JPS62238096A - Flux-cored wire for self-shielded arc welding - Google Patents

Abstract

PURPOSE:To obtain a defectless weld metal having a good impact value by packing a specifically composed flux at specific % into a steel sleeve contg. specific components. CONSTITUTION:The steel sleeve contg. 0.2-1.5% (wt%, hereafter the same) Si and 0.7-2.5% Mn is prepd. This flux-cored wire for self-shielded arc welding is formed by packing the flux contg., by the total weight of the wire, 5.0-20.0% metallic carbonate, 2.0-15.0% metallic fluoride, 0.14-2.0% Si (including Si in the steel wire), and 0.49-3.0% Mn (including Mn in the steel sleeve) at 10-30% by the total weight of the wire into the above-mentioned steel sleeve. The defectless weld metal which is free from defects such as slag inclusion, pits and blowholes and has the good impact value is obtd. according to the above-mentioned wire.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a flux-cored wire for self/rued arc welding which is applied to all outdoor positions in shipbuilding, bridges, marine structures, etc.

(Prior art) Flux-cored wire for self-shielded arc welding (hereinafter referred to as self-shielded wire) does not require a separate external supply of flux or shielding gas, unlike submerged arc welding or gas-shielded arc welding.
Because it is easy to weld and has excellent wind resistance, it has been adopted especially for outdoor construction.

By the way, the main components of the filling flux used in conventional self-shielding wires include CaF2 and BaF2°S r F, which have slag-forming and shielding effects.
2, fluorides of alkaline earth metals such as Mg, a strong deoxidizing element that has a shielding effect to prevent atmospheric nitrogen and oxygen from penetrating into the weld metal, and phosphorous nitrogen that deoxidizes and intrudes into the weld metal. M has the effect of fixing nitrogen and reducing the harmful effects of nitrogen.
has been used.

However, in the flux-filled self-shield wire as described above, a large amount of M is added as a deoxidizing and nitrogen fixing agent, so a large amount of M remains in the weld metal, and the crystal grains become coarse. Good low-temperature toughness cannot be obtained.

In addition, MgO'P A12, which is a reactive product of Mg'PM,
Since a large amount of 03 is trapped in the molten slag and the melting point of these oxides is considerably higher than the melting point of steel, defects such as slag entrainment and poor fusion are likely to occur. Furthermore, if the shielding by the filling flux is insufficient or if M, which has a nitrogen fixing effect, is insufficient, pores such as pinholes and blowholes are likely to occur.

(Problems to be Solved by the Present Invention) Various studies have been made to improve the above-mentioned drawbacks. For example, Japanese Patent Laid-Open No. 58-148095, Japanese Patent Laid-Open No. 59-42198, etc. are disclosed. The self-shielded wire in the above publication has a mild steel sheath filled with a flux containing metal fluoride as the main component, AQ and Mg, as well as metal composite oxides or Li 2 Co 3. The M content in the weld metal obtained by welding with self-shielded wire is high, and the toughness at -40C or lower is not necessarily sufficient.

The present invention solves the above problems and eliminates defects in weld metal.
The purpose of the present invention is to provide a self-shielded wire that also has good low-temperature toughness.

(Means for Solving the Problems) The gist of the present invention is to provide a steel sheath containing Si; 0.2 to 1.5% (weight %, same hereinafter) and Mn; 0.7 to 2.5%. Metal carbonate based on the total weight of the wire; 5.0~
20.0%, metal fluoride; 2.0-15.0%, Si(
Si in steel sheath); 0.14-2.0%, Mn
(Including Mn in the steel sheath); characterized in that 10 to 30 pieces of flux containing 0.49 to 3.0% are filled with respect to the total weight of the wire, and the above steel sheath or / and filling 7 lux, Ti, A1. .

It is characterized by containing 0.07 to 2.0% of one or more of Mg and Z.

The filling flux for conventional self-shielding wire is mainly composed of metal fluoride as a slag agent and shielding agent, and Mg for atmospheric shielding, deoxidation, and nitrogen fixation.
rA'k is contained, and as a result, the amount of M remaining in the weld metal increases, making it difficult to obtain good low temperature and toughness, and also easily causing welding defects. K At.

Contains no Mg k or At, Mg'
The present invention was achieved by studying the components of a self-shielding wire that would reduce the amount of A8 remaining in the weld metal even if it contained I.

That is, Si is essential as a deoxidizing agent and an alloying agent.

