JPS6352794A - Baked flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To improve the workability of low-alloy steel welding and the toughness of a weld metal by incorporating CaO, MgO, SiO2, Al2O3 and metal fluoride which are slag forming agent components, metal carbonate which is a gas generating agent component and metallic powder at specific ratios into the flux. CONSTITUTION:The compsn. contg., by weight, 12-18% CaO, 22-31% MgO, 8-20% SiO2, 22-35% Al2O3, and 5-15% metal fluoride, 5-12% metal carbonate in terms of CO2, and 1-10% metal powder and satisfying formulas I-III is used for the titled flux. This flux is the baked flux of a high basic component series contg. the metal carbonate at a high ratio and permits satisfactory working in various kinds of weldings even if the flux is used under small heat input welding conditions by increasing the welding speed. Further, this flux has the extremely small quantity of diffusible hydrogen and high cracking resistance and yields the high toughness weld metal.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a fired flux for submerged arc welding, which is particularly used for welding low-alloy steels such as high-strength steel and low-temperature steel, and has good welding workability. The present invention also relates to a sintered flux for submerged arc welding that produces low hydrogen and high toughness weld metal.

(Prior art) Submerged arc welding of welded structures made of low-alloy steel is performed under relatively small current welding conditions due to the performance of the weld metal. In addition, the weld metal must have a low amount of diffusible hydrogen and be resistant to cold cracking, and it must also have good welding workability such as slag removability, bead appearance, and bead shape. Ru.

First of all, a flux with a high basic component that can reduce the elemental content of the weld metal by 1.2 yen is required to obtain a high-toughness soluble metal (+/-). Sintered flux is being proposed.

However, since the high-altitude-based fusion type flux absorbs a large amount of hydrogen during molten manufacturing, it is difficult to completely reduce the amount of diffusible hydrogen in the weld metal, and there is a problem that low-temperature cracking due to hydrogen is likely to occur.

On the other hand, sintered flux is manufactured by adding a fixing agent to a mixed powder of various raw materials, granulating it, and then firing it at a temperature of about 450°C to 600°C.
Since it is possible to contain metal carbonate such as O3 as a gas generating agent component, CO□ gas generated by the decomposition reaction of metal carbonate during welding lowers the hydrogen partial pressure in the arc atmosphere and improves welding. By reducing the amount of hydrogen dissolved in the metal, the amount of diffusible hydrogen in the weld metal can be lowered compared to a highly basic melting type flux. However, in order to significantly reduce the amount of diffusible hydrogen in the weld metal, it is necessary to contain a large amount of metal carbonate, and in addition, raw material powder of high melting point oxides such as alumina, magnesia, and silica sand must be used as a slag forming agent component. Due to its inclusion in the housing, melting during welding is not smooth, and when used for welding low-alloy steel, which is performed under relatively small current heat welding conditions in order to obtain high-toughness weld metal, it is difficult to melt easily during welding. 1. Occurrence of pockmarks (indentations caused by gas on the bead surface), which are surface defects, or roughness of the ♂-1-waveform, or poor compatibility between the bead P toe and the underlying bead or base material wall surface within the groove. Welding workability becomes a problem. For example, recently, in JP-A-61-115694, a submerged arc welding method for high-tensile steel L7 using highly basic sintered Fusix gold containing a large amount of metal carbonate has been proposed. According to experiments by the inventors, in order to shorten the total welding time using the flux of the composition system disclosed in the above publication, welding speed + f total speed 1 - can be used for narrow gap multi-layer welding of extremely N steel and for double-sided single-node ξ of thin plates. Used for welding
In some cases, the potmark resistance is not necessarily sufficient and the bead appearance is similar to that seen when using molten flux.
A smooth B-P with good shape cannot be obtained. In addition, the present inventors have previously reported in Japanese Patent Application Laid-Open No. 1081/1981, 94, that there are disadvantages when using conventionally common high MgO based high basicity sintered flux under small current dwarf heat welding conditions. We proposed a fired flux for Zabmerge mark welding that completely improved welding workability, but as a result of further investigation, we found that welding workability deteriorated when welding was performed at a faster welding speed. Further improvements were needed.

