JPH06234076A - Welding method for double layered steels - Google Patents

Abstract

PURPOSE:To perform butt welding of double layered steels clad on both surface above specified thickness with stainless steel or a Ni-base alloy as surface layer material with high accuracy. CONSTITUTION:In butt welding of double layered steels clad on both surfaces having thickness of >=18mm, the welding method of double layered steels where a double-V groove having the root face of 2-4mm in the vicinity of the central part of thickness is formed as a groove shape of double layered steels, first, welding is performed up to the vicinity of the base height of the surface layer material 1 by using a carbon steel or low alloy steel wire 5 on one side, then, the surface layer material part is welded by using a stainless steel or Ni-base alloy wire 9 and then, the groove face of the opposite side is subjected to lamination welding by the same method is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for butt-welding a double-sided clad multi-layer steel material having a plate thickness of 18 mm or more with a carbon steel or a low alloy steel as an inner layer and a surface layer made of stainless steel or a Ni-based alloy. .

[0002]

2. Description of the Related Art In recent years, from the viewpoint of safety and economy, large diameter line pipes for transporting crude oil and natural gas containing a large amount of corrosive substances, and stainless steel or nickel alloy on the inner surface have been used as a composite material to provide corrosion resistance and acid resistance. The use of clad steel pipes made of carbon steel or low alloy steel, which has good strength and toughness on the outer surface side, is increasing.

In the production of this clad steel pipe, the clad steel plate is formed by a known roll forming and UOE method, and then the clad portion is subjected to vertical seam welding to obtain a product.
In this welding, when the weld metal of the outer surface material comes into contact with the above-mentioned laminated material and a part of the laminated material is melted, elements such as stainless steel such as Ni and Cr are mixed into the weld metal of the outer surface material and cracks occur. Material deterioration may occur.

To prevent this, JP-A-60-154
Japanese Patent Laid-Open No. 87577 discloses a method of widening the opening width of the groove on the side of the mating material, and Japanese Patent Laid-Open No. 1-31577 discloses one-layer welding in which a back wave is generated from a base metal on the outer surface side by a submerged arc. A method of TIG welding a laminated material has been proposed.

[0005]

However, in all of these welding methods, the joining material is only on one side, and the outer surface of the steel pipe has corrosion resistance on both surfaces (hereinafter referred to as surface material). It cannot be applied to the butt welding of multi-layer clad steel made of. That is, when submerged arc welding is performed from the base material on the outer surface side, a part of the surface layer material is melted, and Ni, Cr which are constituent elements such as stainless steel are melted.
And the like are mixed in the deposited metal, causing material deterioration such as cracking.

In the present invention, the surface layer material is stainless steel or N.
The i-based alloy, the inner layer material is a carbon steel or a low alloy steel and is obtained by various studies from various directions for the most preferable method of butt welding the double-sided clad multi-layer steel material with a plate thickness of 18 mm or more by arc. The purpose is to provide a welding method in which the inner layer weld metal component is a carbon steel or low alloy steel similar to the inner layer material component in consideration of strength and toughness, and the surface layer weld metal is stainless steel or Ni-based alloy component close to the surface layer material component. To do.

[0007]

In order to solve the above problems, the present invention uses a carbon steel or a low alloy steel as an inner layer material and a stainless steel or a Ni-based alloy as a surface layer material and has a plate thickness of 18 mm or more. In the butt welding of the double-sided clad multi-layer steel material, the groove of the end face of the multi-layer steel material welded portion is an X-shaped groove having a root surface of 2 to 4 mm in the vicinity of the central portion of the plate thickness, and first one side is carbon steel or Weld the low-alloy steel wire close to the height of the bottom surface of the surface material, then weld the surface material using stainless steel or Ni-based alloy wire, and then stack the groove surface on the opposite side in the same way. The gist is a welding method for a multi-layer steel material, which is characterized by welding. Further, the present invention uses the MAG welding method for the double-sided first layer welding, performs metal touch on both sides, and uses the parallel twin arc MAG welding method for the surface layer welding,
The butt welding of the multi-layer steel materials described above is performed with higher efficiency.

[0008]

The operation of the present invention will be described below with reference to FIG. Surface material 1, 2 made of SUS316L
Further, an X-shaped groove having groove angles of θ1 and θ2 and a root face b of 2 to 4 mm is provided in the vicinity of the central portion of the plate thickness in a multilayer steel plate having a plate thickness t of which the inner layer material 3 is made of SM400. Here, the groove angles θ1 and θ2 need to be 60 ° or more, and the position of the root surface b near the center of the plate thickness is
This is a position where the difference Δd between the groove depths d1 and d2 is within 2 mm. Then, continuous tack welding is performed on the deeper groove of 0 to 2 mm to form the tack bead 4.

