JPH03291192A - Flux cored wire for gas shielded arc welding - Google Patents

Abstract

PURPOSE:To form the finer crystal structure of a deposited metal and to improve low-temp. toughness by incorporating TiO2, metal fluoride, Mn, Si, Mg, and oxide at specific % of the total weight of the wire into a flux. CONSTITUTION:The wire for gas shielded arc welding is constituted by filling the flux into a steel sheath. The component of the following ratios by the total weight of the wire are incorporated into this flux: 2.5 to 6.5% TiO2, 0.36 to 1.5% metal fluoride as the ratio of F, 1.0 to 3.0% Mn, 0.2 to 1.0% Si, 0.1 to 1.0% Mg, <=8.0% oxide including TiO2, further, 0.02 to 0.5% one or >=2 kinds of Ti, B, Al, and Zr may be incorporated therein. The oxygen content in the deposited metal is drastically decreased in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a flux-cored wire for gas-shielded arc welding, which has good welding workability and can yield a weld metal with excellent low-temperature toughness.

[Conventional technology] Flux-cored wire for gas-shielded arc welding, which uses chikunya-based flux as a filler and a single or mixed gas such as carbon dioxide, argon, or helium as a shielding gas, has an excellent bead appearance and shape. and welding workability.

Because it improves work efficiency, it is widely used for welding structures made of mild steel and 50 kg class high-strength steel.

[Problems to be Solved by the Invention] However, the biggest drawback of chikuna-based flux-cored wires is that they have low low-temperature toughness, making it difficult to apply them to high heat input welding of thick plates.

Furthermore, as disclosed in Japanese Patent Publication No. 56-6840, an attempt is made to improve the toughness by adding Ti and B to Chikunya flux, but this is not suitable for low-temperature copper applications that require high toughness at -45 to -60°C. , performance is insufficient.

On the other hand, there is a method for improving low-temperature toughness using a flux other than Chikuna-based flux, for example, in JP-A-52-116746, in which good low-temperature toughness is obtained. It has a poor appearance and shape, and is inferior in all-position welding workability, so it has not been put into practical use.

Furthermore, while maintaining the characteristics of Chikunya flux-cored wire, we have developed a method to improve its low-temperature toughness, which is its drawback.
In Japanese Patent Publication No. 59-44159, conventionally 700~
The amount of oxygen in the weld metal, which was about 900 ppm, was reduced to Mg,
A technique has been proposed to improve low-temperature toughness by reducing the amount to 500 ppm or less through the combined addition of Ti and H.
It has insufficient performance as a welding material for low-temperature steel, which requires high toughness at temperatures below -60°C.

The present invention aims to ensure good welding workability, which is a feature of chikuna-based fluxes, and to extend low-temperature toughness to a lower temperature range. By significantly reducing the oxygen content in the wire (400 ppm or less) and at the same time making the crystal structure of the weld metal finer, it improves low-temperature toughness, eliminates the drawbacks of conventional wires, and expands the field of application. We provide the best flux-cored wire possible.

[Means for Solving the Problems] The present inventors have obtained the results of repeated research aimed at improving the toughness at lower temperatures while maintaining the welding workability that is a feature of Chikunya flux-cored wire. The gist of the structure is that a W4 outer sheath is filled with flux containing the following amounts of components based on the total weight of the wire.

(1) A flux-cored wire for gas-shielded arc welding in which a steel outer sheath is filled with flux, wherein the flux contains the following amount of components based on the total weight of the wire: It's a wire.

Ti1t: 2.5-6.5%, metal bombide; F amount: 0.36-1.5%, Mn: 1.0-3
．． 0%, St: 0.2-1.0%, Mg20, 1-1
．． 0%, oxide: Tin
This is a flux-cored wire for gas shielded arc welding containing 0.2 to 0.5% of one or more of r.

[For production]

Below, the reasons for limiting the component composition of the filling flux used in the present invention will be explained in detail as well as the effects.

