JPH10193177A - Non-low hydrogen based coated electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a non-low hydrogen based electrode having excellent electrode burn resistance in spite of welding using a high current by coating a steel core wire with a coating material contg. a specific ratio of clay ore having a specific amt. of moisture and consisting of potassium feldspar as its essential component and contg. a gas generating agent, arc stabilizer, slag forming agent, deoxidant and binder. SOLUTION: The clay ore contg. 0.015 to 0.060wt.% moisture is incorporated at 3.5 to 15.0wt.% into the coating material. The moisture is released at 300 to 1000 deg.C and the excessive heating of the coating material in non-welded parts is averted by the cooling effect of heat of vaporization. The electrode burn resistance is thus improved. The effect is not admitted at the moisture of <0.015%. If the moisture exceeds 0.06%, arc force increases excessively, giving rise to an undercut and overlap. The clay ore essentially consisting of the potassium feldspar contains much alkaline metal oxide, such as K2 O and Na2 O. Such clay ore improves the arc state and improves welding workability as well as slag having a good flow property is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-low hydrogen-based coated arc welding rod (hereinafter referred to as a non-low hydrogen-based rod) which is excellent in bar burning resistance even when a high current is used.

[0002]

2. Description of the Related Art Non-low hydrogen type rods are inferior to low hydrogen type coated arc welding rods in that the amount of diffusible hydrogen in the weld metal is large, so that crack resistance and impact toughness of welded objects with large constraints are inferior. It is well known that it is widely used for general mild steel because of its good welding workability such as arc state, slag peeling property and bead shape. By the way, such non-low hydrogen rods are often used at a high current for the purpose of improving the welding operation efficiency. However, the coating material for non-low hydrogen rods contains organic substances such as cellulose and starch to secure an appropriate arc force and prevent nitrogen and oxygen from entering the weld metal from the atmosphere. When welding, there is a disadvantage that the coating material in the latter half of the welding rod is decomposed and burned by Joule heat and the welding rod is burnt, that is, the so-called rod burning phenomenon is easily caused. When a welding rod is used in a portion where the bar burn has occurred, the arc becomes unstable at the time of welding, which deteriorates welding workability and also causes welding defects such as blow holes and insufficient penetration.

[0003] Various proposals or implementations have been made for such non-low hydrogen rods. For example, in JP-A-57-206595, the molar ratio of SiO ₂ / Na ₂ O in water glass as a fixing agent is 2.8 to 2.0.
The use of the high-molar-ratio water glass of 3.8 prevents burning. However, as described in JP-A-57-100896, when the molar ratio of water glass is increased, drying cracks of the coating tend to occur in the drying step during production,
Also, when the molar ratio is increased, alkali oxides such as Na ₂ O and K ₂ O are reduced, so that the arc state is deteriorated and there is a problem that scattering of spatter is increased.

On the other hand, in Japanese Patent Publication No. 63-7878, sepiolite, a magnesium silicate, which is a hydrated mineral, is added to a coating agent to improve the sticking property of the coating agent and to improve the sticking resistance when a high current is used. Although improved, sepiolite reserves are limited, and it is an expensive coating material for non-low hydrogen rods that are highly versatile. As described above, it has been very difficult to improve the bar burning resistance when using a high current while satisfying various performances with the current non-low hydrogen type rod. From the industry using coated arc welding rods, there has been a strong demand for non-low hydrogen rods which are excellent in bar burning resistance from the viewpoint of improving work efficiency.

[0005]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention examines coating material and provides a non-low hydrogen-based rod which is excellent in bar burning resistance even when a high current is used. Aim.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has made various investigations. As a result, a coating material for a non-low hydrogen type rod which is excellent in bar burning resistance even when a high current is used. developed. That is, the gist of the present invention is that the water content of the clay mineral containing potassium feldspar as a main component is from 0.015 to 0.
060% by weight (hereinafter referred to as%), and the mineral content is 3.5 to 1%.
5.0% by weight, and a gas generating agent, an arc stabilizer,
A non-low hydrogen rod comprising a steel core wire coated with a coating material comprising a slag forming agent, a deoxidizing agent, and a fixing agent.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have intensively studied means for obtaining excellent sticking resistance even when a high current is used, by examining coating material. Burning of non-low hydrogen rod coatings is mainly caused by decomposition and burning of organic substances due to Joule heat during high current welding because organic substances are used in non-low hydrogen rod coatings as described above. It is caused by Therefore,
First of all, we thought that organic matter should be reduced, but in this case, the arc force is weakened, which causes the occurrence of welding defects and the deterioration of re-arc properties after the interruption of the arc. An appropriate amount of organic matter was required, and the content could not be reduced.

[0008] Next, for the purpose of imparting fire resistance to the entire coating material and preventing the burning phenomenon, application of a high melting point raw material such as magnesia clinker, dolomite, and alumina to the coating material was examined. As a result, although its effectiveness was recognized, the arc force was strong, the arc voltage was excessively high, spatter increased, and the weld metal became more prone to dripping in vertical and upward welding, giving rise to convex beads. The welding workability deteriorated.

