JP4806299B2 - Flux cored wire - Google Patents

Description

  The present invention relates to a flux-cored wire used for gas shield welding for ferritic stainless steel, and more particularly, a flux-cored having excellent burn-off resistance used for arc welding of ferritic stainless steel used for exhaust system parts such as automobiles. Regarding wires.

Conventionally, in exhaust system parts such as exhaust manifolds and mufflers that induce high-temperature gas discharged from automobile engines, high-temperature oxidation resistance is emphasized, and ferritic stainless steels such as SUS430, SUS409, SUS410L, and SUS444 are used. A lot of steel is used. Some of these ferritic stainless steels have a thin plate thickness of less than 1.0 mm or a very thin one up to about 0.5 mm for weight reduction.
The welding wire used for these ferritic stainless steels is generally a solid in which about 17 to 19% by mass of Cr is added, and C, Si, and Mn are adjusted so that the weld metal exhibits a ferrite single phase. Many wires or metal-based flux-cored wires have been put into practical use. In addition, in order to prevent high temperature cracking, an appropriate amount of Nb added for crystal grain refinement has been put into practical use.

  Specifically, solid wires containing Nb, Ti, Ca, Mo, etc. in addition to the basic elements of C, Si, Mn, and Cr have been proposed for the purpose of improving crack resistance and high temperature strength. (For example, patent document 1) And the wire which added Mg for the purpose of improving ductility and toughness is proposed (for example, patent document 2).

On the other hand, as a flux-cored wire, in order to prevent cracking with high heat input, a wire added with Mo, Nb, or Al (for example, Patent Document 3), or Nb, Al, Ti for the purpose of improving weld crack resistance. A wire to which alkali metal carbonate, alkaline earth metal carbonate or the like is added has been proposed (for example, Patent Document 4). In addition, a flux cored wire for welding Cr-based stainless steel has been proposed for the purpose of improving slag peelability, crack resistance, and toughness (for example, Patent Document 5). Furthermore, a flux-cored wire has been proposed in which welding resistance is improved by paying attention to the burn-off resistance (for example, Patent Documents 6 and 7).
JP 2002-35988 A (paragraphs 0011 to 0028) JP-A-9-225680 (paragraphs 0006 to 0020) JP-A-6-691 (paragraphs 0008, 0013-0022) JP 2004-358552 A (paragraphs 0014 to 0034) JP-A-3-42195 (page 2, upper right column, lines 7 to 13) Japanese Examined Patent Publication No. 5-30557 (page 2, right column, line 33 to page 4, right column, line 30) JP 2001-293596 A (paragraphs 0007, 0009 to 0030)

However, the conventional stainless steel wires have the following problems.
SUS steel sheets used for automobile exhaust system parts, etc., are prone to melting during arc welding due to their thinness. Therefore, improvement is desired. is needed.
Therefore, TIG (Tungsten Inert Gas) welding method and plasma welding method which are excellent in burn-off resistance are used. However, these welding methods have a problem that efficiency is low and cost is high. Therefore, it has been desired to improve the burn-off resistance by a consumable electrode type gas shielded arc welding method excellent in welding efficiency and cost, that is, a so-called MAG (Metal Active Gas) welding method or MIG (Metal Inert Gas) welding method.

However, since the wires described in Patent Documents 1 to 4 do not focus on improving the burn-off resistance in ferritic stainless steel, there is a problem that these wires cannot improve the burn-off resistance. there were.
Further, the flux-cored wire of Patent Document 5 is a type in which a large amount of slag is generated, and there is a problem that it cannot be applied in the automobile field where a slag removing process is not assembled after welding.

  The flux-cored wires described in Patent Documents 6 and 7 are focused on improving the resistance to burn-off in a solid wire for stainless steel. Recently, however, the demand for weight reduction has increased, and the thickness of the plate to be welded has further increased. Since the design has been started in the direction of thinning, further improvement of the burn-off resistance is desired. However, these solid wires for stainless steel are intended to improve welding workability mainly by limiting the amount of slag forging agent and flux added. It has not yet achieved a sufficient burn-through resistance.

