JP4560418B2 - Flux-cored wire for gas shielded arc welding - Google Patents

Description

  The present invention can provide a weld metal having excellent workability such as grindability, machinability, and press bendability, and a weld metal having low tensile strength and low hardness, and good weld workability. The present invention relates to a flux-cored wire for welding (hereinafter referred to as a flux-cored wire).

In general, when welding a structure, a so-called metallurgical welding material having a tensile strength equal to or higher than that of a base material is used. However, as the base material of the welded structure, SAPH310 and SAPH370 of JIS G 3113 (hot rolled steel plate and steel strip for automobile structure) and SPHC, SPHD and SPHE of JIS G 3131 (hot rolled mild steel plate and steel strip) are used. As described above, a steel material having a tensile strength of 400 N / mm ² or less is often used. When welding these low-strength base metals using conventional gas shielded arc welding wires, the tensile strength and hardness of the weld metal become excessive, and the weldability of the welded part by a grinder or a milling machine, etc. There is a problem that workability such as press bendability is significantly reduced as compared to the base material.

  The workability of a weld metal tends to be better as its tensile strength and hardness are lower. Regarding welding materials with low tensile strength of weld metal, Japanese Patent Laid-Open No. 11-221672 (Patent Document 1) discloses a solid wire for gas shielded arc welding. There is a problem that it is inferior to wire.

On the other hand, the flux-cored wire includes YFW-C430X and YFW-A430X defined in JIS Z 3313 (arc welding flux-cored wire for mild steel, high-tensile steel and low-temperature steel), but has a tensile strength of 420 N / mm ² or more. Which is the lowest strength welding material. However, even when these flux-cored wires are used, the present situation is that it is impossible to obtain a weld metal having high tensile strength and hardness and excellent workability comparable to the base material.
JP-A-11-221672

  The present invention provides a flux-cored wire for gas shield arc welding that can obtain a weld metal that is excellent in workability such as grindability, machinability, and press bendability, and that provides good welding workability. The purpose is to do.

The gist of the present invention is that in a flux-cored wire for gas shielded arc welding formed by filling a flux in a steel outer sheath, the mass% with respect to the total mass of the wire, the total of the outer sheath and the flux, C: 0.05% or less, Si: 0.3% or less, Mn: 0.2 to 1.0%, one or two of Al and Mg in total of 0.05 to 0.30%, and the flux includes TiO ₂ : 3.5 _{~6.5%, SiO 2: 0.3~1.0%} , ZrO 2: containing 0.1% to 0.5%, gas shielded arc balance being Fe and unavoidable impurities Flux-cored wire for welding.

  According to the flux-cored wire for gas shielded arc welding of the present invention, it is possible to obtain a weld metal having a low tensile strength and low hardness excellent in workability such as grindability, machinability and press bendability, and good. Welding workability can be obtained.

  The present inventors can obtain a weld metal having a low tensile strength and low hardness excellent in workability such as grindability, machinability, press bendability, and the like in welding of a low-strength base metal, Various types of flux-cored wires that can stably produce a small amount of spatter and have good slag encapsulation and good workability were studied.

As a result, by appropriately reducing alloy components such as C, Si, Mn, Al, and Mg, which are elements having an effect of improving the tensile strength and hardness of the weld metal, it is possible to blow at 420 N / mm ² or less. It has been found that a weld metal with low tensile strength and hardness that does not generate pore defects such as holes can be obtained.

In addition, even when there are few deoxidizers such as C, Si, Mn, Al, Mg, etc., an appropriate amount of TiO ₂ , SiO ₂ , ZrO ₂ is contained in order to stabilize the arc and improve the slag encapsulation. It was found that it can be solved by doing.
These effects can be achieved by a single effect and a synergistic effect due to the coexistence of each component composition, and the reasons for the limitation will be described below.

C: 0.05 mass% or less (hereinafter referred to as%)
C is always contained in the steel, but is an element that improves the strength of the weld metal as well as the deoxidation action by the CO production reaction. However, when C exceeds 0.05% in the total of the outer skin and the flux, the tensile strength and hardness of the weld metal become excessive, and excellent workability cannot be obtained. In addition, the arc is strong and slightly unstable, resulting in a large amount of spatter generation. Therefore, C is made 0.05% or less.

