JPH079191A - MAG welding flux-cored wire with little welding deformation - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a mag-welding flux-cored wire that reduces the amount of angular deformation that occurs during welding and that has a good finished bead shape and appearance after welding. [Composition] In a mag-welding flux cored wire in which a steel shell is filled with a titania flux, one or both of the steel shell and the filled flux regulates the amount of Mn, Si and C relative to the total weight of the wire. , And N
i, Cu, Cr, Mo, V, Nb, and any one or more of them are included, and the value of the parameter T determined by the following formula (1) is less than 630 depending on the weight% of each element in the wire. MAG welding flux-cored wire with less welding deformation. T = 630.0-476.5C + 56.0Si-19.7Mn-16.3Cu-26.6Ni-4.9Cr + 38.1Mo + 124.8V + 136.3Ti-19.1Nb + 198.4Al + 3315.0B (1)

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding material for steel materials used in construction, civil engineering, offshore structures, shipbuilding, etc. More specifically, since there is little out-of-plane deformation during welding work, strain relief is achieved. The present invention relates to a titania-based mag-welding flux-cored wire that has an excellent bead appearance and shape that can reduce or omit work.

[0002]

2. Description of the Related Art During welding of steel materials in various steel structures, due to solidification shrinkage of molten metal and subsequent contraction / expansion due to cooling and phase transformation, for example, in the case of joint shape of fillet welding, a surface called angular deformation External deformation occurs. Such residual deformation causes a decrease in structural strength such as a decrease in buckling strength when a compressive load is applied. In addition, if it is attempted to forcibly prevent this deformation with a restraint jig, excessive residual stress will be generated, and further, dimensional accuracy will be insufficient and manufacturing inconvenience will occur, and aesthetics will be spoiled. Become. Therefore, as seen in, for example, "Generation and Prevention of Welding Deformation" serialized in Journal of Welding Society 1983 Vol. 52, No. 4 to No. 5 and No. 7 to No. 9, it occurred at the time of welding. Many empirical methods have been proposed to correct residual deformation by local heating. However, in these methods, deterioration of the material due to reheating of the weld is unavoidable, and in addition, the time and cost required for the correction work are serious obstacles for practical use, and it is not possible to reduce or omit them. It was desired to develop a possible welding method.

Regarding the mechanism of occurrence of residual stress and deformation in the welded portion, Sato's "Welding Structure Manual" 1988,
(Kuroki Publishing) and K. Masubichi's "Analy
"sisof Welded Structures" 1
Details on 980, PERGAMONPRESS. However, the welding deformation does not focus on the detailed characteristics of the welding material used, as the welding deformation is mainly determined by the geometrical shape of the member with respect to the heat input during welding. Although it is specified in this document that the phase transformation temperature of the welded part of a steel structure is a factor that affects residual stress and deformation, the specific degree of influence of the welding material for steel structures Has not been quantified or examined.

There are also reports of studies on relaxation of residual stress and reduction of deformation by paying attention to the superplastic phenomenon of phase transformation (Abstracts of the National Meeting of the Welding Society, 37th p. 314-315, 38th p. 78-79, 39th p.338-34
1). However, all of these are focused on the martensitic transformation temperature of low alloy steels and stainless steels, containing 3.5 to 12% of Ni, and of the ordinary steel materials found in mild steel and 50 kg class high strength steel. It is not a finding that can be directly applied to components and tissues. Further, in the case of containing such a high value of Ni, the welding material cost becomes high, and even if the strain relief work can be omitted, it is not practical from an economic knowledge. Furthermore, when this is applied to ordinary steel and low alloy steel for shipbuilding and offshore structures, the weld metal becomes electrically noble and selective corrosion phenomena occur in the heat affected zone. Inconvenience occurs.

The most influential factor on the welding deformation is the welding heat input with respect to the steel plate thickness, and the phase transformation temperature of the weld metal is next. In addition to these, at the temperature at which the deformation occurs, the strength of the material that resists the deformation can be mentioned. The phase transformation temperature is generally in the range of 400 to 700 ° C,
It can be inferred from the knowledge of high-temperature strength of Cr-Mo steel, for example, that the amount of deformation can be reduced by increasing the strength in this temperature range by adding elements such as Cr, Mo, V, and Nb. However, no studies have been made so far to secure high-temperature strength at the transformation point temperature of the weld metal, and since these additional elements tend to increase the transformation point temperature described above and increase the welding deformation. However, the proper addition amount could not be easily determined.

