JPS596755B2 - Flux for submerged mark welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flux used in supmerged arc welding.

Generally, fluxes for submerged arc welding are required to have good welding workability.

In other words, the arc is stable and the bead shape is good over the widest possible range of welding conditions, eliminating pits, blowholes, and
It is required to be able to efficiently weld without defects such as cracks. However, recently, high-grade steels such as various high-tensile steels and low-temperature steels have been increasingly used, and welds are often required to have particularly high notch toughness and hydrogen cracking resistance.
In order to satisfy these performance requirements, the welding workability has come to be sacrificed to some extent.

That is, for example, when high notch toughness is the goal, the flux composition should be one that has a low oxygen potential (for example, a highly basic one, or a SiO2
, lowering Mn0 and containing a large amount of CaF2, etc.)
Therefore, it is necessary to reduce the oxygen content in the weld metal.

However, such compositional restrictions or selections are extremely poor in terms of welding workability, resulting in problems such as good beads being obtained only within a narrow range of welding conditions. In addition, there are many cases where specific performance other than notch toughness is required, but as in the case of notch toughness, welding workability is usually sacrificed and it is difficult to actually put it on the market. Currently, fluxes for submerged arc welding of high-grade steels have unsatisfactory welding workability. The present invention is a submerged arc welding flank that improves welding workability without deteriorating the various performances required for high-grade steels such as high-strength steel and low-temperature steel. The carbonate with a particle size of 70 inches (weight) or more on the 200 mesh sieve is 70% (on the 200 mesh sieve).
Part or all of a molten flux with a particle size of 100% or more (by weight) is coated with an inorganic binder, and the carbonate in the flux is 0.5% to 6% (by weight) of the total flux. This is a special flux for submerged arc welding.

The reason for limiting the numerical range of the present invention will be explained below. The present invention uses fine-grained carbonates (e.g. CacO3, BacO3,
One of the features is that MfCO3, etc.) is added to relatively coarse-grained molten flux.

This improves the welding workability without producing hook marks on the bead surface, toe, etc. Fine powder to fine-grained carbonates easily decompose when the arc approaches them during welding, generating CO2 gas.This gas generation stabilizes the arc, resulting in good bead formation without causing hook marks over a wide range of welding conditions. give. Furthermore, by making the base particle size relatively coarse, the escape of the generated CO2 gas becomes constant, further improving the bead forming ability.
In this case, the particle size of the carbonate should be 30% or less for coarse particles such as those above a 100 mesh sieve, and 70% or more for those below a 200 mesh sieve. In addition, the particle size of the base molten flux must be relatively coarse, with 70% or more passing through a 200 mesh sieve. If these conditions are not met, hook marks may occur on the bead surface and toe, and a sufficiently good bead shape may not be obtained.

The present invention is also characterized in that the fine carbonate is attached to the base molten flux with an inorganic binder such as water glass, which allows the fine carbonate to be mainly mixed with the coarse carbonate. It has the effect of preventing grain size segregation during base flux work, and provides extremely stable and good welding workability.

The method for coating this carbonate is to first add and mix an inorganic binder such as water glass to the extent that the entire surface of the molten flux that will become the base flux is wetted, and then add and mix finely powdered carbonate. . In this case, if the molten flux and carbonate are added and mixed before adding the binder as in the production of ordinary bonded flux, the carbonates may bind together and become granules, which is a limiting factor for the generation of hook marks.
However, if the base flux and carbonate have completely different particle sizes, such as coarse particles and fine particles, the above problem will not occur even if the two are mixed from the beginning and then the inorganic binder is added. In the case of the present invention, since the base flux is coarse particles, the amount of binder added is extremely small, 1/5 to 1/20 compared to the case of pound flux, which uses ordinary fine powder raw materials. The amount of moisture absorbed after firing at ~600°C is extremely small and does not pose a problem. In addition to water glass, sodium aluminate can also be used as a binder. The amount of carbonate to be added is undesirable because if it is added in excess of 6 (F6), the flux will show an oxidizing tendency and the mechanical performance will decrease, and 0.5 (:
When less than fl) is added, there is almost no effect of improving welding workability.

In addition, coating with a deoxidizer alloy agent of about 1fC2% or less other than carbonate is also possible. The carbonate-coated flux does not need to be sized, except for coarse grains, which are removed using a sieve of about 20 meshes, and can be used. In addition, in the flux of the present invention, carbonate may be uniformly attached to all grains of the molten flux, or carbonate may be attached to some of the molten flux, and then carbonate may be attached to some particles of the molten flux, and then carbonate may be attached to some particles of the molten flux. Either may be used, even if it is mixed with a molten flux. In short, it is sufficient that the particle sizes of the molten 7 lux and the carbonate are as described above, and that the amount of the attached carbonate is within the range of 0.5 to 5% by weight based on the entire flux. Next, an example will be described.

Details of base flux composition, amount of carbonate added, particle size, etc. of the flux of the present invention, welding workability test results when submerged arc welding is performed using this flux, oxygen content of weld metal, 2 mm V-notch mechanical shock values are shown in Table 1VC. The same table also shows the results of comparative fluxes. The welding workability test involved visual observation of the bead appearance and shape during bead-on-plate welding, and a test to determine the weldable limit current value, and a test in which a single pass bead was placed in the groove groove at a relatively high welding speed and also visually observed. with bead shape,
Two tests were conducted to determine the quality of appearance.

The test to determine the limiting current value of the former was conducted using 0.4% Si-1.6 (:F6Mn-0.7) on a 25 m thick flat plate of HT8O steel.
%Cr-0.4%MO wire for 80HT (4.8w
L diameter) to set the current value to 600A1700A1800A
A single bead was welded under 5 conditions of 1900A and 11000A, and the judgment was made. In addition, the welding speed in this case is 30cm
/7!1i! The voltage was set at 30 to 40 V, which was appropriate for each flux and current value. Generally, as the current value increases, the waves on the bead surface tend to become rougher, resulting in a poor shape. For the latter V-groove bead placement test, a V-groove with a groove angle of 60 trials and a depth of 15 m was machined in the same HT8O steel with a thickness of 25 m, and the wire was welded into the groove at a current of 700 A and a speed of 50 cm/-. The voltage is 2
8 to 35, which was suitable for each flux, was adopted. For the impact value of the weld metal, use HT8O steel 25FFjn thickness, welding current 650A, arc voltage 28V1 welding speed 30c
m/-, the wire was the same as the HT8O wire (4.
This is the value of weld metal obtained by multi-layer welding using 8wrIn diameter).

The test piece was a JIS Z3ll2, No. 4 Sharpie test piece, and the notch position was at the center of the weld metal. The oxygen analysis sample was taken from the center of the weld metal. As shown in Table 1, when Flux Blacks 1 to 5 of the present invention were used, the limiting current value was approximately 200 to 400 A larger than that of Comparative Flux Blacks 6 to 9, and the appearance of the weld bead within the groove groove was also improved. I can see that it is being done.

Claims (1)

[Claims] 1 100 mesh sieve 30% (weight) or less and 2
Carbonate with a particle size of 70% (by weight) or more on the bottom of the 00 mesh sieve is coated with an inorganic binder on part or all of the melted flux with a particle size of 70% (by weight) or more on the 200 mesh sieve. A flux for submerged arc welding, characterized in that the carbonate in the flux is 0.5 to 6% (by weight) of the total amount of flux.