JP5021953B2 - Gas shielded arc welding solid wire for weathering steel and gas shielded arc welding method using the same - Google Patents

Description

  The present invention relates to a gas shielded arc welding solid wire and a gas shielded arc welding method for weathering steel, and more particularly to a gas shielding arc for weathering steel that is used for vehicles such as trains and gas shielding arc welding of weathering steel. The present invention relates to a welded solid wire and a gas shielded arc welding method using the same.

  Conventionally, JIS G3114 has been defined as a weather resistant steel. This JIS G3114 has the property of preventing the progress of corrosion by forming a stable and dense state of rust even in an exposed state and forming a protective film. Further, the weather-resistant steel is characterized by adding appropriate amounts of Cu and Cr as well as Cu, Cr and Ni as chemical components. As a welding solid wire applied to this steel material, there is “a carbon dioxide arc welding solid wire for weathering steel” defined in JIS Z3315. These weather-resistant steels and welded solid wires for weather-resistant steels are often used for bridges, etc., which have a long design durability year and a large reduction effect on maintenance.

In recent years, in order to apply the advantages of such weather resistant steel for building construction, a wire having a weather resistant function added to fire resistant steel has also been developed (for example, Patent Documents 1 and 2). Also, aiming at high-efficiency construction of bridges, a weathering steel solid wire for carbon dioxide arc welding has been developed that can obtain high strength and high toughness even at high heat input and high-pass temperature (for example, Patent Document 3). Furthermore, for the purpose of preventing salt damage and corrosion of bridges installed near the coast, a wire containing a large amount of Ni while reducing the Cr content as much as possible has been developed (for example, Patent Documents 4 and 5).
In addition, as a steel material for a vehicle such as a train, there is JRS 51204-2 weathering steel as an old national railway standard, and as a welding material of this JRS 51204-2 weathering steel, a general JIS Z3315 standard material is used. Is used.
JP-A-4-294891 (paragraphs 0013 to 0026) Japanese Patent Laid-Open No. 5-200582 (paragraphs 0013 to 0024) JP 2000-71091 A (paragraphs 0015 to 0036) JP2003-31471A (paragraphs 0005 to 0015) JP 2000-148101 A (paragraphs 0008 to 0030)

However, the welding material wire used for the weathering steel that has been used conventionally has the following problems.
As a field in which weathering steel is often used, in addition to the bridge and construction fields, there is a bogie of vehicles such as trains. However, the welding material wires described in Patent Documents 1 to 5 are suitable for the bridge and construction fields. Since it was developed and presupposes the carbon dioxide welding method, spatter is likely to occur. Therefore, when welding a carriage of a vehicle such as a train using these wires, (1) the appearance of the welded portion is invisible to the human eye, so that spatter generation is very disliked, and (2) the C content is 0. .There are many dissimilar joints of cast iron and cast steel that are as high as 20% by mass or more, and the use of high-strength welding materials and the problem of cracking are likely to occur in carbon dioxide arc welding with deep penetration and high base metal dilution rate. 3) When a sudden component change occurs in a dissimilar material joint, corrosion progresses selectively, so that the weld metal also needs some weather resistance, and (4) the base metal is always exposed to fatigue. (5) Similarly, in order to prevent fatigue failure, post-weld stress relief annealing (SR) is performed to remove residual stress as necessary. Not considered as, How there was a problem.
Recently, a welding method using a mixed gas mainly composed of Ar has been used from the carbon dioxide arc welding method. And since railway construction is progressing especially in cold regions and high altitude regions overseas, in order to improve the collision safety of vehicles in the event of such accidents in such regions, the conventional 0 to -20 ° C is required. Due to the demand for toughness in this temperature environment, low temperature toughness in a temperature environment at a lower temperature of about −45 ° C. has been required.
However, the welding material wires described in Patent Documents 1 to 5 are based on the carbon dioxide gas welding method and do not have low-temperature toughness, so that there is a problem that these requirements cannot be satisfied. It was.
In addition, a general JIS Z3315 standard material is used as a weathering steel welding material for a carriage of a vehicle such as a train. However, in JIS Z3315, the shielding gas classification is not stipulated. Are only 0 ° C and -5 ° C. JIS Z3325 has a low-temperature steel wire, but does not have weather resistance. For this reason, there is a problem that even these wires cannot satisfy the above requirements.
Therefore, on the premise of Ar-based mixed gas, a welding wire having excellent low temperature toughness and weather resistance has not been developed.

  The present invention is a technology developed in view of these circumstances, and has high toughness even in an environment from room temperature to about -45 ° C, has excellent low spattering property, and has good weather resistance and crack resistance even in a dissimilar joint. An object of the present invention is to provide a gas shielded arc welding solid wire having properties and strength and a gas shielded arc welding method using the same.

