JPH04757B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a welding flux containing a powder or granular material of a metal or an intermetallic compound, and in particular, the surface of the powder or granular material is coated with alumina, and the flux is kneaded with water glass or sintered. The present invention relates to a welding flux configured to prevent the surface of the powder from reacting and changing in quality during such processes. This welding flux can be used as a coating flux for coated arc welding rods, a spreading flux for submerged arc welding, a filling flux for composite wires, and the like. [Prior Art] The various welding fluxes mentioned above contain powder particles of various metals and intermetallic compounds for the purpose of adjusting the composition of weld metal and deoxidizing them, as well as slag forming agents and arc stabilizers. body (hereinafter simply referred to as metal powder)
It is often combined with [Problems to be solved by the invention] However, as mentioned above, these powders and granules are inherently highly oxidizable and generally have high reactivity with water glass, so various problems occur as shown below. . In the case of flux for coated arc welding rods Coated arc welding rods are manufactured by uniformly kneading granular flux raw materials with water glass, then coating the outer periphery of the core wire and drying. Fe−Si, Ca−Si, Al−
If metal particles such as Mg are contained, they will react with water glass to generate hydrogen gas, causing dry cracking of the paint flux or falling off due to impact, resulting in a decrease in product yield. Moreover, since the metal powder itself is consumed by the reaction, there is also the problem that the deoxidizing effect and component adjustment effect tend to be insufficient. In the case of sintered flux for submerged arc welding, this flux is normally manufactured by uniformly kneading a powdery flux raw material with water glass, followed by granulation and firing. If granules are included, they will also react with water glass to generate hydrogen gas,
The granules are destroyed and the particle size becomes non-uniform, causing poor bead shape and pockmarks.
Moreover, since metal particles such as Mg and Mo are easily oxidized during the firing process, the oxygen concentration in the weld metal increases, resulting in problems such as deterioration of crack resistance and toughness. In the case of filling flux for composite wires Composite wires are often manufactured by uniformly kneading a granular flux raw material with water glass, granulating and firing it, filling it into a metal sheath, drawing it, and then annealing it. However, if the flux raw material contains metal powder, these will react with water glass and generate hydrogen gas, causing the granules to expand or break and resulting in uneven particle size distribution, making it difficult to fill the filling process. The syntronicity of time worsens. The deterioration of syntron properties manifests itself in variations in flux filling rate, which adversely affects welding workability.
Moreover, for wires that are annealed with or without granulation of powdered flux raw materials, part of the metal powder is oxidized during annealing, which increases the oxygen concentration in the weld metal and deteriorates mechanical properties. do. Under these circumstances, the present invention attempts to solve the above-mentioned problems by preventing the oxidation or reaction with water glass of the metal powder blended as one component of the flux raw material. It is something. [Means for Solving the Problems] The present invention provides a welding flux containing a powder or granule of a metal or an intermetallic compound, wherein the powder or granule contains 0.01% by weight or more based on the powder or granule. The main feature is that it uses alumina coated with aluminum. [Function] In the present invention, an alumina coating layer with high chemical stability is formed on the surface of the metal powder in order to prevent the metal powder from oxidizing and reacting with water glass. Therefore, it is possible to completely avoid problems such as the expansion and destruction of granulated flux due to the generation of hydrogen gas, as well as an increase in oxygen concentration in the weld metal due to oxidation of metal powder. The productivity and quality of coated arc welding rods, submerged arc welding fluxes, and composite wires using fluxes containing powder and granules can be greatly improved. In the present invention, the metal powder is one that is mixed into the flux as a deoxidizing agent or a weld metal component adjustment agent, as described above, and includes, for example, Mg, Mo, Al,
Metals such as Mn, REM, Fe-Si, Ca-Si, Al-
Examples include powders of intermetallic compounds such as Mg and Fe-Mn, and these may be blended individually or in combination of two or more. On the other hand, the alumina coated on the surface of the metal powder is, as is well known, an oxide of aluminum and has extremely high chemical stability.
If the surface of the metal powder is coated with this, the oxidation reaction of the powder and the reaction with water glass will be inhibited. Although the alumina coating method is not particularly limited, the following method is optimal in the present invention, in which fine metal powder is to be coated. That is, (a) alumina sol or Al
(OH) _3-o・nX (n: 0-3, X: lactic acid, tartaric acid,
Water-soluble Al compounds represented by organic acids such as malic acid and oxalic acid, or acid residues of inorganic acids such as phosphoric acid and hydrohalic acid, (b) Al hydroxide, Al fluoride, alumina,
Or poorly soluble or insoluble materials represented by other alumina-based composite oxides and alumina-based composite compounds
An Al compound is used for coating as a colloidal solution or suspension, and this is applied to the surface of the metal powder by a dry method (spray method) or a wet method (spray method, dipping method, etc.), and then By drying and firing, the surface of the metal powder can be coated with alumina. In principle, it is ideal for all of the metal powder used in the present invention to be coated with alumina by the method described above. If so, the object of the present invention can be fully achieved. Even if the amount of alumina coating is constant, the coating thickness will vary considerably depending on the particle size of the metal powder, but the particle size of the metal powder mixed in welding flux is generally 44 μmφ. If the particle size is within this range, a sufficient surface protection effect can be obtained with the above-mentioned amount of alumina coating. However, if the particle size of the metal powder is extremely small, the surface protection effect may not be sufficient with the above amount of alumina coating (0.01% by weight), so in this case, increase the amount of alumina coating. or particle size is 44μm
It is desirable to use metal powder particles with a diameter of about φ or more. The specific effect of alumina coating is as detailed in the following example, but in order to effectively exhibit the effect, it is necessary to apply 0.01
Alumina must be coated in an amount of at least 0.01% by weight, and if the coating amount is less than 0.01% by weight, the thickness of the coating layer will be extremely thin or a large amount of powder will remain uncoated, so oxidation and water glass reactions will be inhibited. The effect will be insufficient. As a coating method other than alumina, it is also possible to oxidize the metal or intermetallic compound powder particles themselves to form an oxide film, or to coat them with a silicon oxide film. However, in the above method, the oxide film is easily destroyed due to changes in the crystal lattice constant due to surface oxidation, and in the case of iron oxide films, oxidation The corrosion resistance of the iron coating is poor, and when it comes into contact with moisture, it is oxidized and red rust occurs, or the moisture content of the metal powder increases, which promotes hydrogen cracking in the weld metal. Furthermore, in the above method, since the silicon oxide film lacks alkali resistance, it melts on contact with water glass, and the purpose of surface protection cannot be effectively achieved. In contrast, alumina has excellent water resistance, water glass resistance, oxidation resistance, and surface coating effect, and has no adverse effect on metals or intermetallic compounds, so it can be said to be the most suitable material for the purpose of the present invention. . Although the method for measuring the amount of alumina coating is arbitrary, it is preferable to adopt the method shown below, since the substantial amount of coating of alumina can be accurately measured. (Coating amount measurement method) Separate the flux from the welding rod or composite wire, collect the flux as it is in the case of submerged arc welding flux, and crush it in a mortar or the like. The pulverized material is sieved to collect coarse particles, which are poured into distilled water and heated and washed. It is then over-dried and only the metal powder or intermetallic compound is picked up while observing it under a microscope. X-ray diffraction for each sample picked up,
In addition to performing SEM and EPMA, the amount of metals and intermetallic compounds and the ratio of alumina are determined by chemical analysis, and the amount of alumina coating is calculated. [Example] Example 1 The surface of Fe-Si powder was coated with an aqueous lactic acid solution or alumina sol by a dipping method, dried (110°C x 60 minutes), and fired (400°C x
60 minutes) to prepare several types of Fe-Si powder particles with different amounts of alumina coating. Each of the obtained alumina coating Fe-Si powder particles was blended with the flux raw materials and water glass shown in Table 1 at a solid content weight ratio of 9:85:6 and kneaded uniformly. Obtained Flux. These fluxes were coated on the outer periphery of each mild steel core wire by a conventional method, and a dried coated arc welding rod was manufactured.
The yield of each product was investigated. The results are shown in Table 2.

