JP2010227949A - Weld metal and welding material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a weld metal capable of obtaining the high strength through the heat treatment after the welding in a short period of time, and having excellent weld cracking resistance. <P>SOLUTION: The weld metal has a composition composed of 0.16-0.35% C, ≤0.5% Si, ≤2.0% Mn, 18-38% Ni, 9-22% Cr, 2.0-6.0% Ti, 0.05-0.65% Al, 0.1-0.6% V, and ≤0.15% N, and the balance Fe with inevitable impurities, while ≤0.02% O, P and S, ≤0.01% P and ≤0.01% S are contained in the inevitable impurities. The weld metal may contain ≤5% Nb. The Vickers hardness of the weld metal is preferably ≥320. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a weld metal and a weld material. Specifically, it is used for welding steel and austenitic materials that are used as materials for various components such as high-pressure gas pipes in energy transportation equipment, especially for high-strength steel and austenitic materials. The present invention relates to a welding material capable of obtaining a weld metal excellent in “weld crack resistance” and a weld metal of the welded member.

  In recent years, research on practical application of transportation equipment using hydrogen, natural gas, or the like as energy has been actively promoted. For practical use, it is necessary to prepare an environment in which these gases can be stored and transported at high pressures, and the materials used are required to have high strength. Has been made.

  For example, with respect to the base material, an austenite-based material has been proposed in which the solubility of N is increased by increasing the Mn content, V is added, and an appropriate heat treatment is performed as necessary to increase the strength. Yes. Specifically, Patent Document 1 and Patent Document 2 disclose a high-strength material having a tensile strength of 1 GPa or more that can be used as a material for a high-pressure gas storage and transport member.

  In general, when used as a structure, the above-described high-strength austenitic material is assembled by welding. And it is possible to use a base material as it is as a welding material in the case of welding.

  However, austenitic weld metals generally have high hot cracking susceptibility during welding. For this reason, the weld metal is required to prevent hot cracking. In addition, in the case of a base material, the structure is adjusted by rolling and heat treatment after melting, and high temperature strength is ensured. On the other hand, weld metal is almost always used in a solid structure.

  Therefore, when the base material is used as a welding material as it is, not only the hot cracking resistance is sufficient, but it is extremely difficult to obtain a high strength equivalent to that of the base material. For this reason, it is necessary to reinforce the weld metal at least as much as the base material by precipitating fine particles by performing “post heat treatment” after welding.

  As a welding material having a tensile strength of 1 GPa or more, for example, ERNiFeCr-2 of AWS A5.14-2005 has already been put into practical use. Patent Document 3 and Patent Document 4 propose a welding material (welded metal) having a tensile strength exceeding 800 MPa by actively utilizing Al, Ti, and Nb. Patent Document 4 also shows that solidification cracking can be prevented by containing an appropriate amount of Ti and / or Al.

  However, in order to increase the strength of these welding materials as well, it is necessary to perform “post heat treatment” for at least 120 minutes after welding. Therefore, when an actual large structure is considered, the long-time post-weld heat treatment as described above is greatly restricted in its application and the manufacturing cost is extremely increased.

WO 2004/083476 WO2004 / 083477 JP-A-5-192785 WO2004 / 110695 publication

  The present invention has been made in view of the above situation, and forms a weld metal having high strength obtained by a short post-weld heat treatment and also having excellent weld crack resistance, and such a weld metal. In particular, a welded structure using as a base material a high-strength steel or high-strength austenitic material having a tensile strength of 1 GPa or more, which has been developed in recent years. Another object of the present invention is to provide a welding material that can also be applied to welding of a weld metal that can also be configured and the high-strength base metal.

  The present inventors have conducted various studies in order to solve the above-described problems. As a result, the following knowledge (a) was obtained.

