JPS60196290A - Baked flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To obtain a low-hydrogen weld metal having high toughness and good welding workability by contg. a specific amt. of specific essential components and specifying the basicity expressed by the specific formula. CONSTITUTION:This baked flux contains 20-50wt% CaO, 10-40wt% SiO2, 10-50wt% Al2O3 and <=40wt% CaF2 as essential components. Said flux contains 10-80wt% the fused flux in which the content of CaO is larger than the content of SiO2 and the total of SiO2 and Al2O3 is 35-60wt% as well as 3.5- 12wt% metallic carbonate in terms of CO2. The basicity expressed by the following calculation equation is 1.50-2.50. The basicity B=(CaOwt%+MgOwt%)/ (SiO2wt%+0.5Al2O3wt%).

Description

[Detailed description of the invention] Industrial applications The present invention is a firing type flare for submerged arc welding.

Regarding sintered fluxes for submerged arc welding, which are used for welding low-alloy steels such as high-strength steels, low-temperature steels, and heat-reduction steels, and provide good welding workability with low-hydrogen, high-toughness weld metals. .

Prior Art When manufacturing welded structures of low-alloy steel by submerged arc welding, wires with a well-designed composition must be used to ensure the required toughness level of the weld, especially the weld metal in question. In addition, the flux used in combination requires a highly basic flux that can reduce the amount of oxygen in the weld metal and obtain high toughness.

Conventionally, fused fluxes or calcined fluxes with various component systems have been used, but when fused fluxes use highly basic component systems, the amount of diffusible hydrogen in the weld metal increases due to hydrogen absorption during melt manufacturing. Therefore, there is a problem that low-temperature cracking is more likely to occur.

On the other hand, sintered flux is produced by blending various raw materials, adding water glass as a fixing agent, granulating it, and then sintering it at a temperature of about 500°C.
Since it is possible to contain metal carbonates such as gC03 as a flux component, the C02 gas generated by the decomposition reaction of these metal carbonates lowers the water vapor partial pressure in the arc atmosphere and increases the amount of diffusible hydrogen in the weld metal. of,
This can be significantly reduced compared to when using highly basic melting type fluffx.

Furthermore, it has the advantage of being simpler in terms of equipment and cheaper in terms of energy production costs than molten flux, which is manufactured through processes such as melting, rapid solidification, drying in the case of water cooling, pulverization, and sizing. . However, as this kind of low-hydrogen high-toughness sintered flux, a flux containing a large amount of MgO as a basic component, such as the flux disclosed in Japanese Patent Publication No. 51-11051, is generally used. Welding workability is good under heat input welding conditions, but when used under dwarf heat welding conditions or narrow gap welding of extra-thick steel, welding workability such as bead shape, appearance, occurrence of internal defects, and slag peelability may be affected. It was not completely satisfactory.

Purpose of the Invention Therefore, the present invention has been proposed to be used for dwarf heat welding and narrow gap welding of low-alloy steel. is obtained,
Furthermore, it is an object of the present invention to provide a sintered flux that has good welding workability.

Structure and Function of the Invention The structure of the present invention is that a fired flux for submerged arc welding is obtained by adding water glass, granulating it, and firing it, with Ca0 = 20 to 50% by weight as the main component, 5i0
7=10-40%, AQ203=10-50%.

Contains CaF2≦40%, and Cao%>5i02%
, 5i02% + AQ203% = 35-60%, 10-80% molten flux, 0 metal carbonate
A sintered flux for submerged arc welding characterized by containing 3.5 to 12% in terms of 02 conversion value and having a basicity B of 1.50 to 2.50 as expressed by the formula (1) below. It is.

The present invention will be explained in detail below.

First, the present inventors conducted a detailed study on improving welding workability in dwarf heat welding and narrow gap welding using prototype fluxes of various component systems. Sintered flux contains a large amount of MgO, which is a high melting point oxide, as a basic component, so the melting point of the slag system that is formed becomes too high, resulting in a convex shape that does not spread during dwarf heat welding. It has been found that the slag becomes a bead and stag entrainment is more likely to occur, and that the slag becomes a hard and hard to break crystalline slag, resulting in poor slag removability in narrow gap welding.

