JP2008030044A - Electrogas arc welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrogas arc welding method that reduces heat input per welding unit length below a conventional level and that makes stable welding speed possible above a conventional level. <P>SOLUTION: In a one-electrode electrogas arc welding method, two steel plates with a thickness of ≥45 mm and ≤75 mm are placed opposite to each other and welded with a single welding wire by single pass vertical position butt welding. The method is characterized in that the welding wire diameter is <2 mm, that the wire extension length is ≥70 mm, and that the heat input per groove volume satisfies 16-27 kJ/cm<SP>3</SP>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vertical electrogas arc welding method for a thick steel plate, particularly a thick steel plate having a thickness of 45 mm or more, and obtains a sound penetration shape and at the same time lowers the welding heat input, and excessive welding heat influence on the steel plate to be welded. The present invention relates to a method for preventing deterioration of various properties due to, obtaining good weld joint performance, and enabling high-efficiency welding.

  Electrogas arc welding is one of the vertical butt welding methods of steel plates as shown in FIG. 6, in which a sliding copper plate 2 is arranged on one side of a groove of a material to be welded 1 and a backing material 3 made of ceramics or copper is arranged on one side. In this welding method, gas shield arc welding is performed by feeding the electrode wire 4 from above to a groove surrounded by the sliding copper plate 2, the workpiece 1 and the backing material 3.

  The electrogas arc welding method is used in a wide range of fields such as ships, oil storage tanks, bridges and the like because high-efficiency welding is achieved compared to other welding methods. Particularly in the marine field, this welding method is also applied to welding of extremely thick plates having a plate thickness of 45 mm or more, such as a chassis rake and a hatch combing portion of a container ship.

  Further, the material to be welded 1 is further thickened, the welding amount is insufficient with a single electrode wire 4, or the welding efficiency needs to be further increased, and further, welding defects such as poor fusion are prevented. When the necessity arises, Patent Document 1 discloses a multi-electrode electrogas arc welding method in which a plurality of electrode wires are arranged in the thickness direction and one or both of them are slid in the thickness direction. Yes.

  In recent years, the tendency of ships to increase in size has been remarkable, and accordingly, the thickness of steel plates applied to the above-described members has been increasing.

  On the other hand, the heat input per unit length of the electrogas arc welding method outlined in FIG. 6 (generally called welding heat input and expressed in units such as kJ / cm) is input from the electrode wire. Since it is obtained by dividing the amount of heat (welding current x welding voltage) by the welding speed, when the input heat amount is constant, the plate thickness of the welded member increases and the welding speed decreases, and the welding unit length The heat input per hit will increase.

  When the heat input per weld unit length increases, the time during which the weld heat affected zone is exposed to a high temperature becomes longer, and the cooling rate from the high temperature decreases, so the toughness of the weld heat affected zone tends to decrease. In recent years, high-strength materials such as YP390 and higher have been used, but generally the toughness of welded joints tends to decrease as the strength of high-strength materials increases. It is necessary to reduce the heat input per welding unit length.

  Patent Document 2 discloses that by increasing the length of the welding wire, the melting rate of the wire increases and the heat input per welding unit length decreases. However, if the protrusion becomes long, it causes meandering of the wire. Therefore, the increase in protrusion is limited, and an extremely long protrusion length such as 70 mm or more has not been attempted.

Further, if the protruding length is lengthened to increase the melting rate of the wire and the heat input per welding unit length is reduced, welding defects such as poor penetration are likely to occur. It is not disclosed what welding conditions can be used for stable welding when the protruding length is increased to reduce the heat input per welding unit length.
Japanese Patent No. 3741402 Japanese Examined Patent Publication No. 61-2480

  The present invention has been made to solve the above-mentioned problems of the prior art, and reduces the heat input per unit length of welding when electrogas arc welding is performed on a thick steel plate of 45 mm or more in one pass. It is an object of the present invention to provide an electrogas arc welding method that enables the above-described welding speed and enables stable welding without causing welding defects such as poor penetration.

  The present invention adopts an extremely long protrusion length of 70 mm or more, which has not been attempted before, and uses the Joule heat generation at the protrusion to increase the melting rate of the wire to reduce the heat input per welding unit length. In such a state, the welding method enables stable welding without generating welding defects such as poor penetration.

  In the Joule heat generation at the protrusion, the heat generation per unit volume is proportional to the square of the current density. Therefore, it is advantageous in heating the wire to increase the current density by reducing the wire diameter.

  In electrogas arc welding, a considerably wide groove having a width of about 1/2 to 1/3 of the plate thickness is employed. The groove is filled with molten metal in the welding wire. The molten metal in which the groove is filled also melts the material to be welded by the heat it holds, and the metal in which the wire and the material to be welded are fused together to solidify to form a weld metal. Heat generation in welding (arc heat generation and Joule heat generation in the wire) is mainly consumed for melting the welding wire and heating the molten pool.

