JP2017177111A - Steel member welding method and welding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably and easily weld a steel member on site. SOLUTION: The total content of at least one element of aluminum, silicon, copper, manganese, and chromium is 5% by weight or less, and boron, tungsten, chromium, molybdenum, niobium, vanadium, hafnium, zirconium, titanium, cobalt, TIG welding or laser welding is performed using a welding material containing at least one element of copper and carbon in an amount of 5% by weight or less in total and containing unavoidable impurities and nickel as the balance. [Selection diagram] Fig. 2

Description

  The present invention relates to a steel member welding method and a welding material.

  Since a steel structure provided in a power plant facility is placed at a high temperature, cracks may occur due to thermal stress applied at the time of starting and stopping.

  In welding performed for repairing such cracks, in order to reduce the thermal stress applied to the repaired part, first, preheating is first performed before welding, and then a welding material (CrMo cast steel or Welding is performed using a welding rod made of CrMoV cast steel or the like, and then heat treatment (post-weld heat treatment) is performed. For example, Patent Document 1 discloses a quenching process, a welding repair process performed after the quenching process, and a welding repair process as a heat treatment regeneration method that regenerates a deteriorated cast steel member that has been degraded by stress or heat. It describes that a tempering step to be performed later is provided.

JP 2009-167485 A

  Generally, advanced technology is required for temperature control of heat treatment in welding repair. However, since steel members such as steam turbine casings and valves are large, they cannot be transported to a repair shop for heat treatment and must be performed on site. For this reason, on-site temperature management becomes inadequate, and there is a possibility that cracks may occur in the repaired part due to rapid cooling of the welded part.

  This invention is made | formed in view of such a problem, The objective is to provide the welding method and welding material of the steel member for performing the welding of a steel member on the spot reliably and easily.

  One of the present invention for achieving the above-mentioned object is a method for welding a steel member, which contains at least one element selected from aluminum, silicon, copper, manganese, and chromium in an amount of 5% by weight or less. Welding containing at least one element of boron, tungsten, chromium, molybdenum, niobium, vanadium, hafnium, zirconium, titanium, cobalt, copper, and carbon in an amount of 5% by weight or less, with the remainder containing inevitable impurities and nickel TIG welding or laser welding is performed using the material.

  Thus, in the welding method of the steel member of the present invention, since the welding material mainly composed of nickel softer than the steel member as the base material is used, the base material welded and repaired thereby is exposed to a high temperature. Can effectively relieve thermal stress and perform reliable repair with high durability. There is no need to prepare a welding material of the same material as the base material for thermal stress countermeasures as in the past. Moreover, since the welding material of this invention is a raw material different from a base material which does not depend on the kind of base material, it is applicable even if what a steel member has what kind of composition.

  In the method for welding steel members of the present invention, as described above, an oxidation resistant element (aluminum, silicon, copper, manganese, or chromium) and a creep strength element (boron, tungsten, chromium, molybdenum, niobium, vanadium, Hafnium, zirconium, titanium, cobalt, copper, or carbon) is contained in an amount of 5% by weight or less, and a welding material in which the balance excluding inevitable impurities is nickel is used. Since the steel member welded with such a weight ratio of the welding material maintains ductility even at high temperatures, as a result, heat treatment during welding becomes unnecessary. Therefore, the process of moving a steel member to another place (for example, carrying to a factory) for heat processing is unnecessary. Furthermore, the steel member welded with such a welding material is excellent in oxidation resistance, has sufficient creep strength, and has high durability after repair.

  Moreover, in the welding method of the steel member of this invention, since welding is performed by TIG welding or laser welding, on-site repair is easy. Moreover, in these methods, the heat-affected zone due to welding is difficult to increase, and as a result, chemical and physical changes in the weld can be suppressed.

  Thus, according to the welding method of the steel member of this invention, a steel member can be reliably and easily repaired on-site without performing heat processing.

  In addition, it is preferable that the content rate of the said nickel is 90 weight% or more.

  Another aspect of the present invention is characterized in that after the TIG welding is performed, submerged arc welding or MIG welding is performed using the welding material.

  Like in the present invention, by using TIG welding together with MIG welding or submerged arc welding, large steel members such as piping provided in power plant facilities can be welded and repaired quickly and reliably. .

  Another aspect of the present invention is characterized in that the initial layer of the welding material is formed by the TIG welding, and then the layers after the initial layer are formed by the submerged arc welding or MIG welding.

  As in the present invention, the initial layer of the welding material is formed by TIG welding, and then the layers after the initial layer are formed by submerged arc welding or MIG welding. The repair members can be joined quickly by accurate joining and subsequent submerged arc welding or MIG welding. By doing in this way, even if a repair object is a large steel member, it can repair accurately and rapidly.

