KR101714462B1 - Root Pass Welding - Google Patents

Abstract

(A) bonding a backing material having a toughness lowering suppressing layer, which suppresses a decrease in toughness of a superficial weld zone, between a pair of backing materials at regular intervals; (b) forming a super welded portion on the backing material; The toughness deterioration inhibiting material contains nickel, so that the toughness of the super-layer welded portion can be increased and the grain growth of the super-layer welded portion can be suppressed by the niobium, titanium and vanadium which suppress the crystal grains of the super-layer welded portion, Nickel, niobium, titanium, and vanadium are precipitated on the fused paper, and the austenite grain growth can be suppressed by the austenite stabilizer during cooling of the fused paper.

Description

{Root Pass Welding}

TECHNICAL FIELD The present invention relates to a super-layer welding method, and more particularly, to a super-layer welding method capable of preventing toughness deterioration of a super-layer welded portion welded between welded base materials, as well as suppressing grain growth.

Generally, welding of two base materials is divided into two-side welding which is welded on both sides and one-side welding which is performed only on one side.

Double-sided welding is a high quality and safety risk of the manufacturing plant because it must be removed because the welding quality is poor on the first welding layer of the first one-side welding, The time required for rearrangement of the base material is increased and the working time is increased.

On the other hand, since the backing material must be detached before and after welding in order to prevent the molten metal from being melted on the back side of the base material, the work space must be secured on the back side of the welding base material and the equipment should be equipped with the backing material. There is a drawback in that there is a risk of the worker's musculoskeletal system.

As described above, the welding of the two base materials is performed by one-side welding or two-side welding in accordance with working conditions.

Welding mainly used in shipbuilding is flux cored arc welding (FCAW) and submerged arc welding (SAW). Welding works include flux cored arc welding and submerged arc welding Welding, or combinations thereof.

Flux cored arc welding is applied to the first welding which has low risk of welding during one side welding because of low welding heat, to prevent the softness and then to complete welding using flux cored arc welding or submerged arc welding.

Gas metal arc welding (GMAW), on the other hand, enables the welding of the required quality by appropriately selecting the welding parameters such as the protective gas and the current, voltage and speed. , Heavy industry, and so on.

The quality of weld joints due to welding is required to be uniform throughout the weld line and is closely related to the shape of the weld bead. Especially, the shape of the backside bead by the superstructure is important in the joint where multi-layer welding is required.

Root pass welding is the initial layer of deposited metal formed by one or more passes. Recently, the demand for welded structures has been increasing, and the importance of the layered welding, which requires productivity and precision, has been emphasized.

On the other hand, there is a case where the backing plate is welded to the bottom of the joint to increase the welding speed without requiring a high level of function. However, when the welding is performed in this way, the thickness difference between the base material and the welded portion is made large, There is a defect that root cracks, slag inclusion and the like are liable to occur.

To reduce these drawbacks, weld joints are mainly designed to be standard V-shaped butt joints, and weld conditions are applied to form uniform backside beads. This layered welding is mainly applied to improve the welding efficiency when welding general structural steel such as ships and offshore structures.

The weld quality is primarily determined by the shape of the weld bead. This is because the shape of the weld bead is the most important factor determining the mechanical properties of the weld.

Semi-automatic welding (FCAW, GMAW) is performed by attaching a backing material to the steel structure and piping when welding it in the middle layer. The currently used backing material is a ceramic material. It does not let it flow down. This backing backing material is removed after the welding is completed.

On the other hand, the semi-automatic welding process (FCAW, GMAW) has a higher production speed than the gas tungsten arc welding (GTAW) and improves the workability by using the same process as welding after the second layer welding.

Semi-automatic welding has a disadvantage in that the toughness of the super-layer welded portion is lowered due to relatively high heat input after welding and dilution of the base material, compared to such a welded portion by manual welding.

For example, a 'butt joint welding method' is disclosed in Patent Document 1 below.

