JP2016083677A - Flux-cored wire for gas shield arc-welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flux-cored wire capable of reducing moisture absorption, and suppressing cold crack of weld metal, in production and storage of a wire.SOLUTION: A flux-cored wire for gas shield arc-welding is characterized in that, at least a part of a flux is a flux produced by an atomization method.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a flux-cored wire for gas shielded arc welding (hereinafter sometimes referred to as FCW) in which a steel outer sheath is filled with a flux, and in particular, an FCW containing a flux produced by an atomizing method. It is about. The FCW of the present invention is used for arc welding of steel materials.

Flux-cored wires are widely used because of their good workability and workability during welding. However, in gas shielded arc welding using a flux-cored wire, generally, the flux filled in the wire is a low base flux mainly composed of TiO ₂ , so that the amount of oxygen in the weld metal is high. For this reason, it is difficult to obtain a weld metal having good toughness as compared with other welding methods.

  As a technique for improving this problem, as a flux, in addition to oxides such as titanium oxide and aluminum oxide, a fluoride is further added to reduce the amount of oxygen in the weld metal. And the like.

  These oxides and fluorides absorb water vapor in the air during the manufacture and storage of the wire in addition to the water contained in the oxides and fluorides, and these moistures cause the amount of hydrogen in the weld metal (diffusible hydrogen content). There were many problems that caused cold cracking of the weld metal. Therefore, in the production of the flux-cored wire, it is necessary to select a raw material having a low moisture content and to strictly control the moisture absorption during the production and storage of the wire.

  In addition, as a technique for reducing the moisture content of the flux, Patent Document 5 discloses that Na, K, Al, and Si, which adhere to the surface of titanium oxide particles and reduce the moisture absorption resistance, are removed by surface polishing. And the technique of reducing the moisture content of a titanium oxide is disclosed.

  However, this technology is effective if the main moisture in the flux is derived from the elements attached to it, but this technology is effective when the main moisture in the flux is derived from absorption of the flux components. Even if it is adopted, it is difficult to exert the effect.

  Further, instead of a flux that easily absorbs moisture, a compound such as a complex oxide that contains elements constituting the flux and hardly absorbs moisture can be used as a flux material. However, since the ratio of the elements contained in the compound is usually determined, it is difficult to adjust the composition of the flux when the compound is used as a flux raw material.

  On the other hand, as a flux for submerged arc welding, a melt-type flux is known, which reduces moisture absorption and is easy to handle and store as compared with a calcined flux. An attempt to use a melt-type flux for a flux-cored wire is disclosed in Patent Document 3 above. However, the invention described in Patent Document 3 does not take into account the moisture absorption during the production and storage of the wire.

  Such a melt-type flux has a reduced moisture absorption compared to a calcined flux, but is generally manufactured by mechanically pulverizing a melted raw material, so that it becomes an angular polyhedral flux and contains moisture. The contact area with air is wide, and there is room for further improvement in reducing the moisture content of the flux.

Japanese Patent Laid-Open No. 06-1555079 JP 08-257785 A JP 09-248694 A JP2013-018012A JP 2012-055970 A

  As described above, attempts have been made to use a melt-type flux for a flux-cored wire. However, moisture absorption during the manufacture and storage of a flux-cored wire containing a melt-type flux, and its cold cracking resistance. The effects on sex have not been studied.

  In view of the above-described problems in the background art, the present invention reduces moisture absorption and suppresses low-temperature cracking of the weld metal in the production and storage of the wire in the flux-cored wire containing the melt-type flux. It is an object to provide a flux-cored wire that can be produced.

  In order to prevent the flux from coming into contact with air during the manufacture and storage of the wire to absorb moisture in the air and increase the amount of diffusible hydrogen in the weld metal, contact between the flux and air It was sufficient to reduce the flux, and a study was made on a flux having a low surface area. The present inventors have found that when at least a part of the flux is produced by the atomizing method, the flux has a substantially spherical shape, and a flux having a low surface area can be obtained.

