JPH0237836B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a filler metal for TIG welding that can obtain a sound bead, especially a back bead, in any welding position without using a backshield gas. [Conventional technology] Single-sided TIG welding is often used when welding stainless steel, Ni alloys, etc. from one side, but when performing such single-sided TIG welding, it is recommended to use backshield gas. is common. However, considering the complexity of welding design and the difficulty of supplying shielding gas in narrow welding, there is a demand for a filler metal for TIG welding that can obtain a sound back bead without using backshielding gas. For example, Japanese Patent Application Laid-Open No. 109595/1983 has been proposed. The filler material is a composite wire in which a cavity surrounded by a metal shell is filled with flux, and the back bead is covered with the produced slag to achieve insulation from the outside air, so that a healthy back bead can be obtained. Can be done. By the way, single-sided TIG welding is often applied to circumferential welding of relatively small-diameter pipes, and since it is common to weld the pipes in a fixed position, it is essential to be able to use all-position welding. has been done. However, the filler metal according to the above proposal can only achieve its purpose in a downward position, and welding workability in an upright position, an upward position, etc. is not necessarily satisfactory. In other words, in the downward position, the slag can cover the back bead relatively easily, but in the upright or upward position, the back bead is insufficiently covered due to insufficient amount of slag dripping down. Therefore, it was not possible to make the back bead sound. Moreover, depending on the formulation, there was a drawback that the tungsten electrode was considerably worn out due to the generation of spatter or the scattering of slag. [Problems to be Solved by the Invention] The present invention has been made in view of these circumstances, and it is possible to obtain a sound back bead in all welding positions without using back shield gas, and also to improve the welding process. The purpose is to provide a filler metal for TIG welding that has good workability. [Means for Solving the Problems] The filler metal of the present invention that has achieved the above object is a filler metal for TIG welding in which a cavity surrounded by a metal skin is filled with flux. Contains _TiO2 : 4.5-8.5%, metal fluoride: 0.20-1.75 (in terms of fluorine amount) _SiO2 : 0.2-2.5%, and the total metal carbonate content is 1.0% based on the total weight of the material.
or less, and the total content of the slag forming agent is 6 to 6.
The gist of this is that it is set at 10%. [Function] The present invention aims to obtain good back bead covering properties, welding workability, slag removability after welding, etc. when performing single-sided TIG welding in all postures including vertical and upward postures. The amount of flux to be filled into the cavity surrounded by the metal shell is defined as follows. Each flux component will be explained in order below. It should be noted that all blending amounts refer to proportions to the total weight of the filler material. TiO ₂ :4.5-8.5% TiO ₂ is the best slag forming agent that can exhibit the above required properties, and is used as a flux component.
It is necessary to contain 4.5 to 8.5%. Content is 4.5%
If it is less than that, the encapsulation of the back bead will not be sufficient. on the other hand
If the content exceeds 8.5%, the meltability of the flux portion is poor, so only the outer metal is melted, leaving the central flux in an unmelted state protruding for a long time, resulting in a marked deterioration in welding workability. Examples of the TiO ₂ source include rutile, titanium white, illuminite, potassium titanate, and the like. Metal fluoride: 0.20 to 1.75% (in terms of fluorine content) Provides appropriate fluidity to the molten slag and improves the encapsulation of the back bead, but if it is less than 0.20%, a sufficient effect cannot be obtained. On the other hand, if the content exceeds 1.75, the slag becomes too fluid and welding workability deteriorates, and the amount of fluorine gas generated by thermal decomposition increases, resulting in a poor welding work environment. Such metal fluorides include CaF ₂ , MgF ₂ , BaF ₂ ,
Examples include AlF ₃ , LiF, NaF, Na ₃ AlF ₆ and the like. SiO ₂ : 0.2-2.5% A slag forming agent that exhibits an excellent effect in stably enclosing the back bead. It imparts appropriate viscosity and surface tension to the slag, so it stabilizes a good back bead. This ensures the integrity of the weld metal and provides good X-ray performance. but
If the content is less than 0.2%, no effect will be observed, while if the content exceeds 2.5%, the slag removability will be poor and a great deal of effort will be required for cleaning work after welding. Examples of such SiO ₂ sources include silica sand, wollastonite, and feldspar. Metal carbonate: 1.0% or less Metal carbonate has an arc stabilizing effect, but it thermally decomposes during welding, causing spatter and scattering of molten slag. Furthermore, the generation of spatter causes the molten slag bath to vibrate, and the spatter and slag adhere to the tungsten electrode, thereby accelerating the wear of the tungsten electrode. As a result, welding workability is significantly hindered. In this way, metal carbonates
It has a significant negative effect on TIG welding, so it is desirable not to include it, but the permissible limit is 1.0%. Carbonates include CaCO ₃ , MgCO ₃ ,
Examples include BaCO ₃ , MnCO ³ , Li ₂ CO ₃ and SrCO ₃ . Total content of slag forming agents: 6 to 10% The slag forming agents include the above-mentioned components, metal oxides, metal fluorides, metal carbonates, and composite compounds thereof in addition to the above-mentioned components. The total content of such slag-forming agents should be 6 to 6 to ensure the necessary amount of slag to shield and protect the back bead from the atmosphere.
Should be 10%. If it is less than 6%, the back bead cannot be completely encapsulated in an upright or upward position. On the other hand, if it exceeds 10%, the amount of molten slag will be excessive and the slag will flow to the front of the groove.
Particularly in the upward position, the slag hangs down, making welding work extremely difficult. Slag forming agents other than those mentioned above include ZrO ₂ , Al ₂ O ₃ , CaO, BaO, MgO,
Examples include MnO, FeO, K ₂ O, Na ₂ O, Bi ₂ O ₃ and the like. The basic structure of the present invention is as described above, which not only gives the molten slag an appropriate viscosity or fluidity, but also prevents the generation of spatter and the scattering of the slag, and also prevents the molten slag from being filled inside the metal shell. Due to the good meltability of the flux portion, the meltability as a filler material is also improved. In addition to adjusting the flux composition as described above, methods for further increasing the meltability of the filler metal include
For example, it is recommended to use a flux raw material whose melting point is lowered by once melting and then solidifying it, so that the effect of improving meltability is further enhanced and excellent welding workability can be obtained. In addition, Si in the filler metal contributes to the formation of the back bead,
In particular, it improves the slag envelopment at the back bead side end. For this reason, it is desirable to contain at least 0.5% of Si, but if it is contained in excess of 1.5%, an undesirable situation will occur in which the cracking resistance of the weld metal and the susceptibility to embrittlement during high-temperature use will increase. . Therefore, it is desirable that the Si content be 0.5 to 1.5%. Note that Si exhibits the same effect not only when added to the filling flux but also when added to the metal sheath, so the amount of Si contained in both the metal sheath and the flux may be within the above range. Regarding the other components of the metal sheath, a matching metal or a non-matching metal may be appropriately selected depending on the type of metal to be welded. [Example] Using a composite wire in which the flux shown in Table 2 was filled in the metal shell having the composition shown in Table 1,
Pipe made of stainless steel plate or Inconel alloy plate specified in JIS-G-4305 (100mm〓×6
mm ^t and 300 mm × 12 mm ^t ) all-position TIG welding was performed. The welding conditions were as follows. The welding results were evaluated based on welding workability, slag encapsulation, back bead formation, slag removability, X-ray transmission test results, etc., and the results shown in Table 2 were obtained. (Welding conditions) Welding power source: DC drooping characteristics Polarity: DC positive Welding voltage: 10 to 15V Welding current: 80 to 130A Conditions: 1 layer, 1 pass Welding electrode: Thorium-containing tungsten 3.2 mm Shielding gas: Ar, 15/min Groove shape: As shown in Figure 1

