JP2000326090A - Tig welding flux of stainless steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable deep penetration welding without generating a fluorine gas by containing SiO2, CrO and specifying the range of the content ratio of Cr2O3/SiO2. SOLUTION: This flux in which a content ratio value of Cr2O3/SiO2 is in a range of 0.15-2.0. When using the flux in which a content ratio of Cr2O3/SiO2 is mixed to a range of 0.15-2.0, the surface tension of a molten pool is turned to <=600 dyne/cm, the surface tension is greatly reduced as compared to the case except this range. Furthermore in the range of a content ratio of 0.15-2.0, regardless of the increase in the input heat quantity, the surface tension is maintained in a prescribed range. The flux, in TIG welding of a stainless steel, increases the penetration depth to improve welding part quality and to shorten a welding time. The flux does not generate a fluorine gas, a simple clothing is acceptable for working, and set up time is shortened as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a stainless steel T
The present invention relates to a flux used when performing IG welding.

[0002]

2. Description of the Related Art When performing TIG welding on stainless steel,
As shown in FIG. 5, the penetration depth is somewhat
It is known that it depends on the content of. The horizontal axis of FIG. 5 indicates the content (% by weight) of sulfur S contained in stainless steel, and the vertical axis indicates penetration D. In the figure, a
The curve indicated by the curve represents the case where the input current during welding was 160 A, and the curve indicated by the curve b indicates the case where the input current was 140 A. As shown in curves a and b, the content of sulfur S contained in the stainless steel is 8
%, The penetration depth D becomes substantially constant irrespective of the content of sulfur S, but up to a content of 6% by weight, the penetration depth D increases in proportion to the sulfur content. I have.

Conventionally, when performing TIG welding on a fixed pipe formed of stainless steel, a U-shaped groove shown in FIG. 6 or a V-shaped groove shown in FIG. 7 is provided. In this case, the root face RF is a length from the bottom surface of the stainless steel to the bottom of the groove, the root gap RG is a distance between opposing surfaces of the groove bottom formed in the stainless steel, and the bottom surface is parallel to the bottom surface of the stainless steel. If the length L of the parallel portion, which is the distance from the open front end surface of the groove bottom, is not appropriately changed according to the content of sulfur S contained in the stainless steel, poor penetration may occur.
Inconveniences such as Uranami dents occur.

On the other hand, in order to improve the efficiency of welding, it is necessary to reduce the surface area of the groove as much as possible. Therefore, it is conceivable to form the groove in an I-shape. However, the bevel is I
It is difficult to secure deep penetration if normal TIG welding is performed using a mold (see FIG. 8).

[0005] There are several methods for ensuring a sufficient penetration depth, such as the flux shown in the experimental report of TWI in the United Kingdom, the United States,
There is a method of applying a flux from EWI to stainless steel. However, in these methods, since the flux contains NaF which is a fluorine compound, fluorine gas may be generated. Therefore, it is necessary to make the equipment of the welding operator heavy equipment, which requires time for setup, and the total working time has not always been reduced.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and when performing TIG welding on stainless steel, the stainless steel can be deeply penetrated without generating fluorine gas. And a flux for TIG welding.

[0007]

In [SUMMARY OF THE The present invention relates to a flux used for TIG welding of stainless steel, the flux contains SiO ₂ and Cr ₂ O _3, Cr ₂ O
₃ / the value of the component ratio of SiO ₂ to solve the above problems by TIG welding flux Stainless steel is the range of 0.15 to 2.0.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

Generally, the welding depth is determined by the surface tension, viscosity, molten metal temperature and other factors of the base material. According to various experiments by the inventor of the present invention, TIG was added to stainless steel.
When welding was performed, it was found that the component ratio of SiO ₂ and Cr ₂ O ₃ contained in the flux used at the time of welding affects the surface tension of the molten pool.

When a flux in which the component ratio of Cr ₂ O ₃ to SiO ₂ is mixed in the range of 0.15 to 2.0 is applied to the surface of stainless steel to be welded and TIG-welded, the surface tension of the molten pool is obtained. Is 600 dyne / cm or less, and the surface tension can be significantly reduced as compared with the case outside the above range. In contrast, Cr ₂
If the component ratio of O ₃ to SiO ₂ is smaller than 0.15, the surface tension of the molten pool increases. Conversely, Cr ₂ O ₃
The surface tension of the molten pool increases even if the component ratio of SiO ₂ to SiO ₂ is larger than 2.0.

When the component ratio is in the range of 0.15 to 2.0, the surface tension can be kept in a predetermined range regardless of the increase in the heat input. The ratio of Cr ₂ O ₃ to SiO ₂ is preferably 0.5 to 0.8, and more preferably 0.6 to 0.7.

