JPS6253277B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coated arc welding rod, and in particular to a high cellulose coated arc welding rod that exhibits excellent welding workability in butt downward welding of fixed pipes, etc., and has improved X-ray performance at welded joints. It is. High cellulose-based coated arc welding rods have a strong arc force and produce a small amount of slag, so they are suitable for downward welding, and their arc properties also allow for easy welding. In addition, extremely high welding speeds can be obtained during the first layer welding of downward welding of fixed pipes, so it has long been used in Europe and America for on-site welding of pipelines. However, since the coating material contains a large amount of cellulose-based organic matter, it is more likely to cause stick burn when using a high current compared to coated arc welding rods such as low-hydrogen or illuminite types, so keep the current low. need to use. However, when performing uranami welding on the first layer as the pipeline moves downward, sufficient penetration cannot be obtained, so it is necessary to use a high current to form a proper uranami bead, and in addition, a welding rod is required. Since the electric arc end is pressed strongly against the inner root of the groove while operating the rod, it is easy to cause stick burn. If this happens, the arc becomes unstable, causing poor penetration and the Uranami bead being disturbed, making it impossible to obtain a sound Uranami welded joint. In addition, even in downward welding of the second and subsequent layers, welding workability such as sufficient arc strength, penetration, and crater spread is poor. In addition, the deposit tends to sag, causing defects such as poor penetration and pits, resulting in poor X-ray performance of the welded joint. Therefore, if a high current is used, stick burn occurs and the same phenomenon as above occurs. Therefore, it is required that welding workability such as sufficient arc strength, penetration, and spread of craters at low currents is good, and that the welded joint has good X-ray performance. The present inventors focused on the above-mentioned circumstances, and without sacrificing the above-mentioned features of the high cellulose coated arc welding rod, the strength of the arc, the penetration,
In order to provide a cellulose-based welding rod that has good welding workability such as crater spread and X-ray performance of welded joints, we have conducted various studies and found that the addition of Na ₂ CO ₃ is effective. The present invention was completed as a result of such research, and consists of a high-cellulose coating material made by kneading coating material raw materials containing a large amount of cellulose with a binder and coating the outer periphery of the steel core wire. The coated arc welding rod contains water glass as a binder in a solid content of 14 to 30% (weight %: the same hereinafter) based on the total weight of the coating material, and also contains Na ₂ CO ₃ in the coating material.
0.3-7%, _MnCO3 0.3-8%, cellulose
17-40%, metallic Mn and/or Fe-Mn
3-10% in terms of Mn, 8-25% in _TiO2 , _SiO2
15-30%, MgO 2-12%, ZrO ₂ 0.3-7
%, 1 to 17% iron oxide converted to FeO, 0.3 to 4% hydrated minerals containing crystallized water released at temperatures above 500°C, converted to crystallized water released at temperatures above 500°C, The weight ratio of the coating material to the total weight of the welding rod is
The gist lies in the range of 0.1 to 0.18%. The effects of each component used in the present invention and the basis for setting the content will be explained below. Na ₂ CO ₃ 0. 3-7% This is an important requirement in the present invention, and the arc strength, penetration,
It is a necessary raw material to improve welding workability such as crater expansion and the X-ray performance of the joint.It is necessary to obtain sufficient arc strength, penetration, and crater expansion, and to improve the X-ray performance of the joint. In order to improve this, it is necessary to contain 0.3% or more. However, if it exceeds 7%, the amount of slag increases too much and downward welding becomes difficult. MnCO ₃ 0.3 to 8% MnCO 3 has the effect of making the slag porous and increasing the peelability of the slag, and must be contained at 0.3% or more. However, if it exceeds 8%, the fluidity of the slag becomes excessive and downward welding becomes difficult. Cellulose 17-40% It plays the role of a gas generating agent, and is an essential component to provide the original characteristics of high cellulose. If it is less than 17%, deep penetration and a powerful arc cannot be obtained, making it suitable for downward welding. It is not possible to obtain appropriateness as a.
