JPH0323097A - Submerged arc welding wire and flux for weather resistant refractor steel - Google Patents

Abstract

PURPOSE:To obtain a weld metal having a good high-temp. characteristic, toughness and weatherability by using the submerged arc welding wire and flux for weather resistant refractory steels specified in component compsn. CONSTITUTION:The component compsn. of the submerged arc welding wire for weather resistant refractory steels is composed to contain, by weight, 0.01 to 0.15% C, <=0.5% Si, 0.4 to 2.5% Mn, 0.20 to 0.55% Cu, <=0.80% Ni, 0.30 to 0.80% Cr, 0.06 to 0.80% Mo, 0.003 to 0.030% Nb, and the balance Fe and unavoidable impurities and is specified to 0.15 to 1.25% (Mo+20Nb). The component compsn. of the submerged arc welding flux for weather resistant refractory steels is composed to contain, by weight, 5 to 35% SiO2, 5 to 35% MgO, 5 to 25% CaO, 1 to 8% F, 0.1 to 2.0% Cu, <=2.0% Ni, 0.1 to 2.5% Cr, 0.1 to 1.0% Mo, 0.01 to 0.14% Nb, and is specified to 0.3 to 2.0% (Mo+10Nb). The welding of the weather resistant refractory steels is executed by using the above- mentioned wire and flux.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to steel with excellent weather resistance and fire resistance (hereinafter referred to as weather-resistant fire-resistant steel) used in various buildings in the fields of architecture and bridges, etc. More specifically, it relates to a submerged arc welding wire and flux that provides a weld metal with high weather resistance, excellent high temperature yield strength at 600°C, and good toughness. (Prior Art) Conventionally, weathering steel has been widely used in bridges since it is possible to omit painting of the surfaces of the members.

On the other hand, the surfaces of steel components in buildings, offices, residences, and other structures that are closely connected to daily life are coated with fireproof coatings to prevent the temperature from rising above 350°C in the event of a fire. This is because the proof strength decreases to 60 to 70% of that at room temperature, potentially causing the building to collapse.Because of this type of coating, weathering steel has rarely been used in the construction field.By the way, Recently, ropes with excellent high-temperature properties are being developed that can ensure a yield strength of 70% or more at room temperature at an even higher temperature of 600°C, and can be lightly coated or uncoated, reducing construction costs. Weathering and fire-resistant steel with added weather resistance is also being considered.However, it is difficult to obtain a weld metal that has excellent weather resistance and high-temperature properties that can be applied to welding weather-resistant fire-resistant steel, and is also useful in terms of cost. Submerged arc welding materials were not available in the past.For this reason, even if a building is made of weather-resistant and fire-resistant steel, if construction is carried out using submerged arc welding materials for conventional steel, the welded part will be welded using slag wool, rock, etc. Spraying based on wool, glass wool, etc., spreading felt materials,
It is necessary to carefully apply a fireproof covering such as fireproof mortar.

From the viewpoint of high-temperature properties, there are submerged arc welding materials for Cr-Mo steel, and for welding wires, for example, JP-A-53-95146 discloses examples containing a large amount of Cr, and for fluxes, For example, Japanese Patent Laid-Open No. 59-4994 discloses a flux with a specific basicity intended for use in combination with a high Cr-containing wire.

On the other hand, Japanese Patent Publication No. 48279/1983 discloses an example of a wire and flux for submerged arc welding using a highly weather resistant tempering plate to obtain a Cu-Cr-Ni weld metal. (Problems to be Solved by the Invention) There is a problem in improving high-temperature properties in the well-known welding materials for highly weather-resistant steel sheets that provide the strength of Cu-Cr-Ni weld metals. On the other hand, although welding materials for Cr-Mo steel have good high-temperature properties, there is a problem in improving weather resistance. Furthermore, the toughness of the weld metal is ensured by performing SR after welding, and the toughness as welded is very poor. Therefore, it cannot be used for architectural purposes. Furthermore, Cr −
Wires for Mo steel are very expensive because they contain a large amount of alloy fraction, and have the disadvantage that there is no cost advantage in omitting the fireproof coating. In addition, conventional Cr −
Mo steel flux has poor high-temperature properties when combined with conventional steel wire used in building structures.

The purpose of the present invention is to maintain sufficient weather resistance and further
The object of the present invention is to obtain a weld metal that has excellent high-temperature properties at 0'C and good impact toughness as welded, and to provide a submerged arc welding wire and flux for weather-resistant fire-resistant steel that have good welding workability.

