JP5473796B2 - Stainless steel sheet welding method and welded joint - Google Patents

Description

  The present invention relates to a method of arc welding stainless steel plates arranged in a vertical direction and a welded joint obtained by the method, and in particular, when welding stainless steel plates arranged in a vertical direction having a thickness of about 4 mm to 12 mm. The present invention relates to a welding method for reducing welding distortion and angular deformation.

Conventionally, stainless steel has been welded by TIG welding, MIG welding, coated arc welding, or the like, but has a drawback in that welding strain increases due to its lower thermal conductivity than carbon steel. In particular, welding of an austenitic stainless steel sheet having a thickness of 4 mm or more has a problem that welding strain must be increased in two or more passes, resulting in a very large welding strain. FIG. 5 schematically shows a state in which distortion occurs in the direction indicated by the arrow on both sides of the welded portion and multi-pass welding of two or more passes causes angular deformation.
As shown in FIG. 5 (a), the mechanism in which the angular deformation is increased by multi-pass welding of two or more passes is followed by two passes as shown in FIG. 5 (b) after the first pass welding (53) is performed. When the eye (55) is welded, when the second pass solidifies and shrinks after welding, the first pass welding becomes a constraint and the stainless steel plate (51) rotates in order to prevent the shrinkage, as shown in FIG. When the third pass (57) is welded as shown in FIG. 5 (c), the welding of the first pass and the second pass is restrained, and further angular deformation occurs. Thus, the number of passes is reduced. As it increases, angular deformation increases gradually.
On the other hand, FIG. 6 schematically shows that the entire thickness is welded in one pass, but shrinkage of 1 to 2 mm occurs toward the weld as shown by the arrow in the figure, but no angular deformation occurs. Has been.
The reason why the angular deformation does not occur by welding the full thickness in one pass is that the stainless steel plate (51) does not rotate because there is no constraint that causes rotation when solidifying and shrinking after welding.

  Therefore, in Patent Document 1, for example, in a stainless steel plate arranged horizontally, the groove interval of the I groove is set to 4 mm to 9 mm, and a ceramic backing material is attached to one side and welded, thereby performing the conventional multilayer sorting. In place of welding, it has been proposed to weld each layer in one pass, but since the entire plate thickness cannot be welded in one pass, the problem of welding distortion is not solved.

  In addition, as a method for enabling welding in one pass, in Patent Document 2, in butt welding of a horizontal member or an inclined member having an inclined portion or an arc portion, a lower surface is provided on the groove lower surface and the groove upper surface of the member to be welded. A method has been proposed in which arcing is performed by placing the stopper metal and the upper metal element so as to slide as the welding progresses, inserting the tip of the welding torch into the groove surrounded by the two metal elements in the welding direction. ing.

  However, both of the methods disclosed in Patent Documents 1 and 2 perform welding by horizontally arranging stainless steel plates, and are used, for example, in wall portions of various containers and arranged vertically. It cannot be applied when welding a stainless steel plate in a state.

  On the other hand, for example, according to the electroslag welding method or the electrogas welding method, it is known that welding can be performed in one pass even in a longitudinal arrangement. However, these welding methods use two base materials to be welded. It is surrounded by a water-cooled copper plate and can be applied when the base material to be welded has a certain thickness, and is not suitable for welding with a plate thickness of 12 mm or less, for example.

In the welding of austenitic stainless steel, carbides of the deposited metal and the alloy component of the heat-affected zone are precipitated at the crystal grain boundary due to the influence of heat in the place maintained for a long time in the temperature range of 500 to 800 ° C. Thus, there is a known problem called sensitization that deteriorates corrosion resistance and causes intergranular corrosion.
This sensitization is the same as the problem that when the entire thickness is welded in one pass, the amount of welding heat input becomes large and sensitization is likely to occur.

  In addition, since austenitic stainless steel does not undergo phase transformation to ferrite unlike carbon steel, once it is distorted, it cannot be heated and corrected like carbon steel.