First of all, TiO□ has excellent encapsulation and peeling properties not found in other slag forming agents, and is an essential component as an arc stabilizer.
On the other hand, if it exceeds 6.5%, the amount of slag generated will be excessive, slag entrainment will occur, and since it is an acidic component, it will be difficult to separate as slag during welding, and it will form as non-metallic inclusions in the weld metal. It tends to remain, increases the amount of oxygen in the weld metal, and deteriorates notch toughness. Therefore 2
．． The range is 5 to 6.5%. As a TiOx source,
Rutile, synthetic rutile, titanium slag, etc. are used.

Metal fluorides have the effect of increasing arc stability and improving the low-temperature toughness of the weld metal through dehydrogenation. These effects are effectively exhibited by adding 0.36% or more in terms of F amount. However, if it exceeds 1.5%, the fluidity of the slag becomes excessive, resulting in poor slag envelopment and poor bead shape. Therefore, it should be in the range of 0.36 to 1.5%. Examples of fluoride include Na, Li, Mg, and Ca.
Fluorides of alkali metals and alkaline earth metals are commonly used.

Mn is the fluidity of the slag. It is added to improve the bead shape, promote deoxidation of weld metal, and provide suitable strength to welded joints.

If it is less than 1.0%, the necessary strength cannot be obtained;
If it exceeds 1%, the strength will improve, but the toughness will deteriorate. Therefore, the amount of Mn added is 1.0 to 3.0%. Note that Mn is used alone, as well as in Fe-Mn, Fe-5i
-6 Can be used in the form of iron alloys such as Mn.

Si is an effective deoxidizing agent and improves the appearance of the bead shape and welding work, but if it is less than 0.2%, these effects cannot be obtained; however, if it exceeds 0.0%, it will degrade the Excessive Si is undesirable since it deteriorates toughness, so the content of Si is set at 0.2 to 1.0%. Note that Si is a simple substance or Fe-5i, Fe-3i -Mn
It can also be used in the form of iron alloys such as.

Mg is a strong deoxidizer. In particular, it is best for reducing the amount of oxygen in weld metal. If the amount added is less than 0.1%, the effect will not be sufficiently obtained, while if it exceeds 1.0%, welding workability will deteriorate, the amount of spatter will increase, and low temperature toughness will deteriorate. Therefore, the appropriate range for Mg is 0.1 to 1
．． 0Mg, which is defined as 0%, is a single substance or Ni-Mg+Ca
-Mg, Fe-Mg, Fe-5i-Mg, etc. may be added in the form of Mg alloys.

Next, Ti, B, Al2. Zr's lf! Alternatively, the reason for adding 0.02 to 0.5% of two or more types is that it has the effect of improving the toughness by refining the crystal grains of the weld metal. T
Various studies have already been conducted on the notch toughness-improving effects of Nos. 1 and B, and they have the effect of promoting the formation of a fine acicular ferrite structure and fixing solid solution nitrogen that adversely affects toughness. Further, by adding a small amount of Aff and Zr, the effects of Ti and B are further promoted. Therefore, Ti, B, Al2. One or two types of Zr
The addition range is 0.02 to 0.5% for seeds and above. 002
If Ti, B, and Aβ are added in an amount less than 0.5%, these effects will be small, and if added in an amount exceeding 0.5%, the weld metal will become brittle and the toughness will decrease, which is not preferable.

Zr can be added alone or as Fe-Ti1.
Fe-B, Al2-Mg, Fe-Al2. In addition to alloys such as Zr-5t, B and Zr can be added in the form of oxides and reduced with a sclerotic acid.

Further, in the present invention, iron oxide is used as a slag forming agent.

5iCh, AlzOx, 2rOt, MnO, MgO
, BIOs, Nano, KtO, etc., can be used in combination, but the above Tie.

If the total amount of oxides added, including oxides, exceeds 8.0%,
The main purpose of the present invention is to reduce the oxygen content in the weld metal to 400p.
The present invention was achieved as a result of detailed study of the effects of the filling flux composition.