(Means for Solving the Problems) Although the present invention overcomes the above-mentioned problems and achieves the objectives,
In weight percent, C: 0.0 1-0. 1. 5%, s
i: 0.5% or less, Mn: 0. 4-2. 5%
, Cu: 0.20 to 0.55%, Ni: 0.80% or less, Cr: 0. 30 to 0.80%, Mo: 0
．． 0 6 ~ 0.8 0%, Nb: 0.003 ~ 0
．． (Mo+20Nb): 0.030%, and the remainder consists of Fe and unavoidable impurities. 1 5-1
．． This is a submerged arc welding wire for weathering and fire-resistant steel, characterized in that the welding temperature is 25%.

Furthermore, the present invention provides, in weight %, StO. :5-35%, Mg
O: 5-35%, CaO: 5-25%, F: 1-8%,
Cu: 0. 1-2. 0%, Ni:2. 0% or less, cr: 0. 1-2. 5%, Mo: 0.1-1.0
%, Nb: 0.01 to 0.14%, (Mo+
10Nb): 0. 3 ~2. This is a submerged arc welding flux for weathering and fire-resistant steel, characterized in that the flux is 0%.

(Function) In order to obtain a submerged arc welding wire and flux for weathering and fire-resistant steel, the inventors first studied existing welding materials, and found that the yield strength of the weld metal at 600"C was 70% at room temperature. It was concluded that materials satisfying % or more are difficult to put into practical use.

That is, wire or flux that can provide the necessary high-temperature proof strength has large amounts of expensive alloying elements added to it, increasing the cost of welding materials, which offsets the construction cost reduction effect achieved by reducing the fireproof coating. Naturally, sufficient weather resistance cannot be obtained.

Furthermore, unlike Cr-Mo steel, which is originally used at high temperatures, when weld metal containing a large amount of alloying elements is applied to steel structures such as bridges and buildings, which are intended for use at room temperature, the weld metal has high strength. It was also found that the cracking resistance became a problem due to excessive corrosion, and the as-welded toughness was extremely poor.

Therefore, in order to obtain weather resistance in the weld metal, we contain the metal components of Cu, Ni, and Cr, which are guaranteed to have sufficient weather resistance as stipulated by JIS, and then weld metal with detailed instructions to further improve its high-temperature properties. As a result of repeated studies, the wire and flux of the present invention were obtained.

Below, the precept elements and their addition amounts in the present invention will be explained.

First, the welding wire is characterized in that it has sufficient weather resistance due to the inclusion of Cu, Ni, and Cr, and sufficient high-temperature yield strength due to the combined addition of Mo and a small amount of Nb.

Cu: 0.2 0-0.5 5%, Ni: 0.80%
Below, Cr: 0. 3 The specific value between 0 and 0.80% is
In order to obtain sufficient weather resistance of weld metal, JIS 2 3
The wire composition for weathering steel was within the range specified in 183.

Mo and Nb form fine carbonitrides, and Mo increases high-temperature yield strength through solid solution strengthening, but it is difficult to obtain sufficient yield strength at 600°C by adding Nb alone. In other words, the minimum amount of each precept to obtain a combined effect is 0.06% for Mo and 0.003% for Nb.
Must be included. On the other hand, if Mo or Nbi is too large, the room temperature strength will be too high and the toughness will deteriorate.
The upper limits of Mo and Nb contents are 0.80% and 0.80%, respectively.
It is necessary to set it to 030%.

Furthermore, even if Mo and Nb are each within the above-mentioned specific values, if the sum of these components is too small, the target high-temperature proof strength cannot be obtained. Moreover, even if the content is excessive, the toughness of the weld metal may deteriorate, so it is necessary to limit the content of Mo and Nb in the wire. In other words, it was found that Nb has an effect equivalent to about 20 times the addition amount of Mo in the wire, and when Mo + 20Nb is added in an amount of 0.15 to 1.25%.
By setting it in this range, it is possible to obtain adequate room temperature strength and good toughness while obtaining sufficient high temperature yield strength of the weld metal.

C is necessary to ensure room temperature strength and to exhibit the effect of adding Mo and Nb, and for this purpose, 0.01
% is the lower limit. Further, if it exceeds 0.15%, hot cracking susceptibility increases and toughness deteriorates, so the upper limit of C is set to 0.15%.

Regarding St, it can be added to the weld metal from the combined welding flux, and there is no particular lower limit specified for the welding wire. However, if Si exceeds 0.5%, the toughness of the weld metal decreases, so if Si exceeds 0.5%, the toughness of the weld metal will decrease. It needs to be 5% or less.

Mn is an essential element for ensuring strength and toughness, and must be contained in an amount of 0.4% or more. On the other hand, if it exceeds 2.5%, it increases hot cracking susceptibility and deteriorates toughness, so the upper limit of Mn is set at 2.5%. The ingredients of the wire of the present invention are as described above, and the remainder consists of Pa and unavoidable impurities.

Next, the flux of the present invention will be explained in detail.

Similar to the above-mentioned wire, it is important for Franks to contain specific amounts of Cu, Ni, and Cr, which improve the weather resistance of the weld metal, and to add Mo and Nb in combination.

