JP2017127895A - Flux-cored wire, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flux-cored wire capable of reducing a diffusible hydrogen content of a weld joint, and a manufacturing method thereof.SOLUTION: A flux-cored wire comprises: a steel coat; a copper plating formed on the outer face of the steel coat; and a flux filled inside of the steel coat. The opening total area of the cracking, as viewed from the surface of the copper plating, is 3.0% or less in the total area of the cracking opening observed from the surface of the copper plating.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a flux-cored wire and a method for manufacturing the same.

  Welding members such as steel structures are often welded, and various welding materials are known as various welding materials (for example, gas shielded arc welding), and various wires have been proposed. Yes.

For example, Patent Document 1 discloses a technique related to a solid wire in which a large number of cracks are formed on the surface layer. The technique disclosed in Patent Document 1 generates a large number of cracks on the surface of the solid wire, thereby increasing the retention capacity of the lubricating oil, reducing the supply resistance of the solid wire in the conduit, It relates to a technology that enhances feeding performance.
Patent Document 2 discloses a technique related to a welding material in which the average length of cracks having a width of 1 μm or more present on the surface of a steel wire is 12 μm or less.
The technique disclosed in Patent Document 2 relates to a technique for improving the feedability of a solid wire by forming the above-described crack on the surface of the solid wire.

Japanese Examined Patent Publication No. 04-048553 JP 09-141487 A

  By the way, since welding defects cause direct or indirect causes of various destruction accidents, the quality of welded members such as steel structures is often determined by the state of welding. Among welding defects, low temperature cracks are harmful defects that can be the starting point of fatigue cracks and brittle fractures, and suppression of low temperature cracks is an extremely important technical issue.

  It is known that reducing the amount of diffusible hydrogen is effective in suppressing cold cracking, and many findings have been disclosed so far.

For example, paying attention to the lubricating oil applied to the surface of the wire, the lubricating oil generally contains hydrogen like a hydrocarbon represented by C _m H _n (m, n: positive integer). The lubricating oil applied to the wire tends to cause an increase in diffusible hydrogen in the welded joint. Therefore, application of an excessive amount of lubricating oil tends to be harmful from the viewpoint of increasing the risk of cold cracking.
However, if no lubricating oil is applied to the wire, there is a problem that the wire buckles due to friction with the conduit cable and the welding is interrupted.
For this reason, the amount of lubricating oil applied to the surface should be kept to a minimum that can ensure wire feedability in terms of suppressing the buckling of the wire while reducing the amount of diffusible hydrogen in the welded joint. is there.

For example, as described above, Patent Document 1 discloses a technique for increasing the retention capacity of a lubricating oil by generating a large number of cracks on the surface of a solid wire.
As described above, Patent Document 2 discloses a technique related to a solid wire having a specific size crack on the wire surface.
However, if the lubricating oil infiltrates into the cracks on the surface of the solid wire, the lubricating oil may be applied more than necessary. Lubricating oil that has entered the interior of the crack is difficult to remove even if the surface of the solid wire is wiped off, which can increase the amount of diffusible hydrogen in the welded joint.

The techniques described in these patent documents are limited to solid wires, and mainly improve the feedability of solid wires. Furthermore, the techniques described in these patent documents are not related to flux-cored wires, but the knowledge of suppressing cracks on the wire surface and reducing the amount of diffusible hydrogen in welded joints is completely disclosed for flux-cored wires. There wasn't.
Thus, in the flux-cored wire, the actual situation is that a technique for suppressing cracking of the surface of the flux-cored wire and reducing the amount of diffusible hydrogen in the welded joint has not been established.

  This invention is made | formed in view of the said situation, and provides the flux cored wire which can reduce the amount of diffusible hydrogen of a welded joint, and its manufacturing method.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that the total opening area of cracks observed on the surface of the flux-cored wire is 3.0% or less in terms of the area fraction with respect to the observation target area. Thus, it was found that a flux-cored wire capable of reducing the amount of diffusible hydrogen in the welded joint can be obtained.
Further, the flux-cored wire of the present invention has a total content of at least one element of Si, Mn, Al, Ti, Zr, and Cr among the alloy components of the steel sheet to be a steel outer sheath of 1.00% by mass or less. It is found that the steel sheet is obtained by annealing into a tubular body after tube forming in an atmosphere having an oxygen partial pressure of 0.5 Torr or less in the middle of wire drawing and at least one after completion of wire drawing. It was.
That is, the gist of the present invention is as follows.

