JP4251844B2 - Solid wire for gas shielded arc welding - Google Patents

Description

【００５５】
【表２】

【００５６】
【表３】

【００５７】
【表４】

【００５８】
【表５】

【００５９】
【表６】

【００６０】
【表７】

【００６１】
【表８】

【００６２】
【表９】

【００６３】
この表７に示すように、実施例１乃至１８は本発明の請求項１を満足するものであるので、いずれも強度及び靭性が高く、ビード外観が良好であり、スパッタが少なく、スラグ量も少なく、スラグ剥離性、耐高温割れ性が優れているものである。但し、実施例１はＣが若干少なく、溶接金属の強度が若干低い（５２５Ｎ／ｍｍ^２）。実施例３はＳｉがやや少なく、溶接金属の強度が若干低い（５２７Ｎ／ｍｍ^２）。また、母材とのなじみがやや悪い。実施例４はＳｉがやや多く、溶接金属の靭性がやや低い（１１０Ｊ）。また、スラグ量及びスパッタ量がやや多い。実施例５はＭｎがやや少なく、溶接金属の強度及び靭性がやや低い（５３１Ｎ／ｍｍ^２及び１０６Ｊ）。実施例６はＭｎがやや多く、スラグ量及びスパッタ量がやや多い。実施例１０は表面Ｓが若干少なく、スパッタ量がやや多い。実施例１２はめっきＣｕがやや少なく、溶接金属の靭性がやや低い（１１５Ｊ）。またスパッタ量がやや多い。実施例１３は請求項２を満足する実施例の中で、Ｍｏが若干少ないので、溶接金属の強度がやや低い（５２０Ｎ／ｍｍ^２）。実施例１６はＴｉが若干多くスラグ量がやや多い。
【００６４】
これに対し、表８に示す比較例１９乃至３６は、本発明の請求項１から外れるものである。比較例１９はＣが少なく、溶接金属の強度が低い（５０３Ｎ／ｍｍ^２）。比較例２０はＣが多く、高温割れが発生した。比較例２１はＳｉが少なく、溶接金属の強度が低い（４８８Ｎ／ｍｍ^２）。また、母材とのなじみがやや悪い。比較例２２はＳｉが多く、溶接金属の靭性が低い（６３Ｊ）。また、スラグ量及びスパッタ量が多い。比較例２３はＭｎが少なく、溶接金属の強度及び靭性が低い（５１２Ｎ／ｍｍ^２及び６５Ｊ）。比較例２４はＭｎが多く、溶接金属の靭性が低い（８１Ｊ）。スラグ量及びスパッタ量が若干多い。比較例２５はＰが多く、高温割れが発生した。比較例２６は全Ｓが少なく、母材とのなじみがやや悪い。比較例２７は全Ｓが多く、高温割れが発生した。比較例２８は表面Ｓが少なく、スパッタ量が多い。比較例２９は全Ｃｕが多く、高温割れが発生した。比較例３０はめっきＣｕが少なく、溶接金属の靭性が低い（９５Ｊ）。またスパッタ量が多い。また、比較例３１はＭｏが少なく、溶接金属の強度が低い（４９２Ｎ／ｍｍ ^２ ）。比較例３２は、Ｍｏが多く低温割れが発生し、耐低温割れ性が低いものであった。比較例３３はＴｉが少なく、スパッタ量が多い。比較例３４はＴｉが多く、溶接金属の靭性が低い（８５Ｊ）。また、スラグ量が若干多い。比較例３５はＢが多く、高温割れが発生した。比較例３６はＡｓ＋Ｓｂ＋Ｓｎが多く、高温割れが発生した。
【００６５】
【発明の効果】
以上詳述したように本発明によれば、軟鋼及び４９０Ｎ／ｍｍ^２級高張力鋼を、入熱４０ｋＪ／ｃｍ、パス間温度３５０℃のような大入熱・高パス間温度での高能率溶接においても、優れた機械的性質の溶接金属が得られると共に、高温割れ感受性が低い溶接金属を得ることができる。また、上記のような大入熱溶接においてもスパッタ量、アーク安定性などの溶接作業性が良好となる。従って、本発明により高能率溶接を実施しながら、従来よりも健全な溶接金属が得られため補修工程も大幅に低減できる上に、溶接作業性が良好であるためオペレータにかかる負担も軽減できる。
【図面の簡単な説明】
【図１】ワイヤ製造工程を示すフローチャート図である。
【図２】継手形状を示す図である。
【図３】試験片採取位置を示す図である。
【図４】試験体の形状及び寸法を示す図である。
【図５】拘束板及び試験体の形状及び寸法を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid wire for gas shielded arc welding widely used for welding steel frames, bridges, shipbuilding, automobiles and the like, and in particular, mild steel or 490 N / mm.²Solid wire for gas shielded arc welding that can provide high-efficiency, high mechanical properties and welding workability, good low temperature cracking susceptibility, and good and healthy weld metal when welding high-grade steel About.
[0002]
[Prior art]
The application of the gas shielded arc welding method using carbon dioxide gas or the like as a shielding gas has rapidly spread due to its high efficiency and has become the welding method with the largest amount of use at present. Furthermore, with the widespread use of welding robots, the welding efficiency has improved dramatically, enabling an increase in welding current and continuous welding. However, when conventional welding solid wires are used, these high-efficiency weldings result in high heat input due to high current and high interpass temperature due to continuous welding, which deteriorates the strength and toughness of the weld metal. As a result, the weld metal cannot satisfy the required mechanical properties. Furthermore, as the current increases, the amount of spatter increases rapidly and the arc stability also deteriorates, so the burden on the welding operator is large.
[0003]
In view of the above problems, several welding wires and welding methods that have improved mechanical properties in consideration of high heat input and high-pass temperature welding have been proposed as described below.
[0004]
By prescribing the contents of Ti, B, N, and further C, Si, Mn, O, Mo, etc., sufficient strength, impact toughness, even when welding at high heat input and high interpass temperature, Further, a gas shielded arc welding wire capable of obtaining COD characteristics is described in Japanese Patent Laid-Open No. 11-090678 (hereinafter referred to as Patent Document 1).
[0005]
Further, the contents of C, Si, Mn, P, S, Cu, Ti, B, Al, O, and the contents of V and Nb are defined, and Mp (= C + Si + Mn / 20 + Ti / 10 + V / 4 + Nb / 2 + 5B) 0.21% or more, Cs (= Mn / 5 + 20B + P + S-2C = Ti) is 0.25% or less, and Al / O is 0.2 to 2.2. However, a gas shielded arc welding wire that does not deteriorate the strength and toughness of the weld metal is described in Japanese Patent Application Laid-Open No. 2001-287086 (hereinafter referred to as Patent Document 2).
[0006]
