JPH0565276B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is directed to welding an inclined welding line at high speed.
This invention relates to a melt-type flux for submerged arc welding, which is used in the manufacture and welding of spiral steel pipes, and in particular is used in the manufacture and welding of relatively thin steel plates with a thickness of about 9 to 14 mm, enabling even higher speed welding. . (Conventional technology) In pipe manufacturing welding of spiral steel pipes, improvements in welding speed have traditionally improved productivity. Now, if we compare the amount of pipes produced (tons) per unit time (month), we need to weld even faster than pipes made 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, Japanese Patent Application Laid-Open No. 75143/1983 proposes a flux in which TiO ₂ in the welding flux component is replaced with ZrO ₂ to increase slag viscosity.
Furthermore, Japanese Patent Application Laid-Open No. 55-40029 discloses that the components and bulk density are specified, the slag layer thickness is thinned, and the slag viscosity is increased to prevent melt flow.
Melting type fluxes have been proposed to improve beads that have an excessively concave shape, but none of them
The welding speed is approximately 2.5m/min.
Furthermore, current welding for making thick plates requires deep penetration, which requires a groove, and the amount of deposited metal needed to fill the groove, which results in a large welding heat input and the molten metal tends to flow. The above-mentioned fluxes are 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, 3.5 mm
A welding speed of m/min is required. In pipe manufacturing using thin plates, increasing the current as the welding speed increases will cause the arc to penetrate the steel plate during welding, causing metal to fall or burn through. ×60÷
(welding speed) must be reduced. the result,
The aforementioned fluxes with increased slag viscosity and fluxes with thinner slag layer thickness caused spot marks and undercuts, and could not be used at a welding speed of 3.5 m/min, so it was necessary to develop a flux with a new composition. . (Problems to be Solved by the Invention) As mentioned above, the present invention solves the problem of the plate thickness 8 to 8, which cannot be used due to the occurrence of welding defects such as pot marks and undercuts when using conventional flux.
The purpose is to provide a melt-type flux for submerged arc welding that enables spiral pipe welding of 14 mm and a welding speed of 3.5 m/min, and also has good slag removal performance and bead appearance. (Means for Solving the Problems) The present inventors have developed a method for high-speed welding on flat surfaces using a conventional fused flux, which is not currently used for inclined welding. The molten flux has extremely excellent welding performance, has low slag viscosity, and is suitable for undercuts and welding.
It was thought that this would be effective in preventing defects such as pot marks. Therefore, the main component system shown in Table 1, which has been conventionally used for high-speed welding on flat surfaces, is SiO ₂ −TiO ₂ −
A welding test was conducted using Al ₂ O ₃ based flux and SiO ₂ -MnO based flux for welding spiral steel pipes. This test method, as shown in Figure 2a,
Using the wire shown in Table 2 on the inner surface of the steel pipe 1 of 12 mm, inner diameter/m, and length 1.5 m, with the components shown in Table 2, a leading electrode 2 (DC.RP.1100A, 27V) and a trailing electrode 3 were attached.
(A.700A, 31V) tandem submerged arc welding bead,
This was done by placing the pipe in a spiral shape at an angle of 45° to the longitudinal direction. Further, the welding speed s was set by synchronizing and changing the rotational speed r and the moving speed v of the pipe according to the relationship shown in FIG. 2b. Further, the position of the leading electrode 2 was moved 20 mm in the downhill direction from the bottom line of the inner surface of the pipe.
(Hereinafter, it will be referred to as off-center: downhill 20mm, or OC~: downhill 20mm.) In this welding test, the results were performed at a welding speed of 3.5 m/min, and the bead cross-sectional shape in the rightmost column of Table 1 As shown, it was impossible to use any of them at 3.5 m/min. However, SiO ₂ −TiO ₂
−For Al ₂ O ₃ based conventional flux, the welding speed was 2.5 m/
min or off center: downhill
When the diameter was 120 mm, the concave shape of the bead was extremely flat as shown in Figure 3a, and overlap occurred. Therefore, welding tests were conducted with various welding speeds and off-center settings, and welding conditions were obtained that were considered to have the best shape, with a welding speed of 3.0 m/min and an OC of 70 mm downhill. The cross-sectional shape of the bead is a concave shape, as shown in Figure 3c, and is a very unstable shape in which overlap and undercut occur at the same time, and the shape changes greatly due to slight variations in welding conditions, making it difficult to use in actual pipe manufacturing. It was impossible to use it for However, the bead rising angle α shown in FIG.
β or the smoothness of the bead external surface was very good. In addition, for the SiO ₂ -MnO flux shown in Table 1, experiments were conducted with the same test conditions changed, and the results showed that the welding speed was 4.0 m/min,
Alternatively, at OC~: uphill, 30 mm, the bead will be as shown in Figure 3c, but under good conditions it will be similarly narrow and it is considered inappropriate to use it in actual pipe making, and furthermore, the bead will rise. The angle was relatively large and the bead appearance was somewhat poor. From these experimental results, the present inventors found that the amount of welding heat input changes as the welding speed changes, and furthermore,
Slag viscosity changes with changes in slag temperature, and in the first place, if the melting temperature of the flux is different, the slag viscosity measured at a constant temperature of 1400°C or higher will be different if the welding heat input is low.
It was thought that the softening temperature, melting temperature, and the temperature difference between them had the greatest influence on bead formation when the heating time was kept constant, without having any major significance. Therefore, the softening and melting temperatures of conventional fluxes were measured. In this method, as shown in Figure 1b, 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 height of the sample is set at room temperature. The melting temperature is the temperature when the temperature reaches 1/2 of the time. As a result of this measurement, as shown in Figure 1a, the conventional SiO ₂ -TiO ₂ -Al ₂ O ₃ flux is
The softening temperature is 1330℃ and the melting temperature is 1350℃, compared to the conventional SiO ₂ -MnO flux of 1130℃ and 1180℃.
In addition, the viscosity tended to decrease rapidly. Therefore, based on the experimental results on the inner surface of the pipe mentioned earlier, we believed that a flux with a melting temperature of over 1180℃ and below 1350℃ would produce a good bead, so we prototyped fluxes with various components. Then, the flux melting temperature was measured and a melting test was conducted. 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 was made based on the above findings, and its gist is that the ingredients are expressed in weight%.
_SiO2 : 15-30% _{, Al2O3} : 15-30%, _TiO2 : 5
~18%, MnO: 10~25%, BaO: 6~30%,
