JP2022061813A - Method for manufacturing weld joint, and flux-cored cut wire for groove filling - Google Patents

Abstract

To provide a method for manufacturing a weld joint which can secure corrosion resistance of weld metal, and can obtain a weld joint so as to be advantageous in terms of work environment and cost, and a flux-cored cut wire used in the same.SOLUTION: There are provided a method for manufacturing a weld joint that includes a flux-cored cut wire welding step of filling at least a part in a groove with a flux-cored cut wire having a flux containing a predetermined corrosion-resistant element; and a flux-cored cut wire used in the same, in which the flux-cored cut wire is composed of a steel sheath and a flux containing a predetermined corrosion-resistant element that is made to fill the inside of the steel sheath as metal and/or an alloy.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a welded joint in which a cut wire is filled in a groove provided between base materials and welded, and a flux-cored cut wire for filling the groove used therein.

In recent years, the demand for safety of structural materials has become more and more stringent. The requirements include, for example, mechanical properties (tensile strength and toughness) and corrosion resistance. Highly corrosion resistant materials are suitable for structures exposed to severe corrosive environments.

Welded structural steel with excellent strength and weldability is used in the oil tanks of crude oil tankers that transport crude oil and the oil tanks that store crude oil above and below ground. The steel oil tank is exposed to a corrosive environment due to water, salt, corrosive gas components and the like contained in the crude oil. In particular, the inner surface of the oil tank of a crude oil tanker has a unique corrosive environment due to volatile components in crude oil, mixed seawater, salt content in oil field salt water, and dew condensation due to temperature fluctuations during the day and night. do. The most effective way to prevent full-scale or local corrosion is to apply a heavy coating on the surface to shield it from the corrosive environment. However, in the painting work, the area to be applied is enormous, and repainting is required due to deterioration of the coating film, which incurs enormous costs for inspection and painting.

Therefore, conventionally, a technique for improving the corrosion resistance of a welded portion of a steel sheet has been proposed. For example, Patent Documents 1 to 3 disclose that the corrosion resistance of a welded portion is improved by controlling the ratio of Cu, Mo or W in the weld metal and the steel sheet. Further, Patent Documents 4 to 5 propose flux-cored wires for gas shielded arc welding having excellent corrosion resistance.

However, in general, an element that guarantees corrosion resistance deteriorates the high temperature crack resistance and toughness of the weld metal. Further, corrosion resistance is mainly required on the surface of the joint, and there is little need to ensure corrosion resistance even inside the joint. Furthermore, it is assumed that the corrosive environment differs between the front surface and the back surface of the joint. However, all of the techniques described in Patent Documents 1 to 5 above are premised on the use of a predetermined welding material over the entire joint. For this reason, in many cases, it takes time and effort to change the welding material, and there is a problem that an excessive manufacturing cost is required.

Therefore, in the technique for improving the corrosion resistance of the welded portion of the steel sheet, the type of the corrosion resistant element can be simply applied so that the necessary corrosion resistant element can be supplied to the required part of the welded joint and the appropriate corrosion resistant element can be applied. There is a need for technology to change the situation.
Further, from the viewpoint of improving construction efficiency, submerged arc welding (SAW), which is mainly used for plate joint welding, requires a welding material capable of large heat input welding such as single-sided welding and double-sided single-layer welding.

Japanese Unexamined Patent Publication No. 2005-21981 Japanese Unexamined Patent Publication No. 2005-23421 Japanese Unexamined Patent Publication No. 2012-1810 Japanese Unexamined Patent Publication No. 2013-226757 Japanese Unexamined Patent Publication No. 2013-226578

In view of the various problems in the above-mentioned method for manufacturing a welded joint, the present inventors have ensured the corrosion resistance of the welded portion of the steel plate, particularly the surface of the welded portion exposed to the corrosive environment, by a simple method, and the resistance of the weld metal. As a result of diligent studies on a welding joint manufacturing method that can prevent high-temperature cracking and deterioration of toughness as much as possible, and that can also be used for large heat input welding, it contains a predetermined corrosion-resistant element. We have found that the above problems can be solved by filling the groove with a cut wire containing flux and welding, and completed the present invention.

Therefore, it is an object of the present invention that a necessary corrosion-resistant element can be supplied to a necessary part of a welded joint to perform an appropriate corrosion-resistant treatment, and a welded joint having excellent corrosion resistance can be easily obtained. It is an object of the present invention to provide a method for manufacturing a welded joint that can also be used for thermal welding.

Another object of the present invention is to provide a flux-cored cut wire used in such a method for manufacturing a welded joint.

That is, the gist of the present invention is as follows.
(1) A method for manufacturing a welded joint in which a cut wire is filled in a groove provided between base materials and welded.
A flux-cored cut wire having a steel outer skin and a flux filled inside the steel outer skin is filled in any one or more layers from the first layer to the final layer in the groove and welded. Is the way
A method for producing a welded joint, wherein the flux contains one or more corrosion-resistant elements selected from the group consisting of Cr, Mo, Cu, W, Sn, and Sb as a metal and / or an alloy. ..
(2) The flux-cored cut wire is a mass ratio of the flux-cored cut wire to the total mass.
The total content of the corrosion-resistant element is 0.05% or more and 98.00% or less, and the content of the chemical component consisting of C, Si, Mn, Ni, Nb, V, Ti, Al, B, and Bi is C: 0.120% or less, Si: 2.00% or less, Mn: 3.50% or less, Ni: 5.00% or less, Nb: 0.50% or less, V: 0.500% or less, Ti: 0.50% or less, Al: 1.70% or less, B: 0.020% or less, and Bi: 0.030% or less, and also.
The method for manufacturing a welded joint according to (1) above, wherein the content of the impurity element composed of P and S is P: 0.030% or less and S: 0.020% or less.
(3) The above-mentioned (1) or (2), wherein the flux-cored cut wire is filled in the first layer in the groove, and then the solid cut wire cut from the solid wire is filled and welded. How to manufacture welded joints.
(4) The method for manufacturing a welded joint according to any one of (1) to (3) above, wherein the welding is submerged arc welding or gas shielded arc welding.

