JP2781470B2 - Flux-cored wire for gas shielded arc welding for refractory steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux cored wire for gas shielded arc welding for welding refractory steel used in the fields of construction, civil engineering and offshore structures, and more particularly to a high temperature at 600.degree. Excellent proof stress,
The present invention relates to a flux cored wire for gas shielded arc welding, which can obtain a weld metal having good toughness and also has weather resistance.

[0002]

2. Description of the Related Art Flux-cored wires for various structures in the fields of construction, civil engineering and offshore structures are known as arc welding flux-cored wires for mild steel and high-tensile steel (JISZ33).
13) A carbon dioxide gas arc welding flux cored wire (JIS Z3320) for weathering steel is widely used.
For example, JP-B-59-44159 and JP-A-59-6-6
No. 4,195, and JP-B-63-7879 disclose titania-based wires. In addition, Japanese Patent Publication No. 64-2
As disclosed in Japanese Patent No. 4124, Japanese Patent Application Laid-Open No. 52-125439, etc., wires mainly containing metal fluoride are disclosed.

[0003] Among various structures, particularly, a welded portion constructed by using the welding wire in a building closely adhered to daily life, such as a building, an office or a dwelling, is provided with a sufficient fireproof coating to ensure fire safety. It is obligatory to perform welding, and various building-related laws and regulations stipulate that the temperature of a welded portion does not become 350 ° C. or more at the time of a fire.

This is because the proof stress at about 350 ° C.
This is because it may be reduced to about 70% and cause collapse of the building. For this reason, in addition to spreading a slag wool, rock wool, glass wool, asbestos-based spraying material or felt on the surface of the welded part, a method of wrapping with fireproof mortar and metal Careful application of a coating, such as a method of protecting with a thin film, such as aluminum, stainless steel, or a steel thin plate, is performed to prevent thermal damage in the event of a fire. Therefore, the construction cost of the refractory coating is higher than the welding material price itself, and it is unavoidable that the construction cost is significantly increased.

[0005]

As described above, when a known wire is used for a building, the wire is inexpensive but has low high-temperature characteristics, so that it cannot be used without coating or light coating. Therefore, there is a problem that the construction cost is increased because of the necessity of the construction, the space used for the building is narrowed, and the economic efficiency is reduced.

On the other hand, molybdenum steel and chromium molybdenum steel mag welding flux-cored wire (JIS Z331)
According to the wire for heat-resistant steel shown in 8), the high-temperature characteristics are good, but the price is extremely high, and it is difficult to use it in welding work.

[0007] In recent years, the construction of buildings has been increasing in height, and the fire-resistant design has been reviewed from the viewpoint of the improvement of design technology and its reliability, and a new fire-resistant design law for buildings has been enacted in 1987. The high temperature strength of the weld and the load actually applied to the building could also determine the ability of the refractory coating without the 350 ° C. temperature limitation mentioned above. However, there is currently no wire from which a weld metal having excellent fire resistance can be obtained. Developed a wire that can provide a weld metal that has excellent high-temperature properties at 600 ° C, good impact toughness, and also weather resistance. Recently, the problem of weld fatigue has been taken up with the rise of buildings in buildings. The present inventors have conducted research to solve these problems, and as a result, have found that they can be solved by a combination of flux compositions. An object of the present invention is to provide a flux cored wire from which a weld metal capable of improving fire resistance and fatigue strength can be obtained.

[0008]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a steel sheath having a cavity of TiO ₂ : 0.5 to 0.5 wt.
2.4% (wt%: hereinafter the same), SiO _2: 0.3~3
_{%, ZrO 2: 0.5~4%,} MgO: 0.5~3%,
Iron oxide: 0.5 to 3% in terms of FeO, deoxidizer: 1.0
Mo: 0.10 to 0.50% based on the total weight of the wire in one or both of the steel sheath and the filler flux in a flux-cored wire for gas shielded arc welding filled with a flux containing 6.0%. , Nb:
0.005 to 0.025%, (0.5 Mo + 1
0Nb) is a flux-cored wire for gas shielded arc welding for refractory steel, characterized in that the content is 0.1 to 0.4%. Further, the present invention provides an additional component comprising Ti: 0.05 to
One or two types of 0.35%, B: 0.005 to 0.015% are contained in one or both of the steel shell and the filling flux, and Cu: 0.20 as an additional component if necessary.
0.60%, Cr: 0.30 to 0.75%, Ni:
It is a flux-cored wire for gas shielded arc welding for fire-resistant steel, containing one or more of 0.05 to 0.70% in one or both of a steel sheath and a filling flux.

