JPS62240196A - Low hydrogen type coated electrode - Google Patents

Abstract

PURPOSE:To improve the low-temp. toughness and sea water corrosion resistance of a weld metal by coating a coating material which contains a specific ratio of Cu and is added with adequate ratios of Si, Ni, and Ti, Al, Mg as well as metallic carbonate and metallic fluoride onto a carbon steel core wire. CONSTITUTION:The coating material contg. 1.2-2.9wt% Cu, 1.1-3.8% Si, 0.9-4.8% Ni, 3.1-5.8% >=1 kinds among Ti, Al, Mg, 33-60% metallic carbonate, 12-25% metallic fluoride, and deoxidizing agent, arc stabilizer, slag forming agent, binder and if necessary, <=0.6% Cr, <=0.8% Mo is prepd. Such coating material is coated on the carbon steel core wire. Since such low hydrogen type coated electrode has the excellent sea water corrosion resistance and low-temp. toughness and therefore, the electrode is effective for welding of ocean structures in frozen ocean areas, building of icebreakers, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The welding rod of the present invention relates to a low-hydrogen coated arc welding rod that has excellent low-temperature toughness and excellent seawater corrosion resistance.

(Conventional technology) In recent years, the development of energy resources has been moving toward polarization and deepening of the ocean, and for this reason, even in the construction of icebreakers and offshore structures,
There has been a demand for the development of steel materials and welding materials that have excellent low-temperature toughness and seawater corrosion resistance.

Conventionally, as a method for preventing corrosion of steel materials for underwater structures and their welded parts, it has been common to apply sufficient coating. However, in places where ice is present, such as in the Arctic Ditch, scratches occur on the painted surface due to collisions with the ice, and corrosion occurs from these areas, so it cannot be said to be a sufficient anti-corrosion measure. Particularly if the coating is insufficient, general corrosion and local corrosion of the steel material will occur. Of these, countermeasures can be taken to prevent general corrosion of the steel material, such as increasing the plate thickness, but localized corrosion has become a major problem as it causes stress concentration and can cause fatigue and other types of damage. 9. The chemical composition of the welded part is different from that of the base metal.
This is a particularly problematic location for localized corrosion, as differences in thermal history cause differences in corrosion resistance.

one! , fC1 Up until now, emphasis has been placed on seawater corrosion resistance in the construction of underwater structures, but as the range of use has become more polarized, there has also been a growing demand for structures with excellent low-temperature toughness. It has become a point.

On the other hand, Japanese Patent Publication No. 56-7799 discloses a coated arc welding rod with good seawater corrosion resistance due to the control of Si, Cu, Cr, and Mo in the coating material, but the low-temperature toughness is We have not yet reached a point where we can significantly improve this.

Further, in Japanese Patent Publication No. 53-19296, Cu is disclosed.

Although a welding rod with a controlled coating of St and Cr bond is described, it is a welding rod with excellent sulfuric acid dew point corrosion resistance, and does not refer to a coated arc welding rod with excellent low temperature toughness and seawater corrosion resistance. do not have.

(Problems to be Solved by the Invention) In view of the current situation, the present invention provides a weld metal that exhibits excellent low-temperature toughness and has excellent seawater corrosion resistance for use in the construction of marine structures and icebreakers in frozen areas. The present invention provides a coated arc welding rod obtained by the present invention.

(Means for Solving the Problems) The gist of the present invention is that Cu1.2 to 2.9 weight range (hereinafter, all numbers indicate weight range), Stl,
1-3.8%, Ni0.9-4.8 r TtrAt+
One or more types of Mg in a range of 3.1 to 5.8, metal carbonate in a range of 33 to 5.8
60 chi.

Metal fluoride 12-25%, in addition, deoxidizer other than the above,
A coating containing an arc stabilizer, a slag forming agent and a binder, or if necessary, Cr0.6'16 or less and Mo
A low hydrogen-based coated arc welding rod is characterized in that a carbon steel core wire is coated with a coating agent containing one or two of the above 0.8% or less.

It has been known that the addition of Cu and Cr is effective in improving the seawater corrosion resistance of steel. Welded parts in steel structures are particularly susceptible to localized corrosion because their chemical composition and thermal history are different from those of the base metal. In particular, if the weld metal undergoes selective corrosion before the base metal, the corrosion will progress rapidly depending on the area ratio with the base metal, which may lead to destruction. To prevent this, it is necessary to add Cu r Cr r Ni or the like to the weld metal to make the weld metal more electrochemically sensitive than the base metal. In particular, Cu is effective in improving corrosion resistance, but Cu has a low solidification temperature and tends to segregate at grain boundaries during the solidification process of weld metal, causing embrittlement of weld metal and deterioration of low-temperature toughness. was.