【table】
(%)

【table】

[Table] In Nos. 1 and 2, the TiO ₂ content was low, so the slag envelopment of the back bead was poor, and a satisfactory bead could not be formed. No.3 is _TiO2
In the comparative example where the slag content is excessive, the slag coverage is good and a back bead is formed, but the flux in the wire is difficult to melt and protrudes, resulting in poor welding workability and welding in an upward position. It was confirmed by an X-ray transmission test that unmelted wire was mixed into the metal. No. 4 had poor slag encapsulation due to lack of metal fluoride. In No. 5, the fluidity of the slag became excessively high due to the excessive amount of metal fluoride, and in the downward position, the molten slag flowed forward inside the groove, worsening welding workability. Furthermore, in the upright or upward position, the slag flows out, resulting in poor slag envelopment of the back bead, making it impossible to form a satisfactory back bead. In No. 6, due to the lack of SiO ₂ , the slag envelopment was slightly poor and the ability to form a back bead was also slightly poor. No. 7 is a comparative example with too much SiO ₂ .
Approximately good results were obtained, but the slag removability was not satisfactory. Nos. 8 and 9 had poor workability because they contained more than 1.0% of metal carbonate. No. 10 had poor slag envelopment and poor back bead formation due to insufficient slag forming agent.
In Nos. 11 to 13, the total content of slag forming agents was excessive, so the front part of the groove was filled with molten slag especially in the downward position, resulting in poor welding workability. No.14～21
are all examples that satisfy the requirements of the present invention,
Good results were obtained. Next, a case will be described in which a flux that has been melted and then cooled is added as the flux. Using a composite wire filled with the flux shown in Table 4 in the metal sheath shown by A in Table 1,
All positions of stainless steel plate pipes (100mm〓×6mm ^t and 300〓×12mm〓) specified in JIS-G-4305
When TIG welding was performed under the same welding conditions as above, the results shown in Table 4 were obtained. The chemical composition and melting point of the melt-treated flux are shown in Table 3, and the flux component composition indicates the composition of the flux including the melt-treated flux and the single flux.

[Table] All of the melt-treated fluxes shown in Table 3 have melting points lower than the melting points of the simple substances (TiO ₂ : 1640°C, CaF ₂ : 1386°C), and have the property of being easier to melt than the simple substance fluxes.

【table】

〔Effect of the invention〕

The present invention is constructed as described above, and when performing TIG welding without using back shield gas in all welding positions, it is possible to obtain a sound back bead by using the filler metal according to the present invention. can.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view showing the groove shape.

Claims (1)

[Scope of Claims] 1. A filler metal for TIG welding in which a cavity surrounded by a metal shell is filled with flux, wherein the flux contains TiO ₂ at 4.5 to 8.5% (meaning the percentage relative to the total weight of the filler metal). , hereinafter the same) Metal fluoride: 0.20 to 1.75% (in terms of fluorine amount) SiO ₂ : 0.2 to 2.5%, the metal carbonate content is 1.0% or less, and the total content of slag forming agents is 6%. ~Ten
% filler metal for TIG welding.