JPS62179894A - Fused flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To use a fused flux for submerged arc welding for making a relatively thin steel sheet into a pipe by welding and to permit welding at the much higher speed by specifying the components of said flux. CONSTITUTION:The components of the flux are required to contain, by weight %, 15-30% SiO2, 15-30% Al2O3, 5-18% TiO2, 10-25% MnO, 6-30% BaO, and 7-15% CaF2. The other components required to be incorporated therein are <=8% CaO, <=3% MgO, <=4% iron oxide as FeO, and <=3% Na2O+K2O. Welding is thereby made possible at a high speed without generating welding defects and the productivity in making the relatively thin steel sheet into the pipe by welding is improved.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is used for high-speed welding of inclined weld lines, welding of spiral steel pipes, etc.
The present invention relates to a melting type flux for submerged arc welding, which can be used for pipe making welding of relatively thin steel plates of approximately 4+n and enables even higher speed welding.

(Conventional technology) In pipe manufacturing welding of spiral steel pipes, improvements in welding speed, in other words, improve productivity, so conventional efforts have been made to improve the welding speed, but especially in pipe manufacturing welding using thin steel plates. So,
Comparing the pipe making It (tons) per unit time (month), it is necessary to aim for even higher speed welding than pipe making of thick steel plates.

However, most of the fluxes that have been proposed so far for pipe making and welding are intended for relatively thick plates. That is, JP-A-50-75143 proposes a flux that increases slag viscosity by replacing TiO2 in the welding flux component with ZrO, and JP-A-50-75143 proposes a flux that increases slag viscosity by replacing TiO2 in the welding flux component with ZrO.
Publication No. 40029 proposes a melt-type flux that prevents melt flow and improves bead formation with an excessive concave shape by specifying the components and bulk density, reducing the thickness of the slag layer, and increasing the slag viscosity. However, in both cases, the welding speed is approximately 2.5 m/min. Furthermore, current welding for thick plate pipes requires deep weld penetration, which requires a groove, and the amount of weld metal needed to fill the groove, resulting in a large welding heat input, which prevents the molten metal from flowing. The above-mentioned flaxox is highly effective.

However, in pipe making welding using relatively thin steel plates with a thickness of 8 to 14 mm, in order to improve productivity, the welding speed is 3.5 m/min.
A welding speed of

In pipe manufacturing using this thin plate, as the welding speed increases,
Increasing the current means that the arc penetrates the steel plate during welding,
Since the metal will fall and the melt will drop, the welding heat input (current x voltage x 60 ÷ welding speed) must be reduced. As a result, the above-mentioned fluxes with increased slag viscosity and fluxes with reduced slag layer thickness caused pock marks and undercuts, and could not be used at a welding speed of 3.5 m/min. It needed to be developed.

(Problems to be Solved by the Invention) As mentioned above, the present invention solves the problem of using conventional flux for plate thicknesses of 8 to 14 mm, which could not be used due to the occurrence of welding defects such as pock marks and undercuts. , welding speed 3.
The object of the present invention is to provide a melt-type flux for submerged arc welding that enables spiral pipe welding at a speed of 5 m/min and also has good slag removal performance and bead appearance.

(Means for Solving the Problems) The present inventors used a conventional molten flux, which is not currently used for inclined welding, to perform high-speed welding on a flat surface and improve bead appearance, slag removability, etc. We believe that molten flux, which has extremely excellent welding performance, has low slag viscosity and is effective in preventing defects such as undercuts and pock marks.

Therefore, the main component system shown in Table 1 that has been conventionally used for high-speed welding on flat surfaces is Sing -TiO2-A2□
A welding test was conducted using 03 series flux and 5402-MnO series flux for welding spiral steel pipes.

This test method is as shown in Figure 2(a), with a plate thickness of 12 mm.
A leading electrode 2 (
DC, RP, 1100A, '27 ■) and trailing type i
3 (AC, 700A, 31V) by placing tandem submerged arc welding beads in a spiral shape at an angle of 45° to the longitudinal direction of the pipe.

