JPH03118993A - Flux-cored wire for self-shielded arc welding - Google Patents

Abstract

PURPOSE:To suppress the occurrence of defects especially at the time of three o'clock multi-layer welding and to improve welding performance such as toughness and bendability by using a flux-cored wire for self-shielded arc welding obtd. by filling the flux into a steel shell under specified conditions. CONSTITUTION:In order to obtain a sound weld zone, a flux-cored wire enhancing shielding property, rendering proper physical properties to slag and having a stable rate of the flux is required. The flux filled into a steel shell is prepd. with a metal fluoride, a metal carbonate, Li, deoxidizers, iron powder, etc., as essential components and the rate of the flux is regulated. The flux-cored wire for selfshielded arc welding is obtd. by filling the flux 2 having a compsn. contg., by weight, 2-15% metal fluoride, 0.1-4% Li, 4-15% Al, 0.5-10% Mg, 0.2-8% Mn and 30-60% iron powder as essential components in 0.25-0.7 ratio of the metal fluoride to the iron powder into the steel shell 1 at 17-23wt.% rate of the flux.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a self-shielded arc welding flux-cored wire, in particular a self-shielded arc welding flux that generates less spatter and can stably obtain a sound welded part without welding defects. Concerning the inlet wire. (Conventional technology and problems to be solved) Self-shielded arc welding causes pits due to wind. It has features that make it suitable for outdoor welding, such as there is less risk of defects such as blowholes, and it is easy to handle because it does not require external shielding gas, making it a welding method suitable for construction sites. I can do it. However, although self-shielded arc welding has the above-mentioned advantages, spatter is generated in large quantities and tends to adhere to the steel plate, so it takes many man-hours to remove the spatter after welding. In addition, workability changes significantly depending on welding conditions, so advanced welding techniques are required, and in multilayer welding of thick plates, there are many chances of welding defects (slag inclusions, poor fusion), and it is difficult to maintain a sound weld. It can be said that it is extremely difficult to obtain. Defects are particularly likely to occur in the horizontal position commonly used at construction sites. For this reason, gas shielded arc welding is used for welding at construction sites. However, gas-shielded arc welding is susceptible to the effects of wind, so it is necessary to take wind-proof measures, and there are drawbacks such as the welding work having to be interrupted especially when the wind speed is strong. For these reasons, there is a desire to develop a self-shielded arc welding wire that generates less spatter and can easily produce sound welds. No. 25479 and the like have been proposed, but they are not necessarily sufficient for horizontal welding. Furthermore, Japanese Patent Publication No. 10011/1983 has a disadvantage in that a large amount of spatter is generated due to the large amount of calcium fluoride added. The present invention eliminates the drawbacks of the above-mentioned prior art and provides a self-shielded arc welding flux-cored wire that has an extremely low incidence of welding defects, especially during multilayer welding in a horizontal position, and has excellent welding performance such as toughness and bending ductility. The purpose is to (Means for Solving the Problems) In order to achieve the above object, the present inventor first analyzed the factors that tend to cause welding defects in welded parts using conventional self-shielded arc welding flux-cored wire, and found the following. It has been found that welding defects are likely to occur due to such factors. ■Since the beads are convex, narrow grooves are formed between the beads, resulting in slag inclusions and poor fusion. ■Because the beads tend to drip, a cold wrap is formed. ■Improper bead alignment causes unevenness, which can lead to poor fusion and slag inclusions. ■Since slag is baked into the bead, it is difficult to remove it sufficiently, and when welding over baked-on slag, slag inclusions and cold laps are likely to occur. ■Since the arc is not stable, it is difficult to obtain stable penetration and stable melting conditions, which can easily cause welding defects. ■If the protruding length of the wire becomes short or the arc voltage is too high, bits will occur, making it vulnerable to fluctuations in one condition and narrowing the range of welding conditions. Among these factors, ■～■ are due to the physical properties of the slag,
It is thought that (2) is due to the stability of the flux rate, and (2) is due to the shielding property6.Therefore, the present inventors strengthened the shielding property, gave the slag appropriate physical properties, and
We conducted extensive research based on the knowledge that a healthy weld can be obtained by creating a flux-cored wire with a stable flux rate. As a result, we discovered that it is possible to fill the S shell with metal fluorides, metal carbonates, Li, deoxidizing agents, iron powder, etc. as essential components and by regulating the flux rate. The present invention has been made in this way. That is, 1 the self-shielded arc welding flux-cored wire according to the present invention has a steel outer shell in which the flux cored wire is
same). Metal fluoride: 15-30% Strontium fluoride 60% or more of dimetallic fluoride Metal carbonate: 2-15% Li: 0.1-4% Al: 4-15% Mg: 0.5-10% Mn: 0.2-8% Iron powder: 30-60% However, if the flux has a composition containing metal fluoride/iron powder: 0.25-0.7% as essential components, the flux rate is 1.
