Melting type flux for submerged arc welding

Abstract

To provide a melting type flux for submerged arc welding, that suppresses insufficiency in scattering thickness even when a flux blow-up phenomenon occurs during submerged arc welding, and that is superior in welding workability such as arc stability, slag releasability and bead shape.SOLUTION: A melting type flux for submerged arc welding satisfies the following expression (1), when X% denotes a mass ratio of foam formation flux particles relative to the total flux mass, and Y% denotes a mass ratio of flux particles excluding the foam formation flux particles.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a molten flux for submerged arc welding used when welding steel structures.

Background Art

[0002] Submerged arc welding is a method in which granular flux is previously scattered along a welding part, a welding wire is continuously supplied into the flux, and an arc is generated between a base material to be welded and the tip of the welding wire while being covered with the flux to perform welding. For the purpose of improving welding workability in submerged arc welding, various studies have been conducted. For example, Patent Documents 1 to 3 disclose that by foaming flux particles to form porous particles and reducing the bulk density, welding workability such as slag detachability and bead appearance is improved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the welding phenomenon of submerged arc welding is not steady, and the gas in the arc cavity may blow up sequentially with a certain probability, and a phenomenon (blow-up phenomenon) of blowing away the flux may occur. When such a blow-up phenomenon occurs, there is a concern that the spraying thickness of the conventional foaming type molten flux will be insufficient. If the spraying thickness of the flux is insufficient, the arc can be directly visually recognized, and a sound weld metal that excludes the influence of the atmosphere cannot be obtained. The reason for this is that when a part of the arc is exposed to the atmosphere, the nitrogen content of the weld metal increases, resulting in problems such as welding defects such as pits, blowholes, and pockmarks.

[0005] The present disclosure has been devised in view of the above-described problems, and even when a blow-up phenomenon of the flux occurs during submerged arc welding, it is possible to suppress a shortage of the spraying thickness, and an object thereof is to provide a molten flux for submerged arc welding excellent in welding workability such as arc stability, slag detachability, and bead shape.

Means for Solving the Problems

[0006] The gist of the present disclosure for solving the above problems is as follows. <1> A molten flux for submerged arc welding that satisfies the following formula (1) when the mass ratio of the foaming flux particles is X% and the mass ratio of the flux particles other than the foaming flux particles is Y% with respect to the total mass of the flux.

[0007]

Number

[0008] <2> The molten flux for submerged arc welding according to <1>, wherein the flux particles having a particle size in the range of more than 0.3 mm to 1.4 mm are 90% by mass or more with respect to the total mass of the flux. <3> The bulk density is 0.6 to 1.3 g / cm 3 The molten flux for submerged arc welding according to <1> or <2>.

Advantages of the Invention

[0009] According to the present disclosure, even if a flux blowing phenomenon occurs during submerged arc welding, a decrease in the spraying thickness is suppressed, and a molten flux for submerged arc welding excellent in welding workability such as arc stability, slag detachability, and bead shape is provided.

Brief Description of the Drawings

[0010]

Figure 1

Modes for Carrying Out the Invention

[0011] Hereinafter, an embodiment which is an example of a molten flux for submerged arc welding (in the present disclosure, may be referred to as "molten flux" or simply "flux") according to the present disclosure will be described. In the present disclosure, a numerical range represented by "~" means a range including these numerical values as the lower limit value and the upper limit value when "more than" or "less than" is not attached to the numerical values described before and after "~". Further, a numerical range in the case where "more than" or "less than" is attached to the numerical values described before and after "~" means a range not including these numerical values as the lower limit value or the upper limit value. In the numerical ranges described step by step in this specification, the upper limit value of a certain stepwise numerical range may be replaced with the upper limit value of the numerical range of other stepwise descriptions, or may be replaced with the value shown in the examples. Further, the lower limit value of a certain stepwise numerical range may be replaced with the lower limit value of the numerical range of other stepwise descriptions, or may be replaced with the value shown in the examples. Regarding the content, "%" means "mass%" unless otherwise specified.

