JP2010240661A - Alloy powder for coated arc welding electrode, and low hydrogen coated arc welding electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alloy powder for a coated arc welding electrode capable of securing weld metal having high toughness at low temperature with no fluctuation while satisfying satisfactory welding operation and to provide a low hydrogen coated arc welding electrode. <P>SOLUTION: In the alloy powder added to a coating agent when the coated arc welding electrode is produced, an alloy containing 8 to 40 mass% Ni, 0.5 to 8.5 mass% Ti, 1.0 to 11.5 mass% Mo, 8.5 to 24.5 mass% Mn, 13 to 25 mass% Si, and 20 to 42 mass% Fe is made into a powder having 30 to 150 μm average particle diameter. In the low hydrogen coated arc welding electrode wherein a soft steel core line is coated with a coating agent, 17 to 42 mass% alloy powder is incorporated to the total mass of the coating agent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an alloy powder added as a coating material for a coated arc welding rod and a low hydrogen-based coated arc welding rod (hereinafter referred to as a low hydrogen-based rod) using the same, and in particular, the toughness of the weld metal is good. Further, the present invention relates to an alloy powder for a coated arc welding rod and a low hydrogen-based rod that are less varied and satisfy the welding workability.

  Low hydrogen rods contain a large amount of carbonate such as calcium carbonate in the coating, and are suitable for welding large structures due to the good crack resistance and toughness of the weld metal. It is also used for welding steel.

  In recent years, various improvements have been made to low hydrogen rods in response to the demand for higher toughness of weld metal. For example, Japanese Patent Laid-Open No. 4-319092 (Patent Document 1) discloses a technique for ensuring high toughness by reducing the amount of oxygen in a weld metal by adding metal Mg to the coating agent and defining its particle size. It is shown. Japanese Patent No. 3026899 (Patent Document 2) discloses a technique that is excellent in low-temperature toughness in high-strength steel materials by the steel core wire component, the main component of the coating agent, and the particle size regulation of metal Mg. . However, in these techniques, the metal Mg is contained in the coating agent, so that the melting point of the welding slag is increased, the fluidity of the slag is deteriorated, and further, the welding workability is deteriorated such as the deterioration of the protective cylinder.

  On the other hand, as an improvement in toughness by adding an alloy, Japanese Patent Application Laid-Open No. 10-272594 (Patent Document 3) defines Ni, Mo, etc. in a coating material, and ensures excellent low temperature toughness of a weld metal for high strength steel materials. . JP-A-58-53393 (Patent Document 4) uses Ti and B in combination for the purpose of refining the structure of the weld metal to ensure high toughness at low temperatures. However, although these techniques have excellent toughness as an average value, segregation may occur because the alloy in the coating agent has a higher specific gravity than the metal carbonate or metal fluoride that is the coating material of the low hydrogen rod. There is a problem that the toughness of the weld metal tends to vary. As described above, it has been difficult to obtain a low hydrogen rod that has good welding workability, has little variation in the low temperature toughness of the weld metal, and can ensure high toughness.

Japanese Patent Laid-Open No. 4-319092 Japanese Patent No. 3026899 Japanese Patent Laid-Open No. 10-272594 JP 58-53393 A

  An object of the present invention is to provide an alloy powder for a coated arc welding rod and a low hydrogen-based coated arc welding rod which can ensure a weld metal having high toughness at low temperatures without satisfying satisfactory welding workability.

  The gist of the present invention is an alloy powder that is added to a coating agent when a coated arc welding rod is manufactured, and Ni is 8 to 40 mass%, Ti is 0.5 to 8.5 mass%, and Mo is 1 0.0-11.5% by mass, Mn 8.5-54.5% by mass, Si 13-25% by mass, Fe 20-42% by mass, and other alloys composed of inevitable impurities, The alloy powder for coated arc welding rods is characterized in that the powder has a diameter of 30 to 150 μm. Further, in the low hydrogen-based coated arc welding rod in which a coating agent is coated on a mild steel core wire, the alloy powder is contained in an amount of 17 to 42% by mass with respect to the total mass of the coating agent. It is in the system coated arc welding rod.

  According to the alloy powder for a coated arc welding rod and the low hydrogen-based coated arc welding rod of the present invention, it is possible to secure a weld metal with high toughness at low temperatures without variation, while satisfying good welding workability. Can be improved.

