JPH0362518B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a flux-cored wire for self-shielded arc welding, and more particularly, it relates to a flux-cored wire for self-shielded arc welding, and more specifically, a flux-cored wire for self-shielded arc welding.
This invention relates to a low-silicate Li-based flux-cored wire for self-shielded arc welding. (Conventional technology and problems to be solved) Many technologies have been proposed for a long time as flux-cored wires for self-shielded arc welding, and the main flux types are fluoride-based and Li oxide. There are two types of systems. As the gas generating agent for the former fluoride wire, CaF ₂ and BaF ₂ are mainly used, and a small amount of carbonate is also used. Since this type contains a large amount of fluoride, it generally has good slag removability and bead appearance, but because the arc is unstable, spatter is extremely common. Further, the amount of fume generated is extremely large, making welding work difficult, which is a disadvantage. On the other hand, the latter Li oxide wire uses Li oxide as a gas generating agent, so it does not require much fluoride. Therefore, the amount of spatter and fume generated is slightly improved compared to the above-mentioned fluoride wire. As a typical technology for this Li oxide wire,
Japanese Patent Publication No. 62-25479 (Arc Welding Electrode, Lincoln Company) has been proposed. In this, CaF ₂ , BaF ₂ , and NaF are used as fluorides, and 6.3% (the total amount of these fluorides per weight of the electrode) is indicated as a preferable amount. In general, it is possible to suppress the amount of spatter and fume generated by reducing the amount of fluoride added, but since the former fluoride wire can cause pits and blowholes, It is technically difficult to make it extremely low. On the other hand, with the latter Li oxide wire, when the amount of fluoride added is small, pits and blowholes do not occur, but on the contrary, the fluidity of the slag becomes poor, and poor fusion and slag inclusions are likely to occur.
It becomes impossible to perform sound welding. In addition, welding work is difficult because slag sticks to the bead surface and is difficult to remove. Furthermore, flux-cored wire for self-shielded arc welding generally has problems with power supply characteristics.
Compared to gas-shielded arc welding, there is a problem in that stable welding is difficult, especially when using small diameter wires. That is, the conventional fluoride wire is generally welded with an AC or DC power source with drooping characteristics,
Recently, with the spread of CO ₂ gas welding, power supplies with DC constant voltage characteristics have come to be used, and they have also come to be applied to welding self-shielded wires. However, considering that ordinary gas-shielded arc welding has deep penetration and good workability, welding is generally performed with DC reverse polarity, so reverse polarity is also applied in self-shielded welding. However, since there are many spatters and workability is poor, welding is often performed with positive polarity due to arc characteristics. Moreover, since positive polarity tends to cause the arc to become unstable, particularly when a thin wire of 1.6 mmφ or less is used, the instability of the arc becomes significant and stable welding cannot be performed. On the other hand, although small-diameter wires are desired because they are easy to weld, they are rarely used because of the problems described above. The present invention was made in order to solve the above-mentioned problems regarding flux-cored wires for self-shielded arc welding, especially Li oxide wires, and has low spatter and improved slag fluidity and slag peelability. To provide a Li-based flux-cored wire for self-shielded arc welding that is excellent, has good workability, provides a sound welded part, and can be stably welded with either direct current reverse polarity or positive polarity regardless of the wire size. The purpose is to (Means for Solving the Problems) In order to achieve the above object, the present inventor discovered that although the amount of spatter can be reduced by reducing the amount of fluoride added in the Li oxide system as described above, the fluidity of the slag As workability such as peelability is poor, as a result of intensive research to find a compensation method that can prevent problems associated with reduction of fluoride, we have found that
It was discovered that by regulating the amount of SiO ₂ in relation to the amount of lithium composition, it was possible to prevent the deterioration of workability due to the reduction of fluoride.Based on this knowledge, the wire configuration was studied in more detail, and the present invention was developed. This is what was done. That is, the present invention reduces totalN to 100 ppm or less,
The steel shell, which limits Si to 1% or less, contains 0.5 to 6% total SiO ₂ based on the total flux weight, suppresses total F to 3% or less, and contains lithium ferrite, lithium aluminate, and lithium. Lithium composition consisting of one or more of silicate, lithium titanate and lithium manganate is 10 to 25 as Li ₂ O
% (however, Li ₂ O / SiO ₂ ≧2.5), Al: 15 to 25%, Mg: 5 to 10%, Mn: 0.5 to 5%, Zr: 0.5 to 5%, Ti: 0.5 to 5%. If necessary, a flux containing 1.5% or less of at least one type of Li metal in the form of Al-Li and Mg-Li is added at a flux rate of 12 to 30.
%.
The gist is Si, low F type flux-cored wire for self-shielded arc welding. The present invention will be explained in more detail below. First, the reason for limiting the components of the flux composition will be explained. Note that the amounts of each component are per total weight of flux. Lithium composition (Li ₂ O): The lithium composition in the present invention contains Li ₂ O and other oxides (iron oxide, Al oxide, Si oxide and
(one or more types of Mn oxides), and is contained in a range of 10 to 25% as Li ₂ O. Li ₂ O decomposes during welding and acts as a shielding agent. It is effective in preventing welding defects such as pits and blowholes, and is also effective in removing slag. It is necessary to add it so that However, if it exceeds 30%, the amount of fume increases, which is not preferable. Other oxides combined with Li ₂ O affect arc stability, slag fluidity, and slag removability, so a suitable blending ratio is required. That is, since lithium ferrite produces a relatively fluid slag without impairing the stability of the arc, it is essential as a main raw material for a Li ₂ O replenishment source, and it is desirable to add about 30 to 60%. Although lithium aluminate does not impair the stability of the arc, it increases the viscosity of the slag and causes slag entrainment, so it is best to add it in an amount of 8% or less. Lithium silicate reduces the "wetting" angle of the bead and exerts a good effect, but if it is too large, the slag releasability becomes extremely poor, so it is desirable to add 8% or less. Lithium titanate impairs slag releasability and slag fluidity, so it is best to add it in an amount of 10% or less. Lithium manganate gives good results to the fluidity of the slag and the peelability of the slag, but if it is too large, it impairs the arc stability and increases the amount of spatter, so it is best to add 10% or less. Note that, as Li ₂ O in the above-mentioned lithium composition, those shown in Table 1 are usually used.

