JPS6129834B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a melt-type flux for submerged arc welding that forms a slag with good peelability and provides a weld metal with good toughness. As a high-speed welding method for thin plates, submerged arc welding using a flux containing SiO ₂ or MnO as the main components is known.
By adjusting the ratio given by SiO ₂ /MnO, there is an advantage that welding workability (for example, slag removability) and mechanical properties of the welded part can be adjusted relatively freely. In other words, the flux can be selected depending on the intended use. However, in cases where it is difficult to remove slag, such as when welding the inner surface of a spiral pipe, or when multiple welding passes are overlapped in succession, such as when welding the body and end plate of a cylinder, slag peeling is difficult. Although it is necessary to place particular emphasis on performance, other performances cannot be ignored, and the reality is that slag removability must be sacrificed to some extent. The present invention has been made with attention to these points, and it does not deteriorate the mechanical properties of the welded part.
The object of the present invention is to provide a melting type flux for submerged arc welding that can significantly improve slag removability. That is, the flux according to the present invention is SiO ₂ :
20-60%, MnO: 20-60%, CaO: 20% or less,
MgO: 20% or less, Al ₂ O ₃ : 1-30%, CaF ₂ : 20
% or less, BaO: 0.01 to 4%, and Pb and/or
Bi: Compounded in the form of oxide or fluoride, and
It contains 0.01 to 0.2% in terms of Pb and/or Bi, and the ratio given by SiO ₂ /MnO is 0.7.
~2.6. In addition, in order to alleviate the tendency for impact resistance to decrease, which is a drawback especially when Bi is added,
The present invention includes the addition of TiO ₂ and FeO. The reason for blending each component in the flux of the present invention and the reason for setting each range will be described below. SiO ₂ :20-60% Together with MnO, it constitutes the base of the flux of the present invention, and if it is less than 20%, it becomes difficult to melt in relation to the amount of MnO blended. Moreover, if it exceeds 60%, melting becomes difficult for the same reasons as above, and the amount of oxygen in the weld metal increases, and slag entrainment occurs frequently, resulting in deterioration of the mechanical properties of the weld metal. Furthermore, a more preferable upper limit is about 35%, considering the purpose of suppressing the tendency of slag to seize. MnO: 20-60% When MnO is added, the amount of Mn in the weld metal tends to increase, which greatly contributes to balancing toughness and tensile strength and preventing hot cracking. Furthermore, since the thickness of the slag increases, the residual stress in the slag increases and the peelability improves. However, if it is less than 20%, these effects will not be exhibited, and if it exceeds 60%, melting will become difficult. SiO ₂ /MnO: 0.7 to 2.6 Select from the above range depending on the location and purpose of flux application, but as SiO ₂ /MnO increases, the bond between slag and weld metal increases and the slag itself becomes thinner. The internal stress due to this decreases, and the self-separation force becomes poor. Therefore, from the viewpoint of slag removability, it is desirable to make the size small, but if the size is made small, the following problems arise. (1) The viscosity of the slag decreases, and in extreme cases, the bead ripples become disordered and humping (beads become serpentine) becomes more likely. Therefore, from the viewpoint of the bead condition, it is desirable to keep the ratio between 0.7 and 1.5, and within this range, it is recommended to use a ratio on the smaller side to improve the spread of the bead. Ru. (2) The melting point of the flux decreases, making it easier to melt; the viscosity of the slag decreases, causing surrounding unmelted flux grains to stick together or being more likely to undergo secondary melting; or the arc becoming more likely to spread; Since the specific gravity of MnO is about twice that of SiO ₂ , even if the same volume of slag is produced, the weight increases, etc., and the amount of flux consumed increases. From this point of view, the lower limit of the ratio given by SiO ₂ /MnO was set at 0.7. On the other hand, the upper limit was set at 2.6 as a limit that does not adversely affect slag removability. Therefore, by adjusting each of the above properties within the range of 0.7 to 2.6, and by varying SiO ₂ /MnO, the content of Si, Mn, O, etc. in the weld metal is controlled, and the Charpy impact value and tensile strength are Adjustment of mechanical properties such as strength is recommended. CaO: 20% or less It is blended as an auxiliary component to SiO ₂ and MnO, and has the effect of adjusting the viscosity of slag and improving basicity, and as a result, can improve the mechanical properties of weld metal. . But 20
If it exceeds %, the viscosity decreases too much, causing bead constriction (a condition in which the bead width becomes locally narrow) and disordered bead ripples. MgO: 20% or less It has the function of increasing the basicity of flux and preventing an increase in oxygen content in the weld metal. However, when it exceeds 20%, the viscosity of the slag increases rapidly, resulting in frequent undercuts, as well as the formation of pits and blowholes due to flux crystallization and increased hygroscopicity. Al ₂ O ₃ : 1 to 30% 1% or more is required to exhibit the function of increasing the viscosity of the slag and adjusting the appearance of the bead. Furthermore, in the case of a flux that incorporates TiO ₂ , TiO2 is incorporated into the weld metal.
It also exhibits the function of promoting reduction addition, and addition of 1% or more is also desired (the significance of adding TiO ₂ will be described later). However, if it exceeds 30%, the viscosity becomes excessive and pockmarks, waviness, etc. occur on the bead surface. Since the bead shape was affected by the ratio of the Al ₂ O ₃ content to the SiO ₂ content, it is desirable that the ratio be 1/15 to 1/3. CaF ₂ : 20% or less Has the function of reducing the oxygen content in the welding arc cavity and in the weld metal, improving the mechanical properties of the weld metal. Furthermore, since the melting point of the flux itself is lowered, melting is easy and the bead shape is improved. Although there is no lower limit for exhibiting the above effects, a blending amount of 2% or more is preferable. On the other hand, if it exceeds 20%, slag burning tends to occur. Pb and/or Bi: 0.01-0.2% These are oxides such as Bi ₂ O ₃ and PbO, or BiF ₃ and
