JPS6125470B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flux-cored wire for welding that has a good welding condition. Flux-cored wire for welding is a wire with a composite structure in which the outer steel pipe is filled with powdery flux consisting of a deoxidizing agent, slag forming agent, etc., and is used for a wide range of applications from welding mild steel to low-alloy steel, high-alloy steel, etc. It is used. There are two types of flux-cored wires for welding.One is that after forming a thin steel strip into a U shape, it is uniformly filled with powder-like welding flux whose composition has been adjusted to a specified level. It is a flux-cored wire manufactured by a method of forming the wire into a predetermined cross-sectional shape and then drawing it. Since this wire has seams, it has various disadvantages. That is, the seams are likely to open, and moisture on the outer surface of the wire or organic substances such as lubricants used during the manufacturing process enter the flux inside the sheathed steel pipe through the openings. When welding using such a wire, the mechanical performance of the weld may be affected by increasing the amount of diffusible hydrogen in the weld metal or by promoting oxidation of the outer skin wall surface on the inner surface of the wire, increasing oxygen in the weld metal. This will lead to deterioration. Also, since it has seams, it cannot be plated and therefore has poor rust resistance. The other one is Special Publication No. 45-30937 and Special Publication No.
This is a seamless welding wire made by filling a seamed steel pipe such as a seamless steel pipe or an electric resistance welded pipe with flux, as described in Publication No. 51-45544. This flux-cored wire for welding can optionally contain slag forming agents, arc stabilizers, etc. that are not contained in the actual wire, and even if the steel pipe that is the outer skin has the same composition, alloying agents and deoxidizing agents can be added to the filling flux. By adding an appropriate amount of agent, it is possible to manufacture welding wire that is compatible with each grade.
Suitable for high-mix, low-volume production. In addition, the rust resistance, which was a drawback of flux-cored wires with seams, can be overcome by applying surface treatment such as copper plating.Since there are no seams, the filling flux does not absorb moisture, and the weld metal Since the amount of diffusible hydrogen can be reduced to the same level as that of the actual wire, a welded joint with good quality can be obtained. An object of the present invention is to provide a flux-cored wire for welding without an opening in the longitudinal direction of the wire, that is, a seam, by specifying the cross-sectional shape of the wire and the tensile strength of the outer steel pipe, thereby achieving a good welding condition. An object of the present invention is to provide a flux-cored wire for welding. The present invention achieves this object by providing a flux-cored wire for welding with a small diameter D = 1.0 to 2.0 mm, which is a welded steel pipe with a seam welded and filled with welding flux. D is 0.15≦t/D≦0.35, and the tensile strength T of the outer skin is T=70/√～100Kgf/mm ²
A flux-cored wire for welding, characterized by: It is. The contents of the present invention will be explained in detail below. The flux-cored wire for welding of the present invention is a flux-cored wire obtained by filling a welded steel pipe with welded joints with welding flux and then drawing the wire to a required size, and has a joint in the longitudinal direction of the wire in the outer skin part. This eliminates the drawbacks of conventional wires, which have no seams. As for the means of filling flux into steel pipes, drawn steel pipes or high frequency welding,
An electric resistance welded tube may be filled with flux by TIG welding or the like, or a welded tube may be finished by the above-mentioned welding method while being filled with flux. As shown in Table 1, the fluxes to be filled in the wire of the present invention include titania-based, lime-based,
Various filling fluxes such as lime titania type are applicable.

