JPS6233091A - Submerged arc welding method by which high-toughness weld metal is obtained - Google Patents

Abstract

PURPOSE:To obtain a high-toughness weld metal by specifying the content of N2 in a wire and adding AlF3 to a flux having specific flux basicity in the stage of welding a mild steel and high tensile steel. CONSTITUTION:The wire limited to <=0.0055% N2 by weight % and the fused flux which has >=1.0 basicity calculated by equation I and is added and mixed with 1-15% aluminum fluoride AlF3 are used. Ti or Ti compd. is incorporated at <=0.5% calculated by equation II into either the wire or flux, then submerged arc welding is executed. The respective components are by weight %. The high-toughness weld metal is thereby obtd.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a submerged arc welding method for obtaining high-toughness weld metal, and more specifically, high-toughness welding of single-layer or multi-layer welds when welding mild steel or high-strength steel. It concerns a submerged arc welding method for obtaining metal.

(Prior Art) Recently, many types of offshore structures for oil drilling have been manufactured, but with the trend of depletion of petroleum resources, more and more structures are being built for cold regions near the North Sea and the Arctic Ocean. The steel materials and welded parts of offshore structures for use in cold regions are required to have extremely high toughness in order to withstand brittle fracture at low temperatures, and these requirements are becoming increasingly strict. ing.

Conventionally, as a means to increase the low-temperature toughness of weld metal in mild steel and high-strength steel, as is known from Japanese Patent Publication No. 52-906 and Japanese Patent Publication No. 51-48448, Tt or Ti compounds are added to the wire or 7 lacs. Ti and B are added to the low-oxygen weld metal by adding B or B compounds.
It has been revealed that high toughness can be obtained by containing .

On the other hand, there are two types of submerged arc flux: molten type flux and sintered type flux. Of these, fused type flux has the advantage of good slag releasability, good bead shape during high-speed welding, less pulverization, and less hygroscopicity. It is used in many fields due to its advantages such as no component segregation and stable performance. By combining this molten flux with good workability and a wire containing Tf or TI-B, or by including TIOh or TiO2 and B2O2 in the molten flux component, TI or Ti can be added to the weld metal. A welding method using so-called TI-B welding material gold containing -B is becoming widely used.

However, in recent years, severe low-temperature toughness has been required, and it has become clear that such a welding method cannot sufficiently meet this requirement (problem to be solved by the invention). When using molten flux, especially when the flux has a highly basic composition so as to obtain a low oxygen weld metal, which is a necessary condition for obtaining high toughness,
Unlike fired flux, the flux does not contain gas generating agents such as carbonates, so the air (N2) existing between the flux particles directly enters the weld metal, and this N2
2 is the toughening effect of T1 or Ti-H, that is, T
It has been found that iO does not act as a generation nucleus for ash killer ferrite, and B segregates at the r-grain boundaries, reducing the effect of preventing the precipitation of pro-eutectoid ferrite. The amount of increase in N21ft varies depending on welding conditions, flux particle size, etc., but it is known to reach 10 to 40 ppm.
It has become clear that there is a limit to the effect of improving the toughness of weld metal using FCA arc solution welding using a Ti-B welding material with good core liquid workability.

(Means for solving all the problems) Welding wire and As a result of examining both sides of the flux, we found that aluminum fluoride (ALF,
It has been found that by using a flux to which an appropriate amount of N2 is mixed and added, an extremely high toughness weld metal without any increase in the amount of N2 can be obtained without impairing workability at all.

That is, when welding mild steel and high-strength steel, the present invention limits N2'Ik to 0.0055- or less in weight percent, and the basicity calculated by the following formula (9) is 1.0. Using the above-mentioned molten flux mixed with 1 to 15 g of aluminum fluoride, at least one of these wires or fluxes contains a KTi or T1 compound, calculated using the following formula (B), to contain not more than 5 l. or at least one of the above wires or fluxes contains B or B oxide, calculated using the following formula (C): 0.01
(This is a submerged arc welding method in which a submerged arc welding method is obtained by containing less than 1 liter of submerged arc welding material.

however, (However, each ingredient weighs 1 inch) (However, each component is ERW) The present invention will be explained in detail below.

(Function) First, the term "mild steel" and "high tensile strength region" as used in the present invention refers to steel materials that can be joined to m, and refers to all carbon steels to low alloy steels with a tensile strength of 41 kg to 80 kg, as per JIS G 3101, 3106, 88.
41, 5M41 or higher strength equivalent, rough 53001° JIS G3128 equivalent, or As A316,
A337.

This applies to products equivalent to A333 and A317 steel.

The target is a wide range of plate thicknesses, from around 10w to extremely thick materials of around 200m. Also, high toughness here means that at a low temperature of -30 to -100°C,
2.8k17-m~5.
It means a level of 6 kg-m or more.

Next, regarding the components of the wire used in the present invention, it is necessary to limit the amount of N2 to 1 kO, 00551 or less.

