JPH03118978A - Root submerged arc welding method for extra-thick plate multilayer welding - Google Patents

Abstract

PURPOSE:To prevent the occurrence of weld defects of the joint part root and to improve welding efficiency at the time of performing multilayer welding on extra-thick plates by submerged arc welding by using two electrodes by regulating Y-shaped groove shape dimensions and performing submerged arc welding of the root part under specified welding conditions. CONSTITUTION:In multilayer welding of the extra-thick plates 1 and 1 by submerged arc welding by using the two electrodes of a preceding electrode L and a succeeding electrode T having 5.3-8.0mm<phi> diameter and a wire shape on a Y-shaped groove joint having 1-8mm root face (l) and 40-55 deg. groove angle theta, the root part is subjected to submerged arc welding under the welding conditions of the distance (d) of 40-80mm between the electrodes, a wire tilt angle alpha of -15 deg.-+5 deg. at the preceding electrode L and 0 deg.-+20 deg. at the succeeding electrode T, wire extension length (h) of 40-120mm at the preceding electrode L and 50-120mm at the succeeding electrode T, 1000-2000A current of the L electrode and 800-1800A current of the T electrode, the current different of 100-600A between both electrodes L and T, the current ratio of 0.75-1.0 between both electrodes L and T and the welding speed of 15-45cm/min.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to multilayer welding of very thick plates having a thickness of 60 mm+ or more, and particularly to a submerged arc welding method that enables highly efficient construction of box column angle joints.

(Prior art and problems to be solved) Generally, multi-layer welding has been used for box-column corner joints with a plate thickness of 60 mm or more, and as shown in Fig.
Take a gap (g) of about 20mm+ and place the bottom layer with CO2
It is constructed by gas-shielded arc welding, and the upper layer is constructed by submerged arc welding. However, with this construction method,
Since the cross-sectional area of the groove is large and CO2 gas shielded arc welding is less efficient than submerged arc welding, it has the disadvantage that productivity cannot be improved.

On the other hand, if the cross-sectional area of the groove is reduced and multi-layer welding is performed using latent arc welding with large heat input from the first layer, highly efficient construction can be achieved, but defects are particularly likely to occur in the welded part of the first layer. No solution has been found to solve this problem.

The present invention has been made in order to solve the above-mentioned problems of the prior art regarding multi-layer welding of ultra-thick plates, and in particular to provide a welding method that can perform latent arc welding with high efficiency without welding defects on the first layer. The purpose is to

(Means for Solving the Problems) As described above, when high heat input latent arc welding is performed from the first layer of an extremely thick plate, there is a problem in that defects are likely to occur particularly in the welded portion of the first layer. That is, since the bead width of the first layer weld is limited by the groove surface, the weld has a shape where penetration is deep and the bead width is narrow, and hot cracking due to the so-called pear-shaped bead shape is likely to occur. Furthermore, since the groove width in the initial layer portion is narrow, undercuts are likely to occur, and slag removability also deteriorates rapidly.

Therefore, as a result of intensive research on the submerged arc welding conditions for the first layer and the groove shape, we adopted a Y-type groove joint with a groove angle of 40 to 55 degrees, and the wire inclination angle.

It was discovered that economical (small groove cross-sectional area) and efficient construction is possible by regulating conditions such as wire protrusion length, current voltage, welding speed, etc., and the present invention was thus made. It is.

That is, the present invention provides root face ρ: 1 to 8 mm,
A Y-type groove joint with groove angle θ: 40 to 55 degrees, diameter 5,
3-8. In multi-layer welding of very thick plates in latent arc welding using Ommφ wire-shaped leading electrodes (L) and trailing electrodes (T), the initial layer is separated by a distance between electrodes d=40-80aI11
1 Wire inclination angle α (L) = -15° ~ +5°〃 α
(T)=O'~+20゜Wire protrusion length h (L)=40~120mn+h
(T) = 50~120mm (L) pole current: 1000~200OA (T) pole (7
) IT: 800-1800 A (L) pole - (T) pole current difference: 100-600 A (L) pole/(T) pole voltage ratio: 0.75-1. OO welding speed: 15-45cm/m
This method is characterized by submerged arc welding under conditions of in.