The gas shielded arc welding solid wire for weathering steel according to claim 1 is a gas shielding arc welding solid wire for weathering steel using a mixed gas of Ar and one or more of CO ₂ or O _2. The wire is a steel alloy wire with a Cu plating layer provided on the surface thereof. C: 0.01 to 0.12% by mass, Si: 0.20 to 1.00% by mass, Mn: 1 0.00-2.00 mass%, P: 0.007-0.030 mass%, S: 0.025 mass% or less, Cu: 0.30-0.60 mass%, Cr: 0.50-0. 80% by mass, Al: 0.020% by mass or less, Ti: 0.05 to 0.17% by mass, Mo: 0.10% by mass or less, N: 0.0090% by mass or less, O: 0.0150% by mass Containing the following, the balance consisting of Fe and inevitable impurities , Cu: 0.30 to 0.60 of the mass%, the Cu plating layer content Cu: is 0.25 wt% or less, with a content of content and P of C, C × P × 10 ^The coefficient calculated by ⁴ is 22 or less.

According to such a configuration, it is possible to prevent a decrease in toughness of the weld metal at the time of SR by suppressing O and N in addition to Ti and Al as precipitation elements. Obtainable. In addition to Cu and Cr, P which is not usually added is added in a predetermined range to ensure weatherability even in the case of dissimilar joints with non-weatherproof steel, and to prevent local corrosion. Can be secured. Further, by defining the upper limit range of the correlation parameter that affects the crack resistance of the weld metal of C and P, it is possible to prevent cracking while ensuring the weather resistance of the weld metal. In addition, by containing a predetermined amount of C, Si, Mn and suppressing Mo, the strength of the weld metal can be improved, and by containing a predetermined amount of S, the compatibility with the base material is improved.
Further, by applying the Cu plating layer, the wire drawability is excellent, and rust resistance and chip wear resistance can be improved. When a Cu plating layer is applied, the welding metal can be sputtered low by defining the Cu of plating low.

The gas shielded arc welding solid wire for weathering steel according to claim 2 is the same as the gas shielding arc welding solid wire for weathering steel, further comprising Ni: 0.05 to 0.80 mass%, B: 0.0005. 0.0030 mass%, K: It contains 1 or more types among 0.5-20 ppm, It is characterized by the above-mentioned.

  According to such a configuration, by including a predetermined amount of Ni, B, and K, it is possible to further promote the improvement of the weather resistance, the low temperature toughness, and the low sputtering of the weld metal.

A gas shielded arc welding method according to claim 3 uses the above-described gas shielded arc welding solid wire for weathering steel and welds the weathering steels to each other or between weathering steel and carbon steel. In the method, Ar: 75 to 95% by volume of the remaining CO ₂ , Ar: 90 to 98% by volume of the remaining O ₂ , and Ar: 75 to 95% by volume of the remaining CO ₂ + O ₂ as the shielding gas It is characterized by using a mixed gas.

According to such a configuration, as a shielding gas, a mixed gas of Ar + CO ₂ , Ar + O ₂ or Ar + CO ₂ + O ₂ is used, and by setting these gas compositions to a predetermined range, blowhole resistance, low sputter resistance, A weld metal excellent in high toughness and bead shape improvement can be obtained.

According to the gas shielded arc welding solid wire for weathering steel according to the present invention, by defining the components of the solid wire within a predetermined range, the weathering steels that are optimal for welding of vehicle carriages or the like, or weathering steel and All of the dissimilar joints with carbon steel such as cast steel and cast iron have excellent weather resistance, low temperature toughness, strength, and crack resistance, as well as low spatter, bead shape, blow hole resistance, wire feedability, etc. Can also be an excellent weld metal.
In addition, according to the gas shielded arc welding method of the present invention, by defining the composition of the shielding gas within a predetermined range, it is possible to obtain a weld metal having excellent blowhole resistance, low spatter resistance, low temperature toughness, and bead shape. In addition, good welding can be performed in any of weather resistant steels or in dissimilar joints of weather resistant steel and carbon steel such as cast steel and cast iron.
Therefore, the wire and welding method according to the present invention can contribute to improvements in safety, durability, fatigue characteristics, aesthetics, and the like of vehicles.

Hereinafter, embodiments of the present invention will be described in detail.
The present invention is characterized in that the component of the solid wire is defined within a predetermined range, the gas shielded arc welding solid wire for weathering steel, and the wire is used, and the composition of the shielding gas is defined within a predetermined range. This is a gas shielded arc welding method.
Until now, since the welding wire for weathering steel has been developed and used only for the bridge and construction fields, it was a component design based on CO ₂ welding and assuming only a metal joint. However, the object of the present invention is to provide Ar mixed gas (Ar + CO ₂ , Ar + O ₂ , Ar + CO ₂ + O ₂₎ in consideration of high toughness at low temperature, low spattering property, dissimilar joint weather resistance, performance stability in SR treatment, and the like. It is a weather-resistant solid wire optimized for use.
The solid wire is made of a steel alloy wire and contains a predetermined amount of C, Si, Mn, P, S, Cu, Cr, Al, Ti, Mo, N, and O, with the balance being Fe. In addition, the upper limit range of the correlation parameter affecting the crack resistance of the weld metal of C and P is defined.
Further, a Cu plating layer may be provided on the surface of the wire.