  Another aspect of the present invention is a welding material, which contains at least one element selected from the group consisting of aluminum, silicon, copper, manganese, and chromium in an amount of 5% by weight or less, and includes boron, tungsten, chromium, and molybdenum. Niobium, vanadium, hafnium, zirconium, titanium, cobalt, copper, and carbon are contained in an amount of 5 wt% or less, and the balance is inevitable impurities and nickel.

  According to the present invention, welding of a steel member can be reliably and easily performed on site.

It is a figure which shows the outer shell member 10 of a steam turbine casing. It is a figure explaining the component of the welding material of Example 1. FIG. 3 is a flowchart illustrating an example of a procedure of a welding repair method according to the first embodiment. It is a figure for demonstrating the process of S1. It is a figure for demonstrating the process of S2 and S3. It is a figure explaining an example of the welding method of piping concerning Example 2. FIG.

<Example 1: Welding repair of steam turbine casing>
FIG. 1 shows an outer shell member 10 of a steam turbine casing provided in a thermal power plant or a nuclear power plant. The outer shell member 10 is made of, for example, CrMo cast steel or the like, and receives thermal stress as it starts and stops. As a result, creep damage occurs in the outer shell member 10 and a crack 11 is generated on the surface thereof. Hereinafter, the welding method of the steel member of a present Example is demonstrated by taking as an example the case where this crack 11 is repaired by welding.
First, the welding material to be used will be described.

  FIG. 2 is a diagram for explaining the components of the welding material of the present embodiment. As shown in the figure, the welding material of the present example contains an element having an oxidation resistance (hereinafter referred to as an oxidation resistance element) of 5% by weight or less, an element for controlling the grain boundary and increasing the creep strength (hereinafter referred to as an oxidation resistance element). 5% by weight or less) (referred to as grain boundary element or creep strength element). The balance is inevitable impurities and nickel (Ni). The nickel content is preferably 90% by weight or more.

  The oxidation resistant element is, for example, aluminum (Al), silicon (Si), copper (Cu), manganese (Mn), chromium (Cr), etc., and in this embodiment, among these oxidation resistant elements As long as at least one is included.

Examples of the creep strength element include boron (B), tungsten (W), chromium (Cr), molybdenum (Mo), niobium (Nb), vanadium (V), hafnium (Hf), zirconium (Zr), and cobalt (Co ), Copper (Cu), and carbon (C). In this embodiment, at least one or more of these creep strength elements may be included.
Next, a welding repair method using such a welding material will be described.

  FIG. 3 is a flowchart for explaining an example of the procedure of the welding repair method of this embodiment. As shown in the figure, the crack 11 is first removed to form a recess (S1).

  Here, FIG. 4 is a figure for demonstrating the process of S1. As shown in the figure, first, the periphery of the crack 11, that is, the surface of the outer shell member 10 is cut to a predetermined depth so as to include all the cracks 11 extending from the surface of the outer shell member 10 to the inside thereof. The recess 12 is formed.

  Next, as shown in S2 of FIG. 3, the repair member is fitted into the recess 12 formed in S1. And this repair member and the outer shell member 10 are TIG (Tungsten Inert Gas) welded using the said welding material (S3).

  Here, FIG. 5 is a figure for demonstrating the process of S2 and S3. As shown in the figure, a repair member 13 having a shape corresponding to the recess 12 (for example, substantially the same shape as the recess 12) and molded into a lump is fitted into the recess 12. The material of the repair member 13 is, for example, a steel material that is the same as or close to that of the outer shell member 10. In this case, the surface of the repair member 13 may be ground so that the surface of the repair member 13 fitted therein is aligned with the surface of the outer shell member 10.

  And the welding rod 15 which consists of said welding material is heated and melted with the TIG welding machine 14, and the outer shell member 10 and the repair member 13 are joined. In addition, the temperature of a welding part is adjusted so that it may become about 1600 degreeC, for example.

  In addition, you may weld the outer shell member 10 and the repair member 13 by laser welding instead of TIG welding used here. For the laser welding, for example, a laser welding machine using a YAG (Yttrium-Aluminium-Garnet) laser or the like (a small one is preferable when working in the field) is used.

  Thus, in the welding method of the steel member of the present embodiment, a welding material mainly composed of nickel softer than the base material steel is used, so that the base material welded and repaired is exposed to a high temperature. Can effectively relieve thermal stress and perform reliable repair with high durability. There is no need to prepare a welding material of the same material as the base material for thermal stress countermeasures as in the past. Moreover, since the welding material of a present Example is a raw material different from a base material which does not depend on the kind of base material, it is applicable regardless of what composition a steel member has.