It is characterized by being filled with 7 to 23 wt%. The present invention will be explained in more detail below. (Function) First, the reason for limiting the components of the flux used in the self-shielded arc welding flux-cored wire of the present invention will be explained. Clamping: Metal fluoride is a shielding agent as well as a major sludge-forming agent, and is added in a range of 15 to 30%. The shielding effect increases as the amount added increases, but the amount of spatter and fume becomes excessive, which significantly impairs welding workability. If the amount exceeds 30%, the melting point of the slag will be lowered, and in horizontal welding, the bead will tend to drip down, and this will cause cold lap. From the viewpoint of shielding properties and workability, the optimum content is 20 to 26%, but it is permissible as long as it is below the upper limit. On the other hand, the lower the amount of metal fluoride, the better the workability tends to be, but if it is too small, shielding becomes insufficient and defects such as pits and blowholes occur, so it is desirable to keep the lower limit at 15%. Note that various metal fluorides can be used. However, from the viewpoint of suppressing the amount of spatter generated, strontium fluoride is most desirable, and in order to obtain a clear effect, strontium fluoride must be added in an amount of 60% or more of the metal fluorides. Figure 1 shows the amount of spatter generated when strontium fluoride and calcium fluoride are used together, and the amount of spatter generated is approximately 50% when strontium fluoride is added at 60% or more.
It turns out that it can be reduced. Fluorides that can be used in combination with strontium fluoride are not particularly limited, but include LiF, 2SiF, NaF, and BaF2.
, CaF, etc. can be used. 4: Metal carbonate has the effect of improving the peelability of the slab and the viscosity of the slag. Therefore, a glossy bead surface is obtained, and the dripping of the bead is improved, and a uniform and smooth bead shape is obtained. Furthermore, it also acts as a shielding agent. For this purpose, the metal carbonate is added in a range of 2 to 15%. The greater the amount added, the better the slag releasability, bead shape, and shielding properties will be, but if it exceeds 15%, extremely large spatter will occur due to decomposed gas (CO□) generated during welding, making it difficult to perform one operation. Sexually undesirable. The optimal amount is 4~
7%, but up to 15% is acceptable. On the other hand, if the content is less than 2%, the slag tends to seize and the viscosity of the slag becomes low, making it impossible to obtain a uniform and smooth bead shape. The most suitable metal carbonate is CaC○, but also includes BaC0:+, 5rCO, Li,
One or more types of CO2 etc. can also be used in combination. ↓1: LL has the effect of suppressing the generation of pits due to fluctuations in arc voltage and protrusion length, so it is added in a range of 0.1 to 4%. FIG. 2 shows the results of testing a self-shielded arc welding flux-cored wire that does not contain Li using the bead-on-plate welding method, and shows the situation in which pits occur as the protrusion length becomes shorter. From the results shown in Figure 2, the protrusion length (1
Fig. 3 shows the results of a test on a self-shielded arc welding flux-cored wire containing Li. From the figure, it can be seen that Li is effective in suppressing pits and expanding the arc voltage range. However, if it is less than 0.1%, the effect will be small, and if it exceeds 4%, the slag will flow easily, and the bead will sag and become convex, especially in horizontal welding, which is not preferable. Note that Li alone is not suitable as a raw material because it reacts violently with the atmosphere. Therefore, it is preferable to use a powder alloyed with other metals as a raw material for the Li source.
l-Li is optimal. In this case, the Li content of Al-Li is desirably about 1.5 to 6%; if it exceeds 6%, the reaction with the atmosphere becomes violent and the explosiveness increases, so it is not preferable. As the raw material for the Li source, in addition to Al-Li, lithium carbonate, lithium ferrite, lithium manganate, lithium zirconate, lithium silicate, etc. can be used. Note that lithium carbonate decomposes to produce CO2 and increases the occurrence of spatter, so it is preferable to suppress it to 10% or less. By appropriately using Al-Li, lithium carbonate, or a compound other than lithium carbonate in combination, pit resistance can be improved over a wide range of conditions without impairing workability. A) Al acts as a deoxidizing agent and fixes N that has entered the weld metal to prevent pits and blowholes, so it is added in an amount of 4 to 15%. However, if it is less than 4%, pits and blowholes will occur, making it impossible to obtain a sound weld. Also, if it exceeds 15%,
This is not preferable because the amount of Aff remaining in the weld metal increases, causing the crystal grains to become coarser and significantly impairing ductility. In addition,
Al raw materials include metal aluminum, Fe-Al, An
- It is preferable to use alloys such as Mg, Al-Li, Ca-Al, etc. Ml: Mg is added in the range of 0.5 to 10% because it turns into vapor and shields the weld zone and also acts as a deoxidizing agent. However, if it is less than 0.5%, it is difficult to suppress pits and blowholes. Further, excessive addition lowers the viscosity of the slag, promotes dripping of beads, and also significantly increases the amount of fume, so it is not preferable to add more than 10%. In addition. In addition to Mg powder, Mg raw materials include AQ-Mg,
Alloys such as Fe-31-Mg and Ni-Mg are optimal. Mn: Mn acts as a deoxidizing agent and provides appropriate tensile strength to the weld metal, so it is added in a range of 0.2 to 8%. However, if it is less than 0.2%, the tensile strength will be insufficient, and if it exceeds 8%, the tensile strength will be excessive and the bending ductility will be significantly impaired, which is not preferable. In addition to Mn powder, Mn raw materials include Fe-Mn,
Alloys such as FeFe-8i- are suitable. Note: Iron powder increases the fluidity of flux, making the flux rate stable. Also, as a function during welding. It is thought that it plays the role of heat conduction and promotes the melting of the metal fluoride. Therefore, iron powder stabilizes the arc and provides a stable molten state.
