JPH0239359B2 - SERUFUSHIIRUDOAAKUYOSETSUYOFURATSUKUSUIRIWAIYA - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flux-cored wire for self-shielded arc welding (hereinafter simply referred to as flux-cored wire) that can perform welding without supplying shielding gas or flux from the outside, and in particular, it generates little welding fume and This invention relates to a flux-cored wire that can provide good welding workability and bead appearance in all positions. Most flux-cored wires currently in use contain large amounts of CaF ₂ , Mg, Mg alloys, etc. with high vapor pressure as slag forming agents and shielding agents, and a large amount of fume is generated during welding. There are problems such as difficulty in observing fumes, frequent replacement of welding mask filters, and significant contamination of the working environment, and the demand for reducing fumes has been increasing year by year. In addition, flux-cored wires based on general CaF ₂ -Al-Mg type flux tend to have beads that sag during vertical advancement welding, resulting in convex beads.
Problems were also pointed out regarding welding efficiency, such as the ability to obtain a proper weld bead only with a low current of around 150A. On the other hand, Japanese Patent Application Laid-open No. 155139/1983, which improves the bead shape in vertical advancement welding,
No. 56-74395, Special Publication No. 52-50022, No. 53-
There are wires disclosed in publications such as No. 10011,
Although these contain BaF ₂ as a flux component, they are still unsatisfactory in terms of bead appearance in all-position welding, and no particular improvement effect has been obtained in terms of the amount of fume generation. Under these circumstances, the present inventors focused on improving the bead shape and reducing the amount of fume in all-position welding, and achieved the above objectives by particularly devising the composition of the filling flux. We have been conducting research to the best of our ability. The present invention was completed as a result of such research, and has a flux-cored wire in which a steel sheath is filled with granular flux, in which the flux is SrF ₂ +BaF ₂ per total weight of the wire. : 1.5-4.5% CaF ₂ : 0.1-1.0% Mg: 0.3-1.0% Al: 1.8-3.0% MgO: 0.05-2.0%, and [SrF ₂ amount/(SrF ₂ amount + BaF ₂
amount)] is 0.05 to 0. and (Mg+Al) is 2.1% or more
The gist is that it is filled with a substance that satisfies the condition of 3.5% or less. The flux-cored wire of the present invention reduces the amount of weld fume generated, which is a disadvantage of conventional wires of this type, and improves workability and bead appearance in all-position welding, and is suitable for general use in mild steel and high-strength steel. In particular, its characteristics can be most effectively exhibited by applying it to welding light structures. The reasons for determining the component composition of the filling flux in the present invention will be explained in detail below. First, in the present invention, as an essential slag forming agent,
Although BaF ₂ , SrF ₂ and CaF ₂ are used, these fluorides are the main cause of weld fume generation together with Mg, which will be described later. Therefore, the following experiment was conducted to first clarify the relationship between the total content of the fluorides in the filling flux and the amount of welding fume generated. That is, the first
A 2 mm flux-cored wire was made using the mild steel sheath material shown in the table and the filling flux shown in Table 2, current: 250 (A), voltage: 21 (V), wire protrusion length: 20 mm, polarity. : Perform bead-on-plate welding on a mild steel flat plate under DC (wire) conditions,
The amount of welding fume generated was investigated in accordance with JIS Z3930.