In the butt joint welding method according to the following Patent Document 1, two base materials having a thickness of 10 to 35 mm are placed in a state of being opposed to each other with an interval of 8 to 20 mm, a step of contacting the back surface of the butt- Attaching a backing material so as to close the gap, performing a flux cored arc welding or a combination of flux cored arc welding and submerged arc welding one to three times above the gap closed by the backing material, There is disclosed a step of welding two base materials while left and right weaving an arc welding wire.

The following Patent Document 2 discloses a welding method of a pipe member.

A welding method for a pipe member according to the following Patent Document 2 is a welding method for a joint portion having an improvement angle of 50 to 60 degrees with respect to a joint portion between two base materials to be welded and a root interval of 0 to 1 mm, Layer welding is performed outside the joint region, and then internal welding is performed inside the joining portion of the base material, and flux cored arc welding or gas metal arc welding is disclosed for the super-layer welding and the internal welding, respectively.

Korean Patent Publication No. 10-2008-0081799 (published on September 10, 2008) Korean Patent Publication No. 10-2012-0029650 (published on Mar. 27, 2012)

However, the conventional multi-layer welding method has a problem that the toughness of the welded portion of the superstructure is lowered due to the high heat applied to the base material and the dilution of the base material during the multi-layer welding by semi-automatic welding.

An object of the present invention is to provide a layered welding method capable of densely forming crystal grains in a superstructure welded portion by including a toughness lowering inhibiting material for suppressing grain growth in a backing material.

Another object of the present invention is to provide a layered welding method capable of increasing the toughness of a superstructure welded portion by a toughness lowering inhibiting material.

It is still another object of the present invention to provide a super-layer welding method capable of suppressing austenite grain growth during cooling of a super-layer welded portion.

According to the present invention, there is provided a method of welding a base material, comprising: (a) bonding a backing material having a toughness reduction inhibiting layer, b) forming a super-layer weld on the backing material.

In the step (a), the toughness-lowering inhibiting material may be coated or coated on the backing material and then bonded to the base material.

In the step (a), the toughness-lowering inhibiting material is coated or coated with the toughness-lowering inhibiting material while being bonded to the base material.

The toughness-lowering inhibiting material is coated or coated on the surface of the backing material.

The toughness lowering inhibiting material may be at least one selected from the group consisting of nickel (Ni), which increases the toughness of the super-layer weld, and niobium (Nb), titanium (Ti) and vanadium .

The material for inhibiting grain growth is characterized by being ferro-Nb, ferro-Ti, and ferro-V, which are mixed with iron and stabilized in the atmosphere.

The toughness lowering inhibiting material is characterized by mixing 59.7 to 73.7 wt% of nickel (Ni), 6.3 to 8.3 wt% of niobium (Nb), 6.3 to 10.3 wt% of titanium (Ti), and 13.7 to 19.7 wt% of vanadium (V) .

And the toughness-lowering inhibiting material is precipitated as nitride or carbide in the welding portion forming step.

And the toughness lowering inhibiting material is mixed with an adhesive.

The toughness-lowering inhibiting material is mixed with the adhesive in an amount of 40 to 60: 60 to 40% by weight.

The adhesive is characterized by being a liquid protein-based adhesive mainly containing carbon (C), hydrogen (H), oxygen (O) and nitrogen (N).

Also, in order to achieve the above object, the backing according to the present invention is characterized in that a toughness lowering inhibiting material is formed on the surface.

Wherein the toughness lowering inhibiting material includes a substance that inhibits grain growth of a super-layer welded portion and a substance that increases the toughness of the super-layered welded portion.

And the material for increasing the toughness is nickel (Ni).

The crystal grain inhibiting material is characterized in that at least one of niobium (Nb), titanium (Ti), and vanadium (V) is mixed.

As described above, according to the multi-layer welding method of the present invention, since nickel as a toughness lowering inhibiting substance is contained, it is possible to increase the toughness of the multi-layer welded portion and to improve the toughness of the niobium, titanium and vanadium It is possible to suppress the growth of crystal grains in the super-layer welded portion and to obtain an effect that nickel, niobium, titanium and vanadium are precipitated on the melting paper and the austenite grain growth can be suppressed by the austenite stabilizer during cooling of the melting paper.

