JPH0525599B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is a coated arc welding rod used as the core wire of a wire manufactured by a continuous casting process, which has excellent stick burn resistance even when used at high current, and has good arc conditions. The invention relates to a coated arc welding rod that can ensure a sound weld metal. (Prior Art) Conventional core wire rods for welding rods have been manufactured from rimmed steel or capped steel, but these manufacturing methods have had major drawbacks in terms of yield and energy saving. Therefore, in recent years, in order to overcome the drawbacks of conventional core wires, continuous casting core wires for welding rods have been developed and have come into practical use. However, compared to welding rods with conventional core wires, welding rods made of continuous cast core wires have poor stick burn resistance when welded at high currents, and welding rods that have suffered stick burn phenomena are susceptible to deterioration of the arc condition. In addition, the appearance of the bead is poor due to increased scattering of spatter, and since the deoxidizing agent and gas generating agent in the coating material have already decomposed, they no longer perform their functions, resulting in frequent blowholes and pits, and the damage to the sound weld metal. I had a problem where I couldn't get it. Therefore, when welding rods using continuously cast core wires are used at high currents, the area where normal welding can be performed becomes short, increasing the amount of welding rods used, and at the same time reducing welding efficiency and making it difficult to manufacture structures. It was increasing costs. Various proposals and implementations have been made to improve continuously cast core wires for welding rods. For example, in Japanese Patent Publication No. 63-57154,
By limiting the O content of C in the core wire, good arc conditions and bead appearance can be achieved by using coating materials such as illuminite, high titanium oxide, and iron powder iron oxide.
However, it has not been possible to improve stick burn resistance when using high currents, and currently it cannot contribute to improving welding efficiency. be. In addition, the present inventors previously reported in Japanese Unexamined Patent Publication No. 176097/1987 that MnO, FeO, which are inclusions in the core wire,
We propose that by limiting the content of Al ₂ O ₃ and SiO ₂ , a welding rod with a high melting rate can be obtained, which reduces the heating phenomenon of the welding rod at high currents and improves stick burn resistance. It was also suggested that it could improve the However, limiting these inclusions was not sufficient to provide excellent burn resistance while maintaining good arc stability. Furthermore, in JP-A-57-156892,
It was proposed that blowhole resistance could be improved when using high current by limiting the content of Al, N, and O, but this also had the problem of not being able to obtain a good arc condition, and it was difficult to satisfy all welding performance requirements. It didn't reach that point. (Problem to be solved by the invention) As described above, the current continuously cast core wire for welding rods has excellent stick burn resistance when used at high current, maintains a good arc condition, and produces spatter and slag. Satisfies welding workability such as condition and bead appearance,
Moreover, it has been extremely difficult to obtain a sound weld metal that does not generate blowholes or pits. However, there has been a strong demand from various industries to obtain a welding rod with a continuously cast core that satisfies all of these requirements. In view of the above-mentioned circumstances, the present invention has been made to improve the continuous casting core wire, which has excellent stick burn resistance even when using high current, ensures good arc conditions and sound weld metal, and improves all welding workability. The purpose is to provide a welding rod that satisfies the following. (Means for Solving the Problems) In order to meet the above-mentioned demands, the present invention has been made based on various studies on the components and electrical characteristics of continuous casting core wires.
This product significantly improves stick burn resistance when using high current, and ensures good arc conditions and sound weld metal.
Contains 0.010 to 0.017% by weight (hereinafter referred to as %),
An arc stabilizer, a slag forming agent, a deoxidizing agent, an organic substance and a fixing agent, or a coating material consisting of these and iron powder of 52% or less is applied around a continuously cast core wire with a specific resistance of 11.5 to 14.2 μΩ-cm. The welding rod is characterized by: The present inventors have focused on the fact that in order to improve stick burn resistance while satisfying various welding performances, it is extremely effective to make the arc droplet grains finer and to increase the melting speed. As a result of various studies on continuously cast core wires, we have found that limiting the O content and specific resistance of the core wire is extremely effective and important. O in the core wire reacts with C in the core wire and coating material.
CO and CO ₂ gases are generated to provide a shielding effect from the atmosphere, but these gases also exist within the droplet grains of the arc column, and the internal pressure breaks the droplet grains, making the droplets finer. It has the effect of Therefore, arc stability is improved and spatter scattering is reduced. It was also found that the specific resistance of the core wire is related to the melting rate of the welding rod. If the resistivity value of the core wire is small, the melting speed will be faster and the stick-scorch resistance will be improved when using high current. However, if this value is too small, the deoxidizing agent, which is the governing factor of the resistivity, will be affected by the alloying agent. It was found that if the amount decreased too much, a sound weld metal could not be obtained and the mechanical performance would also deteriorate. On the other hand, if the specific resistance value is excessively large, the melting rate will be considerably slow and the coating material will be burned by the Joule heat, preventing the formation of a normal coating cylinder, resulting in poor arc directionality and deoxidation. It has been found that blowholes and pits are likely to occur in the weld metal due to decomposition of the agent and gas generating agent, resulting in poor stick burn resistance. Therefore, it was necessary to place importance on finding an appropriate value of specific resistance of the core wire. The present invention has been made based on the above findings. (Function) The function of the present invention will be explained in detail below. First, the following experiment was conducted to investigate the appropriate O content and specific resistance of the continuously cast core wire. That is,
