JPS6123597A - Bonded flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To give satisfactory weldability and mechanical performance to bonded lux by specifying its composition, particle sizes, bulk density and particle strength. CONSTITUTION:The flux contains 5-25wt% TiO2 and/or 0.1-3.0wt% Ti, 5- 50wt% MgO, 1-10wt% metallic carbonate expressed in terms of CO2, metallic 3-25wt% fluoride, 20wt% SiO2 or below, 30wt% Al2O3 or below, and 0.1- 1.0wt% B2O3. Further, a particle fraction whose particle sizes exceed 840mum accounts for 15-60wt%, and a fraction whose particle sizes are smaller than 210mum accounts for 40wt% or below, and its bulk density is within 1.1-1.6g/ cm<2>. In addition, its particle strength measured by a specified particle strength measuring method is 10 or below.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a bond flux used in submerged arc welding, which can maintain good welding workability and good mechanical performance even after repeated use. It concerns bond flux.

(Prior art) In recent years, energy development has become active, and LPG tanks,
PG ships, pipes for cold regions, etc.The construction of structures that require toughness at low temperatures, such as oil drilling rigs, is becoming popular.

Along with this, research is being conducted on welding materials that can weld low-temperature steels, high-strength steels, etc. with high efficiency and provide excellent low-temperature toughness. Particularly recently, methods of incorporating Ti and B into the weld metal to refine the microstructure and obtain excellent low-temperature toughness include single-sided latent arc welding, double-sided latent arc welding, and horizontal latent arc welding for 50 kg class steel. The bond flux used for these welding was published in
This method has been proposed in Japanese Patent Publication No. 510, Japanese Patent Publication No. 52-17507, Japanese Patent Application Laid-Open No. 55-44166, etc.

Incidentally, flux for submerged arc welding is generally divided into melt flux and real flux.

Among these, bond flux uses the blended raw materials with a binder such as water glass;
It is used after being fired and sized at a temperature of about 00°C. Therefore, it is possible to add iron powder, alloying elements, deoxidizing agents, gas generating agents, etc. to the flux, which has the advantage that the performance of the weld metal can be adjusted relatively easily.

However, individual particles of bonded flux are merely physically bonded to each particle of the blended raw materials via a binder, and are susceptible to heat and impact and easily pulverize. Therefore, when the flux after welding is suctioned and collected by a collecting machine and used repeatedly, the flux becomes powdered and the dust content increases, as shown in FIG.

Figure 1 shows a cycle of welding and suction recovery using a flux recovery machine at °C, with the same flux composition as the symbol FIO in Table 5, and a flux containing ordinary iron powder used for single-sided welding with a particle size of 12 x 100 mesh. This shows the change in particle size distribution when this was repeated five times. The 5-cycle franks (A) is 84% compared to the initial flux (B).
0 μm or more and 840 μm ~ 2] 0 μm? It can be seen that the composition ratio of particle size n decreases, and the composition ratio of grain size 21.0 μm or less increases accordingly.

When the flux becomes powdered and the dust content increases in this way, the air permeability of the flux is impaired and pog marks are generated on the bead surface. Furthermore, iron powder, alloying elements, deoxidizing elements, etc. are segregated in the dust, and the component composition values deviate from the flux design values.

Therefore, welding flux that easily powders like this
If the suction and recovery cycle is repeated, the dust may dissipate or segregate and be supplied to the welding area, causing the chemical composition of the weld metal to deviate from its proper value. As a result, the mechanical properties vary, particularly the toughness deteriorates, making it impossible to obtain the desired performance.

In order to prevent the above-mentioned drawbacks, it is necessary to use a flux that does not easily become powder even after repeating the cycle of welding and suction recovery. To powderize (to make flux,
In the past, studies have been made such as investigating the composition of flux, increasing the concentration of binder, or increasing 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. Also, in Japanese Patent Application Laid-Open No. 58-11949,
In order to improve the collapse resistance of flux, a method has been proposed in which Portland cement is mixed into flux.