  The present inventors have intensively studied means for improving a low hydrogen rod that can secure a weld metal having high toughness at a low temperature, has little variation in toughness, and provides good welding workability. In general, components such as Ni, Mo, and Ti are used to secure the low temperature toughness of the weld metal. These components use metal powders such as metal Ni, Fe—Mo, and Fe—Ti, respectively, as a coating material. . Therefore, segregation of these metal powders can be considered as a factor of toughness variation.

  First, it tried to improve Ni which is a component indispensable for ensuring low-temperature toughness from the surface of the coating material. In order to prevent segregation, it is important to improve dispersibility in the weld metal. Fe-Ni is used to create a low hydrogen rod with a blending flux adjusted so that the amount of Ni in the coating is equivalent. As a result of the welding test, the results showed little variation while maintaining high toughness. However, due to the increase in Fe content, carbonate mineral, which is the main raw material for low hydrogen rods, is reduced, resulting in insufficient air shut-off and weld defects such as blow holes. Further, Fe-Ni has a problem that it is difficult to grind at the time of raw material production.

  Subsequently, the raw material which reduced the Mo and Ti content of Fe-Mo and Fe-Ti with comparatively little addition amount was used. That is, the metal powder which increased Fe like Fe-Ni was created, and it aimed at improving the dispersibility of Mo and Ti. As a result, the variation in toughness tended to be improved, but the arc state was deteriorated, the amount of spatter was increased, and the welding workability was deteriorated.

  Furthermore, the addition of Ni, Mo, and Ti to the coating agent was stopped, and as a result of using a metal core that contained these in the core, excellent toughness with little variation could be secured. However, the specific resistance value of the core becomes high, and when a high current is used, there is a problem that the welding rod is easily burnt due to Joule heat, and good welding workability cannot be obtained.

  Therefore, as a result of detailed examination of component segregation of Ni, Mo and Ti, it is caused by the small amount of metal powder containing these components added to the coating, and is indispensable for these components and low hydrogen rods. It has been found that if it is added as a single alloy powder containing all of Mn, Si, and Fe, it is incorporated in a large amount into the coating agent, and component segregation is reduced. That is, by using the alloy powder that unifies the metal powder for securing the weld metal component that has been used in the past, the low-temperature toughness of the weld metal can be kept low and high toughness can be secured, and the welding workability can be satisfied. found.

In the production of the alloy powder as described above, all the components to be made into the alloy powder are blended, dissolved in a furnace, solidified into a plate shape, and then pulverized to obtain a powder having a predetermined particle size. Since the alloy of the component of the present invention is brittle, it can be powdered by mechanical crushing in this way. Further, the powder can be directly produced from the molten state by an atomizing method in which high-pressure water or the like is jetted from the surrounding while vertically flowing the molten metal.
Hereinafter, with respect to the alloy powder for a coated arc welding rod and the low hydrogen rod of the present invention, the reasons for limiting the composition of each component of the alloy powder, the particle size and the content in the coating will be described.

  If the Ni content in the alloy is less than 8% by mass (hereinafter referred to as “%”), sufficient toughness of the weld metal cannot be obtained in the range of the amount of alloy powder added to the coating (described later). On the other hand, if it exceeds 40%, the welding workability is deteriorated, for example, the melting point of the weld metal is lowered and the bead shape is deteriorated. Moreover, the pulverizability becomes worse during the production of alloy powder by crushing. Therefore, the Ni content in the alloy is 8 to 40%.

  If Ti in the alloy is less than 0.5%, the stability of the arc is poor and the amount of spatter generated increases within the range of the amount of alloy powder added to the coating, and the toughness of the weld metal also decreases. On the other hand, if it exceeds 8.5%, the strength of the weld metal becomes excessively high and the toughness decreases. Moreover, welding workability | operativity worsens, such as slag peelability worsening. Accordingly, the Ti content in the alloy is set to 0.5 to 8.5%.

  Mo is a component necessary for ensuring strength without adversely affecting welding workability. If the Mo content in the alloy is less than 1.0%, sufficient strength and toughness cannot be obtained within the range of the amount of alloy powder added to the coating, and if it exceeds 11.5%, the strength becomes excessively high and the toughness decreases. To do. Therefore, the Mo content in the alloy is set to 1.0 to 11.5%.