  The present invention is a technology developed in view of these circumstances, and an object thereof is to provide a flux-cored wire used for gas shield welding for ferritic stainless steel which is excellent in resistance to burn-off in an ultrathin steel plate and hardly causes defects. And

In order to solve the above-mentioned problem, a flux-cored wire according to claim 1 is a flux-cored wire that is used for gas shield welding for ferritic stainless steel by filling a metal shell with flux, and the flux-cored wire is made of a steel alloy. The flux filling rate with respect to the total mass of the wire is 5 to 30% by mass, and Si: 0.60 to 1.50% by mass, Mn: 0.40 with respect to the total mass of the wire. -2.00 mass%, S: 0.012-0.100 mass%, Cr: 16.0-20.0 mass% is contained, and also the slag forging agent in the flux total mass is 5 mass% or less. The balance consists of Fe and inevitable impurities, and among the inevitable impurities, C: 0.07 mass% or less, P: 0.025 mass% or less, Ni: 0.30 mass% or less And, the following formula (1)
X = 0.32R ₁ ^eq- 3.86-N ^eq , X ≧ 0 (1)
(In the formula, N ^eq = Ni mass% + 30 C mass% + 0.5 Mn mass%, R ₁ ^eq = Cr mass% + 1.5 Si mass%)
It is characterized by satisfying.

According to such a configuration, by containing a predetermined amount of Si and Mn, the electrical resistance of the wire itself is increased, and so-called protruding portions and tips from the tip / wire conduction point (mainly the tip of the tip) to the arc generation point are provided. The temperature rises by increasing the resistance heat generation of the formed droplet itself, and the welding heat input decreases by reducing the melting due to the arc heat.
Further, by containing a predetermined amount of S, the viscosity and surface tension of the molten pool formed immediately below the arc and behind the weld line are reduced, and the push up of the molten pool by the arc force + surface tension is reduced, so that the molten pool is reduced. The gravity of itself is better and the molten pool is more likely to fall directly under the arc. Thereby, the depth of the molten pool just under an arc becomes large, and the penetration depth reduces.
By these actions, the burn-through resistance is improved.
In addition, by specifying the flux, slag fauxitant, predetermined elements, etc. within a predetermined range, the burn-off resistance, high-temperature oxidation resistance, crack resistance and the like are improved.

The flux cored wire according to claim 2 is a flux cored wire used for gas shield welding for ferritic stainless steel by filling a metal sheath with flux, and the flux cored wire is placed on the surface of a wire wire made of steel alloy. A Cu plating layer is provided, and the flux filling rate with respect to the total mass of the wire is 5 to 30% by mass, and Si: 0.60 to 1.50% by mass, Mn: 0.40 with respect to the total mass of the wire. -2.00 mass%, S: 0.012-0.100 mass%, Cr: 16.0-20.0 mass% is contained, and also the slag forging agent in the flux total mass is 5 mass% or less. And the balance consists of Fe and inevitable impurities, and among the inevitable impurities, C: 0.07 mass% or less, P: 0.025 mass% or less, Ni: 0.30 mass% or less, Serial Cu Cu plating layer as a wire overall composition: and 0.24 wt% or less, and the following formula (1)
X = 0.32R ₁ ^eq- 3.86-N ^eq , X ≧ 0 (1)
(In the formula, N ^eq = Ni mass% + 30 C mass% + 0.5 Mn mass%, R ₁ ^eq = Cr mass% + 1.5 Si mass%)
It is characterized by satisfying.

  According to such a configuration, by providing the Cu plating layer on the surface of the wire element, chip wear is suppressed, and rust resistance, wire drawability during manufacturing, and the like are improved.

The flux-cored wire according to claim 3 is the above-described flux-cored wire, further N: 0.050 mass% or less, Nb: 1.00 mass% or less, V: 1.00 mass% or less, Al: 0 .60% by mass or less, Ti: 0.60% by mass or less, Mo: 2.50% by mass or less, and F: 0.3% by mass or less, and the following formula (2)
X = 0.32R ₂ ^eq- 3.86-N ^eq , X ≧ 0 (2)
(In the formula, N ^eq = Ni mass% + 30 C mass% + 0.5 Mn mass%, R ₂ ^eq = Cr mass% + 1.5 Si mass% + 0.5 (Nb mass% + V mass%))
It is characterized by satisfying.

  According to such a configuration, crack resistance, corrosion resistance / oxidation resistance, arc stability, and the like are further improved by further containing a predetermined amount of a predetermined element.

  In the flux-cored wire according to claim 4, the N is 0.0040 to 0.050 mass%, the Nb is 0.10 to 1.00 mass%, the V is 0.10 to 1.00 mass%, Al is 0.05 to 0.60 mass%, Ti is 0.05 to 0.60 mass%, Mo is 0.05 to 2.50 mass%, and F is 0.01 to 0.3 mass%. It is characterized by being.

  According to such a configuration, the crack resistance, corrosion resistance / oxidation resistance, arc stability, and the like are further improved by further defining the range of the content of the predetermined element.

  The flux-cored wire according to claim 5 is characterized in that, in the flux-cored wire described above, one or more of K, Na, and Li are further contained in a total of 0.30% by mass or less.

  According to such a configuration, by containing a predetermined amount of K, Na, and Li, the arc stability is improved and the burn-off resistance is further improved.