(A) In order to achieve high strength in the weld metal, the content of Ni is restricted to a specific range, Ti and Al are contained, and post-weld heat treatment is performed, whereby Ni ₃ Ti or Ni ₃ ( It is effective to utilize precipitation strengthening by Al, Ti). However, even when these elements are contained in a large amount, a long post-weld heat treatment is required to achieve high strength.

  Therefore, in order to achieve both high strength in post-weld heat treatment in a short time, in particular, a short time of 120 min or less and “weld crack resistance” as weldability, the present inventors first include Ti. Investigation and examination were conducted with various amounts. In addition, about the weld metal in this case, while containing 18 to 38% Ni by mass%, it was supposed to contain 0.1 to 0.6% V by mass%.

  As a result, the following items (b) and (c) were clarified.

(B) When Ti is contained in an amount of 2.0 to 6.0% by mass, Ni ₃ Ti precipitates finely in the matrix and increases the strength when heat treatment after welding is performed.

(C) When Ti is contained alone, long-time heat treatment is required to obtain the precipitation strengthening effect by the above-described Ni ₃ Ti. In addition, “solidification cracks” and “ductility degradation cracks” tend to occur in the weld metal.

  Therefore, various investigations and examinations were conducted on the influence of various elements when Ti was contained in an amount of 2.0 to 6.0% by mass. As a result, the following important knowledge (d) was obtained.

  (D) For a weld metal containing 18 to 38% Ni in mass%, in order to achieve both high strength in a short post-weld heat treatment and “weld crack resistance” as weldability, mass% In addition, Ti is contained in an amount of 2.0 to 6.0%, and the contents of C, Cr, and Al are, respectively, by mass, C: 0.16 to 0.35%, Cr: 9 to 22% And Al: 0.05 to 0.65% is necessary.

  The reason for the above (d) is considered as the following <1> to <6>.

By containing 0.05% or more of Al at <1>% by mass, Ni ₃ (Al, Ti) as a transition phase precipitates in a short time, and then becomes Ni ₃ Ti as the final stable phase. Therefore, the strength is improved by a shorter heat treatment.

  <2> However, when only the above-mentioned amounts of Al and Ti are contained, in particular, Ti is an element that easily solidifies and segregates during solidification of the weld metal, so that the solidification cracking sensitivity is greatly increased.

<3> By containing C and Cr, eutectic solidification of M ₂₃ C ₆ and austenite, which dissolves Ti in the solidification process of the weld metal, is generated, and the disappearance of the liquid phase at the end of solidification is promoted. Since the amount of harmful Ti that solidifies and segregates in the phase and lowers the melting point is reduced, solidification cracking can be prevented.

<4> M ₂₃ C ₆ crystallized during solidification exists after a solidification by forming austenite and a layered structure at the dendrite boundary. For this reason, the segregation of impurity elements is reduced by increasing the final solidification interface area. In addition, since stress concentration on a specific surface is also reduced, it has an effect of preventing ductile deterioration cracks caused by stress acting on the grain boundaries where the impurity elements are segregated and weakened.

<5> However, when a large amount of Ti is dissolved in M ₂₃ C ₆ , the driving force for precipitation of Ni ₃ Ti or Ni ₃ (Al, Ti) decreases, and a long-time heat treatment is required. Further, by crystallizing M ₂₃ C ₆ , it is possible to prevent solidification cracking and ductile deterioration cracking, but M ₂₃ C ₆ is poor in ductility compared to the austenite phase that is a matrix, and therefore, ductility in weld metal. A decrease occurs.

  <6> From the above-mentioned viewpoint, it is necessary to adjust the contents of C and Cr to a specific range, that is, in mass%, C: 0.16-0.35% and Cr: 9-22%. .

  The present invention has been completed based on the above findings, and the gist thereof lies in the weld metal shown in the following (1) and the weld material shown in (2).