(Problems to be Solved by the Invention) Therefore, the present invention uses submerged arc welding of low alloy steel to reduce diffusible hydrogen -1t'lr of the weld metal.
Without losing the characteristic of the sintered flux that it can completely prevent the occurrence of cold cracking, various welding workability is good even when welding is performed by increasing the welding method by 1ffik, especially under small current dwarf heat welding conditions, and The purpose of the present invention is to provide a sintered flux for submerged mark welding that can provide weld metal with high toughness.

(Means for Solving the Problems) As a result of detailed study by the present inventors using various prototype fluxes, the slag forming agent components were CaO, Mg0°8102
, An20. 17 as the main component, containing a metal fluoride, and further containing CaCO3゜M as a gas generating agent component.
The above-mentioned problems were solved by developing a highly basic calcined flux containing metal carbonate such as gCO3 and metal powder in appropriate ranges.

That is, the gist of the present invention is to provide a sintered flux for submerged arc welding consisting of a mixture of a slab forming agent, a gas generating agent, and a metal powder, which contains CaO1,2 to 18% by weight.
Jin, Mg022~31 Jin, 5io2s~20 Jin, A#,
20622-35 壬, metal fluoride 5-15 彊, metal carbonate in 002 equivalent amount 5-12, and metal powder 1-10
This is a sintered flux for Zabmerge mark welding which is characterized by containing 4. and satisfying the following conditions.

(Function) First, the flux of the present invention needs to be a sintered flux, and as mentioned above, in order to satisfy the high toughness level required for weld metal of low alloy steel, the amount of oxygen in the weld metal is It is necessary to use a flux with a highly basic component that can reduce the amount of hydrogen in the weld metal.In this case, a sintered flux that can contain metal carbonate can significantly reduce the total amount of diffusible hydrogen in the weld metal than a molten flux. This is because low-temperature cracking can be completely prevented.

The reasons for limiting the components of the flux of the present invention will be explained below.

Ca, 012 to 1.84: When CaO is less than 12, the basicity of the flux decreases and a high toughness weld metal cannot be obtained. On the other hand, if a large amount of CaO is contained in excess of 18%, pockmarks occur frequently and the waveform becomes rough.
The appearance of the bee P becomes poor, such as the toe becoming uneven.

Mg022 to 31 excellent: If MgO is less than 22, the basicity of the flux decreases and a weld metal with high toughness cannot be obtained. On the other hand, if MgO is contained in a large amount exceeding the ratio 31, a thin convex bead will be formed without spreading, and this defective bead shape may cause slag entrainment defects, for example, in narrow gap multi-layer welding of extra-thick steel. It causes the occurrence.

When SiO□8-20qb:5IO2 is less than 8, the viscosity of the slag is insufficient, resulting in a meandering bead and poor bead shape. Conversely, when 5i02 exceeds 20, the basicity of 7 lux decreases and the toughness of the weld metal decreases.

A#, 20522-35%: If htb2o3 is less than 22mm, a smooth bead with good bead shape and appearance cannot be obtained.On the other hand, if it is contained in a large amount exceeding 35mm, the base 1 of the flux decreases. However, a weld metal with high toughness cannot be obtained, the bead waveform is rough9, the appearance is poor, and slag removability is poor in narrow gap multilayer welding.

Metal fluoride 5-15 exposure: Metal fluoride reduces the oxygen content of the weld metal, improves toughness, lowers the melting point and viscosity of slag, adjusts the fluidity of slag, and improves the overall bead shape. Ingredients to be included: CaF2, Mg
If the total amount of metal fluorides such as F2, NaF, etc. is less than 5, these effects will not be fully exhibited.On the other hand, if the amount exceeds 15, the arc becomes unstable and slag entrainment defects occur. The appearance of the bead and the shape of the bead become poor due to the occurrence of bumps and slag entrainment.