  Furthermore, the flux produced by the atomizing method is substantially spherical, unlike the angular polyhedron flux obtained by mechanical pulverization, so that it is possible to suppress damage to the steel outer shell during wire drawing. .

  This invention is made | formed based on the said knowledge, The place made into the summary is as follows.

(1) A flux-cored wire for gas shielded arc welding, wherein at least a part of the flux is a flux produced by an atomizing method.
(2) The flux produced by the atomization method includes one or more fluorides of BaF ₂ , MgF ₂ , CaF ₂ , SrF ₂ and AlF ₃ , Al ₂ O ₃ , SiO ₂ , ZrO ₂ , The flux for gas shielded arc welding according to (1) above, which is manufactured by an atomizing method using one or more oxides of MgO, CaO, BaO, SrO, MnO and TiO ₂ as raw materials. Cored wire.
(3) The fluoride content is 1.0% or more and 4.0% or less, and the oxide content is 1.0% or more and 4.0% or less in terms of F with respect to the total mass of the wire. The flux-cored wire for gas shielded arc welding as described in (2) above.
(4) The flux-cored wire for gas shielded arc welding according to any one of (1) to (3), wherein the steel outer shell has no slit-like gap.
(5) The flux-cored wire for gas shielded arc welding according to any one of (1) to (3), wherein the steel outer skin has a slit-like gap.
The flux produced by the atomization method does not include metal powder such as Fe powder and Ni powder.

  The flux-cored wire of the present invention can reduce moisture absorption during the manufacture and storage of the wire, and can suppress cold cracking of the welded joint. Furthermore, since the flux produced by the atomizing method has a substantially spherical shape, wire breakage can be reduced during wire drawing.

It is a photograph which shows the scanning electron microscope image of the flux manufactured by the atomizing method. It is a photograph which shows the scanning electron microscope image of the flux manufactured by carrying out the mechanical grinding | pulverization of a melt. Regarding the cut surface of the wire, (a) shows a wire made by welding the edge surfaces, (b) shows a wire made by joining the edge surfaces, and (c) shows a wire made by crimping the edge surfaces. It is.

  In the flux-cored wire, the inventors of the present invention can produce at least a part of the flux by the atomizing method, thereby obtaining a substantially spherical flux and reducing the amount of diffusible hydrogen in the weld metal. The knowledge that it can be obtained.

  Hereinafter, the flux-cored wire of the present invention will be described by being divided into a flux produced by an atomizing method, a flux component, and an alloy component. Unless otherwise noted, “%” in the component composition means “% by mass” with respect to the total mass of the wire.

First, the flux produced by the atomizing method will be described.
The low specific surface area flux can be produced by a conventional atomizing method. Typical atomization methods include the gas atomization method, water atomization method, and disk atomization method. Among them, the gas atomization method easily obtains a powder having a shape close to a true sphere, and thus obtains a flux with a low specific surface area. Therefore, it is a preferable method.

  The gas atomization method is a method for generating powder directly from a molten state by flowing a molten flux from a melting furnace, spraying a gas at a high speed on the flowing molten flux, and dispersing and solidifying the molten flux. .

  At this time, the flux produced by the atomizing method is blown off into the flux collector installed on the side opposite to the high-speed gas spray nozzle, and accommodated in the collector. As the gas sprayed on the molten flux, air, nitrogen, inert gas, mixed gas thereof, or the like can be used, and the gas type is appropriately selected depending on the produced flux component.

As manufacturing conditions for gas atomizing method, a melt flow rate of the melt 20 kg / min or more 1000 kg / min or less, more 0.3MPa pressure atomizing gas 150MPa or less, the flow rate of the atomizing gas 10 Nm ³ / min or more 2000 Nm ³ / min or less Can be adopted. However, the above condition is an example, and is not limited to the above condition depending on the equipment configuration.