[Table] Lithium sources other than the above lithium compositions may include Li ₂ CO ₃ , Al-Li, Mg
−Li metal powder (metallic lithium source) can be used, and it is preferable to use a metallic lithium source. That is, since Li ₂ CO ₃ decomposes during welding and produces only Li ₂ O as an oxide, the fluidity of the slag and the peelability of the slag can be improved. However, if it is added too much, spatter will increase, so if it is added, it should be kept at 20% or less. Al-Li and Mg-Li have a large shielding effect,
A shielding effect 2 to 3 times greater than the equivalent Li in the lithium composition can be obtained. It is also effective in improving workability, and the following effects can be obtained. (1) Increases arc stability and reduces spatter generation. (2) It is also effective in improving slag fluidity and slag peelability. These Al-Li and Mg-Li compounds can be used alone as shielding agents, and can also be used in combination with the above lithium composition. When added, at least one of them should be kept at a Li content of 1.5% or less. _totalSiO2 : _SiO2 is necessary to adjust the viscosity of the slag and obtain a good bead shape with a small wetting angle. However, if it is less than 0.5%, the bead shape becomes convex,
In addition, in the vertical position, slag flows easily;
If it exceeds %, although the bead shape is good, slag sticking occurs and it is difficult to remove the slag. Note that as the SiO ₂ source, in addition to lithium silicate and ordinary silicates, Si alloy can be used in terms of SiO ₂ . Therefore, total SiO ₂ is in the range of 0.5 to 6%. Incidentally, SiO ₂ and Li ₂ O have a close relationship with the fluidity of slag and the removability of slag, and as a result of various studies, the present inventor found that good results were obtained when Li ₂ O / SiO ₂ was set to 2.5 or more. Obtained. This ratio is preferably 3.6~
15. F: Since fluoride increases the amount of spatter and has an unfavorable effect on workability, it is desirable to adjust the F gas in the fluoride to 3% or less. Note that, as the fluoride, fluorides of alkali metals and alkaline earth metals are suitable, but other fluorides are not excluded. Al: Al acts as a deoxidizing and denitrifying agent.
% or less, welding defects such as pits and blowholes occur, which is not preferable. Furthermore, if it is added in an amount exceeding 25%, the amount of Al in the weld metal increases, resulting in a decrease in impact value, which is not preferable. Therefore,
Al should be in the range of 15 to 25%. Me as an Al source.
Al, Fe-Al, Al-Mg, etc. can be used. Mg: Mg generates metal vapor during welding, shields the arc column and molten pool, and has the effect of stabilizing the arc. However, if it is less than 5%, there is no such effect, and if it exceeds 10%, the amount of fume generated becomes excessive, resulting in poor workability. Therefore,
Mg is in the range of 5 to 10%. As a Mg raw material
Me.Mg, Al-Mg, Fe-Mg, Ni-Mg, etc. can be used. Zr: Zr is a deoxidizing and denitrifying agent and can prevent pitting and blowholes. However, if it is less than 0.5%, there is no effect, and if it exceeds 5%, the slag products will inhibit the slag removability, which is not preferable. Therefore, Zr should be in the range of 0.5 to 5%. As a Zr source
Fe-Zr is optimal, but other alloy powders may also be used. Ti: Ti is a deoxidizing and denitrifying agent and can prevent pits and blowholes. However, if it is less than 0.5%, the effect will not be sufficient, and if it exceeds 5%, the slag product will inhibit the fluidity of the slag, which is not preferable. Therefore, Ti should be in the range of 0.5 to 5%. Mn: Mn is an effective element that acts as a deoxidizing agent together with Si, improving the cleanliness of the deposited metal, and providing the necessary tensile strength and impact performance. But 0.5%
If it is less than 5%, a sufficient effect cannot be obtained, and if it exceeds 5%, the tensile strength becomes too high and the impact performance becomes low, which is not preferable. Therefore, Mn is 0.5 to 5
% range. Me.Mn, Fe as Mn raw material
-Mn, MnO, or a compound or composition containing MnO can be used in terms of Mn. Although good results can be obtained with a flux composition containing the above components, it is permissible to add the following components as necessary. C: C increases arc stability, helps reduce the amount of spatter, and can improve slag encapsulation. However, since adding more than 1% increases the tensile strength more than necessary, the content of C is set to 1% or less. Although graphite is most suitable as a C source, similar effects can be obtained with alloy powder. Iron powder: It is effective to add iron powder when you want to increase the amount of welding or change the fluidity of flux.
