WO2014109402A1 - 耐水素脆化感受性に優れた溶接金属及びサブマージアーク溶接用ソリッドワイヤ - Google Patents
耐水素脆化感受性に優れた溶接金属及びサブマージアーク溶接用ソリッドワイヤ Download PDFInfo
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- B23K9/00—Arc welding or cutting
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Definitions
- the present invention relates to a weld metal that is used in a welded structure and can reduce sensitivity to hydrogen embrittlement. Specifically, in evaluating the hydrogen embrittlement susceptibility using the SSRT (Slow Strain RateRTechnique) method, hydrogen resistance is maintained even when testing is performed using a large specimen that tends to contain more systematic weakened parts.
- the present invention relates to a weld metal that can be excellent in embrittlement sensitivity.
- the present invention also relates to a solid wire for submerged arc welding suitable for forming the above weld metal.
- Patent Document 1 discloses a technique for preventing low-temperature cracking by dispersing Mo carbide (carbide containing Mo) having a high hydrogen trap capability in a weld metal.
- Mo carbide carbide containing Mo
- a special welding technique is used to control the maximum heating temperature of the weld metal obtained on the inner surface side. It must be adopted and cannot be applied to general welding of steel materials.
- Patent Document 2 proposes a technique for preventing cold cracking by managing the cooling time during welding. This technology requires strict construction management according to chemical components, and has a problem that the work load is high.
- Patent Document 3 proposes a technique for preventing cold cracking by setting the retained austenite fraction for trapping diffusible hydrogen to 1% or more in the weld metal.
- this technique is premised on double-sided one-pass seam welding in steel pipes, and cannot be applied to general welding of steel materials.
- Patent Document 4 proposes a technology for improving cold cracking resistance by reducing the amount of diffusible hydrogen and appropriately controlling the strength and chemical composition. However, even in this technique, since a satisfactory strength level is affected by the components, the number of application points is limited in actual construction.
- Patent Documents 5 and 6 disclose a special welding method called laser-arc hybrid welding. This method has a merit that a weld metal with excellent crack resistance can be obtained while obtaining a construction efficiency similar to that of a large heat input submerged arc welding with a low heat input, but there is a problem that it cannot be applied to general arc welding. .
- the present inventors have developed a technique for improving the hydrogen embrittlement resistance of an HT780 MPa class weld metal by controlling the retained austenite form.
- the welding method assumed in this technique is gas shielded arc welding mainly using a flux cored wire (FCW).
- FCW flux cored wire
- region in a weld metal is evaluated. In an actual weld metal, the structure greatly varies depending on the observation position. Therefore, in order to evaluate the hydrogen embrittlement susceptibility with higher accuracy, a method capable of evaluating a relatively wide region in the weld metal is required.
- weld metals used for offshore structures are required to have excellent resistance to hydrogen embrittlement at a strength of 780 MPa so that they can be used in cold regions.
- the wire component composition is specified to improve the strength and low temperature toughness of the weld metal part.
- the assumed use temperature is up to about ⁇ 20 ° C., and it cannot meet the requirement on the lower temperature side, and for example, characteristics such as toughness become insufficient at ⁇ 60 ° C.
- Japanese Unexamined Patent Publication No. 2005-40816 Japanese Unexamined Patent Publication No. 2003-33876 Japanese Laid-Open Patent Publication No. 2002-115032 Japanese Unexamined Patent Publication No. 11-147196 Japanese Unexamined Patent Publication No. 2007-260715 Japanese Unexamined Patent Publication No. 2007-260716 Japanese Unexamined Patent Publication No. 2012-176434 Japanese Unexamined Patent Publication No. 2004-337863
- the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a weld metal having excellent resistance to hydrogen embrittlement even if the tensile strength is high strength exceeding 780 MPa. It is another object of the present invention to provide a solid wire for submerged arc welding suitable for forming the weld metal.
- the weld metal with excellent hydrogen embrittlement susceptibility according to the present invention that has solved the above-mentioned problems means C: 0.02 to 0.12% (meaning “mass%”. ), Si: 0.18 to 2.00%, Mn: 0.90 to 2.5%, Ni: 1.0 to 3.5% Cr: 0.3 to 2.0%, Al: 0.030% or less (excluding 0%), N: 0.015% or less (not including 0%), and O: 0.050% or less (not including 0%),
- the balance consists of iron and inevitable impurities, Containing 2,500 particles / mm 2 or more of retained austenite particles having an equivalent circle diameter of 0.15 ⁇ m or more, and a volume fraction of the retained austenite phase is 4.3% or more of the entire structure;
- the main point is that the ratio [Cr] / [Mn] of the Cr and Mn content is 0.20 or more.
- the size of the retained austenite particles to be used in the measurement of the number density was set to be equal to or greater than the measurement limit, and the equivalent circle diameter was set to be 0.15 ⁇ m or more.
- the equivalent circle diameter is a diameter assuming a circle having an equal area by paying attention to the size of residual austenite particles observed on the observation surface of the optical microscope.
- the weld metal of the present invention as other elements, (a) Mo: 0.95% or less (not including 0%), Ti: less than 0.040% (not including 0%), V: 0 .1% or more selected from the group consisting of 60% or less (not including 0%) and Cu: 1.0% or less (not including 0%), (b) Zr: 0.10% or less (0% (C) B: 0.0050% or less (not including 0%) and the like are also preferable, and the characteristics of the weld metal are further improved depending on the type of element to be included.
- it is formed by submerged arc welding.
- the solid wire for submerged arc welding according to the present invention has C: 0.07 to 0.20%, Si: 0.05 to 1.60%, Mn: 1.30 to 3.20, based on the total mass of the wire. %, Ni: 1.00-3.70%, Cr: 0.3-2.2%, Mo: 2.0% or less (including 0%), with the balance being Fe and inevitable impurities Is.
- the Mn content (%) is [Mn]
- the Ni content (%) is [Ni]
- the Cr content (%) is [Cr]
- the Mo content is%.
- Cu 0.07 to 0.40%
- V 0.019% or less
- Zr 0.050% or less
- Ti 0.010% or less
- B may contain at least one of 0.0050% or less.
- the number density and volume fraction of the retained austenite particles are appropriately controlled together with the chemical component composition, so that a weld metal having excellent resistance to hydrogen embrittlement can be realized even at a high strength exceeding 780 MPa. .
- the inventors have improved the hydrogen embrittlement susceptibility measured by the SSRT test by controlling the retained austenite form and oxide form in the invention of Patent Document 7 (hereinafter referred to as the prior invention), for example. ing.
- the assumed welding method is mainly gas shielded arc welding using FCW, and the heat input during welding is limited to 2.5 kJ / mm or less. It has been shown in the prior invention that when the heat input of welding exceeds 2.5 kJ / mm, the predetermined retained austenite form cannot be obtained, and the predetermined characteristics cannot be satisfied by the SSRT test.
- the present inventors appropriately control the chemical composition of the welding material, and at the same time, the ratio of Cr and Mn content in the weld metal [Cr] / [Mn] (that is, Cr content [ Cr] and Mn content [Mn] ratio) and Ti content were suppressed to less than 0.040% (including 0%).
- Cr content [ Cr] and Mn content [Mn] ratio Cr content [ Cr] and Mn content [Mn] ratio
- the greatest difference between the present invention and the prior invention is the Ti content in the weld metal.
- the Ti content in the weld metal is 0.040 to 0.15%, and the microstructure of the Ti oxide starting point is developed to ensure the number density of residual austenite particles and to prevent hydrogen embrittlement.
- the cooling rate during welding decreases, so the bainite (grain boundary bainite) structure from the prior austenite grain boundaries is the main component, and the microstructure of the Ti oxide origin is Not enough.
- Ti itself is a ferrite forming element and has an adverse effect on the stabilization of retained austenite.
- the weld metal does not contain Ti, or even if Ti is contained if necessary, its content is less than 0.040%, and the residual austenite is stabilized.
