JP3798345B2 - Covered arc welding rod - Google Patents

Description

【００３４】
【表２】

【００３５】
【表３】

【００３６】
【表４】

【００３７】
【表５】

【００３８】
【表６】

【００３９】
【表７】

【００４０】
（１）溶接条件
溶接条件は下記表８に示すとおりである。極性は直流である。
【００４１】
【表８】

【００４２】
（２）作業性評価
厚さ３ｍｍ、幅５０ｍｍ、長さ３００ｍｍのＳＵＳ３０４製溶接母材によりＴ字すみ肉試験片を作成し、水平すみ肉溶接により、作業性を評価した。
【００４３】
（３）ヒューム採取法
ＪＩＳ Ｚ３９３０（被覆アーク溶接棒の全ヒューム量測定方法）に準拠して行った。即ち、下部が開放され、上部にハイボリュームエアサンプラーを備えた鉄製の箱内で溶接しながら、ヒュームを吸引し、グラスファイバー製の濾紙にてヒュームを採取した。
【００４４】
（４）ヒューム分析法
ヒュームを０．４〜１．０ｇ吸着した濾紙にてヒュームを２５０ｍｌの水中に浸漬し、常温常圧で５分間振とうした後、恒温振とう水槽にて７０℃に２時間振とうした。この液を静置し、室温まで冷却した後、ガラス繊維フィルター（０．４５μｍ）にて濾過し、溶出検液とした。この溶出検液をＪＩＳ Ｋ０１０２にて測定し、測定値からヒューム中の水に可溶性のＣｒ含有量を決定した。
【００４５】
下記表９乃至表１１は、この溶接試験により得られた評価結果を示す。なお、作業性評価欄において、◎は極めて優れている場合、○は優れている場合、○△は可の場合、△はやや劣る場合、×は劣る場合である。
【００４６】
【表９】

