JPS60187495A - Fused flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To obtain an excellent fused flux for submerged arc welding by constituting the flux of a specific amt. of SiO2, CaO, F, Al2O3, TiO2 and one or >=2 kinds of MgO and BaO, one or >=2 kinds among K2O, Na2O, Li2O and MnO. CONSTITUTION:A fused flux for submerged arc welding is made of the compsn. contg., by weight %, of >35 SiO2, <10 CaO, 1.5-6 F, <15 Al2O3, 1-8 TiO2 and 10-25 total of MgO and BaO. A (one and >=2 kinds among K2O, Na2O and Li2O)/F ratio is made 0.1-0.4, SiO2+Mn is made 55-70 and an SiO2/MnO ratio is made 1.4-1.9.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a molten flux for submerged arc welding, and more specifically to a 50 to 60 kg mild steel flux used in the construction of buildings, bridges, shipbuilding, etc. / am Submerged arc welding is mainly used for fillet and butt welding of class 2 high tensile strength steel, and has excellent slag releasability, bead shape, and appearance, low diffusivity hydrogen meter, and high toughness. This provides a molten type flux for use in

(Prior Art) Generally, for fillet welding in architecture, bridges, and shipbuilding, the submerged arc welding method is used because it provides a good bead shape and appearance and is highly efficient. Bamboo arc flux is classified into molten type and sintered type, and molten type flux is less likely to absorb moisture than sintered type, and there is less precipitation of flux components.
Since the appearance of the weld bead is excellent, it is suitable for fillet welding where it is important to obtain a good bead appearance without surface defects such as pits and pockmarks.

Among molten fluxes, fluxes whose main components are SiO2 and MnO, which are shown in Japanese Patent Publication No. 51-46653 and Japanese Patent Publication No. 55-42671, are slag which is important in downward fillet welding with dwarf heat. Although the releasability and bead shape are good, under relatively large heat input conditions, that is, long-leg welding conditions, slag may burn onto the surface of the bead.
It was unavoidable that the uniformity of the bead shape was poor and undercuts were likely to occur. However, since the flux composition of 8102-MnO yarn is acidic, it is essentially difficult to obtain high toughness of the weld metal.

Frozen, a flux containing a large amount of CaO and CaF 2 and excellent in toughness and hydrogen cracking resistance.
No. 81445, etc., but because it contains a large amount of CaO and CaF2 components, the slag removability was not satisfactory.

In order to improve the slag removability, the TlO2 component was added to 2 parts.
It has been proposed in JP-A-55-10356 and JP-A-57-14496 to make the content constant to about 0.

However, when a large amount of TlO2 component is contained, the slag density increases, and in downward fillet welding, the bead shape becomes a so-called medium-high bead in which only the center portion is high, and it cannot be applied to fillet welding where shape and appearance are important.

1 In the field of construction, architecture, bridges, and shipbuilding, fillet joint welding and butt joint welding are included in one structure, and welding of joints with mild steel and 60 kg class high-strength steel is also included. Depending on the purpose, we use different fluxes for welding parts of the same structure, such as 7-Lux, which emphasizes workability, or flux, which takes into account the toughness of the welded parts. In other words, 5i02-MnO-based flux cannot be used in welded parts that require high toughness, and a neutral or basic flux must be used, which may result in poor slag removability, poor bead shape and appearance, etc. Even though it is there, I use it out of necessity.

Poor slag removability requires a process to remove slag adhering to the bead surface, and repair welding is required to repair defects such as bits and cracks, resulting in a decrease in work efficiency.

(Purpose of the Invention) The present invention is suitable for neutral or basic welding, which can provide high toughness of the welded part, but has problems with bits, blowholes, and weld cracks due to the bead shape and high diffusive hydrogen deposition in fillet welding. Good slag removability in downward fillet welding with flux and relatively small heat, smooth concave bead shape, and low diffusivity hydrogen meter, so contact defects caused by hydrogen do not occur. This is an unprecedented melting type flux for submerged arc welding that has the advantages of acidic fluxes, which provide a good bead appearance but not high toughness, and also has no deterioration in welding workability even during high heat input welding. The purpose is to live apart.

