JPS59127994A - Low hydrogen type coated electrode - Google Patents

Abstract

PURPOSE:To provide a low hydrogen type coated electrode which yields the weld metal having no defects such as slag inclusion, lack of penetration, blowhole, or the like in a narrow groove by packing Ti, B and other specific packing material in a carbon steel pipe and covering the outside circumferential part with a flux. CONSTITUTION:A flux consisting of 0.05-4% >=1 kind among Ti, Al, Mg and Zr, 0.01-0.5% oxide of B in terms of B, 0.3-3$ Si as a deoxidizing agent, 1- 5% Mn and 0.5-5% TiO2 is packed in the carbon steel pipe at a ratio of 7- 40% with respect to the weight of a carbon steel pipe. A flux consisting of 35- 80% >=1 kind among CaCO3, MgCO3 and BaCO3, 1-45% >=1 kind among CaF2, MgF2 and AlF3 and the balance consisting of a slag forming agent, arc stabilizer and binder is coated on the outside of said carbon steel pipe, whereby a low hydrogen type coated electrode is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to a low-hydrogen-based coated arc welding rod using a flux-cored core, which makes it possible to obtain a weld metal with particularly good low-temperature toughness.

With the development of the petroleum industry in recent years, petroleum-related structures have become increasingly diverse. Moreover, many of them are used at low temperatures.

For example, a tank for storing propane or butane has 150
Exposure to temperatures around ℃. In addition, oil extraction has come to be carried out not only in hot places like the Middle East, but also in the cold and harsh oceans, and so-called offshore structures for oil extraction are now being built.
It must be able to withstand wind, rain, and waves at temperatures as low as 0°C or below.

Therefore, low-temperature storage tanks, offshore structures, etc. especially need to have good low-temperature toughness.

In addition to the conventional Charpy impact test, methods for evaluating low-temperature toughness include OOD (Orack Opening Dis).
The pla-cement (cracks opening displacement amount) test has come to be widely used. COD is a test method that has recently become important around the world as it indicates the difficulty of generating brittle fractures that lead to the destruction of structures.

In order to obtain a welded joint with a good C0T) value, it is necessary to weld with an extremely low welding heat input when using a conventional low hydrogen base, low Ni welding rod with a range from 05%N+ to 3.5X Nii. 1. The inefficient construction method of trying to make the structure of the weld metal finer and tougher is necessary. Must be. Moreover, in that case, a problem arises in that the heat-affected zone of the base material becomes highly hard.

On the other hand, Ti--B welding rods have recently been developed and put into practical use as low-hydrogen welding rods that can be welded with normal welding heat input to yield joints with good COD values. A Ti-B welding rod is one that contains appropriate amounts of Ti and B in the weld metal.
The C
This is because the OD value is good.

However, T
Even with i-B welding rods, if the groove conditions of the joint deteriorate, defects such as slag entrainment and blowholes may occur, and the toughness including the COD value may decrease, requiring repair welding. Sometimes.

The present invention solves the problems of the low-hydrogen TI-B welding rod, and enables low-hydrogen Ti-B coated arc welding that is resistant to defects such as slag entrainment and blowholes even under poor groove conditions. It provides a stick.

Eliminate defects such as slag entrainment and poor penetration in a narrow groove.KH High current can be used to deepen the penetration, but depending on the welding position, the molten metal may drip or the welding heat input may be excessive. The toughness deteriorates. Therefore, the present inventors focused on a flux-cored core wire that can be used at high currents, can obtain high current density, and has deep melt penetration. Filled with a B source such as boron oxide, a deoxidizing agent or alloying agent such as 8i, Mn, and a Ti source such as titanium oxide, and coating the outer periphery with a gas generating agent, slag forming agent, etc. By using the obtained low-hydrogen coated arc welding rod, uniformly refined Ti-B weld metal without defects such as slag entrainment, poor penetration, and blowholes can be obtained even within a narrow groove. I discovered that.

The gist of the present invention is that the filling rate of the filling flux is 7X in weight%.
~40X1 and 0.05X~4% of one or more of Ti, AL, Mg, and Zr based on the weight of the carbon steel pipe
, B of 0.0 IX~0.5%, 8i of 0.3X~3%, Mn of IX~5X1, TiO of 0.5X~5X. The core wire is 35% to 8ON of one or more of 0aO031Mg0OB I BaO03 in weight%.

