JP5409459B2 - Flux-cored wire for welding austenitic stainless steel - Google Patents

Description

  The present invention provides a bead appearance and a good bead shape with good mechanical performance of the weld metal, a small amount of temper color, a small amount of spatter generation, and excellent welding workability. Regarding wires.

  Since the flux-cored wire is highly efficient and provides good welding workability, the replacement of the flux-cored wire has been progressed due to the demand for the coated arc welding rod, and is the welding material that is used most frequently in the case of stainless steel welding.

  However, when austenitic stainless steel is welded using a commercially available austenitic stainless steel welding flux-cored wire, a temper color is generated on the bead surface, and this temper color deteriorates corrosion resistance and impairs the appearance. Surface treatment such as pickling is required. Therefore, when cost merit such as shortening the construction period is taken into consideration, a flux-cored wire with a small amount of temper collar and good welding workability is strongly demanded.

  As a flux cored wire for austenitic stainless steel welding, for example, Patent Document 1 describes optimization of alloy components such as C, N, Cr, Ni, Mo, Nb, Cu, Ti, Si, and Mn, and oxides in the flux. The proposed stainless steel flux cored wire has been proposed. However, in the technique described in Patent Document 1, since slag peeling starts immediately after welding, there is a problem that the bead surface is oxidized and a temper color is generated.

  Patent Document 2 proposes a flux cored wire for welding austenitic stainless steel that has good welding workability and can suppress the amount of spatter generated. However, the technique described in Patent Document 2 has a problem that even if the amount of spatter generated can be reduced, the amount of temper color generated cannot be reduced.

Japanese Patent No. 3027313 Japanese Patent No. 2667634

  The present invention provides a bead appearance and a good bead shape with good mechanical performance of the weld metal, a small amount of temper color, a small amount of spatter generation, and excellent welding workability. The object is to provide a wire.

The temper color is a phenomenon in which the difference in reflected light interference occurs due to the thickness of the oxide film on the metal surface and the color tone changes.When the hot bead surface immediately after welding is exposed to the atmosphere, the temper color Generate. Since this temper color deteriorates the corrosion resistance and impairs the aesthetic appearance, surface treatment is required.

  In order to solve the above problems, the present inventors have made various studies on the metal and slag agent components of the flux filled in the austenitic stainless steel skin. As a result, it has been found that adding Mg to the flux is effective in reducing the amount of temper color produced on the bead surface. Mg reduces the amount of oxygen in the weld metal by deoxidation and adjusts the viscosity and melting point of the slag. It has also been clarified that the amount of temper color produced can be reduced by suppressing the oxide film produced by delaying the timing of slag peeling caused by the difference in thermal shrinkage between the weld metal and slag.

  On the other hand, addition of Mg caused further problems because the viscosity of the slag was increased and the droplet transfer was not performed smoothly, resulting in a decrease in welding workability. As a result, it has been found that by adding Al, it is possible to improve the viscosity of the slag, and to reduce the amount of temper color generated on the bead surface without impairing the welding workability, thereby completing the present invention. .

  The gist of the present invention is as follows.

(1) In the flux-cored wire filled with fluxes into the steel sheath,
% By mass with respect to the total mass of the wire,
C: 0.06% or less,
Si: 0.3 to 1.0%,
Mn: 0.5 to 3.0%
Ni: 8-14%,
Cr: 17 to 25%,
Mo: 0.01 to 3.0%,
Cu: 0.01 to 0.75%,
Bi: 0.01 to 0.15%,
Al: 0.002 to 0.1%,
Mg: 0.005 to 0.1%, and the sum of Al and Mg: 0.01 to 0.15%
In addition, as a slag agent component,
TiO ₂ : 0.1 to 3.0%,
SiO ₂ : 0.5 to 5.0%,
Al ₂ O ₃ : 0.1 to 1.5%,
ZrO ₂ : 0.1 to 2.5%,
F conversion value of metal fluoride: 0.01 to 0.15%
In addition, as an arc stabilizer component,
One or more of Li, Na or K alkali metal oxides: 0.02 to 2.0%
Containing and metal oxides and the sum of metal fluorides from 4.2 to 11.4%
And the balance is Fe and an inevitable impurity, The flux cored wire for austenitic stainless steel welding characterized by the above-mentioned.