(Problems to be Solved by the Invention) In welding to obtain high toughness using bond flux, the present invention solves the problem of powdering of the flux and segregation of components when the welding-suction recovery cycle is repeated. Fluctuations in composition, deterioration of welding workability and mechanical properties.
In particular, the present invention provides a bond flux that can prevent deterioration of toughness.

(Means and effects for solving the problems) The present invention provides T.
i0z 5-25 weight factor and/or T101-30 weight factor, MgO5-50 weight factor, metal carbonate converted to CO2 amount 1-10 weight factor, metal fluoride 3-25 weight factor, 8
10220 weight ratio or less, Al2Oa 30 weight ratio or less, B
Particles containing 2O3ol to 10% by weight, particles larger than 840 μm occupy 15 to 60% by weight, particles smaller than 210 μm occupy 40% by weight, and have a bulk density of 11 to 1.6910 nb3. , the bond flux for submerged arc welding has a particle strength C of 10 or less as measured by the method described below.

That is, in order to obtain high toughness, the flux composition is specified. Furthermore, in order to obtain small powdering even when used with edge-turning, and therefore small fluctuations in the composition of the weld metal, good welding workability, and stable high toughness, we have determined the particle size structure of the flux particles, the bulk density of the flux, and the flux. It is an optimal continuation of the physical properties of particle strength.

That is, first, the composition of the flux is (1
) By adding TiO2 and/or Ti and B20a in combination, the microstructure of the weld metal is uniformly refined and high toughness is obtained. (2) By adding appropriate amounts of MgO and Al2O3, fire resistance is improved and large heat input is achieved. (3) A weld metal with high hardenability that can obtain high toughness at low temperatures by adding an appropriate amount of metal carbonate to reduce the amount of diffusible hydrogen in the weld metal. (4) Add an appropriate amount of metal fluoride to reduce the amount of oxygen in the bath-welded metal, and promote high-temperature toughness. (5) Limit SiO2 to less than 20% by weight to keep oxygen in the weld metal low, and
Add an appropriate amount of flux to adjust the viscosity of the slag during welding and obtain good workability.Secondly, regarding the physical properties of flux, (1)
Obtaining a good weld bead by keeping the particle size structure of the flux within an appropriate range. (2) By maintaining the bulk density within an appropriate range, the degree of particle pulverization is reduced, and segregation of flux components due to pulverization is prevented. At the same time, it is possible to obtain appropriate air permeability while maintaining a good bead shape, and (3) by regulating the particle strength, the flux is prevented from becoming powder even after repeated use, and component segregation is reduced. It maintains the good mechanical performance of the weld metal for a long time, has appropriate air permeability, and prevents pock marks.

Hereinafter, the present invention will be explained in detail along with its functions.

First, we will explain the reasons for limiting the temperature of each component of the flux.

It is necessary to add 25 to 25% by weight of Ti and/or 101 to 30% by weight of T. By adding B2O3 in combination, the microstructure of the weld metal is refined and high toughness is obtained. If TlO2 and/or Ti is less than the lower limit, the microstructure will not be refined and the toughness will deteriorate. Additionally, if the upper limit is exceeded, TiC may be present in the weld metal.
etc., resulting in excessive tensile strength and deterioration of toughness. Moreover, TiO□ used in this case is rutile,
A titanium slag or the like is used as appropriate, and a titanium product with a low amount of N, such as a Na-reduced product, is used as appropriate.

B20. is a composite addition with TiO□ and/or T1 to obtain high toughness, and if the content is less than 0.11% by weight, the effect will not be fully exhibited and the toughness will deteriorate. Moreover, if the weight exceeds 10%, high-temperature cracking occurs in the bath-welded metal, which is not desirable at ℃・
. As B2O3, fused borax (Na2B+0+),
Borax (Naz B407 ・l OHzO), colemanite (2Ca0 ・3 B2O3' 5 H2O),
Borax crow (SiO□B2O3K2O, 8102B2O
Oxides such as 3N'azO) are used as appropriate.

