JP5670305B2 - Solid wire for gas shielded arc welding of high strength steel sheet - Google Patents

Description

The present invention relates to a solid wire for gas shielded arc welding of a high strength steel plate of 780 MPa class or more, and more particularly to a solid wire for gas shielded arc welding of a high strength steel plate having excellent toughness in a low temperature region of a weld metal.

  In recent years, as steel structures such as buildings, bridges, and offshore structures have become more demanding for larger size and lighter weight, the steel plates used have been increased in tension, and recently the tensile strength is higher than 780 MPa class. Tensile steel has become commonly used. In the manufacture of structures using these high-tensile steels having a tensile strength of 780 MPa or more, a gas shield arc welding method is often used which has a small amount of hydrogen and excellent crack resistance and is suitable for high efficiency.

  Conventionally, solid wire for gas shielded arc welding of high-strength steel is used for high-strength steel to which an appropriate amount of Ni, Cr, Mo or the like is added as disclosed in, for example, Japanese Patent Application Laid-Open No. 57-159293 (Patent Document 1). Steel wire is used. However, the wire described in Patent Document 1 is for TIG welding, and when applied to consumable electrode type MAG welding, tensile strength and excellent toughness at low temperatures cannot be obtained.

  Japanese Patent Publication No. 60-57953 (Patent Document 2) specifies the contents and ratios of acid-soluble and acid-insoluble components of Al and Ti in addition to components such as Ni, Cr, and Mo. Thus, a technique for reducing the microstructure of the weld metal and improving toughness is disclosed. However, even in the technique described in the cited document 2, excellent toughness at a low temperature cannot be obtained.

  Furthermore, in Japanese Patent Application Laid-Open No. 2007-253163 (Patent Document 3), as a wire for arc shield welding of high-strength steel of 490 to 780 MPa class, even under welding conditions of high current, high heat input and high interpass temperature, There is a technical disclosure that can stably secure a weld metal having excellent toughness and strength. However, the wire described in Patent Document 3 cannot secure toughness at low temperatures when applied to a steel sheet having a tensile strength of 780 MPa or more.

On the other hand, Japanese Patent Application Laid-Open No. 2006-110581 (Patent Document 4) discloses a gas shielded arc welding wire for a high-tensile steel plate from which a weld metal having a tensile strength of 1200 MPa or more is obtained. However, the wire described in Patent Document 4 has a problem that the carbon equivalent (Ceq) is high, the tensile strength of the weld metal is too high, and the toughness at low temperature cannot be ensured.
JP 57-159293 A Japanese Patent Publication No. 60-57953 JP 2007-253163 A JP 2006-110581 A

  The present invention has been made to solve the above-mentioned problems, and a weld metal having an appropriate strength and good and stable toughness in a low temperature region can be obtained in welding of a high strength steel of 780 MPa class or higher. An object of the present invention is to provide a steel wire for gas shielded arc welding of a high-strength steel plate.

  The gist of the present invention is mass% with respect to the total mass of the wire, C: 0.02 to 0.10%, Si: 0.1 to 1.0%, Mn: 1.0 to 1.95%, Cu: 0 0.5 to 1.5%, Ni: 1.5 to 5.0%, Cr: 0.3 to 1.2%, Mo: 0.3 to 1.0%, Ti: 0.02 to 0.30 %: S: 0.030% or less, P: 0.030% or less, N: 0.010% or less, O: 0.010% or less, the balance being made of Fe and inevitable impurities It is a solid wire for gas shielded arc welding of high-strength steel sheet.

  According to the solid wire for gas shielded arc welding of the high strength steel sheet of the present invention, the arc at the time of welding is stable, the strength of 780 MPa class or more is ensured, and the stable high toughness and defect free high quality. It is possible to provide a solid wire for gas shielded arc welding of a high-strength steel plate from which a simple weld metal can be obtained.