The present invention will be explained in more detail below.

(Function) In the present invention, there are two wire-shaped leading electrodes and trailing electrodes.
This method is based on multilayer welding in which a Y-shaped groove joint is submerged arc welded using an electrode.

In this case, the Y-type groove joint has a root face a of 1 to 8 mm and a groove angle θ of 40 to 55'', as shown in Fig. 2.
′.

If the root face Q is less than 1 mm, the penetration will be too thin and deep, and the melt will fall off, making it easy for hot cracks to occur.
When Q is more than 8 mm, insufficient penetration tends to occur.

In addition, if the groove angle θ is smaller than 40″', slag releasability and hot cracking resistance will deteriorate, while if θ is larger than 55°, the groove area will be too wide and welding efficiency will be poor, making it uneconomical. It is true.

Furthermore, the leading electrode and trailing electrode used have a diameter of 5°3~8.
, O[1110φ wire shape. If the wire diameter is thinner than 5.3 mm, the penetration will be excessive and the bead width at the bottom of the bead will become narrow, making it more likely that defects such as hot cracking, poor fusion, and slag entrainment will occur. Moreover, the wire feeding speed increases, making it difficult to feed the wire. On the other hand, if the wire diameter is larger than 8.0 mm, the wire becomes hard, making it inconvenient to handle, and also making it difficult to straighten the wire, making it difficult to position the wire in a predetermined position, and causing misalignment.

Next, the conditions for submerged arc welding of the first layer will be explained.

The distance d between the leading electrode (L) and the trailing electrode (T) (the third
(see figure) shall be 40 to 80 mm. As a result, a pool of molten metal is formed by the trailing electrode when the pool of molten metal formed by the leading electrode is in a semi-solidified state, so that the molten metal is formed in a so-called semi-solid state.
High temperature cracking is prevented.

However, if the inter-electrode distance d is less than 40++ un, one-pool welding occurs, which is the same as when welding with one electrode, and hot cracking occurs. On the other hand, if the interelectrode distance d exceeds 80 mm, welding progresses in a so-called two-pool manner, in other words, the trailing electrode passes through after the pool formed by the leading electrode has completely solidified, and this occurs in the weld metal of the leading electrode. The hot crack remains without disappearing even after passing the trailing electrode.

■Wire 1 α When tilting the electrode, as shown in Figure 3, Oo is when it is perpendicular to the welding direction, (+) is when it is tilted backwards, and (-) is when it is tilted forward. Then, the wire inclination angle α(L) of the leading electrode (L) is -15° to +5°
The wire inclination angle α(T) of the trailing electrode (T) is 0° to +20°.

However, as the wire inclination angle α(L) of the preceding electrode (1,) is made stronger toward the (-) side, the penetration becomes deeper and the bead width becomes narrower, but if α(L) is smaller than -15°, In other words, if the bead is strongly tilted forward beyond -15°, penetration will be excessive, the bead width at the bead bottom will be narrowed, the bead shape will become convex, and hot cracking will easily occur. On the other hand, when the wire inclination angle α(L) is larger than +5°, the molten metal flows forward and the slag tends to advance, resulting in unstable penetration.

Poor fusion occurs.

Also, the wire inclination angle α(T) of the trailing electrode (T) is 00
If it is smaller, the bead width becomes narrower and the bead shape becomes convex. On the other hand, when the wire inclination angle α(T) exceeds +2o°, the penetration of the trailing electrode (T) becomes shallow and the leading electrode (
The weld metal L) is more likely to undergo hot cracking, the bead width becomes wider, and undercuts occur, resulting in poor slag removability.

■Wire length h The wire protrusion length is the distance h from the current-carrying part of the electrode to the bottom of the groove (see Figure 3), but in general, the longer the protrusion length, the more Joule heat is generated. Since the wire melting speed is high, welding efficiency improves, but it must be determined appropriately taking into consideration the prevention of welding defects, etc. In the case of the present invention, the wire protrusion length h( L) is 40
120 mm, and the wire protrusion length h (T) of the trailing electrode (T) is 50 to 120 mm.