(1) a steel outer shell,
Copper plating formed on the outer surface of the steel outer skin,
A flux filled in the steel outer shell,
Have
A flux-cored wire having a total area of crack openings observed from the surface of the copper plating of 3.0% or less in terms of an area fraction with respect to the observation target area.
(2) Of the components contained in the steel outer shell, the total content of at least one element selected from the group consisting of Si, Mn, Al, Ti, Zr, and Cr is a mass relative to the entire steel outer shell. The flux cored wire according to (1), which has a ratio of 1.00% or less.
(3) The flux cored wire according to (1) or (2), wherein a lubricating oil is applied to a surface of the copper plating.

(4) Among the components contained in the steel outer shell, the total content of at least one element selected from the group consisting of Si, Mn, Al, Ti, Zr, and Cr is a mass ratio with respect to the entire steel outer shell. Forming a steel sheet of 1.00% or less into an open pipe, filling the open pipe with a flux, closing the opening of the open pipe filled with the flux, forming the pipe, and then drawing. ,
Pickling after the wire drawing;
Performing copper plating on the outer surface of the steel outer skin after the pickling;
Have
A method of manufacturing a flux-cored wire that anneals the tubular body after being tube-formed in an atmosphere having an oxygen partial pressure of 0.5 Torr or less at least during or after the wire drawing.
(5) The method for manufacturing a flux-cored wire according to (4), further including a step of applying a lubricating oil to the surface of the copper plating formed on the outer surface of the steel outer skin.

  ADVANTAGE OF THE INVENTION According to this invention, the flux cored wire which can reduce the amount of diffusible hydrogen of a welded joint, and its manufacturing method can be provided.

It is a figure which shows the microscope picture of the flux-cored wire surface of the example of this invention. It is a figure which shows the microscope picture of the flux-cored wire surface of a comparative example.

  In the flux cored wire of the present invention, the amount of diffusible hydrogen in the welded joint is reduced. Specifically, the flux-cored wire of the present invention can reduce the amount of lubricating oil infiltrating into the cracks by reducing the surface cracks. The amount of hydrogen is reduced. For this reason, the basis of the present invention is how to reduce cracks on the surface of the flux-cored wire. From this point of view, the present inventors have conducted research focusing on grain boundary oxidation on the surface of the flux-cored wire.

  The cause of cracks on the surface of the flux-cored wire is grain boundary oxidation that occurs when the flux-cored wire is annealed, and the grain boundary oxidized part is locally discharged by pickling, which is a pre-process of copper plating, and cracks occur. Will occur. For this reason, how to suppress grain boundary oxidation is important for suppression of cracking.

  So far, cracks have been studied mainly for solid wires (sometimes referred to as steel wires). From the viewpoint of ensuring the toughness of the weld metal by keeping the oxygen content of the weld metal below a certain level, deoxidizing elements such as Si and Mn are essential components, and metal elements such as Si and Mn are alloy elements in the solid wire. As contained. However, the present inventors have paid attention to the fact that elements such as Si and Mn are easily concentrated due to grain boundary segregation, which causes grain boundary oxidation.

On the other hand, in the flux-cored wire, the component of the steel outer shell and the component of the flux filled in the steel outer shell can be separated and controlled. That is, the deoxidizing element, which is an element for grain boundary oxidation, is contained in the steel outer shell in a certain amount or less, and the content of the deoxidizing element necessary for the entire wire can be supplied from the flux as metal powder. .
For this reason, the inventors have found that the flux-cored wire of the present invention can almost completely suppress grain boundary oxidation, which was difficult to suppress with a solid wire.