Further, the contents of C, Si, Mn, Ti, Cr, Mo, B, Cu, Ni, K, and S are specified, and CEQ (= C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4) is 0.40. % Or more, MEQ (= {0.2 × (Mo + Cr) +0.07} / CEQ) is 0.10 to 0.20, KEQ (= 50 × K + 0.5 × S) / (Ti + Si + Al)) is 0.02 By defining ˜0.10, welding workability under low heat input welding conditions can be satisfied at the same time while ensuring the mechanical performance of the weld metal under welding conditions of high heat input and high pass temperature. A gas shielded arc welding wire is disclosed in Japanese Patent Application Laid-Open No. 2002-79395 (hereinafter, Patent Document 3).
[0007]
Furthermore, the contents of C, Si, Mn, Ti, B, Al, Cr, Mo, Cu and P are defined, and further P_BT= [B] x 10³/ P calculated by [Ti]_BT12 ≦ P_BT≦ 40, P_BS= [B] x [S] x 10⁵P calculated by_BSFor gas shielded arc welding, the mechanical performance of the weld metal can be ensured and the crack resistance can be improved under welding conditions of high heat input and high pass temperature. A wire is disclosed in Japanese Patent Laid-Open No. 10-230387 (hereinafter referred to as Patent Document 4).
[0008]
Furthermore, several welding wires and welding methods that have reduced spatter generation and improved arc stabilization have been proposed as follows.
[0009]
A welding wire in which one of the elements such as Li, Na, K, and Ba having a low ionization voltage is adhered to the surface of the welding wire to stabilize the arc is disclosed in Japanese Patent Laid-Open No. 58-3797 (hereinafter referred to as Patent Document). 5).
[0010]
In addition, for the refinement of droplets, O having surface tension lowering effect is utilized by the action of oxygen enriched in the surface layer by grain boundary oxidation using the annealing process in the welding wire manufacturing process. A welding wire designed to stabilize and reduce spatter is disclosed in Japanese Patent Publication No. 63-21595 (hereinafter referred to as Patent Document 6).
[0011]
Furthermore, as a wire surface treatment technique, a welding wire in which the thickness index of the copper plating layer on the surface of the wire is controlled is proposed in Japanese Patent Application Laid-Open No. 7-100687 (hereinafter referred to as Patent Document 7).
[0012]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-090678
[Patent Document 2]
JP 2001-287086 A
[Patent Document 3]
JP 2002-79395 A
[Patent Document 4]
JP-A-10-230387
[Patent Document 5]
JP 58-3797 A
[Patent Document 6]
Japanese Patent Publication No. 63-21595
[Patent Document 7]
Japanese Patent Application Laid-Open No. 7-100687
[0013]
[Problems to be solved by the invention]
However, in the solid wires for welding described in Patent Documents 1 to 4, the mechanical properties of the weld metal in high-efficiency welding with a heat input of 40 kJ / cm and an interpass temperature of 350 ° C. are sufficient for a certain plate thickness and groove angle. However, it is difficult to say that it is a welding material with excellent hot cracking susceptibility under high heat input and high pass temperature while responding to the recent trend of increasing plate thickness and narrowing of the groove. The same was true for welding workability under high current conditions.
[0014]
Also, Patent Document 5 has a problem that it is difficult to apply these elements to the wire surface uniformly and stably industrially.
[0015]
Furthermore, Patent Document 6 can achieve a certain degree of effect, but under the recent trend of increasing the thickness and narrowing of the groove, the sensitivity to high temperature cracking under high heat input and high pass temperature is sufficiently increased. However, the amount of slag generated increases due to enrichment of oxygen, and there is a problem that it takes time and cost to remove the weld slag.
[0016]
Furthermore, Patent Document 7 aims at adhesion of the plating film and focuses only on the amount and thickness of the copper plating. Under the recent tendency to increase the plate thickness and the tendency to narrow the groove. The high temperature cracking sensitivity under high heat input and high pass temperature was insufficient.
[0017]
In order to obtain a weld metal having excellent mechanical properties even under large heat input and high-pass temperatures, as specified in the invention described in Patent Document 7, an alloy having a certain level or more is included in the weld wire. Although an element will be contained, the hot cracking susceptibility increases due to this. Further, in high heat input welding, welding workability such as spatter amount and arc stability is remarkably deteriorated due to an increase in arc force due to a high current and an increase in droplet size.
