JP2002346791A - Coated arc welding electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity by improving the coating suitability of a coating material in the production of a coated arc welding electrode, and to improve the quality of the coated electrode by preventing the gaseous expansion and dry cracks of the coated surface in the production and obtaining a better coated surface condition as well. SOLUTION: The coated electrode has characteristics in the components of a coating material, and, by mass, 12 to 30% TiO2 (wherein, 0.5 to 4.0 mass % consists of titanium oxide such as white titanium in which particles having a particle size <1 μm are present in >=95%, and 8.0 to 29.5% consists of titanium oxide such as rutile), 5 to 9% CaCO3 , 15 to 30% SiO2 , 2 to 5% MgO, 4 to 10% Fe-Mn, a 2.0 to 5.0% organic matter and 20 to 40% iron powder, in mass are contained, and in which TiO2 /CaCO3 is also >=2.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to coated arc welding in which the quality of coating is improved by improving the coatability of the coating during production of the coated arc welding rod to improve productivity and obtaining a good coated surface condition. It relates to a rod (hereinafter, welding rod).

[0002]

2. Description of the Related Art Welding rods are classified according to the type of coating agent, and include illuminite type, lime titania type, low hydrogen type and the like. Among them, lime titania-based welding rods specified in JISZ3211 D4303 are widely used in the fields of lightweight steel frames, automobile parts, segments, mild steel thin plates such as drums, medium-thick steel plates, etc. because of their good welding workability and welding performance. ing.

Although many techniques relating to lime titania welding rods have been disclosed, there are still many problems.

For example, Japanese Patent Laid-Open Publication No. Sho 60-30597 discloses an improved technique relating to re-arcing after arc interruption and so-called "cup chipping". However, this technique has a problem in that since the content of CaCO ₃ is as large as 10 to 30%, the arc spraying at the time of welding becomes too strong and is not suitable for welding thin plates. The particle size of the titanium oxide used is -325 mesh (44 μm)
Is 99% or more, and this example of particle size regulation corresponds to relatively coarse titanium oxide, so that the coating surface is not uniform, and there is a problem that productivity is deteriorated.

Japanese Patent Application Laid-Open No. 56-71597 discloses
It is a description about lime titania-based welding rods.
Only the use of rutile as an O ₂ source does not disclose its particle size or re-arc properties. On the other hand, only the improvement of slag removability is disclosed while maintaining the viscosity of slag in the relationship between MgO and water of crystallization.

[0006] Further, Japanese Patent Application Laid-Open No. 10-118784 discloses a technology of sodium alginate to be contained in a coating agent with respect to the productivity of a welding rod. However, since sodium alginate is an alkali component and an organic substance, it is difficult to produce it. Although the improvement of the performance and the occurrence of manufacturing defects can be suppressed, there are problems of an increase in welding fume and moisture absorption of the welding rod.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, the present invention improves the coating property of a coating agent during the production of a welding rod, improves productivity, and prevents gas swelling and drying cracks on the coating surface. It is another object of the present invention to provide a coated arc welding rod having improved quality by obtaining a better coated surface state.

[0008]

In order to solve the above-mentioned problems, the present inventor has proposed a method of improving the coating property of a coating agent at the time of manufacturing, improving the productivity, and obtaining a good coated surface state for a welding rod. Has been studied diligently in terms of coating raw materials. as a result,
The present invention was completed by finding that the addition of titanium oxides having different particle sizes to the coating material had a great effect of significantly improving the productivity and did not adversely affect various welding performances. The gist is characterized by the component of the coating agent of the coated arc welding rod, and TiO ₂ : 12 to 30% by mass (hereinafter, referred to as%).
(However, 0.5 to 4.0% of the TiO ₂ has a particle size of 1
95% or more of titanium oxide particles having a particle size of less than μm, balance 8 to 2
9.5% by mass is titanium oxide having a particle diameter of 1 μm or more),
CaCO ₃ : 5 to 9%, SiO ₂ : 15 to 30%, Mg
O: 2 to 5%, Fe-Mn: 4 to 10%, organic matter:
0 to 5.0%, iron powder: 20 to 40%, and Ti
A coated arc welding rod characterized in that O ₂ / CaCO ₃ is 2.0 or more.

Further, MgO as a coating agent is used as a magnesia clinker, a coated arc welding rod having a particle diameter of less than 50 μm of 60% or more, and an average particle diameter of the iron powder of 50% or more.
In a covered arc welding rod having a diameter of not more than μm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The components of the coating agent of the welding rod according to the present invention, and the structure and the phenomena exerting the effects of the components will be described.