Si: 0.3% or less Si is added for deoxidation and strength adjustment. However, if Si exceeds 0.3% in the total of the outer skin and the flux, the tensile strength and hardness of the weld metal are excessive as in C, and excellent workability cannot be obtained. Therefore, Si is 0.3% or less. If Si is 0.05% or more, the above effect can be obtained. Si is added as a flux component, such as ferrosilicon, metal silicon, or silicomanganese.

Mn: 0.2 to 1.0%
Mn is added for deoxidation and strength adjustment in the same manner as Si. However, if Mn is less than 0.2% in total of the outer skin and the flux, the toughness of the weld metal is lowered. On the other hand, if it exceeds 1.0%, the tensile strength and hardness of the weld metal are increased, and excellent workability cannot be obtained. Therefore, Mn is set to 0.2 to 1.0%. Mn is added as a flux component such as ferromanganese, metallic manganese, silicomanganese.

Total of one or two of Al and Mg: 0.05 to 0.30%
Al and Mg are elements having strong deacidification. If the total of one or two of Al and Mg is less than 0.05% in total of the outer shell and the flux, the deoxidation effect is small and the weld metal is oxidized, and pore defects such as blow holes are generated. On the other hand, if it exceeds 0.30%, as a result of increasing the yield of C, Si, and Mn, the tensile strength and hardness of the weld metal become excessive, and excellent workability cannot be obtained. Further, the arc becomes somewhat unstable, and the amount of spatter generated increases. Accordingly, one or two of Al and Mg are set to 0.05 to 0.30%. Al and Mg are added as a flux component by metallic aluminum, ferroaluminum, metallic magnesium, aluminum magnesium, or the like.

TiO _2: 3.5~6.5%
TiO ₂ is a basic component of the slag forming agent, and has the effect of increasing the slag encapsulation and arc stability and reducing the amount of spatter generated. If the TiO ₂ content is less than 3.5% with respect to the total mass of the wire, the encapsulation of the slag becomes insufficient, the bead appearance and shape become poor, the arc becomes unstable, and the amount of spatter generated increases. On the other hand, if it exceeds 6.5%, the amount of slag becomes excessive, and welding defects such as slag entrainment tend to occur. Therefore, TiO ₂ is set to 3.5 to 6.5%. TiO ₂ is added to the flux by means of rutile, titanium slag, sodium titanate, potassium titanate or the like.

SiO _2: 0.3~1.0%
SiO ₂ has the effect of lowering the solidification point of the slag and reducing the viscosity, and has the effect of improving the bead appearance and shape by adjusting the viscosity of the slag. When SiO ₂ is less than 0.3% with respect to the total mass of the wire, there is no effect of improving the bead appearance and shape. On the other hand, if it exceeds 1.0%, the fluidity of the slag becomes excessive, and the bead appearance and shape become poor. Thus, SiO ₂ is 0.3 to 1.0%. SiO ₂ is added to the flux by silica sand, potassium feldspar, zircon sand, sodium silicate, or the like.

ZrO ₂ : 0.1 to 0.5%
ZrO ₂ has the effect of increasing the freezing point of the slag and increasing the viscosity, and has the effect of improving the bead appearance and shape by adjusting the viscosity of the slag. If ZrO ₂ is less than 0.1% with respect to the total mass of the wire, there is no effect of improving the bead appearance and shape. On the other hand, if it exceeds 0.5%, the fluidity of the slag becomes excessive and the bead appearance and shape become poor. Therefore, ZrO ₂ is 0.1 to 0.5%. ZrO ₂ is added to the flux by zircon sand, zircon oxide or the like.

Moreover, as a flux component, another oxide, fluoride, etc. can be added in an appropriate quantity as needed. For example, an oxide such as Al ₂ O ₃ or MnO can be added as a slag forming agent in order to adjust the viscosity of the slag. As the arc stabilizer, oxides such as Na ₂ O and K ₂ O and fluorides such as NaF, MgF ₂ and K ₂ SiF ₆ can be added.

The flux-cored wire of the present invention has a predetermined wire diameter (1.0 to 1.6 mm) by die drawing or roller rolling after the flux is filled in the outer shell of mild steel with about 10 to 20% of the total mass of the wire. It is manufactured with a reduced diameter. The cross-sectional shape of the flux-cored wire is not particularly limited, and the outer skin produced by winding the flux into the tube made of a strip-shaped steel plate as a raw material, the outer skin by a manufacturing method such as filling the tube with the flux and reducing the diameter Any of the seamless types can be used. The welding shield gas is generally CO ₂ gas, but a mixed gas such as Ar—CO ₂ can also be used.

