JPS594238B2 - Backing material for single-sided welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a backing material for single-sided welding, and more particularly to a backing material for single-sided welding that provides a beautiful back bead without welding cracks.

As the back bead forming layer of the backing material, powdery flux,
A solid flux obtained by solidifying the flux with water glass, etc.
Inorganic fibers such as glass fibers, or composite materials made by combining these fibers are used.

Among these, the backing material with inorganic fiber as the back bead forming layer has good flexibility and can be easily applied to single-sided welding of grooves with misalignment or curved welding such as welding of steel pipes. There are advantages such as However, raw materials and material components for inorganic fibers are severely restricted from the viewpoint of productivity, and raw materials with good productivity generally contain components that melt into the weld metal and adversely affect the quality of the welded part. It often deteriorates the strength, physical properties (particularly cracking resistance), and appearance. By the way, it is believed to be the component that has the most negative effect on the quality of the back bead.V) It has been confirmed that when the amount of B2O3 in inorganic fibers exceeds 6%, cracks are likely to occur in the back bead. (Special Publication No. 50-3548810). Therefore, B2O3 should be reduced as much as possible, but in order to form inorganic fiber raw materials into fibers, B2O3 is added as a viscosity-lowering component.
was considered essential. Under the above-mentioned circumstances, the inventors of the present invention have been conducting research to develop a technology that can be formed into a fibrous shape even when B2O3 is reduced to zero. As a result, SiO2 and Al2O3, which are the main components of inorganic fiber raw materials,
If the content of these inorganic fibers is adjusted, there will be no inconvenience when forming it into a fiber, and since this inorganic fiber does not contain B2O3, there is no risk of reducing the cracking resistance of the back bead.
Ta. However, as the viscosity of the welding slag increases, the air bubbles generated from the slag become difficult to escape and are left behind between the weld metal and the back bead, causing air bubble marks (pockets) to appear on the back bead, resulting in a significantly poor appearance. Therefore, in order to improve the appearance of the back bead, we thought that it was necessary to take concrete measures to reduce the viscosity of the welding lag, and we reviewed the composition of the raw materials and researched the effect of adding a third component. We have been progressing.

The present invention was completed as a result of such research, and its configuration is that a backing material for single-sided welding has a molded body made of inorganic fibers as a bead forming layer, and the inorganic fibers are Si.
O2: 50-80%, Al2O3: 1-20% and Z
The gist lies in the fact that it contains rO2: 10-25%, Na2O and/or 20:5-20%, and substantially does not contain B2O3. The basis for setting the component composition in the present invention will be clarified below.

SiO2 is the main component of inorganic fibers. They give the inorganic fibers an appropriate melting point and increase fire resistance. SiO2 accounts for 50-80%, and Al2O3 accounts for 1-2%.
Each must be set within the range of 0%.

However, if the SiO2 content is less than 50%, the melting point of the fiber will be low, and the D shape with too much back bead will tend to become uneven.On the other hand, if it exceeds 80%, the melting point will be too high, and no back bead will be formed. In either case, a proper and beautiful back bead cannot be obtained. Also, Al2O3 is a component that increases the melting point of fibers like SiO29, and should be set in the range of 1 to 20% in relation to the SiO2 content. Furthermore, Al
2O3 also affects the physical properties (particularly viscosity) of the slag produced during welding, and if it is too much, the viscosity of the slag will increase, making gas escape difficult and reducing the aesthetic appearance of the back bead, but if it is within the above range. These problems do not occur either. ZrO2 is the most important component in the present invention. ．． When an appropriate amount of ZrO2 is added to the portion D that does not substantially contain B2O3, the viscosity of the fiber material is reduced and the productivity of the fiber is improved.The viscosity of the slag is also improved, and air bubbles generated in the slag are removed. The bead is improved and you can get a beautiful back bead without any pockmarks.

Furthermore, unlike B2O3, ZrO2 does not impede the cracking resistance of the weld metal, and can satisfy the mechanical properties and appearance of the back bead at the same time. In order to effectively exhibit these effects, the content must be 10% or more, but if it is too large, the melting point of the fibers will rise and defects such as minus beads will appear, so it should be kept at 25% or less. Na2O＜5K
20 is an essential component for imparting appropriate strength and flexibility to fibers, and must be contained in an amount of 5% or more.

However, these have hygroscopic properties, and if too much of them are present, the hydrogen source (water) will be mixed into the back bead forming layer, reducing the cracking resistance of the weld metal and furthermore making the fibers more likely to weather. , should be kept below 20%. Furthermore, Na2O and K
Since 2O is a substance with the same effect, the action and effect are the same whether used alone or in combination. The specific form of this inorganic fiber when used as a bead forming layer is not particularly limited, and it may be used as a molded article such as a sheet bundle, a tape, a mat, or a cloth knit. These inorganic fiber molded bodies may constitute the backing material by themselves, but usually the molded bodies are arranged as a bead forming layer in the uppermost layer, and a layer of refractory material such as asbestos is placed below. It is used by laminating shape-retaining materials such as cardboard, and in some cases, it may be covered with a heat-shrinkable film or the like.
In addition, this backing material may be made into a long plate-like body of a certain size and fixed to the back side of the groove using an appropriate backing jig, or it may be made into a long band-like body and pressed against the back side of the groove with a copper plate, etc. It may also be welded. The backing material of the present invention is roughly constructed as described above, but the key point is that inorganic fibers with a special component composition that does not substantially contain B2O3 are used as the back bead forming layer.
EXAMPLES Next, Examples and Comparative Examples will be given to clarify the effects of the present invention.

Example 1 S102: 63%, Al2O3: 5%, Na2OFK2
O: 14%, ZrO2: 13% and other components: 5%
A glass fiber tape with a thickness of 1 Tm was created using this fiber, and a backing material was created by stacking two pieces of this tape as a back bead forming layer, and the following conditions were applied. Single-sided welding was performed.

[Welding conditions]

Welding wire: MG5OT (1.2rmψ) Base material:
SM5OA (25tfrmt) Bevel angle: 50 degrees V Shielding gas: 100% carbon dioxide, 25t/min Welding conditions: 3
00A-28V-20cm/min The bead shape of the joint obtained (reference photo 1) was uniform in both height and width, and had good gloss. No defects were observed in the X-ray performance test.

Comparative example 1S102: 55%, Al2O3: 13.7%
, CaO: 21.4%, B2O3: 8.2%, others:
A backing material was prepared in the same manner as in Example 1 except that glass fiber containing 1.7% was used, and a single-sided welding test was conducted under the same welding conditions.

Although the resulting joint had a good bead shape (Reference Photo 2), cracks were observed in the first layer weld in the cross section (Reference Photo 3), and cracks were also confirmed in the X-ray performance test.

That is, when glass fiber containing B2O3 is used, although a good back bead is formed, the cracking resistance of the joint becomes poor.
Comparative example 2 S102: 65%, Al2O3: 22.5%, MgO:
A backing material was prepared in the same manner as described above using glass fiber having a rating of 9.5 (!), others: 30/) and substantially free of B2O3, and a single-sided welding test was conducted under the same welding conditions.

Claims (1)

[Claims] 1 In a backing material for single-sided welding in which a molded body made of inorganic fiber is used as a bead forming layer, the inorganic fiber is SiO_2:50
~80%, Al_2O_3: 1-20% and ZrO_2
: 10 to 25%, Na_2O and/or K_2O: 5 to 20%, and substantially free of B_2O_3.