JPH10277777A - Ni base coated electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain the weld metal having excellent welding workability preventing the deterioration of an arc condition and the phenomena of slab burning, capable of executing efficient welding and further having an excellent mechanical performance, porosity resistance and high temperature crack resistance by reducing the consumption quantity due to oxidation of alloy constituents as much as possible even though a coated electrode generates electrode burning phenomena due to welding under a severe executing condition. SOLUTION: In this electrode, metal powder or alloy powder selected from alloy constituents composing the core wire and metal powder of one kind or two kinds or above of Al, Si, Ti as the deoxidizer or alloy powder containing these metal constituents are granulated in 300-150 μm for the Ni-Cr base core wire containing alloy constituents of Mn, Nb, Mo, Cr. And granulated grains are mixed with the coating constituent agent of a metallic carbonate, metallic fluoride, silicate and silicate compound, potassium compound or the like to make the coating flux, and the Ni-Cr base core wire is coated with the coating flux.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a welding material of a high Ni alloy used for welding 9% Ni steel for an LNG storage tank, and more particularly, to an improved welding workability. Ni-based coating that can easily obtain a weld metal with good mechanical performance, porosity resistance and hot crack resistance.
It relates to a welding rod.

[0002]

2. Description of the Related Art The consumption of natural gas is increasing rapidly as a clean energy alternative to petroleum, and the amount of natural gas transport / storage tanks is increasing accordingly. Cool natural gas for the purpose of simplifying transportation and storage of natural gas (-16
Liquefied natural gas (2 ° C.) is liquefied natural gas (LNG), and 9% Ni steel is mainly used as an LNG container. This steel is a ferritic alloy steel excellent in low-temperature toughness, has high strength and excellent weldability, and many Ni-Cr-based welding materials having excellent low-temperature toughness are used for welding. In addition to Ni and Cr, M
A material to which alloy components such as n, Mo, Nb, and W are appropriately added is mainly used. For example, in JP-A-53-37555, the present inventors used a Ni-Cr-based core wire and used a core wire. Also disclosed is a coated arc welding rod containing Ta in one or both of the coating agents and controlling the total water content of the coating agent to improve the micro crack resistance of the weld metal.

[0003] A coating arc using a Ni-Cr alloy for the core wire.
In the welding rod, the core wire glows red due to electric resistance heat during welding,
The burning of the stick, which deteriorates the coating agent and deteriorates the welding workability, is likely to occur. As a technique for improving the stick burning phenomenon, the present inventors disclosed in Japanese Patent Publication No. Sho 62-51716 a method of controlling the particle size of limestone in a coating material on a Ni-Cr type core wire and coating the coating material containing a Li compound. This strengthens the protection tube during welding,
A coated arc welding rod having improved bar burning resistance is disclosed.

In recent years, there has been a tendency to increase the welding current in order to increase the work efficiency, and as the current value increases, the bar burn resistance becomes insufficient with the prior art, and the oxidative consumption of deoxidizers and easily oxidizable alloy components increases. Insufficiently deoxidation deteriorates the pore resistance performance, destabilizes the arc, deteriorates welding workability such as slag peeling, and lacks the alloy component added from the coating agent for the purpose of improving performance. Problems such as deterioration of mechanical properties and crack resistance have occurred. In particular, slag seizure tends to occur during vertical welding with large heat input, which requires not only a large number of man-hours to remove the slag, but also a defect on the bead surface in color check inspection of fillet welds. Since a pseudo pattern is generated, it is necessary to shape the bead surface, and there is also a problem that the number of steps is increased and the construction efficiency is reduced. The development of a Ni-based coated arc welding rod that has good welding workability when welding at high current, and also has good porosity and cracking resistance of the weld metal and easily obtains the desired mechanical performance. Is desired.

[0005]

As described above, the Ni-based coated arc welding rod used for welding 9% Ni steel for LNG storage tanks is accompanied by the burning of the coating agent due to the use of high current. Deterioration of welding efficiency due to deterioration of porosity, cracking resistance and mechanical performance of weld metal due to oxidative consumption of alloy components, deterioration of welding workability such as instability of arc and poor slag peeling property And so on.