  According to the flux-cored wire for welding austenitic stainless steel of the present invention, a bead appearance with a small amount of temper color and a good bead shape can be obtained in welding of austenitic stainless steel, and welding workability is low with less spatter generation. In addition, the weld metal is excellent in mechanical performance and a high-quality weld is obtained.

  The present invention can be achieved by independent and synergistic effects due to the coexistence of each component composition of the outer sheath of the flux-cored wire for welding austenitic stainless steel and the filling flux, and particularly reduces the amount of temper color produced on the bead surface. Therefore, it is effective to add Mg to the flux in an amount of 0.005 to 0.1% by mass with respect to the total mass of the wire. However, the addition of Mg increases the viscosity of the slag and facilitates droplet transfer. Therefore, the workability of the slag is improved by adding 0.01 to 0.15% of the total amount of Al and Mg with respect to the total mass of the wire. We found that it is possible to reduce the amount of temper collar generated on the bead surface without damaging it, and austenitic stainless steel welding flux Ri is obtained subjected to component design of the wire.

  The reason for addition and limitation of each component composition will be described below. In addition, content% of each component composition is shown by the mass% with respect to the wire total mass.

  First, the slag agent component will be described.

TiO ₂ : 0.1 to 3.0%,
TiO ₂ stabilizes the arc. When TiO ₂ is less than 0.1%, the arc becomes unstable. On the other hand, if it exceeds 3.0%, the slag peeling time is advanced and a temper color is generated. Therefore, TiO ₂ is that 0.1 to 3.0%, preferably 0.15 to 2.75%. As TiO ₂ , rutile, titanium slag, illuminite, potassium titanate, sodium titanate and the like can be used.

SiO _2: 0.5~5.0%,
SiO ₂ is necessary for adjusting the viscosity of the slag and makes the slag encapsulation and bead shape good. If SiO ₂ is less than 0.5%, the viscosity of the slag is high and the bead shape is not uniform. On the other hand, if it exceeds 5.0%, the slag tends to flow, the slag encapsulation is poor, and the bead appearance is poor. Accordingly, SiO ₂ is 0.5 to 5.0%, preferably 1.0 to 4.50%. As SiO ₂ , potassium feldspar and the like can be used in addition to cinnabar and meteorite.

Al ₂ O ₃ : 0.1 to 1.5%,
Al ₂ O ₃ stabilizes the arc. If Al ₂ O ₃ is less than 0.1%, the arc becomes unstable due to lack of arc concentration. On the other hand, if it exceeds 1.5%, the slag removability deteriorates, so Al ₂ O ₃ is 0.1 to 1.5%, preferably 0.13 to 1.13%.

ZrO ₂ : 0.1 to 2.5%,
ZrO ₂ has the effect of improving slag encapsulation. If ZrO ₂ is less than 0.1%, the viscosity of the slag is low and sufficient slag encapsulation is not obtained, resulting in poor bead appearance. On the other hand, if it exceeds 2.5%, the slag viscosity increases and the droplet transfer is not performed smoothly, and the amount of spatter generated increases. Accordingly, ZrO ₂ is a 0.1 to 2.5%, preferably from 1.2 to 2.21%.

F converted value of metal fluoride: 0.01 to 0.15%,
The metal fluoride is necessary for adjusting the slag melting point and is added for the purpose of improving the slag encapsulation and slag peelability. If the F-converted value of the metal fluoride is less than 0.01%, the slag encapsulation is poor and the bead appearance and slag peelability are poor. However, if it exceeds 0.15%, the melting point of the slag is remarkably lowered and the bead shape becomes poor. Therefore, the F conversion value of the metal fluoride is set to 0.01 to 0.15%. As the metal fluoride, NaF, LiF, CaF ₂ , AlF ₃ , K ₂ ZrF ₆ , K ₂ SiF _{6 and the} like can be used, and the same effect can be obtained even when any metal fluoride is used.