However, as the ratio of iron powder increases, the required element ratio decreases, making it impossible to obtain the desired performance.
Excessive amount of iron powder should be avoided, and iron powder should be added at 30% or less. MgO: Addition of MgO tends to favor slag fluidity and slag release properties. but,
If it exceeds 5%, it will encourage the occurrence of spatter, so
MgO should be 5% or less. MgO as a raw material for MgO
Silicates alone or containing MgO are desirable. CaO: Addition of CaO tends to favor slag fluidity and slag release properties. However, 3
If it exceeds %, it will encourage spatter.
CaO shall be 3% or less. As a raw material for CaO,
CaCO ₃ , Ca−Si, Re.Ca−Si, etc. are preferable,
It can be used by converting it into CaO. The wire of the present invention has the above-mentioned flux filled in a steel jacket, and this jacket component is an important component in achieving the performance of the wire of the present invention. According to the inventor's experimental research, Si
It was found that it was necessary to create a steel shell with a composition that regulated the amount of N to 1% or less and the total N to 100 ppm or less.
These components tend to affect the arc characteristics and increase the amount of spatter, especially in total N.
Since this can cause pits and blowholes, the maximum allowable value has been set as described above. Also, the flux rate in wire configuration is 12-25%
It needs to be within the range. If the flux rate is less than 12%, it will not be possible to secure the required amount of slag, and workability will deteriorate. Moreover, if it exceeds 25%, wire breakage will occur during wire drawing, making efficient production impossible, so it should be avoided. Note that the method for manufacturing the wire of the present invention is not particularly different from the method for manufacturing ordinary flux-cored wires, and can be manufactured in the same manner.
Further, there are no particular restrictions on the cross-sectional shape of the wire. Furthermore, since the flux-cored wire for self-shielded arc welding of the present invention has the above-mentioned configuration, it can be used with either DC reverse polarity or positive polarity, and can perform stable welding even with particularly small diameter wires. can. Next, examples of the present invention will be shown. (Example) Fluxes with the ingredient combinations shown in Table 3 at the mixing ratios shown in Table 2 were: C: 0.07%, Si: 0.30%,
Mn: 0.40%, P: 0.023%, S: 0.08%, N:
0.005%, Al: 0.04%, Ti: 0.01% chemical composition filled steel shell with flux rate of 19% to 1.2mm.
A flux-cored wire of φ was made, and the welding current was 280A and the voltage was
Welding tests were conducted under the conditions of 25V and a speed of 30cpm with reverse polarity of DC. During the welding test, slag removability and slag fluidity were examined, and after the welding test, the amount of spatter generated was measured, and weld defects and bead shapes were examined. The results are also listed in Table 3. In addition, slag fluidity and slag removability were observed and evaluated during lamination. The amount of spatter generated was determined by repairing and weighing the entire amount, and after repairing the spatter, the bead shape was evaluated by observing. For evaluation of weld defects,
The X-ray transmission test was carried out using V with a joint angle of 50° and a gap of 5mm.
Development was conducted on a product finished with 4 layers and 7 passes (19 mm thickness) and evaluated. In Table 3, No. 1 to No. 3 are comparative examples,
Although reducing the fluoride content is effective in suppressing spatter, it results in a loss of slag removability. It can also be seen that slag inclusions are likely to occur due to the high viscosity of the slag. In Comparative Example No. 4, lithium silicate and Li ₂ CO ₃ were excessive, so the amount of slag burning and spatter was large. Comparative example No. 5 has less Li ₂ O and Li ₂ O/
Since the SiO ₂ ratio is small, pits and blowholes occur frequently, and slag removability is poor. In Comparative Example No. 8, since the amount of SiO ₂ is small, the bead shape becomes convex, and poor fusion tends to occur. Comparative Example No. 12 has less Mg, so the arc concentration is poor and the amount of spatter generated is large. Comparative examples No. 13 to No. 15 have less Al, Ti, and Zr, so
A pit has occurred. On the other hand, No. 6, No. 7, No. 9 to No. 11, and No. 7 of the present invention examples.
Good results were obtained for all samples No. 16 to No. 21.