- the ratio [Cr] / [Mn] of Cr and Mn content in the weld metal is set to 0.20 or more to disperse many residual austenite particles. Succeeded.
- the resistance to hydrogen embrittlement when the heat input is large cannot be ensured only by dispersing the amount of retained austenite and the number of retained austenite particles equivalent to the invention of the prior application. This is because, as described above, when the heat input is large, the prior austenite structure becomes coarse and adversely affects the resistance to hydrogen embrittlement (by controlling the ratio [Cr] / [Mn] It is the bainite structure in the former austenite grains).
- Nb which is a ferrite forming element has a disadvantageous action from the viewpoint of stabilizing retained austenite, it is controlled to an impurity level ( ⁇ 0.01%) in the present invention and is not actively added.
- high strength means a material having a tensile strength TS exceeding 780 MPa, preferably about 800 to 980 MPa.
- excellent in resistance to hydrogen embrittlement means that when the resistance to hydrogen embrittlement is evaluated by the method described in Examples described later, the elongation at break when using a large test piece is 2.0. It means something that satisfies over%.
- the weld metal of the present invention has C: 0.02 to 0.12%, Si: 0.18 to 2.00%, Mn: 0.90 to 2.5%, Ni: 1.0 to 3.5%, Cr: 0.3 to 2.0%, Al: 0.030% or less (not including 0%), N: 0.015% or less (not including 0%), and O: 0 0.055% or less (excluding 0%), the balance of which is composed of iron and inevitable impurities, the residual austenite particles having an equivalent circle diameter of 0.15 ⁇ m or more and 2500 particles / mm 2 or more, The volume fraction of the phase is 4.3% or more with respect to the entire structure, and the ratio [Cr] / [Mn] of the content of Cr and Mn is 0.20 or more.
- the residual austenite particles present in the weld metal are controlled to 2500 particles / mm 2 or more, and the volume fraction of the retained austenite phase (ratio to the entire structure) is controlled to 4.3% or more. According to the present invention, since the retained austenite particles are dispersed at an appropriate number density, a weld metal excellent in resistance to hydrogen embrittlement can be obtained.
- the above-mentioned requirements are defined for retained austenite present in the raw material portion among weld metals. Residual austenite in the weld metal decomposes due to the influence of the post-pass during welding, so the amount of retained austenite tends to vary depending on the measurement location, particularly in the reheated part, while the original part of the final pass This is because the amount of retained austenite is easily evaluated accurately without being affected by the heat of the back pass.
- retained austenite serves as a trapping site for diffusible hydrogen, it has already been reported that it has a function of reducing diffusible hydrogen and contributes to improvement of hydrogen embrittlement resistance.
- the amount of retained austenite ratio in the whole structure
- no attention has been paid to its dispersion state (number density).
- the desired hydrogen embrittlement resistance cannot be obtained unless the dispersion state is appropriately controlled. (For example, see Experiment Nos. 39 and 43 in Table 7 of Examples described later).
- the amount of retained austenite serving as a diffusible hydrogen trap site is secured, and the number of retained austenite particles is increased by making the matrix structure finer ( Specifically, it has been found that the dispersion effect of 2,500 / mm 2 or more maximizes the trapping effect of diffusible hydrogen and greatly improves the resistance to hydrogen embrittlement.
- the experiment Nos. 39 and experiment no. 43 is an example in which the volume fraction of retained austenite particles is 4.3% or more as defined in the present invention, and a predetermined amount of retained austenite exists.
- the resistance to hydrogen embrittlement when using a large-sized test piece is lowered.
- the number density of retained austenite particles is preferably as high as possible, preferably 3000 / mm 2 or more, and more preferably 3300 / mm 2 or more.
- the upper limit is not particularly limited from the viewpoint of improving the hydrogen embrittlement susceptibility, but may be, for example, 7500 pieces / mm 2 or less.
- the volume fraction of the retained austenite phase in the entire structure is preferably as large as possible, preferably 4.7% or more, and more preferably 5.0% or more.
- the upper limit is not particularly limited from the viewpoint of improving hydrogen embrittlement susceptibility, but considering the fact that the yield stress decreases if it exists in excess, for example, 10% or less, preferably 9% or less, more preferably It may be 8% or less.
- the present invention is characterized by controlling the amount of retained austenite phase (volume fraction) and the number density of retained austenite particles among the structures constituting the weld metal, and the structure other than retained austenite is limited in any way.
- any structure that is usually included in the weld metal may be used.
- bainite is included as a main structure (a structure having a volume fraction of 50% or more, preferably 70% or more, more preferably 90% or more with respect to the entire structure), and in addition, grain boundary ferrite, martensite, and the like. May be included.
- the bainite, intergranular ferrite and martensite are all types of “ferrite phase”, and the fraction of the retained austenite phase measured by the method (Example) described later is the retained austenite, bainite, grain boundary. It is a ratio to the total of ferrite and martensite. Moreover, the amount of bainite is calculated
- C is an element indispensable for securing the strength of the weld metal, and in order to exert such effects, the lower limit of the C content is set to 0.02% or more. Preferably it is 0.04% or more, More preferably, it is 0.05% or more. However, if the C content exceeds 0.12%, the strength increases excessively and the hydrogen embrittlement susceptibility increases (that is, the hydrogen embrittlement susceptibility deteriorates), so the upper limit is 0.12% or less. And The upper limit with preferable C content is 0.10% or less, More preferably, it is 0.08% or less.
- Si exists in a solid solution state, thereby delaying carbide formation and stabilizing retained austenite. If the Si content is less than 0.18%, the predetermined retained austenite cannot be ensured, and the above-described effects are not effectively exhibited. Therefore, the lower limit of the Si content is set to 0.18% or more. Preferably it is 0.30% or more, more preferably 0.35% or more. On the other hand, if the Si content is excessive, the hydrogen embrittlement susceptibility increases due to a significant increase in strength, so the upper limit is regulated to 2.00% or less. Preferably it is 1.5% or less, More preferably, it is 1.0% or less.
- Mn is an element necessary for ensuring the strength of the weld metal, and in order to exert such effects, the lower limit of the Mn content is set to 0.90% or more. Preferably it is 1.2% or more, More preferably, it is 1.4% or more. However, if the Mn content exceeds 2.5%, the hydrogen embrittlement susceptibility increases due to a significant increase in strength, so the upper limit is made 2.5% or less. Preferably it is 2.2% or less, More preferably, it is 2.0% or less.
- Ni is an element necessary for ensuring the strength of the weld metal, and in order to exert such effects, the lower limit of the Ni content is set to 1.0% or more. Preferably it is 1.2% or more, More preferably, it is 1.5% or more. However, if the Ni content exceeds 3.5% and becomes excessive, the hydrogen embrittlement susceptibility increases due to an excessive increase in strength, so the upper limit is made 3.5% or less. Preferably it is 3.0% or less, More preferably, it is 2.8% or less.
- Cr is an element that contributes to fine dispersion of the retained austenite particles by refining the grain boundary bainite structure.
- the lower limit of the Cr content is set to 0.3% or more. Preferably it is 0.4% or more, More preferably, it is 0.5% or more.
- the upper limit is made 2.0% or less. Preferably it is 1.8% or less, More preferably, it is 1.5% or less.
- Al 0.030% or less (excluding 0%)
- Al is added as a deoxidizing element. If added in excess, the formation of AlN causes an excessive increase in strength and deteriorates the resistance to hydrogen embrittlement, so the upper limit is made 0.030% or less. Preferably it is 0.025% or less, More preferably, it is 0.020% or less.
- N 0.015% or less (excluding 0%)]
- N is one of the elements inevitably mixed in, and it is difficult to make it 0% industrially.
- N is effective for improving the strength of the weld metal.
- the upper limit of the N content is 0.015% or less.
- it is 0.010% or less, More preferably, it is 0.006% or less.
- O 0.050% or less (excluding 0%)
- O is an element inevitably contained in the weld metal, and it is difficult to make it 0% industrially. If the O content exceeds 0.050%, Si oxide is formed, and the amount of retained austenite cannot be ensured due to a decrease in solute Si, so the upper limit is made 0.050% or less. Preferably it is 0.045% or less, More preferably, it is 0.040% or less.
