JPH0239357B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a melting type flux for submerged arc welding such as high-speed welding of thin steel plates such as mild steel and 50HT steel, single-layer welding on both sides, fillet welding, and other surface hardening welding. (Prior art) As a measure to improve the welding workability of high MnO-SiO ₂ type flux for submerged arc welding,
There is a method of foaming to form porous particles as shown in Japanese Patent Publication No. 46653, and a method of adding lead oxide to the flux composition as shown in Japanese Patent Publication No. 55-42671. However, as shown in Japanese Unexamined Patent Application Publication No. 13340/1983, flux made of particles made porous by foaming them has a large substantial surface area due to its porous nature, and contains a large amount of moisture such as adhering moisture and crystallization water. It is known that this moisture gasifies during welding and causes welding defects. On the other hand, as shown in Japanese Patent Publication No. 51-46653, it is known that a flux with a clearly lower bulk density has better welding performance. Therefore, if a flux that does not contain porous particles and has a low bulk density can be provided, it is expected that welding efficiency will be greatly improved. Therefore, the present inventors proposed a high MnO--SiO ₂ -based submerged arc welding flux that does not contain foamed particles and has a bulk density of 1.3 to 1.55 g/cm ³ in Japanese Patent Application Laid-Open No. 54-42339. When this flux was actually used as a mesh of particle size 12 x 150,
It was found that there were variations in welding performance between flux production charges, and that improvements were needed. (Objective of the invention) The present invention improves welding efficiency by providing a good bead appearance, no welding defects, good slag removal, and stable welding performance. The purpose of the present invention is to provide a molten flux for submerged arc welding. (Technical Background of the Invention) The above-mentioned variation in welding performance between flux manufacturing charges was thought to be caused by variation in flux components, flux particle size structure, and bulk density. Therefore, the present inventors investigated the flux components in Japanese Patent Application Laid-open No.
The components shown in Publication No. 54-42339 were reviewed. Regarding the particle size structure and bulk density of flux, as a result of a comparative investigation of the particle size structure and bulk density of fluxes with different welding performance between manufacturing charges, it was found that the bulk density was within the standard range of 1.3 to 1.55 g/cm ³ . Furthermore, it was found that there were variations in welding performance even within the product specifications for fluxes whose particle size structure passed through a Tyler No. 12 mesh sieve but did not pass through a 150 mesh sieve. Therefore, we further classified the flux particle size composition into JIS standards,
Using a standard sieve, we investigated the welding performance of flux depending on the relationship between the content of relatively coarse flux particles and bulk density. In other words, the flux composition is approximately equal amounts of SiO ₂ and MnO, totaling approximately 80%, CaF ₂ approximately 3%, and MgO approximately 4%.
%, high MnO-SiO ₂ system with a small amount of at least one of Bi ₂ O ₃ or PbO added, the particles of the prototype flux were opened, and the particle content that passed through a 1410 μm sieve and did not pass through a 149 μm sieve was determined to be 90% or more. After that, the welding performance of the prototype flux was investigated by changing the content of relatively coarse particles that do not pass through a sieve with an opening of 850 μm and the bulk density of the flux.
As a result, as shown in Fig. 1, even if the bulk density is the same, if the content of flux grains that do not pass through a sieve with an 850 μm opening is small, welding performance will be poor, and if the content of flux particles that does not pass through a sieve with an 850 μm opening is low, welding performance will be poor. It was found that even if the amount was the same, when the bulk density was large, the welding performance was poor. That is, it was found that the content of flux particles that do not pass through a sieve with an opening of 850 μm and the bulk density are related to the welding performance of the flux. In addition, the mark ◯ in FIG. 1 indicates that the welding performance is good, and the mark x indicates that either one or both of the slag peeling performance and bead appearance performance is poor. In addition, the measurement of bulk density is based on JIS.K-6721.
Particle size distribution measurement is based on JIS.Z-
Using a mesh sieve shown in No. 8801, the measurement was performed using a rotary tap type particle size distribution analyzer for 5 minutes. (Structure of the Invention) The gist of the present invention is that "the components are
SiO ₂ + MnO: 70-90%, MnO: 38% or more,
MnO/ _SiO2 : 0.8-1.3%, MgO: 3-7%,
_CaF2 : 1.5-4.5%, at least one of PbO or _Bi2O3 0.005-0.5%, CaO: 5.0% or less _{, Na2O}
High MnO−SiO ₂ containing +K ₂ O: 0.75% or less
In the system melt type flux, its particle size composition is
Contains 90% by weight or more of flux grains that pass through a sieve with an opening of 1410 μm but do not pass through a sieve with an opening of 850 μm, and the content of flux grains that do not pass through a sieve with an opening of 850 μm A and the bulk density of the flux B
Melting flux for submerged arc welding whose relationship is 1.40≦B≦1.70-1/A-20 (where A>20).
It is in. Note that % in the present invention means % by weight. Below, reasons for limiting numerical values such as content of flux components and component ratios in the present invention, and limiting numerical values such as bulk density and particle size, and reasons for limiting the relational expressions thereof will be described. SiO ₂ + MnO: 70-90%, MnO: 38% or more,
MnO/SiO ₂ : 0.8 to 1.3%; For welding mild steel and HT50 steel, fluxes mainly designed for welding performance are used, and conventionally high MnO-high SiO ₂ fluxes have been used. I came here. These generally have a SiO ₂ +MnO component of 70~
It was 90%. Furthermore, in fillet welding, if the MnO content was less than 38%, deoxidation was likely to be insufficient, and pits and blowholes were likely to occur. On the other hand, MnO/
The _SiO2 ratio is related to the melting point and peelability of the slag.
When the amount of SiO ₂ is less than 0.8, the melting point of the slag becomes too high and undercuts are likely to occur, and when the amount exceeds 1.3 and the amount of MnO is high or the amount of SiO ₂ is low, the slag removability deteriorated. MgO: 3 to 7%; By containing the MgO component at 3% or more,
