JPS6036875B2 - Melting type flux for submerged arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a melt-type flux for port arc welding that provides weld metal with excellent porosity resistance and pockmark resistance.

In high-speed submerged arc welding, fillet submerged arc welding, etc. using molten flux, it is common to appropriately adjust the shape and dimensions of the flux in order to obtain good workability and bead shape.

However, the secondary molten flux generally has a large porosity, and when welded under high temperature and humidity, defects such as blowholes and pock marks are likely to occur in the weld metal. Moreover, there is a problem in that nitrogen, hydrogen, etc. in the air contained in the voids of the flux penetrate into the weld metal, resulting in poor impact resistance of the physical properties of the weld metal. The present inventors focused on the above-mentioned circumstances, and
We have been conducting research with the aim of developing a method that does not cause the aforementioned defects even when welding under high temperature and humidity conditions, without sacrificing the high speed welding properties and excellent workability obtained by molten flux. .

As a result, by adjusting the particle size structure of the flux and adopting a structure in which fine particles of flux are filled into the gaps between the fluxes of relatively phase particles, and by appropriately adjusting the specific surface area of the fine particles, flux dispersion is possible. It has been found that the amount of outside air contained in the layer is reduced, and a weld metal with good pockmark resistance, porosity resistance, and mechanical properties can be obtained. The present invention was completed based on this knowledge, and its structure is such that the particle size structure is 32 mesh or less: 5 to 30% (
Weight%: same below), more than 32 mesh and less than 20 mesh: 15-50%, more than 20 mesh and less than 12 mesh: 2
0 to 70%, more than 12 mesh: 20% or less, and the specific surface area of particles with a particle size of 32 mesh or less is 0.02
The gist lies in the fact that ~0.13〆/evening.

Based on the knowledge that the above-mentioned defects are caused by the porosity of the molten flux, the inventors have discovered that high quality can be achieved by creating a particle size structure that fills the gaps between coarse particles with fine particles. We conducted an experiment to clarify the relationship between the particle size structure of the flux and welding defects.

That is, as shown in Table 1, various molten fluxes having different particle size compositions were prepared, and the pockmark resistance and porosity resistance of weld metals obtained using each flux were examined. Results first
All are shown in the table. However, the composition of the flux used and the welding conditions were as follows. [Flux component composition] Si02: 46.2%, Mn○: 38.5%, Ca○:
4.8%, CaF2: 5.4%, AI203: 2.8%
, Others: 2.3% [Welding conditions] Base material: SS41,
16 side thick joint shape: Fillet (horizontal position) Wire: US-36 4. Misaki? Welding current: 600A Welding voltage: 36V Welding speed: 80g/min Welding atmosphere: 30oo x 80%R. Day. Table 1: ◎Very good ○Good, △Slightly poor, When flux is used, weld metal with good pockmark resistance and porosity resistance can be obtained (No.
．． 3 to 8) If it is out of the above range, high quality welded metal cannot be obtained.

The reason for this can be considered as follows. In other words, if the content of fine particles of 32 mesh or less is less than 5% (No. 1, 2), the gaps between the coarse particles are not sufficiently filled with fine particles, and a considerable amount of voids remain in the flux layer. This is thought to be due to the air contained in it causing adverse effects. Also, fine particles are 30
% (No. 9, 10), the specific surface area of the entire flux increases and the amount of moisture absorbed under high temperature and humidity increases.
Gas generated during welding will not escape easily, making it impossible to obtain high-quality joints. In addition, the specific surface area of fine particles is closely related to the occurrence of defects; if the specific surface area is too small, fine particles will be densely packed between coarse particles, making gas release difficult and reducing porosity resistance (experimental On the other hand, if the specific surface area is too large, defects will appear due to increased hygroscopicity (Experiment No. 12). Therefore, in order to obtain a flux that does not cause these defects, the ratio of fine particles of 32 mesh or less must be It is necessary to determine the surface area from 0.02 to 0.13/s.

Incidentally, Figure 1 shows the amount of moisture absorbed by flux obtained by keeping the content of fine particles of 32 mesh or less constant at 30% and varying the specific surface area (left for 24 hours at 30C○ x 80%R.day). This is a graph showing the results of examining the amount of moisture absorbed (later moisture absorption), and this graph also shows that when the specific surface area exceeds 0.13, the amount of moisture absorbed increases rapidly. Like this 3
By setting the specific surface area and content of fine particles of 2 mesh or less within a specific range, the gaps between coarse particles can be minimized without impeding gas release or moisture absorption, improving pockmark resistance and resistance. A welded metal with excellent porosity can be obtained.