In order to improve this, the present inventors first included a high content of not only MgO but also CaO as a basic component of the necessary flux, thereby lowering the melting point and forming a slag system that is difficult to crystallize. We have found that highly basic calcined flux is preferable. That is, 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, CaO and MgO among the slag forming agent components are oxidized by CaCO3 and MgCO3, which occupy the gas generating agent. CaO≧18.5% by weight, including the amount equivalent to the physical equivalent value
, the metal fluoride content is 3 to 10%, and the metal carbonate as a gas generating agent is 3.5 to 12% in terms of 002.
By using a sintered flux for submerged arc welding that contains 15% or less of metal powder and trace elements and impurities, good welding workability can be achieved even in dwarf heat welding and narrow gap welding. It became clear that

However, in order to form such a CaO-rich slag system, wollastonite or limestone has been commonly used as a CaO source for calcined fluxes. Of course, quicklime, which is a product of high-temperature treatment of limestone, is also considered, but its high hygroscopicity makes it almost impossible to put it to practical use as a raw material for calcined flux. but,
As shown in Table 1, which shows composition examples of commercially available wollastonite and limestone, wollastonite contains more 5i02 than CaO, so when wollastonite is used in large quantities as a CaO source, it inevitably contains more 5i02 than CaO. A larger amount of 5i02 is contained in the flux. Furthermore, when a large amount of limestone is used as a CaO source, the amount of CO2 gas generated increases significantly, and this causes a problem in that welding workability deteriorates.

First, regarding the amount of 5i02, the amount of 5i02 contained in the flux due to water glass (silicate), which is added in a considerable amount as a fixing agent during flux granulation, is In order to minimize powderization in consideration of use, the flux should account for at least 3% of the total weight of the total weight, and if magnesia clinker or fluorite is used, a small amount of 5i02 should be included in these raw materials. Alternatively, it is contained as a trace component, and the increase in 5i02 due to these raw materials must also be considered. Therefore, if a large amount of wollastonite is used, the flux will contain more than an appropriate amount of 5i02, which tends to cause frequent pockmarking on the bead surface and extremely poor slag removability. 5 more inches
An increase in the amount of 2 reduces the basicity of the flux.

On the other hand, limestone is decomposed into CaO and CO2 gas by the reaction during welding, and is a gas generating agent as well as a powerful CaO source. However, when used in large quantities as a CaO source, the amount of CO2 gas generated is Excessive amount causes the arc to become unstable, resulting in poor bead shape and frequent pockmarks, as well as severe arc blow-up, especially in narrow gap welding, resulting in severe welding workability such as frequent slag entrainment. . Furthermore, the generation of excessive 002 gas poses a problem to welders from the viewpoint of the working environment.

Next, Figure 1 shows the CaO content and 5i0 of the calcined flux when wollastonite and limestone are used simultaneously as CaO sources.
Shows the relationship between two quantities. In addition, this figure assumes that the amount of water glass added is constant (the amount added that makes the amount of 5i02 by water glass 5% of the total weight of 7 lux), and that limestone is also added at a rate of 8.1 to 28ZCCO2, taking into account the amount of CO2 gas generated. Approximately 3.5 in converted value
The amount of CaO in the flux obtained by changing the content of wollastonite and 5i () when limiting the content to ~12%),
This is the result of calculating the relationship between quantities. Line A in the figure shows the lower limit (3.5%) of the amount of CO□ gas generated required for low hydrogenation of Franx, when 8.1z of limestone is included.
Line B-E contains 10%, 15%, 20% limestone,
In the case of 25% limestone content, line F contains 28% limestone, which is the upper limit (12%) of 002 gas generation from the viewpoint of welding workability.
% content is shown respectively. As mentioned above, in order to obtain good welding workability, CaO must be 18.5
% or more, and the upper limit is approximately 33% due to the relationship with MgO.
%Must. On the other hand, the amount of Si et al. is 10-30%
is the preferred range. The preferable range of the amount of CaO and 5i() is the range surrounded by a, b, c, and d in FIG.

On the other hand, from the viewpoint of welding workability when using wollastonite and limestone as a CaO source and the amount of 002 gas generated, the preferred ranges of CaO amount and 5i02 amount are e, f, d, h, g in the same figure. , b. That is, when wollastonite and limestone are used as CaO sources, this region is the maximum possible range of the CaO amount and the sl content, and is also the region where highly satisfactory welding workability can be obtained.

However, when it is desired to increase the amount of water glass added or when it is desired to reduce the amount of CO2 gas generated, the preferred range shifts in the direction of line A, and the region 1 becomes narrow. In addition, in the vicinity of lines E and F, where the calcareous content is high, it is necessary to increase the amount of deoxidizing agent added in order to suppress the occurrence of pockmarks due to the increase in the amount of CO2 gas generated.
Depending on the composition of the wires used in combination, slag may stick to the bead surface and deteriorate the slag removability.

