JPH0455790B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a flux for high-speed submerged arc welding of spiral steel tubes.The present invention uses a mixed type of nickel slag and melt flux, and specifies the component composition to achieve good slag peeling and excellent This invention relates to a flux for submerged arc welding that can produce spiral beads with high efficiency. (Prior art) Submerged arc welding can use a relatively large current and has good welding efficiency, and is widely used in the field of welding steel structures such as pipes, ships, offshore structures, steel frames, and bridges. ing. The manufacture of spiral steel tubes is one example of this, and since increasing welding speed directly leads to improved productivity in the manufacture of spiral steel tubes, studies have been conducted to increase welding speed. Generally, with spiral steel pipes, internal welding is performed at an upwardly inclined position and external surface welding is performed at a downwardly inclined position, considering welding workability and bead shape.
Instead of downward slope welding, the inner surface slopes upward and the outer surface slopes downward at the point where the arc occurs, and during the solidification process of the weld metal and slag, the inner surface slopes downward and the outer surface slopes upward until it reaches a steeply sloped position, and gradually sag due to gravity. For this reason, in internal welding, the concave increases and becomes a convex bead, which tends to cause undercuts and overlaps. On the other hand, external welding tends to result in convex beads and undercuts. The occurrence of such defects increases as the welding speed increases, and tends to be particularly noticeable in internal welding. In order to improve these problems, conventionally the flow of slag has been suppressed mainly by adjusting flux components and physical property values. That is, Japanese Patent Application Publication No. 1983-
In JP-A No. 176098 and JP-A-59-104290, a melt flux for inclined welding was proposed in which the flux components were specified, and in JP-A-59-47069, the flux components and physical property values were specified, and the welding position and A combined welding method, JP-A-59-66979 proposes a welding method that combines welding conditions with a bond flux whose flux composition and grain size structure are specified. However, if an attempt is made to suppress the flow of slag by increasing the viscosity of the flux, pockmarks will occur on the bead surface and high-speed welding performance will be inhibited. As shown in each of the examples, these fluxes correspond to welding speeds of less than 5 m/min, and defects are unavoidable at welding speeds of 5 m/min or higher. Unexamined Japanese Patent Publication 1983-
In the bond flux proposed in Publication No. 66979, welding is performed at a speed close to 5 m/min in the examples, but when welding spiral steel pipes where the flux is repeatedly collected and reused, it tends to powder. A bond flux with a large value has problems such as deterioration of welding workability and segregation, and is therefore difficult to use in practice. (Problems to be Solved by the Invention) The present invention relates to high-speed submerged arc welding of spiral steel tubes, and is concerned with high-speed submerged arc welding of spiral steel pipes. The object of the present invention is to provide a submerged arc welding flux that can be obtained. (Means for Solving the Problems) The gist of the present invention is to use 30 to 80% by weight (or less) of nickel slag and 20% by weight of melt flux.
Contains ~70%, _SiO2 : 40~60%, MgO: 7~40
%, _Al2O3 : 0.5-5% _, CaO: 0.5-5%,
The flux for high- _speed submerged arc welding of spiral steel tubes is characterized by having CaF2: 0.5-5% and MnO: 0.5-30% as main components. The structure and function of the flux of the present invention will be explained below. (Function) First, the flux of the present invention is produced by mechanically mixing nickel slag and melt flux. Unlike melt flux, there is no need to select a material with a soluble composition, allowing relatively free flux design, and unlike bond flux, it can be granulated with a fixing agent such as water glass. This is because there are no problems with moisture absorption or powdering due to repeated use. Furthermore, the manufacturing process does not require melting all the raw materials, and can be manufactured at low cost. Here, the nickel slag in the present invention is
It is the slag after nickel is removed from nickel ore by dissolution reduction in the nickel refining process, and its composition is SiO ₂ : 50-60%, MgO:
The main component is 30 to 40%, and in addition Al ₂ O ₃ : 5% or less,
It is composed of CaO: 5% or less and T.Fe: 10% or less. The flux of the present invention contains 30 to 80% of the above-mentioned nickel slag, which is SiO ₂
This is because MgO is extremely important as a flux component. That is, SiO ₂ is a component in the molten slag that is useful for increasing the viscosity of the slag and producing a smooth and familiar bead shape, and is particularly effective in improving the bead shape during high-speed welding.
On the other hand, MgO has a high melting point and is effective in increasing the fire resistance of slag, preventing slag dripping, and providing uniformity to the bead shape. It is an effective component for reducing the amount of oxygen and improving the toughness of weld metal. In this case, when MgO is added as a single oxide, its melting point is extremely high at 2800°C, and in bond fluxes in which MgO is added as a single oxide, the flux becomes difficult to melt during welding, which inhibits the fluidity of the slag. , defects such as a horseback bead shape and poor fitting of the toe end occur. On the other hand, if a melt flux contains a large amount of MgO, it will also become difficult to dissolve, making the production of the flux itself difficult or impossible. However, in the present invention, many