In addition, as raw materials containing all of the above slag forming agent components, CaO sources include wollastonite, calcium carbonate, etc.
MgO sources mainly include magnesia clinker-1 magnesium carbonate, 5102 sources mainly include wollastonite, silica sand, and silicates (water glass used as a binder), and A1205 sources mainly include metal fluorides such as alumina powder. The source is mainly goldstone,
Magnesium fluoride, sodium fluoride, etc. Also,
It is also possible to use a melt-type flux that contains two or more of the above-mentioned components and is artificially melted and produced as part of the raw material.

Metal carbonate CO2 equivalent amount: 5 to 12: Metal carbonate generates all CO2 gas due to decomposition reaction during welding, and is used to reduce the partial pressure of water vapor in the arc atmosphere metalworking and the amount of diffusible hydrogen in weld metal. This is a component to be included. Considering the moisture absorption of flux from the atmosphere during welding, CaCO3, Mg
The total amount of 002 equivalent amount of metal carbonates such as CO3 is 5qb
If it is less than 1, the amount of diffusible hydrogen in the weld metal is insufficiently reduced, and for example, when welding HT2O steel at a preheat source [100'C or less], cold cracking is likely to occur.

However, when the CO2 equivalent amount exceeds 124, welding workability becomes extremely poor, such as unstable arc, poor bead shape, frequent occurrence of pock marks, and occurrence of slag entrainment.

In addition, CaO, M produced by the decomposition reaction of metal carbonates
Metal oxides such as gO act as slag forming agent components, and in the flux of the present invention, the contents of CaO and MgO include the amounts of each acid (CaCO3 and MgCO6) in terms of arsenic.

Further, the type of metal carbonate is not particularly limited, and in addition to CaCC)5 and MgCO3, BaCO3
, r6003°SrCO3+ LS2CO5, etc. can also be included as appropriate.

Metal powder 1 to 10: Metal powder is mainly used as a deoxidizing agent.
By containing large amounts of deoxidizing elements such as Mn, A#, Ti, etc. alone or in the form of alloys, it suppresses an increase in the amount of oxygen in the weld metal, suppresses the tendency to generate pock marks, and provides good bead performance. In order to obtain the P appearance, it is necessary to contain P at least once. Furthermore, in addition to the above deoxidizing elements, N is added to improve the strength and toughness of the weld metal.
i, Cr, Mo, Nb.

It is possible to add various alloying elements such as V, or to include Fe powder to improve welding efficiency, but if the metal powder is contained in a large amount exceeding a factor of 10, granulation during production of 7 lacs will occur. Weld metal performance deteriorates due to segregation of metal powder due to powdering due to flux recombination, and furthermore, slag seizes, spatter-like metal particles adhere to the bead surface, and bits occur. The characteristics of the flux of the present invention tend to be lost, such as shaky υ and poor shivy P shape due to the increased bulk density of the flux in narrow gap multi-layer welding, so the total amount of metal powder is Must be less than 10 times.

Furthermore, the flux of the present invention is limited to a specific range that satisfies the following conditions in terms of the content range of each of the above components.

By defining the relationship between the contents of CaO and MgO, which are basic components, the bead shape can be particularly smoothed and a sound weld metal without internal defects can be obtained. CaO and M
When the content ratio of gO is less than 0.50, that is, Ca
If the content of O is low (if the content of MgO is too high, the melting point of the slag will rise, for example, both sides of a thin plate 1). The potency, shape, and appearance became defective, and the thick plate
~40'V groove, especially first pass welding and 1 layer 1 of extra-thick steel
In narrow-gap multilayer welding using pass welding, internal defects such as poor fusion and slag entrainment due to poor bead shape are likely to occur.

