JP5289760B2 - Flux-cored wire for welding stainless steel and method for producing the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a flux cored wire for welding stainless steel, and a flux cored wire for welding stainless steel that reduces the amount of hexavalent Cr soluble in water of slag generated during welding (hereinafter referred to as eluted Cr). And a manufacturing method thereof.

  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. In addition, the amount of slag produced is significantly less than that of clad arc welding and submerged arc welding, leading to reduction of slag that is treated as industrial waste, and is used in many fields such as shipbuilding, construction, vehicles, and containers. Yes.

  However, although the amount of weld slag produced is small, the slag contains dissolved Cr that is considered harmful. As an example of industrial waste regulations, in the specially controlled industrial waste mine in Tokyo, the dissolved Cr is 1.5 mg / liter or less according to Article 2-4 No. 5 of the Ordinance. Must be kept low.

  As a technique for solving this problem, for example, Patent Document 1 discloses a flux-cored wire for welding stainless steel that can reduce the amount of Cr eluted from welding slag by optimizing the amounts of Si, Ti, Zr, Cr, Na, and K. Proposed. However, the amount of Cr eluted from the welding slag described in the above technology may not be suitable as industrial waste that is subject to strict regulations on environmental issues.

  Patent Document 2 proposes a stainless steel welding flux-cored wire that can suppress the amount of Cr eluted from welding fume by optimizing the Mn concentration and pH. However, the above-described technique has a problem that even if the eluted Cr of the welding fume can be reduced, the eluted Cr of the weld slag cannot be reduced.

Japanese Patent No. 3765772 JP 2007-50452 A

  It is an object of the present invention to provide a stainless steel welding flux cored wire and a method for manufacturing the same, in which the amount of Cr eluted from the weld slag produced when welding is performed using a stainless steel welding flux cored wire. .

  In order to solve the above-mentioned problems, the present inventors have conducted 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 it is effective to add N to the outer skin and the flux in order to reduce the amount of dissolved Cr in the weld slag. It has been clarified that N reacts with Cr to stabilize water-insoluble trivalent Cr and reduce the amount of Cr eluted from the weld slag.

  On the other hand, the addition of N causes a problem that the slag releasability is lowered, and thus further studies have been made. As a result, by adding a certain amount of Na compound and K compound in the flux to N which promotes stabilization of trivalent Cr, the amount of Cr eluted from the weld slag can be reduced without impairing the slag peelability. Found that it would be possible.

  Furthermore, it has also been found that the amount of Cr eluted from the weld slag can be reduced by lowering the Ca of the outer shell and the flux.

  Based on the above knowledge, it is possible to reduce the elution Cr of welding slag by containing an appropriate amount of N with respect to the amount of Cr in the flux-cored wire for stainless steel welding, and to add appropriate amounts of Na and K from Na compounds and K compounds. It has been clarified that the amount of Cr eluted from the welding slag can be reduced by lowering the slag.

  In addition, as a result of studying the reduction of the amount of Cr dissolved out of the welding slag from the manufacturing method, the wire cored wire was annealed in a hydrogen gas atmosphere during the wire manufacturing process, so that Cr was excessively reduced. It was found that the amount of eluted Cr can be further reduced.

  This invention is made | formed by the above knowledge, The place made into the summary is as follows.

This invention is made | formed by the above knowledge, The place made into the summary is as follows.
(1) A flux-cored wire for stainless steel welding in which a flux is filled in an austenitic stainless steel outer shell and the total amount of Cr contained in the outer shell and the flux is 23.4 to 32% by mass. %, In total in the outer skin and flux, Cr: 23.4 to 32%, C: 0.01 to 0.1%, Si: 0.1 to 0.9%, Mn: 0.5 to 4.0 %, P: 0.03% or less, S: 0.03% or less, Ni: 6-25%, Mo: 5% or less, and N is 0.005-0.06%, Na compound and It contains 0.01 to 0.5% in total of one kind or two kinds of K converted value and Na converted value of K compound, Ca is 0.01% or less, Cr, N, Na converted value, K The converted value and Ca are 60 or less in the D value of the following formula (A), and A flux-cored wire for welding stainless steel, characterized by containing a slag agent: 3.0 to 10% in the flux and comprising the remainder Fe and inevitable impurities .
D = 1.5Cr-800N + 1950Ca + 87 (Na + K) Formula (A)
(2) The flux-cored wire for stainless steel welding according to claim 1, further comprising Cu: 3% or less in total in the outer sheath and the flux in mass% with respect to the total mass of the wire.
(3) The flux-cored wire element described in (1) or (2) is also annealed in a hydrogen gas atmosphere.

  According to the flux-cored wire for welding stainless steel of the present invention and the manufacturing method thereof, the remarkable effect that the amount of Cr eluted from the weld slag generated during welding can be reduced and the environmental contamination by the eluted Cr can be suppressed. Play.

  The present invention can be achieved by a single effect and a synergistic effect due to the coexistence of each component composition of the austenitic stainless steel skin and the filling flux. The reasons for addition and limitation of each component composition will be described below.