(5) A cut wire for groove filling that fills the groove provided between the base materials to manufacture a welded joint.
It has a steel husk and a flux filled inside this steel husk,
For groove filling, wherein the flux contains one or more corrosion resistant elements selected from the group consisting of Cr, Mo, Cu, W, Sn, and Sb as a metal and / or an alloy. Flux-filled cut wire.
(6) By mass ratio to the total mass of the flux-cored cut wire
The total content of the corrosion-resistant element is 0.05% or more and 98.00% or less, and the content of the chemical component consisting of C, Si, Mn, Ni, Nb, V, Ti, Al, B, and Bi is C: 0.120% or less, Si: 2.00% or less, Mn: 3.50% or less, Ni: 5.00% or less, Nb: 0.50% or less, V: 0.500% or less, Ti: 0.50% or less, Al: 1.70% or less, B: 0.020% or less, and Bi: 0.030% or less, and also.
The flux-containing cut wire for groove filling according to (5) above, wherein the content of the impurity element composed of P and S is P: 0.030% or less and S: 0.020% or less.
(7) The above-mentioned (5) or (6), wherein the layer is filled in any one or more layers from the first layer to the last layer in the groove provided between the base materials. Flux-filled cut wire for groove filling.

According to the present invention, for example, even in the case of submerged arc welding of a steel plate, the necessary corrosion-resistant element can be supplied to a necessary part of the welded joint to perform an appropriate corrosion-resistant treatment, and the corrosion resistance is easily excellent. In addition to being able to manufacture welded joints, it is also possible to handle large heat input welding.

FIG. 1 is an explanatory diagram showing an example of a flux-cored cut wire welding process in the present invention. FIG. 2 is an explanatory diagram showing another example of the flux-cored cut wire welding process in the present invention. FIG. 3 is an explanatory diagram showing the groove shape used for the evaluation in the embodiment and the state of filling the flux-cored cut wire. FIG. 4 is an explanatory diagram showing a cutout position A of the corrosion resistance test piece for evaluating the corrosion resistance of the weld metal in the examples. FIG. 5 is a schematic diagram for explaining the state of the corrosion test apparatus used for the full-scale corrosion test in the examples. FIG. 6 is a schematic diagram for explaining the state of the corrosion test apparatus used for the local corrosion (pitting corrosion) test in the examples.

The present invention uses a flux-cored cut wire having a steel outer skin and a predetermined flux filled inside the steel outer skin, and the first layer to the final layer in the groove provided between the base materials. A welded joint is manufactured by providing a flux-cored cut wire welding step in which one or more of the layers up to (corresponding to the outermost layer of the groove surface) is filled with the flux-cored cut wire and welded. ..
Hereinafter, the flux-cored cut wire according to the present invention will be described, and a method for manufacturing a welded joint using the cut wire will be described.

[Cut wire with flux]
First, the flux-cored cut wire contains one or more corrosion-resistant elements selected from the group consisting of Cr, Mo, Cu, W, Sn, and Sb as a metal and / or an alloy. Use. These corrosion-resistant elements have a function of remarkably improving the corrosion resistance of the weld metal, but are also elements that can impair the high-temperature cracking resistance and toughness of the weld metal. Therefore, it is desirable to specify the content of these corrosion-resistant elements in the flux-cored cut wire within a predetermined range in order to secure the corrosion resistance of the weld metal without deteriorating the high-temperature cracking resistance and toughness of the weld metal. Here, the corrosion-resistant element is used as a metal and / or an alloy because it melts and solidifies during welding and effectively contributes to the development of corrosion resistance as a part of the weld metal.

From the above viewpoint, the total content of corrosion-resistant elements (Cr, Mo, Cu, W, Sn, and Sb) in the flux-cored cut wire is 0.05% or more as a mass ratio to the total mass of the flux-filled cut wire. It is preferably 98.00% or less. Here, the lower limit value is preferably 0.10% or more, more preferably 0.20% or more, still more preferably 0.30% or more, and the upper limit value is 95.00%. , 90.00%, or 80.00%. The total content of the corrosion-resistant elements represents the total amount of the corrosion-resistant elements contained in the steel outer skin constituting the flux-containing cut wire and the flux filled therein, and each corrosion-resistant element contained in the flux. As long as the total mass ratio of (Cr, Mo, Cu, W, Sn, or Sb) is 0.05% or more and 98.00% or less, the content of each corrosion-resistant element is 98.00 including 0.00%. It is not particularly limited in the range of% or less, and can be obtained from the following formula 1.
0.05% ≤ [Cr] + [Mo] + [Cu] + [W] + [Sn] + [Sb] ≤ 98.00% …… Equation 1
[However, the element symbol with square brackets in Equation 1 is the mass ratio (mass%) of the element corresponding to each element symbol in the chemical component of the flux-filled cut wire to the total mass of the flux-filled cut wire. ]
When the corrosion resistant element is added to the flux-cored cut wire, the entire flux-cored cut wire melts and solidifies to become a part of the weld metal during welding. Therefore, the steel outer skin of the flux-cored cut wire and the flux. It can be done for either one or both.