  For this reason, heat generated in welding (welding current × welding voltage) is first transmitted to the molten metal filling the groove, and this heat further melts the workpiece. The inventor pays attention to this and is closely related to how much heat the molten metal that fills the groove has per unit volume can melt the welded material. I found out.

  That is, if the heat input per groove volume is large, the material to be welded will also melt, and unmelted residue will hardly occur.If the heat input per groove volume is small, the material to be welded will be less melted and unmelted. It tends to occur. By managing the heat input per groove volume within an appropriate range, stable welding can be performed even when the heat input per weld unit length is reduced.

The heat input q _g (kJ / cm ³ ) per groove volume is calculated from the equation (from the welding current I (A), the welding voltage V (V), the welding speed v (cm / s), and the groove area s (cm ² ). It is required as in 1).

q _g = IV / (1000 vs) (1)
The optimum range of heat input per groove volume varies depending on the plate thickness and the number of electrodes, and the optimum range is set for each.

  Also, if the wire protrusion is extremely long, it may be difficult to feed the wire to the groove center due to the meandering of the wire. If the wire approaches either of the grooves, the penetration becomes uneven. In extreme cases, the wire comes into contact with the groove or the metal and welding becomes extremely unstable. In order to solve such a problem, it is effective to attach a wire guide electrically insulated from the contact tip at the tip of the contact tip.

  The present invention has been made on the basis of the above-described findings, and the gist thereof is as follows.

1. A first invention is a one-electrode electrogas arc welding method in which two steel plates having a thickness of 45 mm or more and 75 mm or less are opposed to each other and one-pass vertical butt welding is performed with one welding wire. The electrogas arc welding method is characterized in that the welding wire protrusion length is less than 2 mm, the welding wire protrusion length is 70 mm or more, and the heat input per groove volume satisfies 16 to 27 kJ / cm ³ .

2. A second invention is a two-electrode electrogas arc welding method in which two steel plates having a thickness of 65 mm or more and 95 mm or less are opposed to each other, and these are welded in one pass by butt welding with two welding wires. The electrogas arc welding method is characterized in that the protruding length of at least one welding wire is less than 2 mm, 70 mm or more, and the heat input per groove volume satisfies 15 to 24 kJ / cm ³ .

  3. A third invention is the welding method according to the first invention or the second invention, wherein a wire guide electrically insulated from the contact tip is provided at the tip of the contact tip. Is the method.

    According to the present invention, it is possible to significantly reduce the welding heat input of electrogas arc welding, so that it is possible to prevent a decrease in the toughness of the weld heat affected zone. Moreover, although the heat input is reduced as compared with the conventional electrogas arc welding, the welding speed can be increased more than before, so that the welding efficiency is improved.

  One mode for carrying out the present invention will be described with reference to FIG. Here, the case of one-electrode electrogas arc welding will be described. A current is supplied to the contact tip 7 from the welding power source 13. The other terminal of the welding power source 13 is electrically connected to the workpiece 1. The wire 4 is supplied by a wire supply device 14. The protruding portion 11 is set to be considerably longer than the conventional method. Power is supplied to the welding wire 4 from the contact tip 7, and the wire is Joule-heated at the protruding portion 11. Thereafter, the wire is melted by the heat of the arc 5 generated from the tip of the wire and is transferred as a droplet 8 to a material to be welded to form a molten pool 9. The molten pool 9 melts a part of the material to be welded and then solidifies to become the weld metal 10.

  Another embodiment for carrying out the present invention will be described with reference to FIG. In the case of two-electrode electrogas arc welding, another wire 18, a wire guide 17, a contact tip 16, a wire supply device 21, and a welding power source 22 are added in parallel to the configuration of FIG. The same reference numerals in FIG. 2 as those in FIG. Note that 19 is an arc, 20 is a droplet, and 23 is a protruding portion.

  The most important thing in the present invention is that the protruding portions 11 and 23 are made significantly longer than before, the wires 4 and 18 are preheated to increase the melting rate of the wires, and welding can be stably performed even in such a state. It is to be.

  First, in the present invention, the diameters of the welding wires 4 and 18 are less than 2 mm. If the wire diameter is large, the current density flowing through the wires 4 and 18 decreases, so the preheating effect at the protruding portions 11 and 23 of the welding wire is small. For this reason, the effect of increasing the melting rate of the wire is small, and the effect of reducing heat input is also small. For this reason, the wire diameter is limited to less than 2 mm.

  If the protrusions 11 and 23 are lengthened, the wire is preheated by resistance heating, so that the melting rate of the wire can be increased and welding heat input can be reduced. However, if the protrusions 11 and 23 are less than 70 mm, the effect is small. The protruding length of one wire is 70 mm or more. However, if the protrusion length is too long, the heat input per groove volume becomes small, and is preferably 110 mm or less.