Flux can also sufficiently improve slag removability, which is a problem in narrow-gap multi-layer welding of extra-thick steel, which is becoming increasingly popular due to the recent desire to shorten welding time and reduce hot material costs. In order to do this, it is necessary to make the slag that is generated glassy and easy to break.
The content of 5i02, which promotes vitrification of the slag, is extremely important. On the other hand, CaO and MgO are components that crystallize slag to form a very hard and unbreakable slag.

In addition, 5in2 is also a component that maintains the overall viscosity of the slag from 1 to 1 and improves the bead shape. Therefore, the content of SiO2 must be determined in relation to the content of CaO and MgO.

If it is less than 0.15, crystallization of the slag progresses, resulting in poor slag removability and insufficient viscosity of the slab, resulting in poor bead shape. Conversely, the viscosity increases, fluidity is insufficient, and bead shape becomes poor in narrow gap multilayer welding.

fully satisfies the high toughness level required of the weld metal in welding low-alloy steel, and in addition to the addition of the metal fluoride and deoxidizing agent, it forms a highly basic molten slag. It is necessary to reduce oxygen ftff of the weld metal as much as possible by deoxidizing reaction.

It is contained as a slag forming agent component and represents a basic modification of the basic component light flux, and no welding style can be obtained. In addition, the upper limit is 2.50 from the viewpoint of welding workability.
It is preferable that it is below.

In addition to the above-limited components, the flux of the present invention also contains Ti.
Metal oxides such as O2, MnO, and ZrO2 can also be included as necessary. Moreover, Na2O, which is a component of water glass used as a fixing agent, effectively contributes to improving arc stability. Furthermore, although the effect of adding B to provide a highly malleable weld metal center has been known for a long time, it is also possible to include an oxide of B in the 7 lac.

Hereinafter, the effects of the present invention will be illustrated in more detail with reference to Examples.

(Example 1) Sintered flux (F1 to F14) whose components are shown in Table 1
'! A prototype was manufactured. The manufacturing method is to add water glass to a mixed powder of various raw materials, and after granulation, the Franks temperature is 530℃ (±
Firing was performed at 10° C. for 90 min. In addition,
The particle size structure of the flux after firing is 8 meshes or less, coarser than 12 meshes, and 100 meshes or less, finer than 10 meshes, and the bulk density of the flux is measured according to JIS Z 2504! 5
0.90~L15? /crl range. After re-drying these fluxes under the conditions of holding at 350°C for 1 hr, they were combined with wire Wl (wire diameter: 4 mm) having the chemical composition shown in Table 2, and the plate thickness t having the chemical composition shown in Table 3 was obtained.
-80 angle HT80@B1 with the shape shown in Fig. 1(a), tl = 5011a, R1-6 simple R9α, -4° U
Figure 1 (b) with groove groove and welding conditions shown in Table 4.
As shown in Figure 2, a narrow gap multi-layer welding test for IJdIA welding was conducted.

First, welding workability during welding was observed, as well as internal defects in the weld diameter and the occurrence of cold cracks.

Next, as shown in FIG. 1(b), the plate thickness direction t2-25
JI84 No. 2 sm V-notch Charpy impact test piece A with a notch B in the center of the weld metal with the seagull position as the center
and JISA No. 2 tensile test piece C1, and an analysis sample was taken from the same position as the same tensile test piece and subjected to the test. These results are summarized in Table 5.

Testers 1 to 5 used slacks of the present invention (Fl to 5), and in all cases, good welding workability was achieved, no cold cracking occurred in the weld metal, and high impact values were obtained. Exam A6
-14 are cases in which comparison fluxes (F6 to F14)'Jk were used, and good welding work was achieved because the respective components of the fluxes of the present invention were outside the limited range (indicated by underlines in Table 1). In addition, since the basicity of the slack in Uchiya 6 is too low, the amount of oxygen in the weld metal increases and the impact value decreases, and in A7 and 8, the flux contains less metal carbonate. Cold cracking occurred due to too much heat.