CaF ₂ : Must be 7 to 15%, other components include CaO 8% or less, MgO 3% or less, iron oxide 4% or less as FeO, Na ₂ O + K ₂ O
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) Setting the SiO ₂ content to 15 to 30%: The SiO ₂ 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 pot marks occur. Furthermore, if it exceeds 30%, the slag layer becomes too thick, causing flow and overlapping. Al ₂ O ₃ should be 15 to 30%: The Al ₂ O ₃ component is a component that adjusts the flux melting temperature, and if it is less than 15%, the flux melting temperature will become too low, making it difficult to perform high-speed welding. Molten metal flows and the cross-sectional shape of the bead becomes concave, and if it exceeds 30%, the flux melting temperature becomes too high, resulting in the cross-sectional shape of the bead becoming convex and undercutting. TiO ₂ should be 5 to 18%: TiO ₂ is a component that adjusts the arc strength, and if it is less than 5%, the arc strength will be weak.
As a result of being too long, the amount of flux melting increases and the amount of slag increases, causing molten metal flow.
If it exceeds %, the arc strength becomes too strong, the penetration depth increases, and undercuts occur because the penetration is not completely filled. MnO should be 10-25%: MnO is a slag forming agent along with SiO ₂ and is also an arc stabilizer, and if it exceeds 25%,
In high-speed welding, the bead meanderes, and if the amount is less than 10%, the effect is insufficient and the arc becomes 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 removability effect is insufficient, and if it exceeds 30%, the bead surface becomes ugly. The _CaF2 content should be between 7% and 15%: The _CaF2 component is a gas-generating component that prevents the occurrence of pockmarks.If it is less than 7%, the anti-pockmark performance will be insufficient, and if it exceeds 15%, it will cause slag. Seizes on the bead surface and deteriorates peelability. The above are essential ingredients, other ingredients are:
Although it is better to have less amount, it is contained as an impurity in the raw material ore, and if it is contained excessively in the flux as a residue, it has an adverse effect, and an upper limit is set. CaO content must be 8% or less: In a molten flux, the CaO component is composed of two components: _CaF2 decomposed in the melting furnace and present as a CaO component, and impurities in other raw material ores present in the flux. Although sometimes referred to as the total, in the present invention, the F component in the flux is calculated as the original CaF ₂ component, and other CaO is kept below 8%. etc., so it was set to 8% or less. MgO should be 3% or less: The MgO component is a high-temperature melting, fire-resistant component,
A component that increases the flux melting temperature. Therefore, if it exceeds 3%, the cross-sectional shape of the bead becomes convex and undercuts occur, so it was set to 3% or less. Iron oxide is less than 4% as FeO: Iron oxide is contained as an impurity in the raw ore,
It is also contained in flux as iron oxides such as Fe ₂ O, FeO, and Fe ₂ O ₃ . Therefore, there is no particular problem if it is less than 4% in terms of FeO, but if it is intentionally added in excess of 4%, the bead rise angle becomes large, the concave depth becomes deep, and wrinkles appear in the center of the bead. Since shrinkage lines occur and the appearance deteriorates, the FeO content was set to 4% or less. Na ₂ O + K ₂ O must be 3% or less: Both Na ₂ O and K ₂ O components extremely reduce slag viscosity, and if they are contained in excess of 3%, they cause melt flow and the bead cross-sectional shape. Because it has a flat concave shape and overlaps, 3% Na ₂ O + K ₂
The following was made. The particle size structure and bulk density of the flux are as follows:
Although not particularly limited, the particle size structure has traditionally been
A flux containing a relatively large amount of coarse particles is used, and the flux of the present invention also passes through a nominal size of 2.80 mm using a JIS.Z8801 standard mesh sieve.
Particles that do not pass through 106μm are 90% of the total flux.
It is desirable that the amount is at least % by weight. Regarding the bulk density, when welding on a flat surface at a welding speed of about 1.5 to 2.5 m/min, a light flux of 1.5 g/cm ³ or less containing many foam particles is good, but when welding at a high speed of 3.0 m/min or more, When used for welding, the gas in the foamed particles has an adverse effect, so the flux of the present invention complies with JIS
Measured according to K6721 standard, does not contain foam particles,
It is desirable that the bulk density is 1.6 g/cm ³ or more. Examples of the present invention will be described below. (Example) A bead placement test was conducted using steel pipes and submerged arc welding wires with the components shown in Method 2, under the welding conditions shown in Table 3, and in the manner shown in Figure 2. The prototype flux is shown in Table 4.The prototype flux is made by blending and mixing the raw material ores to the target composition, melting it in a melting furnace, and then cooling it on a steel plate or in the gap of a rotating drum to a temperature below 1000℃. This prototype was made by crushing, drying, and sizing at low temperatures. The results of this welding test are as shown in Table 5, with all fluxes of the present invention, the bead cross-sectional shape was good, the slag removability was good, and no welding defects occurred. However, the comparative flux H
In this case, compared to the product of the present invention, its components are less SiO ₂ , MnO
Because the amount of Al ₂ O ₃ and TiO ₂ was too low, the flux melting temperature was slightly lowered to 1340°C, but the bead shape was convex, undercuts occurred, and slag peeling was poor. In addition, compared to the product of the present invention, comparative flux I contains excessive amounts of SiO ₂ and MnO,
Due to the insufficient amount of Al ₂ O ₃ and TiO ₂ , 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. Comparative slacks J has its components CaF ₂ , Na ₂ O+
With too much K ₂ O, the flux melting temperature dropped significantly to 1130°C, resulting in a bead shape that became even more flat and concave, and the overlap became large, causing slag to get caught in the overlap area, resulting in poor peelability. It was bad. Comparative flux K has too much MnO component,
Due to insufficient BaO content, the arc becomes unstable,
The bead meandered and some undercuts occurred, resulting in poor slag removal. Comparative flux L had an excessive amount of BaO and CaO components, so the bead shape and slag removability were almost good, but the bead appearance was ugly and there were many pockmarks. Comparative flux M has too little CaF ₂ and too much MgO, so the flux melting temperature is low.
As a result of the temperature being too high (1370℃), the bead shape becomes convex and undercuts occur on all lines at both ends of the bead.
As a result of the slag being trapped, removability was poor. Comparative flux N is a flux in which an excessive amount of FlO is 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. As shown in FIG. 4, the bead cross-sectional shape was judged as good if the concave depth () was less than 1 mm, and if it was 1 mm or more, the concave was large. Also, the bead rising angle is the rising angle α at both ends of the bead,
The average angle of β was defined as less than 90° as good and 90° or more as poor.