【００４７】
【表１０】

【００４８】
【表１１】

【００４９】
本発明の実施例Ａ１〜Ａ１０は、本発明の請求項１乃至５の全ての構成要件を満足するため、いずれも、生産性、ヒューム中の水に可溶性のＣｒ、溶接作業性の全てについて良好な値を示しており、水に可溶性のＣｒ量が少なく、溶接作業性が優れたものであった。
【００５０】
なお、実施例Ａ６は、被覆剤中のＳｉ成分が若干少ないものの、請求項１及び２を満足するため、良好な作業性を維持している。また、実施例Ａ７は逆に被覆剤中のＳｉ成分が若干高いものの、請求項１及び２を満足するため、溶接作業性は良好である。実施例Ａ８は被覆剤層の外径が若干大きいものの、請求項１を満足するため、溶接作業性は未だ良好である。実施例Ａ９は被覆剤層の外径が若干小さいものの、請求項１を満足するため、アークの安定性は損なわれていない。実施例Ａ１０は、ＴｉＯ_２微粉末の配合量が若干少ないが、請求項４を満足するため、アークの強さは足りており、姿勢溶接が可能である。実施例Ａ１１は、ＴｉＯ_２微粉末が多めに配合されているが、請求項４は満足するので、乾燥割れはほぼ良好である。
【００５１】
また、実施例Ａ１２は、ＴｉＯ_２微粉末を含むものの、その配合量が少ない（請求項２から外れる）ため、アークスタート性及びスパッタの抑制が若干不十分となる。実施例Ａ１３は、ＴｉＯ_２微粉末の配合量が多すぎる（請求項４から外れる）ため、乾燥割れが生じ、歩留が若干悪化した。参考例Ａ１４は、被覆剤層の外径が請求項１の範囲から外れて太すぎるため、保護筒が長くなり、アーク切れが発生する傾向がみられる。参考例Ａ１５は、逆に、被覆剤層の外径が請求項１の範囲から外れて細すぎるため、アークの不安定が発生している。
【００５２】
更に、参考例Ａ１６は、加水分解可能なＮａ及びＫ量が被覆剤全体のそれに対して少なく、請求項２から外れるため、ヒューム中の水に可溶性のＣｒ量が高めになっている。実施例Ａ１７は、被覆剤中にフッ化アルミニウムが含まれていないため、水に可溶性のＣｒ量及び溶接作業性（特に、アークの安定性）が若干劣っている。実施例Ａ１８は、フッ化アルミニウムを最少量含んでいるので、溶接作業性（アークの安定性）が実施例Ａ１７よりも良好である。実施例Ａ１９は、フッ化アルミニウムの量が多すぎる（請求項５から外れる）ため、スラグの粘性が低く、スパッタが若干多い傾向にある。なお、実施例Ａ１１乃至Ａ１３及び実施例Ａ１７乃至１９において、特性が若干低いのは、実施例Ａ１乃至Ａ１０に比較した場合であって、従来の被覆アーク溶接棒に対しては特性が優れている。
【００５３】
比較例Ｂ１は、Total（Ｎａ_２Ｏ＋Ｋ_２Ｏ）が１．２０％と請求項１から外れているので、被覆剤中のＮａ及びＫの含有量が高くなりすぎ、ヒューム中の水に可溶性のＣｒ量が極めて高い。
【００５４】
比較例Ｂ２は、被覆剤中のＳｉ量が１４％と低く、請求項１から外れているので、溶接作業性、特に、アークスタート性が悪いという問題点がある。
【００５５】
比較例Ｂ３は、被覆剤のＳｉ量が３６％と高すぎ、請求項１から外れているので、多量のスパッタが発生した。
【００５６】
比較例Ｂ４は、ＴｉＯ_２微粉末を含まず、請求項１から外れているので、アークスタートが困難であり、また溶接時にショートし易いという問題点がある。
【００５７】
【発明の効果】
以上説明したように、本発明によれば、ヒューム中の水に可溶性のＣｒ量を低減できると共に、アークスタート性及びアーク安定性等の作業性が優れた被覆アーク溶接棒を得ることができる。
【図面の簡単な説明】
【図１】被覆剤層の外径ｄ２と、心線径ｄ１との間の好ましい範囲を示すグラフ図である。
【図２】ワイヤの断面を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coated arc welding rod containing Cr in at least one of a core wire and a coating material. More specifically, the present invention reduces Cr soluble in water in fumes generated during welding, and further improves arc stability. The present invention relates to a coated arc welding rod having good welding workability by dramatically increasing.
[0002]
[Prior art]
Cr is generally widely added as an indispensable component in welding materials for stainless steel, some low alloy heat resistant steels, and some hardfacing. However, a part of the Cr contained in the welding material is released into the atmosphere as a fume by welding, and the water-soluble oxidation state (+ VI) Cr contained as a part of the fume is harmful. It is said. In addition, it is necessary to treat the fumes collected in the exhaust device as industrial waste. However, because waste is regulated by water-soluble Cr, it takes time and effort for the treatment. Yes. For this reason, it is necessary to radically reduce the amount of Cr soluble in water contained in the fume itself, and there is a demand for the development of a welding material that enables this.
[0003]
Therefore, various studies have been made in the past in order to reduce the amount of Cr soluble in water contained in the fume in the Cr-containing coated arc welding rod. Japanese Patent Application Laid-Open No. 52-114447 discloses that the amount of Cr soluble in water in the fume can be effectively reduced by regulating the contents of Na and K in the coating agent. . Japanese Patent Laid-Open No. 53-19154 discloses a covered arc welding rod that reduces soluble Cr in water in the fume by using Li and other additive raw materials, and has good coating adhesion and welding workability. Is disclosed. Further, Japanese Patent Application Laid-Open No. 55-149796 proposes a technique for reducing the amount of spatter generated and improving welding workability.
[0004]
[Problems to be solved by the invention]
However, in the prior art using a titania-based coating containing TiO ₂ as a main material and a metal carbonate, metal fluoride, and metal powder as a secondary material, Na and K in the coating are reduced. In such a case, there is a problem that arc start properties and arc stability are extremely deteriorated, and welding workability is deteriorated.
[0005]