Cr is added for the purpose of obtaining the most important corrosion resistance as stainless steel. When the Cr contained in the outer sheath and the flux is less than 12 mass% (hereinafter referred to as “%”), the amount of Cr eluted from the generated weld slag is 1 ppm or less, which is not a problem. On the other hand, if it exceeds 32%, it cannot be produced due to wire breakage when the diameter of the wire is reduced. In the present invention, Cr: 23.4% shown in the examples was set as the lower limit.
N reacts with Cr to produce water-insoluble Cr nitride and promotes stabilization of trivalent Cr, thereby reducing the amount of Cr eluted from the weld slag. When N exceeds 0.06% in the total of the outer shell and the flux, a nitrided layer is formed between the weld metal and the slag, so that the slag is seized and the slag peelability is deteriorated. On the other hand, if it is less than 0.005%, the trivalent Cr in the weld slag is less likely to exist stably, so the amount of eluted Cr increases. Moreover, the more preferable range from which an effect is acquired is 0.01 to 0.03%.

The total of one or two of Na converted value and K converted value of Na compound and K compound adjusts the arc length and improves the arc stability. Moreover, since glassy slag with a weak bonding force is generated and seizure of slag is reduced, slag peelability is improved. Therefore, 0.01% or more is added. On the other hand, if the amount exceeds 0.5%, the amount of fumes generated increases. Further, NaO ₂ and K ₂ O coexisting in the slag react with the trivalent Cr, and the eluted Cr of the weld slag is generated. Therefore, the Na conversion value of Na compound and K compound and the total of one or two kinds of K conversion value are 0.01 to 0.5%. Moreover, the more preferable range in which an effect is acquired shall be 0.1 to 0.3%.

When Ca exceeds 0.01%, the oxidation reaction is promoted and the amount of slag becomes excessive, so that the slag encapsulation becomes worse, the bead shape becomes uneven, and the bead appearance becomes worse. Further, Ca is oxidized as a result of welding heat and coexists in the slag and reacts with trivalent Cr to produce eluted Cr. Therefore, Ca is preferably as low as possible.
Cr, N, Na conversion value, K conversion value, and Ca shall be 60 or less by D value of a following formula (A).

D = 1.5Cr-800N + 1950Ca + 87 (Na + K) Formula (A)
FIG. 1 shows the relationship between the D value and the amount of dissolved Cr in the weld slag. As is apparent from FIG. 1, the amount of Cr eluted from the weld slag can be reduced as the D value becomes lower. The D value calculated from Cr, N, Na converted value, K converted value and Ca is an index for reducing the amount of Cr dissolved out of the weld slag with respect to the Cr amount of the flux-cored wire, and the D value is set to 60 or less. As a result, the amount of Cr eluted from the welding slag can be significantly reduced.

Welding slag due to the synergistic effect of Cr, N, Na, K and Ca when the D value exceeds 60, even if the total of one or two of Na converted value and K converted value of Na compound and K compound is appropriate The effect of reducing the amount of Cr eluted is insufficient, and the amount of Cr eluted from the weld slag increases. Accordingly, the D value is 60 or less. Moreover, the more preferable range where an effect is acquired shall be 45 or less.
As the flux-cored wire for stainless steel welding of the present invention, any wire that is usually used may be used. In addition to the above components, in order to satisfy the mechanical performance of the steel plate component to be welded and the weld metal, C: 0.01 to 0.1%, Si: 0.1 to 0.9%, Mn: 0.5 to 4.0%, P: 0.03% or less, S: 0.03% or less, Ni : 6-25%, Mo: 5% or less, and Cu: 3% or less as required. Further, TiO ₂ , SiO ₂ , ZrO ₂ , Al ₂ O ₃ , FeO, Fe ₂ O ₃ , MgO, and various metal fluorides may be used as a slag agent in the flux in a total amount of about 3.0 to 10%. it can.

  In the manufacturing process of the stainless steel welding flux cored wire, the flux cored wire is annealed in a hydrogen gas atmosphere, so that Cr in the wire is excessively reduced and the Cr oxide in the slag generated after welding is stabilized 3 The value Cr can be obtained. In an inert gas atmosphere such as Ar, an active gas atmosphere such as ammonia decomposition gas, and an air atmosphere, Cr in the wire is unstablely oxidized, and the amount of Cr eluted from the weld slag increases. Fig. 1 Flux-cored wire strand (1.4mm diameter) is eluted in a hydrogen gas atmosphere (annealing conditions 1050 ° C x 1 min) (white circle mark) and weld slag elution Cr when there is no annealing (black circle mark) The measurement result of quantity is shown. It can be seen that even when the D value is high, the amount of Cr eluted from the weld slag is lowered by annealing in a hydrogen gas atmosphere.

  There are various annealing conditions for the flux-cored wire, such as a tunnel-type continuous annealing apparatus and a fixed furnace apparatus, but the apparatus form is not limited as long as the atmosphere is hydrogen gas. The annealing temperature is set to about 800 to 1200 ° C., and the holding time varies depending on the wire diameter. Even if annealing is performed for a long time or repeated multiple times, the weld metal performance and welding workability are not affected.