The sum of the metal oxide and metal fluoride slag agent components is 4.2 to 11.4%,
The sum of the metal oxide and metal fluoride slag agent components in the flux improves the slag encapsulation, slag release and bead shape. If the sum total of a slag agent component is less than 4.2%, the amount of slag will decrease and a bead shape will deteriorate. On the other hand, when the total of the slag agent components exceeds 11.4%, the amount of slag becomes excessive, and the slag is encapsulated non-uniformly, so that the bead appearance and slag peelability are deteriorated. Therefore, the total of the slag agent components is set to 4.2 to 11.4%.

  In addition, an alloying agent (including iron powder), a deoxidizing agent, and an arc stabilizer can be added to the flux as in the conventional case.

As in the past, as an alloying agent, it can be added as a metal powder or an alloying powder, and as a deoxidizing agent added to obtain the mechanical performance of the weld metal, it is included in the steel outer shell and the flux component. For example, C, Si, Mn or their iron alloys can be contained, and as the arc stabilizer, Li, Na, K, etc. are combined in the form of fluoride, carbonate, oxide, etc. By adding 02% or more, preferably 0.05 to 2.0%, an extremely stable arc can be obtained.
Next, the steel outer shell and other components in the flux will be described.

Al: 0.002 to 0.1%,
Al is effective in stabilizing the arc by containing 0.002% or more. On the other hand, if Al exceeds 0.1%, the arc becomes unstable. Therefore, Al is made 0.002 to 0.1%.

Mg: 0.005 to 0.1%,
Mg has the effect of improving the timing of slag peeling caused by the difference in thermal shrinkage between the weld metal and slag, and reducing the amount of temper color produced. If the Mg content is less than 0.005%, the effect of reducing the temper color generation amount cannot be obtained. On the other hand, if it exceeds 0.1%, the viscosity of the slag increases and the slag peelability deteriorates. Therefore, Mg is 0.005 to 0.1%, preferably 0.02 to 0.08%.

Sum of Al and Mg: 0.01 to 0.15%,
Furthermore, by making the sum of Al and Mg 0.01 to 0.15%, preferably 0.05 to 0.12%, the melting point and viscosity of the slag are improved, and the arc is stabilized. If the sum of Al and Mg is less than 0.01%, the arc becomes unstable. On the other hand, if it exceeds 0.15%, the amount of slag increases and the slag peelability deteriorates.

C: 0.06% or less,
Since C forms a carbide by combining with Cr and deteriorates the corrosion resistance and toughness of the weld metal, the C content is preferably 0.06% or less. Preferably it is 0.04% or less.

Si: 0.3 to 1.0%,
Si adjusts the viscosity of the slag to improve the bead shape. Moreover, it has the effect of improving the toughness of the weld metal by deoxidation. If it is less than 0.3%, the deoxidation reaction is not promoted, the amount of O in the weld metal becomes high, and the toughness deteriorates. On the other hand, if it exceeds 1.0%, the bead shape becomes convex. Therefore, Si is made 0.3 to 1.0%.

Mn: 0.5 to 3.0%
Mn has the effect of improving the toughness of the weld metal by deoxidation. If Mn is less than 0.5%, the toughness of the weld metal deteriorates, and if it exceeds 3.0%, the droplets grow greatly and the amount of spatter generated increases. Therefore, Mn is 0.5 to 3.0%.

Ni: 8-14%,
Ni has an effect of stabilizing the austenite structure of the weld metal. If Ni is less than 8%, the amount of crystallization of austenite decreases, the amount of ferrite increases, and the toughness deteriorates. On the other hand, if it exceeds 14%, the amount of austenite increases and the strength decreases. Therefore, Ni is 8 to 14%.

Cr: 17 to 25%,
Cr has the effect of stabilizing the ferrite structure of the weld metal and ensuring strength. If Cr is less than 17%, the amount of ferrite crystallized decreases and the strength decreases. On the other hand, if it exceeds 25%, the droplets become coarse and the amount of spatter generated increases. Therefore, Cr is 17 to 25%.

