KR20030016731A - Sintered flux for submerged arc welding - Google Patents

Abstract

PURPOSE: A sintered flux for submerged arc welding is provided to secure superior welding workability as well as good toughness at low temperature in downward fillet welding, butt welding and multi-layer welding of heavy and thick plates. CONSTITUTION: The sintered flux for submerged arc welding comprises 3.0 to 11.5 wt.% of CaO, 18.5 to 37.0 wt.% of MgO, 15.5 to 25.5 wt.% of SiO2, 13.5 to 30.0 wt.% of Al2O3, 4.5 to 14.5 wt.% of CaF2, 3.0 to 12.5 wt.% of MnO0.5 to 2.5 wt.% of CO2 as a converted value in carbonate ore, 0.05 to 4.5 wt.% of the sum of one or more constituents selected from Na2O, K2O and Li2O and a balance of metal powder and alloy iron on the basis of the total weight of the flux, wherein basicity (B) of the flux represented as in the following expression 1 satisfies 0.95 to 2.10, and particle size distribution of the flux comprises 5 wt.% or less of particles having diameter of 1.7 mm or more, 15 to 30 wt.% of particles having diameter that is 1.00 mm or more and less than 1.7 mm, 65 to 85 wt.% of particles having diameter that is 0.30 mm or more and less than 1.00 mm, and 10 wt.% or less of particles having diameter less than 0.3 mm on the basis of the total weight of the flux.

Description

Sintered flux for submerged arc welding

The present invention relates to a sintered flux for submerged arc welding, and more particularly, to a single layer and a multilayer of one electrode or two electrodes of mild steel and 50 kgf / mm 2 medium and thick plates mainly used in steel, shipbuilding, bridges, etc. The present invention relates to a sintered flux for submerged arc welding that can be used universally for welding.

In general, in order to ensure good toughness of the welded part at a low temperature of about -60 ° C. during submerged arc welding, a method of removing gaseous components (oxygen, etc.) in the weld metal using a metal powder deoxidizer, or by using an alloy powder The method of refine | miniaturizing the metal structure of a weld part, etc. by adjusting the alloy component in a weld metal, etc. have been used.

However, as various structures are enlarged and heavy and heavy plates of mild steel and 50kgf / mm2 high tensile steel (carbon steel) are used as materials of the structure, it is more important to secure welding workability as well as toughness at low temperature for the welded part. Was done.

The present invention is to meet the needs as described above, it is an object to provide a sintered flux for submerged arc welding to ensure excellent toughness at low temperatures and improved welding workability.

1 is an improved shape of the downward fillet welds,

2 is an improved shape of the butt welded portion,

3 is a cross-sectional view showing an improved shape of a multilayer welded part.

The above object of the present invention is a flux for submerged arc welding, with respect to the total weight of the flux, 3.0 to 11.5% by weight of CaO, 18.5 to 37.0% by weight of MgO, 15.5 to 25.5% by weight of SiO ₂ , 13.5 to 30.0 wt% Al ₂ O ₃ , 4.5-14.5 wt% CaF ₂ , 3.0-12.5 wt% MnO, 0.5-2.5 wt% CO ₂ , Na ₂ O, K ₂ O, Li in terms of carbonate mineral One component or the sum of one or more components selected from ₂ O is 0.05 to 4.5% by weight, and consists of metal powder and ferroalloy as remainder,

The basicity (B) value of the flux represented by Equation 1 below satisfies 0.95 to 2.10,

..... Equation 1

As the particle size distribution of the flux, 5 to 30% by weight of particles having a particle size of 1.70 mm or more, 15 to 30% by weight of particles less than 1.70 mm and 1.00 mm or more, and 65 to 85% by weight of particles less than 1.00 mm and 0.30 mm or more , Submerged arc welding fluxes characterized by less than 10% by weight of particles less than 0.3 mm.