However, in order to reliably achieve the above features, it is considered necessary to clarify the particle size structure not only of fine particles but also of coarse particles exceeding 32 mesh. Therefore, the content of fine particles of 32 mesh or less was set within a range that satisfied the above requirements, and fluxes with various particle size compositions of coarse particles of more than 32 mesh were adjusted, and each flux had pockmark resistance and porosity resistance. We investigated the impact on gender.

Table 2 shows the particle size structure and test results of the flux.

However, the flux composition and welding test method were the same as in Table 1. Table 2: ◎Extremely good, 〇Good, △Slightly bad, ×Poor, XXExtremely bad Messenger: JISZ 8801 (1966) No. 2
From the table, it can be considered as follows.

The content of particles having a particle size of more than 32 mesh and 20 mesh or less is preferably in the range of 15 to 50%.

In other words, particles in this particle size range are intermediate in size between fine particles of 32 mesh or less and coarse particles, and some of them fill the gaps between coarse particles and have the effect of reducing the porosity. If the amount is too large, the content of coarse particles will be too low, resulting in poor gas release and reduced pore resistance. In other words, if the particles in this range are less than 15% (Experiment Nos. 21 and 23), the porosity of the flux as a whole cannot be sufficiently reduced, and pock marks occur due to the influence of the hygroscopic air contained in the flux layer. and blowholes are more likely to occur. On the other hand, if it exceeds 50% (Experiment No. 20), the average particle size of the flux as a whole becomes too small, resulting in poor gas release and poor porosity resistance. (2) The content of particles having a particle size of more than 20 mesh and 12 mesh or less is preferably in the range of 20 to 70%.

Particles in this range of particle size function as coarse particles and have the effect of increasing the permeability of the flux layer and improving gas release. Porosity decreases. On the other hand, if it exceeds 70%, the porosity of the entire flux becomes high and becomes susceptible to the influence of moisture-absorbing air. [3} The content of coarse particles larger than 12 mesh should be 20% or less.

Although these coarse particles have the effect of increasing air permeability, the voids formed between the particles are too large to fill, making it difficult to fill them and making them susceptible to the effects of moisture-absorbing air. Especially when it exceeds 20% (Experiment Nos. 19, 21, and 23), this tendency clearly appears. Therefore, it is preferable to have less coarse particles with a size exceeding 12 mesh, but if it is less than 20%, the above-mentioned problems will hardly occur because the gaps will be sufficiently filled with fine particles. '4 - In other words, by using a flux with a particle size composition that satisfies all of the requirements in '1) to '3} above, the porosity of the flux can be made sufficiently small without impeding air permeability, and the porosity of the flux can be reduced to a sufficient degree without impairing the air permeability. Pore resistance is enhanced.

In addition, as a method for determining the preferred content of mallet grains exceeding 32 mesh, there is a method of determining the content based on the amount of fine grains of 32 mesh or less.

For example, Figure 2 shows 32
32-20 mesh for fine particles below mesh, 2
The content of each aggregate of 0 to 12 mesh and more than 12 mesh is shown in a triangular graph, and the symbols in the figure indicate the experiment No. in Table 2. The white circles indicate those with good test results, and the black circles indicate those with poor test results. As is clear from the results in Figure 2, when the amount of fine particles of 32 mesh or less is taken as 100%, those of 32 to 20 mesh are 1
5-70%, 20-12 mesh 25-75%
, 12 meshes or less to 25% or less, it is possible to obtain a molten flux that meets the purpose of the present invention. The present invention is configured as outlined above,
By setting the particle size structure and the specific surface area of the fine particles within a specific range, it has become possible to provide a molten type flux with low porosity and good gas release.

As a result, the amount of air in the flux layer is suppressed to a low level, suppressing pock marks and blowholes caused by air intrusion, as well as preventing deterioration of the physical properties of the molten metal. Regardless of the circumstances, it is now possible to obtain high-performance welded joints.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between specific surface area and hygroscopicity of fine particles of 32 mesh or less in flux, and Figure 2 is a graph showing the relationship between specific surface area and hygroscopicity of fine particles of 32 mesh or less in flux.
It is a triangular graph showing the preferred content range of each coarse particle when the content of fine particles below the mesh is taken as 100%. Figure 1 Figure 2

Claims (1)

[Claims] 1 Particle size composition: 32 meshes or less: 5 to 30% (weight%: the same below), more than 32 meshes and 20 meshes or less: 1
5-50%, more than 20 meshes but less than 12 meshes: 20-50%
70%, more than 12 meshes: 20% or less, and 3
The specific surface area of particles with a particle size of 2 mesh or less is 0.02 to 0.
．． A melting flux for submerged arc welding characterized by a flux of 13 m^2/g.