  In order to solve such a sensitization problem, for example, Patent Document 3 proposes a method of directly water-cooling the surface of a welded metal, and Patent Document 4 proposes a method of cooling by spraying dry ice powder. Has been. Patent Document 5 proposes a method in which a welded portion of austenitic stainless steel is cooled to −50 ° C. or lower before welding over a range of 250 mm or more from the center.

  These methods are effective as countermeasures against the problem of sensitization, but have the disadvantage that the apparatus or method becomes complicated and complicated, and do not solve the above-described problem of welding distortion.

JP 59-125268 A JP 2001-276970 A Japanese Patent Laid-Open No. 8-11824 JP-A-8-155650 JP 58-31270 A

  In the present invention, when arc welding is performed on a stainless steel plate arranged vertically, in order to eliminate angular deformation and welding distortion, the entire plate thickness is welded in one pass, particularly in the range of about 4 to 12 mm. The total thickness of the stainless steel plate is intended to be welded in one pass. In addition, when welding the entire thickness in one pass, since the welding heat input is large and the problem of sensitization is likely to occur, a means for preventing this is also provided.

  In order to achieve the above object, in the butt welding of stainless steel plates arranged vertically, a ceramic backing material is attached to one side of the groove with an I groove, and flux is entered from the opposite side. The whole plate thickness is welded in one pass by gas shielded arc welding using a wire.

The configuration of the present invention is as follows.
(1) In the method of butt welding a stainless steel plate having a thickness of 4 mm to 12 mm arranged adjacent to each other in the vertical direction, the stainless steel plate is an I groove, and the groove interval of the I groove is 3 mm to 9 mm, A ceramic backing material is attached to one side of the welded portion of the stainless steel plate, and a welding current is set to 100 to 200 A by gas shielded arc welding using a flux-cored wire from the opposite side of the one side of the stainless steel plate. A welding method characterized by welding the thickness in one pass.
(2) A water cooler having a water flow function is attached in the vicinity of the groove of the stainless steel plate, water is passed during welding, and the stainless steel plate is forcibly welded from the contact surface with the stainless steel plate of the water cooler. The welding method according to (1), wherein the part is cooled.
(3) A welded joint having a base material made of a stainless steel plate and a joint part joining the base material, wherein the joint part has a total plate thickness by gas shield arc welding in a state where the austenitic steel plate is faced up. A welded joint formed by welding in one pass.
(4) The welded joint according to (3) above, wherein the stainless steel plate has a thickness of 4 mm to 12 mm, and a width of the joint is 3 mm to 9 mm.

  An austenitic stainless steel plate having a thickness of about 4 to 12 mm arranged adjacently in the vertical direction can be welded in one pass with the entire plate thickness by arc welding. A weld joint having a weld with reduced angular deformation can be provided. In addition, the problem of sensitization can be solved.

The arrangement | positioning of a groove cross section and a torch in the welding method of this invention is shown. (A) shows a water-cooled copper plate in which a copper tube 9 for circulating cooling water is arranged in the vicinity of the groove portion of the copper plate, (b) shows an example in which a water-cooled copper plate is attached to a ceramic backing, and (c) shows The example in which the water-cooled copper plate was attached to the back side of a copper plate is shown. The detailed drawing of an example of a water-cooled copper plate is shown. A sketch of the wall panel of the large tank is shown. The example of the distortion change (angular deformation) in the conventional multipass welding is shown. The example of the distortion change in full thickness 1 pass welding is shown.

  The present invention is applied to welding of stainless steel plates arranged vertically. In particular, austenitic stainless steel plates are excellent in strength, workability, and corrosion resistance, and are therefore used in various facilities such as liquid containers and tanks used for industrial and agricultural purposes. In applications such as containers and tanks, it may be necessary to weld together austenitic stainless steel plates that are arranged adjacently in the vertical direction as wall portions.