In the present invention, by containing a large amount of components useful for reducing the amount of oxygen in the flux to promote the movement of gas components, such as oxygen, which adversely affects the toughness from the molten metal to the molten slag, toughness at low temperatures is improved. In addition, by optimizing the optimum content range and flux particle size distribution of the deoxidizer and alloying agent on the metal powder contained in the flux, good weldability and excellent welding workability were secured.

Hereinafter, the configuration as described above of the present invention, and unless otherwise specified,% means the weight% of the total sintered flux (hereinafter, flux) for submerged arc welding.

CaO is an additive that determines the basicity, viscosity, and freezing point of molten slag and reduces oxygen in molten metal. When the content is less than 3.0 wt%, the effect cannot be expected. Sex and bead appearance may deteriorate or a fork mark may occur. Therefore, the CaO content in the flux is preferably set to 3.0 to 11.5% by weight.

MgO is a component that promotes the movement of gaseous components such as oxygen in molten metal to the inside of molten slag by increasing the basicity like CaO, and has the function of lowering the gas content of the deposited metal and improving toughness. . However, if the MgO content is less than 18.5% by weight, the effect is insignificant. If the content of MgO is more than 37.0% by weight, the slag peelability is very poor and a part of the flux is burnt out and a fork mark is generated. Therefore, the MgO content in the flux is preferably 18.5 to 37.0% by weight.

SiO ₂ serves as a representative acidic component to control basicity, and acts as a slag forming agent to improve slag peelability after welding. If the SiO ₂ is less than 15.5% by weight, slag peelability is remarkably lowered, resulting in a problem in that the bead width and the left and right shapes are uneven. In addition, when the content of SiO ₂ exceeds 25.5% by weight, the viscosity of the molten slag is increased, there is a problem that the spreading of the beads deteriorate. Therefore, the SiO ₂ content in the flux is preferably 15.5 to 25.5 wt%.

Al ₂ O ₃ improves arc concentration and stability during high current welding along with the ability to adjust the viscosity and melting point of basicity and molten slag to improve welding workability. If Al ₂ O ₃ is less than 13.5% by weight, the viscosity and melting point will be low, the arc will be unstable and the width and grain of the weld bead will be uneven and undercut will occur. In addition, when Al ₂ O ₃ exceeds 30.0% by weight, the viscosity becomes too high and convex beads appear, as well as the solidification temperature is increased to generate meandering beads. Therefore, the content of Al ₂ O ₃ contained in the flux is preferably 13.5 to 30.0% by weight.

CaF ₂ is a very strong basic component that improves arc stability and smoothes beads during high current welding. Also, CaF ₂ generates fluorine gas during welding to reduce the partial pressure of water vapor, thereby reducing the hydrogenation in the deposited metal. If CaF ₂ is less than 4.5% by weight, this effect is not only significantly reduced, but also a fork mark is generated and the slag peeling is poor. On the other hand, when the content of CaF ₂ exceeds 14.5% by weight, the arc is unstable and frequently breaks up, which impairs workability and increases fluidity, resulting in defects such as meandering beads or undercuts. Therefore, the CaF ₂ content in the flux is 4.5 to 14.5% by weight.

MnO improves the appearance of beads during welding, and is used as a deposited metal as an Mn alloy element to improve strength and toughness. If the MnO is less than 3.0% by weight, such an effect is hardly exhibited. If the MnO is more than 12.5% by weight, the flowability of the molten slag is too high to damage the bead appearance. Therefore, the MnO content in the flux is preferably set to 3.0 to 12.5% by weight.

Oxides of alkali metals, that is, Na ₂ O, K ₂ O, Li ₂ O improves the arc stability during welding to improve the workability, it is effective to ensure the depth of penetration by ensuring the arc concentration. If the sum of one or more components selected from Na ₂ O, K ₂ O, Li ₂ O is less than 0.05% by weight, the effect is less. If the content exceeds 4.5% by weight, the hygroscopicity is deteriorated. Causes a defect. Therefore, the sum of one component or one or more components selected from Na ₂ O, K ₂ O, and Li ₂ O in the flux is preferably 0.05 to 4.5% by weight.