(Technical background of the invention) When viewed from the flux composition aspect, in the conventional technology, welding workability and toughness can be said to have contradictory performances. Therefore, in trying to obtain a flux that satisfies both performances, we first considered that a certain amount of K as a basic component is essential to ensure high toughness, and investigated the effects of each basic component to be included on welding workability. Ta. In addition, we considered that stabilizing the arc is one of the conditions for obtaining good welding workability (5). In other words, by maintaining an unbroken arc state, the waves on the bead surface become finer, which in turn weakens the slag entanglement on the bead surface, which can be expected to improve slag removal and reduce the occurrence of pock marks and bits. Naturally, it is considered to be effective for From these points of view,
In order to achieve this goal, various experiments were repeated.

An experimental example is shown below.

The welding workability of various prototype fluxes is 25 as specified in JIS Z3311 Type 4, as shown in Table 1.
6 Mn-containing wire size 4.8φ (symbol W2),
A plate of 50 kg class high tensile strength steel specified by JIS G3106 Type 2 with a thickness of 16 sq.
The investigation was conducted by performing downward fillet welding under the welding conditions of 1 welding speed of 35 cm/min.

For the evaluation of toughness, the same type of wire and steel plate as those used for downward fillet welding with a size of 4.0φ (symbol Wl) and a plate thickness of 25 mm (symbol 82) were used, and the same type of wire and steel plate as those used for downward fillet welding was used. Welding current 55oA, arc voltage 30V as shown in
The impact value of weld metal welded in multiple layers under welding conditions of 1 welding speed of 40 cyn/min was investigated. The test piece is JIS
A No. 4 Charpy test piece specified in Z3112 was used, and the notch position was at the center of the welding stage.

The diffusible hydrogen meter has a welding current of 500A as shown in Table 2.
, arc voltage 33 V, and welding speed 30 cy/min under the welding conditions, using the glycerin substitution method according to the method for measuring the amount of hydrogen in submerged arc welds stipulated in JIS Z3116.

(9) First, regarding the necessity of basic components CaO, MgO, and BaO, and the influence of alkali metal compounds, we prototyped a molten flux (particle size: 20×D mesh) with the composition shown in Table 3, and tested its performance. investigated. Flux A1 in the table
was used as the basic flux in this experiment on the premise that good toughness could be obtained, and the composition contained a large amount of CaO, which is widely used as a basic component because it is an inexpensive raw material, and low in 8402. It is similar to the commercially available flux for 60 kg/mm'' grade steel, which also contains a small amount of TiO2.

(10) The value of each component of the flux is expressed as a numerical value obtained by converting the measured value of each element as a chemically stable oxide.

Regarding F, in the case of melting type flux, CllF21
Since MgF'2 y AlIF5 is defined only as F regardless of the components of F#i, it is not written as C a F 2 as conventionally used.

The results are shown in Table 4. CaO was reduced based on the components of flux A1, and the same I was replaced with MgO or B.
By substituting with aO, slag removability was improved. However, the Charpy impact value deteriorates, and in order to obtain toughness equivalent to that of the basic flux, it is necessary to further replace a portion of 5i02 and MnO with MgO or BaO as in flux A9. However, the appearance of B-P deteriorated, pockmarks were observed, and the amount of diffusible hydrogen increased.

On the other hand, by reducing CaO and adding an alkali metal compound like Flux AIO, compared to Flux A3 which inevitably contains a very small amount of alkali metal from the flux raw material used, it has improved slag removability, peed resistance, and Charpy impact. It has been found to be a very beneficial ingredient, greatly increasing the value.

(13) (14) Table 5 shows that F, which is necessary to ensure good toughness but is known to have a negative effect on slag removability and bead shape, was improved by adding it in the previous experiment. We investigated the relationship with alkali metal compounds that showed excellent performance.

The results are shown in Table 6, and it was found that the relationship between the alkali metal compound and F is extremely important.

(17) That is, the alkali metal compound is flux B2,
As with B4, the effect was hardly seen in less than 10% of F needles. Furthermore, when the flux B8 contains F at a factor of 50, the welding arc length becomes too long and the bead shape becomes medium-height like the flux B4.