  Under these manufacturing conditions, a flux having a substantially spherical shape and a low specific surface area can be efficiently manufactured. Furthermore, if the melt is mechanically pulverized to produce a flux, it takes a lot of time to mechanically pulverize the melt, and only an angular polyhedral-shaped flux can be obtained. It can be manufactured in about 1/30 of the time, and the production efficiency is remarkably improved.

  The substantially spherical flux thus obtained includes not only a true sphere but also an ellipsoid, a partially deformed sphere, a sphere with some irregularities, and a sphere with a plurality of spheres combined. The shape can be confirmed by a scanning electron micrograph (SEM photograph). Next, scanning electron micrographs of manufactured fluxes will be described in the following examples.

  FIG. 1 is a photograph showing a scanning electron microscope image of a flux produced by the atomizing method. Most of the fluxes produced by the atomizing method have a true spherical shape, and there are few surface irregularities. On the other hand, FIG. 2 is a photograph showing a scanning electron microscope image of a flux produced by mechanically grinding a melt. The flux produced by mechanically pulverizing the melt has an angular polyhedron shape and has many dents on the surface. From the scanning electron micrographs of these fluxes, it is clear that the surface area of the flux produced by the atomization method is smaller than that of the flux produced by mechanically grinding the melt.

The specific surface area of the substantially spherical flux is 0.03 m ² / g or less, and the contact between the flux and air is reduced. On the other hand, a decrease in specific surface area causes an increase in particle size. When a steel outer shell is filled with a flux having a large particle size, voids are generated between the particles, resulting in a wire containing a large amount of air, and nitrogen in the weld metal is increased. Since the increase in nitrogen causes a decrease in the toughness of the weld metal, the lower limit value of the specific surface area is preferably set to 0.001 m ² / g or more.

  As described above, the gas atomizing method has been described in the production of the flux by the atomizing method, but the present invention is not limited to the gas atomizing method, and the flux may be produced by a disk atomizing method or another atomizing method. However, when the water atomization method is used, a hydrate may be generated in the flux. Therefore, it is preferable to re-dry at 500 ° C. or more and 1000 ° C. or less.

  In addition to the advantages described above, when a molten flux is produced by the atomizing method, in addition, by itself, a highly hygroscopic component is melted together with other components to form a solidified product having a different composition. It can be converted into a material with low hygroscopicity.

  For example, the fluorides used in Patent Documents 1 to 4 have deliquescent properties, so that they must be handled with care. By dissolving this together with the oxide and producing the flux by the atomizing method, a flux with reduced deliquescence can be obtained. Further, the flux produced by the atomizing method can be made crystalline or amorphous by selecting production conditions, and various characteristics can be adjusted.

  In the atomizing method, since droplets are continuously formed from the same molten metal, the flux obtained by atomizing the mixture has a very small compositional difference between particles. Furthermore, the difference in composition between particles having different dimensions is also reduced. Therefore, the flux-cored wire containing this flux has a uniform flux composition over its entire length and can perform stable gas shield arc welding.

Next, an application example of a flux-cored wire (melted flux-cored wire) containing a flux produced by the atomizing method will be described.
For example, a flux-cored wire is a flux containing 1.0% or more and 4.0% or less of fluoride in terms of F, 1.0% or more and 4.0% or less of oxide, and other carbonates. Can be exemplified by a flux and a flux containing a flux produced by an atomizing method.
Hereinafter, with respect to such a flux-cored wire, first, the flux component and the reason for its addition will be described.

Fluoride The fluoride of the flux component is a metal fluoride. Specifically, BaF ₂ , MgF ₂ , CaF ₂ , SrF ₂ , AlF _{3 and} the like are effective. Fluoride encapsulates the weld metal as a slag agent to improve the bead shape, promote slag floating separation from the weld metal, and reduce the oxygen and hydrogen content of the weld metal to improve toughness. And added to form good mechanical properties.