This N2 is the most harmful component in Ti and T%-B weld metals, especially when high toughness at low temperatures below -60°C or even toughness after stress relief annealing is required. This N2 needs to be as low as possible. When the amount of N2 exceeds 0.0055 $, there is almost no effect of adding aluminum fluoride (AtF) to the static flux to suppress the increase in N2 and obtain high toughness of the weld metal.

As other wire components, the following component ranges can be used. That is, C0.16% or less, 810.50% or less, Mn 2.
The basic components are 709b or less, Ni 8% or less, Cr 1.0% or less, Mo 0.8% or less, Cu 1.
Contains one or more of the following: 2% or less, T10, 50% or less, Vo, 03% or less, Nb O, 02% or less, P
, SO, 03% or less, 0□0.02% or less, and also contains F and inevitable impurities.

The basicity of the flux needs to be 1.0 or more according to the following formula (A). If this is less than 1.0, the cumulative acid content of the weld metal will exceed 0.04%, and T1 or Ti-B
This effect is no longer observed and low toughness is exhibited.

However, this (At formula) is recognized by the International Institute of Welding (IIW) and is a commonly used formula for indicating flux basicity.

Next, it is assumed that AtF mixed and added to the flux becomes gaseous in the arc atmosphere during welding and removes N2 between the flux particles.
If the amount of F' added is less than 1%, the effect of suppressing the increase in N is not sufficient, and almost no effect is seen on improving toughness. On the other hand, if it is added in excess of 15 inches, the appearance and shape of the peas will be poor, which is not preferable.

The particle size of AtF is preferably a particle size that matches the particle size structure of the melting type flux used, and is suitably 20 mesh or less.

Next, in order to make the weld metal high toughness, T% or Ti −
It is necessary to add it to at least one of the B'i wire or the flux, and in the case of T1, it can be added at a maximum of 0.50% in the wire. When adding from flux, oxides such as TIO□ can also be added, but from the viewpoint of workability, the maximum amount is 30-.

When adding from both flux and wire, see below (
It can be added up to 0.50% using formula B). The value of (B) is 0,
If it exceeds 5%, the hardening property will increase due to the relationship with N2, resulting in low toughness.

(However, each component is Mgol.) This equation (B) was determined experimentally from the viewpoint of the yield and toughness of T1 to the weld metal, and the reason for dividing the TlO2 value in the flux by 50 is to 11 companies and m
This is because the yield of T1 to the welding base is almost equivalent.

Also, when adding B to this, it is the same as T% (it can be added to formula 0 from the plow wire and flux, but if it is added from the wire, it needs to be 0.010'S or less.

When adding flux, it can be added as a fermentation product or compound such as borax.

However, if too much B is added, high-temperature cracking will occur, and in the case of a low N21W weld metal such as the present invention, it will conversely reduce the toughness, so it must be kept at 0.010% or less in formula (C).

However, (however, each component is 1% by weight) This formula (C) was obtained experimentally from the viewpoint of the yield of B in the weld metal and the toughness, and the B2 in the flux
This is because the amount of B in the wire and the yield of B in the weld metal are equivalent to dividing the O3 equivalent value (H) by 100.

Next, regarding the composition of the m-melting type flux, those having the following composition range as the main component exhibit good performance.

It goes without saying that all of the fluxes listed below must satisfy formula 9. Of these, the upper limit of 5to2II, CaF
The lower limit of 2il (5chi) is important.

(TiO type) T1027~30chi, SiO□10~30
%, AtO5-40%, CaF25-35%Other Ca
025% or less, Mg 025% or less, BaO 30% or less,
It is possible to add up to 50 T of one or more of MnO of up to 15 T, and also Z ro 2, FeO or NIL.
Alkaline oxides such as 20 and N20 can be added in a total of 15 or less.

(Non-TlO2-based) 810210-40%, CaF
'25~50chi, kt2035~45%, C 05~4
5chi, other Mg030% or less, Ba030% or less, M
It is possible to add one or more of the following in an amount of 40% or less, and further add an alkali oxide such as TiO2, ZrO2, F'eO or Na2O in a total amount of 15% or less.

Among these, TiO2 is limited to 5 or less from the viewpoint of slag releasability.

A flux particle size of 12 mesh or less can be used.

Using the above combination of wire and flux,
Submerged arc welding is performed by conventional means. The desirable conditions are to use a wire diameter of 1.6 mφ to 6.4 mφ, the number of electrodes to be 1 to 5, and a welding current of 9200 O per electrode.
It can be used for single-layer and multi-layer welding on one side and single-layer and multi-layer welding on both sides with a heat input of 150,000 J/cm or less.

(Example) Hereinafter, the effects of the present invention will be illustrated in more detail with reference to Examples.

