JPS6061195A - Flux for electroslag build-up welding - Google Patents

Abstract

PURPOSE:To improve remarkably slag removability by contg. a specific amt. of CaF2, Al2O3, CaF, MgF2 and or AlF3, Mg and or BaO and contg. (MgF2+Al) and SiO2 under specific conditions. CONSTITUTION:A flux for electroslag build-up welding is composed to contain, by wt%, 30-60 CaF2, 10-30 Al2O3, 5-15 SiO2, <10 CaO, 3-10 MgF2 and or AlF3 and 2-15 MgO and or BaO. The conditions >0.5 (MgF2+AlF3)SiO2 are satisfied. The flux is incorporated therein with 0.01-0.1 (in terms of S) S alone and or S compd. in order to improve further the seizure resistance of slag.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flux for overlay welding that has good slag releasability, and more particularly, to a flux for overlay welding that has good releasability and that can be used in electro-slag overlay welding using a strip electrode, particularly in high-speed overlay welding. The present invention relates to a flux composition that provides a slag that does not seize with metal.

Overlay welding using a strip electrode is classified into submerged arc welding type and electroslag welding type, but with the latter welding method, there is less dilution by the base metal, so it is possible to obtain overlay metal that matches the design even with one layer welding. In addition, since the bead is formed smoothly, there are fewer defects such as poor fusion, and the range of application is being expanded. However, in the case of electroslag welding, low-speed welding (usually about 15 cm/min) is performed, which tends to cause dissociative cracking due to hydrogen at the interface between the weld metal and the base metal, and coarse grains in the HAZ of the base metal. As the technology progresses, problems such as ductility deterioration and cracking are becoming apparent, and products that had been steadily expanding their application range are now being forced to stop. Therefore, the welding speed is set to 3, for example.
It has been proposed to increase the welding current to about 0 cm/min (however, it is necessary to ensure the build-up thickness, so the welding current is also increased at the same time).

However, when this method was applied to electroslag overlay welding of SUS 347 stainless steel, which is used in oil refineries and chemical reaction equipment, the slag peelability was very poor, especially when the slag was baked on the bead surface. It became clear that it would be difficult to carry out liquid penetrant testing due to the occurrence of adhesion. Moreover, it is not only a problem in carrying out inspections, but also a huge amount of labor and time is required to remove the slag before the next bus welding, and in areas where the peeling is insufficient, slag gets caught in the next pass welding, resulting in welding defects. It was the cause.

The inventors of the present invention have long been concerned about the above-mentioned situation, and first invented the 7 lux described in Japanese Patent Application Laid-Open No. 58-20398,
He made a significant contribution to overlay welding of various stainless steels, including the aforementioned SUS 347 series. However, subsequent research revealed that even when the 7 lux of the invention was used, some slag burning phenomenon remained at the edges of the bead during high-speed welding, and it became clear that further improvements were needed.

The present invention was made under these circumstances, and it is an object of the present invention to provide a flux that can improve slag releasability and seizure resistance in two ways.

72 of the present invention that satisfactorily achieves the above objectives.
Tsukusu has CaF2: 30-60% A1. O,: 10-30q6 sio□; 5-15% Cab: 10% or less MgF, and/or AIF: 3-2o MgO in total
and/or Bad: Contains 2 to 15% in total, and (MgFg + AIFs)/s to, : 0.5
The gist is to satisfy 0 or more conditions.
As a result, all of the above objectives have been achieved, but in order to further improve the seizure resistance of the slag, there are also cases in which a total of 0.01 to 0.1% (S equivalent) of S alone and/or compounds is contained. Included in the gist of the invention.

Among the above components, Ca F2 + A I20 (1rS
lolCaO and MgO are from the above-mentioned Japanese Patent Application Publication No. 58-203.
It has the same ingredients as No. 98 7 Lux. Mg F! *
A I Fs + B a O and S (alone or as a compound) are the components particularly selected in the present invention, but since the content rate is determined for each component, the reasons for selection and composition range setting will be explained in detail below. explain.

It is a component that increases the electrical conductivity of slag, and is an essential component for electroslag welding.

However, if it is less than 30 inches, sufficient electrical conductivity cannot be obtained and electroslag welding itself cannot be carried out. the other 6
If it exceeds 0q6, the fluidity of the slag becomes excessive and it becomes difficult to obtain a good bead shape.

It is a component that improves the smoothness of the bead and the wettability and linearity of the bead toe, but this effect is not exhibited if the thickness is less than 10 inches. On the other hand, if it exceeds 30q6, the electrical conductivity of the slag is lowered and current conductivity is hindered, resulting in poor welding workability.

