JPH0335034B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a stainless steel coated arm welding rod, and particularly to a stainless steel coated arm welding rod that has excellent welding workability in all positions. Technological developments in the chemical and nuclear industries have been remarkable in recent years, and with the increase in the size of various equipment due to technological innovation, all-position welding and pipe welding in on-site assembly of structures using stainless steel coated arc welding rods are becoming more and more common. All-position welding is increasing, and inspections for welding defects such as spatter, cuts, slag entrainment, and poor fusion, which should be avoided as causes of deterioration of corrosion resistance and strength in welded parts, are becoming more stringent. In conventional stainless steel coated arc welding rods, stainless steel is usually used as the core wire. However, stainless steel has an electrical resistivity that is about 10 times that of mild steel, and when welded with high current, the welding rod becomes red hot, the arc becomes unstable, and the so-called stick burn phenomenon occurs, such as uneven melting of the coating. Therefore, the current of one size lower than that of a mild steel bar (for example, the operating current range of 3.2φ for a mild steel bar and the operating current range of a stainless steel bar)
It is almost the same as that of 4.0φ, and similarly 4.0φ of mild steel bar.
and a stainless steel rod (5.0φ with almost the same operating current range) are used. Therefore, there is a problem that welding defects such as poor fusion and slag entrainment are likely to occur because the current density becomes low. In addition, as a coating material, there are so-called lime titanium-based coating materials whose main components are TiO ₂ and CaCO ₃ , and CaCO ₃ and CaCO 3.
The so-called lime type, which has CaF ₂ as its main component, is most commonly used, but the former has excellent bead shape in downward and horizontal positions, and slag removability in vertical and upward positions. The latter has poor welding workability, and although the latter can be easily welded in all positions, it has problems such as poor bead shape and slag removability in downward and horizontal positions. Furthermore, both methods are still unsatisfactory in terms of spatter, and there have been cases where large spatter has sometimes adhered and caused local corrosion. In any coating system, when stainless steel is used as the core wire, there remains a major problem in that a considerable level of skill is required to perform sound welding without welding defects such as cuts, slag entrainment, and poor fusion. . Recently, welding rods have been put into practical use that use a mild steel core wire and all alloying components such as Cr and Ni are added from the coating as a countermeasure against the stick burn phenomenon mentioned above. If there is an excessive amount of weld metal, there will be large and large segregation in the weld metal, and there may be areas where the added alloy is not completely melted, making it difficult to obtain a uniform weld metal.Therefore, emphasis should be placed on corrosion resistance. The current situation is that it has not yet been adopted in some areas. In view of the above-mentioned problems, the present inventors conducted numerous research experiments to improve the problem, and as a result, the present inventors discovered a carbon steel that contains metal powders such as Cr and Ni, which are the main alloy components of stainless steel. By using a welding rod that uses a pipe as a core wire and coats it with a so-called lime titania coating, it does not impair the beautiful bead appearance and good slag removability during downward and horizontal welding, which are the features of lime titania coating. It has been found that welding workability is excellent in all positions, including vertical and upward, and that welding defects such as cuts, poor fusion, and slag entrainment are less likely to occur, and stainless steel can be welded with less spatter. In other words, by using carbon steel as the outer sheath of the core wire, the electrical resistivity is reduced and the stick burn phenomenon does not occur.Moreover, the cross-sectional area of the carbon steel outer sheath where the arms are generated is small, so the current density is increased and the contained metal powder is reduced. Coupled with the presence of , it has been found that compared to conventional stainless steel coated arc welding rods, it is possible to weld more easily and with fewer spatters in all positions, and weld metal with fewer weld defects can be obtained. The present invention was made based on the above findings, and in covered arc welding of stainless steel,
This makes it possible to provide a welding rod with excellent welding workability. The gist of the invention is that 40-75% of the total weight of the filler
Filler containing one or both of Cr powder, 20-40% NI powder, 2-10% Mn powder and 2-15% Mo powder based on the total weight of carbon steel pipe and filler.
The core wire is a carbon steel pipe with 25 to 50% encapsulation.