In addition, the welding speed (S) is set at the rotational speed of the pipe (r
) and the moving speed (V) were changed in synchronization according to the relationship shown in FIG. 2(b). Further, the position of the preceding electrode 2 was moved 20 m in the downhill direction from the bottom line of the inner surface of the pipe. (Hereinafter referred to as off center: downhill 20 dragon, or OC: downhill 2o.)
In this welding test, the results were performed at a welding speed of 3.5 m/min, as shown in the bead cross-sectional shape in the rightmost column of Table 1, and it is impossible to use at a welding speed of 3.5 m/min. Met. However, Sing-Ti(h-A
l For 203 series conventional flux, the welding speed is 2.5 m.
/min or off center: downhill 1
When the length was 20 m, the concave shape of the bead was extremely flat as shown in FIG. 3(a), and overlap occurred. Therefore, as a result of welding tests with various welding speeds and off-center changes, the welding speed was 3.0 m/mi.
n, QC: Welding conditions considered to have the best shape were obtained with a downhill slope of 70 mm, but the cross-sectional shape of the bead was a concave shape, as shown in Figure 3 (c), and an extremely difficult condition in which overlap and undercut occurred at the same time. It had an unstable shape, and the shape changed significantly with slight changes in welding conditions, making it impossible to use it for actual pipe manufacturing.

However, the bead rising angles α and β shown in FIG. 4 and the smoothness of the bead external surface were very good.

In addition, with the 5i02-MnO-based flanks shown in Table 1, as a result of conducting experiments with similarly different test conditions, the welding speed was set to 40 m/min, or OC: uphill,
At 30mm, the bead will be as shown in Figure 3(c),
In a good condition range, it is similarly narrow and is considered inappropriate for use in actual pipe manufacturing, and furthermore, the bead rise angle is
It was relatively large and the bead appearance was somewhat inferior.

Based on these experimental results, the inventors found that the amount of welding heat input changes as the welding speed changes, and that the slag viscosity changes as follows:
It should be noted that it changes depending on the change in slag temperature, and that if the melting temperature of the flux differs in the first place, 14
The slag viscosity measured at a constant temperature of 00℃ or higher does not have much meaning when the welding heat input is low, and the softening temperature, melting temperature, and the temperature difference have the greatest influence on bead formation when the heating time is constant. I thought it would give. Therefore, the softening and melting temperatures of conventional fluxes were measured.

In this method, as shown in Figure 1(b), a flux sample is made into a square longitudinal section at room temperature, heated in a furnace, the temperature at which the upper corner begins to melt roundly is taken as the softening temperature, and the sample height is The melting temperature is defined as the temperature when the temperature reaches 172 at room temperature.

As a result of this measurement, as shown in Figure 1(a),
The conventional 5in2-TiO□-A J,O,-based flux has a softening temperature of 1330°C and a melting temperature of 1350°C, which is 113% higher than that of the conventional 5iOz MnO-based flux.
0℃.

The temperature was higher than 1180°C, and the viscosity tended to decrease rapidly.

Therefore, the melting temperature of the flux exceeds 1180°C, and 1
We believe that if the flux is below 350°C, a good bead can be obtained based on the experimental results on the inner surface of the pipe mentioned above.
We made trial fluxes with various components, measured the flux melting temperature, and conducted melting tests. As a result, the inner surface of the pipe was welded at a welding speed of 3.5 m/min, and a flux with good slag removability and bead appearance without any welding defects was obtained.

The present invention has been made based on the above findings, and its gist is that the components are SiO□: 15% by weight.
~30%, AAz03: 15~30%, Ti(h
: 5-18%, MnO: 10-25%, BaO: 6
~30%, CaF2: 7~15%, other components include CaO: 8% or less, Mg
O is 3% or less, iron oxide is 4% or less as FeO, Na2
A melt-type flux for submerged arc welding characterized by containing O+K2O of 3% or less.

The reasons for limiting the components of the flux of the present invention will be described below, along with their effects.

(Function) SiO2 should be 15 to 30%: The SiO□ component is a slag forming agent, and if it is less than 15%, the slag layer becomes thin and welding defects such as undercuts and pock marks occur. do. Moreover, if it exceeds 30%, the slag layer becomes too thick, causing melt flow and overlapping.

Setting Al2O2 to 15-30%: Al! The toz component is a component that adjusts the flux melting temperature, and has a content of 1
If it is less than 5%, the flux melting temperature will be too low, resulting in melt flow during high-speed welding, and the bead cross-sectional shape will become concave. If it exceeds 30%, the flux melting temperature will be too high, resulting in a bead cross-sectional shape. The shape becomes convex and an undercut occurs.

