JPS63278697A - Flux cored wire for gas shielded arc welding - Google Patents

Abstract

PURPOSE:To improve the quality by filling up the flux adding one or two kinds or more of a silicate mineral and silicon chloride and Si, Mn, etc. to the specified amt. of a metal fluoride and carbonate in the steel made sheath contg. a nitrogen in <=specified amt. CONSTITUTION:The flux contg. 1-12% metal fluoride, 0.1-1.5% metal carbonate, 0.2-3% one or >=two kinds of a silicate mineral and silicon chloride, 0.2-2% Si, 1-2.5% Mn, 0.05-0.3% Ti and 0.1-1% Mg is filled up at 10-30% of the total wire weight into the steel made sheath contg. a nitrogen in <=30ppm. With this composition, the quality can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a flux-cored wire for gas shield welding that has excellent low-temperature toughness.

[Conventional technology]

Flux-cored wires (hereinafter referred to as wires) for gas shield welding that have been conventionally used are mainly titania-based wires, which have excellent arc stability, less spatter, and excellent welding workability and beat appearance compared to solid wires. It is used.

[Problem that the invention seeks to solve]

In recent years, with the increasing demand for energy resources in polar regions, there has been a demand for higher grade and tougher steel materials. However, conventional titania-based wires have the disadvantage that the performance of weld metals with a high oxygen content of 500 ppm or more is poor.

゛In order to eliminate these shortcomings, for example,
As shown in Japanese Patent Laid-Open No. 24124, Japanese Patent Application Laid-open No. 125437/1983, there are wires that aim to improve low-temperature toughness. The wire shown there has improved low-temperature toughness by adjusting the metal fluoride, metal carbonate, slag forming agent, and strong deoxidizing agent, but the stability of the impact value and welding workability have been improved. It is not always satisfactory in this respect. Manen JP-A No. 58-119490 attempts to improve the low-temperature toughness of titania-based flux by regulating the amount of nitrogen in the steel shell and iron powder, but the biggest drawback of titania-based flux is the deoxidizing element. It is impossible to reduce the amount of oxygen in the weld metal to 4 o ppm or less even if a large amount of is added.

The present invention aims to eliminate the drawbacks of the conventional wires and expand the field of application, and provides a flux-cored wire that can stably obtain low-temperature toughness down to a lower temperature range. Means for Solving the Problem] The present invention provides a steel outer shell having a nitrogen content of 30 ppm or less, a metal fluoride of 1 to 12 wt% based on the total weight of the wire, and a metal carbonate of 20, 1 to 1. 5 wt%, 1 type of silicate mineral, silicate compound''! 2 or more types 20.2 to 3 wt%, Si: 0.
2-2 wt%, Mn: 1-2.5 wt 9k, Ti: 0.05
~0.3 wt%, My:o, t~1 wt% of the flux is filled as an essential component to the total weight of the wire, and the metal powder contained in the flux is This flux-cored wire for gas shield welding has excellent low-temperature toughness, and is characterized in that the total amount of nitrogen is 25 ppm or less based on the total weight of the wire.

The reason why the wire according to the present invention has the above structure will be explained in detail below.

[For production]

First, in the present invention, the nitrogen content in the steel shell is limited to 309 pffl or less, and the total nitrogen content in the metal powder is limited to 55 pffl or less, as shown below. This is to be sure that if the content exceeds ppm, the toughness will be completely deteriorated.

Sixth, the nitrogen in the wire transfers directly to the weld metal.In order to lower the nitrogen in the weld metal, the nitrogen in the wire must be lowered.Most of the nitrogen in the wire is unavoidable in the steel sheath and the metal powder in the flux component. Because it contains
Both of these need to be lowered. Therefore, as described below, iron powder, which is sometimes added from the viewpoint of welding efficiency or alloy addition, and metal powder other than Si, Mn, Ti, and MP are
The total nitrogen content in all metal powders is kept to 2599 m or less, taking into account the nitrogen t from the outer skin, which will be described later.

In the present invention, a flux having the essential components described below is filled into a skin made of low carbon steel or low alloy steel with a nitrogen content of 30 ppm or less, and the nitrogen content of the skin is 30 ppm or less.
The reason for setting it below m is based on the experimental results shown in FIG.

That is, the nitrogen content is 17 ppm, 30 ppm
, 42 ppm, 559 pm, and 80 ppm CaF23.
0 (Is Potassium feldspar 1.5%, CaCO30.2%, F
e-8i (40% Sth 1.OS.

Fe-Mn (75%Mn33.0%, Fe-TL(
40chi Ti 10.2%.

A flux-cored wire, 2Wφ, containing a flux consisting of 6% MPO and 5.5% iron powder was prototyped, and the relationship between the nitrogen content of the steel sheath and the toughness of the weld metal was investigated.