CO ₂ is obtained from carbonate minerals such as calcite, manganese carbonate, and magnesite, and decomposes during welding to generate CO ₂ gas, which reduces the partial pressure of nitrogen, oxygen and water vapor from the deposited metal, and prevents penetration into molten metal. There is an effect to improve. If the content of CO ₂ (equivalent in carbonate minerals) is less than 0.5% by weight, the effect of improving toughness is insignificant. If it exceeds 2.5% by weight, the bead surface deteriorates and excessive gas is generated, such as a fork mark. do. Therefore, the content of CO _{2 in} the flux is preferably 0.5 to 2.5% by weight in terms of carbonate minerals.

Flux uses the above-mentioned components as a component, and remainder consists of metal powder and ferroalloy. Si and Mn contained in ferroalloy act as deoxidizer and alloying element to improve welding efficiency during welding, reduce oxygen in welding area and improve mechanical properties.

On the other hand, the flux should satisfy the basicity (B) represented by the following formula 1 in addition to the above content to improve the weldability is 0.95 ~ 2.10.

..... Equation 1

If the basicity (B) is less than 0.95, the basicity is excessively reduced and gas components such as oxygen in the molten metal are not sufficiently removed, so that the effect of toughness is hardly improved. If it exceeds 2.10, the gas component is good but the slag after welding is good. Peelability deteriorates and damages weldability. Therefore, the optimum basicity (B) value for securing both toughness and weldability is preferably 0.95 to 2.10.

The flux having the composition described above is heated and dried for about 30 to 60 minutes at 200 to 500 ° C firstly after the components are uniformly mixed and granulated. After cooling the dried flux and sintering again to 700 ~ 800 ℃ to produce a flux having a predetermined particle size. This process follows the conventional method for producing sintered flux for submerged arc welding.

Properly adjusting the particle size distribution of the completed flux ensures good bead shape during welding and prevents undercutting. In addition, by maintaining an appropriate particle size distribution, there is an advantage that the gas component generated during welding can be effectively released to the outside, and also prevent the invasion of components in the atmosphere into the molten metal.

Suitable particle size distributions for fluxes having such composition and basicity include 5% by weight of particles having a flux particle diameter of 1.70 mm or more, 15 to 30% by weight of particles having a particle size of 1.70 mm or more, and less than 1.00 mm or less 0.30 to the total weight of the flux. It is preferable to set it as 65 to 85 weight% of the particle | grains which are mm or more, and 10 weight% or less of the particle | grains less than 0.30 mm.

If the particles having a particle size of 1.70 mm or more exceed 5% by weight, the molten slag is discharged during the high heat input welding such as double-sided single layer welding, resulting in uneven appearance of the beads, and the space between the fluxes increases, so that the components in the atmosphere are molten metal. As it penetrates into, it degrades the mechanical properties of the weld.

In addition, when the particle size of less than 1.70 mm and less than 1.00 mm is less than 15% by weight, the width of the beads is not uniform during the low current welding of the downward fillet welding, and undercut occurs. On the other hand, when the particle size of less than 1.70 mm and more than 1.00 mm exceeds 30% by weight, the beads tend to be convex during the high heat input welding of the double-sided single layer welding.

When less than 65% by weight of particles less than 1.00 mm and less than 0.30 mm, beads are convex or rough in the heat input welding of double-sided single layer welding, and when the particles less than 0.30 mm and less than 1.00 mm are 85% by weight or more, downward fillet welding The bead width is non-uniform in the low current welds of and undercut is likely to occur.

In addition, when particles smaller than 0.3 mm exceed 10 wt% of the total weight of the flux, gas components generated during welding cannot be released, and flux and molten slag are discharged to impair welding workability.

Therefore, the particle size distribution of the flux is 5% by weight of particles having a flux particle diameter of 1.70 mm or more, 15 to 30% by weight of particles less than 1.70 mm and 1.00 mm or more, and 65 to 85 weight of particles less than 1.00 mm and 0.30 mm to the total weight of the flux. It is preferable to make the particle | grain less than% and 0.30 mm into 10 weight% or less.