0aP1 tMgll, 1% or more of AlF3
A low hydrogen-based coated arc welding rod characterized in that the outer periphery of the core wire is coated with a coating flux consisting of 45% of the carbonate, a slag forming agent excluding metal fluorides, an arc stabilizer, and a binder, the remainder being the carbonate and metal fluoride. It is in. Note that X used hereinafter refers to weight X.

Next, the type of filling flux for the welding rod of the present invention and the reason for limiting its range will be described.

In addition, during the experiment, after filling a carbon steel pipe with an outer diameter of 12 m with filling flux, it was drawn until the outer diameter became 4 mK.
After cutting it into a length of 400 m, coating the outer circumference of the flux cored core wire with a coating flux using the usual method,
A prototype welding rod was created by firing at 400°C. Then, 500 Y-shaped grooves were formed on an aluminum-killed steel plate with a thickness of 25 m, and vertical welding was performed using the welding rod at a welding current of 160 A.
Impact tests and COD tests on these weld metals were conducted at -50°C.

In addition, welding was performed within a ■-shaped narrow groove with a welding workability Fi of 30°.

The carbon steel nozzle is preferably a seamless pipe or a pipe with welded seams.

TI, M, Mg, and Zr act as deoxidizing agents, and Ti retained in the weld metal works to uniformly refine the weld metal in relation to B, which will be described later.

Since Ti, AI, Mg, and Zr are strong deoxidizing agents, they are not added to the weld metal by reducing Ti, titanium oxide, 9Ti, and boron oxide by reducing B.

Furthermore, Ti, AI, and Zr also have the function of fixing nitrogen in the weld metal as their respective nitrides.

Note that Ti, AI, Mg, and Zr are these alone or re-Ti, Fe-AL, Fe-Zr, Al-Mg
It can be added in alloys such as.

If the total of one or more types of T + HAI HM gr Z r is less than 0.05% based on the weight of the carbon steel pipe, the system that supplies Ti and B to the weld metal in the amount necessary to refine the weld metal However, the effect of fixing nitrogen in the weld metal as nitrides cannot be obtained, and if the concentration exceeds 4N, excessive Ti and B are added to the weld metal, which deteriorates the toughness and also reduces the fluidity of the molten slag. This may result in poor bead shape and poor slag retention, so the amount should be 0.05% to 4% based on the weight of the carbon steel pipe.

B is added in order to uniformly refine the weld metal in relation to the above-mentioned Ti, but B is carbon steel, 647% by weight.
If it is less than 0.01%, a synergistic effect with Ti in the weld metal cannot be obtained.
, it is not possible to obtain a uniformly refined structure of the weld metal. Furthermore, if B is added in excess of 0.5X, B in the weld metal becomes excessive and the toughness deteriorates, so the range should be 0.01 to 0.5X relative to the weight of the carbon steel pipe. As the oxidation source, any of boron oxides, boron oxide compounds, boron compounds, etc. may be used.

Si and Mn are added as deoxidizers or alloying agents, but if Si is less than 0.3% based on the weight of the carbon steel nozzle, deoxidation is insufficient, causing bits and deteriorating welding workability. , if added in excess of 3N, Si in the weld metal
is excessive and deteriorates toughness, so the range is set to 0.3% to 3% based on the weight of the carbon steel pipe. Furthermore, if Mn is less than 1% based on the weight of the carbon steel pipe, the strength will be insufficient, and 5N
If it exceeds this, the weld metal will become hard and the toughness will deteriorate, so the range should be 1 to 5 times the weight of the carbon steel pipe. Note 8
i, Mn are their single substances or Fe-8i
, Fe-Mn, 81-Mn, etc.
may be used.

TiO2 is one of Ti, AI, Mg, and Zr, which is a strong deoxidizing agent.
TiO2 is added to the weld metal by reducing and supplying it to the weld metal to stabilize the arc and adjust the viscosity of the molten slag.
If it is less than 5%, there will be no effect, and if it exceeds 5%, the viscosity of the molten slag will increase and welding workability will deteriorate, so the range is carbon steel,
0.5X to 5X relative to 647 weight. Furthermore, Ti
As the 01 source, rutile, illuminite, titanium slag, etc. are used.

