JPH0239358B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a bond flux used in submerged arc welding, which is particularly resistant to powdering even after repeated use, has appropriate air permeability, and can maintain good welding workability for a long time. It concerns flux. Prior Art Submerged arc welding fluxes are generally divided into melt fluxes and bond fluxes. Among these, bond flux is made by granulating the blended raw materials using a binder such as water glass.
It is used after being fired and sized at a temperature of about 300 to 600°C. Therefore, it is possible to add iron powder, alloying elements, deoxidizing agents, gas generating agents, etc. to the flux, and there is an advantage that the performance of the weld metal can be adjusted relatively easily. However, the individual particles of bond flux are merely physically bonded to each particle of the blended raw materials via a binder, and are susceptible to heat and shock and easily pulverize. For this reason, when the flux after welding is suctioned and collected by a collection machine and used repeatedly, the flux becomes powdered and the amount of dust increases, as shown in FIG. 1, for example. Figure 1 shows a cycle of welding and suction recovery using a flux recovery machine repeated five times using ordinary iron powder-containing flux used for single-sided welding with a particle size of 12 x 100 mesh and the composition indicated by the symbol in Table 2. This shows the change in particle size distribution when the flux is 840μm or more and 840μm after 5 cycles compared to the initial flux.
The composition ratio of particles with a diameter of ~210μm decreases, and
It can be seen that the composition ratio of 210 μm or less is increasing. When the flux becomes powdered and the dust content increases in this way, the air permeability of the flux is impaired and pockmarks occur on the bead surface. Conventionally, in order to prevent the above defects, the composition of flux has been studied, and the concentration of binder has been increased.
Alternatively, studies have been made to increase the firing temperature. For example, JP-A-51-52953 discloses a method in which clay minerals are contained in flux, granulated with an alkaline aqueous solution, and fired in an atmosphere containing carbon dioxide gas. Furthermore, Japanese Patent Laid-Open No. 119491/1983 proposes a method of mixing portland cement into flux in order to improve the collapse resistance of the flux. Purpose of the Invention The present invention provides a flux that is resistant to powdering even after repeated use and that maintains good air permeability and welding workability for a long time by optimally maintaining the physical properties of the flux. It is something. In other words, in the particle size composition of the flux, (1) particle strength can be increased by increasing the proportion of large particles compared to conventional ones, and at the same time, appropriate air permeability can be maintained even if the flux is powdered to some extent; (2) By keeping the bulk density within an appropriate range,
In addition to reducing the degree of particle pulverization, appropriate air permeability can be obtained while maintaining a good bead shape; and (3) by controlling the particle strength, appropriate air permeability can be achieved even after repeated use. The present invention was completed based on the discovery that it has the same properties and can prevent pockmarks. Structure and operation of the invention That is, the present invention is characterized in that particles having a particle size larger than 840 μm account for 30 to 60% by weight, particles smaller than 210 μm account for 20% by weight or less, and further have a bulk density of 1.1 to 1.6 g/ cm ³ and a particle strength C of 10 or less as determined by the measuring method described below. The present invention will be explained in detail below. First, it is necessary for the flux to contain 30 to 60% by weight of particles with a particle size larger than 840 μm, and 20% by weight or less of particles with a particle size smaller than 210 μm. This is to ensure proper air permeability of the flux, and the proportion of particles with a particle size larger than 840 μm must be less than 30% by weight, and after repeated use, proper air permeability cannot be maintained and pockmarks will occur. do. If it exceeds 60% by weight, the fire resistance of the flux will be too high, resulting in irregular beads and undercuts. Furthermore, if the proportion of particles with a particle size smaller than 210 μm exceeds 20%, air permeability deteriorates and pockmarks occur during repeated use. Furthermore, even in the flux having the above particle size structure, it is necessary to set the bulk density to 1.1 to 1.6 g/cm ³ . In other words, the bulk density is necessary to reduce powdering of the flux and to optimize air permeability.If it is less than 1.1 g/ ^cm3 , powdering will be severe during repeated use, and breathability will deteriorate; /