Commercially available 50HT with a plate thickness of 25 wm and the chemical components shown in Table 1
, For 60HT and 80HT steel, the wire shown in Table 2 as a latent arc welding material (○ marks are materials that meet the requirements of the present invention, the others are comparative materials, wire diameter is 4.8 φ) and the wire shown in Table 3 The flux shown in Fig. 1 (marked with Q is a material that satisfies the requirements of the present invention, and the others are comparative materials) was combined with the groove shape shown in Fig. 1 and the laminated layer method. 20',
Using a groove with a root gap g = 16 sm and a backing metal made of the same steel plate as the welding test plate, multi-layer stacking was performed for 1 layer and 2 layers, as shown in Figure 2 from weld metal 3. According to the sampling procedure, take round bar test piece 4 (J) from 12.5 points.
ISAI) and V-notch Charpy impact test piece 5 (
JI No. 84) were collected and tested. Note that 6 is the notch position. Also, the welding conditions are 750A, 3
Single electrode welding at 2V, 50cpm, no preheating, and interpass temperature of 150°C.

Table 4 shows the combinations of wire and flux and the various test results using them. In the table (categories), the ○ marks indicate combinations representing examples of the present invention, and the others are comparative examples.

The N2R of the weld metal obtained by the method of the present invention is close to that of the wire component, and the impact arc value is E-75, c value).
All are good (vE-751: > 4.8 kgf-
Comparative examples that do not meet the requirements of the present invention show unsatisfactory values of vE-75T:, or vE-60'C. That is, in Comparative Examples 2.5 and 8, AtF was not added to the flux, and the N2Jii of the m weld metal was 0.0023 from N2 Company in the wire.
~0.00301 increase, indicating low toughness, Comparative Examples 3 and 10 were discarded in the wire KN2il10.0068~0
．． 0073%, indicating low toughness.

In Comparative Example 6, the basicity of the flux was as low as 0.77, the amount of oxygen in the weld metal increased, and the effects of Ti and B were not observed, resulting in low toughness.

In Comparative Example 11, the value of formula (B1) was as high as 0.61% and the value of formula (C) was as high as 0.0128%, and due to not only excess T1 but also excess B, hot cracking occurred and the test was completely discontinued. Comparative example 13
The value of formula (B) is as high as 0.64 cm (excessive Ti indicates hardening and low toughness).

In Comparative Example 14, the addition of AtF'3 to the flux was excessive, resulting in unstable arc and poor weld bead shape, and the test was discontinued.

(Effects of the Invention) As is clear from the above examples, according to the method of the present invention, Ti or T
For example, the low-temperature toughness of i-B weld metals at -75°C deteriorates due to the increase in N2 during welding, but it is now possible to increase the toughness without any deterioration in workability, and in the future, we will be able to improve the toughness at even more severe temperatures at -75°C. This will greatly contribute to the various types of welding work that are becoming increasingly required.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the groove shape and layering method of the welding test plate used in the example, and FIG. 2 is a diagram showing the various test piece collection procedures used in the example. 1... Welding test plate 2... Backing metal 3... Welding metal 4... Tensile test piece 5... Impact test piece 6... Notch position. Figure 1 Figure 2 ゛

Claims (2)

[Claims] (1) When welding mild steel and high-strength steel, wire with N_2 limited to 0.0055% or less by weight and the following (
A) A molten flux with a basicity calculated by formula 1.0 or more and 1 to 15% aluminum fluoride is used, and Ti or a Ti compound is added to at least one of the wire or flux as shown below ( B) A submerged arc welding method for obtaining a high-toughness weld metal, characterized in that submerged arc welding is performed with a content of 0.5% or less as calculated by formula. However, [CaO+MgO+BaO+CaF_2+Na_2O+
K_2O+1/2MnO]/[SiO_2+1/2(A
l_2O_3+TiO_2)]...(A) (However, each component is weight%) Ti% (in wire) + [TiO_2 conversion value % (in flux)]/50...(B) (However, each component is weight%) %) (2) When welding mild steel and high-strength steel, wire with N_2 limited to 0.0055% or less by weight and the following (
A) A molten flux with a basicity calculated by formula 1.0 or more and 1 to 15% aluminum fluoride is used, and Ti or a Ti compound is added to at least one of the wire or flux as shown below ( Calculated using formula B), the content is 0.5% or less, and at least one of the wire or flux contains B or a B compound as shown below (
C) A submerged arc welding method for obtaining a high-toughness weld metal, characterized in that submerged arc welding is performed with a content of 0.010% or less as calculated by formula. However, [CaO+MgO+BaO+CaF_2+Na_2O+
K_2O+1/2MnO]/[SiO_2+1/2(A
l_2O_3+TiO_2)]...(A) (However, each component is weight%) Ti% (in wire) + [TiO_2 conversion value % (in flux)]/50...(B) (However, each component is weight%) %) B% (in wire) + [B_2O_3 conversion value % (in flux)]/100...(C) (However, each component is weight%)