The wire protrusion length h (L) of the leading electrode (L) is 40 m1
When it is less than 1, the bead width at the bottom of the bead becomes narrow, making it easy for hot cracking to occur. Also, the melting rate of the wire is slow, which is inefficient. Furthermore, the generated molten slag tends to drag, and the appearance of the bead deteriorates. on the other hand,
When the protrusion length h (L) exceeds 120 mm, insufficient melt penetration tends to occur.

Furthermore, if the wire protrusion length h (T) of the trailing electrode (T) is less than 50+ nm, the wire melting speed will be slow, resulting in inefficiency, and the generated molten slag will be easily dragged, resulting in poor bead appearance. to degrade. Furthermore, the penetration of the (T) electrode becomes deep, making it easy for hot cracks to occur in the bead caused by the trailing electrode. On the other hand, if the protrusion length h(T) exceeds 120 mm, the bead width becomes narrow and overlap occurs, deteriorating the bead appearance. Furthermore, since the penetration of the trailing electrode is insufficient, hot cracking is likely to occur in the bead formed by the leading electrode.

Maro-cho 11L wave The current of each electrode is high current, and the current of the preceding electrode (L) is 1
000-2000A, the current of the trailing electrode (T) is 800-
It is assumed to be 1800A. However, the current of the leading electrode (L) is 1
If it is less than 00OA, penetration will be insufficient.

Moreover, if it exceeds 200 OA, melt dripping occurs, the bead shape deteriorates, and hot cracking occurs. On the other hand, if the current of the trailing electrode (T) is less than 800A, the bead will not spread sufficiently, causing overlap and slag entrainment, and if it exceeds 1800A, the melt will drop or the bead shape will deteriorate. At the same time, hot cracking occurs.

■ In order to prevent electrical hot cracking between the electrodes and to make the bead shape appropriate, the current difference between the leading electrode (L) and the trailing electrode ('r), that is, (leading electrode current) - ( The value (LT) of the trailing m-pole current is in the range of 1oO to 6oOA. If this difference (L - T) is smaller than 100 A, hot cracking occurs in the bead caused by the trailing electrode, while if it is larger than 600 A, hot cracking occurs in the bead caused by the leading electrode.

■ Electrode and voltage In general, the lower the voltage, the deeper the bead will be formed, and the higher the voltage, the better the spread of the weld bead. The voltage difference between the electrodes, that is, the ratio of (preceding electrode voltage)/(tracing electrode voltage) is in the range of 0.75 to 1.00. The value of this ratio is 0.
If it is less than 75, undercuts tend to occur and slag removability deteriorates, and if it exceeds 1,00, ohper wrap and slag entrainment occur.

14 (If the deep welding speed is less than 15 cm/sin, the speed will be too slow and slag will advance, making penetration unstable, and a root surface will remain, resulting in poor fusion.) On the other hand.

If the speed exceeds 45 cm/min, hot cracking is likely to occur.

Although other conditions are not particularly limited, the following points can be considered.

First, it is preferable to apply a DC voltage to the leading electrode. This is to stabilize penetration.

In addition, when connecting a three-phase AC power source to both the leading electrode and the trailing electrode, the wiring method of the leading electrode and the trailing electrode should be reversed.
It is preferable to use a wire connection. This is to improve the bead appearance and bead width and to stabilize penetration.

Furthermore, it is preferable that the ground position be the crater side ground. This is also to stabilize the bead appearance and penetration.

There are no particular restrictions on the flux, but
It is preferable to use a flux having a composition (wt%) containing the components shown below.

(Flux composition) SiO□: 10-25%, AM, O,: 4-20
%, MgO: 10-25%, CaC0,: 4-12%
, Mi○/Sin, ratio: 0.9 to 1.5°.The reasons for limiting these components are as follows.

1α-8io is an acidic component and is an essential component for adjusting the viscosity of the slag, but if it is less than 10%, the viscosity of the slag becomes insufficient and the bead width becomes unstable or non-uniform. On the other hand, if it exceeds 25%, the viscosity of the slab becomes excessive and the bead tends to spread insufficiently. In addition, the basicity becomes low, and the toughness in high heat input welding tends to deteriorate.

flJh Ag2O, is a neutral component and is an effective component for adjusting the viscosity and solidification temperature of the slag without impairing the toughness of the weld metal, but if it is less than 4%, the viscosity and solidification temperature of the slag will be low, Bead width becomes uneven. On the other hand, 20%
If the temperature exceeds , the solidification temperature of the slag becomes too high.
Beads tend to spread insufficiently.