- the basic components contained in the weld metal of the present invention are as described above, with the balance being iron and inevitable impurities.
- Inevitable impurities include elements (for example, P and S) that are brought in depending on the status of raw materials, materials, manufacturing equipment, and the like.
- impurities segregate at the grain boundaries to lower the grain boundary strength and promote low temperature cracking.
- P 0.02% or less (excluding 0%)
- S 0.025% or less ( It is preferable to suppress each of them.
- the basic components in the weld metal of the present invention are as described above, as other elements, (a) Mo: 0.95% or less (not including 0%), Ti: less than 0.040% (0%) 1) or more selected from the group consisting of V: 0.60% or less (not including 0%) and Cu: 1.0% or less (not including 0%), (b) Zr: 0 .10% or less (not including 0%), (c) B: 0.0050% or less (not including 0%), etc. may be included, and the characteristics of the weld metal depend on the type of element to be included. Further improvement.
- the elements belonging to (a), (b) and (c) may be contained alone or in appropriate combination.
- Mo 0.95% or less (not including 0%), Ti: less than 0.040% (not including 0%), V: 0.60% or less (not including 0%), and Cu: 1.
- One or more selected from the group consisting of 0% or less (excluding 0%)] Mo, Ti, V, and Cu are useful as elements for improving the strength of the weld metal, and may be contained alone or in combination of two or more.
- Mo is an element effective for securing the strength.
- the upper limit is preferably 0.95% or less. More preferably, it is 0.85% or less, More preferably, it is 0.50% or less.
- the Mo content for obtaining the effect of improving the strength is preferably 0.05% or more, more preferably 0.20% or more.
- the Ti is effective in improving strength, but has the effect of destabilizing retained austenite. Therefore, when the Ti content is excessive, the retained austenite becomes martensite due to stress-induced transformation during a large SSRT test. It is impossible to secure a high hydrogen embrittlement resistance.
- the Ti content is preferably less than 0.040%. More preferably, it is 0.035% or less, More preferably, it is 0.030% or less.
- the Ti content for obtaining the effect of improving the strength is preferably 0.010% or more, more preferably 0.015% or more.
- V and Cu are useful as elements for improving the strength of the weld metal, and the preferred lower limit for exhibiting these effects is 0.02% or more for V and 0.05% or more for Cu.
- the content of these elements is excessive, the hydrogen embrittlement susceptibility increases due to an excessive increase in strength. Therefore, with respect to the upper limit of the amount of each element, V is 0.60% or less (more preferably 0.50% or less, more preferably 0.40% or less), and Cu is 1.0% or less (more preferably 0.5%). % Or less, more preferably 0.2% or less).
- Zr 0.10% or less (excluding 0%)
- Zr is a strong deoxidizing element and has the effect of promoting the increase in retained austenite due to the increase in solid solution Si.
- a preferable lower limit for effectively exhibiting such an effect is 0.010% or more.
- the upper limit of the Zr content is preferably suppressed to 0.10% or less (more preferably 0.050% or less).
- B 0.0050% or less (excluding 0%)
- B is an element that contributes to improving the strength by suppressing the formation of ferrite from the prior austenite grain boundaries.
- the lower limit of the B content is preferably set to 0.0010% or more.
- the upper limit is preferably suppressed to 0.0050% or less (more preferably 0.0030% or less).
- the welding method for producing the weld metal of the present invention is not limited, but submerged arc welding (SAW) having a large heat input and good construction efficiency is preferable.
- SAW submerged arc welding
- the following wires and fluxes are used.
- the amount of heat input at the time of welding is affected, and it is preferably 2.0 kJ / mm to 3.0 kJ / mm. If the heat input during welding exceeds 3.0 kJ / mm, the cooling rate during welding decreases, and the decomposition of residual austenite is promoted. As a result, desired residual austenite particles (number density and volume fraction) cannot be obtained. More preferably, it is 2.8 kJ / mm or less. The smaller the amount of heat input, the better. However, from the viewpoint of construction efficiency, it is preferably 2.0 kJ / mm or more. More preferably, it is 2.5 kJ / mm or more.
- C 0.07 to 0.20%
- Si 0.05 to 1.60%
- Mn 1.30 to 3.20%
- Ni 1..00 to 3.70
- %, Cr 0.3-2.2%
- Mo 2.0% or less (including 0%), with the balance being Fe and inevitable impurities.
- C 0.08 to 0.20%
- Si 0.05 to 0.50%
- Mn 1.50 to 3.00%
- Ni 1.50 to 1.95%
- Cr 0 0.5 to 1.5%
- Mo 0.10 to 0.45%
- P 0.015% or less
- S 0.015% or less
- the balance being Fe and inevitable impurities It is a wire.
- C 0.07 to 0.20%
- C is an element indispensable for ensuring the strength of the weld metal.
- the C content is less than 0.07%, the strength of the weld metal is insufficient or the effect of stabilizing toughness is insufficient.
- the C content exceeds 0.20%, the strength becomes excessive and the low temperature toughness of the weld metal deteriorates. Therefore, the C content is 0.07 to 0.20%.
- the C content is preferably 0.10% or more, and from the viewpoint of improving low temperature toughness, the C content should be 0.15% or less. Is preferred.
- Si 0.05 to 1.60%
- Si exists in the weld metal in a solid solution state, and thus has an effect of delaying carbide formation and stabilizing residual austenite.
- the Si content is set to 0.05 to 1.60%.
- the Si content is preferably 0.5% or less, and more preferably 0.20% or less.
- Mn is an element necessary for ensuring the strength of the weld metal.
- Mn content is less than 1.30%, the strength of the weld metal is insufficient and the low temperature toughness is also deteriorated.
- the Mn content exceeds 3.20%, the strength and hardenability become excessive, and the low temperature toughness decreases. Therefore, the Mn content is 1.30 to 3.20%.
- the Mn content is preferably 1.50% or more, particularly 1.80% or more. From the viewpoint of improving low-temperature toughness, the Mn content is 3. It is preferable to set it to 00% or less, particularly 2.40% or less.
- Ni is an element necessary for ensuring the strength and toughness of the weld metal.
- the Ni content is less than 1.00%, the effect of improving the strength and toughness of the weld metal becomes insufficient, and the necessary retained austenite amount cannot be obtained, and the hydrogen embrittlement susceptibility deteriorates.
- the Ni content exceeds 3.70%, the low temperature toughness deteriorates. Therefore, the Ni content is 1.00 to 3.70%.
- the Ni content is preferably 1.60% or more, and from the viewpoint of improving the low temperature toughness, the Ni content is 1.95% or less, particularly 1. 90% or less is preferable.
- Cr 0.3-2.2%
- Cr is an element that contributes to the refinement of residual austenite grains by refining the grain boundary bainite structure.
- the Cr content is less than 0.3%, the hardenability of the weld metal is significantly lowered, the transformation temperature is increased, and both the strength and the low temperature toughness are lowered.
- the Cr content exceeds 2.2%, the generation of retained austenite is suppressed, the necessary retained austenite amount cannot be obtained, and the resistance to hydrogen embrittlement resistance of the weld metal deteriorates. Therefore, the Cr content is set to 0.3 to 2.2%.
- the Cr content is preferably 0.5% or more, particularly preferably 0.9% or more. From the viewpoint of improving the resistance to hydrogen embrittlement resistance of the weld metal, the Cr content The amount is preferably 1.5% or less, particularly preferably 1.2% or less.
- Mo 2.0% or less (including 0%)
- Mo is an element useful for improving the strength in the weld metal.
- the Mo content exceeds 2.0%, the generation of retained austenite is suppressed, the necessary amount of retained austenite cannot be obtained, and the resistance to hydrogen embrittlement resistance of the weld metal deteriorates. Therefore, the Mo content is set to 2.0% or less.