【table】

[Table] Next, regarding the thickness of the wire sheath, if the sheath thickness is too thin, the sheath will harden during wire drawing, reducing productivity.Furthermore, since the wire is hard, wire feedability will be poor, and in severe cases. This causes problems such as breakage within the conduit cable. On the other hand, if the outer skin thickness is too thick, although the drawability is good, it is not possible to fill the inside of the wire with a sufficient amount of welding flux, causing problems in welding workability as a flux-cored wire. Therefore, the present inventors determined the appropriate range of the outer skin thickness through experiments. Figure 1 shows wire diameter D = 1.0~2.0mm
Thickness t of flux-cored wire for welding with a small diameter
The ratio t/D and the wire diameter D and the filling rate (flux weight/flux weight + outer steel pipe weight) q (%)
This relationship is expressed using the flux density ρ _f (g/cm ³ ) as a parameter. ρ _f varies depending on the composition of the flux and the strength of pressure during wire drawing after filling, but ρ _f = 2 to 5 g/cm ³ as shown in Figure 1.
It is usually within the range of . As is clear from Figure 1, when t/D is less than 0.15, the outer skin thickness becomes thinner, and because the strength of the wire is maintained in the outer steel pipe section, wire breakage occurs frequently during the wire drawing process. It greatly hinders productivity. Furthermore, the wire tends to break during the process of winding it onto a spool, and the wire tends to break during welding, which poses many problems as a product. On the other hand, when t/D exceeds 0.35, as is clear from Fig. 1, the filling factor q becomes 6 even when ρ _f is large.
% or more, and as a result, the amount of the necessary deoxidizing agent and slag forming agent in the flux is insufficient, and the welding performance of the flux-cored wire for welding cannot be exhibited. In other words, the ratio of the outer skin thickness t and the wire diameter D of the flux-cored wire for welding is:
A range of 0.15 to 0.35 is preferable from the viewpoint of manufacturing and product use (wire feedability, welding workability). The outer diameter of the wire targeted by the present invention is 1.0
The diameter of flux-cored wire for welding is ~2.0mm, which is in the small diameter category. This means that unless the rigidity of the wire itself is maintained above a certain value, a buckling phenomenon will occur in the wire when feeding the wire during welding, making it useless as a welding wire. Therefore, the inventors of the present invention have determined that the stiffness of the wire is represented by the tensile strength of the outer steel pipe, and as a result of their research, they have found that there is a good range in relation to the wire diameter. In other words, the tensile strength T of the outer steel pipe is 70/√Kg
If it is less than f/mm ² , buckling of the wire will occur during welding. If it exceeds 100 Kgf/mm ² , the ductility will be extremely reduced, causing problems such as wire breakage during the wire drawing process or wire breakage during welding. √~100Kgf/ ^mm2 is preferred. Table 2 shows the wire diameter D = 1.2 mm, the ratio of the outer skin thickness t to the wire diameter D = t/D = 0.24, and the plate thickness using a wire filled with titania flux at a filling rate of 12%.
Welding current on 12.5mm JISG-3114, SMA-50B steel plate
These are the experimental results of downward welding performed under the welding conditions of 280A, welding voltage 30V, welding speed 30cm/min, and shielding gas CO ₂ 20/min. The tensile strength of the outer skin was varied by drawing the wire by changing the area reduction rate of the wire after the final heat treatment during the wire manufacturing process. As can be seen from Table 2, the tensile strength T of the wire sheath is 64Kgf/mm ² (=70/
Good range from √) to 100Kgf/mm ² and 64Kgf/mm ²
When the wire is fed, the wire tends to buckle inside the conduit cable, resulting in poor wire feeding performance and welding workability. On the other hand, if the tensile strength of the outer sheath exceeds 100Kgf/mm ² , the wire may break during wire manufacturing or wire drawing, or breakage may occur during welding or wire feeding, resulting in poor wire feedability and welding. Both workability was poor. The wire feedability was determined by measuring the feed motor armature current, and judging whether the wire was good or bad was determined based on the magnitude of the current.