Therefore, the present inventors investigated ways to improve the low-temperature toughness of the deposited metal of welding rods containing Cu, and by reducing Si in the coating as much as possible and adding an appropriate amount of N1, the low-temperature toughness was significantly improved. This is what I found possible.

On the other hand, Si in the coating material is an effective deoxidizing agent in low-hydrogen welding rods, and it is a material that controls the viscosity of molten metal and molten slag to provide good welding workability, so it is simply reduced. If this is done, embrittlement will occur due to insufficient deoxidation, and welding efficiency will deteriorate, making stable welding impossible and causing welding defects. It has been found that in order to solve this problem, it is sufficient to add appropriate amounts of strong deoxidizers such as Tl, At, and Mg. When added to the coating material, these elements have a strong deoxidizing power, so even if the St content is low, they form a weld metal with a low oxygen content and good toughness, and increase the viscosity of the molten metal, improving welding workability. I found out that it can be improved.

The present invention was made based on this knowledge,
This will be explained in detail below along with the action.

(Function) One of the features of the present invention is that Cu is added to the coating material to significantly improve seawater corrosion resistance.

Figure 1 shows 46% lime carbonate and 17 pieces of stone.

Rutile 4'1Mn3.8%yNi 1.5%1Cr0
．． 2%.

Mo O-4% t T'11.8 '4 v At-
Mg 3-1%-Fe-8t (42%81)7.
A coating material consisting of 8% CuO, 3.5% CuO, 7.6% binder, and the balance iron powder was coated with a diameter of 4.0 mm and a length of 400 mm.
After coating the carbon steel core wire so that the outer diameter of the coating was 6.3 mmK, it was dried and fired6) to produce 12 types of welding rods, C0.1%, C0. Si0.2%, Mn1.1%, Cu0.
3% = Ni 0.4 'IytCr 0.1%
Welding current 170A, heat input 15 for steel material 25m+ thick
Welded at kJ/cm, a test piece with a thickness of 5 mm was taken from 1 fi below the surface and subjected to a rotational immersion test for 3 months in a 3-momentary saline solution.The results are shown below. In the figure, the horizontal axis represents the amount of Cu in the coating material, and the vertical axis represents the corrosion loss of the weld metal. As shown in Figure 2, the corrosion weight loss is the minimum thickness t of the metal welded to the measurement part after the corrosion test, and the difference between that and the thickness of the test piece before the test (5 wm). It is.

For weld metal using a welding rod that does not contain Cu in the coating,
The corrosion weight loss was 1.9 gourds, and the Cu content in the coating material was 1.9 gourds.
All coatings with Cu of less than 2 modulus exceed 0.6 tm, whereas all coatings with Cu of over 1.2 modulus exhibit good seawater corrosion resistance at 0.4 m or less. Ta.

Even if Cu is added in an amount exceeding a coefficient of 2.9, no significant effect is observed in improving corrosion resistance, and on the contrary, low temperature toughness deteriorates.

Therefore, the amount of Cu added in the present invention is limited to 1.2 to 2.9 parts.

Next, in order to prevent deterioration of low temperature toughness due to Cu addition,
The amount of St in the coating material was reduced and an appropriate amount of Ni was added.

As mentioned above, Si is added mainly as Fe-8i as a deoxidizing agent and to ensure welding workability, but when the amount of St increases, it coarsens the crystal grains of the weld metal and deteriorates the toughness. Therefore, reducing the amount of Si in the coating material is effective in improving low temperature toughness. Further, when N1 is added, the toughness of the weld metal can be significantly improved due to the solid solution effect in ferrite, and the deterioration in low-temperature toughness caused by the addition of Cu can be sufficiently compensated for.

Figure 3 shows carbonate lime 42 to 48 inches, falling stone 16.8 inches,
3.6% a Mn 0.84 e Cr
C04% pFe-TI (40qbTi) 3.
6%, Mg 2.4%, Cu 2.2%, F
e-81 (4291) Si) 2.2 to 12.64
17 types of welding rods with a core wire diameter of 4 and Orms were prepared in the same manner as above using a coating material consisting of 4 to 4.2% pNlO, 7.3% binder, and the remainder iron powder. These welding rods were subjected to a weld metal impact test according to JIS Z3212, and the results are shown below. In addition,
For the impact test, three 2 mV Notch Charpy impact test pieces were taken and conducted at 60° C. according to JIS Z2242 to determine the absorbed energy.

As is clear from the figure, Ni is contained at 1.0% or more,
The weld metal of the welding rod with Fa-81 of 8.9 inches, that is, the st amount of 3.7 coefficients or less, had an absorbed energy of 1 kgf-m or more. However, when N1 is 0.41, the absorbed energy is less than 5 f-m regardless of the amount of Si, and when Fe-8t is 9.8 cm, that is, St
In all cases in which the value exceeded 41 cm, the absorbed energy was less than 9 yi-m.