Here, in order to secure the corrosion resistance of the weld metal, it is desirable that the total content of the corrosion resistant elements (Cr, Mo, Cu, W, Sn and Sb) is 0.05% or more. Further, the upper limit of the total content of corrosion-resistant elements does not exist in particular, but in the flux-containing cut wire of the present invention, the flux is filled inside the steel outer skin, so that it is substantially 98.00%. .. That is, even if the flux-containing cut wire of the present invention contains a large amount of corrosion-resistant elements, most of the weld metal is made of a welding material other than the flux-containing cut wire [for example, flux and wire in submerged arc welding (SAW)]. Does not affect the deterioration of toughness. Therefore, from the viewpoint of improving the corrosion resistance, the upper limit of the mass ratio of the corrosion resistant element is not particularly limited.

Further, in the flux-containing cut wire of the present invention, in addition to the above-mentioned metal and / or alloy of corrosion resistant elements (Cr, Mo, Cu, W, Sn and Sb), for example, the chemical component and carbon equivalent (Ceq) of the weld metal are used. ) Etc. may be contained (hereinafter, these chemical components and alloy components are simply referred to as "chemical components"). When such a chemical component is added to a cut wire containing a flux, if the added chemical component is a powder of a metal or an alloy, it melts at the time of welding in the same manner as a steel outer skin, so that it has corrosion resistance. The addition of chemical components other than elements may be added to the flux in the form of metal powder or alloy powder, for example, may be contained in the form of a steel outer skin, and further may be contained in the form of a steel outer skin. It may be included as a plating on the outer surface, and in either case, the same effect is obtained. In the case of the present invention, the chemical components other than the corrosion-resistant element are not required to have arc stability and omnidirectional weldability, unlike the case of the conventional flux-containing wire which is not a cut wire, and oxides and carbonates are not required. Since it is not necessary to be in the above state, chemical components other than the above-mentioned corrosion-resistant element can be contained in the form of metal powder or alloy powder.

Specifically, the flux-containing cut wire of the present invention contains the corrosion-resistant element contained as a metal and / or an alloy at a ratio of 0.05% or more and 98.00% or less in terms of mass ratio to the total mass of the flux-containing cut wire. In addition to containing, any one or more chemical components selected from the group consisting of C, Si, Mn, Ni, Nb, V, Ti, Al, B, and Bi are contained as optional components, and each of them is contained. The content of chemical components is C: 0.120% or less, Si: 2.00% or less, Mn: 3.50% or less, Ni: 5.00% or less, Nb: 0.50% or less, V: 0. .500% or less, Ti: 0.50% or less, Al: 1.70% or less, B: 0.020% or less, and Bi: 0.030% or less, and an impurity element composed of P and S. The contents are preferably P: 0.030% or less and S: 0.020% or less, respectively. In the present invention, by including the above-mentioned corrosion-resistant element, the corrosion resistance can be improved without including the chemical component as the optional component, so that the lower limit of the content of each of these chemical components is 0%. Is.

Of these, among the chemical components as optional components, C in "C: 0.120% or less" is an important element for ensuring the proof stress and tensile strength of the weld metal by solid solution strengthening. However, if the C content in the flux-containing cut wire exceeds 0.120%, the C content in the weld metal becomes excessive, the yield strength and tensile strength of the weld metal increase excessively, and the toughness of the weld metal Decreases. In order to stably secure all of the toughness, proof stress, and tensile strength of the weld metal, it is preferable to set the upper limit of the C content to 0.10%. On the other hand, the lower limit of the C content is 0%, but if necessary, the lower limit of the C content is 0.010%, 0.020%, 0.030%, 0.040%, or 0.050%. May be. Similarly, the upper limit of the C content may be 0.100%, 0.090%, 0.080%, or 0.070%.

Si in "Si: 2.00% or less" is a deoxidizing element and has a function of reducing the amount of oxygen in the weld metal and increasing the cleanliness of the weld metal. When the Si content in the flux-cored cut wire exceeds 2.00%, Si deteriorates the toughness of the weld metal. In order to stably secure the toughness of the weld metal, the upper limit of the Si content may be 1.90%, 1.80%, 1.70%, or 1.50%. On the other hand, the lower limit of the Si content is 0%, but if necessary, the lower limit of the Si content may be 0.01%, 0.02%, 0.03%, or 0.04%.

Mn in "Mn: 3.50% or less" is an element necessary for ensuring the hardenability of the weld metal and increasing the strength of the weld metal, but may be 0%. In order to increase the strength of the weld metal, the lower limit of the Mn content in the flux-cored cut wire may be 0.50%, 0.75%, or 1.0%. On the other hand, when the Mn content exceeds 3.50%, the grain boundary embrittlement sensitivity of the weld metal increases and the toughness of the weld metal deteriorates. Therefore, the upper limit of the Mn content is 3.50%, but the upper limit of the Mn content may be 3.00%, 2.50%, or 2.00%.

Since Ni in "Ni: 5.00% or less" is not an essential component, the lower limit of the Ni content in the flux-cored cut wire is 0%. Further, if the Ni content is too large, solidification cracking is likely to occur. Therefore, the upper limit of the Ni content is preferably 4.00%, 3.00%, or 2.00%. The lower limit of the Ni content is preferably 0.05%, 0.1%, or 0.15%.

Since Nb in "Nb: 0.50% or less" is not an essential component, the lower limit of the Nb content in the flux-cored cut wire is 0%. On the other hand, Nb forms fine carbides in the weld metal, and the fine carbides cause precipitation strengthening in the weld metal, so that Nb improves the tensile strength of the weld metal. In order to obtain the effect sufficiently, the Nb content is preferably 0.005% or more. However, it is not preferable that the Nb content exceeds 0.50% because Nb forms coarse precipitates in the weld metal and deteriorates the toughness of the weld metal. The upper limit of the Nb content is preferably 0.40%, 0.30%, 0.20%, or 0.10%.