Slag removability improved. However, when the content exceeds 7%, the viscosity of the molten slag becomes too high, making the arc unstable, undercuts likely to occur, and the bead shape becoming convex, resulting in poor bead appearance. CaF ₂ : 1.5 to 4.5%; CaF ₂ is a necessary component that decomposes during welding, generates fluorine gas, and serves as a shielding gas generating component that prevents the occurrence of pits, blowholes, etc. If it is less than 1.5%, shielding gas will not be generated enough,
When the content exceeds 4.5%, the slag tends to stick to the bead surface and the slag removability deteriorates. At least one _of PbO or _Bi2O3 from 0.005 to 0.5
%; Low melting point metal oxides such as PbO and Bi ₂ O ₃ had the effect of assisting the effect of the MgO component, which improves slag removability. Slag removability tended to improve as the MgO content increased, but slag viscosity also tended to increase as the MgO content increased. However, if at least one of PbO or Bi ₂ O ₃
Adding 0.005% or more lowers the viscosity of slag and increases the vitality of the slag-metal interface.
The MgO component helped improve the peelability. This effect was the same whether PbO or Bi ₂ O ₃ was added alone, or both were added in an amount of 0.005% or more. However, when the content is less than 0.005%, the effect is small, and when the content exceeds 0.5%, the viscosity of the slag decreases too much, the flow resistance deteriorates, the bead waveform becomes disordered, and the appearance deteriorates. This deterioration in appearance is due to PbO or Bi ₂ O ₃
Even if an ingredient is added alone in excess of 0.5%,
The results were the same even when both were added in excess of 0.5%. CaO: 5.0% or less; If CaO content exceeds 5.0% in the flux, slag will easily seize on the bead surface.
Peelability deteriorated. Na ₂ O + K ₂ O: 0.75% or less; Na ₂ O and K ₂ O components are contained as impurities in SiO ₂ and MnO raw material ores, and as they increase in flux, they affect slag removal performance, bead appearance, Both tended to worsen. Na ₂ O + K ₂ O exceeds 0.75%,
If it is included in the flux, the arc strength will be weakened and the arc will become unstable, which will disrupt the bead waves and cause slag to become trapped.
It was found that as the bead appearance deteriorated, the slag removability also deteriorated. As mentioned above, the lower the Na ₂ O + K ₂ O content, the better the bead appearance and slag removability. Even with high MnO- _SiO2 fluxes within the above composition range, the flux particles may foam and become porous, resulting in overlay welding in which the upper layer is continuously welded, or when the flux is heated to temperatures above about 150°C. When fillet welding preheated steel plates, the slag removal performance was poor. The flux particle size structure contains 90% by weight or more of flux particles that pass through a sieve with an opening of 1410 μm and do not pass through a sieve with an opening of 149 μm, among which flux particles with an opening of 850 μm,
Weight percentage of flux grains that do not pass through the sieve
The relationship between A and bulk density B of flux is 1.40≦
B≦1.70-1/A-20 (however, A>20); The flux of the present invention is manufactured by mixing and dissolving raw material ores according to the target composition, and then pouring it into a jet water stream and pulverizing it. do. Therefore, the bulk density of the flux particles obtained by the coarse packing method can be reduced by forming the flux particles into needle-shaped, antler-shaped, spherical, or scale-shaped mixed particles, and the particle surface area can be reduced by the same bulk density. Compared to foamed particles, the moisture content is much smaller than that of foamed particles, thereby reducing the amount of moisture adhering to the particle surface and preventing the occurrence of welding defects.
Therefore, even if the particles have the same particle shape, if a large amount of fine particles are included in the flux, the effective surface area of the flux becomes large, and as a result, welding defects cannot be prevented from occurring. Therefore, it is necessary to use a flux containing a large amount of coarse particles that will not cause welding defects. Containing a large amount of flux that does not pass through a sieve with an opening of 1410 μm reduces the shielding effect of the flux, making welding defects more likely to occur.Furthermore, flux containing a large amount of particles that pass through a sieve with an opening of 149 μm reduces the shielding effect of the flux. Since the permeability of gasified gases such as adhered moisture generated during welding deteriorates and defects such as spot marks occur, it is recommended that the content of particles that are too coarse or too fine be less than 10%, which will affect welding performance. It was good and warm. However, for flux grains that are a mixture of needle-shaped, antler-shaped, spherical, or scaly particles, which differ from the conventional particle shape, we measured the bulk density using the rough packing method and determined whether coarse particles or fine particles were used. We believe that there is a problem in measuring only the grain size excluding coarse grains and fine grains.
The welding performance of the prototype flux was investigated regarding the relationship between the content of particles that do not pass through an 850 μm sieve and the bulk density of the coarse packing. As a result, the bulk density of flux with good welding performance is 1.40 g/cm ³ or more,
Aperture that is less than 1.70g/cm ³ and relatively coarse grain
The particle content that does not pass through an 850 μm sieve is 20
It was necessary to exceed %. However, when the bulk density of the entire flux is small, relatively coarse particles
Good welding performance was obtained even with a relatively small amount, but when the bulk density is relatively large, in order to obtain good welding performance, it is necessary not to pass through a sieve with an opening of 850 μm.
Relatively large amounts of relatively coarse flux particles were required. (Example) The effects of the present invention will be described below with reference to Examples.
A prototype flux with the composition and grain size shown in Table 3 was manufactured, and the steel plates shown in Table 1 were assembled as shown in Figure 2. The wire shown in Table 1 was used as a fillet weld test piece, and the wire shown in Table 2 was assembled. Under welding conditions, after preheating the test pieces to 150°C, downward fillet welding was performed, and the slag removal performance and bead appearance of each flux were investigated.