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[Table] (Effects of the invention) As explained above in detail, by using the flux of the present invention, welding can be performed at a high welding speed of 3.5 m/min without causing welding defects. As a result, it is possible to improve the productivity of pipe manufacturing and welding of relatively thin steel plates with a thickness of 8 to 14 mm, and the effect is very large.

[Brief explanation of drawings]

Figure 1a is a graph showing the measurement results of the flux softening and melting temperature, Figure 1b is a graph showing the change in shape of the flux sample at each temperature, and Figure 2a is a graph showing the results of the flux softening and melting temperature measurement. Pipe arrangement diagram, Figure 2b is an explanatory diagram of welding speed setting, Figure 3 is a schematic diagram of the bead cross-sectional shape, Figure 4 is a detailed diagram thereof, and Figures 5a and b are in Table 1. Diagrams showing the bead cross-sectional shapes in the welding results column, Figures 6a to 6h are the 5th
It is a figure which shows each bead cross-sectional shape in the column of bead cross-sectional shape of a table|surface. 1... Steel pipe, 2... Leading electrode, 3... Trailing electrode, OC ~... Off center, r... Rotating direction and speed of steel pipe, v... Moving direction and speed of steel pipe, s...
Weld line direction and speed.

Claims (1)

[Claims] 1 Components are in weight%, SiO ₂ : 15-30%, Al ₂ O ₃ :
15-30%, _TiO2 : 5-18%, MnO: 10-25%,
BaO: 6 to 30%, _CaF2 : 7 to 15% are essential, and other components include CaO of 8% or less, MgO of 3% or less, and iron oxide as FeO of 4%.
The following describes a melting type flux for submerged arc welding characterized by containing 3% or less of Na ₂ O + K ₂ O.