Since V in "V: 0.500% or less" is not an essential component, the lower limit of the V content in the flux-cored cut wire is 0%. On the other hand, V is an element effective for increasing the strength of the weld metal because it improves the hardenability of the weld metal. In order to obtain the effect sufficiently, the V content is preferably 0.010% or more. When this V content exceeds 0.500%, the precipitation amount of V carbide in the weld metal becomes excessive, the weld metal is excessively hardened, and the toughness of the weld metal is deteriorated. The upper limit of the V content is preferably 0.400%, 0.300%, 0.200%, or 0.100%.

Since Ti in "Ti: 0.50% or less" is not an essential component, the lower limit of the Ti content in the flux-cored cut wire is 0%. On the other hand, Ti is a deoxidizing element and has an effect of reducing the amount of oxygen in the weld metal. Further, Ti contained in the flux-cored cut wire remains slightly in the weld metal to fix the solid solution N, and thus has an effect of alleviating the adverse effect of the solid solution N on the toughness of the weld metal. Therefore, the flux-cored cut wire may contain 0.01% or more of Ti. However, if the Ti content exceeds 0.50%, the toughness of the weld metal may deteriorate due to the formation of excessive precipitates. Here, when Ti is contained in the flux-cored cut wire, it is conceivable that ferrotitanium (an alloy of iron and titanium) is contained in the flux. The upper limit of the Ti content is preferably 0.40%, 0.30%, 0.20%, or 0.10%.

Al in "Al: 1.70% or less" is a deoxidizing element, and like Si, it reduces the amount of oxygen in the weld metal and has an effect of improving the cleanliness of the weld metal. When the Al content in the flux-cored cut wire exceeds 1.70%, Al forms nitrides, oxides and the like, and reduces the toughness of the weld metal. Therefore, the upper limit of the Al content in the flux-cored cut wire is set to 1.70%. This upper limit is preferably 1.60%, 1.50%, 1.40%, or 1.30%. The lower limit of the Al content is preferably 0.005%, 0.010%, 0.050%, 0.100%, 0.150% or 0.200%.

Since B in "B: 0.020% or less" is not an essential component, the lower limit of the B content in the flux-cored cut wire is 0%. On the other hand, since B is combined with the solid solution N in the weld metal to form a BN, it has an effect of reducing the adverse effect of the solid solution N on the toughness of the weld metal. Further, B has an effect of improving the strength of the weld metal because it enhances the hardenability of the weld metal. Therefore, the flux-cored cut wire may contain 0.0005% or more of B. However, when the B content exceeds 0.020%, B in the weld metal becomes excessive, forming coarse BN and B compounds such as Fe ₂₃ (C, B) ₆ and deteriorating the toughness of the weld metal. It is not preferable because it causes The upper limit of the B content is preferably 0.015%, 0.010%, 0.005%, 0.003%, or 0.001%.

Since Bi in "Bi: 0.020% or less" is not an essential component, the lower limit of the Bi content in the flux-cored cut wire is 0%. On the other hand, Bi is an element that improves the peelability of slag. In order to sufficiently obtain the effect, the Bi content is preferably 0.005% or more, 0.010% or more, or 0.012% or more. On the other hand, when the Bi content exceeds 0.020%, solidification cracks are likely to occur in the weld metal, so the upper limit of the Bi content is 0.020%. The upper limit of this Bi content is preferably 0.015%, 0.010%, or 0.005%.

Further, since P in "P: 0.030% or less" existing as the impurity element lowers the toughness of the weld metal, it is necessary to reduce the P content in the flux-cored cut wire as much as possible. Therefore, the lower limit of the P content is 0%. Further, when the P content is 0.030% or less, the adverse effect on the toughness of P is within an acceptable range. More preferably, the P content is 0.020% or less, 0.015% or less, or 0.010% or less in order to prevent solidification cracking of the weld metal.

If S in "S: 0.020% or less" existing as the impurity element is excessively present in the weld metal, both the toughness and ductility of the weld metal are deteriorated. Therefore, the S content in the flux-cored cut wire is as much as possible. It is desirable to reduce it. Therefore, the lower limit of the S content is 0%. Further, when the S content is 0.020% or less, the adverse effect of S on the toughness and ductility of the weld metal is within an acceptable range. More preferably, it is 0.010% or less, 0.008% or less, 0.006% or less, or 0.005% or less.

The flux-containing cut wire in the present invention may or may not contain the above-mentioned chemical components, but in addition to these chemical components and the corrosion-resistant element and the impurity element, Fe and impurities. Of these, Fe may contain iron powder in addition to the steel outer skin. That is, iron powder may be contained in the flux, if necessary, in order to adjust the packing rate of the flux in the flux-containing cut wire or to improve the welding efficiency. The content of this iron powder is not particularly limited, but it is possible that the oxygen adhering to the surface layer of the iron powder increases the oxygen content of the weld metal and lowers the toughness. The mass ratio to the total mass should be less than 90.0%, preferably less than 80.0%. The upper limit of the iron powder content may be limited to 8.0%, 6.0%, 4.0%, 2.0%, or 1.0%. Of course, since iron powder is not essential in the flux-cored cut wire according to the present invention, the lower limit of the iron powder content is 0%.

Impurities are components derived from raw materials or mixed due to various factors in the manufacturing process when the flux-cored cut wire is industrially manufactured. These are meant to be permissible as long as they do not adversely affect the flux-cored cut wire according to the present invention.