Mn (also auxiliary deoxidizing agent, Ti, Ag, Mg, Zr as alloying agent) Th is mainly contained in the steel sheath, and the filling flux is mainly metal carbonate which has an atmospheric shielding effect and a slag forming effect. Since it contains all salts and metal fluorides, the filling flux provides sufficient atmospheric shielding during welding, and thus AA, Mg
There is no need to add a large amount of /U, so the amount of /U remaining in the weld metal is small, and good low-temperature toughness can be obtained. And, Al,
Welding defects such as slag entrainment caused by the presence of a large amount of high melting point oxides of Mg AL, O, MgO in the molten slag are eliminated.

Next, the effects of each component of the present invention and the reasons for limiting the numerical values will be described.

(Function) In the present invention, metal carbonates and metal fluorides are mainly used as atmospheric 7-rubbing agents and slag agents, and the metal carbonates are used in an amount necessary to reliably shield the welding arc atmosphere from the atmosphere. Salts and metal fluorides must be included in the wire. Therefore, in the present invention, most of Si and Mn as deoxidizing agents and alloying agents are contained in the steel sheath.

If the Sl content in the steel sheath is less than 0.2 mm, bits are likely to occur in the weld metal due to insufficient deoxidation. Conversely, if the content of 81 in the steel sheath exceeds 1.5%, the steel sheath becomes hard and becomes difficult to draw, so the Si content in the steel sheath is set to 0.2 to 1.5%.

Mn in the steel sheath has a deoxidizing effect and is retained in the weld metal to improve strength, but if it is less than 0.7 mm, the strength of a soft @50 kg class steel is ensured. Can not. Conversely, if the Mn in the steel sheath exceeds 2.5%, the steel sheath becomes hard and wire drawing becomes difficult, so the Mn in the steel sheath is 0.7%.
~2.5%.

By adding metal carbonate into the wire, the metal carbonate is decomposed by the welding arc heat to generate carbon dioxide gas, and the arc atmosphere is protected from the atmosphere.

Oxygen in the atmosphere that has entered the arc atmosphere or the weld metal combines with the above-mentioned Si, Mn, etc., and the product is likely to turn into slag, but in the case of nitrogen in the atmosphere, Mn.

Even when reacted with a denitrifying agent such as Ti or Zr, the products tend to become slag and remain in large quantities in the weld metal.
In addition, unreacted free nitrogen also exists.

Nitrogen present in such weld metal is
This is extremely harmful to toughness, and in the present invention, metal carbonates are added to the wire to generate carbon dioxide gas due to arc heat and shield the arc atmosphere from the atmosphere.

When the metal carbonate content is less than 5.0%, the amount of carbon dioxide gas generated due to arc heat is small and 1. Insufficient atmospheric shielding may cause the weld metal to deteriorate in toughness or cause bits to form. On the other hand, if it exceeds 20.04 t, the viscosity of the slag becomes high, the bead shape becomes convex, the arc becomes unstable, and spatter increases and becomes thinner. Therefore, the addition range of metal carbonate is preferably 5.0 to 20.0%.

As metal carbonates, CaCO3, BaCO3, 5rC
Os.

MgCO3, Li2CO3, Na2CO3, K2CO3
, MnCO3.

FeCO3 and the like can be used alone or in appropriate combinations.

Metal fluoride is added to adjust the viscosity of molten slag, adjust the bead shape, and create a slag that allows welding in various welding positions. Some of it also turns into steam or generates decomposition gas, which has the effect of shielding the atmosphere. Fluorides that have this effect include CaF2,
BaF2, MgF2. SrF2゜LiF, N
aF, KF, A7IF, MnF2, MnFs
, etc., and can be used alone or in appropriate combinations.

Furthermore, complex salts such as Na5AεF6 and K2ZrF6 have similar effects and can be used. If the metal fluoride content is less than 2.0%, the above effects cannot be obtained, and 15
．． If it exceeds 0%, the slag will flow easily, making it difficult to weld in a vertical position and deteriorating the bead shape, so the range of addition of metal fluoride is preferably 2.0 to 15.0%. .

As mentioned above, Si and M as deoxidizers or alloys
Although n is contained in the steel sheath, in the present invention, a part of the required amount may be contained in the filled flank. Si and Mn in the filling flux are similar to Si and Mn in the steel sheath,
It acts as a deoxidizing agent or an alloying agent, and has the effect of stabilizing the arc and improving droplet migration.