Specifically, at least one selected from the group consisting of alloy elements that cause internal oxidation, that is, Si, Mn, Al, Ti, Zr, and Cr, among the components contained in the steel sheath of the flux-cored wire. The total content of the two elements is 1.00% or less in terms of the mass ratio of the flux-cored wire to the entire steel outer sheath, and the oxygen partial pressure during annealing of the flux-cored wire is 0.5 Torr or less. It has been found that oxidation can be suppressed almost completely.
As a result, the present inventors have found that a flux-cored wire that can reduce the amount of diffusible hydrogen in a welded joint can be obtained.

Hereinafter, the flux-cored wire of the present invention will be described together with a manufacturing method.
In addition, in this specification, the numerical range represented using "to" means the range which includes the numerical value described before and behind "to" as a lower limit and an upper limit.

  The method for producing a flux-cored wire of the present invention is a method of forming a steel sheet having a total content of specific elements of 1.00% or less in a mass ratio with respect to the entire steel outer shell into an open pipe, filling the open pipe with a flux, After the opening of the open pipe filled with the flux is closed and formed into a pipe, the step of drawing, the step of pickling after drawing, and the step of copper plating on the outer surface of the steel outer shell after pickling Have. Then, the tubular body after being tube-formed is annealed in an atmosphere where the oxygen partial pressure is 0.5 Torr or less at least during or after the drawing.

Specifically, the flux-cored wire of the present invention can be manufactured by the following manufacturing process.
First, the total content of at least one element selected from the group consisting of Si, Mn, Al, Ti, Zr, and Cr, which is a steel outer shell, is 1.00% or less in terms of mass ratio with respect to the entire steel outer shell. A steel strip (steel plate) is prepared. And the flux mix | blended so that a flux etc. may become predetermined | prescribed content is prepared. As for the component of the flux, the slag component contained in the flux and the component of the metal flux are determined according to the steel strip (steel plate) having the above components.

  Next, while feeding the steel strip in the longitudinal direction, it is formed into an open tube (U-shaped) with a forming roll to form a steel outer cover. During the molding, flux is supplied from the opening of the open tube, the opposing edge surfaces of the opening are butted and a slit-like gap is welded. A slit-like tube having no gap obtained by welding is drawn to obtain a slit-like wire having a desired wire diameter.

The method for producing a flux-cored wire according to the present invention includes a slit for controlling the oxygen partial pressure to 0.5 Torr or less (preferably 0.3 Torr or less) in the middle of wire drawing and at least one after completion of wire drawing. The tubular body is annealed after being formed into a pipe having no gap.
In addition, as a method for controlling the oxygen partial pressure within the above range, an industrial method can be appropriately selected as in a vacuum atmosphere, an active gas atmosphere such as argon, nitrogen, or the like. The lower limit of the oxygen partial pressure is not particularly limited, but is preferably 0.1 Torr or more from the viewpoint of wire productivity.
Although annealing conditions are not specifically limited, For example, the temperature range of 400 to 800 degreeC is mentioned. The annealing applied to at least one of the wire drawing and after completion of the wire drawing can be performed at least once, and may be performed on the tubular body in the middle of wire drawing, or may be performed on the tubular body after the wire drawing is completed. Also good.

  And after drawing (including annealing), the flux-cored wire of the present invention is obtained through the steps of pickling and copper plating. Pickling and copper plating are not particularly limited, and may be performed according to a conventional method.

  Furthermore, lubricating oil is applied to the surface of the flux-cored wire obtained through the above-described process and subjected to copper plating. After applying lubricating oil to the surface of the flux-cored wire, excess lubricating oil is wiped off by a wiping means such as felt.

  Next, each element of the flux cored wire of the present invention will be described.

