JPS61206572A - All position welding method of stainless steel - Google Patents

Abstract

PURPOSE:To obtain an optimal welding conditions and to improve all position welding operability by welding with pulse conditions using a flux cored wire. CONSTITUTION:The nozzle 3 enabling the automatic feeding of welding flux cored wire 2 is set up on the weld zone of the beam metal 1 made of stainless steel. The all position arc welding is performed by pulse welding current by covering the weld zone with the release of shielded gas 4 from the nozzle 3, by making the welding flux cored with 2 + electrode and by making the base metal 1 - electrode. The welding heat-input is thus eliminated and the corrosion resistance on the weld zone is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an all-position welding method for stainless steel.

[Conventional technology]

Current all-position welding methods for stainless steel include TIG and covered arc welding methods as manual welding methods, and JISZ
3821 (Stainless Steel Welding Joint Certification). Additionally, there is a TIG welding method as an automatic welding method for stainless steel in all positions.

[Problem that the invention seeks to solve]

However, the sheathed arc welding method has a welding speed of about 2027 minutes, which is inefficient. Furthermore, in the case of the covered arc welding method, since a welding rod is used, there are many bead joints, and defects due to craters and re-arcing are likely to occur in these parts. Also, the arc time rate is low and the efficiency is poor. Furthermore, when welding in all positions, particularly in upward and vertical positions, a fusion defect (α) in which the weld boundary surfaces of the welded portion are not sufficiently fused as shown in FIG. 5 is likely to occur. This tends to occur between layers or passes in a multi-layer stack, and there is a high possibility that this defect will occur when the welding current is small in conventional construction. Furthermore, the weld metal sag (b) defect shown in FIG. 6 is likely to occur. This tends to occur when the welding current is large or when the rod is used incorrectly, and requires a highly skilled welding technique.

Also, the welding speed of TIG welding method is about 8 to 10? /minute, which is inefficient. Also, depending on the work being welded, semi-automatic welding may be considered preferable to fully automatic welding, but semi-automatic welding using the TIG welding method is theoretically difficult, so semi-automatic welding using the TIG welding method is currently used. It is common that it is done, but it is not done.

In addition, as shown in Table 1, the welding heat input (J/crn) becomes large in both the shielded arc welding method and the TIG welding method, so as shown in FIG. (There is a high possibility that corrosion resistance will deteriorate due to the precipitation of force and a lack of chromium content, and in welded joints where corrosion resistance is a particular problem, it is necessary to increase the welding speed or welding current at the expense of welding workability.) It became necessary to find ways to reduce welding heat input by adopting construction methods such as lowering the welding heat input.

[Means for solving problems]

In order to solve the above-mentioned problems, in the present invention, in a consumable electrode type gas shield welding method, a stainless steel arc welding flux-cored wire is used to perform all-position welding with a pulsed welding current.

[For production]

Since welding is performed under pulsed conditions using flux-cored wire, the average value of the welding current is small and the welding speed is high, which eliminates problems such as poor fusion defects, weld metal sagging defects, and deterioration of corrosion resistance due to chromium carbide precipitation. There is little occurrence of welding, and welding workability in all positions is good. Furthermore, the radiographic examination of the welded joint constructed by the welding method of the present invention was grade 1.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the implementation state of the welding method of the present invention,
A nozzle (3) capable of automatically feeding a welding slack-cored wire (2) is movably installed at a welded part of a stainless steel base material (1), and a shielding gas (4) is released from the nozzle (3). Cover the welding area with welding flux-cored shear wire (2
) is used as the ten electrode, and the base material (1) is used as the - electrode, and full-position arc welding is performed using a pulsed welding current.

Here, welding flux core or wire (2) is 0.8φ~
A 1.6φ stainless steel arc welding flux-cored wire can be used. As the shielding gas (4), a gas having a composition of 0 to 70% carbon dioxide and 100 to 30 g of argon can be used, preferably 20% carbon dioxide and 80 g of argon.

Furthermore, as shown in Figure 2, the pulse welding current is expressed with the vertical axis representing the current and the horizontal axis representing the time.The pulse welding current is 250 to 500 A, and the pulse width T is 0 to 2. , pace current 1b, average value of welding current ■αν is 80 to 160
It is within the range of A.

When the stainless steel base material (1) is welded in all positions as described above, it is not necessary to separately supply a wire as in the TIG welding method because it is a consumable electrode type. Therefore, the nozzle (
3) can be made into a unit and can be easily attached and detached, so the torch can be removed and semi-automatic welding can be performed if necessary. Furthermore, continuous feeding of the welding flux-cored wire (2) eliminates peads and reduces welding defects. Furthermore,
Since the welding flux-cored wire (2) is continuously supplied as ten electrodes, the welding speed is faster and more efficient than when the welding flux is supplied secondarily as in the TIG welding method. As the current decreases,
The welding heat input decreases from the above formula. By changing the pulse conditions using a pulse generator or the like, appropriate welding conditions can be easily obtained and stable welding can be performed.