(Example 2) Flux of components shown in Table 1 (Fl, 4 and F 7
, 8 , 9 , 11)'! rIn combination with wire W2 (wire diameter 4.0 mm) having the chemical composition shown in Table 2, 3.5 mm N1 with the chemical composition shown in Table 3 having a plate thickness t=14sn
Steel B2' has the shape shown in Fig. 2 (a) and tl = 7 m.
, α.

A 1-nog welding test was conducted on both sides under the welding conditions shown in Table 4, with a butt Y groove of =70°. Observation of welding workability and P under the condition of 600'ex Ihr after welding.
Figure 2(b) shows weld metal subjected to WHT treatment.
As shown in , JISA No. 2 impact test piece A and JISA No. 2 tensile test piece C were taken, with a notch Bi placed in the center of the weld metal centered at the position of t2 = 7 + m in the plate thickness direction.
Each was subjected to a test. Table 6 shows the results.

Tests A 15 and A 16 were conducted using the flux of the present invention (Fl
.

B-P with good shape and appearance when using F4)
was obtained, and a very high impact value was obtained. Ya 17-20 are comparative fluxes (F7, 8, 9).

11), the bead appearance and shape were poor.

(Example 3) Flux of components shown in Table 1 (Fl, F4°F8)'
Immediately after re-drying at 350°C for 1 hour and after absorbing moisture in a constant temperature and humidity chamber at 30°C and humidity of 80 m, the weld metal was tested for diffusible hydrogen by gas chromatography according to WES1003. I did it. Table 7 shows the results.

Test boil 21 and Ya 22 are the flux of the present invention (Fl,
F'4), 3. even after moisture absorption. Ome/Welding amount showed an extremely low value of 1009, whereas A2
3 is the case of comparative flux (F8), metal carbonate (C
Since the content of aCO3) was too low, the amount of diffusible hydrogen, especially after moisture absorption, was significantly increased compared to the flux of the present invention.

*2) Metal powder: Fe-8t, St, Fe-
Mn, Fe-A#.

Aj3, deoxidizing agent such as Fe-Ti, *3) remainder:
K2O, Na2O, L120, FeO and inevitable impurities, etc.

Table 6 3.54Ni steel double-sided IA steel welding test result 1
) Flux symbol, *mark: Invention flux, no mark:
Comparison flux 2) The impact value is the average value of each three pieces (Effect of the invention) The present invention uses dwarf heat welding, which is performed at a high welding speed using a sintered flux with a highly basic component system containing a large amount of metal carbonate. A sintered flux for submerged arc welding for low-alloy steel that has good welding workability even when used under various conditions, has an extremely low amount of diffusible hydrogen, has excellent cracking resistance, and produces high-toughness weld metal. Moreover, it has extremely high industrial practicality.

[Brief explanation of the drawing]

Fig. 1 shows the construction, Fig. 2 (3) shows the groove shape, Fig. 2 (b) shows the layering method, and the sampling positions of the impact test piece and the tensile test piece. A... Sampling position of JI84 No. 2 + mV notch impact test piece B... Same notch position C... Sampling position representative of JI K2 tensile test piece
Patent Attorney Masaaki Akizawa Mitsunobu 1 Nagishi, 2 Figures Voluntary Procedure Amendment 1: September 22, 1986

Claims (1)

[Claims] (1) In a fired flux for submerged arc welding consisting of a mixture of a slag forming agent, a gas generating agent, and a metal powder, in weight percent, CaO 12-18%, MgO 22-31%, SiO_2 8-20%, Al_2O_3 22 -35%, metal fluoride 5-15%, metal carbonate 5-12% in terms of CO_2, and metal powder 1-10%, and CaO%/MgO%≧0.50, SiO_2%/ CaO%+MgO%+SiO_2%=0
．． 15~0.30(CaO%+MgO%)/(SiO_
A sintered flux for submerged arc welding, characterized in that it satisfies the following condition: 2%+0.5Al_2O_5%)≧1.50.