JPS5834228B2 - Gas shield door - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a gas shielded arc welding method,
It is particularly applicable to welding not only workpieces with clean surfaces, but also workpieces with a tensile strength of 50 kg or less, which have surfaces that are generally not clean due to adhesion of primer, rust, moisture, oil, etc. This relates to a gas-shielded arc welding method that aims to enable welding that is unlikely to cause welding defects such as the following.

Currently, there is a demand for automatic welding materials that can save labor and reduce welding costs in various industries such as shipbuilding, bridge construction, and the steel frame industry.

Under these trends, automation of welding is still hindered due to the problem of pore formation during fillet welding in steel sheets coated with anti-rust paint.

It has been empirically recognized that this pore formation is more pronounced when high current and high speed welding is performed from the viewpoint of welding work, and the more strongly deoxidized welding materials are used.

Welding methods having such a tendency include submerged arc welding, CO2 arc welding, CO2Ar arc welding, CO2+02 arc welding, and no-gas arc welding.

To address this problem, the automatic welding systems described above either burn away this toxic paint along the weld line, mechanically abrade it away, or, at the expense of welding efficiency, remove the toxic paint from the surface of the welding material. At present, we have no choice but to take measures such as adopting a welding rod made of iron powder and iron oxide.

In addition, as a more proactive measure, research has been conducted on welding materials suitable for automatic welding in such cases, as well as various studies on paints, but so far no success has been found.

In general, shop primer consists of three main components: a color vehicle, a pigment, and a solvent.The reason why many pores occur when welding primer-coated steel sheets is due to the high-molecular organic compounds such as epoxy resins and vinyl resins used as color vehicles. It is thought that this is a combined effect with metal zinc powder as a pigment with anti-rust function.

On the other hand, from the perspective of welding materials, in the case of manual welding rods,
Since the coating system can be freely selected, welding materials with excellent porosity resistance can be easily developed.

However, it goes without saying that manual welding rods have poor welding efficiency and are not suitable for the current situation where automation is strongly required.

On the other hand, automatic welding aimed at improving efficiency generally uses a high current, so reactions near the welding arc become active, and deoxidation must be strengthened.

This deoxidation strengthening activates dissolved hydrogen, which has a negative effect on the porosity resistance during welding of primer-coated steel sheets.

This is particularly noticeable in gas-shielded arc welding using a solid wire in which the action of flux cannot be expected, and in this respect, gas-shielded arc welding using a wire that is flanked is actually superior.

The present invention solves the problems of conventional welding as described above, and provides a new gas-shielded arc welding method that can prevent the generation of pores during automatic welding of primer-coated steel plates.

That is, the present invention provides a franking wire containing 0.1 to 12 wt% of iron oxide as an essential component, or a wire containing a hydrogen source compound at a rate of 17 wt% to the wire.
This is a gas-shielded arc welding method characterized by using a flux-cored wire containing tφ or less and using a shielding gas having a total hydrogen content of 0.1 volφ or more.

In the welding method of the present invention, the reason why the wire composition and gas composition are determined as described above and the effects thereof will be explained below.

(1) Hydrogen-containing gas As described above, the main feature of the present invention is that a hydrogen-containing gas is used as a shielding gas.

In other words, the welding gas used in conventional gas-shielded arc welding methods is carbon dioxide gas (JIS K1106 Class 2 and 3) with the impurity components as limited as possible, since water and hydrogen are both hydrogen sources and cause pore formation. , Alcon gas (JIS Kl 105) and oxygen gas (JIS Kl 105)
KIIOI) is used.

In contrast, the present invention is completely different from conventional welding methods in that hydrogen-containing gas is used as a shielding gas.

When this hydrogen-containing gas is used as a shielding gas, it is possible to prevent the intrusion of nitrogen due to the gas shielding effect, and prevent the formation of pores and embrittlement of the weld metal due to nitrogen. As the hydrogen content of the molten metal increases, the growth distance of the bubbles formed in the fillet weld metal of the shop prime coated steel plate is promoted, resulting in a porosity-free weld bead.

However, this effect is maximized when an appropriate amount of oxygen is present.

Here, in the present invention, a wire containing iron oxide as an essential component is used.

By the way, as is clear from the experimental results shown in FIG. 1, the total amount of hydrogen in the shielding gas that exhibits the most effect in the present invention is found to be 0.1 vol.phi. or more.