Although it is blended as a fluoride such as PbF ₂ , it dissociates due to arc heat and produces Bi and Pb with high vapor pressure. That is, Bi and Pb have a low melting point and generate Bi and Pb vapor even during the solidification process of the slag, filling the space between the slag and the beads and preventing the slag from seizing. In order to exhibit such an effect, Bi and Pb must be used.
0.01% or more is required. Generally, slag seizure occurs when the SiO ₂ /MnO ratio is high.
More specifically, this becomes noticeable when the ratio exceeds 1.05, but at the same time, there is also the problem that as the ratio increases, the Shalpy impact value decreases. On the other hand, since Pb and/or Bi, especially Bi, is an element that worsens the Shapey impact value, the more Bi is required in areas where seizure prevention is required (areas where the SiO ₂ /MnO ratio is high and the Shapey impact value is low). It is a very ironic situation that the oxidation property increases, and in order to alleviate this inconvenience, the upper limit of Bi should be set at 0.2%, and the ratio given by SiO ₂ /MnO should be 1/25.
The following is desirable. Note that the mechanical property deterioration tendency due to Bi is also compensated indirectly by the aforementioned Al ₂ O ₃ . In addition, the upper limit for Pb should be set in the same way as for Bi, since the bead surface becomes backskin-like due to excessive blending. BaO: 0.01 to 4% It has the effect of promoting the decomposition of Bi and Pb oxides or fluorides, and is an essential component for expressing the above-mentioned effects of Bi and Pb. Therefore, the amount of Bi and Pb added as oxides or fluorides can be kept low as mentioned above, and in particular, the decrease in the Sharpy impact value due to Bi can be suppressed as much as possible, and cracking of the weld metal due to Bi segregation can be suppressed. is also suppressed as much as possible. The minimum amount of BaO required to exhibit the above-mentioned decomposition promoting effect is
It is 0.01%. On the other hand, the upper limit is 4%;
%, blowholes and pits occur frequently. TiO ₂ :30% or less It is a source of Ti supply to the weld metal and improves the toughness of the weld metal. Furthermore, since it has the function of making the flux easier to melt without significantly lowering the viscosity of the slag, it is a particularly suitable component for high-grade steel welding fluxes or high-speed welding fluxes. Furthermore, as mentioned above, when Bi ₂ O ₃ or the like is added, the mechanical properties of the weld metal deteriorate, so TiO ₂ is a significant component in the sense of compensating for this. in this case
The standard is to mix TiO ₂ in an amount of at least 5 times the amount of Bi ₂ O ₃ , but if it is mixed in more than 30% of the total flux, the viscosity of the slag will become too low and the bead ripples will become irregular. Instead, the precipitation of Ti compounds tends to cause embrittlement of the weld metal and slag seizure. FeO: 0.1 to 10% FeO decomposes in an arc atmosphere and supplies oxygen to the molten steel, reducing oxidation of C, Si, Mn, etc. in the molten steel. As a result, the impact value of the weld metal is improved.
In addition, it is a substance with the same effect as TiO ₂ in the sense of compensating for the deterioration of mechanical properties caused by Bi ₂ O ₃ and the like. In order to achieve the above effect, the content must be at least 0.1%, but if it exceeds 10%, the viscosity of the slag becomes too low and the bead edge becomes meandering. Although the essential component composition of the present invention has been explained above, the following components can be further blended into the flux. ZrO ₂ : 20% or less Can be substituted for part of SiO ₂ or Al ₂ O ₃ as an acidic or neutral component. Although ripples on the bead surface can be suppressed or smoothed, if it exceeds 20%, the viscosity of the slag becomes excessive, causing bead undulations and pockmarks. Na ₂ O, K ₂ O: 5% or less This exhibits an arc stabilizing effect, but if it exceeds 5%, the hygroscopicity of the flux increases, causing pits and blowholes. Li ₂ O: 5% or less Since it reduces the viscosity of slag, it can be partially substituted for CaF ₂ . However, if it exceeds 5%, it has the disadvantage of increasing the hygroscopicity of the flux. The above-mentioned flux is usually provided as a molten type, and although there are no restrictions on the manufacturing method, generally all the raw materials are mixed uniformly and melted while being poured into a melting crucible little by little. If manufactured in this manner, segregation of Bi ₂ O ₃ and PbO in the flux will be reduced, and segregation of Bi and Pb in the weld metal will be prevented from the stage where it occurs. When a flux having the above-mentioned structure was adopted, the slag removability was improved without adversely affecting the properties of the weld metal or the bead shape, and welding workability was significantly improved. Although there are no particular restrictions on the welding wire used in combination with the above-mentioned flux, particularly preferred wire compositions are as follows. C: 0.3% or less Si: 0.6% or less Mn: 0.2-3% O: 0.001-0.05% N: 0.001-0.05% P: 0.1% or less S: 0.1% or less In addition to the above compositions Ti: 1% or less Al: Examples include wires containing 0.1% or less, Mo: 0.5% or less, and Soluble B: 0.001% or less. First, an experimental example will be shown. Experimental Example 1 Melting type flux (F-
1) to (F-6) were prepared (all comparative fluxes), and the relationship between SiO ₂ /MnO and the state of slag exfoliation was investigated. As a consumable electrode, 2.4 mmφ high Mn type (C: 0.10%, S: 0.03%, Mn: 1.91%, O:
0.006%, N: 0.05%), DC, 400A x 30V
×100cm/min condition SS-41 steel plate with black skin (9
mm ^t ) on which a bead-on plate was formed.
The results are shown in Table 1, and SiO ₂ /
When MnO was less than 0.67, the slag warped into an arch shape immediately after welding and spontaneously peeled off, but at 0.87, natural peeling did not occur during welding, and external force was applied with a scale hammer etc. after the test plate came to room temperature. In most cases, it could be removed without much difficulty. or
When the value exceeded 1.10, it could not be easily removed by hitting with a hammer, etc., and baked-in slag was observed over the entire length of the bead and edge.