[0012]

Example 1 A test flux was applied to stainless steel, a bead-on-plate test was performed by TIG welding, and the penetration depth was measured. The test flux was Cr ₂ O ₃
And SiO _2, and the ratio of Cr ₂ O ₃ is 70 to 40.
Wt%, it was used that the ratio of SiO ₂ was varied in the range of 30 to 60 wt%. In addition, a bead-on-plate test was similarly performed on SS7 containing a fluorine compound manufactured by EWI. The test flux was Cr
₂ O ₃ and SiO ₂ were dissolved in acetone and applied to a stainless steel groove with a brush. The stainless steel used was SUS304 having the chemical composition shown in Table 1 and had a thickness of 6 mm.

[0013]

[Table 1]

FIG. 1 shows the relationship between the amount of heat input and the penetration depth when a test was performed with the arc length fixed at 3 mm. The vertical axis of this figure is the penetration depth (mm), and the horizontal axis is the heat input (K
J / cm). In addition, the data shown in the figure shows that Cr ₂ O ₃ and S
The content of iO ₂ is for the fluxes shown in Table 2.

[0015]

[Table 2]

As is apparent from this figure, the test flux has generally deeper penetration than SS7 containing a fluorine compound. When the test fluxes used are compared with each other, if the heat input amounts are the same, the penetration depth is such that the Cr ₂ O ₃ ratio is 40% by weight and the SiO ₂ ratio is 60% by weight. You can see the deepest.

FIG. 2A shows that the heat input is reduced to 12 KJ / cm.
Penetration depth when fixing and Cr_TwoO_ThreeSiO_TwoTo
Percentage, Cr_TwoO_Three/ SiO_TwoShows a relationship with
You. Cr _TwoO_ThreeSiO_TwoWith a different ratio to
Of which, Cr_TwoO_Three/ SiO_TwoIs between 0.15 and 2
If it is within the range, compare it with SS7 containing fluorine compounds.
It has almost deep penetration. In particular, Cr_TwoO_Three/ Si
O_TwoValue of 0.5 to 0.8 to obtain deep penetration
Is peaked when it takes a value of about 0.7,
Its value is about 6 mm.

On the other hand, FIG. 2B shows an aspect ratio D / W
(See FIG. 3) and Cr_TwoO_ThreeSiO _TwoTo the ratio (C
r_TwoO_Three/ SiO_Two). From this figure
Clearly, Cr_TwoO_Three/ SiO_TwoIs 0.6-
In the vicinity of 0.7, the aspect ratio is extremely good at about 0.8.
It shows good values.

[0019]

Example 2 A groove shown in FIG. 4 was formed in a stainless steel pipe material having a thickness of 6 mm, and Cr ₂ O ₃ was formed on the groove.
When a flux consisting of SiO ₂ and SiO ₂ was applied and TIG welding was performed, the welding time was reduced to about 1/5 as compared with the conventional case in which a 70 ° V-shaped groove was formed and TIG welding was performed.

[0020]

As described above, the flux of the present invention can deepen the penetration when performing TIG welding on stainless steel, and improves the quality of the welded portion. Further, the deeper the penetration, the shorter the welding time can be. Furthermore, in the flux according to the present invention,
Since no fluorine compound is contained, no fluorine gas is generated, the equipment required for work can be lightened, and the setup time is also reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a heat input amount and a penetration depth in a bead-on-plate test of Example 1.

FIG. 2 shows the penetration depth of Cr ₂ O ₃ / SiO ₂ and the Cr ₂ O ₃ in the bead-on-plate test of Example 1.
/ Shows the relationship between the aspect ratio between the depth and width penetration for SiO _2.

FIG. 3 is a diagram showing a penetration depth D and a penetration width W in a bead-on-plate test.

FIG. 4 is a view showing the shape of a groove formed on a stainless steel pipe material in Example 2.

FIG. 5 is a diagram showing a general relationship between a penetration width and a penetration depth for S added to stainless steel.

FIG. 6 is a view showing a U-shaped groove formed in stainless steel.

FIG. 7 is a view showing a V-shaped groove formed in stainless steel.

FIG. 8 is a diagram showing an I-shaped groove formed in stainless steel.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E084 AA03 AA15 CA19 DA31 EA09 HA01

Claims (1)

[Claims] 1. A flux used for TIG welding of stainless steel, wherein the flux contains SiO ₂ and Cr ₂ O ₃ ,
A flux for TIG welding of stainless steel, wherein a value of a component ratio of r ₂ O ₃ / SiO ₂ is in a range of 0.15 to 2.0.