Next, the characteristics of the low temperature toughness and welding workability of the flux having the configuration according to the present invention will be more specifically described through Examples, but the present invention is not limited to the following Examples.

In order to evaluate the low temperature toughness and welding workability of the flux satisfying the composition and particle size distribution as described above, each flux was prepared according to the composition and particle size distribution of Table 1 and Table 2. The flux having the composition of Table 1 was first dried at 300 ° C. for 30 minutes, and then sintered at 800 ° C. for 1 hour to obtain a sintered flux. The obtained flux was screened according to the particle size distribution of Table 2 to obtain the final flux. Other components in Table 1 include Na ₂ O, K ₂ O, Li ₂ O and the balance metal powder and ferroalloy.

division Flux Components, Weight% B CaO MgO SiO ₂ Al ₂ O ₃ CaF ₂ MnO CO ₂ Other Ingredients Sum Inventive Example One 8 31 21 26 5 4 1.0 4.0 100.0 1.15 2 10 36 19 19 6 8 1.0 1.0 100.0 1.61 3 10 34 17 15 8 7 1.5 7.5 100.0 1.80 4 6 30 23 28 5 3 1.5 3.5 100.0 0.97 5 9 28 22 27 7 5 0.5 1.5 100.0 1.04 6 9 27 18 25 9 9 2.0 1.0 100.0 1.18 7 6 27 17 25 10 11 1.5 2.5 100.0 1.12 8 6 26 19 29 11 5 2.5 1.5 100.0 0.96 9 11 31 16 15 13 11 2.0 1.0 100.0 1.79 Comparative example 10 4 17 30 32 10 4 1.0 2.0 100.0 0.46 11 10 33 19 19 6 8 2.0 3.0 100.0 1.51 12 15 39 16 14 6 6 2.0 2.0 100.0 2.35 13 2 15 21 25 20 15 1.5 0.5 100.0 0.51 14 5 22 23 28 8 11 1.0 2.0 100.0 0.73 15 8 26 17 23 7 5 2.0 12.0 100.0 1.19 16 6 30 20 24 9 8 1.5 1.5 100.0 1.13 17 7 28 10 27 11 9 2.5 5.5 100.0 1.49 18 17 22 20 21 5 10 2.5 2.5 100.0 1.28

division Particle size distribution of flux, weight% 1.70mm or more Less than 1.70mm More than 1.00mm Less than 1.00mm 0.30mm Less than 0.30mm Sum Inventive Example One One 20 75 4 100.0 2 One 21 73 5 100.0 3 2 19 74 5 100.0 4 2 26 69 3 100.0 5 3 18 75 4 100.0 6 One 23 71 5 100.0 7 One 16 81 2 100.0 8 2 25 69 4 100.0 9 2 24 70 4 100.0 Comparative example 10 2 17 81 - 100.0 11 10 45 44 One 100.0 12 2 21 75 2 100.0 13 One 21 76 2 100.0 14 One 23 72 4 100.0 15 2 17 79 2 100.0 16 - 17 67 16 100.0 17 2 51 39 8 100.0 18 3 28 68 One 100.0

Using the prepared final flux, the test base material of the standard shown in Table 3 was welded with the welding wire of the standard shown in Table 4, each welding condition is shown in Tables 5 to 7, and the evaluation results are shown in Tables 8 to 10. . In Table 3, the division of B1 to B4 is referred to FIGS. 1 to 3, and in Table 4, the division of W1 and W2 is referred to Tables 5 to 7.

division Steel grade Thickness (mm) Chemical composition of the base material, weight percent C Si Mn P S B1 SM490 15 0.15 0.30 1.38 0.010 0.001 B2 SM490 20 0.15 0.32 1.35 0.010 0.001 B3 SM490 40 0.16 0.32 0.39 0.009 0.001 B4 SM490 50 0.15 0.31 1.40 0.010 0.001

division Wire diameter (mm) Chemical composition of the wire, weight percent C Si Mn P S W1 4.8 0.07 0.03 1.92 0.011 0.008 W2 6.4 0.07 0.03 1.93 0.011 0.007

Table 5 shows down fillet welding conditions, Table 6 shows butt welding conditions, and Table 7 shows multilayer welding conditions.