Contains 0.004% to 0.021% O and has a specific resistance of 9.1% to 9.1%.
The core wire changed to 17.6 μΩ-cm was coated with an all-position welding rod illuminite coating shown in Table 1, and dried welding rods were prepared to evaluate stick burn resistance, arc conditions, and weld metal properties. Blohol resistance was investigated.
The welding rod size is 4.0 mmφ x 450 mm, and the core wire contains 0.004 to 0.012% C, 0.001 to 0.042% Si,
The one containing 0.31 to 0.69% Mn was used. As shown in Figure 1, the method for measuring the specific resistance of a core wire is to apply a current from a constant current generator 2 to a length of approximately 430 mm within the entire length of the core wire 1, and calculate the resistivity obtained from the value and voltage. The internal resistance of the wire, the core wire cross-sectional area A, and the inter-electrode distance l were measured, and the specific resistance was calculated using the following formula, and the average value of three repeated measurements was determined. Specific resistance (μΩ-cm) = resistance due to current flowing inside × cross-sectional area of core wire / distance between electrodes Each test condition and its pass/fail judgment criteria were as follows. In other words, in the stick burn resistance test, mild steel plates (plate thickness
12.7mm, width 100mm, flow rate 500mm) were welded downward at a current of 200A using an AC welding machine. The method for determining this is to extinguish the arc at the position where the coating material in the unmelted part burns, preventing the formation of a normal coating tube, and suddenly changing, and then determining the remaining welding rod length at that time (hereinafter referred to as the remaining rod length). expressed. The value is the average value of five test welding rods, and less than 60 mm is marked O for good, 60 mm or more and less than 90 mm is marked △ for slightly poor, and 90 mm or more is marked poor for ×. Next, to investigate the arc condition, a T-shaped fillet test piece was prepared using the above-mentioned steel plate, and welding was performed in a horizontal fillet position and in a vertical position. The current is 200A in the horizontal fillet,
When 160A was used in a vertical position, a stable arc and an appropriate arc force were judged to be good. In addition, in the investigation of the blowhole resistance of weld metal,
In accordance with the fracture surface test method for fillet welded joints of the NK method, welding was performed using the aforementioned T-shaped fillet test piece and electric current so that the bead length was approximately 350 mm, and fractured by applying external force. A case where the sum of the lengths of the blow holes was 10% or less of the total weld length was considered good, and the value was the average value of three repeated tests. The results obtained from the above tests are shown in FIG. If the O content in the core wire is less than 0.010%, the arc droplets will not become fine particles, so the arc will be unstable, spatter will be scattered more, and the bead appearance will deteriorate.
If it exceeds 0.017%, there will be an excessive amount of CO or CO ₂ gas in the arc, the arc voltage will become high, and the arc force will become abnormally strong, resulting in a lot of spatter, and the bead tends to droop in the vertical position. The specific resistance of the core wire is 11.5μΩ−
If it is less than cm, deoxidizing components such as Si and Mn in the core wire decrease, resulting in poor blowhole resistance, and the sum of the lengths of blowhole points exceeds 10% of the total weld length. However, since the specific resistance value was small, there was no deterioration of the coating material and the burn resistance was good.
On the other hand, when the resistivity exceeds 14.2 μΩ-cm, the coating material burns and deteriorates, so a coating tube is not formed and normal welding is impossible, resulting in a short usable molten rod length and a remaining rod length of 60 mm or more. The stick scorch resistance deteriorated over time. It was also found that those with high specific resistance had poor blowhole resistance due to the deterioration of the coating material. From the results shown in Figure 2, in order to obtain excellent stick burn resistance, good arc conditions, and sound weld metal when using a high current, the O content of the core wire must be set to 0.010.
~0.017%, and the specific resistance of the core wire is 11.5~14.2μΩ−
I found out that I needed to set it to cm. Furthermore, it has been confirmed that the present invention can also be applied to coating materials such as lime titania type, high titanium oxide type, iron powder iron oxide type, and low hydrogen type. In addition, the arc stabilizer in the present invention includes rutile, illuminite, feldspar, etc., the slag forming agent includes silica sand, carbonated lime, fluorite, magnesite, magnesia clinker, mica, talc, etc., and the deoxidizing agent includes It refers to ferromanganese, metal manganese, ferrosilicone, ferrotitanium, ferroaluminum, etc., organic substances include cellulose, starch, dextrin, sodium alginate, etc., and fixing agents refer to sodium silicate and potassium silicate. Each of these can be used alone or in combination of two or more. Furthermore, iron powder is added mainly for the purpose of improving work efficiency, but the reason why it is set at 52% or less in the claims of the present invention is that if it is added in excess of this, the sheathing tube is likely to short-circuit and the arc will not occur. This is because it becomes stable and the bead appearance deteriorates. (Example) Next, the effects of the present invention will be described in more detail with reference to Examples. Table 2 shows the chemical composition and specific resistance of the core wires used in the welding rods of the present invention and comparative welding rods, and Table 3 shows the