  Mn is indispensable as a deoxidizer and needs to be at least 8.5% in the range of the amount of alloy powder added to the coating. On the other hand, if it exceeds 24.5%, the toughness decreases. The melting point of the slag is excessively lowered and welding workability is deteriorated. Therefore, the Mn content in the alloy is set to 8.5 to 24.5%.

  Si is a deoxidizer like Mn, but is also effective in improving welding workability such as slag removability and bead shape. Moreover, it is effective in improving the pulverizability during the production of alloy powder by crushing. If Si is less than 13%, the grindability deteriorates during the production of the alloy powder, and the welding workability also deteriorates within the range of the amount of alloy powder added to the coating. On the other hand, if it exceeds 25%, the toughness decreases. Therefore, the Si content in the alloy is 13 to 25%.

  Fe is added for the purpose of improving the solubility and grindability of the alloy powder, and at least 20% is necessary. If it exceeds 42%, the arc becomes unstable and the amount of spatter is increased, resulting in poor workability. Therefore, the Fe content in the alloy is 20 to 42%.

  The average particle size of the alloy powder is also important. If the average particle size is less than 30 μm, dry cracking of the coating material occurs in the welding rod drying process. Further, the arc becomes weak during welding, resulting in insufficient penetration. On the other hand, if it exceeds 150 μm, the amount of spatter generated increases. Therefore, the average particle diameter of the alloy powder is 30 to 150 μm.

  In addition, it is preferable to use what is baked and given the oxide film so that it may not react with water glass at the time of manufacture of a welding rod as the alloy powder for coated arc welding rods of this invention. In the case of producing a powder by the atomizing method, an oxide film can be formed by making the atmosphere in the atomizing apparatus oxidizing without using a non-oxidizing gas which is usually employed.

  As a result of applying the alloy powder thus obtained to a low hydrogen rod, it has been found that the low temperature toughness is extremely good, there is no variation, and the welding workability is also good. The content of the alloy powder in the coating material is 30% as a standard with respect to the total weight of the coating material in terms of the balance with the metal carbonate and metal fluoride which are the main components of the coating material in the low hydrogen rod, A range of 25 to 35% is preferable. If the alloy content is less than 17%, the dispersibility in the weld metal is poor and component segregation occurs, resulting in large variations in toughness. On the other hand, if it exceeds 42%, the arc state is disturbed and welding workability is deteriorated. Therefore, the content of the alloy powder in the coating agent is 17 to 42% with respect to the total weight of the coating agent.

  Among other raw materials used for coatings, metal carbonate is added to block the atmosphere, but if the content is low, oxygen and nitrogen in the weld metal increase, and if added excessively, arc state and Since the bead shape is deteriorated, the content of the metal carbonate is preferably 20 to 60%. Furthermore, metal fluoride is indispensable for obtaining good slag fluidity, and if its content is low, it will not be effective, and if it is excessive, the arc state and slag peelability will deteriorate. 13 to 30% is desirable. In addition, arc stabilizers and slag generators are usually used as low hydrogen-based coating raw materials.

The effects of the present invention will be specifically described with reference to examples.
Each alloy of the components shown in Table 1 was examined for grindability by a ball mill, then fired at 700 to 900 ° C. to form an oxide film, and alloy powders having various average particle diameters shown in Table 2 were obtained.

Steel of JIS G3523 SWY11 having a diameter of 4.0 mm and a length of 400 mm obtained by adding the alloy powder shown in Tables 1 and 2 to the coating material of the low hydrogen rod for 780 N / mm grade ² low temperature steel shown in Table 3 After coating the core wire, it was dried and various low-hydrogen rods were prototyped, and the impact toughness and welding workability of the weld metal were investigated.

Judgment of pulverizability at the time of producing the alloy powder was made with good ◯ marks for those that could be easily crushed, and with x marks for those that required time for grinding.
The weld metal has an impact toughness of 170 A (AC) current, 90-130 ° C pre-pass / pass temperature, 17 kJ / cm average heat input, and welded according to the weld metal test of JIS Z3211. From JIS Z2202, No. 4 impact test piece was collected. The test temperature was −40 ° C., and eight tests were performed. The average value of absorbed energy was 80 J or more, and the minimum value was 60 J or more.