5 iot: s~15 t This is a component that improves the bead shape and bead appearance by imparting appropriate viscosity to the molten slag, but if it is less than 5 t, its effect is not exhibited.

On the other hand, if it exceeds 15 inches, the viscosity of the slag becomes excessive, resulting in poor slag removability and severe seizing of the slag.

In addition to smoothing the bead surface, it is a component that increases the basicity of the slag and improves the cleanliness of the weld metal. These effects are proportional to their abundance, and there is no need to set a lower limit, but it is particularly recommended to mix 1 or more.

On the other hand, as for the upper limit, if it exceeds 10 inches, the fluidity of the molten slag becomes excessively stiff, deteriorating the bead shape and appearance.

MgF and/or AIF: 3 to 20% in total These two components are the most characteristic components of the present invention in that they improve the peelability and seizure resistance of slag, but both can be used alone or in combination. The above effect is achieved regardless of the method. However, when the total amount is less than 3q6, the above effect is insufficient, and on the other hand, when it exceeds 20 parts, the fluidity of the molten slag becomes excessive, resulting in deterioration of the bead shape, such as uneven bead toe. invite

All of them are components that contribute to improving slag removability, and exhibit an effective effect regardless of whether they are used alone or in combination; however, when the total amount is less than 2%, the above effects are insufficient. On the other hand, if it exceeds 15 inches, the bead conformability deteriorates, and defects such as slag entrainment, poor fusion, and even undercuts are likely to occur.

The present invention includes at least the above components, and may optionally include other components such as FeO, Na*O, alloy components, etc., but the types and contents of other components are subject to particular restrictions. There is no. However, the following S is mentioned as a particularly important component.

S (alone or as a compound): 0.01 to 0.196 (
When a flux containing 0.01% or more of S (single substance) and/or a compound (sulfide such as FeS or MnS) in terms of S is used, the seizure resistance of the slag is further improved. That is, S
is a strong surface-active component that engages in reactions at the interface between molten metal and molten slag, changing the interfacial properties, thereby preventing the formation of compounds that cause slag burning, thereby promoting slag peeling, and This is thought to improve the seizure resistance of Such effects are particularly remarkable in 7 lux containing a large amount of fluoride (CaF2.MgFt, AIF, etc.) as in the present invention, and are thought to be due to the phase opening effect. However, if an excessive amount of S is contained, the S content in the weld metal increases and performance such as hot cracking resistance deteriorates, so the upper limit was set at 0.1 inch.

The components added to the flux have been explained above, but the ratio given by (MgF, +AIFg)/Sio□ also has a significant effect on the removability and seizure resistance of the slag, so it will be further explained. That is, as understood from the above description, SiO□ does not have an adverse effect on the releasability and seizure resistance of the slag, so the smaller the amount, the better. However, for the purpose of improving the bead shape and bead appearance,
I have no choice but to combine 15 yuan. However, 810. If MgF and/or AIF coexist, it is not sufficient that MgF and/or AIF be blended within the above range, but S10.
It is necessary to mix more than half of the content (content rate calculation) as a guaranteed amount, and if the value given by the ratio is less than 0.5, slag seizure will occur.

We have explained each of the active ingredients above, but in order to stably exhibit each of the above effects, it is especially recommended that the amount of hydrogen contained in the flux be 150 pIn or less, so we will provide supplementary information below. Explain. In other words, the hydrogen contained in flux is occluded as moisture (mainly crystalline water), but some of the hydrogen generated from this moisture may enter the weld metal during welding and cause cracks. It is well known that this will happen. On the other hand, part of the water in the flux is gasified by the welding heat and scattered to the outside through the slag, but part of it is trapped in the slag and makes the slag porous. As a result, the slag itself becomes easily crushed, but such slag does not peel off uniformly as a whole, and may remain on the bead surface in the form of fine burns in some areas.

It has been found that the above-mentioned porosity of the slag becomes significant when the amount of hydrogen in the flux exceeds 1501111m, so the present invention recommends that the amount of hydrogen in the flux be 150m or less. Such conditions are easily satisfied with a molten type flux, but in the case of a sintered type flux, the sintering temperature can be kept below isoprm by setting the sintering temperature to 500° C. or higher.

The present invention can be provided regardless of whether it is a melted type or a sintered type, but in the latter case, M n HN t + Cr tN
It is possible to add alloy components such as b+Mo.

Since the flux of the present invention is constructed as described above, as can be understood from the examples shown below, SUS 347
In electroslag overlay welding of stainless steel, which is represented by the electroslag type, the peelability and seizure resistance of the slag have been improved to a satisfactory degree, especially since this was achieved under high-speed welding conditions. We were able to greatly contribute to the generalization of slag overlay welding.