Furthermore, similar tests were conducted on sl and Nl added to the layered coating material.
The appropriate range was determined. When Si exceeds a modulus of 3.8, Sii of the weld metal increases and low-temperature toughness deteriorates.

Further, if the ratio is less than 1.1, deoxidation is insufficient, the arc becomes unstable during welding, the viscosity of the molten metal decreases, and welding workability becomes extremely poor. For this reason, the addition range of si in the coating material was determined to be 1.1 to 3.8.

In addition, if Ni1d is added less than 0.9%, the effect of improving low-temperature toughness is not sufficient, and if it is added in excess of 4 or 8 modulus, the effect is saturated and no further significant improvement effect can be obtained. The range was defined as 0.9 to 4.8.

Both Tl * Att Mg are strong film acid agents, and by adding them to the coating material, even if the si in the coating material is significantly reduced, a clean weld metal with a low oxygen content can be obtained. Furthermore, good welding workability can be obtained by controlling the viscosity of the molten metal. If the total of one or more types of Ti = Att Mg is less than 3.1, the effect is insufficient,
If it is added in excess of 5.7, the fluidity of the molten slag will deteriorate, the bead shape will deteriorate, and the arc will become unstable).
Increase in arm ivy. Furthermore, since the peeling of slag becomes worse, the ratio was set in the range of 3.1 to 5.8. Next, the metal carbonate referred to in the present invention is caco.

BaCO5+ MgCO3* MnCO5 etc.
CaCO5 is essential, and other substances are combined as necessary to make the total content 33 to 60%. These metal carbonates decompose in the arc, generate Co2 gas, cut off the molten metal from the atmosphere, lower the partial pressure of water-based and nitrogen gases in the arc atmosphere, and have the effect of generating base column slag. have If the amount added is less than 33%, the melting point of the slag decreases, the encapsulation of the slag deteriorates, and good beads cannot be obtained. In addition, because the amount of gas generated that interrupts the atmosphere is insufficient, pits and blowholes occur, the amount of hydrogen in the weld metal increases, and cracking resistance deteriorates.

On the other hand, if more than 60 g is added, the amount of gas generated will be excessive, resulting in frequent pits, and the melting point of the slag will rise, resulting in poor fluidity of the slag, resulting in uneven compatibility with the welding base metal, resulting in a shabby shape. Deteriorate.

Furthermore, the metal fluoride referred to in the present invention is CaF2 t Ba
F2 vMgF2. AtF2. MnF,,tL
It refers to iF, etc., and contains CaF 2 as essential, and other substances are combined as necessary to make the total content 12 to 25. All of these metal fluorides lower the melting point of the slag and create a slag with good fluidity. In addition, fluorine decomposed in the arc reacts with hydrogen in the molten metal and molten slag, lowering the hydrogen content in the weld metal and creating a weld metal with good crack resistance. If the amount of these additives is less than 12 parts, appropriate slag fluidity cannot be obtained, resulting in poor bead shape and pit formation, and an increase in the amount of hydrogen in the weld metal, resulting in cracks. On the other hand, if it is added in excess of 25%, the slag's viscosity will be insufficient and the bead shape will deteriorate, and the sheathing tube will also become weaker, resulting in poor welding workability.

Next, other deoxidizers to be included in the coating material.

The arc stabilizer and slag forming agent refer to Mn, iron powder, alkali components, rutile, etc. The amount added is not particularly specified, but it is desirable that the total amount is 5 to 25 parts from the viewpoint of welding workability. In addition, the binder refers to a binder component such as water glass represented by sodium silicate and potassium silicate, and is a binder component such as 5102 and Na2O in water glass, which is mixed with an alkali component such as 20. molar ratio of 1.5 to 3.5
It is desirable to use water glass in the range of .

The above are the main components contained in the coating material of the welding rod of the present invention, but in addition to these, Cr and/or Mo may be contained as necessary.

Cr is effective in improving seawater corrosion resistance, but too much Cr can cause pitting corrosion, so a maximum of 0.6 Ft2 is used.
.

Mo improves hardenability, increases strength, and is effective in improving low-temperature toughness, but when added in excess of 0.84, the strength increases too much and low-temperature toughness deteriorates, so the maximum coefficient was set at 0.8.

The welding rod of the present invention is coated with the above-mentioned coating material around the carbon steel core wire using a normal welding rod coating machine so that the weight of the coating material is 25 to 35 times the weight of the welding rod. It is manufactured by firing at 300 to 550°C to remove.

The carbon steel core wire referred to in the present invention is a coated arc welding rod core wire defined in JIS G3523.

Next, the effects of the present invention will be illustrated in more detail with reference to Examples.