The present invention has been made in view of such problems, and provides a Cr-containing coated arc welding rod that can reduce the amount of Cr soluble in water in the fume and has excellent arc startability and arc stability. With the goal.
[0006]
[Means for Solving the Problems]
The coated arc welding rod according to the present invention is a coated arc welding rod containing Cr in either one or both of a core wire and a coating material. The composition of the coating material is a Na-containing component and K per total mass of the coating material. The total content of sodium and potassium obtained by converting the content components to Na ₂ O and K ₂ O is 1% by mass or less, and the content of silicon obtained by converting the Si content components to SiO ₂ is 15 to was 30 wt%, seen containing a TiO ₂ powder having a diameter composed of particles smaller than 10 [mu] m, the diameter of the core wire d1, the outer diameter of the coating layer when the d2, d1 and d2 satisfies the following equation 1 and 2 are satisfied .
[0007]
Another coated arc welding rod according to the present invention is a coated arc welding rod containing Cr in one or both of a core wire and a coating material, and the composition of the coating material is a Na-containing component per the total mass of the coating material. And the total content of sodium and potassium obtained by converting the K-containing component into Na ₂ O and K ₂ O, respectively, is 1% by mass or less, and the silicon content obtained by converting the Si-containing component into SiO ₂ a 15 to 30 wt%, seen containing a TiO ₂ powder having a diameter composed of particles smaller than 10 [mu] m, hydrolyzable Na component and a K component contained respectively Na in ₂ O and _{K 2} O in the coating Obtained by converting the sodium and potassium contents obtained by conversion into sol. Na ₂ O and sol. K ₂ O, respectively, and converting the Na component and K component contained in the coating into Na ₂ O and K ₂ O, respectively. Nat When the contents of lithium and potassium are T. Na ₂ O and T. K ₂ O, respectively, ( sol. Na ₂ O + sol. K ₂ O) / ( T. Na ₂ O + T. K ₂ O) It is characterized by being 0.5 to 1.0 .
[0008]
[Expression 1]
When d1 is less than 3 mm, 1.67 × d1 + 0.17 ≦ d2 ≦ 1.67 × d1 + 0.47
[0009]
[Expression 2]
When d1 is 3 mm or more 1.28 × d1 + 1.43 ≦ d2 ≦ 1.28 × d1 + 1.83
[0010]
Also in the coated arc welding rod according to claim 1 of the present application, sodium obtained by converting both the hydrolyzable Na component and K component contained in the coating agent into Na ₂ O and K ₂ O, respectively, and Sodium and potassium contents obtained by converting the potassium content to sol.Na ₂ O and sol.K ₂ O, respectively, and converting the Na component and K component contained in the coating to Na ₂ O and K ₂ O, respectively. Are T.Na ₂ O and T.K ₂ O, respectively, (sol.Na ₂ O + sol.K ₂ O) / (T.Na ₂ O + T.K ₂ O) is 0.5 to 1.0 Preferably there is.
[0011]
Furthermore, it is preferable to contain 3 to 15% by mass of the TiO ₂ fine powder with respect to the total mass of the coating agent. Furthermore, it is preferable that the coating material contains 0.5 to 5% by mass of aluminum fluoride per the total mass of the coating material.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail. Na and K contained in the coating have the effect of lowering the arc starting voltage, facilitating arc generation, increasing the stability of the arc, and increasing the adhesion of the coating, thereby improving welding workability. It is known that there is. However, as described in JP-A-52-114447, in order to reduce Cr soluble in water in the fume, it is necessary to limit the contents of Na and K in the coating agent. When the content of Na and K in the inside is reduced, there is a problem that welding workability and the fixing force of the coating agent are lowered.
[0013]
The present inventors are soluble in the water in the fume while maintaining the arc stability and the adhesion of the coating and maintaining the welding workability even when the amount of Na and K in the coating is reduced. In order to reduce the amount of Cr, the present invention was completed by intensive studies on the formulation and manufacturing method of the coating agent.