MgO MgO is a basic component and is effective in adjusting the viscosity of slag while ensuring the toughness of weld metal.
If it is less than 0%, the viscosity of the slag is insufficient and the bead width tends to become non-uniform. Furthermore, since the basicity is low, the toughness in high heat input welding tends to deteriorate. On the other hand, if it exceeds 25%, the viscosity of the slag becomes too high and gas defects such as pock marks are likely to occur, and the peelability of the slag deteriorates, making it easy for the slag to seize on the bead surface.

During welding, CaC0□ is decomposed into CaO and CO2, and C
O2 gas is an effective component for shielding the weld zone from the outside air, lowering the partial pressure of impurity gases (such as Hz or N2), and preventing them from entering the weld metal. However, if it is less than 4%, the shielding effect of CO2 gas is insufficient, the amount of hydrogen and nitrogen in the weld metal increases, and cold cracking and toughness are likely to decrease. On the other hand, if it exceeds 12%, the amount of CO2 gas generated will be excessive, and the gas will not be released uniformly, resulting in extremely frequent blow-up phenomena during welding, and the bead appearance will likely deteriorate.

MO/SiO ratio The ratio of MgO/Si○2 makes the basicity appropriate, and
In order to ensure welding workability, it is preferable to set the value to 0.9 to 1.5. If the value of this ratio is less than 0.9, the basicity is too low, resulting in a decrease in toughness in high heat input welding. Furthermore, undercant is likely to occur on the bead surface. On the other hand, 1.5
Exceeding this will increase pockmarks and slab burn-in.

Regarding other ingredients, about 20-40% iron powder can be added into the flux. Thereby, the welding speed can be increased and the welding heat input can be reduced. If the amount of iron powder added is less than 20%, this effect is small;
%, slag becomes more likely to be involved.

Further, the [Til content in the weld metal is 0.005 to 0.
0.30%, a Ti source such as a Fe-Ti alloy and/or TiO can be added to the flux, or an appropriate amount of Ti can be added to the electrode wire. In this case, a Ti source may be added to both the flux and the electrode wire.

Furthermore, the [B] content in the weld metal is 0.0015 to 0.
Fe--B alloy and/or B, 03 can be added to the flux so that the amount becomes 0.050%. This B source may be added from the electrode wire, or may be added from both the flux and the wire.

In this way, by adding appropriate amounts of Ti and B to the weld metal, toughness in high heat input welding can be ensured.

However, when the contents of Ti and B are less than 0.005% and less than 0.0015%, respectively, the effect of improving toughness is small. Moreover, when the Ti content exceeds 0.030%,
On the contrary, the toughness decreases, and the B content is 0.00.
If it exceeds 50%, hot cracking is likely to occur.

Next, examples of the present invention will be shown.

(Example) A Y-shaped groove joint with the shape shown in FIG. 5 and the dimensions shown in Tables 3 and 4 was prepared using 5M50B with dimensions of 80 mJ and X10X100O as a test steel plate.

JIS Z 3351 YS- as the test wire
JIS Z 3352 as a flux by using a wire equivalent to 36 and having the wire diameter and chemical composition shown in Table 1.
Using a flux with chemical components shown in Table 2, equivalent to FS-BTI (nominal size = 10 x 48 mesh),
The first layer was submerged arc welded under the welding conditions shown in Tables 3 and 4.

Subsequently, the second and subsequent layers were deposited in multiple layers by submerged arc welding using the lamination method shown in FIG.

The initial layer was inspected by full-line ultrasonic flaw detection, internal defects were investigated using five cross-sectional macro test pieces, and the appearance of the bead was visually observed. The results are also listed in Tables 3 and 4.

As is clear from Tables 3 and 4, invention examples &1~
All of Nα5 have no internal defects and have good welding workability and bead appearance.