In addition to the purpose of achieving low spattering, the present inventors have found that it is necessary to suppress the amount of Ti and Al as precipitation elements and to suppress O and N in order to prevent toughness reduction during SR. Furthermore, in order to ensure the weather resistance, in addition to Cu, Cr, and optionally Ni, in addition to P, which is not usually added, a predetermined range is added to ensure weather resistance performance in the case of dissimilar joints with non-weather resistant steel. It was found that local corrosion can be prevented. Further, when P is positively added, crack resistance generally decreases. However, a correlation that affects the crack resistance of C and P is found, and cracking is ensured by ensuring the upper limit range of the correlation parameter while ensuring weather resistance. It led the range that can be prevented. On the other hand, when Cu plating is performed, considering the droplet transfer characteristics in Ar + CO ₂ welding, the Cu content is regulated for each of the total wire amount and the plating amount, thereby further reducing the spatter. It has been found that a wire satisfying excellent low temperature toughness, low spattering property, weather resistance, crack resistance and the like can be obtained by these methods.
Hereinafter, the reasons for limiting the components of the solid wire will be described.

<C: 0.01 to 0.12% by mass>
C is an element necessary for ensuring the strength of the weld. In order to obtain a strength of 490 N / mm ² or more, which is the most general steel strength in the vehicle and bridge fields, the C content needs to be at least 0.01% by mass. Therefore, the C content is 0.01% by mass or more. On the other hand, when the content of C exceeds 0.12% by mass, high temperature cracking, low temperature cracking, and sputtering due to CO explosion easily occur. Therefore, the C content is 0.12% by mass or less. In addition, since it is preferable from the viewpoint of corrosion resistance, it is more preferably 0.08% by mass or less.

<Si: 0.20 to 1.00% by mass>
Si is an element necessary for the deoxidation reaction. When the Si content is less than 0.20 mass%, blow holes are generated due to insufficient deoxidation, and the strength is insufficient. Therefore, the Si content is 0.20% by mass or more, more preferably 0.40% by mass or more. On the other hand, when the content of Si exceeds 1.00% by mass, the toughness decreases, and the spatter also increases in size and increases. Therefore, the Si content is 1.00% by mass or less, and more preferably 0.60% by mass or less.

<Mn: 1.00 to 2.00% by mass>
Mn is also an element necessary for the deoxidation reaction, and is also necessary for securing the strength. When the Mn content is less than 1.00% by mass, blowholes are generated due to insufficient deoxidation, and toughness and strength are insufficient. Therefore, the Mn content is 1.00% by mass or more. On the other hand, if the Mn content exceeds 2.00% by mass, the strength of the welded portion increases so as to cause cold cracking. Therefore, the Mn content is 2.00% by mass or less, and more preferably 1.80% by mass or less from the viewpoint of low sputtering property.

<P: 0.007 to 0.030 mass%>
P is generally well-known as an element that deteriorates cracking resistance and is preferably as small as possible for general steel materials. However, P has an effect of improving weather resistance and is essential for the present invention. In the case of dissimilar joints with steel materials such as cast iron and cast steel that do not have weather resistance functions as well as between weather resistant steels, other weather resistant function components such as Cu and Cr are diluted and the weather resistance function of the weld metal Is prone to decline. Therefore, the weather resistance function can be secured by adding P to some extent. P is effective with a small amount of content, but at least 0.007% by mass is necessary, so the content of P is 0.007% by mass or more. On the other hand, if the P content exceeds 0.030% by mass, the crack resistance deteriorates. Therefore, the P content is 0.030% by mass or less.

<S: 0.025 mass% or less>
S is also an element that degrades cracking resistance and lowers toughness, but there is no problem if it is 0.025% by mass or less. Therefore, the content of S is set to 0.025% by mass or less. On the other hand, S has the effect of improving the conformability with the base material and improving the fatigue strength. Preferably, the S content is 0.005% by mass or more, while satisfying the crack resistance and the appearance. And joint fatigue performance can be improved. However, since it is preferable that S is small, no lower limit is set.

<Cu: 0.30 to 0.60 mass%>
Cu here is the total of the Cu content in the wire and the amount of adhesion of the plating when the wire is plated.
Cu is an element necessary for enhancing the weather resistance, and the content of Cu is required to be at least 0.30% by mass as the entire wire. Therefore, the Cu content is set to 0.30% by mass or more. On the other hand, if it exceeds 0.60 mass%, hot cracking is likely to occur, so the Cu content is set to 0.60 mass% or less.

<Cr: 0.50 to 0.80 mass%>
Cr is also an element necessary for improving the weather resistance. Cr is harmful to salt corrosion resistance, but when used for vehicles and general bridges, salt corrosion resistance is not required, so it is actively added to obtain performance for general weather resistant steel. To do. In order to increase the weather resistance, a minimum of 0.50% by mass is necessary. Therefore, the Cr content is 0.50% by mass or more. On the other hand, if it exceeds 0.80% by mass, the strength becomes too high and low-temperature cracking is likely to occur, and the toughness also decreases. Therefore, the Cr content is 0.80 mass% or less.