  Moreover, in the welding method of the steel member of the present embodiment, as described above, a welding material containing 5% by weight or less of each of the oxidation resistance element and the creep strength element and the balance excluding inevitable impurities is nickel is used. Yes. Since the steel member welded with such a weight ratio of the welding material maintains ductility even at high temperatures, as a result, heat treatment during welding becomes unnecessary. Therefore, the process of moving a steel member to another place (for example, carrying to a factory) for heat processing is unnecessary. Furthermore, the steel member welded with such a welding material is excellent in oxidation resistance, has sufficient creep strength, and has high durability after repair.

  Moreover, in the welding method of the steel member of a present Example, since it welds by TIG welding or laser welding, repair on the spot is easy. Moreover, in these methods, the heat-affected zone due to welding is difficult to increase, and as a result, chemical and physical changes in the weld can be suppressed.

  Thus, according to the welding method of the steel member of a present Example, a steel member can be repaired reliably and easily on-site, without performing heat processing.

<Example 2: Welding repair of large piping>
In Example 1, the case where the local crack which arose on the surface of the steam turbine casing was repaired by TIG welding or laser welding was demonstrated. However, although TIG welding has an advantage that accurate welding can be performed, it is usual that the welding material must be manually supplied by a welding rod or the like. For this reason, when a portion to be welded is large, it is preferable to combine other welding methods.
Therefore, in the present embodiment, a welding method for a steel member when welding a large pipe made of cast steel will be described.

  FIG. 6 is a diagram illustrating an example of a pipe welding method according to the present embodiment. In this embodiment, in the initial stage of welding, welding is performed by TIG welding to form an initial layer of welding material, but thereafter, welding is performed by MIG (Metal Inert Gas) welding or submerged arc welding. That is, as shown in the figure, when joining the pipe 21 and the pipe 22 made of cast steel, first, welding by TIG welding is performed in the same manner as in Example 1 to form the initial layer 23. Thereafter, MIG welding or submerged arc welding is performed by using a welding torch or a welding machine 25 provided with a welding wire 24 made of the above-described welding material to form the second and subsequent layers 26.

  Thus, by using TIG welding together with MIG welding or submerged arc welding, large steel members such as piping provided in the power plant facility can be welded and repaired quickly and reliably.

  In addition, the initial layer of the welding material is formed by TIG welding, and then the layers after the initial layer are formed by submerged arc welding or MIG welding, so that, for example, repair members to be welded are accurately joined by TIG welding. Then, the repair members can be quickly joined by submerged arc welding or MIG welding. By doing in this way, even if a repair object is a large steel member, it can repair accurately and rapidly.

  The above description of the embodiments is intended to facilitate understanding of the present invention and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  For example, in the above embodiment, the case where cast steel is welded or repaired has been described. However, the present invention is a chromium steel member made of 9Cr steel, 12Cr steel, 2.25Cr steel, or 1.5Cr steel ( Even when welding or repairing various steel members such as boiler piping), the present invention is applicable.

10 outer shell member, 11 crack, 12 recess, 13 repair member 14 TIG welding machine 15 welding rod, 21 piping, 22 piping, 23 first layer, 24 welding wire, 25 welding torch or welding machine, etc. layer

Claims (5)

  Contains 5% by weight or less of at least one element of aluminum, silicon, copper, manganese, and chromium, boron, tungsten, chromium, molybdenum, niobium, vanadium, hafnium, zirconium, titanium, cobalt, copper, and carbon A welding method for a steel member, wherein TIG welding or laser welding is performed using a welding material containing 5% by weight or less of a total of at least one element, and containing the inevitable impurities and nickel as the balance.   The steel member welding method according to claim 1, wherein after the TIG welding, submerged arc welding or MIG welding is performed using the welding material.   The method for welding a steel member according to claim 2, wherein the initial layer of the welding material is formed by the TIG welding, and then the layers after the initial layer are formed by the submerged arc welding or MIG welding. .   The method for welding steel members according to any one of claims 1 to 3, wherein the nickel content is 90% by weight or more.   Contains 5% by weight or less of at least one element of aluminum, silicon, copper, manganese, and chromium, boron, tungsten, chromium, molybdenum, niobium, vanadium, hafnium, zirconium, titanium, cobalt, copper, and carbon A welding material characterized by containing at least one element among them in an amount of 5% by weight or less and containing inevitable impurities and nickel as the balance.

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