  The flux-cored wire according to claim 6 is characterized in that the total of one or more of K, Na, and Li is 0.002 to 0.30 mass%.

  According to such a configuration, by further defining the range of the contents of K, Na, and Li, the arc stability is improved and the burn-off resistance is further improved.

  According to the flux-cored wire of the present invention, by defining the various components of the wire within an appropriate range, in addition to high-temperature oxidation resistance, the burn-out resistance is extremely good, and the metallographic state, crack resistance, arc Stability, bending performance (ductility), etc. are also good. Therefore, even if the plate thickness of the exhaust system parts is reduced in order to reduce the weight of the automobile, the application of the wire can reduce the burn-out failure and improve the productivity in the welding process.

Hereinafter, embodiments of the present invention will be described in detail.
The present invention is a flux cored wire used for gas shield welding for ferritic stainless steel, characterized in that the components of the flux cored wire are defined within a predetermined range.
The flux-cored wire is made of a steel alloy wire, contains a predetermined amount of Si, Mn, S, Cr, suppresses the slag forging agent to a predetermined amount or less, and the balance is Fe and inevitable. In this case, C, P, and Ni are suppressed to a predetermined amount or less as unavoidable impurities.
Further, a Cu plating layer may be provided on the surface of the wire.

First, arc welding in the case of using a conventional wire and in the case of using a wire according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram schematically showing the state of arc welding, (a) is a schematic diagram showing a case where a conventional wire is used, and (b) is a case where a wire according to the present invention is used. It is a schematic diagram which shows.

As shown in FIG. 1 (a), in the arc welding using a conventional wire 31, the viscosity of the molten pool 6, surface tension is large, the push-up P ₁ of the molten pool 6 by arc force + surface tension, gravity P large for _2, therefore, a small drop due to gravity P ₂ of the molten pool 6 itself. Also, small depth L ₁ of the molten pool 6 of an arc immediately below, a large penetration depth L _2.
Further, the resistance heat generation of the so-called protruding portion A from the tip 2 / wire 31 energization point (mainly the tip 2 tip) to the generation point of the arc 5 and the droplet 4 itself formed at the tip is low.

Therefore, the present inventors, as shown in FIG. 1B, (1) increase the electrical resistance of the wire 3 itself, thereby increasing the resistance heat generation of the protruding portion A and the droplet 4 itself to increase the temperature. , remove from heat input by reducing the melt by arc heat, (2) the arc 5 immediately below the viscosity of the molten pool 6 formed weld line rearwardly from, to decrease the surface tension, that P ₁ is small, P ₂ overcomes causes dropped the molten pool 6 to the arc just below. Thereby, the depth L ₁ of the molten pool 6 immediately under the arc is increased, and the penetration depth L ₂ is reduced by preventing the action of the arc force (1) and (2). By combining these, we succeeded in improving the anti-spilling resistance of ultra-thin plates.

Incidentally, the flux-cored wire is generally more excellent in resistance to burn-off than the solid wire because the electrical resistance of the wire 3 itself is increased in shape and the heat capacity is reduced. In the present invention, in addition to the effect, not only the electric resistance of the wire 3 itself but also the electric resistance of the droplet 4 is increased in composition, and the viscosity and the surface tension of the molten pool 6 are adjusted, so that the steel (base material) 1 It is a means to mitigate the influence of the arc force on.
Specifically, Si and Mn are increased for increasing the electrical resistance in (1), and Nb and V are increased as necessary, and S is increased for decreasing the surface tension and viscosity of the molten pool in (2). Achieved.
Hereinafter, the reason for limiting the components of the wire will be described.

<Flux filling ratio: 5 to 30% by mass>
As described above, the flux-cored wire is generally superior in the burn-off resistance than the solid wire.
However, when the flux filling rate (the mass of the flux with respect to the total mass of the wire) is less than 5% by mass, a lot of voids are generated in the cylindrical portion formed by the metal sheath, and the flux is not uniformly distributed, thereby stabilizing the wire. Manufacturing becomes difficult and arc stability decreases. Therefore, the flux filling rate is 5% by mass or more. On the other hand, if the filling rate of the flux exceeds 30% by mass, the thickness of the metal outer skin is relatively reduced, the strength of the wire is remarkably impaired, and it is easy to break, so that it is difficult to stably manufacture the wire. Become. Therefore, the flux filling rate is 30% by mass or less.