Next, as shown in FIG. 1, a wire 5 having a component similar to that of SM400 is used from the opposite side of the groove where the temporary bead 4 is placed, without causing burn-through in MAG welding, and First layer welding is performed by selecting welding conditions such that the amount of deposition reaches the bottom surface of the surface layer material 1 or becomes slightly lower. And, following this first layer bead 6, S
Stainless steel wires 9 and 9'corresponding to US316L are arranged in parallel and twin arcs 8 and 8'are generated to form the surface bead 10.

After that, the base metal is reversed, and the above-mentioned initial layer and surface layer welding is carried out in the same manner on the groove where the temporary bead 4 is placed. By using the above-mentioned welding means, it is a two-layer welding of a double-sided low alloy component first layer and a stainless steel component surface layer as shown in FIG. 3, and a butt having a performance equivalent to the intended use performance of a multi-layer steel material. Weld beads can be obtained.

Generally, the penetration in MAG welding is shallow, and in double-sided butt welding of thick plates, gouging is performed to ensure a metal touch when welding the opposite side.
Doing this is not preferable in terms of work environment and efficiency. By limiting the groove root height to 2 to 4 mm for a multi-layer steel material having a plate thickness of 18 mm or more, the present inventors can reliably perform a metal touch without gouging when welding the opposite side. Found that there is.

In order to make a metal touch without gouging, it is desirable to make the groove root face as thin as possible. However, in the stable welding condition range in MAG tack welding, burn-through will occur if the root face is less than 2 mm. It tends to occur. Further, if the welding input is reduced so as not to cause burn-through, an unstable welding phenomenon is exhibited, continuous tack beads cannot be formed, and defects occur in the subsequent first layer welding.
Therefore, a root surface of 2 mm or more is required to maintain a stable bead.

On the other hand, when the groove root surface exceeds 4 mm,
Since the groove becomes smaller when the plate thickness is 18 mm, the double-sided first layer MA
In G welding, with a welding current that keeps the wire welding speed reaching the bottom surface of the surface layer joining material, a certain amount of penetration cannot be obtained, and the unmelted portion remains as a defective fusion defect. That is, if the plate thickness is 18 mm and the root surface exceeds 4 mm, there is no welding condition that satisfies both the appropriate wire welding speed and the metal touch, so the root surface needs to be kept to 4 mm or less.

Further, the groove angles θ1 and θ2 of the X-shaped groove are the same as the reason why the root surface exceeds 4 mm, and the groove area becomes smaller as the angle becomes smaller. 18 mm requires at least 60 ° or more. It is not necessary to specify the upper limit of the groove angle,
If it is too wide, it takes time to process and the width of the surface layer weld bead must be widened, and the welding efficiency will decrease.
It is better to keep it to about 0 °.

Further, a root surface b taken near the center of plate thickness
Is the difference Δd between the groove depths d1 and d2.
It is desirable to be within mm. This is because when the difference exceeds 2 mm, with a thin plate thickness of 18 mm, the groove area on the shallow groove depth side becomes small and the balance between penetration and wire welding amount is lost, and the surface layer material is lost. This is because there is a risk of melting or insufficient melting. Δd
Is less than 2 mm, the temporary bead is placed in the deeper part of d so that the welding conditions for the first layer on the inner and outer surfaces can be made substantially the same, so that the condition setting becomes easy.

When the plate thickness is large, after the first layer MAG, the same carbon steel or low alloy steel wire as that of the first layer is used, and laminating welding can be performed until the wire welding amount reaches the bottom surface of the surface layer joining material. Good. At this time, if the groove width exceeds 13 mm, distribution welding is performed to advance the lamination, or the parallel twin arc welding method used in the surface layer welding can be used for this lamination welding to perform efficient welding. .

Although the problem of metal touch can be solved by using the submerged arc welding method capable of obtaining deep penetration in the first layer, it is difficult to keep the wire welding amount at the wire welding speed reaching the bottom surface of the surface layer joining material. Therefore, it is difficult to secure both metal touch and welding amount control at the same time. The generated slag treatment also poses a problem during surface layer welding.

[0018]

[Example] Surface layer material is SUS316L (thickness 2 m each
m), the inner layer material is SM400 and the plate thickness is 18 to 25 mm.
The double-sided clad multi-layer steel sheet of
MAG tack welding was performed on the entire outer surface on one side under the conditions shown in Table 1.