[0018]
The present invention has been made in view of such a problem, and has excellent mechanical properties even in high-efficiency welding at a high heat input / high pass temperature with a conventional heat input of 40 kJ / cm and a pass-to-pass temperature of 350 ° C. In addition to obtaining weld metal, high-heat input and high-pass temperature welding on thick and narrow gap steel sheets are also less susceptible to hot cracking, and have superior weld metal mechanical properties, and even better workability. An object of the present invention is to provide a solid wire for gas shielded arc welding having both of the following.
[0019]
[Means for Solving the Problems]
  The solid wire for gas shielded arc welding according to the present invention is a solid wire for gas shielded arc welding in which a Cu plating layer is formed on the peripheral surface of a steel core wire. C: 0.01 to 0.07 mass%, Si: 0 .50 to 1.00% by mass, Mn: 1.75 to 2.30% by mass,Mo: 0.05 to 0.45 mass%,Ti: 0.13 to 0.28 mass%, P: 0.020 mass% or less, Cu including Cu plating layer and Cu in core wire: 0.33 mass% or less, Cu of plating layer: 0.10 More than mass%, all S including S adhering to the core wire surface: 0.003 to 0.020 mass%, S adhering to the core wire surface and embedded in the core wire surface layer within 50 μm from the core wire surface Total S: 0.03 (g / per 10 kg of wire) or more, B: 0.0009 mass% or less, As + Sb + Sn: 0.01 mass% or less, balance: Fe and inevitable impurities.
[0020]
In the solid wire for gas shielded arc welding, Mo: 0.05 to 0.45 mass% can be further included.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail. The inventors of the present application have conducted extensive experimental research to solve the above problems, and as a result, have encountered problems in conventional high heat input and high pass temperature welding (hot cracking susceptibility, spatter amount, arc stability). ) Was found to be caused by the following phenomenon.
[0022]
<Hot-cracking phenomenon and problems that occur to prevent it>
B in the wire added to obtain good mechanical properties at high heat input and high interpass temperature greatly expands the solid-liquid coexistence temperature range of the Fe-C alloy phase diagram even when added in a small amount. C and S contained in the wire also have the same effect, and when these low melting point liquid phases segregate at the grain boundaries in the final stage of solidification, the risk of hot cracking increases. Further, when there are many γ phases as primary crystals during solidification, low melting point compounds such as S, As, Sb, and Sn are concentrated at the grain boundaries and segregated in the final stage of solidification. Therefore, the more γ-phase stabilizing elements in the wire, the higher the risk of hot cracking, and C and Cu have a greater effect among them. However, with respect to B, C, S, and Cu, the following problems occur when the amount of addition is suppressed in order to prevent hot cracking.
[0023]
Suppression of B: The toughness of the weld metal is lowered under conditions of large heat input and high pass temperature.
[0024]
Suppression of C: The strength of the weld metal decreases under large heat input and high pass temperature conditions.
[0025]
S suppression: In high-current welding, the surface tension of the droplets increases, and the smooth droplets are prevented from detaching, so that the amount of spatter increases and the familiarity between the weld bead and the weld base material deteriorates.
[0026]
Suppression of Cu (Cu plating): Energization with the contact tip becomes unstable in high-current welding, which induces fusion between the contact tip and the wire, arc instability, and an increase in spatter generation. Further, the surface of the droplet at the tip of the wire absorbs oxygen, and the amount of oxygen in the weld metal increases, so that the toughness decreases.
[0027]
<Spatter generation and arc instability>