<Si: 0.60 to 1.50 mass%>
Si is necessary for the deoxidation reaction and is effective in increasing the electric resistance of the protruding portion and the droplet. Since a minimum of 0.60% by mass is required for improving the burn-through resistance, the Si content is 0.60% by mass or more, preferably 0.80% by mass or more. On the other hand, if it exceeds 1.50% by mass, the droplets become large and spatter increases and ductility decreases. Therefore, the Si content is 1.50% by mass or less, preferably 1.30% by mass or less.

<Mn: 0.40 to 2.00% by mass>
Mn is also an element necessary for the deoxidation reaction, and is effective in increasing the electric resistance of the protruding portion and the droplet. However, since it is an element that facilitates the formation of martensite, it is generally limited to less than 0.40 mass%. In the present invention, the Mn content is increased while the martensite formation is suppressed by stabilizing the ferrite phase by reducing the C content and increasing the Si content. The content of Mn is 0.40% by mass or more, preferably 0.75% by mass or more, and more preferably 1.00% by mass or more because it is effective for improving the burn-through resistance at 0.40% by mass or more. . On the other hand, if it exceeds 2.00% by mass, the droplets become large and spatter increases and ductility decreases. Therefore, the Mn content is 2.00% by mass or less.

<S: 0.012-0.100 mass% or less>
S has the effect of reducing the viscosity and surface tension of the molten pool. As a result, the molten metal flows from the rear of the arc directly under the arc to form a deep molten pool. This reduces the penetration depth and improves the burn-off resistance. In order to obtain the effect of improving the burn-through resistance due to the flow of the molten metal, it is necessary to contain 0.012% by mass at least. Therefore, the S content is 0.012% by mass or more, preferably 0.016% by mass or more, more preferably 0.025% by mass or more. Furthermore, when it is 0.050 mass% or more, it is more effective. On the other hand, if it exceeds 0.100% by mass, hot cracking resistance is generated and ductility is lowered, so the S content is 0.100% by mass or less.

<Cr: 16.0 to 20.0 mass%>
Cr is an essential element for obtaining corrosion resistance and oxidation resistance for stainless steel. In order to achieve the same corrosion resistance and oxidation resistance as steel materials used for exhaust system parts such as SUS430, it is preferable that the Cr content is also equivalent. Since there is no problem in corrosion resistance and oxidation resistance if it is 16.0% by mass or more, the content of Cr is 16.0% by mass or more. On the other hand, if it exceeds 20.0 mass%, the cost increases, sputtering increases, and ductility decreases, so the Cr content is 20.0 mass% or less.

<Total mass of slag forging agent in wire: 5% by mass or less>
In order to reduce the amount of slag generated, it is essential to reduce the amount of slag forging agent in the wire.
Here, the slag forging agent means other than the metal powder, and oxides such as TiO ₂ , SiO ₂ , Na ₂ O, K ₂ O, CaO, Al ₂ O ₃ , Li ₂ O, MnO, MgO, LiF, NaF , Fluorides such as CaF ₂ , KF, AlF _{3 and the} like.
If the amount exceeds 5% by mass, the slag is excessive and a problem occurs in the subsequent coating, and the arc stability is lowered. Therefore, the total mass of the slag forging agent in the wire is 5% by mass or less, preferably 3 Less than mass%. In addition, although it is accept | permitted that a slag faux agent is contained in the range which does not prevent the effect of this invention, it is preferable that there are few slag faux agents. Therefore, the lower limit is not set, but may be 0% by mass.

  Hereinafter, the reason why the contents of C, P, and Ni, which are elements included as inevitable impurities, are limited will be described. It is preferable not to contain these inevitable impurities (that is, 0% by mass), but it is allowed to contain them within the range not impeding the effects of the present invention, and if it is below the content shown below, it can be used without any problem. can do.

<C: 0.07 mass% or less>
C lowers the corrosion resistance / oxidation resistance, makes it easier to generate martensite, and lowers the ductility and easily generates cracks. The upper limit is acceptable up to 0.07% by mass. Preferably it is 0.03 mass% or less. Although a lower limit is not provided, since melting is difficult, in reality, about 0.001% by mass is industrially the lower limit.

<P: 0.025 mass% or less>
P is an element that degrades crack resistance, so it is reduced as much as possible. If the upper limit is 0.025% by mass, there is no practical problem, so this is the upper limit. In addition, since it is preferable that there is little P, a minimum is not set, but 0 mass% may be sufficient.

<Ni: 0.30 mass% or less>
Ni is an element unnecessary for ferritic stainless steel. Since the ferrite layer becomes unstable and the high-temperature oxidation resistance decreases as the Ni content increases, it is preferable that the Ni content is small. Since there is no problem if it is suppressed to 0.30 mass% or less industrially, the Ni content is set to 0.30 mass% or less. In addition, since it is preferable that there is little Ni, since a minimum is not set, 0 mass% may be sufficient.