It is necessary to add MgO in a proportion of 5 to 50% by weight, and if it is less than 5% by weight, the fire resistance will be low in high heat input welding, and good workability will not be underestimated. If the weight exceeds 50 kg, horse-shaped protrusions will appear on the surface of the weld bead, and welding workability will deteriorate. Moreover, as MgO, magnesia clinker-1
Magnenia oxide or the like is used as appropriate.

It is necessary to add the metal carbonate in an amount of 1 to 10% by weight in terms of CO□ amount. That is, below the weight ratio, the amount of diffusible hydrogen in the weld metal is high and hydrogen cracking occurs. or,】
If it is added in an amount exceeding 0% by weight, abrasion occurs on the surface of the weld bead, deteriorating welding workability, and the amount of oxygen in the weld metal increases, making it impossible to obtain sufficient low-temperature high toughness.

As metal carbonates, CaC0a', BaC0a
, MgC0a, MnCO5, etc. are used as appropriate.

It is necessary to add the metal fluoride in an amount of 3 to 25% by weight. That is, if the weight is less than 3°C, the oxygen content of the weld metal will not be low and high toughness will not be obtained.

Moreover, if it is added in excess of 25% by weight, the melting point of the welding slag will be lowered, and welding workability will deteriorate in high heat input welding. As the metal fluoride, CaF2. BaF2+AAF
Use 3 etc. as appropriate.

Although 5iOz inevitably comes from the binder or impurities of other raw materials, it is necessary to add an appropriate amount in order to maintain the appropriate viscosity of the slag. In addition, in order to obtain high toughness at low temperatures, it is necessary to limit the oxygen content to 20% by weight or less and reduce the amount of oxygen in the weld metal. As 5102, use silica sand, sandstone, wollastonite, etc. as appropriate.
Ru.

Al2O3 is necessary to improve the fire resistance of flux or adjust the viscosity of slag, but if it is added in excess of 30% by weight, slag-in in the weld metal tends to increase, and the amount of oxygen also increases. , high toughness cannot be obtained. Further, as At203, alumina, chamotte, etc. are used as appropriate.

The reasons for further specifying the physical properties of the flux whose components have been specified in order to obtain high toughness as described above are as follows.

First, it is necessary for the flux that particles with a particle size larger than 840 μm account for 15 to 60 weight fractions, and particles with a particle size smaller than 210 μm account for 40 weight particles or less.

This is to ensure proper flux ventilation.
If the proportion of particles having a particle size larger than 840 μm is less than 15% by weight, proper air permeability cannot be maintained and pock marks occur.

If it exceeds 60% by weight, the fire resistance of the flux will be too high, leading to irregular beats and undercuts. Furthermore, if the proportion of particles having a particle size smaller than 210 μm exceeds 40% by weight, air permeability deteriorates and pock marks occur during repeated use.

Furthermore, also in the flux having the above particle size structure, it is necessary to set the bulk density to 1.1 to 1.6 f/arb3. In other words, the bulk density is necessary to reduce powdering of the flux and to make the air permeability appropriate.
If the amount is less than 10 m3, during repeated use, the components will be severely powdered and segregated, making it impossible to obtain good low-temperature toughness, and at the same time, the air permeability will deteriorate.

If it exceeds 1.69/arrb3, the bead will be pressed down too strongly by the flux, causing the bead to become disordered and at the same time, the air permeability will deteriorate and pock marks will occur.

Furthermore, it is necessary that the particle strength C measured by the particle strength measuring method described below is 10 or less. In other words, if it exceeds 10, even if the particle size structure and bulk density are appropriate, the flux will become powdered, the components will segregate, and good low-temperature toughness cannot be obtained, and at the same time, air permeability will deteriorate and pock marks will occur. occurs.