[0014]
Hereinafter, the reason for limiting the numerical values of the respective compositions in the present invention will be described.
[0015]
“Total of Na-containing component and K-containing component in coating (oxide conversion value): 1% by mass or less”
It is preferable to reduce Na and K in the coating agent as much as possible because the lower the content, the more effective is the suppression of Cr soluble in water in the fume. In this case, when the Na-containing component and the K-containing component exceed 1% by mass in the sum of the Na ₂ O converted value and the K ₂ O converted value, respectively, the effect of reducing Cr soluble in water in the fume is low. The total content of sodium and potassium obtained in terms of Na ₂ O and K ₂ O is 1% by mass or less.
[0016]
“Si-containing component in coating (SiO ₂ equivalent value): 15 to 30% by mass”
In the conventional titania-based coating, when Na and K in the coating are reduced, there is a problem that the arc start property and the arc stability are extremely deteriorated. The present inventors have studied various raw materials, and by adding an appropriate amount of Si in an oxide state, the arc start property and the arc stability are dramatically improved, and at the same time, trace amounts of Na and K are contained in the coating agent. Even in such a case, it has been found that the composition containing a large amount of Si in the oxide state can significantly reduce the amount of Cr soluble in water in the fume. Examples of Si sources include ore powders such as coral and feldspar, slipping agents such as kaolin and talc, and sticking agents such as water glass as oxides. In addition, metallic materials such as metallic Si and ferrosilicon also have the same effect as the addition of Si in the oxide state because Si slags out during welding and acts as an oxide.
[0017]
When Si in the coating agent is less than 15% by mass in terms of SiO ₂ , sufficient effects that contribute to the welding stability as described above cannot be obtained, and arc breakage is likely to occur. Also, Si in the coating agent when the content is more than 30 wt% in terms of SiO _2, an increase in the fluidity of the slag, burn the bead surface occur sputtering is increased, the slag removability is deteriorated. Therefore, Si in the coating is 15 to 30 wt% in terms of SiO _2.
[0018]
“TiO ₂ fine powder: 3 to 15% by mass”
The fixing strength of the coating material has a great influence on the workability of welding, but if this is strong, a protective cylinder is formed during welding, which increases the stability of the arc and improves the concentration of the arc. Workability is significantly improved. As a result of studying various raw materials by the present inventors in order to enhance the adhesion of the coating material, the inventors found that the fine powder of TiO ₂ significantly increases the adhesion strength of the coating material.
[0019]
The fine powder of TiO _2, particle size is less TiO ₂ powder source 10 [mu] m, in general, there is a white titanium, common name, such as titanium white or white titanium. The effect of TiO ₂ fine powder can be obtained by adding a small amount, but in order to obtain a sufficient effect, it is preferable to add 3% by mass or more based on the total mass of the coating agent. However, if it exceeds 15% by mass, dry cracking is likely to occur, so the TiO fine powder is preferably 3 to 15% by mass.
[0020]
“Outer diameter d2 of coating layer: Formulas 1 and 2”