  As unavoidable impurities, it may be possible to contain, for example, O, Zr, etc. in addition to C, P, Ni, but these are allowed to be contained within a range that does not impede the effects of the present invention. Is preferably 0.050% by mass or less.

_{^{<X = 0.32R 1 eq -3.86-}} N eq, X ≧ 0>
(In the formula, N ^eq = Ni mass% + 30 C mass% + 0.5 Mn mass%, R ₁ ^eq = Cr mass% + 1.5 Si mass%)
Here, N ^eq represents Ni equivalent, and R ₁ ^eq represents Cr equivalent. The weld metal formed when X ≧ 0 becomes a ferrite layer. On the other hand, when X <0, a martensite layer is deposited, resulting in a decrease in corrosion resistance and oxidation resistance, a decrease in fatigue performance against thermal cycling, and a decrease in ductility. Therefore, X ≧ 0 is essential.

In the flux cored wire according to the present invention, a Cu plating layer may be provided on the surface of the wire element.
<Cu of plating layer: 0.24 mass% or less>
Cu plating may be applied for the purpose of suppressing chip wear, improving rust resistance, and improving wire drawing at the time of manufacture, but it reduces the electrical resistance at the wire energization point, lowers the heat generation effect of the wire, and resists erosion. It is easy to deteriorate. Therefore, when Cu plating is performed, in the flux-cored wire, if it is 0.24% by mass or less, it is acceptable, so the Cu content of the plating layer is 0.24% by mass or less.

  The flux-cored wire according to the present invention preferably further contains one or more of N, Nb, V, Al, Ti, Mo, and F in addition to the above components. Hereinafter, these reasons for limitation will be described.

<N: 0.050 mass% or less>
N does not have any problem even if it is not added, but a small amount of addition improves hardenability, refines the crystal grains, and improves hot cracking resistance. However, if it exceeds 0.050 mass%, blowholes are generated and ductility is lowered, so the N content is 0.050 mass% or less. Moreover, since this effect becomes remarkable at 0.0040 mass% or more, it is preferable that the content of N is 0.0040 mass% or more.

<Nb: 1.00 mass% or less, V: 1.00 mass% or less>
Nb and V may be added without any problem, but by adding them, ferrite can be stabilized, crack resistance can be improved, and corrosion resistance and oxidation resistance can be improved. However, since ductility will fall when each exceeds 1.00 mass%, content of Nb and V shall be 1.00 mass% or less, respectively. Moreover, since this effect becomes remarkable at 0.10% by mass or more, it is preferable that the contents of Nb and V are each 0.10% by mass or more.

When Nb and V are included, “X = 0.32R ₂ ^eq- 3.86-N ^eq , X ≧ 0” (where N ^eq = Ni mass% + 30 C mass% + 0.5 Mn mass%, R ₂ ^eq = Cr mass% + 1.5 Si mass% + 0.5 (Nb mass% + V mass%)).
Here, N ^eq represents Ni equivalent, and R ₂ ^eq represents Cr equivalent. The weld metal formed when X ≧ 0 becomes a ferrite layer. On the other hand, when X <0, a martensite layer is deposited, resulting in a decrease in corrosion resistance and oxidation resistance, a decrease in fatigue performance against thermal cycling, and a decrease in ductility. Therefore, X ≧ 0 is essential.

<Al: 0.60 mass% or less, Ti: 0.60 mass% or less>
Al and Ti may be added without any problem, but when added in the same manner as Nb and V, the crystal grains can be refined to improve crack resistance, and corrosion resistance and oxidation resistance can be improved. However, if it exceeds 0.60% by mass, ductility is reduced, and a large amount of slag is generated to lower the paintability. Therefore, the contents of Al and Ti are each 0.60% by mass or less. Moreover, since this effect becomes remarkable at 0.05 mass% or more, it is preferable that the contents of Al and Ti are 0.05 mass% or more, respectively.

<Mo: 2.50 mass% or less>
Although there is no problem even if Mo is not added, adding it can refine crystal grains and improve crack resistance, as well as corrosion resistance and oxidation resistance. However, since ductility will fall when it exceeds 2.50 mass%, content of Mo shall be 2.50 mass% or less. Moreover, since this effect becomes remarkable at 0.05 mass% or more, it is preferable that content of Mo shall be 0.05 mass% or more. In particular, when the steel plate is applied to SUS444 or the like in which Mo is an essential addition, it is also essential for the weld metal. In this case, the same amount is added.