[0012] As a result of intensive research to solve the above problems, the inventors have found that, as a molten flux used in performing submerged arc welding, controlling the mass ratio of foamed flux particles and flux particles other than the foamed flux particles (in the present disclosure, the flux particles other than the foamed flux particles may be referred to as "non-foamed flux particles") within a certain range is extremely effective in improving the above-described welding workability. The reason why defining the mass ratio of both is effective in improving the welding workability is not necessarily clear, but the inventors presume that both the foamed flux particles and the non-foamed flux particles interfere with each other and resist the spatter.

[0013] Hereinafter, embodiments of the molten flux for submerged arc welding according to the present disclosure will be described in detail. Note that the molten flux for submerged arc welding according to the present disclosure is not limited to the embodiments described below.

[0014] <Molten Flux for Submerged Arc Welding> The molten flux for submerged arc welding according to the present disclosure is configured to satisfy the following formula (1) when the mass ratio of the foamed flux particles is X% and the mass ratio of the flux particles other than the foamed flux particles (non-foamed flux particles) is Y% with respect to the total mass of the flux.

[0015]

Equation

[0016] By performing submerged arc welding using a molten flux in which the mass ratio X% of the foamed flux particles and the mass ratio Y% of the non-foamed flux particles satisfy the formula (1), that is, the mass ratio of the foamed flux particles is in the range of 1 to 40% with respect to the total mass of the flux, an effect of suppressing the spatter phenomenon can be obtained, and the exposure of the arc to the atmosphere (open arc) can be suppressed. When the mass ratio of the foamed flux particles (X / (X + Y)) is less than 0.01, the overall flux has insufficient foaming and cannot form a stable arc cavity, so bead shape defects are likely to occur. On the other hand, when the mass ratio of the foamed flux particles exceeds 0.40, it cannot resist the sputtering phenomenon and becomes an open arc, and the amount of N in the weld metal increases due to contamination from the atmosphere, and pore defects such as pits and blowholes are likely to occur. Therefore, the molten flux according to the present disclosure has a mass ratio of the foamed flux particles of 0.01 to 0.40, preferably 0.01 to 0.30.

[0017] In the submerged arc welding molten flux according to the present disclosure, the determination of the foamed flux particles and the flux particles other than the foamed flux particles (non-foamed flux particles) is performed by sorting using image analysis software. Specifically, arbitrarily collect 50 g of the flux, and take a photo of the flux using a digital microscope (VH - 900) manufactured by Keyence Corporation (magnification is 30 times). For the taken photo, use image analysis software (JTrim) to binarize 1300×1200 pixels (1,560,000 pixels), and determine the white particles as the foamed particles and the black particles as the non-foamed particles. For binarization, the boundary threshold is set to 150. In addition, particles containing both white and black parts, that is, particles containing both foamed and non-foamed parts, are determined as flux particles other than the foamed flux particles (non-foamed flux particles).

[0018] The inventors measured and verified the bulk density regarding the accuracy of the determination of the foamed flux particles and non-foamed flux particles by image analysis using such magnified photos of the flux. For the flux in which the foamed flux particles and non-foamed flux particles are mixed, a magnifying glass that can be magnified about 5 to 30 times was used to perform a separation operation based on the appearance of the particles. The flux of Invention Example F5 in Table 1 of the examples described later was used. Specifically, it was separated into pumice-like particles A that were entirely white or yellowish, glass-like particles B that were entirely black, and particles C in which white or yellowish parts and black parts were mixed. For the particles A, B, and C sorted based on appearance using an insect eye lens as described above, when the bulk density was measured according to JIS K5101, the particle A was about 0.5 g / cm 3 , the particle B was about 1.5 g / cm 3 , and the particle C was about 1.0 g / cm 3 . From these results, it can be considered that the particle A with a white or yellow tint has a low bulk density because it contains bubbles overall, the particle B with a black tint has a high bulk density because it does not contain bubbles overall, and the particle C with a mixture of white or yellow and black parts contains bubbles partially, so the bulk density is approximately in the middle between particle A and particle B.