First, the content in the flux of the above three components that provide weather resistance will be described. Cu and Cr are each 0.0% relative to the total weight of flux. By adding 1% or more, a weld metal with sufficient weather resistance can be obtained. When the dilution rate of the base metal is large, such as in single-layer or small-layer welding, the minimum necessary amount of Ni from the base metal may be added to the weld metal, so the lower value of Ni added to the flux is is not particularly stipulated.

On the other hand, these 3rIi. The upper limit of the addition amount of
The amount of Cu and Ni that causes deterioration of toughness is determined and set.
and Cr were respectively 2.0% and 2.5%.

Then get weld metal with sufficient high temperature strength? Meni,
Mo and Nb are added in combination, but in order to obtain this combined effect, MO should be added at 0. 1% or more, and Nb needs to be 0.01% or more. Furthermore, if Mo and Nb are in excess, the strength at room temperature becomes too high and the toughness deteriorates, so Mo needs to be 1.0% or less and Nb needs to be 0.14% or less. Further, even if Mo and Nb are each within the above specified values, if the sum of these parts is too small, the target high temperature proof strength cannot be obtained. Furthermore, even if the content is excessive, the toughness of the weld metal may deteriorate, so it is necessary to limit the total content of MO and Nb. In other words, what about Nb in the flux? It was found that the effect was equivalent to about 10 times the amount of Io added, and Mo + 10Nb was added in an amount of 0. 3
~2. By setting it in the range of 0%, it is possible to obtain adequate room temperature strength and good toughness while obtaining sufficient high temperature yield strength of the weld metal. To add MO or Nb to the flux, metal powder or a compound containing these elements, such as oxide or nitride, is used.

SiO■ is a necessary ingredient to adjust the viscosity of the slag and obtain a good bead appearance. St. ．． Is it 5%? If the viscosity is too low, the bead waveform will be rough and the bead width will be uneven. On the other hand, Sin. If it exceeds 35%, the amount of oxygen in the weld metal increases and the toughness decreases. SiO
2 is an ore or composite containing SiO2, such as silica sand, wollastonite, chamotte, zircon sand, and olivine sand.

Furthermore, MgO is a necessary precept to enable highly efficient welding using a large current due to its effect of increasing the slag melting point. To obtain this effect of MgO, a minimum of 5% is required; if it is less than 5%, the bead waveform becomes rough. On the other hand, Mg
When O is added in an amount exceeding 35%, irregularities in the bead toe and box marks occur. MgO is added through ores containing MgO, such as magnesia clinker and olivine sand, or through a mixer.

Further, CaO is an effective ingredient for obtaining good toughness of weld metal, and a minimum content of 5% is required. However, CaO is 2
If it exceeds 5%, the melting point of the slag becomes too high, causing box marks. CaO is added by carbonate lime, wollastonite, etc.

Finally, as an essential precept, F is necessary to reduce the amount of oxygen in the weld metal and obtain good toughness, and is effective when added in an amount of 1% or more. On the other hand, if F is added in excess of 8%, the melting point of the slag will increase, resulting in the formation of bone marks. F
The addition of CaFz. jVF3+ Mg
Metal fluorides such as Fz, BaFz, and N831VF4 are used as raw materials.

The specific precepts in the flux of the present invention have been explained above, but in addition to the above precepts, the flux of the present invention can also contain ordinary fluxes as needed. First, MnO and A1zOs are added as additives to adjust the fluidity of the slag. However, MnO is 1
If it exceeds 5%, the slag removability deteriorates, and for A7,03, if it exceeds 20%, the slag melting point becomes too high and undercuts are likely to occur. A1z03 uses ore or composite material such as alumina or chamotte.

Next, Tie. and BzOx can be added as appropriate for the purpose of improving the toughness of the weld metal. TiCh uses rutile, titanium slag, etc., and fh (h uses borax, colemanite, etc.).

Other BaCO: +. Carbonates such as Na2CO3, Fe
, Aj, ↑i, Ca, Mg, Mn, St, V
Metals such as the like can also be added as appropriate.

The flux of the present invention is produced by granulating each raw material using a suitable fixing agent such as water glass, alumina sol, silica sol, etc., and drying or firing at a high temperature.

(Example) Example: 1 First, 17 types of wires (wire diameter: 4.8 mmφ) of 17 types of m precepts W1 to W17 shown in Table 1 were produced.

Among them, W1 to W9 are wires of the present invention, and wio-w17 is a comparative example. Next, a weather-resistant and fire-resistant steel plate with chemical preservatives shown in Table 2 was prepared with a groove shape shown in Fig. 1 (t=32rnm, θ,
=70'', θ.=65', a=12nw, b=7m+a
, c=g1 3mm) and then welded for 1111 passes under the welding conditions shown in Table 3.