The range of Si in the total amount of wire, including Si f in the steel sheath, was set to 0.14 to 2.0, but the lower limit of 0.14 means that the lower limit of Si in the filler is zero and the maximum This corresponds to the case of the filling rate, and the reason for its setting has already been described. On the other hand, the upper limit is 2
．． If it exceeds 0%, bits and blowholes may occur due to excessive deoxidation, and excessive Si may remain in the weld metal.
The weld metal may become hard and break easily, or its properties may deteriorate. Therefore, the Si in the total amount of the wire including Si in the steel sheath is preferably in the range of 0.14 to 2.0.

The range of Mn in the total amount of wire including Mni in the steel sheath is:
It was set as 0.49 to 3.0 inches, but the lower limit of 0.49 inches is
The lower limit of Mn in the filler is zero, which corresponds to the maximum filling rate, and the reason for setting it has already been described.

On the other hand, when the upper limit exceeds 3.0 cm, Mn in the weld metal
becomes excessive, the weld metal becomes hard, its toughness deteriorates, and it becomes easily cracked. Therefore, the Mn in the total amount of the wire containing Mn in the steel sheath is preferably in the range of 0.49 to 3.0%. In addition, as the Sl added to the filling flux, metal Si
Not only FeSi, Ca5LSiMn
Any form of alloy may be used.

Moreover, as Mn added to the filling flux, metal Mn
'P Alloys such as Fe-Mn and FeSiMn can be used, but in order to obtain Mn as an alloying element, Mnn oxidation alloys such as MnO, MnO2r, CaMnO3 and the like may be used for K.

In addition to the above-mentioned components, the wire of the present invention also contains K, Ti, Al,
.

Mg and Zr can also be contained as necessary.

Strong deoxidizing agents such as Ti, Al', Mg, and Zr completely supplement the deoxidizing power of Si and Mn, and by adding them, the yield of Si and Mn in the weld metal is improved, and therefore, the yield of Si and Mn in the weld metal is improved. It is also possible to reduce the addition of Si and Mn by 4te. It also has the effect of stabilizing the arc.

Furthermore, some of Ti, All, and Zr are present in appropriate amounts in the weld metal, have the effect of refining the structure of the weld metal, and improving toughness. These Ti, All, Mg, and Zr may be contained in either the steel sheath or the filling flux, and T
One or more of i, Ai, Mg, and Zr is 0.07
If it is less than 2.0%, the above effects cannot be obtained, and if it exceeds 2.0%, the arc becomes unstable, resulting in increased spatter and poor slag peeling properties. Therefore, Ti, A added to the steel sheath or/and filling flux.
JI! , Mg, and one or more of Zr is 0.07 to 2.0
% range.

Ti, Al, Mg, added to filling flux
As Zr, each single substance, Fe Ti, F
e kl.

There are alloys such as AA-Mg, FeZr, and ZrSi.

Furthermore, for the purpose of adding *T i T M + Z r as an alloying element to the weld metal, each can be added as an oxide.

The effects and numerical limitations of the steel sheath and filling flux of the present invention are as described above, but the present invention further includes improving the physical properties of the slag, such as its viscosity, solidification point, and surface tension. , S10□+ 'rio21ZrO2, MgO, AJ for the purpose of improving bead shape, welding work in all positions, slag removal property, and improving arcing.
208. Mn0I MnO21Fe2O3.

Oxides such as Bt203, Na2O, K, and o can be added as appropriate.

Furthermore, Ni, Co, or B may be added to improve low-temperature toughness. Naori has a synergistic effect with the above-mentioned Ti, and exhibits a further effect of improving toughness.

Furthermore, if Mo and/or Cr are completely added, the strength and high temperature strength can be improved, and suitable amounts of Cu and Cr can also be added to improve weather resistance.

Note that the above Ni, Co, B, Mo, Cr,
Cu and the like may be added not only to the filling flux but also to the steel sheath within a range that does not impair wire drawability. In addition, the steel sheath contains iron, c, and p in addition to the above-mentioned components.

Contains inevitable components such as S, N, and O.