【table】

【table】

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[Table] ○...Good △...Slightly poor ×...Poor As is clear from Table 2, in Experiments No. 1 and 2, sufficient surface protection effect could not be obtained due to insufficient amount of alumina coating, and the product yield was low. low. On the other hand, the amount of alumina coating on the Fe-Si powder used in Experiment Nos. 3 to 6 satisfies the specified requirements of the present invention, and the reaction between the Fe-Si powder and water glass is sufficiently suppressed. Therefore, the product yield is high. Experiment No. 4 used alumina sol, and Experiment No.
3, 5, and 6 are examples in which Al lactic acid was used as the coating agent, but in all cases, as long as the coating amount as Al ₂ O ₃ was 0.01% by weight or more (relative to Fe-Si), a good product yield was achieved. is obtained. Example 2 After spraying an aqueous solution of lactic acid on the surface of Mo powder, drying (110°C x 60 minutes) and baking (400°C x
60 minutes) and prepared several types of Mo powder with different amounts of alumina coating. These Mo powders, the flux raw materials and water glass shown in Table 3 below,
After blending and kneading uniformly so that the solid content weight ratio is 10:85:5, it is granulated and fired (the firing conditions are 500℃).
x 2 hours) to obtain a sintered submerged arc welding flux. Using each flux, submerged arc welding experiments were conducted under the following conditions, and the oxygen content [O] in the weld metal and impact resistance performance of the weld metal were investigated. Table 4 shows the results.