FIG. 2 is a cross-sectional view of the coated arc welding rod cut in a direction perpendicular to its axis. In the figure, d1 is the diameter of the core wire, and d2 is the outer diameter of the coating layer. In the present invention, Na and K in the coating material are reduced and Si is actively added, so the range of the outer diameter d2 of the coating material layer where the welding workability is optimal is particularly narrow. In the present invention, since Na and K of the coating agent are reduced, it is difficult to ensure arc startability and arc stability. When d2 is small, it is difficult to form a protective cylinder during welding, the arc becomes unstable, and when the spatter is increased, the arc voltage during welding increases and arc breakage occurs. On the other hand, the addition of Si to the coating increases the fluidity of the molten slag, and when the slag is covered, the arc is likely to stop, so it is not preferable that d2 is large. In order to obtain optimum welding workability, the outer diameter (d2) of the covering rod has to be particularly narrow. For this reason, the present inventors conducted various tests on the outer diameter d2 of the coating layer for each welding rod size (core wire diameter d1), and obtained the optimum outer diameter d2 of the coating layer.
[0021]
As a result of the test, it was found that there is a range with good workability as shown in FIG. In FIG. 1, the core axis diameter d1 is taken on the horizontal axis, and the outer diameter d2 of the coating layer is taken on the vertical axis. The combination of (d1, d2), the workability is good, and the workability is bad. And organized. As shown in FIG. 1, in a region where the outer diameter d2 of the coating layer is larger than the line segment L1 and the line segment L2, slag fogging occurred and workability deteriorated. On the other hand, in the region where the outer diameter d2 of the coating layer is smaller than the line segment L3 and the line segment L4, the arc becomes unstable and workability deteriorates due to the occurrence of spatter. On the other hand, workability was good in the area between the line segments L1 and L2 and the line segments L3 and L4.
[0022]
The line segment L1 is represented by d2 = 1.28 × d1 + 1.83, and the line segment L3 is represented by d2 = 1.28 × d1 + 1.43. The line segment L2 is represented by d2 = 1.67 × d1 + 0.47, and the line segment L4 is represented by d2 = 1.67 × d1 + 0.17. The line segment L1 and the line segment L2 and the line segments L3 and L4 intersect with each other with a core wire diameter d1 of about 3 mm, and the region with good workability is a range represented by the above formulas 1 and 2. .
[0023]
If the outer diameter of the coating layer is too large, arc breakage is likely to occur, slag is excessively covered, and welding workability is deteriorated. On the other hand, if the outer diameter of the coating layer is too thin, the arc becomes unstable and the amount of spatter increases, so that the welding workability is deteriorated.
[0024]
“Ratio of hydrolyzable Na and K contained in the coating agent”
Conventionally, if Na and K in the coating material are reduced, fading and dry cracking are likely to occur, making the production difficult, and even if it can be produced, the adhesive has a weak adhesive force, so that sufficient protection is provided during welding. A tube was not formed, and it was difficult to obtain satisfactory welding workability. Therefore, in order to maintain the productivity and workability of the welding rod, a small amount of Na and K are blended as a fixing agent, a swelling agent or a slip agent, and a component that can obtain satisfactory productivity and workability is obtained. Then, the coating composition was examined. As a result, when Na and K contained in the coating agent are added in the form of a hydrolyzable fixing agent or swelling agent, the maximum effect is achieved in reducing Cr soluble in water in fume and ensuring welding workability. It has been found that it is effective to control the ratio of Na and K that can be hydrolyzed.
[0025]