In addition, the Franks combined with these wires are St.
(h=40%, MnO=20%, CaO=25%,
TiO. = 4%, F = 5% welding flux (
The particle size is 20-D mesh).

After welding was completed under the above conditions, a tensile test piece and a Charpy impact test piece were taken from the position shown in FIG. 2 (1/4t on the FP side) and subjected to a mechanical test.

The 6 most important factors when evaluating the mechanical performance of weld metal
The purpose of the proof stress at 00"C was to ensure 70% or more of the minimum yield point of SM5 011i at room temperature, 33kgf/1 specified in JIS G 3106 type 2. In other words, at 600°C Regarding the yield strength of the welded metal in , it was determined that 23 kgf/1 or more was applicable.

Table 4 shows the results of these tests. As is clear from these results, the weld metal made from the wire of the present invention has good room temperature strength and high temperature yield strength, and also has a high impact value, whereas the comparative wire has insufficient high temperature yield strength and low tensile strength at room temperature. Some wires have too high impact values and others have low impact values, so they are not satisfactory as wires for weathering and fireproof steel.

In addition, although we omitted the weather resistance investigation of the weld metal, the chemical composition of the multi-layer weld metal with a groove at a plate thickness of 20 m+, which was conducted separately, was JIS Z for comparison wires other than W14, which has too little Cu and Cr. It has been confirmed that it complies with the weld metal precepts for weathering steel stipulated in 3183.

Example: 2 Next, bond franks of 16 types of groupings F1 to F16 shown in Table 5 were prepared. Of these, F1
~F6 are the fluxes of the present invention, and F7~F16 are comparative examples. These fluxes are produced by first blending and mixing the flux raw materials, then granulating them using water glass as a binding agent.
Burning commands were performed under the conditions of 400"CX2 hours, and
Sorted into mesh.

The test method was to test a weather-resistant fire-resistant steel plate with a chemical content shown in Table 2 with a groove shape shown in Fig. 1 (t = 32 mn +, θ + =
7 0”, θ2=65°, a=12mm, b=7m, c
= 13 mI1), each layer was welded in one pass under the welding conditions shown in Table 3.

The wire combined with these fluxes is W14 in Table 1, and this wire is Mn-based, which is used for conventional welding of structural steel, and does not substantially contain any elements that improve weather resistance. .

After welding was completed, the appearance of the bead was first inspected, and then a tensile test piece and a Charby impact test piece were taken from the position shown in FIG. 2 (1/4t on the FP side) and subjected to a mechanical test. In addition,
As with the wire, it was determined that a yield strength of 23 kgf/1 or more at 600°C of the weld metal could be applied to the flux.

Table 6 shows these results. As is clear from these results, all of the weld metals using the flux of the present invention have good high-temperature yield strength and room-temperature strength, have high impact values, and have no problems in bead appearance.

Comparative Franks, on the other hand, lacks high temperature resistance,
Some Franks have excessive tensile strength or low impact value at room temperature, and some Franks have poor bead appearance. In addition, regarding weather resistance, the chemical precepts of multi-layer welding metal with a groove of 20 mm plate thickness, which was conducted separately, showed that the carbon content in flux was
F7 with too little r and F12 with too little Cu were below the lower limit of the JIS standard. As described above, the comparative flux is not satisfactory as a flux for weathering and fire-resistant steel.

(Effects of the Invention) As described above, the wire and flux of the present invention can provide weld metal with good high-temperature strength characteristics, impact toughness, and weather resistance, and also have good welding workability, so that the wire and flux of the present invention have good weather resistance. When applied to welded parts of fire-resistant steel structures, it is possible to significantly reduce construction costs related to weather-proofing and fire-proofing construction.

[Brief explanation of drawings]

FIG. 1 is a front view showing the shape of the welding groove used in the example, and FIG. 2 is a sectional view showing the test piece collection position. -554- Go to Figure l- /''''' θ2- Figure 2

Claims (1)

[Claims] 1. In weight%, C: 0.01-0.15%, Si: 0.5% or less, Mn: 0.4-2.5%, Cu: 0.20-0. Contains 55% Ni: 0.80% or less, Cr: 0.30-0.80% Mo: 0.06-0.80%, Nb: 0.003-0.030%, and the balance is Fe.
and unavoidable impurities, and (Mo+20Nb): 0.15 to 1.25%. 2. In weight%, SiO_2: 5-35%, MgO: 5-35%, CaO: 5-25%, F: 1-8%, Cu: 0.1-2.0%, Ni: 2.0 % or less, Cr: 0.1-2.5%, Mo: 0.1-1.0%, Nb: 0.01-0.14%, (Mo+10Nb): 0.3-2.0 % submerged arc welding flux for weather-resistant fire-resistant steel.