JP5560504B2 - Tungsten inert gas arc welding flux for steel - Google Patents

Description

  The present invention relates to a welding method and relates to an active flux for inert gas arc welding (TIG welding) of steel and alloys. The present invention is used in one-pass or multi-pass manual or automatic welding, which is essential for industrial products.

Active fluxes of various compositions (hereinafter referred to as “flux”) for increasing the welding depth of different types of steels and alloys are known in the art. For example, (Inventor ID April 30, 1980 No. 730515, IPC ⁷ : B23 35/362, B. # 16) and (Inventor ID October 7, 1987 No. 1342649 A1, IPC ⁷ : B23 35 / 362, B. # 37), (Inventor's certificate December 7, 1991 No. 1696233 A1, IPC ⁷ : B23 35/362, B. # 45).

  The flux is a suspension containing flux powder and an organic volatile solution such as ethyl alcohol, and is applied to the weld joint before welding.

In the prior art of inert gas arc welding flux (Inventor's certificate June 23, 1985, No. 1162565 A, IPC ⁷ : B23 35/362, B. # 23), the welding depth by arc during high-strength stainless steel welding The composition of the flux in this claim is as follows (unit:% by weight).

  The flux is made by mechanically mixing each chemically pure component. The prepared flux essentially has the following disadvantages.

・ Necessity to thoroughly mix each composition element ・ There are toxic substances in the composition element (e.g. vanadium oxide)
・ Contains a large amount of low boiling point (T _boil ) halide salt (LiF boiling point T _boil = 1949 K, NaF boiling point T _boil = 1975 K) up to 57.5%, flux effect during welding at a current exceeding 250A Marked decrease in

In order to make up for the above-mentioned drawbacks, the following composition (% by weight) has been proposed as a flux for stainless steel TIG welding in other conventional techniques (Japanese Patent Laid-Open No. 2000-326091 published on Nov. 28, 2000). IPC ⁷ B23K 35/362).

The flux having the above composition gives a constant level (500-600 dyne / cm) of surface tension to the molten pool.
However, this flux has been overcome only in that it does not contain halide salts, which is part of the disadvantages of prior art fluxes, and has the characteristic of having three components.

This flux has the following essential drawbacks.
-Reduced welding depth (especially when the current is less than 100A). This is due to the fact that materials with a very high melting point (T _melt ) than steel (TiO ₂ T _melt = 2185 K, SiO ₂ T _melt = 1996 K, Cr ₂ O ₃ T _melt = 2548 K) are fluxes. Because it is included. The decrease in welding depth is due to the fact that part of the arc power is used to melt the sparingly soluble oxide film on the base metal surface.
• The need for thorough mixing of each component before using the flux suspension. The main difference between the specific gravity of the composition elements of the flux ([rho) from (2.0 to 2.5-fold) (SiO ₂ of ^{ρ = 2.3-2.6 g / cm 3,} Cr 2 O 3 of ^{ρ = 5.2 g / cm 3)} , suspension flux Each element separates during turbid storage, so the weld geometry may become unstable if not mixed well before use.
Contains toxic components (Cr ₂ O ₃ ).

It is an object of the present invention to provide a flux that does not pollute the environment, reliably increasing the transmission power of the welding arc, and improving the quality of welding.
The quality of the weld can be improved by reducing variations in weld depth and weld width that result from separation and non-uniform distribution of suspension flux composition elements.

  The purpose of the present invention is that the composition element of the flux for TIG welding does not include toxic ones, the melting point of the main composition element that occupies 98% of the flux is a relatively low melting point, and the specific gravity value is close. To be achieved. The flux according to the invention is for tungsten inert gas arc welding (TIG welding) and contains silicon dioxide. Furthermore, this flux is a mixture of iron metasilicate, iron orthotitanate, iron metatitanate, and iron dititanate, and each of these composition ratios (% by weight) is characterized by the following.

・ Silicon dioxide SiO ₂ 2,0

・ Iron metasilicate Fe ₂ SiO ₄
Iron orthotitanate Fe ₂ TiO ₄
Iron metatitanate FeTiO ₃
Iron dititanate FeTi ₂ O ₅ 98,0

  The above composition is determined from the physicochemical properties of each element in order to increase the welding depth, and the mechanism is well known.

  The mechanism of weld depth in TIG welding with an active flux layer is explained by the following main phenomena that occur between the metal-flux-weld pool-arc system:

• Shrinkage of the anode region of the arc • Redispersion of the arc column thermal output within the arc-flux-molten pool interaction region • Reduction of molten pool metal surface tension • Change in melting direction and rate of molten pool metal. Changes from outward facing toward the periphery from the center of the molten pool to inward with high speed from the periphery of the molten pool toward the center and inside of the molten pool

The following can be said based on the mechanism of the melting depth. In prior art fluxes, the surface tension of the weld pool is a factor that has a significant effect on the weld depth, but it is not the only or sufficient factor.
From such a melting depth mechanism, each element of the active flux mainly requires the following physicochemical properties.

-Sufficient oxygen evolution during dissociation-Active interaction with molten pool metal-High enough boiling point-Low melting point-Specific gravity of each element that stabilizes the chemical composition of the flux (multiple compositional elements (When mixed mechanically)

It is a well-known fact that oxygen is the most efficient in producing poorly soluble compounds with dielectric properties among elements with high electronegativity and active surfaces.
As is well known, oxygen dissociation is represented by the following equation.

