JPH07290279A - Flux cored stainless steel wire - Google Patents

Abstract

PURPOSE:To produce a flux cored stainless steel wire excellent in the cracking resistance and bendability of a weld metal and applicable to welding in all attitudes for a stainless steel. CONSTITUTION:The outer surface is constituted of a stainless steel contg., by weight, >=11% Cr. Furthermore, in the flux, metal or alloy powder having >=200 deg.C m.p. (excluding stainless steel powder) is not substantially contained or, in the case it is contained, as for the metal or alloy powder having >=1200 deg.C m.p. (excluding stainless steel powder), the content of powdery grains having <=150mum grain size is regulated to >=80%, and the contents of both P and S are regulated to <=0.13%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel flux-cored wire used for welding stainless steel materials,
Particularly, the present invention relates to a stainless steel flux-cored wire which has excellent crack resistance and bending performance of weld metal and is suitable for all-position welding.

[0002]

2. Description of the Related Art Gas shielded arc welding using a flux-cored wire is highly efficient as compared with welding using a TIG welding and a coated arc welding rod.
The range of application is expanded to various materials. In addition, flux-cored wires were often used in the downward position where a large current can be used initially, but in recent years, all-position welding used with a relatively low current (especially welding in the vertical position and upward position). Usage in the world is growing rapidly.

[0003]

However, when the conventional flux-cored wire is applied to welding of stainless steel material, crack resistance and bending performance can be satisfied in all-position welding used at relatively low current. It wasn't something. Conventionally, the melting point in the flux is 160
It has been proposed to prevent the segregation of the metal powder in the molten metal by defining the particle size of the metal powder at 0 ° C. or higher (JP-A-54-79140). But,
Bending performance can be improved to some extent only by making the particle size of the metal powder fine, but there is a problem that microcracks cannot be prevented.

The present invention has been made in view of the above problems, and provides a stainless steel flux-cored wire which has excellent crack resistance and bending workability of weld metal and can be applied to all-position welding of stainless steel materials. With the goal.

[0005]

The stainless steel flux cored wire according to the first invention of the present application contains 11% by weight of Cr.
In a stainless steel flux cored wire obtained by filling the inside of a stainless steel outer shell containing flux as described above, in the flux, metal or alloy powder having a melting point of 1200 ° C. or higher (excluding stainless steel powder) is substantially used. It is characterized in that it is not included.

The stainless steel flux-cored wire according to the second aspect of the present invention is a stainless steel flux-cored wire obtained by filling the inside of a stainless steel outer sheath containing 11 wt% or more of Cr with flux. Of the metal or alloy powder to be melted, the melting point is 120
Each of the metal or alloy powders having a temperature of 0 ° C. or higher (excluding stainless steel powder) has a content of powder particles having a particle diameter of 150 μm or less of 80% by weight or more and a P content of 0.13% by weight. Hereinafter, the S content is controlled to be 0.13% by weight or less.

[0007]

In the present invention, among the metal or alloy powders contained in the flux, the metal or alloy powders having a melting point of 1200 ° C. or higher (excluding the stainless steel powder) are substantially not contained or are contained. Of the metal or alloy powder having a melting point of 1200 ° C. or higher, the content of the powder particles having a particle diameter of 150 μm or less is 80% by weight or more. For example,
When there is only one kind of metal or alloy powder having a melting point of 1200 ° C. or higher among the metal or alloy powder contained in the flux, 80 wt% or more of the metal or alloy powder has a particle size of 150 μm or less. To occupy. Further, when there are two or more kinds of metal or alloy powder having a melting point of 1200 ° C or higher among the metal or alloy powder contained in the flux, 80% by weight or more of the metal or alloy powder of each kind is grained. The powder particles having a diameter of 150 μm or less are occupied. Particle size in metal or alloy powder is 150μ
When the content of powder particles of m or less is less than 80% by weight,
The amount of unmelted metal in the weld metal increases, bending performance deteriorates, and it causes microcracks. Therefore, in the metal or alloy powder, the content of powder particles having a particle size of 150 μm or less needs to be 80% by weight or more.

Both the P content and the S content in the metal or alloy powder must be 0.13% by weight or less. P content or S content is 0.13% by weight
If it exceeds, P will be generated at the boundary between the unmelted metal and matrix.
Alternatively, S is significantly segregated and causes microcracks. Therefore, with respect to the metal or alloy powder having a melting point of 1200 ° C. or higher contained in the flux, it is necessary that the P content rate and the S content rate are both 0.13% by weight or less.

Further, in the case of metal or alloy powder having a melting point of 1600 ° C. or higher, it is preferable that the content of the powder having a particle size of 150 μm or less is 90% by weight or more. Furthermore, P
By setting both the content rate and the S content rate to 0.05% by weight or less, it is possible to reliably prevent the occurrence of defects in microcracks and bending tests.