Moreover, if it exceeds 40%, burnout cannot be prevented even if other components are adjusted, and the arc becomes unstable. Metal Mn and/or Fe-Mn: 3 to 10% in terms of Mn It is an essential component as a deoxidizing agent, and if it is less than 3%, deoxidizing is insufficient and clean weld metal cannot be obtained.
On the other hand, if it exceeds 10%, deoxidation becomes excessive and pits are likely to occur on the bead surface. TiO ₂ :8-25% In order to stabilize the arc, it is necessary to contain 8% or more, but if it exceeds 25%, the arc force becomes weak and downward welding becomes difficult. SiO ₂ : 15-30% SiO ₂ is a component mixed in as water glass and silicate mineral, and is an essential component to obtain an appropriate amount and viscosity of slag. If it is less than 15%, the amount of slag generated will be insufficient, resulting in poor bead elongation.
A healthy Uranami bead cannot be obtained. On the other hand, if it exceeds 30%, the amount of slag becomes too large and downward welding becomes difficult. MgO: 2 to 12% MgO has the effect of increasing the releasability of slag, and must be contained at 2% or more. However, if it exceeds 12%, the fluidity of the slag becomes excessive and downward welding becomes difficult. ZrO ₂ :0.3-7% It is necessary to contain 0.3% or more in order to improve the arc concentration and the gloss of the bead surface, improve the compatibility between the weld metal and the base metal, and improve the undercut resistance. If it exceeds 7%, the slag becomes dense and the slag removability deteriorates. Iron oxide: 1 to 17% in terms of FeO It must be contained in an amount of 1% or more in order to make the slag porous and improve its removability, as well as to prevent the formation of pits due to excessive deoxidation. If it exceeds 17%, the fluidity of the slag becomes excessive and downward welding becomes difficult. Hydrous minerals containing water of crystallization released at temperatures above 500°C: In terms of water of crystallization released at temperatures above 500°C.
0.3-4% Hydrous minerals such as talc are used and contribute to the formation of arc spray. In order to effectively exhibit this effect, it must be added at 0.3% or more. However, if it exceeds 4%, the arc force decreases and the arc becomes unstable. The reason why it is defined as crystallization water that is released at temperatures above 500°C is that it is defined as crystallization water that is released at temperatures above 500°C.
If moisture is released at temperatures below 500℃, the high temperature during welding will cause the welding rod to wear out and be released into the atmosphere from the coated surface, making it ineffective against the arc. be. The solid content of the binder water glass is 14 to 30%. If the amount of water glass blended is less than 14%, the water glass will not be sufficiently spread between the particles of the coating material raw material, which will not only weaken the bonding force between the raw material particles. The slippage between raw material particles also becomes unstable, creating spaces due to scratches, and the tightness of the coating deteriorates. In addition, if it exceeds 30%, the water glass coating will become too thick, and when it dries, the water glass coating will not only become brittle and reduce the binding force between raw material particles, but also cause the coating material to slip too much, increasing the coating pressure. This will cause the coating to become difficult to tighten. Weight ratio of coating material to total weight of welding rod (coating ratio): 0.1 to 0.1% This is a basic condition to facilitate downward welding of fixed pipes. If it is less than 0.1, the coating will not function adequately as a protective tube. If it exceeds 0.18, the arc becomes unstable, and on the other hand, if it exceeds 0.18, the concentration of the arc decreases, making it difficult to form an underwave bead, and in either case, good downward weldability cannot be achieved. The coated arc welding rod of the present invention satisfies the above-mentioned requirements. In addition, in order to improve the mechanical properties of the deposited metal, appropriate amounts of alloying elements such as Ni, Cr, and Mo may be added, and the welding conditions may be adjusted. In order to improve efficiency and workability, iron powder (usually 25% of the total amount of coating material)
The following) can also be blended. Furthermore, when obtaining welding rods for AC power supplies, a small amount of arc stabilizer is added.
Performance can be further improved by blending K ₂ O. The present invention is configured as described above, and in particular
By adding Na ₂ CO ₃ , it was possible to improve welding workability and the X-ray performance of the welded joint, and further improve the joint performance. An experimental example is shown below. Experimental Example A coated arc welding rod was manufactured by applying a coating having the composition shown in Table 1 to the outer periphery of a steel core wire (4.0 mmφ x 350=l) to a predetermined coverage rate. The obtained welding rods were used to perform downward welding of fixed pipes, and the welding workability and X performance of the welded joints were tested.The results are shown below. The results are summarized in Table 1.

