JPS61232066A - Narrow gap submerged arc welding method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention enables shortening of welding time and saving of welding materials when multi-layer welding steel plates with a thickness of approximately 30 to 120 fi from both sides. This article relates to a narrow gap submerged arc welding method that achieves high efficiency and labor savings.

(Prior Art) Narrow gap submerged arc welding has recently been attracting attention as a highly efficient and economical welding method, and has been actively adopted in actual welding.

However, since these narrow gap welding methods use a U-shaped beam opening, when welding extra-thick steel, the reduction in welding material and man-hours due to the reduction in the groove cross-sectional area is significant;
1111! In the case of the following medium-thick plates, the amount of decrease in the groove cross-sectional area was small (the effect of narrowing the groove was insufficient) although the groove processing cost was high.

In addition, these welds are performed within a narrow groove, and the welding conditions are limited to the amount of heat input. It needed to be done.

In general, the back chisel work in welding construction is often carried out on a separate line from the welding process, and in addition to the man-hours required for the back chisel itself, the time required for sling work and waiting for the crane is considered to be considerable. Must be.

In addition, when back lifting is performed using arc air gouging, the subsequent work with the grinder also generates a lot of noise and dust. Pre-submerged arc welding was desired.

From this point of view, the present inventors have previously
In Publication No. 8982, we proposed a narrow-gap submerged arc welding method for medium-thickness steel plates using an X- or Y-shaped groove that is easy to process.
It is necessary to remove the unfused part that forms at the bottom of the side weld metal (referred to as ``groove welding'') by back lifting, which not only requires time and expense, but also increases the cross-sectional area of the groove. It became.

In addition, in this proposal, it is possible to melt and remove the unmelted part at the bottom of the BP side weld metal by welding in the FP side weld metal without performing back lifting. An X-shaped groove where the face part is biased towards the BP side,
Due to the use of a Y-shaped groove or a Y-shaped groove without a groove on the FP side, the groove cross-sectional area becomes large compared to the plate thickness (, B
Since the number of welding errors was biased towards the P side, there were problems such as large welding distortions.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the above-mentioned problems in the narrow-gap submerged arc welding method using an X-shaped groove, which requires low groove processing costs, and to remove the back side. It is an object of the present invention to provide a more economical and efficient narrow gap submerged arc welding method that enables welding on the FP side without any problems.

(Means for Solving the Problems) The gist of the present invention is that when performing butt multilayer latent arc welding of thick steel plates using an Tip angle 30~50°,
The groove angle on the finishing path side is 45 to 60 degrees, the root face is 511aR or less, and the distance between electrodes is 40 to 80 degrees.
rrr! With two electrodes of n, the current and voltage of the leading electrode and trailing electrode are set to the following conditions, and the welding speed is 30 to 60 ω1/c.
m, the welding heat input is 30 to 50 KJ/a on the backing side! I
A narrow gap latent arc welding method is characterized in that at least the first layer on each of the backing pass side and the finishing pass side is welded under welding conditions of 40 to 60KJ10fn on the finishing pass side.

(1) AL = (125・D+250)±150(
2J AL -AT = 100~250 (3) VL<2
9 (4) VT<31 (5) VL+VT = 48~56 However, AL: Leading electrode current (ampere) D: Leading electrode used wire diameter (scream) AT: Trailing electrode current VL: Leading electrode voltage (volt) ■T : Trailing electrode voltage In order to solve the above-mentioned problems, the present invention has examined in detail the welding conditions for each first layer so that welding on the FP side can be performed without performing reversing on the BP side and the back side. .

In conventional multi-layer welding with an X-shaped groove, in order to prevent hot cracking that occurs in the first layer on the BP side, single-electrode welding is performed with a wide groove, low current, and low speed, sacrificing efficiency. ing.

Furthermore, when welding the FP side, the penetration depth on the BP side becomes shallow due to the low current and low speed welding conditions, and it is necessary to lift the back side to the bottom of the groove on the BP side, so as mentioned above, This not only requires time and cost, but also results in an increase in the cross-sectional area of the groove.

The inventors first investigated using a single electrode with a narrow groove angle, and found that under the conventional low current and low speed conditions, the weld metal did not reach the bottom of the groove, and the unfused area It was found that poor fusion occurs due to the formation of When a relatively high current was used, the bead shape became convex and hot cracking occurred.