As for the welding rod, a method of improving the coating property of the coating agent during production, improving the productivity, and obtaining a good coating surface state has been intensively studied from the viewpoint of the coating raw material.

First, it is known that in order to maintain good productivity in a welding rod, it is necessary to mix a raw material having slipperiness and appropriate elasticity with a coating material. In particular, in a welding rod that emphasizes re-arc properties after welding interruption, a large amount of iron powder makes the coating material slippery, and it is necessary to contain a large amount of coating material to improve productivity. is there. However, as these raw materials, organic substances including hydrous minerals and alkali components are known. However, if the raw materials are simply increased in order to improve productivity, an increase in fume generation and deterioration in welding workability are likely to occur. .

As described above, since various performances cannot be satisfied only by improving the productivity, a study for improving the productivity without causing these problems has been advanced.

As a result, it was found that the addition of titanium oxide having a different particle size to the coating material had an extremely large effect of improving the productivity and did not adversely affect various welding performances.
This is because titanium oxide has the ability to completely cover other particles due to its high ability to encapsulate other powders (encapsulation). It has the property of being uniformly dispersed in the agent to improve the slipperiness of the coating agent in high-speed coating. By utilizing this, the quality can be improved by obtaining a good coating surface state.

Further, the main component, TiO ₂ / CaCO ₃
The most suitable slag fluidity for all position welding is obtained by limiting the ratio of slag. This is because TiO ₂ and CaCO ₃ , which are main components, are added in large amounts, and thus have a large effect on the fluidity of the slag.

The reasons for limiting the numerical values of the constituent elements of the present invention will be described below based on the actions and effects of the respective components described above.

TiO ₂ is an arc stabilizer and a slag regulator. If it exceeds 30%, the slag becomes too dense and the slag removability deteriorates. If it is less than 12%, the fluidity of the slag deteriorates, and the bead appearance deteriorates. In addition, the arc becomes unstable and spatter increases. TiO ₂ is a TiO ₂ conversion value of the raw material, and the main raw material is rutile or titanium oxide. The TiO ₂ usually has a particle size of 1 μm or more.

[0018] Among the TiO ₂ from the viewpoint of encapsulation of TiO _2, the 0.5 to 4.0 percent particle size of less than 1μm is 9
It is indispensable to use 5% or more of titanium oxide such as white titanium. Since titanium oxide such as white titanium has a particle diameter of almost less than 1 μm and substantially no particle diameter of 1 μm or more, white titanium can be suitably used. TiO ₂ has the property of completely covering other particles due to its high encapsulation property, but if titanium oxide having a particle size of less than 1 μm is substantially uniformly dispersed in the coating material, the sliding of the coating material in high-speed coating can be achieved. Properties can be further improved. Utilizing this property, the quality can be improved by obtaining a coated arc welding rod having a good coated surface condition.

That is, in order to further improve the slipperiness of the coating agent and improve the productivity, 0.5 to 4.0% of 12 to 30% of TiO ₂ has a particle diameter of less than 1 μm of 95% or more. TiO ₂ such as white titanium and the remaining 8 to 29.5% are TiO ₂ such as rutile having a particle size of 1 μm or more. This is because the finer the particle size, the greater the encapsulability of other powders and granules, so the effect of completely covering and coating other particles is maximized, and the paintability and coating surface can be improved. It is.

FIG. 1 shows on the horizontal axis 1 μm present in titanium oxide.
It is a figure which shows the pass rate of the appearance inspection of a welding rod in the vertical axis | shaft taking the content of the titanium oxide whose particle size less than m is less than 95% or 95% or more. In addition, the appearance inspection is a ratio of those excluding those having deteriorated appearance such as flaws, dents, blurs, roughness, chippings on the surface of the welding rod after manufacturing, and a pass rate of 9
Those with 5% or more were regarded as good.

FIG. 2 shows the content of titanium oxide on the horizontal axis, as in FIG. 1, and the vertical axis shows the shedding rate of the coating. In addition, the falling-off rate of the coating agent was 55 mm x 300 mm x 500 mm when a welding rod of about 1.5 kg was formed with a thickness of 6 mm.
mm box made of steel, with the longitudinal direction of the box as the axis.
The coating material was rotated at a speed of 40 revolutions per minute for 5 minutes, and the weight ratio of the falling off coating agent was measured.