As a method for solving these problems, the gas shield arc welding method described in JP-A-4-22596 and JP-A-4-22597 has been proposed. The welding material applied to these methods is a steel wire, but when welding with a steel wire, the penetration at the time of welding is deep and it is not always satisfactory in reducing welding deformation.

[0007]

As described above, the effect of the phase transformation point temperature of the welding material on the amount of deformation generated during welding is quantified, given that the welding member / shape and the welding heat input amount are given, It is considered effective to provide design guidelines for welding material components. The present invention focuses on the Ar ₃ transformation point temperature of the welding material for the welded joint of ordinary steel that is most commonly used for steel structures, taking the amount of angular deformation that occurs during T-shaped fillet welding as an example. By studying the relationship between the Ar ₃ transformation point temperature and the amount of angular deformation, the amount of angular deformation that occurs is small, and in addition to reducing the amount of angular deformation as an expanded application, the finished bead shape after welding is significantly reduced. It is intended to provide an improved welding material.

In the present invention, the amount of angular deformation is taken as one of the measures of the amount of deformation, and the application is not limited to angular deformation.

[0009]

As a result of further experiments, the present inventors have found that the flux-cored wire can reduce the welding deformation amount compared with the steel wire. It was found that the penetration of steel wire is deep during welding, and the penetration of flux-cored wire is shallower than that of steel wire, so the amount of deformation can be further reduced.

That is, the gist of the present invention is that it is made of steel.
TiO for the total weight of the wire on the skin ₂2.5-6.5
%, TiO₂Other than arc stabilizers and slag formers;
Fill with a titania-based flux containing 0.3 to 2.5%.
Mug welding flux cored wire filled with steel
Either or both of the skin and the packing flux
C: 0.03 to 0.15% based on the total weight, preferably
Is C: 0.03 to 0.09%, Si: 0.2 to 1.0
%, Mn; 0.3 to 3.0%, preferably Mn; 0.5
.About.3.0%, further Ni: 0.2 to 5.0%,
Cu; 0.1-1.5%, Cr; 0.1-3.0%, M
o: 0.1-2.0%, V: 0.1-0.7%, preferred
Ku V: 0.1 to 0.5%, Nb: 0.01 to 0.50
%, Preferably Nb; 0.01-0.05%, whichever is
Contains one or more of them and occupies them in the wire
Parameter determined by the following formula (1) according to the weight% of each element
Low welding deformation, characterized by a T of less than 630
There is no MAG welding flux cored wire. T = 630.0-476.5C + 56.0Si-19.7Mn-16.3Cu-26.6Ni-4.9Cr + 38.1Mo + 124.8V + 136.3Ti-19.1Nb + 198.4Al + 3315.0B (1)

[0011]

The Ar ₃ transformation point temperature T can be roughly estimated by the equation (1) in the range of the cooling rate of the usual arc welding method. As is clear from this formula, a predetermined amount of γ-former Ni, Mn, Cu, Nb, and C is added to make Ar ₃
It is possible to lower the transformation point. Generally, the lower the transformation temperature is, the larger the transformation expansion amount is, which reduces the residual welding deformation caused by the shrinkage during cooling. Therefore, it is considered that the increase of the transformation expansion amount contributes to the reduction of the welding deformation. . However, the transformation of supercooled austenite does not simply show a clear correspondence with the transformation expansion amount due to the appearance of the bainite structure, etc. Therefore, the Ar ₃ transformation point temperature was focused here.

On the other hand, the amount of angular deformation generated in the T-shaped fillet welded joint has a clear relation with the Ar ₃ transformation point temperature of the welding material as shown in FIG. 1, and the transformation point temperature is a low value. It was found that the amount of angular deformation that occurs so much is a small value.
This fact seems to be because the transformation temperature becomes low and the transformation expansion amount becomes large, and the shrinkage due to solidification is eliminated to some extent.

