JPS6123076B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a welding material such as a coated arc welding rod or a composite wire, which is integrally composed of a flux, a metal core wire, and/or a metal case, and particularly relates to a welding material that is integrally composed of a flux, a metal core wire, and/or a metal case, and more particularly, This invention relates to a Cr-containing welding material in which spatter generated during welding is reduced as much as possible. The above-mentioned Cr-containing welding materials have excellent performance as welding materials for stainless steel or Cr-Mo high-tensile steel and welding materials for hardfacing, and their application fields tend to increase year by year. It is in. In other words, stainless steel has excellent corrosion resistance, oxidation resistance, heat resistance, etc., as well as good workability and mechanical properties, and is widely used in various industrial fields such as petrochemicals, textile industry, and nuclear power industry. Since there are
It is thought that the demand for Cr welding materials will increase along with this. In addition, low alloy heat resistant steel and heat resistant alloys are
In addition to high-temperature and high-pressure fields such as thermal power generation and the petrochemical industry, welding materials for hardfacing are increasingly being used in various fields such as civil engineering, construction, mining, and agriculture. As described above, the excellent performance of Cr-containing welding materials is utilized in many industrial fields, and it is clear that the demand for them will continue to grow. However, the Cr-containing welding materials that have been used so far have the problem of containing harmful soluble Cr in the weld fume generated during welding, which is not desirable in terms of health care for welding workers. In response to these, the present applicant has previously published Japanese Patent Application Laid-Open No. 52-114447
No. 53-19154 and proposed a technology to reduce the amount of soluble Cr in hume. In other words, these techniques reduce the amount of soluble Cr in the welding fume as much as possible by reducing the amounts of Na and K in the flux that constitutes the Cr-containing welding material and by using lithium silicate as a fixing agent. It was successful. The inventors of the present invention have continued to conduct further research in order to achieve practical application of the technology described in the above-mentioned publication and to further improve its performance. As a result, the previously developed Cr-containing welding material has good mechanical properties and corrosion resistance of the weld metal, and also has soluble Cr in the fume.
Although it was possible to significantly reduce the amount of spatter, it was found that a large amount of spatter was generated during the welding process, which was an obstacle to achieving practical application. That is, the occurrence of spatters causes various problems, such as impairing the aesthetic appearance of the welded structure, reducing corrosion resistance due to the adhesion of spatters, and reducing welding efficiency as it takes time to remove the spatters. Therefore, in order to effectively demonstrate the effect of reducing soluble Cr in welding fume in practical terms, it is necessary to take measures to reduce spatter at the same time. The present invention has focused on the above-mentioned circumstances, and has carried out extensive research with the aim of developing a Cr-containing welding material that reduces soluble Cr in the welding fume and also improves welding workability and does not cause problems such as spatter. It was created as a result of repeated efforts, and its composition is a Cr-containing flux that suppresses the Na and K components in the flux to 1% by weight or less in terms of their oxides, and reduces the amount of soluble Cr in the fume. The gist of the welding material is that the flux contains at least 1 to 15% by weight of calcium titanate to significantly reduce the occurrence of spatter. The occurrence of spatter during welding varies depending on the welding conditions (polarity, current value, etc.), welding method (arc length, wire feeding angle, etc.), and the composition of the flux. It is said that spatter can be reduced by lowering the viscosity of the slag produced and by making the flux basic. Therefore, the shortest way to reduce spatter is to adjust the composition of the flux in accordance with the above findings. However, in the present invention, the Cr-containing
Since the welding material has significantly reduced amounts of Na and K components in order to reduce the amount of soluble Cr as described above, general spatter reduction measures cannot be directly applied to the present invention. Therefore, without being bound by the conventional knowledge described above, the present inventors conducted intensive research to clarify the optimal flux component composition from the viewpoint of reducing the amount of soluble Cr in the fume and reducing spatter during welding. As a result of these efforts, we have arrived at the present invention. First, in the present invention, the Na and K components in the flux are converted to their oxides (Na ₂ O and K ₂ O) and
It is a prerequisite that the amount must be kept below % by weight. This is to reduce the amount of soluble Cr in the welding fume.
The reason for numerical limitation is JP-A-52-114447 and JP-A No. 53-
As explained in issue 19154. In the present invention, an appropriate amount of calcium titanate is added to the flux. In other words, calcium titanate is an essential component for reducing spatter generated during welding without impairing the original performance required of Cr-containing welding materials, and the preferred blending ratio is 1 to 15% by weight in the total flux. is within the range of
The reason why spatter is reduced by adding calcium titanate is because of the CaO and TiO ₂ contained in it.
This is thought to be because all of these have the function of increasing arc concentration and do not contain gas-generating components, which is one of the causes of spatter. In order to exhibit these effects significantly, it is necessary to contain at least 1% by weight or more in the total flux. However, if it exceeds 15% by weight, the arc becomes constricted and the bead becomes convex, degrading joint performance, so it should be kept below this range. Calcium titanate includes CaTiO ₃ , CaTi ₃ O ₇ , Ca ₃ Ti ₂ O ₇ and the like, and a molten flux containing CaO: 20-50% and TiO ₂ : 15-75% can also be applied and has the same effect. It is also possible to substitute magnesium titanate as a substance. As described above, the greatest feature of the present invention is that spatter is reduced by incorporating an appropriate amount of calcium titanate into the flux. In order to further enhance its functionality, it is desirable to incorporate appropriate amounts of calcium carbonate, fluorite, rutile, etc. That is, calcium carbonate has a function as a gas generating agent and is extremely effective in enhancing the shielding effect. However, if the amount is too large, the amount of spatter will increase and the effect of adding calcium titanate will be weakened, and the amount of carbon in the weld metal will increase, which tends to deteriorate the mechanical properties.
Considering these points, the most preferred amount of calcium carbonate is 10 to 35% by weight. Fluorite has the effect of imparting fluidity to the slag and improving the X-ray characteristics of the weld metal. However, if the amount is too large, the arc concentration tends to decrease and spatter increases, so the amount is usually selected from the range of 1 to 15% by weight. Rutile is extremely effective in softening the arc and further reducing spatter, but if too much rutile is used, the fluidity of the slag becomes excessive, deteriorating the bead shape and reducing the peelability of the slag.
It is usually selected from the range of 20 to 60% by weight. In addition, it is advantageous to incorporate approximately 0.01% by weight or more of bismuth oxide into the flux because it can further improve the slag releasability. However, if the amount is too large, the bead shape will deteriorate, and the flux itself is more expensive than other flux components. Therefore, considering practicality, the upper limit should be about 1% by weight. In the present invention, since the Na and K components in the flux must be reduced as much as possible, it is not preferable to use the most common fixing agents, such as sodium silicate and potassium silicate, and instead use lithium silicate, etc. as the fixing agent. It is hoped that The present invention is generally constructed as described above, but the point is that by incorporating an appropriate amount of calcium titanate into the flux, the generation of spatter can be significantly prevented. The significance of being able to eliminate the problem of spatter, which is an obstacle to the practical application of Cr-containing welding materials with reduced Na and K components in the flux to reduce Cr, is significant. Next, experimental examples of the present invention are shown, but like the embodiments described in the claims, the following does not limit the present invention, and can be carried out with appropriate changes in accordance with the spirit of the above and below. All of these are within the scope of the present technology. Experimental Example Using fluxes with varying amounts of calcium titanate as shown in Table 1, lithium silicate (SiO ₂ : 20% by weight, Li ₂ O: 4% by weight) was used as a fixing agent, and this was attached to a metal core. Wire (20% Cr-10%
A coated arc welding rod was obtained by coating Ni, 4.0 mmφ x 350 mm ^l ) to a coating diameter of 6.5 mmφ.