1 and 2 are examples in which titanium oxide having a particle size of less than 1 μm contains less than 95%, and ▲ indicates that a particle size of less than 1 μm contains 95% or more of titanium oxide. This is an example in the case of having been performed.

According to FIG. 1, when the content of titanium oxide having an average particle size of less than 1 μm was less than 0.5%, the effect of titanium oxide could not be sufficiently exerted, and the pass rate of appearance inspection was less than 95%. Further, as shown in FIG. 2, when the content exceeds 4.0%, the slipperiness of the coating material is improved and the appearance is improved, but it can be seen that the falling rate of the coating material is deteriorated. Therefore, in the present _invention, it was TiO 2 12~30% 0.5~4.0% over 95% particle diameter of less than 1μm of the.

CaCO ₃ is a gas generating agent, which decomposes in the arc to generate CO ₂ gas, so that the weld metal and the molten slag are shielded from the atmosphere, preventing the entry of nitrogen and oxygen and securing the arc force. And, it adjusts the fluidity and viscosity of the slag. If this is less than 5%, the fluidity and peelability of the slag deteriorate. On the other hand, if it exceeds 9%, the encapsulating property of the slag deteriorates, and the bead appearance deteriorates. The raw material is carbonated lime or the like.

The reason why the ratio of TiO ₂ / CaCO ₃ is 2.0 or more is to obtain the optimum fluidity of the slag. If it is less than 2.0, the fluidity of the slag deteriorates. The slag is easily entangled with the tip of the welding rod, and a sound bead cannot be obtained.

SiO_TwoIs the material for adjusting the fire resistance, the viscosity of the slag
Acts as a conditioner, if less than 15%, the slag encapsulation property
The slag removability deteriorates. On the other hand, if it exceeds 30%
The arc becomes worse due to the coating tube becoming too deep and the bead wave
Shape also worsens. Note that SiO _TwoAs raw materials, silica sand etc.
is there.

MgO acts as a slag conditioner.
If it is less than 5%, the viscosity of the slag is insufficient, and the slag is liable to be entangled with the tip of the welding rod due to the deterioration of the fluidity of the slag in the vertical welding. If it exceeds 5.0%, the encapsulating property of the slag deteriorates and the bead appearance deteriorates.

Magnesia clinker is used as the MgO source. The reason for this is that the material is calcined at 1800 ° C. or higher as compared with other MgO raw materials, and thus has a property of losing its activity. For this reason, since the reactivity with alkali components such as sodium silicate and potassium silicate in the fixing agent is low, and it is stable even when the coating agent and the fixing agent are mixed, good coatability is obtained. However, other MgO raw materials may react with the fixing agent due to their activity, and after coating and coating the coating agent and the coating agent, expansion and shrinkage of the coating layer are liable to occur. Also, gas swelling is likely to occur. Therefore, it is preferable to use magnesia clinker as MgO. The particle size is preferably less than 50 μm and 60% or more. The reason is that the finer the particle size, the denser the coating surface.
This improves the quality by obtaining a good coating surface condition.

Fe-Mn has a function of welding workability and an alloying agent. If it is less than 3%, the fluidity of the slag deteriorates, and the bead appearance deteriorates. Also, it does not act as an alloying agent. 1
If it exceeds 0%, the slag viscosity is reduced, and the slag encapsulability is deteriorated in vertical and upward welding, so that the weld metal drips to form a convex bead. The Mn content of Fe-Mn (ferromanganese) is preferably from 50 to 85% by mass.

The organic substance is added in order to carbonize the tip portion of the coating cylinder during welding to improve the re-arc property after the welding is interrupted together with the iron powder and to make the arc spray strength appropriate.
As the organic substance, sodium alginate, dextrin, wood flour, CMC and the like can be suitably used. Organic matter 2
%, The re-arcing property deteriorates and the arc spraying becomes insufficient, so that sufficient penetration cannot be obtained. On the other hand, if it exceeds 5%, the re-arc property becomes good, but the spraying of the arc becomes too strong and the spatter increases. In addition, when used for high current welding, the coating material deteriorates, causing a stick burn phenomenon, and a healthy weld metal cannot be obtained. For this reason, the organic matter is set to 2 to 5%.

Iron powder is added to improve the electric conductivity, improve the re-arcing property after the interruption of welding, increase the amount of welding, and improve the efficiency of welding work. Iron powder content is 2
If it is less than 0%, the re-arc property deteriorates, and if it exceeds 45%, the sheath becomes shallow and the arc is unstable and short circuit is easily caused. If the conductivity of the sheath becomes excessive, an arc may be generated in other than the sheath. Not preferred for safety.