(Steel hull)
The steel plate used for the steel outer shell will be described. The total content of at least one element selected from the group consisting of Si, Mn, Al, Ti, Zr, and Cr among the components contained in the steel sheet used as the steel outer shell is based on the entire steel outer shell of the flux-cored wire. The mass ratio is 1.00% or less.
The reason why the total content is limited to 1.00% or less by mass ratio with respect to the entire steel outer sheath of the flux-cored wire is to suppress grain boundary oxidation and to suppress cracking of the flux-cored wire surface as described above. . The total content of at least one element selected from the group consisting of Si, Mn, Al, Ti, Zr, and Cr is 0.80% by mass or less in terms of further suppressing grain boundary oxidation. Preferably, it is 0.50 mass% or less.
There is no particular restriction on the lower limit of the total content of each element of Si, Mn, Al, Ti, Zr, and Cr, but if the alloy elements are extremely reduced, the steel outer shell is soft and the strength tends to be insufficient, There is a concern of breaking when drawing. For this reason, it is preferable that the minimum of the total content of the said component is 0.20 mass% or more.

The elements contained in the steel outer shell may contain elements such as Ni, Cu, Mo, C, V, and Nb, which are elements that do not cause internal oxidation, but contain these elements. The amount is not limited.
And the remainder of the steel plate used as a steel outer shell consists of Fe and impurities. In addition, an impurity refers to the component contained in a raw material, or the component mixed in in the process of manufacture, and was not intentionally contained in the steel plate.

(flux)
The component contained in the flux is not particularly limited, for example, metal powder such as Si, Mn, Al, Ti, and Zr; does not cause internal oxidation such as Ni, Cu, Mo, C, V, and Nb Metal powders; metal oxides such as Si oxide, Mn oxide, Al oxide, Ti oxide, and Zr oxide; arc stabilizers and the like.
The flux-cored wire of the present invention is limited in the content of Si, Mn, Al, Ti, Zr, and Cr in the steel outer shell, and when a desired component cannot be obtained in the weld metal, It can be compensated by preparing a metal component. What is necessary is just to determine the content of the component contained in a flux according to the component in the steel outer shell, the quality of the weld joint which formed the weld metal, etc.

  Moreover, it is preferable that the mass% (filling rate) of the flux filled in the steel outer shell with respect to the total mass of the flux-cored wire is 6.0% to 18.0%. The flux contained in the steel outer shell is in a powder state, and the flux is wound from the steel outer shell to stabilize the position in the flux-cored wire. When the flux filling rate is 6.0% or more, the flux filled in the space inside the steel outer sheath is suppressed from moving in the flux-cored wire, and the position is stabilized. Generation | occurrence | production of the disconnection at the time of performing a wire drawing at the time of flux cored wire manufacture as a flux filling factor is 18.0% or less is suppressed.

(Copper plating)
Copper plating suppresses the wear of the contact tip, improves the power supply from the contact tip, and stabilizes the arc. Although the thickness of copper plating is not specifically limited, For example, it is good that they are 0.3 micrometer-1.2 micrometers.

(Lubricant)
There is no restriction | limiting in particular in the lubricating oil apply | coated to the surface of a flux cored wire, For example, you may use any lubricating oil, such as a machine oil type | system | group, palm oil type | system | group, animal and vegetable oil type | system | group. Further, for example, various additives such as an additive (antioxidant) for preventing oxidation of the lubricating oil may be added.

  The amount of lubricating oil applied to the surface of the flux-cored wire is a mass ratio (ppm) with respect to the total mass of the flux-cored wire as the amount after wiping with a wiping member such as felt from the point of reducing the amount of diffusible hydrogen. It is preferably 30 ppm or less, preferably 25 ppm or less, more preferably 20 ppm or less, and further preferably 15 ppm or less. Although it does not specifically limit as a minimum, It is good to set it as 2 ppm or more from points, such as wire feeding property.

  Next, cracks observed from the surface of the flux-cored wire of the present invention will be described.

  In the flux-cored wire of the present invention obtained by the manufacturing method described above, the total area of the crack openings observed from the copper-plated surface is 3.0% or less in terms of the area fraction with respect to the observation target area. In the flux-cored wire of the present invention, the total area of the opening of cracks observed on the surface of the flux-cored wire is 2.0% or less in terms of the area fraction with respect to the observation target area in that the amount of diffusible hydrogen is further suppressed. It is preferably 1.5% or less, more preferably 1.0% or less, still more preferably 0.5% or less, and particularly preferably 0%. That is, the total area of the openings is 0% to 3.0% in area fraction.