[Table] Using the obtained Cr-containing welding rod for testing, tests were conducted based on the welding conditions, hume analysis method, spatter sampling method, etc. shown below. (1) Welding conditions: 145A x 20~25V: AC (2) Base metal: 19mm ^t x 75mm ^w x 400mm ^l : Mild steel (3) Humidity analysis method: (Sampling method) The lower part is open and the upper part is filled with high volume air. While welding in an iron box with a sampler, the air sampler sucks the fume and collects it using glass fiber paper. (Analysis method) Soluble Cr in fume: Atomic absorption method Na ₂ O, K ₂ O in flux: Atomic absorption method (4) Sputter collection method: Welding on mild steel material under the above welding conditions (speed of approximately 25 mm/min)
(min) to form a 25 cm long overlay bead, and collect and weigh the spatter generated during this time. (5) Bead cross-sectional shape: Form a built-up bead on SUS304 under the above welding conditions and observe its cross-sectional shape. The results are shown in Table 2.

【table】

[Table] As is clear from the results in Table 2, by incorporating an appropriate amount of calcium titanate into the flux, spatter can be significantly reduced while keeping the amount of soluble Cr in the hume low. However, if the amount of calcium titanate is too large (sample bar G), the bead becomes convex and the joint performance deteriorates, which is not preferable.

Claims (1)

[Claims] 1. The flux is integrally formed with a metal core wire and/or a metal case, and at least one of these contains Cr, and the flux contains Na.
and a welding material in which the K component is suppressed to 1% by weight or less in terms of its oxides (Na ₂ O and K ₂ O), characterized in that the flux contains at least the following components: Cr-containing welding material. Calcium carbonate: 10-35% by weight Fluorite: 1-10% by weight Rutile: 20-60% by weight Calcium titanate: 1-15% by weight