In the case of stainless steel powder, even if the content of powder particles having a particle size of 150 μm or more is less than 80% by weight, no significant segregation of the components occurs in the weld metal, crack resistance and bending resistance. Does not affect performance. Therefore, in the case of stainless steel powder, it is not necessary to specify the particle size. Further, since the flux-cored wire according to the present invention is used for welding a stainless steel material, it does not impair the uniformity of the weld metal and suppresses the amount of alloy addition from the flux (that is, the flux is overfilled). In order to prevent this, the material of the outer skin needs to be stainless steel with a Cr content of 11 wt% or more. As the stainless steel containing 11% by weight or more of Cr, for example, SUS4 specified in JIS G4306 is used.
10L, 430LX, 304L and 316L.

[0011]

EXAMPLES Examples of the present invention will be described in more detail below. The inventors of the present application conducted various experimental studies in order to provide a stainless steel flux-cored wire applicable to all-position welding of stainless steel materials. As a result, the following was revealed. That is, in a flux-cored wire having a stainless steel outer shell, the wire diameter is 1.2 mm,
When the minimum current value that can be practically used in all-position welding is 120 A, the metal or alloy powder in the flux (hereinafter,
(Hereinafter simply referred to as “metal powder”) having a melting point of less than 1200 ° C., such as Cu and Al, even if the metal powder has a large particle size of up to 250 μm,
No unmelted metal is observed in the weld metal.

However, when the metal powder has a melting point of 1200 ° C. or higher such as metals such as Mo, Cr and Mn or alloys of these metals and iron, unmelted metal is observed in the weld metal and Defects were observed in cracking and bending tests. The cause of such cracks or defects is considered to be segregation of the metal powder filled in the flux-cored wire.

Next, the inventors of the present invention conducted tests by changing the particle size distribution of the metal powder. As a result, the bending performance of the weld metal was improved to some extent by reducing the particle size of the metal powder, but it was not possible to sufficiently suppress microcracks. In FIG. 1, the horizontal axis indicates the particle size of 15 in the metal powder.
The content of powder particles of 0 μm or less is taken, and the vertical axis is the number of defects per bending test piece. The welding current is 180 A.
It is a graph figure which shows the number of defects generation at the time of and 120A. As can be seen from FIG. 1, the particle size is 150 μm.
By setting the content of the following powder particles to 80% by weight or more, the number of defects generated becomes substantially 0 when the welding current is 180 A, and the number of defects becomes approximately 5 or less even when the welding current is 120 A. .

However, the number of defects in the bending test can be reduced but the microcracks cannot be suppressed only by reducing the particle size of the metal powder. Therefore, the inventors of the present application conducted various experimental studies to clarify the cause of microcracks. As a result, it was found that microcracks were generated at the boundary between the unmelted metal and the matrix, where the metal powder could not be sufficiently stirred and melted in the matrix. EPMA (Electron Probe Microanalysis)
Microanalysis) analyzed the components at the boundary between the unmelted metal and the matrix. As a result, P or S supplied from the metal powder was significantly segregated at this boundary. From the above, the present inventors have found that the cause of microcracks is S or P contained in the metal powder.

In FIG. 2, the abscissa represents the P and S contents, and the ordinate represents the number of microcracks per cm ² of the speculum. The relationship between the P and S contents in the metal powder and the number of microcracks is shown. It is a graph figure which shows. As can be seen from FIG. 2, by setting both the P content and the S content in the metal powder to 0.13 wt% or less, microcracks can be sufficiently suppressed.

By the way, the metal powder to be filled in the flux is filled with the oxidative consumption at the time of welding and secures a predetermined chemical composition of the weld metal to obtain corrosion resistance and heat resistance.
Alternatively, it is added as a deoxidizing agent in order to improve the cleanliness of the weld metal and secure characteristics such as ductility and toughness. As the metal powder, Ni, Cr, Fe, Mo, Nb, W, Mn, S
There are i, Ti, Cu, Al, Mg and Zr and alloys of these metals. However, in the case of a stainless steel powder having a component similar to that of the outer shell, even if the content of powder particles having a particle size of 150 μm or less is less than 80% by weight, significant component segregation does not occur, crack resistance and bending resistance Does not cause performance deterioration. Therefore, it is not necessary to regulate the powder particle size of the stainless steel powder.

Hereinafter, the flux-cored wire according to the present invention is actually manufactured, welding is performed using these wires, and a test piece is sampled from the weld metal, and a bending test causes defects and micro-cracks. Regarding the result of examining the occurrence,
This will be described in comparison with a comparative example.

First, a stainless steel hoop material (having a width of 9 mm and a thickness of 0.
4 mm) was prepared. In addition, as the metal powder raw material to be filled in the outer skin, metal powders of the types shown in Table 2 below were prepared. Table 2 also shows the melting point, particle size composition, P and S content of these metal powders. Then, as shown in Table 3 below, the hoop material and the metal powder were combined to manufacture a flux-cored wire. In this case, 23% by weight of the total weight of the wire was added of the building agent. This forming agent is SiO ₂ ; 2% by weight, TiO ₂ ; 10% by weight, ZrO based on the total weight of the wire.
₂ ; 2% by weight and Al ₂ O ₃ ; 2% by weight, the balance being metallic Fe. Further, this metallic Fe has a melting point of 15
The temperature is 38 ° C., the content of powder particles having a particle size of 150 μm or less is 93% by weight, the P content is 0.02% by weight, and the S content is 0.02% by weight.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

Each wire was finish-drawn to a diameter of 1.2 mm and then electrically heated to reduce the water content to 500 ppm or less based on the total weight of the wire.