The core wire is coated with a coating consisting of 15 to 55% titanium compound, 5 to 25% metal carbonate, 3 to 25% metal fluoride, and 30% or less metal powder based on the total weight of the coating. Features include stainless steel coated arc welding rods. Note that % used in this specification refers to % by weight. The present invention will be explained in detail below. First of all, the reason why carbon steel pipes (hereinafter referred to as pipes) are used as the outer skin of the core wire is to reduce the electrical resistivity of the core wire to prevent burning, and to increase the current density by reducing the cross-sectional area. This is to prevent welding defects such as poor fusion and slag inclusion. Note that the carbon steel pipe referred to here refers to ordinary mild steel, but it is desirable that the carbon content be determined appropriately depending on the use of the welding rod. The outer diameter of the pipe is 8mm to 25mm, and the wall thickness is 0.5mm to 3mm.
is desirable from the viewpoint of pipe productivity. Next, the filler components to be filled into the pipe will be described. The amount of Cr powder filled must be at least 40% of the total weight of the filler to ensure corrosion resistance and mechanical properties at low, normal and high temperatures as stainless steel, and to obtain a sound weld metal with little segregation. Up to 75% of the Cr content of the weld metal is sufficient to obtain the Cr content of Cr-Ni stainless steel specified in JIS Z3221. Therefore, Cr powder accounts for 40 to 75% of the total weight of the filler.
And so. Note that Cr powder is metal Cr or Fe-
Filled with Cr alone or in combination. The filling amount of Ni powder is 20% of the total weight of the filler in order to ensure the corrosion resistance and mechanical properties at low, normal and high temperatures as a Cr-Ni stainless steel, and to obtain a sound weld metal with less segregation. or more, and the weld metal is Cr specified in JIS Z3221.
−40 to obtain the Ni content of Ni-based stainless steel
% is sufficient. Therefore, the Ni powder should account for 20 to 40% of the total weight of the filler. Note that the Ni powder is filled in the form of metallic Ni. The filling amount of Mn powder is set at 2% of the total weight of the filler in order to stabilize the austenite structure and maintain hot cracking resistance.
% or more is required, and filling more than 10% will have little effect. Therefore, Mn powder accounts for 2 to 20% of the total weight of the filler.
10%. Note that Mn powder is metal Mn or Fe.
- Filled with Mn alone or in combination. Mo powder is required to account for 2% or more of the total weight of the filler in order to improve corrosion resistance in a reducing atmosphere and high-temperature properties, and if it exceeds 15%, ductility and toughness deteriorate. Therefore, the amount of Mo powder should be 2 to 15% of the total weight of the filler. Note that the Mo powder is filled in the form of metal Mo or Fe-Mo, singly or in combination. 25 filler for the total weight of pipe and filler
The reason for setting it at ~50% is as follows. i.e. 25
If the coating material is less than %, main alloy components such as Cr and Ni must be included in excess in the coating material in order to obtain the corrosion resistance and mechanical properties of stainless steel, which may cause segregation and result in poor welding. I can't get metal. Moreover, if it exceeds 50%, it becomes difficult to uniformly fill and draw the wire, reducing pipe productivity. Therefore, the filler is 25% for the total weight of pipe and filler.
~50%. Next, the coating material components will be described. The titanium compound is blended as an arc stabilizer and a slag agent, but if it is less than 15% based on the total weight of the coating material, the arc becomes unstable and the slag encapsulation properties deteriorate. If it exceeds 55%, the fluidity of the slag deteriorates and vertical welding becomes difficult, so it should be set at 15 to 55%. Note that the titanium compound referred to herein refers to rutile, titanium white, potassium titanate, illuminite, titanium slag, and the like. Metal carbonates are used as gas generating agents to shield molten metal with _CO2 gas generated by decomposition and prevent welding defects such as pits and blowholes.
% or more. However, if the content exceeds 25%, the slag releasability becomes poor, so the content should be 5 to 25%. Note that the metal carbonates mentioned here refer to limestone, barium carbonate, magnesium carbonate, lithium carbonate, manganese carbonate, and the like. Metal fluoride improves the fluidity of the slag and flattens the bead shape, but if it is less than 3% it has no effect.
If it exceeds 25%, the slag releasability will be poor and spatter will occur more often, so it should be set at 3 to 25%. Note that the metal fluoride mentioned here refers to fluorite, cryolite, aluminum fluoride, magnesium fluoride, barium fluoride, etc. The metal powder may be Mo, Fe-Mo, Nb, Fe-Nb, Cr,
Fe-Cr, Mn, Fe-Mn, Ni, Cu, V, Fe-V
etc. as alloying agents, Al, Fe-Al, Ti, Fe-Ti,
By blending Si, Fe-Si, etc. as a deoxidizing agent, we aim to improve the corrosion resistance, mechanical properties, and soundness of the weld metal.
The amount of these auxiliary alloying agents or deoxidizers to be selected and blended as appropriate depending on the application is determined by considering the yield of transfer from the coating material to the weld metal and the deoxidizing effect.