- the Mo content is preferably 0.10% or more, particularly preferably 0.20% or more.
- the amount is preferably 0.45% or less, particularly preferably 0.40% or less.
- P significantly reduces the low temperature toughness of the weld metal. Specifically, if the P content exceeds 0.015%, the low temperature toughness of the weld metal is insufficient. Therefore, the P content is restricted to 0.015% or less. From the viewpoint of improving low temperature toughness, the P content is preferably regulated to 0.010% or less.
- S significantly reduces the low temperature toughness of the weld metal. Specifically, when the S content exceeds 0.015%, the low temperature toughness is insufficient. Therefore, the S content is restricted to 0.015% or less. From the viewpoint of improving low temperature toughness, the S content is preferably regulated to 0.007% or less.
- Cu contributes little to the strength and low temperature toughness of the weld metal and does not need to be positively added to the wire body.
- Cu plating when Cu plating is applied to the wire surface, it has a great effect on rust prevention.
- the Cu content when the Cu content is less than 0.07%, the rust prevention effect is small, and when the Cu content exceeds 0.40%, the wire feedability is lowered. Therefore, in the solid wire of the present embodiment, when Cu plating or the like is performed, the Cu content is preferably set to 0.07 to 0.40%.
- V 0.019 mass% or less
- V is an element that increases the strength, particularly the proof stress, by adding a small amount due to precipitation strengthening, and can be added as necessary.
- the V content exceeds 0.019%, the strength of the weld metal increases, the low-temperature toughness decreases, and the formation of residual austenite is inhibited. The susceptibility to deterioration deteriorates. Therefore, when V is added, the content is made 0.019% or less.
- Zr 0.050% or less
- Zr is an element that increases the strength, particularly the yield strength, by adding a small amount due to precipitation strengthening, and therefore can be added as necessary.
- the Zr content exceeds 0.050%, the strength of the weld metal increases, the low-temperature toughness decreases, and the formation of residual austenite is hindered. The embrittlement susceptibility deteriorates. Therefore, when adding Zr, it is made into 0.050% or less.
- Ti like V and Zr, is an element that increases the strength, particularly the yield strength, by adding a small amount by precipitation strengthening, and can be added as necessary. However, if the Ti content exceeds 0.010%, the strength of the weld metal increases, the low-temperature toughness decreases, and the formation of residual austenite is hindered. The susceptibility to deterioration deteriorates. Therefore, when adding Ti, it is made into 0.010% or less.
- B has the effect of suppressing the formation of ferrite from the prior austenite grain boundaries and improving the strength of the weld metal.
- B content exceeds 0.0050 mass%, the strength of the weld metal is remarkably increased, and the hydrogen embrittlement resistance is deteriorated. Therefore, when adding B, it is 0.0050% or less.
- the balance in the solid wire of this embodiment is Fe and inevitable impurities.
- inevitable impurities in the solid wire of the present embodiment include O, N, Al, Nb, Ca, and Mg.
- the solid wire is preferably used in combination with a sintered flux.
- the composition of the flux is not particularly limited.
- MgO 25 to 35%
- Al 2 O 3 10 to 20%
- CaF 2 12 to 22%
- SiO 2 8 per total mass of the flux.
- CaO 10 to 15%
- metal Si 1 to 4%
- MgO not only increases the basicity of the flux, but also acts to suppress oxygen in the weld metal as a deoxidizer, so that it is effective in reducing oxygen and further increases the fire resistance of the slag.
- this effect is not exhibited when the MgO content of the flux is less than 25%.
- the MgO content of the flux is preferably 25 to 35%.
- Al 2 O 3 acts as a slag forming agent and has an effect of ensuring the slag peelability of the beads. Moreover, Al 2 O 3 also has a function of improving the concentration and stability of the arc. However, when the Al 2 O 3 content of the flux is less than 10%, the slag peelability is deteriorated, the arc becomes unstable, and welding may be difficult. On the other hand, if the Al 2 O 3 content of the flux exceeds 20%, oxygen in the weld metal increases and the toughness may deteriorate. Therefore, the Al 2 O 3 content of the flux is preferably 10 to 20%.
- CaF 2 has an effect of reducing oxygen in the weld metal in addition to the generally known action of adjusting the melting point of the produced slag.
- the CaF 2 content of the flux is less than 12%, these effects cannot be obtained, and when the CaF 2 content of the flux exceeds 22%, the arc becomes unstable and the bead appearance deteriorates.
- a pock mark may be generated on the bead. Therefore, the CaF 2 content of the flux is preferably 12 to 22%.
- SiO 2 has the effect of arranging the bead appearance and bead shape as slag forming agent. However, this effect is not exhibited when the SiO 2 content of the flux is less than 8%, and when the SiO 2 content of the flux exceeds 18%, oxygen in the weld metal increases and the toughness deteriorates. Sometimes. Therefore, the SiO 2 content of the flux is preferably 8 to 18%.
- the metal carbonate is gasified by welding heat, lowers the partial pressure of water vapor in the arc atmosphere, and has an arc shielding effect that reduces the amount of diffusible hydrogen in the weld metal.
- this effect cannot be obtained when the metal carbonate content of the flux is less than 3% in terms of CO 2 .
- the metal carbonate content of the flux is preferably 3 to 9% in terms of CO 2 .
- examples of the metal carbonate added to the flux include CaCO 3 and BaCO 3 .
- CaO increases the basicity of the flux and is effective in reducing oxygen in the weld metal. However, this effect is not exhibited when the CaO content of the flux is less than 10%. Moreover, when the CaO content of the flux exceeds 15%, the arc stability and the bead appearance deteriorate. Therefore, the CaO of the flux is preferably 10 to 15%.
- Metal Si has a deoxidation effect that suppresses the amount of oxygen in the weld metal.
- this effect cannot be obtained when the metal Si content of the flux is less than 1%.
- the metal Si content of the flux exceeds 4%, the deoxidation effect is not improved, the bead shape of the weld metal is deteriorated, the strength is increased, and the toughness is lowered. Therefore, the metal Si content is preferably 1 to 4%.
- the metal Si is added to the flux in the form of Fe—Si, Fe—Si—Mn alloy or the like.
- Components other than the above in the flux are components other than the CO 2 equivalent value in the metal carbonate, alkali metal oxides, unavoidable impurities, and the like.
- the solid wire detailed above can control retained austenite and improve the resistance to hydrogen embrittlement and low temperature toughness of the weld metal.
- Example 1 Using a combination of the fluxes (F1 to F9) having the chemical composition shown in Table 1 below and the wires (W1 to W52) having the chemical composition shown in Tables 2 and 3 below, the welding metal is used under the following (A) welding conditions. Produced. In the columns of Tables 2 and 3, “-” means no addition (not contained).
- the peaks of the lattice planes of (110), (200), (211), and (220) of the ferrite phase, and the lattice planes of (111), (200), (220), and (311) of the retained austenite phase are calculated based on the integrated intensity ratio of each peak, and the average value (arithmetic average) of these is obtained. This was designated as “volume fraction of retained austenite phase”.
- Experiment No. 34 is an example in which an appropriate flux F1 was used, but welding was performed under a heat input condition (d) with a large amount of heat input. As a result, the volume fraction of retained austenite particles in the weld metal decreased, and the hydrogen embrittlement susceptibility of large test pieces decreased.
- Experiment No. No. 35 is an example using the flux F6 with a small amount of SiO 2 .
- the volume fraction of retained austenite particles in the weld metal was reduced, and the hydrogen embrittlement susceptibility of large specimens was also reduced.
- the C content in the weld metal is low, and the tensile strength is reduced.
- Experiment No. 36 is an example using the flux F7 with a large amount of SiO 2 .
- the Si content of the weld metal was increased, the strength was remarkably increased, and the hydrogen embrittlement susceptibility of the large specimen was decreased.
- the Mn content in the weld metal is increased, and the tensile strength is remarkably increased.