<Al: 0.020 mass% or less>
Al is an element that deteriorates low-temperature toughness during SR and increases spatter. When the Al content exceeds 0.020% by mass, the toughness is remarkably reduced, and spatter increases. Even today, deoxidation and denitrification treatment called aluminum kill is often performed to increase the cleanliness during melting, but in this case, the Al content often exceeds 0.020 mass%. Therefore, the steel making process should be carried out with careful attention so that the Al content is 0.020% by mass or less. In addition, since it is preferable that Al is less, no lower limit is set.

<Ti: 0.05 to 0.17% by mass>
Ti has a strong oxidizing property, and is combined with an oxidizing gas such as O ₂ or CO ₂ in the shielding gas, and a part thereof remains in the slag and a part thereof in the weld metal. Ti in the weld metal can be refined by an appropriate amount to obtain high toughness. However, when it becomes excessive, it becomes a coarse precipitate and becomes a starting point of brittle fracture. Particularly in SR treatment, the toughness is significantly reduced. Compared with the carbon dioxide gas, the Ar mixed gas has a lower partial pressure of the oxidizing gas, and therefore, by adding a small amount of Ti, the crystal grains of the weld metal can be refined and high toughness can be obtained. Specifically, if the Ti content exceeds 0.17% by mass, the toughness decreases, so the Ti content is 0.17% by mass or less, more preferably 0.14% by mass or less. Furthermore, if it is 0.10 mass% or less, the toughness at the time of SR will be improved, the spatter will be reduced, and the welding workability will be excellent. On the other hand, if the Ti content is less than 0.05% by mass, the effect of crystal grain refinement is lost, and it is not suitable for use at about -45 ° C. In addition, since a relatively large amount of sputters having a small particle size are generated, the Ti content is 0.05% by mass or more, more preferably 0.07% by mass or more from the viewpoint of improving the arc stability. In addition, Ti is not prescribed | regulated to JIS specification Z3315 of the solid wire for weatherproof steel. In general, for carbon dioxide gas, Ti: 0.18 to 0.25% by mass is added for high current, and no addition is often used for low current for short circuit welding. However, the present invention is optimally added in a small amount for an Ar mixed gas.

<Mo: 0.10% by mass or less>
Mo is an element generally used to improve the strength of weld metal. However, as described above, since there are many dissimilar joints with cast iron and cast steel having a high C content as described above, the weld metal tends to have excessive strength, and the excessive strength leads to the occurrence of cold cracking. Therefore, it is necessary to avoid overmatching of excessive strength with respect to the steel material. If the Mo content exceeds 0.10% by mass, cracking due to excessive strength tends to occur. Therefore, the Mo content is 0.10% by mass or less, preferably 0.05% by mass or less. In addition, since it is preferable that there is little Mo, a minimum is not set.

<N: 0.0090 mass% or less>
N is an element that reduces toughness. Even when the shield is defective, nitrogen is mixed in from the atmosphere, so management is necessary, but it is preferable to reduce it as much as possible from the wire. When the N content exceeds 0.0090% by mass, the toughness is significantly reduced. Therefore, the N content is 0.0090% by mass or less, and more preferably 0.0070% by mass or less. In addition, since it is preferable that N is small, a lower limit is not set.

<O: 0.0150 mass% or less>
Although a larger amount of oxygen on the wire surface or droplet surface is preferable for improving droplet transfer characteristics, oxygen forms an oxide when it enters the weld metal, and precipitates and embrittles during SR. Therefore, it is preferable that the number of wires as a whole is small. Therefore, the O content is 0.0150% by mass or less, preferably 0.0100% by mass or less, and more preferably 0.0050% by mass or less. In addition, since it is preferable that O is small, a lower limit is not set.

<Inevitable impurities>
As unavoidable impurities, for example, it may be possible to contain Nb, V, Zr, etc., but it is allowed to contain them within a range not impeding the effects of the present invention, and the content thereof is 0.050 mass. % Or less is preferable.

<Coefficient calculated by C × P × 10 ⁴ : 22 or less>
As described above, C is effective for strengthening the strength and P is effective for assisting the weather resistance function in the case of the dissimilar material joint. However, inclusion of these increases the sensitivity to hot cracking. However, hot cracking can be prevented by defining the coefficient calculated by C × P × 10 ⁴ to 22 or less using the C content and the P content. That is, for C and P, it is necessary to satisfy these expressions while defining the respective ranges. In addition, More preferably, it is 17 or less.