When welding steel plates with a thickness of 45 mm or more and 75 mm or less by one-electrode electrogas arc welding, the heat input per groove volume is less than 27 kJ / cm ^3, and the effect of reducing the heat input per unit length is small. Therefore, it shall be 27 kJ / cm3 or less. Further, if it is less than 16 kJ / cm ³ , undissolved residue is generated, so that it is 16 kJ / cm ³ or more.

Further, when welding steel plates having a thickness of 65 mm or more and 95 mm or less by two-electrode electrogas arc welding, the heat input per groove volume is set to 15 to 24 kJ / cm ³ for the same reason.

  Moreover, if the protrusion parts 11 and 23 become long, it will become difficult to supply a wire to the target position by the bending of a wire. In order to solve this problem, it is effective to provide wire guides 15 and 17 that are electrically insulated from the contact chips 7 and 16 before the contact chips 7 and 16. The wire guides 15 and 17 are manufactured by combining a heat-resistant resin, ceramic, or these and a metal.

  Examples of the present invention will be described below in comparison with comparative examples that are out of the scope of the present invention.

  It is an example of 1 electrode electrogas arc welding. A YP390N / mm2 grade steel plate having a thickness of 50, 60, 65, and 70 mm was used as the material to be welded 1, a water-cooled copper plate 2 on the groove front side, and a ceramic fixed backing material 3 on the back side.

  As the welding wire 4, a flux-cored wire having a diameter of 1.6 mm (equivalent to JIS Z3319 YFEG-22C) was used, and carbon dioxide gas was allowed to flow at 30 l / min as the shielding gas. As the welding power source 13, a DC constant voltage power source was used, and the welding wire 4 side was a plus (DCEP).

  FIG. 3 is a diagram showing the groove shape, and the groove width is W1 on the back side and W2 on the front side. FIG. 4 is a view showing a feeding position of the welding wire 4. The welding wire 4 oscillated from a position of 6 mm from the groove front side to a position of 10 mm on the back side with the groove center as a target position.

  When the protruding length was 70 mm or more, the wire guide 15 was attached to the tip of the contact chip 7 in order to prevent the wire 4 from meandering. The wire guide 15 is made of tubular alumina. When the protruding length of the wire is 70 to 90 mm, the wire guide 15 has a length of 50 mm, and when the protruding length exceeds 90 mm, the wire guide 15 has a length of 75 mm. In both cases, the hole diameter at the tip of the wire guide was 2.0 mm.

  About 500 mm long welding was performed under the welding conditions shown in Table 1. The weld section cross section sample and the bead appearance were examined for the presence of unmelted weld sections.

  In Table 1, A to D are examples in which a steel sheet having a thickness of 50 mm is welded. A has a protruding length of 40 mm and is a conventional welding condition. B and C are examples of the present invention in which the protruding lengths are 73 and 95 mm, respectively, and the heat input per groove volume is within the scope of the present invention. Compared with conventional welding conditions, the heat input per unit length of welding was greatly reduced, but no undissolved residue was observed. D is an example in which the protruding length is 120 mm. However, since the protruding length is too long, the heat input per groove volume falls below the range of the present invention, and unmelted residue is generated.

  E to N are examples in which steel plates having a thickness of 60 mm are welded. H is a conventional welding condition. M is an example in which the protruding length is 120 mm. Since the heat input per groove volume is below the range of the present invention, undissolved residue was generated. E, F, G, J, K, L, and N are examples of the present invention. However, the heat input per weld unit length is greatly reduced and no undissolved residue is seen in comparison with the conventional conditions. It was.

    P to V are examples in which a steel plate having a thickness of 65 mm is welded. P, Q, and R are conventional welding conditions. U is an example in which the protruding length is 120 mm. Since the heat input per groove volume is below the range of the present invention, undissolved residue is generated. Although S, T, and V are examples of the present invention, the heat input per unit length of welding was greatly reduced as compared with the conventional conditions, and no undissolved residue was observed.

    W to Z are examples in which a steel plate having a thickness of 70 mm is welded. W is a conventional welding condition. Z is an example in which the protruding length is 115 mm, and since the heat input per groove volume is below the range of the present invention, undissolved residue is generated. X and Y are examples of the present invention, but in both cases, the heat input per weld unit length was significantly reduced compared to the conventional conditions, and no undissolved residue was found.

  It is an example of the electrogas arc welding of 2 electrodes. As the material 1 to be welded, YP390N / mm2 grade steel plates having a thickness of 80, 70, and 90 mm were used, a water-cooled copper plate 2 was installed on the groove front side, and a ceramic fixed backing material 3 was installed on the back side.

