JPS61195794A - Backing strip for one-side welding - Google Patents

Abstract

PURPOSE:To improve the adhesiveness of a backing strip to the rear surface of a base metal and the removal of formed gas and to form penetration beads having no blowhole defects and pock marks, etc. by attaching a glass fiber sheet having a specific thickness and moisture content to the upper part of solid refractories contg. specific components. CONSTITUTION:The backing strip is constituted by attaching the glass fiber sheet 2 having 0.05-2.5mm thickness and <=1.5% moisture content to the upper part of the solid refractories 1 contg. 45-60% SiO2 (wt%, hereinafter the same), 25-38% Al2O3, 3-15% MgO, 0.3-3.2% >=1 kinds of alkaline metallic oxides and 0.01-0.25% moisture as essential components.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a backing material for single-sided welding used in gas-shielded arc welding using solid wire or flux-cored wire, and in particular, to The present invention relates to a backing material for single-sided welding that not only has good adhesion but also good release of generated gas, and is capable of forming a sound back bead without pore defects or pockmarks.

[Prior art J - Conventionally, as a backing material for single-sided welding (aluminum inorganic glass fiber moldings (Japanese Patent Publication No. 50-35488 and No. 59)
-4238 etc.) and (bl refractory molded body (JP-A-59-
137193, etc.), or (C) a laminate in which a glass fiber molded body is attached to the top of a refractory molded body, etc. are widely used. However, when single-sided welding is performed using these backing materials, it has been pointed out that the following problems occur, and the development of improvement measures is awaited.

That is, although the glass fiber molded article (a) has the property of good adhesion to the back surface of the base material, it has a relatively low melting point and is structurally insufficient to retain molten metal. Therefore, the back bead tends to have excessive excess. Also (b
) In the case of the refractory molded product, the refractory degree can be adjusted by any five points by adjusting the component composition, which increases the retention effect of the molten metal, resulting in a back bead with a good shape. Although the refractory has the advantage of being easily exposed, it is difficult for generated gas (hydrogen, etc.) to escape due to the high airtightness of the refractory, and defects such as pores and pockmarks are likely to occur on the back bead surface. Furthermore, in the laminated backing material (C), the refractory molded body (b
Although it has the advantage of improving adhesion to the back surface of the base material compared to a single method, it also has the advantage of improving adhesion to the back surface of the base metal. Since it is confined to the side, pore defects on the back bead become more noticeable.

[Problem to be solved by the invention J The present invention has been made with attention to the above-mentioned circumstances, and its purpose is to form a healthy and beautiful back bead without pore defects or pockmarks. The purpose of the present invention is to provide a backing material for single-sided welding that can be used for single-sided welding.

[Means for solving problems]

The composition of the long material of the present invention that can achieve the above objects is as follows: 5i02: as~60% AI2O3: 25~38% MgO: 3~15% One or more alkali metal oxides = 0.3~ 3.2%, and a moisture content of 0.01 to 0.25% as essential components, and the thickness is 0.3%.
The gist is that it is made by adding a glass fiber sheet with a length of 0.5 to 2.5 m and a moisture content of 1.5% or less.

[Effect]

The operation of the present invention will be clarified while clearly explaining the reasons for determining the types and content rates of the above-mentioned four constituent components.

First of all, solid refractories mainly serve as a base material to maintain good appearance, shape, height, etc. of the back bead, and the reason why the types and amounts of the four essential components were determined as described above is as follows. That's right.

Si'02: 45-60% This is the main component of the solid refractory; if it is less than 45%, the fire resistance will be insufficient, resulting in too much back bead formation, or a large amount of molten material will be generated due to arc heat. This causes arc instability. On the other hand, if it exceeds 60%, the fluidity of the generated slag becomes excessive,
Not only is it impossible to form a uniform back bead, but there are also drawbacks such as defects such as undercuts and slag entrainment, and poor hot cracking resistance. As the 5in2 source, silica, waxite, clay, feldspar, wollastonite, chamotte, cordierite, mullite, etc. are used.