The crack of the surface of the flux-cored wire is investigated by observing a range of 100 μm × 500 μm (flux-cored wire width direction × flux-cored wire longitudinal direction) with a 100 × optical microscope. In the optical microscope image, the crack opening is observed in black, and the portion without crack is observed in white. This is binarized by image processing, and the total area of crack openings within the observation area is calculated by computer processing.
In addition, in this specification, the crack of the surface of a flux cored wire observes the copper plating surface given to the surface of the steel outer shell.

  When the surface crack of the flux-cored wire of the present invention is in the above range, the amount of diffusible hydrogen measured using the flux-cored wire of the present invention according to JIS Z 3118 is 2 ppm or less. Reduced. It is also possible to reduce the amount of diffusible hydrogen to less than 1 ppm by controlling the total opening area of the cracks observed on the wire surface.

  The flux-cored wire of the present invention is not limited to the one obtained by the above manufacturing method, and the total area of the opening of cracks observed from the surface plated with copper is 3 as an area fraction with respect to the observation target area. Even when the wire surface is intentionally cracked so as to be 0.0% or less, there may be an effect of reducing the amount of diffusible hydrogen in the welded joint.

  The wire diameter of the flux-cored wire of the present invention is not particularly limited, but is preferably in the range of 1.2 mm to 1.6 mm, for example, from the viewpoints of welding efficiency and productivity of the flux-cored wire.

The flux cored wire of the present invention can be used as follows, for example.
The flux cored wire of the present invention can be applied as a welding material for gas shielded arc welding, and can be used as a welding material for a welding method in which two steel materials are welded by gas shielded arc welding.
In addition, the flux-cored wire of the present invention is used as a welding material for gas shield arc welding, so that a weld metal formed by gas shield arc welding is formed, and a weld joint in which the weld metal is formed is obtained. Examples of the welded joint include those having a weld metal and two steel materials sandwiching the weld metal. For example, a welded member including a welded joint having a weld metal and two steel materials sandwiching the weld metal can be manufactured using the flux-cored wire of the present invention.

When the flux-cored wire of the present invention is used as a welding material for gas shield arc welding, the shield gas used when performing gas shield arc welding is not particularly limited, and a conventionally known shield gas can be used. Examples of the shielding gas include a single gas such as Ar gas, He gas, CO ₂ , and a mixed gas obtained by mixing at least one gas of O ₂ and CO ₂ with at least one gas of Ar gas and He gas. It is done.

  Since the welded joint welded using the flux-cored wire of the present invention has a reduced amount of diffusible hydrogen, the occurrence of cold cracking is suppressed. Thereby, a welding member with few welding defects is obtained.

  The present invention is not limited to the above. The above is an exemplification, and any technology that has substantially the same configuration as the technical idea described in the claims of the present invention and has the same operational effects can be used. To be included in the scope.

  Hereinafter, although the result of having verified the effect of the present invention based on an example is indicated, the present invention is not limited to this. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

  Table 1 shows the steel outer skin components of the prototyped flux-cored wire. Each element is shown in mass%. The balance is iron and 0.05 mass% C and impurities. After forming the steel sheath of the components shown in Table 1 into an open tube, the flux of the components shown in Table 2 was filled so as to be a mass ratio of 13% with respect to the total mass of the flux-cored wire, and wire drawing was performed. In the middle of wire drawing, annealing was performed at an oxygen partial pressure shown in Table 1 and in an Ar atmosphere at 700 ° C. for 10 hours. After pickling, Cu plating was performed on the outer surface of the steel outer skin. Thereafter, vegetable oil was applied as a lubricating oil to the surface of the wire plated with Cu, and the excess lubricating oil was wiped off with a felt to finish a flux-cored wire. In this way, a flux-cored wire with an outer diameter of 1.2 mm, in which a flux was filled in a steel outer shell with a plate thickness (wall thickness) of 0.16 mm, was produced. Note that all the flux-cored wires prepared were wires having no slit-like gaps in the seam-welded steel outer sheath.