(Example) Table 1 shows the coating composition and various test results of the welding rod of the present invention and the welding rod used for comparison.

In Table 1, A-1 to A-10 are welding rods of examples of the present invention, and B-1 to B-8 are welding rods of comparative examples.

The diameter of each rod is 4.0 square meters.

C13) In order to investigate the seawater corrosion resistance of these welding rods,
C0.1%, Si0.2% shouldering the 0m V groove? Mn
1.1%, CuO, 3%, N10.4%
, Cr 0.196.

Welding current 170A, heat input 15 for steel material 2511m thick
kJ/m, a test piece with a thickness of 5 mm was taken from 1 mile below the surface and subjected to a rotational immersion test for 3 months in saline solution. Weight loss was measured. The test results were evaluated as good if the corrosion weight loss was 0.5 or less.

In addition, in order to investigate low temperature toughness, welded metal was prepared according to JIS Z3212, three 2 mm V-notch Charpy impact test specimens were taken, and the test pieces were tested at -60°C according to JIS Z2242.
An impact test was conducted to determine the absorbed energy. The test results were evaluated as good if the average value of absorbed energy at -60°C was 10 f-m or more. Furthermore, welding workability tests were also conducted on these welding rods.

The seawater corrosion resistance of the weld metal using the welding rod of the present invention is Cu
Corrosion weight loss is 0.4m due to the corrosion resistance improvement effect of addition.
It was less than The low-temperature toughness of the weld metal was also good due to the effect of the reduction of Sl and the addition of Ni, and the absorbed energy at =60°C exceeded 12 kg and 7'm. Saratic
The welding workability was also good due to the effects of , Ti, Kl, and Mg.

On the other hand, Cu is not added to the coating material or 0.
Welding rods B-4, B-1, and B-7, which are 9mm or less, do not have sufficient corrosion resistance and the corrosion loss exceeds 0.8fi, and in particular, welding rod B-4 without Cu addition has a corrosion loss of 2fi. It's gotten closer. On the contrary, welding rod B-2 containing a large amount of Cu had good corrosion resistance, but the Cu caused embrittlement and low low temperature toughness.

Welding rod B-8, in which Cu was added and St was added as much as 4.5, had low absorbed energy despite the addition of Ni.

Welding rod B-6°Ni with no Ni added in the coating material
B-1 with Mo of 0.6% and B-7 with Mo of 1.04 are
The absorbed energy was low despite the low St.

Welding rod B-6 containing 1.0% Cr suffered from pitting corrosion during the corrosion resistance test, resulting in a large corrosion loss.

Furthermore, welding rods B-3, TI, and At have too low st.

B-5 is too low in Mg, B-8 is too high, and the amount of metal carbonate and metal fluoride is inappropriate -2゜B-3, B
-5 and B-6 had poor welding workability.

(Effects of the Invention) As described above, the welding rod of the present invention has extremely excellent seawater corrosion resistance and significantly improved low-temperature toughness.

This is something that conventional seawater-resistant welding cannot achieve, and it is particularly effective in the construction of offshore structures and icebreakers in icy areas such as the Arctic Trench, contributing to the development of these industries. It's very much a dog.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between Cu content in the coating and corrosion loss in seawater corrosion resistance tests, Figure 2 is a diagram showing the measurement procedure for corrosion loss in seawater corrosion resistance tests, and Figure 3 is welding. Fe- in coating materials in metal impact tests
3 is a diagram showing the relationship between the amount of 3t (Si), the amount of Ni, and the absorbed energy at -60°C. t: Measuring part (minimum thickness of weld metal) Procedural amendment June 4, 1939 A7

Claims (2)

[Claims] (1) Cu1.2-2.9% by weight, Si1.1-3.8
Weight%, Ni0.9-4.8weight%, Ti, Al, Mg
3.1 to 5.8% by weight of one or more of the following, 33 to 5.8% by weight of metal carbonate
The carbon steel core wire is coated with a coating agent containing 60% by weight, 12 to 25% by weight of metal fluoride, and a deoxidizing agent other than the above, an arc stabilizer, a slag forming agent, and a binder. Characteristic low hydrogen coated arc welding rod. (2) Cu1.2-2.9% by weight, Si1.1-3.8
Weight%, Ni0.9-4.8weight%, Ti, Al, Mg
3.1 to 5.8% by weight of one or more of the following, 0.6% by weight of Cr
One or two of the following and 0.8% by weight or less of Mo, 33 to 60% by weight of metal carbonates, 12 to 25% by weight of metal fluorides, and deoxidizing agents other than those listed above, arc stabilizers, and slag forming agents. and a low hydrogen-based coated arc welding rod, characterized in that it is made by coating a carbon steel core wire with a coating agent containing a binder.