Further, the reason why the average particle size of the iron powder is limited is to improve the re-arc property after the interruption of welding, and to reduce the average particle size of the iron powder.
m or less.

The components constituting the coating agent in the present invention include, in addition to the above components, feldspar, wollastonite, alumina, mica, etc. which are added to the coating agent for ordinary non-low hydrogen coated arc welding rods. And sodium silicate, potassium silicate, etc. as fixing agents, and unavoidable impurities such as C, P, S, Cl, etc., but the addition of these components does not impair the effects of the present invention and is included in the present invention. .

[0034]

Next, the present invention will be described in detail with reference to examples and comparative examples.

The coating materials having the constitutions shown in Tables 1 and 2 were used for coating with a diameter of 4.
0 mm, 450 mm long mild steel core wire (JIS G352
3 After coating and coating on the coated arc welding rod core, it was dried to produce 40 types of test welding rods. The effects of the titanium oxide and other components were examined, the appearance of the coating was inspected, and the coating agent was used. The re-arcability and welding workability were investigated using the AC welding machine. Table 3 shows the test results. In Tables 1 and 2, Fe-Mn as a blending material used had a Mn content of 76% by mass.

The appearance inspection of the coating was carried out by the above-mentioned experimental method, and the evaluation criteria were "good" if the pass rate was 95% or more. Further, those with 97% or more were marked with ◎. Pass rate is 9
Those with less than 5% were rejected and judged as x.

The falling-off rate of the coating agent was also determined by the above-described experimental method, and the evaluation criteria were "good" if the falling-off rate was less than 1%. In addition, those with 1% or more were rejected, and the judgment was marked with x.

In the re-arc test, the thickness was 9 mm and the width was 100 m.
m, to the steel plate of SM490B 300mm in length, using an AC welding machine, 180A downward welding for 10 seconds,
The remaining welding rod is left for 10 minutes. Thereafter, the coating cylinder of the welding rod was lightly brought into contact with the steel plate, and the one in which an arc was immediately generated was determined to be a pass, and the evaluation was repeated with a total of 10 passed. Regarding the evaluation criteria, a passing number of 7 or more out of 10 was marked with ○, and a passing number of 9 or more was marked with ◎. In addition, when the number of passing pieces is less than seven, it is marked with x.

The investigation of the welding workability was carried out according to SM490B described above.
A steel plate was assembled in a T-shape, and welding was carried out in horizontal fillet, standing up, down and up using the appropriate current in each welding position, and the arc state, slag state, bead shape, etc. were investigated.

As a judgment criterion for each workability investigation item, the arc state is defined as a state in which welding is performed from the front end to the end of the welding rod in each welding position, and the arc has no fluctuation and stable spraying and spread can be obtained. ○, arc fluctuation during welding, spraying too strong or too weak
And

The fluidity in the slag state was evaluated as follows.
Those that were entangled with the tip of the welding rod and made welding difficult were marked as x.

The encapsulation property is particularly high in horizontal fillet welding.
も の indicates that the slag was uniformly covered during welding, and x indicates that the bead appearance was impaired without uniformly covering the slag during welding.

In each welding position, the slag which can be removed by light hammering after welding in each welding position was evaluated as ○.
The mark, which cannot be removed unless a strong blow was given, and made welding difficult, was marked X.

The bead appearance was evaluated as ○ when a good appearance was obtained in each welding position, and as X when defects such as undercut, overlap and pits were generated. The judgment was made as a comprehensive judgment of each welding posture, and a good one was marked with a circle and a poor one was marked with a cross. Table 2 summarizes the results of these investigations and the overall judgment.

In Example No. of the present invention, 1 to No. 20 is
The individual components satisfied the requirements of the present invention, and a welding rod of improved quality was obtained by obtaining a good coating surface condition, and the welding workability was also good.

No. in the comparative example. 21 and No. 21. 25
Since the total amount of TiO _{2 in} the coating agent was small, the arc state deteriorated. In addition, the fluidity of the slag deteriorated, and the bead appearance also deteriorated. TiO ₂ / CaCO ₃ is 2.0
Because of this, the slag was easily entangled with the tip of the welding rod in vertical downward welding, and the bead appearance deteriorated.

No. 22 and No. In No. 26, since the total amount of TiO _{2 in} the coating agent was large, the slag became too dense, and the releasability was deteriorated.

