JPS637877B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a backing material for single-sided welding used in gas-shielded arc welding, etc., and particularly to a backing material that can be applied to a wide range of welding currents and has excellent porosity resistance. This invention relates to a backing material for single-sided welding that can be obtained. [Prior art] Backing materials for single-sided welding have traditionally been (a) inorganic glass fiber molded bodies, (b) refractory molded bodies, or (c) glass fiber molded bodies on top of refractory molded bodies. Laminated products etc. loaded with are commonly used. However, it has been pointed out that when single-sided welding is performed using these backing materials, the following problems occur, and the development of an improvement measure is awaited. That is, the glass fiber molded article (a) above has the back surface of the matrix,
Although it has the property of particularly good adhesion to curved parts, it has a relatively low melting point and is easily melted by welding heat. Therefore, the slag becomes excessive and the shape of the back bead tends to be uneven, and high current welding (e.g.
There is a problem that it is difficult to apply it to a wire with a diameter of 1.2 mm and a current of 200 A or more. In addition, the refractory molded article (b) can have a good shape because the refractory degree can be adjusted arbitrarily by adjusting the component composition, and the molten metal retention effect can be adjusted accordingly. It has the advantage that a back bead can be easily obtained.
However, due to poor release of gases (hydrogen, carbon dioxide, etc.) generated during the welding process, pore defects and pockmarks are likely to occur on the back bead, and adhesion to the back of the base material, especially at curved parts, is poor and there is a high risk of breakage. There are some drawbacks. In addition, this kind of refractories include SiO ₂ ,
Flux powder containing components such as Al ₂ O ₃ , CaO, and MgO is usually mixed with a binder such as water glass, then molded, and then fired at a relatively low temperature of 300 to 500°C. 100-300 before use to easily absorb moisture in the atmosphere and obtain good porosity resistance.
The problem of having to re-dry at ℃ was also pointed out. Furthermore, the laminated backing material (c) has better adhesion to the back surface of the base material than the refractory molded product (b) alone, but since the glass fibers are melted by welding heat, Similar to a), there is the problem of uneven back bead shape due to excess slag, making it difficult to apply to high current welding. [Problems to be Solved by the Invention] The present invention has been made by paying attention to the above-mentioned circumstances, and its purpose is to provide a fabric with excellent porosity resistance and a good shape over a wide range of welding current. The object is to provide a backing material for single-sided welding that can form a bead. [Means for solving the problems] The composition of the backing material of the present invention that achieves the above objects is as follows: SiO ₂ : 45-60% Al ₂ O ₃ : 25-38% MgO: 3-15 % of one or more alkali metal oxides: 0.3 to 3.2% and water: 0.01 to 0.25% as essential components, and at least a part of the above SiO ₂ , Al ₂ O ₃ and MgO is present as cordierite. The gist is there. [Function] The present invention specifies the components and the content of each component in the solid backing material as described above, and also allows SiO ₂ , Al ₂ O ₃ and MgO among the essential components to exist as cordierite. In the following, we will explain the reasons for establishing these requirements and clarify the effects of the present invention. SiO ₂ :45-60% This is the main component of the backing material of the present invention,
If it is less than 45%, the fire resistance will be insufficient, resulting in excessive back bead formation, or a large amount of molten material will be generated due to arc heat, leading to arc instability. On the other hand, if it exceeds 60%, the fluidity of the generated slag becomes excessive, which not only prevents the formation of a uniform back bead, but also causes problems such as defects such as undercuts and slag entrainment, and poor hot cracking resistance. . As the SiO ₂ source, silica, waxite, siyamoto, cordierite, mullite, etc. are used. Al ₂ O ₃ : 25-38% This is an essential component for raising the melting point of the backing material and increasing the viscosity of the generated slag to adjust the shape of the back bead. 5
This is an important component for adjusting the shape of the back bead when the bead is wider than the diameter (about mm). In order to effectively demonstrate these functions, it is necessary to contain at least 25% Al ₂ O ₃ , but on the other hand, if the content exceeds 38%, the fire resistance will increase too much and the viscosity of the produced slag will become excessive, causing gas release. Because of this, not only are defects such as pits, blowholes, and pockmarks more likely to occur, but also it is difficult for back beads to appear. As the Al ₂ O ₃ source, alumina, feldspar, mica, siyamoto, cordierite, mullite, waxite, etc. are used. MgO: 3 to 15% MgO has a function as a fire resistance adjusting material and also has the effect of improving slag removability, and in order to effectively exhibit this effect, it must be contained at 3% or more. However, if it exceeds 15%, the refractoriness becomes too high and the viscosity of the produced slag becomes excessive, making it difficult to release gas and causing defects such as pits, blowholes, and pockmarks. Examples of MgO sources include magnesia, talc, dolomite, spinel, and forsterite. One or more types of alkali metal oxides: 0.3 to 3.2% Li ₂ O, Na ₂ O, K ₂ O, etc. have the minimum mechanical properties (compressive strength, bending strength) required