Regarding the cause of spattering, the following phenomenon is generally recognized. In arc welding, when the droplet formed at the tip of the welding wire is short-circuited to the molten pool, the short-circuit is released due to an increase in current that accompanies it, and an arc is generated again. When the arc is regenerated by opening the short circuit, a part of the droplet or the molten pool scatters to the surroundings, which becomes spatter. Due to the pushing up action of the regenerated arc, the droplet remaining on the tip of the welding wire is strongly pushed upward, and the droplet that has become relatively large is short-circuited to the molten pool, and occasionally the droplet moves to the molten pool. Arc may occur again. As a result, the short circuit is opened in a state where the droplet remains as a large mass at the tip of the welding wire, and large grains or a large amount of spatter is generated by the arc force. Further, when the droplet becomes large at the tip of the wire, the droplet shakes violently due to the repulsive force of the arc, and the arc becomes unstable. Therefore, it is necessary to make the droplets finer in order to prevent spattering and arc instability.
[0028]
While considering these findings, the present inventors have suppressed the addition of elements that increase the hot cracking susceptibility, while adjusting the amount of addition of other elements, the conventional heat input of 40 kJ / cm, interpass temperature. A solid wire having excellent mechanical properties and excellent welding workability even at a high heat input of 350 ° C. and high-pass temperature welding was completed by the method described below.
[0029]
That is, when the amount of B in the wire was dissolved, it was regulated to be equal to or less than the amount necessarily contained (≦ 0.0009 mass%), thereby suppressing the lowering of the melting point due to B and reducing the hot cracking susceptibility. However, by specifying Si: 0.50 to 1.00% by mass and Mn: 1.75 to 2.30, the reduction in toughness under large heat input and high-pass temperature conditions is compensated.
[0030]
By regulating the total amount of Cu in the wire to 0.33% by mass or less, γ phase stabilization and grain boundary segregation by Cu were prevented, and the hot cracking susceptibility of the weld metal was reduced. Furthermore, by limiting the amount of Cu plated on the surface of the wire to 0.10% by mass or more, wire fusion, arc instability, and increase in spatter at the contact tip during high current welding are suppressed, and the tip of the wire is not fixed. Since the surface of the droplet connected to the molten portion is covered with Cu, the oxygen absorption of the droplet is suppressed and the amount of oxygen in the weld metal is reduced, so that the toughness can be improved even at high heat input and high interpass temperature.
[0031]
By defining the total amount of S in the wire to 0.020% by mass or less, the generation of low melting point compounds by S was suppressed, and the hot cracking susceptibility was reduced. In addition, the surface tension of the droplets is lowered by making the sum of the amount of S adhered to the wire surface and the amount of S embedded in the surface layer within 50 μm from the surface 0.03 (g / wire 10 kg) or more. As a result, the droplets were refined and the amount of spatter was reduced.
[0032]
Next, the reasons for limiting the numerical values of the composition defined in the present invention will be described in detail.
[0033]
C: 0.01 to 0.07% by mass
C is an element useful for ensuring the strength of the weld metal and also has an effect as a deoxidizing element. On the other hand, as described above, C is a γ-stabilizing element, and if added excessively, the solid-liquid coexistence temperature range is expanded, so that the hot cracking susceptibility is deteriorated. If the content is less than 0.01% by mass, the strength of the weld metal is insufficient, and if it exceeds 0.07%, hot cracking is likely to occur, so 0.01 to 0.07% by mass is specified.
[0034]
Si: 0.50 to 1.00% by mass
Si is a deoxidizing element, CO₂It is an essential element for welding and MAG welding wires. When the content of Si is less than 0.50%, the deoxidation effect is insufficient and blowholes are easily generated, and the compatibility with the weld base metal is deteriorated, and the strength of the weld metal is also insufficient. Moreover, when it exceeds 1.00 mass%, content in a weld metal will become excessive, toughness will fall, and the amount of slag and the amount of spatters will also increase. Therefore, it is defined as 0.50 to 1.00% by mass.