Al2O: 25-38% An essential component for increasing the melting point of solid refractories and increasing the viscosity of the produced slag to shape the back bead.
It is an important component especially for adjusting the shape of the back bead when the groove root interval is wider than the standard (about 4 to 5 wx). In order to effectively demonstrate these functions, Al2O,
The content must be at least 25%, but on the other hand, if the content is too high, the fire resistance will be too high and gas release will be difficult, making defects such as pits, blowholes, and pockmarks more likely to occur, as well as making it difficult for back beads to form. Therefore, in order to avoid such problems, Al2O,11 should be suppressed to 38% or less. As the Al2O3 source, alumina, feldspar, mica, chamotte, cordierite, mullite, waxite, etc. are used.

MgO: 3 to 15% MgO has a function as a fire resistance adjuster and also has the effect of improving slag removability, and in order to effectively exhibit this effect, it must be contained in an amount of 3% or more. However, if it exceeds 15%, the fire resistance will increase too much and it will be difficult for the back bead to appear. MgO sources include magnesia, talc,
Magnesite, Garareru.

One or more alkali metal oxides20.3-3.2%ti
2o, Nλ20, K, 0, etc. are essential to obtain the minimum mechanical properties (compressive strength, bending strength, impact strength, etc.) and formability required as a refractory for backing material. If the content of 2O is less than 33%, these effects will not be effectively exhibited, while if it exceeds 3.2%, not only will the slag releasability and fire resistance be poor, but the moisture resistance will also be poor. The most common alkaline earth metal oxides are Li oxide and N
Li oxide sources include lithium water glass, lithium silicate, lithium ferrite, lithium manganite, veratite, lithium carbonate, etc., and Na oxide sources include sodium water glass, lithium carbonate, etc.
Feldspar, soda ash, anhydrous sodium silicate, sodium aluminate, etc. are used, and as oxides, potash water glass, feldspar, potash glass, potassium titanate, etc. are used, respectively.

Moisture: 0.01 to 0.25% It acts to increase sinterability by intervening between the powder particles that make up the refractory, and if it is less than 1% 2O3, these effects are not effectively exhibited, so the mechanical properties and formability becomes worse.

However, moisture will gasify due to welding heat and cause pits, blowholes,
Since it may cause pock marks etc., it must be kept below 25%. Examples of the moisture source include water, alcohol, higher fatty acids, aluminum hydroxide, bentonite, cellulose, and sodium alginate.

The four essential components of the solid refractory used in the present invention are as described above, and ZrO2, TiO2, and CaO are further added to the extent that the prescribed requirements for the four components can be satisfied.

SrO, Bad, FeO, Fe, 04. Fe2O,,M
nO.

Oxide of M n 02, B acol, S rcO
B, carbonate of CaCO3, CaF2. SrF...
BaF2. LiF, NaF.

It is also possible to contain an appropriate amount of abutments such as K and Si 16.

The glass fiber sheet added to the top surface of solid refractories with such a structure supplements the flexibility that solid refractories lack, and improves adhesion to the back surface of the base material (particularly when bending or mismatching). It is used to increase the applicability to grooves with
3. Ordinary inorganic glass mainly composed of oxides of alkali metals such as ZrO2, CaO, and N@ resin is used, but in order to achieve the purpose, the thickness of the sheet material must be 0°0.
5 to 2.5% and a moisture content of 1.5% or less must be used.

However, if the glass fiber sheet is thinner than 0.05+m, its adhesion to the back surface of the base material (particularly its adaptability to curved sections and grooves with misalignment) will deteriorate, resulting in a back bead with the desired shape. Not only is it difficult to form, but also the generated gas is not sufficiently released, making it easy for pore defects and pockmarks to occur on the back bead. However, if the thickness of the glass fiber sheet exceeds 2.5 mm, the fire resistance of the sheet itself is low and there is a risk that the back bead will protrude excessively or hot water will spill from the backing material. Further, the form of the glass fiber sheet is not particularly limited, and may be a single-layer sheet, a stack of multiple sheets, a tape, a mat, a cross-knitted sheet, etc. A portion of the glass fiber sheet melts due to welding heat and becomes a component of slag, but the moisture contained inside gasifies due to welding heat and causes pore defects, etc. In order to prevent this, it is necessary to suppress the moisture content in the glass fiber sheet to 1.5% or less.

Figures 1 and 2 are partial sketches illustrating the basic structure of a single-sided backing material, which is created by attaching a glass fiber sheet 2 to a solid refractory 1 having the above-mentioned composition. Ru. In addition, in FIG. 1, the top surface of the solid refractory 1 is formed as a flat surface, and in FIG. The cross-sectional shape of the refractory 1, the presence or absence of the groove 3, the shape thereof, etc. do not impose any restrictions on the present invention.