[0009]

The refractory steel material currently being developed is designed and manufactured so that the high temperature proof stress at 600 ° C. is 70% or more of that at normal temperature. Therefore, the welded portion must have a high temperature proof stress value equal to or higher than that of this refractory steel material. For example, it is economical even from the viewpoint of the whole building, requires only a small amount of expensive metal elements, and makes it possible to reduce the thickness of the refractory coating of the welded portion. When the fire load is small, it can be used without coating. The present invention has developed a wire capable of obtaining a weld having excellent fire resistance performance that meets such conditions.

Here, the characteristic component elements according to the present invention and the added amount thereof will be described. A feature of the invention is that small amounts of M
The object of the present invention is to limit the sum of (0.5Mo + 10Nb) by adding o and Nb to 0.1 to 0.4%. Nb and Mo form fine carbonitrides, and Mo increases the high-temperature strength by solid solution strengthening.
It is difficult to obtain sufficient proof stress in a high temperature range of ° C.

The present inventors have conducted tests and researches on various prototype wires. As a result, it was found that Nb and Mo
Has been found to be extremely effective. However, if the amounts of Nb and Mo are too large, the weldability deteriorates and the toughness deteriorates. Therefore, the upper limits of the Nb and Mo contents need to be 0.025% and 0.50%, respectively. The minimum amounts obtained are 0.005% and 0.10%, respectively.

When the sum of (0.5Mo + 10Nb) is 0.1 to 0.4%, the high-temperature proof strength at 600 ° C. is equal to or higher than that of the refractory steel material within the above-mentioned range. And the impact toughness becomes better.
5Mo + 10Nb) was limited to the range of 0.1 to 0.4%. Nb and Mo may be added to one or both of the shell and the flux. Although the use of Mo to increase the high-temperature strength is known in conventional wires for heat-resistant steel, a small amount of Mo is used as a wire for construction.
There is no known flux cored wire for welding refractory steel to which Nb is added in addition to Nb.

Next, the reason why Ti and B are added in addition to the wire will be described. Ti forms a Ti oxide, refines the microstructure of the weld metal, and is effective in improving toughness.
If less than 0.05%, this effect cannot be expected and the lower limit is 0.05%
And If it exceeds 0.35%, the toughness is significantly impaired, so the upper limit is made 0.35%.

Since B is a strong deacidifying refractory forming element, its addition to the wire promotes the crystal nucleation action in the weld metal and prevents the growth of columnar crystals, thereby reducing the crystal grains. Become In addition, there is an effect of enhancing the quenchability of the weld metal. To obtain such an effect, a minimum amount of 0.005% of B is required. If the amount is less than that, there is no effect. The upper limit is set to 0.015%, since it easily occurs. Note that Ti and B may be added to one or both of the outer coat and the flux similarly to Nb and Mo.

The above is a means for improving the fire resistance performance. The present inventors have further considered using the film without a fire-resistant coating and without coating (expansion of application field), and examined whether it is possible to combine weather resistance. . As a result, carbon dioxide arc welding flux cored wire for weathering steel (JIS Z332)
In the case of the P and W type component ranges of 0), it was confirmed that the high-temperature characteristics at 600 ° C., which is the object of the present invention, were sufficiently satisfied, though the strength as welded was somewhat high. Therefore C
u: 0.20 to 0.60%, Cr: 0.30 to 0.75
%, Ni: 0.05 to 0.70%, one or more of them can be contained in one or both of the steel shell and the filling flux. Note that Cu can also be added as a plating component on the surface of the wire.

In the present invention, the content of each component is determined as follows based on the above characteristics. TiO ₂ : 0.5 to 2.4% TiO ₂ is an effective component as an arc stabilizer and has an effect of improving the bead shape by the generated slag. If it is less than 0.5%, the above effect cannot be obtained. On the other hand, 2.
When added in an amount exceeding 4%, the arc is stable, but the viscosity of the slag becomes excessive, and the conformability of the bead toe, which is one of the features of the present invention and improves the fatigue strength of the welded portion, deteriorates.
Therefore, the addition amount of TiO ₂ is set in the range of 0.5 to 2.4%. The TiO ₂ source includes rutile, titanium slag, illuminite, and the like.

