JP5406236B2 - Method for producing ceramic backup material for gas shielded arc welding - Google Patents

Description

  The present invention relates to a ceramic backup material for gas shield arc welding (FIG. 2) that is attached to the back surface of a base metal joint as shown in FIG. 1 in welding joining of steel structures such as shipbuilding, bridges, building steel frames, pressure tanks, and construction machinery. A) of the production method.

  In the field of shipbuilding and steel structure welding, a double-sided welding method that involves gouging with an electrode rod has been conventionally used. On the other hand, the ceramic back-up material shown in FIG. Adopting a single-sided welding method, in which only one side is welded from the top surface, is mainly used. As shown in FIG. 3, the above double-sided welding method uses the electrode rod to scrape the back surface (dotted line portion in FIG. 3c) of the weld metal (b in FIG. 3) welded from the upper surface, and then repeat that portion (in FIG. 3). When d) is welded, when the weld base material cannot be reversed, it is turned upside down and the upward work is forced, and it is difficult to ensure the quality of the appropriate weld metal.

However, at present, the ceramic backup material shown in FIG. 2 used in this single-side welding method is generally made of a refractory material, and the porosity of the ceramic piece (1 in FIGS. 1 and 2) is It is more than 20% porous.
In such a backup material, when the hot molten metal contacts the surface of the ceramic piece, the surface is melted, and the ceramic itself expands, further increasing the expansion of the pores and opening the closed pores. .
This ceramic piece (1 in FIG. 1 and FIG. 2) itself causes expansion and contraction, which causes a problem that the back bead has depressions and excessive heights to cause unevenness in the back bead. is there.
In addition, when the ceramic back-up material is left unpacked, outdoor work in high-humidity weather, and when it encounters rain, it causes moisture and water absorption in the pores and voids.
Even if the surface of the ceramic piece that has absorbed and absorbed moisture due to the above causes is dry, it is difficult to completely dry up to the internal opening and closing pores. There is.
In welding work using such a hygroscopic / water-absorbing ceramic backup material, this moisture adversely affects the metallurgical reaction in the weld pool, causing instability of the welding arc, generating blowholes in the weld metal and large amounts of spatter. There is a problem that the quality of the deposited metal is remarkably lowered.

This porous conventional ceramic back-up material is an aluminum sheet (2 in FIG. 2) that contains the gas and ceramic pieces (1 in FIG. 2) accumulated in the voids (pores) during welding, even in a normal dry state. Gas generated by the decomposition and volatilization of the organic additive (4 in FIG. 2) attached to the glass reaches the solubilized surface of the ceramic surface through the gaps between the ceramics and the ceramic pieces.
There is also a problem that this gas is pushed out to the molten metal (slag) interface between the weld metal and the ceramic surface to form numerous indentations on the surface of the weld back bead, thereby causing defective defects in the weld metal.

  The present invention fundamentally solves the various defects that occur due to the chemical composition and porosity of the conventional backup material described above, and has an extremely high porosity (porosity) without using an organic waterproofing agent or glaze. It is an object of the present invention to provide a method for producing a ceramic back-up material for welding, which can produce a ceramic back-up material for welding which has a low, high moisture-proof and waterproof ability and can secure a high quality weld metal.