The compositions of the steel sheath and the filling flux have been explained above, but in order to fully exhibit their effects, the filling rate is also important. If the filling rate is less than 10%, the amount of gas generated for shielding the atmosphere and the amount of slag will be insufficient, making it easy for bits and blowholes to occur, and the ability to form beads will deteriorate. On the other hand, if it exceeds 30%, the amount of slab becomes excessive, resulting in deterioration in bead shape, slag releasability, etc., and difficulty in wire drawability. Therefore, the filling rate is 10
A range of ~30 inches is good.

In addition, the cross-sectional shape of the wire of the present invention may be either an og seam wire that has a seam on the circumference of the steel sheath or a closed seam wire that does not have a seam on the circumference. Since the filling flux does not absorb moisture, the amount of diffusible hydrogen in the weld metal is small (
It is advantageous in terms of low-temperature cracking, and the surface of the wire can be plated with copper, which has advantages in terms of electrical conductivity and wire feedability.

(Example) A steel sheath shown in Table 1 was filled with the flux shown in Table 1 and wire-drawn to produce a flux wire with a wire diameter of 2.0 mrxφ. Welding was carried out under the following conditions, and welding workability and performance of weld metal were fully investigated. Second result
Shown in the table.

[Welding conditions]

Test steel plate...SM-50B, 25'll
llt groove shape: 60', V groove (Fig. 1) Welding posture: Vertical welding current: 200A.

Welding voltage...19V Welding heat input...30KJ,/cm In Figure 1, a; 25m1. b;71111. c;
6 units, θ; 450.

As shown in Table 2, the wires A1 to A14 of the present invention are:
Welding workability was good in all cases, and all side bending test pieces were bent without any defects, indicating that the interior of the weld metal was sound. Further, the tensile strength shows a value necessary for welding mild steel and 50 kg class steel, and the impact value at -40C is good at 5.7 kff-m or more.

Next, the comparison wire will be explained.

A15 had a small amount of Si in the steel sheath, so pits were generated due to insufficient K and deoxidation, and defects occurred in the side bending test. A16 has too high a Si content in the steel sheath, so it is boiled again.
In No. 8, the Mn content in the steel sheath was too high, so the wire broke during wire drawing and the wire could not be manufactured. Flat No. 17 had a low tensile strength of 41.4 kg (/mya2) because the Mn content in the steel sheath was too low, and defects also occurred in the side bending test piece.

A 19 (i) Due to the small amount of metal carbonates in the flux and the low filling rate, the atmospheric air is insufficiently rolled, causing bits to form, resulting in extremely poor welding workability and the ability to weld joints. A20 has a large amount of metal carbonate and has a too high filling rate, so the slag has high viscosity and the amount is too large, resulting in poor bead appearance and poor slag removability.
Because of the low amount of metal fluoride, the viscosity of the slag became extremely high, making joint welding impossible.

A22 has too much metal fluoride, so the slag flows easily and the bead appearance is poor. A23 had too much Si content in the wire, and A24 had too much Mn content in the wire, so the weld metal became hard and the impact value decreased. Boiled 5
Since the amount of a strong deoxidizing agent such as TH+ M HMg TZr in the wire was too large, the arc became unstable and the slag peeling performance in particular deteriorated.

(Effects of the Invention) As explained above, according to the self-shielded wire of the present invention, a sound weld metal with no defects such as slag entrainment, bits, blowholes, etc., and a good impact value can be obtained, and the welded part can be reliable. It contributes to sexual improvement.

[Brief explanation of drawings]

FIG. 1 shows an explanatory diagram of the groove shape of the test plate used for vertical joint welding.

Claims (1)

[Claims] 1, Si; 0.2 to 1.5% (weight %, same hereinafter) Mn
metal carbonate; 5.0 to 20.0% metal fluoride; 2.0 to 15.0% Si (steel (including Si in the sheath); 0.14-2.0%M
Flux containing n (including Mn in the steel sheath); 0.49 to 3.0%, based on the total weight of the wire, 10 to 30%
A flux-cored wire for self-shielded arc welding characterized by being filled. 2. Steel sheath containing Si: 0.2-1.5% Mn: 0.7-2.5% Metal carbonate: 5.0-20.0% Metal fluoride based on the total weight of the wire ;2.0~15.0% Si (including Si in the steel sheath);0.14~2.0%M
n (including Mn in the steel sheath); 0.49 to 3.0% Ti
, Al, Mg, and Zr (including one or more of Ti, Al, Mg, and Zr in the steel sheath); 0.07 to 2.0% based on the total weight of the wire, 10-3
A flux-cored wire for self-shielded arc welding characterized by being filled with 0%.