The flux-containing cut wire of the present invention also contains fluorides, oxides, carbonates and the like of metal elements other than the above-mentioned corrosion-resistant elements, chemical components and impurity elements as long as the characteristics are not impaired. May be good. In this case, the fluorides, oxides, and carbonates of the other metal elements are not included in the above-mentioned corrosion-resistant elements, chemical components, impurity elements, and the contents of Fe and impurities. However, it means that the case where these other metal elements such as fluorides, oxides and carbonates are contained is not excluded. That is, the flux-containing cut wire in the present invention contains the above-mentioned corrosion-resistant element in a predetermined ratio, and the contents of the above-mentioned chemical components and impurity elements are each in a predetermined range, and the balance is Fe and impurities or Fe. , Impurities, and fluorides, oxides, and carbonates of these other metal elements. Preferably, the above-mentioned corrosion-resistant element is contained in a predetermined ratio, the contents of the above-mentioned chemical components and impurity elements are each in a predetermined range, and the balance has a chemical composition consisting of Fe and impurities.

Further, as long as the above-mentioned matters are satisfied, the steel outer skin of the flux-containing cut wire according to the present invention is not particularly limited. For example, when the steel outer skin is made of a mild steel outer skin, the chemical composition of the outer skin is mass. C: 0.1% or less, Si: 0.10% or less, Mn: 3.00% or less, P: 0.030% or less, S: 0.020% or less, Al: 0.1% or less , And N: 0.030% or less, and the balance may be iron and impurities.

The flux-cored cut wire in the present invention can be obtained by finely cutting a steel outer skin into a predetermined length in the form of a wire filled with flux. There is no particular limitation on the shape of the cut wire containing flux, and the small-diameter steel wire can be cut into small pieces to a predetermined length to make it similar to a general cut wire having a circular cross section. However, considering that the flux is filled, the diameter thereof is preferably φ1.0 to φ3.0 mm. Incidentally, the diameter of the conventional cut wire is about φ1.0 to φ2.0 mm. On the other hand, the length of the flux-cored cut wire is preferably 0.5 to 3.5 mm. The length of a general cut wire is equivalent to 0.5 to 2.0 times the wire diameter.

Further, the flux filling rate is not particularly limited as long as the above-mentioned conditions are satisfied. For example, the lower limit of the flux filling rate may be 10% or 12% as a mass ratio to the total mass of the flux-cored cut wire. Further, the upper limit of the flux filling rate may be 80% or 90%.

Here, in the production and storage of the flux-cored cut wire of the present invention, in order to reduce the amount of diffusible hydrogen in the weld metal and prevent the problem of low-temperature cracking, it is preferable to use the appropriate method described later during production and storage. Correspondingly, it is preferable that the amount of hydrogen contained in the flux-cored cut wire is 12 ppm or less with respect to the total mass of the flux-cored cut wire. This amount of hydrogen may invade during the manufacture of the flux-cored cut wire and may increase due to the intrusion of moisture during storage of the flux-cored cut wire, and when the period from the manufacture of the cut wire to the use is long. It is desirable to store the wire while preventing the ingress of moisture.

In manufacturing the flux-cored cut wire in the present invention, the procedure and the like are not particularly limited, but the following example can be shown as a method for manufacturing the wire filled with the flux before cutting.
First, as a method for manufacturing a seamlessly shaped flux-containing cut wire in which the seams of the steel outer skin are welded and there are no slit-shaped gaps, a step of preparing the flux so that the corrosion-resistant elements, chemical components, etc. are within a predetermined range. In addition, a process of forming a U-shaped open tube by forming it using a forming roll while feeding the steel strip in the longitudinal direction, a process of supplying flux into the open tube through the opening of the open tube, and a process of supplying flux to the open tube. During or completed the process of butt-welding the opposing edges of the openings to obtain a seamless tube, the process of drawing a seamless tube to obtain a flux-filled wire having a predetermined wire diameter, and the process of drawing. A step of baking the flux-containing wire later is provided. Then, by cutting the wire to a predetermined length, a flux-cored cut wire can be obtained.

Here, the butt welding is performed by electric stitch welding, laser welding, TIG welding, or the like. Further, during the wire drawing process or after the wire drawing process is completed, annealing is performed to remove water in the wire. Preferably, the annealing temperature is 650 ° C. or higher and the annealing time is 4 hours or longer so that the H content contained in the wire is 12 ppm or less. However, in order to prevent deterioration of the flux, the annealing temperature is set to 900 ° C. or lower. Even if the gaps in the steel outer skin are brazed instead of the butt welding, a wire having no slit-shaped gaps can be obtained.

Further, it is also possible to obtain a flux-cored cut wire having a slit-shaped gap without welding the seam of the steel outer skin. In that case, instead of the process of butt-welding the ends of the open pipes to obtain a seamless pipe, the process of forming an open pipe and butt-butting the ends of the open pipes to obtain a pipe with a slit-shaped gap is performed. It is the same as the method for manufacturing a wire having a seamless shape except that the wire has a seamless shape. The method of manufacturing a wire having a slit-like gap may further include a step of crimping the end of the abutted open tube. In the method of manufacturing a wire having a slit-shaped gap, the pipe is drawn with the slit-shaped gap.

As described above, the flux-containing cut wire according to the present invention may be a wire having a seamless shape in which the seam of the steel outer skin is welded and has no slit-shaped gap, and the seam of the steel outer skin may be cut. A wire having a slit-shaped gap may be cut without being welded, but a flux-containing cut wire obtained by cutting a wire having no slit-shaped gap in a steel outer skin is preferable. .. H (hydrogen) that invades the welded portion during welding diffuses into the weld metal and the material to be welded, accumulates in the stress concentration portion, and causes low-temperature cracking. There are various sources of H, but if the cleanliness of the weld and the welding conditions are strictly controlled, the moisture (H ₂ O) contained in the flux-cored cut wire can be the source of H. Therefore, the amount of this water may affect the amount of diffusible hydrogen in the welded joint. Therefore, it is desirable to cut a seamlessly shaped wire without a slit-shaped gap, but if the wire having a slit-shaped gap is cut, for example, it is vacuum-packed and stored or dried. The flux-packed cut wire may be stored in a container that can hold the state.