[0019] On the other hand, for the sorted flux particles A, B, and C, when image analysis of the magnified photographs was performed by the method described above, the particle A was identified as a white particle, the particle B was identified as a black particle, and the particle C was identified as a particle with a mixture of white and black. From such results, the presence or absence of foaming of the flux particles can be accurately determined by the image analysis described above. That is, in the submerged arc welding molten flux according to the present disclosure, in the binarization process of the above-described image, white particles are regarded as foamed flux particles, and black particles and particles with a mixture of black and white are distinguished as non-foamed flux particles. Then, 50 g of the flux is arbitrarily collected, white particles are separated from other particles (black particles and particles with a mixture of black and white) by the above-described binarization process, and by measuring the total mass of the white particles, the mass ratio X% of the foamed flux particles and the mass ratio Y% of the non-foamed flux particles can be obtained.

[0020] The components constituting the submerged arc welding molten flux according to the present disclosure are not particularly limited, but the following describes preferred components.

[0021] [SiO2: 30 - 55%] SiO2, which uses silica sand, wollastonite, etc. as raw materials, adjusts the viscosity of the molten slag to improve the bead shape. When SiO2 is 30% or more, the viscosity of the molten slag is insufficient, and welding defects such as undercut and slag entrainment are less likely to occur. On the other hand, when SiO2 is 55% or less, the viscosity of the slag does not become too high, and the bead shape is likely to be good. Therefore, it is preferable that SiO2 is 30 - 55%. More preferably, it is 35 - 50%.

[0022] [Al2O3: 6 - 20%] Al2O3, which uses alumina, etc. as raw materials, is an effective component for adjusting the viscosity of the molten slag. When Al2O3 is 6% or more, the decrease in the viscosity of the molten slag is suppressed, and undercut is less likely to occur. On the other hand, when Al2O3 is 20% or less, the viscosity of the molten slag does not become too high, and the bead becoming convex is suppressed. Therefore, it is preferable that Al2O3 is 6 - 20%. More preferably, it is 6 - 15%. [MgO: 5 - 20%] MgO, which uses magnesia clinker, magnesium oxide, etc. as raw materials, adjusts the viscosity of the molten slag to improve the bead shape. When MgO is 5% or more, the insufficient viscosity of the molten slag is suppressed, and the meandering and undercut of the bead are less likely to occur. On the other hand, when MgO is 20% or less, the widening of the bead width is less likely to be discontinuous. Therefore, it is preferable that MgO is 5 - 20%. More preferably, it is 10 - 20%.

[0023] [FeO: 0.5 - 5%] FeO, which uses mill scale, etc. as raw materials, adjusts the viscosity and melting point of the molten slag to improve the bead shape. Also, it has the effect of enhancing the pockmark resistance. When FeO is 0.5% or more, the meandering of the bead and pockmarks are less likely to occur. On the other hand, when FeO is 5% or less, the slag sticking and slag peeling property becoming poor are suppressed. More preferably, it is 1 - 4%.

[0024] [MnO: 18 - 28%] MnO, which uses manganese oxide, roasted manganese, etc. as raw materials, is an effective component for adjusting the viscosity of molten slag and slag detachability. To obtain this effect, it is preferable to contain 18% or more of MnO. On the other hand, excessive addition of MnO deteriorates the bead shape, so the upper limit is preferably set at 2⑧%. More preferably, it is 20~26%.

[0025] [TiO2: 2~6%] TiO2, which uses rutile, titanium oxide, etc. as raw materials, is effective for obtaining the smoothness of the bead surface. To obtain this effect, it is preferable to contain 2% or more of TiO2. On the other hand, excessive addition of TiO2 deteriorates the slag detachability, so the upper limit is preferably set at 6%. More preferably, it is 3~5%.

[0026] [CaF2: 5~9%] CaF2, which uses fluorite, etc. as raw materials, has the effect of adjusting the fluidity of molten slag and improving slag detachability. To obtain this effect, it is preferable to contain 5% or more. On the other hand, excessive addition of CaF2 increases the gas component and generates pockmarks, so the upper limit is preferably set at 9%. More preferably, it is 5~8%.