In the gas shielded arc welding solid wire for weather resistant steel according to the present invention, a Cu plating layer may be provided on the surface of the wire element.
<Cu of plating layer: 0.25 mass% or less>
By applying the Cu plating layer, the wire drawability is excellent, and production at a low cost becomes possible. Further, the rust resistance and the wear resistance of the chip can be improved.
In order to ensure hot ductility, Cu is not added to the strands, but there is a means for adding the total amount of Cu only by the amount plated on the wire, but this is not possible with the present invention. The reason for this is that, for conventional CO ₂ welding methods, the plating content does not contribute much to the stability of droplet transfer, but in the case of the Ar + CO ₂ welding of the present invention, the stability of spray droplet transfer is a wire. It is strongly affected by the amount of oxygen near the droplet surface. That is, since Cu is non-oxidizing, if the plated Cu is thick, the amount of oxygen on the wire surface is low, and the oxidation reaction near the droplet surface does not proceed. As a result, the amount of oxygen in the droplets is kept low, the surface tension and viscosity are small, and the droplet detachment property is lowered. That is, large spatters are generated and wobbling occurs, and welding workability is reduced. Accordingly, the Cu content in the plated layer is preferably low, and if it is 0.25% by mass or less, it is an allowable range for suppressing the sputtering amount. Therefore, the Cu content in the plating layer is 0.25% by mass or less, more preferably 0.20% by mass or less. The Cu content in the plating layer is 0% by mass, that is, there is no problem even if there is no plating.

  Here, the wire component preferably contains one or more of Ni, B, and K. Hereinafter, these reasons for limitation will be described.

<Ni: 0.05 to 0.80 mass%>
Ni is effective for improving the weather resistance. Since it is difficult to use unpainted specifications with Cu, Cr, and P alone, it is used for painting, but it is possible to achieve unpainted specifications by adding an appropriate amount of Ni. If the Ni content is less than 0.05% by mass, the effect is not exerted, so 0.05% by mass or more is preferable, and 0.15% by mass or more is more preferable. On the other hand, when the Ni content exceeds 0.80% by mass, not only the weather resistance effect is saturated, but also the viscosity of the droplets is increased so that the amount of spatter is easily increased and the bead becomes convex. It is easy to deteriorate. Moreover, since Ni is an expensive element, the cost tends to be excessive. Therefore, the Ni content is preferably 0.80% by mass or less.

<B: 0.0005 to 0.0030 mass%>
B has the effect of promoting the refinement of crystal grains by adding a small amount and improving the low temperature toughness. The content of B is preferably 0.0005% by mass or more, and more preferably 0.0010% by mass or more because the effect of miniaturization is not exhibited unless the content is at least 0.0005% by mass. On the other hand, B also has a defect that easily causes hot cracking. If the content of B exceeds 0.0030% by mass, cracking is likely to occur. Therefore, the content of B is preferably 0.0030% by mass or less, and considering a dissimilar joint with cast iron / cast steel having a high C content, 0.0020% by mass or less is more preferable.

<K: 0.5 to 20 ppm>
K is effective as an element that stabilizes the arc and reduces spatter during mixed gas welding with Ar as the main element. Carbon dioxide welding generally does not have this effect. Since it is difficult to add K at the time of melting, generally (1) use K-drawing lubricant such as potassium carbonate during the drawing process to leave the surface, and (2) immerse in a solution containing K. After annealing, it is added by a method such as annealing and diffusing into the grain boundaries or grains on the surface of the wire, or (3) existing in the vicinity of the surface by means of copper plating using a potassium cyanide solution. Since the effect is effective from 0.5 ppm, the content of K is preferably 0.5 ppm or more. On the other hand, if the K content exceeds 20 ppm, the arc stabilizing effect is saturated and the lubricity of the wire surface is lost, and the wire feedability is liable to deteriorate, and the plating adhesion deteriorates and the copper plating peels off. After all, it is easy to impair the wire feedability. Therefore, the content of K is preferably 20 ppm or less.

Next, the gas shield arc welding method will be described.
The gas shielded arc welding method of the present invention uses the above-described gas shielded arc welding solid wire for weathering steel, welds the weathering steels together, or weathering steel and carbon steel, , Ar + CO ₂ , Ar + O ₂ or Ar + CO ₂ + O ₂ mixed gas is used.

<Shield gas composition: Ar + CO ₂ , Ar + O ₂ , Ar + CO ₂ + O ₂ >
The shield gas is mainly composed of Ar and presupposes a composition mixed with a small amount of oxidizing gas CO ₂ or O ₂ . Balance in Ar is 75-95 volume percent in the case of the balance _{O 2, Ar + CO 2 +} O 2 if in the case of Ar + CO ₂ Ar is the balance _{CO 2,} Ar + _O 2 at 75-95% by volume Ar is 90 to 98 vol% Let CO ₂ + O ₂ .
When the shielding gas is Ar + CO ₂ , Ar + CO ₂ + O ₂ , Ar is less than 75% by volume, and when Ar + O ₂ , if Ar is less than 90% by volume, the droplet transfer cannot maintain the spray state, and spatter is generated. The toughness decreases due to excessive oxidation of the molten pool. Furthermore, the bead shape also has poor conformability and becomes an overlap shape.
When the shielding gas is Ar + CO ₂ , Ar + CO ₂ + O ₂ , Ar is 95% by volume, and when Ar + O _{2 is used} , if Ar exceeds 98% by volume, an excessive spray arc state occurs, and Ar is involved and blow holes are generated. To do. In addition, the viscosity of the molten pool becomes too high and the bead shape becomes convex, and if the oxygen source is too small, the base-side cathode spot becomes unstable, the arc generation direction fluctuates, and a lot of spatter is generated. .

