JPS6045993B2 - Low hydrogen coated arc welding rod - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low hydrogen coated arc welding rod that has good pit resistance and welding workability.

Steel materials for large structures are coated with anti-corrosion primer, and when welded downward or horizontally fillet welded with a low-hydrogen coated arc welding rod, pifts are likely to occur, and pitting must be repaired. requires a great deal of effort.

Therefore, low-hydrogen covered arc welding rods with a coating material mainly composed of CacO3-CaF2, which does not generate pits, have been used, but these have extremely poor welding workability, especially in horizontal fillet welding due to the bead shape. Currently, MgCO3-CaF2 is used mainly for welding workability, especially good bead shape, and bit resistance has also been improved to reduce the amount of hydrogen in the weld metal as much as possible. , welded iron is used. However, although it has been considerably improved, the current situation is that the bit resistance against primer-coated steel sheets is still inferior compared to welding rods mainly made of CacO3-CaF2. Also,
It is said that when horizontal fillet welding is performed on a steel plate coated with a rust-preventing primer, bits are likely to occur due to gas components in the primer, especially hydrogen gas.
In order to prevent this adverse effect, efforts have been focused on creating coating components that reduce the amount of hydrogen in the weld metal as much as possible.

However, the present inventors further changed their viewpoint regarding bit generation and conducted various experiments as described below in order to investigate the relationship between not only hydrogen but also hydrogen and oxygen and bit generation.

Figure 1 shows the plate thickness 16? This is the result of investigating the relationship between the tendency of bit generation and the amount of hydrogen and oxygen in the weld metal when horizontal fillet welding was performed using 50 kg class high tensile strength steel using various conventional welding rods.

As is clear from Figure 1, bits are more likely to occur during horizontal fillet welding as the amount of hydrogen and oxygen in the weld metal increases. It can be seen that the bit generation area expands to the lower side for both the amount of oxygen and the amount of oxygen.

Therefore, in the case of primer-coated steel sheets, the amount of hydrogen and oxygen in the weld metal should be reduced as much as possible. In order to reduce the amount of hydrogen, it is effective to include a large amount of carbonate and fluoride in the coating material, but on the other hand, arc breakage is more likely to occur. .

In addition, in order to reduce the amount of oxygen in the weld metal, it is necessary to use
i,. In order to achieve the desired oxygen content using only a deoxidizing agent such as Mn, a large amount of deoxidizing agent is required, and as a result, Si, . As the amount of Mn increases and the weld metal hardens, the cracking resistance deteriorates.

Therefore, the present inventors investigated various deoxidizing elements and deoxidizing alloys in response to these problems, and found that they had poor deoxidizing properties.The inventors found that the oxygen in the weld metal could be reduced without deteriorating the cracking resistance. A new finding has been obtained that these problems can be solved by adding SlC and A'-Mg to the coating material as materials that also have good arc breakage resistance.

That is, FIG. 2 shows the effect of Af-Mg on arc breakage.

A. It can be seen that arc breakage is significantly improved by adding 0.75% or more of e-Nlg. Furthermore, Figure 3 shows the change in the amount of oxygen in the weld metal when SiC is added to the coating material, and it can be seen that the amount of oxygen in the weld metal decreases significantly due to the addition of SiC. .

The present inventors also conducted a confirmation experiment regarding the question of whether the same effect could be obtained when Si (5C, which has the composition of SiO) was added to the coating material. As shown in Figure 3, it was found that the deoxidizing effect as great as that of SiC was not obtained, and that the addition of SiC was very effective.

As mentioned above, these SjC. ! :A'-Mg is effective in reducing the amount of oxygen and preventing arc breakage, but it is clear from these findings that SjC is particularly effective in reducing the amount of oxygen and A'-Mg is effective in preventing arc breakage. It is.

The present invention was made based on the above findings, and the gist thereof is that SiC: 0.2 to 30%,
Ae-Mg: 0.5-20%, MgCO3: 5-25%
, CaF2: Total of one or more of MgF2 and A'F3:
1~13%, SjO2: 10~20%, TiO2: 5~
15%, MgO: 1-20%, Mn: 3-10%, Fe
: Contains 10 to 50%, or further contains (A) Ca
CO3: 8% or less and/or the total of one or both of Si and Ti: 2% or less, or BNi, Cr, V, MO, C
A. u, Nb containing 10% or less in total. A low hydrogen-based coated arc welding rod is obtained by adding a binder to a coating material containing one or both of B and coating it on a steel core wire.

The coating material components of the welding rod of the present invention will be explained in detail below.

First of all, SiC has the above-mentioned effects, but 0.
If it is less than 2%, this effect will not be exhibited and bits will occur.