The particle strength in the present invention is determined by adding the composition ratio A weight of particles smaller than 210 μm to a flux 50f measured in advance.
was placed in a cylindrical container with an inner diameter of 4.0 m and a length of 300 m, along with 9 iron balls with a diameter of 8 m, and from the center of both ends of the container,
Centered on a point 150 degrees in the axial direction, around a line passing through that point and perpendicular to the cylinder axis, at a rotation speed of 30 revolutions/minute.
After rotating for 0 minutes, the composition ratio B weight coefficient of particles smaller than 210 μm is measured, and the value C obtained from C=B−A is taken as the particle strength.

In this measurement method, when evaluating the particle strength of flux, we considered that it would be closer to the actual powdering tendency. That is.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example Twenty-eight types of 7 luxes shown in Table 1 were produced.

Flux containing iron powder F5. FIO-F1.2. F17.
F]8 and F23 to F25 were fired at 380°C for 2 hours, and other fluxes containing no iron powder were fired at 500°C for 2 hours. Flux symbols F1 to F12 correspond to examples of the present invention,
Flux symbols F], 3 to F28 are comparative examples.

Among the comparative examples, F20. F22. F24. F25 and F27 are flux components, F16. F23 and F
26 is the flux component and particle size composition, F21 and F28
F18 and F19 are the flux component and particle strength, F18 and F19 are the particle size structure, F17 is the bulk density, F15 is the bulk density and particle strength, and F13 and F14 are the particle strengths that are out of the appropriate range.

Using the above flux, first perform flat plate bead welding on the steel plate F3 shown in Table 3 under the conditions shown in Table 4 using the wire Wl shown in Table 2, and after welding, the flux is sucked up with a flux recovery machine. Recovered. After performing this welding-suction recovery cycle five times, welding shown in Table 5 was performed.

That is, flux Fl-F3. F6. F13~F1
．． 5 and F26 are two-electrode one-layer welding, flux F4. F"7~F'9. Fl 6. F19~F22
．． F27 and F28 are 1 redundant multilayer bath welding, flux F5°Fl0. Fl7 and F24 are 3-electrode flash, single-layer welding on one side of Tsuku packing, flux FI], F1
2°Fl8. For F23 and F25, three-electrode flux/copper backing single-layer welding was performed on one side.

Welding workability inspection, UST for each contact part
Inspection and impact tests were conducted. Welding workability was judged based on the presence or absence of pockmarks, the presence or absence of undercuts, and the appearance of the bead surface. UST inspection is 7
Welding was carried out at a 0° oblique angle from just above the bead in a direction parallel to the welding direction, and suspected defects were confirmed using cross-sectional macro photography.

In addition, for the impact test, specimens were taken from 2 nm below the plate surface for single-layer welding and single-layer welding on one side, and from 5 + nm below the plate surface for multi-layer welding, with the notch placed in the center of the welding area. Three copies of each were created and implemented.

The results of these welding tests are summarized in Table 5. That is, flats 1 to 2 are examples using flux according to the present invention, but all of them have poor welding workability.
Good results were obtained in both the ST test and the impact test. On the other hand, when using the flux of the comparative example] 3 to 28
In both cases, they had drawbacks and were not satisfactory.

13 and A, 14 are particle strength; 5 is a flux whose particle strength and bulk density are outside the appropriate range. The variation indicated by the difference in was unstable. In addition, since the Ivy 16 used a flux in which the amount of metal fluoride and the particle size composition were out of the appropriate range, the toughness and welding workability deteriorated. Boiled 17 is bulk density, A
18 and 19 used fluxes whose particle size composition was outside the appropriate range, resulting in poor welding workability. Flat 20 is C
Hydrogen cracking occurred because a flux with an O2 content below the lower limit of 1 was used.

