JPH01273675A - Overhead one-side gas shielded arc welding method - Google Patents

Abstract

PURPOSE:To prevent the defect of a welded joint and to improve working efficiency by controlling the flux component and flux packing density in a wire respectively at specific weight ratios and executing welding while limiting the weld currents of the 1st, 2nd and subsequent layers. CONSTITUTION:The components in the flux by the total weight of a wire are controlled to 0.1-3% arc stabilizer, 3-18% slag forming agent and 1.5-10.5% deoxidizing agent and the Mn/Si ratio is controlled to 2-8. The flux packing density is controlled to 10-30% and one-side overhead welding is executed by using a refractory backing strip while the weld zone is shielded by gaseous Ar-CO2. The welding current of the 1st layer is limited to 100-180A and the welding current of the 2nd and subsequent layers to 150-300A. The backing strip and sealing gas are used and the welding currents are controlled to the optimum values and, therefore, the slag inclusion, burn-through and lack of fusion are prevented. The defect of the welded joint is, therefore, prevented and the working efficiency of welding is improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an upward single-sided gas-shielded arc welding method, and more specifically, the present invention relates to an upward single-sided gas-shielded arc welding method, and more particularly, it uses a flux-cored wire and a true welding material to The present invention relates to a method that can be applied to alloy steel and the like to obtain a sound upward weld.

(Conventional technology and problems to be solved) Upward single-sided welding is used for welding ship bottoms in shipbuilding and box girders in bridges, etc., but since it is welded in an upward position, melting of the weld metal is reduced. When this occurs, welding often has to be interrupted.

In order to solve this problem, various improvement measures have been proposed in the past, but the applicant has previously proposed
In this issue, we proposed an upward gas-shielded arc welding method that enables stable welding even with large groove variations.

However, with conventional welding wires and methods, including this proposal, the range of conditions in which good results can be obtained is narrow, and unsuitable conditions can cause slab entrainment, especially when performing upward single-sided welding of multilayer welding. There were practical problems such as poor fusion.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide an upward single-sided gas-shielded arc welding method that can prevent slag entrainment and poor fusion in the welded portion, especially during multi-layer welding. This is the purpose.

(Means for Solving the Problems) In order to achieve the above object, the present inventor conducted various studies on welding flux-cored wires and welding conditions that allow a sound multilayer welded joint to be obtained in upward single-sided welding, and found that: In particular, they have found that this is possible by controlling the flux composition and flux filling rate of the wire and the welding conditions.

That is, in the upward single-sided gas-shielded arc welding method according to the present invention, the flux components are 0.1 to 3% of the arc stabilizer, 3 to 18% of the slag forming agent, and the Mn/Si ratio based on the total weight of the wire. is 2 to 8 and contains a deoxidizing agent containing Mn and Si: 1.5 to 10.5%, and a flux-cored wire for welding and a fire-resistant backing material having a flux filling rate of 10 to 30% by weight. Ar-Go is used as shielding gas.
The method is characterized in that upward single-sided welding is performed using gas and under the following welding conditions: a welding current of 100 to 180 A for the first layer, and a welding current of 150 to 300 A for the second and subsequent layers.

The present invention will be explained in more detail below.

(Function) (1) First, the reasons for limiting the flux components in the flux-cored wire for welding will be explained.

Note that the content (%) of each component is a ratio to the total weight of the wire.

The amount of the arc stabilizer is in the range of 0.1 to 3%. If it is less than 0.1%, arc instability will occur, and not only will spatter become noticeable, but defects such as slag entrainment and blowholes due to shield disturbance will occur, and if it exceeds 3%, the arc strength and This is not preferable because the concentration becomes excessive, which increases the occurrence of spatter, causes molten metal to drip, increases fume, and impairs workability.

Examples of arc stabilizers include oxides and fluorides of Na, Li, etc., as well as graphite and carbides.

Sura 3 S1 Good skin slag forming agent is in the range of 3 to 18%. If it is less than 3%, the amount of slag will be insufficient and a good bead appearance shape will not be obtained.
Moreover, if it exceeds 18%, the amount of slag becomes excessive, causing defects such as slag entrainment in addition to arc instability.