However, if it exceeds 3.0%, the weld metal will be significantly hardened and its cracking resistance will deteriorate. Therefore, the SiC content was set to 0.2 to 3.0%. Next, as mentioned above, if A'-Mg is less than 0.5%,
There is no effect of preventing arc breakage, and if it exceeds 2.0%, the arc becomes weak and the bead shape becomes convex, which is inappropriate.

Therefore, Ae-Mg was set to 0.5 to 2.0%. Furthermore, Ae
-The composition of Mg is Ae6O%, Mg4O%, and Ae
Powder, Fe-Ae. ．． It may be added in the form of Mg powder or the like. Furthermore, MgCO3 is required to be at least 5%; if it is less than this, bits will occur due to insufficient shielding and the amount of hydrogen in the weld metal will increase, making it impossible to achieve the effect of improving bit resistance, which was the initial objective of the present invention. .

If it exceeds 25%, pockmarks will occur in the bead and the bead shape will become convex.

Therefore, MgCO3 was set at 5 to 25%. Furthermore, if the total content of one or more of the fluoride components CaF2, MgF2, and A'F3 is less than 1%, the amount of hydrogen in the weld metal cannot be reduced, and therefore the bit resistance is significantly reduced.
If it exceeds 13%, arc breakage will occur even if Ae-Mg is added.

Therefore, the total content of one or more of CaF2, MgF2 and AeF3 was set to 1 to 13%. Next, SiO2 acts as a slag forming agent and greatly affects slag fluidity, but if it is less than 10%, the slag will lack viscosity and the bead shape will become convex;
If the welding temperature is too high, the viscosity of the slag becomes excessive, and the slag gets entangled with the welding rod, making the arc unstable.

Therefore, SjO2 was set to 10 to 20%. Further, TlO2 has the same function as SlO2 and also has the function of stabilizing the arc, but if it is less than 5%, the arc becomes unstable and the amount of slag is insufficient, resulting in a convex bead shape.

If it exceeds 15%, the fluidity of the slag becomes excessive, so that the slag takes the lead and forms a two-stage bead.

Therefore, TlO2 was set at 5-15%. Furthermore, MgO is a slag viscosity regulator, but if it is less than 1%, it not only makes the slag encapsulation uneven and the bead shape irregular, but also deteriorates the peelability of the slag, and if it exceeds 20%, it causes arcing. The surface becomes rough, spatter increases, and undercuts also increase. Therefore, the MgO content was set to 1 to 20%. On the other hand, Mn is added as a deoxidizing agent, and the deoxidizing products produced affect workability.

Therefore, the amount should be considered from the viewpoint of weldability and workability; if it is less than 3%, the fluidity of the slag will be poor and bits will occur due to insufficient deoxidation. As mentioned above, if it exceeds 10%, the Mn content of the weld metal increases and hardens, resulting in deterioration of crack resistance.

Therefore, Mn was set to 3 to 10%. Further, the purpose of Fe is to increase welding efficiency, and if it is less than 10%, this effect will not be exhibited and the stability of the arc will deteriorate.

If it exceeds 50%, the arc becomes weak and the insulation properties of the coating deteriorate.

Therefore, the Fe content was set to 10 to 50%. In the present invention, perfect weldability and workability can be obtained with the above component composition, but even if CacO is added at 38% or less and one or both of SI and Tl is added at a total of 2% or less, no weldability or workability is obtained. There's nothing wrong with it.

This is used as an auxiliary agent mainly to stabilize the arc state and supplement weldability. However, if CacO3 exceeds 8%, the slag tends to flow, and if the sum of one or both of Si and Ti exceeds 2%, the arc weakens, so it is inappropriate to add more than the respective upper limit. In addition, if higher strength and toughness of the weld metal is required, one or more of Ni, Cr, ■, MO, Cu, and Nb may be added as alloy additives used in high-strength steel, weathering steel, etc. If the total amount is 10% or less, there will be no deterioration in weldability or workability.

A coating material containing the above-mentioned components can be produced by coating and drying a steel core wire using a binder such as water glass in a normal welding rod manufacturing process.

The steel core wire used in the welding rod of the present invention is ISG35.
Refers to the core wire that corresponds to Type 1 No. 1 of No. 23. Next, the effects of the present invention will be described in more detail based on Examples. 6. Coating material having the composition shown in Table 1. It was coated on a soft steel core wire of φ×70-, dried, and welding rods A-1 to A-19, B-1 to B-1 were coated.
3 was prototyped.

A wash primer coated steel plate was welded using the above test bar.

The welding conditions are shown in Table 2. Cracking resistance was determined by making a cross fillet weld crack test piece (dimensions: Wft) shown in Figure 4a, and welding it at room temperature under the welding conditions shown in Table 2 and in the welding sequence shown in Figure 4b. After the welding time, a test piece of the cross section of the weld bead was taken and the occurrence of cracks in the weld bead cross section was investigated.The test results are summarized in Table 3.The ○ mark indicates good condition, and the △ mark indicates good condition. Slightly poor, × mark means poor. 3rd
The results shown in the table are summarized as follows.