SiO ₂ : 0.3 to 3% SiO ₂ adjusts the viscosity of the slag and improves the bead shape. However, if it is less than 0.3%, these effects cannot be obtained. On the other hand, if it exceeds 3%, the fluidity of the slag deteriorates and the bead shape also deteriorates. Therefore, the amount of SiO ₂ is in the range of 0.3 to 3%. The SiO ₂ source includes silica sand, feldspar, zircon sand, wollastonite, and the like.

ZrO ₂ : 0.5 to 4% ZrO ₂ has the effect of increasing the solidification point of the slag, preventing seizure of the slag, improving the removability of the slag, and imparting gloss to the bead. However, if the content is less than 0.5%, the above effect is not obtained. On the other hand, if the content exceeds 4%, the viscosity of the slag becomes excessive and the bead shape is deteriorated. Therefore, the addition amount of ZrO ₂ is set in the range of 0.5 to 4%. The ZrO ₂ source includes zircon sand, zircon and the like.

MgO: 0.5-3% MgO has the effect of smoothing the bead shape in horizontal fillet welding, particularly the shape of the bead toe, for improving fatigue strength, which is one of the features of the present invention. . At 0.5%, there is no effect of improving the beat shape, and when added over 3%, the encapsulation of the slag deteriorates, and the bead shape deteriorates. Therefore, the added amount of Mg is set in the range of 0.5 to 3%. MgO sources include magnesium clinker, olivine sand, electrofused magnesium, talc and the like.

Iron oxide: 0.5 to 3% (in terms of FeO) Iron oxide has the effect of smoothing the bead shape in horizontal fillet welding, particularly the shape of the bead toe, like MgO. If it is less than 0.5%, the above effect cannot be obtained. On the other hand, if it exceeds 3%, it reacts with Si, Mn, etc. added as a deoxidizing agent to cause insufficient deoxidation, and defects such as blowholes in the weld metal. Generate. Therefore, the added amount of iron oxide is FeO
The range is 0.5 to 3% in conversion. Examples of iron oxide include mill scale, hematite, and ferrite compounds.

Deoxidizing agent: 1.0 to 6.0% Deoxidizing agent is a component effective for reducing non-metallic inclusions in the weld metal and improving the physical properties of the weld metal by deoxidation as the name implies. Yes, typical ones are Si, Mn, Al, M
g or the like, or an iron alloy thereof. If the deoxidizing agent is less than 1.0% based on the total weight of the wire, the deoxidation becomes insufficient and the X-ray performance deteriorates, so the lower limit was made 1.0%.
On the other hand, if it exceeds 6.0%, deoxidation becomes excessive and the toughness and crack resistance of the weld metal decrease, so the upper limit was made 6.0%.

The above are essential components, but iron powder is added for the purpose of improving welding efficiency. As an arc stabilizer, a substance which is easily ionized in an arc, for example, Li, Na,
Oxides such as K, Ca, Sr, and Ba, fluorides, carbonates, and the like can be added as necessary.

In the present invention, the filling rate of the flux is preferably in the range of 8 to 25% based on the total weight of the wire. If it is less than 8%, a sufficient amount of the slag forming agent cannot be contained, and good welding workability cannot be obtained. On the other hand, if it exceeds 25%, the amount of slag becomes excessively large, deteriorating the welding workability and frequently causing troubles such as disconnection during wire production.

There is no restriction on the cross-sectional shape of the wire, 2 mm
If the diameter is smaller than φ, a relatively simple cylindrical one
In the case of a wire having a large diameter of about 2.4 to 3.2 mmφ, a wire having a structure in which a sheath material is complicatedly folded inside is generally used. In the case of a seamless wire, plating the surface with Cu or the like is also effective.