Furthermore, the arc is stabilized by the shielding gas (4), and the shielding gas (4) and the welding flux-cored wire (
2) Oxidation of the molten metal is prevented by the action of the flux, and since the bead (5) is also covered with the slag (6), oxidation of the bead portion is prevented and the surface of the bead (5) becomes clean.

Next, the welding method of the present invention and the conventional welding method will be performed and compared.

The welding speed and welding heat input when welding the weld metal cross section (7) 0.33 cIl shown in FIG. 3 are as shown in Table 1.

Table 1 Welding speed and welding heat input for each welding method * Average current is shown for pulse control type welding.

Although the welding speed and welding heat input in Table 1 are described for vertical welding, they are almost the same for upward welding, and horizontal welding involves multiple passes in one layer, so the welding heat input is the first. smaller than the table.

As shown in Table 1, it can be seen that the welding method of the present invention can perform welding with higher efficiency than conventional welding methods, and also requires less welding heat input.

As can be easily seen from the results shown in Table 1, the welding method of the present invention has a welding heat input of 1 compared to the conventional welding method.
/3 or less. Therefore, as described above, deterioration in heat resistance of the heat affected zone can be reduced.

Next, welding was performed using the test material (8) such as 8US3o4 shown in Fig. 4 by the welding method of the present invention and the conventional welding method, and the results of welding workability and radiographic examination of the welded part were reported. It is shown in Table 2.

Table 2 Welding workability and radiographic test results for each welding method *Welding workability judgment score 5: Excellent 4: Good 3: Fair (same as covered arc) 2: Fairly good 1: Poor The welding materials are as follows. That's right.

TIG welding method: JIS Z3321 Y308 Welding method of the present invention: JIS Z 3525 YF 308C
Covered arc welding method: JIS Z 3221 D
308 Since the range of appropriate welding conditions for the welding method of the present invention is wide, the stable ranges of Ia* and IpSTp Vav are shown in parentheses.

The welding positions tested were vertical, upward, and horizontal welding; downward welding was not tested because there was no problem with downward welding.

The side bending and tensile test results of each welded joint welded as described above are shown in Table 3 below.

Table 3 Side bending and tensile test results for each welded joint *Judgment of side bending test depends on the size of the defect ◎: No defect
○: Defect of 1.6 sa+ or less X: Defect of 3.2 m or more.

It should be noted that the stainless steel all-position welding method of the present invention is not limited to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, the stainless steel all-position welding method of the present invention exhibits various excellent effects as described below.

(I) Since pulsed welding current is used, optimal welding conditions can be easily obtained and welding in all positions is possible.

(n) Since pulsed welding current is used, welding heat input is reduced and corrosion resistance of the welded zone, especially the heat affected zone, is improved.

Since it is a side consumable electrode type, it is possible to feed filler wire continuously, improving the arc time rate and achieving high efficiency.

Since it is a consumable electrode type, the filler wire feeding mechanism can be integrated with the torch, and since the torch can be made into a unit, it can be attached to and detached from the welding equipment, and it is possible to switch between fully automatic welding and semi-automatic welding. It can be done easily.

(V) Arc can be stabilized by shielding gas method.

(To) The molten pool can be completely shielded by using shielding gas and welding flux-cored 9 wire.

■ Since the welding flux in the welding flux-cored wire covers the bead surface, oxidation of the bead surface is prevented and a good pead is obtained.

The synergistic effect of pulsed welding current, consumable electrode, and welding flux-cored wire increases the welding speed and enables highly efficient welding.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of the welding method of the present invention, FIG. 2 is an explanatory diagram of pulsed welding current in the welding method of the present invention,
FIG. 3 is an explanatory diagram of a cross section of welded metal welded by the welding method of the present invention and the conventional welding method, and FIG. 4 is an explanatory diagram of a test material for comparing the welding method of the present invention and the conventional welding method.
Fig. 5 is a diagram showing a fusion defect caused by the conventional welding method;
FIG. 6 is a diagram showing a sagging defect caused by a conventional welding method, and FIG. 7 is a diagram showing a heat affected zone when welded by a conventional welding method. (11 is the base metal, (2) is the welded 7 lux wire, (
3) is a nozzle, (4) is a shielding gas, (5) is a bead, (6) is a slag, (7) is a cross section of welded metal, and (8) is a test material.

Claims (1)

[Claims] 1) An all-position welding method for stainless steel, which is a consumable electrode type gas shield welding method, characterized in that all-position welding is performed by pulsed welding current using a stainless steel arc welding flux-cored wire.