Mo: 0.01 to 3.0%,
Mo has the effect of stabilizing the ferrite phase of the weld metal and improving the strength. If Mo is less than 0.01%, sufficient strength cannot be obtained. On the other hand, if it exceeds 3.0%, a σ phase, which is a brittle intermetallic compound, is generated and the toughness deteriorates. Therefore, Mo is set to 0.01 to 3.0%.

Cu: 0.01 to 0.75%,
Cu has an effect of suppressing the generation of spatter by addition of a very small amount. However, if Cu is less than 0.01%, the effect of suppressing the generation of sputtering cannot be obtained. On the other hand, if Cu exceeds 0.75%, an intermetallic compound containing Cu is precipitated and the toughness deteriorates. Therefore, Cu is made 0.01 to 0.75%.

Bi: 0.01 to 0.15%,
Bi is added for the purpose of improving the slag peelability. If Bi is less than 0.01%, the slag removability deteriorates. On the other hand, if it exceeds 0.15%, a low melting point compound phase is generated between the weld bead and the slag, and the slag is peeled off immediately after welding, and the bead surface is exposed to the atmosphere to generate a temper color. Therefore, Bi is set to: 0.01 to 0.15%.

The balance of the components described above is Fe and inevitable impurities from the Fe content of the steel outer shell, the Fe content of the alloying agent, the Fe content of the deoxidizer, and the like. As for the flux filling rate into the stainless steel skin, if the flux filling rate into the stainless steel skin is less than 18%, the thickness of the outer skin becomes thick, the droplets enlarge, and the arc becomes unstable. On the other hand, if it exceeds 30%, the thickness of the outer skin is thin, the amount of slag becomes excessive, and the slag encapsulation is deteriorated. Therefore, the flux filling rate is preferably 18-30%.

  Referring to the method for manufacturing the flux-cored wire, for example, when the outer skin is formed into a tubular shape from a steel strip, the filled flux that has been blended, stirred, and dried is filled into a U-shaped groove and then formed into a round shape. The wire diameter is drawn. At this time, a seamless type flux-cored wire can be obtained by welding the shaped outer seam. When the outer skin is a pipe, the pipe is vibrated to be filled with a flux and drawn to a predetermined wire diameter.

  The filling flux can be granulated by adding a fixing agent (aqueous solution of potassium silicate and sodium silicate) so that supply and filling can be performed smoothly. In particular, when a fine Ti oxide is added, granulating the filling flux prior to filling is extremely effective in improving the filling property and preventing segregation.

  Hereinafter, the present invention will be described in more detail with reference to examples.

  Various types of flux-cored wires for welding stainless steel with a wire diameter of 1.2 mm having the composition shown in Table 2 were prepared using austenitic stainless steel skins having chemical components shown in Table 1. The flux filling rate was 18-30%.

  For welding, a weld metal test was performed based on JIS Z 3323 using austenitic stainless steel. The weld metal performance was based on JIS Z 3111, and a tensile test and an impact test were performed. As for the weld metal performance, the tensile strength: 520 MPa or more and the absorbed energy at −20 ° C .: 30 J or more were considered good. Moreover, the corrosion test was based on JISG0577. The test piece was tested in a bead state after welding in consideration of a decrease in corrosion resistance due to generation of a temper collar. The corrosion resistance was good when the pitting potential was 300 mV or more.

  For welding workability, horizontal fillet welding was performed using austenitic stainless steel, and arc stability, spatter generation, slag encapsulation, slag peelability, bead shape, and temper color generation state were investigated.

In addition, the welding current of the welding metal test and the investigation of the welding workability was performed at 180 to 250 A, and the shielding gas was CO ₂ . The results are summarized in Table 3.