  Further, in order to reduce the oxygen content in the weld metal and the diffusible hydrogen content of the welded joint and improve the toughness and cold cracking resistance of the weld metal, the fluoride is converted to 1. It is preferable to add 0% or more. However, if it exceeds 4.0%, the welding fume is excessively generated, the arc becomes unstable, and the amount of spatter generated may increase. For this reason, the fluoride content is preferably 1.0% or more and 4.0% or less in terms of F. Further, if necessary, the lower limit of the fluoride content may be set to 2.0%.

The oxide of the oxide flux component is Al ₂ O ₃ , SiO ₂ , ZrO ₂ , MgO, CaO, BaO, SrO, MnO, TiO ₂ or the like. The oxide affects the wettability of the molten slag, and is added to optimize the bead shape and prevent undercut.

  In order to obtain the effect of preventing undercut, it is preferable to add 1.0% or more of oxides in total. However, if the oxide content exceeds 4.0%, the bead shape becomes convex, and the weld toe shape may deteriorate accordingly. The upper limit of the oxide content may be 2.0%.

Carbonate may be further added to the carbonate flux component for the purpose of enhancing arc concentration. The carbonate is CaCO ₃ , BaCO ₃ , SrCO ₃ , MgCO ₃ or the like. In order to improve arc concentration, it is preferable to add less than 0.6% of carbonate. If the carbonate content is 0.6% or more, the arc concentration is too strong and the amount of spatter generated may increase. Therefore, when these carbonates are contained, the total content is preferably less than 0.6%. Even if the content of these carbonates is 0%, there is no practical problem.

Arc stabilizer As the arc stabilizer, oxides, fluorides, and carbonates of Li, Na, and K are used, and the content is preferably 0.001% or more and 0.5% or less.

  Next, the alloy component of the wire will be described. Alloy elements include C, Si, Mn, P, S, Cu, Ni, Cr, Mo, V, Nb, Al, Ti, B, etc. It may be adjusted according to the mechanical properties such as strength and toughness required for reference, but the Pcm value defined by the following formula is adjusted to 0.15% or more and 0.40% or less. Is preferred.

Pcm (%) = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60
+ Cr / 20 + Mo / 15 + V / 10 + 5B
Pcm is edited by the Japan Welding Society, “Introduction to Welding and Joining Techniques”, published by Sangyo Publishing, Tokyo, 1998 p. 118. For elements not contained, 0 is substituted.

  Next, the form of the melt type flux cored wire will be described.

  A melt-type flux-cored wire has a structure in which a steel outer shell is formed into a pipe shape and filled with a melt-type flux. As shown in Fig. 3 (a), the steel outer shell formed in the manufacturing process is combined. Wires with slit-like gaps with welded eyes (also called seamless wires) and wires that leave slit-like gaps without welding the seams, as shown in FIGS. 3 (b) and 3 (c) it can.

  Any structure can be adopted for the flux-cored wire of the present invention. A wire without a slit-like gap in the steel outer shell has little moisture absorption during wire storage, and by using the flux of the present invention, moisture absorption during wire production is suppressed and cold cracking resistance is improved. On the other hand, a wire having a slit-like gap in the steel outer skin is suppressed in moisture absorption during wire storage and wire production by using the flux of the present invention, and the cold cracking resistance is improved.

  The flux cored wire of the present invention can be manufactured by the same manufacturing process as that of a normal flux cored wire manufacturing method. That is, first, a steel strip as an outer skin, and a flux prepared by an atomizing method, a flux blended so as to have a predetermined content of a carbonate, an alloy component, and an arc stabilizer are prepared. While feeding the steel strip in the longitudinal direction, it is formed into an open tube (U-shaped) by a forming roll to form a steel outer shell. During this forming, flux is supplied from the opening of the open tube, and the opposing edge surfaces of the opening Are butt welded. As the welding method, electric seam welding, laser welding, or TIG welding is used. A tube obtained by welding is drawn to obtain a slit-like gapless wire having a desired wire diameter. Moreover, the wire which has a slit-shaped clearance gap is obtained by drawing, without welding.