- Experiment No. 37 is an example using the flux F8 with a small amount of metal Si. As a result, the volume fraction of retained austenite particles in the weld metal was reduced, and the hydrogen embrittlement susceptibility of large specimens was also reduced. Further, due to the welding wire used, the Mn content in the weld metal is reduced, and the tensile strength is reduced.
- Experiment No. 38 is an example using the flux F9 with a large amount of metal Si.
- the Si content in the weld metal increased, the strength increased significantly, and the hydrogen embrittlement susceptibility of large test pieces decreased.
- the Ni content in the weld metal is increased, and the tensile strength is significantly increased.
- Experiment No. 39 is an example in which the ratio [Cr] / [Mn] of the content of Cr and Mn in the weld metal is small. As a result, the number density of retained austenite particles in the weld metal was reduced, and the hydrogen embrittlement susceptibility of large specimens was reduced. Moreover, due to the welding wire used, the C content in the weld metal is increased, and the tensile strength is significantly increased.
- Experiment No. 40 is an example in which the Si content in the weld metal is low. As a result, the volume fraction of the retained austenite phase in the weld metal was reduced, and the hydrogen embrittlement susceptibility to large specimens was reduced.
- Experiment No. 41 is an example with much Si content in a weld metal. As a result, the tensile strength was remarkably increased, and the hydrogen embrittlement susceptibility of the large specimen was decreased.
- Experiment No. 42 is an example in which the ratio [Cr] / [Mn] of the content of Cr and Mn in the weld metal is small.
- the number density of retained austenite particles in the weld metal was reduced, and the hydrogen embrittlement susceptibility of large specimens was reduced.
- the O content in the weld metal is increased, the volume fraction of retained austenite particles in the weld metal is decreased, and the hydrogen embrittlement susceptibility of large test pieces is also lowered from this point.
- the Ni content in the weld metal has become scarce and the tensile strength has been reduced.
- Experiment No. 43 is an example in which the ratio [Cr] / [Mn] of the content of Cr and Mn in the weld metal is small. As a result, the number density of retained austenite particles in the weld metal was reduced, and the hydrogen embrittlement susceptibility of large specimens was reduced.
- Experiment No. 44 is an example with a large Cr content in the weld metal. As a result, the strength of the weld metal increased excessively, and the hydrogen embrittlement susceptibility of the large specimen decreased.
- Experiment No. 45 is an example in which the Mo content in the weld metal is high. As a result, the strength of the weld metal increased excessively, and the hydrogen embrittlement susceptibility of the large specimen decreased.
- Experiment No. 46 is an example in which the Al content in the weld metal is high. As a result, the strength of the weld metal increased excessively, and the hydrogen embrittlement susceptibility of the large specimen decreased.
- Experiment No. 47 is an example in which the N content in the weld metal is large. As a result, the strength of the weld metal increased excessively, and the hydrogen embrittlement susceptibility of the large specimen decreased.
- Experiment No. 48 is an example with a large Ti content in the weld metal. As a result, the strength of the weld metal increased excessively, and the hydrogen embrittlement susceptibility of the large specimen decreased.
- No. 49 is an example with much V content in a weld metal. As a result, the strength of the weld metal increased excessively, and the hydrogen embrittlement susceptibility of the large specimen decreased.
- Experiment No. 50 is an example in which the Cu content in the weld metal is high. As a result, the strength of the weld metal increased excessively, and the hydrogen embrittlement susceptibility of the large specimen decreased.
- Experiment No. 51 is an example with much Zr content in a weld metal. As a result, the strength of the weld metal increased excessively, and the hydrogen embrittlement susceptibility of the large specimen decreased.
- Experiment No. 52 is an example with much B content in a weld metal. As a result, the strength of the weld metal increased excessively, and the hydrogen embrittlement susceptibility of the large specimen decreased.
- Example 2 Here, a preferred wire composition was verified.
- the solid compositions (wire diameter 4.0 mm) of Examples and Comparative Examples were prepared with the component compositions shown in Table 8 below, and a performance confirmation test was performed. Note that the wires W101 to W113 shown in Table 8 below are examples within the preferred range, and the wires W114 to W124 are comparative examples outside the preferred range. Moreover, the remainder in the component composition of the wire shown in Table 8 below is Fe and inevitable impurities.
- the obtained weld metal was measured for its mechanical properties and volume fraction of retained austenite phase by the following method, and evaluated for hydrogen embrittlement resistance.
- ⁇ Tensile test> A JIS Z3111 No. A1 test piece was collected from the center of the weld metal at the center of the weld metal, and a tensile test was performed using this test piece at a test temperature of room temperature (20 to 23 ° C.). As a result, those having a tensile strength of 770 MPa or more were accepted.
- ⁇ Impact test> A V-notch test piece of JIS Z3111 was sampled from the center of the weld metal at the center of the plate thickness, and an impact test was performed using this test piece at a test temperature of ⁇ 60 ° C. As a result, a sample having an absorbed energy at ⁇ 60 ° C. of 47 J or more on average was regarded as acceptable.
- ⁇ Volume fraction of retained austenite phase> The surface of the final pass original part of the weld metal was electrolytically polished, and X-ray diffraction measurement was performed with a secondary micro part X-ray diffractometer RINT-RAPIDII manufactured by Rigaku Corporation. From the results, the ferrite phase peaks (110), (200), (211), (220) and the retained austenite phases (111), (200), (220), (311) For the lattice plane peaks, the volume fractions of (111), (200), (220), and (311) of the retained austenite phase were calculated based on the integrated intensity ratio of each peak. And the average value (arithmetic average) of these was calculated
- JIS Z3111 A0 test piece is taken from the center of the weld metal in parallel to the welding direction, and after charging with hydrogen under the conditions shown in (A) below, it is shown in (B) below to prevent hydrogen escape. Zinc plating was performed under conditions. Using this test piece, an SSRT test (low strain rate tensile test) was performed with a crosshead speed of 3.0 ⁇ 10 ⁇ 2 mm / min (strain rate: 6.94 ⁇ 10 ⁇ 6 / sec). As a result, the test piece with an elongation at break exceeding 2.0% was evaluated as “excellent in hydrogen embrittlement resistance”.
- Comparative Example 1 using a W114 wire with a C content less than the preferred range had a low low temperature toughness of the weld metal and a low tensile strength. Further, in Comparative Example 5 using the W118 wire having a C content exceeding the preferable range, the low-temperature toughness of the weld metal was remarkably lowered, and the hydrogen embrittlement resistance was inferior.
- Comparative Example 2 using a W115 wire containing no Si and further having a Cr content exceeding the preferable range had low temperature toughness and tensile strength, and was also inferior in resistance to hydrogen embrittlement.
- Comparative Example 7 using a wire of W120 having a Si content exceeding the preferable range also had a low low temperature toughness of the weld metal and was also inferior in resistance to hydrogen embrittlement.
- Comparative Example 3 using a W116 wire having a Mn content less than the preferred range and a Mo content exceeding the preferred range was inferior in resistance to hydrogen embrittlement resistance of the weld metal.
- the comparative example 6 using the wire of W119 where Mn content exceeds the preferable range was inferior in the low temperature toughness of the weld metal.
- Comparative Example 4 using the W117 wire having a P content exceeding the preferable range, the low temperature toughness of the weld metal was remarkably lowered.
- Comparative Example 8 using the wire of W121 whose S content exceeds the preferable range, the low temperature toughness of the weld metal is remarkably lowered, and the hydrogen embrittlement resistance is also inferior.
- Comparative Example 9 using a W122 wire whose Ni content is less than the preferred range, the low temperature toughness of the weld metal was lowered. On the other hand, the low temperature toughness of the weld metal was lowered in Comparative Example 11 using the W124 wire whose Ni content exceeded the preferred range. In Comparative Example 10 using the W123 wire not containing Cr, the low temperature toughness of the weld metal was lowered and the tensile strength was also low.
- the present invention provides a weld metal that can be applied to various welded structures and is excellent in resistance to hydrogen embrittlement.