【table】

[Table] The results are shown in Figure 1. In general, the standard allowable amount of welding fume generated in indoor work is 1500 mg/min or less under the conditions of wire diameter 2 mm and welding current 250 (A). Although it varies depending on the amount, when the Mg amount is 1.0%, by suppressing the total fluoride amount to 5.5% or less, the amount of welding fume generation can be suppressed to below the standard value. However, the above-mentioned fluorides do not have the same function as filling flux components;
Each has its own advantages and disadvantages. i.e. BaF ₂
In addition to the advantage of reducing spatter and promoting spray-like droplet transfer, it also has excellent shielding performance and vertical orientation.
It has various properties such as suppressing the dripping of molten metal in an upward position, and these properties are most effectively demonstrated by the polarity of the direct current (wire).
However, BaF ₂ combines with Al ₂ O ₃ and MgO derived from Al and Mg, which are also used as deoxidizing and denitrifying agents, to form a complex salt with an extremely high melting point and increase the viscosity of slag, resulting in problems such as slag entrainment. In addition to easily causing defects, it also deteriorates the bead appearance and slag removability. or
CaF ₂ improves the bead appearance and slag removability, but has the drawbacks of promoting convex bead formation in vertical advance welding, significantly increasing the amount of fume, and impeding arc stability and increasing spatter. ing. SrF ₂ is similar to BaF ₂ and CaF ₂ in terms of physical properties.
It is an intermediate effect, and its own effect is
Although it has better bead appearance and arc stability than BaF ₂ , it has poor bead formation properties in the upright position and cannot be said to have good slag removability. Therefore, if the characteristics of each of these fluorides are taken into account, it is thought that an optimal blending ratio exists for these three types. Therefore, while considering the individual characteristics of each fluoride and the total amount of fluoride, various studies were conducted on the optimal blending ratio of each fluoride, and the total amount of BaF ₂ and SrF ₂ was 1.5 to 4.5% based on the total weight of the wire. It has become clear that the ratio of both should be [SrF ₂ amount/(SrF ₂ amount + BaF ₂ amount)] ratio of 0.05 to 0.5, and that the CaF ₂ amount should be 0.1 to 1%. But BaF ₂
If the total amount of SrF2 and SrF ₂ is less than 1.5%, the bead appearance will be uneven due to insufficient slag amount, while if it exceeds 4.5%, the amount of fume generation will increase and it will not be possible to apply it to small diameter wires of 1.6 mm or less. Sometimes the arc tends to become unstable. Also, [SrF ₂ amount/(SrF ₂ amount + BaF ₂ amount
If the amount) is less than 0.05, no improvement effect on the bead appearance or arc stability (arc concentration) will be observed, while if it exceeds 0.5%, the slag will seize and become difficult to peel off. As the amount of CaF ₂ added increases, the bead appearance and slag removability improve, but these effects are not effectively exhibited when less than 0.1% is added. On the other hand, if it exceeds 1%, a convex bead tends to form during upward welding, making efficient welding impossible. Incidentally, FIG. 2 is a graph of experimental results showing the influence of the mixing ratio of BaF ₂ and SrF ₂ (the total amount of both added is 4.5%) and the amount of CaF ₂ added on the vertical advancement welding limit current. However, the limit current for vertical advancement welding is when welding a T-shaped fillet weld joint with a plate thickness of 12 mm in one pass so that the leg length is 9 mm, and the excess welding is 1.6 mm.
The current value was calculated as follows. As is clear from Figure 2, when CaF ₂ exceeds 1%, BaF ₂ and
No matter how the blending ratio of SrF ₂ is adjusted, the limiting current value cannot be increased sufficiently. Next, in the present invention, 0.3 to 1% Mg and 1.8 to 3% Al are used as deoxidizing agents and denitrifying agents based on the total weight of the wire.
(However, the total amount of both should be 3.5% or less). In other words, Mg easily turns into metal vapor at a temperature considerably lower than the melting point of steel, blocks the atmosphere, and exhibits a strong shielding effect. If it is less than 0.3%, the shielding effect becomes insufficient and the Al Denitrification and nitrogen fixation effects become insufficient, and pore defects are more likely to occur. However, if it exceeds 1%, the amount of fume generation increases significantly and the amount of spatter also increases. still
If metallic Mg is used as a Mg source, vaporization due to arc heat will occur explosively and spatter will increase significantly, so AI-Mg, which has a relatively slow vaporization reaction,
It is desirable to use it in the form of an alloy such as Mg-Si, Mg-Si-Ca, Ni-Mg, or Li-Mg. In addition to exhibiting deoxidizing, denitrifying, and nitrogen fixing effects, Al also has the effect of preventing weld metal from dripping in the upright advancing position and increasing welding efficiency, but if it is less than 1.8%, these effects will not be effectively exhibited. . On the other hand, if it exceeds 3%, the strength of the weld metal, especially the yield strength, will be abnormally reduced, and the crystal grains will become coarser, resulting in poor impact performance and bending performance. In addition to metal Al, Al sources include Fe-Al, Al-Mg, Zr-Al, Li-Al.