That is, in this experiment, the wire weight was 8, owt
% illuminite (Fed: 25wt%, Fe203
:21 wt%), 0.8wt% manganese dioxide, 0.7w silica sand, 2.0wt alumina, 3.0wtφ potassium feldspar, 5.0wt% manganese and 0.5wt% iron. Using a wire with a diameter of 24mm containing powder, the current was 330A (alternating current), the voltage was 30-31V, and the speed was 3.
Horizontal fillet welding of a 20 μ thick zinc-rich primer-coated steel plate was performed under conditions of 5 cm /vtin and a gas flow rate of 25 l/iyt, and the occurrence of surface pores on the second bead side was investigated.

In FIG. 1, hydrogen, acetylene, and propane are typically added to the shielding gas as a hydrogen source gas.

In either case, the total amount of hydrogen in the shielding gas is 0.1v
It was found that no surface pores were generated at o1% or higher.

In addition, hydrocarbons such as acetylene and butane, and organic compounds were also investigated as hydrogen source gases, but the same results as above were obtained.

In this case, iron oxide, which is an essential component of the wire, was added from illuminite mineral.

Therefore, the total amount of hydrogen in the hydrogen-containing shielding gas in the present invention is in the range of 0.1 volφ or more.

According to experiments, it has been found that hydrogen in the shielding gas in the present invention is effective in any gas form as long as it is Q, 1v□1% or more.

That is, these hydrogen source gases have the general formula CoH2o
Methane, ethane, propane, butane, pentane, hexane of the methane hydrocarbon organic compound group represented by +2,
Pentane, octane, nonane, decane, etc., CnH2n
Ethylene, propylene, butadiene (isobutadiene, 1.
3-butadiene), butylenes (isobutylene, n-butylene), etc. In addition to acetylene of the acetylenic hydrocarbon organic compound group represented by C2nH2o, methylacetylene, vinyl acetylene, etc., hydrogen is included, and one or more of these are included. It is a mixture.

In the present invention, this hydrogen source gas is mixed with a gas consisting of one or more of carbon dioxide, alkone, helium, and oxygen, and the amount of hydrogen is 0.1 vo# in terms of hydrogen based on the total shielding gas.
% or more, and if the amount of hydrogen generated by decomposition of water in the gas is also 0.1vo1% or more,
The above effects can be obtained.

In particular, the reason why the above effects can be obtained by using these hydrocarbon organic compounds is that these compounds are decomposed by the arc heat during welding and have a large effect of increasing the hydrogen partial pressure in the arc atmosphere, similar to when hydrogen is added alone. can be given.

(2) Iron oxide The present invention requires adding iron oxide to the wire.

Iron oxide acts as an oxygen source, increasing the oxygen partial pressure in the welding arc atmosphere, promoting the combustion of high-molecular organic compounds in the shop primer sandwiched between the groove surfaces, and also promoting the activation of hydrogen in the metal. In order to suppress the amount of iron oxide to an appropriate level and to prevent the formation of bubbles due to hydrogen under excessively deoxidized conditions, which is often seen in so-called illuminite vinegar sticks, the wire used in the present invention has a second amount of iron oxide. From the experimental results shown in the figure, it is characterized in that it is added in a range of 0.1 wt % to 12 wt % based on the total weight of the wire.

That is, 2.5 wt% of silica sand, 1
5wt% alumina, 0.8wt% potassium feldspar, 2.5
wt% rutile, 1.7wt% magnesium oxide,
4.5 wt %c manganese 80
Horizontal fillet welding similar to the experiment shown in FIG. 1 was performed under a gas shield containing a mixture of vo#% CO2 and 20 volφ hydrogen.

Figure 2 shows the amount of iron oxide and horizontal fillet 2 for the wire.
The relationship between the number of surface pores on the bead side is shown, and the amount of iron oxide is 0.
．． It can be seen that at 1 wt% or more, there are no pores.

However, if it exceeds 12 wt%, not only the physical properties of the formed slag, especially the fluidity, will be extremely deteriorated, but also the amount of added oxygen will be excessive, which may cause pores to be formed again.

On the other hand, the reason why pore formation cannot be prevented at less than 0.1 wt% is thought to be because the oxygen partial pressure in the arc atmosphere is unreasonably low in this range, and the combustion of the high molecular organic compound in the primer progresses incompletely. It will be done.

Therefore, the amount of iron oxide added to the wire in the present invention is suitably in the range of 0.1 to 12 wt%.

Incidentally, the iron oxide in the present invention is composed of an iron element and an oxygen element, and may be any oxide containing a compound of iron and oxygen that is easily decomposed by arc heat and releases oxygen.