However, even if the alkali metal is about 30 times the amount of F,
With Fil, 24 like flux B1, the diffusible hydrogen t is high and the impact value is low, and when the F amount is 7.0 like flux B9, a good concave bead is formed with a downward fillet. It was also found that there is a limit to the amount of F. In addition,
The alkali metals K, Na and Li are obtained from oxides, carbonates or fluorides, and according to the results of separate experiments,
K, Na, and Ll showed equivalent welding performance.

Furthermore, as a result of separate experiments, when 5io2 is less than about 35, the viscosity of the slag is low and the fluidity is high.
A good concave bead could not be obtained in fillet welding. In addition, if the 5102//MnO ratio is large, the oxygen content of the weld metal becomes high and high toughness cannot be obtained, and even if the ratio is too small, the bead shape is difficult to become concave.
It was found that there is an appropriate range of 5I02/MnO ratio.

As mentioned above, replacing CaO with MgO or BaO,
Furthermore, by adding an alkali metal compound in relation to F and limiting 8102, MnO, etc., we have created a melting type that can improve welding workability such as slag removability and bead shape, and also achieve high toughness and low hydrogen. Although a flux was obtained, even better slag removability could be obtained by adding an appropriate amount of one or both of PbO and B12O3, which are low melting point metal compounds.

(Structure of the Invention) The present invention is based on the above-mentioned findings, and its major characteristics are: (1) The flux basicity is neutral, and it can be said to be essential as a basic component in order to obtain good slag removability. The CaO component, which was very important, was limited to as low as possible.

■ As a component to obtain high toughness in place of CaO,
Contains a large amount of MgO or BaO.

■ Alkali metal compounds, which are arc stabilizing components and are extremely useful for improving slag removability and toughness, are not desirable for obtaining good slag removability and bead shape, but are used to reduce the amount of oxygen in weld metal 4. In order to obtain a low diffusible hydrogen receptacle, the effective content ratio with F should be specified.

Through the synergistic effects of these components within a very limited range, a flux with excellent welding workability and toughness was obtained.

That is, the gist of the present invention is the weight section, 5i02
: More than 35%, CaO: 1096 or less, F: 1
．． 5 to 6 chi, Al2O3: 15% or less, TiO2: 1
~8chi, total of one or two of MgO and BaO: 1
Contains 0 to 25% K2O, Na2O and Li
02)/Ftf, 0.1
~0.4.5IO2+MnO: 55-70%, 8102
/MnO ratio: 1.4 to 1.9. A melting type flux for submerged arc welding.

And, in order to obtain even better slag removability, one or both of pbo or B12O3 may be added to 0,
A submerged arc (21
) Found in molten flux for welding.

The reasons for limiting the components, component amounts, and component amount ratios of the present invention will be explained below.

8102: S102 exceeding 35% is a basic component of flux, and must be contained in an amount exceeding 35% in order to maintain appropriate slag viscosity and fluidity necessary for good bead formation. . Below 35 inches, the slag has low viscosity and high fluidity, making it impossible to obtain a good concave bead in fillet welding, and particularly under long leg welding conditions, the bead becomes medium-height.

CaO: 10% or less CaO is a strong basic component, and in conventional fluxes it is contained in large amounts in order to obtain high toughness, but in the present invention it must be as small as possible, to 10% or less. 1
If it exceeds 0%, slag will firmly adhere to the weld bead surface and removal of the slag will become extremely difficult.

F amount: 1.5 to 6 F is calcium fluoride, aluminum fluoride, (22
) It is added from metal fluorides such as magnesium fluoride and lead fluoride, and is necessary to reduce the amount of oxygen in the weld metal and obtain high toughness. If the F content is less than 1.5%, the effect will be small and the amount of diffusible hydrogen will also increase, making it more likely that bits, blowholes, and weld cracks will occur. Moreover, when the coefficient exceeds 6, the slag viscosity decreases, the arc becomes unstable, the bead forming ability deteriorates, and the slag removability deteriorates like CaO.

Al2O,: 15% or less Al2O3, if in an appropriate amount, increases slag viscosity like the 5I02 component without significantly increasing the amount of oxygen in the weld metal.
Contributes to the formation of a glossy and good fillet bead. However, if it exceeds 15%, the slag viscosity becomes too high and pock marks occur.