Using these wires, JIS Z33
In accordance with No. 23, a current was 120 A, a voltage was 25 V, and CO ₂ (100%) was used as a shielding gas to prepare a completely welded metal in a vertical posture. Then, a micro test piece was cut out from this deposited metal and inspected for cracks. Also, JI
A longitudinal bending test was performed according to SZ3323 to examine the presence or absence of defects. The results are shown in Table 4 below. However, the micro-cracking was rated as × when there were 4 or more micro-cracks per 1 cm ² of the microscopic field of view, and as ◯ when there were 3 or less micro-cracks, and as ◎ when there were no cracks. In addition, the bending test results were evaluated as × when there were 4 or more defects with respect to one test piece, ◯ when there were 3 or less defects, and ◯ when there were no defects. Furthermore, from these results, the performance as a flux-cored wire for stainless steel materials was evaluated. The results are also shown in Table 4. However, the case where it is suitable as a flux-cored wire for stainless steel materials is shown by O, and the case where it is not suitable is shown by X.

[0024]

[Table 4]

Wire Nos. 1, 10 and 20 (Comparative Example 1,
In Nos. 4, 6), the content of the powder particles having a particle diameter of more than 150 μm is 20% by weight or more, so that unmelted metal is observed,
A large number (4 or more) of defects were generated in the bending test, and the bending performance was not sufficient.

Wire Nos. 2, 3, 15, and 24 (Comparative Examples 2, 3, 5, and 7) had a P or S content of the metal powder of 0.1.
Since it exceeds 3% by weight, even if the content of powder particles having a particle size of 150 μm or less is 80% by weight or more, segregation of P or S occurs during the melting process and microcracks occur.

In the wire Nos. 11 and 12 (Examples 7 and 8), since the melting point of the metal powder was less than 1200 ° C., no unmelted metal was observed and the bending performance was good.

Wire Nos. 5, 6, 8, 9, 14, 16,
17, 19, 21, 22, 23 (Examples 2, 3, 5,
6, 10, 11, 12, 14 to 17), some defects were observed in the micro-cracking and bending tests, but they were practically acceptable.

Wire No. 7 (Example 4) had some microcracks, but no defects were found in the bending test. Wire Nos. 4, 13, 18 (Example 1,
9 and 13) had no microcracks and no defects in the bending test.

The stainless-steel flux-cored wire for all-position welding of the present invention can be applied not only for common metal welding of stainless steel, but also for welding dissimilar materials such as carbon steel and stainless steel.

[0031]

As described above, according to the present invention, the flux does not substantially contain the metal or alloy powder having a melting point of 1200 ° C. or higher, or when it contains the powder, the melting point is 1200.
The content of powder particles having a particle size of 150 μm or more of metal or alloy powder of 80 ° C. or more is 80% by weight or more, and
Since the P content and the S content are both regulated to 0.13% by weight or less, it is possible to avoid the occurrence of defects due to microcracks and bending tests. For example, the welding current is about 120A.
It is possible to obtain a good weld metal even at a low current. Therefore, the stainless steel flux-cored wire according to the present invention is capable of excellent welding in all-position welding of stainless steel materials.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the content of metal powder having a particle size of 150 μm or less and the number of defects generated in a bending test.

FIG. 2 is a graph showing the relationship between P and S contents in metal powder and microcracks.

Claims (5)

[Claims] 1. A stainless steel flux cored wire obtained by filling a flux inside a stainless steel skin containing 11% by weight or more of Cr, wherein the flux contains a metal or alloy powder having a melting point of 1200 ° C. or higher ( However, a stainless steel flux-cored wire which is substantially free of (except for stainless steel powder). 2. A stainless steel flux cored wire obtained by filling a flux inside a stainless steel skin containing 11 wt% or more of Cr, wherein the melting point of the metal or alloy powder contained in the flux is 1200 ° C.
Each of the above metal or alloy powders (excluding stainless steel powder) has a content of powder particles having a particle size of 150 μm or less of 80% by weight or more and a P content of 0.1 or less.
A stainless steel flux-cored wire characterized in that the content of S is regulated to 3% by weight or less and the S content is regulated to 0.13% by weight or less. 3. The metal or alloy powder having a melting point of 1600 ° C. or higher among the metal or alloy powders contained in the flux has a content of powder particles having a particle diameter of 150 μm or less of 90% by weight or more, respectively. The stainless steel flux cored wire according to claim 2. 4. The P content of each metal or alloy powder having a melting point of 1600 ° C. or higher is regulated to 0.05% by weight or less and the S content is regulated to 0.05% by weight or less. 3. The stainless steel flux-cored wire according to item 3. 5. The P content of each of the metal or alloy powders having a melting point of 1200 ° C. or higher is regulated to 0.05% by weight or less, and the S content thereof is regulated to 0.05% by weight or less. 2. The stainless steel flux-cored wire according to 2 or 3.