[0035]
Mn: 1.75 to 2.30% by mass
Mn is not only an indispensable element as a deoxidizing element together with Si, but also an element that improves the mechanical properties of the weld metal. If the Mn content is less than 1.75% by mass, the content in the weld metal is insufficient, so that sufficient strength and toughness cannot be obtained. However, if the content exceeds 2.30% by mass, the content in the weld metal becomes excessive and the toughness deteriorates, and the slag amount and spatter generation amount also increase. Therefore, it is specified to be 1.75 to 2.30% by mass.
[0036]
Ti: 0.13 to 0.28 mass%
Ti has the effect of stabilizing the arc and reducing spatter in a gas shielded arc welding wire with a relatively high heat input, preventing the occurrence of blowholes, and at the same time improving the mechanical properties. However, if the content is less than 0.13% by mass, those effects are poor. On the other hand, if it exceeds 0.28% by mass, the amount of slag increases and the toughness also deteriorates. Therefore, it is specified to be 0.13 to 0.28 mass%.
[0037]
P: 0.020% by mass or less
P is an element having extremely great adverse effects on welding, and remarkably deteriorates hot cracking susceptibility and low temperature toughness. Therefore, since it is necessary to suppress the P content in the wire as much as possible, it is set to 0.020% by mass or less in the present invention.
[0038]
The total Cu amount of the wire including the Cu plating part and Cu in the original wire is 0.33% by mass or less, and the plating Cu amount is 0.10% by mass or more.
When the total amount of Cu including Cu in the Cu plating portion and the original wire exceeds 0.33 mass%, the amount of Cu in the weld metal becomes excessive, and high temperature cracks are very likely to occur. Moreover, if the amount of plating Cu which covers the wire surface is less than 0.10% by mass, current conduction becomes unstable and oxygen is absorbed from the surface of the droplets, and the toughness of the weld metal decreases. On the other hand, if the amount of Cu plated is 0.10% by mass or more, the energization is stabilized and Cu covers the droplet surface leading to the unmelted portion at the tip of the wire, so that oxygen absorption of the droplet is suppressed and welding is performed. Since the amount of oxygen in the metal decreases, it exhibits good toughness even at high heat input and high pass temperatures. Therefore, the total Cu amount is regulated to 0.33% by mass or less, and the plating Cu amount is regulated to 0.10% by mass or more.
[0039]
The total amount of S in the wire is 0.003 to 0.020% by mass, and the sum of the amount of S attached to the wire surface and the amount of S embedded in the surface layer within 50 μm from the surface: 0.03 g / 10 kg or more
As described above, S is an element that increases the hot cracking susceptibility. Also in the welding wire of the present invention, when the total amount of S in the wire exceeds 0.020% by mass, hot cracking is very likely to occur. On the other hand, if the total amount of S in the wire is less than 0.003% by mass, the surface tension of the molten pool becomes excessive, and the bead shape becomes convex, so that the familiarity with the welded base material becomes worse. Therefore, the total S amount of the wire is set to 0.003 to 0.020 mass%. In addition, by making the total amount of S adhering to the wire surface and S amount embedded in the surface layer within 50 μm from the surface 0.03 g / 10 kg or more, the surface tension of the droplet is lowered and the droplet is refined. Therefore, the generation of spatter can be suppressed.
[0040]
B is 0.0009 mass% or less
B promotes refinement of crystal grains and improves toughness. Therefore, a certain amount or more of B is contained in the welding wire used under the conventional high heat input and high interpass temperature. However, as described above, B also has a drawback of greatly increasing the hot cracking susceptibility, and its detriment is particularly great under large heat input and high pass temperature welding. Therefore, the amount of B in the wire is specified to be 0.0009 mass% or less, which is an amount that is inevitably contained at the time of melting.