1 is a process diagram showing a multi-layer welding method according to a preferred embodiment of the present invention,
2 is a cross-sectional view illustrating a multi-layer welding method according to a preferred embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a multi-layer welding method according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a process diagram illustrating a multi-layer welding method according to a preferred embodiment of the present invention, and FIG. 2 is a cross-sectional view illustrating a multi-layer welding method according to a preferred embodiment of the present invention.

According to a preferred embodiment of the present invention, there is provided a multi-layer welding method comprising the steps of: (a) bonding a backing material formed with a toughness inhibiting material for suppressing crystal grain growth between welded backing materials at regular intervals; (b) And forming a welded portion.

As shown in FIGS. 1 and 2, in the ultra-layer welding method according to the embodiment of the present invention, a backing material 11 is bonded to the bottom surface of two base materials 10 spaced apart at regular intervals to form a multi- The toughness lowering suppressing layer 13, to which the toughness lowering inhibiting material is applied or coated, may be formed on the backing material 11.

The backing material 11 may be made of a ceramic material having a predetermined thickness and the backing material 11 may be bonded to the base material 10 by a tape 12 made of aluminum.

Since the backing material 11 and the tape 12 are conventional ones, a detailed description thereof will be omitted.

The toughness lowering inhibiting layer 13 is a layer coated or coated with the toughness lowering inhibiting material and may be formed to have a predetermined thickness on the upper surface of the backing material 11 as shown in Fig.

The toughness lowering inhibiting material may be applied or coated on the surface of the backing material 11, more preferably on the upper surface of the backing material 11. The toughness lowering inhibiting material may be nickel Ti, and vanadium (V), which are materials for suppressing grain growth of the super-layer welded portion 14 and Ni, Nb,

Here, it is to be understood that the super-layer welded portion 14 refers to a welded portion formed by a semi-automatic welding (FCAW, GMAW, etc.) to a predetermined thickness, that is, a fused paper.

Niobium (Nb), titanium (Ti), and vanadium (V), which exist as trace elements, can be used as pure elements, but they can be oxidized in the atmosphere. Ferro-Nb, ferro-Ti, and ferro-V are preferably used.

The toughness lowering inhibiting material is preferably at least one of niobium (Nb), titanium (Ti), and vanadium (V) that inhibits crystal growth of nickel (Ni) increasing the toughness of the superstructure welded portion (14) , The mixture of 59.7 to 73.7% by weight of nickel, 6.3 to 10.3% by weight of niobium, 6.3 to 10.3% by weight of titanium and 13.7 to 19.7% by weight of vanadium can be mixed.

Nickel (Ni) is an element that forms an austenite and has an effect of stabilizing the toughness of the weld metal. When the content of nickel (Ni) is less than 59.7% by weight, the toughness of the weld metal decreases.

On the other hand, when the content of nickel (Ni) exceeds 73.7% by weight, the weld metal becomes austenite solidified, and the texture of the weld metal coarsens and toughness deteriorates. Therefore, nickel (Ni) is 59.7 to 73.7% by weight. As the nickel (Ni) source, metal Ni, Fe-Ni or Ni-Mg may also be used.

When the content of niobium (Nb) is less than 6.3 wt%, the inhibition of grain growth of the weld metal deteriorates. On the other hand, when the content of niobium (Nb) exceeds 10.3% by weight, niobium (Nb) in the weld metal is excessive and the inhibition of grain growth is reduced. Therefore, the niobium (Nb) may be 6.3 to 10.3% by weight.

Titanium (Ti) is an element having an effect of inhibiting the growth of reheated austenite grains while being relatively stable to a high temperature region of austenite by being bonded with nitrogen (N) in a molten metal to become nitride (TiN).

When the content of titanium (Ti) is less than 6.3% by weight, crystal grain growth of the weld metal deteriorates. On the other hand, if the content of titanium (Ti) exceeds 10.3% by weight, the amount of titanium (Ti) in the weld metal is excessive and the suppression of the grain growth is deteriorated. Therefore, titanium (Ti) may be 6.3 to 10.3% by weight. As the titanium (Ti) source, metal Ti or Fe-Ti may be used.