  The stainless steel plate used in the present invention has a thickness of 4 to 12 mm. Large industrial and agricultural containers often require such a thickness from the viewpoint of strength, workability, and durability. In addition, tanks with a thickness of less than 4 mm can be welded in one pass by the conventional method without using the present invention, and those with a thickness of more than 12 mm can be electroslag welded as described above. According to the method and the electrogas welding method, welding can be performed in one pass even in a vertically oriented arrangement. Therefore, in the present invention, a stainless steel plate having a thickness of about 4 to 12 mm is targeted.

  Next, the gas shielded arc welding method of the present invention will be described with reference to the drawings. Referring to FIG. 1 (a), two austenitic stainless steel plates 1 are I-grooves, are held at a groove interval 8, and a ceramic backing material 2 is attached to one side of the welded portion of the steel plate 1. Using the flux-cored welding wire 3 from the opposite side of the one side, welding is performed while holding the welding torch so that the welding wire 3 is located at the center of the groove. As shown in FIG. 1 (b), welding is performed while confirming penetration so that a weld bead 7 can be formed by a welding arc 6. When the formation of the surface bead 7 is insufficient, the formation of the weld bead 7 is improved by moving the welding wire 3 slightly to the surface side. On the contrary, when the formation of the front surface bead 7 is excessive, the excessive formation of the weld bead is improved by moving the welding wire slightly to the back surface side.

  In the gas shielded arc welding method of the present invention, since the entire plate thickness is welded in one pass, the amount of heat input becomes large. Therefore, in order to prevent sensitization, a cooler is preferably used for welding near the groove of the steel plate. Should be installed. Although the means of a cooler is not specifically limited, in FIG. 2A, a water-cooled copper plate in which a copper tube 9 for circulating cooling water is installed in the vicinity of the groove portion of the copper plate is attached. 2B shows an example in which a water-cooled copper plate is attached to the ceramic backing, and FIG. 2C shows an example in which the water-cooled copper plate is attached to the back side of the copper plate. Further, the water-cooled copper plates shown in FIGS. 2A, 2B, and 2C can be appropriately combined and arranged.

  FIG. 3 shows a detailed view of an example of a water-cooled copper plate. 3A is a plan view of the water-cooled copper plate, FIG. 3B is a side view of the water-cooled copper plate, and FIG. 3B shows details of the cross-sectional view of the AA ′ portion. A water permeable copper pipe 9 is brazed 11 on the U-shape.

  Next, arc welding conditions will be described. In the gas shielded arc welding according to the present invention, in order to weld the stainless steel plates arranged in the vertical direction without any melting of the groove or dripping of the weld metal in one pass, the above-described movement control of the welding wire is performed. At the same time, arc welding conditions are important.

  The welding current is preferably 100 to 200A. If it is less than 100 A, the welding wire and the steel sheet are hardly melted and welding defects such as insufficient melting occur. If it exceeds 200 A, the amount of heat input is too large and the molten metal tends to sag and form a surface bead. The problem of not being able to occur. A preferable welding current is, for example, 130 to 170 A when the plate thickness is 6 mm.

  The welding voltage of the present invention is preferably 20V to 30V. If it is less than 20V, the arc becomes unstable and uniform bead formation cannot be achieved. If it exceeds 30V, the arc length becomes excessive, and the surface bead cannot be formed in the same manner as when the welding current exceeds 200A. . A more preferable welding voltage is, for example, 22V to 24V when the plate thickness is 6 mm.

  Further, in the gas shielded arc welding of the present invention, a stainless steel plate is formed with an I groove and a groove interval (gap) is set to 4 mm or more and 8 mm or less, and a flux cored wire having a diameter of 1.2 mm, for example, is used as the flux wire.

  The reason for using the flux-cored wire in the gas shielded arc welding of the present invention is to prevent the surface beads from dripping. As the flux-cored wire, for example, a metal having a composition equivalent to that of the austenitic steel sheet to be welded and containing rutile as a flux is used.

  In the present invention, a ceramic backing material is used. The type of the ceramic material is not limited, but a material mainly composed of alumina or silica can be used. By forming a groove having a width of 8 to 16 mm in the center of the backing material, it is possible to easily form a bead (back wave) on the back surface.