[0019]

[Table 1]

Then, MAG welding was performed from the groove surface on the side opposite to the tack welded surface under the welding conditions shown in Table 2.
In addition, the shield gas component in temporary attachment and inner layer welding is 20
% CO ₂ + Ar, 100% CO ₂ in surface layer welding, and the flow rate is 20 liters / minute in each case.

[0021]

[Table 2]

The wire to be tested is J for temporary attachment and inner layer welding.
IS Z 3312 YGW12 equivalent solid wire (abbreviated as solid), JIS Z 331 for surface layer welding
A 1.2 mm diameter flux-cored wire (abbreviated as FCW) equivalent to 3YFW24 was used. Wire protrusion length is 15m
m. Then, the welding condition was observed, a bead inspection was performed after welding, and the quality of the bead was determined. The results are shown in Table 3.

[0023]

[Table 3]

In Comparative Example A, a plate having a thickness of 18 mm and a root surface of 1 m
Although a groove of m was prepared and tack welding was performed under the standard conditions of Table 1, the subsequent welding could not be performed because a burn-through occurred during the welding. Therefore, in Comparative Example B, the tack welding was set to a low input condition to prevent burn-through in tack welding, but since the root surface was thin and the tack bead was small, burn-through occurred in the inner surface first layer welding. . on the other hand,
In Comparative Example C in which the root face was too thick, fusion failure occurred in the central portion of the plate thickness. Further, in Comparative Example D in which the groove depth was unbalanced, the amount of welding of the inner surface first layer bead having a shallow groove depth was excessive and the surface layer component was mixed in, resulting in cracking. Also,
Since the weld metal in the first layer was piled up near the surface of the surface layer, the excess amount of weld metal in the surface layer became too high, and the bead appearance deteriorated. Furthermore, in Comparative Example E in which the surface layer was welded with a single wire, the bead width did not widen, and a groove residue and an undercut occurred.

On the other hand, the test No. to which the present invention was applied was applied to the multi-layer steel sheet having a plate thickness of 18 to 25 mm. For F, G, H and I, there is no temporary burn-in, no burn-through in the first layer welding of the inner surface, the amount of welding in the first layer is controlled slightly below the bottom surface of the surface material, and the metal touch and bead appearance are also good and sound. A good weld is obtained.

[0026]

As described above, by applying the present invention to the butt welding of multi-layer steel sheets, which has been difficult with the conventional welding method for single-sided clad steel, a sound welded joint can be obtained without gouging during welding. It is possible to obtain a welded joint having properties similar to those of the multi-layer steel sheet.
Therefore, it is a technology that can be widely used for processing new materials, and has a great industrial effect.

[Brief description of drawings]

FIG. 1 is a perspective explanatory view showing a welding method for a multi-layer steel product according to the present invention.

FIG. 2 is a view showing a groove shape in the welding method of the present invention.

3 is a photograph showing a macro metal structure of a cross section (test No. G) of a welded portion obtained by butt-welding a multi-layer steel material according to the present invention.

[Explanation of symbols]

 1 outer surface side surface material 2 inner surface side surface material 3 inner layer material 4 temporary bead 5 carbon steel or low alloy steel wire 6 first layer welding bead 7 first layer welding arc 8, 8'surface layer welding arc 9, 9'surface layer welding wire 10 Surface weld bead θ1, θ2 Groove angle d1, d2 Groove angle b Root surface t Plate thickness

Claims (3)

[Claims] 1. A plate thickness 18 comprising carbon steel or a low alloy steel as an inner layer material and stainless steel or a Ni-based alloy as a surface layer material.
In butt welding of a double-sided clad multi-layer steel material of mm or more, the groove of the end surface of the multi-layer steel material welded portion is an X-shaped groove having a root surface of 2 to 4 mm in the vicinity of the central part of the plate thickness, and first one side is carbon Welding is performed using steel or low alloy steel wire up to near the bottom surface of the surface layer material, and then stainless steel or N
A welding method for a multi-layer steel material, comprising welding a surface material portion using an i-based alloy wire, and then laminating and welding the groove surface on the opposite side by a similar method. 2. The method for welding a multi-layer steel product according to claim 1, wherein MAG welding is used for both-side first layer welding to perform metal touch on both sides. 3. The welding of a multi-layer steel product according to claim 1, wherein two wires are arranged in a direction substantially perpendicular to the welding direction and a MAG welding method in which a parallel twin arc is generated is used for the surface material welding. Method.