When a flux having the composition shown in Table 1 was prepared and overlay welding was performed under the following conditions, the results shown in Table 1 were obtained.

<Welding conditions> (1) Base material mild steel: 50mm'X500mmWX600mm' (2
) Strip electrode size used: 0.4mmtX75mmW Ingredients: 0.01%C-0,2%S amount-1,84Mn 1
1%N1-21%Cr- 1.1%Nb (remainder Fe and unavoidable impurities) (3) Electroslag welding conditions DC-RP 1200A-25V-15cm/min and 2100A-2
Under both conditions of 5V and 30cm/min, single-layer overlay welding Nfll contains less CaFl and too much AI and O, causing defects such as undercuts and slag burning. The bead appearance and shape were also poor.

Nn2 had an excessive amount of CaFg, had a poor appearance and shape, and was also found to have poor fusion.

1Jn3 is an example in which Al2O is insufficient, and good beads cannot be obtained as well.

Nn4 is S10. As a result, the slag removability was satisfactory, but the bead shape was poor.

m5 is sio! In cases where there was too much, the bead was removed, but the slag was severely burned.

N[16 is an example with a large amount of CaO, and the bead shape is poor.

N[L7 is an example in which MgF and AIF fields were insufficient, and the slag peelability was poor and there was seizure.

Positive 8 is an example in which neither MgO nor BaO is contained, and like 11h7, the slag removability and seizure resistance were poor.

In N119, the sum of MgF2 and AIF3 is excessive, leading to deterioration of the repeat shape.

Nn1O contains too much MgO and has poor bead shape.

N[111 is (Mg F2 + AI FB )/
The ratio of S 10t was too small, and the slag peelability was poor, and baking was also observed.

On the other hand, Nn12 to Nn20 are examples that satisfy each condition of the present invention, and satisfactory results are obtained for all items.

Applicant: Kobe Steel Co., Ltd. Procedural Amendment October 9, 1982 1, Description of the case 1982 Patent Application No. 143482 2, Name of the invention Electroslag overlay welding flux 3, Person making the amendment Case and Relationship: Patent applicant: 3-18 (119) Wakihama-cho, Chuo-ku, Kobe City; Representative: Fuyuhiko Maki, 4; Representative: Shinko Building, 2-3-7 Dojima, Kita-ku, Osaka City, Kobe Steel, Ltd., 530 "Claims" and "Detailed Description of the Invention"
Each column 6, Contents of amendment (1) "Claims" will be corrected as shown in the attached sheet.

(2) "Flux composition" in Table 1 on page 14 of the specification.

The values listed in column 18.19゜20 of the invention example number in the ``Others'' column are corrected as follows.

"(Incorrect) (Correct) Claim (1) CaF2: 30-60% (meaning of weight %, the same applies hereinafter) A1203: 10-30% 5i02: 5-15% Cab: 10% or less M g F 2 and/or AlF3: 3 to 20% in total MgO and/or Bad: 2 to 15% in total, and (MgF 2 +A IF3 ) /S i 02
A flux for electroslag overlay welding, characterized in that it satisfies the following conditions: 0.50 or more.

(2) C&F2: 30-60% Al2O3: 10-30% 5i02: 5-15% CaO: 10% or less MgF2 and/or AlF3: 3-20% in total MgO and/or Bad: 2 in total ~15% S simple substance and/or compound: 0. O1 to 0.1% (in terms of S), and (MgF2+A IF3 )/S i 02 :0.
A flux for electroslag overlay welding, characterized in that it satisfies conditions of 50 or more.

Claims (2)

[Claims] (1) CaFl: 30 to 60% (meaning of weight %, same below) A1.0. :10~30q6 S10. : 5-15 Excellent Cab: 10- or less MgF and/or AIF: 3-20% in total MgO and/or Bad: 2-15% in total, and (Mg Fg + A I Fm )/S log :0
A flux for electric four-slag overlay welding, characterized in that it satisfies conditions of 150 or more. (2) Ca Ft: 30-60 q6 AI, O Hatake: 10-30 q6 SiO! : 5 to 15 days; Cab: 10% or less MgF and/or AIF: 3 to 20 in total MgO and/or Bad: 2 to 15 in total q6S simple substance and/or compound: 0.01 to 10% in total 0.1 (S conversion) and (MgFl + A IFm )/810! : 0.5
A fussicle for electros 2-g overlay welding, characterized in that it satisfies a condition of 0 or more.