[0041]
As + Sb + Sn is 0.01% by mass or less
In the final stage of solidification, if low melting point compounds such as As, Sb and Sn are concentrated and segregated at the grain boundaries, the hot cracking susceptibility is significantly deteriorated. Therefore, these impurity elements are specified so that the sum total is 0.01 mass% or less.
[0042]
Mo: 0.05 to 0.45 mass%
Mo is an element that improves hardenability by adding a small amount to a weld metal, prevents coarsening of crystal grains under high heat input and high interpass temperature, and improves strength and toughness. If the amount of Mo in the wire is less than 0.05% by mass, this effect cannot be obtained. Moreover, when it exceeds 0.45 mass%, hardenability will become high too much and a weld metal will harden | cure at the time of low heat input welding, and it will become easy to generate | occur | produce a low temperature crack. Therefore, it is specified to be 0.05 to 0.45 mass%.
[0043]
Hereinafter, the manufacturing method of the solid wire of this invention is demonstrated. Usually, a steel wire is processed into a diameter of about 5 mm through steps of melting, hot rolling, and wire drawing, and used as a raw wire for each step of wire manufacture. As shown in the flowchart on the left side of FIG. 1, the original wire whose total component composition has been adjusted in the molten steel stage undergoes an annealing process, a Cu plating process, an intermediate wire drawing process, a finish wire drawing process, etc., as shown in the flowchart on the left side of FIG. Finished product. Or as shown to the flowchart on the right side of FIG. 1, it is set as a product through an intermediate | middle wire drawing process, an annealing process, Cu plating process, and a finish wire drawing process. Below, each process of a pre-processing process, an annealing process, Cu plating process, and a wire drawing process is demonstrated.
[0044]
(1) Pretreatment process
In the present specification, a process for removing scale such as pickling or mechanical polishing is referred to as a pretreatment process. In this process, the pickled pits or cracks on the surface of the wire formed by removing the biting portion of the scale or the wedge-shaped cracks are used to apply the sulfides applied during intermediate drawing or finish drawing to these pits or cracks. By embedding in the surface, S on the surface and the surface layer portion can be concentrated.
[0045]
(2) Annealing process
In the annealing process, a crack-like grain boundary oxide layer is formed in the wire surface layer portion, and the sulfide applied at the time of intermediate wire drawing or finish wire drawing is embedded in the crack of the grain boundary oxide layer, so that S on the surface and the surface layer portion is Can be thickened. However, if annealing is performed in an atmosphere having a strong oxidizing power, thick and deep grain boundary oxidation is generated, and the grain boundary oxidation of the surface layer is scale-lossed. Therefore, the generation state of the grain boundary oxidation becomes irregular. In the wire of the present invention, in order to generate thin and uniform grain boundary oxidation having a depth of 50 μm or less in the annealing process, the atmosphere gas is 0.5% CO or less, 0.3% CO₂0.4% O₂The remaining N₂It is necessary to set the annealing temperature to 700 to 800 ° C. and the annealing time to 30 to 120 minutes.
[0046]
(3) Cu plating process
Welding wire plating methods include a method using a 5 mm diameter original wire, a method using an intermediate diameter of about 2 mm, and a method using a final product diameter. There are various methods such as electroplating and chemical plating. is there. For example, when the wire of the present invention is implemented by copper cyan plating at an intermediate diameter as shown in the flowchart on the right side of FIG. 1, the plating bath temperature is 60 to 80 ° C., the CuCN concentration is 90 to 160 g / liter, and the NaCN concentration is 3-9 g / liter, Na₂CO₃The concentration is 40 to 170 g / liter.
[0047]
(4) Wire drawing process