The results of various performance tests for combinations of the core wire and coating material are shown. The coating systems of the test welding rods are non-low hydrogen welding rods in all positions, low hydrogen welding rods, and fillet welding rods, and the sizes are different from non-low hydrogen welding rods in all positions and low hydrogen welding rods. Various welding rods were made, with a welding rod of 4.0mmφ x 450mm and a fillet welding rod of 4.0mmφ x 550mm. In addition, each test condition and its pass/fail judgment criteria were as follows. First, in the stick burn resistance test, a mild steel plate (thickness 12.7
(mm, width 100mm, length 700mm) was used for downward welding with an AC welding machine, and the current was 200A for non-low hydrogen welding rods and low hydrogen welding rods in all positions, and 190A for fillet welding rods.
And so. The method for determining this is to extinguish the arc at a position where the coating material in the unmelted part is heated and burned by the Joule heat and no longer forms a coating cylinder, measure the remaining bar length at that time, and use that value for the test welding. The average value of the five bars was taken, and less than 60 mm was considered good, 60 mm or more and less than 90 mm was slightly poor, and 90 mm or more was poor. In order to investigate the arc condition, a T-shaped fillet test piece was made from the steel plate mentioned above, and welding was performed in horizontal fillet and vertical positions, and the current was applied to both non-low hydrogen welding rods and low hydrogen welding rods in all positions. In the case of horizontal fillet welding, use 200A and vertical fillet welding of 160A, and in the case of fillet welding rods, perform horizontal fillet welding and use 190A.The stability of the arc and the arc force were investigated, and the judgment method was good. It was marked O, slightly inferior was marked △, and poor was marked X. In addition, in the investigation of the blowhole resistance of weld metal, we used the horizontal fillet test piece described above and current, and measured the bead length to approximately
Welded to a length of 350mm and approximately 600mm using a fillet welding rod, applied an external force to break it, and measured the blowhole. The judgment method is that it is good if the sum of the lengths of the blow hole parts is 10% or less of the total weld length, and 11 to 20
% as slightly inferior and 21% or more as inferior, and the values were expressed as the average value of three repeated measurements. In addition to these welding performance investigations, welding workability such as the slag condition, amount of spatter, and bead appearance for each welding position was also investigated at the same time. The evaluation method was as follows: good was marked with O, slightly poor was marked with △, and poor was marked with ×. In addition, in the overall evaluation, good is marked O, and slightly poor is marked △.
The results were marked with a mark, and those that were inferior were marked with an x. In Table 3, the present invention welding rods E-1 to E-6,
For E-7 to E-12 and E-13 to E-18, the amount of O in the core wire is 0.01 to 0.017%, and the specific resistance is 11.5 to
Because it is 14.2 μΩ-cm, it has excellent stick burn resistance when using high current, and has good arc condition and blowhole resistance at that time, as well as good welding workability such as slag condition, spatter, and bead appearance. It was hot. On the other hand, E-19 to E-36 are examples of comparative welding rods, and E-19, E-25 and E-31 contain 0.013% O in the core wire, so the arc condition is good. Because the specific resistance of the core wire is too high, the stick scorch resistance is poor, and the deoxidizing agent and gas generating agent in the coating material decomposes, making it impossible to obtain normal function, resulting in a deterioration in the blowhole resistance of the weld metal, and slag. The encapsulation properties deteriorated and the bead appearance deteriorated. Welding rods E-20, E-26, and E-32 had too little O content in the core wires, resulting in poor arc stability, weak arc force, and many spatters, resulting in poor welding workability. However, since the specific resistance of the core wire was appropriate, the stick burn resistance and blowhole resistance were good. In E-21, E-27 and E-33, the amount of O in the core wire was excessively high, so the arc force was too strong, causing many spatters to fly, the bead appearance to deteriorate, and welding workability to deteriorate. Furthermore, since the specific resistance of the core wire was high, the stick burn resistance and blowhole resistance were poor. E-22, E-28 and E-34 are O in the core wire.
Since the amount was too small, the arc condition deteriorated, there were many spatters, and welding workability deteriorated. Furthermore, since the specific resistance of the core wire was too low, the content of C, Si, etc. in the core wire was low, causing deterioration in the blowhole resistance of the weld metal, but the stick burn resistance was good. E-23 and E-35 have 0.010% O in the core wire.
Because of the presence of Ni, good arc conditions and welding workability were obtained, but the blowhole resistance was slightly deteriorated due to the low specific resistance. E-29 contains 0.010% O in the core, but too much iron powder in the coating material deteriorates arc stability and welding workability, and the low specific resistance of the core makes it resistant to blowholes. The quality has deteriorated slightly. E-24, E-30, and E-36 have an extremely high O content in the core wire, so the arc force is too strong and there are many spatters, and the slag coverage is poor, resulting in poor bead appearance and poor welding workability. It got worse. Further, since the specific resistance of the core wire was too small, the blowhole resistance was poor, but the stick burn resistance was good.