【table】

【table】

[Table] The results are shown in Table 4. Comparative flux I had bulk density and particle size structure outside the range.
Slag removability and bead waves were rough, and welding performance was poor. Comparative flux J had poor slag removability because the bulk density and particle size structure were outside the range.
Comparative flux K had a poor bead appearance because the bulk density and particle size structure were out of range. Comparative flux L is also similar to comparative flux K, and comparative flux M also has bulk density and particle size structure outside the range,
Slag removal performance and bead toe conformability were poor. Comparative flux N had too little bulk density, too much MgO and too little Bi ₂ O ₃ or PbO, and had bad slag removability and bad bead appearance. Comparative flux 0 had bulk density and particle size structure within the range, but the flux components CaF ₂ and MgO were too low and PbO was too high, resulting in poor slag removability and poor bead appearance. Comparative flux P had bulk density and particle size composition within the range, but the components CaF ₂ and CaO were excessive, and Na ₂ O +
Since the K ₂ O component was also excessive, the slag removability and bead appearance were both poor. In this way, in the comparative flux,
There was no flux that had good slag removability and bead appearance, but the flux of the present invention had
All fluxes showed good performance in terms of slag removability and bead appearance.

【table】

[Table] Evaluation criteria in Table 4 (1) Regarding slag removability, ○ indicates that the slag will peel off naturally or that the slag can be removed by light tapping, and × indicates that the slag will be burned. I took it as a thing. (2) Concerning the conformability of the bead toes, ○ indicates that the bead toes are aligned and there is no undercutting, slag entrapment, etc., and × indicates that the bead toes are not aligned, or The slag adhered to the bead toe due to , undercut, and slag entrainment. (3) Regarding the wavy pattern of the bead, if the wavy pattern of the bead is fine, smooth, and shiny, mark it as ○.
Beads with coarse wavy lines or convex beads were marked with an x. (Effects of the Invention) As described above in detail, the flux of the present invention has a limited flux composition compared to conventional fluxes, does not contain expanded particles, contains relatively large amounts of coarse particles, and is bulky. By using a flux with a low density, the bead appearance is better than that of conventional fluxes, and the slag removability is even better, so welding efficiency is further improved, and as a result, its industrial value is extremely large.

[Brief explanation of drawings]

Figure 1 shows the bulk density of the flux and the particle size structure of the flux, that is, the opening in the flux.
A diagram showing the effect of relatively coarse particle content that does not pass through an 850 μm sieve on welding performance,
FIG. 2 is an assembly drawing of a test piece for investigating slag peeling performance and bead appearance. 1: Polished surface.

Claims (1)

[Claims] 1 Components are weight percent, SiO ₂ +MnO: 70
~90%, MnO: 38% or more, MnO/ _SiO2 : 0.8~
1.3, MgO: 3-7%, _CaF2 : 1.5-4.5%, PbO
or at least one of Bi ₂ O ₃ at 0.005-0.5%,
In the high MnO-SiO ₂ type fused flux containing CaO: 5.0% or less, Na ₂ O + K ₂ O: 0.75% or less, the particle size structure is such that the flux particles pass through a sieve with an opening of 1410 μm but do not pass through a sieve with an opening of 149 μm. of
Contains 90% by weight or more of flux grains that do not pass through a sieve with an opening of 850 μm (%A)
A melting type flux for submerged arc welding in which the relationship between B and the bulk density of the flux is 1.40≦B≦1.70-1/A-20 (provided that A>20).