That is, in the present invention, in addition to compounds of iron and oxygen such as hematite, magnetite, and mill scale, inorganic compounds containing iron oxides such as illuminite, dicrostone, and mullite clinker, and further heat decomposition to oxidize iron. Iron carbonate, etc., can be used singly or in combination of two or more.

Furthermore, iron powder having iron oxide on the surface is added to the wire, or the wire is annealed at high temperature to oxidize the surface, and iron oxide is added to the wire to the extent necessary in the present invention. You can also do that.

(3) Hydrogen Source Compound In the present invention, a hydrogen source compound is used within a range of 17 wt % based on the wire, if necessary.

The purpose of adding this hydrogen source compound is to utilize the explosive force generated when the hydrogen source rapidly decomposes due to arc heat or resistance heat generation at the protruding portion of the wire to promote detachment of droplets and turn the arc into a spray.

Furthermore, a so-called self-shielding effect can be expected in which the molten pool is shielded from the outside air by the hydrogen released from the hydrogen source, and the damage caused by lice, which is generally a weak point of gas-shielded arc welding, can be suppressed as much as possible.

As a result of the experiment, this hydrogen source compound was 17wt for the wire.
If it exceeds %, the arc becomes rougher and spatter is emitted more intensely, and overall welding workability deteriorates.
It is preferable to set it below this.

Therefore, the hydrogen source compound added to the wire in the present invention is suitably 17 wt% or less.

By the way, the hydrogen source compound used in the present invention is cellulose, which is generally used as a flux material for welding materials.
Organic compounds such as starch and wood flour; inorganic compounds with water of crystallization or bound water such as talc, mica, asbestos, and powdered water glass; or magnesium hydroxide, aluminum hydroxide, calcium hydroxide, barium hydroxide, and sodium hydroxide. , inorganic compounds with hydroxyl groups such as iron hydroxide.

Furthermore, the above effect can also be obtained by adding up to 17 wt % of a hydrogen source compound to the wire by filling it with oils and fats or moisture-absorbing flux that adhere to the wire during wire making or coiling.

In addition, water can also be added to the wire by adding an appropriate amount of water glass as a fixing agent to the above-mentioned flux, granulating it with an appropriate device, and filling the flux with a mixture that has been dried at a low temperature.

(4) Other flux materials In addition to the above-mentioned essential components, the wire of the present invention contains metal oxides, metal carbonates, metal lumps, deoxidizers, and metal powders, which are generally used as welding flux materials, as appropriate depending on the application. It can be added in ratio.

(5) Flux filling rate In the wire used in the present invention, the inside of the wire having a metal sheath is filled with the flux having the above structure at a ratio of 3 to 40 φ with respect to the total weight of the wire.

If the diameter is less than 3φ, a beautiful bead appearance cannot be obtained in horizontal fillet welding.

On the other hand, if it exceeds 40φ, the balance between the weight of the flux and the wire sheath metal will be lost, and the reaction between the wire sheath metal and the flux will be insufficient during welding, causing abnormal protrusion of unmelted flux and spatter phenomenon, so this is not preferable. do not have.

The present invention provides welding with excellent porosity resistance even when welding unclean workpieces with primer, rust, water, oil, etc. attached, but on the other hand, welding defects caused by hydrogen gas are a concern. It can be done.

That is, when welding steel materials with extremely high tensile strength, low-temperature cracking such as root cracking due to diffusible hydrogen in the weld is likely to occur.

Therefore, in consideration of this point, the present invention is preferably used for steel materials having a tensile strength of 50 kg or less.

Next, the present invention will be explained in more detail with reference to Examples.

Table 1 shows the compositions of the hydrogen-containing gases 01 to G and 6 used in the present invention and the comparative shielding gas.

As a comparative shielding gas, the JIS standard (K 11
06) The second type of carbon dioxide gas is illustrated.

Table 2 also shows wires W, 1 to W, 6r used in the present invention.
Shows wire components.

Furthermore, the table also includes wires outside the range of wire components used in the present invention for comparison.

These wires were made of a very mild steel sheath, and the wires were filled and finished to a diameter of 2.41 EIφ.

Hereinafter, the gas in Table 1 and the wire in Table 2 are combined as appropriate, current is 350 A (DC), voltage is 31 to 32 V, and speed is 20 to 3.
The following describes the results of various welding operations performed under the following conditions: 5 cm/Mn, gas flow rate 251 J/vtin.

First, fillet welding of a steel plate coated with a zinc-rich primer (20 μm thick) was performed using a combination of all the shielding gases shown in Table 1 and the wire W, 2 that does not contain a hydrogen source compound shown in Table 2. As shown in Figure 3, a fillet bead with no surface pores was obtained.