By applying sulfide and / or embedding it in the grain boundary oxide layer at the time of intermediate wire drawing or finish wire drawing, S on the surface and surface layer portions is concentrated. Sulfide is MoS₂, WS₂A solid powder composed of FeS or the like is dispersed in a composite lubricating oil using one kind of base oil among vegetable oil, animal oil, mineral oil, and synthetic oil. The method of applying this to the surface of the wire is a method of applying with a skin pass as a wire drawing lubricant, or a method of applying it by impregnating it with a felt or the like and applying it to the surface of the wire, and further atomizing the composite lubricant, into the mist There is a method of passing a wire and applying it to the surface of the wire. In addition, as a method of firmly embedding these applied substances in the wire surface layer portion, by using a hole die or a roller die in the intermediate wire drawing step and the finish wire drawing step, it is thin and uniform in the pretreatment step or the annealing step. There is a method of uniformly embedding these composite lubricants in the crack or grain boundary oxide layer of the wire surface layer generated in the above.
[0048]
In addition, the S amount of the surface layer portion within 50 μm from the wire surface and the surface is obtained as follows. The entire wire is ultrasonically cleaned in an organic solvent such as ethanol, acetone or petroleum ether. After the washing liquid is filtered through a filter paper, the filter paper is dried. After the filter paper is dried, the filter paper and surface deposits (MoS) are mixed with a mixed aqueous solution (an aqueous solution in which sulfuric acid (concentrated sulfuric acid: water is 1: 1), concentrated chloric acid, and concentrated nitric acid).₂, WS₂, FeS, etc.) and dissolve. Then, Mo, W, Fe, etc. are quantified by atomic absorption method. This measured amount is defined as (a).
[0049]
MoS embedded in the surface layer within 50 μm from the surface by immersing the wire after washing with an organic solvent in a hydrochloric acid solution and dissolving it.₂, WS₂, FeS and the like can be liberated. And after filtering this solution with a filter paper, Mo, W, Fe, etc. are quantified in the process similar to said method. Let this measurement amount be (b).
[0050]
Then, the total amount (c) of Mo, W, Fe, etc. in the surface layer portion within 50 μm from the wire surface and the surface can be calculated by the following formula 1.
[0051]
[Expression 1]
(C) = (a) + (b)
[0052]
Then, (c) is converted into an S amount, and the amount per 10 kg of wire is calculated.
[0053]
【Example】
Next, examples of the present invention will be specifically described in comparison with comparative examples. Using the wire of the chemical composition shown in Table 1 (Example) and Table 2 (Comparative Example) below, the opening of the mold shown in FIG. A pointed joint was welded and tested for the mechanical properties (strength, toughness) of the weld metal. In addition, as shown in FIG. 3, the collection | collection position of each test piece cuts out the column-shaped area | region centering on the position below 7 mm from the surface of a welding side from the weld metal part. Moreover, the unit of the numerical value of Table 1 and Table 2 is the mass% except the amount of S of a surface and a surface layer. The amount of S on the surface and the surface layer is the number of grams per 10 kg of wire. Then, bead-on-plate welding was performed in a sputter collection box under the welding conditions shown in Table 4, and spatter was sampled and evaluated. Furthermore, welding was performed under the welding conditions shown in Table 3 and the groove shape shown in FIG. 2, and slag was collected. At that time, the amount of slag peeling after leaving the test specimen for 1 hour was separately collected, and the slag peeling property was also evaluated. About the hot crack, the presence or absence of the hot crack was confirmed using the C-type jig restraint butt crack (Fisco) crack test (JIS Z 3155), the welding conditions shown in Table 5, and the thick plate restraint test specimen shown in FIG. About the low temperature crack, the window frame restraint cracking test was implemented using the U-type welding crack test (JIS Z3157), the welding conditions shown in Table 6, and the test body shown in FIG. 5, and the presence or absence of the crack was confirmed. The test results are shown in Tables 7 and 8 below. Table 9 shows the determination criteria.
[0054]
[Table 1]