Further, the present inventors have focused on a coating material having a high moisture content, and the moisture promotes a cooling action by heat of vaporization at the time of releasing moisture from the coating material during welding, and further increases the arc voltage. It was considered that the coating rate of the unwelded portion was not excessively heated because the melting rate was increased, and it could greatly contribute to the improvement of bar burning resistance. Moisture referred to in the present invention is 300 ° C to 1
Moisture released when heated to 000 ° C, 300
Adsorption and adhesion moisture released by heating at a temperature lower than 0 ° C. were not taken into consideration because they had no effect on improving the sticking resistance. As a result of various studies on the coating materials containing water, it was found that clay minerals containing sericite, talc or potassium feldspar as main components exhibited the effect.

[0010] However, among these raw materials, with respect to clay minerals whose main component is sericite, since sericite itself is an insulating mineral, deterioration of re-arc properties after interruption of the arc becomes a serious problem, and scattering of spatter often occurs. Caused some disadvantages. In addition, in the case of clay minerals containing talc as a main component, the arc becomes unstable, spatters are often scattered, and undercut defects are generated. The welding workability deteriorated.

On the other hand, clay minerals mainly composed of potassium feldspar
(Hereinafter referred to as potassium feldspar clay)
Greatly improves bar burn resistance without observing deterioration of welding performance
The effect has been shown. Rather, it is K for potassium feldspar clay._TwoO or N
a_TwoContains a large amount of alkali metal oxides such as O
Good arc condition and good slag flow
It was found that welding workability was improved. Also book
The potassium feldspar clay of the invention is a plagioclase (α-K) of potassium feldspars.
AlSi_ThreeO₈), Feldspar (β-KAlSi)_ThreeO ₈)
The main component is other soda feldspar (NaAlSi_ThreeO₈)
And muscovite mica _TwoSi_ThreeAlO_Ten(OH)_Two}and
Includes inclusion water obtained by heating at 200 to 800 ° C
However, these are raw materials having various contents.
Potash feldspar clay can be used alone or in combination of two or more
I also understood.

Next, it should be noted in the present invention that the content of water (hereinafter referred to as potassium feldspar released moisture) in the coating agent obtained by multiplying the content of potassium feldspar clay by the water content in potassium feldspar clay is high. This has a great effect on bar burning resistance, and can be remarkably improved as its content increases. However, if the amount is too large, the arc force becomes strong, so that spatter increases, the slag encapsulation property deteriorates, and welding defects such as undercut and overlap are likely to occur. Is the most important part in completing the present invention.

Further, the content of potassium feldspar clay in the coating material determines the content of potassium feldspar-released water, contributes to improvement in bar burning resistance and relates to welding performance. Proper content of potassium feldspar clay to cause deterioration of slag encapsulation property in horizontal fillet, dripping of bead in vertical and upward posture, and deterioration of welding workability due to increase in alkali oxides and decrease in viscosity of slag It is also important to find the quantity.

First, the present inventors conducted the following experiment in order to examine the appropriate amount of water released from potassium feldspar. That is,
As shown in Table 3, three kinds of potassium feldspar clays having different water contents are used in combination with two or more kinds of non-low hydrogen type rods shown in Table 1 as shown in Table 3. Then, the total content thereof is changed from 5.4 to 14.2%, and the obtained potassium feldspar release moisture is reduced from 0.007 to 0.07%.
The coating material changed to 4% was changed to 4.0 mm in diameter and 450 mm in length.
JIS G 3523 SWY11 mm steel core wire was coated and coated to prepare 12 types of welding rods, and welding performance was examined using an AC welding machine.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

In the bar burning resistance test of the coating agent, downward welding was performed using an alternating current welding machine on a mild steel plate having a thickness of 12 mm, a width of 100 mm, and a length of 600 mm.
A was used. The judgment method utilized a welding phenomenon peculiar to a non-low hydrogen rod. That is, since non-low hydrogen rods contain organic matter, when welding is performed at a high current, the coating material of the unwelded part is deteriorated, so that the coating cylinder is not suddenly formed, and the arc state also changes suddenly and the arc state changes. There is a part where the force begins to drop. Therefore, the arc is extinguished at that position, the remaining welding rod length at that time, that is, the remaining welding rod length that cannot perform normal welding is measured, and the value is expressed as an average value of 10 test welding rods. Good. In addition, in the investigation of welding workability, the plate thickness was 12 mm, the width was 100 mm, and the length was 450 mm.
Were assembled in a T-shape, using an AC welding machine, the current was 220 A for horizontal fillet and 160 A for upright, and the arc state, slag state, bead shape, etc. of each were investigated. In the determination, each welding posture was comprehensively determined, and was determined to be good, slightly inferior, or inferior.

The results obtained from the above tests are indicated by the black circles in FIG. If the potassium feldspar release moisture is less than 0.015%, the coating will have poor sticking resistance under high current use, and if it is 0.015% or more, the cooling action due to heat of vaporization when releasing moisture from the coating will become active, and the melting will occur. Since the speed is increased, excellent bar burning resistance can be obtained. The value is 0.060
%, The arc force becomes excessively strong, the fillet of the slag deteriorates due to the horizontal fillet, the bead shape deteriorates, and undercut occurs on the upper plate side. It began to take shape. Therefore, in order to obtain excellent bar burning resistance while securing good welding performance, the potassium feldspar release moisture in the coating agent must be 0.015.
It was found that it should be ~ 0.060%.