MgO is added from nickel slag. Since the MgO in this nickel slag forms a eutectic composition with SiO ₂ , the melting point is significantly lowered to about 1600°C, which can prevent the above-mentioned defects seen in bond flux. There are also no problems like melt flux. Furthermore, since nickel slag has a higher melting point than melt flux, these mixed fluxes have higher melting points than the base melt flux. This prevents the spiral steel tube from sagging at a steeply inclined position during the solidification process during welding, and prevents the cone from increasing.
The effect of preventing undercuts and overlaps can be obtained. In addition, nickel slag is a slag obtained by melting carefully selected ores, and contains extremely low amounts of harmful impurities and does not contain water such as crystallization water. In the present invention, the content of nickel slag is limited to 30 to 80%, but if it is less than 30%, the above effects cannot be obtained. On the other hand, if the nickel slag content exceeds 80%, pockmarks tend to occur on the bead surface. Therefore, the amount of nickel slag should be 30 to 80%, and the rest should be mainly melt flux. Here, as a countermeasure against potmarks, the above mixed flux may be supplemented with deoxidizing agents such as Ca, Mg, Al, Si, and Mn, gas generating agents such as CaCO _{3 and} MgCO ₃ , or Ni, Mo, which improves the toughness of the weld metal. In some cases, alloying agents such as Cr are mixed. Next, the reasons for limiting each component of the flux of the present invention will be explained in detail. Sio: 40 to 60% A slag forming agent and a necessary component to increase the viscosity of slag and ensure high-speed weldability, but if it is less than 40%, the slag will flow easily during inclined welding and the above-mentioned effects will not be obtained. do not have. On the other hand, if it exceeds 60%, the viscosity becomes too large, and the gas generated during welding cannot escape completely, resulting in pockmarks. MgO: 7-40% A slag forming agent that lowers the viscosity of slag.
It is a basic component that not only raises the melting temperature of slag, but also is a necessary component to enhance the deoxidizing effect of flux, but if it is less than 7%, this effect cannot be obtained. On the other hand, if it exceeds 40%, the cross-sectional shape of the bead becomes convex, causing not only undercuts but also pockmarks. Al ₂ O ₃ : 0.5-5% This is a necessary component as a slag viscosity modifier and a slag melting temperature modifier, but if it is less than 0.5%, the slag melting temperature will drop, the slag will flow easily during inclined welding, and cone cave The depth is great. On the other hand, if it exceeds 5%, pockmarks are likely to occur. CaO: 0.5-5% It is a basic component that not only enhances the deoxidizing effect of flux but also is a necessary component to adjust the slag melting temperature, but if it is less than 0.5%, the effect will not be obtained. If it exceeds %, pockmarks will be noticeable. _CaF2 : 0.5-5% This is a basic component and is a necessary component to enhance the deoxidizing effect of flux, but if it is less than 0.5%, the effect cannot be obtained. On the other hand, if it exceeds 5%, the slag viscosity decreases significantly, the slag tends to flow during inclined welding, and the cone cave depth of the bead increases. MnO: 0.5-30% MnO not only serves as a slag forming agent but also has a property of increasing slag removability, but if it is less than 0.5%, this effect cannot be obtained. On the other hand, if it exceeds 30%, the melting temperature of the slag decreases, the slag tends to flow during inclined welding, and the bead shape deteriorates. (Example) External shape using steel strip (SM-41B) with a plate thickness of 12 mm
Multi-electrode welding was performed under the welding conditions shown in Table 2 using fluxes with the mixing ratio and composition shown in Table 1 for internal welding of a spiral steel tube of 800 mmφ, and the results shown in Table 3 were obtained. The cone cave depth d is measured as shown in Figure 1, and the undercut is the total length of the undercut ΣΔl relative to the bead length l as shown in Figure 2. Undercut = ΣΔl/2l x 100 (%) ). As shown in Table 3, due to the effects of welding using fluxes A to D of the present invention, the bead shape was good even in high-speed welding, and no welding defects occurred. Comparative flux E had a good bead shape, but because it contained only nickel slag, undercuts occurred and many pock marks appeared on the bead surface. Flux F is running out of nickel slag,
Because MgO was low and CaO and CaF ₂ exceeded the upper limit, the slag lacked viscosity and the cone cave became deep. Pockmarks also appeared frequently. Flux G is running out of nickel slag,
Because the MnO content exceeds the upper limit, the arc becomes unstable, the bead meandering, slag flows, the cone cave becomes deeper, and overlap occurs.
Undercutting occurred, and the slag releasability also deteriorated. In Flux H, SiO ₂ exceeded the upper limit and CaO was low, resulting in deep cone caves, overlaps, and frequent pockmarks. Flux I had less SiO ₂ and Al ₂ O ₃ and CaO exceeding the upper limit, so the bead shape was convex and undercut occurred. Pockmarks also appeared. Flux J has less SiO ₂ and CaF ₂ and MnO exceeding the upper limit, so the cone cave becomes deeper.
The overlap has also increased.

【table】

【table】

【table】

[Table] (Effects of the Invention) The present invention is constructed as described above, and a good bead shape can be obtained without defects such as undercuts and cone cave marks during high-speed welding of 5 m/min or more.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a method of measuring the cone cave depth, FIG. 2 is a diagram showing a method of calculating an undercut, and FIG. 3 is a cross-sectional view of a bead shape in each weld of an example.

Claims (1)

[Claims] 1 Contains 30-80% by weight of nickel slag, 20-70% by weight of melt flux, SiO ₂ : 40-60% by weight, MgO: 7-40% by weight, Al ₂ O ₃ : A flux for high-speed submerged arc welding of spiral steel pipes, characterized in that the main components are 0.5 to 5% by weight, CaO: 0.5 to 5% by weight, CaF ₂ : 0.5 to 5% by weight, and MnO: 0.5 to 30% by weight.