<Weather-resistant steel>
The weather resistant steel to be applied is a commonly used Cu-Ni, Cu-Cr, or Cu-Cr-Ni 400-490 N / mm grade ² steel. Moreover, it is suitable also for dissimilar material welding with these weathering steels and carbon steels, such as cast steel and cast iron. Although it is suitable for a vehicle as a field of application, there is no problem for general weather resistance, so there is no problem in using it in other fields such as bridges.

Next, the solid wire according to the present invention will be specifically described by comparing an example satisfying the requirements of the present invention with a comparative example not satisfying the requirements of the present invention.
First, steel materials were welded under the welding conditions shown in Table 4 using wires having the compositions shown in Tables 1 to 3. In welding, the shielding gas of the shielding gas composition shown in Tables 1-3 was used. In addition, in a comparative example, about the thing which does not satisfy | fill the structure of this invention, it shows by underlining a numerical value.
As steel materials, 490N / mm grade ² weather resistant steel (a) and cast steel (b) shown in Table 5 are used,
2 of joints of weathering steels (a) (hereinafter referred to as (a) / (a)) and dissimilar joints of weathering steel (a) and cast steel (b) (hereinafter referred to as (a) / (b)) Various types of welding tests were conducted.
FIG. 1 is a schematic view showing a joint groove cross-sectional shape of a weld base material. As shown in FIG. 1, a steel material 1 (weather-resistant steel (a)) having an inclined end face and a plate thickness of 19 mm, and a steel material 2 (weather-resistant steel (a) or cast steel having a plate thickness of 25 mm ( The two steel materials 1 and 2 of b)) were arranged with their inclined end faces facing each other and the ends of the end faces separated by 5 mm. And the weld metal 3 was formed by carrying out gas shield arc welding with respect to the formed groove | channel.

  Next, sensory evaluation of blowhole resistance, beat shape, and wire feedability was performed on the obtained weld metal, along with the following strength, low temperature toughness, weather resistance, crack resistance, and low spatter resistance tests. It was.

<Strength>
For strength, the weld metal was subjected to SR treatment at 620 ° C. × 1 hour and subjected to a tensile test using the (a) / (a) joint and the (a) / (b) joint.
In the tensile test, the tensile strength of 490 N / mm ² or more in the (a) / (a) joint was regarded as an acceptable value.

<Low temperature toughness>
About low temperature toughness, the Charpy absorbed energy of -45 degreeC and 0 degreeC by (a) / (a) joint and (a) / (b) joint was measured by the Charpy impact test.
Charpy absorbed energy was determined to be 27 J or more at −45 ° C. for both the (a) / (a) joint and the (a) / (b) joint.

<Weather resistance>
Regarding the weather resistance, a weather resistance performance evaluation test was performed on the joint (a) / (a) and the joint (a) / (b). As the weathering performance evaluation test, a dew type corrosion test which is a corrosion acceleration test method recommended by JSSC (Japan Steel Structure Association) was used. Table 6 shows the corrosion test conditions. As for the weather resistance performance, the corrosion weight loss was 80 mg / cm ² or less in the case of the (a) / (a) joint, and the joint (a) / (b) which is a dissimilar joint was regarded as 100 mg / cm ² or less.

<Crack resistance, blow hole resistance, bead shape, wire feedability>
(A) / (a) and (a) / (b) X-ray transmission tests on joints, confirmation of presence or absence of cracks (hot cracking and cold cracking) and blowholes by ultrasonic testing, and bead shape during welding Sensory evaluation of wire feedability was performed. For cracks and blowholes, pass no defects, and for the bead shape, pass the case where grinder shaping is not necessary to prevent poor fusion, or when it is judged that the conformity with the surface of the base material is good ( (Circle)) When the grinder shaping was necessary in order to prevent the fusion failure, or the case where it was judged that the compatibility with the surface of the base material in the surplus was bad, it was determined as reject (x). The wire feedability was determined to be acceptable (◯) when no arc interruption due to poor feeding occurred and rejected (×) when arc interruption due to poor feeding occurred.

<Low spattering property>
The low spattering property was evaluated based on the amount of spatter generated by collecting spatter adhering to the shield nozzle after welding and measuring the weight during welding. The low sputtering property was accepted as the low sputtering range with an adhesion amount of 2.0 g or less.
These test results are shown in Tables 7-8.
The tensile strength of the (a) / (b) joint and the absorbed energy at 0 ° C. of the (a) / (a) joint and (a) / (b) joint are shown as reference values.
Further, the low spatter property, blowhole resistance, beat shape, and wire feedability are shown for the (a) / (a) joint.