When filling a carbon steel pipe with the filling flux obtained by mixing the flux components explained above, if the weight of the filling flux is less than 7N with respect to the weight of the carbon steel pipe, the effect as a flux-filled core wire, i.e. Although a high current can be used, a high current density can be obtained, but the effect of deepening the melt penetration cannot be obtained, and defects such as slag entrainment are likely to occur within the narrow groove. Moreover, if it exceeds 40X, it becomes difficult to draw a core wire with Franks, so the filling rate of the filling flux is set to 7N to 40% of the weight of the carbon steel pipe.

Note that the filling rate of the filling flux refers to the amount of carbon steel bi 1M Table 1 shows composition examples of the filling flux when the filling rate is different.

The filling flux may be granulated using a binder such as water glass, fired, and then filled into the carbon steel pipe.

Next, the coating agent to be applied to the outer periphery of the flux-cored core wire cut to a predetermined length will be described.

Carbonates such as 0aO03, Mg0O1, and BaO03 are decomposed by arc heat to generate CO2 and have the function of capturing the arc atmosphere from the atmosphere, but the total of one or more of them is 3
If it is less than 5%, there will be a lack of sealing P in the atmosphere, and a large amount of nitrogen in the atmosphere will dissolve into the weld metal, deteriorating the toughness. If it exceeds 80%, the melting point of the molten slag will become high, the bead shape will deteriorate, and the slag will deteriorate. The range of 35% to 80% is preferable since the peeling property is also deteriorated.

Metal fluorides such as 0aF1, Mg1i', , AJ, and F3 are added to adjust the fluidity of each molten lug, but
If the total of one or more of them is less than IX, the fluidity of the molten slag will deteriorate, and if it exceeds 45X, the arc will become unstable, so a range of 1 to 45% is appropriate.

Incidentally, these carbonates and metal fluorides may be partially added to the packed 7 lac, but the same effect can be obtained in that case.

For pipes, any carbon steel may be used, but to further improve impact and COD characteristics at low temperatures, the nitrogen content in the carbon steel nozzle should be 70 ppm or less, oxygen Content is 200ppm~6
A range of 0.00 ppm is desirable. That is, the low-temperature impact and COD characteristics of weld metal are influenced by the chemical components of weld metal, and the influence of nitrogen is particularly large. The nitrogen in the weld metal is the sum of the nitrogen that entered from the atmosphere, the residual nitrogen contained in the nozzles and flux, and the nitrogen that migrated from the base metal due to dilution of the base metal. Therefore, by regulating nitrogen in the nozzle and flux, it is possible to reduce nitrogen in the weld metal and improve low-temperature toughness. Furthermore, the amount of oxygen in the nozzle affects the yield of alloy components and welding workability. That is, if the amount of oxygen in the nozzle exceeds 600 ppm, the yield of alloying elements such as Mn, Ti, B, etc. will decrease, and the toughness will also deteriorate, and if it is less than 200 ppm, welding workability will deteriorate.

As explained above, the welding rod of the present invention has good welding workability even under bad groove conditions, and the obtained weld metal has good impact toughness and COD value, but the strength of the weld metal is improved. Appropriate amounts of Ni, Or, M are added to the filling flux for
It is also possible to add a single substance such as o or an alloy thereof.

Furthermore, an appropriate amount of iron powder can be added to the filling flux or coating flux to improve the welding efficiency.

Next, examples of the present invention will be described.

Table 2 shows the components of the filling flux and coating flux of the welding rods of the present invention, conventional welding rods, and comparison welding rods, the impact characteristics and OOD characteristics of the weld metal obtained by welding with these welding rods, and the welding workability in narrow gaps. This is what is written. N
al is a conventional welding rod, floors 2 to N17 are welding rods of the present invention, number 8
- Part 15 are comparative welding rods.