A-1 was an example containing a large amount of MgCO3, and the heat had pockmarks, resulting in a convex heat.

A-2 is MgCO. There were few pits due to poor shielding. A-3 was an example with a large amount of SIC, and the cracking resistance deteriorated due to hardening of the weld metal. A-4 had a small amount of SiC and had no oxygen reduction effect, so pits were generated. A-5
There was a lot of Al-Mg, the arc was weakened, and the heat shape was convex. A-6 had less Al-Mg and arc breakage occurred. A-7 is an example with a large amount of Mn, and the weld metal was hardened and the cracking resistance deteriorated. In A-8, the fluidity of the slag was poor due to the low Mn content, and pits were formed due to insufficient deoxidation.
A-9 had a lot of Si and the arc was weakened. A-10 is C
aF. In cases where Al--Mg was added up to the upper limit, arc breakage occurred. In A-11, since the amount of CaF2 was low, it was not possible to reduce the amount of hydrogen in the weld metal, and pits were generated. Since A-12 had a large amount of SiO2, the viscosity of the slag was excessive, and the slag became entangled with the welding rod, making the arc unstable and worsening the heat shape. A-
In No. 13, the viscosity of the slag was insufficient due to a small amount of SlO2, resulting in a convex heat shape. In A-14, the fluidity of the slag was excessive due to the large amount of TiO2, and the slag took the lead, resulting in two-stage heat. A-15 is TiO. Since the amount of slag was small and the amount of slag was insufficient, the shape of the heat became convex and the stability of the arc was also poor. A-16 was an example of a high MgO content, which resulted in rough arcs, increased spatter, and increased undercuts. A-1
7 has less MgO, so the slag encapsulation becomes uneven,
The shape of the heat became irregular and the slag peelability became poor. A-18 was an example with a large amount of Fe, and the arc was weak and the insulation of the coating was also poor. A-19 was an example in which the amount of Fe was small, and the effect of increasing the welding efficiency could not be obtained, and the arc stability was also poor. Tests B-1 to B-13 satisfied all the requirements of the present invention and passed all items.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the amount of hydrogen and oxygen in the weld metal and the tendency for pitting to occur with horizontal fillet welding time.
? - A diagram showing the relationship between the amount of Mg added and arc breakage, Figure 3 is a diagram showing the relationship between the amount of SiC and Si+C added and the amount of oxygen in the weld metal, and Figure 4 is an explanatory diagram of the cross fillet weld crack test. , Figure a is a diagram showing the shape and dimensions of the test piece, and Figure b is a diagram showing the welding order.

Claims (1)

[Claims] 1 SiC: 0.2~3.0%, Al-Mg: 0.5~
2.0%, MgCO_3: ~5-25%, CaF_2,
Total of one or more types of MgF_2 and AlF_3: 1 to 13
%, SiO_2: 10-20%, TiO_2: 5-15
%, MgO: 1-20%, Mn: 3-10%, Fe: 1
A low hydrogen-based coated arc welding rod made by adding a binder to a coating material containing 0 to 50% and coating it on a steel core wire. 2 SiC: 0.2~3.0%, Al-Mg: 0.5~
2.0%, MgCO_3, 5-25%, CaF_2, M
Total of one or more types of gF_2 and AlF_3: 1 to 13%
, SiO_2: 10-20%, TiO_25-15%,
MgO: 1-20%, Mn: 3-10%, Fe: 10-
50%, further CaCO_3: 8% or less and/or S
A low hydrogen-based coated arc welding rod made by adding a binder to a coating material containing 2% or less of i, Ti or both in total and coating it on a steel core wire. 3 SiC: 0.2~3.0%, Al-Mg: 0.5~
2.0%, MgCO_3:5-25%, CaF_2, M
Total of one or more types of gF_2 and AlF_3: 1 to 13%
, SiO_2: 10-20%, TiO_25-15%,
MgO: 1-20%, Mn: 3-10%, Fe: 10-
A low hydrogen-based coated arc made by adding a binder to a coating material containing 50% and a total of 10% or less of one or more of Ni, Cr, V, Mo, Cu, and Nb and coating it on a steel core wire. Welding rods. 4 SiC±0.2~3.0%, Al:0.5~2.0
%, MgCO_3: 5-25%, CaF_2, MgF_
Total of one or more of 2 and AlF_3: 1 to 13%, Si
O_2: 10-20%, TiO_2: 5-15%, Mg
O: 1-20%, Mn: 3-10%, Fe: 10-50
%, CaCO_3: 8% or less and/or Si, Ti
Total of one or both of: 2% or less, plus Ni, Cr, V,
A low hydrogen-based coated arc welding rod made by adding a binder to a coating material containing 10% or less of one or more of Mo, Cu, and Nb in total and coating it on a steel core wire.