JPH11192585A - Coated electrode for austenitic stainless steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coated electrode for austenitic stainless steel having a superior welding workability in all positions. SOLUTION: The electrode is formed such that a stainless steel core wire is covered with a coating flux which contains, as essential components in overall weight % of the coating flux, 15-30% metallic fluoride (in terms of F), 10-25% metallic carbonate (in terms of CO2 ), 1-5% K oxide (in terms of K2 O), and 2-8% Ti and/or Ti oxide (in terms of TiO2 ), which satisfies 1.0-1.5 as a conversion ratio of F/CO2 , which controls Na oxide (in terms of Na2 O) to be 1% or less, and which contains 30% or less metallic powders.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lime-based all-position coated arc welding rod for austenitic stainless steel, and in particular, has excellent welding workability in all-position welding, especially excellent slag peeling and rod burning resistance. And a coated arc welding rod for austenitic stainless steel.

[0002]

2. Description of the Related Art Austenitic stainless steel is widely used as a structural material for various plant-related equipment such as petroleum refining, chemical, and food due to its excellent properties such as rust resistance, corrosion resistance, oxidation resistance, and heat resistance. ing. Regarding the coated arc welding rod for austenitic stainless steel, the coating agent is designed according to the usage environment,
Generally, lime based on limestone and fluorite
And lime-titania coating materials mainly containing limestone and rutile. In particular, a lime-based coated arc welding rod is used for all-position welding of fixed tubes and the like (including not only downward welding but also vertical and upward welding in which beads are easily dropped due to the influence of gravity).

[0003]

However, in the conventional lime-based coated arc welding rod for austenitic stainless steel, the slag viscosity is increased by fluorite as a main component, so that the bead is used in vertical welding and upward welding. Good bead shape can be obtained without dripping, but the arc stability is inferior when AC welding power is used due to the high fluorite content, and the protection tube shape is uneven due to insufficient bar burning resistance. There was a problem that it was apt to become easily. Further, during downward welding, slag is thinly covered on the bead, and seizure of the slag occurs, which makes it very difficult to remove the slag, which requires a lot of trouble.

On the other hand, in order to improve such bar burning resistance and slag peeling property, an improved lime-based coated arc welding rod as disclosed in, for example, JP-A-53-52256 has been proposed. However, the improvement is not sufficient and the slag removability is not particularly satisfactory.

[0005] As described above, in the coated arc welding rod for austenitic stainless steel used in all positions, each item of slag peeling property, bar burning resistance (protective cylinder forming property), bead shape, arc stability, and spatter. In other words, there is a demand for a coated arc welding rod having excellent welding workability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a coated arc welding rod for austenitic stainless steel having good welding workability in all positions.

[0007]

In order to achieve the above-mentioned object, a coated arc welding rod for austenitic stainless steel according to the present invention has a metal fluoride (in F conversion value) of 15 by weight based on the total weight of the coating agent. ３０30%, metal carbonate (in terms of CO ₂ ): 10 to 25%, K oxide (in terms of K ₂ O):
Contains 1 to 5%, Ti or / and / or Ti oxide (in terms of TiO ₂ ): 2 to 8% as an essential component, and
(Converted value) / CO ₂ (converted value) ratio: Satisfies 1.0 to 1.5, regulates Na oxide (in terms of Na ₂ O) to 1% or less, and contains metal powder. Is 30% or less coated on a stainless steel core wire.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In order to achieve the above object, the present inventor has made various studies on bar burning resistance and slag removability, which have been difficult to improve in the past. As a result, to form a protective cylinder of an appropriate shape that does not melt or chip off at the end of the welding rod during welding, that is, the bar burning resistance, which indicates the degree of difficulty in forming a good protective cylinder, A metal fluoride that increases the melting rate and is effective for improving bar burning resistance, and a metal carbonate that, when its content is large, is decomposed by heating due to resistance heating of the core wire during welding, making it difficult to form a protective cylinder Use a potassium-based water glass containing K oxide to form a protective cylinder of appropriate shape that does not chip off in the adhesive for coating the core wire with the coating agent while regulating the ratio to a specific range. It was found that the resistance to bar burning could be improved. In addition, as for slag releasability, it was found that slag removability can be improved without impairing the above-described bar burning resistance by adding Ti or / and Ti oxide to the coating agent.

The present invention having the above features has been made based on these findings, and the reasons for limiting the coating components in the present invention will be described in detail below. The content of each component of the coating agent is the weight ratio of the entire coating agent, that is,% by weight based on the total weight of the coating agent.