The same figure shows J gas in which the total amount of hydrogen is less than the range of the gas used in the present invention.
The welding results using IS standard (K1106) type 2 carbon dioxide gas are also shown.

As is clear from this figure, carbon dioxide gas having a lower total hydrogen content than the gas used in the present invention is less able to prevent surface pores than the hydrogen-containing shielding gas used in the present invention.

Furthermore, welding of a mild steel (20 mm thick) joint was performed in a downward position to obtain a welded part free from X-ray defects.

Furthermore, 2 mtt of the weld metal at 0°C in this case
t Vnotch Charpy shock absorption energy is found to be 0
．． 1 has an average of 11.4 Kg-m, 0.2 has an average of 1
2.3 Ky-m.

G,3 has an average of 11.9 Ky-m, G,4 has an average of 1
0.8KP-m, 0.5 average 10.3Kp-m,
G.5 obtained an excellent value of 10.4 Ky-m on average.

Next, fillet welding of the zinc-rich primer-coated steel plate was performed by combining wires W and 5 containing all the shielding gases shown in Table 1 and the hydrogen source compounds shown in Table 2.
As shown in FIG. 4, a fillet bead with no surface pores was obtained.

Similar to the results described above, the figure shows that surface pores cannot be prevented with type 2 carbon dioxide gas in which the total amount of hydrogen is smaller than that of the gas used in the present invention.

Furthermore, when determining the impact absorption energy of the weld metal at 0°C in this case, 0.1 is an average of 11.6 Ky -rn
+ G,2 has an average of 12.7 Ky-m, G,3 has an average of 12, IKp-m, G,4 has an average of 11.3 Kp
-m,G,5 has an average of 10.4Kii-m,G,
6 obtained an excellent value of 411-m with an average of 10.7.

Further, as a result of fillet welding using a combination of gas 0.2 shown in Table 1 and various wires shown in Table 2, weld beads without surface pores were obtained as shown in FIG. 5.

The figure also shows welding results using a wire with less iron oxide than the wire used in the present invention.

As is clear from the figure, the generation of surface pores cannot be prevented with a wire containing less iron oxide than the wire used in the present invention.

Furthermore, joint welding was performed in a downward position to obtain a welded part that was X-ray-free.

When the impact absorption energy at O'C of the weld metal in this case was determined, W,1 was 11.6 Kf-m on average,
W,2 has an average of 12.3 9-m, W,3 has an average of 12.3 Kp-m, W,4 has an average of 11.9Kp
-mtW,5 showed an average of 12.7Kg-m, and W,5 showed an average of 11.6Kp-m.

Although the embodiments of the present invention have been described above based on the results obtained by direct current welding, similar studies were conducted separately for alternating current welding, and it was confirmed that the results were not significantly different.

In addition, by combining the wire used in the present invention with a commonly used flux for submerged arc welding, and by spouting a hydrogen-containing shielding gas within the composition range of the present invention around the molten pool, the molten pool can be shielded from the outside air. It was also confirmed that by performing submerged arc welding, a welded part with high toughness and no welding defects such as pores could be obtained, which is the same as the results described above.

As described above, when the welding method of the present invention is used, a fillet bead with excellent tenacity and no surface pores can be obtained when fillet welding steel plates that have shop primer, rust, moisture, or oil attached. It turned out that.

This is something that cannot be accomplished using conventional gas-shielded arc welding methods, and it is extremely valuable in contributing to the development of various industries.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the total amount of hydrogen in the shielding gas and the number of surface pores in the fillet weld bead, and Figure 2 shows the relationship between the amount of iron oxide and the number of surface pores in the fillet weld bead relative to the total weight of the wire. Figures 3 and 4 are diagrams showing the relationship between the hydrogen content in the shielding gas and the number of pores on the surface of the weld bead, and Figure 5 is the relationship between the wire components and the number of pores on the weld bead surface. FIG.

Claims (1)

[Claims] 1. A flux-cored wire containing 0.1 to 12 wt% iron oxide as an essential component to the wire, a shielding gas with a total hydrogen content of 0.1 volφ or more, and a tensile strength of 50 A gas-shielded arc welding method that is characterized by welding steel materials of kg class or less. 2. Using a flux-cored wire in which 0.1 to 12 wt% of iron oxide is an essential component and a hydrogen source compound is further added to the wire at 17 wtφ or less,
A gas shielded arc welding method characterized in that steel materials having a tensile strength of 50 kg or less are welded using a shielding gas having a total hydrogen content of 0.1 VO 1% or more.