  (1) By mass%, C: 0.16-0.35%, Si: 0.5% or less, Mn: 2.0% or less, Ni: 18-38%, Cr: 9-22%, Ti: 2.0 to 6.0%, Al: 0.05 to 0.65%, V: 0.1 to 0.6% and N: 0.15% or less, with the balance being Fe and impurities, and A weld metal characterized in that O, P and S in the impurities are O: 0.02% or less, P: 0.01% or less and S: 0.01% or less, respectively.

  The “impurities” in the remaining “Fe and impurities” refer to materials that are mixed due to raw materials such as ores or scraps and other various factors when industrially producing metal materials.

  The above weld metal can include Nb: 5% or less in mass%, instead of a part of Fe in “Fe and impurities” as the balance.

  The weld metal preferably has a Vickers hardness (hereinafter referred to as “HV hardness”) of 320 or more.

  The “welded metal” refers to a portion where a part of the base metal and the welding material are melted and solidified during welding.

  (2) By mass%, C: 0.16-0.35%, Si: 0.5% or less, Mn: 2.0% or less, Ni: 18-38%, Cr: 9-22%, Ti: 2.0 to 6.0%, Al: 0.05 to 0.65%, V: 0.1 to 0.6% and N: 0.15% or less, with the balance being Fe and impurities, and O, P, and S in the impurities are O: 0.02% or less, P: 0.01% or less, and S: 0.01% or less, respectively.

  As described above, “impurities” in the remaining “Fe and impurities” refer to materials mixed by raw materials such as ore or scrap and other various factors when industrially producing metal materials.

  This welding material can contain Nb: 5% or less in mass% instead of a part of Fe in “Fe and impurities” as the balance.

  Here, welding is performed on a member to be welded using the “welding material” in (2) above (in other words, the base material of the “welded structure”) or the base material of the “welded structure”. When the high-strength austenitic material or high-strength steel having a tensile strength of 1 GPa or more is used as the base material when the “welded metal” of the above (1) is formed, the present invention The base material may be in any shape as long as the effectiveness of the material is remarkably recognized and it can be used for welding joining such as plate, rod or tube.

  Since the weld metal of the present invention can ensure high strength by a short post-weld heat treatment and has excellent weld cracking resistance, the welded structure having the weld metal of the present invention is energy transport. It can be suitably used as various welding members such as high-pressure gas piping in equipment. The weld metal of the present invention can be obtained by welding using the welding material of the present invention.

It is a figure explaining the groove shape given to the longitudinal direction of the steel plate for welding base materials used in the Example.

  Hereinafter, the effect of each component element contained in the weld metal and the weld material of the present invention and the reason for limiting the content thereof will be described without distinguishing between the weld metal and the weld material. In the following description, “%” display of the content of each element means “mass%”.

C: 0.16-0.35%
C is an element related to the basis of the present invention together with Ti, Al, and Cr, and has an effect of preventing solidification cracking and ductile deterioration cracking. That is, C combines with Cr, Ti, etc. to produce eutectic carbides when the weld metal solidifies, thereby accelerating the disappearance of the liquid phase, and the structure of the final solidified portion is a layered structure of M ₂₃ C ₆ and austenite. Organization. As a result, the residual form of the liquid phase changes from a planar shape to a point shape, stress concentration on a specific surface is suppressed, and the final solidification interface area that becomes a segregation site of impurities increases, so that solidification cracking and ductility Decline cracking can be prevented. In order to sufficiently obtain the above C effect, a C content of 0.16% or more is necessary. On the other hand, if the content of C becomes excessive, especially exceeding 0.35%, C that does not become carbide during solidification increases, and on the contrary, the melting point of the liquid phase decreases and the solidification cracking susceptibility increases. Furthermore, since a large amount of carbide is formed, the ductility of the weld metal is reduced, and the amount of Ti present as the carbide increases, so that the precipitation driving force of Ni ₃ Ti or Ni ₃ (Al, Ti) contributing to strengthening is increased. A decrease occurs. Therefore, the C content is 0.16 to 0.35%. The desirable lower limit of the C content is 0.18%, and the desirable upper limit is 0.32%.