Furthermore, Ni, Mn and C which are gamma formers
In the case of containing the elements Cu, Cr, Mo, Nb, and V in addition to the component system of (1), the value of the phase transformation temperature T given by the equation (1) is slightly higher than that in the case of not including the latter. Even if there is, it was found that the amount of angular deformation that occurs is small.
This fact is considered to be because the elements Cr, Mo, Nb, and V all increase the mechanical strength at the temperature at which the transformation occurs, thereby restraining the deformation. Due to welding deformation, for example, the buckling strength against compressive load is reduced, and from consideration of dimensional accuracy in joint manufacturing, the transformation point temperature that gives the limit value of the angular deformation amount that does not require the above-mentioned deformation correction work is Cr. As a result of considering the effect of the addition of the elements, Mo, Nb, and V, the relational expression (T <630) of the present invention was found.

The present invention is based on a typical welding cooling rate,
Ar of various components contained in welding material ₃Phase transformation temperature T
Given by the formula (1), T = 630.0-476.5C + 56.0Si-19.7Mn-16.3Cu-26.6Ni-4.9Cr + 38.1Mo + 124.8V + 136.3Ti-19.1Nb + 198.4Al + 3315.0B (1 ) Check the relationship between the phase transformation temperature of the welding material and the amount of angular deformation that occurs.
From the discussion, the amount of deformation that occurs practically is sufficiently small
It gives the relationship of equation (2), which is judged to be a large value.
is there. T <630 (2)

The specific values of the constituent elements of the welding wire in the present invention and the addition amounts thereof will be described below (the value of the addition amount of elements is% by weight based on the total weight of the wire). C has the effect of lowering the transformation point, and 0.03% or more is necessary also from the viewpoint of strength. However, excessive addition leads to an increase in hot crack susceptibility of the weld metal and a decrease in toughness, so 0.15%
It is preferably 0.09% or less.

Si has the effect of reducing the amount of oxygen in the weld metal and improving the bead shape, and at least 0.
2% or more is required. However, excessive addition lowers the toughness of the weld metal, so the upper limit must be 1.0%. Mn has a large effect of lowering the transformation point, and assists Ni by at least 0.3% or more, preferably 0.5% or more,
More preferably, it is necessary to add 0.8% or more. On the other hand, excessive addition leads to an increase in hot cracking susceptibility of the weld metal and a decrease in toughness, so the upper limit must be 3.0%.

The above elements are elements that are effective in lowering the transformation point. In the present invention, in addition to this, the strength in the temperature range where transformation occurs is increased and the following N
It contains one or more elements of i, Cu, Cr, Mo, V, and Nb. Ni is a typical gamma former and has a large effect of lowering the transformation point. At least 0.2%
More preferably, it is necessary to add 3.0% or more. However, if the added amount is too large, the cost will increase, and in addition, for example, in the case of offshore structures, the weld metal will become too noble electrically, forming a local battery and selectively affecting the heat affected zone. Will be corroded by. Therefore, the upper limit of the amount of Ni added needs to be 5.0%.

Since Cu also has the effect of lowering the transformation point, it is necessary to add it in an amount of 0.1% or more. On the other hand, excessive addition leads to a decrease in the toughness of the weld metal, so the upper limit is 1.5.
%. The effect of increasing the strength due to Cr is recognized with the addition of 0.1% or more. However, if the addition amount is too large, the room temperature strength and hardness increase, the toughness deteriorates, and the weldability also decreases, so the upper limit is made 3.0%.

From the viewpoint of strength, Mo must be added in an amount of 0.1% or more. However, since Mo is an element that raises the transformation temperature, the upper limit is 2.0%. Regarding V, addition of 0.1% or more has the effect of increasing strength. However, excessive addition causes deterioration of toughness due to an increase in strength and hardness at room temperature and raises the transformation temperature, so the upper limit is 0.7%.

With respect to Nb, addition of 0.01% or more has the effect of increasing strength. However, excessive addition brings about an increase in normal temperature strength and hardness, so the upper limit is made 0.50%,
Further, in order to prevent deterioration of toughness, the content is preferably 0.05% or less. The method of adding the above elements is
It may be added to one or both of the fluxes.