As shown in Table 7 , N o. 1-32 are examples or reference examples in which all wire components and gas shield compositions satisfy the scope of the present invention , and (a) / (a) (weatherproof steels) joints, (a ) / (B) All the dissimilar joints (weather resistance and cast steel) have excellent Charpy absorption energy, weather resistance and crack resistance from 0 ° C to -45 ° C, and the tensile strength of the base metal The lower limit of the standard is secured. In addition, in the (a) / (a) joint, blowholes, bead shape defects and the like do not occur at all. Moreover, it is excellent in low spattering property and wire feeding property.

  On the other hand, as shown in Table 8, Comparative Example No. No. 33 was insufficient in strength because the C content was less than the lower limit. Comparative Example No. In No. 34, since the C content exceeded the upper limit, hot cracking occurred, the strength increased, cold cracking also occurred, and there were many spatters. Comparative Example No. In No. 35, since Si was less than the lower limit, not only the strength was insufficient, but blow holes were also generated due to insufficient deoxidation. Comparative Example No. In No. 36, since Si exceeded the upper limit, the absorbed energy was low, and spatter was also high. Comparative Example No. No. 37 was not only insufficient in strength because Mn was less than the lower limit, but also generated blowholes due to insufficient deoxidation, and the absorbed energy was low. Comparative Example No. In No. 38, since Mn exceeded the upper limit, the strength became too high, low-temperature cracking occurred, and spatter increased. Comparative Example No. 39 and 40 had both P less than the lower limit, so the weather resistance was lost during dissimilar joints and there was a lot of corrosion weight loss. Comparative Example No. No. 41 was hot cracked because P exceeded the upper limit.

Comparative Example No. For 42, 43, and 44, the respective ranges of C and P each satisfy the specification, but C × P × 10 ⁴ exceeds the range of the present invention, so that hot cracking occurred. Comparative Example No. In No. 45, since S exceeded the upper limit, hot cracking occurred. Moreover, although the absorption energy was barely satisfied between the weather resistant steels, the dissimilar joint was not satisfied. Comparative Example No. No. 46 constituted the copper component only by the plating component, but its value was less than the lower limit value, so that the corrosion weight loss was large and the weather resistance was insufficient. Comparative Example No. In No. 47, since Cu exceeded the upper limit, hot cracking occurred. Comparative Example No. In No. 48, since the copper plating amount exceeded the upper limit, surface oxidation during the formation of the droplets was suppressed, so that the surface tension increased and the droplet detachment property was poor, and there was a lot of sputtering. Comparative Example No. In No. 49, since Cr was less than the lower limit, the corrosion weight loss was large and the weather resistance was insufficient. Comparative Example No. No. 50 had insufficient absorbed energy because Cr exceeded the upper limit. Moreover, cold cracking occurred due to excessive strength in the dissimilar joint. Comparative Example No. In 51, since Al exceeded the upper limit, the absorbed energy was insufficient, and there was a lot of sputtering.

Comparative Example No. In No. 52, since Ti was less than the lower limit, the crystal grains were coarse and the absorbed energy was low. In addition, the arc stability was poor and there were many spatters. Comparative Example No. 53 is a JIS Z3315 YGA-50W wire as it is, and does not contain Ti. For this reason, the crystal grains are also coarse, the absorbed energy is low, the arc stability is inferior, and there is much sputtering. Comparative Example No. 54 is a wire for CO ₂ and Ti exceeds the upper limit. Therefore, the absorbed energy was reduced due to the precipitation of excess Ti oxide during the SR treatment. Comparative Example No. In No. 55, since Mo exceeded the upper limit, the strength was excessive in the case of the dissimilar joint, and cold cracking occurred. Comparative Example No. As for No. 56, since N exceeded the upper limit, blow holes were generated, and the tensile strength was also low. Moreover, it was embrittled and the absorbed energy was low. Comparative Example No. In 57, since O exceeded the upper limit, deoxidation in the molten pool was promoted, and the absorbed energy decreased. No. As for No. 58, since Ni exceeded the upper limit, spatter increased and the viscosity of the molten pool became excessive, and the bead shape became convex. Therefore, grinding shaping is necessary for each pass. No. In 59, since B exceeded the upper limit, hot cracking occurred. No. Since K exceeded the upper limit of 60, the lubricity of the wire surface was impaired, the wire feedability was poor, and the arc was unstable.