  In the present invention, in order to prevent sensitization, it is preferable to provide a cooler that forcibly cools the vicinity of the welded portion of the steel plate. The cooler is not particularly limited as long as it can cool the vicinity of the welded portion of the steel plate, and examples thereof include a water-cooled tube and a water-cooled plate that circulate cooling water to cool the vicinity of the welded portion of the steel plate. Preferably, water-cooled tubes and water-cooled plates for cooling the vicinity of the welded portion of the steel sheet by circulating cooling water are installed at both ends of the groove portion of the steel sheet.

In the following examples, austenitic stainless steel is used, but it goes without saying that the present invention can be applied to general stainless steels including duplex stainless steels.
Example of Arc Welding Two austenitic stainless steel (SUS316L) steel sheets (plate thickness 6 mm, width 1 m × length 1.5 m) were butted together with an I groove at a groove interval of 5 mm, welding current 170 A, welding voltage As a result of welding with a wire protruding length of 15 to 25 mm at 24 V and a welding speed of 155 mm / min to 175 mm / min, the angular deformation was extremely small, 1/900 to 7/900. The horizontal shrinkage deformation (lateral shrinkage) in the thickness direction was 1.2 mm on average.
Example of Welding of Tank Side Wall FIG. 4 shows an example of a tank made of an austenitic stainless steel plate manufactured by employing the welding method of the present invention. In FIG. 4, the side wall of the tank is composed of a vertical panel 41 made of an austenitic stainless steel plate that is divided in a large number in the circumferential direction, so that it is not necessary to carry out circumferential lateral welding at the assembly site. The welded portion is hidden by the decorative plate 43. By arc-welding the end of the vertical panel 41 under the conditions shown in the above embodiment, butt welding can be performed by one pass, and angular deformation is prevented, so stress concentration in the column can be prevented. . Also, the amount of work can be greatly reduced.

  Stainless steel plates with a thickness of 4 to 12 mm arranged adjacent to each other in the vertical direction can be welded in a single pass for the entire plate thickness by arc welding. Efficiently reduces welding distortion and angular distortion. Since a welded portion can be formed, in particular, a tank, a container, and various devices made of an austenitic stainless steel plate can be easily manufactured, and industrial applicability is high.

DESCRIPTION OF SYMBOLS 1 Stainless steel plate 2 Ceramic backing 3 Welding wire 4 Contact tip 5 Welding nozzle 6 Welding arc 7 Weld bead 8 Groove interval 9 Water-cooled water-permeable copper tube 10 Copper plate 11 Brazing 41 Vertical panel 43 Dressing plate 45 Bottom plate 47 Roofing material 51 Austenitic stainless steel sheet 53 Weld bead (1 pass)
55 Weld Bead (2 passes)
57 Weld beads (3 passes)

Claims (4)

  In the method of butt welding a stainless steel plate having a thickness of 4 mm to 12 mm arranged adjacent to each other in the vertical direction, the stainless steel plate is an I groove, and the groove interval of the I groove is 3 mm to 9 mm. A ceramic backing material is attached to one side of the welded portion, and a welding current is set to 100 to 200 A by gas shielded arc welding using a flux-cored wire from the opposite side of the one side of the stainless steel plate, and the total thickness is 1 A welding method characterized by welding by a pass.   A water cooler having a water flow function is attached near the groove of the stainless steel plate, water is passed during welding, and the welded portion of the stainless steel plate is forcibly cooled from the contact surface of the water cooler with the stainless steel plate. The welding method according to claim 1, wherein:   A weld joint having a base material made of a stainless steel plate and a joint part for joining the base material, wherein the joint part has a total thickness of one pass by gas shield arc welding in a state where the austenitic steel plate is faced up. A welded joint formed by welding.   4. The welded joint according to claim 3, wherein a thickness of the stainless steel plate is 4 mm to 12 mm, and a width of the joint portion is 3 mm to 9 mm.

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