Further, the flux-cored cut wire in the present invention may have an oil (lubricant) coated on its surface. The lubricant applied to the surface of the filler has the effect of suppressing the generation of rust during storage. As such a lubricant, various kinds (for example, vegetable oil such as palm oil) can be used, but in order to suppress low temperature cracking of the weld metal, a perfluoropolyether oil containing no H (hydrogen) is used. It is preferable to use (PFPE oil). When the flux-cored cut wire has plating on its surface, the lubricant is applied to the surface of the plating.

[Manufacturing method of welded joint]
Next, in manufacturing a welded joint using the above-mentioned flux-cored cut wire, in the present invention, at least a part of the groove provided between the base materials is filled with the flux-cored cut wire and welded. Provide a wire welding process. That is, in manufacturing a welded joint, the flux-cored cut wire according to the present invention is filled in the groove of the base metal and welded in any one or more of one pass to the final pass. If there is only one pass for welding, the flux-cored cut wire of the present invention is used in that one pass.

In particular, in this flux-cored cut wire welding process, at least the first layer or the final layer (the outermost layer of the groove surface) in the groove is filled with the flux-cored cut wire according to the present invention and welded. preferable. That is, the corrosion resistance of the welded portion can be improved by filling the surface of the welded portion where corrosion resistance is required with a flux-cored cut wire.

1 and 2 show an example of a flux-cored cut wire welding process in the present invention, respectively. Of these, FIG. 1 is an example in which a flux-cored cut wire 4 is filled in a part of the groove 3 provided between the base material 1 and the base material 2 and welded.
First, as shown in FIG. 1A, the backing material 5 is attached to the back surfaces of the base materials 1 and 2, and then the first layer in the groove 3 is filled with the flux-containing cut wire 4 according to the present invention. do. When corrosion resistance is required only on the surface on the first layer side, the subsequent welding is filled as shown in FIG. 1 (b) without using the flux-cored cut wire of the present invention. The welding wire 6 may be arranged on the flux-cored cut wire 4 to manufacture a welded joint.

Further, if the welding amount is insufficient only in the first layer, or if corrosion resistance at the full thickness is required, as shown in FIG. 1 (c), the flux-cored cut wire 4 filled in the first layer 4 The flux-cored cut wire 4 of the present invention is sprayed again on the weld metal 7 obtained by containing the above to fill the groove 3, and the welding wire 6 is arranged to perform welding. After that, this may be repeated until the required welding amount is reached, and welding may be performed without using the flux-cored cut wire of the present invention.

If corrosion resistance is required only in the final layer in the groove (the outermost layer of the groove surface), as shown in FIG. 1 (d), the backing material 5 is formed on the back surfaces of the base materials 1 and 2. After mounting, the welding wire 6 is arranged in the groove 3 to generate an arc, and the operation of welding is repeated as many times as necessary, and as shown in FIG. 1 (e), the flux-containing cut of the present invention is used. A plurality of weld metals 8 not including wires are joined (here, an example is shown in which about 80% of the height inside the groove is joined with three weld metals 8), and then this welding is performed. The flux-containing cut wire 4 of the present invention is sprayed and filled on the metal 8, and then, as shown in FIG. 1 (f), the welding wire 6 is placed on the substantially central portion of the filled flux-containing cut wire 4. To produce a welded joint having a final layer 9 containing the flux-containing cut wire 4 of the present invention by arranging and welding by generating an arc.

Further, as shown in FIG. 2, the flux-cored cut wire welding process according to the present invention comprises flux-cored cut wire filling 1-pass welding in which the flux-filled cut wire is filled in the groove and welded in one pass. You may do it. That is, as shown in FIG. 2A, after the backing material 5 is attached to the back surfaces of the base materials 1 and 2, in the example of FIG. 2, almost all of the groove 3 is, for example, a groove. The flux-containing cut wire 4 according to the present invention is sprayed so as to fill about 80% of the inner height. Next, as shown in FIG. 2 (b), the welding wire 6 is arranged on the substantially central portion of the filled flux-cored cut wire 4, and an arc is generated for welding, as shown in FIG. 2 (c). As described above, the welded joint is manufactured by the weld metal 7 including the flux-cored cut wire 4.
In the example of the flux-cored cut wire welding process shown in FIG. 2, since the flux-cored cut wire according to the present invention is used in almost all of the grooves, it is possible to ensure corrosion resistance over the entire plate thickness of the welded portion. can.

In FIGS. 1 and 2, an example of a so-called V-shaped groove is shown in which the groove between the base materials is a so-called V-shaped groove. , Re-shaped, K-shaped, J-shaped, X-shaped, U-shaped, H-shaped, or the like, or any other shape of the groove may be used. Further, in the present invention, single-sided welding may be used, and double-sided welding may be applicable. Further, in the case of multi-layer welding as in the example of FIG. 1, each layer may be divided into two or more passes for welding.

The welding method (welding means) used in the present invention is not particularly limited, but is preferably submerged arc welding or gas shielded arc welding in order to reliably melt the flux-cored cut wire filled in the groove. It is good to be. However, in vertical welding or upward welding, it may be difficult to fill the groove with the flux-cored cut wire, so it is desirable that the welding posture is downward or sideways.