【table】

[Table] Next, in the wire of the present invention, since there is no seam in the outer sheath, it is possible to apply metal plating to the wire surface. Metal plating refers to metal plating such as copper, nickel, manganese, aluminum, etc., which facilitates wire drawing after plating, provides good power supply and conductivity during welding, and is easy to store. It also has excellent rust resistance over time. In other words, as mentioned above, conventional flux-cored wire has a seam in the outer sheath,
Therefore, it has not been possible to coat the wire surface with a metal surface coating such as copper, as is the case with solid wires.
This is because in either chemical plating or electroplating, the wire is immersed in the plating solution to perform plating, and the plating solution enters the flux through the open seam. Conventional flux-cored wires do not have a metal surface coating on the wire surface, and many have lubricants applied or adhered to the relatively rough surface of the wire, resulting in problems with wire feedability and rust resistance. It was hot. The flux-cored wire of the present invention completely solves these problems. Practically speaking, copper plating with a thickness of about 0.3 to 0.9 microns is adopted, but if embrittlement of the copper component in the weld metal due to radiation or post-heat treatment is expected. For this purpose, plating with Ni, Mn, Al, etc. or thinning with copper is used. Further, oil and fat for wire drawing lubrication inevitably remain on the wire surface, but if this amount is appropriate, the wire feedability will be further improved and the rust resistance will also be improved. This amount is preferably 0.2 to 1.5 gr per 10 kg of wire. The effects of the present invention will be explained below with reference to Examples shown in Table 3. Table 3 shows the wire diameter D = 1.2 mm, the outer skin thickness t is changed, the ratio t/D of the outer skin thickness t and the wire diameter D is changed, and the tensile strength T of the outer skin is changed, the ratio t/D, and the outer skin tensile strength. Eight types of welding flux-cored wires with different strengths T were manufactured and subjected to welding, and the results were compared. The wire is JISG-
It is manufactured by using 3141SPCE material as the starting steel strip, forming the steel strip to obtain a welded steel pipe, filling the steel pipe with flux, and then subjecting it to wire drawing and copper plating. The wires shown in the table were manufactured by adjusting the ratio t/D, adjusting the area reduction rate of the wire applied after the final heat treatment in the manufacturing process, and changing the tensile strength of the outer skin. The welding conditions are 280A−30V−30cm/min−CO ₂ 20ml/min, which is the same as in Table 2.
Downward welding was performed on JISG-3114, SMA-50B steel plates with a thickness of 12.5 mm. In Table 3, No. 3, No. 4, and No. 5 wires are t/D,
Examples of the present invention where both T are appropriate, No. 1, No. 2, No. 6,
Wires No. 7 and No. 8 are comparative wires in which at least one of t/D and T is not appropriate. No. 1 wire had too small a ratio t/D, too thin outer skin thickness, and too small tensile strength T of the outer skin, so buckling of the wire occurred during welding, resulting in poor wire feedability and welding workability. Wire No. 2 had an appropriate ratio t/D, but the tensile strength T of the outer sheath was small, so the wire feedability and welding workability were both somewhat poor. No.3,
For wires No. 4 and No. 5, both the ratio t/D and the tensile strength T of the sheath were within appropriate ranges, and both wire feedability and welding workability were good. No. 6 wire has an appropriate ratio t/D, but the tensile strength T of the outer sheath is large, so both wire feedability and workability are somewhat poor.
No. 7 wire has an appropriate tensile strength T of the outer skin, but the ratio t/D is too large and the outer skin thickness is too thick, so the wire feedability is good, but the required amount of welding flux is inside the wire. The slag cannot be filled and the amount of slag generated is insufficient, resulting in poor workability and failure to obtain high-quality weld metal. No. 8 wire has too large ratio t/D and tensile strength T of the outer sheath, so wire feedability is poor.
Workability was also poor.

[Table] As explained above, according to the flux-cored wire for welding of the present invention, it is a small diameter wire and the ratio of the wire outer skin thickness to the wire diameter and the outer skin tensile strength are regulated within appropriate ranges. Therefore, the welding condition (wire feeding performance, welding workability) is improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the ratio t/D of the wire outer skin thickness t and the wire diameter D and the flux filling rate q (%).

Claims (1)

[Claims] 1 A welded steel pipe with welded joints filled with welding flux is a small diameter welding flux-cored wire with a wire diameter D = 1.0 to 2.0 mm, and the outer skin thickness t and wire diameter D are 0.15≦t/D≦ 0.35, and the tensile strength T of the outer skin is T=70/√~100Kgf/
Flux-cored wire for welding, characterized in that mm ² .