Si: 0.5% or less Si is added as a deoxidizer. However, if the Si content increases and exceeds 0.5%, it segregates at the columnar grain boundaries during solidification of the weld metal, lowers the melting point of the liquid phase, and increases the susceptibility to solidification cracking. Therefore, the Si content is 0.5% or less. The Si content is desirably 0.4% or less, and more desirably 0.3% or less. In addition, although it is not necessary to set a minimum in particular about content of Si, excessive reduction leads to the increase in manufacturing cost while the deoxidation effect is not fully acquired but the cleanliness of an alloy falls. Therefore, the desirable lower limit of the Si content is 0.01%. If at least 0.01% of Si is contained, a deoxidizing effect can be obtained.

Mn: 2.0% or less Mn is added as a deoxidizer in the same manner as Si. However, if the Mn content increases and exceeds 2.0%, ductility and toughness are reduced. Therefore, the Mn content is set to 2.0% or less. The Mn content is desirably 1.8% or less, and more desirably 1.6% or less. In addition, although it is not necessary to set a minimum in particular about content of Mn, excessive reduction will not obtain the deoxidation effect enough, but will cause the increase in manufacturing cost while the cleanliness of an alloy falls. Therefore, the desirable lower limit of the Mn content is 0.01%. If at least 0.01% of Mn is contained, a deoxidizing effect can be obtained.

Ni: 18-38%
Ni is an element that not only obtains a stable austenite structure but also finely disperses as Ni ₃ (Al, Ti) or Ni ₃ Ti and has a function of greatly improving the strength of the weld metal. In order to obtain the above Ni effect, a Ni content of 18% or more is necessary. On the other hand, if the Ni content increases and exceeds 38%, embrittlement may occur depending on the type of gas contact environment. Therefore, the Ni content is 18 to 38%. The desirable lower limit of the Ni content is 20%, and the desirable upper limit is 35%.

Cr: 9-22%
Cr is an element that has the effect of improving the corrosion resistance, and is an element related to the basis of the present invention together with C, Ti, and Al, and has an action of preventing solidification cracking and ductile deterioration cracking. That is, Cr causes eutectic solidification of M ₂₃ C ₆ that dissolves Ti and austenite in the solidification process of the weld metal, promotes the disappearance of the liquid phase at the end of solidification, and solidifies and segregates in the liquid phase. It has the effect of preventing solidification cracking by reducing the amount of harmful Ti that lowers the melting point. In addition, the above-mentioned M ₂₃ C ₆ exists after forming austenite and a layered structure at the dendrite boundary after solidification, so that segregation of impurity elements and stress concentration on a specific surface are reduced, resulting in reduced ductility. Cracking can be prevented. Ni ₃ Ti and Ni ₃ (Al, Ti), which contributes to strengthening by heat treatment after welding for a short time, are deposited while ensuring these effects sufficiently and making the solid solution amount of Ti in M ₂₃ C ₆ appropriate. In order to achieve this, the Cr content needs to be 9% or more in the Ni content range of 18 to 38% of the present invention. However, when the content of Cr is excessive and exceeds 22%, a large amount of M ₂₃ C ₆ is generated and the weld metal ductility is lowered. Therefore, the Cr content is 9 to 22%. The desirable lower limit of the Cr content is 11%, and the desirable upper limit is 20%.

Ti: 2.0-6.0%
Ti is an element related to the basis of the present invention together with C, Al and the like. That is, Ti precipitates finely as Ni ₃ Ti or Ni ₃ (Al, Ti) and has the effect of increasing the strength of the weld metal. Furthermore, the weld metal can be strengthened to some extent by precipitation of Ti in the grains as fine carbonitride. In order to obtain the above Ti effect, a Ti content of 2.0% or more is necessary. However, when the Ti content becomes excessive and exceeds 6.0%, the above-described strengthening effect is saturated, and Ni ₃ Ti or Ni ₃ (Al, Ti) is coarsened, resulting in a decrease in weld metal ductility. Invite. Therefore, the content of Ti is set to 2.0 to 6.0%. The desirable lower limit of the Ti content is 2.5%, and the desirable upper limit is 5.5%.