Further, in the method for manufacturing a welded joint in the present invention, the type and shape of the base metal are not particularly limited, but the application in a situation where corrosion is a problem is most effective. That is, it is typically welding of oil tanks for transporting or storing crude oil, such as oil tanks for crude oil tankers and above-ground or underground crude oil tanks for storing crude oil.

(Example)
Next, the present invention will be described more specifically based on examples and the like. However, the following examples do not have the property of limiting the present invention, and it is within the technical scope of the present invention to change the design only for the purposes of the preceding and the following.

The flux-containing cut wires (Sample Nos. 1-44) of the present invention example and the comparative example were manufactured by the following method.
First, a U-shaped open pipe was obtained by molding using a forming roll while feeding the steel strip in the longitudinal direction. Flux was supplied into the open pipe through the opening of the open pipe, and the opposing edges of the opening of the open pipe were butt-welded to obtain a seamless pipe. This seamless tube was drawn to obtain a flux-cored wire having no slit-shaped gap. However, at that time, some of the samples were made into a tube having a slit-shaped gap without seam welding, and the wire was drawn to form a wire. In this way, a wire containing a flux having a final filler diameter of φ2.0 mm was prototyped.
In the middle of the wire drawing work of these wires, the flux-cored wire was annealed in the temperature range of 650 to 950 ° C. for 4 hours or more. After the trial production, a lubricant was applied to the surface of some wires. Then, the produced flux-cored wire was cut to a length of 2.0 mm, and each sample of the flux-cored cut wire was prepared.
When preparing the flux, the corrosion-resistant elements shown in Table 1 are used as the ferrochrome alloy powder and the ferromolybdenum alloy powder for each element of Cr and Mo, respectively, and each element of Cr, W, Sn and Sb is used. Are used as the metal powders thereof, and are shown in Tables 1 and 2 in terms of the mass ratio of each element.
The configurations of these flux-cored cut wires are shown in Tables 1 and 2.

The unit of the content of the corrosion-resistant element disclosed in Tables 1 and 2, the chemical component as an optional component and iron powder (Fe powder), and each element contained as an impurity element is the mass ratio to the total mass of the flux-filled cut wire. (Mass%).

Further, the balance in the chemical composition of the flux-cored cut wire (that is, components other than the elements disclosed in Tables 1 and 2) is iron (including intentionally added Fe powder) and impurities. The wire structure of each flux-cored cut wire is as shown in Table 1, and oil is not applied unless otherwise specified in the remarks column. On the other hand, each element contained as a chemical component in the flux-cored cut wire disclosed in Table 2 is contained in the form of a steel outer skin or a metal powder. In Tables 1 and 2, the blanks in the table relating to the contents of the corrosion-resistant element, the chemical component, and the Fe powder mean that the corrosion-resistant element, the chemical component, and the Fe powder are not intentionally added. do. In addition, corrosion-resistant elements and chemical components may be inevitably mixed.

The flux-containing cut wires of the invention example and the comparative example were evaluated by the method described below.
SAW welding was performed on SM490A having a plate thickness of 20 mm under the welding conditions and one pass shown in Table 3. At that time, the groove shape was V-shaped as shown in FIG. 3, and the spray thickness of the flux-containing cut wire 4 in the groove 3 was 18 mm. Further, NF-100 manufactured by Nippon Steel & Sumikin Welding & Co., Ltd. was used as the welding flux, and Y-DS (wire diameter φ4.8 mm) manufactured by Nippon Steel & Sumikin Welding & Co., Ltd. was used as the welding wire. The weld wire was installed perpendicular to the steel plate.

(Evaluation of corrosion resistance of weld metal)
(1) Full surface corrosion test In order to evaluate the corrosion resistance against full surface corrosion on the back surface of the upper deck of the tanker, a rectangular piece with a width of 15 mm, a length of 60 mm, and a thickness of 5 mm (corrosion resistance test for evaluation of corrosion resistance) so that only weld metal is used. The piece 11) was cut out from the cutout position A of the evaluation joint of FIG. 4 manufactured under the welding conditions shown in Table 3, and the surface thereof was polished with 600-count emery paper. The back surface and the end surface were sealed with tape so as not to be corroded, and a full-scale corrosion test was performed using the corrosion test apparatus shown in FIG.

This corrosion test apparatus is composed of a corrosion test tank 12 and a temperature control plate 13, and water 16 whose temperature is maintained at 36 ° C. is injected into the corrosion test tank 12 and is contained in the water 16. A mixed gas (introduced gas 14) consisting of 4 vol% O ₂ , 13 vol% CO ₂ , 0.01 vol% SO ₂ , 0.05 vol% H ₂ S, and the balance N ₂ was introduced into the corrosion test tank 12. It is filled with supersaturated water vapor and reproduces the corrosive environment behind the upper deck of the crude oil tank. Then, the corrosion resistance test piece 11 set on the upper and lower surfaces of the test tank is subjected to a temperature change of 180 ° C. × 3 hours + 50 ° C. × 21 hours as one cycle via a temperature control plate 13 having a built-in heater and cooling device. It was repeatedly applied for a day to generate dew condensation water on the surface of the corrosion resistance test piece 11 so as to cause total corrosion. In FIG. 5, 15 indicates the exhaust gas from the test tank.

After the above test, the rust on the surface of each corrosion resistance test piece was removed, and the amount of mass reduction due to corrosion was obtained from the mass change before and after the test, and this value was converted into the plate thickness reduction (corrosion rate on one side) per year. .. As a result, when the corrosion rate was 0.10 mm / y or less and no local corrosion was observed, the total corrosion resistance was evaluated as good.