Alloys such as can be used. By the way, Al
If the total addition amount of Mg and Mg is too large, the amount of
The Al content increases, and the slag has a high melting point.
Al ₂ O ₃ and MgO increase. As a result, the viscosity of both the weld metal and the slag increases abnormally, which worsens the bead conformity, especially in multilayer welding, and makes it more likely to cause defects such as slag wrapping and poor fusion.To avoid these problems, The amount of each addition should be adjusted so that the total amount of both is 3.5% or less. Furthermore, if the amount of (Mg+Al) is less than 2.1%, shielding properties and denitrification/nitrogen fixation effects will be insufficient and pore defects will easily occur, so it is necessary to have an amount of 2.1% or more. Furthermore, MgO has the effect of improving slag encapsulation, bead shape, and welding workability, and must be contained at 0.05% or more in order to achieve this purpose. However, if it exceeds 2%, the fluidity of the slag becomes excessive, and the encapsulation of the slag worsens, especially in vertical or horizontal positions. The essential components of the filling flux used in the present invention are as described above, but if necessary, other slag forming agents may be added such as LiBaF ₃ , LiF, MgF ₂ , K ₂ ZrF ₆ , NaF
fluorides such as Al ₂ O ₃ , ZrO ₂ , MnO, MnO ₂ ,
NiO, CaO, _TiO2 , _LiFeO2 , _{Li2MnO3 ,}
Oxides such as Li ₂ SiO ₃ , Sr ₂ FeO ₄ , or BaCO ₃ ,
Carbonates such as SrCO ₃ , CaCO ₃ , Li ₂ CO ₃ , MgCO ₃ and Na ₂ CO ₃ can also be added as supplements. Furthermore, it is also effective to add C or Mn to adjust the strength of the weld metal. However, since C and Mn tend to significantly increase quench hardenability and inhibit cracking resistance, the content in the steel sheath should be taken into consideration and should be 0.01 to 0.25% and 0.20 to 2.00%, respectively, based on the total weight of the wire. It is desirable to adjust so that As C sources, in addition to carbonates, graphite, high C Fe-Mn, cast iron powder, cellulose, etc. are used, and as Mn sources, electrolytic Mn,
Fe-Mn, Fe-Si-Mn, or MnO, _MnO2 ,
Oxides such as Li ₂ MnO ₃ are used. It is also effective to add an appropriate amount of Si, and furthermore to add appropriate amounts of Ni, Ti, Zr, B, etc. to improve the notch toughness of the weld metal. In other words, Ni is an austenite-forming element and has the effect of suppressing the coarsening of ferrite grains caused by Al and increasing notch toughness, but if it is too much, the strength becomes excessive and cracks are likely to occur, so it is necessary to increase the total weight of the wire. However, it should be kept below 4%.
Ni sources include metal Ni, Fe-Ni-Cr, Ni-Mg
Alloys such as NiO can be used, and oxides such as NiO are also effective. Ti and B also have the effect of refining the grains of the weld metal, and Ti is 0.002% or more.
B exhibits a remarkable notch toughness improvement effect at 0.025% or more. However, if the amount of Ti is too large, the slag removability will be abnormally reduced, the bead appearance will be poor, and the B
If the amount is too large, the notch toughness improvement effect will be reduced, and
The quench hardenability becomes too high, resulting in excessive strength and poor cracking resistance, so Ti should be 0.3% or less.
B should be suppressed to 0.025% or less. Ti
Sources include metal Ti, alloys such as Fe-Ti, or
Oxides such as rutile, illuminite, calcium titanate, Li ₂ TiO ₃ containing TiO ₂ and Ti ₂ O ₃ can also be used. Examples of B sources include alloys such as Fe-B, special glasses containing boron oxide (B ₂ O ₃ ), colemanite, oxides such as Li ₂ B ₄ O ₇ and Na ₂ B ₄ O ₇ . Like Ti and B, Zr also has the function of increasing the notch toughness of the weld metal, and this effect is effectively exhibited by containing 0.01% or more of the total weight of the wire. However, if it is too large, the slag removability will decrease and the bead appearance will also deteriorate, so 1.0
It is best to keep it below %. Fe−Zr as a Zr source
ZrO 2 , alloys such as Zr-Si, ZrO ₂ , zircon sand containing ZrO ₂ , Li ₂ ZrO ₃ and other oxides can be used. The filling rate of the above-mentioned flux into the steel sheath is not particularly limited, but the most common range is 7 to 25% (based on the total weight of the wire). However, if the filling rate is less than 7%, the absolute amount of the generated slag and the generated shielding gas may be insufficient, and the characteristics of the present invention may not be effectively exhibited.On the other hand, if the filling rate exceeds 25%, the wire drawability may deteriorate. This is because it becomes difficult to manufacture thin wires with a diameter of 2 mm or less. The present invention is constructed as described above, but the point is that the amount of fume generation can be reduced by strictly regulating the type and content of fluorides contained in the filling flux, and the content of Al, Mg, and MgO. Self-shielding has extremely low welding properties and has good welding workability, including bead appearance and slag removability, and can perform efficient welding in all postures, including standing and advancing postures, without causing bead sag. It is now possible to provide a flux-cored wire for arc welding. Next, the configuration and effects of the present invention will be specifically explained using experimental examples. Experimental example Mild steel with the chemical composition shown in Table 3 was used as the sheath material.
A 2 mm thick flux-cored wire was prepared using the filling flux shown in the table.