The area surrounded by a, e, and f in the same figure (■) is also the maximum possible range of Can amount and 5i02 amount that can provide good welding workability, but this area is Not applicable with type flux. In this way, in calcined fluxes that use wollastonite and limestone as CaO sources, even if we try to increase the content of CaO in order to obtain good welding workability in dwarf heat welding and narrow gap welding, there is a limit. Some measures are required to increase the CaO content. As a result of various studies on this point, it has become possible to increase the CaO content of fired flux by using molten flux containing a considerable amount of CaO as a CaO source, improving the toughness of weld metal and improving welding workability. The present invention having the above-mentioned structure has been made based on the discovery that the present invention is also aimed at.

Regarding the component system of the molten flux, which is a feature of the present invention, the molten flux is used as a CaO source as described above, and it is preferable to contain as much GaO as possible, but it contains at least 20% of GaO. In addition, in order to suppress the increase in the amount of SI in the firing flux, Ca
It is an essential condition that O is contained in a larger amount than 5i07.

The main components of the molten flux other than CaO include 5i
02 by 10 to 40%, and A9203 by 10 to 50%, provided that the total of SiO; and A9203 is 35 to 60%, and it is possible to further contain 40% or less of CaF2. The component ranges defined for each of these components were determined in consideration of the solubility of the flux during production by melting, and melt-type slacks with such component systems have a low melting point and good solubility. In addition, each of the above components is a slag type (CaO-MgO-5i07-AQ 703-
The molten flux of such a component system serves as a CaO source, as well as an effective MgO source, Sin source, AQ203 source, and CaF2 source. In addition, in order to improve the solubility of the melting type flux, a small amount of Na70, K2O, etc. may be included.

Next, regarding the amount of molten flux to be included in the sintered flux, the composition of the molten flux (especially CaO
It can be freely changed depending on the component system selected depending on the amount) and the intended use of the calcined flux, but if it is less than 10%, it cannot be expected to be very effective as a CaO source.

In addition, the upper limit is [,
Considering the need to contain various raw materials to adjust the composition of the slag system, the content was limited to 80% or less. By containing the above-mentioned molten flux, a slag system with a large amount of CaO can be easily formed, and when a calcined type flux manufactured using wollastonite and limestone with almost the same composition is used, the slag type is compared to the slag type. The slag becomes more brittle and the slag removability in narrow gap welding is further improved.

Next, metal carbonates (CaCO3, MgCO3, etc.) are included to lower the amount of diffusible hydrogen in the weld metal and prevent the occurrence of cold cracking, and are used as fluxes used in welding low-alloy steel. is at least 3.5z in terms of CO2 (CO2 sludge generation amount); it must be contained. However, the content of metal carbonate is 12 in 002 conversion value.
If it exceeds 0.002%, the amount of 002 force generated becomes excessive and the arc becomes extremely unstable, resulting in extremely poor welding workability such as arc blow-off, poor heat shape, frequent pockmarking, and slag entrainment. In particular, in narrow gap welding, the adverse effects of excessive CO2 gas generation are significant, and therefore the content of metal carbonates should be kept to 12% or less in terms of CO2.

Further, in order to obtain a weld metal with high toughness, a flux with a highly basic component is required, and the basicity B expressed by the following formula (1) must be 1.50 or more.

If the basicity B is less than 1.50, the amount of oxygen in the weld metal increases and the toughness decreases. However, when the basicity B becomes higher than 2.50, the arc becomes unstable and welding workability is significantly deteriorated, such as poor repeat shape and poor reslag removability in which slag tends to crystallize.

By using fused flux as a CaO source, the present invention provides even better welding workability even in the composition range that can be manufactured using wollastonite and limestone as CaO sources, as shown in the area work in FIG. 1. It will be done. In addition, it is now possible to easily produce the component range shown in Region II, which was impossible when wollastonite and limestone were used as CaO sources, which is a disadvantage of conventional high Mgo based high basicity calcined fluxes. This greatly improved welding workability in dwarf heat welding and narrow gap welding, and made it possible to obtain weld metal with extremely low hydrogen content and high toughness when used for welding low alloy steel. Below, according to the example,
Specifically demonstrate the effects of

Examples Using the ingredients shown in Tables 1 and 2, wollastonite (natural stone), limestone, and molten fluxes M1 to M5 as CaO sources, the compositions shown in Table 3 along with various raw materials are shown in Table 4. Ingredients (CaO-MgO-3i 02 A9
203Ca F2-007 series) firing type flux B1
-B15 was manufactured as a trial product. There was no problem with the solubility of the above-mentioned melting type flux, and all of the trial firing type fluxes were granulated by adding water glass.
It was manufactured by firing at 0°C for 1 hour. By using these prototype fired fluxes and combining them with wires (Wl, W2, wire system each 4.0 mm) with the chemical composition shown in Table 5, we made steel plates (Sl, S2) with the chemical composition shown in Table 6.
) Regarding (1) Low heat input double-sided one-pass welding test of thin steel plate,
(2) A narrow gap welding test on extra-thick steel and (3) a diffusible hydrogen test on weld metal were conducted.