[Table] Experimental example 2 For the raw material of the flux (F-4) composition in Table 1
Bi ₂ O ₃ was added and mixed uniformly, and the fluxes (A-1) to (A-11) (Table 2) were prepared by adding it little by little into the melting crucible, and the fluxes were heated under the same conditions as in Experimental Example 1. The slag removability was investigated while forming a bead on plate. At the same time, high Mn welding wire (components are the same as before: 4.0 mmφ) was used on a 12 mm ^t black mild steel plate (SS-41), BP: AC, 700 A x 35 V.
×60cm/min and FP: AC, 800A×36V×55cm/
One butt welding was performed at 1 min, and a sharpie impact test was conducted. The changes in welding workability are shown in Table 2, and the slag removability was slightly improved with Bi ₂ O ₃ :0.013% (A-2), and considerably improved with Bi 2 O 3 :0.03% (A-3). Also 0.07% (A-4) to 0.38% (A-8)
The range has been greatly improved. On the other hand, bead skin maintains its luster up to 0.19% (A-6), but 0.27%
(A-7) does not lose its luster, 0.43% (A-9)
As it goes higher, it feels a little rougher, 0.67%
(A-10) gives an appearance similar to backskin, and at the same time begins to have an adverse effect on slag removability. On the other hand, looking at the results of the Charpy impact test, it is found that as Bi ₂ O ₃ increases, the impact values vary, and especially when it exceeds 0.2%, the difference between the maximum and minimum values becomes extremely large. This seems to be based on the segregation of Bi.