No. 23, no. 29 and no. 34
Since the amount of fine titanium oxide particles having a particle size of less than 1 μm in the coating agent was small, the pass rate of the appearance inspection of the coating decreased. In addition, No. Sample No. 29 also contained a small amount of SiO ₂ in the coating agent, so that the slag was poor in encapsulation and the peelability was also deteriorated. No. In No. 34, since the amount of Fe-Mn in the coating agent was large, the viscosity of the slag was reduced, so that the encapsulating property was deteriorated in vertical and upward welding, and the weld metal dripped to form a convex bead.

No. 24 and No. 37 has a particle size of 1μ
Since the amount of fine titanium oxide particles less than m was large, the appearance of the welding rod was good, but the shedding rate of the coating deteriorated. In addition, No.
37 has much CaCO _3, so the encapsulation of slag deteriorates,
Bead appearance deteriorated. In addition, since the amount of iron powder was small, the re-arc property was deteriorated.

No. In No. 27, since the amount of CaCO ₃ was large, the encapsulating property of the slag was deteriorated, and the bead appearance was deteriorated.

No. 28 and No. 28. 35 is CaCO
_Since there was little ₃ , the fluidity and peelability of the slag deteriorated.
In addition, No. Since 35 had little organic matter, the re-arc property was deteriorated, the spraying of the arc was too weak, and the penetration was insufficient.

No. In No. 30, since the amount of SiO ₂ was large, the coating cylinder was too deep, the arc state was poor, and the bead waveform was deteriorated.

No. In No. 31, since the MgO is small, the viscosity of the slag is insufficient, and the slag is easily entangled with the tip of the welding rod due to the deterioration of the fluidity in the vertical welding.

No. In No. 32, since the content of MgO was large, the encapsulating property of the slag was deteriorated, and the bead appearance was deteriorated.

No. 33 has little Fe-Mn,
The fluidity of the slag was poor, and the bead appearance deteriorated.

No. In No. 36, the re-arc property was good because of a large amount of organic matter, but the spraying of the arc became too strong and the spatter increased. In addition, when used for high-current welding, the coating material is deteriorated, and it is easy to cause burning.

No. In No. 38, since the amount of iron powder is too large, the arc is unstable and a short circuit is easily caused. Further, an arc may be generated even in a case other than the coated tube, which is not preferable in terms of safety.

No. 39 and no. In the case of No. 40, the content of each coating agent is appropriate, but TiO ₂ / CaCO ₃ is 2.0
Because of this, the fluidity of the slag was deteriorated, and the slag was easily entangled with the tip of the welding rod in the vertical downward welding, and the bead appearance was deteriorated.

[0059]

[Table 1]

[0060]

[Table 2]

[0061]

[Table 3]

[0062]

According to the present invention, as described in detail above,
The disadvantages of the conventional coated arc welding rod can be overcome, the productivity can be improved by improving the coating property of the coating agent, and the quality can be improved by obtaining a good coated surface state.
In addition, good re-arc properties can be obtained in welding workability, and welding in a wide range can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing the titanium oxide content and the pass rate of appearance inspection.

FIG. 2 is a diagram showing a titanium oxide content and a coating falling rate.

Continuation of the front page (72) Inventor Kentaro Iwate 7-6-1 Higashi Narashino, Narashino-shi, Chiba F-term in Nippon Steel Welding Industry Co., Ltd. 4E084 AA02 AA26 BA02 BA23 DA01

Claims (3)

[Claims] 1. A coated arc welding rod obtained by coating a mild steel core wire with a coating material, wherein the coating material is TiO ₂ : 12 to 30% by mass.
(However, 0.5 to 4.0% by mass of the TiO ₂ is titanium oxide having 95% or more of particles having a particle size of less than 1 μm, and the remaining 8 to 29.5% by mass is oxidation of particles having a particle size of 1 μm or more.) Titanium), CaCO ₃ : 5 to 9% by mass, SiO ₂ : 15 to 30
% By mass, MgO: 1.5 to 5.0% by mass, Fe-Mn:
3 to 10% by mass, organic matter: 2 to 5% by mass, iron powder: 20 to
Containing 45 wt%, and TiO ₂ / CaCO ₃ is 2.0
A covered arc welding rod characterized by the above. 2. The coated arc welding rod according to claim 1, wherein MgO is a magnesia clinker, and the particle size is 60% or more when the particle size is less than 50 μm. 3. The coated arc welding rod according to claim 1, wherein the iron powder has an average particle diameter of 50 μm or less.