Said subject is achieved by the manufacturing method of the ceramic backup material for welding of this invention of the structure of following (1)-(3).
(1)
The surface of the granular raw material prepared by kneading and kneading the ceramic powder raw material is coated with 0.4 to 5.0 parts by mass of an inorganic caking agent with respect to 100 parts by mass of the granular raw material. A gas shield characterized in that a ceramic backup material for gas shield arc welding having a porosity of 15% or less is manufactured by forming a molded product into a predetermined shape using a ceramic and firing the molded product. A method for producing a ceramic backup material for arc welding ,
The particle size of the granular raw material coated with the inorganic binder used for the molding does not exceed 4 mmφ,
Mass content of chemical components of the ceramic backup material produced _{is, SiO 2: 30~55%, Al} 2 O 3: 30~50%, Fe 2 O 3: 0.1~1.5%, MgO and / Or CaO: 3 to 17%, Na ₂ O and / or K ₂ O: 0.8 to 5.0%, TiO ₂ and / or ZrO ₂ : 0.5 to 5.0% Manufacturing method of ceramic backup material for gas shielded arc welding.
(2)
The method for producing a ceramic backup material for gas shielded arc welding according to (1 ), wherein the caking agent is sodium silicate.
(3)
Mass content of chemical components of the ceramic backup material produced _{is, SiO 2: 37~53%, Al} 2 O 3: 30~45%, Fe 2 O 3: 0.1~1.5%, MgO and / Or CaO: 3 to 17%, Na ₂ O and / or K ₂ O: 0.8 to 5.0%, TiO ₂ and / or ZrO ₂ : 0.5 to 5.0%, and the porosity is The method for producing a ceramic backup material for gas shielded arc welding according to (1) or (2), which is 12% or less.

According to the present invention, a ceramic piece 1 having a very low porosity and a high moisture-proof and waterproof property can be obtained through the selection of an optimal high-purity raw material and its raw material preparation / molding / firing process, and it is essential for welding. (Metal slag peelability) and metallurgical performance.
The ceramic backup material manufactured according to the present invention solves the problems of physical properties of conventional backup materials in the construction of gas shielded arc welding, and the back bead of the weld metal is formed uniformly and smoothly in any welding position. And a sound weld metal can be secured.
In addition, the ceramic backup material manufactured according to the present invention has a very low porosity and high moisture-proof and waterproof performance, making it ideal for humid environments and outdoor construction, and is highly expected for its wide range of applications and convenience. It is what is done.

It is sectional drawing which showed the positional relationship which attached the backup material of this invention to the welding base material. 1 is a general view of the present invention. It is an illustration of the double-sided welding method.

First, the ceramic backup material for gas shielded arc welding manufactured by the manufacturing method according to the embodiment of the present invention has a mass content of chemical components of SiO ₂ : 30 to 55%, preferably 37 to 53%, Al. ₂ O ₃ : 30 to 50%, preferably 30 to 45%, Fe ₂ O ₃ : 0.1 to 1.5%, MgO and / or CaO: 3 to 17%, Na ₂ O and / or K ₂ O: 0 0.8 to 5.0%, TiO ₂ and / or ZrO ₂ : 0.5 to 5.0%, and the porosity is 15% or less, preferably 12% or less.
In the production of the ceramic piece of the backup material (1 in FIGS. 1 and 2), a high-purity oxide powder raw material is blended, kneaded and granulated based on the mass content value of the chemical component described above, and the granules After coating the surface of the raw material with an inorganic caking agent corresponding to 0.4 to 5.0 parts by mass with respect to 100 parts by mass of the raw material, the porosity can be lowered by going through a molding process and a sintering process. .