[0027] [Total of one or both of Na2O and K2O: 0.5~2.0%] Na2O and K2O, which use sodium carbonate, potassium carbonate, etc. as raw materials, have the effect of improving the stability of the arc. To obtain this effect, it is preferable to add 0.5% or more. On the other hand, excessive addition of Na2O and / or K2O deteriorates the bead shape, so the upper limit of the total of one or both of Na2O and K2O is preferably set at 2.0%.

[0028] [Bi2O3: 0.05% or less] Bi2O3, which uses bismuth oxide etc. as a raw material, has the effect of improving slag detachability. If Bi2O3 is 0.05% or less, deterioration of the toughness of the weld metal is suppressed. Therefore, it is preferable that Bi2O3 be 0.05% or less. Note that although Bi2O3 has the effect of improving slag detachability with a small amount of addition, it is preferably 0.001% or more in order to obtain that effect.

[0029] [B2O3: 1.5% or less] B2O3, which uses boron oxide etc. as a raw material, has the effect of suppressing the growth of primary ferrite formed at the austenite grain boundaries of the weld metal and improving toughness. If B2O3 is 1.5% or less, deterioration of hot cracking of the weld metal is suppressed. Therefore, it is preferable that B2O3 be 1.5% or less. Note that although B2O3 has the effect of improving the toughness of the weld metal with a small amount of addition, it is preferably 0.01% or more in order to obtain that effect.

[0030] [CaO: 5.0% or less] CaO, which uses calcium oxide etc. as a raw material, has the effect of improving the toughness of the weld metal. If CaO is 5.0% or less, deterioration of the bead shape is suppressed. Therefore, it is preferable that CaO be 5.0% or less. Note that although CaO has the effect of improving the toughness of the weld metal with a small amount of addition, it is preferably 0.01% or more in order to obtain that effect.

[0031] [BaO: 5.0% or less] BaO, which uses barium oxide etc. as a raw material, has the effect of improving the toughness of the weld metal. If BaO is 5.0% or less, deterioration of the bead shape is suppressed. Therefore, it is preferable that BaO be 5.0% or less. Note that although BaO has the effect of improving the toughness of the weld metal with a small amount of addition, it is preferably 0.01% or more in order to obtain that effect.

[0032] The remainder of the flux of the present disclosure is impurities such as P and S contained in trace amounts in the raw material.

[0033] [Particle size] Next, the particle size of the flux will be described. The content of the flux based on the particle size is also expressed in mass% with respect to the total mass of the fusion-type flux according to the present disclosure, and is simply described as %.

[0034] Flux particles with a particle size exceeding 0.3 mm to 1.4 mm are important particles for forming a stable bead shape. Also, such flux particles have the effect of improving slag detachability. If the flux particles with a particle size exceeding 0.3 mm to 1.4 mm are 90% or more, it is possible to suppress the bead shape from becoming a convex shape, suppress the deterioration of gas venting, and make it difficult for pop marks to occur. Also, it becomes difficult for the flux to be pulverized. Therefore, for the flux according to the present disclosure, it is preferable that the total mass of the flux particles with a particle size exceeding 0.3 mm to 1.4 mm is 90% or more. Note that the smaller the content of particles with a particle size of 0.3 mm or less and particles with a particle size exceeding 1.4 mm, the more preferable.

[0035] The particle size of the flux particles is measured in accordance with "6.3 Particle Size Test of Flux" in JIS Z3352:2017 Flux for Submerged Arc Welding and Electro-Slag Welding. Sieves with corresponding nominal mesh openings (300 μm and 1.4 mm) in JIS Z8801-1:2019 "Test Sieves - Part 1: Wire Mesh Sieves for Metals" are used, and the sieving time is 4 minutes. Mechanical sieving is performed in accordance with JIS Z8815:1994 "General Rules for Sieving Test Methods", and a rotary tap type sieve shaker is used as the measuring instrument. The flux used in the test is 200 g. In such a particle size test of the flux, the flux particles that pass through the sieve with a nominal mesh opening of 1.4 mm and do not pass through the sieve with a nominal mesh opening of 300 μm are the flux particles with a particle size exceeding 0.3 mm to 1.4 mm.