(1) Low heat input double-sided l-pass welding test of thin steel plate Plate thickness Lt = 1
0 mm of 3.5% Ni 1ll (steel plate symbol SL) is butted in the shape shown in Fig. 2 (a) with a groove, and combined with the wire Wl, as shown in Fig. 2 (b), AC power source 500A-2 [
Table 7 shows the welding workability observation results in one pass welding on both sides with low heat input performed under welding conditions of IVolt -40 cm/min.

Tests Nos. 011 to 9 were conducted using fluxes 81 to B9 of the present invention, and extremely good welding workability was obtained without any problems in arc stability, bead shape, or appearance.

No. 10 was because the amount of CaO in flux BIO was too small.

Due to this, the heat end does not fit well, and it becomes a convex bead that does not spread.For No. 11, the limestone content of flux B12 is too high, resulting in an excessive amount of CO2 scum, resulting in arc instability and deoxidation. Even though a large amount of the agent was added, there were many pockmarks on the surface of the dome, and slag burning was observed on the surface. In No. 12, the basicity B of flux B15 was high, exceeding 2.50, resulting in arc instability, a convex bead with poor adaptation, and a slightly meandering bead.

(2) Narrow gap welding test of 8i thickness A316, Gr70 steel (steel plate symbol S2) with plate thickness t7=loomm was used in the shape shown in Fig. 3(a) (t R = 12m
m, a -4°), and in combination with wire W2, narrow gap multi-layer welding of one layer and one pass welding was performed as shown in Figure (b). Welding conditions are AC power source 500-550A
-26 to 28 Volt -30 to 35 cm/min, preheating temperature 50°C, interpass temperature 150°C1, and post-heat treatment for dehydrogenation after welding was omitted. In addition to observing welding workability and investigating internal defects using
The same figure (C
), from the plate thickness center position A to JTS, No. 4, 2 mm.
A V nonchalpy impact test piece was taken and subjected to the test. Naori conducted an analytical test for the amount of oxygen in the weld metal using a sample taken from the same position as the upward impact test piece during the test. These results are summarized in Table 8.

Test Nos. 1 to 9 were conducted using fluxes 81 to B8 of the present invention, and the arc stability, bead shape, appearance, and slag removability were extremely good, and a good bead with no internal defects such as slag entrainment was obtained. It was done. In addition, the amount of oxygen in the weld metal was low, and high impact values were obtained both after AW'8 and after USR. No. 10 to 13 are cases where comparative fluxes were used. No.

In No. 10, Flux BIO with too low CaO content was used, which resulted in poor bead shape and slag entrainment, as well as formation of hard and unbreakable slag, resulting in slag peeling, similar to when conventional high-MgO fluxes were used. The quality was extremely poor. No. 11 is a case where flux Bll containing a large amount of wollastonite was used as a CaO source, and due to the increased S i O ) content of the flux, the melting point of the slag system decreased too much, causing pock marks on the bead surface. occurred frequently, and the amount of oxygen in the tin increased, resulting in a decrease in impact value. No.

12 used flux B12 containing a large amount of limestone as a CaO source, which resulted in an excessive amount of CO2 gas generated during welding, resulting in extremely unstable arcs, arc blowouts, and poor bead shape. Welding workability was extremely poor, including frequent occurrence of pockmarks and slag entrainment, and poor slag removability. No.

In No. 13, almost satisfactory welding workability was obtained, but because the basicity of Slacks 814 used was less than 1.50, the amount of oxygen in the weld metal increased and the impact value decreased. Note that No. 10 and No. 12, in which welding workability was extremely poor, were given an average score of d2 in the impact test and oxygen analysis test.