The technical explanation of the melting point, porosity, metallurgical reaction, etc. of the ceramic piece will be described in detail below.
(1) In welding using a ceramic backup material, the surface of the ceramic piece in the first layer is partly melted by the molten metal heat to form a molten metal (slag) between the molten metal and the molten metal. There is a metallurgical reaction.
In order to stabilize the good metallurgical reaction and secure a sound weld back bead, good demetallization (slag peeling) is required in order to prevent the ceramic hot metal from infiltrating into the molten metal.
The chemical composition related to the melting point of the ceramic piece is an important key for this demolition property.
In the welding operation, the molten metal starts to crystallize when the welding arc moves in the traveling direction and the molten pool bottom cools to the metal melting point. At this time, if the melting point of the ceramic piece of the backup material is higher than the melting point of the metal (1,535 ° C), the hot metal of the ceramic solidifies before the molten metal, making it difficult to peel off (remove) the hot metal from the metal. As a result, unevenness occurs on the back bead surface of the weld metal, and the mechanical strength of the weld metal is also lowered.
Therefore, the ceramic piece requires chemical metallurgical performance and its melting point must not be higher than the melting point of the metal.
(2) The hot metal (slag) generated by the melting of the ceramic surface during the solidification process of the molten metal in the welding operation using the ceramic back-up material must have an appropriate viscosity and surface tension. If the hot metal viscosity and surface tension are too high, molten metal may be entrained (defects) in the molten metal, and it will not be possible to ensure a smooth weld back bead surface. Some weld metal cannot be obtained.
On the other hand, when the viscosity and surface tension of the hot metal are too low, the hot metal becomes unstable, and a sound back bead and an appropriate weld metal cannot be ensured as described above.
(3) When the content of SiO ₂ (silicon oxide) and Al ₂ O ₃ (aluminum oxide) is high in the chemical composition of the ceramic piece of the backup material for welding, the melting point of the ceramic and the viscosity of the hot metal produced Rises.
In particular, when the content ratio of the latter Al ₂ O ₃ is high, the melting point rises remarkably, and is unsuitable for the physical properties of the backup material for the reasons described above.
In order to lower the viscosity of the generated hot metal (slag) and suppress the melting point, it can be solved by increasing the contents of MgO (magnesium oxide) and CaO (calcium oxide), which are effective.
Therefore, the reason why cordierite (a mineral crystal composed of a ternary system of 2MgO · 2Al ₂ O ₃ · 5SiO ₂ ) has been basically applied to a ceramic backup material for the above technical reasons.
In the ceramic piece of the present invention, CaO, which has the same action as MgO, is added to achieve a quaternary ceramic composition of MgO and / or CaO to suppress the melting point rise and optimize the hot metal (slag) viscosity and surface tension. .
Na ₂ O and K ₂ O are the same as the above components in that they have the effect of suppressing the melting point and reducing the surface tension of the molten iron (slag). The addition of sodium silicate used (Na ₂ O · 2SiO ₂ ) is the best means.
Further, when the content of Fe ₂ O ₃ is high, the surface tension of the hot metal (slag) is also increased, and the melting point is remarkably lowered. Therefore, in the present invention, the upper limit is 1.5% and the lower limit is 0.1%.
In addition, TiO ₂ has a catalytic effect, ZrO ₂ has an effect of promoting sintering, and in order to stabilize the welding arc and suppress the melting point, the upper limit is 5.0% and the lower limit is 0.5%. It is.
As described above, the best mode regarding the chemical component is the range of the content ( mass %) of each chemical component described in [0006] of the present invention.
(4) Although the void ratio (porosity) of the ceramic piece of the present invention is 15% or less, the best mode is determined based on the results of welding experiments shown in Tables 2 and 3, and Examples 1 to 1 described in Table 1 8 is most preferably in the range of 12.0% or less and 0.1%. The above-mentioned porosity (porosity) of the ceramic piece is ensured by adding sodium silicate as a caking agent in the raw material preparation step based on the chemical component value, and further using the granulated raw material surface after the granulation step as a raw material of 100 mass. This is achieved by adding a manufacturing step of coating with 0.4 to 5.0 parts by mass of sodium silicate with respect to parts.
The particle size of the granular clay raw material to which this coating process is added is preferably 4 mmφ or less in order to easily seal the gap between the skeletons of the granular clay in the glass solid phase generated in the sintering process.
A low porosity (porosity) can be obtained even when the sodium silicate is excessively added or the particle diameter exceeds 4 mmφ, but on the other hand, the glass piece is excessively formed, and the ceramic piece itself is caused by a significant decrease in melting point and thermal shock resistance. Cracks and fractures occur during welding, resulting in welding failures.
Therefore, the above range is the best mode for the amount and particle size of the coating agent.