(2) Local corrosion (pitting corrosion) test In order to evaluate the corrosion resistance of the bottom plate of the tanker oil tank to pitting corrosion, a small piece of a rectangular piece (corrosion resistance test) having a width of 15 mm, a length of 60 mm, and a thickness of 5 mm so that only weld metal is used. The piece 17) was cut out from the cutting position A of the evaluation joint of FIG. 4 manufactured under the welding conditions of Table 6, and the entire surface thereof was polished with 600-count emery paper.

Next, a test solution prepared by preparing a 10 mass% NaCl aqueous solution to a Cl ion concentration of 10 mass% and a pH of 0.85 using concentrated hydrochloric acid was prepared, and the test solution was hung through a 3 mmφ hole opened in the upper part of the corrosion resistance test piece through a Tegs to perform one corrosion resistance test. A corrosion test was performed in which each piece was immersed in 2 L of the test solution for 168 hours. The test solution was preheated and maintained at 30 ° C., and replaced with a new test solution every 24 hours.

The apparatus used for the corrosion test is shown in FIG. This corrosion test device is a double type device of a corrosion test tank 18 and a constant temperature bath 19. The test solution 20 is put in the corrosion test tank 18, and the corrosion resistance test piece 17 is suspended by a fishing line 21 and immersed in the test solution 20. Has been done. The temperature of the test solution 20 is maintained by adjusting the temperature of the water 22 placed in the constant temperature bath 19.

After the above corrosion test, after removing the rust generated on the surface of the corrosion resistance test piece, the mass difference before and after the test is calculated, and this difference is discounted by the total surface area to determine the amount of decrease in plate thickness per year (corrosion rate on both sides). I asked. As a result, when the corrosion rate was 0.50 mm / y or less, the local corrosion resistance was evaluated as good.

The results of each test evaluated by the above method are shown in Table 4.
When welding was performed using the flux-cored cut wire of the embodiment of the present invention, the corrosion resistance was good, all the weld metals passed, and the weld metal having excellent corrosion resistance could be produced. On the other hand, the comparative example was rejected due to insufficient corrosion resistance.
When welding was performed using the flux-containing cut wire of the embodiment of the present invention, high-temperature cracking did not occur, and using a No. 4 Charpy test piece cut out from the weld metal 7, JIS Z3111: 2005 As a result of the Charpy impact test conducted in accordance with the above, the Charpy absorption energy at -20 ° C was 45 J or more, and there was no problem with low temperature toughness.

As described above, according to the present invention, a welded joint having excellent corrosion resistance can be manufactured, and the construction can be advantageously carried out in terms of cost.

1, 2: Base material (steel material), 3: Groove 4: Flux-filled cut wire, 5: Backing material, 6: Welding wire, 7, 8: Welded metal, 9: Final layer (groove surface) Outermost layer), 11, 17: Corrosion resistance test piece, 12, 18: Corrosion test tank, 13: Temperature control plate, 14: Introduced gas, 15: Exhaust gas, 16, 22: Water, 19: Constant temperature bath, 20: Test Liquid, 21: Tegus, A: Cutting position of corrosion resistance test piece.

Claims (7)

It is a method of manufacturing a welded joint in which a cut wire is filled in a groove provided between base materials and welded.
A flux-cored cut wire having a steel outer skin and a flux filled inside the steel outer skin is filled in any one or more layers from the first layer to the final layer in the groove and welded. Is the way
A method for producing a welded joint, wherein the flux contains one or more corrosion-resistant elements selected from the group consisting of Cr, Mo, Cu, W, Sn, and Sb as a metal and / or an alloy. .. The flux-cored cut wire is a mass ratio of the flux-cored cut wire to the total mass.
The total content of the corrosion-resistant element is 0.05% or more and 98.00% or less, and the content of the chemical component consisting of C, Si, Mn, Ni, Nb, V, Ti, Al, B, and Bi is C: 0.120% or less, Si: 2.00% or less, Mn: 3.50% or less, Ni: 5.00% or less, Nb: 0.50% or less, V: 0.500% or less, Ti: 0.50% or less, Al: 1.70% or less, B: 0.020% or less, and Bi: 0.030% or less, and also.
The method for manufacturing a welded joint according to claim 1, wherein the content of the impurity element composed of P and S is P: 0.030% or less and S: 0.020% or less. The method for manufacturing a welded joint according to claim 1 or 2, wherein the flux-cored cut wire is filled in the layer in the groove, and then the solid cut wire in which the solid wire is cut is filled and welded. The method for manufacturing a welded joint according to any one of claims 1 to 3, wherein the welding is submerged arc welding or gas shielded arc welding. A cut wire for groove filling that fills the groove provided between the base materials to manufacture a welded joint.
It has a steel husk and a flux filled inside this steel husk,
For groove filling, wherein the flux contains one or more corrosion resistant elements selected from the group consisting of Cr, Mo, Cu, W, Sn, and Sb as a metal and / or an alloy. Flux-filled cut wire. By mass ratio to the total mass of the flux-cored cut wire
The total content of the corrosion-resistant element is 0.05% or more and 98.00% or less, and the content of the chemical component consisting of C, Si, Mn, Ni, Nb, V, Ti, Al, B, and Bi is C: 0.120% or less, Si: 2.00% or less, Mn: 3.50% or less, Ni: 5.00% or less, Nb: 0.50% or less, V: 0.500% or less, Ti: 0.50% or less, Al: 1.70% or less, B: 0.020% or less, and Bi: 0.030% or less, and also.
The flux-containing cut wire for groove filling according to claim 6, wherein the content of the impurity element composed of P and S is P: 0.030% or less and S: 0.020% or less. The groove filling according to claim 5 or 6, wherein the layer is filled in any one or more layers from the first layer to the final layer in the groove provided between the base materials. Flux-filled cut wire.

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