The metal fluoride is converted to an F-equivalent value of 15 to 30.
%: Metal fluoride has the effect of increasing the melting rate of the coated welding rod, and also has the effect of adjusting the fluidity of the slag as a slag forming agent. However, if it is less than 15%, such an effect is not obtained, and if it exceeds 30%, the arc becomes unstable and the fluidity of the slag becomes excessive, making it difficult to perform welding in a vertical or upward posture. Therefore, the amount of metal fluoride is set in a range of 15 to 30% in terms of a converted value. Examples of the metal fluoride include fluorite (CaF ₂ ), cryolite (Na ₃ AlF ₆ ), potassium silicofluoride (K ₂ SiF ₆ ), and the like.

The metal carbonate is converted to a CO ₂ conversion value of 10 to 25.
%: Metal carbonate has a shielding effect due to generation of CO ₂ gas as a gas generating agent for preventing oxidation or nitriding of the molten metal. However, if the content is less than 10%, such an effect is not obtained. If the content is more than 25%, the coating material is heated by the resistance heating of the stainless steel core wire during welding, and the decomposition of the metal carbonate is remarkable. And the arc concentration, directivity, and blowing force are deteriorated. Therefore, the metal carbonate content is 10 in terms of CO ₂ value
The range is 25%. The metal carbonate includes limestone (CaCO ₃ ), manganese carbonate (MnCO ₃ ), barium carbonate (BaCO ₃ ), and the like.

When the ratio of F conversion value / CO ₂ conversion value is 1.0 to
1.5: the most characteristic configuration of the present invention;
To obtain good welding workability in all positions, the F conversion value /
It is necessary to limit the ratio of the CO ₂ conversion value to the above specific range. If this ratio is less than 1.0, the stick burning resistance deteriorates (deteriorates), making it impossible to form a strong and appropriately shaped protective cylinder, making it difficult to weld in all positions. On the other hand, if this ratio exceeds 1.5, the arc stability deteriorates and spatter increases. Therefore, the ratio of F conversion value / CO ₂ conversion value is set to 1.
Adjust to the range of 0 to 1.5.

K oxide is converted to K_Two1-5% in O equivalent:
The coated arc welding rod is used to apply water
Add a fixing agent such as water and knead to give appropriate viscosity.
Is applied to the core wire and then fired at a high temperature.
Being manufactured. The fixing action to the core wire by this fixing agent is
Insufficient weakness causes chipping of the protective sleeve during welding
The arc concentration and directivity are poor, and the arc
Stable and bad bead shape. On the other hand, the fixing action is too strong
In this case, the protective cylinder is too strong and its length is too long.
As a result, an arc break occurs. So, the proper shape
Type of adhesive to form a protective cylinder
And the amount added. As a result, in the present invention
Potassium silicate (K_TwoSiO_Three)of
Potassium-based water glass, which is an aqueous solution, proves to be effective
Was. Water glass to which K oxide such as potassium feldspar is added
However, it was found that a good protective cylinder could be formed. This
For this reason, the amount of K oxide is K_Two1 to 5% in O equivalent
And In addition, as the K oxide, the potassium-based water glass is used.
K feldspar (K_TwoO ・ Al_TwoO_Three・ 6SiO
_Two), Potash glass (CaO ・ K_TwoO ・ SiO_Two) And the like.

₂ to 8% of Ti or / and Ti oxide in terms of TiO ₂ : Ti has conventionally been added for the purpose of deoxidation, but the coating agent component system of the present invention has poor slag release properties. This has the effect of making it easier to remove slag, which was newly found. It was also found that the same effect was obtained when Ti was added in the form of Ti oxide.
To obtain this effect, the total amount of Ti and / or Ti oxide must be 2% or more in total. On the other hand, the addition amount is 8%
If it exceeds, spatter increases, and in vertical welding, the bead becomes slightly convex and the bead shape becomes poor. Therefore, the total Ti and / or Ti oxide is 2 to 8 percent range in terms of TiO ₂ value. Ti may be added in the form of ferro-titanium (Fe-Ti) in addition to metallic titanium. Ti oxides include rutile (TiO ₂ ), illuminite (FeO.TiO ₂ ), and titanic acid. Potassium (K ₂ Ti
O ₃ ) and calcium titanate (CaTiO ₃ ).

Na oxide is 1% or less in terms of Na ₂ O: Na oxide degrades arc stability and increases spatter. Therefore, the amount of Na oxide is N
It must be 1% or less in terms of a ₂ O. In addition, Na
Na in water glass used as a fixing agent as an oxide
Examples include Na oxides such as ₂ O.