  A flux-cored wire (corresponding to JIS Z3319 YFEG-22C) having a diameter of 1.6 mm was used for both the welding wire 4 on the front side and the wire 18 on the back side, and carbon dioxide gas was allowed to flow at 30 l / min as the shielding gas. As the welding power source, a DC constant voltage power source was used, the front side wire 4 (table 2 wire X) was wire plus (DCEP), and the back side wire 18 (table 2 wire Y) was wire minus (DCEN).

  The groove shape is the same as that of the first embodiment. FIG. 5 is a view showing a feeding position of the welding wires 4 and 18. The welding wires 4 and 18 were aimed at the groove center, and the wire X oscillated from a position 10 mm from the groove front side to a position 10 mm from the wire Y. The back side wire Y was fixed at a position 30 mm from the back side of the groove.

  When the protruding length was 70 mm or more, the wire guides 15 and 17 were attached to the tips of the contact tips 7 and 16 in order to prevent the wires from meandering. The wire guide is made of tubular alumina. When the protruding length of the wire is 70 to 90 mm, the wire guide is 50 mm long. When the protruding length exceeds 90 mm, the wire guide is 75 mm long. In both cases, the hole diameter at the tip of the wire guide was 2.0 mm.

  About 500 mm long welding was performed under the welding conditions shown in Table 2. The weld section cross section sample and the bead appearance were examined for the presence of unmelted weld sections.

  In Table 2, a to g are examples in which a steel plate having a thickness of 80 mm is welded. a, b, and c are conventional welding conditions. d, e, and f are examples of the present invention. Compared with conventional welding conditions, the heat input per unit length of welding was greatly reduced, but no undissolved residue was observed. “g” is an example in which the protruding length is 125 mm. However, since the protruding length is too long, the heat input per groove volume falls below the range of the present invention, and undissolved residue is generated.

  hm is an example in which a steel plate having a thickness of 70 mm is welded. h is a conventional welding condition. m is an example in which the protruding length is 120 mm. Since the heat input per groove volume is below the range of the present invention, undissolved residue was generated. Although j and k are examples of the present invention, the heat input per unit length of welding was greatly reduced as compared with the conventional conditions, and no undissolved residue was observed.

  ns is an example in which a steel plate having a thickness of 90 mm is welded. n is a conventional welding condition. s is an example in which the protrusion is 120 mm, and since the heat input per groove volume is below the range of the present invention, undissolved material is generated. p, q, and r are examples of the present invention, but in all cases, compared with the conventional conditions, the heat input per unit length of welding was greatly reduced, and no undissolved residue was observed.

  t is an example in which a steel plate having a thickness of 70 mm is welded, and the protruding length of the wire X is 60 mm and the protruding length of the wire Y is 140 mm. This is an example of the present invention in which the heat input per groove volume falls within the scope of the present invention. Compared to the conventional conditions, the heat input per weld unit length was significantly reduced and no undissolved residue was found.

According to the present invention, the following effects are obtained, which is extremely useful industrially.
1. Since it is possible to significantly reduce the welding heat input of electrogas arc welding, it is possible to prevent a decrease in the toughness of the weld heat affected zone and improve the safety of the structure.
2. In spite of the reduced heat input compared to the conventional electrogas arc welding, the welding speed can be greatly increased compared to the conventional one, and the welding efficiency is improved.

It is a figure which shows one embodiment of this invention. It is a figure which shows another one embodiment of this invention. It is a figure which shows the shape of a groove | channel. It is a figure which shows the supply position of the wire in a groove | channel in 1 electrode welding. It is a figure which shows the supply position of the wire in a groove | channel in 2 electrode welding. It is explanatory drawing which showed the electrogas arc welding method typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 To-be-welded material 2 Sliding copper plate 3 Backing material 4, 18 Wire 5, 19 Arc 7, 16 Contact tip 8, 20 Droplet 9 Molten pool 10 Weld metal 11, 23 Protruding part 13, 22 Welding power source 14, 21 Wire Supply device 15, 17 Wire guide

Claims (3)

In a one-electrode electrogas arc welding method in which two steel plates having a thickness of 45 mm or more and 75 mm or less are opposed to each other and one-pass vertical butt welding is performed with one welding wire, the welding wire diameter is less than 2 mm, An electrogas arc welding method characterized in that the protruding length is 70 mm or more and the heat input per groove volume satisfies 16 to 27 kJ / cm ³ . In a two-electrode electrogas arc welding method in which two steel plates having a thickness of 65 mm or more and 95 mm or less are opposed to each other and they are butt welded in one pass with two welding wires, the welding wire diameter is less than 2 mm, and at least one The welding length of the welding wire is 70 mm or more, and the heat input per groove volume satisfies 15 to 24 kJ / cm ³ .   3. The welding method according to claim 1, wherein a wire guide electrically insulated from the contact tip is provided at the tip of the contact tip.

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