As the slag forming agent, TiO□ is preferable because it has good encapsulation and peelability of the generated slag, and in addition, ZrO,...
Sin,,AQ,O,,MgO,Fe,O,.

There are FeO, etc., and these can also be added as necessary.

Note that among the arc stabilizers made of oxides and fluorides, those having a slag-forming effect can be added as a slag-forming agent.

Deoxidizers Deoxidizers include Mn, Si, etc. alone or in alloys. In the present invention, Mn and Si sources are essential, and appropriate amounts are used so that the ratio (Mn/Si) falls within a predetermined range. Add. In other words, when the Mn/Si ratio is less than 2, the bead shape is good, but slag entrainment and inclusions are likely to occur. Entrainment and poor fusion are likely to occur.

Therefore, the Mn/Si ratio is in the range of 2 to 8.

Furthermore, if the deoxidizing agent containing Mn and Si is less than 1.5%, deoxidation will be insufficient, defects such as blowholes will occur, and strength will be insufficient, so that it cannot be used for steel materials with an HT50 or higher. On the other hand, if it exceeds 10.5%, the strength will increase more than necessary.
Bending performance, cracking resistance and impact performance are reduced. Therefore, the amount of deoxidizing agent containing Mn and Si is 1.5 to 10.5
% range.

As the Mn source, there are Fe-Mn, FeFe-8i-, metal Mn, etc., and as the Sjg, Fe-3L.

There are FeFe-3L-, Sl-Mg, etc. Other deoxidizing agents include A Q + Zr, Mg, Ti, and alloys thereof, and these can also be used in combination with one or two types as necessary.
More than seeds can be added.

In addition, other components such as Ni and B (Bz Oa may also be used) may be added to the flux to improve impact performance, and alloying elements such as MO may be added to adjust the strength.

Flux filling rate The flux filling rate (% by weight of flux with respect to the total weight of the wire) is in the range of 10 to 30%.

Less than 10% contains sufficient flux, ie, arc stabilizers, slag formers and deoxidizers.

Therefore, welding workability deteriorates and defects occur. On the other hand, if it exceeds 30%, the thickness of the mild steel plate used as the metal casing of the wire must be made thinner to expand the internal volume, and as the metal casing becomes thinner, the wire becomes softer and its conductivity deteriorates. , the arc becomes unstable.

The appearance of the bead shape deteriorates.

Note that the metals that should be filled with flux include carbon steel,
Hoops and pipes made of low alloy steel or the like may be used.

(2) Next, the fire-resistant backing material used in the present invention will be explained. In short, the backing material may be of any type that does not melt during welding. For example, the constituent components of the fire-resistant backing material include 5io2:4i5-60%, AΩ, 0
3: 25-38%, MgO: 3-15%, one or more alkali metal oxides 20.3-3.2%, and water: 0.0
1 to 0.25%, Sio, Al1.0. Among these and MgO, those in which at least a portion is present as cordierite are most preferred, and have appropriate fire resistance and provide an excellent back bead shape and appearance. Components other than these components are not preferable because the shape and appearance of the back bead are poor and defects are likely to occur on the bead surface.

In addition, if the gap between the groove surfaces is large, a tape made of glass fiber can be used in combination with the above-mentioned refractory solid material.

(3) The shielding gas used in the present invention is Ar-
A mixed gas of Go is used. Especially the A of Ar-CO2 gas.
When the ratio of r is used at 50% or more, good welding workability such as arc stability and spatter can be obtained. In addition to the usual shielding method, inner Ar C
Even with a double shield of og and outer cO8, good welding workability similar to the above can be obtained.

(4) As for welding conditions, it is necessary to use welding currents within specific ranges, particularly for the first layer and the second and subsequent layers. Other conditions may be established as appropriate.

If the welding current for the first layer is less than 100 A, the stability of the arc will deteriorate and the bead shape, especially the shape and appearance of the uranami bead, will deteriorate; if it exceeds 180 A, the molten metal will deteriorate. The bead shape is poor due to sagging.