Since oxides increase the amount of slag produced, make it easier to entrain slag, and increase the amount of oxygen in the weld metal, the results of the present invention cannot be achieved if the oxide is added in an amount exceeding 8.0%. do not have.

The composition required for the filled slack used in the present invention is as described above, but other alloying elements etc. may also be used in combination within the range that can satisfy the above requirements.For example, iron powder,
High efficiency can be achieved by increasing the amount of welding. In addition, in order to ensure strength of 60 to 80 kg class, Ni, Cu, Cr, Mo
, V, etc. can be added to obtain the necessary strength.

As the steel outer skin, cold-rolled steel and hot-rolled steel with good deep drawability are used from the viewpoint of filling workability. Further, the filling rate of flux is not particularly limited, but in consideration of wire drawability, a range of 10 to 30% based on the total weight of the wire is most appropriate.

There are no restrictions6 on the cross-sectional shape of the wire; in the case of a wire with a small diameter of 2 mmφ or less, a relatively simple cylindrical one is preferable, and in the case of a large diameter wire of about 2.4 to 3.2 mmφ, a wire with a sheath 6, which has a structure in which the material is intricately folded inside, is common. Furthermore, for seamless wires, it is effective to plate the surface with Cu or the like.

Further, the m-type welding target is generally low-temperature steel and high-strength steel, but it can also be applied to welding low-alloy steel, high-alloy steel, etc. depending on the application.

[Example] Table 1 shows the configuration of the prototype wire, and Table 2 shows the test results. In Table 2, Nos. 1 to 6 are comparative examples, and Nos. 7 to 16 are examples of the wire according to the present invention.

Using wires finished to 1.2+nmφ wire using a mild steel outer sheath, the tensile properties and impact properties of the welded metal obtained by welding under the following conditions were investigated, and the results shown in Table 2 were obtained. .

Welding conditions Welding current: DC reverse polarity, 270A welding
Voltage = 29v Welding speed: 25cm/min Shielding gas: C0□25C/min Wire protrusion length: 20mm Bevel shape: 45°V groove root gap 1.2mm.

Backing material 9mm Base material, plate thickness 20mm, Abrasive quality: Low temperature steel plate J
IS 5LA33B lamination method 20 layers 12 baths The physical properties of the welded metal were investigated using test pieces taken from the center in the plate thickness direction and groove width direction.

As is clear from the test results in Table 2, N
o, 1 = No, 5, the amount of oxygen in the weld metal was as high as 450 ppm or more, the transition temperature was about -45°C, and no improvement in toughness was observed. NO.6 also has a low oxygen content of 255 ppm and low temperature toughness of 11+.
When the amount of metal fragments was outside the scope of the present invention, spacks occurred frequently during welding, the slag encapsulation was poor, and the bead was deteriorated.On the other hand, the wires of Examples No. 7 to N816 of the present invention all had Since the aging temperature was 160°C or less, it was confirmed that the low-temperature toughness was also good.

[Effect of the invention 1] The flux-cored wire of the present invention is constructed as described above, and is made of 1'Ir! J and Y, which specify the combination of 15 ingredients and the amount added, ``Upward welding: Significantly reduce the oxygen content in the welding layer, and at the same time refine the crystal structure of the welding entertainment. Improved 6 As a result, Chikucho-Ya system-7
Ratsu, Pushi←Sagi”, '-74 “yani 7) Eliminate major illness 7
．． This will expand its use to large books.

Claims (2)

[Claims] (1) A flux-cored wire for gas-shielded arc welding in which a steel outer sheath is filled with flux, wherein the flux contains the following amount of components based on the total weight of the wire: wire. TiO_2: 2.5-6.5% Metal fluoride: 0.36-1.5% as F amount Mn: 1
．． 0-3.0% Si: 0.2-1.0% Mg: 0.1-1.0% Oxide: 8.0% or less including TiO_2 (2) One or more of Ti, B, Al, and Zr is 0
．． The flux-cored wire for gas shielded arc welding according to claim 1, wherein the flux-cored wire contains 0.02 to 0.5%.