  In order to solve the above-mentioned problems, the present inventors have appropriate strength and high toughness that is stable in a low temperature region (−60 ° C.) in gas shielded arc welding of a high strength steel plate of 780 MPa class or higher. The composition of the steel wire for gas shielded arc welding that can form the resulting weld metal was investigated. As a result, in order to achieve the improvement of low temperature toughness at the same time as the appropriate strength, the amount of C, Si, Mn, Ni, Cr and Mo should be optimized and the proper strength and stable toughness at low temperature should be secured. Therefore, it has been found that it is effective to contain a predetermined amount of Cu.

  Hereinafter, the reasons for limiting the components of the solid wire for gas shielded arc welding of the high-strength steel sheet of the present invention will be described. In the following description, the chemical component of the solid wire is expressed by mass%, which is a ratio with respect to the total mass of the wire, and description relating to the mass% is simply described as%.

C: 0.02-0.10%
C is an element necessary for improving the strength of the weld metal by solid solution strengthening. However, if C is less than 0.02%, this effect cannot be obtained. On the other hand, if it exceeds 0.10%, the weld cracking sensitivity becomes high.

Si: 0.1 to 1.0%
Si is added for securing the strength of the weld metal and for deoxidation. If Si is less than 0.1%, the strength is low and deoxidation is insufficient, the toughness is lowered, and the arc becomes unstable. On the other hand, if it exceeds 1.0%, the strength of the weld metal increases and the toughness decreases.

Mn: 1.0 to 1.95%
Mn is a main deoxidizer like Si and is added to ensure strength. If Mn is less than 1.0%, the strength and toughness of the weld metal cannot be sufficiently secured. Also, the arc becomes unstable. On the other hand, if it exceeds 1.95%, the strength of the weld metal increases and the toughness decreases.

Cu: 0.5 to 1.5%
Cu has a precipitation strengthening action, lowers the transformation temperature, refines the structure, and stabilizes strength improvement and toughness. If Cu is less than 0.5%, sufficient strength cannot be obtained. In addition, stable low temperature toughness cannot be obtained. On the other hand, if it exceeds 1.5%, precipitation embrittlement occurs and toughness decreases. Moreover, it becomes easy to generate | occur | produce a hot crack. Therefore, Cu is 0.5 to 1.5%, but is preferably 0.55 to 1.4% from the viewpoint of stabilization of toughness and crack resistance.
In addition, when Cu plating is given to the wire surface for rust prevention, this Cu plating amount is also contained in Cu content in this invention.

Ni: 1.5-5.0%
Ni lowers the transformation temperature to refine the structure, and has the effect of increasing the strength without causing solid solution in the weld metal and lowering the toughness. If Ni is less than 1.5%, the effect of preventing the strength and toughness from being lowered cannot be sufficiently obtained. On the other hand, if it exceeds 5.0%, the grain boundary becomes brittle and the toughness decreases.

Cr: 0.3-1.2%
Cr has the effects of lowering the transformation temperature, refining the structure, and improving the strength and toughness. When Cr is less than 0.3%, these effects cannot be obtained sufficiently. On the other hand, if Cr exceeds 1.2%, the weld metal is markedly hardened and the toughness is lowered.

Mo: 0.3-1.0%
Mo, like Ni and Cr, improves the strength and toughness by lowering the transformation temperature and refining the structure. If Mo is less than 0.3%, these effects cannot be obtained sufficiently. On the other hand, if it exceeds 1.0%, the weld metal is significantly hardened and the toughness is lowered.

Ti: 0.02 to 0.30%
Ti acts as a deoxidizer and produces a fine oxide of Ti in the weld metal to improve the toughness of the weld metal. If Ti is less than 0.01%, the toughness decreases. On the other hand, if it exceeds 0.30%, the solid solution Ti increases and the toughness decreases.

In addition, since S and P reduce the toughness of a weld metal, it is preferable to make the content each into 0.030 mass% or less.
N is an unavoidable impurity. In order to stably improve the toughness of the weld metal, it is essential to reduce the solid solution N in the weld metal. If N exceeds 0.010%, the toughness of the weld metal decreases. O is not more than 0.010% because it forms oxides (non-metallic inclusions) with Si or Mn in the weld metal and lowers toughness.

The shielding gas is Ar—CO ₂ , but the amount of CO ₂ mixed is in the range of 5 to 20% by volume to reduce the oxygen content of the weld metal. Further, the gas flow rate is preferably 20 to 35 liters / minute in order to prevent defects and to prevent nitrogen from being mixed in from the atmosphere.