FIG. 3 is a partial sketch showing a more practical example that takes advantage of the technical idea of the present invention, and has been devised in consideration of ease of attachment to the back surface of the base material.

That is, in this example, double-sided adhesives 4, 4 are bonded to the upper and lower surfaces of both side edges of the glass fiber sheet 2, and this fiber sheet 2 is bonded to the upper surface of the solid refractory 1. Then, a support sheet (for example, aluminum foil, etc.) 5 is covered on the back side of the solid backing material 1, and the sheet 5 is made to extend further in the width direction than both side edges of the solid refractory material, and is bonded to this part. A release paper 7 is pasted on the top surface of the adhesive 6 in consideration of ease of handling. Note that the pores 8 formed along the side edges of the glass fiber sheet 2 of the support sheet 5 indicate gas vent holes.

When this backing material is applied to single-sided welding, after peeling off the release paper 7, it may be attached along the groove weld line on the lower surface of the base material M as shown in FIG. 4, and then welding may be performed.

〔Example〕

A single-sided backing material with the ridge shape shown in Fig. 4 was prepared using a solid refractory having the composition shown in Table 1 and a glass fiber sheet having the thickness and moisture content shown in the same table. After attaching it to the back side, a single-sided welding experiment was conducted under the following conditions. The components of the glass fibers are shown in Table 2.

(Welding conditions) Welding wire: Solid wire for carbon dioxide arc welding, M
G-5QT% 1.2 mφ Base material: JIS G 3106.5M-5O
A (19'x 150wx600':m) Groove shape: Groove angle 50 degrees, root width 5m Welding current
: 25OA, DC/wire (10) Welding voltage: 30v Wire protrusion length: Approx. 25m Seal gas x: Co, 257/min Welding posture
: Downward results are shown in Table 3.

Table 3 *l, Evaluation criteria: ○ mark is good, Δ mark is slightly poor, X mark is defective From the above results, it can be considered as follows.

Backing materials &1 to 10 are examples that satisfy all of the specified requirements of the present invention, and good results have been obtained in all of them.

On the other hand, backing materials Groups 11 to 17 are comparative examples that lack any of the specified requirements, and have problems with the quality of the backing beads as described below.

&11: Because the amount of water in the solid refractory is too large, blowholes and bits are seen on the back bead, and the bead appearance is poor.

&12 Because the moisture content in the glass fiber sheet is too high, A
Similar results were obtained with ll.

&13: Not only is there too much Al2O,i in the solid refractory (because there is not enough S iOz fIk, it is difficult to form a back bead and the speed is uneven.

&14 Because the glass fiber sheet is too thick, the topography is also poor with excessive back bead.

&15 Because the glass fiber sheet is too thin, it is difficult for generated gas to escape.Pits and blowholes are observed on the back bead.

&16: In addition to the excessive amount of 5i02 in solid refractories, AI
Due to the lack of 2O3 and MgO, the shape of the back bead is irregular and the slag removability is poor.

&17: Because there is too much MgO in the solid refractory, it is difficult to form a back bead and the appearance of the bead is poor.

[Effects of the Invention] The present invention is configured as described above, but the key point is to strictly define the four components of the solid refractory, and to determine the thickness and thickness of the glass fiber sheet attached to the upper surface of the refractory. Strictly regulating the water content1 has made it possible to provide a backing material for single-sided welding that provides an extremely sound back bead with excellent porosity resistance, appearance, shape, etc.

[Brief explanation of the drawing]

Fig. 1.2 is a partial sketch illustrating the basic shape of the backing material for single-sided welding according to the present invention, Fig. 3 is a partial sketch illustrating an embodiment with practical improvements, and Fig. 4 The figure is a schematic cross-sectional view showing an example of installation on the back surface of the base material.

Claims (1)

[Claims] SiO_2: 45 to 60% (weight %: same below) Al_
2O_3: 25-38% MgO: 3-15% One or more alkali metal oxides: 0.3-3.2% and moisture 0.01-0.25% or less in the upper part of the solid refractory as essential components , the thickness is 0.
A backing material for single-sided welding, characterized in that it is equipped with a glass fiber sheet having a thickness of 0.05 to 2.5 mm and a moisture content of 1.5% or less.