as refractories for backing materials. , impact strength, etc.) and formability. If it is less than 0.3%, these effects will not be effectively exhibited, while if it exceeds 3.2%, fire resistance and slag removability will be poor. Not only that, but the moisture resistance also deteriorates. The most common alkali metal oxides are Li oxide, Na oxide, and K oxide, and Li oxide sources include lithium water glass, lithium silicate, lithium ferrite, lithium manganite, peratite, lithium carbonate, etc. As sources of Na oxides, sodium water glass, feldspar, soda ash, anhydrous sodium silicate, sodium aluminate, etc. are used, and as sources of K oxides, potassium water glass, feldspar, potash glass, potassium titanate, etc. are used. Moisture: 0.01 to 0.25% Moisture is present between the above powder particles that make up the refractory and has the effect of increasing sinterability, and if it is less than 0.01%, these effects cannot be effectively exerted, resulting in poor mechanical properties and formability. Become. However, moisture must be kept below 0.25%, as it gasifies due to welding heat and causes pits, blowholes, pockmarks, etc.
The moisture here refers to the total moisture, which is the sum of hygroscopic water, attached water, and crystallized water.The analysis method is to weigh the sample into a porcelain boat and heat it to 1000℃ in an oxygen stream. There is a method of heating, absorbing the released moisture with magnesium perchlorate, measuring the weight, and calculating the moisture from the increased weight.This method is based on AWS
It is also standardized in the standard (A5.5). As the moisture source, water, alcohol, higher fatty acids, aluminum hydroxide, bentonite, sodium alginate, cellulose, etc. are used. Incidentally, FIG. 1 is a graph showing the results of an experiment in which the influence of the amount of moisture contained in a single-sided backing material on the occurrence of pore defects and pockmarks on the surface of the backing bead was investigated. However, the experimental conditions were as follows. (Composition and dimensions of backing material) Composition...SiO ₂ : 49%, Al ₂ O ₃ : 32%, MgO: 10%,
_Na2O : 0.20%, _K2O : 1.5%, moisture: 0.03~
0.30%, remainder: other components Dimensions: 10mm ^t × 30mm ^W × 600mm ^L , see Figure 2, (sample plate) Steel type: JIS G 3106, SM-50A Dimensions: 16mm ^t × 150mm ^W × 600mm ^L bevel Shape: Groove angle 50 degrees, groove width 5 mm, see Figure 3 (Welding conditions) Welding wire: Flux-cored wire for CO ₂ gas arc welding (1.2 mmφ) (JIS-Z-3313 YFW-
(equivalent to 24, using titania flux) Welding current: 180 to 250 (A), DC wire (+) Welding voltage: 22 to 29 (V) Wire protrusion length: 20 mm Shielding gas: CO ₂ , 25/min Welding posture: As is clear from Figure 1, when the water content in the backing material exceeds 0.25%, defects such as pits and blowholes on the back bead surface become significant. The essential components constituting the backing material for single-sided welding of the present invention are as described above, but MnO, MnO ₂ , FeO,
Fe ₂ O ₃ , Fe ₃ O ₄ , TiO ₂ , ZrSiO ₄ , ZrO ₂ , CaO,
It is also possible to contain appropriate amounts of oxides such as SrO and BaO, fluorides such as CaF ₂ , NaF, and LiF. The essential components of the present invention are as described above, but in order to achieve the purpose, in addition to the above components,
SiO ₂ , Al ₂ O ₃ and MgO included as essential components
At least a portion of cordierite (2MgO・
2Al ₂ O ₃ .5SiO ₂ ) must exist as a crystal of a composite oxide. However, when the above three types of oxides are only dispersed individually, for example, alumina (Al ₂ O ₃ , melting point 2050°C), magnesia (MgO, melting point 2800°C), spinel (MgO.
Al ₂ O ₃ , melting point 1830℃), mullite (3Al ₂ O ₃
Oxides such as 2SiO ₂ (melting point 1830℃) have too high a melting point and cannot provide good back bead shape or pore resistance, while silica (SiO ₂ , melting point 1720℃) has a relatively low melting point, but Excessive fluidity of slag, making it more likely to cause slag entrainment and high-temperature cracking. However, when these are contained in the form of cordierite, these composite oxides provide appropriate performance such as fire resistance, thermal shock resistance, and strength, resulting in a back bead with excellent quality and shape. be able to. The specific method for making the complex oxide as described above exist is not particularly limited, but the general method is (1) to mix SiO ₂ , Al ₂ O ₃ and MgO in the form of cordierite from the beginning. Method, and (2) Blending of raw material powder → Addition of binder → Kneading → Press molding →
In forming a backing material by sequentially drying and firing, examples include a method in which a composite oxide is formed by setting the firing temperature to 1200 to 1350°C. By the way, pores are formed in the product backing material as a result of the escape of gas produced during firing, and it has been confirmed that porosity affects fire resistance, moisture absorption, etc. In order to prevent an increase in moisture content, it is best to keep the apparent porosity to 30% or less. [Example] Backing materials for single-sided welding having the chemical composition and crystal composition shown in Table 1 (the dimensions and shape are the same as those shown in Figure 2) were prepared, and single-sided welding was performed using each backing material. I conducted an experiment. However, the experimental conditions were a welding current of 220
(A) The conditions were the same as those used in the experiment shown in Figure 1, except that the welding voltage was 20 (V). The quality of each welded part (back bead) obtained is shown in Table 2. However, the quality evaluation criteria in Table 2 are as follows: ○ mark: good, △ mark: slightly poor, × mark: poor. Regarding pores, pits and blowholes on the bead surface were visually inspected.