  A cross section obtained by cutting a wire without slit-like gaps made by butt seam welding looks like FIG. If this cross section is polished and etched, welding marks are observed, but if not etched, no welding marks are observed. Therefore, it may be called seamless as described above. For example, “New Edition Introduction to Welding and Joining Technology” edited by the Japan Welding Society (2008); Reference numeral 111 denotes a seamless type.

  FIG. 3B shows an example in which the edge surfaces are butted together, and FIG. 3C shows an example in which the edge surfaces are crimped. After the butting as shown in FIG. 3B, brazing or FIG. Even after brazing as in c), a wire having no slit-like gap can be obtained. In FIGS. 3B and 3C, the wire as it is without brazing becomes a wire having a slit-like gap.

  The wire diameter is preferably 1.0 mm or more and 2.0 mm or less. When the wire diameter is 1.0 mm or more and 2.0 mm or less, the current density at the time of welding can be increased and a high welding rate can be obtained. More preferably, it is 1.2 mm or more and 1.6 mm or less.

  Moreover, Cu plating effective for rust prevention, electrical conductivity, and chip wear resistance may be applied to the wire surface.

In the present invention, the object can be achieved by forming a weld metal by performing gas shielded arc welding on a steel plate using a flux-cored wire. The method of gas shield arc welding is not particularly limited, and a commonly used method can be adopted. For example, as the shielding gas, in addition to 100% CO ₂ gas, a mixed gas of Ar gas and 3 to 20% CO ₂ gas can be used.
In addition, the welding conditions such as current and voltage may be those usually used.

  The shape of the welded joint to be manufactured is determined according to the application or the like and is not particularly limited. It can be applied to welded joints that form grooves, such as ordinary butt joints, square joints, and T joints. Therefore, the shape of the steel plate to be welded is not limited as long as at least the portion that forms the weld joint is plate-shaped. Moreover, it is not limited to what is comprised from a separate steel plate, The butt-welding joint of what shape | molded one steel plate in predetermined shapes, such as a tubular shape, may be sufficient.

  Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on these one example conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
Tables 1 and 2 show the compositions of the test fluxes. A substantially spherical test flux was produced by the atomization method (described as A in the table) as follows. The fluorides and oxides shown in Tables 1 and 2 were put into a container, and heated to a temperature higher than the melting temperature of the oxides and fluorides by a heater for heating the container to form a melt. Then, the melt is caused to flow downward from the nozzle at the bottom of the container at a molten metal flow rate of 60 kg / min, and high pressure air is supplied from the injection port disposed in the vicinity of the nozzle with a pressure of 2 MPa and a gas flow rate of 70 Nm ³ / min. A test flux was produced. In the table, M is a conventional mechanical grinding method.

  The obtained test flux was encapsulated in a wire so as to have the presence or absence of slit-like gaps in the steel outer skin shown in Tables 1 and 2. The test flux was sealed in the wire as follows. While forming the steel shell of the components shown in Table 3 in the longitudinal direction, it is formed into an open tube by a forming roll, and a sample flux is supplied from the opening of the open tube in the middle of this forming, and the opposing edge surface of the opening protrudes. By welding together, a tube having no slit-like gap was formed, and annealing was performed during the drawing process of the formed wire, and a test wire having a final wire diameter of φ1.2 mm was made as a prototype. In addition, a part of the tube was a slit-like gap that was not welded, and a test wire with a wire diameter of φ1.2 mm was prototyped by drawing it.

  Test steel materials having the components shown in Table 3 were subjected to bead-on-plate welding using the obtained test wires under conditions where the current was 280 A, the arc voltage was 28 V, the welding speed was 20 cm / min, and the shielding gas was carbon dioxide. The amount of diffusible hydrogen, the amount of spatter generated, the height of surplus and the undercut were evaluated. Tables 4 and 5 show the results of the amount of diffusible hydrogen, the number of breaks at the time of wire drawing, the amount of spatter generation, the surfacing height, and the undercut.