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Abstract
Description
Si:0.18~2.00%、
Mn:0.90~2.5%、
Ni:1.0~3.5%、
Cr:0.3~2.0%、
Al:0.030%以下(0%を含まない)、
N :0.015%以下(0%を含まない)、および
O :0.050%以下(0%を含まない)を夫々含有し、
残部が鉄および不可避的不純物からなり、
円相当直径が0.15μm以上の残留オーステナイト粒子を2500個/mm2以上含有し、残留オーステナイト相の体積分率が、組織全体に対して4.3%以上であり、
CrとMnの含有量の比[Cr]/[Mn]が0.20以上であるところに要旨を有するものである。
Cは、溶接金属の強度を確保するために欠くことのできない元素であり、こうした効果を発揮させるため、C含有量の下限を0.02%以上とする。好ましくは0.04%以上であり、より好ましくは0.05%以上である。しかしながら、C含有量が0.12%を超えると、強度が過大に上昇して水素脆化感受性が高くなる(すなわち、耐水素脆化感受性が劣化する)ため、その上限を0.12%以下とする。C含有量の好ましい上限は0.10%以下であり、より好ましくは0.08%以下である。
Siは、固溶状態で存在することで炭化物形成を遅らせ、残留オーステナイトを安定化する作用を有する。Si含有量が0.18%未満であると、所定の残留オーステナイトを確保できず、上述した作用が有効に発揮されないため、Si含有量の下限を0.18%以上とする。好ましくは0.30%以上、より好ましくは0.35%以上である。一方、Si含有量が過剰になると、強度の著しい上昇により水素脆化感受性が高くなるため、上限を2.00%以下に規制する。好ましくは1.5%以下であり、より好ましくは1.0%以下である。
Mnは、溶接金属の強度を確保する上で必要な元素であり、こうした効果を発揮させるため、Mn含有量の下限を0.90%以上とする。好ましくは1.2%以上、より好ましくは1.4%以上である。しかしながら、Mn含有量が2.5%を超えると、強度の著しい上昇により水素脆化感受性が高くなるため、その上限を2.5%以下とする。好ましくは2.2%以下であり、より好ましくは2.0%以下である。
Niは、溶接金属の強度を確保する上で必要な元素であり、こうした効果を発揮させるため、Ni含有量の下限を1.0%以上とする。好ましくは1.2%以上、より好ましくは1.5%以上である。しかしながら、Ni含有量が3.5%を超えて過剰になると、強度の過大な上昇により水素脆化感受性が高くなるため、その上限を3.5%以下とする。好ましくは3.0%以下であり、より好ましくは2.8%以下である。
Crは、粒界ベイナイト組織を微細化させることで、残留オーステナイト粒子の微細分散に寄与する元素であり、こうした効果を発揮させるため、Cr含有量の下限を0.3%以上とする。好ましくは0.4%以上、より好ましくは0.5%以上である。しかしながら、Cr含有量が2.0%を超えて過剰になると、強度の過大な上昇により水素脆化感受性が高くなるため、その上限を2.0%以下とする。好ましくは1.8%以下であり、より好ましくは1.5%以下である。
Alは脱酸元素として添加される。過剰に添加すると、AlNを形成することで強度の過大な上昇をもたらし、耐水素脆化感受性が劣化するため、上限を0.030%以下とする。好ましくは0.025%以下であり、より好ましくは0.020%以下である。
Nは、不可避的に混入してくる元素の一つであり、工業的に0%とすることは困難である。Nは、溶接金属の強度向上に有効であるが、過剰に含有すると、強度の過大な上昇により水素脆化感受性が高くなる。そのため、N含有量の上限は0.015%以下とする。好ましくは0.010%以下であり、より好ましくは0.006%以下である。
Oは、溶接金属中に不可避的に含まれる元素であり、工業的に0%とすることは困難である。O含有量が0.050%を超えるとSi酸化物が形成され、固溶Siが減少することで残留オーステナイト量が確保できなくなるため、その上限を0.050%以下とする。好ましくは0.045%以下であり、より好ましくは0.040%以下である。
Mo、Ti、VおよびCuは、溶接金属の強度向上元素として有用であり、単独で含有しても良いし、2種以上を併用しても良い。このうちMoは、強度確保に有効な元素であるが、過剰に含有させると強度の過大な上昇をもたらし、耐水素脆化感受性が劣化する。そのため、上限を0.95%以下とすることが好ましい。より好ましくは0.85%以下であり、更に好ましくは0.50%以下である。強度向上の効果を得るためのMo含有量は、好ましくは0.05%以上、より好ましくは0.20%以上である。
Zrは、強脱酸元素であり、固溶Si増加による残留オーステナイト増加を促進する作用がある。このような作用を有効に発揮させるための好ましい下限は、0.010%以上である。但し、Zr含有量が過剰になると、酸化物起点の粒内変態が減少し、組織粗大化により水素脆化感受性が高くなる。そのため、Zr含有量の上限は0.10%以下(より好ましくは0.050%以下)に抑制することが好ましい。
Bは、旧オーステナイト粒界からのフェライト生成を抑制することで強度の向上に寄与する元素である。このような作用を有効に発揮させるため、B含有量の下限を0.0010%以上とすることが好ましい。但し、B含有量が過剰になると、強度が著しく上昇し、水素脆化感受性が高くなるため、その上限を0.0050%以下(より好ましくは0.0030%以下)に抑制することが好ましい。
CrとMnの含有量の比[Cr]/[Mn]を0.20以上に制御することで、旧オーステナイト粒界からのベイナイト組織が微細化され、残留オーステナイト粒子の高密度分散が可能となる。好ましくは0.25以上、より好ましくは0.40以上である。
Cは、溶接金属の強度を確保するために欠くことのできない元素である。ただし、C含有量が0.07%未満であると、溶接金属の強度が不足したり、靭性を安定化させる効果が不足する。一方、C含有量が0.20%を超えると、強度が過剰となり、溶接金属の低温靭性が劣化する。よって、C含有量は、0.07~0.20%とする。
Siは、溶接金属中に固溶状態で存在することで、炭化物形成を遅らせ、残留オーステナイトを安定化させる作用がある。ただし、Si含有量が0.05%未満の場合、脱酸不足により、溶接金属の強度及び靭性が低下する。また、Si含有量が1.50%を超えると、マトリックス中のフェライトが脆化して、溶接金属の低温靭性が低下する。よって、Si含有量は、0.05~1.60%とする。なお、溶接金属の低温靭性向上の観点から、Si含有量は0.5%以下とすることが好ましく、0.20%以下とすることがより好ましい。
Mnは、溶接金属の強度を確保する上で必要な元素である。ただし、Mn含有量が1.30%未満の場合、溶接金属の強度が不足し、低温靭性も劣化する。また、Mn含有量が3.20%を超えると、強度及び焼き入れ性が過多となり、低温靭性が低下する。よって、Mn含有量は、1.30~3.20%とする。
Niは、溶接金属の強度及び靭性を確保すると上で必要な元素である。ただし、Ni含有量が1.00%未満の場合、溶接金属の強度及び靭性を向上させる効果が不十分となり、また、必要な残留オーステナイト量が得られず、耐水素脆化感受性が劣化する。一方、Ni含有量が3.70%を超えると、低温靭性が劣化する。よって、Ni含有量は、1.00~3.70%とする。
Crは、粒界ベイナイト組織を微細化させることで、残留オーステナイト粒子の微細化に寄与する元素である。Cr含有量が0.3%未満の場合、溶接金属の焼入れ性が大幅に低下し、変態温度が上がって、強度及び低温靭性が共に低下する。Cr含有量が2.2%を超えると、残留オーステナイトの生成が抑制されて、必要な残留オーステナイト量を得られず、溶接金属の耐水素脆化感受性が劣化する。よって、Cr含有量は、0.3~2.2%とする。
Moは、溶接金属中の強度向上に有用な元素である。ただし、Mo含有量が2.0%を超えると、残留オーステナイトの生成が抑制され、必要な残留オーステナイト量を得られず、溶接金属の耐水素脆化感受性が劣化する。よって、Mo含有量は、2.0%以下とする。
Pは、溶接金属の低温靭性を著しく低下させる。具体的には、P含有量が0.015%を超えると、溶接金属の低温靭性が不足する。よって、P含有量は、0.015%以下に規制する。なお、低温靭性向上の観点から、P含有量は0.010%以下に規制することが好ましい。