In order to obtain a good bead shape and prevent high-temperature cracking, high voltage was applied, which resulted in poor slag removal and the formation of an unfused area as the weld metal did not reach the bottom of the groove, resulting in poor fusion. It has also been found that when a relatively low current and low voltage is used, although no fusion failure occurs, the bead shape becomes convex, which causes problems such as high-temperature cracking.

Therefore, the number of electrodes was changed to two, and the hot cracks that occurred at the leading electrode were remelted and erased at the trailing electrode. At the same time, the slag removability was good, and the penetration depth was large, resulting in poor fusion. Various welding methods were investigated.

As a result, first, the distance between the electrodes was set to about 60#,
Then, the leading electrode current (hereinafter referred to as AL) is determined by the diameter of the wire used in the leading electrode (hereinafter referred to as RI), and the trailing electrode current (hereinafter referred to as AT) is determined to be approximately 200 A lower than AL. By lowering the welding voltage significantly lower than conventionally used voltage, and by setting the welding speed and welding heat input within a certain range, the first layer has a good bead shape, good slag releasability, and no hot cracking. Welding is now possible.

Furthermore, the root face should be small to avoid fusion failure. However, if the groove angle on the BP side is too wide or the welding heat input is too high, the weld metal will melt and the B
It is necessary to narrow the P-side groove angle, keep the welding heat input within a certain range, and ensure that the weld metal penetrates to the bottom tip of the groove.

Since it is necessary to completely melt the root face, the FP side groove angle needs to be wider than the BP side groove angle so as not to increase the groove cross-sectional area.

Also, the amount of welding heat input will completely melt the root face5.
It is necessary to set the amount of heat higher than that of the welder on the BP side.

By satisfying the above requirements, we have found a method that allows welding of the first layer on the BP side and the FP side without causing fusion failure, and have accomplished the present invention.

(effect) The present invention will be explained in detail below.

The reason why the groove shape is an X-shaped groove is that it is easy to process the groove, and with a Y or V-shaped groove, the cross-sectional area of the groove is large (not only large) in relation to the plate thickness. This is because the number of welding passes is biased toward the BP side, resulting in increased distortion.

Regarding the BP side groove angle, if it is less than 30°, it will be difficult to obtain melt penetration to the bottom of the groove. On the other hand, if the angle exceeds 50°, the groove cross-sectional area becomes large, the economic effect of narrowing the groove decreases, and furthermore, the weld metal melts.

Regarding the FP side groove angle, in FP side welding, in order to avoid fusion failure at the root part 5, and to ensure deeper weld penetration than the BP side, the groove angle is 45 to 60' wider than the BP side groove angle. It needs to be within the range.

In other words, if the groove angle on the FP side is less than 45°, it will not be possible to achieve the deep penetration necessary for the FP side, and if it exceeds 60°, the cross-sectional area of the groove will become too large, resulting in a narrow opening. This is due to the loss of the characteristics of pre-welding. The dimension of the root face must be 58 or less. If it exceeds 5Wan, poor fusion will occur.

Next, the distance between the electrodes was set to 40 to 80 degrees. This is because the trailing electrode is placed just before the weld metal solidified by the leading electrode, and the hot cracks caused by the leading electrode are removed after the weld metal is solidified. In addition to being remelted and removed by the row electrode, the bead itself formed by the trailing electrode does not generate hot cracks, which is a necessary condition for keeping the arc stable and improving the bead shape. .

If the distance between the electrodes is less than 40 ffll11, there will be one molten pool and one columnar crystal after solidification, so hot cracking will occur as in the case of welding with a single electrode. On the other hand, when it exceeds 80113, there are two molten pools, and the weld penetration by the trailing electrode becomes shallow (as a result, the hot cracks that occurred in the leading electrode can be remelted and removed by the trailing electrode and eliminated). As the slag disappears, the slag generated by the leading electrode begins to solidify, making the arc of the trailing electrode unstable and causing slag entrainment defects.

Also, depending on the wire diameter used with AL, (125・D+25
0) ±150 was achieved by changing D and AL variously.
This was obtained experimentally. That is, AL<(
125·D+250)-150, the melt penetration depth becomes shallow, an unmelted part remains on the BP side, and the root face is not completely melted on the FP side, resulting in poor fusion. On the other hand, when AL>(125·D+250)+150, the depth of the hot crack increases, it is remelted by the trailing electrode, and cannot be erased.

