JPH01157797A - Sintered flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To obtain excellent bead appearance and weld metal performance even in the high heat input one-pass welding of a thick steel plate by controlling the flux composition in a specified range, and also controlling the particle size of a flux. CONSTITUTION:One-side one-pass welding is applied to the edge-prepared SM50 steel plate by using a welding wire under specified conditions. The flux to be used at this time contains, by weight and based on the total flux, 25-45% Fe, 5-20% SiO2, 15-30% MgO, 5-15% Al2O3, <=15% CaFe, <=10% CaO, <=10% MnO, <=5% BaO as the carbonate, and <=8% one or >=2 kinds between Si and Mn as the deoxidizer. The content of <=36-mesh particles in the total flux particles is controlled to <=20wt.%, and the content of 36-14-mesh particles to >=60wt.%. A thick steel plate can be welded by using the obtained flux.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a flux for latent arc welding, and a flux that provides good welding workability even in high heat input welding where the welding heat input exceeds 250 kJ/cm. This is similar to the sintered flux for submerged arc welding, which has excellent toughness and can produce a beautiful weld bead.

(Prior Art) Sintered flux for submerged arc welding is a mixed combination of oxides, mineral chlorates, metal powders, etc., and generally has a high melting point and is suitable for high heat input welding. Particularly, single-side, single-pass welding is often performed using flux containing iron powder to increase welding efficiency.

In recent years, due to improvements in steel material properties, thickness 40
Although one-pass welding of 1 mm or more is possible, such high heat input welding tends to cause problems in welding workability and bead appearance.

For example, Japanese Patent Application Laid-open No. 53-60343 describes iron, MgO, 5iO in flux components in single-sided submerged arc welding.
A method has been proposed to obtain welds with excellent bead appearance by regulating the flux composition such as z, but it is difficult to ensure good weldability by regulating the flux composition alone. For bus welding,
There is a great possibility that slag will blow up frequently. In addition, as an example referring to the particle size of flux, JP-A-52-32
There is Publication No. 844, and in this example, it is stated that the amount of fine particles is 10% or less to ensure gas venting, but such regulations are not sufficient for high heat input welding, and it is necessary to avoid blowing up of slag. Can not.

(Problems to be Solved by the Invention) The present invention is capable of producing a suitable amount of slag and less blowing up of molten slag in one-pass welding of thick steel plates with high heat input, while also achieving good bead formation with good welding workability. The purpose of this study is to propose a sintered flux that produces weld metal with excellent appearance and toughness.

In particular, the key point of this invention is to not only specify the flux composition within an appropriate range, but also to adjust the particle size distribution of the flux for high-heat-input welding, which may cause problems in welding work due to the blow-up of molten slag. By specifying this, it is possible to obtain a welded part having good bead appearance and weld metal performance even in high heat input welding exceeding 250 kJ/cm without causing the above-mentioned disadvantages.

(Means for solving the problem) When welding thick steel plates by one-pass welding, as the plate thickness increases, heat input inevitably increases, and the amount of molten slag and gas produced increases. As a result, slag blows up and arc stability is impaired, resulting in deterioration of welding workability and bead appearance. In order to suppress this, iron powder is added to increase melting efficiency and the melting point of flux is raised to reduce the amount of slag, but this alone naturally has its limits, and it also improves welding workability. In order to improve this, it is important to appropriately select the particle size composition.

That is, in the flux composition, MgO, Al□0. .

Although it is possible to improve workability to some extent by blending 5in2 in an appropriate amount and ratio to raise the melting point and optimize the amount of slag, if the gas component in the flux is reduced too much, the weld metal It is difficult to suppress the gas generation itself because the amount of hydrogen inside increases and the risk of micro-cracks increases. Therefore, in order to prevent slag from being blown up due to bumping due to excessive pressure within the arc during welding, it is effective to reduce the bulk specific gravity of the flux by optimizing the particle size composition and to make it easier for the generated gas to escape. be.

This invention was developed as a result of a comprehensive study of the above findings, and its gist and structure are as follows.

That is, in this invention, in addition to the metal components re: 25 to 45 wt
0%, 81203: 5-15%, CaF,: 1
5% or less, CaO: 10% or less, and MnO: 10
% or less, and has a composition containing 5% or less BaO as a carbonate and 8% or less in total of one or both of St and Mn as deoxidizers, the flux having a composition that contains all flux particles Among them, 3 are grain type.
This is a fired flux for submerged arc welding, in which 20% or less of the flux is finer than 6 meshes, and 60% or more is 36 meshes or more and 14 meshes or less.

The reason why the component composition and particle size structure of the flux are limited to the above range in this invention will be explained below.

SiO□: 5-20% Sing is an important component as a slag forming agent, but if it is less than 5%, the melting point of the produced slag will rise excessively and the viscosity will become low, making it difficult to maintain a good slag appearance. On the other hand, if it exceeds 20%, the melting point will drop too much and the repeat appearance will deteriorate, so it was set at 5 to 20%.

MgO: 15-30% MgO not only effectively contributes to maintaining the basicity of slag and ensuring the toughness of weld metal, but also is useful for adjusting the melting point of the generated slag, but less than 15% On the other hand, if it exceeds 30%, the melting point of the produced slag will rise too much and the bead width will narrow, making it impossible to maintain a good bead appearance, so we limited it to a range of 15 to 30%. .