Al: 0.05 to 0.65%
Al is one of the elements according to the present invention together with Ti and the like. That is, by containing Al, Ni ₃ (Al, Ti) as a transition phase leading to Ni ₃ Ti, which is the final stable phase, is generated, and as a result, the strength of the weld metal can be improved by a short post-weld heat treatment. To. In order to obtain this effect, an Al content of 0.05% or more is necessary. However, if the Al content becomes excessive and exceeds 0.65%, it will float as oxidized slag during welding, so the effect will be saturated, and the aesthetics and welding workability of the weld bead will be impaired. become. Therefore, the Al content is 0.05 to 0.65%. The desirable lower limit of the Al content is 0.10%, and the desirable upper limit is 0.60%.

V: 0.1-0.6%
V is an element having an action of strengthening the weld metal by being precipitated in the grains as fine carbonitride. In order to obtain this effect, a V content of 0.1% or more is necessary. However, if the content of V is excessive and exceeds 0.6%, the above effects are saturated and the cost is increased, and the strengthening effect may be impaired due to coarsening of carbonitrides. is there. Therefore, the V content is 0.1 to 0.6%. The desirable lower limit of the V content is 0.15%, and the desirable upper limit is 0.55%.

N: 0.15% or less N is an element having an action of increasing the strength of the weld metal by forming a fine nitride while forming a solid solution in the matrix. However, if the N content becomes excessive and exceeds 0.15%, it precipitates as TiN or AlN and suppresses the precipitation of Ni ₃ (Al, Ti) and Ni ₃ Ti necessary for increasing the strength. . Therefore, the N content is 0.15% or less. In addition, although there is no need to set a lower limit in particular for the N content, an extreme reduction causes a significant increase in steelmaking costs. Therefore, the desirable lower limit of the N content is 0.001%. If at least N is contained by 0.001%, an effect of improving the strength can be obtained.

  One of the weld metals of the present invention has a chemical composition in which the balance is composed of Fe and impurities in addition to the elements described above. One of the welding materials of the present invention also has a chemical composition in which the balance is composed of Fe and impurities in addition to the elements described above.

  As already described, the “impurities” in the remaining “Fe and impurities” refer to materials that are mixed due to raw materials such as ore or scrap and other various factors when industrially producing metal materials. In addition, content regulation of the specific element in an impurity is mentioned later.

  The other one of the weld metal and welding material of the present invention has a chemical composition containing 5% or less of Nb in place of a part of Fe in the “Fe and impurities” as the balance. is there.

  Hereinafter, the effect of Nb which is an arbitrary element and the reason for limiting the content will be described.

Nb: 5% or less Nb precipitates finely as Ni ₃ Nb and has the effect of increasing the strength of the weld metal. Furthermore, the weld metal can be strengthened to some extent when Nb is precipitated in the grains as fine carbonitride. Therefore, you may contain Nb for intensity | strength increase. However, even if Nb is contained in an amount exceeding 5%, the above effect is saturated and the cost is increased. Therefore, the content when Nb is contained is set to 5% or less. The Nb content is preferably 4% or less.

  On the other hand, in order to reliably obtain the above-described effect of improving the strength of Nb, the lower limit of the Nb content is preferably 0.1%, and more preferably 0.5%.

  Next, the content restriction of the impurity element will be described.

  In the weld metal and the weld material of the present invention, the contents of O, P and S in the impurities are regulated as follows.