The above is the means for reducing the amount of angular deformation that occurs during welding. However, the present inventors have found that the penetration during welding is shallow and the appearance and shape of the finished bead after welding are improved (expansion of fields of use). ), The improvement of welding workability was also examined. As a result, they have found that the use of titania-based flux can improve the bead appearance and shape after welding, and can reduce the amount of spatter generated during welding.

In the present invention, based on the above characteristics, the content ratio of each component is determined as follows. TiO ₂ ; 2.5-6.5% TiO ₂ enhances arc stability and slag encapsulation,
It is an indispensable component for improving all-position weldability,
If it is less than 2.5%, the effect cannot be obtained. However, 6.
If it exceeds 5%, the slag viscosity becomes too high, the bead shape deteriorates, and excessive reduced titanium is retained in the weld metal to reduce mechanical properties (particularly toughness). Therefore, T
The iO ₂ is in the range of 2.5 to 6.5%.

Arc stabilizers other than TiO ₂ and slag forming agents; in the wire of the present invention containing 0.3 to 2.5% TiO ₂ as a main component, these are used in order to stabilize the arc and reduce the amount of spatter generation. Needs to be added. The arc stabilizer here is L
Examples thereof include alkali metals such as i, Na and K and compounds thereof. The slag forming agent needs to be added within a range that does not lower the deposition rate in order to improve the bead shape. When the arc stabilizer other than TiO ₂ and the slag forming agent are less than 0.3%, the bead shape improving effect is not recognized,
On the other hand, if it exceeds 2.5%, the amount of slag increases, defects such as slag inclusion occur, and the welding efficiency decreases. Therefore, the arc stabilizer and the slag forming agent should be 0.3 to 2.5%. Incidentally, as the slag forming agent, SiO ₂ , Zr
_{O 2, Al 2 O 3,} MnO, oxides such as MgO, CaF
Fluoride such as ₂ , BaF ₂ , MgF ₂ , LiF and Ca
Carbonates such as CO ₃ and BaCO ₃ can be used.

The above are the essential components of the wire of the present invention.
Iron powder may be added for the purpose of improving the welding efficiency. Furthermore, the flux filling rate of the wire according to the present invention is preferably set to 8 to 20%. The reason is that if the filling rate exceeds 20%, wire breakage troubles frequently occur during wire drawing and productivity deteriorates, and if it is less than 8%, arc stability is impaired.

There is no restriction on the cross-sectional shape of the wire,
When the diameter is 2 mm or less, a relatively simple cylindrical shape is generally used. Further, it is also effective to subject the surface of the seamless wire to a plating treatment such as Cu.

[0026]

[Examples] Table 1 shows the steel shell used for the wires of this example. Tables 2 and 3 (continued from Table 2-1) and Table 4 (Table 2
Continuation-2) and Table 5 (Continuation-3 of Table 2), the flux composition of the example wire and Ar calculated by the equation (1) are shown.
₃ points (T) are shown. The wire diameter is 1.2 mm in each case. As the steel plate, a JIS G3106 SM400B material was used (chemical components are shown in Table 6). This steel plate is shown in FIG.
In order to manufacture a fillet welded test piece, one-pass welding was performed on both sides under the welding conditions shown in Table 7. After the welding was completed, the amount of angular deformation δ was measured, and then the longitudinal section of the weld metal was observed to determine the presence or absence of cracks in the weld metal and the bead shape. As a comprehensive evaluation, the magnitude of the angular deformation amount δ is calculated by the equation (3) using the values of w and d shown in FIG. 3, δ = 0.5 sin ⁻¹ (2d / w) (3) Is less than 1.2 × 10 ^-2 radians,
And no cracks are seen, and the bead shape,
Those with excellent appearance were accepted, and others were rejected. Table 8 shows the test results.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

[0032]

[Table 6]

[0033]

[Table 7]

[0034]

[Table 8]