The sodium and potassium contents obtained by converting the hydrolyzable Na component and K component contained in the coating agent into Na ₂ O and K ₂ O, respectively, are sol.Na ₂ O and sol.K ₂ O, respectively. When the sodium and potassium contents obtained by converting the Na component and K component contained in the coating material into Na ₂ O and K ₂ O, respectively, are T.Na ₂ O and T.K ₂ O, respectively. , (Sol.Na ₂ O + sol.K ₂ O) / (T.Na ₂ O + T.K ₂ O) is preferably 0.5 to 1.0. When (sol.Na ₂ O + sol.K ₂ O) / (T.Na ₂ O + T.K ₂ O) is less than 0.5, a large amount of Na and K in the coating material is contained in the blended raw material, and the fixing agent And since it is small in a swelling agent, while a protection cylinder becomes weak and workability | operativity deteriorates, soluble Cr increases in the water of a fume. In principle, (sol.Na ₂ O + sol.K ₂ O) / (T.Na ₂ O + T.K ₂ O) cannot take a value higher than 1. Therefore, (sol.Na ₂ O + sol.K ₂ O) / (T.Na ₂ O + T.K ₂ O) is preferably set to 0.5 to 1.0.
[0026]
In the present invention, the values in terms of oxides of Na and K contained in the coating are referred to as T.Na ₂ O and T.K ₂ O, respectively, and hydrolysis is added in the form of a sticking agent and a swelling agent. The values obtained by converting the possible Na and K into oxides are handled as Sol.Na ₂ O and Sol.K ₂ O, respectively, and both are handled separately. For hydrolysable Na and K, the following method is used. Can be separated and measured.
[0027]
That is, Sol.Na ₂ O and Sol.K ₂ O were prepared by pulverizing the coating material peeled off from the coating rod in an agate mortar, adding distilled water to a certain amount of coating material, and maintaining boiling for 4 hours. It can be measured by analyzing the dissolved component by atomic absorption.
[0028]
“Aluminum fluoride contained in coating agent: 0.5 to 5% by mass”
Furthermore, the inventors of the present application have examined various additive raw materials in order to improve welding workability and reduce the amount of Cr soluble in water in the fume. It has been found that it is effective for exerting the above characteristics. Aluminum fluoride reduces Cr soluble in water in the fumes, but does not increase the amount of fumes generated, and at the same time has the effect of softening the arc.
[0029]
When aluminum fluoride is less than 0.5% by mass per total mass of the coating agent, a sufficient effect is not seen, and when it exceeds 5% by mass, the flowability of slag becomes too high and spatter increases. For this reason, the aluminum fluoride contained in the coating agent is 0.5 to 5% by mass.
[0030]
In addition, oxide raw materials such as alumina and zircon sand can be used as the slag former. Metal raw materials such as Mn, Cr, Ni, and Mo can be used for adjusting the components of the weld metal.
[0031]
【Example】
Hereinafter, the effect of the Example of this invention is demonstrated compared with the comparative example which remove | deviates from the scope of the present invention. The coated arc welding rods of Examples and Comparative Examples were manufactured, and the amount of Cr soluble in fume water and welding workability were evaluated. As a coating agent, prepare a flux material mixed with a fixing agent such as water glass, lithium silicate, colloidal silica, colloidal alumina, etc., apply this coating agent around the metal core, and then coat A coated arc welding rod is produced by drying the agent. Usually, the content of the fixing agent in the coating of the coated arc welding rod is 3 to 10% by weight. Table 1 below shows the composition of the core wire. Tables 2 to 4 and Tables 5 to 7 below show the core wire diameter, the composition of the coating layer, and the outer diameter.
[0032]
As shown in Tables 2 to 4 and Tables 5 to 7, the chemical composition of the coating agent, the core wire diameter, and the outer diameter of the coating layer were variously changed, and the coating material was a metal core wire (20Cr -10Ni stainless steel) and dried to produce a coated arc welding rod. In addition, lithium silicate was mainly used for the fixing agent, and a small amount of soda water glass and potassium glass were mixed and used. The produced coated arc welding rod was evaluated by the following welding conditions and test methods.
[0033]
[Table 1]