[Table] Example 1 According to the experiments conducted so far, the effect of Bi ₂ O ₃ on improving the slag removability was adversely affected by variations in impact values. Therefore, in order to investigate the compensation effect of BaO, Bi ₂ O ₃ and BaO were introduced into the same furnace as in Experimental Example 2 using the flux (F-4) in Table 1.
The fluxes of series B, C, and D in Table 3 were obtained. Using these fluxes, welding workability and slag removability were confirmed in the same manner as in Experimental Example 2. The result is the third
As shown in the table. First, when Bi ₂ O ₃ was 0.06% (B series), good results were obtained in slag releasability up to 3.9% BaO, but slightly unsatisfactory at 5.2%, and the same was true for the bead skin. Bi ₂ O ₃ is 0.12% (C series), 0.18%
(D series) as well, there is a limit to the amount of BaO added in terms of welding workability, bead integrity, etc., and as in the case of B series, it should not exceed 4%. Recognize. On the other hand, the variation in impact values was eliminated by adding BaO, indicating that Bi segregation was eliminated.

【table】

[Table] Example 2 The effects of Bi ₂ O ₃ and BaO have been confirmed above, so it is important to know whether the same effect as Bi ₂ O ₃ can be obtained with PbO, or what happens when PbO coexists with BaO. In order to find out whether a significant effect can be obtained, fluxes of the E series (PbO only) and F' series (PbO+BaO) shown in Table 4 were created and investigated in the same way. First, regarding welding workability, in the E series,
PbO: At 0.21%, the gloss on the bead surface is lost, and at 0.24
%, it became completely backskin-like, and the slag removability also deteriorated slightly. In addition, in the F' series, when BaO was excessive at 4.5%, bead skin roughness and pitting were observed, but when BaO was 3.8% or less, no particular damage to the bead was observed. On the other hand, as noted in Table 4, there were no problems with changes in the Shalpy impact value in the range where PbO was 0.2% or less. However, PbO
At 0.21% (E-4), the impact value varied widely as in the case of Bi ₂ O ₃ . On the other hand, when BaO was added, the variation in impact values was suppressed.

【table】

[Table] Example 3 Fluxes (G-1) to (G-5) prepared by adding an appropriate amount of Bi ₂ O ₃ and around 6% TiO ₂ to the raw material having the flux (F-4) composition shown in Table 1. Using this, slag removability and Charpy impact value were investigated according to Examples 1 and 2. The results are summarized in Table 5.

[Table] That is, the Charpy impact value was improved by adding TiO ₂ , and even in G-5 with Bi ₂ O ₃ : 1.12%,
Almost the same value as in the case of 0% Bi ₂ O ₃ (E _VO =5.48 Kg-m) was obtained, and the compensation effect of TiO ₂ is obvious. Example 4 Fluxes (H-1) to (H-5) obtained by adding Bi ₂ O ₃ to the flux (F-6) in Table 1, and among them (H-3), TiO ₂ was further added. The fluxes (I-1) to (I-3) were adjusted (Table 6) and welding was carried out in the same manner as in Experimental Example 1. The results are also listed in Table 6.

[Table] Slag removability shows slight signs of improvement even at 0.05% Bi ₂ O ₃ , and considerable improvement is observed at 0.1% or more. Also (I-1) to (I-3)
In this case, the addition of TiO ₂ improved the Charpy impact value.

Claims (1)

[Claims] 1 SiO ₂ : 20-60%, MnO: 20-60%, CaO:
20% or less, MgO: 20% or less, Al ₂ O ₃ : 1 to 30%,
_CaF2 : 20% or less, BaO: 0.01-4%, and Pb
and/or Bi: blended in the form of oxide or fluoride, and from 0.01 to Pb and/or Bi
A melt-type flux for submerged arc welding characterized by containing 0.2% of each and having a ratio given by SiO ₂ /MnO of 0.7 to 2.6. 2 _SiO2 : 20-60%, MnO: 20-60%, CaO:
20% or less, MgO: 20% or less, Al ₂ O ₃ : 1 to 30%,
_CaF2 : 20% or less, BaO: 0.01-4%, and Pb
and/or Bi: blended in the form of oxide or fluoride, and from 0.01 to Pb and/or Bi
In addition to containing 0.2% respectively, _TiO2 : 30% or less and
FeO: Contains at least one of 0.1 to 10%, and the ratio given by SiO ₂ /MnO is 0.7
A melting type flux for submerged arc welding characterized by a temperature of ~2.6.