Hereinafter, the effect of the present invention will be described in detail with reference to examples.
Prototype steel wires with various chemical components shown in Table 1 having a wire diameter of 1.2 mm, processing a 950 MPa class steel plate with a plate thickness of 26 mm into a groove with a backing metal with a groove angle of 20 ° and a root interval of 16 mm, Multi-layer welding was performed under the welding conditions shown in Table 2.

評価は、溶接時のアークの安定性および溶接後にＸ線透過試験（ＪＩＳ Ｚ３１０６）による欠陥の有無を調査し、さらに溶接金属の機械的性能を調査した。

In the evaluation, the stability of the arc during welding and the presence or absence of defects by an X-ray transmission test (JIS Z3106) after the welding were investigated, and the mechanical performance of the weld metal was further investigated.

  In order to investigate the mechanical performance of weld metal, mechanical specimens were collected from specimens (JISZ2241 10) and Charpy specimens (JIS Z2242 V-notch specimens) centered on the thickness 1 / 2t of the weld specimen. did. Evaluation of tensile strength made 950 MPa or more favorable. For evaluation of toughness, five Charpy impact tests at −60 ° C. were performed, and the absorbed energy was determined to be good with an average value of 70 J or more and a minimum value of 50 J or more. These survey results are summarized in Table 3.

表１および表３に示すワイヤ記号１〜１２は本発明例、ワイヤ記号１３〜２６は比較例である。

The wire symbols 1 to 12 shown in Tables 1 and 3 are examples of the present invention, and the wire symbols 13 to 26 are comparative examples.

  The wire symbols 1 to 12, which are examples of the present invention, have appropriate amounts of C, Si, Mn, Cu, Ni, Cr, Mo and Ti of the wire, so that the arc is stable, there is no welding defect, and the tensile strength of the weld metal The strength and absorbed energy were also good and very satisfactory results.

  Since the wire symbol 13 in the comparative example has a high C, the crater portion was cracked. Moreover, since Ti was high, both the average value and the minimum value of the absorbed energy of the weld metal were low. Since the wire symbol 14 had a low C, the tensile strength of the weld metal was low. Moreover, since Ti was low, both the average value and the minimum value of the absorbed energy of the weld metal were low.

  Since the wire symbol 15 is high in Si, the wire symbol 17 is high in Mn, the wire symbol 23 is high in Cr, and the wire symbol 25 is high in Mo, so the tensile strength of the weld metal is high and the absorbed energy is high. Both average and minimum values were low. Since the wire symbol 16 was low in Si and the wire symbol 18 was low in Mn, the arc was unstable and both the average value and the minimum value of the tensile strength and absorbed energy of the weld metal were low.

Since the wire symbol 19 is high in Cu, hot cracking occurred in the weld layer of the first layer. Moreover, both the average value and the minimum value of the absorbed energy of the weld metal were low. Since the wire symbol 20 has low Cu, the tensile strength of the weld metal was low and the minimum value of absorbed energy was also low. Since the wire symbol 21 is high in Ni, the average value of the absorbed energy of the weld metal was low. Since the wire symbol 22 is low in Ni, the wire symbol 24 is low in Cr, and the wire symbol 26 is low in Mo, both of which have a low tensile strength of the weld metal, and both the average value and the minimum value of the absorbed energy. It was low.


Patent Applicant Nippon Steel & Sumikin Welding Industry Co., Ltd.
Attorney Attorney Shiina and others 1

Claims (1)

In mass% with respect to the total mass of the wire, C: 0.02 to 0.10%, Si: 0.1 to 1.0%, Mn: 1.0 to 1.95%, Cu: 0.5 to 1.5 %, Ni: 1.5 to 5.0%, Cr: 0.3 to 1.2%, Mo: 0.3 to 1.0%, Ti: 0.02 to 0.30%, S : 0.030% or less, P: 0.030% or less, N: 0.010% or less, O: 0.010% or less, with the balance being Fe and inevitable impurities, gas of high strength steel sheet Solid wire for shielded arc welding.