【table】

【table】

【table】

[Table] As is clear from Tables 1 and 2, in the examples (Nos. 1 to 7) that meet the specified requirements of the present invention, the appearance, shape, slag removability, porosity resistance, and cracking resistance of the back bead were Although good results have been obtained in both properties, the comparative examples after Experiment No. 8 lack any of the requirements stipulated by the present invention, and therefore have the following problems. Experiment No. 8: All components except water are within the specified range, and the appearance and shape of the bead are good, but pits and blowholes occur in the bead due to the large amount of water. Experiment No. 9: Because the amount of Al ₂ O ₃ is excessive and the amount of SiO ₂ is insufficient, the fire resistance is too high, pits and blowholes are observed due to poor gas release, and the bead shape is also poor. Experiment No. 10: Not only is the MgO content too high, but the moisture content is also above the specified range, resulting in pits and blowholes, as well as poor bead shape. Experiment No. 11: Because the amount of SiO ₂ is too large, the fire resistance is insufficient, and the back bead is not only excessive but also has a bad shape. Experiment No. 12: In addition to the amount of SiO ₂ exceeding the specified range,
Fire resistance is insufficient due to insufficient amounts of Al ₂ O ₃ and MgO, the shape of the back bead is irregular, slag removability is poor, and blowhole defects are observed. [Effects of the Invention] The present invention is constructed as described above, but the key point is to specify the type and content of the components constituting the backing material, to strictly define the moisture content, and to further specify the content of the essential components. By making SiO ₂ , Al ₂ O ₃ and MgO exist in the form of crystals made of specific composite oxides, we have developed a single-sided welding backing that has moderate fire resistance, excellent physical properties, and provides an outstanding quality backing bead. This material can be obtained.

[Brief explanation of the drawing]

Figure 1 is a graph of experimental results showing the influence of moisture content in the backing material and welding current on pore defects in the back bead, and Figure 2 is a diagram showing the dimensions and shape of the backing material used in the above experiment. , FIG. 3 is an explanatory diagram showing the groove shape adopted in the same experiment.

Claims (1)

[Claims] 1 SiO ₂ : 45-60% (weight %: the same below) Al ₂ O ₃ : 25-38% MgO: 3-15% One or more alkali metal oxides: 0.3-3.2% and Moisture: Contains 0.01-0.25% as an essential component,
A backing material for single-sided welding, characterized in that at least a part of the SiO ₂ , Al ₂ O ₃ and MgO is present as cordierite.