81203: 5 to 15% Al2O, effectively contributes to raising the melting point of the produced slag without reducing the viscosity, and is an important component in particular for ensuring viscosity, but if it is less than 5%, the effect is reduced. Scarce, while 1
If the content exceeds 5%, the melting point of the produced slag will rise too much and the appearance of the bead will deteriorate, so the content is limited to a range of 5 to 15%.

CaFz: 15% or less CaF2 is a necessary component to maintain the basicity of the slag and ensure the toughness of the weld metal, but if it is contained in excess of 15%, the viscosity of the slag decreases and the appearance of the bead deteriorates. At the same time, fluorine-containing gas is generated and the slag tends to blow up.

CaO: 10% or less CaO is an important component for maintaining the basicity of the slag and adjusting the melting point of the slag, but if it is contained in excess of 10%, the slag releasability deteriorates and the melting point also increases. Since it tends to be too much, it is necessary to keep it below 10%.

Note that if the blending amount is less than 3%, the effect of the addition will be poor, so
% or more is preferable.

MnO: 10% or less MnO effectively contributes to suppressing slag seizure, but if it is included in excess of 10%, the melting point of the generated slag will drop too much and the bead appearance will deteriorate, so the content should be 10% or less. It is necessary to do so. Note that if the amount is less than 2%, it is unfavorable in terms of slag seizing, so it is desirable to add 2% or more.

BaO: 5% or less BaO is a component that not only effectively contributes to improving the releasability of slag, but also is a useful component in reducing hydrogen in the weld metal by including it in the flux as a carbonate.
If the content exceeds 5%, the melting point of the slag is likely to drop too much, so the content must be kept at 5% or less. However, if it is less than 2%, it will not contribute at all to reducing the hydrogen content in the weld metal, so it is preferable to mix it in an amount of 2% or more.

Si and/or Mn: 8% or less Si and Mn
Both are useful components as deoxidizers, but if they are contained in large amounts exceeding 8%, deoxidation becomes excessive, especially in high heat input welding exceeding 250 kg/cm, and the weld metal deteriorates. 8 because tensile elongation, reduction of area, and toughness deteriorate significantly.
% or less. Note that if the amount is less than 2%, the effect of addition is poor, so it is desirable to add 2% or more.

Fe: 25-45% Fe is effective in increasing the welding speed and reducing welding heat input, but less than 25% is less effective;
If the content exceeds 25% to 45%, the arc becomes unstable and the appearance of the bead deteriorates, so the content was determined to be between 25 and 45%.

Next, the particle size composition of the flux is an important requirement to maintain good gas release during high heat input welding.If less than 60% of particles are 36 mesh or more and 14 mesh or less, gas release is insufficient. This makes it easy for slag to blow up during welding, leading to problems such as the inability to carry out continuous welding work. In addition, if more than 20% of fine grains with a mesh size of 36 mesh or less are included, gas release becomes worse and slag is more likely to seize. % or less, 36 mesh or more, 14 mesh or less 60%
It was limited to the above range.

(Example) A 5M50i plate with grooves shown in FIG. 1 was welded in one pass on one side under the welding conditions shown in Table 1.

As the welding wire, a 2% Mn diameter wire with a diameter of 6.4 mm was used, and as the flux, 10 types of flux having the composition and particle size configuration shown in Table 2 were used.

Table 3 shows the results of investigating the welding workability and toughness of the weld metal at this time.

When fluxes (A) to (F) according to the second invention are used, all exhibit good welding workability, and the bead appearance and
A weld with excellent weld metal toughness was obtained.

On the other hand, fluxes (G) to (J) outside the composition range and particle size composition range have poor welding workability, bead appearance,
It was not possible to simultaneously achieve good results for all aspects of the toughness of the weld metal.

In other words, for flux (G), Sing is out of the appropriate range, so the slag melting point is low (the molten slag swings a lot, making it difficult to obtain a good bead appearance, and the amount of slag produced is excessive, making it easy to blow up). Ta.

Flux (H) contained more than the appropriate amount of MgO and contained fine particles of -36 mesh or less outside the specified range, resulting in frequent slag blow-up and poor bead appearance. For flux (1), At, o,
, Since the CaO content exceeded the appropriate range, the slag melting point was too high, giving the appearance of a narrow bead width, and the slag had poor releasability.For flux (J), -14 to +36 mesh particles were below the specified range. Due to the small amount of slag, a lot of slag was blown up, which hindered welding workability.

(Effects of the Invention) As described above, according to the present invention, it is now possible to weld thick steel plates of 40 mm or more, which was conventionally thought to be impossible to weld with one pass, and to perform corner seam welding of extremely thick box columns. We can expect great benefits in increasing the efficiency of complete welding using a true welding plate.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the groove shape.

Claims (1)

[Claims] 1. Fe: 25 as a metal component with respect to the total flux
-45 wt%, SiO_2: 5-20 wt%, MgO: 15-30 wt%, Al_2O_3: 5-15 wt%, CaF_2: 15 wt% or less, CaO: 10 wt% or less, and MnO: 10 wt% or less, and contains BaO as a carbonate. A flux having a composition containing 5 wt% or less and a total of 8 wt% or less of one or both of Si and Mn as a deoxidizing agent, and whose particle size is finer than 36 mesh among all flux particles. is 20 wt% or less, and 60 wt% or more of the flux is 36 mesh or more and 14 mesh or less.