Next, the action of the components in the present invention and the detailed reason for limiting the range will be described. (Potassium) Feldspar release moisture; 0.015 to 0.060%) Defining the amount of potassium feldspar release moisture is the most important part in the present invention, and when welding is performed at a high current, a coating agent is used. It promotes the cooling effect by the heat of vaporization when releasing moisture from the steel, and also has a high melting rate, which reduces the heat generated by the coating material on the unwelded part, and is very effective in obtaining excellent bar burning resistance. With potassium feldspar release moisture of 0.01
The reason for setting the content to 5 to 0.060% is as follows. That is,
At less than 0.015%, the effect is not seen at all,
If it exceeds 60%, the arc force becomes excessively strong, and undercuts and overlaps occur in horizontal fillets,
In the upright position, the bead is apt to sag and the welding workability deteriorates.

(K-feldspar clay: 3.5 to 15.0%) It is important to contain 3.5 to 15.0% of potassium feldspar clay in the coating agent in order to obtain excellent bar burning resistance. However, there is also a purpose of securing an excellent arc state and ensuring good welding workability because the slag becomes a good fluidity. 3.5%
If it is less than 10, the arc becomes unstable and spatter increases, and the fluidity of the slag is poor, so that the bead shape deteriorates. Also, 1
If it exceeds 5.0%, the melting point of the slag is reduced, so that the slag encapsulating property is deteriorated by the horizontal fillet, and the bead is liable to drop in the upright posture, thereby deteriorating the welding workability. The gas generating agent, arc stabilizer, slag forming agent, fixing agent, and steel core wire in the coating agent used in the present invention are used for ordinary non-low hydrogen rods.

[0022]

EXAMPLE A coating agent obtained by further changing the combination and content of potassium feldspar clay shown in Table 2 with respect to the coating agent shown in Table 1 was used in accordance with JIS G 3523 having a diameter of 4.0 mm and a length of 450 mm.
After coating and coating the steel core wire of SWY11, it is dried and dried.
We prepared various kinds of test welding rods, and investigated the bar burning resistance and welding workability using an AC welding machine according to the welding conditions, measurement conditions, and judgment methods used in the above-mentioned K-feldspar release moisture effect investigation. did. The results are shown in Table 4 and the values indicated by the triangles in FIG.

In Table 4, welding rod No. 1 to No. 1
0 is an example of the present invention; 11-No. Reference numeral 20 denotes a comparative example. The non-low hydrogen rod of the present invention has the following No. 1 to No. Sample No. 10 satisfies the requirements of the present invention, has a potassium feldspar release moisture of 0.015 to 0.060%, has excellent bar burning resistance, and has good welding workability. No. 11, No. 1
2, No. No. 18 was poor in bar burning resistance due to low potassium feldspar release moisture. 11 and No. In No. 18, since the content of the potassium feldspar clay mineral in the coating agent is appropriate, welding workability such as arc state and slag fluidity is good. N
o. In No. 12, since the amount of potassium feldspar clay mineral was small, the stability of the arc was inferior in each posture and the spatter increased.

No. 15, No. 17, No. No. 20 was excellent in bar burning resistance due to a large amount of potassium feldspar released moisture, but the arc became excessively strong and the bead was easily drooped in a standing posture, resulting in a convex shape. No. In the case of No. 20, the melting point was lowered due to too much potassium feldspar clay, so that the slag encapsulating property was deteriorated in the horizontal fillet and the bead drooping in the vertical position became a problem, resulting in extremely poor welding workability. No. 13, N
o. 14, No. 16, No. In No. 19, although the potash feldspar release moisture was in an appropriate amount, the bar burning resistance was excellent, but the welding workability was inferior because the content of potassium feldspar clay was not proper.
No. In the case of No. 14, the stability of the arc is particularly poor because the content is small. 13, No. 16, No. Conversely, in No. 19, since the content was large, a slag encapsulating property of the horizontal fillet was deteriorated, resulting in a convex bead.

[0025]

[Table 4]

[0026]

As described above, the non-low hydrogen type rod of the present invention can provide a welding rod which can remarkably improve the burning resistance of the rod and, at the same time, can secure good welding workability. Since high current can be used, it can greatly contribute to improvement of welding work efficiency.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram for investigating the influence of a change in potassium feldspar release moisture in a coating agent on bar burning resistance and welding workability.

Claims (1)

[Claims] 1. A clay mineral containing potassium feldspar as a main component has a water content of 0.015 to 0.060% by weight, the mineral being 3.5% by weight.
-15.0% by weight, and a coating agent comprising a gas generating agent, an arc stabilizer, a slag generating agent, a deoxidizing agent, and a fixing agent is applied to a steel core wire, and the non-low hydrogen is characterized by being coated. Series coated arc welding rod.