[0006] In view of these circumstances, the present invention, when welding 9% Ni steel with a coated arc welding rod, the alloy does not burn even if the coated arc welding rod causes a rod burning phenomenon under severe working conditions. By reducing the oxidative consumption of components as much as possible,
It has good welding workability by preventing deterioration of the welding condition and seizure of slag, enables efficient welding, and facilitates welding metal with good mechanical performance, pore resistance and hot cracking resistance. An object of the present invention is to provide a Ni-based coated arc welding rod obtained as described above.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a coating in which the type, amount and method of addition of an alloy component containing a deoxidizer in a Ni-Cr base wire are changed. As a result of trial production of coated arc welding rod coated with the agent and investigation of welding workability and weld metal performance, the method of adding metal components was preliminarily treated by providing a granulation process and compounded. It has been found that, even when the welding rod glows due to welding at a high current and the rod burns, the grain size of the alloy component is controlled to reduce the oxidative consumption of the alloy component and improve the yield.

[0008] More specifically, a powder of a metal component to be blended in a coating agent is granulated and subjected to a pretreatment for sizing to a specific particle size, and after mixing this granulated alloy component with another coating agent, A coated arc welding rod formed by coating a Ni-Cr core wire with a binder was prototyped, and welding performance, mechanical properties of the weld metal, pore resistance and crack resistance were investigated. The porosity resistance was determined by an X-ray transmission test by performing joint welding of a thin plate in an upward welding position where porosity is likely to occur. The cracking performance cannot be clearly determined in the C-type jig restrained welding crack test specified in JISZ3115, which evaluates hot cracking resistance. One-pass welding was performed in a U-groove in a lateral orientation that was originally devised, and the test bead was ground by about 1 mm sequentially from the surface, and the occurrence of cracks was inspected several times to determine.

[0009] As a result, compared to the case where the alloy component was added while the untreated particle size distribution was maintained at 180 to 45 µm, granulation,
Drying and processing to a specified particle size range reduces the oxidative consumption of alloys due to burning, reduces the amount of slag of alloys by improving the prevention of oxidative consumption, degrades the arc state and burns in slag. It has been found that the phenomenon can be prevented and welding workability can be improved. In addition, since the deoxidizing effect is improved, even if the amount of the deoxidizing agent added is reduced as compared with the conventional case, good porosity resistance of the weld metal can be obtained, and Si, Al, Ti which enhances the hot metal cracking resistance of the weld metal can be obtained. It has also been found that the addition amount can be reduced and the hot crack resistance of the weld metal can be improved. In addition, it has been found that the yield can be improved, the amount of alloy addition for obtaining good mechanical performance and pore resistance can be reduced, and an economic effect can be obtained.

That is, the metal component powder is granulated into predetermined particles and added, thereby converting several types of fine particles of metal components into one large alloy component particle, and increasing the size of the alloy particles to thereby form a weld. Alloy particles scatter inside and oxidize,
It has been found that the transfer to the atmosphere of the welding arc is facilitated while preventing the wear, and that the alloys for the purpose of improving the performance improve the yield and the deoxidizing agent improves the deoxidizing efficiency.