[0034]
[Table 2]

[0035]
[Table 3]

[0036]
[Table 4]

[0037]
[Table 5]

[0038]
[Table 6]

[0039]
[Table 7]

[0040]
(1) Welding conditions The welding conditions are as shown in Table 8 below. The polarity is direct current.
[0041]
[Table 8]

[0042]
(2) Workability evaluation T-shaped fillet specimens were prepared from a SUS304 welded base material having a thickness of 3 mm, a width of 50 mm, and a length of 300 mm, and workability was evaluated by horizontal fillet welding.
[0043]
(3) Fume sampling method This was performed in accordance with JIS Z3930 (a method for measuring the total fume amount of a coated arc welding rod). That is, the lower part was opened, the fume was sucked while welding in an iron box equipped with a high volume air sampler on the upper part, and the fume was collected with a glass fiber filter paper.
[0044]
(4) Fume analysis method Fume is immersed in 250 ml of water with a filter paper on which 0.4 to 1.0 g of fume is adsorbed, shaken at room temperature and normal pressure for 5 minutes, and then heated to 70 ° C. in a constant temperature shaking water bath. Shaking time. The solution was allowed to stand, cooled to room temperature, and then filtered through a glass fiber filter (0.45 μm) to obtain an elution test solution. This elution test solution was measured by JIS K0102, and the content of Cr soluble in water in the fume was determined from the measured value.
[0045]
Tables 9 to 11 below show the evaluation results obtained by this welding test. In the workability evaluation column, ◎ is extremely excellent, ○ is excellent, ○ △ is acceptable, Δ is slightly inferior, and × is inferior.
[0046]
[Table 9]

[0047]
[Table 10]

[0048]
[Table 11]

[0049]
Since Examples A1 to A10 of the present invention satisfy all the constituent requirements of claims 1 to 5 of the present invention, all of them are good in terms of productivity, Cr soluble in water in fume, and welding workability The amount of Cr soluble in water was small, and the welding workability was excellent.
[0050]
In Example A6, although the Si component in the coating agent was slightly less, the workability was maintained in order to satisfy claims 1 and 2 . On the other hand, Example A7, on the contrary, has a slightly high Si component in the coating agent, but satisfies the claims 1 and 2 and therefore has good welding workability. In Example A8, although the outer diameter of the coating layer is slightly large, the workability of welding is still good in order to satisfy Claim 1 . In Example A9, although the outer diameter of the coating layer is slightly smaller, the stability of the arc is not impaired in order to satisfy claim 1 . In Example A10, although the blending amount of the TiO ₂ fine powder is slightly small, since it satisfies claim 4 , the strength of the arc is sufficient, and posture welding is possible. In Example A11, TiO ₂ fine powder was added in a large amount, but since Claim 4 is satisfied, dry cracking is almost satisfactory.
[0051]
In addition, although Example A12 contains TiO ₂ fine powder, the blending amount thereof is small (departing from claim 2), so that the arc start property and the suppression of sputtering are slightly insufficient. In Example A13, since the blending amount of the TiO ₂ fine powder was too large (departed from claim 4 ), dry cracking occurred and the yield was slightly deteriorated. In Reference Example A14, the outer diameter of the coating layer is out of the range of claim 1 and is too thick, so that the protective cylinder becomes longer and arc breakage tends to occur. On the contrary, in Reference Example A15, since the outer diameter of the coating layer is too small outside the range of claim 1 , arc instability occurs.
[0052]
Furthermore, in Reference Example A16, the amount of Na and K that can be hydrolyzed is small compared to that of the entire coating material, and deviates from claim 2. Therefore, the amount of Cr soluble in water in the fume is increased. In Example A17, since aluminum fluoride is not contained in the coating agent, the amount of Cr soluble in water and welding workability (particularly, arc stability) are slightly inferior. Since Example A18 contains a minimum amount of aluminum fluoride, the welding workability (arc stability) is better than that of Example A17. In Example A19, since the amount of aluminum fluoride is too large (departing from claim 5), the viscosity of the slag is low and the amount of spatter tends to be slightly high. In Examples A11 to A13 and Examples A17 to A19 , the characteristics are slightly lower than those in Examples A1 to A10, which are superior to the conventional coated arc welding rod. .
[0053]
In Comparative Example B1, the total (Na ₂ O + K ₂ O) is 1.20%, which is outside the scope of claim 1, so that the contents of Na and K in the coating become too high and are soluble in the water in the fume. The amount of Cr is extremely high.
[0054]
Since Comparative Example B2 has a low Si content in the coating agent of 14% and deviates from Claim 1, there is a problem that welding workability, particularly arc startability is poor.
[0055]
In Comparative Example B3, the amount of Si in the coating agent was too high at 36%, which was outside the scope of claim 1, and therefore a large amount of spatter was generated.
[0056]
Since Comparative Example B4 does not contain TiO ₂ fine powder and deviates from Claim 1, there is a problem that arc starting is difficult and short-circuiting is likely to occur during welding.
[0057]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a coated arc welding rod that can reduce the amount of Cr soluble in water in the fume and is excellent in workability such as arc start performance and arc stability.
[Brief description of the drawings]
FIG. 1 is a graph showing a preferred range between an outer diameter d2 of a coating layer and a core wire diameter d1.
FIG. 2 is a view showing a cross section of a wire.