The following table shows the AL for the diameter of the wire used in the preceding electrode.

Note that the diameter of the wire used in the preceding electrode is preferably between 3.2 and 4.8. If it is less than 3.2 m1, deep melt penetration can be obtained, but the depth of hot cracks also becomes large, and it may not be possible to erase them by remelting with the trailing electrode. 4.8
If the gap is exceeded, an arc will occur between the groove sidewalls, the weld metal will not reach the bottom of the groove, an unmelted part will remain on the BP side, and the root face will not be completely melted on the FP side, resulting in poor fusion.

The reason for setting AL-AT to 100 to 250 is that when AT is less than 100, the AT is too high and hot cracks generated by the leading electrode are remelted and disappear, but hot cracking occurs by the trailing electrode. If it exceeds 250, the AT is too low and the hot cracks generated by the preceding electrode cannot be removed by remelting.

Furthermore, the reason why we set the leading electrode voltage (hereinafter referred to as VL) and the trailing electrode voltage (hereinafter referred to as VT) to VL<29 and V+<31, which are significantly lower than the conventional voltages, is because VL>29 Therefore, the penetration depth of the melt becomes shallow,
On the BP side, the weld metal does not reach the bottom of the direct light, leaving an unmelted part, and on the FP side, the root face is not completely melted, resulting in poor fusion. When VT > 31, the amount of slag is large (
At the same time, the undercut becomes a generation hole and the slag removability becomes poor.

The reason why VL+VT=48 to 56 is that a Teja bead of less than 48 becomes convex, which causes hot cracking. 56
If this value is exceeded, the amount of slag will increase and undercuts will occur, resulting in poor slag removal properties (as well as unmelted parts remaining on the BP side and failure to melt the root face on the FP side, resulting in poor fusion). .

The welding speed must be 30 to 60 (up to) 7 times.

If it is less than 30 tjfn/m, the molten metal caused by the leading electrode will advance in the direction of solution flow, and an arc will be generated on the molten metal, making it impossible to obtain a sufficient penetration depth, resulting in BP
An unfused portion remains on the side, and the root face is not completely melted on the FP side, resulting in poor fusion. If it exceeds 60η1, hot cracking will occur in the bead formed by the trailing electrode.

The welding heat input is the total of the leading electrode and trailing electrode, and is 30 to 50 KJ/ayb on the BP side and 40 to 60 KJ/ayb on the FP side.
Must be KJ/e. The heat value of the welder on the BP side is 30
If KJ is less than 10 In, the arc will not reach the bottom of the groove, leaving an unfused portion. If you exceed 50 KJloR,
The weld metal will melt. Further, even if the melt is prevented from falling off using a backing material such as a Cu plate, the amount of slag increases and undercuts occur, resulting in poor slag removability.

If the adult heat value on the PP side is less than 40 KJ/e, the root face will not be completely melted and poor fusion will occur. 60KJ/
If it exceeds an, the amount of slag increases and undercuts occur, resulting in poor slag releasability.

Naturally, the second and subsequent layers on the BP side and FP side can also be welded under the same conditions as the first layer, but the
Since there is no need to obtain a melt penetration depth like a layer, and there is almost no need to consider hot cracking resistance, construction can be performed under the conventional single-electrode and two-electrode conditions.

In addition, when performing tack welding by gas-shielded arc welding or shielded arc welding, the method of the present invention will not be adversely affected if it is applied up to 7+m from the bottom of the groove on either the BP side or the FP side, but if it exceeds 71 Iol, , the penetration depth of the melt becomes leaky, resulting in poor fusion.

In addition, the flux used in the method of the present invention must have a stable arc even when the bath contact voltage is low, and have good bead shape and slag releasability. 24 chi, one or both of A40x and Ti1t = 8 to 55 chi, metal fluoride:
3-16%, CaO: 10-30%, MgO: 15
~35%, metal powder: 15% or less, and in addition to the above composition, in order to keep the arc stable especially under low welding voltage conditions,
Preferably, it is a fired type 7 lux to which 3.5 to 12% of metal carbonate is added in terms of CO2.

(Example) The present invention will be specifically explained below using examples.

By combining fluxes F-1 and F-2 shown in Table 1 with wires W-1 and W-2 shown in Table 2, and using a groove having the shape shown in FIG. Thickness 501EII
5M-50B steel and plate thickness 75+o+1100A
The first layer of 316Gr70 steel on the BP side and the FP side was welded under the respective welding conditions shown in Table 4.