A; 21 is the amount of TiO2, metal fluoride and particle strength,
Flat 22 is MgO amount and A t2Q3 amount, Tsuta 23 is T
i12 and/or Ti amount and particle size structure, A26 is B
2O3 amount and particle size composition, A28 used a flux whose CO2 amount and particle strength were out of the appropriate ranges, respectively, resulting in deterioration in welding workability and impact value. Notification 24 is T
The impact value deteriorated because a flux whose amount was outside the appropriate range was used.

Since A25 used a flux in which the amount of SiO2 and the amount of TiO2 and/or Tl were outside the appropriate range, the impact value deteriorated. In Notification 27, the amount of NIgO and B2O3 were out of the appropriate range, so welding workability and impact value deteriorated, and hot cracking occurred.

(Effect of the invention) By using the flux of the present invention, which specifies the component composition and the amount added and maintains the particle size structure, bulk density, and particle strength within appropriate ranges, it is possible to achieve good welding workability even when used repeatedly. Good weld metal performance, especially stable and high toughness, can be obtained.

[Brief explanation of the drawing]

Figure 1 is a graph showing an example of the change in particle size distribution when welding and recovery using a flux recovery machine are repeated five times using normal iron powder-containing flux; Figure 2 (a)
, (b) is a front view showing the groove shape of the test plate used in the example of the present invention, and Fig. 3 (a), (b), (c)
FIG. 2 is a front view showing the position where an impact test piece was taken in an example of the present invention. ``Niki 5 Futatsushi 〜2/θμm Small Japanese 3rd figure (t
l) Figure 3 (c) Procedural amendment (voluntary) August 10, 1980 Commissioner of the Patent Office Manabu Shiga Indication of the case 1988 Patent Application No. 14.4368
Name of No. 2 invention Bond flux for submerged arc welding 3 Person making the amendment Relationship to the case Patent applicant Location 2-6-3 Otemachi, Chiyoda-ku, Tokyo Name (
66'5) Nippon Steel Corporation Food Coloring Representative Takeshi 1)
Toyo 4th generation Osamu Address 3-3-3 Nihonbashi, Chuo-ku, Tokyo 5 Date of amendment order Showa 1920 Month, day (shipment date) 6 Number of inventions increased by amendment 7 Subject of amendment Detailed description of the invention in the specification Explanation and l Specification page 18, Table 1, symbol F13 C0J-@ +il (*
1) Correct "4.2" to "3.8go". 2 Particle intensity C "2" of symbols F13 and F14 in Table 1 on page 18, "2" is "12", "12"11o,;8
” to be corrected. 4 Same page 24, Table 5 (continued) No. 15 Groove shape [Figure 2 (b) ``Figure 2 tal t2 = 20 tj = 25θ
Correct 2-20° to θ, =900. a=16 J a=17 j (5) 1st
Correct the figure as shown in the attached sheet.

Claims (1)

[Claims] TiO_25-25% by weight and/or Ti0.1-3.
0 wt%, MgO5-50 wt%, metal carbonate CO_
1 to 10% by weight, metal fluoride 3 to 25% by weight, SiO_220% by weight or less, Al_2O_330
% by weight or less, containing 0.1 to 1.0% by weight of B_2O_3 and having a particle size larger than 840 μm is 15 to 60
40% by weight of particles with a particle size smaller than 210 μm
It occupies the following, and the bulk density is 1.1 to 1.6 g/cm^
Bond flux for submerged arc welding, characterized in that the particle strength C measured by the method described below is 10 or less. [Method for measuring particle strength] Put 50 g of flux whose composition ratio (weight %) of particles smaller than 210 μm is A into a cylindrical container with an inner diameter of 40 mm and a length of 300 mm together with nine iron balls of 8 mm in diameter. Centered on a point 150mm in the axial direction from the center of both ends, around a line passing through that point and perpendicular to the cylinder axis,
After rotating for 60 minutes at a rotation speed of 30 revolutions/minute, 210
Measuring the composition ratio (weight %) B of particles smaller than μm,
Let the value C obtained by the following formula be the particle strength. C=B-A