The welding rods used in the test were both conventional welding rods and welding rods using flux-cored wire, and the rod diameter was 4 m, and the test steel plate had a tensile strength of 50 k.
5 for g7'Ij class aluminum killed steel plate thickness 25cm
Welding was carried out in a vertical position using a welding rod with a Y groove of 0°, and the welding current was 15OA using a conventional welding rod and a 160A1 welding heat input using a flux-cored core wire at a welding heat input of 30kJ/++. Then, three 2mV Notch Charpy impact test pieces and three standard 00D test pieces were collected, all of which were -5
Tested at 0°C. The C0T) test is based on British Standard B S
5762-1979. Regarding impact properties, when the average absorbed energy is 13 kf, a or more at 150°C, the minimum value for COD properties is 0.
A distance of 25 m or more was considered good. In addition, welding work
The evaluation was made by vertically welding a ■-shaped narrow groove of 0.

No. 1 is a conventional welding rod with good impact value and 0OT) value, but when a narrow gap is formed, defects such as slag entrainment and blowholes are likely to occur because the current gap is small.

N [12 to 7 are welding rods of the present invention, and the impact value is 13.11?
, ffi or more, and the lowest value of 00D value is 0.35- or more, which is good. In addition, welding workability is also good, with no defects such as slag entrainment or blowholes.

1&L8 has a low filling rate of 6.5X, so the impact value is 00
Although the D value is good, defects such as slag entrainment are likely to occur when welding with a narrow gap because the current density is low.

Na9 and Mn are small at 0.8% relative to the weight of the carbon steel pipe, and B is excessive at 0.6% relative to the weight of the carbon steel pipe. Although this has good welding workability, it has a low impact value. ,
The COD value is also bad.

Number 10 is Ti, A! , Mg, and Zr are as high as 4.2% relative to the weight of the carbon steel pipe (and Si is as low as 0.2% relative to the weight of the carbon steel pipe), the arc is unstable and the slag The sharpness is also poor, and T in the weld metal
Since i becomes excessive, both the impact value and the COD' value are low.

ml has good welding workability, but since B is 0.007N relative to the weight of carbon steel, a uniform and fine weld metal structure cannot be obtained, and both impact value and COD value are low.

N112 is a small amount of Ti, M, Mg, Zr (type 01 or more) at 0.04% of the total carbon steel pipe weight.
Since O2 is also as low as 0.4X relative to the carbon steel pipe weight fK, the viscosity of the molten slag is insufficient, resulting in poor fluidity, furthermore, it is difficult to obtain a uniform and fine weld metal structure, and Mn is Since the amount of Mn is 5.1% relative to the weight of the carbon steel pipe, the Mn content in the weld metal is excessive, resulting in low impact values and COD values.

No. 13 is carbon steel, which has a large Si content of 3.2X relative to the e-beam weight, so 81 in the weld metal becomes excessive, resulting in an impact value of 00
The D value has decreased significantly. Also, Tie is 5. IX, the viscosity of the molten slag increased and welding workability deteriorated.

Order 14 has a high carbonate content of 81N and a metal fluoride content of 0.
When the viscosity of the slag was as low as 9 N, the viscosity of the slag became high, the bead shape deteriorated, and slag entrainment also occurred.

? Contrary to N114, a15 has a low carbonate content of 34N and a high metal fluoride content of 46X, making the arc unstable.
Slab entrainment also occurs, and the impact value and 00D value are also low.

As explained above, using the welding rod of the present invention, it is possible to weld without welding defects even under poor welding conditions such as burrs, burrs, and narrow grooves, and it also has good impact toughness at low temperatures, O
OD@! [A good welded joint can be obtained with both.

Claims (1)

[Claims] (1) The filling rate of the filling flux is 7% to 40% by weight.
, and T i , Ai in weight with respect to carbon steel pipe weight
, Mg, Zr at 0.055X to 4%, B
fo, 01%-0.5%, 8i 0.3%-3%. 1% to 5% Mn. A carbon steel pipe containing a filling flux containing 0.5X to 5X of TiO2 is used as a core wire, and one or more of 0aO03, Mg00s, BaO03 is added at 3% by weight.
A coating flux consisting of 5% to 80%, 1% to 45% of one or more of OaF2, MgF2, and AlF3, and the remainder consisting of a slag forming agent, an arc stabilizer, and a binder excluding the carbonates and metal fluorides. A low hydrogen-based coated arc welding rod, characterized in that the outer periphery of the core wire is coated with.