[0036] [Bulk density] The bulk density of the flux acts on the shielding property of the molten pool from the atmosphere during welding and the spread of the weld bead. When the bulk density of the flux is 0.6 g / cm 3If it is above this level, the flux blow-up phenomenon is less likely to occur, and insufficient shielding, which causes pockmarks, is suppressed. On the other hand, if the bulk density of the flux is 1.3 g / cm 3 or less, it becomes difficult for the bead to spread, and the occurrence of undercut is suppressed. Therefore, the bulk density of the flux according to the present disclosure is preferably 0.6 to 1.3 g / cm 3 . A more preferable range is 0.6 to 1.2 g / cm 3 . The measurement of the bulk density of the flux can be carried out in accordance with JIS K5101-12-1:2004. Bulk density (g / cm 3 ) = (mass of the receiver containing the sample (g) - mass of the receiver (g)) / internal volume of the receiver (cm 3 )

[0037] <Method for manufacturing a submerged arc welding flux in a molten state> Next, a method for manufacturing a submerged arc welding flux in a molten state according to the present disclosure will be described. The method for manufacturing the flux in a molten state according to the present disclosure is not particularly limited as long as the foamed flux particles and the non-foamed flux particles are included so as to satisfy formula (1). For example, a plurality of types of fluxes having different mass ratios of the foamed flux particles and the non-foamed flux particles may be manufactured, and the mass ratio (X / (X + Y)) of the foamed flux particles and the non-foamed flux particles may be blended so as to satisfy formula (1). From the viewpoint of ease of manufacture, a method of manufacturing the flux such that the foamed flux particles and the non-foamed flux particles are formed at a mass ratio that satisfies formula (1) by adjusting the raw materials and manufacturing conditions is preferable.

[0038] The molten flux for submerged arc welding according to the present disclosure can be manufactured, for example, by formulating raw materials to contain the aforementioned components and cooling the flux melted by heating with water. When manufacturing the flux by cooling the thus-melted flux with water, the mass ratio of the foamed flux particles in the manufactured flux depends on manufacturing conditions such as raw materials and cooling rate. For example, when melting a raw material having a composition containing relatively reducible oxides such as elements Mn and Si at a high temperature (for example, 1300 to 1700 ° C) together with a reducing agent (such as C and Al), the proportion of the foamed flux particles tends to increase.

[0039] Further, as a method for adjusting the bulk density of the flux, after mixing various raw materials of the flux and melting them in an electric furnace, the melted flux is cooled in warm water to slow down the cooling rate to foam the flux, or the melted flux is cooled in jet water cooling to form a flux in which acicular, antler-shaped, spherical, and scaly particles are mixed, thereby adjusting the bulk density of the flux.

[0040] Further, as a method for adjusting the particle size of the flux, for example, a method of directly applying impactive jet water to the melt can be mentioned. By controlling the water pressure, water volume, and the amount of the flux in the molten state, crushing and sieving can adjust the particle size of the flux.

Example

[0041] Hereinafter, the effects of the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to the following examples.

[0042] [Manufacture of Molten Flux for Submerged Arc Welding] Prototype molten fluxes with each component composition, mass ratio, and bulk density shown in Table 1 were produced. In Table 1, the underlines indicate that they are outside the scope of the present disclosure. Also, "0", "0.0", or "0.00" means that the component is not included (not added).

[0043] (Manufacture of Molten Flux F1) The raw materials were blended and mixed so as to become the components shown by the flux symbol F1 in Table 1, heated to 1350 °C in an electric furnace to obtain a molten flux (melt), and then poured into a large amount of water for cooling. The temperature of the cooling water before pouring the molten flux was set at 20 °C.