<F: 0.3 mass% or less>
There is no problem even if F is not added, but adding it is effective in improving the stability and concentration of the arc. However, if it exceeds 0.3% by mass, the stability of the arc is lowered and spatter is increased. Therefore, the content of F is set to 0.3% by mass or less. Moreover, since this effect becomes remarkable at 0.01 mass% or more, it is preferable that content of F shall be 0.01 mass% or more. In general, it is difficult to add F from the metal shell, and F is added from the flux. Typical examples of the fluoride for adding F include LiF, NaF, BaF, CaF ₂ , and AlF ₃ .

Furthermore, the flux-cored wire according to the present invention preferably contains at least 0.30% by mass of one or more of K, Na, and Li in addition to the above components. Hereinafter, these reasons for limitation will be described.
<K, Na, Li total: 0.30 mass% or less in total as flux>
There is no problem even if K, Na, and Li are not added, but it works as an arc stabilizer in welding using Ar + oxidizing gas (O ₂ , CO ₂ ). When the arc is unstable, the arc length changes and the arc force also fluctuates, but this deteriorates the burn-off resistance, so that the arc is preferably as stable as possible. However, since arc stability will be impaired conversely when it exceeds 0.30 mass%, the total of K, Na, and Li shall be 0.30 mass% or less. Further, when an arc stabilizer is contained, it is effective for improving the burn-through resistance, but since the effect is effective at 0.002% by mass or more, the total of K, Na, and Li is 0.002% by mass or more. It is preferable to do this. The addition method of a flux _K 2 _O, Na 2 O, an oxide such as Li ₂ O, carbonates such as _Li 2 CO _3, to use an alloy such as Li ferrite as a starting material is common.

<Others>
It does not matter whether the additive component is added from the metal sheath or from the flux, but in order to generate more heat at the protruding portion of the wire, it is effective to add the component to the metal sheath and increase the electrical resistance. .

Next, the flux-cored wire according to the present invention will be specifically described by comparing an example that satisfies the requirements of the present invention with a comparative example that does not satisfy the requirements of the present invention.
First, a 1.2 mmφ flux cored wire was prototyped using the metal shells α and β shown in Table 1. Tables 2 and 3 show the composition of the wires and the steel plates (test plates) used. In Tables 1 to 3, those that do not contain components are indicated by “-”, and in Table 3, those that do not satisfy the configuration of the present invention are underlined. In Tables 2 and 3, FCW is a flux-cored wire.

  Next, with regard to the wire, in addition to the following tests for burn-off resistance, high-temperature oxidation resistance, metallographic state, crack resistance, arc stability, and bending performance, X-ray transmission tests are performed to determine blowhole resistance, wire feed Sensory evaluations such as feedability and slag generation were performed.

<Sold-off resistance>
With respect to the burn-through resistance, SUS430 or a partly SUS444 stainless steel plate having a thickness of 2.0 mm was used, and downward I-type butting without a groove and without a root gap was performed at a speed of 80 cm / min. The shielding gas is Ar 80 volume% + CO ₂ 20 volume%, and the welding machine is a constant voltage inverter controller (no pulse). By changing the wire feed speed, the maximum welding amount at which no meltdown occurred was determined as the limit welding amount. It was evaluated that the larger the limit welding amount, the better the burn-out resistance. 40 g / min or more was good, and less than that was rejected.

<High temperature oxidation resistance>
For high-temperature oxidation resistance, a total weld metal test was performed in accordance with JIS Z3321, and an oxidation test piece having a thickness of 1.5 mm, a width of 10 mm, and a length of 40 mm was collected from the center of the weld metal, and 900 ° C. × 200 hours in the atmosphere. The weight before and after the test was measured. It was judged that the smaller the increase in oxidation, the better the high-temperature oxidation resistance. 5 g / m < ² > or less was good, and those exceeding it were rejected.

<Metallic state>
With regard to the metallographic state, it was determined by observation of the microstructure of the weld metal that the ferrite single phase was acceptable, and the one with the martensite phase precipitated was judged inappropriate for ferritic martensitic steel.

<Crack resistance>
According to JIS Z3155 “C-type jig restraint butt weld cracking test method”, the welding conditions were the current, voltage, and welding speed when the critical welding amount of the burn-off resistance was obtained. Those in which cracks occurred were rejected, and those that did not occur were determined to be acceptable.

<Arc stability>
As for the arc stability, the stability was evaluated by a sensuality in the test for burn-through resistance. It was considered good when the droplet transfer was stable and there was little spatter, the wire feedability was good, and the arc length was not disturbed. When the droplet transfer was unstable and there was a lot of spatter, the wire feedability was poor, and the arc length was disturbed, it was judged as rejected (x).

<Bending performance (ductility)>
Regarding the bending performance, 5 mm of the front side of the plate thickness was sliced out from the joint of the all-welded metal test, and the surface bending test was performed according to JIS Z3122 “Bending test method of butt welded joint”. 180 ° bending was performed at R10 mm, and the presence or absence of cracks was confirmed. Those with no defects and good ductility were accepted and cracked, and were rejected (x).