The present invention has been made based on the above findings. The gist of the invention is as follows: (1) A Ni-Cr core containing an alloy component of Mn, Nb, Mo, Cr in a Ni-base coated arc welding rod. Wire, a metal powder or alloy powder selected from alloy components constituting the core wire, Al, Si as a deoxidizer,
One or more metal powders of Ti or an alloy powder containing these metal components is granulated to 300 to 150 μm, and the granulated particles are mixed with a metal carbonate, a metal fluoride, a silicate and a silicate. A Ni-base coated arc welding rod, wherein a coating component such as a salt compound or a potassium compound is mixed to form a coating, and the Ni-Cr base wire is coated with the coating. (2) Ni-
55 to 55% by weight of the Cr base wire with respect to the total weight of the core wire;
75%, Cr; 12 to 20%, Mo; 0.5 to 3.0
%, Mn: 0.5 to 3.0%, Nb: 0.5 to 2.5%
(1) The Ni-based coating alloy according to (1),
Welding rod. (3) The coating agent is weight% based on the total weight of the coating agent.
And Mn: 0.5 to 6.0%, Nb: 0.5 to 3.0
%, Mo; 0.5 to 6.0%, further Al: 1.5 to
4.0%, Si; 0.1 to 2.0%, Ti; 0.1 to
The Ni-based coated arc welding rod according to (1) or (2), wherein the Ni-based arc welding rod contains 2.0% or more of one or more types.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, it is the greatest requirement that the alloys to be blended into the coating be pretreated and coated, and the metal area is formed by granulating the alloys and sizing to a grain size of 300 to 150 μm. It has been made based on the finding that the yield rate is improved by mixing and adding the metal region as compared with the case where the metal region is added with the particle size of each alloying agent. The alloying agent added by granulating the alloys is uniformly stirred to prevent segregation in the coating agent, and the particle size is regulated to 300 to 150 μm or more, so that it is remarkable in addition to the conventional fine metal powder. The amount of alloys that were scattered during welding and oxidized during welding was reduced, the yield of alloy components added for the purpose of improving performance was improved, and the deoxidizing agent was used to satisfy the porosity resistance of the weld metal. The addition amount can be reduced, and the crack resistance of the weld metal is improved without sacrificing the porosity. When the particle size of the metal particles is less than 150 μm, there is almost no effect of granulating the alloys, and as in the non-granulated state, the amount of oxidative consumption of the alloying agent increases, and a sufficient effect cannot be obtained. The peelability and the porosity resistance of the weld metal also deteriorate. The particle size is 300μ
If it exceeds m, the coatability of the coating material will deteriorate, and the uniformity of the coating material will be insufficient, which may cause segregation of alloy components. Therefore, the particle size of the metal particles is limited to 300 to 150 μm. It should be noted that even if powders such as Ni and W are added in addition to the metal components, the effect is not changed, and other alloying agents may be added as needed.

The Ni-Cr base line component and the reason for limiting the amount will be described.

Ni is a main element constituting the matrix and is required to be 55% or more in order to obtain various properties of the weld metal. However, in order to contain alloy components such as Cr, Mo, and Nb as necessary, 75% is the limit. Therefore 55-
Limit to 75%.

Cr is a main element for maintaining the strength characteristics of the weld metal, etc.
2% or more is necessary, but if it exceeds 20%, toughness and ductility deteriorate. Therefore, it is limited to 12 to 20%.

Mo forms a solid solution in the weld metal matrix,
It is effective in improving the strength, and if it is less than 0.5%, the effect is small, and if it exceeds 3.0%, the forgeability and drawability in the core wire manufacturing process deteriorate. Therefore, it is limited to 0.5 to 3.0%.

Mn is effective in improving the toughness of the weld metal, but if it is less than 0.5%, the effect is small, and if it exceeds 3.0%, the forgeability and rollability in the manufacturing process of the core wire deteriorate. Therefore, it is limited to 0.5 to 3.0%.

Nb is effective for improving the strength of the weld metal, but if it is less than 0.5%, the effect is small, and if it exceeds 2.5%, the toughness is deteriorated. Therefore, it is limited to 0.5 to 2.5%.

Next, the reason for limiting the amount of the coating component and the amount thereof will be described. The metal component, which is an alloy necessary for the weld metal, has a better yield rate when added from the core wire than when added from the coating material, and is added from the core wire. Although it should be, there are cases where it is impossible in terms of the forgeability and workability of the core wire, and it can not be added only from the core wire to obtain the required performance of the weld metal, so it may be added from the coating agent, It is inevitable to add an alloying agent from steel.
First, the reasons for limiting the amount of the alloy component to the total weight of the coating agent will be described.

As described above, Mn is effective in improving the toughness of the weld metal and improving the porosity resistance.
If it is less than 6.0%, the effect is small and if it exceeds 6.0%, the bead shape tends to be convex and the welding workability tends to deteriorate. Therefore, it is limited to 0.5% to 6.0%. Preferably, 1.0
６6.0%.