Electrode position Wire type Current (A) Voltage (V) Speed (cm / min) Electrode spacing (mm) Leading electrode W1 1100 32 65 45 Trailing electrode W2 850 41

Weld Electrode position Wire type Current (A) Voltage (V) Speed (cm / min) Electrode spacing (mm) Front Leading electrode W1 1200 35 45 45 Trailing electrode W2 1050 41 back side Leading electrode W1 1300 36 45 45 Trailing electrode W2 1100 42

pass Electrode position Wire type Current (A) Voltage (V) Speed (cm / min) Electrode spacing (mm) One Leading electrode W1 650 32 35 - 2 Leading electrode W1 850 33 50 45 Trailing electrode W2 800 35 3 Leading electrode W1 900 34 45 45 Trailing electrode W2 850 35 4 Leading electrode W1 950 35 40 45 Trailing electrode W2 900 37 5 Leading electrode W1 1000 35 45 45 Trailing electrode W2 950 38 6-10 Leading electrode W1 1000 35 40 45 Trailing electrode W2 950 38

In addition, Table 8 is a welding workability evaluation results of the downward fillet welding, Table 9 is a welding workability evaluation results of the butt welding, Table 10 is a welding workability evaluation results of the multi-layer welding. For evaluation of low temperature toughness for butt welding and multi-layer welding, impact test specimens were taken with the V-notch at the center of the weld section (half position of thickness), and Charpy V-notch impact at -60 ℃. Absorption energy (J) by the test is shown. In each table, O is good, Δ is normal, and X is inferior, and the comparative examples are shown for the invention examples and the comparative examples.

division Slag peelability Bead Appearance Bead Waveform Bead parallelism Undercut Penetration depth Inventive Example One O O O O O O 2 O O O O O O 3 O O O O O O 4 O O O O O O 5 O O O O O O 6 O O O O O O 7 O O O O O O 8 O O O O O O 9 O O O O O O Comparative example 10 △ X X X O △ 11 O △ X △ O △ 12 X X X X △ O 13 △ X X △ X O 14 O O O O O O 15 △ X X X O △ 16 △ X X △ O △ 17 X △ △ X △ O 18 △ X △ O O O

division Slag peeling Bead Appearance Bead Waveform Bead parallelism Undercut Penetration depth Absorbed energy (J) Inventive Example One O O O O O O 78 2 O O O O O O 92 3 O O O O O O 98 4 O O O O O O 74 5 O O O O O O 77 6 O O O O O O 77 7 O O O O O O 76 8 O O O O O O 73 9 O O O O O O 96 Comparative example 10 O X X X O △ 30 11 O X X X O △ 56 12 X X X △ △ O 112 13 △ X X △ X O 29 14 O O O O O O 24 15 △ X X X O △ 73 16 △ X X △ O △ 75 17 X X X X △ O 85 18 △ X X △ O O 79

division Slag peeling Bead Appearance Bead Waveform Bead parallelism Undercut Penetration depth Absorbed energy (J) Inventive Example One O O O O O O 88 2 O O O O O O 101 3 O O O O O O 103 4 O O O O O O 85 5 O O O O O O 84 6 O O O O O O 86 7 O O O O O O 89 8 O O O O O O 91 9 O O O O O O 103 Comparative example 10 O X X X O △ 32 11 △ △ X △ O △ 51 12 X X X △ △ O 114 13 △ X X △ X O 25 14 O O O O O O 21 15 △ X X X O △ 90 16 △ X X △ O △ 89 17 X △ △ X △ O 83 18 △ X X △ O O 92

When comprehensively evaluating Tables 8 to 10, the invention example showed good weldability in down fillet welding, butt welding and multi-layer welding, and the absorbed energy value, which is an evaluation item of low temperature toughness, was also higher than that of the comparative example. In particular, Inventive Examples 2, 3 and 9 showed a relatively high toughness with a slightly higher basicity than other Inventive Examples.