30% or less is sufficient. In addition, a proportion exceeding 30% may cause segregation in the weld metal or welding defects such as poor fusion and slag entrainment. Therefore, the total amount of one or more of the metal powders should be 30% or less. As described above, the present invention provides Cr powder, Ni powder and
Using a welding rod whose core wire is a pipe filled with one or both of Mn powder and Mo powder, and the core wire is coated with a coating agent consisting of a titanium compound, metal carbonate, metal fluoride, and metal powder. When welding stainless steel, it is easy to weld in all positions, and there is almost no stick burn phenomenon, resulting in cuts, poor fusion, and
Welding defects such as slag entrainment are less likely to occur, and sound welding with fewer spatters is possible. Here, referring to an example of the method for manufacturing the welding rod of the present invention, a pipe is filled with powder such as Cr, Ni, Mn, etc., and then drawn to a suitable diameter of 2.6, 3.2, 4.0, or 5.0 mm. Cut into lengths of 300 to 450 mm depending on the diameter and use these as core wires. This core wire is coated by mixing the coating powder with a suitable binder such as water glass (potassium silicate solution + sodium silicate solution).
Dry and bake at 300-450℃ for about 1 hour. Examples of the present invention will be described below. Example Table 1 shows the chemical composition of the carbon steel pipe used. The outer diameter of the pipe is 12.7 mm and the wall thickness is 2 mm.

[Table] Table 2 shows the composition of the core wire based on the combination of carbon steel pipe and filler. Core wire dimensions are 4.0mm in diameter.
The length is 350mm. Table 3 shows the composition of welding rods based on the above-mentioned combinations of core wire and coating material. Table 4 shows the chemical composition of the weld metal of these welding rods. The welding method is JIS Z3221 ``stainless steel coated arc welding rod'', and the welding current is 140A AC. Using SUS 304 steel pipes with an outer diameter of 250 mm and a wall thickness of 20 mm, we perform butt welding in horizontal positions with the steel pipes fixed vertically (vertical fixed pipes) and butt welding in all positions with the steel pipes fixed horizontally (horizontal fixed pipes). Table 5 shows the welding workability and X-ray performance when the welding process was carried out. The groove is
A 60°V bevel, a root gap of 6 mm, a root face of 1 mm, and a backing metal of 3 mm thick SUS 304 were used. Welding conditions are 120 to 140A for vertical fixed pipes.
(AC) -14~25cm/min, 100~ for horizontal fixed pipe
140A (AC) - 6 to 22 cm/min. The X-ray performance is based on the classification of Type 2 defects (elongated slag entrainment and similar defects) according to JIS Z3106 "Radiation transmission testing method and transmission photograph grading method for stainless steel welds". . As a result, welding rod symbols No. 1, 2, and
Nos. 3, 5, 6, 7, 9, 10, 11, 13, 14, 15, 16 and 18 have good welding workability in both downward and vertical positions with almost no spatter, cuts, etc. Moreover, since welding defects such as slag entrainment and poor fusion do not occur, the X-ray performance is also good, with all Type 2 defect classifications being 1st class. On the other hand, Comparative Example No. 4 has less than 15% titanium compound in the coating composition, No. 8 has more than 30% metal powder, and No. 12 has more than 25% metal fluoride. No. 17 has more than 30% metal powder, and No. 19 and
In No. 20, the filler weight is less than 25% of the total weight of the carbon steel pipe and filler, and the metal powder in the coating composition exceeds 30%, and in No. 21, the Cr powder is 75% of the total weight of the filler. %, the Ni powder is less than 20%, and the coating composition contains more than 30% metal powder, and in No. 22, the Cr powder is 40% of the total weight of the filler.
Since the Ni powder exceeds 40% and the metal powder exceeds 30% in the coating composition, welding workability or X-ray performance deteriorates as shown in Table 5. There are problems such as: As explained above, when the welding rod of the present invention is used, the welding workability is good in all positions including the vertical position, and there are few welding defects such as slag entrainment and poor fusion, and the X-ray performance is also good.

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Claims (1)

[Claims] 1 Cr powder, 40-75% of the total filler weight, 20-40
% Ni powder and 2~10% Mn powder and 2~15%
A carbon steel pipe containing 25 to 50% of the total weight of the carbon steel pipe and filler containing one or two types of Mo powder is used as a core wire, and the core wire contains a filler containing 25 to 50% of the total weight of the coating material. A stainless steel coated arc welding rod characterized by being coated with a coating consisting of 15 to 55% titanium compound, 5 to 25% metal carbonate, 3 to 25% metal fluoride, and 30% or less metal powder. .