For those with no hot cracks or undercuts on the bead surface (and good slag releasability), the second layer and subsequent layers on the BP side and FP side were AL : 500-700A, AT: 45
0~700A%VL:26~32v1VT:26~34
Multilayer welding was performed under welding conditions of V, welding speed: 40 to 60 va/=, welding heat input: 35 to 45 KJ/h11b, and the soundness of the joint was confirmed by an X-ray transmission test.

Note that the wire diameter used was the same for both the leading electrode and the trailing electrode. The results are shown in Table 4.

In other words, Test Examples 1.2.3.4 and 5 based on the method of the present invention had extremely good results, such as no welding defects such as hot cracking or undercuts, good slag peelability, no fusion defects, and a small number of welding passes. An economical and sound welded joint was obtained.

On the other hand, in Trial Example 6 of the comparative examples, poor fusion occurred because the groove angle on the BP side was narrow. In Test Example 7, poor fusion occurred because the groove angle on the FP side was narrow.

In Test Example 8, since the groove angle on the BP side was wide, the weld metal melted away in the first layer on the BP side.

In Test Example 9, the groove angle was wide on both the BP side and the FP side, but since the Cu plate was applied to the FP side, although the melt did not drop, the number of welding passes was large, resulting in poor efficiency and economy. In Test Example 10, the root face was thick, so poor fusion occurred. In Test Example 11, poor fusion occurred because the AL on the BP side was low. Test example 12 has a high AL on the FP side, so
High temperature cracking was observed in the X-ray transmission test.

In Test Example 13, high-temperature cracking occurred on the bead surface because AL-AT was small. In addition, due to the high VT, undercutting occurred, and the slag had poor release properties.In Test Example 14, because the AL-AT on the FP side was thick, hot cracking was observed in the X-ray transmission test. .

In Test Example 15, poor fusion occurred because the VL on the BP side was high. In Test Example 16, the bead became a convex bead due to low VL + VT, and hot cracking also occurred on the surface. In Test Example 17, since VL + VT was high, undercut occurred and the slag releasability was poor.

Also, because the welding speed was high, hot cracks also occurred on the bead surface.

In Test Example 18, poor fusion occurred because the welding speed on the BP side was slow. In Test Example 19, poor fusion occurred due to low adult calorific value on the BP side. In Test Example 20, undercut occurred due to the high heat input on the BP side, resulting in poor slag releasability. Also, because the distance between the electrodes was short, hot cracks also occurred on the bead surface.

In Test Example 21, poor fusion occurred due to low adult calorific value on the FP side. In Test Example 22, since the adult heat value on the FP side was high, undercutting occurred and the slag releasability was poor. In Test Example 23, since the distance between the BPP electrodes was long, the trailing electrode became unstable, and hot cracking and slag entrainment were also observed in the X-ray transmission test.

Table 1 Table 2 Table 3 (Effects of the invention) As is clear from the above examples, the method of the present invention does not cause welding defects, reduces the number of welding passes, and saves welding materials. A significant reduction in welding costs can be expected, and the industrial value of the present invention is extremely high.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the groove shape used in the example. t: Plate thickness θB: BP side groove angle t+: B
P side groove depth θF: FP side groove angle tz: FP side groove depth R: Root face

Claims (1)

[Claims] When performing butt multilayer submerged arc welding of thick steel plates using an X-shaped groove without lifting the back side, a groove angle on the backing pass side is 30 to 50°, and a groove angle on the finishing pass side. 45
~60°, the root face is 5 mm or less, two electrodes with an interelectrode distance of 40 to 80 mm, the current and voltage of the leading and trailing electrodes are as follows, and the welding speed is 30 to 60.
cm/mm, the welding heat input is 30 to 5 on the backing pass side.
0KJ/cm, finishing path side 40~60KJ/
A narrow gap submerged arc welding method characterized by welding at least the first layer on each of the backing pass side and finishing pass side under welding conditions of cm. (1) A_L=(125・D+250)±150 (2) A_L-A_T=100-250 (3) V_L≦29 (4) V_T≦31 (5) V_L+V_T=48-56 However, A_L: Leading electrode current (A ) D: Leading electrode wire diameter (mm) A_T: Trailing electrode current V_L: Leading electrode voltage (V) V_T: Trailing electrode voltage