<Others>
When blowholes were found in the weld metal in the X-ray transmission test, the wire feedability was poor, the slag amount was large and the concern about paintability deterioration was high, and so on.
These results are shown in Tables 4 and 5. In Table 5, those numerical values that are not acceptable for burn-through resistance and high-temperature oxidation resistance are underlined.

  As shown in Table 4, Example No. In Nos. 1 to 23, since all the wire components satisfy the scope of the present invention, burn-off resistance, high-temperature oxidation resistance, metallographic state, crack resistance, arc stability, bending performance (ductility), wire feeding All payability is excellent.

  On the other hand, as shown in Table 5, in No. 24, since the C content exceeded the upper limit, martensite was generated and cracking occurred. In the bending test, cracks occurred and the high-temperature oxidation resistance was poor. In No. 25, since the Si content was less than the lower limit, the electric resistance of the protruding portion and the droplets was insufficient, and the burn-off resistance was not improved. In No. 26, since the Si content exceeded the upper limit, the droplets became large and the sputtering was excessive. Moreover, ductility also fell and the crack was produced in the bending test. In No. 27, since the Mn content was less than the lower limit, the electric resistance of the protruding portion and the droplet was insufficient, and the burn-off resistance was not improved. In No. 28, since the Mn content exceeded the upper limit, the droplets increased and the sputtering was excessive. Moreover, ductility also fell and the crack was produced in the bending test.

  In No. 29, since the P content exceeded the upper limit, hot cracking occurred. In No. 30, since the S content was less than the lower limit, the viscosity of the molten pool did not decrease, the depth of the molten pool directly under the arc was too small, and the burn-off resistance was not improved. In No. 31, since the S content exceeded the upper limit, hot cracking occurred. Moreover, ductility fell and the crack was produced in the bending test. No. 32 had low high-temperature oxidation resistance because the Cr content was less than the lower limit. In No. 33, the Cr content exceeded the upper limit, so the viscosity of the droplets became excessive and spatter increased. Moreover, ductility fell and the crack was produced in the bending test. No. 34 had low high-temperature oxidation resistance because the Ni content exceeded the upper limit. In No. 35, since the N content exceeded the upper limit, blowhole defects occurred during welding. In addition, the ductility decreased due to embrittlement, and cracking occurred in the bending test.

  In No. 36, Cu plating was applied to the wire, but since the Cu content of the plating exceeded the upper limit, the electrical resistance at the energization point was insufficient and the burn-off resistance was not improved. In Nos. 37, 38, and 39, there is no problem in the content of each element, but the parameter X is less than 0, and the weld metal is not a ferrite single phase. Since the martensite phase was precipitated, the ductility was lowered and cracking occurred in the bending test. Moreover, high temperature oxidation resistance was also inferior. In Nos. 40 and 41, the contents of Nb and V exceeded the upper limit, respectively, so that the ductility was lowered and cracking occurred in the bending test. In Nos. 42 and 43, since the contents of Al and Ti exceeded the upper limits, the ductility was lowered and cracking occurred in the bending test. Furthermore, the amount of slag generated was very large.

  In No. 44, since the Mo content exceeded the upper limit, the ductility was lowered and cracking occurred in the bending test. In No. 45, fluoride was excessive, arc stability was poor, and spatter was high. In No. 46, the total content of alkali metals K, Na, and Li exceeded the upper limit, resulting in poor arc stability and high spatter. In No. 47, the flux filling rate was less than the lower limit, so it was difficult to stably produce a uniform wire in the length direction of the flux. Therefore, the arc stability was also poor. In No. 48, since the flux filling rate exceeded the upper limit, the outer layer thickness was too thin, the strength was insufficient, the wire breakage occurred frequently during wire drawing, and the wire could not be manufactured stably. In No. 49, since the ratio of the slagging agent in the flux exceeded the upper limit, slag was excessively generated. Further, the arc stability was poor in a low current region of 200 A or less used for thin plate welding.

  Nos. 50 and 51 are examples of SUS430 and SUS444 flux cored wires that are generally distributed. In No. 50, since Si, Mn, and S are less than the lower limit, the depth of the molten pool just below the arc due to insufficient electrical resistance of the protruding portion and droplets and insufficient viscosity of the molten pool is both effective. The burn-off resistance was poor. In No. 51, since Si, Mn, and S are less than the lower limit, the electric resistance of the protruding portion and the droplets is insufficient, and the depth of the molten pool just below the arc due to the insufficient viscosity of the molten pool is both effective. The burn-off resistance was poor. Furthermore, cracks occurred because P exceeded the upper limit. Moreover, since Ti exceeded the upper limit, the amount of slag was excessive for thin plates, the ductility was lowered, and cracking occurred in the bending test. Moreover, since the ratio of the faux-forming agent in the flux exceeded the upper limit, the arc stability was poor.