Hereinafter, the effect of the present invention will be described in more detail with reference to examples.
C: 0.005-0.015%, Si: 0.02-0.05%, Mn: 0.22-0.30%, P: 0.008-0.010%, S: Using a steel strip having a chemical composition of 0.005 to 0.008% and Al: 0.01 to 0.02%, a flux-cored wire having a wire diameter of 1.2 mm having a composition shown in Table 1 was made.

  A JIS G 3113 SAPH 370 steel plate (plate thickness 12 mm) is used as a base material, and a test plate having a groove shape with a root gap of 5 mm and a groove angle of 60 ° is welded to a length of 500 mm, and a multi-layer gas shield under the welding conditions shown in Table 2 Arc welding was performed.

During welding in each test, the stability of the arc, the amount of spatter generated, the slag encapsulation and the bead appearance were observed. In addition, after welding is completed, the presence or absence of defects is investigated by X-ray transmission tests. Tensile test pieces of JIS Z 3111 A2 and JIS Z 3111 No. 4 impact test pieces are collected from the center of the thickness of each test plate and mechanically tested. went. Moreover, the Vickers hardness test of the weld metal surface was done. In the mechanical test results, a tensile strength of 420 N / mm ² or less, an impact test with a Charpy absorbed energy at 0 ° C. of 47 J or more (average of 3), and a Vickers hardness of 150 or less were considered good. The results are shown in Table 3.

In Table 3, wire No. 1 to 9 are examples of the present invention, wire Nos. 10 to 21 are comparative examples.
Wire No. which is an example of the present invention. 1-9, since each component composition is an appropriate amount, the arc is stable, the amount of spatter generation is small, the slag encapsulation and bead appearance, the shape is good and there are no weld defects, and the tensile strength, absorbed energy and The Vickers hardness was good and very satisfactory.

  In the comparative example, the wire No. No. 10 was high in C, so the arc was strong during welding, somewhat unstable, and a large amount of spatter was generated. Moreover, since C was high, the tensile strength and Vickers hardness of the weld metal were high, and the absorbed energy was low.

Wire No. No. 11 is high in Si, and wire No. Since No. 12 had high Mn, the tensile strength and Vickers hardness of the weld metal were high, and the absorbed energy was low.
Wire No. Since No. 13 had a low Mn, the absorbed energy of the weld metal was low.

Wire No. In No. 14, the total of Al and Mg was high, so the arc was slightly unstable during welding and the amount of spatter was increased. Moreover, the tensile strength and Vickers hardness of the weld metal were high, and the absorbed energy was low.
Wire No. No. 15 had a low sum of Al and Mg, so the deoxidation effect was small, and the weld metal was oxidized to generate pits. Moreover, the absorbed energy of the weld metal was low.

Wire No. Since TiO ₂ was low in No. 16, the slag encapsulation was insufficient, the bead appearance was poor, the arc was somewhat unstable, and the amount of spatter was increased.
Wire No. No. 17 was high in TiO ₂ , so the amount of slag was excessive and the bead appearance and shape deteriorated. In addition, slag entrainment occurred.

Wire No. No. 18 had a low SiO ₂ , so the viscosity of the slag was too large, the encapsulation of the slag was poor, and the bead appearance and shape were poor. On the other hand, wire No. In No. 19, since SiO ₂ was high, the viscosity of the slag was too small, the fluidity of the slag became excessive, and the bead appearance and shape deteriorated.

Wire No. No. 20 has a low ZrO ₂ , so the viscosity of the slag was too small, and the bead appearance and shape deteriorated. On the other hand, wire No. Since No. 21 is high in ZrO ₂ , the viscosity of the slag is too large, the encapsulation of the slag is deteriorated, and the bead appearance and shape are deteriorated.

Claims (1)

In a flux-cored wire for gas shielded arc welding, in which a steel outer sheath is filled with a flux, the mass is based on the total mass of the wire, and the total of the outer sheath and the flux is C: 0.05% or less, Si: 0.3% Hereinafter, Mn: 0.2 to 1.0%, one or two of Al and Mg in total 0.05 to 0.30%, and the flux includes TiO ₂ : 3.5 to 6.5%, A flux-cored wire for gas shielded arc welding, comprising SiO ₂ : 0.3 to 1.0%, ZrO ₂ : 0.1 to 0.5%, and the balance consisting of Fe and inevitable impurities.