Here, E is an element, O is atomic oxygen, O ₂ is an oxygen molecule, EO is an oxide, i, j is the number of atoms of ЕiOj molecule, η _oq , η ₀₂ , η ₁₀ , and η _mn are m, n − 1,2. . . Is an integer coefficient.
For example, SiO ₂ dissociates at a temperature exceeding 3000K and forms a gas phase as follows.

From the calculation experiment, it was found that the presence of molecular oxygen (O ₂ ) in the vapor phase of monoxide at the boiling point is essential for deep welding. Calculated molecular oxygen content in the gas phase, must to be no less than 0.1 cm ³ in a constant ratio of oxygen (4x10 ^-4 cm ^3). It has also been found that the boiling point of oxygen is 3400K or less. An oxide that meets these conditions
_{SiO 2, TiO 2, Cr 2} O 3, MgO, Ga 2 O 3, V 2 O 5, CoO, MnO, FeO, SnO 2, GeO 2, ZnO, B 2 O 3, and higher order oxide ( Fe ₂ O ₃ etc.).
From the experimental results, the most effective oxide for welding depth is
It was found to be SiO ₂ , TiO ₂ , Cr ₂ O ₃ , MgO, CoO, MnO, FeO.

Weld slag oxide composed of oxides such as SiO ₂ , TiO ₂ , Cr ₂ O ₃ , MnO, Mn ₂ O ₃ , FeO, and Fe ₂ O ₃ exhibits the strongest interaction with the molten pool.
However, all of these oxides have a high melting point, and the welding depth is reduced by the redistribution of arc power in the arc-metal-weld pool region during welding. SiO ₂ , TiO ₂ , FeO, and Fe ₂ O ₃ are non-toxic oxides. Chemical compounds composed of the above oxides that have a lower melting point than steel are Fe ₂ SiO ₄ , FeTiO ₃ , and Fe ₂ TiO ₄ .

A small amount (2% by weight) of silicon dioxide (SiO ₂ ) in the active flux according to the invention is intended to prevent rapid separation of the flux from the organic liquid when used in suspension.

  It is possible to provide welding with high arc permeability by mixing active flux compositional elements with known characteristics and new functions.

The flux according to the invention satisfies the following requirements:
- presence of oxygen molecules in the gas phase of the monoxide in boiling (O ₂₎ is the boiling point of the constant ratio (4x10 ^-4 cm ³⁾ 0.1cm ³ below, sufficient heat intensity in (flux of oxygen 2500 3266K)
・ Main component of flux is low melting point (below the melting point of steel (1638 ~ 1673K))
・ The specific gravity of each component of the flux should be close (iron olivine: 4.3 g / cm ³ , iron metatitanate: 4.7 g / cm ³ )
・ Non-toxic

  Study the difference in the geometric size of the weld between TIG welding by the conventional method and TIG welding using the flux by the conventional technology due to the difference in the composition ratio of the composition element of the flux, and the effect and the optimum composition element of the flux Evaluated. The experiment was performed using 5 mm and 10 mm thick steel plate 08Kh18N10T (austenato stainless steel) and steel 20 plate (low carbon steel) under the following conditions.

・ Welding current: 100 to 200 A
・ Arc length: 1.5 mm
・ Welding speed: 2 mm / s
The flux is a mixture of Fe ₂ SiO ₄ , Fe ₂ TiO ₄ , FeTiO ₃ , FeTi ₂ O ₅ , and the ratio of each element is changed at 0 to 100% (in 10% increments).

この結果から、従来技術によるフラックス、あるいは本発明によるフラックスを使ってTIG溶接を行うと、(フラックスを使わない)TIG溶接に比べ、通常100〜300%溶接深さが深くなると分析される。また、本発明によるフラックスを使った場合、従来技術のフラックスを使った場合と比較して約15%溶接深さが深くなった。最大溶接深さを得られる最適なフラックスの構成要素は以下である (単位は重量%)。 After the experiment, the weld was divided into sections and the size was measured. The experimental results are shown in Table 1 below.

From this result, it is analyzed that when the TIG welding is performed using the flux according to the prior art or the flux according to the present invention, the welding depth is usually 100 to 300% deeper than the TIG welding (without using the flux). Further, when the flux according to the present invention was used, the welding depth was increased by about 15% compared to the case where the flux of the prior art was used. The optimum flux components for maximum weld depth are as follows (unit: wt%).

・ Silicon dioxide SiO ₂ 2,0

・ Iron metasilicate Fe ₂ SiO ₄
Iron orthotitanate Fe ₂ TiO ₄
Iron metatitanate FeTiO ₃
Iron dititanate FeTi ₂ O ₅ 98,0

Claims (1)

Silicon dioxide (SiO ₂ ) ( 2.0 wt% ),
An iron mixture (98.0% by weight) composed only of iron metasilicate (Fe ₂ SiO ₄ ) and iron orthotitanate (Fe ₂ TiO ₄ ),
An iron mixture (98.0 wt%) composed solely of iron metasilicate (Fe ₂ SiO ₄ ), iron orthotitanate (Fe ₂ TiO ₄ ), and iron metatitanate (FeTiO ₃ ),
Or composed of iron mixture (98.0 wt%) consisting only of iron metasilicate (Fe ₂ SiO ₄ ), iron orthotitanate (Fe ₂ TiO ₄ ), iron metatitanate and iron dititanate (FeTi ₂ O ₅ ) It is characterized by being
Active flux for tungsten inert gas arc welding for steel.