[0055]
[Table 2]

[0056]
[Table 3]

[0057]
[Table 4]

[0058]
[Table 5]

[0059]
[Table 6]

[0060]
[Table 7]

[0061]
[Table 8]

[0062]
[Table 9]

[0063]
  As shown in Table 7, Examples 1 to 18 are claims of the present invention.1Satisfyingis thereTherefore, all have high strength and toughness, good bead appearance, little spatter, little slag, excellent slag peelability and hot crack resistance.The HoweverIn Example 1, C is slightly less and the strength of the weld metal is slightly lower (525 N / mm).²). In Example 3, there is a little Si, and the strength of the weld metal is slightly low (527 N / mm).²). Also, familiarity with the base material is a little bad. In Example 4, the amount of Si is slightly higher and the toughness of the weld metal is slightly lower (110J). Moreover, the amount of slag and the amount of spatter are slightly large. In Example 5, Mn is slightly less, and the strength and toughness of the weld metal are slightly low (531 N / mm).²And 106J). In Example 6, the amount of Mn is slightly higher, and the amount of slag and the amount of sputtering are slightly higher. In Example 10, the surface S is slightly small and the amount of sputtering is slightly large. In Example 12, the plating Cu is slightly less, and the toughness of the weld metal is slightly lower (115J). In addition, the amount of spatter is slightly large. In Example 13, which satisfies Claim 2, Mo is slightly less, so the strength of the weld metal is slightly low (520 N / mm).²). In Example 16, Ti is slightly larger and the amount of slag is slightly larger.
[0064]
  In contrast,Comparative Examples 19 to 36 shown in Table 8 depart from Claim 1 of the present invention.Comparative Example 19 has little C and the strength of the weld metal is low (503 N / mm²). In Comparative Example 20, there was much C, and hot cracking occurred. Comparative Example 21 has little Si and the weld metal has low strength (488 N / mm).²). Also, familiarity with the base material is a little bad. Comparative Example 22 contains a large amount of Si and has low weld metal toughness (63J). In addition, the amount of slag and the amount of spatter are large. In Comparative Example 23, Mn is small and the strength and toughness of the weld metal are low (512 N / mm).²And 65J). The comparative example 24 has much Mn and the toughness of a weld metal is low (81J). Slag and spatter are slightly higher. In Comparative Example 25, P was large and hot cracking occurred. In Comparative Example 26, the total S is small, and the familiarity with the base material is slightly poor. In Comparative Example 27, the total S was large, and hot cracking occurred. Comparative Example 28 has a small surface S and a large amount of sputtering. In Comparative Example 29, the total amount of Cu was large, and hot cracking occurred. The comparative example 30 has few plating Cu, and the toughness of a weld metal is low (95J). In addition, the amount of sputtering is large.In Comparative Example 31, the amount of Mo is small and the strength of the weld metal is low (492 N / mm). ² ). In Comparative Example 32, there was much Mo and cold cracking occurred, and the cold cracking resistance was low.Comparative Example 33 has a small amount of Ti and a large amount of sputtering. The comparative example 34 has much Ti and the toughness of a weld metal is low (85J). In addition, the amount of slag is slightly large. In Comparative Example 35, there was much B, and hot cracking occurred. In Comparative Example 36, there were many As + Sb + Sn, and hot cracking occurred.
[0065]
【The invention's effect】
As detailed above, according to the present invention, mild steel and 490 N / mm²Even in high-efficiency welding with high heat input and high pass temperature such as high heat input such as high heat input such as high heat input such as high heat input 40kJ / cm and interpass temperature 350 ° C, A weld metal with low cracking sensitivity can be obtained. In addition, in the high heat input welding as described above, welding workability such as the amount of spatter and arc stability is improved. Therefore, while performing high-efficiency welding according to the present invention, a weld metal that is sounder than before can be obtained, so that the repair process can be greatly reduced, and the burden on the operator can be reduced because the welding workability is good.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a wire manufacturing process.
FIG. 2 is a view showing a joint shape.
FIG. 3 is a diagram showing a specimen collection position.
FIG. 4 is a diagram showing the shape and dimensions of a test specimen.
FIG. 5 is a diagram showing shapes and dimensions of a restraint plate and a test body.

Claims (1)

In a solid wire for gas shielded arc welding in which a Cu plating layer is formed on the peripheral surface of a steel core wire, C: 0.01 to 0.07 mass%, Si: 0.50 to 1.00 mass%, Mn: 1. 75 to 2.30 mass%, Mo: 0.05 to 0.45 mass%, Ti: 0.13 to 0.28 mass%, P: 0.020 mass% or less, Cu plating layer and Cu in the core wire Total Cu included: 0.33 mass% or less, Cu of plating layer: 0.10 mass% or more, Total S including S adhering to the core wire surface: 0.003 to 0.020 mass%, core wire surface The total of S adhering to the core wire and S embedded in the core wire surface layer within 50 μm from the surface of the core wire: 0.03 (g / per 10 kg of wire) or more, B: 0.0009 mass% or less, As + Sb + Sn: 0.00. 01% by mass or less, balance: Fe and non A solid wire for gas shielded arc welding characterized by being an inevitable impurity.

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