[0044] (Production of molten fluxes F2 to F17) Molten fluxes F2 to F17 were produced in the same manner as molten flux F1, except that the blending of the raw materials was changed so as to become the components shown in Table 1 respectively.

[0045] (Production of molten fluxes F21 to F22) Molten fluxes F21 to F22 were produced in the same manner as molten flux F1, except that the blending of the raw materials was changed so as to become the components shown in Table 1 respectively.

[0046] [Measurement] 50 g of each flux produced as described above was arbitrarily collected, separated into foamed flux particles and other particles (non-foamed flux particles) by the above-described image analysis, and the mass ratios (%) X and Y of each particle were measured. In addition, the bulk density of each flux was measured by a method conforming to JIS K5101-12-1:2004 described above. Furthermore, regarding the particle size of each flux, using a rotary tap type sieve shaker (manufactured by Ito Seisakusho Co., Ltd., product name: rotary tap type sieve shaker model S), the mass ratio (%) of flux particles having a particle diameter exceeding 0.3 mm to 1.4 mm was measured by a method conforming to JIS Z8815:1994 "General Rules for Sieving Test Methods".

[0047]

Table 1

[0048] [Evaluation] Submerged arc welding was carried out using the trial-produced molten flux. Specifically, bead-on-plate welding was performed using a solid wire with a wire diameter of 4.8 mm of JIS Z3351:2012 YS-S6 shown in Table 4 under the welding conditions shown in Table 2, and a steel plate with a thickness of 16 mm of JIS G3136:2012 SN490B shown in Table 3. Note that except for the components shown in Tables 3 and 4, they are Fe and impurities.

[0049]

Table 2

[0050]

Table 3

[0051]

Table 4

[0052] For the evaluation of welding workability, the stability of the arc, slag detachability, bead shape (presence or absence of undercut, pits, irregularity of the bead surface), and presence or absence of blowholes were investigated. The stability of the arc was regarded as "stable" if the welding voltage fluctuation during welding was within ±5 V. Regarding slag detachability, since the slag after welding peels off naturally, the slag was removed with a brush, the area of the remaining slag that could be visually confirmed was estimated, and a slag detachment rate of 95% or more was regarded as "good", and 98% or more as "very good". Regarding the irregularity of the bead surface, within a range of a welding length of 150 mm, if the difference between the minimum value and the maximum value of the bead width was 7 mm or less, it was regarded as "good", and 5 mm or less as "very good". Also, if the difference between the minimum value and the maximum value of the bead width exceeded 7 mm, it was regarded as "bad", and if a defect in the bead shape occurred, the defect was described. For blowholes, tests were conducted based on the radiographic test method for steel welded joints shown in JIS Z3104:1995, and it was regarded as defect-free if no flaws occurred. The evaluation results are summarized in Table 5.

[0053]

Table 5

[0054] In Table 1, Table 5, and Table 6, the flux symbols F1 to F17 are examples of the present invention, and the flux symbols F21 to F22 are comparative examples. For the flux symbols F1 to F17 which are examples of the present invention, the mass ratio of the foamed flux particles is within the range of the present disclosure. In bead-on-plate welding using these fluxes, the arc was stable, no undercut, pits, etc. occurred, the bead shape was good, the slag detachability was also good, no pits or blowholes occurred, and the welding workability was good.

[0055] For the flux symbol F21 in the comparative example, since the mass ratio of the foamed flux particles was small, the arc was not stable and undercut occurred. For the flux symbol F22 in the comparative example, since the mass ratio of the foamed flux particles was large, it became an open arc, the arc was not stable, and the bead shape became poor. Also, pits and blowholes occurred.

Explanation of Reference Signs

[0056] 1 Foamed flux particles (foamed flux particles) 2 Non-foamed flux particles (non-foamed flux particles)

Claims

【Claim 1】 A submerged arc welding flux in the form of a fused flux that satisfies the following formula (1), where the mass ratio of the foamed flux particles is X% and the mass ratio of the flux particles other than the foamed flux particles is Y% with respect to the total mass of the flux. [Equation 1]

Images