The test plate was a 25m thick steel plate of 32 sizes assembled with a 50°V groove, a circumscribed current of 270A, an arc voltage of 30V, and a welding speed of 2.
5/min, shielding gas (80 Chi Ar-20% CO2
) The relationship between the toughness at -50°C and the amount of nitrogen in the circumscribed metal was investigated under the conditions of 2517 minutes. As is clear from the experimental results shown in FIG. 1, as the amount of nitrogen in the steel jacket increases, the amount of nitrogen in the weld metal also increases proportionally. The experiment was conducted in a laboratory with automatic circumscription and no wind, and there was no air entrainment due to circumscription.
It deteriorates rapidly above ppm. The nitrogen content of the steel shell at that time is 60 ppm, but in order to ensure toughness, the nitrogen content in the steel shell must be regulated to 30 ppm or less, taking into account the increase in nitrogen in the metal powder. .

The present inventors also conducted an experiment regarding oxygen in weld metal, and the results are shown in FIG.

In the experiment, a soft and hard outer skin with a photonitrogen content of 30 pprn used in the above experiment was used, and CaF was added to the total weight of the wire.
23.0 To, Potassium feldspar 1.5%, CaCO
30.2%.

Fe-8i (40%Si) 1.0%, Fe-M
n (75%Mn) 3.0%, Fe-Ti (40%Ti
I 0.2%, Mg 0, 0.2.0.4.
0.8.1.0 inch, add the remaining iron powder, and the filling rate is 1.
Welding was carried out under the same welding conditions as above using a wire of 1.2 wφ which was prototyped to have a concentration of 5%, and the relationship between the amount of oxygen in the bath welded metal and the toughness was investigated. As is clear from the experimental results shown in FIG. 2, as the amount of Mg added increases, the amount of oxygen in the weld metal decreases. Low-temperature toughness improves once, but then decreases. As is clear from this experimental result, toughness is significantly improved by reducing the amount of oxygen in the weld metal to 350 ppm or less.

Therefore, it has become clear that low-temperature toughness can be improved to a lower temperature range by suppressing gas absorption in each contact metal.

In the present invention, the amount of nitrogen is limited based on the above findings, and the reasons for limiting the filling flux components are as follows.

The metal fluoride encapsulates the weld metal as a slag agent, improves the bead shape, and cleans the weld metal by floating impurities in the molten metal. This improves toughness. Metal fluorides include CaF2, MgF2,
BaF2, MnF2, etc. are effective, but the use of alkali metal fluorides improves arc stability. 1
If it is less than 1% by weight, these characteristics will not be fully exhibited, while if it exceeds 1+ or 2% by weight, the arc will become unstable and the amount of slag produced will be excessive, deteriorating the bath welding workability. Therefore, the metal fluoride should be in the range of 1 to 12 wt%. In addition,
As the alkali metal fluoride, K2SiF6. NaF
, Na2SiF6, etc. are effective. When using a mixture of Ar, etc. as a shielding gas, use inexpensive CaF.
Since CaF2 alone can reduce the occurrence of sputtering, it is also possible to use only CaF2 as the metal fluoride. However, when using CO2 gas as a shielding gas, sputtering will increase if only CaF2 is used.
Combination use with alkali metal fluorides is preferred.

The metal carbonate is added to adjust the viscosity of the slag, and if it is less than 0.1 Wt1, it has no effect.1.
If it exceeds 5 wt%, the viscosity of the slag will become excessive, and C in the CO2 gas decomposed in the arc atmosphere will remain in the weld metal and deteriorate the toughness, so the appropriate range is 0.1 to 1. .5 wt%. Examples of metal carbonates include CsCO5, Li2CO3, and K2CO3.

BaCO3, MtCO5, MnCO3, SrCO3, etc. are effective.

Silicate minerals or compounds have the effect of adjusting the viscosity of the slag and acting as an arc stabilizer, 0.2 Wt 1
If it is less than 3w%, these effects cannot be obtained, and if it exceeds 3w%, the amount of slag becomes too large, deteriorating the bath welding workability, and 5i02min is deoxidized by a strong deoxidizing agent and becomes Si, resulting in m contact. Gold wind yield and reduce toughness. Therefore 0.2
The borosilicate mineral in the range of ~3 wt% may contain silicates such as silica sand, potassium feldspar, soda feldspar, and wollastonite. Compounds refer to artificially created materials such as artificial wollastonite.

SI is an effective deoxidizing agent, but if it is less than 2 wt%, deoxidation is insufficient, and if it exceeds 2 wt%, Si in the weld metal becomes excessive and deteriorates toughness. Therefore, Si is 0.2~
It is set to 2wt%. Note that Si is simple or Fe-8i
, Fe-8i-Mn, or other iron alloys may be added.

:b5Mn addition amount is 1~2.5wl and the following reason is as follows.
This is to provide suitable strength to the bath welding joint. If it is less than 1 wt%, the required strength cannot be obtained. On the other hand, 2.5wtcI
Exceeding b improves strength, but conversely deteriorates toughness. Therefore, the amount of Mn added is 1 to 2.5 wt%. In addition to being used alone, Mn can also be used in the form of an iron alloy such as Fe--Mn.