  In No. 52, there is no problem in the content of each element, but the parameter X is less than 0, and the weld metal is not a ferrite single phase. Since the martensite phase was precipitated, the ductility was lowered and cracking occurred in the bending test. Moreover, high temperature oxidation resistance was also inferior. In No. 53, since the S content was less than the lower limit, the viscosity of the molten pool did not decrease, the depth of the molten pool immediately below the arc was too small, and the burn-off resistance was not improved.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and can be modified without departing from the scope of the present invention.

It is the schematic diagram which showed the mode of arc welding typically, (a) is a schematic diagram which shows the case where the conventional wire is used, (b) is the schematic diagram which shows the case where the wire which concerns on this invention is used. It is.

Explanation of symbols

1 Steel (base material)
2 chip 3, 31 wire 4 droplet 5 arc 6 molten pool

Claims (6)

In the flux-cored wire used for gas shield welding for ferritic stainless steel by filling the metal shell with flux,
The flux-cored wire is made of a steel alloy wire,
The flux filling rate with respect to the total mass of the wire is 5 to 30% by mass, and Si: 0.60 to 1.50% by mass, Mn: 0.40 to 2.00% by mass, S: 0.0. 01-20.100% by mass, Cr: 16.0-20.0% by mass, and further, the slag forging agent in the total mass of the flux is suppressed to 5% by mass or less, and the balance is Fe and inevitable impurities. Of the inevitable impurities, C: 0.07 mass% or less, P: 0.025 mass% or less, Ni: 0.30 mass% or less, and the following formula (1)
X = 0.32R ₁ ^eq- 3.86-N ^eq , X ≧ 0 (1)
(In the formula, N ^eq = Ni mass% + 30 C mass% + 0.5 Mn mass%, R ₁ ^eq = Cr mass% + 1.5 Si mass%)
Flux-cored wire characterized by satisfying In the flux-cored wire used for gas shield welding for ferritic stainless steel by filling the metal shell with flux,
The flux-cored wire is provided with a Cu plating layer on the surface of a wire wire made of a steel alloy,
The flux filling rate with respect to the total mass of the wire is 5 to 30% by mass, and Si: 0.60 to 1.50% by mass, Mn: 0.40 to 2.00% by mass, S: 0.0. 01-20.100% by mass, Cr: 16.0-20.0% by mass, and further, the slag forging agent in the total mass of the flux is suppressed to 5% by mass or less, and the balance is Fe and inevitable impurities. Of the inevitable impurities, C: 0.07% by mass or less, P: 0.025% by mass or less, Ni: 0.30% by mass or less, and the Cu plating layer is Cu: 0 as a whole wire composition. .24 mass% or less and the following formula (1)
X = 0.32R ₁ ^eq- 3.86-N ^eq , X ≧ 0 (1)
(In the formula, N ^eq = Ni mass% + 30 C mass% + 0.5 Mn mass%, R ₁ ^eq = Cr mass% + 1.5 Si mass%)
Flux-cored wire characterized by satisfying The flux-cored wire according to claim 1 or 2, further comprising: N: 0.050 mass% or less, Nb: 1.00 mass% or less, V: 1.00 mass% or less, Al: 0.60 mass. %: Ti: 0.60% by mass or less, Mo: 2.50% by mass or less, F: 0.3% by mass or less, and the following formula (2)
X = 0.32R ₂ ^eq- 3.86-N ^eq , X ≧ 0 (2)
(In the formula, N ^eq = Ni mass% + 30 C mass% + 0.5 Mn mass%, R ₂ ^eq = Cr mass% + 1.5 Si mass% + 0.5 (Nb mass% + V mass%))
Flux-cored wire characterized by satisfying   The N is 0.0040 to 0.050 mass%, the Nb is 0.10 to 1.00 mass%, the V is 0.10 to 1.00 mass%, and the Al is 0.05 to 0.60 mass%. %, Ti is 0.05 to 0.60 mass%, Mo is 0.05 to 2.50 mass%, and F is 0.01 to 0.3 mass%. The flux cored wire described in 1. In the flux cored wire according to any one of claims 1 to 4,
Furthermore, the flux-cored wire characterized by containing one or more of K, Na, and Li in a total of 0.30 mass% or less.   The flux-cored wire according to claim 5, wherein the total of one or more of K, Na, and Li is 0.002 to 0.30 mass%.

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