O: 0.02% or less O exists as an impurity, and when it is contained in a large amount, the workability of the welding material and the ductility of the weld metal are deteriorated. Therefore, it is preferable to reduce the O content as much as possible. However, if the content is 0.02% or less, no remarkable deterioration is observed in the characteristics of the weld metal or the weld material of the present invention. Therefore, the content of O is set to 0.02% or less.

P: 0.01% or less P is contained as an impurity, and lowers the melting point of the final solidified portion during solidification of the weld metal, and remarkably increases the susceptibility to solidification cracking. Furthermore, it segregates at the grain boundaries and increases the susceptibility to ductile drop cracking. Therefore, it is preferable to reduce the P content as much as possible. However, extreme reduction of the P content leads to an increase in steelmaking cost, and if it is 0.01% or less, the weld metal or welding material of the present invention. There is no noticeable deterioration in the characteristics. Therefore, the P content is 0.01% or less.

S: 0.01% or less S is contained as an impurity in the same manner as P, and lowers the melting point of the final solidified portion during solidification of the weld metal, and remarkably increases the susceptibility to solidification cracking. Furthermore, it segregates at the grain boundaries and increases the susceptibility to ductile drop cracking. Therefore, it is preferable to reduce the S content as much as possible. However, as in the case of P, the extreme reduction of the S content leads to an increase in steelmaking costs. There is no noticeable deterioration in the characteristics of the weld metal or welding material of the invention. Therefore, the S content is 0.01% or less.

  In addition, as a welded structure, the chemical composition of the “welded metal” obtained as a result of melting and mixing a part of the base material and the welding material only needs to satisfy the above-described requirements. For this reason, the chemical composition of the “welding material” needs to be selected according to the chemical composition of the “base metal” used, but the “base metal dilution” defined as “the ratio of the base metal composition in the composition of the weld metal” The “rate” varies depending on the groove shape, welding method and welding conditions, but is generally about 30 to 60%. Therefore, in the chemical composition range of the welding material described in (2) above, it is desirable to select the composition of the welding material in consideration of dilution by the base material.

  As the base material, a high-strength material having a tensile strength of 1 GPa or more is suitable, and the shape may be any shape as long as it can be used for welding joining such as a plate shape, a rod shape, or a tubular shape. It is as already mentioned that there is nothing.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these Examples.

  A steel plate having a thickness of 10 mm, a width of 50 mm, and a length of 100 mm is welded to a weld mother from an ingot in which a material having the chemical composition shown in Table 1 is melted and cast in a laboratory by hot forging, hot rolling, heat treatment and machining. It was produced as a material.

  Further, from the same ingot, a welding wire (welding material) having an outer diameter of 1.2 mm and a length of 1000 mm was produced by hot forging, hot rolling and machining.

  It is described in JIS Z 3224 (1999) on a commercially available SM400A steel plate having a thickness of 25 mm, a width of 200 mm, and a length of 200 mm by performing the groove processing shown in FIG. Further, four-circle restraint welding was performed using a coated arc welding rod of “DNiCrFe-3”.

  Next, the average heat input by TIG welding is performed using the above-described welding wire having an outer diameter of 1.2 mm, which has the same chemical composition as that of the steel sheet for the weld base material, in the groove formed on the steel sheet for the weld base material. Multi-layer welding was performed at about 10 kJ / cm. In addition, since it is restrained in the case of this TIG welding, the thermal stress by welding arises and it becomes easy to generate | occur | produce a crack.

  After welding, a micro test piece, a side bend test piece and an aging hardness test piece having a weld metal part at the center were collected and used for each test.

  The micro test piece was mirror-finished by buffing, and then all the weld metal parts were observed with an optical microscope at a magnification of 100 to 500 times, and the occurrence of "solidification cracking" and "ductility-reducing cracking" was observed. . The target was that neither “solidification cracking” nor “ductility degradation cracking” occurred.

  The side bend specimen was bent 180 ° with a bending radius twice the plate thickness, and the presence or absence of cracks in the weld metal and the ductility were examined. The goal was to prevent cracking.