As can be seen from Table 8, all the welded joints made of the wire according to the present invention have a small amount of angular deformation, no cracking, and a good bead shape and appearance. ． 22, 26, 27, 29, 31,
In No. 33, the weld metal hardened and cracked due to the high amount of curable element, and the T value exceeded 630 and the amount of angular deformation was large. No. In Nos. 23 and 28, Ni and Cr, which have a large effect of lowering the transformation point, were not added, and therefore the amount of angular deformation was large, and they were rejected. In addition, No. No. 32 had no effect because the amount of Si added was excessive. When the element group that increases the high temperature strength is not added, No. As shown in 25, even if the value of T is 584, the amount of angular deformation is large. Moreover, even if the alloys were within the scope of the present invention, No. No. 1 in which the slag component for improving the bead shape and appearance, which are the features of the present invention, is outside the scope of the present invention. In Nos. 24 and 30, the value of T and the amount of angular deformation were also within the scope of the present invention, but the finished bead shape or appearance was poor and the test was rejected.

In this experiment, the SM400B material was used, but since the base material dilution is small, the effect of reducing the amount of angular deformation of the wire of the present invention is not lost even if the type of steel sheet changes. Furthermore, regarding the composition of the shield gas, Ar-CO ₂
Even if the wire according to the present invention is used after being changed to a mixed gas, a good amount of angular deformation can be obtained without affecting the performance.

[0037]

Although the welded joint is an essential technical element in the production of steel structures, the prevention of welding deformation and its correction technology are often obtained empirically. Recently, welding deformation reduction technology has been demanded from the viewpoints of steel structure design, rationalization, aesthetics, etc., and at the same time, welding materials with less deformation that occur due to lack of skilled welders and automation of welding process are supplied. It was desired to do.

According to the present invention, the welding deformation is reduced in the automatic and semi-automatic welding process without deteriorating the various characteristics of the joint portion, and the work for correcting the deformation can be omitted within the economically acceptable range. The remarkable effect that the above-mentioned added value can be realized is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a transformation temperature and an amount of angular deformation.

FIG. 2 is a diagram showing an outline of a T-shaped fillet welded joint.

FIG. 3 is a diagram illustrating the definition of an angular deformation amount δ.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Kojima 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Corporate Technology Development Division

Claims (3)

[Claims] 1. A steel outer cover made of TiO based on the total weight of the wire.
₂ ; 2.5-6.5%, arc stabilizer other than TiO ₂ and slag forming agent; Mag-welding flux-cored wire filled with titania-based flux containing 0.3-2.5%, steel C: 0.03 to 0.09% Si; 0.2 to 1.0% Mn; 0.5 to 3.0% Ni; 0 based on the total weight of the wire in one or both of the outer shell and the filling flux. 2 to 5.0% Cu; 0.1 to 1.5%, and further Cr: 0.1 to 3.0% Mo; 0.1 to 2.0% V; 0.1 to 0. 0.5% Nb; 0.01 to 0.05% of any one kind or two kinds or more, and the parameter T determined by the following formula (1) is 630 depending on the weight% of each element occupying in the wire. MAG welding flux cored wire with less welding deformation characterized by less than T = 630.0-476.5C + 56.0Si-19.7Mn-16.3Cu-26.6Ni-4.9Cr + 38.1Mo + 124.8V + 136.3Ti-19.1Nb + 198.4Al + 3315.0B (1) 2. A steel outer cover made of TiO based on the total weight of the wire.
₂ ; 2.5-6.5%, arc stabilizer other than TiO ₂ and slag forming agent; Mag-welding flux-cored wire filled with titania-based flux containing 0.3-2.5%, steel In one or both of the outer skin and the filling flux, C; 0.03 to 0.15% Si; 0.2 to 1.0% Mn; 0.3 to 3.0% based on the total weight of the wire. Further, Cu; 0.1 to 1.5% Cr; 0.1 to 3.0% Mo; 0.1 to 2.0% V; 0.1 to 0.7% Nb; 0.01 to 0 Welding deformation, characterized in that it contains any one or more of 50%, and that the parameter T determined by the following formula (1) by the weight% of each element occupying the wire is less than 630. Low flux MAG welding flux cored wire. T = 630.0-476.5C + 56.0Si-19.7Mn-16.3Cu-26.6Ni-4.9Cr + 38.1Mo + 124.8V + 136.3Ti-19.1Nb + 198.4Al + 3315.0B (1) 3. The mag-welding flux-cored wire according to claim 2, which contains Ni: 0.2 to 5.0% based on the total weight of the wire.