Add in a range of 0%. However, if it is less than 30%, the formation of flux columns is observed, which is not preferable for suppressing welding defects, and there is a problem of increased spatter. Moreover, if it exceeds 60%, the amount of metal fluoride added is relatively reduced, causing problems such as a reduction in shielding, which is not preferable. Note that the bulk specific gravity of the iron powder is preferably 2.5 to 3.7%, and there are no particular restrictions on the components. The present inventor investigated welding phenomena in relation to metal fluoride, which is a major slag-forming agent for iron powder. It has been found that the ratio of (metal fluoride)/(iron powder) has a close relationship with the arc condition, and is extremely effective in the range of 0.25 to 0.7%. That is, as shown in FIG. 4, when the ratio of (metal fluoride)/(iron powder) exceeds 0.7%, the stability of the arc is impaired and the amount of spatter generated tends to increase. On the other hand, 0
．． If it is less than 25%, shielding failure etc. will occur. The feature of the present invention is that this ratio is defined. The desired welding performance can be obtained by filling the flux having the above composition into a steel shell at the following flux rate. λj Ekosu: The flux rate in the wire configuration should remain within the range of 17-23%. If it is less than 17%, the necessary amount of slag cannot be secured, resulting in deterioration of workability. Also, 2
If it exceeds 3%, wire breakage will occur during wire drawing, making efficient production impossible, and should be avoided. In addition, in the present invention, the following components can be added as needed to manufacture the flux-cored wire. Ni: Since Ni improves toughness, it is added at 0.0% per total weight of the wire.
It can be added in a range of 2 to 3%. However, if it is less than 0.2%, no effect will be obtained, and if it exceeds 3%, the tensile strength of the welded metal will become excessive and the toughness will be impaired, which is not preferable. Ti, Zr: Since Ti and Zr improve toughness, they can be added to the flux in a range of 0.1 to 2%. However, if it is less than 0.1%, no effect can be obtained, and if it exceeds 2%, the tensile strength of the weld metal becomes excessive, which impairs toughness, which is not preferable. Note that Ti and Zr can provide similar effects, so
Can be used alone or in combination. F/CoW Lr: It is recommended that the moisture content of the wire is in the range of 300 to 2000 ppm. If it is less than 300 ppm, it will have poor shielding properties, and if it exceeds 2000 ppm, it will have poor pit resistance. Each has problems in terms of cracking. Note that the moisture content of the wire is a value measured according to JIS K 0113 (1979). The wire of the present invention has a steel outer sheath filled with a flux mixed with the above components, and the chemical composition of the outer sheath is not particularly limited, but Sj: 1% or less, Tot
alN: Desirably has a composition of 100 ppm or less. These components tend to affect the arc characteristics and increase the amount of spatter generated, and N in particular causes pits and blowholes, so it is desirable to control them as described above. Furthermore, the method for manufacturing the self-shielded arc welding flux-cored wire of the present invention is not particularly different from the method for manufacturing ordinary flux-cored wires, and can be produced in the same manner. Further, the cross-sectional shape of the wire is not particularly limited, and wires having the cross-sectional shape illustrated in FIG. 5 can be used. (b) is better in terms of workability. Wire diameters of 1.2 to 2.4 mm + φ are applicable, but from the standpoint of ease of use and performance, we especially recommend wire diameters of 1.6 mm φ and 2 mm.
．． 0mmφ is good. The target steel types are mainly mild steel, HT-50, and low temperature steel, but are not particularly limited. The polarity is preferably positive (D CE N). Next, examples of the present invention will be shown. (Example) According to the specifications shown in Tables 1 and 2, the wire diameter is 2 mmφ.
A flux-cored wire was created. The cross-sectional shape of the wire is as shown in FIG. 5(c), and the steel outer skin component is C:0.
07%, Mn: 0.3%, Si: 0.1%, Cr:
0.05%, T, N near 0 ppm, etc. Next, using this flux-cored wire, semi-automatic welding of a 25 m+nt V-shaped groove (gap 6III+, groove angle 35°) was performed in a horizontal position, and the performance and workability of the welded part were investigated. The welding conditions are DCEN, 300A.
-24 to 26V1'. Workability was evaluated based on observations made during the preparation of test plates. Table 3 shows the test results, which are discussed as follows. Nα1 to Na1O are examples of the present invention, and all have workability (
Bead shape, slag removability, arc stability, spatter,
Good results have been obtained, with excellent welding performance (strength, bending ductility, toughness, and welding defects). In particular, the reduction in spatter generation was remarkable. Nα11 to Ha12 are comparative examples in which the blending ratio of metal carbonate is not appropriate; if it is too large, the arc becomes unstable, the amount of spatter is large, and the welding performance is not good. If it is too small, the bead shape and slab peelability will be poor, and the welding performance will also be poor. Na13 to Nct14 are comparative examples in which the amount of metal fluoride compounded is not appropriate, and if it is too much, there will be a lot of spatter and welding workability will be poor. If it is too small, welding defects will increase. Nα15 to Na16 are comparative examples in which the blending amount of Li is not appropriate, and if it is too small, there will be many pits and the welding performance will be poor. Too much will result in poor bead shape and poor welding performance. Nα17 to N018 are comparative examples in which the ratio of (metal fluoride)/(iron powder) is not appropriate; if this ratio is too high, there will be a lot of spatter, and if this ratio is too low, the welding performance will be poor. Nα19 to Nα2o are comparative examples in which the blending ratio of Mg or Al is not appropriate, Nα21 to Nα22 are comparative examples in which the blending amount of Mn or Ni is too large, and Nα23 to Nci24
is a comparative example in which the blending ratio of iron powder was not appropriate, and good results were not obtained in any of the comparative examples. Also, 425 is (strontium fluoride)/(metal fluoride)
This is a comparative example with an inappropriate ratio of , and good results were not obtained.