【table】

【table】

[Table] Using each of the obtained wires, welding experiments were conducted in the following manner. (1) Welding conditions Weld metal performance test: 240-260(A)×20-24(V) Lamination method…6 layers 12 passes, plate thickness…19mm Vertical bending test of welded part: 190-210(A)× 19~23 (V) Lamination method...2 layers, 2 passes, plate thickness...6.4mm Other conditions: Wire protrusion length...20~25mm Power polarity...DC - wire (-) Test plate material...JIS G 3106, SM- 50A (2) Performance and chemical composition of weld metal: Tested in accordance with JIS Z 3313 (3) X-ray transmission test of welded part Tested in accordance with JIS Z 3104 (4) Vertical bending test of welded part: AWS A Test in accordance with 5.27 (5) Evaluation of welding workability: ◎...Excellent, 〇...Good, △...Poor (6) Measuring method of vertical advancement welding limit current: Measured in the same manner as in Fig. 2 ( 7) Welding fume measurement method: Measured in the same manner as in Figure 1. The results are summarized in Table 5.

【table】

[Table] From Table 5, the following can be considered. The wires (Nos. 1 to 7) of the present invention have good workability such as bead appearance, are difficult to sag during vertical advancement welding, are efficient, and generate less fume. Among these wires, wires Nos. 6 and 7 in particular contain grain refining elements such as Ti, so the impact value of the weld metal is high. On the other hand, the comparative wires each have the following drawbacks. Wire No. 8 had excessive Al content, so not only did the ductility of the weld metal become poor, but also poor X-ray performance occurred due to poor fusion. Wires No. 9 and No. 11 had insufficient Al and Mg, respectively, so pores were significantly generated and the X-ray performance was poor. Wire No. 10 had excessive Mg, so there were many spatters and fumes, and the workability was poor.
Wire No. 12 had a poor bead appearance because the SrF ₂ /(BaF ₂ +SrF ₂ ) ratio was too small. wire
In No. 13, the SrF ₂ /(BaF ₂ +SrF ₂ ) ratio was too large, so the slag removability was poor. Wire No.14
Because of excess CaF ₂ , it was inefficient because it easily sagged when placed vertically, and many spatters occurred. Wire No. 15 had poor bead appearance and slag removability due to insufficient CaF ₂ . Wire No.16
Because it does not contain BaF ₂ , it tends to sag when placed vertically, making it inefficient. Wire No.17 and 18 are
When MgO was excessive or insufficient, the slag coverage became uneven, resulting in poor bead appearance. No. 19 is an example that does not contain SrF ₂ or BaF ₂ , and has poor bead appearance and slag removability.
Also, a lot of hyoum occurred. No.20 is BaF ₂ ,
This is an example that does not contain SrF ₂ and tends to sag when placed vertically.
It was inefficient and caused a lot of fumes.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the amount of fluoride in the filling flux and the amount of fume generation, and Figure ₂ is a graph showing the relationship between the amount of fluorides in the packed flux and the amount of fume generated.
It is a graph showing the relationship between the amount and the vertical advancement welding limit current.

Claims (1)

[Claims] 1. A flux-cored wire in which a powdery flux is filled in a steel sheath, in which the flux is based on the total weight of the wire, SrF ₂ +BaF ₂ : 1.5 to 4.5% CaF ₂ : 0.1 to 1.0% Mg : 0.3 to 1.0% Al: 1.8 to 3.0% Mgo: 0.05 to 2.0%, and [SrF ₂ amount/(SrF ₂ amount + BaF ₂
amount) is 0.05 to 0.5 and (Mg+Al) is 2.1% or more
A flux-cored wire for self-shielded arc welding, characterized in that it satisfies the condition of 3.5% or less.