Sは、溶接金属の低温靭性を著しく低下させる。具体的には、S含有量が0.015%を超えると、低温靭性が不足する。よって、S含有量は、0.015%以下に規制する。なお、低温靭性向上の観点から、S含有量は、0.007%以下に規制することが好ましい。
前述した各成分の組成により、溶接金属の低温靭性及び耐水素脆化感受性の両方を確保することができるが、本発明者は、更に、Cr及びMnの総含有量とMn及びNiの総含有量との比(=([Mn]+[Ni])/([Cr]+[Mo]))を特定の範囲にすることにより、低温靭性及び耐水素脆化感受性を向上できることを見出した。
Cuは、溶接金属の強度及び低温靭性に対する寄与が小さく、ワイヤ本体に積極的には添加する必要はないが、ワイヤ表面にCuめっきを施すと、防錆に大きな効果がある。ただし、Cu含有量が0.07%未満の場合、防錆効果が小さく、また、Cu含有量が0.40%を超えると、ワイヤ送給性が低下する。そこで、本実施形態のソリッドワイヤでは、Cuめっきなどを施す場合は、Cu含有量を0.07~0.40%とすることが好ましい。
Vは、析出強化により、少量の添加で強度、特に耐力を上昇させる元素であるため、必要に応じて添加することができる。ただし、V含有量が0.019%を超えると、溶接金属の強度が上昇し、低温靭性が低下すると共に、残留オーステナイトの生成を阻害するため、必要な残留オーステナイト量が得られず耐水素脆化感受性が劣化する。よって、Vを添加する場合は、0.019%以下とする。
Zrは、Vと同様に、析出強化により、少量の添加で強度、特に耐力を上昇させる元素であるため、必要に応じて添加することができる。ただし、Zr含有量が0.050%を超えると、溶接金属の強度が上昇し、低温靭性が低下すると共に、残留オーステナイトの生成を阻害するため、必要な残留オーステナイト量が得られず、耐水素脆化感受性が劣化する。よって、Zrを添加する場合は、0.050%以下とする。
Tiは、V及びZrと同様に、析出強化により、少量の添加で強度、特に耐力を上昇させる元素であるため、必要に応じて添加することができる。ただし、Ti含有量が0.010%を超えると、溶接金属の強度が上昇し、低温靭性が低下すると共に、残留オーステナイトの生成を阻害するため、必要な残留オーステナイト量が得られず耐水素脆化感受性が劣化する。よって、Tiを添加する場合は、0.010%以下とする。
Bは、旧オーステナイト粒界からのフェライト生成を抑制し、溶接金属の強度を向上させる効果がある。ただし、B含有量が0.0050質量%を超えると、溶接金属の強度が著しく上昇し、耐水素脆化感受性が劣化する。よって、Bを添加する場合は、0.0050%以下とする。
本実施形態のソリッドワイヤにおける残部は、Fe及び不可避的不純物である。なお、本実施形態のソリッドワイヤにおける不可避的不純物としては、O、N、Al、Nb、Ca及びMgなどがある。
MgOは、フラックスの塩基度を高めると共に、脱酸剤として溶接金属中の酸素を抑える作用があるため、酸素低減に効果があり、更に、スラグの耐火性も高まる。ただし、フラックスのMgO含有量が25%未満の場合、この作用が発揮されない。また、MgO含有量が35%を超えるフラックスを用いると、スラグの剥離及びビード外観が劣化することがある。よって、フラックスのMgO含有量は、25~35%であることが好ましい。
Al2O3は、スラグ形成剤として作用し、ビードのスラグ剥離性を確保する効果がある。また、Al2O3は、アークの集中性及び安定性を高める働きもある。しかしながら、フラックスのAl2O3含有量が10%未満の場合、スラグ剥離性が劣化して、アークが不安定となり、溶接困難になることがある。また、フラックスのAl2O3含有量が20%を超えると、溶接金属中の酸素が増加し、靭性が劣化することがある。よって、フラックスのAl2O3含有量は、10~20%であることが好ましい。
CaF2は、一般的に知られている生成スラグの融点を調整するという作用に加えて、溶接金属中の酸素を低減させる効果も有する。しかしながら、フラックスのCaF2含有量が12%未満の場合、これらの効果が得られず、またフラックスのCaF2含有量が22%を超えると、アークが不安定になり、ビード外観が劣化し、またビード上にポックマークが発生することがある。よって、フラックスのCaF2含有量は、12~22%であることが好ましい。
SiO2は、スラグ形成剤としてビード外観及びビード形状を整える作用がある。しかしながら、フラックスのSiO2含有量が8%未満の場合、この効果が発揮されず、またフラックスのSiO2含有量が18%を超えると、溶接金属中の酸素が増加して、靭性が劣化することがある。よって、フラックスのSiO2含有量は、8~18%であることが好ましい。
金属炭酸塩は、溶接熱によりガス化し、アーク雰囲気中の水蒸気分圧を下げて、溶接金属中の拡散性水素量を低下させるアークのシールド効果を有する。しかしながら、フラックスの金属炭酸塩含有量が、CO2換算で、3%未満の場合、この効果が得られない。
CaOは、フラックスの塩基度を高め、溶接金属中の酸素低減に効果がある。しかしながら、フラックスのCaO含有量が10%未満の場合、この効果は発揮されない。また、フラックスのCaO含有量が15%を超えると、アーク安定性及びビード外観が劣化する。よって、フラックスのCaOは、10~15%であることが好ましい。
金属Siは、溶接金属中の酸素量を抑える脱酸効果を有している。しかしながら、フラックスの金属Si含有量が1%未満の場合、この効果が得られない。また、フラックスの金属Si含有量が4%を超えると、脱酸効果が向上せず、溶接金属のビード形状が劣化すると共に強度が上がり、靭性が低下する。よって、金属Si含有量は1~4%であることが好ましい。ここで、金属Siは、Fe-Si、Fe-Si-Mn合金などの形態で、フラックスに添加される。
フラックスにおける上記以外の成分は、金属炭酸塩におけるCO2換算値以外の成分、アルカリ金属酸化物及び不可避的不純物などである。
下記表1に示す化学成分組成のフラックス(F1~F9)、および下記表2、3に示す化学成分組成のワイヤ(W1~W52)を組み合わせて用い、下記の(A)溶接条件で溶接金属を作製した。表2、3の欄において「-」とは、無添加(含有せず)を意味する。
溶接方法:サブマージアーク溶接(SAW)
ワイヤ径:4.0mmφ
溶接母材:80キロ級厚鋼板(板厚:32mm)
開先形状:開先角が30°となるV形開先で、ルート間隔を13mmとして裏当て材を使用(図1参照)
極性:DCEP(直流逆極性)
入熱条件(電流-電圧-速度):
(ア)500A-29V-40cpm(2.2kJ/mm)
(イ)550A-30V-40cpm(2.5kJ/mm)
(ウ)550A-30V-36cpm(2.8kJ/mm)
(エ)580A-32V-36cpm(3.1kJ/mm)
積層法:9層19パス
予熱-パス間温度:140~160℃
得られた溶接金属の中央部より、溶接方向に平行に図2に示す引張試験片を採取し、JIS-Z2241に準拠して引張試験を実施した。そして引張強度TSが780MPaを超えるものを合格とした。
得られた溶接金属の最終パス原質部を鏡面研磨し、レペラ試薬で腐食させ、光学顕微鏡にて1000倍の画像を2視野撮影した。残留オーステナイト粒子の白い腐食コントラストを、画像解析ソフト(「Image-Pro Plus」 Media Cybernetics社製)により解析し、円相当直径が0.15μm以上の大きさの残留オーステナイト粒子の個数密度を算出した。
得られた溶接金属の最終パス原質部について、その表面を電解研磨し、リガク社製の二次微小部X線回折装置(「RINT-RAPIDII」)にてX線回折測定を実施した。フェライト相の(110)、(200)、(211)、(220)の各格子面のピーク、および残留オーステナイト相の(111)、(200)、(220)、(311)の各格子面のピークについて、各ピークの積分強度比に基づき、残留オーステナイト相の(111)、(200)、(220)、(311)の体積分率をそれぞれ算出し、これらの平均値(算術平均)を求め、これを「残留オーステナイト相の体積分率」とした。
得られた溶接金属の中央部より、溶接方向に平行に図3に示す大型試験片を採取し、下記条件(B)で水素チャージを行なった。
水溶液:1L中にNaCl(30g)とKSCN(1g)を溶解した溶液
電流密度:0.1A/dm2
チャージ時間:100時間
(C)めっき条件
水溶液:1L中に、ZnSO4・7H2O(350g)、97%のH2SO4(20.6g)およびNa2SO4(60g)を溶解した溶液
浴温:60℃
電流密度:50A/dm2
めっき時間:3分