When vanadium (V) is less than 13.7 wt%, the inhibition of crystal grain growth of the weld metal deteriorates. On the other hand, when vanadium (V) exceeds 19.7 wt%, vanadium (V) in the weld metal is excessive, and the inhibition of grain growth is reduced. Therefore, vanadium (V) can be 13.7 to 19.7% by weight.

If the toughness-lowering inhibiting material is lower than the minimum content of any one element, the element may not sufficiently melt in the melting zone during the super-layer welding, so that the toughness of the super-layer welded portion due to the element or the effect of inhibiting grain boundary coarsening may not be obtained.

On the other hand, since the toughness lowering inhibiting material is in the form of a powder, it can be mixed with a protein-based adhesive such as glue to be coated or coated on the backing material 11. The protein adhesive may be a paste-like liquid such that the toughness lowering inhibiting substance is adhered to the backing material 11. [

The mixing ratio of the toughness-decreasing inhibitor to the adhesive may be in the range of 40:60 to 60:40. That is, the adhesive is intended to coat or coat the backing material 11 with the toughness lowering inhibiting material.

The adhesive is for coating or coating the surface of the backing material 11 with a toughness inhibiting material so as to be precipitated as a nitride or a carbide while spreading in a super-layer weld 14 (melting paper) formed by semi-automatic welding (FCAW, GMAW) .

Since the adhesive can not directly coat or coat the toughness lowering inhibiting material in powder form on the backing material 11, the toughness lowering inhibiting material may be applied to the backing material 11 in a liquid state like a paste, can do.

The main component of the protein adhesive is carbon (C), hydrogen (H), oxygen (O) and nitrogen (N), and contains 50 to 59% by weight of carbon (C), 6 to 8% 20 to 24% by weight of (O) and 15 to 18% by weight of nitrogen (N), and it is preferable to use an adhesive free of sulfur (S).

Since the sulfur (S) may cause high-temperature cracking in the super-layer welded portion 14, it is preferable to use a protein-based adhesive in a liquid state not containing sulfur.

In other words, it is applied or coated on the surface of the ceramic backing material to be applied after uniformly mixing liquid type protein adhesives such as gelatin (glue) and atmospheric stabilized powders of Ferro-Nb, Ferro-Ti and Ferro-V powders .

The toughening inhibiting material thus coated or coated can be used in powder form of ferro-Nb, for example, as the water (H ₂ O) is evaporated by applying or coating (drying or artificial drying) A hardened crystal grain inhibiting material consisting of ferro-Ti, ferro-V, carbon, and nitrogen and nickel (Ni) increasing toughness are applied or coated to a predetermined thickness .

FIG. 1 and FIG. 2 illustrate a multi-layer welding method according to a preferred embodiment of the present invention step by step.

As shown in FIGS. 1 and 2, in a super-layer welding method according to an embodiment of the present invention, two base materials 10 to be welded are provided, and these base materials 10 are maintained at a predetermined distance.

The backing material 11 is bonded to the bottom surface of the base material 10, which is maintained at a predetermined gap. 2 (a), the backing material 11 can be bonded with the tape 12, and the backing material 11 can be temporarily adhered not only to the aluminum tape but also by adhesive, spot welding or the like.

The tackiness reducing inhibiting material may be coated or coated on the backing material 11. The tacking or coating of the tackiness reducing inhibiting material may increase the toughness and toughness of the protein based adhesive such as glue (gelatin) (Nb), titanium (Ti), and vanadium (V), which is a crystal grain inhibiting material, in a liquid state and then drying it.

That is, the toughness-lowering inhibiting material may be coated or coated with the toughness-lowering inhibiting material while being bonded to the base material 10.

Alternatively, the toughness lowering inhibiting material may be applied or coated at the time of manufacturing the backing material 11, and the toughness lowering inhibiting material may be applied or coated by drying the toughness lowering inhibiting material mixed with the adhesive after the backing material 11 is prepared (S10).