Ti is effective in improving low-temperature toughness by refining the bath-welded metal structure, but if it is less than 0.05 wt%, this effect cannot be obtained, whereas if it exceeds 0.3 wt%, it deteriorates the low-temperature toughness. Therefore, TiFio is set to 05 to 0.3wt. Note that Ti can be used alone or in the form of an iron alloy such as Fe-Tl. ′=! Alternatively, it is also possible to add Ti in the form of an oxide such as TiO2 and reduce Ti by the MW of a strong deoxidizing agent so that it remains in the adjacent metal.

MW is a strong deoxidizing agent. In particular, it is best for reducing the amount of oxygen in weld metal. If the amount added is less than 0.1 wt%, the effect will not be sufficiently obtained, while if it exceeds 1 wt%, welding workability will deteriorate, the amount of spatter will increase, and low temperature toughness will also deteriorate. Therefore, the appropriate range for Mg is 0.1
~1wt. Mg may be used alone, or Ni-M
It may also be added in the form of Mg alloys such as Mg, Ca-MW, Fe-MW, and Fe-8i-Mg. Incidentally, when kl, which is a strong deoxidizing agent like Mg, coexists with MW, it causes a yield of At in the weld metal and deteriorates the toughness.

In addition, 0.5 to 15 wt% of one type or 2s or more of metal powder other than Si, Mn, Ti, and MP, or iron powder as necessary.
May be contained. Iron powder is intended to increase the amount of welding and improve efficiency, but if it is less than 0.5 wt%, these effects cannot be obtained. Next, to ensure the strength of 60 to 80 kg, Ni
, Cr, Mo, V, B, etc. can be added to obtain the necessary strength. However, if it exceeds 15 wt%e, 2. OWφ
The following small diameter wires have poor wire drawability and are difficult to manufacture. Therefore, the content range is preferably 0.5 to 15 wt.

In the present invention, the flux filling rate is 1 to the wire weight.
If it is less than 10 inches, which is set in the range of 0 to 30 inches, a sufficient amount of slag forming agent cannot be contained, and welding workability cannot be satisfied. On the other hand, if it exceeds 30 inches, the amount of slag becomes too large, which deteriorates welding workability.

There are no restrictions on the cross-sectional shape of the wire, and in the case of a wire with a small diameter of 2ffφ or less, a relatively simple cylindrical wire may be used.
, 4 to 3.2 diameter wires generally have a structure in which the sheath material is folded inside in a complicated manner. Also,
It is also effective to plate the surface of the seamless wire with Cu or the like.

Further, although mild steel and high-strength steel are generally used as the steel types for bath welding, it is also possible to weld low-alloy steel, high-alloy steel, etc. depending on the application.

〔Example〕

Table 1 shows the structure of the prototype hole wire, and Table 2 shows the test results. &1 to 6 are comparative examples, and &7 to 16 are examples of the present invention.

Both are finished with a 1.2Wφ wire using a mild steel outer sheath.
Low temperature steel plate JIS 5LA33B 25wt 5
It was assembled in a V groove of 0' and welded in 5 layers and 7 passes at 27OA, and the composition and mechanical properties of the weld metal were investigated. Note that a mixed gas of 80% Ar and 20% CO2 was used as the shielding gas.

As is clear from the test results in Table 2, the transition temperature of the wires 1 to A5, which contained too much nitrogen in the sheath and metal powder, was low even though the amount of oxygen in the weld metal was 350 ppm or less. No improvement in toughness was observed at about -25°C. In addition, A6 has a low nitrogen content of 35 ppm, but because it does not contain Mg, a strong deoxidizing agent that is an essential component of the present invention, the oxygen content in the weld metal was high at 420 ppm, and no improvement in toughness was observed. . On the other hand, it was confirmed that flats 7 to 416 also had good low-temperature toughness because the transition temperatures were all below -50°C.

〔Effect of the invention〕

The present invention is constructed as described above, and is a flux for gas shield welding that can obtain good low-temperature toughness by suppressing gas absorption in the welding metal, and can achieve higher quality and higher toughness of the weld metal. Natsu hole to provide the wire.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the amount of nitrogen in the mild steel outer skin and the nitrogen and toughness of the bath weld metal, and Figure 2 is a diagram showing the relationship between the amount of Mg added and oxygen in the weld metal and toughness. Agent Patent attorney Masaaki Aki Sawa Mitsunobu 1 talent 1 figure?

Claims (1)

[Claims] (1) A steel shell with a nitrogen content of 30 ppm or less,
Metal fluoride: 1 to 12 wt%, Metal carbonate: 0.1 to 1.5 wt%, One or more types of silicate minerals and silicate compounds: 0.2 to 3 wt%, based on the total weight of the wire. A flux containing as essential components Si: 0.2 to 2 wt%, Mn: 1 to 2.5 wt%, Ti: 0.05 to 0.3 wt%, and Mg: 0.1 to 1 wt% based on the total weight of the wire. For gas shield welding with excellent low-temperature toughness, characterized in that the total amount of nitrogen in the metal powder contained in the flux is 25 ppm or less based on the total weight of the wire. Flux-cored wire.