  The diffusible hydrogen amount measurement test was performed by a gas chromatograph method in accordance with JIS Z 3118 (Method for measuring the hydrogen amount of steel welds 2007). And it was judged that the amount of diffusible hydrogen passed 2.0 ppm or less, and the thing of 1.0 ppm or less expressed that the effect of diffusible hydrogen reduction expressed especially clearly. The number of breaks during wire drawing was determined to be 2 or less.

  As for the amount of spatter generated, it was judged that the spatter weight generated was 2 g or less, and that the sputter reduction effect was clearly manifested when the spatter was 1.0 g or less. In the evaluation of the convex bead, it was judged that the effect of obtaining a smooth bead was manifested particularly clearly when the surplus height was 8 mm or less and the height was 5 mm or less. Undercut is the sum of the weld lengths of the generated parts, and if it is 50 mm or less, it was judged to be acceptable, and if it was 10 mm or less, it was judged that the effect of undercut suppression was particularly clearly expressed. Further, in the production of 1 ton of wire, the number of breaks during wire drawing was measured.

  As shown in the test results of Tables 4 and 5, Test Nos. 1 to 15 and Test Nos. 23 to 64, which are invention examples, were determined to be acceptable in all items and were good results. Moreover, the wire breakage in the wire drawing process did not occur and good manufacturability could be confirmed. In particular, in Test Nos. 1 to 10, the amount of fluoride and oxide that the present invention is considered to be preferable are contained in FCW, and since there is no slit in the FCW steel shell, diffusible hydrogen, spatter generation amount, The test results were noteworthy in all items of undercut and convex bead avoidance.

  On the other hand, test numbers 16 to 22, which are comparative examples, used a mechanically pulverized molten flux, so that the surface area of the flux increased and diffusible hydrogen increased. In addition, many wire breaks occurred during wire drawing, which failed.

  In Test Nos. 23 to 29, the content of fluoride did not satisfy the lower limit value considered to be preferable in the present invention. Therefore, the diffusible hydrogen did not become 1 ppm or less, but the effect of reducing hydrogen was exhibited. Test numbers 30 and 31 deviate from the upper limit of the range in which the fluoride content is considered preferable in the present invention. For this reason, the spatter generation amount was slightly increased, but it was acceptable.

  Test Nos. 54 to 62 are examples of the invention, but the oxide content deviates from the lower limit of the present invention. did. On the other hand, Test Nos. 63 and 64 were judged to be acceptable because the oxide content deviated from the upper limit value, resulting in convex beads and a high surplus height, but less diffusible hydrogen and less spatter.

  According to the present invention, moisture absorption is reduced during the manufacture and storage of the wire, low-temperature cracking of the weld metal can be suppressed, and damage to the steel outer shell can be suppressed during wire drawing. And the industrial applicability is extremely high.

Claims (5)

  A flux-cored wire for gas shielded arc welding, wherein at least a part of the flux is a flux produced by an atomizing method. The flux produced by the atomization method includes one or more fluorides of BaF ₂ , MgF ₂ , CaF ₂ , SrF ₂ and AlF ₃ , Al ₂ O ₃ , SiO ₂ , ZrO ₂ , MgO, CaO. _2. The flux-cored wire for gas shielded arc welding according to claim 1, wherein the flux-cored wire is manufactured by an atomizing method using one or more oxides of BaO, SrO, MnO, and TiO ₂ as raw materials.   The fluoride content is 1.0% or more and 4.0% or less and the oxide content is 1.0% or more and 4.0% or less in terms of F with respect to the total mass of the wire. The flux-cored wire for gas shielded arc welding according to claim 2.   The flux-cored wire for gas shielded arc welding according to any one of claims 1 to 3, wherein the steel outer shell has no slit-like gap.   The flux cored wire according to any one of claims 1 to 3, wherein the steel outer shell has a slit-like gap.