Welding workability was investigated by assembling a 780 N / mm grade ² steel plate with a plate thickness of 16 mm, a width of 100 mm, and a length of 450 mm into a T shape, using an AC welder, horizontal fillet welding with a current of 170 A, and vertical posture welding with 150 A. Welding was conducted under the conditions described above, and the arc state, slag state, and the amount of spatter generated were investigated. The determination was made by comprehensively evaluating the evaluation of each posture welding, and the good was marked with a circle, and the poor was marked with an x. These results are also summarized in Table 2.

In Table 1 and Table 2, welding rod No. 1-No. No. 12 is an example of the present invention, welding rod no. 13-No. 28 shows a comparative example.
The welding rod no. 1-No. No. 12, the content of Ni, Ti, Mo, Mn, Si, Fe in the alloy powder is appropriate, the grindability is good, the average particle size is appropriate, and the amount of alloy powder in the coating is also appropriate. Good absorption energy with little variation was obtained in the weld metal test, which was a very satisfactory result.

In the comparative example, the welding rod No. No. 13 had poor welding workability such as a weak arc and poor slag peelability due to a large amount of Ti in the alloy powder. Further, the absorbed energy of the weld metal was low.
Welding rod no. No. 14 had poor pulverizability during the production of the alloy powder because of the large amount of Ni in the alloy powder. In addition, the melting point of the molten metal was lowered, and the beads were drooped in a standing posture, resulting in poor welding workability.

Welding rod no. No. 15 had a low absorption energy of the deposited metal because there was little Mo in the alloy powder.
Welding rod no. No. 16 had poor pulverizability at the time of producing the alloy powder because there was little Si in the alloy powder. Further, the familiarity of the beads was poor and the welding workability was poor.

Welding rod no. In No. 17, since the Ti in the alloy powder was small, the arc was unstable, the amount of spatter was increased, the welding workability was poor, and the absorbed energy of the deposited metal was also low.
Welding rod no. No. 18 had a large average particle size of the alloy powder, so that the amount of spatter was large and welding workability was poor.

Welding rod no. In No. 19, since the Mn in the alloy powder was large, the melting point of the slag was lowered, and the weld metal dropped into a convex bead in a standing posture, resulting in poor welding workability.
Welding rod no. In No. 20, since the average particle size of the alloy powder was small, the arc was weakened, resulting in insufficient penetration and poor welding workability.

Welding rod no. No. 21 had a low absorption energy of the deposited metal because there was little Ni in the alloy powder.
Welding rod no. No. 22 had a large variation in the absorbed energy of the weld metal because the amount of alloy powder added in the coating was small.

Welding rod no. In No. 23, the amount of Fe in the alloy powder was so large that the arc became unstable and the amount of spatter generated was large, resulting in poor welding workability.
Welding rod no. In No. 24, since Mn in the alloy powder was small, deoxidation was insufficient and the absorbed energy of the deposited metal was low.

Welding rod no. In No. 25, since the amount of alloy powder added in the coating material was large, the arc state was disturbed and the welding workability was poor.
Welding rod no. No. 26 had a low absorption energy of the deposited metal because there was a lot of Mo in the alloy powder.

Welding rod no. In No. 27, since the amount of Si in the alloy powder was large, the absorbed energy of the deposited metal was low.
Welding rod no. No. 28 had poor solubility and grindability during the production of the alloy powder since Fe in the alloy powder was small.

Claims (2)

An alloy powder added to a coating agent when a coated arc welding rod is manufactured, comprising 8 to 40% by mass of Ni, 0.5 to 8.5% by mass of Ti, and 1.0 to 11.5 of Mo An alloy containing 8% to 24.5% by mass of Mn, 8.5% to 24.5% by mass, 13% to 25% by mass of Si, 20% to 42% by mass of Fe, and other unavoidable impurities, having an average particle size of 30 to 150 μm Alloy powder for coated arc welding rods, characterized in that it is powdered. A low hydrogen based arc welding rod in which a coating material is coated on a mild steel core wire, wherein the alloy powder according to claim 1 is contained in an amount of 17 to 42% by mass with respect to the total mass of the coating material. Coated arc welding rod.