[Left below]

(Effects of the Invention) As detailed above, according to the self-shielded arc welding flux-cored wire of the present invention, it is possible to easily obtain a sound weld. , bending performance, etc.) can be dramatically improved in the soundness of horizontal welds whose properties have not been sufficiently guaranteed.

[Brief explanation of drawings]

Figure 1 shows the relationship between the (strontium fluoride)/(metal fluoride) ratio and the amount of spatter generated, and Figure 2 shows the protrusion length of a conventional flux-cored wire (without LL additives). Figure 3 shows the relationship between the Li content, the number of pits, and the upper limit voltage at which pits do not occur in the flux-cored wire of the present invention. Figure 4 shows (metal fluoride) / (iron powder) and the amount of N in the sputtered and welded metal, Figure 5 (a) ~
(d) is a diagram showing an example of the cross-sectional shape of a flux-cored wire. 1...Sheath metal, 2...Flux.

Claims (5)

[Claims] (1) In the steel shell, in weight percent (the same applies hereinafter): Metal fluoride: 15-30% Strontium fluoride: 60% or more of metal fluoride Metal carbonate: 2-15% Li: 0. 1-4% Al: 4-15% Mg: 0.5-10% Mn: 0.2-8% Iron powder: 30-60% However, metal fluoride/iron powder: 0.25-0.7% A flux with a composition containing as an essential component has a flux rate of 1
A self-shielded arc welding flux-cored wire, characterized in that it is filled with a flux of 7 to 23 wt%. (2) The self-shielded arc welding flux-cored wire according to claim 1, containing 0.2 to 3% Ni based on the total weight of the wire. (3) 0.1 or more of Ti or Zr in flux
The self-shielded arc welding flux-cored wire according to claim 1, containing ~2%. (4) The self-shielded arc welding flux-cored wire according to claim 1, wherein the wire has a moisture content of 300 to 2000 ppm. (5) Al-Li alloy as a Li source (Li content: 1.
5-6.5%) self-shielded arc welding flux-cored wire according to claim 1.