If it exceeds ^cm3 , the bead will be pressed down too strongly by the flux and the bead will become disordered, and at the same time, air permeability will deteriorate and pockmarks will occur. Furthermore, the particle strength C measured by the particle strength measurement method described below
must be 10 or less. That is, if it exceeds 10, even if the particle size structure and bulk density are appropriate, the flux becomes powdered to a large extent, resulting in poor air permeability and the formation of pockmarks. The particle strength in the present invention is determined by adding 50 g of flux, whose composition ratio A weight % of particles smaller than 210 μm has been measured in advance, together with 9 iron balls of 8 mm in diameter,
mm, length 300 mm, and rotated at a rotation speed of 30 revolutions per minute around a line passing through the center at a point 150 mm in the axial direction from the center of both ends of the container and perpendicular to the cylindrical axis. After rotating for a minute, 210μm
The composition ratio B weight % of smaller particles is measured, and C
The value C obtained from =B-A is taken as the particle strength. In order to quantitatively evaluate the particle strength of flux, this measurement method uses flux with the same particle size structure as that used in actual welding as the test flux, in order to approximate the actual powdering tendency. It is. Hereinafter, the present invention will be specifically explained with reference to Examples. Example: The flux having the composition shown in Table 2 was granulated with water glass.
The mixture was fired at ℃ for 1 hour to produce 11 types of fluxes shown in Table 1. In Table 1, flux
F1 to F5 correspond to the examples of the present invention, and fluxes F6 to F5 correspond to the examples of the present invention.
F11 is a comparative example. i.e. F6, F9 and
F11 is a comparative example in which the particle size structure is outside the appropriate range, F8 is the bulk density, F10 is the particle strength, and F7 is the comparative example in which the bulk density and particle strength are each out of the appropriate range. Using the above flux, welding was first performed, and the flux with good welding workability was collected with a recovery machine, and then suction and recovery was performed using the recovery machine four times.
Welding was performed after recovering the material five times in total.
The welding conditions in this case are as shown in Table 3, 1.5
Using %Mn (JISZ3311 SAW31 applicable) wire,
Flat plate bead welding was performed on a 0.14% C, 0.29% Si, 1.37% Mn (corresponding to NK standard K32D) steel plate. Workability was evaluated based on the presence or absence of pock marks, the presence or absence of undercuts, and the appearance of the bead surface. Table 4 shows the results, and in contrast to the cases of the present invention in which excellent welding workability is obtained, all of Comparative Examples F6 to F11 have drawbacks. In other words, defects occur in F8 and F11 when welding with a new flux that has not been subjected to a welding-recovery cycle, and in F6, F7, F9, and F10, pockmarks occur when welding with flux that has been recovered five times, which is preferable. It wasn't something.

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Figure 1 shows that using ordinary flux containing iron powder,
It is a graph showing an example of a change in particle size distribution when collection by a welding-flux collection machine is repeated five times.

Claims (1)

[Claims] 1. Particles with a particle size larger than 840 μm account for 30 to 60% by weight, particles with a particle size smaller than 210 μm account for 20% by weight or less, and further have a bulk density of 1.1 to 1.6 g/cm ³ A bond flux for submerged arc welding, characterized in that the particle strength C measured by the following method is 10 or less. [Method for measuring particle strength] Composition ratio of particles smaller than 210 μm (weight %)
50g of flux with A is 8mm in diameter iron ball 9
placed in a cylindrical container with an inner diameter of 40 mm and a length of 300 mm, and rotated at a rate of 30 revolutions per minute around a line perpendicular to the cylindrical axis, passing through the center at a point 150 mm in the axial direction from the center of both ends of the container. After rotating for 60 minutes, the composition ratio (weight %) B of particles smaller than 210 μm was measured, and the value C obtained from the following formula was taken as the particle strength. C=B-A