Comparative Example No. In 61, the shielding gas is Ar + CO ₂ , but since the Ar ratio is less than the lower limit, the droplet transfer cannot maintain the spray state, and the amount of spatter generated is large. Also, the absorbed energy was low due to excessive oxidation of the molten pool. In addition, the bead shape was poorly conformable and became an overlapped shape. Comparative Example No. 62 is an Ar + CO ₂ system, but since the Ar ratio exceeded the upper limit, an excessive spray arc state occurred, and Ar was entrained to generate blowholes. Moreover, the viscosity of the molten pool became too high, and the bead shape became convex. Comparative Example No. In No. 63, the shielding gas is Ar + O ₂ , but since the Ar ratio is less than the lower limit, the droplet transfer cannot maintain the spray state, and the amount of spatter generated is large. Also, the absorbed energy was low due to excessive oxidation of the molten pool. In addition, the bead shape was poorly conformable and became an overlapped shape. Comparative Example No. 64 is an Ar + O ₂ system, but since the Ar ratio exceeded the upper limit, it became an excessive spray arc state, and Ar was entrained to generate blowholes. Moreover, the viscosity of the molten pool became too high, and the bead shape became convex. Furthermore, the oxygen source was too small, the base-side cathode spot became unstable, the arc generation direction was changed, and a lot of spatter was generated.

Comparative Example No. 65 is an Ar + CO ₂ + O ₂ system, but since the Ar ratio is less than the lower limit, the droplet transfer cannot maintain the spray state, and the amount of spatter generated is large. Also, the absorbed energy was low due to excessive oxidation of the molten pool. In addition, the bead shape was poorly conformable and became an overlapped shape. Comparative Example No. No. 66 is an Ar + CO ₂ + O ₂ system, but the Ar ratio exceeded the upper limit, so that an excessive spray arc state occurred, and Ar was entrained to generate blowholes. Moreover, the viscosity of the molten pool became too high, and the bead shape became convex. Comparative Example No. 67 is an example of a combination of a kind of CO ₂ for wire and CO ₂ gas. Therefore, the spatter generation amount is very large, the conformability of the bead shape is poor and overlapped, the absorbed energy is low, cold cracking due to excessive penetration in the dissimilar material joint, the occurrence of hot cracking, the dissimilar material joint There were a number of disadvantages, such as low weather resistance.

No. 68, C, although P alone ranges satisfies the provisions, for C × P × 10 ⁴ is beyond the scope of the present invention, hot cracking occurred. No. 69 is a wire for CO _2, in which Ti exceeds the upper limit. Therefore, the absorbed energy was reduced due to the precipitation of excess Ti oxide during the SR treatment. No. In No. 70, the shielding gas is Ar + CO ₂ , but since the Ar ratio is less than the lower limit, the droplet transfer cannot maintain the spray state, and the amount of spatter generated is large. Also, the absorbed energy was low due to excessive oxidation of the molten pool. In addition, the bead shape was poorly conformable and became an overlapped shape. No. 71 is an Ar + O ₂ system, but since the Ar ratio exceeded the upper limit, it became an excessive spray arc state, and Ar was entrained to generate blowholes. Moreover, the viscosity of the molten pool became too high, and the bead shape became convex. Furthermore, the oxygen source was too small, the base-side cathode spot became unstable, the arc generation direction was changed, and a lot of spatter was generated.
The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and can be modified without departing from the scope of the present invention.

It is a schematic diagram which shows a joint groove cross-sectional shape.

Explanation of symbols

1 Weather-resistant steel 2 Cast steel or weather-resistant steel 3 Weld metal

Claims (3)

In gas shielded arc welding solid wire for weathering steel using a mixed gas of Ar and one or more of CO ₂ or O ₂ ,
The solid wire is provided with a Cu plating layer on the surface of a wire element made of steel alloy,
C: 0.01-0.12 mass%, Si: 0.20-1.00 mass%, Mn: 1.00-2.00 mass%, P: 0.007-0.030 mass%, S: 0.025 mass% or less, Cu: 0.30 to 0.60 mass%, Cr: 0.50 to 0.80 mass%, Al: 0.020 mass% or less, Ti: 0.05 to 0.17 mass% %, Mo: 0.10% by mass or less, N: 0.0090% by mass or less, O: 0.0150% by mass or less, with the balance being Fe and inevitable impurities, Cu: 0.30-0 Among the 60 mass%, the Cu plating layer content is Cu: 0.25 mass% or less, and the coefficient calculated by C × P × 10 ⁴ using the C content and the P content is 22 A gas shielded arc welding solid wire for weatherproof steel, characterized by: In the gas-shielded arc-welded solid wire for weatherproof steel, Ni: 0.05 to 0.80 mass%, B: 0.0005 to 0.0030 mass%, and K: 0.5 to 20 ppm The gas-shielded arc-welded solid wire for weatherproof steel according to claim 1, comprising the above. In the gas shielded arc welding method using the gas shielded arc welding solid wire for weathering steel according to claim 1 or claim 2 and welding the weathering steels or between the weathering steel and the carbon steel,
As a shielding gas, Ar: 75 to 95% by volume of the remaining CO ₂ , Ar: 90 to 98% by volume of the remaining O ₂ , and Ar: 75 to 95% by volume of the remaining CO ₂ + O ₂ A gas shielded arc welding method characterized by using gas.

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