(3) Diffusivity hydrogen test of weld metal The fluxes B1, B3, B8 of the present invention and comparative slack B13 were re-dried at 300°C for 1 hour.
Immediately after that and in the atmosphere (temperature 24-25℃, humidity 73-
75%) for 6 hours, the weld metal was subjected to a diffusible hydrogen test under the conditions shown below. After removing scale on the surface of a 5N-50 steel sheet with a thickness of 2 h and performing dehydrogenation treatment at 350°C for 10 hours, a test piece was cut out and the wire diameter was 4. Using Omra's C-Mn wire, welding conditions 8
25A -28Volt -55crn/ff1in
Diffusible hydrogen in the weld metal was collected after holding the weld metal at 45°C for 72 hours by gas chromatography. As shown in Table 9, Test Nos. 1 to 3 are metal carbonate CO2 equivalent values of 8 to 8% of the total flux weight.
When slacks containing 6%, 669%, and 3.6% are used, the amount of diffusible hydrogen per 100g of welded metal is approximately 5 cc or less even after being left in the atmosphere for 6 hours (average value of 3 pieces). ), whereas N014 had a low metal carbonate content in flux B13 and C02
Since the converted value is less than 3.5z, there is a clear tendency for the amount of diffusible hydrogen to increase (approximately 7
cc) was shown.

Effects of the Invention By using a molten flux as a CaO source, the present invention greatly improves welding workability in low heat input welding and narrow gap welding, which were the drawbacks of conventional high MgO based, highly basic fired fluxes. It is possible to obtain a weld metal with extremely low hydrogen content and high toughness when used for welding low-alloy copper, and the effect on welding work is extremely large.

Table 1 Component examples of wollastonite and limestone (wt%) Table 2 Components of molten flux C1 Shio's J) Other components include Na70, K2O, BaO, TiO2 and inevitable impurities Table 4 Components of calcined flux ( Weight%)1)
Main mark: Invention flux, 1: Comparison flux 2) Its positive components include Na2O, K2O, BaO, TiO2 and unavoidable impurities, etc. Table 7 Double-sided l-pass welding test results 1) Yo mark 9 Invention flux, No mark: Comparison Flux Table 9 Diffusible hydrogen test results for molten metal 1) Makuin Niki invention flux, unmarked: Comparative flux 2) Diffusible hydrogen The average value of each three is shown.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the amount of CaO and the amount of S + 07 in calcined fluffx when wollastonite and limestone are used as CaO sources. Figure 2 (a) is the groove shape of a thin steel plate, (b) is an explanatory diagram showing the layering method, Figure 3 (a) is the groove shape of an extremely thick sheet, (b) is the layering method, ( C) is an explanatory diagram showing sampling positions of impact test pieces. #jt Patent Application Applicant Nippon Steel Corporation Representative Patent Attorney Masao Inoue Figure 1 7 Amount of 510Z (≠> 1238 (weight =
/=) Figure 2 (Q) (b) Procedural Amendment May 9, 1980 Director-General of the Patent Office Kazuo Wakasugi 1. Indication of Matter I. 1989 Patent Application No. 52242 2. Invention Name: Sintered flux 3 for submerged arc welding, relationship with the JE captor case Patent applicant address: FJ 2-6-3 Otemachi, Chiyoda-ku, Kyoto Name (
665) Nippon Steel Corporation Food Coloring Representative Takeshi 1) Yutaka 4, Agent 103 Address Japan @ 2-2-1 Kyodo Building (Gofukubashi), Chuo-ku, Tokyo Column 6 for detailed explanation of the invention in the specification , Details of the amendment (+) "In weld metal" on page 4, line 4 of the specification is corrected to "weld metal." (2) rl on page 6, line 6, 25-2.504,
Correct it to 50~2.504. (3) Same] On page 5, line 9, change “(natural stone)” to “(natural product)”
” he corrected. (4) r wire system on page 15, line 20, each 4. Oa+m
Correct J to "wire diameter 4.0+++raφ". (5) On page 17, line 19, "under test" is corrected to "test piece." (C) r on page 20, line 2 4. OmmJ r 4. O
mmφ”. (7) In Table 7 on page 25, rsiJ in the steel plate symbol column for test No. 1=12 is corrected to rS IJ. Agent Patent Attorney Masao Inoue

Claims (1)

[Claims] In the fired flux for submerged arc welding, which is made by adding ellipsoids to hydraulic laths, granulating them, and firing them, the main component is Ca.
20-50% by weight of O, 10-40% by weight of 5in7,
10-50% by weight of AQ203, 40% by weight of CaF2
The content of CaO is greater than the content of 5i02, and the total content of 5i07 and Au203 is 35 to 60% by weight, 10 to 80% by weight, and the metal carbonate is 3.0% by weight in terms of 002. A sintered flux for submerged arc welding characterized by containing 5 to 12% by weight and having a basicity B of 1.50 to 2.50 as expressed by the following formula.