[0025]

EXAMPLES Table 1 shows typical refractory steel materials used in the test, Table 2 shows the steel sheath components used in the test, Table 3 shows the composition of flux-cored wire for welding fire-resistant steel, and Table 4 shows the welding composition. The workability and mechanical performance results are shown.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

[Table 6]

[0032]

[Table 7]

No. Nos. 1 to 15 are examples of the present invention. 16-2
3 is a comparative example. All the wires were finished to 1.2mmφ.
Welding was carried out by horizontal fillet welding using 12.7t under the following welding conditions: current 270A, voltage 30V, shielding gas CO ₂ 100
The percentage was evaluated by the shape of the toe of the beat. The procedure for examining the mechanical performance was as follows. The steel sheet shown in Table 1 was used with a thickness of 20 mm. The groove was JIS, and the welding conditions were the same as those described above for the welding workability procedure.

As is clear from the investigation results in Table 4, the wire No. of the present invention was used. All of Nos. 1 to 15 have good room temperature and high temperature strength, high impact toughness, and good welding workability. On the other hand, in the comparative example wire no. Reference numeral 16 denotes a composition of a wire component, in which the amount of TiO _{2 and the} amount of Mo are exceptional in the present invention, the welding workability is inferior, and the high temperature proof stress at 600 ° C. is low. No.
In No. 17, the amounts of FeO and Nb are too large, resulting in poor welding workability and toughness. No. No. 18 is inferior in welding workability due to insufficient MgO content.
No. No. 19 does not have high temperature proof stress because Nb which is an essential component of the present invention is not added. No. Nos. 20 and 21 have good high-temperature proof stress and toughness, but are inferior in welding workability due to excessive amounts of TiO ₂ and SiO ₂ . No. In No. 22, the Mo content is out of the range of the present invention and high temperature proof stress cannot be obtained. No. No. 23 is inferior in welding workability due to lack of slag in the flux. As described above, the wire of the present invention is insufficient in high-temperature proof stress, has low impact toughness, is inferior in welding workability, and is unsuitable as a wire for fire-resistant steel.

[0035]

According to the present invention, the high-temperature properties of the weld metal obtained by adding Mo and Nb to one or both of the steel shell and the filling flux can be improved, and in addition, Ti and B are added. By doing so, the impact toughness of the weld metal can also be improved. Ni, Cr, Cu
Can be added to the weld metal to provide weather resistance, and can be used without coating without a fire-resistant coating. The achievement of the smoothness of the shape can improve the fatigue strength of the welded portion, improve the welding workability at the time of welding, and significantly reduce the cost of fireproofing the welded portion. Therefore, the flux cored wire for gas shielded arc welding of the present invention is extremely useful in industry.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hirotoshi Ishide 5-10-1 Fuchinobe, Sagamihara-shi, Kanagawa Prefecture Nippon Steel Corporation 2nd Technical Research Institute (56) References Japanese Patent Publication No. 5-20198 (JP, B2) Japanese Patent Publication No. 5-20199 (JP, B2) Japanese Patent Publication No. 59-44159 (JP, B2) Japanese Patent Publication No. 63-16239 (JP, B2) Patent 2687006 (JP, B2) (58) Fields investigated (Int) .Cl. ⁶ , DB name) B23K 35/368

Claims (3)

(57) [Claims] Relative to the total wire weight to claim 1. A steel sheath _{lumen, TiO 2: 0.5~2.4%, SiO} 2: 0.3~3%, ZrO 2: 0.5~4% , MgO: 0.5 to 3%, iron oxide: 0.5 to 3% (in terms of FeO), deoxidizer: 1.0 to 6.0%, gas-shielded arc filled with a flux containing In the flux cored wire for welding, Mo: 0.10 to 0.50%, Nb: 0.005 to 0.025%, based on the total weight of the wire in one or both of the steel sheath and the filling flux. , (0.5Mo + 10Nb) is 0.1 to 0.4
% Flux-cored wire for gas shielded arc welding for refractory steel, characterized in that the content of the flux cored wire is 0.1%. 2. As an additional component, one or two of Ti: 0.05 to 0.35% and B: 0.005 to 0.015% are further contained in one or both of the steel shell and the filling flux. The flux-cored wire for gas-shielded arc welding for refractory steel according to claim 1, which is formed. 3. One or more of Cu: 0.20 to 0.60%, Cr: 0.30 to 0.75%, and Ni: 0.05 to 0.70% as an additional component. The flux-cored wire for gas shielded arc welding for fire-resistant steel according to claim 1 or 2, further comprising one or both of the outer shell and the filling flux.