On the other hand, Comparative Examples Na 6 to Na 16 have at least internal defects or have poor welding workability or bead appearance.

That is, although Comparative Example NQ6 is an example in which the groove angle O is small, hot cracking occurs, undercutting occurs, and the slag removability is poor.

Comparative example Nα7 is an example in which the interelectrode distance d is short and there is no current difference between the leading electrode and the trailing electrode, but hot cracking occurred.

Comparative Example Na 8 is an example in which the groove angle θ is large and the voltage difference between the leading electrode and the trailing electrode is large, but slag entrainment occurs in some parts, overlap occurs, and slag removability is poor. ing.

Comparative example 9 is an example in which the root face a is large, the wire diameter of the leading electrode is large, and the inclination angle α (T) of the trailing electrode is large, but insufficient penetration occurs in the entire wire, and undercuts occur. Because of this, the slag removability is poor.

Comparative example Nα1o is an example in which the current difference between the leading electrode and the trailing electrode is large and the voltage ratio is small, but hot cracking occurred in all the wires and undercutting occurred, so the slag removability was poor.

Comparative Example No. 11 is an example in which there is no root face Q, the distance between poles is large, and the wire diameter of the leading electrode is small, and hot cracking occurred in all the wires.

Comparative example Nα12 is an example in which the wire protrusion lengths of both the leading electrode and the trailing electrode are long, but slag entrainment, insufficient penetration, and overlap occurred in some parts.

Comparative Example &13 is an example in which the wire inclination angle α(T) of the trailing electrode is small, but some slab entrainment and overlap occurred.

Comparative example Nα14 has a wire inclination angle α(L) of the preceding electrode.
This is an example where the welding speed is small, the current in the leading and trailing electrodes is high, and the welding speed is high. However, hot cracks occur on the entire wire, and the bead shape is uneven, resulting in poor bead appearance and slag removability. .

Comparative example Nα15 has a wire inclination angle α(L) of the preceding electrode.
In this example, the welding speed was high and the welding speed was low, but insufficient penetration occurred.

Comparative example Nα16 is an example in which the wire protrusion lengths of both the leading electrode and the trailing electrode are short and the current of the leading electrode is small, but there is insufficient penetration and some fusion failures, and the bead meandering. Poor appearance.

[Margin 1 below (Effect of the invention) As detailed above, according to the present invention, the plate thickness is 60 mm.
When performing multi-layer welding of the above-mentioned super-thick plates by submerged arc welding, the shape and dimensions of the Y-shaped groove are specified, and the submerged arc welding of the first layer is performed under specific welding conditions to avoid welding defects in the first layer. Since there is no occurrence of this process, and the work can be performed with good workability, it is possible to perform highly efficient construction, especially for box column angle joints of ultra-thick plates.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the procedure for conventional multilayer welding, Figure 2 is a sectional view showing the shape of a Y-shaped groove joint, and Figure 3 is the distance d between the leading and trailing electrodes, and the wire inclination angle. FIG. 4 is an explanatory diagram showing the lamination method for the second and subsequent layers. FIG. 5 is a sectional view showing the shape and dimensions of the Y-shaped groove joint used in the embodiment of the present invention. 1... Super thick plate (base material), 2... Backing, L... Leading electrode, T... Trailing electrode.

Claims (1)

[Claims] Root face l: 1 to 8 mm, groove angle θ: 40 to 5
In multilayer welding of ultra-thick plates, a 5° Y-shaped groove joint is submerged arc welded using a wire-shaped leading electrode (L) and trailing electrode (T) with a diameter of 5.3 to 8.0 mm. The distance between the poles of the first layer d = 40 to 80 mm Wire inclination angle α (L) = -15 ° to +5 ° α (T)
=0゜～+20゜Wire protrusion length h(L)=40～120mm〃h(T
)=50~120mm (L) pole current: 1000~2000A (T) pole: 800~1800A (L) pole - (T) pole current difference: 100~600A (L)
Pole/(T) pole voltage ratio: 0.75-1.00 Welding speed:
A submerged arc welding method for the first layer in multilayer welding of a super-thick plate, characterized by submerged arc welding under conditions of 15 to 45 cm/min.