In the examples of the present invention, 10 types of ceramic pieces of backup material were produced by the following method.
Detailed numerical values regarding the chemical composition and porosity of this example are as shown in Table 1.
(1) Chemical component content% of ceramic pieces of Example 1 to Example 10) SiO ₂ : lower limit 30.19%, upper limit 51.90%, Al ₂ O ₃ : lower limit 30.15%, upper limit 48 0.000%, Fe ₂ O ₃ : lower limit 0.31%, upper limit 1.08%, total of MgO and CaO: lower limit 8.90%, upper limit 16.45%, total of Na ₂ O and K ₂ O: lower limit 1.47%, upper limit 2.52%, total of TiO ₂ and ZrO ₂ : lower limit 1.60%, upper limit 3.93%, and 3 parts by weight of sodium silicate as a caking agent was added to 100 parts by weight of these oxide powders .
(2) The surface of the granular raw material obtained by kneading and granulating this powder raw material is 0.4 to 5.0 parts by mass (shown in Table 1) of sodium silicate as a caking agent with respect to 100 parts by mass of the granular raw material. A coating process was added to make a clay whose particle size does not exceed 4 mmφ.
(3) After forming and sintering the granular clay, a ceramic piece having a porosity of 0.8% lower limit and 15.0% upper limit is produced and attached to an aluminum sheet as shown in FIG. A ceramic back cover material was completed.

Welding experiment The welding test is conducted under the following conditions.
Specimen: Rolled steel plate for welding (JIS3106) 12 mm thick, 400 mm weld length
Groove shape: Butt joint, V-shaped 50 ° groove, root gap 6mm
Welding machine: Carbon dioxide shielded arc semi-automatic welding machine Welding material: Cored wire with flux, 1.2mmφ
Welding conditions: Downward welding (Experiment 1) 200-210A, 27V
Vertical welding (Experiment 2) 160-180A, 24V

Experimental Specimen Table 1 shows the chemical composition values and porosity of the ceramic pieces used in the welding experiment.
(1) Examples 1 to 10 are ceramic pieces manufactured in Example [0008] shown in Table 1.
(2) Comparative Example Two types of ceramic pieces are conventional and commonly used porous ceramic backup materials shown in Table 1. Comparative Example 1 is a ceramic composition composed of three components and based on chemical component content ( mass %) SiO ₂ : 54.30%, Al ₂ O ₃ : 29.80%, MgO: 13.80%. And the porosity is 24.3%.
Comparative Example 2 is a three-component system similar to Comparative Example 1, but has a high content of SiO ₂ and is a strongly acidic porous material.
The above 12 types were mounted on the test specimens described in [0009] to conduct welding experiments.
In addition, the measurement of the chemical component value described in this Table 1 took the average value of three by quantitative analysis. The porosity is determined by Japanese Industrial Standards (JIS
R2205) is an average of 6 measured values each.

Welding Experiment Procedures The welding experiments in this case were carried out in two types of welding postures under the welding conditions listed in [0009] for 12 types listed in Table 1. The experimental procedure is as follows.
(1) Welding experiment 1 is a total of 12 types of ceramic pieces, 10 types shown in Table 1 and 2 types of comparative examples, filled with cold water in a pallet, dipped in it for 15 minutes, and then water droplets on the surface with a cloth Was wiped off, attached to an aluminum sheet, mounted on the back surface of the test base material, and then in a downward welding position.
(2) Welding Experiment 2 is a test sample in which all of the 12 types of ceramic pieces of Example 10 and Comparative Example 2 shown in Table 1 were attached to an aluminum sheet in a dry state. We put it on the back side and performed upward welding.

（２）溶接実験２の結果
（表３）

Results of Welding Experiment The results of Welding Experiment 1 are evaluated and shown in Table 2, and the results of Welding Experiment 2 are evaluated and shown in Table 3.
For the evaluations in Tables 1 and 2, a five-step display and a short comment were added to the ◎ ○ △ ▲ × formula.
Item 5 was displayed as a comprehensive evaluation, mainly by performing an appearance inspection on the uniformity of the back bead.
(1) Results of welding experiment 1 (Table 2)

(2) Results of welding experiment 2 (Table 3)