[Table] (Welding conditions) Welding wire: US9N, 3.2mmφC…0.05, Mn…1.2,
Si…0.43, Ni…9.40, Cr…0.30, Mo…0.5, balance Fe (weight%) Base material: 9% Ni steel, 25mm ^tGroove shape: 60°Y groove, root face 5mm Welding position: Downward welding Current: 500A Welding voltage: 30V Welding speed: 30cm/min

[Table] As is clear from Table 4, in Experiments Nos. 7 and 8, the amount of alumina coating was insufficient, so the Mo powder particles in the granulated flux were oxidized during the firing process, and as a result, the weld metal As the amount of [O] increases, the toughness of the weld metal shows a lower value. On the other hand, in experiments No. 9 to 13, the surface of the Mo powder was sufficiently coated with alumina.
Oxidation of Mo powder particles is prevented, the amount of [O] in the weld metal is reduced, and the weld metal has excellent toughness. In Experiment No. 13, more reliable alumina coating was achieved by performing the coating process twice, and the best results were obtained. Example 3 22% REM-18% Ca-Si powder (however, REM is
After adding and mixing aluminum lactate powder to (representing rare earth elements whose main components are Ca and La), approximately 15% by weight of water was added, wet-mixed, and dried (110℃ x 60 minutes).
And by baking (250℃ x 60 minutes), the fifth
As shown in the table, several types of REM-Ca-Si powders with different amounts of alumina coating were prepared. These REM-Ca-Si powders, flux raw materials and water glass having the composition shown in Table 6 were mixed in terms of solid content weight ratio.
After blending in a ratio of 10:85:5 and kneading uniformly, the mixture was granulated and fired (500°C x 60 minutes) to obtain a flux for filling a flux-cored wire. The obtained filling flux was filled into a mild steel pipe having the composition shown in Table 7 so that the flux ratio was 14%, and the wire was drawn according to a conventional method to obtain a wire diameter.
A seamless flux-cored wire with a diameter of 1.2 mm was obtained. Using each of the obtained seamless flux-cored wires, the bead shape was investigated when welding was performed under the following conditions. Welding conditions: 280A x 30V x 30cpm Polarity: DC reverse polarity Position: Downward Shielding gas: 100% CO ₂ 25/min Test plate: SM50A

【table】

【table】

【table】

[Table] As is clear from Table 8, Experiment No. 14
Due to the insufficient amount of alumina coating on the REM-Ca-Si powder, sufficient water-resistant glass reactivity cannot be obtained, and the particle size distribution of the granulated flux becomes uneven, deteriorating the syntronic properties during flux filling and causing flux to enter. Longitudinal REM−Ca− in wire
This is an example of a large variation in the distribution of Si powder particles, and as a result, the viscosity of the generated slag fluctuates, resulting in a defective weld bead (the width of the bead is not constant and the irregularities are large). In other words, REM acts as a deoxidizing agent during welding and is mixed into the slag as an oxide, but since REM oxide has a high melting point (approximately 2000℃), if there is variation in the distribution of REM, the produced slag The viscosity becomes non-uniform in the longitudinal direction, making the weld bead shape unstable. In contrast, the REM− used in experiments No. 15 to 18
The Ca-Si powder particles are coated with an appropriate amount of alumina, and the reactivity between the REM-Ca-Si powder particles and water glass is sufficiently suppressed, so the particle size distribution of the granulated flux is Since the REM-Ca-Si powder particles are uniform and have good flow during filling, the viscosity of the slag produced during welding is also uniform, resulting in a good bead shape. [Effects of the Invention] The present invention is constructed as described above, and since the metal powder is coated with chemically stable alumina, water is not absorbed during kneading with other flux raw materials and water glass. Reaction with glass is prevented, hydrogen gas is no longer generated, swelling of the coated flux and dry cracking are drastically reduced, and product yield and quality are significantly improved. In addition, since oxidation during firing is prevented, the yield of metal powder as a deoxidizing component and component adjusting agent is improved, and a high-performance weld metal suitable for the purpose can be obtained. In addition, especially when used as a flux for submerged arc welding or as a filling flux, the granules do not expand or break due to the reaction between water glass and metal powder, so the particle size distribution of the granulated and fired flux is uniform. can be,
It is possible to enjoy many benefits such as being able to improve the uniformity of the spread flux and the uniformity of the filling rate as the filling flux.

Claims (1)

[Claims] 1 Welding flux containing powder or granules of a metal or intermetallic compound, which is coated with alumina in an amount of 0.01% or more by weight based on the powder or granules. Characteristic welding flux.