Claims (5)

In the coated arc welding rod containing Cr in one or both of the core wire and the coating agent, the composition of the coating agent is such that the Na-containing component and the K-containing component are Na ₂ O and K ₂ , respectively, with respect to the total mass of the coating agent. The total content of sodium and potassium obtained by converting to O is 1% by mass or less, the content of silicon obtained by converting the Si-containing component to SiO ₂ is 15 to 30% by mass, and the diameter is 10 μm or less. look including the TiO ₂ fine powder consisting of particles, the diameter of the core wire d1, the outer diameter of the coating layer when the d2, shielded metal arc, characterized in that d1 and d2 satisfy the following formula Welding rods.
When d1 is less than 3 mm, 1.67 × d1 + 0.17 ≦ d2 ≦ 1.67 × d1 + 0.47
When d1 is 3 mm or more 1.28 × d1 + 1.43 ≦ d2 ≦ 1.28 × d1 + 1.83 In the coated arc welding rod containing Cr in one or both of the core wire and the coating agent, the composition of the coating agent is such that the Na-containing component and the K-containing component are Na ₂ O and K ₂ , respectively, with respect to the total mass of the coating agent. The total content of sodium and potassium obtained by converting to O is 1% by mass or less, the content of silicon obtained by converting the Si-containing component to SiO ₂ is 15 to 30% by mass, and the diameter is 10 μm or less. the viewing including the TiO ₂ fine powder consisting of particles, the content of sodium and potassium obtained by converting the hydrolyzable Na component and a K component contained in the coating agent in each Na 2 _O and K _{2 O} each sol. Na 2 _O and sol. K 2 _O and to husband the content of sodium and potassium obtained by converting the Na component and a K component contained in the coating agent, respectively Na 2 _O and K _{2 O} people T. when the a ₂ O and _{T. K 2 O, (sol.} Na 2 O + sol. K 2 O) / (T. Na 2 O + T. K 2 O) is from 0.5 to 1.0 Coated arc welding rod characterized by The sodium and potassium contents obtained by converting the hydrolyzable Na component and K component contained in the coating agent into Na ₂ O and K ₂ O, respectively, are sol.Na ₂ O and sol.K ₂ O, respectively. When the sodium and potassium contents obtained by converting the Na component and K component contained in the coating material into Na ₂ O and K ₂ O, respectively, are T.Na ₂ O and T.K ₂ O, respectively. _{, (sol.Na 2 O + sol.K 2} O) / (T.Na 2 O + T.K 2 O) is covered electrode as claimed in claim 1, characterized in that from 0.5 to 1.0. The covered arc welding rod according to any one of claims 1 to 3, wherein the TiO ₂ fine powder is contained in an amount of 3 to 15% by mass based on the total mass of the coating agent.   The coated arc welding rod according to any one of claims 1 to 4, wherein the coating material contains 0.5 to 5% by mass of aluminum fluoride per total mass of the coating material.

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