Metal powder is 30% or less: Cr, Ni, M
Metal powders such as o and Nb can be appropriately added to adjust the components of the weld metal. However, if the amount of the metal powder exceeds 30%, the blowing force of the arc becomes weak, the arc becomes unstable, and the amount of spatter increases. Therefore, the amount of the metal powder is set to 30% or less.

[0017]

EXAMPLE An austenitic stainless steel core wire having the chemical composition shown in Table 2 was coated with a coating material having the composition shown in Tables 3 and 4, and coated arc welding rods for austenitic stainless steel of the present invention and comparative examples were obtained. Produced. The core wire dimensions were 3.2 mm in diameter and 300 mm in length, and the coverage (coating agent weight based on the total weight of the welding rod) was 30%.

Each welding rod was subjected to a welding workability evaluation test. The test is 6mm thick x 50mm wide x 300m long.
A T-shaped fillet joint is formed using a test steel sheet of
Fillet welding was performed in each of the vertical and upward positions.
The welding current value in the downward welding was 105 A, and the welding current value in the vertical and upward welding was 85 A, and an AC welding power source was used in each case. Table 1 shows the chemical components of the test steel sheet (austenitic stainless steel).

The test results are shown in Tables 5 and 6. The evaluation was ◎: extremely excellent, ：: normal (no problem in practical use), Δ: slightly inferior, ×: inferior (impractical).

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

[Table 5]

[0025]

[Table 6]

As is clear from Table 5, the present invention examples (welding rods No. 1 to No. 9) have very good welding workability (slag peeling property, bar burning resistance, bead shape, Arc stability and the amount of spatter).

On the other hand, the comparative examples (welding rods No. 10 to No. 18) whose evaluation results are shown in Table 6 lack any of the requirements specified in the present invention, and therefore have the following problems. That is, No. 10 is the amount of metal fluoride, and F conversion value / C
The ratio of the O ₂ conversion value is lower than the lower limit, the sticking resistance is remarkably deteriorated, and the bead shape is slightly deteriorated. N
o. In No. 11, the ratio of the F conversion value / CO ₂ conversion value exceeds the upper limit value, the arc stability is slightly deteriorated, and the spatter amount is slightly increased. No. In No. 12, the ratio of the metal fluoride content and the F-converted value / CO ₂ -converted value exceeds the upper limit, and particularly the arc stability and bead shape in vertical / upward welding are extremely poor.
No. No. 13 had poor bead shape due to insufficient shielding because the metal carbonate was below the lower limit, and the amount of Ti oxide (Ti
(In terms of O ₂ ) exceeds the upper limit, the amount of spatter is very large, and in vertical / upward welding, the bead tends to be convex and the shape is poor.

In addition, No. No. 14 shows that the metal carbonate exceeds the upper limit value and the ratio of F conversion value / CO ₂ conversion value is lower than the lower limit value, so that the bar burning resistance is remarkably poor, the arc is unstable in all postures, and the bead shape deteriorates. ing. No. No. 15 shows that the protective cylinder is excessively strong because the K oxide exceeds the upper limit value, and that the length of the protective tube is too long, so that the arc is frequently broken, the arc becomes remarkably unstable, and the Na oxide becomes the upper limit value. Spatter occurred frequently. No. 1
In No. 6, since the amount of metal powder exceeded the upper limit, the arc spraying force was weak, the arc became extremely unstable, and the amount of spatter generated was somewhat large. No. In No. 17, since the K oxide falls below the lower limit value, the bar burning resistance is extremely poor, the protective tube is chipped off during welding, the arc becomes extremely unstable, and the bead shape is also poor. No. No. 18 has a Ti content of TiO ₂
Since the converted value was below the lower limit, slag removal was extremely difficult.

[0029]

As described above, according to the coated arc welding rod for austenitic stainless steel of the present invention, in welding of austenitic stainless steel in all positions,
Easy slag removal, excellent bar burning resistance (protective tube formation), good arc stability, good bead shape, excellent welding workability with little spatter, and all-position welding of fixed pipes etc. It can contribute to higher efficiency of welding and improvement of welding quality.

Claims (1)

[Claims] 1. A metal fluoride (in terms of F): 15 to 30%, a metal carbonate (in terms of CO ₂ ): 10 to 25%, and a K oxide (K ₂ O) Conversion value): 1
5%, Ti and / or Ti oxide (in terms of TiO ₂ ): 2 to 8%, as an essential component, and a ratio of F converted value / CO ₂ converted value: 1.0 to 1.5 Satisfy N
a The oxide (in terms of Na ₂ O) is regulated to 1% or less, and a coating agent having a metal powder content of 30% or less is coated on a stainless steel core wire. Covered arc welding rod for austenitic stainless steel.