On the other hand, Comparative Example 10 had a good particle size distribution, but the MgO content was very low toughness was measured, the content of SiO ₂ and Al ₂ O ₃ was exceeded, the appearance of beads, bead waveform and bead parallelism was very poor.

In Comparative Example 11, all the chemical components of the flux satisfy the conditions of the present invention, but in the particle size distribution, the content of the particles of 1.70 mm or more and the particles of less than 1.70 mm or more and 1.00 mm or more exceeded the range, and the particles of the particles less than 1.00 mm and 0.30 mm or more. The content was less than the range and showed very poor bead appearance, bead waveform, and bead parallelism in butt welding.

In Comparative Example 12, the content of CaO and MgO exceeded the range, and the basicity was high, indicating very good toughness. However, weldability such as bead appearance was very poor.

In Comparative Example 13, the content of CaO and MgO was less than the range, and the basicity was very low, indicating poor toughness. In addition, the content of CaF ₂ and MnO exceeded the range of the bead appearance was poor, undercut occurred.

In Comparative Example 14, both the chemical composition and the particle size distribution constituting the flux satisfied the scope of the present invention, but showed a low toughness compared to good welding workability due to the low basicity.

In Comparative Example 15, the basicity value and the particle size distribution satisfy the scope of the present invention, but the sum of one or more components selected from Na ₂ O, K ₂ O and Li ₂ O is too high, making the arc very unstable and convex during welding. Beads occurred and the appearance of beads was very poor.

In Comparative Example 16, although the flux chemical composition and basicity value satisfied the scope of the present invention, the particle size distribution was less than 0.30 mm, the toughness was good because the content of the particles exceeded the range, but the appearance of the beads was poor, in particular, the double-sided single layer weld The bead parallelism and the bead waveform were very poor in the high heat input welding.

In Comparative Example 17, the content of SiO ₂ was less than the range, resulting in poor slag peelability and bead parallelism. In addition, in the particle size distribution, the content of the particles less than 1.70 mm and more than 1.00 mm exceeded the range, and convex beads occurred after double-layer welding.

In Comparative Example 18, the content of CaO exceeded the range, resulting in poor bead appearance and generation of fork marks.

As described above, in the present invention, by optimizing the chemical composition and particle size distribution of the flux, it is possible to obtain excellent welding workability in the bottom fillet welding, butt welding and multilayer welding of the middle and thick plates, especially basicity (CaO + MgO) Good low-temperature toughness could be secured by adjusting the value of / (SiO ₂ + 0.5Al ₂ O ₃ ).

Claims (1)

In the flux for submerged arc welding, The flux is 3.0 to 11.5 wt% CaO, 18.5 to 37.0 wt% MgO, 15.5 to 25.5 wt% SiO ₂ , 13.5 to 30.0 wt% Al ₂ O ₃ , 4.5 to 14.5 wt% Of CaF ₂ , 3.0 to 12.5% by weight of MnO and carbonate minerals in terms of 0.5 to 2.5% by weight of CO ₂ , Na ₂ O, K ₂ O and Li ₂ O 4.5 wt%, consisting of metal powder and ferroalloy as remainder, The basicity (B) value of the flux represented by Equation 1 below satisfies 0.95 to 2.10, ..... Equation 1 As the particle size distribution of the flux, the particle size of the flux is not less than 5% by weight of particles of 1.70 mm or more, 15 to 30% by weight of particles less than 1.70 mm and 1.00 mm or more, and 65 to 85 weight of particles less than 1.00 mm and 0.30 mm or more. %, Sub-merge arc welding flux, characterized in that the particles less than 0.3mm 10% by weight or less.