  In addition, an aging hardness test piece was used to perform an aging heat treatment simulating post-weld heat treatment, and a test force was set to 98 N, and an HV hardness test was performed. The aging heat treatment is performed at a temperature of 750 ° C. for 1 to 180 minutes, and it is necessary to reach the HV hardness 320 corresponding to 1 GPa which is the target tensile strength of the weld metal from the conversion formula described in ASTM E140. Aging time was investigated. And it aimed at aging time being 120 min or less.

  Table 2 shows the observation results of occurrence of “solidification cracks” and “ductility-reducing cracks” in micro test pieces, observation results of occurrence of cracks in side bending test pieces, and HV hardness 320 when aging heat treatment is performed at 750 ° C. Indicates the time required to reach.

  From Table 2, in the case of steel whose chemical compositions in test numbers 1 to 5 are within the range specified by the present invention, a sound welded joint free from solidification cracking and ductile deterioration cracking is obtained, and it has sufficient bending ductility. Is clear. In addition, the HV hardness of the weld metal becomes 320 or more by a short aging heat treatment of 60 min or less, and it can be seen that the weld metal can be strengthened by a short post-weld heat treatment.

On the other hand, in the case of the steel in which the C and Ti contents in Test No. 6 deviate from the range specified in the present invention, solidification cracks and ductile deterioration cracks occurred, and cracks occurred in the side bend specimens. The bending ductility was also inferior. This is based on the fact that the amount of M ₂₃ C ₆ produced is small, the effect of promoting the disappearance of the liquid phase during the solidification process cannot be obtained, and the dispersion of the impurity elements due to the increase in segregation sites is not sufficient. Furthermore, in the case of the steel in this test number 6, since the Ti content was below the range specified in the present invention, the target hardness of the weld metal could not be obtained even after aging heat treatment for 180 minutes.

  In the case of steel in which the Al content in the test number 7 is out of the range specified in the present invention, the weld metal is hardened to a target hardness of HV320 by aging heat treatment at 750 ° C., but a long aging heat treatment of 180 min is required. there were.

In the case of steel in which the C content in Test No. 8 deviated from the upper limit specified in the present invention, the side bending test piece was cracked and inferior in bending ductility. This is based on the formation of excess M ₂₃ C ₆ .

  The weld metal of the present invention can ensure high strength by a short post-weld heat treatment and has excellent weld crack resistance. For this reason, the welding structure which has the weld metal of this invention can be used suitably as various welding members, such as high-pressure gas piping in an energy transport apparatus. The weld metal of the present invention can be obtained by welding using the welding material of the present invention.

Claims (5)

  In mass%, C: 0.16-0.35%, Si: 0.5% or less, Mn: 2.0% or less, Ni: 18-38%, Cr: 9-22%, Ti: 2.0 -6.0%, Al: 0.05-0.65%, V: 0.1-0.6% and N: 0.15% or less, with the balance being Fe and impurities, and in impurities The weld metal according to claim 1, wherein O, P and S are respectively O: 0.02% or less, P: 0.01% or less and S: 0.01% or less.   2. The weld metal according to claim 1, wherein the weld metal contains Nb: 5% or less in mass% instead of a part of Fe as the balance.   The weld metal according to claim 1 or 2, wherein the Vickers hardness is 320 or more.   In mass%, C: 0.16-0.35%, Si: 0.5% or less, Mn: 2.0% or less, Ni: 18-38%, Cr: 9-22%, Ti: 2.0 -6.0%, Al: 0.05-0.65%, V: 0.1-0.6% and N: 0.15% or less, with the balance being Fe and impurities, and in impurities A welding material characterized in that O, P, and S are O: 0.02% or less, P: 0.01% or less, and S: 0.01% or less, respectively.   It replaces with a part of Fe as remainder, and contains Nb: 5% or less by mass%, The welding material of Claim 4 characterized by the above-mentioned.

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