In particular, the first layer has a narrow groove and a convex bead shape, and defects such as slag entrainment and poor fusion occur in the second layer. Therefore, the welding current for the first layer is 100 to 180
The range shall be A.

Welding current for second and subsequent layers If the welding current for the second and subsequent layers is less than 150 A, penetration will be insufficient, causing slag entrainment and poor fusion.
If it exceeds 0A, it will burn through and the bead shape will be poor. Therefore, the welding current for the second and subsequent layers is in the range of 150 to 300A.

Next, examples of the present invention will be shown.

(Example) Using 5M50A (plate thickness 16@ni) as the base material, the first
Welding upward on one side under the welding conditions shown in Table 1 using a flag-inserted wire filled with a flux having the composition shown in Table 3 into a hoop material having the composition shown in Table 3, and a backing material having the composition shown in Table 2. I did it. The results are also listed in Table 1.

In addition, other welding conditions are as follows.

Bevel shape: root gap 6m+a, 50” V groove shielding gas: 80%Ar-20%CO, flow rate 25Q
/min Wire diameter: 1.2mmφ Weaving frequency: 1st layer...30-40 times/min 2nd layer...40-50 times/min Wire protrusion length: 1st layer...10-20 Shoulder 2nd layer = 15 to 30 mm As is clear from Table 1, very good results were obtained in the invention examples (NQ4 to 6) that met the requirements of the present invention, but comparative examples (Nol to Nα3 , Nα7 to Nα14) lack any of the requirements stipulated by the present invention, and therefore have the following problems.

Comparative Examples Nα1 to Nα3 are examples in which welding conditions were changed. If the welding current for the first layer is too low (Nα1), the back bead shape and appearance are poor, and defects such as slag entrainment and poor fusion occur. Moreover, when the welding current for the second and subsequent layers is too high (Nα2), burn-through occurs and the bead shape becomes defective. Even if the welding current for the first layer is too high and the welding current for the second and subsequent layers is too low (Nα3), the bead shape,
Appearance is poor.

Comparative Examples Nα7 to Nα12 are examples in which the Franks component was changed. When the arc stabilizer is too small (Nα7), welding workability is poor, and when it is too large (Nα8), spatter and fume are increased. If there is too little slag forming agent (island 9), the bead shape and appearance will be poor, and if there is too much (N(110)), the arc will become unstable.M
When the n/Si ratio is low (Nα11), slag entrainment occurs, and when it is high (Nα12), the bead shape is poor.

Comparative Examples Nα13 to Nα14 are examples in which the flux filling rate was changed. If the flux filling rate is too low (Nα1
3) When welding workability is poor and the welding temperature is too high (Nα14)
The arc becomes unstable and the bead shape and appearance deteriorate.

[Margin below f] (Effect of the invention) As explained above, according to the present invention, the flux composition and flux filling rate of the black-cored wire used in upward single-sided gas shielded arc welding and the type of shielding gas are regulated. In addition, since a fire-resistant backing material is used and the welding current for the first and second layers is regulated, it is possible to weld a single-sided upward weld of a multi-layer weld without any defects such as slag entrainment or poor fusion. It has the excellent effect of allowing welded joints to be obtained without reducing welding workability or efficiency.

Patent applicant: Kobe Steel, Ltd. Representative Patent Attorney Takashi Nakamura

Claims (1)

[Claims] The flux component is the total weight ratio of the wire, and the arc stabilizer is 0.
．． 1-3%, slag former: 3-18%, and Mn/
A deoxidizer having a Si ratio of 2 to 8 and containing Mn and Si: 1.
Using a welding flux-cored wire and a fire-resistant backing material containing 5 to 10.5% and a flux filling rate (weight % of flux relative to the total weight of the wire) of 10 to 30%,
Multi-layer welding using Ar-CO_2 gas as a shielding gas and performing upward single-sided welding under the following welding conditions: a welding current of 100 to 180 A for the first layer, and a welding current of 150 to 300 A for the second and subsequent layers. One-sided gas-shielded arc welding method.