In Table 2 and Table 3, the wire No. 1 to 10 are examples of the present invention, wire No. 11 to 20 are comparative examples. Wire No. which is the present invention. 1 to 10 are TiO ₂ , SiO ₂ , Al ₂ O ₃ , ZrO ₂ , Al, Mg, sum of Al and Mg, F converted value of metal fluoride, total of slag agent components, C, Si, Mn, Ni The amount of Cr, Mo, Cu and Bi is appropriate, the arc is stable, the amount of spatter generation is small, the slag encapsulation, slag peelability and bead shape are good, and the generation of temper color is extremely low. The results were extremely satisfactory, such as good weld metal performance.

In the comparative example, the wire No. No. 11 had a large amount of Mn and therefore a large amount of spatter was generated, and since TiO ₂ was large, a temper color was generated and the pitting potential was low.

Wire No. In No. 12, since there was much Bi, a temper color was generated and the pitting potential was low. Further, since the amount of TiO ₂ was small, the arc was unstable. Furthermore, since Mn is small, the absorbed energy was low.

Wire No. No. 13 had a poor bead shape due to the small amount of SiO ₂ , and the arc was unstable due to a small amount of Al ₂ O ₃ . Further, since the amount of Si is small, the absorbed energy is low.

Wire No. No. 14 had a poor slag removability because there was a lot of SiO ₂ , and slag encapsulation was high, and since Si was high, the bead shape and Al ₂ O ₃ were high.

Wire No. No. 15 had poor slag encapsulation because ZrO ₂ was small, and the amount of spatter was large because Cr was large. Further, since the amount of Ni is small, the absorbed energy is low.

Wire No. No. 16 had a large amount of spatter due to a large amount of ZrO _{2 and a} small amount of Bi, so that the slag peelability was poor. Moreover, since there is much Ni, tensile strength was a low value.

  Wire No. In No. 17, since the Al content was large, the arc was unstable, and the F-converted value of fluoride was small, so the slag encapsulation and slag peelability were poor. Moreover, since the temper color was formed because Mg was low, the pitting corrosion potential was low. Furthermore, since there is little Cr, the tensile strength was low.

  Wire No. No. 18 had a poor bead shape because there was a lot of Mg, so the slag peelability was high, and the F-converted value of fluoride was large. Moreover, since there is much Cu, the absorbed energy was a low value.

  Wire No. No. 19 had a poor sum of Al and Mg, so the slag peelability was poor, and the total amount of slag agent was small, so the bead shape was also poor. Moreover, since there is little Mo, tensile strength was a low value.

  Wire No. In No. 20, the arc was unstable because the sum of Al and Mg was small. Moreover, since there was much sum total of a slag agent, slag encapsulation and slag peelability were unsatisfactory. Furthermore, since there is much Mo, the absorbed energy was low.

  Wire No. In No. 21, since the amount of Al was small, the arc was unstable. Moreover, since there was much C, the absorbed energy was low and the pitting corrosion potential was also low. Furthermore, since Cu was low, spatter was frequently generated.

Claims (1)

In flux-cored wire filled with fluxes into the steel sheath,
% By mass with respect to the total mass of the wire,
C: 0.06% or less,
Si: 0.3 to 1.0%,
Mn: 0.5 to 3.0%
Ni: 8-14%,
Cr: 17 to 25%,
Mo: 0.01 to 3.0%,
Cu: 0.01 to 0.75%,
Bi: 0.01 to 0.15%,
Al: 0.002 to 0.1%,
Mg: 0.005 to 0.1%, and the sum of Al and Mg: 0.01 to 0.15%
In addition, as a slag agent component,
TiO ₂ : 0.1 to 3.0%,
SiO ₂ : 0.5 to 5.0%,
Al ₂ O ₃ : 0.1 to 1.5%,
ZrO ₂ : 0.1 to 2.5%,
F conversion value of metal fluoride: 0.01 to 0.15%
In addition, as an arc stabilizer component,
One or more of Li, Na or K alkali metal oxides: 0.02 to 2.0%
Containing and metal oxides and the sum of metal fluorides from 4.2 to 11.4%
And the balance is Fe and inevitable impurities, a flux-cored wire for welding austenitic stainless steel.