Evaluation of Experiment (1) In the downward welding test in the state immediately after the water absorption test of the welding experiment 1 and the upward upward welding test in the dry state of the welding experiment 2, the evaluation of Examples 1 to 8 of the present invention is as follows. As shown in Tables 2 and 3, the formation of the back bead of the weld metal was excellent.
In the welding experiment process, the welding arc was stable and no welding defects were observed.
However, in Example 9 of the present invention in welding experiment 1, as shown in Table 1, although there was some anxiety about the turbulence of the arc and the defatting property, there was no problem. ) Good. In the welding experiment 2 of Example 9, the evaluation in all items was excellent. In Example 10 of the present invention, a very small amount of blowholes and spatter were generated as indicated by item 4 in Table 1 in welding experiment 1, but since there was no problem as a welding defect, overall evaluation 5 (○) was good. In the upward welding of welding experiment 2 of this example 10, there was no spatter or blowhole that was somewhat uneasy in welding experiment 1, there was no problem in the uniformity of the back bead, and the overall evaluation was excellent. It was.
(2) The results of the downward welding immediately after the moisture absorption (water) test in welding experiment 1 of comparative example 1 and comparative example 2 are normal because the arc is unstable, a large amount of spatter and large blowholes are generated. Welding was impossible.
(3) In the standing upward welding in the dry state in the welding experiment 2 of the comparative example 1 and the comparative example 2, the welding arc was stable in both the example and the comparative example, and the occurrence of blowholes was good. However, in Comparative Examples 1 and 2, an infinite number of minute convex-shaped projections were generated on the surface of the back bead. In addition, a depression due to atmospheric pressure was also generated.
This phenomenon is because the ceramic piece is porous, and even if a small amount of spatter is generated (*), it adheres to the surface of the ceramic piece where the welding arc proceeds, It was not meltable by the subsequent welding arc.
(4) As shown in the above experimental results, the ceramic backup material of the present invention has a high waterproof / moisture-proof ability by ensuring each chemical component value range and a very low porosity, and can prevent even spatter adhesion. I confirmed that it was.
As described above, as can be confirmed from the results of welding experiment 1 and welding experiment 2, the ceramic backup material for gas shielded arc welding according to the present invention is excellent in that it can ensure a good back bead and sound weld metal under all conditions. It has metallurgical chemical performance.

A General view of ceramic backup material 1 Ceramic piece of backup material 2 Aluminum foil part 3 Base material to be welded 4 Adhesive sticking part 5 Adhesive protective paper a Weld base material b Weld metal on top surface c Weld with electrode rod Part d Back welded part

Claims (3)

The surface of the granular raw material prepared by kneading and kneading the ceramic powder raw material is coated with 0.4 to 5.0 parts by mass of an inorganic caking agent with respect to 100 parts by mass of the granular raw material. A gas shield characterized in that a ceramic backup material for gas shield arc welding having a porosity of 15% or less is manufactured by forming a molded product into a predetermined shape using a ceramic and firing the molded product. A method for producing a ceramic backup material for arc welding ,
The particle size of the granular raw material coated with the inorganic binder used for the molding does not exceed 4 mmφ,
Mass content of chemical components of the ceramic backup material produced _{is, SiO 2: 30~55%, Al} 2 O 3: 30~50%, Fe 2 O 3: 0.1~1.5%, MgO and / Or CaO: 3 to 17%, Na ₂ O and / or K ₂ O: 0.8 to 5.0%, TiO ₂ and / or ZrO ₂ : 0.5 to 5.0% Manufacturing method of ceramic backup material for gas shielded arc welding. The method for producing a ceramic backup material for gas shielded arc welding according to claim 1, wherein the caking agent is sodium silicate. Mass content of chemical components of the ceramic backup material produced _{is, SiO 2: 37~53%, Al} 2 O 3: 30~45%, Fe 2 O 3: 0.1~1.5%, MgO and / Or CaO: 3 to 17%, Na ₂ O and / or K ₂ O: 0.8 to 5.0%, TiO ₂ and / or ZrO ₂ : 0.5 to 5.0%, and the porosity is The method for producing a ceramic backup material for gas shielded arc welding according to claim 1 or 2, wherein the content is 12% or less.

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