Ti0.2: 1 to 8% TiO2 has the effect of improving the toughness of the weld metal by refining the grains, but if it is less than 1 inch, the effect is not clear;
If it exceeds 8 inches, the slag removability will deteriorate and the fillet bead shape will be difficult to form a good concave shape.

Total of one or two of MgO and BaO; 10-25
%MgO and BaO are necessary components to maintain an appropriate degree of salinity and ensure high toughness without containing CaO, which is a strong basic component. It has been confirmed through experiments that MgO and Rao have almost equivalent performance in terms of flux physical properties and weldability, and when used alone or in combination, if the total is less than 10%, there is no effect of improving toughness as a component that replaces CaO. First, if it exceeds 25 LII, the slag viscosity increases, which tends to cause pock marks, and the amount of diffusible hydrogen increases, causing bits, blowholes, and weld cracks.

(Total of one or more of K2O, Na2O and LiO2)/F ratio: 0.1 to 0.4 The alkali metal compound is contained as an arc stabilizing component, and improves slag removability and bead shape. In addition to being extremely effective in improving the appearance of metal, M
By including it in place of gO and BaO components, toughness is improved. This appropriate content is defined in relation to F, which is an arc destabilizing component. When the F content of the alkali metal compound is less than 10%, arc stabilization and improvement in toughness cannot be obtained, and when the F content exceeds 40%, welding workability deteriorates, especially in fillet welding. becomes difficult to obtain.

Therefore, (K,20, N&20 and LIo,
2)/F ratio of 0.1 to 0
．． It needs to be 4.

8102 +MnO: 55-701 If it is less than 551, the appropriate slag viscosity required for the formation of B-P cannot be obtained, and the same is true even if it exceeds 70%, and high toughness cannot be obtained.

8402/MnO ratio: 1.4-1.98102/
As the MnO ratio increases, the amount of oxygen in the weld metal increases, and 1
．． If it exceeds 9, high toughness cannot be obtained.

Furthermore, as the ratio becomes smaller, the slag viscosity decreases and the bead shape deteriorates. In particular, if it is less than 1.4, the amount of diffusible hydrogen increases and bits and blowholes occur. Therefore, the toughness and welding workability are within a good range.
102/MnO ratio of 1.4 to 1.9 (25).

PBO or old, total of 1 or 2 types of 03: 0.00
Although it is necessary to obtain slag removability even better than 5 to 0.2 yen, if the content of the low melting point metal in the form of oxide exceeds 0.2%, the toughness deteriorates significantly, and the present invention Furthermore, if the content is less than 0.005%, there is hardly any effect on slag removability. In addition, PbO and Bi2
O3 had the same effect on improving slag removability and on the tendency to deteriorate toughness. Therefore, it is necessary that at least one of PbO and Bi2O3 be in the range of 0.005 to 0.2.

(Example) Next, the effectiveness of the present invention will be described with reference to Examples.

Melting flux with the composition shown in Table 7 (particle size: 20 x D
The same test as in the previous experimental example was conducted. Welding workability is determined by JIS 2331 as shown in Table 1.
2% Mnn-containing wire size 48φ (symbol W2> and JISz3106) (26) specified in Type 4 of 1. Plate thickness 16 mm of 50 kg class high tensile strength steel specified in Type 2.
(Symbol S1.) was examined by performing downward fillet welding with the surface black scale intact under the welding conditions of 900 A of welding current, 31 v of arc voltage, and 35 tyn/min of welding speed as shown in Table 2.

The amount of diffusible hydrogen is as shown in Table 2 at a welding current of 500A.
The measurement was carried out under the welding conditions of , arc voltage 33 V, and welding speed 30 z/min by the glycerin substitution method according to the method for measuring the amount of hydrogen in submerged arc welds specified in JIS Z3116.

For the evaluation of toughness, we used the same type of wire and steel plate as those used for downward fillet welding, with a size of 4.0φ (symbol Wl) and a plate thickness of 25 mm (symbol 82), as shown in Table 2. The impact value of weld metal welded in multiple layers under the welding conditions of 550A welding current, 30v arc voltage, and 40 tyn/min welding speed was investigated. The test piece is JIS z311
The No. 4 Charpy test piece specified in 2 was used, and the notch position was at the center of the weld metal.