【table】

[Table] From Table 1, the following conclusions can be drawn. 1 Code 12 is a typical example of a conventional high-cellulose coated arc welding rod, which does not contain Na ₂ CO ₃ or ZrO ₂ , so it is difficult to control arc strength, crater spread, melting, conformation, sag of weld metal, etc. Welding workability is poor, and the X-ray performance of welded joints is poor due to poor fusion and blowholes. 2 Code 13 has too much ZrO ₂ added, so the slag becomes dense and the slag peelability becomes poor.
Moreover, since too little FeO is added, the deoxidation is excessive, causing pits and blowholes to occur on the bead surface, resulting in poor X-ray performance. 3 Code 14 is an example where too much Na ₂ CO ₃ is added,
Because the amount of slag is too large, the slag gets in the way during downward welding, making the arc unstable and causing poor fusion.
Line performance is poor. 4 No. 15 indicates that the addition of TiO ₂ is too small, making the arc unstable. Also, because the amount of Mn added is too small, deoxidation is insufficient and blowholes are generated.
Line performance deteriorates. 5 Code 16 is an example where too little cellulose is added, the arc is weak, and the crater spreads.
Welding cannot be performed because welding workability such as penetration is too poor. 6 Code 17 is an example where the coverage is too low and stick burn occurs, which deteriorates welding workability such as arc strength, crater spread, melting, bead conformity, etc., and pits and blowholes occur on the bead surface. X-ray performance deteriorates. 7 No. 18 has too much MgO and FeO, so the viscosity of the slag becomes too bad due to the synergistic effect of the two, and welding cannot be performed because the slag gets in the way. 8. In the case of code 19, the coverage is too high and crystal water is not included, so the mutual action of the two causes the concentration of the arc to decrease and the penetration to become shallow, so that no Uranami bead is formed. 9. Reference numeral 20 is an example in which too much cellulose is added, which causes stick burn and deteriorates welding workability such as arc strength, penetration, and crater spread, and also causes pits and blowholes to occur, resulting in poor X-ray performance. Also, since MgO is not added, the slag removability is also poor. 10 Code 21 has a large amount of TiO ₂ added, so the arc becomes weak, slag gets in the way, making it difficult to perform downward welding, resulting in poor fusion and poor X-ray performance. 11 Since no MnCO ₃ is added to code 22, the slag does not become porous, so the peeling of the slag becomes somewhat difficult. Furthermore, since too much Mn is added, excessive deoxidation occurs, causing pits and proholes, resulting in poor X-ray performance. 12 In contrast, numerals 1 to 11 are examples that satisfy all the requirements stipulated by the present invention, and have good welding workability such as arc strength, crater spread, penetration, conformation, and slag removability. Moreover, since there were no defects such as poor fusion, the X-ray performance could be improved, and the welded joint performance could be further improved.

Claims (1)

[Claims] 1. In a high-cellulose-based coated arc welding rod in which the outer periphery of a steel core wire is coated with a coating material made by kneading a coating material containing a large amount of cellulose with a binder, water glass is added as a binder to the total weight of the coating material. In addition, the coating material contains 0.3 to 7% by weight of Na ₂ CO ₃ , 0.3 to 8% by weight of MnCO ₃ , 17 to 40% by weight of cellulose, metal Mn and/or Fe-Mn is 3-10% by weight in terms of Mn, TiO ₂ is 8-25% by weight, SiO ₂ is 15-30% by weight, MgO is 2-12% by weight, ZrO ₂ is 0.3-7% by weight, Iron oxide converted to FeO is 1 to 17% by weight, 500
0.3 to 4% by weight of minerals containing crystallized water released at temperatures above 500°C, converted to crystallized water released at temperatures above 500°C.
A high cellulose-based coated arc welding rod, characterized in that the weight ratio of the coating material to the total weight of the welding rod is 0.1 to 0.18.