Ti (h should be 5 to 18%: TiO□ component is a component that adjusts arc strength,
If it is less than 5%, the arc strength will be weak, and as a result of being too long, the amount of flux melting will increase, and the amount of slag will increase, resulting in melt flow, and if it exceeds 18%, the arc strength will be strong. As a result, the depth of the weld penetration increases and the weld penetration cannot be filled completely, resulting in an undercut.

Setting MnO to 10 to 25%: MnO is a slag forming agent along with Sing, and is also an arc stabilizer. If the amount is less than this, the effect will be insufficient and the arc will become unstable.

Setting BaO to 6 to 30%: The BaO component is effective in adjusting slag viscosity and improving slag removability. However, if it is less than 6%, the slag releasability effect is insufficient, and if it exceeds 30%, the bead surface becomes ugly.

CaFz should be 7 to 15%: Cab is a gas-generating component that prevents pockmarks from occurring. If it is less than 7%, the anti-pockmark performance is insufficient, and if it exceeds 15%, slag Seizes on the bead surface and deteriorates peelability.

The above are essential components, and the other components are contained as impurities in the raw material ore, although it is better to have less of them, and if they are excessively contained in the flux as a residue, they will have a negative effect, so there is an upper limit. This is to establish the following.

CaO content must be 8% or less: In a melting type flux, the CaO component is
In some cases, it refers to the sum of the Fz that is decomposed and exists as a CaO component and the impurities in other raw material ores that are present in the flux, but in the present invention, the F component in the flux is the original CaF component. The other CaO content is calculated to be 8% or less, and if it exceeds 8%, pock marks and herringbones will occur, so
% or less.

MgO content should be 3% or less: The MgO component is a high-temperature melting, fire-resistant component, and is a component that increases the flux melting temperature. Therefore, 3%
If it exceeds 3%, the cross-sectional shape of the bead becomes convex and undercut occurs, so it was set to 3% or less.

Iron oxide is 4% or less as FeO: Iron oxide is
Contained as an impurity in raw ore, F is also present in flux
It is contained as iron oxides such as ezO, FeO, Fe, O, etc. Therefore, there is no particular problem if it is 4% or less in terms of FeO, but if it is intentionally added in excess of 4%, the bead rise angle becomes large and the concave depth becomes deep (as well as wrinkles in the center of the bead). Since shrinkage lines occur and the appearance deteriorates, the FeO content was set to 4% or less.

NazO + KzO must be 3% or less: All 20 components of Nazo resin extremely reduce slag viscosity,
If the content exceeds 3%, the water temperature will increase and the cross-sectional shape of the bead will become flat and overlap, so the content was set to 3% or less for NazO + KZO.

Although the particle size structure and bulk density of the flux are not particularly limited, conventionally a flux containing a relatively large amount of coarse particles has been used, and the flux of the present invention also complies with the JIS, Z 8801 standard. Using a mesh sieve, it is desirable that particles passing through a nominal size of 2.80 mm and not passing through a diameter of 106 μm account for 90% by weight or more of the entire flux. In addition, the bulk density is 1.5 to 2.
When welding at a welding speed of about 5 m/min,
A light flux of 1.5 g/cm3 or less containing many foamed grains is good, but when used for high-speed welding of 3.0 m/min or more, the gas in the foamed grains has an adverse effect, so the flux of the present invention is JIS K6721. It is desirable that the bulk density is 1.6 g/cm' or more when measured according to the standard and does not contain foamed particles.

Examples of the present invention will be described below.

(Example) Using steel pipes and submerged arc welding wires with the components shown in Table 2,
A bead placement test was conducted under the welding conditions shown in Table 3 and as shown in Figure 2. The prototype flux used in the test is shown in Table 4. After compounding, mixing, and melting in a melting furnace, it was cooled on a steel plate or in the gap of a rotating drum, and then pulverized, dried, and sized at a low temperature of 1000°C or less to produce a prototype.

As shown in Table 5, the results of this welding test show that all fluxes of the present invention had good bead cross-sectional shapes, good slag removability, and no welding defects. However, in comparison flux H, its components were too small in Sing, MnO, and Al1203, compared to the product of the present invention.
Due to excessive TiO□, the flux melting temperature is 134
Although the temperature decreased slightly to 0°C, the bead shape became convex, undercasting occurred, and slag peeling was poor. In addition, compared to the product of the present invention, the comparative flux ■ has sio of its components,
With too much MnO, A j! Due to insufficient amounts of zos and TiQz, the flux melting temperature was 1190°C, but the bead shape was a flat concave shape, overlap occurred at both ends of the bead, and the slag removal performance was poor.