As described above, the crack was examined by observing a visual field range of 100 μm × 500 μm (flux-cored wire width direction × flux-cored wire longitudinal direction) with a 100 × microscope. In the microscopic image, the crack opening is observed in black, and the portion without crack is observed in white. This was binarized by image processing, and the total area of crack openings in the observation area was calculated by computer processing to calculate the area fraction relative to the observation target area. The results are shown in Table 5.
The amount of lubricating oil applied to the surface of the flux-cored wire was calculated as a mass ratio (ppm) with respect to the total mass of the flux-cored wire from the mass difference generated before and after washing the lubricating oil with an organic solvent. The results are shown in Table 5.
Table 3 shows the components of the test steel used for measuring the amount of diffusible hydrogen. The amount of diffusible hydrogen was measured according to the method defined in JIS Z 3118 and welded under the welding conditions shown in Table 4. Table 5 shows the measurement results of the amount of diffusible hydrogen. In this example, the amount of diffusible hydrogen was determined to be 2 ppm or less, and when it was 1 ppm or less, it was determined that a clearer hydrogen reduction effect was expressed.

  Since the wire numbers 1 to 10 are prevented from cracking the wire surface, the amount of lubricant applied is reduced. For this reason, the amount of diffusible hydrogen was reduced to 2 ppm or less, and all passed. In wire numbers 8 to 10, the amount of the component contained in the steel outer shell that causes grain boundary oxidation is particularly low, so that the amount of lubricating oil is particularly low. Therefore, the amount of diffusible hydrogen was less than 1 ppm, and a clearer diffusible hydrogen reduction effect was expressed.

  On the other hand, No. 11 to No. 18 contained a large amount of components that cause grain boundary oxidation, so that cracking of the wire surface could not be suppressed and the amount of lubricating oil could not be reduced. For this reason, the amount of diffusible hydrogen did not satisfy the standard value, and it was rejected.

  In order to verify this result, the result of observing the flux-cored wire surface is shown in FIG. 1 and FIG. When the photograph of the wire surface (a) of wire number 10 according to the present invention (see FIG. 1) and the wire surface (b) of wire number 19 (see FIG. 2) as a comparative example are compared, the amount of cracks generated is It can be recognized that there is a clear difference.

  The flux-cored wire of the present invention is useful in that the amount of diffusible hydrogen in a welded joint can be dramatically reduced even when subjected to welding. In addition, the flux-cored wire of the present invention can be used for welding by using a conventional flux-cored wire welding apparatus as it is, and there is no need to improve the equipment. Therefore, the flux-cored wire of the present invention has great industrial applicability.

Claims (5)

A steel hull,
Copper plating formed on the outer surface of the steel outer skin,
A flux filled in the steel outer shell,
Have
A flux-cored wire having a total area of crack openings observed from the surface of the copper plating of 3.0% or less in terms of an area fraction with respect to the observation target area.   Among the components contained in the steel outer shell, the total content of at least one element selected from the group consisting of Si, Mn, Al, Ti, Zr, and Cr is 1 by mass ratio with respect to the entire steel outer shell. The flux cored wire according to claim 1, which is 0.000% or less.   The flux cored wire according to claim 1, wherein a lubricating oil is applied to a surface of the copper plating. Among the components contained in the steel shell, the total content of at least one element selected from the group consisting of Si, Mn, Al, Ti, Zr, and Cr is 1. Forming a steel plate of 00% or less into an open tube, filling the open tube with a flux, closing the opening of the open tube filled with the flux, forming a tube, and then drawing;
Pickling after the wire drawing;
Performing copper plating on the outer surface of the steel outer skin after the pickling;
Have
A method of manufacturing a flux-cored wire that anneals the tubular body after being tube-formed in an atmosphere having an oxygen partial pressure of 0.5 Torr or less at least during or after the wire drawing.   Furthermore, the manufacturing method of the flux cored wire of Claim 4 which has the process of apply | coating lubricating oil to the surface of the said copper plating formed in the outer surface of the said steel outer shell.