[Table] * Others include arc stabilizer, slag forming agent, and sodium silicate in the fixing agent.
Represents solid components such as lithium and potassium silicate.

【table】

【table】

[Table] *Others represent solid components such as slag forming agent, arc stabilizer, and sodium silicate and potassium silicate in the fixing agent.
(Effects of the invention) As explained above, the welding rod of the present invention improves the continuously cast core wire, has excellent stick burn resistance even when using high current, and ensures good arc condition and sound weld metal. Since it can satisfy all welding workability requirements, it can greatly contribute to improving work efficiency in welding work.

[Brief explanation of the drawing]

Figure 1a is a circuit diagram showing the method for measuring the specific resistance of welding rod core wires, Figure 1b is an X-enlarged view of Figure a, and Figure 2 is the ratio of the O content in the core wire to the core wire. FIG. 3 is a diagram showing the influence of resistance on burn resistance, arc state, and blowhole resistance. 1... Welding rod core wire, 2... Constant current generator, 3...
...Ammeter, 4...Voltmeter, 5...PT line.

Claims (1)

[Claims] 1 Contains 0.010 to 0.017% by weight of O, and has a specific resistance of
A coated arc welding rod comprising a continuously cast core wire having a diameter of 11.5 to 14.2 μΩ-cm and coated with a coating agent consisting of an arc stabilizer, a slag forming agent, a deoxidizing agent, an organic substance, and a fixing agent. 2 Contains 0.010 to 0.017% by weight of O, and has a specific resistance of
A coating consisting of arc stabilizer, slag forming agent, deoxidizing agent, organic matter, fixing agent, and iron powder containing 52% by weight or less is applied around the continuously cast core wire having a diameter of 11.5 to 14.2 μΩ-cm. Characteristic coated arc welding rod.