Comparison flux J is its component CaFz+ NazO+
Due to the excessive amount of KZO, the flux melting temperature was significantly lowered to 1130° C., so the bead shape became a flattened concave shape, the overlap was large, the slag got caught in the overlap part, and the peelability was poor.

The comparison flux had too much MnO component and too little BaO component, so the arc became unstable, the bead meandered, and some undercuts occurred, resulting in poor slag releasability.

Comparative flux L contained too many BaO and CaO components, so the bead shape and slag removability were quite good, but
The bead appearance was ugly and pockmarks occurred frequently.

Comparative flux M has too little CaFz as a component, and M
Due to excessive nO, the flux melting temperature was 1370℃
As a result of this being too high, the bead shape became convex, undercutting occurred on the entire line at both ends of the bead, and as a result, the slag was caught, resulting in poor peelability.

Comparative flux N is a flux with an excessive amount of FeO added, and as a result, the bead shape has a large rising angle and concave depth, poor slag removability, and a wrinkle-like shrinkage line in the center of the bead. It occurred and the appearance deteriorated.

Regarding the judgment of the bead cross-sectional shape, as shown in FIG. 4, a concave depth of less than 1 m was considered good, and a concave depth of 1 mm or more was considered large. In addition, the bead rising angle is
The average angle of the rising angles α and β at both ends of the bead is 90
Less than 90° was considered good, and 90° or more was bad.

(Effects of the invention) As explained in detail above, by using the flux of the present invention, welding can be performed at a high welding speed of 3.5 m/win without causing welding defects. , the productivity of pipe making and welding of relatively thin steel plates with a plate thickness of 8 to 14 mm can be improved, and the effect is very large.

[Brief explanation of drawings]

Figure 1 (a) is a graph showing the measurement results of Franks softening and melting temperature, Figure 1 (b) is a graph showing the change in shape of the flux sample at each temperature, and Figure 2 (a) is a graph showing the welding test method. Figure 2 (b) is an explanatory diagram of the welding speed setting, Figure 3 is a schematic diagram of the bead cross-sectional shape, Figure 4 is a simple diagram of the arrangement of the pipe, Figure 5 ( a) (b) are diagrams showing the bead cross-sectional shapes in the welding results column of Table 1, and Figures 6 (a), (h) to (n) are each bead cross-section in the bead cross-sectional shape column of Table 5. It is a figure showing a shape. 1... Steel pipe, 2... Leading electrode, 3... Trailing electrode,
0.0...Off center, r...Rotating direction and speed of the steel pipe, ■...Moving direction and speed of the steel pipe, S...Welding line direction and speed. Figure 1 /100 /200 /
J00 /41K) Temperature ('c) (b) (Even 9 temperature) (F large change) (Melting vs. h) () Fig. 2 (a-) (b) θ, Fig. 3 Fig. 4 m Engraving of the surface (no change in content) ((L> (b) (C)
<d) (e) (f)
<gn (-/b) Procedural amendment (method) % formula % 1. Indication of the case 1985 Patent Application No. 018041 2. Name of the invention Melting type flux for submerged arc welding 3. Person making the amendment Case and Relationship Patent applicant 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665) Nippon Steel Corporation Representative Takeshi 1) Yutaka 4, Agent 100-5 Date of amendment order March 25, 1988 Day 6 (shipping date): Detailed Description of the Invention column and Brief Description of Drawings column 1 of the specification to be amended - (1) Table 5 on page 21 of the specification is amended as shown in the attached sheet. (2) 4 lines from the bottom of No. 22 [Fig. 6 (a), (h) to
(n)” is corrected to “Fig. 6 (a) to (h)”. (3) Correct Figure 6 as shown in the attached sheet. Procedural amendment (voluntary). April 18, 1986

Claims (1)

[Claims] The components are weight%, SiO_2: 15-30%, Al_
2O_3: 15-30%, TiO_2: 5-18%, M
nO: 10-25%, BaO: 6-30%, CaF_2
: Must be 7 to 15%, and other components include CaO of 8% or less, MgO of 3% or less, and iron oxide of F.
A melting type flux for submerged arc welding, characterized in that eO is 4% or less and Na_2O+K_2O is 3% or less.