As mentioned above, although the reason for limitation of the constituent requirements of the flux cored wire for stainless steel welding of the present invention and the manufacturing method thereof has been described, when the manufacturing method of the flux cored wire is further described, for example, when the outer skin is formed into a tubular shape from the strip steel Is filled with a mixed, stirred, and dried filling flux into a U-shaped groove, then formed into a round shape, and drawn to a predetermined wire diameter. At this time, a seamless type flux-cored wire can be obtained by welding the formed outer seam. When the outer sheath is a pipe, the pipe is vibrated and filled with flux, and the wire is annealed in a hydrogen gas atmosphere in the middle of wire drawing, and then drawn to a predetermined wire diameter.
The filling flux can be used in the form of a bond flux by adding a fixing agent (an aqueous solution of potassium silicate and sodium silicate) so that supply and filling can be performed smoothly.

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

  Various types of flux-cored wires for welding stainless steel having the compositions shown in Table 2 were prepared using austenitic stainless steel skins having chemical components shown in Table 1. The wire diameter was 1.2 mm. The flux filling rate was 20-23%. Moreover, annealing at the time of wire manufacture was performed under the condition of 1000 ° C. × 1 min in a hydrogen gas atmosphere with a wire diameter of 1.4 mm.

  For the measurement of the amount of generated fume, a SUS304 plate thickness of 20 mm was used, and the amount of generated fume per minute was measured according to JIS Z 3930.

  The measurement of the dissolved Cr amount of the weld slag was performed by analyzing the slag generated from the third layer by performing two-layer buttering using a plate thickness of SM490B steel of 20 mm. The method for analyzing the amount of Cr eluted from the collected slag was based on the hexavalent Cr analysis method specified in JIS K 0120, and the amount of Cr eluted was detected by diphenylcarbazide spectrophotometry. The amount of Cr dissolved out of the weld slag was 30 ppm or less.

The welding conditions were as follows: welding current: 180 to 250 A, shield gas: CO ₂ . The results are summarized in Table 3.

In Table 2, wire No. 1 to 5 are examples of the present invention, wire Nos. 6 to 11 are comparative examples. Wire No. which is the present invention. 1 to 5 are the total amount of Cr, N, Na compound and K compound in Na converted value and K converted value, and Ca and D values are appropriate, so the arc is stable, the amount of fume generation is small, and the slag elution Cr amount The result was extremely satisfactory.
In addition, wire No. which was not annealed in a hydrogen gas atmosphere in the flux-cored wire manufacturing process. 5 is wire No. Compared with 1-4 , the amount of Cr eluted from slag was slightly higher.

In the comparative example, the wire No. No. 6 had a high N, so the slag peelability was poor.

Wire No. No. 7 had high Ca, so the slag encapsulation was poor and the bead appearance was poor. Moreover, the amount of eluted Cr was also high.

Wire No. Since No. 8 had a low N and a high D value, the amount of eluted Cr was high.

Wire No. No. 9 had a low total amount of Na converted value and K converted value of the Na compound and K compound, so the arc was unstable and the slag peelability was poor. Further, since annealing was not performed in a hydrogen gas atmosphere, the amount of eluted Cr was slightly high despite the low D value.

Wire No. In No. 10 , the total amount of Na converted value and K converted value of the Na compound and K compound was high, so the amount of fume generation was high. Moreover, the amount of eluted Cr was also high.

Wire No. Since No. 11 had a high D value, the amount of eluted Cr was high.

It is a figure which shows the relationship between D value and the amount of elution Cr of welding slag.

Claims (3)

In a flux cored wire for welding stainless steel, in which the flux is filled in the austenitic stainless steel outer shell and the total amount of Cr contained in the outer shell and the flux is 23.4 to 32% by mass, in mass% with respect to the total mass of the wire, In total for the outer skin and the flux, Cr: 23.4 to 32%, C: 0.01 to 0.1%, Si: 0.1 to 0.9%, Mn: 0.5 to 4.0%, P : 0.03% or less, S: 0.03% or less, Ni: 6-25%, Mo: 5% or less, and N is 0.005-0.06%, Na compound and K compound It contains 0.01 to 0.5% in total of one or two of Na converted value and K converted value, and when Ca is 0.01% or less, Cr, N, Na converted value, K converted value and Ca is a D value of the following formula (A) of 60 or less, and Slag agent hex: contains 3.0 to 10%, the balance Fe and flux-cored wire for stainless steel welding, characterized in that it consists of inevitable impurities.
D = 1.5Cr-800N + 1950Ca + 87 (Na + K) Formula (A)   The flux-cored wire for welding stainless steel according to claim 1, further comprising Cu: 3% or less in total in the outer sheath and the flux in mass% with respect to the total mass of the wire.   A method for producing a flux-cored wire for stainless steel welding, wherein the flux-cored wire according to claim 1 or 2 is annealed in a hydrogen gas atmosphere.

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