, which is about twice the welding speed of conventional pipe making. Figures 3 and 4 show the electric resistance welding machine used to manufacture the above-mentioned spiral steel pipe. The frequency is l 1 (
Can be used in H2-500 K1-1z. FIG. 3 is a side view of the welding machine, and shows that power is supplied from a high frequency oscillator 19 installed on the lower surface of the pipe 2 and the steel plate 1 to the pipe side and the steel plate side via the welding head 21 and the contact tip 221. Apply current at welding point 7. The electric resistance welding head 21 has variable power supply position, angle, and force for pushing and pushing the contact tip, and the pipe side and the steel plate side are each independently adjustable. FIG. 4 shows a plan view in which the electric resistance welding device is arranged along the side edge of the steel plate, and the entire device is mounted on the pretreatment frame 234. Applicable to pipe making of size. Furthermore, the present invention will be explained in detail using an example in which a pipe was actually made with a plate thickness of 12 mm.

As already explained, ■ in FIG. 2(b) is a composite welded joint of electric resistance welding and arc welding that was actually made into a pipe. In order to control the ratio of the electric resistance welded part and the arc welded part in this composite welded joint, data such as those shown in FIGS. 5 and 6 are required.

First, in order to control the throat thickness Sc of the electric resistance welded part, it is necessary to know the relationship between the negative gap amount λ (wrap allowance) and the thickness Sc. According to FIG. 6, the relationship is shown that the larger the amount of wrapping, the larger the throat thickness, and by selecting the amount of wrapping, the target thickness can be determined. Furthermore, in FIG. 5, an appropriate amount of heat input can be determined in accordance with the welding speed. The highest speed can be achieved when the throat thickness is made as large as possible to minimize the area to be remelted by arc welding. Figures 7 and 8 are diagrams showing the relationship between throat thickness Sc and groove depth G with respect to plate thickness, and the relationship between welding speed, and high-speed welding is possible based on the results of actual pipe manufacturing. The reason is briefly shown. By increasing the groove thickness Sc obtained by electric resistance welding with respect to the plate thickness.

The depth G of the groove to be remelted later becomes extremely small, and accordingly arc welding is performed as a decorative bead.
It has been shown that the speed is increased by i.

Whether electric resistance welding and arc welding are performed in the same process or in different processes, the efficiency of pipe manufacturing is determined by the speed of arc welding, so the speed-up effect of this decorative plate is significant. Thick.

Next, we will discuss the quality effects of composite welded joints of electric resistance welds and arc welds. The first effect is that internal and external arc welding [because electrical resistance welding is performed first, internal defects such as blowholes and slag entrainment are drastically reduced, similar to when CO□ temporary +1 welding is performed. As the next effect, the joint performance investigation results are shown in Figure 9.10゜11. Generally, performance evaluation of welded joints is performed by tensile test, impact test, and hardness of the welded part.

Figure 9 shows the relationship between the length of the electrical resistance weld remaining in the composite joint and the joint strength (removal of reinforcement 9).The joint strength of the composite joint is equivalent to that of conventional double-sided single-layer arc welding, and the joint strength Even if the (ratio of arc weld length to electric resistance weld length δ) is changed, the joint strength does not change. Figure 10 shows the impact values of electric resistance welds at various speeds. Electrical resistance The impact value of the weld zone depends on the welding speed, and shows a better value when the speed is high.When performing electric resistance welding and arc welding in the same process, the welding speed should be between 40 l and 10 l. However, it can be seen that the impact value shows a sufficient value even when the pipe is made at a low speed, which is disadvantageous for electric resistance welding.Figure 11 shows the hardness distribution after only electric resistance welding. Furthermore, a comparison of the hardness distribution of electric resistance welded parts after arc welding is shown (Vickers hardness, load 1
0KLri. The maximum hardness is about -1v-220, which is a good value, and after arc welding, the maximum hardness is even lower due to the reheating effect.

In other words, it can be seen that the quality of the composite welded joint of electric resistance welding and arc welding is not inferior to that of conventional arc welded joints, and that it has excellent joint performance.

As described above, the present invention is a welding method applied to the manufacture of spiral steel pipes, in which the electrical resistance welded part is temporarily made into a permanent bead, and by performing decorative arc welding on the inner and outer surfaces, the final product is Higher quality than conventional methods,
Moreover, it becomes possible to improve the tube manufacturing efficiency by more than double. It is now possible to manufacture joints with a different ratio of electric resistance welding and arc welding depending on the depth and condition, and ultimately it will be possible to manufacture products using only electric resistance welding, achieving remarkable effects. It's coming. In particular, the method of performing electric resistance welding and arc welding in the same process has an industrial effect in that it has made it possible to manufacture high-efficiency and high-quality spiral steel pipes without increasing the number of process equipment personnel compared to the conventional method. It is extremely large and has no other ζζ example.

[Brief explanation of the drawing]

Figure 1 (a, l is a plan view showing the welding order of spiral steel pipes according to the conventional method and a cross-sectional view of the weld bead formed at each position, and Figure 1 (b) is a plan view showing the positions of internal and external arc welding in the conventional method. The diagrams shown in FIG. 2(a) are cross-sectional views of the welding order and weld beads formed at each position according to the present invention, and FIG. 2(b)
) is a cross-sectional photograph of a composite welded part obtained by actually manufacturing a pipe, FIG. 2 is a diagram showing an electric resistance pressure welding method for spiral steel pipes, and FIG. 3 is an electric resistance welding machine and welding position according to the present invention. 4 is a plan view of the electric resistance welding machine and welding position according to the present invention, FIG. 5 is a diagram showing the relationship between throat thickness and heat input, and FIG. 6 is a diagram showing the relationship between ramping and throat thickness. Figure 7 is a diagram showing the relationship between plate thickness and groove depth, Figure 8 is a diagram showing an example of improving welding speed with respect to plate thickness, and Figure 9 is a diagram showing the relationship between IW part length and joint. FIG. 10 is a diagram showing the relationship between strength and impact value. FIG. 11 is a diagram showing the hardness distribution before and after arc welding. 5... Electrode for internal arc welding, 6... Electrode for external arc welding, 11... Butt portion, 12... Squeezed out metal, 13... Shaped metal, 1
4...Outer surface arc welding bead, 15...Inner surface arc welding bead, 1G...Outer surface decorative bead, 17...
- Inner surface decorative bead, 18... Excess bead 523 due to electrical resistance contacting... Pre-processing frame. Patent Applicant Representative Patent Attorney Ya Fuki Tomoyuki Fig. 2 (a) @ Fig. 2 (shi) <C) ζy 5 關 1 fi 6 Fig. 1 711 nails) @8 Hei Hibi (7n71tl

Claims (2)

[Claims] (1) In the manufacture of spiral steel pipes, one side line and the other side edge of the steel strip are in a state where the root gap is negative λ
The butt parts on both sides are continuously electrically resistance welded using electrical resistance welding at the point where they meet, and the outer and inner surfaces are welded continuously or continuously using arc welding to create a molten pressure welded part and an arc welded part. High quality in the manufacture of spiral steel pipes, characterized by the composite formation of
Highly efficient welding method. (2) By setting the throat thickness of the welded part melt-welded by electric resistance welding to be as large as 50% to 100% of the plate thickness, the amount of welding and penetration of the subsequent arc welding on the outer and inner surfaces can be reduced. 2. The welding method according to claim 1, wherein the welding is carried out in such a manner that part or all of the thickness of the melt-welded welded portion remains.