ここでは、好ましいワイヤ組成の検証を行った。
実施例及び比較例の各ソリッドワイヤと、下記表9に示す焼結型フラックス(IIW塩基度BL=3.5)とを用いて、下記表10に示す組成の引張強さ780MPa級鋼板を母材とし、下記表11に示す条件にて溶接を行った。なお、下記表10に示す鋼板の成分組成における残部は、Fe及び不可避的不純物である。
溶接金属中央で板厚中央の位置から、JIS Z3111のA1号試験片を採取し、この試験片を用いて、試験温度を室温(20~23℃)とし、引張試験を行った。その結果、引張強さが770MPa以上のものを合格とした。
溶接金属中央で板厚中央の位置から、JIS Z3111のVノッチ試験片を採取し、この試験片を用いて、試験温度を-60℃として、衝撃試験を行った。その結果、-60℃の吸収エネルギーが平均47J以上であったものを合格とした。
溶接金属の最終パス原質部について、その表面を電解研磨し、リガク社製の二次微小部X線回折装置 RINT-RAPIDIIによりX線回折測定を実施した。その結果から、フェライト相の(110)、(200)、(211)、(220)の各格子面のピーク及び残留オーステナイト相の(111)、(200)、(220)、(311)の各格子面のピークについて、各ピークの積分強度比に基づき、残留オーステナイト相の(111)、(200)、(220)、(311)の体積分率をそれぞれ算出した。そして、これらの平均値(算術平均)を求め、これを「残留オーステナイト相の体積分率」とした。
溶接金属の中央部から、溶接方向に平行にJIS Z3111のA0号試験片を採取し、下記(A)に示す条件で水素チャージを行った後、水素の逃散を防ぐために下記(B)に示す条件で亜鉛めっきを施した。この試験片を用いて、クロスヘッド速度を3.0×10-2mm/分(歪速度:6.94×10-6/秒)としてSSRT試験(低歪速度引張試験)を実施した。その結果、試験片の破断伸びが2.0%を超えたものを、「耐水素脆化感受性に優れる」と評価した。
・処理溶液:水1L中にNaCl:30gとKSCN:1gとを溶解した水溶液
・電流密度:0.1A/dm2
・チャージ時間:100時間
・めっき液:水1L中にZnSO4・7H2O:350g、97体積%のH2SO4:20.6g及びNa2SO4:60gを溶解した水溶液
・浴温:60℃
・電流密度:50A/dm2
・めっき時間:3分間
本出願は、2013年1月11日出願の日本特許出願(特願2013-004074)、2013年10月31日出願の日本特許出願(特願2013-226438)に基づくものであり、その内容はここに参照として取り込まれる。
Claims (6)
- C :0.02~0.12%(「質量%」の意味。化学成分組成について、以下同じ)、
Si:0.18~2.00%、
Mn:0.90~2.5%、
Ni:1.0~3.5%、
Cr:0.3~2.0%、
Al:0.030%以下(0%を含まない)、
N :0.015%以下(0%を含まない)、および
O :0.050%以下(0%を含まない)を夫々含有し、
残部が鉄および不可避的不純物からなり、
円相当直径が0.15μm以上の残留オーステナイト粒子を2500個/mm2以上含有し、残留オーステナイト相の体積分率が、組織全体に対して4.3%以上であり、
CrとMnの含有量の比[Cr]/[Mn]が0.20以上であることを特徴とする耐水素脆化感受性に優れた溶接金属。 - 更に、Mo:0.95%以下(0%を含まない)、Ti:0.040%未満(0%を含まない)、V:0.60%以下(0%を含まない)、Cu:1.0%以下(0%を含まない)、Zr:0.10%以下(0%を含まない)及びB:0.0050%以下(0%を含まない)の少なくとも1種を含有する請求項1に記載の溶接金属。
- サブマージアーク溶接によって形成されたものである請求項1または2に記載の溶接金属。
- ワイヤ全質量あたり、
C :0.07~0.20%、
Si:0.05~1.60%、
Mn:1.30~3.20%、
Ni:1.00~3.70%、
Cr:0.3~2.2%、
Mo:2.0%以下(0%を含む)
を含有し、残部がFe及び不可避的不純物からなるサブマージアーク溶接用ソリッドワイヤ。 - 更に、Cu:0.07~0.40%、V:0.019%以下、Zr:0.050%以下、Ti:0.010%以下及びB:0.0050%以下の少なくとも1種を含有する請求項4または5に記載のサブマージアーク溶接用ソリッドワイヤ。
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KR1020157017743A KR101747574B1 (ko) | 2013-01-11 | 2014-01-10 | 내수소취화 감수성이 우수한 용접 금속 및 서브머지드 아크 용접용 솔리드 와이어 |
US14/649,712 US20150314400A1 (en) | 2013-01-11 | 2014-01-10 | Weld metal with excellent resistance to hydrogen embrittlement, and solid wire for submerged arc welding |
EP14738291.5A EP2944417A4 (en) | 2013-01-11 | 2014-01-10 | WELDED METAL WITH EXCELLENT RESISTANCE TO HYDROGEN PRESSURE AND FULL WIRE FOR UNDERPULSE WELDING |
RU2015133463A RU2618036C2 (ru) | 2013-01-11 | 2014-01-10 | Металл сварного шва с повышенной устойчивостью к водородному охрупчиванию и проволока сплошного сечения для дуговой сварки под флюсом |
CN201480004350.3A CN104955608B (zh) | 2013-01-11 | 2014-01-10 | 耐氢脆化敏感性优异的焊接金属和埋弧焊用实芯焊丝 |
CA2892428A CA2892428A1 (en) | 2013-01-11 | 2014-01-10 | Weld metal with excellent resistance to hydrogen embrittlement, and solid wire for submerged arc welding |
SG11201504087XA SG11201504087XA (en) | 2013-01-11 | 2014-01-10 | Weld metal with excellent resistance to hydrogen embrittlement, and solid wire for submerged arc welding |
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JP2018187640A (ja) * | 2017-05-01 | 2018-11-29 | 株式会社神戸製鋼所 | アーク溶接方法及び溶接ワイヤ |
US11529697B2 (en) * | 2017-09-29 | 2022-12-20 | Lincoln Global, Inc. | Additive manufacturing using aluminum-containing wire |
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EP2944417A1 (en) | 2015-11-18 |
RU2618036C2 (ru) | 2017-05-02 |
KR20150087425A (ko) | 2015-07-29 |
CA3023415A1 (en) | 2014-10-01 |
EP2944417A4 (en) | 2016-08-24 |
CN104955608B (zh) | 2018-04-27 |
KR101747574B1 (ko) | 2017-06-14 |
RU2015133463A (ru) | 2017-02-16 |
SG11201504087XA (en) | 2015-09-29 |
US20150314400A1 (en) | 2015-11-05 |
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