Nb stabilizes the arc and is effective in improving the strength of the weld metal, but less than 0.5% has little effect.
If it exceeds 0%, the crack resistance of the weld metal tends to deteriorate. Therefore, it is limited to 0.5% to 3.0%.

Mo is effective for stabilizing the arc and improving the strength of the weld metal.
%, The formability of the protective cylinder during welding deteriorates. Therefore, it is limited to 0.5% to 6.0%.

Al is very effective for improving the porosity resistance of the weld metal and is required to be 1.5% or more, but 4.0%.
If it exceeds 300, the crack resistance of the weld metal tends to deteriorate. Therefore, it is limited to 1.5% to 4.0%.

[0024] Si is effective for improving the porosity resistance of the weld metal and improving the fluidity of the slag. 0.1% or more is necessary, but if it exceeds 2.0%, the crack resistance of the weld metal deteriorates. Therefore, it is limited to 0.1% to 2.0%.

Ti, like Si, is effective for improving the porosity resistance of the weld metal and improving the fluidity of the slag. 0.1% or more is required, but if it exceeds 2.0%, the crack resistance of the weld metal deteriorates. Therefore, 0.1% to 2.0
Limit to%.

Examples of the coating component include metal carbonates such as calcium carbonate, barium carbonate, and magnesium carbonate;
Metal fluorides such as fluorite and barium fluoride, silicates and silicates such as silica lime, and potash compounds such as potash glass and potash titanate, etc., must be used as coating components. Can be.

Hereinafter, the effects of the present invention will be specifically described with reference to examples.

[0028]

EXAMPLE The core wire used in the experiment was melted and then forged, rolled and drawn to a size of 4.0 mmφ × 350 mm.
Table 1 shows the core composition.

[0029]

[Table 1]

[0030]

[Table 2] Table 2 shows the composition of the coating agent coated on the core wire of Table 1,
1 to F5 are coating agents used in the present invention, and include F1N, F1B,
F2N and F3B are coating agents used in Comparative Examples.

Referring to the method of manufacturing the coated arc welding rod, water glass such as potassium silicate, sodium silicate, etc. was added to the coatings shown in Table 2 in an amount of about 20% based on the weight of the coatings, and wet-coated. The coating agent was applied to the core wires shown in Table 1 so that the coating ratio became 30%, and baked at about 400 ° C. for about 60 minutes.

Table 3 shows the chemical components of the 9% Ni steel used in the experiment. 9% Ni steel (20 mmt) shown in Table 3 was used as a welding rod obtained by combining the core wire shown in Table 1 and the coating agent shown in Table 2 in Tables 4 and 5.
5 shows the chemical composition of the weld metal welded at a current value of 155 A, which is higher than the conventional one, in a downward position, and the mechanical performance of the weld metal.

[0033]

[Table 3]

[0034]

[Table 4] Table 5 shows the mechanical performance of the welded metal in the upright position, the results of the evaluation of the welding workability, the results of the pore resistance evaluation in the upward position, and the results of the hot crack resistance evaluation in the horizontal position.
The weld metal performance test was performed according to JISZ3225. The weld metal performance of the joints was 9% Ni steel (30 mm
At t), the groove shape shown in FIG. 1 was formed, a double-sided butt welding was carried out in a vertical position under welding conditions of a welding current of 130 A and a speed of 50 to 100 mm / min, and a short gauge tensile test (joint tensile test piece: JIS Z 3121, No. 1) and an impact test (impact test piece: JIS Z 3111, No. 4). The impact test was performed at -196 ° C to determine the absorbed energy. Welding workability was determined simultaneously with joint welding.

The evaluation of the porosity resistance was performed using the 9% Ni steel (8 m
mt), the groove shape shown in FIG. 4 was formed, and a double-sided butt welding with a welding length of 400 mm was performed under the welding conditions of a welding current of 120 A and a speed of 60 to 120 mm / min in an upward posture, and an X-ray transmission test ( It was determined according to JISZ 3106).