【table】

【table】

[Table] (Effects of the Invention) As detailed above, the flux-cored wire for self-shielded arc welding of the present invention has a specific composition of Li-based low fluoride and low silicate type, so spatter is generated. The amount is small, the slag has excellent fluidity and slag removability, and it is possible to obtain a sound welded joint with good workability. Moreover, it can be used with either DC reverse polarity or positive polarity, and even small diameter wires can be stably welded.

[Brief explanation of drawings]

FIGS. 1 and 2 are views showing a welding apparatus used in an example, with FIG. 1 being a side view and FIG. 2 being a plan view. DESCRIPTION OF SYMBOLS 1...Wire control device, 2...Torch, 3...Observation window, 4...Spatter repair device, 5...Traveling trolley.

Claims (1)

[Claims] 1 In terms of weight percentage (the same applies hereinafter), totalN
Total SiO2: _0.5 ~ per total weight of flux in a steel shell with Si regulated to 100ppm or less and 1% or less
6% and suppresses totalF to 3% or less, and is composed of lithium ferrite and one or more of lithium aluminate, lithium silicate, lithium titanate, and lithium manganate _. as 10~25
% (however, Li ₂ O / SiO ₂ ≧2.5), Al: 15 to 25%, Mg: 5 to 10%, Mn: 0.5 to 5%, Zr: 0.5 to 5%, and Ti: 0.5 to 5%. The flux rate is 12 to 30.
%.
Si, low F type flux-cored wire for self-shielded arc welding. 2 In a steel shell with total N regulated to 100 ppm or less and Si regulated to 1% or less, per total flux weight,
totalSiO ₂ : A lithium composition containing 0.5 to 6%, suppressing totalF to 3% or less, and consisting of lithium ferrite and one or more of lithium aluminate, lithium silicate, lithium titanate, and lithium manganate. 10~25 as _Li2O
% ( _Li2O / _SiO2 ≧2.5), Al: 15-25%, Mg: 5-10%, Mn: 0.5-5%, Zr: 0.5-5%, Ti: 0.5-5%, Li A flux containing at least 1.5% of at least one metal in the form of Al-Li and Mg-Li, with a flux rate of 12 to 30%.
It is characterized by being filled so that
Si, low F type flux-cored wire for self-shielded arc welding.