The toughness lowering inhibiting material is a mixture of nickel (Ni) that increases the toughness of the layered weld 14, niobium (Nb) that inhibits grain growth, titanium (Ti), and vanadium (V) , 6.3 to 10.3% by weight of niobium, 6.3 to 10.3% by weight of titanium, and 13.7 to 19.7% by weight of vanadium.

After the backing material 11 is bonded to the base material 10, a multi-layered weld 14 is formed on the backing material 11 (S20).

Such a layered weld 14 may be made by semi-automatic welding such as flux core arc welding (FCAW) or gas metal arc welding (GMAW).

As shown in FIG. 2 (b), the toughness inhibiting material coated or coated on the backing material 11 is melted in the form of nitride or carbide in the layered weld 14 (melting paper) as the semi-automatic welding is performed.

That is, in the welding portion, the toughness is increased due to precipitation of nickel (Ni) contained in the toughness lowering inhibiting material coated or coated on the backing agent 11 as well as the welding, and niobium (Nb), titanium (Ti) and vanadium (V) are precipitated, growth of crystal grains is suppressed.

After the super-layer welding is completed, the super-layer welded portion 14 is cooled, and the austenite grain growth is suppressed during cooling of the super-layered welded portion 14. [

Nb, Ti, and V, which are the crystal grain inhibiting materials, are combined with carbon (C), nitrogen (N), and the like in the layered weld 14 to form carbide or nitride (Nb (C, N), Ti (C, N), or the like) is formed so as to suppress growth of austenite grains in the super-layer welded portion 14.

Nickel (Ni), which is a toughness-increasing material, is melted in the melting zone of the multi-layer weld zone 14 and inhibits the growth of austenite grains as an austenite stabilizer during cooling of the multi-layer weld zone 14.

Although the present invention has been described in detail with reference to the above embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.

10: base metal
11: backing material
12: tape
13: Toughness lowering inhibiting layer
14:

Claims (15)

(a) joining a backing material having a toughness lowering suppressing layer which suppresses a decrease in toughness of a super-layer welded portion to a bottom surface between the base materials,
(b) forming a layered weld over the backing material,
The toughness lowering inhibiting material for forming the toughness lowering inhibiting layer of the backing material may be selected from the group consisting of nickel (Ni), which increases the toughness of the super-layer weld, and niobium (Nb) and titanium Mix one or more of them with vanadium (V)
The toughness-lowering inhibiting material may be a mixture containing 59.7 to 73.7% by weight of nickel, 6.3 to 8.3% by weight of niobium, 6.3 to 10.3% by weight of titanium and 13.7 to 19.7% by weight of vanadium (V) Wherein the welding is carried out at a high temperature. The method according to claim 1,
In the step (a), the toughness-lowering inhibiting material is coated or coated on the backing material and then bonded to the base material. The method according to claim 1,
In the step (a), the toughness-lowering inhibiting material is applied or coated with the toughness-lowering inhibiting material while being bonded to the base material. The method according to claim 1,
Wherein the toughness lowering inhibiting material is coated or coated on the surface of the backing material. delete The method according to claim 1,
Wherein a material for suppressing grain growth of the super-layer welded portion is ferro-Nb, ferro-Ti, and ferro-V, which are mixed with iron and stabilized in the atmosphere . delete The method according to claim 1,
Wherein the toughness lowering inhibiting material is precipitated as a nitride or a carbide in the welding portion forming step. The method according to claim 1,
Wherein the toughness lowering inhibiting material is mixed with an adhesive. 10. The method of claim 9,
Wherein the toughness-lowering inhibiting material is mixed with the adhesive in an amount of 40 to 60: 60 to 40% by weight. 10. The method of claim 9,
Wherein the adhesive is a liquid protein-based adhesive mainly containing carbon (C), hydrogen (H), oxygen (O) and nitrogen (N). The backing member according to any one of claims 2 to 3, wherein the toughness-lowering inhibiting substance is formed on the surface. delete delete delete

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