The hot cracking resistance is as shown in Table 3 for 9% Ni steel (30%).
mmt), the groove shape shown in FIG. 2 is formed, and the constraint shown in FIG.
The test bead was welded 500 mm in a horizontal position under the conditions of a welding current of 150 A and a welding speed of 20 cm / min, and the bead surface was ground three times for about 1 mm each to perform a color check test to measure the number and length of cracks. Judgment was made by a total of three times.

In the example of the present invention, 1 to No. No. 6 is a non-granulated alloy or a particle size of 300 to 15
No. 0 of the comparative example in which the core wire was covered outside the range of 0 μm. 7
-No. The welding workability is better than that of No. 19, and the content of the alloy component added from the flux for the purpose of improving the performance is large, and a better mechanical performance than the comparative example is obtained. In addition, the porosity resistance and the hot crack resistance of the weld metal were better than those of the comparative example. No. of the comparative example. 7-No.
19 indicates that the alloys are non-granulated or have a particle size of 300 to 15
When the test is conducted at a high current, the welding workability, the mechanical performance of the weld metal, the porosity resistance, and the crack resistance are inferior to those of the examples of the present invention because the core is covered with a core wire having a length of 0 μm or less.

[0038]

[Table 5] Note 1) The criterion for the porosity resistance was determined according to the following grades based on the size and number of defects observed at a welding length of 400 mm. A; no defect B: no defect exceeding 0.5 mm and no defect less than 0.5 mm 5 or less C; defect exceeding 0.5 mm 2 or less or 0.5 m
5 to 10 defects less than m D; 3 to 5 defects greater than 0.5 mm, or 0.5 m
10 to 20 defects less than m E; 5 or more defects greater than 0.5 mm, or 0.5 m
20 or more defects less than m Note 2) Judgment of arc stability is good if welding can be performed without changing the arc state such as the spraying strength of the arc to the end during welding. A case where welding could not be performed in the same arc state until the end, such as a decrease in strength or a break in the arc, was regarded as defective. The slag peelability was evaluated as good when slag seizure did not remain on the bead surface when slag was removed immediately after welding, and as poor when slag seizure was observed.

[0039]

As described above, the present invention provides a coated arc welding rod made of a Ni-based alloy which has a good arc state and slag releasability when welding at a high current, and has a high temperature cracking resistance and a pore resistance. The present invention provides a coated arc welding rod that can easily obtain a healthy welding genus without welding defects.
This greatly contributes to efficient and economical welding of 9% Ni steel.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a groove shape for joint welding used in Examples.

FIG. 2 is a sectional view showing a groove shape for a crack test used in Examples.

FIG. 3 is a diagram showing a restrained state for a crack test used in an example.

FIG. 4 is a sectional view showing a groove shape for investigating porosity used in Examples.

Claims (3)

[Claims] 1. An Ni-coated arc welding rod comprising:
A Ni—Cr base wire containing alloy components of n, Nb, Mo, and Cr, a metal powder or an alloy powder selected from alloy components constituting the wire, and Al, Si, and Ti as deoxidizing agents. 1
A seed or two or more kinds of metal powder or an alloy powder containing these metal components is granulated to 300 to 150 μm, and the granulated particles are mixed with a metal carbonate, a metal fluoride, a silicate and a silicate compound,
By mixing with a coating component such as a potash compound and forming a coating,
A Ni-base coated arc welding rod, wherein the Ni-Cr base wire is coated with the coating agent. 2. Ni-Cr base wire is 55% to 75% by weight of Ni relative to the total weight of the core wire; 12% to 20% of Cr;
o: 0.5 to 3.0%, Mn: 0.5 to 3.0%, N
b: The Ni-based coated arc welding rod according to claim 1, which contains 0.5 to 2.5%. 3. The coating composition according to claim 1, wherein the Mn content is 0.5 to 6.0%, the Nb content is 0.5 to 3.0% by weight, based on the total weight of the coating material.
Mo: 0.5 to 6.0%, further Al: 1.5 to 4.0
%, Si; 0.1 to 2.0%, Ti; 0.1 to 2.0%
3. The Ni-based coated arc welding rod according to claim 1 or 2, comprising one or more of the following.