The test results are shown in Table 8, and each of the comparative fluxes has drawbacks. That is, the flux D1 is 5
The main components are tO2 and MnO, and since it contains almost no MgO and BaO, it has very poor toughness.

Flux D2 is 5i02, MnO.

Even if it satisfies the constituent requirements of the present invention such as CaO and MgO, it is inferior to the present flux in terms of slag removability, bead appearance 1, and toughness because the amount of alkali metal compound is small relative to the amount of F. Flux r') 3, CaO-rich (MgO
If the flux is low, the slag exfoliating property is particularly poor, and even when FLLH exceeds the constituent requirements like flux D4, the slag exfoliating property is poor, and the bead shape is medium to high and the bead surface is rough. In addition, flux D5 is pbo and B12O3
When CaO is contained in an amount exceeding 0.2 inches, the slag removability is good even if the CaO content exceeds 10 inches, but the toughness is extremely poor. As described above, the performance of the comparative flux that does not meet the constituent requirements of the present invention is not satisfactory, but the flux of the present invention has excellent welding workability and toughness, and has a low amount of diffusible hydrogen.

(Effects of the Invention) The flux of the present invention has excellent welding workability such as slag removability and bead shape, which are not found in conventional fluxes, and can provide a highly tough weld metal. , it is possible to weld steel types from mild steel to 60 kg class high-strength steel with one type of flux, and slag can be easily removed even in fillet welding with long legs, greatly improving welding work efficiency. The industrial value is extremely large.

(31) Procedural amendment 1, indication of the case Showa (2 hands) Relationship with case No. 4z:zb3 Applicant's address (residence): Chiyo Il1 Ward, Tokyo 11
No. 6 No. 3 Name (Name) (665) Nippon Seikagaku Co., Ltd. 4, Agent address No. 116 No. 2 Marunouchi, 3308 Shizusu Building, 2-r Kuunouchi, Chodai M-ku, Tokyo, as amended. Contents Amendments as shown in the attached document The following matters have been amended in the specification of the application.

Record 1. The scope of claims is amended as shown in the attached sheet.

2, page 21, line 13, page 24, line 11, page 25, line 5
The words "LiO2" in the lines are corrected to "L120".

Claim 1 Weight % Te, 5in2: more than 35%, OaO: 1
0% or less, F: 1.5-6tI6, Al2O3:1
(K2O
, Na2O and Li2O are also 1. < is the sum of two or more types)/F' ratio: 0.1 to 0.4.5in2+MnO:
55-70%, 5iOv/MnO ratio: 1.4-1.9
A melting type flux for submerged arc welding, which is characterized by:

2 wt%te, 5in2: more than 35%, Cab: 10
% or less, F': 1.5-6%, Al2O3: 15% or less, TiO2-+: 1-8%, 1 of MgO and BaO
Species or total of two species: 10-25 and pbo and B1
Total of one or two types of 2O3: 0.005-0.2%
Containing I7, (K2O, Na2O and 1 type also (
7 is the sum of the two types) / 1i'' ratio 20.1 to 0.4.5I
O2+MnO: 55-70chi, SiO□/MnO ratio:
A melting type flux for submerged arc welding, characterized in that the flux is 1.4 to 1.9.

Claims (1)

[Claims] 1 wt%, 5I02: more than 35%, Cab: 10
% or less, F: 1.5 to 6 inches, Al2O3: 15% or less,
TlO2: 1 to 8, one or two of MgO and BaO
Total seeds: Contains 10-25 seeds, (K2O+ Na2
Total of one or more of O and L102)/F
Ratio: 0.1~0.4.5in2+ MnO: 55~7
0%, 5I02/MnO ratio: 1.4 to 1.9. A melting type flux for submerged arc welding. 2 weight 11%, exceeding 8102:35%, CaO:1
0'1 or less, F: 1.5-6%, Ag2o3: 15
% or less, TiO2: 1-8%, MgO and BaO 1
Species or total of 2 species: 10 to 25 species and pbo and B
Total of one or two types of i zo3: 0.005 to 0.
2% (K2O+ Na2O and LiO2
one type or the sum of two types)/F ratio: 0.1 to 0.4.
5i02 +MnO: 55-70%, 8102/
A melting type flux for submerged arc welding, characterized in that the MnO ratio is 1.4 to 1.9.